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Review of Doe’s Vision 21 Research and Development Program—Phase I 3 Vision 21 Technologies INTRODUCTION This chapter reviews the technology areas under development in the Vision 21 Program and identified in the Vision 21 Technology Roadmap (NETL, 2001). The areas addressed are gasification; gas purification; gas separations; fuel cells; turbines; environmental control technology; sensors and controls; materials; modeling, simulation and analysis; synthesis gas (syngas) conversion to fuels and chemicals; and advanced coal combustion. Each section of this chapter contains (1) a brief introduction to the technology and its importance to the Vision 21 Program; (2) milestones and goals for the technology; (3) progress, significant accomplishments, and current status in the technology area; (4) responses to recommendations from the committee’s 2000 report; (5) issues of concern and remaining barriers to technology development; and (6) findings and recommendations. Further detail and background on the technologies can be found in the committee’s 2000 report, in the Vision 21 Program Plan and in the Vision 21 Technology Roadmap (NRC, 2000; DOE, 1999a; NETL, 2001). GASIFICATION Introduction Fuel-flexible gasification systems convert carbon-containing feedstocks (coal, petroleum coke, residual oil, wastes, biomass, etc.) by reacting them with oxygen, usually at 95 percent purity and elevated pressure and temperature, to produce syngas, a mixture of carbon monoxide and hydrogen. Steam can be
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Review of Doe’s Vision 21 Research and Development Program—Phase I injected to adjust the ratio of hydrogen to carbon monoxide in the syngas and/or as a temperature moderator. As produced, this gas contains impurities, which can be stripped out using well-developed refinery gas cleanup having very high demonstrated removal rates (Meyers, 1997). Shifting from direct coal combustion in air to gasification in oxygen can become more attractive and more cost-effective as emissions regulations are further tightened. After cleaning to meet the requirements for subsequent processing, the syngas can be converted into electricity by combined cycle technology (gas turbine plus steam turbine), fuel cells, or gas turbine plus fuel cell hybrid power plants at high energy conversion efficiencies. These are the most likely combinations of coal-conversion technology and energy-conversion technology with the potential to achieve the 60 percent higher heating value (HHV) efficiency target of the Vision 21 Program. By reaction with additional steam downstream of the gasification reactor, syngas can also be converted into a mixture of hydrogen and CO2. This mixture can then be separated into essentially pure streams of hydrogen for fuel or chemical use and CO2 that can be sequestered (NRC, 2000). Other approaches to coal gasification have been developed that utilize air instead of high-purity oxygen. The potential reward for using air is avoidance of the cost of an air separation plant to produce oxygen and the energy consumed in the plant’s operation. These cost-saving factors are offset by the large amount of nitrogen introduced into the system, which increases the size and energy costs associated with cleanup of the relatively dilute syngas stream. The presence of nitrogen also increases the cost of separating CO2 from the syngas as part of a sequestration scheme. As a result, air-blown gasification is not considered to be compatible with sequestration systems. One of the most important advantages of oxygen-blown coal gasification technology relative to coal combustion technologies that use air, as well as coal gasification technologies that use air, is that it is compatible with the need for relatively low-cost CO2 separation required for CO2 sequestration. Gasification plants that process feed materials with very low or negative cost, such as petroleum coke and residual oil, can be commercially justified today for various combinations of hydrogen, by-product steam, and power production. Coal gasification for hydrogen production for chemical manufacturing is also widely practiced. More than 160 gasification plants worldwide are in operation producing the equivalent of 50,000 megawatts (thermal) (MWt) of syngas (Simbeck, 2002). Four coal-fueled integrated gasification combined cycle (IGCC) single-train demonstration power plants with outputs greater than 250 MW have been built since 1995, two in Europe and two in the United States. Each of these plants was built with a significant subsidy as part of a government-sponsored program. As expected, each of the plants has taken 3 to 5 years to approach the upper range of availability, 70-80 percent, that was predicted when they were designed.
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Review of Doe’s Vision 21 Research and Development Program—Phase I The cost of these plants was between $1,400 and $2,000/kW.1 Experience gained from the operation of these demonstration plants, as well as from the design, construction, and operation of coke and residual-oil-fired gasification plants can be used to reduce costs to the range $1,200 to $1,500/kW (NRC, 2000). However, to be competitive with natural-gas-fueled, combined-cycle units after 2015 at natural gas prices of $3.50-$4.00/MMBtu, the investment for a mature plant of this type will have to be reduced to less than $800/kW (overnight basis for engineering, procurement, and construction costs only) in an IGCC configuration that can achieve 45 percent (HHV) efficiency (DeLallo et al., 1998; EPRI, 1999) and to less than $1,000-$1,100/kW in an integrated gasification combined cycle/fuel cell (IGCCFC) configuration that can achieve 60 percent efficiency (HHV) (neither configuration includes the losses associated with CO2 capture) (NRC, 2000). In addition, recent surveys of the market for gasification technologies indicate that plant owners will require 90 percent availability for power production plants and 97 percent availability for chemical production plants (DOE, 2002a). Meeting the 2015 goal of the Vision 21 Program—having competitive IGCC plant designs available for implementation on normal commercial terms—will require the development of new technology to meet the investment cost, efficiency, and availability requirements of the market. Improvements in all five sections of the IGCC plant—feed solids handling, air separation, gasification, gas cleanup, and power generation—will be necessary. Milestones and Goals The current goals of the gasification program are as follows: Fuel flexibility up to 10 percent (large units) and 30 percent (small units) of fuel other than coal (biomass, waste products, etc.); Improved gasifier performance: greater than 95 percent availability, greater than 82 percent cold gas efficiency; Gasifier cost target of $150/kW (includes syngas cooling and auxiliary but not air separation); syngas cost target of $2.50/MMBtu (at a coal cost of $1.25/MMBtu); More efficient, more reliable, lower cost feed system to operate at up to 70 atmospheres; and Novel gasifier concepts that do not require oxygen but utilize instead internal sources of heat, e.g., residual heat produced by a high-temperature fuel cell.2 1 Throughout this report, capital costs include only the costs of plant equipment and installation, except as noted. 2 G.J. Stiegel, NETL, “Gasification,” Presentation to the committee on May 20, 2002.
