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Air Quality and Stationary Source Emission Control (1975)

Chapter: 12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems

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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

CHAPTER 12
CONTROL OF AMBIENT SULFUR DIOXIDE CONCENTRATIONS WITH TALL STACKS AND/OR INTERMITTENT CONTROL SYSTEMS

(Chapter 12 was written by Robert W. Dunlap under the general supervision of the committee, which reviewed the work at several stages and suggested modifications which have been incorporated. While every committee member has not necessarily read and agreed to every detailed statement contained within this report, the committee believes that the material is of sufficient merit and relevance to be included in this report.)

INTRODUCTION

Air quality implementation plans were enacted by the states in 1972 to bring about local compliance with national ambient air quality standards (AAQS). Not surprisingly, sulfur dioxide emission limitations for electric utility power plants varied widely in these plans. Much of the variation can be ascribed to regional fuel availability considerations, to state-imposed air quality standards or timetables, and to differing methodologies for relating emissions and air quality. Some of the variation, however, represents moot recognition of the different capacities of regional atmospheres to safely assimilate specific emission levels. For example, Pennsylvania’s regulations (Table 12–1) allow about an eightfold difference in emission rates, dependent upon source location. These allowed spatial differences in emission rates, with all rates designed to meet the same sulfur dioxide

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–1

Pennsylvania Sulfur Dioxide Regulations for Steam Power Plants (Existing Sources)

Area

Allowed Lbs SO2/10° BTU

Allowed Coal % S*

Philadelphia

-

0.3

Allegheny County (Pittsburgh)

0.6–1.0

0.4–0.6

Beaver Valley, Monongahela, and SE Pennsylvania Air Basins

0.6–1.0

0.4–0.6

Allentown-Easton, Erie, Harrisburg, Johnstown, Lancaster, Reading, Scranton-Wilkes Barre, York Air Basins

1.8–3.0

1.1–1.9

All Other Regions

4.0

2.5

* Assumes 12,500 BTU/Lb Coal.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

AAQS, are understandable in terms of different numbers of sources, background sulfur dioxide levels, meteorological characteristics, and topography for Pennsylvania’s air basins.

Temporal variations in emission limitations were not part of most states’ implementation plans, except as part of emergency episode criteria. However, the situation here is roughly analogous to the spatial variation situation. At any given emission rate, it can be generally stated that carefully chosen temporal fluctuations about that rate will provide air quality benefits, since variability in meteorological conditions causes significant changes in the air quality impact of any given level of emissions. With temporal controls, when dispersive characteristics of the atmosphere are unfavorable, minimum emission rates are demanded; when optimal atmospheric dispersion conditions exist, higher emission rates than the base rate are permitted.

This air quality management concept, i.e., that emissions can be spatially and temporally varied to achieve compliance with air quality standards, has only been partially accepted by regulatory agencies over the past several years. In particular, temporal emission controls for sulfur dioxide, here termed intermittent control systems (ICS), have been recognized in this country only in specific situations, and have been a focal point of a lively debate between regulatory agencies and some parts of the electric utility industry.1 This position paper details some of the aspects of this debate in order to assess current and future public policy concerning ICS programs.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TALL STACKS AND ICS PROGRAMS

An intermittent control system can be defined as “…system whereby the rate of emissions from a source is curtailed when meteorological conditions conducive to high ground-level pollutant concentrations exist or are anticipated” (FR 1973). For power plants, two intermittent control strategies are potentially available: (a) fuel switching, i.e., using a temporary supply of low sulfur fuel; (b) load shifting, i.e., shifting a portion of the electrical load to an interconnected generating station with capacity in excess of demand.

Tall stacks are closely associated with ICS programs, since increased stack height can yield decreased needs for intermittent emission reductions, assuming that control of ambient sulfur dioxide concentrations is the sole objective. For example, TVA’s comparison of estimated maximum ground level concentrations of sulfur dioxide associated with different meteorological dispersion conditions and stack heights between 60–360 meters is shown in Figure 12–1 (Carpenter 1971). Three critical meteorological conditions are depicted, each corresponding to a different plume transport condition: coning, inversion breakup, and trapping (mixing depths between 760–1065 meters).2 For coning and inversion breakup conditions, an inverse relationship between stack height and concentration applies. For trapping conditions, concentrations are primarily determined by the elevation and magnitude of the subsidence inversion or stable layer aloft; stack height does play a role if the plume emitted from the stack penetrates the layer of stable air and is not trapped below it (concentrations for plume penetration cases are approximately zero and are not shown in Figure 12–1). Based on dispersion model results such as these, as well as ambient air quality data, TVA suggests the anticipated requirements for ICS measures at its Kingston steam plant will drop from 55 days per year (7-hour average duration) for the plant’s current stack configuration (four 250-foot stacks and five 300-

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

FIGURE 12–1: Maximum Relative Concentration of SO2 as a Function of Meteorological Conditions and Stack Height (Carpenter et al. 1971)

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

foot stacks) to zero days per year for two 1000-foot stacks (TVA 1973).

Two basic types of tall stack-ICS programs are thus apparent. In the first, stacks of sufficient height are built so that ground-level concentrations do not abrogate standards, even without use of ICS measures. This approach is advocated in Great Britain (Stone and Clark 1967, Lucas 1974), and also by some utilities in this country for plants located in relatively flat terrain where no limitations on stack height (e.g., limitations imposed by flight safety requirements near airports) exist (Frankenberg 1970, Smith and Frankenberg 1974). In the second approach, applicable where ambient sulfur dioxide standards cannot be met simply by increasing stack height, tall stacks are coupled with ICS measures to control ground-level sulfur dioxide concentrations. Controversy has existed over whether tall stacks alone can adequately control ground-level sulfur dioxide concentrations. It seems clear, however, that as stack height increases, the required frequency of use of ICS measures decreases for most, if not all, given control situations. The frequency of ICS use is also dependent on emission rate, other stack parameters (stack gas velocity, temperature), meteorological conditions, and topography.

Regulations proposed by the Environmental Protection Agency (EPA) do not accept increases in stack height beyond levels of “good engineering practice” as acceptable air quality control measures, unless this is accomplished as part of an approved ICS program (FR 1973). These same proposed regulations impose stringent limitations on the types of sources and situations for which ICS programs are acceptable, and include the following constraints:

  • The ICS program must be a supplement to constant emission controls; the source must undertake research and development programs to accelerate development of applicable constant emission reduction technology.

  • The system must exhibit a high degree of reliability (ability to protect against violation of AAQS) and must be legally en-

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

forceable. Elements of such an ICS are shown in Figure 12–2 (PEDCO 1974) and include:

  • A sulfur dioxide monitoring network sufficient to allow calibration of a dispersion model, as well as interpolation between samplers.

  • An operating model which relates meteorological inputs, emission rates, source data, terrain and location factors to current and future air quality.

  • Meteorological inputs suitable for use in air quality forecasting.

  • Objective rules for emission control, relating air quality predictions to controlled emission schedules.

  • A requirement for continuous evaluation and systematic improvement of ICS reliability (upgrade system).

Figure 12–2 indicates the two different modes in which an ICS may be operated: (1) open-loop emission control, in which the decision to reduce emissions is made based on the output of the predictive model; and (2) closed-loop emission control, an emergency operating mode, in which real-time measurements from the air quality monitoring network are used to override the operating model in making the control decision. The closed-loop mode occurs when the open-loop mode of operation has failed, i.e., when ambient air quality measurements exceed specified threshold values and/or AAQS.

From the system diagram presented in Figure 12–2, ICS reliability and performance depend on a number of factors:

  1. The adequacy and accuracy of monitoring the pertinent emissions, air quality, and meteorological parameters;

  2. The ability to forecast meteorological inputs to the operating model, including transition periods between different types of weather and potential interactions between meteorology and terrain;

  3. The adequacy of the air quality forecast model or models, which must represent all possible meteorological conditions, account for terrain and location factors, and estimate anticipated emission rates;

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

FIGURE 12–2: Elements of an Intermittent Control System (PEDCO 1974)

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
  1. The ability to control source emissions in a timely manner in order to meet forecast objectives;

  2. The ability to combine elements (1)–(4) into an operational system with adequate flexibility to meet the objectives of the system.

Each of the system requirements can be achieved with some probability of success; however, the likelihood of attaining a given degree of system performance will depend upon the ability to satisfy all of the system requirements concurrently. Typically, a factor of safety must be invoked to insure adequate system response. This factor of safety is usually embodied within the threshold values of the system; i.e., those forecasted levels of sulfur dioxide which necessitate control measures. The upgrade system is then applied as part of an ongoing effort to select proper forecast values, so that curtailment of emissions are invoked often enough to meet the ambient standards, but are not put into effect unnecessarily often. System performance and reliability are clearly related to the number and severity of forecasted sulfur dioxide levels estimated to occur in excess of the standards; the ICS approach has the greatest chance for success where the required number of curtailments of emissions is low.

