Trace-Element Geochemistry of Coal Resource Development Related to Environmental Quality and Health (1980) / Chapter Skim
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COAL COMBUSTION
COAL COMBUSTION
Pages 64-102
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From page 64... ...
. COMBUSTION RESIDUES Residues from coal-fired power-qeneration plants in qeneral can be assiqned to the followinq cateqories: •boiler bottom ash (boiler slaq)
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From page 65... ...
. boilers for major electric power qeneration stations is diminishinq1 however, their use in smaller industrial plants is expected to increase as these plants convert from oil firinq to coal firinq.
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From page 66... ...
FURNACE: DUST ELECTROSTATIC COAL CYCLONE COLLECTOR: PRECIPITATOR: PULVERIZER - - - - WET BOTTOM LARGE FINE DRY BOTTOM PARTICU- FLY ASH LATES CLARIFIER PYRITE ,.._........__.,. RECYCLE 5-15% SOLIDS I BOTTOM HYDROBIN WATER I ASH FLY FLY FGD SLUDGE OR SLAG ASH ASH I ~ I + • \:ffaofhWJ:•:·:AS0~r·5ff+trN |
From page 67... ...
The estimated amounts of 25 trace elements discharqed into the atmosphere from three coal-fired steam plants with a combined daily coal consumption of 25,000 tons are shown in Table 18. The need to remove substantial quantities of S01 from the flue qases is dictated by the Federal Clean Air Act and by state and local requlations.
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From page 68... ...
. A more recent technoloqy to minimize S02 emission from coal combustion uses fluidized-bed combustion boilers where crushed coal is burned on a bed of inert ash and crushed limestone.
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From page 69... ...
Particle size of bottom ash and boiler slags ranges from coarse gravel to fine sand. They overlap at the fine end with fly ash.
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From page 70... ...
. b The bulk density of FGD sludge depends on the moisture content of the material.
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From page 71... ...
Compositions of different particle sizes of each from a qiven plant may differ, and the residues are causally related to the ash, sulfur, and calcium content of the coal consumed. As was shown in Table 13, the process of coal cleaninq removes a number of trace elements from coal, which alters the chemical composition of the residues.
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From page 72... ...
-.J N FIGURE 13 Plerosphere with submicrometer spherical inclusions and attached surface spheres: (a)
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From page 73... ...
(197S) have shown that as residues pass through stages of the power-plant configuration from bottom ash to inlet fly ash to outlet fly ash, progressive increases in the concentrations of copper, zinc, arsenic, molybdenum, antimony, lead, selenium, and mercury occur (Table 24)
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From page 74... ...
. Table 25 illustrates the effect of particle size of fly ash on the concentration of 17 trace elements as reported by Ondov et al.
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From page 75... ...
cBottom ash sluiced to a settling pond wire. dAsh obtained by electrostatic precipitator.
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From page 76... ...
, and outlet TABLE 25 Effect of Fly-Ash Particle Size on the Concentration of Some Trace Elements (ppm)
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From page 77... ...
. The chemical composition of bottom ash and FGD sludge produced in a western power station in relation to the chemical composition of the source coal is shown in Table 26.
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From page 78... ...
Coal Coal Bottom Ash Mn 3300 2200 41 28 0.7 p 1800 1700 2.8 2.7 0.9 Sr 970 860 7 6 0.9 Sb 0.49 0.82 1.1 1.9 1.
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From page 79... ...
those of the bottom ash. Exceptions were arsenic, bismuth, copper, fluorine, lead, selenium, and zinc, which were concentrated by more than a factor of 2 in FGD sludqe compared with bottom ash, and barium, hafnium, iodine, lithium, terbium, and uranium, which were concentrated by more than a factor of 2 in bottom ash than in FGD sludqe.
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From page 80... ...
80 TABLE 27 Chemical Composition of Fly Ash and Soila Range Average Element Fly Ash Soil Fly Ash Soil Element (percent)
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From page 81... ...
Water Extracts from Residues As the basic concern is the availability of trace elements to the biological systems, measurement of water solubility of the elements is used to reflect this bioavailability. The major- and trace-element contents in saturation extracts (extracts obtained from soils saturated with water)
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From page 82... ...
. Atmospheric Deposition The quantity of trace elements emitted to the atmosphere from stationary sources depends on such factors as concentration in coal, boiler confiquration and load, properties of the element and its compounds, and the effectiveness of particle control devices.
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From page 83... ...
Concentration in Leachate Reconunended Maximum Concentration forb froma Public Water Irrigation Element Coal Ash FGD Sludge Supplies Wat ere Arsenic <0.002 <0.002 0.10 0.10 Barium 40 2.0 1.0 Beryllium 0.003 0.002 0.10 Boron 0.03 2.6 0.75 Cadmium <0.001 0.0005 0.01 0.01 Chromium <0.001 0.001 0.05 0.10 Fluorined 2.3 31.5 1.4-2.4 1.0 Mercury 0.0006 0.0005 0.002 Lead 0.0068 0.0056 0.05 5 Manganese <0.002 <0.002 0.05 0.20 Molybdenum 0.047 0.063 0.01 Nickel <0.05 <0.05 0.20 Selenium 0.009 0.045 0.01 Vanadium <0.10 |
From page 84... ...