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Review of Doe’s Vision 21 Research and Development Program—Phase I The current milestones for the gasification program are as follows: Test prototype gasifiers at pilot scale (2005) Transport reactor and partial gasifier module at the Power Systems Development Facility (PSDF); Test pilot-scale novel gasifier that does not require oxygen separation (2005) General Electric–Energy and Environmental Research fuel-flexible gasification-combustion technology; Commercial deployment of advanced fuel-flexible gasifiers (2008); and Commercially ready gasifier designs that meet Vision 21 requirements (2010). Progress, Significant Accomplishments, and Current Status DOE-sponsored programs are under way to develop technology to meet each of the listed objectives and milestones, as follows: A novel high-pressure feed system has been designed for introducing low-cost, waste solids into the second stage of the 250-MW Wabash River gasifier. Implementation is uncertain in view of the lack of funds for capital improvements at the plant. In the area of improving gasifier availability, laboratory work has identified a new refractory that has the potential for significantly improved refractory life. Much work is required to further develop this material and then confirm its performance in a full-scale gasifier. New approaches to sensors and data-processing systems that can accurately measure temperatures in the gasifier between 2000°F and 3000°F and survive for extended periods of time are ready for testing in full-scale systems. A design optimization study has indicated that capital cost reductions of 20 percent and a reduction in the overall IGCC commercial plant project timetable (design and construction) from 57 months to 46 months are possible. Preliminary experimental work has identified a sorbent that decomposes in the gasifier to supply oxygen directly to the coal for gasification. Significant progress has been made in demonstrating that the transport-reactor gasifier at the large pilot-scale PSDF can achieve greater than 95 percent carbon conversion when operating on air and Powder River Basin coal. Initial experiments in this gasifier with oxygen in place of air achieved 90-94 percent carbon conversion. This is a major step forward in the development of this potentially lower cost gasification system. Further experiments are planned to determine if higher conversion levels can be achieved. Higher conversion levels in oxygen-blown systems are required
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Review of Doe’s Vision 21 Research and Development Program—Phase I for compatible, low-cost integration with CO2 separation systems. Tests with bituminous coals using both air and oxygen are planned to determine their performance in the transport reactor system. Achievement of the two pilot-scale gasification milestones by 2005 appears to be feasible. However, the milestones for commercial deployment of advanced fuel-flexible gasifiers by 2008 and for commercially ready gasifier designs that meet Vision 21 requirements by 2010 appear too optimistic in view of the current state of technology development coupled with the time it takes to prove the commercial readiness of key components. Among the improved components that are needed for commercially viable Vision 21 plants are single-train gasifiers with capacities of 400-500 MW, 400-500 MW syngas-fueled combined cycles, low-cost oxygen separation plants, improved refractories, and improved diagnostic instrumentation. Progress in a number of these areas that can contribute to lowering plant capital cost requirements is discussed elsewhere in the report. Response to Recommendations from the Committee’s 2000 Report The committee recommended as follows: Recommendation. The Vision 21 Program should encourage industry-led demonstrations of new technologies. The Vision 21 commercial designs and cost estimates will be of great value if they can be validated against existing data-bases and component demonstrations, which would encourage deployment by industry. One of the important actions taken by Congress was to authorize DOE to launch the Clean Coal Power Initiative (CCPI) program, which is described as follows by DOE (2002b): The CCPI is a cost-shared partnership between the government and industry to demonstrate advanced coal-based, power generation technologies. The goal is to accelerate commercial deployment of advanced technologies to ensure the United States has clean, reliable, and affordable electricity. This ten-year initiative will be tentatively funded at a total Federal cost share estimated at $2 billion with a matching cost share of at least 50%. CCPI provides a mechanism for subsidizing demonstrations of improved IGCC technologies in full-size plants. Two proven methods of validating the potential usefulness of improved technology are to test components in operating IGCC plants so that those components are exposed to realistic environments and to test processes in slipstream units at existing large coal-gasification plants. DOE should be encouraged to carry out these kinds of test programs in commercial-scale facilities. Recommendation. The U.S. DOE should pursue both revolutionary and evolutionary approaches to the development of gasification systems to achieve its performance and cost targets. Because the gasification sections of IGCC and IGCCFC plants contain many highly integrated gasification components (coal handling, oxygen production, gasifica-
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Review of Doe’s Vision 21 Research and Development Program—Phase I tion, gas cleaning, heat exchange) significant cost reductions in all sections will be necessary to meet the overall Vision 21 goal. The key areas in other sections of the plant targeted for R&D focus are oxygen production, hydrogen separation, carbon dioxide capture and high-temperature fuel cells. In most cases DOE responded appropriately to the committee’s recommendation in 2000 to pursue both revolutionary and evolutionary improvements in all the sections of a gasification-based power plant. R&D programs have been initiated that relate to the gasification section, oxygen production, hydrogen separation, CO2 capture, and high-temperature fuel cells. Issues of Concern and Remaining Barriers Broad market acceptance of coal gasification as measured by a significant number of new orders for gasification-based power plants in the years after 2015 will require commercial-scale experience to provide the appropriate design bases that can be replicated. At this time, only the 250-MW Tampa Electric Polk power station and the Wabash River coal gasification project, which utilize modern Texaco and E-Gas entrained gasification technologies, respectively, for power production, are in operation in the United States. Because they need to generate power at competitive costs, both plants operate extensively on blends of coal and lower cost petroleum coke or on coke alone. The Great Plains Coal Gasification plant in North Dakota uses the older, more costly fixed-bed Lurgi gasification technology for the production of synthetic natural gas. The transport reactor system under development at the PSDF has demonstrated significant potential for the air-blown and oxygen gasification of low-cost subbituminous Powder River Basin Coal. Its applicability to the conversion of bituminous coal is being evaluated experimentally at this time. Unfortunately none of these systems provides an adequate basis for competitive future IGCC power plants with the potential for low-cost CO2 capture to meet Vision 21 goals. Significant scale-up to 400- to 500-MW single-train size and operating improvement to overall IGCC plant availability of greater than 90 percent are both required if IGCC plants are to reach the cost goal of $800/kW (overnight basis for engineering, procurement, and construction costs only) with coal at $1.25/MMBtu so that they will be competitive with natural gas combined-cycle plants fueled with $3.50-$4.00/MMBtu natural gas. Substantial operating experience with full-scale (400-500 MW), single-train gasification power plants with greater than 90 percent availability is needed to provide investors with the confidence they need to make investments with the same degree of risk as other types of power plants. Achieving that reliability requires the reliability growth normally experienced with building a number of plants over a number of years. Permitting, design, and construction of power plants of this size normally require 5-8 years. The first few plants of a series are