LEGAL BACKGROUND

The suggestion that tall stacks be used with or without intermittent controls to meet sulfur dioxide standards is a highly controversial one. On the one hand, these techniques have been shown to be effective, at relatively low costs, for reducing ground-level concentrations of sulfur dioxide in the vicinity of power plants burning high sulfur coal (Frankenberg 1970, Smith and Frankenberg 1974, Montgomery et al. 1973, Montgomery and Frey 1974, TVA 1974). On the other hand, the application of these techniques normally provides, over an extended length of time, only a negligible reduction in the amount of pollutants emitted. Primarily for this reason EPA “…considers constant emission

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

reduction techniques, such as flue gas desulfurization, far superior to dispersion techniques and has proposed regulations that limit the use of such dispersion techniques to situations where constant emission reduction controls are not available” (EPA 1974). EPA further claims “…the concept is not compatible with the Clean Air Act requirement that constant emission limitations be used whenever possible” (EPA 1974b).

In the most important legal decision on this subject, Natural Resources Defense Council v. EPA, the 5th Circuit Court of Appeals held that the Clean Air Act requires Georgia to attain national ambient air standards primarily through actual emission reductions rather than dispersion enhancement techniques; application of dispersion techniques is allowed only if exclusive reliance on emission control is infeasible (48a F. 2d. 390, 1974). In reaching this decision, the court determined that the section of the 1970 Clean Air Act amendments which requires that state implementation plans “include emission limitations, schedules, and timetables for compliance with such limitation, and such other measures as may be necessary to insure attainment and maintenance of such primary or secondary standards” (42 USC 1857c-5(a) (2)b) indicates a Congressional intent that emission reduction is the preferred method of meeting ambient air quality standards. Therefore, Georgia’s tall stack strategy for controlling power plant sulfur oxide emissions could be included in its implementation plan “only (1) if it is demonstrated that emission limitation regulations included in the plan are sufficient, standing alone, without the dispersion strategy, to attain the standards; or (2) if it is demonstrated that emission limitation sufficient to meet the standard is unachievable or infeasible, and that the state has adopted regulations which will attain the maximum degree of emission limitation achievable.”

This decision suggests that utilities which want to implement tall stack-ICS strategies rather than flue gas desulfurization (FGD) must convince state control agencies that FGD

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

technology is commercially or technically infeasible. TVA is presently bringing a suit (TVA v. EPA) in the 6th Circuit Court of Appeals which involves this issue as well as the issues of fact and law considered in the Georgia decision. If the 6th Circuit decision differs from NRDC v. EPA, ultimately the Supreme Court may have to resolve the conflict.

Two previous cases, Appalachian Power Co. et al. v. EPA and Pennsylvania v. Pennsylvania Power Co., reached opposite conclusions regarding FGD technology. In the first of these, the U.S. Circuit Court of Appeals for the District of Columbia rejected a claim by several power companies that technology was not available to meet EPA’s new source performance standards. The court, ruling in September 1973, said the evidence “…convinces us that the systems proposed are adequately demonstrated, that cost has been taken into consideration, and that emission standards are achievable.” The court added, however, that EPA’s consideration of the sludge disposal problem was insufficient, and remanded the record in the case to EPA for further explanation of sludge effects; EPA has not yet responded with the information. In the Pennsylvania Power case, a Pennsylvania state court upheld a county court opinion that adequate scrubbing technology does not exist. In a February 1974 decision, the court concluded that “flue gas scrubbing devices…are available in theory only, and are not available and proven from an operational or practical viewpoint.” A Lawrence County, Pennsylvania court had previously determined that “the only conclusion to date…is that the most feasible present method is high stack control.”

Recently, a September 1974 Ohio EPA hearing examiner’s report favored the tall stack-intermittent control approach, stating that “flue gas desulfurization is not a presently available, technologically feasible method of sulfur dioxide control…” and that “tall stacks, either alone or in combination with supplementary control systems, are a technologically feasible and economically reasonable means of meeting ambient air quality standards for sulfur dioxide” (Ohio EPA 1974).

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

However, the hearing examiner’s report served only as a recommendation to the Director of Ohio EPA; subsequent (December 12) findings and orders issued by the Director differed substantially from the recommendations of the examiner. Specifically, FGD technology was found by the Director to satisfy criteria for feasibility and reliability. However, he did rule that it would be inappropriate to require the use of FGD systems in Ohio until recent air quality data from power plants were collected and analyzed, and after further examination of the efficacy of scrubber technology takes place.

Each of the judicial or administrative decisions referred to above interprets requirements of the Clean Air Act amendments of 1970. More recent legislation, the Energy Supply and Environmental Coordination Act of 1974 (ESECA) (PL 93–319; enacted by Congress June 24, 1974), provides further insight into Congressional intent regarding the implementation of FGD and tall stack-ICS technologies. According to the provisions of ESECA, utilities permitted by EPA to convert to coal can be granted either short-term suspensions of emission limitations until as late as June 30, 1975 or compliance date extensions until as late as January 1, 1979 for meeting emission standards. Plants allowed an extension, however, must prepare a plan for achieving compliance before expiration of the extension with “the most stringent degree of emissions reduction” required by the state implementation plan in force at the time conversion was ordered. Under present EPA regulations this would include contractual commitments for obtaining long-term supplies of low-sulfur coal or installing continuous emission controls. Use of ICS is permitted only under certain circumstances; for example, these systems can be used to comply with interim requirements under emission standard extensions, but only in those cases where ICS utilization is directly enforceable by EPA.

For purposes of discussion, the following presentation assumes that tall stack-ICS technology is in itself a legally valid method of sulfur dioxide control, even though current EPA regulations and ESECA suggest otherwise.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

For the moment, however, tall stacks and ICS measures are assumed to provide an important technological option, at the very least for reasons pointed out in EPA’s proposed regulations (FR 1973):

  • These measures provide alternative means for attaining and maintaining sulfur dioxide AAQS, rather than relying solely on FGD systems or low sulfur fuels.

  • Implementation of these measures can result in attainment of AAQS in a shorter time than would otherwise be possible.

  • These measures can be important interim techniques, given limitations on availability of FGD systems and low sulfur fuels over the next few years, given difficulty in retrofitting some facilities with FGD systems, and given distribution and allocation problems associated with low sulfur fuels.

ASSESSMENT OF THE TECHNOLOGY

Four aspects of tall stack-ICS technology are assessed here, including system performance, availability, cost, and secondary environmental impacts.

Performance

ICS measures are currently being implemented at a small number of installations on the continent, including (1) a number of TVA power plants; (2) other power plants operated by Ontario Hydro (Canada) and Long Island Lighting Company (New York); (3) a number of western smelters operated by American Smelting and Refining Company (ASARCO), Kennecott Copper Corporation, and others; (4) the Dow Chemical plant at Midland, Michigan. Only limited data are available to assess performance of these systems.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
TVA-Paradise Steam Plant

Data for the TVA Paradise steam plant are most extensive, and the distribution of 3-hour and 24-hour sulfur dioxide concentrations above AAQS levels before and after initiation of ICS measures are indicated in Table 12–23 (TVA 1974). Standards were exceeded prior to September 1960 with a two-unit plant (two 704 MW generating units, each with a 600-foot stack); capacity was increased by 82 percent on September 19, 1969 by installation of an 1150 MW unit with an 800-foot stack, with ICS measures also initiated to control high ground-level concentrations. No violations of 3- or 24-hour AAQS have occurred at the monitoring network since initiation of the ICS program, although four occasions in which sulfur dioxide concentrations were above the 3-hour standard level have been noted; details concerning possible violations at non-monitored locations are not available. At Paradise, plant generation reductions are instituted during adverse conditions for plume dispersion; these periods are predicted through on-site meteorological measurements. If nine meteorological and plume dispersion criteria (Table 12–3) fall within a critical range of values, the magnitude of sulfur dioxide emission reduction needed is determined with a dispersion model, and a load reduction takes place. Emission or load reductions are implemented independent of wind direction or monitor readings; the monitoring network is used for validation of the dispersion model and for checking system performance.

ASARCO-Tacoma Smelter

Data are also available which demonstrate the degree of effectiveness of ICS measures initiated at ASARCO’s smelter in Tacoma, Washington (Tables 12–4, 12–5) (Nelson et al. 1973, Welch 1974). The data obtained from 5 ASARCO monitoring stations in continuous operation since 1969 indicate substantial and consistent improvement in the performance of the

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–2

Sulfur Dioxide Concentrations Above Ambient Air Quality Standard Levels Before and After Implementation of ICS Program for TVA’s Paradise Steam Plant (TVA 1974)

Time Period

Above 3-hour Standard Level (0.5 ppm)

Above 24-hour Standard Level (0.14 ppm)

4/28/63–9/18/69 (Before Control)

10*

8*

9/19/69–3/31/74 (After Control)

4

0

* Include violations of ambient air quality standards, which allow abrogation of standard level only once per year per location.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–3

Meteorological Criteria for ICS Measures at TVA’s Paradise Steam Plant (TVA 1974)

NO.