Some of the basic assumptions of this model are emission rate, l.OS tons/h; deposition velocity, 0.03 to 0.1 m/sec; particle size distribution for particles >10 1'111 that was 3 percent of 2S-l'lll radius, S percent of 12.S-l'lll radius, and 10 percent of 7.S-1'111 radius. Deposition rates established by this model are shown in Figure 14 for the winter, spring, summer, and fall seasons.
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From page 85... ...
These estimates show measurable, but small, enrichments in plants or soils in trace elements originating from stack emissions.
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From page 86... ...
In situations where the residues are spread onto land that supports either agricultural crops or native vegetation, trace elements in fly ash could adversely affect the productivity of the land or the quality of the vegetation grown. Therefore, a comprehensive understanding of the chemical, physical, and biological changes that occur when residues from coal-fired power plants are mixed with soils is essential to evaluate the effect that these changes will have on the productivity of the land and trace-element composition of the vegetation.
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From page 87... ...
Chemical Properties of Fly-Ash-Amended Soila Table 33 presents the pH, electrical conductivity, and soluble calcium plus maqneaium, boron, and S04 -S (sulfur present as S04 but expressed as elemental sulfur) in soils amended with Mojave fly ash, at rates ranging up to 8 percent by weight (-180 metric tons/ha)
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From page 88... ...
Soila with coarser texture and/or higher base saturation will probably require leaser amounts of fly ash to attain the same final pH. The increase in electrical conductivity of the soil saturation extract (ECe)
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From page 89... ...
Application of 8 percent fly ash produced boron concentration in saturation extracts from the Arizo and Redding soils of approximately 8 and 11 ~g/ml, respectively (Table 33)
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From page 90... ...
Physical parameters such as water content at 20 cbar, water release, bulk density, hydraulic conductivity, and modulus of rupture were measured. Results showed that the addition of up to 10 percent fly
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From page 91... ...
Mineral Composition of Plants Grown on Fly-Ash-Amended Soils Effects of fly-ash incorporation in soils on the mineral composition of alfalfa qrown on calcareous and acid soils amended with up to 8 percent fly ash are shown in Table 35. Plants were adequately fertilized with nitroqen, phosphorus, and potassium from a mixed fertilizer.
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From page 92... ...
. TABLE 36 Dry Matter Yield, Sulfur Content of Tissue, and Sulfur Uptake of Turnips Grown on Josephine Soil Amended with Three Rates of Fly Ash-Sulfur, Gyps\Dll-Sulfur, and Sewage Sludge-Sulfura Rate of Sulfur Dry Matter Sulfur Content (percent, Addition Yield dry wei2ht)
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From page 93... ...
. Table 37 shows selected analyses of molybdenum in various plant species grown on calcareous and acid soils amended with fly ash.
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From page 94... ...
Application of 2.6 to 5.2 percent fly ash to Fredrick silt loam nearly doubled the yield of corn as a result of increased availability of zinc {Schnappinqer et al., 1975)
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From page 95... ...
. TABLE 39 Tolerance of Some Crop Species to Pulverized Fuel Asha Moderately Moderately Tolerant Tolerant Sensitive Sensitive Red beets Cabbage Brussels sprouts Barley Spinach Turnip Cauliflower Oats Sweet clover Rape Rye Broad bean Perennial White mustard Wheat Dwarf bean ryegrass Radish Peas Red fescue Carrot Potatoes Red clover Buckwheat White clover Lettuce Alfalfa Strawberry clover Meadow fescue Meadow grass.
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From page 96... ...
(1977) with plants qrown on calcareous and acid soils amended with Mojave fly ash are summarized in Table 41.
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From page 97... ...
capacity to reduce excessive concentrations of phosphorus and also to remove undesirable color and organic contaminants from these waters. The reduction in phosphate concentrations is attributed to the formation of insoluble calcium-phosphate compounds under conditions of high pH and high content of free ca~ ions, which are prevalent in water extracts from many fly ashes.
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From page 98... ...
Approximately 65 to 70 percent of the total orqanic materials in Stone Lake water were removed also by the addition of 10 q of fly ash/l to the lake water (Tenney and Echelberqer, 1970)
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From page 99... ...
HEALTH EFFECTS Occupational Health Health effects from occupational exposure to trace metals from steamelectric plant processes have not been documented. Public Health The potential impact on the environment will come from stack emissions of fine particulates, which are subsequently deposited on the biological systems and from the disposal of collected residues.
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From page 100... ...
(1975) modeled the behavior and accumulation of trace metals in soil, water, biota, and humans that could be emitted from a hypothetical 1400-MWe coal-fired plant sited in a semiarid western watershed and burninq representative western coal.
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From page 101... ...
Cadmium, molybdenum, and tunqsten showed 30 to 100 percent increases in qreen plants, assuminq partial solubility of exoqenously supplied metals. The incremental burden for the remaininq metals was about 11 percent of reported content.
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From page 102... ...
These residues contain the less-volatile trace elements, but acidification of fly ash increases the solubility of most elements, an indicator of bioloqical availability for leachinq. Arsenic, lead, and selenium are present in the scrubber liquor in concentrations qreater than the allowable drinkinq-water standards (Bern, 19761 U.S.
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