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Review of Doe’s Vision 21 Research and Development Program—Phase I likely to take 3-5 years to achieve the reliability and performance required for commercialization. The CPPI program is the only program currently in place to provide subsidies for these kinds of plants. The total of $2 billion over the next 10 years is sufficient to provide for 50 percent funding of several full-scale plants. However, sufficient operating experience is unlikely to be achieved by 2015 to support competitive designs. DOE has recognized the following critical barriers to competitive IGCC power generation and has R&D programs in place to resolve the issues associated with each one: Transport reactor scale-up and oxygen blowing, Cost and reliability of advanced gasifiers, Syngas cooling materials, operability, and cost, Solids transport and removal, Dry gasifier feedstock capability, variability, cost, Availability greater than 90 percent, Risk reduction management, and CO2 capture compatibility. Findings and Recommendations Finding. Under current conditions in the United States, heavy-oil- and coke-fueled integrated gasification combined-cycle (IGCC) plants, as well as gasification plants for the production of hydrogen and other chemical feedstocks, are economically viable today because the feedstocks for these plants have near-zero or negative value. However, commercial-scale coal-gasification-based power plants are not currently competitive with natural gas combined-cycle power plants at today’s relative natural gas and coal prices, nor are they projected to be so by 2015 without significant capital cost reductions. Even if the projected cost of these plants reaches the required levels, investors need confidence that these plants will run as designed, with availability levels in excess of 90 percent. The only way to achieve this is to build additional plants incorporating the necessary lower cost improvements and to allow extended periods for start-up so the improved technologies can mature sufficiently to meet their goals. The pace of development and demonstration appears to be too slow to meet the goal of having coal gasification technology qualified for the placement of commercial orders by 2015. Recommendation. The U.S. Department of Energy should cooperate with industry on technology development programs to lower the cost and improve the reliability of the first few commercial-scale Vision 21 plants. The Clean Coal Power Initiative (CCPI), recently authorized by Congress, is an example of the
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Review of Doe’s Vision 21 Research and Development Program—Phase I kind of program that can provide support for the construction of high-risk, early commercial plants. These plants should demonstrate and perfect the technology that will make coal gasification-based power plants suitable for deployment on normal commercial terms. Finding. Experimental work, sponsored by DOE, is under way to further develop and evaluate air-blown coal gasification as a potentially lower cost approach to power production in competition with conventional coal combustion and oxygen-blown coal gasification. Because the product gas is diluted with nitrogen, air-blown gasification is not considered appropriate for making syngas for subsequent chemical production. However, this technology may in fact find a market for power production in the nearer term (pre-Vision 21) regulatory situation, which is presumed to not include CO2 emission capture requirements. Recommendation. The U.S. Department of Energy should continue to fund air-blown gasification R&D, but outside the Vision 21 Program, because it is not compatible with the CO2 sequestration-ready requirements that the committee is recommending for a more focused Vision 21 Program. Finding. The U.S. Department of Energy development programs for Vision 21 technologies for gas cleanup, fuel cells, and power production with advanced gas turbines do not currently include adequate testing of these technologies on actual coal-derived synthesis gas (syngas). The most effective way to accomplish the required testing is to install slipstream units in existing coal-fueled gasification plants so that the needed performance data can be collected. This is not being done at this time. One example of a slipstream project is a 2-MW molten carbonate fuel cell that has been scheduled for installation at the Wabash River IGCC in the third quarter of 2003. Recommendation. The U.S. Department of Energy is encouraged to set up programs for the installation and operation of slipstream units to obtain data needed from commercial-scale gasification plants. GAS PURIFICATION Introduction Gas purification can help achieve the stated objectives of the Vision 21 Program, namely, the elimination of air emissions, an increase in energy efficiency, and in a decrease in the cost of using coal to produce electricity, fuels, and chemicals. The predominant contribution of this part of the Vision 21 Program is in the removal of contaminants from process streams to prevent their eventual
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Review of Doe’s Vision 21 Research and Development Program—Phase I release or damage to downstream components. Originally, the program appeared to include a wide range of filters and contaminant removal strategies applicable at very high temperatures. The committee’s 2000 report recommended a shift to the mid-temperature range (300°-700°F), which is most relevant to gasification processes, and the required changes appear to have been incorporated into the most recent activities, although significant components addressing hot gas filters remain in the program (NRC, 2000). The program has greatly increased its emphasis on the removal of hydrogen sulfide (H2S) and CO2, consistent with the overall Vision 21 evolution toward a coal gasification strategy within a carbon-constrained energy environment. Milestones and Goals The objectives of the Vision 21 gas purification program are these:3 Near-zero environmental emissions from gasification-based processes and Reduce synthesis gas contaminant levels to protect downstream components Mid-temperature operation (300°-700°F) is emphasized; Contaminants of concern include both gas-phase contaminants and particulates at Vision 21 concentration levels. The milestones for the Vision 21 gas purification program are these (DOE, 1999a): Complete pilot-scale testing of subsystem components (e.g., sulfur control, particulate control, trace contaminant control) (2002); Test prototypes of integrated gas-cleaning systems (2004); and Complete design basis of commercial-scale gas purification system (2010). A number of things are not clear from these milestones or from Stiegel4 and DOE (1999a): the implementation time frame, the intermediate milestones, or the guiding principles that would permit an assessment of progress and likelihood of success throughout the course of this program. It is also unclear which specific activities would be required for success and which performing organizations would be responsible for each specific milestone. 3 G.J. Stiegel, NETL, “Gas Purification,” Presentation to the committee on May 20, 2002. 4 G.J. Stiegel, NETL, “Gas Purification,” Presentation to the committee on May 20, 2002.