Criteria

Parameter Value

Remarks

1.

Potential temperature gradient between stack top, 183 m, and 900 m

Identifies the mean atmospheric stability throughout the layer involved in the plume height calculation

2.

Potential temperature gradient between stack top, 183 m, and 1,500 m

Identifies the mean atmospheric stability throughout the layer involved with the thermally induced mixing of the plume effluent

3.

Difference between daily minimum and maximum surface temperature

Tmax−Tmin≥6°K

Identifies the potential magnitude of insolation as it affects the rate of development of thermally induced mixing

4.

Maximum daily surface temperature

Tmax≤298°K

Identifies the temperature used in calculation of the maximum mixing height

5.

Maximum mixing height

MMH≤2,000 m

Identifies the maximum level of the mixing height when SO2 concentrations might exceed the ambient standard levels

6.

Maximum mixing height and plume centerline heights

MMH≥He

Identifies the related height at which thermally induced mixing will penetrate the plume and uniformly mix the effluent to the surface

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

7.

Time for mixing height to develop from plume centerline to critical mixing height

T≥3,960 sec.

Identifies the potential for persistence of concentrations above the ambient standard levels. The critical mixing height (CMH) is the upper limit of the thermally induced mixing layer when concentrations could exceed the ambient standard levels

8.

Mean wind speed between stack top, 183 m, and 900 m

Identifies the wind speed used in plume rise and CMH calculations

9.

Cloud cover

CC<80%

Identifies the availability of insolation which affects the thermally induced mixing

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–4

Sulfur dioxide Concentrations in Violation of National Ambient Standard Levels at ASARCO Smelter (5 Monitoring Stations), Tacoma, Washington (Nelson et al. 1973, Welch 1974)

 

3-hour Standard Violations (0.5 ppm)

24-hour Standard Violations (0.14 ppm)

Annaul Standard Violations (0.3 ppm)

Time Period

Number

Maximum

Number

Maximum

Number

Maximum

1969

26

0.72 ppm

9

0.250 ppm

0

0.019 ppm

1970

13

0.85

2

0.160

0

0.013

1971

3

0.53

0

0.116

0

0.012

1972

0

0.45

0

0.096

0

0.021

1973

0

0.45

0

0.100

0

0.015

1974 (Jan–Sep)

0

0.57

0

0.092

0

0.010

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

ICS program. National AAQS have not been exceeded since March 1971 at either the ASARCO stations or stations of the Puget Sound Air Pollution Control Agency (PSAPCA). However, more stringent local AAQS (Table 12–5) have been repeatedly violated, although with decreasing frequency since 1969.4 ICS control at this location represents a greater challenge than at the TVA-Paradise plant due to the greater emission rate, moderate stack height, and more limited plume rise (565-foot stack, 15 feet/second plume exit velocity), significant terrain effects (local maximum elevations within 250 feet of stack elevation) and complications introduced by the maritime climate meteorology. Plant curtailments are typically initiated in the morning on the basis of meteorological forecasts; during May-October, operations must be curtailed to some degree almost every day. Forecasts are continuously updated on a short-term basis; monitoring station data (both ASARCO and PSAPCA) are then used to further modify curtailment actions. On the basis of controlling ambient sulfur dioxide concentrations, the Tacoma ICS can be considered a success. However, the system is designed to meet local standards as well; here reliability is not adequate. Initiation of improved continuous emission controls have recently dropped SOx emissions an additional 40 percent at full load; this continuous emission reduction may help bring about attainment of local as well as national AAQS for sulfur dioxide.

ASARCO-El Paso Smelter

Further insight into ICS performance is provided by a case study of ASARCO’s ICS program at its El Paso smelter. The case study was recently completed by Environmental Research and Technology, Inc. (ER&T) for EPA, as part of a larger effort to develop procedures to analyze ICS programs quantitatively (Gaertner et al. 1974). The El Paso smelter represents a difficult location for ICS control techniques due to severe terrain effects. Emissions from copper and lead smelting operations are

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–5

Number of Violations of Local Ambient Standards at ASARCO Smelter (5 Monitoring Stations), Tacoma, Washington (Welch 1974)

Time Period

1.0 ppm, 5 minutes*

0.4 ppm, 1-hour+

0.25 ppm, 1-hour#

0.1 ppm, 24-hr+

Total Violations

1969

364

273

370

28

1035

1970

257

175

173

8

613

1971

31

29

29

1

90

1972

25

16

5

0

46

1973

10

10

4

0

24

1974 (Jan–Sep)

5

6

2

0

13

* Allowed one exceedance in 8-hour period.

+ Not to be exceeded.

# Allowed two exceedances in 7 days.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

separately released (828-foot and 611-foot stacks, respectively) with stack tops corresponding to sea-level elevations of approximately 4,600 and 4,400 feet. To the northwest of the smelter, the Franklin Mountain Range (peaks at 6,000–6,600 feet) extends north-south, and acts as a barrier to the ASARCO plume during southwesterly wind flows; the Sierra del Christo Key peak rises to a 4,700-foot elevation to the west of the smelter and interferes with plume transport to the northwest. ER&T analyzed ICS reliability for the 36-day period March 5-April 9, 1971, evaluating system performance in meeting national AAQS as well as a state variance standard calling for 1-hour concentrations ≤0.5 ppm. The following conclusions are apparent from the study:

  • ICS measures were effective in reducing the number of excess concentrations east of the plant, but were less effective for concentrations northwest of the plant.

  • Without meteorologically-based controls, both long and short-term sulfur dioxide concentrations would have been dramatically higher during the 36-day period. Percent reductions in average sulfur dioxide concentrations at the 17-station ASARCO monitoring network due to use of ICS controls ranged from 27.9 to 65.2 percent.

  • As shown by Table 12–6, frequency distributions of concentrations measured by the monitoring network shifted toward the lower end of the spectrum, with the greatest shifting at the highest concentrations.

Although these performance characteristics indicate a substantial improvement in air quality due to ICS controls, system reliability in meeting all AAQS during the 36-day period was not adequate:

  • The state variance standard (1-hour, 0.5 ppm standard) was violated on 9 occasions (Note that Table 12–6 indicates 17 violations, but 8 of these occurred at stations in New Mexico where the Texas standard was not a control objective).

  • Violations of the 3-hour, 0.5 ppm national AAQS ocurred at one station.

  • Violations of the 24-hour, 0.14 ppm national AAQS ocurred at two stations.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–6.

Distribution of Hourly SO2 Concentrations for 17-Station ASARCO Monitoring Network ASARCO/El Paso ICS Program (March 5–April 9, 1971) (Gaertner et al. 1974)

Case

Number of 1-hour SO2 Concentrations

 

Total

>0.1 ppm

>0.2 ppm

>0.3 ppm

>0.4 ppm

>0.5 ppm

>0.6 ppm

>0.7 ppm

>0.8 ppm

>0.9 ppm

>1.0 ppm

Full Load Operation

14508

1187

599

360

225

142

88

62

45

37

31

ICS Control

14508

660

249

98

42

17

7

5

2

2

1

% Reduction due to ICS Control

-

44.4

58.4

72.8

81.3

88.0

92.0

91.9

95.6

94.6

97.0

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

Meteorological evaluations of five separate periods of high sulfur dioxide concentrations during the 36-day period did reveal methods by which system reliability could be improved, principally through improved forecasting and modeling of terrain disturbances.

Further evidence of the difficulty in meeting national AAQS with the El Paso ICS is provided by Table 12–7 (Nelson 1974). These data, derived from 13 stations in the ASARCO monitoring network which have operated continuously since 1970, indicate continuing violations of national AAQS.

Boston AIRMAP Network

System reliability in any ICS program is closely related to the accuracy of air quality forecasts. Unfortunately, no direct comparisons of air quality forecasts with observed air quality levels are available for operating ICS programs. Information of this type is available, however, from ER&T for their Boston AIRMAP network, an 11 station, real-time sulfur dioxide monitoring and forecasting system in operation since December 1971 (Gaut 1973, Gaut 1975). In Figure 12–3 the percentages of time for which differences between forecasted and observed values are within specified absolute limits (≤0.005 ppm, ≤0.010 ppm, ≤0.020 ppm) are indicated. Predictions are within 0.010 ppm between 80–95 percent of the time. ER&T concludes that these statistics indicate a forecasting skill better than the minimum required for a reliable ICS program. These forecasts are applicable for a multi-source, urban area; forecasts for regions dominated by single sources may be even more reliable. However, specific terrains, source configurations, and local meteorologies can pose signficant difficulties in air quality forecasting, as earlier examples show. Also, typical 24-hour sulfur dioxide concentrations in the Greater Boston area are relatively low (peak concentrations are in the range of 0.05–0.10 ppm); thus, percent error rather than absolute

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

FIGURE 12–3: Absolute 24-Hour SO2 Concentration Forecasting Errors (ppm), Greater Boston AIRMAP Network (Gaut 1975)

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–7

Number of SO2 Concentrations above Ambient Air Quality Standard Levels for 13 Station ASARCO-El Paso Monitoring Network (Nelson 1974)

 

Number of SO2 Concentrations

 

 

Year

0.14 ppm (24 Hour Standard)

0.5 ppm (3 Hour Standard

Total

1970

1

8

9

1971

2

1

3

1972

12

1

13

1973

3

9

12

1974 (Jan.–Nov.)