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Review of Doe’s Vision 21 Research and Development Program—Phase I Progress, Significant Accomplishments, and Current Status The current program includes NETL activities addressing the development of selective sulfur sorbents and sulfur oxidation processes, as well as the operation of a facility for the development and demonstration of gas cleanup technologies. A program led by Research Triangle Institute (RTI) is exploring removal strategies involving sorbents and membranes for H2S, CO2, ammonia (NH3), and hydrogen chloride (HCl). Siemens Westinghouse leads a project that aims to develop two-stage processes for H2S and HCl removal to parts per billion (ppb) levels. The NETL Gas Process Development Unit has been certified for operation and will start evaluations of sorbents and process configurations shortly. In-house NETL research appears to have led to packed-bed adsorbents that decrease H2S concentrations to less than 1 ppm at moderate temperatures. It is stated that this is a significant improvement over commercial processes, which lead to 60-80 ppm at 25 percent higher costs. The properties of these materials in fluid and transport bed systems are currently being explored. It is not clear, however, whether the systems are compared with sulfur removal processes at higher temperatures, since low- and medium-temperature adsorbents capable of sulfur removal to less than 1 ppm are routinely used to purify synthesis gas in refining, gas conversion, and methanol synthesis. The committee was informed (after requesting some clarification) that the new materials are regenerable, in contrast with those used in available technologies for deep sulfur removal. In view of the thermodynamic requirements for strong adsorption (for removal of sulfur to 1 ppm), the guiding principles and mechanism by which regeneration occurs completely and with high energy efficiency need to be carefully examined before significant outlays for additional research. NETL research activities have also led to a selective H2S oxidation process, which could bring significant reductions in the costs associated with synthesis gas cleanup. The RTI-led project has also developed a selective H2S oxidation process, although it is unclear what “developed” means in this context and as used throughout the descriptions of various Vision 21 projects. A comparison of the RTI-led project and the NETL project is not possible in the absence of additional details (or even a common basis of comparison).5 Clearly, such a comparison and the systematic exchange of information between the RTI and NETL oxidation projects would minimize any duplication of effort and exploit the likely synergies between the two projects. Response to Recommendations from the Committee’s 2000 Report The committee report (NRC, 2000) recommended that the time frame for development of contaminant removal technology be extended to match the imple- 5 G.J. Stiegel, NETL, “Gas Purification,” Presentation to the committee on May 20, 2002.
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Review of Doe’s Vision 21 Research and Development Program—Phase I mentation milestones of the gasification processes envisioned in the Vision 21 Program. That report also recommended that medium-temperature removal schemes be preferred to removal schemes at high temperatures, in view of the recommended increased emphasis on gasification relative to combustion research. These two recommendations have been reflected within the emerging program, although some residual activities in hot gas filtering remain in the Vision 21 Program. The cost analyses carried out for some of the technologies also reflect the recommendations of the committee. Less visible in the current program is any closer integration with science-based initiatives within and outside DOE or any attempt at the rational or theory-guided design of materials, which were included as general recommendations in the earlier committee report. Issues of Concern and Remaining Barriers Several issues are apparent from the emerging gas purification programs. The current emphasis on H2S may well have orphaned the required concurrent efforts in CO2, HCl, and NH3 removal, and it is unclear if or how these last-named three have been accommodated within parallel efforts in DOE’s environmental control program and the materials program, or how any exchange of information is taking place, or how technical synergies among purification, separations, materials, and environmental control areas are being encouraged and exploited. The depth and rigor of the economic analyses is not apparent from the information made available, and the comparisons among the various approaches under development and between each approach and existing commercial processes are not treated consistently. The 2002 milestone (complete pilot-scale testing of subsystem components, e.g., sulfur control, particulate control, trace contaminant control) does not seem realistic in view of the limited progress to date. Finally, the extension of fixed-bed materials to transport or fluid-bed systems remains uncertain as does the path by which models and experiments will be used to assess the likelihood of success and to guide the design of new materials that meet the proposed performance and cost requirements. Findings and Recommendations Finding. The objectives of the gas purification program are not stated quantitatively or with the required cost targets, and the milestones are insufficiently detailed to permit intermediate assessments of progress towards goals. Recommendation. The objectives and milestones need to be more rigorously defined and stated and the responsibility for accomplishing each milestone assigned clearly to a performing organization. Intermediate milestones with a
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Review of Doe’s Vision 21 Research and Development Program—Phase I Response to Recommendations from the Committee’s 2000 Report The committee had a number of recommendations in its 2000 report (NRC, 2000). They are recounted below, along with DOE’s response. Recommendation. The Vision 21 Program Plan should be modified to address the need for a hierarchy of models suitable for preliminary design and scoping studies, as well as for detailed final designs. This hierarchy should range from simple, transparent models showing basic mass and energy balances, costs for process units, and integrated systems to more complex and detailed models of components and systems. The hierarchy should also reflect the differing needs for dynamic simulations and steady-state models of components and systems. It should also include the capability of coupling performance models and cost models, as well as analyzing the effects of uncertainty. In response to this recommendation, DOE has awarded several modeling contracts under the Vision 21 Program solicitation and related programs. One project at the NFCRC is analyzing designs for Vision 21 reference plants. A basic description of five possible plant configurations should be completed by the end of 2002. Other projects are developing software capabilities to analyze Vision 21 plants at various levels of detail. However, there appears to be no formal coordination among these projects, nor is it clear whether, or to what extent, DOE and others will have access to these modeling capabilities in all cases. Recommendation. The U.S. DOE should work closely with potential model users and model developers in industry, academia, government, and nongovernmental organizations (NGOs) to define the specific goals, objectives, and priorities of the component modeling and systems modeling for Vision 21. The goals, objectives, and priorities should reflect the integration of, and need for, experimental or field data to support computer models. Vision 21 workshops have been held to increase outreach to potential model developers. These have mainly concentrated on detailed modeling of components and on advanced computing frameworks for creating new methods of modeling systems. Almost all of the projects are with academia and government laboratories. Interface with industry and evaluation of the use of engineering models for design, cost, and performance still seems to be a weak point of the modeling effort. It is not clear to what extent these activities have been used to set priorities in modeling across the Vision 21 Program. Recommendation. The U.S. DOE should review the current state of the art of science-based modeling capabilities at both the component and systems levels and use this review as a basis for refining its expectations for Vision 21 models. This assessment should clearly identify and distinguish among modeling capabilities at different levels of detail (e.g., mechanistic (molecular or microscale) modeling vs. more empirically based engineering models). It appears to the committee that there is still a strong emphasis in the Vision 21 Program on developing very detailed (e.g., CFD-based) models of
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Review of Doe’s Vision 21 Research and Development Program—Phase I process components, with less attention to engineering models better suited to research guidance. Recommendation. The U.S. DOE should develop a management plan and an institutional capability to carry out computer-based modeling, systems analysis, and systems integration activities. The management plan should include mechanisms for verifying or qualifying the performance of models; assessing and characterizing their reliability; maintaining and updating all Vision 21 models and modeling capabilities: and ensuring that models and modeling capabilities are openly developed, validated, and made available to interested parties. The outsourced projects funded under recent Vision 21 solicitations are not responsive to this recommendation. Creation of an institutional capability to develop, validate, and maintain a set of models appropriate for Vision 21 will require a much higher level of resources and management attention. Issues of Concern The current project in Vision 21—to develop a framework for very detailed (e.g., CFD) models coupled with dynamic systems simulation—is a noble goal. It should be pursued insofar as these capabilities may eventually be very useful. However, the approach is very complex, and it is far too early in its development to provide the research guidance needed right now for system design, selection of the technology components critical for success, and ongoing economic evaluation of overall systems concepts integrated directly into the program. The engineers and project developers of the stakeholder company that will have to invest in the new technologies that go into a Vision 21 plant (as well as the management, which must commit funds) will need to understand the implications and advantages of the system in the terms (such as engineering model language) with which they are familiar. For any company evaluating the commercial use of a specific externally developed technology, there is always a tortuous exercise of incorporating the vision and the cost assumptions into the local systems and models used by the company to determine its own view of the viability and attractiveness of the proposition. This is true even if the purveyor of the technology develops and uses models that have been validated and accepted in the industry over many years of practice. In the case of Vision 21, the problem is compounded by the fact that the plants will be complex systems that include many new technologies developed and implemented by different industries (e.g., power production, chemical production, fuel cells, carbon sequestration). Each company considering participation in this endeavor will have to assess not only the attractiveness and risk of its own part of the system, but also the risk of nonperformance of the other parts of the system. For this, they are likely to look to companies in other industries that are their potential partners for assurance (or possibly even guarantees) that their