0

1

1

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

error comparisons of the ER&T data would be less impressive.

Recapitulation

Only limited data are available to assess performance of operating ICS technology. Those data which are available pertain to individual sources of sulfur dioxide, either power plants (TVA) or smelters (ASARCO). System performance is varied; a “typical” ICS cannot be described based on these data. Indeed, ICS performance seems to be highly dependent on local meteorology, terrain and source characteristics, and particular system operating procedures. In general, currently operating systems provide significant reductions in peak ambient sulfur dioxide concentrations measured near the emission source. However, all relevant ambient air standards are still not met in the vicinity of several of the sources which have implemented ICS technology, particularly the short-term local standards which are more stringent than the present Federal standards.

This review has demonstrated that a need exists for a fully-documented analysis of an operating ICS system. Such a study should generate sufficient records of source data, meteorological data, and actual as well as forecasted air quality data to permit a definitive estimate of ICS reliability under various conditions. A 120-day study of a power plant burning eastern coal and applying ICS measures is suggested.

Availability

Two separate issues regarding availability of the tall stack-ICS approach are considered here:

  1. Availability of the generating unit itself, due to meteorologically-based load reductions, including constraints imposed by load shifting or fuel switching.

  2. Availability of trained personnel and/or firms with requisite forecasting and

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

monitoring capabilities to implement ICS controls.

Generating Unit Availability

The first of these issues can be partially assessed with TVA data which forecast anticipated load reductions at 9 power plants if ICS measures are imposed through load shifting alone (Table 12–8) (TVA 1973). Without construction of 5 new tall stacks at 3 plants (Kingston, Shawnee, Widows Creek), power output drops of 346,000 MW-hours per year are forecast; this represents 0.25 percent of the generating capacity of the 9 plant network (0.4 percent at an average load factor of 0.61). With construction of new stacks, reductions of 107,500 MW-hours/year are anticipated (0.08 percent of full load or 0.13 percent of average load). Predicted and actual performance can be compared for the Paradise plant, for the first 39 months of ICS control (September 1969-November 1972) (Montgomery et al. 1973). Reductions would have been required 106 days during this time (33 days/year) if the plant were at or near full capacity; actual load reductions totaled 41 days (13 days/year) with an average length 3.6 hours and size 454 MW (22 percent reduction).

Several points associated with this topic deserve further explanation:

  1. Although average load reductions required in the TVA system are low, reductions required for other plants may not be in this range. For example, the two ASARCO smelters considered earlier represent much more difficult applications of ICS technology, and require correspondingly greater average reductions in plant output (15–17 percent yearly average curtailment at Tacoma, 27–35 percent at El Paso).

  2. Additional reserve capacity requirements are implied if ICS control is exercised through load shifting rather than fuel switching. For example, preliminary studies by TVA indicate that additional reserve requirements on the order of 3–4 percent of peak

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–8

Anticipated Load Reductions at TVA Power Plants due to ICS Measures (TVA 1973)

Plant

Stack Height

Estimated Frequency of Reductions

Equivalent

Number

Height (ft.)

Days/Year

Hours/Day

% Hours/Year

MW/Hours/Year

Allen

3

400

1

6

0.1

2,000

Colbert

4

300

24

5.5

1.5

25,000

 

1

500

 

Cumberland

2

1000

10

3

0.3

15,000

Gallatin

2

500

7

4.5

0.4

9,000

Johnsonville

8

273–400

7

6

0.5

12,000

Kingston (Current)

4

250

55

7

4.4

100,000

 

5

300

 

Kingston (Planned)

2

1000

0

0

0.0

0

Paradise

2

600

13

3.5

0.5

22,000

 

1

800

 

Shawnee (Current)

10

250

42

6

2.9

87,000

Shawnee (Planned)

2

800

3

3

0.1

4,500

Widows Creek (Current)

6

270

25

6

1.7

75,000

 

2

500

 

Widows Creek (Planned)

2

500

12

3

0.4

18,000

 

1

1000

 

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

power system load would be needed if fuel switching were not utilized, and if load switching were confined to the TVA network.

  1. The ability to load switch is limited if large scale adverse meteorology affects a large region rather than only one plant and one locality; the frequency of occurrence of this condition differs in various parts of the country. For example, in the Tennessee Valley, TVA has noted 100 occasions since September 24, 1973 when the meteorological conditions appropriate for generation reduction occurred at one or more of the following plants: Allen, Cumberland, Gallatin, Paradise, and Widows Creek. (These plants are located in a three-state area within the Tennessee Valley.) During this period of time, the potential need for simultaneous generation reduction at two plants existed on 17 days; because of plant operating conditions, simultaneous reductions were necessary on only 3 of the 17 days. The potential need for simultaneous generation reductions at 3 plants existed on one day; curtailments at all three plants were not necessary on that day due to operating conditions (Montgomery 1974).

  2. Load shifting for environmental reasons is currently not practiced in the nation’s power pools, with the exception of plants in the Los Angeles basin, where minimum NOx dispatch5 is practiced (i.e., power plants are brought on line to provide power with minimum total NOx emissions in the basin) (Schweppe 1974). Dispatch of power based on air quality constraints is potentially available, but time would be needed to work out new pool agreements, and some increases in computer control costs and power costs could be expected. However, an individual plant’s ability to load shift for ICS purposes would depend on its particular situation (location, power system, and pool arrangement). Some systems, notably American Electric Power Service Corporation, do not operate within a pool, and plants within that system could shift independent of pool agreements. Some plants within power pools could arrange interim load shifts easily, if the pool were willing to treat an environmental

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

outage as a forced power outage. In other cases, however, interim or long-term pool arrangements to allow ICS load shifting could be more difficult to bring about.

  1. It is important to note that the practicality of implementing ICS actions which demand load reductions can be questioned, since the desire to meet AAQS may conflict with the desire of utilities to maintain an adequate power supply. For example, TVA has stated “…There are two power system operational conditions in which the Paradise Steam Plant would not reduce generation load below a minimum level during a designated sulfur dioxide emission limitation period. These restrictive conditions became effective when further limitation in load would cause power system instability and risk a failure in the supply of firm power to customers” (Montgomery et al. 1973). These two competing objectives—reliable sulfur dioxide control and reliable power—could presumably clash if load reductions are implemented on a large scale in ICS programs.

Most of the constraints suggested above are applicable to ICS approaches which depend on load shifting as a means for controlling emissions during adverse meteorological periods.

Constraints are also applicable for fuel switching (PEDCO 1974):

  1. Many coal-fired plants require major modifications in coal handling and feeding systems before they have a fuel-switching capability based on low sulfur coal. These modifications include provision of separate storage stockpiles of low sulfur fuel, erection of conveyers to move coal from storage areas, and construction of separate or partitioned bunkers for feeding the low sulfur coal supply to the boiler.

  2. The time required to effect a fuel switch to low sulfur coal can prevent the attainment of the federal 3-hour AAQS, or other short-term local standards. Fuel switching times can be expected to vary from 20 minutes (with partitioned bunkers) to 3 or more hours (when no bypass exists for high sulfur coal in the bunkers).

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
  1. Operating problems can be encountered in units not designed for low sulfur coal when this fuel is burned for prolonged periods of time. Such problems are associated with the higher moisture content, lower heating value, and different ash characteristics of low sulfur coals; the problems include (a) increased emissions of particulate matter and reduced collection efficiency of electrostatic precipitators, (b) reduced capacity of generating units and associated mechanical equipment such as pulverizers and coal bunkers, and (c) increased slagging.

  2. Burning low sulfur fuel oil as an alternate fuel in units with dual firing capabilities eliminates the constraints mentioned above. However, this alternate firing capability (with storage and piping facilities) in units not so equipped will cost from $12–$40/kw, depending on the size of the unit. In addition, assured supplies of low sulfur oil may not be available.