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Review of Doe’s Vision 21 Research and Development Program—Phase I technology will function properly. This process of separate internal modeling, cross validation, and risk minimization is likely to be very slow and hampered by miscommunication. It will also probably result in suboptimal plant designs because each participating partner will optimize its own part separately. If the Vision 21 Program is to be successful in defining technologies and systems that will be commercially viable and implementable within the time frame of 15 years, it is essential for DOE to develop robust, credible capabilities to model Vision 21 systems using widely available engineering modeling tools. This capability should be developed in partnership with industry, academia, professional associations, and other stakeholders, but DOE should be the central point at which this capability resides. It is a concern of the committee that the priorities for the modeling efforts in the Vision 21 Program are biased too far toward the development of advanced modeling tools as opposed to engineering performance and cost models for Vision 21 plants and components that can be used internally for program planning and assessment. One of the critical activities that clearly needs more attention is providing research guidance for the Vision 21 projects. Research guidance studies aim to identify the critical technical issues that need to be addressed by the project team. These critical issues can include both cost and operability considerations. The starting point for a research guidance study is an analysis of the chemistry, physics, and engineering of the process under review with particular attention to fundamental limitations arising from thermodynamic considerations. The next step is identifying the process steps likely to have a major impact on the cost and operability of the process. For each step the team can identify the performance target that needs to be demonstrated if the process is to be economical. For example, in most membrane processes the mass flux through the membrane and the installed cost of the membrane are critical issues to be addressed early in the R&D plan. In fuel cells, scale-up and membrane assembly cost are critical; in separations, mass flux per unit cross-sectional area; in reactors, catalyst productivity and also mass flux per area; and so forth. Once integrated plant designs have been identified, the reliability, availability, and maintainability (RAM) of the overall facility must be analyzed. Here the focus is on interactions among the various components of a complex plant. One of the most effective ways to address these problems is for the Vision 21 Program to provide models and cost analyses of Vision 21 plants using widely available modeling tools. These models would be developed and backed up by a team of experienced design engineers who are integrated with the project and colocated with Vision 21 program management. If these models are not developed by the Vision 21 Program and validated through several years of interaction with the project teams and the relevant target industries, then the overall engineering systems model will have to be developed after the fact by a consortium of interested companies. It may be difficult to “recruit” companies willing to com-
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Review of Doe’s Vision 21 Research and Development Program—Phase I mit their own resources to this multicompany process. This glitch could easily delay implementation of Vision 21 projects by many years. Finding and Recommendations Finding. As it is being implemented, the Vision 21 Program Plan will not create adequate capability to build credible and useful engineering and cost models of Vision 21 plants. The program still lacks a clear plan for managing the development of computer-based modeling capabilities necessary for overall success of the program. There still appears to be inordinate confidence in the ability to develop advanced computing capabilities to create “frameworks” for very detailed mechanistic models to be tied together into systems models that can be used for engineering evaluations and dynamic simulations. While this may well be a laudable long-term goal, this particular set of projects cannot be counted on to provide credible systems performance modeling or useful guidance for system selection and research guidance within the time frame of Vision 21. That is still an unrealistic expectation within the program and may be leading to a misallocation of resources in the modeling component of the Vision 21 Program. Based on this finding, the committee believes the focus should be on developing an engineering modeling team that is integrated directly with the Vision 21 management to provide engineering analysis and research guidance. This team can provide an independent perspective within the project on the value of various technologies in the context of Vision 21 schemes as well as on the probability of successful development. In the process of developing Vision 21 flowsheets, they can identify the technology bottlenecks—that is, in the most promising schemes, What are the most critical technologies yet to be developed? and What is the risk-weighted value of developing those technologies? The continued refinement of the process schemes and iteration with the project teams can be used in this way to manage the portfolio of specific technology development projects according to their value and probability of success. Recommendation. Sufficient resources should be redeployed to create an engineering modeling team that will be colocated with the program leadership. The objectives of this team will be to develop the capability to create credible engineering and cost models for Vision 21 plants (including major components of plants), provide research guidance to program leadership and to project teams for evaluation and selection of critical technologies in the context of Vision 21, and to validate the engineering modeling capabilities and results with relevant industry partners. Recommendation. One of the first assignments of the engineering modeling team should be a quick benchmarking study on the modeling, optimization, and
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Review of Doe’s Vision 21 Research and Development Program—Phase I management of large, complex systems as practiced by established industries in similar situations. Large refineries are one good example of well-developed systems that manufacture many products: in producing and exporting power, they optimize around downtime or changing performance characteristics of key components or changing feedstock specifications. Recommendation. Systems modeling capability should be an integral aspect of the Vision 21 Program. It is important for the Vision 21 project management as well as the entire project team to interact regularly with the modeling team. A process should be created in the Vision 21 Program for regular interaction of all of technology development teams and project management with the engineering modeling team to review and understand the overall system models and the cost implications of specific technology issues. This process should be utilized to create new process and technology concepts. CONVERSION OF SYNTHESIS GAS TO FUELS AND CHEMICALS Introduction Commercial production of liquid fuels from coal-derived synthesis gas (syngas) was started in the mid-1950s in South Africa. The basis for this industrial complex was the pioneering work done by Franz Fischer, H. Tropsch, and others in Europe in the earlier part of the 20th century. The economic driver for this technology commercialization was the desire to make fuels from the abundant coal resources in the country. The need for this technology was reinforced later on by the embargo on trade with South Africa by most other nations. Pilot-scale demonstrations of coal-based Fischer-Tropsch (F-T) fuels have also taken place in the United States, Japan, and Russia. Moreover, before and during World War II, significant quantities of F-T fuels were made in Germany from coal. The catalyst of choice for coal-derived syngas conversion to F-T fuels is iron, with promoters added for reduced attrition of catalysts, sintering, and increased reactivity. Reactor technology has evolved from early fixed-bed reactors to the preferred option today, three-phase (gas, liquid, and solid catalyst) liquid fluidized reactors. Coal-based syngas is also used to make other important industrial products, including methanol and hydrogen. The technology has improved along the same time line. The catalyst of choice for methanol is copper, and for hydrogen production, nickel. The preferred reactors are fixed-bed or tubular reactors. While the technology for making fuels and chemicals is widely available and has been commercially demonstrated, only a small fraction of overall production is from coal-derived syngas. The main reasons are the higher cost of making syngas from coal than from natural gas and the lower molar ratio (<1.0) of hydrogen to carbon monoxide produced in coal gasifiers. Production of syngas
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Review of Doe’s Vision 21 Research and Development Program—Phase I from methane gasifiers or steam reformers is significantly cheaper, and the molar ratio is closer to the desired ratio (>2.0) for making methanol and fuels. When syngas from a coal gasifier is used to make these products, about half of the carbon monoxide has to be reacted with steam to produce carbon dioxide and hydrogen (water gas shift reaction). The key reason why iron is the preferred catalyst when making fuels from coal-derived syngas is that iron catalyzes both the water gas shift and the F-T fuels reactions. In the last two decades a major effort has been under way to produce fuels from methane-derived syngas. These efforts, which are international in scope, are based on sophisticated scientific and engineering concepts and enjoy strong participation by the energy and chemical industry. The Proceedings of the Sixth Natural Gas Conversion Symposium, published by Elsevier, capture the breath and depth of the effort under way (Elsevier, 2001). Previous symposia whose proceedings were also published by Elsevier, give an excellent retrospective on the evolution of this technology (Elsevier, 1997, 1998). In the Vision 21 Program, one option considered is the conversion of a portion of the syngas from coal gasifiers to fuels and chemicals. The committee does not dispute the technical feasibility of the scheme. Rather, its assessment is based on seeking the best allocation of the resources available to advance Vision 21 technologies to commercial readiness by 2015. If for either strategic reasons (the need to increase domestic production of fuels and chemicals) or economic reasons (price of crude oil well above $30/barrel) large-scale production facilities were needed in the United States or other parts of the world, such as China, the technology is available from industry. A second factor also leads the committee to question the proposed development and demonstration program—namely, the high level of research, development, and commercialization activity currently being pursued by private industry (estimated at close to $100 million per year) in the United States and other countries (McWilliams, 1997). Milestones and Goals The goal of the clean fuels effort by the Office of Fossil Energy is to promote the development and deployment of affordable technologies that produce clean, high-performance liquid and gaseous fuels from a variety of secure energy resources. The objective of the Vision 21 Program is to develop technologies that integrate well with Vision 21 plants and that can narrow the cost difference between coal and petroleum-based fuels. The specific milestones identified for the syngas to fuels/chemicals activity are as follows: Start-up prototype plants coproducing power and fuels/chemicals (2010); Complete Vision 21 advanced coproduction plant designs (2010); and
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Review of Doe’s Vision 21 Research and Development Program—Phase I Start-up of commercial coproduction plants using advanced Vision 21 technologies (2015). Current Status and Significant Accomplishments The Vision 21 team highlighted the following accomplishments specific to syngas to fuels/chemicals activities: Texaco and Waste Management and Processors of Gilberton, Pennsylvania, are on schedule to complete engineering design of coproduction complexes by early 2004. The University of Kentucky’s Center for Applied Energy Research is working on iron catalyst technology and has developed new catalysts, tested catalysts for industry, and trained personnel to be employed by industry. At the LaPorte, Texas, facility operated by Air Products, Texaco tested the Rentech F-T technology and Air Products completed tests to make dimethyl ether (DME) and methanol. New catalyst formulations were identified, and their reaction mechanism was validated. A Consortium of Fossil Fuel Science was established with the objective of reducing the cost of synthesis gas conversion to products. Research is under way on supercritical F-T synthesis, new catalysts for the conversion of methanol to ethylene and propylene, and nanoscale iron catalysts for the conversion of methane to hydrogen, and carbon nanotubes. Research on modeling slurry reactors and on computational chemistry for iron catalysts has been funded. Response to the Recommendations from the Committee’s 2000 Report The Vision 21 team seems to have responded positively to the recommendation to place greater emphasis on chemistries, catalysts, and reactor schemes other than iron-based F-T synthesis catalysts and slurry reactors (NRC, 2000). However, work continues on detailed engineering design/economic feasibility studies of coproduction complexes and on pilot-plant demonstration runs, all aimed at making F-T fuels and methanol/DME. These activities parallel activities by industry and should not be part of the program. Issues of Concern and Barriers Remaining The committee is concerned about the focus and level of effort in this area. As mentioned before, the conversion of syngas to fuels and chemicals is being pursued very intensely by industry, and the efforts range from research to commercialization. While the preferred source of syngas is “remote” (and thus
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Review of Doe’s Vision 21 Research and Development Program—Phase I inexpensive) natural gas, the desired composition of the feed used in the syngas conversion reactors is determined by the desired product (fuel or chemical), not by the source of the syngas (coal, methane). It is important to note that even with inexpensive natural gas as the feed, syngas conversion plants are at best marginally competitive with fuels from crude oil. Moreover, every credible economic analysis of coal to fuels vs. electric power complexes has shown fuels to be even less attractive (Gray and Tomlinson, 1997). The key to improving the economics is finding a much cheaper way to make syngas in coal gasifiers. A fundamental limitation in the conversion of coal to fuels (including hydrogen) is the thermal and carbon efficiency of the process. The Vision 21 Program objectives include a 75 percent efficiency objective for fuels-only plants. This target efficiency is based on an analogy to the efficiency of processes such as petroleum refining and other syngas routes to fuels. This analogy is incorrect. Indeed, it is possible to calculate the maximum theoretical efficiency from fundamental principles of thermodynamics. The chemical equations that define this analysis are these: 2.25 CH0.8 + 1.25 O2 → CH2 + 1.25 CO2 2.25 CH0.8 + 2.25 O2 → H2 + 2.25 CO2 The maximum theoretical carbon efficiency when making hydrocarbon fuels is less than 50 percent, and more carbon is produced as CO2 than is retained in the fuel. In the case of hydrogen the thermal efficiency of the process is only 30 percent. These theoretical maximum efficiencies can be compared with the results of engineering analyses of coal-to-fuels complexes (Gray and Tomlinson, 1997). That study, conducted for the DOE, estimated the carbon efficiency of the fuels-only plant at 42 percent. The efficiencies should also be compared with the efficiency of a natural gas-to-fuels process, where the theoretical efficiency is 75 percent and actual plant experience shows efficiencies of 60-63 percent. Findings and Recommendations Finding. The program plan in Vision 21 for syngas to fuels/chemicals is heavily focused on activities that parallel R&D and commercialization activities by private industry throughout the world. This particularly applies to pilot-plant demonstrations, engineering design/feasibility studies, and testing of commercial catalysts and reactors. Finding. A positive trend in the syngas to fuels/chemicals program is the initiation of some exploratory research on catalysts aimed at making higher-value fuels and chemicals from coal-derived syngas. Since this is an area of research that has already been thoroughly investigated, the specific research directions and the rate of progress should be carefully monitored by DOE/NETL.