Availability of Personnel and Firms with ICS Capabilities

A number of different potential ICS applications exist, with individual applications of this technology requiring different forecasting, modeling, and monitoring efforts and capabilities. At one end of the spectrum are plants located in relatively flat terrain, equipped with tall stacks, and burning fuels with low to intermediate sulfur content. Without other complicating factors, these plants could presumably implement ICS programs which would feature relatively few emission reductions per year. Forecasting, modeling, and monitoring problems, although significant, would be minimized. At the other end of the spectrum would be plants located in areas where there are severe meteorological conditions or where plume patterns are significantly affected by disturbances of air patterns created by nearby structures or terrain. Implementation of ICS programs in these situations would feature relatively large numbers of emission reductions

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

per year, and forecasting-modeling-monitoring problems would be significantly increased.

The technical efforts exerted to initiate and operate an ICS program at either extreme are significant, but of a different order of magnitude. If the more complex ICS systems were implemented for many sources, current capabilities of competent, trained personnel and firms which can deliver such services could be inadequate. Even more significant constraints, applicable to all ICS applications, could be hardware needs (specifically ambient air quality and emissions monitoring equipment and telemetry) and time requirements to reach full operation of an ICS program.6

Costs

Costs for tall stack-ICS programs can be expected to vary considerably from plant to plant, with an obvious trade-off existing between amount spent for tall stack construction and fuel or load switch costs. The amount TVA spent to develop its tall stack-ICS program at nine plants could be illustrative of average plant costs, and is shown in Table 12–9 (Montgomery and Frey 1974, TVA 1974, Frey 1974).

The TVA program includes construction of five new tall stacks (800–1000 feet in height) at three plants (replacing 25 stacks with heights between 250–300 feet), construction of coal switching capabilities at three plants, and development of ICS programs and monitoring at all nine plants. Fuel switching will be practiced at Colbert, Cumberland, and Johnsonville plants; load switching at Allen, Gallatin, Paradise, Shawnee, and Widows Creek plants; Kingston will rely on tall stacks alone. Operating costs presented in Table 12–11 include annualized capital charges, replacement power or low sulfur fuel charges for an equivalent of 107,500 MW-Hours of electrical power, and operation-maintenance expenses.

TVA average costs of approximately $4/kw capital and approximately 0.15 mills/kwh operating cost appear to be low estimates in at least two respects, if these expenditures are to

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

be considered accurate for all situations. Reserve capacity of the TVA system would need to be increased if load switching were undertaken without purchase of replacement power from other utilities; capital and operating costs cited could be at least doubled if reserve requirements on the order of 3–4 percent of system load were required. Also, the per-kilowatt costs may be too low an estimate for other plants due to the large average size (about 1750 MW) of the TVA plants included in the nine plant network; tall stack costs and ICS program-monitoring costs should be relatively independent of plant capacity. For example, note that per plant costs shown in Table 12–9 are capital costs, $6.7 million; annual costs, $1.2 million. If these costs are associated with a 1000 MW plant operating at 65 percent load factor, average costs are increased to $6.70/kw for capital costs and 0.2 mills kw-hour for annual costs.

Hence, costs for operating a tall stack-ICS program at an average power plant can best be stated in terms of a relatively broad range, accounting both for the TVA experience and possible cost increments due to increased reserve requirements and plant size effects.

Capital Costs:

$4–10/kw

Operating Costs, including annualized capital charges:

0.15–0.04 mills/kwh

These costs can be compared to previous estimates by MacDonald (1973) (capital costs, $5/kw; operating costs, 1 mill/kwh) and Jimeson et al. (1974) (operating costs in the range of 0.02–1.4 mills/kwh, dependent on whether load or fuel switching is used).7

Secondary Environmental Impacts

Much of the controversy surrounding use of the tall stack-ICS technology is not specifically associated with control of ambient sulfur dioxide concentrations, but rather with possible secondary environmental impacts of the tech-

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

nology. Since the technique essentially relies on dispersion (i.e., dilution) to reduce ambient concentrations, long-term sulfur dioxide pollutant loadings vented to the atmosphere are usually only negligibly reduced. Possible environmental effects associated with these atmospheric loadings include:

  • impact of suspended sulfate aerosol concentrations, including possible health effects (increased morbidity and mortality), damage to materials and plants, and aesthetic effects (visibility reduction, climate and weather changes).

  • impact of acid rainfall, due to acidification of soils and water.

Unfortunately, most of these impacts are unquantified at present, or are clouded with scientific uncertainty. Acceptance of the tall stack technology, therefore, depends on a subjective decision that the risks and uncertainties associated with potential environmental impacts due to these effects are outweighed by the incremental cost of continuous emission controls.

EPA Viewpoint

EPA suggests concentrations of suspended sulfates in the 6–10 ugm/m3 range (24 hour or longer exposure) are associated with adverse human health effects (Finklea 1974). Altshuller’s analysis of National Air Surveillance Network (NASN) data for 1964–1968 indicated that such low levels of sulfate concentration were widespread, and correlated with correspondingly low levels of sulfur dioxide concentrations in urban areas. Altshuller also suggested that high sulfate concentrations at eastern and midwestern non-urban locations were attributable to the chemical conversion of sulfur dioxide to sulfate during transport downwind from urban areas, with sulfate levels of at least 5 ugm/m3 carried into urban areas. Assuming this analysis was correct, Altshuller concluded that, for eastern and midwestern portions of the United States, “…a uniformly large reduction in sulfur

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

dioxide is necessary…to secure substantial decreases in sulfate concentration levels at many urban sites and at all non-urban sites (Altshuller 1973). In a later analysis of NASN data for the period 1964–1970, Frank modified the earlier, general sulfur dioxide-sulfate correlation, finding “sulfate concentrations…are not clearly related to ambient sulfur dioxide concentrations at individual locations and can be better described by the concentration of total suspended particulate matter and the general geographic locality of the monitoring station.” Frank’s analysis did indicate that a broad geographic similarity exists between overall ambient concentration levels of sulfur dioxide, the sulfate fraction of total suspended particulate matter, and area-wide sulfur dioxide emission densities; in addition, his analysis tended to substantiate the existence of a higher background of sulfate concentrations in the eastern United States. Since most sulfate particulate formation probably results from atmospheric reactions of sulfur dioxide, Frank concluded that “…the influence of more distant sulfur dioxide emissions on sulfate concentrations could satisfactorily explain both the general geographic similiarity of sulfate levels and the apparent differences in ambient sulfur dioxide and sulfate concentrations” (Frank 1974).

Finklea has recently sharpened this argument, pointing out that sulfur dioxide emissions in major cities decreased by 50 percent between 1960–1970, while nationwide sulfur dioxide emissions increased, with 80 percent of these emissions due to power plants east of the Mississippi River. Finklea argues that long-range transport of acid-sulfate aerosols from one region to another is plausible, based on an analysis of turbidity levels, acid rainfall patterns, and high annual average sulfate levels in the eastern United States. However, as Finklea points out, there are significant scientific uncertainties in the sulfate data base: limited historical data; limited monitoring information, especially simultaneous monitoring in urban, suburban, and rural areas; limited understanding of mechanisms and rates of

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

transformation of sulfur dioxide to acid-sulfate aerosols in plumes and in the atmosphere; inadequate dose-response functions for addressing health effects; and lack of precise predictive models showing effects of long-range transport and stack height on ambient pollutant concentrations. Despite these uncertainties, EPA has concluded that: (1) failure to reduce SOx emissions may result in thousands of excess deaths and illnesses; (2) reduction of SOx emissions from urban and rural power plants will be required; (3) conversion of power plants to high sulfur fuels and use of tall stack-ICS approaches will aggravate the sulfate problem (Finklea 1974).

An Opposing Viewpoint

Arguments disputing the EPA sulfate analysis as it applies to tall stack-ICS strategies have been put forth by TVA (1973), by the Federal Energy Administration (1974), and, in a major advertisement series, by American Electric Power Service Corporation. A number of recurrent themes are identifiable in these and other arguments which support tall stack-ICS technology:

  1. This technology does not have the secondary impacts associated with flue gas desulfurization technologies, namely sludge creation and disposal problems or relatively high energy requirements (5–7 percent of output power) to operate the FGD systems;

  2. Tall stack-ICS technology is capable of meeting existing AAQS for sulfur dioxide, even in those situations where current emission regulations will not guarantee meeting ambient standards;

  3. If acid-sulfate aerosols pose dangers to health, welfare, and aesthetics as suggested by EPA, AAQS for this class of pollutants should be established, following the procedures set forth in the 1970 Clean Air Act Amendments. If information regarding sulfates is not sufficient to issue a criteria document, then tall stack-ICS technology should not be rejected on the basis of present information.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
  1. EPA’s advocacy of oxidation catalysts for vehicles, a control technology which might produce high ambient sulfate concentrations in transportation corridors and in center-city areas, is not consistent with its stance on tall stack-ICS technology. Each technology may exacerbate the sulfate problem, yet EPA is an advocate of oxidation catalyst technology, an opponent of tall stack-ICS technology.

  2. Use of tall stack-ICS methods allows immediate increased combustion of coal, the nation’s most plentiful fuel resource. Use of this technology will ease the nation’s clean fuels deficit and still allow compliance with sulfur dioxide AAQS.

Recapitulation

Judging the persuasiveness of arguments on both sides of this controversy is a major task of the current NAS/NAE study. The controversy centers about two issues:

  1. What are the health, welfare, and aesthetic effects associated with present and anticipated levels of sulfate aerosols and sulfur dioxide in the atmosphere?

  2. What role do power plants employing ICS technology and/or tall stacks play, both now and in the future, in the relationship?

Decisions regarding these issues may have to rest on subjective as well as objective appraisals. For the tall stack-ICS technology, two separate levels of inquiry appear to be warranted:

  1. Should tall stack-ICS technology be considered as a permanent emission control technique?

  2. If not, is this technology practicable as an interim control technique?

In making these judgments, a potential compromise position can be identified which seems to be within the existing data base. The tall stack-ICS technology could be rejected as a permanent control technique on the basis of the probability of substantial potential risks associated with increased atmospheric loading of sulfur compounds. At the same time, the

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

technology could be accepted for carefully defined situations as an interim control technique, on the basis of the need to:

  1. Select suitable interim sulfur dioxide control techniques during large scale implementation of FGD technology, and

  2. Reduce the clean fuels deficit while allowing compliance with sulfur dioxide AAQS, if not potential sulfate standards. It would appear that the Ford Administration has recently adopted this position, in a November 22 statement of the Energy Resources Council. The Council agreed to support the policy of requiring continuous emission controls for all new and existing power plants, subject to deferral of compliance by those plants where implementation of ICS technology is deemed a feasible and enforceable alternative for meeting primary sulfur dioxide standards. Power plants in some instances could use the ICS approach until as late as January 1, 1985. Ambient air standards would have to be met during the interim, and compliance schedules for installing permanent controls would have to be agreed to before use of ICS controls would be allowed (Environment Reporter 1974).

ENFORCEMENT

An important issue regarding the efficacy of ICS technology concerns the legal enforceability of these systems. Principal attention here has been focused on the question of whether AAQS can be attained without enforcing emission limitations. The issue was pointedly referred to by Senator Edmund Muskie in Senate discussion of ESECA:

An important clarification in the conference report relates to enforcement of interim procedures to assure compliance. Senate conferrees insisted that the Environmental Protection Agency’s determination that emissions from coal converters would not cause primary standards to be

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

exceeded must be articulated in emission limitations or other, precise enforceable measures for regulating what comes out the stack. The conference report on this bill underscores the fact that it is not ambient standards which are enforced but emission limitations or other stack related emission control measures. Ambient standards are only a guide to the levels of emission controls which must be achieved by specific sources. In 1970, we recognized that a control strategy based on a determination of ambient air pollutant levels in relation to each individual source would be unenforceable. Existing clean air implementation relies specifically on the application of enforceable controls against specific sources. We have continued that procedure in this law (Cong. Rec. 1974).

Emissions-Based versus Air Quality-Based Enforcement

The relative lack of enforceability of AAQS compared to the relative simplicity of enforcing compliance emission standards is not in question. In the first situation (AAQS), the contribution of a single pollutant source to resulting ambient air quality is difficult to determine; in the other case (emission standards) specific standards are applicable to individual source. The key to effective enforcement of ICS control, then, appears to be rooted in enforcement of specific emission limitation violations rather than (or in addition to) enforcement of AAQS violations. In ICS enforcement based on emission standards, predetermined emission rates (calculated by forecasting meteorology and modeling air quality, and monitored by in-stack measurements) form the basis for determination of individual source compliance; in ICS enforcement based on air quality standards, measured ground-level

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

ambient concentrations are the sole information source relied upon for enforcement.

EPA Proposed Regulations

EPA’s proposed regulations (FR 1973) for ICS systems, as well as the agency’s recently proposed rule-makings (FR 1974a, 1974b) for ICS controls for certain western smelters, recognize the importance of emission-based controls for practicable enforcement. Specifically, the following measures are provided:

  1. Air quality violations are defined as “non-compliance with stated and agreed upon emission curtailment conditions and procedures” as well as “a single ambient concentration that exceeds the standard at any point in the area significantly affected by the source emissions” (FR 1973).

  2. The emission source must “establish, maintain, and continuously operate monitors for detecting the pollutant emission rate, air quality, and meteorological variables.” Furthermore, the agency must be granted “continuous access to all emission, air quality, and meteorological data collected by the source,” as well as “authority to inspect, test, and calibrate all sensors, recorders, and other equipment operated by the source to collect these data” (FR 1973).

  3. The emission source is required to assume liability for violation of AAQS within a “designated liability area,” i.e., the geographic area within which emissions from a source may significantly affect the ambient air quality.8

  4. Before approval of ICS controls will be granted, the emission source must submit to the EPA Administrator a comprehensive report of a study which demonstrates the capability of the ICS, in conjunction with other control measures, to meet ambient air standards (FR 1974b). The study must include a test period of at least 120 days, during which ICS controls are developed and operated. The report must:

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
  • describe and identify various elements of the ICS (monitoring, forecasting, determination of emission rates);

  • estimate the frequency of necessary emission rate reductions;

  • include data and results from objective reliability tests; and

  • demonstrate that implementation of ICS and other control measures will result in attainment and maintenance of AAQS.

  1. Before approval of ICS controls can be granted, the emission source must submit to the Administrator an operational manual (FR 1974b) for the ICS which:

  • specifies number, type, and location of ambient air quality monitors, in-stack monitors, and meteorological instruments to be used;

  • describes techniques, methods, and criteria for forecasting, as well as methods for systematically evaluating and improving the reliability of the sytem;

  • specifies maximum emission rates for all probable meteorological and air quality situations so that AAQS will not be exceeded in the designated liability area; and

  • describes specific curtailment actions which will be taken when meteorological conditions demand and/or when specified air quality deterioration occurs.

  1. The source is required to follow certain recordkeeping procedures, including submission of monthly reports describing and analyzing actual ICS performance compared to the approved operations manual.

Assessment of Enforceability

Enforcement based on these factors should be considerably more effective than enforcement based on violations of AAQS alone, for the following reasons (Gaertner et al. 1974):

  1. Workable enforcement procedures can be established prior to the control agency’s authorization of an ICS.

  2. Justification for the ICS and operational details of the ICS are subject to evaluation and approval before authorization of

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

the system. In particular, the agency can demand use of conservative diffusion modeling techniques and data interpretations to help insure that emission reductions will be instituted at least as often as required to maintain ambient standards.

  1. With the ICS application well defined by preliminary documents, enforcement should principally involve:

    1. Determining whether the emission source is operating according to the approved operational manual. Emission rate reductions provided for in the manual and not actually instituted would constitute violations of standards; surveillance of emission rates would detect these violations.

    2. Deciding when violations of AAQS occur. Accurate monitoring of air quality would detect these violations.

Tacit recognition of the accuracy of this assessment appears in the text of a recent EPA decision concerning a Nevada smelter (FR 1974b):

“By allowing the use of [ICS], the Administrator is acknowledging that [ICS] can incorporate design and enforcement features that will provide a reliable means to attain and maintain national sulfur dioxide standards.”

Costs of Monitoring and Enforcement

The monitoring and enforcement effort required of regulatory agencies to supervise implementation of ICS technology is greater than that required for continuous emission controls. Hence, agency monitoring and enforcement costs are expected to be higher, although it is difficult to predict the exact level of added resources which will be required.

Estimates of the amount of resources expended by PSAPCA in enforcement of control of emissions from the ASARCO-Tacoma smelter have been referred to in previous evaluations of ICS controls (Cong. Rec. 1974, Slater 1974). Costs per year to the agency for activities associated with control of all smelter emissions are variously estimated as $100,000, $160,000–

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

$200,000, and $200,000; the current annual total budget of the agency is $1,000,000 (Dammkoehler 1974). At the upper limit, these costs are of the same order of magnitude as those required by ASARCO to operate the ICS, if lost production output is not charged to ICS control. At the lower limit, these costs (about 10 percent of the agency budget) appear reasonable in view of the significance of ASARCO emissions compared to total emissions for the area.

Whatever PSAPCA costs may have been for the administrative, technical, and legal efforts involved in regulating this source, it would appear that costs for future activities by other control agencies cannot easily be estimated from this example:

  1. PSAPCA costs are not easily disaggregated on a source-by-source basis, accounting for the relatively wide disparity in cost figures cited above.

  2. Enforcement at Tacoma has principally been of AAQS, rather than of emission limitations specified by an operational manual. Costs involved in these two types of enforcement methodologies may differ widely.

  3. Many of the enforcement provisions described in the previous discussion have not been applied in Tacoma.

Agency costs for monitoring and enforcement of ICS systems represent a hidden cost of control, not included in Table 12–9. Proposed EPA regulations (FR 1973) suggest that the additional monitoring and enforcement costs involved can be defrayed by licensing of ICS programs and imposition of fees. This suggestion appears equitable, and will increase costs shown in Table 12–9.

STATEMENT OF FINDINGS AND CONCLUSIONS

  1. Although current EPA regulations and the Energy Supply and Environmental Coordination Act of 1974 suggest a different interpretation, tall stack-ICS technology is considered here as a potentially important technological option for control of ambient sulfur dioxide concentrations. At the very least, it provides

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

TABLE 12–9

Estimated Capital and Annual Costs for ICS Programs at Nine TVA Coal-Fired Power Plants (Montgomery and Frey 1974, TVA 1974, Frey 1974)

Capital Costs

Amount

Development, installation of ICS programs and monitoring networks at nine plantsa

$ 5 million

New tall stacks at three plantsb

47 million

Coal switching capability at three plantsc

8 million

Additional reserve capacityd

Total Capital Cost

$ 60 million

 

$ 3.80/KW1

Annual Costs

 

 

Capital charges, $60 million at 9.64 per cent

$ 5.8 million

Capital charges, additional reserve capacitye

-

Operation and Maintenance

3.0 million

Monitors & ICS Programs

$2.1 million

 

Stacks

0.9 million

 

Replacement power chargesf

1.1 million

Incremental costs for low-S coal

0.6 million

Fuel costsg

$0.3 million

 

Transportation & handling

0.3 million

 

Total Annual Costs

$10.5 million

 

0.13 mills/KW-Hrh

a Total 9-plant capacity, 15713 MW.

b Kingston (2 @ 1000'); Shawnee (2 @ 800'); Widows Creek (1 @ 1000').

c Colbert, Cumberland, Johnsonville plants.

d Option not selected by TVA and costs not estimated.

e Five plants, 55.5×103 MWH @ 20 mills/KWH, purchased.

f Three plants, 52×103 MWH.

g Average load factor, 0.61.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

an alternate means of attaining and maintaining existing AAQS, an important capability given uncertainties or capacity limits regarding other control strategies.

  1. Tall stack dispersion is closely related to ICS control, since increased stack height decreases the need for intermittent emission reductions, assuming control of ambient sulfur dioxide concentrations is the sole objective.

  2. In the most important legal decision concerning the use of dispersion techniques to meet AAQS, Natural Resouces Defense Council v. EPA, the 5th Circuit Court of Appeals ruled that emission reduction is the preferred method of meeting ambient standards. A case involving similar issues of fact and law (TVA v. EPA) is now being litigated in the 6th Circuit.

  3. A spectrum of potential applications of ICS technology exist, with individual situations requiring different forecasting, modeling, and monitoring efforts and capabilities. The frequency and extent of emission reductions necessary to maintain national AAQS with ICS control appear to be simple indicators which demonstrate the degree of difficulty associated with a given use of this technology.

  4. Tall stacks and ICS methods have generally proven effective in reducing the number and extent of excess concentrations of sulfur dioxide in the vicinity of single isolated sources. Reliability (i.e., ability to meet AAQS) of existing systems is as follows:

  1. At TVA’s Paradise Steam-generating Plant, ICS reliability appears good; national AAQS have been met since initiation of ICS controls in 1969. Emission reductions are necessary at Paradise 0.5 percent of the year.

  2. At ASARCO’s Tacoma smelter, system reliability is inadequate to meet local AAQS, although performance has been improving. However, national AAQS have not been exceeded since March 1971 at this installation. Average yearly load curtailment at Tacoma due to ICS control is 15–17 percent of full output.

  3. At ASARCO’s El Paso smelter, based on operating results for a 36-day period in 1971, performance characteristics indicated a

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

substantial improvement in air quality due to ICS controls, but system reliability was inadequate to consistently meet national or local AAQS. Average yearly load curtailment at El Paso due to ICS control is 27–35 percent of full output.

  1. System reliability in an ICS program is a function of the accuracy of air quality forecasts. One set of forecasted air quality predictions for a multi-source, urban area (Greater Boston) appears relatively accurate. Other comparisons of forecasted and actual air quality are not available.

  2. A need exists for a fully-documented study of an operating ICS system. Such a study should examine information about source data, meteorological data, and actual as well as forecasted air quality measurements in order to permit a definitive analysis of system reliability under various conditions. A 120-day study of a power plant burning high sulfur eastern coal and applying ICS measures is suggested.

  3. This concept, if adopted for eastern power plants with ICS controls, would severely limit potential applications of the technology. A recent EPA memo indicates only 18 plants in 15 eastern states have emissions which constitute 90 or more percent of total emissions within their restricted geographical area (U.S. Environmental Protection Agency 1974). TVA suggests the designated liability area concept should be applied as an alternative to emissions-based enforcement procedures, rather than as an additional requirement (Montgomery 1975).

  4. Use of the ICS approach with load shifting to reduce emissions during adverse meteorology has a number of implications:

  1. Additional reserve requirements are needed; preliminary assessments by TVA indicate these requirements may be as high as 3–4 percent of peak power system load.

  2. The efficacy of load shifting can be limited when large-scale, adverse meteorology affects more than one plant in a given region. Over a one-year time period, TVA noted the potential need for simultaneous generation

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

reduction at two of five plants on 17 of 100 days. Because of plant operating conditions, simultaneous reductions were necessary on only three of the 17 days.

  1. The ability of an individual plant to load shift for ICS purposes depends on its particular situation, i.e., location, power system, and pool arrangement. For some plants, no serious constraints exist; for other plants, interim or long-term power pool arrangements to allow load shifting for ICS purposes could be difficult to bring about.

  2. The practicality of implementing control actions which demand load reductions can be questioned. Two competing objectives—reliable sulfur dioxide control and reliable power—could presumably conflict if large scale load reductions are needed for implementation of programs.

These constraints do not apply if emission reductions occur through fuel switching as part of ICS programs.

  1. The constraints which are applicable to ICS systems using fuel switching to reduce emissions during adverse meteorology include the following:

  1. Many coal-fired plants will require major modifications in coal handling and feeding systems in order to provide a fuel switching capability based on low sulfur coal.

  2. The time required to effect a fuel switch to low sulfur coal may prevent the reliable attainment of short-term AAQS in some situations.

  3. Operating problems with low-sulfur coal may be encountered in units not designed for this fuel. These problems include increased particulate emissions, reduced generating capacity, and increased slagging.

  4. Burning of low sulfur fuel oil as an alternate fuel in units with dual firing capabilities eliminates these problems. However, converting units without this capability to a dual firing capability is costly ($12–$40/kw), and assured supplies of low sulfur oil may not be available.

These constraints do not apply if emission reductions occur through load shifting.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
  1. Technical efforts to initiate and operate an ICS program are significant for all systems, but of differing orders of magnitude depending on the complexity of the system. The following constraints exist:

  1. If ICS programs are installed in highly compex situations (e.g., ASARCO-El Paso situation) for many sources, trained personnel and firms needed to deliver ICS services may be in short supply.

  2. More significant constraints, which are applicable to all ICS programs, could be hardware needs (monitoring equipment) and the time requirements for full operation of the ICS program.

  1. Costs for implementing the tall stack-ICS approach are significantly less than comparative costs for FGD systems, both in terms of capital and annual expenditures. Based on TVA experience, with an expanded range of costs to account for increased reserve requirements and application to smaller plants, costs can be expected to be as follows:

Capital Costs:

$4–10/kw

Operating costs, including annualized capital charges:

0.15–0.4 mills/kwh

Regulatory agency expenses for monitoring and enforcement of ICS programs represent hidden costs of control, not included in the above estimates. Defraying these costs by licensing and imposition of fees appears equitable.

  1. Much of the controversy surrounding implementation of the tall stack-ICS approach is associated with the impact of this technology on acid-sulfate aerosol formation, and effects of these aerosols on health, welfare, and aesthetics. Major disagreements exist in interpreting the limited data base available for understanding this issue.

  2. A potential compromise position regarding public policy toward implementation of tall stack-ICS technology can be identified. The technology could be rejected as a permanent control technique, on the basis of the proba-

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

bility of substantial potential risks associated with increassed atmospheric loadings of sulfur dioxide. At the same time, the technology could be accepted for carefully defined situations as an interim control technique, because of its ability to meet AAQS during implementation of FGD systems and because of its role in reducing the current clean fuels deficit.

  1. An important issue regarding implementation of ICS technology concerns the legal enforceability of these systems. Regulations proposed recently by EPA for ICS control emphasize enforcement of prescribed emission limitations included within an approved operational manual for each ISC system, in addition to enforcement based on AAQS. Enforcement based on this dual strategy should be more effective than enforcement based on AAQS alone, since most of the critical elements of the enforcement procedure can be established by the regulatory agency prior to approval of the ICS installation.

FOOTNOTES

1  

These systems are variously referred to as intermittent control systems, closed-loop systems, dynamic emission control systems, and sulfur dioxide emission limitation systems. ICS is used here as a generic term for these concepts.

2  

These plume transport conditions are briefly described as follows: (2) Coning: Near neutral stability conditions, moderate-to-high wind speeds, generally occurring on cloudy and windy days or windy nights.

Inversion breakup or fumigation: Stable atmosphere, transport of plume downwind with minimum vertical dispersion, followed by uniform dispersion to ground by thermally induced vertical mixing.

Trapping or limited mixing layer dispersion: Subsidence inversion or stable air aloft, uniform dispersion to surface.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

3  

Locations and number of monitoring stations have not remained fixed. Data are compared on the basis of equal numbers of observations at different locations before and after implementation of the ICS program. The monitoring network has included from 4 to 14 sulfur dioxide monitors, located in a 22.5 degree area northeast of the plant, at distances ranging from 3 to 17 kilometers from the plant; currently 9 monitors are in operation.

4  

Until mid-1974, ASARCO operated under a variance which allowed violations of the lppm-5 minute standard. Civil penalties have been repeatedly assessed for violations of the 1-hour standards (24 penalties in 1972 for violations at 4 PSAPCA stations; 16 penalties in 1973 for violations at 4 PSAPCA stations) (Dammkoehler 1974).

5  

Dispatch of power refers to the scheduling of power generation from an interconnected network of plants. Normally, plants are scheduled to operate so as to minimize the total cost of producing electricity.

6  

TVA estimates a system for one of their plants would require 16–18 months to become fully operational, including field study, design, and installation phases (Montgomery et al. 1974). PEDCO quotes a 12–24 month period for full operation, with some systems then requiring 1–2 years to achieve reliability (PEDCO 1974).

7  

Jimeson et al. (1974) cite costs for a 1000-MW plant of $0.88, and 7.6×106/year, using three ICS strategies. An operating factor of 0.65 was assumed to compute costs per kwh.

8  

This concept, if adopted for eastern power plants with ICS controls, would severely limit potential applications of the ICS technology. For example, a recent internal EPA memo indicates only 18 plants in 15 eastern states have emissions which constitute 90 or more percent of total emissions within their “liability area” (EPA 1974).

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

LITERATURE CITED

Altshuller, A.P. (1973) Atmospheric Sulfur Dioxide and Sulfate, Environmental Science and Technology 7(8):709–712, August.


Carpenter, S.B. et al. (1971) Principal Plume Dispersion Models: TVA Power Plants, Journal of the Air Pollution Control Association, 21(8):491–495, August.

Congressional Record (1974) Senate, June 12.


Dammkoehler, A.R. (1974) Puget Sound Air Pollution Control Agency, Seattle, Washington, private communication, December 6.


Environment Reporter (1974) Train Reports Administration Accord on Permanent Controls for Power Plants, 5(32):1232–1233, December 6.


Federal Energy Administration (1974) The Clean Fuels Deficit—A Clean Air Act Problem, August.

Federal Register (1973) Use of Supplementary Control Systems and Implementation of Secondary Standards, Volume 38, No. 178, pp. 25697–25703, Friday, September 14.

Federal Register (1974a) 39(195):36018ff, Monday, October 7.

Federal Register (1974b) 39(209):38104ff, Tuesday, October 29.

Finklea, J.F. (1974) Keynote Address to Symposium on Flue Gas Desulfurization, U.S. Environmental Protection Agency, Atlanta, Georgia, November 4–7.

Frank, N.H. (1974) Temporal and Spatial Relationships of Sulfates, Total Suspended Particulates, and Sulfur Dioxide, paper #74–245, Annual Meeting of the Air Pollution Control Association, Denver, Colorado, June 9–13.

Frankenberg, T.T., I.A.Singer, and M.E.Smith (1970) Sulfur Dioxide in the Vicinity of the Cardinal Plant of the American Electric Power System, Proceedings of the Second International Clean Air Congress, Washington, D.C.

Frey, J.W. (1974) Tennessee Valley Authority, Muscle Shoals, Alabama, private communication, November 1.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

Gaertner, John P. et al. (1974) Analysis of the Reliability of a Supplementary Control System for Sulfur Dioxide Emissions from a Point Source, Environmental Research and Technology, Inc., Lexington, Massachusetts, June, under contract to EPA.

Gaut, Norman E. (1975) Environmental Research and Technology, Inc., Concord, Massachusetts, private communication, January 6.

Gaut, Norman E. et al. (1973) Dynamic Emission Controls: A Cost Effective Strategy for Air Quality Control, Annual Conference of the Instrument Society of America, Houston, Texas.


Jimeson, Robert M. et al. (1974) Fossil Fuels and Their Environmental Impact, Symposium on Energy and Environmental Quality, Illinois Institute of Technology, Chicago, Illinois, May 10.


Lucas, D.H. (1974) The Effect of Emission Height with a Multiplicity of Pollution Sources in Very Large Areas, Ninth World Energy Conference, Detroit, Michigan, October.


MacDonald, B.I. (1973) Conserving Energy Resources, in A Seminar on an Innovative Air Quality Control Strategy for Stationary Sources, Office of Environmental Affairs, U.S. Department of Commerce, Washington, D.C., July.

Montgomery, T.L. (1975) Tennessee Valley Authority, Muscle Shoals, Alabama, private communication, February 12.

Montgomery, T.L. (1974) Tennessee Valley Authority, Muscle Shoals, Alabama, private communication, December 4.

Montgomery, T.L. and J.W.Frey (1974) Tall Stacks and Intermittent Control of Sulfur Dioxide Emissions—TVA Experience and Plans, American Mining Congress, Las Vegas, Nevada, October 7–10.

Montgomery, T.L. et al. (1973) Controlling Ambient Sulfur Dioxide, Journal of Metals 25(6):35–41, June.


Nelson, K.W. (1974) American Smelting and Refining Company, New York, New York, private communication, December 11.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

Nelson, K.W., M.A.Yeager, and C.K.Guptill (1973) Closed-Loop Control System for Sulfur Dioxide Emissions from Non-Ferrous Smelters, American Smelting and Refining Company, New York, New York.


Ohio Environmental Protection Agency (1974) Consolidated Electric Utility Hearing Examiner’s Report and Recommendations, Columbus, Ohio, September 6.


PEDCO Environmental (1974) Assessment of Alternative Strategies for the Attainment and Maintenance of National Ambient Air Quality Standards for Sulfur Oxides, Preliminary draft report to USEPA, December 6.


Schweppe, F.C. (1974) Massachusetts Institute of Technology, Boston, Massachusetts, private communication, December 6.

Slater, H.H. (1974) Environmental Protection Agency, Research Triangle Park, North Carolina, private communication, November 26.

Smith, M.E. and T.T.Frankenberg (1974) Improvement of Ambient Sulfur Dioxide Concentrations by Conversion from Low to High Stacks, September, in press.

Stone, G.N. and A.J.Clarke (1967) British Experience with Tall Stacks for Air Pollution Control on Large Fossil-Fuelled Power Plants, Combustion, 39:41–49, October.


Tennessee Valley Authority (1973) Technical Presentation on TVA’s Program for Meeting Ambient Sulfur Dioxide Standards, Chattanooga, Tennessee, September 14.

Tennessee Valley Authority (1974a) Tennessee Valley Authority Programs for Sulfur Oxide Control at Electric Power Plants, Knoxville, Tennessee, July, (Draft).

Tennessee Valley Authority (1974b) Summary of Tennessee Valley Authority Atmospheric Dispersion Modeling, Conference on the TVA Experience at the International Institute for Applied Systems Analysis, Schloss, Laxenburg, Austria, October.


U.S. Environmental Protection Agency (1974a) Report of the Hearing Panel, National Public Hearings on Power Plant Compliance with Sulfur Oxide Air Pollution Regulations,

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×

Washington, D.C., January. U.S. Environmental Protection Agency (1974b) National Strategy for Control of Sulfur Oxides from Electric Power Plants, Washington, D.C., July 10. U.S. Environmental Protection Agency (1974) Implications of Alternative Policies for the Use of Permanent Controls and Supplemental Control Systems (SCS), November 18.


Welch, R.E. (1974) American Smelting and Refining Company, Tacoma, Washington, private communication, December 6.

Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
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×
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×
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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 498
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Page 499
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 500
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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 514
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 515
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 516
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 517
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 518
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 519
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 520
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 521
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 522
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 523
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 524
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 525
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 526
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 527
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 528
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 529
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 530
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 531
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 532
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 533
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 534
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 535
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 536
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
×
Page 537
Suggested Citation:"12 Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks and/or Intermittent Control Systems." National Research Council. 1975. Air Quality and Stationary Source Emission Control. Washington, DC: The National Academies Press. doi: 10.17226/10840.
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Page 538
Next: Section 3: Analysis of Alternative Emissions Control Strategies »
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