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Review of Doe’s Vision 21 Research and Development Program—Phase I Recommendation. The committee recommends a modest effort in exploratory catalysis research aimed at the selective conversion of syngas to high-value fuels and chemicals. Recommendation. Detailed engineering design/economic feasibility studies of coal coproduction complexes and large-scale, pilot-plant demonstration runs of conventional processes to make low-value fuels such as diesel, methanol, and DME should not be funded by the Vision 21 Program. ADVANCED COAL COMBUSTION Introduction The Advanced Combustion Technologies Program is a very important component of the Office of Fossil Energy R&D program. It offers a near-term technological solution to improving efficiency and environmental performance in existing fossil-fuel power plant units, especially coal-fired power plants, and new units that may need to be constructed before Vision 21 systems are available or if Vision 21 systems prove unable to achieve the desired levels of performance and costs. The advanced combustion program encompasses the development of high-performance combustion systems, both suspension fired and fluidized bed, including ultra-low-NOx combustion and combustion systems that burn fuels in O2/CO2 mixtures and produce exhaust streams containing only CO2 and water. These advanced combustion systems, except perhaps the O2-based combustion, will not achieve the goals of a Vision 21 system; rather, they are a technology bridge between today’s combustion systems and the point in time when Vision 21 systems are commercially ready.18 The Advanced Combustion Technologies Program will offer the opportunity to repower, modernize, and upgrade existing electric generating units or to install new units to replace the existing fleet before Vision 21 plants are commercially available. These early commercial applications of advanced combustion systems can serve as a platform on which Vision 21 equipment will gain operating experience and construction know-how, while increasing reliability and decreasing costs. Opportunities for proving Vision 21 components will allow achieving the overall goal—commercial designs by 2015— because the marketplace will be able to rely on the experience gained during these advanced combustion system applications. The Advanced Combustion Technologies Program provides an enabling opportunity as well as a fallback position for Vision 21 technologies and the nation’s electric generating technology. 18 J. Marion, ALSTOM Power Inc., “The Evolution of Coal Combustion Technology for Electric Power,” Presentation to the committee on May 21, 2002.
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Review of Doe’s Vision 21 Research and Development Program—Phase I Milestones and Goals The Advanced Combustion Technologies Program objective is the development, demonstration, and commercial deployment of advanced coal-fired combustion systems in the United States and abroad. These power plants will offer significant improvements in performance and cost. Key goals19 include: By 2005, develop a 42 percent (HHV) efficient low emission boiler system (LEBS) with lower emissions and cost than existing pulverized coal (PC) technology, for repowering or retrofitting existing plants. By 2010, develop a 47 percent (HHV) efficient indirectly fired power system (IFPS)—gas turbine combined cycle and advanced PC boiler— with lower emissions and costs than existing PC plants. By 2010, demonstrate pressurized, fluidized-bed combustion (PFBC) with over 50 percent (HHV) efficiency and better environmental performance and lower cost than other combustion systems. Response to Recommendations from the Committee’s 2000 Report In 2000, the committee found that the advanced combustion technologies in the Office of Fossil Energy’s core power generation program were limited by practical engineering to efficiencies of 45 to 50 percent, which are substantially below Vision 21 Program goals of 60 percent (NRC, 2000). A second finding was that the dilute CO2 stream from combustion would be more expensive to separate than that from gasification. For these reasons the committee recommended that the advanced combustion program not be included in the Vision 21 Program unless new approaches were conceived that could achieve the 60 percent goal. Innovative configurations to achieve the Vision 21 goals using advanced combustion have been investigated by DOE, but no ready solution has emerged. However, the O2/CO2 combustion option appears to hold some promise for increased efficiency and carbon sequestration options. Issues of Concern and Remaining Barriers The issues of advanced combustion system’s efficiency and the dilute CO2 stream from combustion remain as large hurdles to advanced combustion systems achieving Vision 21 goals and remaining in the program. 19 NETL Advanced Combustion Technologies Program Goals, available online at <http://www.fetc.doe.gov/coalpower/combustion/index.html>.
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Review of Doe’s Vision 21 Research and Development Program—Phase I Finding and Recommendation Finding. The Advanced Combustion Technologies Program is an important component of the Office of Fossil Energy R&D program and should be vigorously pursued, but outside the Vision 21 Program. The advanced combustion technologies have the potential to significantly improve efficiency and environmental performance over today’s electric generating technologies and can enable the upgrading of the existing fleet of power plants or the construction of new plants. The advanced combustion technologies can also serve as a fallback alternative if the Vision 21 goals prove unobtainable technically or economically. Recommendation. The Advanced Coal Combustion Technologies Program should be vigorously pursued outside the Vision 21 Program in order to meet any commercial needs for coal-fired generating capacity with much better performance and emission levels than current combustion technologies before Vision 21 technologies are commercially available.
Representative terms from entire chapter: