Vision 21 Fossil Fuel Options for the Future (2000) / Chapter Skim
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3 Enabling Technologies
3 Enabling Technologies
Pages 26-60
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From page 26... ...
For several reasons, the bulk of funding for enabling technologies should be focused on coal-gasification technologies, the major element of the fuel-flexible gasification program. First, coal, coke, and heavy-oil gasification processes produce a fuel gas that can be cleaned and converted to electricity in fuel-flexible gas turbines and fuel cells at high efficiency.
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From page 27... ...
to compete with plants that use natural gas in the same types of fuel-flexible gas turbines, will require innovative, high-risk R&D. The committee encourages DOE to investigate new ideas relating to novel, as well as existing, gasification processes.
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From page 28... ...
The relative economics and environmental acceptability of the alternatives described above will affect the commercial attractiveness of combustion and gasification technologies for power production. If direct, on-site separation of carbon dioxide is favored economically, then gasification technologies will be favored because they produce a concentrated carbon dioxide stream at the production plant site.
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From page 29... ...
Therefore, the Vision 21 Program for the gasification technology will have to adopt an integrated approach that includes gas cleaning and heat recovery. TABLE 3-1 Typical Costs for a Current Gasification Plant Process Unit Percentage of Total Costs Solids handling and slurry-feed preparation Gasifier, high-temperature heat recovery, and slag removal Gas cleanup and low-temperature heat recovery Air separation Combined-cycle power block Off-site facilities Total 6 24 10 12 25 23 100
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From page 30... ...
Most gasification plants are not dedicated solely to power generation (Figure 3-2) , although the number of power generation plants is increasing.
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From page 31... ...
Coal-based technology, whether conventional combustion technology or costlier new gasification technology, will not be the preferred power generation technology in the United States for the foreseeable future because of competition from natural gas. The capital costs and nonfuel operating costs of a natural gasfired combined-cycle plant is lower than those of a coal-fed IGCC plant.
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From page 32... ...
Financing will also be more readily available as confidence in the overall plant performance increases. Proposed Program Plan The current Vision 21 Program Plan for fuel-flexible gasification employs a portfolio approach with R&D programs in two categories: · technologies to improve the performance of the gasifies, such as improved burner design, improved carbon conversion, more reliable solidfeed systems, better refractory materials, more efficient dry particulate removal systems, and better hot-gas handling · technologies to improve the overall gasification plant performance, such as increased oxygen production, gas turbines that can use syngas and hydrogen fuel, more efficient waste-heat recovery, better hot-gas cleanup, and improved coproduction processes, such as Fischer-Tropsch liquid and production of all-methyl ether The committee agrees that these technologies should be part of the gasification portfolio, although it is not clear that DOE has developed a mechanism to ensure that the second group of technologies is focused on gasification-related issues.
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From page 33... ...
However, if the coal and natural gas prices projected by EIA for the United States for 2000 to 2015 are correct, coal-gasification technology will only be economically competitive in the United States in a carbon-constrained environment in which all plants must use carbon capture and sequestration technology. In China, India, and other industrializing countries with less developed gas markets, coal is far more competitive.
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From page 34... ...
Coal-gasification systems produce syngas (a mixture of carbon dioxide and hydrogen) that can be converted into electricity by IGCC, fuel cells, or gas turbine/fuel cell hybrid systems at high electrical conversion efficiencies.
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From page 35... ...
The program plan has many options in common with the gasification R&D plan for both power generation (e.g., using oxygen in place of air) and fuel gas (e.g., using fuel gas in high performance gas turbines and fuel cells)
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From page 36... ...
The efficiency level is more likely to be about 50 percent, which may, in fact, be competitive in the future because combustion technologies generally require somewhat smaller capital investments than gasification technologies, but there is no indication, however, that a first- or second-generation PFBC power plant will have a lower cost than an IGCC plant. Meeting the program goal of 60-percent efficiency will probably require that these combustion cycles be integrated with high-efficiency gas turbines and fuel cells.
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From page 37... ...
First, power plants that use PFBC and IFC advanced combustion technologies cannot meet the 60-percent efficiency goals. In addition, because of lower carbon dioxide concentrations in the gaseous effluent from combustion power plants, carbon dioxide separation will be more expensive than for gasification plants.
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From page 38... ...
Finding. All advanced combustion technologies that are currently included in the DOE core power generation R&D program are limited by practical engineering considerations to efficiencies in the range of 45 to 50 percent, which is substantially below the Vision 21 Program goal of 60 percent.
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From page 39... ...
The fuels and chemicals produced in coal-based coproduction complexes will be competing with similar products made from more attractive feeds. Oxygenates will be competing with those made from remote or cheap natural gas.
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From page 40... ...
It is important to keep in mind that the capital cost of plants that produce fuels and chemicals from coal will be approximately $40,000 per barrel per day of capacity. At the same time, the capital cost of producing fuels and chemicals from natural gas will be about $20,000 per barrel per day, and from conventional petroleum less than $13,000 per barrel per day.
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From page 41... ...
Therefore, fuels and chemicals made from coal-based synthesis gas will suffer a price penalty. Second, liquid transportation fuels made from petroleum have a cost advantage over similar fuels made from remote, low-cost natural gas.
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From page 42... ...
Because more than two-thirds of the cost of producing fuels and chemicals from coal is associated with the production of synthesis gas, the focus in R&D should be on breakthroughs in synthesis gas technology. As a result of major R&D investments by energy companies worldwide, the cost of converting synthesis gas from sources other than coal to fuels and chemicals has been reduced significantly.
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From page 43... ...
. Therefore, most energy companies have opted to use remote natural gas as the feedstock for producing liquid fuels (via reaction with steam to produce synthesis gas)
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From page 44... ...
When fuels and chemicals are produced by coal-based plants using conventional Fischer-Tropsch technology, three tons of carbon dioxide are produced per ton of hydrocarbon product. If natural gas is used as the feedstock instead of coal, less than one ton of carbon dioxide is produced per ton of hydrocarbon product.
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From page 45... ...
The Vision 21 Program should focus much more on step-out technologies for reducing the cost of producing synthesis gas from coal and other high-carbon content solid fuels; breakthroughs may reduce the cost of producing fuels and chemicals from coal to a more competitive level with the cost of similar products made from petroleum and natural gas. Significant improvements in coal reactivity and novel concepts for minimizing impurities in the synthesis gas would be worth pursuing.
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From page 46... ...
The costs of current units, which are still manufactured in small development facilities, are far higher than the cost requirements of the distributed powergeneration market, which in turn are far higher than the even more stringent cost requirements of the central station market. Cost reduction is the greatest challenge to the development of fuel cells for central station coal gasification-fueled units.
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From page 47... ...
for natural gas-fired generating systems. Meeting both goals will require that high-temperature fuel cells be combined with gas turbines in hybrid systems.
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From page 48... ...
DOE/NETL has already selected a fuel cell and system type for the longterm, Vision 21 goal based on fossil fuel: · high-temperature, solid-state fuel cell · hybrid fuel cell/gas turbine power-generating system DOE/NETL has also designated an intermediate goal of a natural gas-fired distributed power-generation or cogeneration system based on high-temperature solid-oxide or molten-carbonate fuel cells. Meeting this goal will require the development of economical, effective, reliable fuel cell modules and certain critical system components (e.g., small gas turbines, heat exchangers, power conversion equipment, instrumentation, control systems)
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From page 49... ...
Heat Exchangers High-temperature heat exchangers will be required for high-efficiency fuel cell power systems for preheating fuel and air reactant streams to the fuel processing and/or the fuel cell systems making use of the hot exhaust stream from combustion turbines. Heat exchangers will be required to tolerate top temperatures of 1,400°F to 1,600°F in either oxidizing or reducing conditions and pressure differences of 2 to 4 atmospheres over the surface.
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From page 50... ...
DOE is now working on incorporating this information into more detailed program plans (Williams, 1999~. Schedules and Milestones The fuel cell program extends from 2000 to 2015.
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From page 51... ...
Short-term return on current investments would encourage their continued participation in the fuel cell program to deal with central station issues, attract the high-level funding required to demonstrate large-scale systems lowering the fuel cell and system production costs, and enhance the effectiveness of system designs and production processes. The goals of the second focus area (development of twenty-first century high-temperature fuel cells)
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From page 52... ...
The problem was complicated because the fuel cell program may require technical input from other Vision 21 component programs (e.g., gasification, gas turbines, heat exchangers, materials and manufacturing, and computer simulation) for the IGCCFC facilities that will be necessary to meet the efficiency targets.
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From page 53... ...
to competitive levels in many market niches where power is supplied from the electricity grid. These cost reductions will, to a large extent, benefit the large-scale central station power-generation focus of Vision 21, and system design will be focused on natural gas as a fuel rather than on hydrogen or syngas.
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From page 54... ...
Combustion turbines are Brayton-cycle machines with thermodynamic efficiencies determined approximately by the firing temperature of the machine and the exit temperature of the exhaust gases. Firing temperatures in modern gas turbines are approximately 2,500°F, and temperatures of 2,700°F are anticipated soon.
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From page 55... ...
Increasingly, customers for power generation machines are demanding and obtaining guaranteed levels of reliability and availability. Proposed Program Plan The focus of planned Vision 21 activities is the development of advanced combustion turbine technology for systems that can operate under high temperatures (3,000°F)
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From page 56... ...
Over the commercial life of that model, improvements in materials, cooling, and thermal barrier coatings are periodically introduced to allow operation at increased firing temperatures. Therefore, the ATS model gas turbines, which are proposed as the core engine for Vision 21 plants, should be able to incorporate proposed technology developments for the Vision 21 Program and may enable operation at increased firing temperature (up to 3,000°F)
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From page 57... ...
Modified components may be required to enable conventional natural gas-fired machines to use hydrogen-rich fuel gases. If syngas is converted to hydrogen for use in gas turbines, the "cradleto-grave" costs and environmental effects of this conversion must be considered from a fuel life-cycle and systems perspective to determine potential trade-offs vis-a-vis carbon emissions, efficiencies, and costs, and whether lost energy (and therefore more carbon emissions)
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From page 58... ...
Because Advanced Turbine System (ATS) -based machines will be approaching the end of the current gas turbine model life cycle in 2015, improved system performance is likely in the next generation of commercial machines, when commercialization of Vision 21 technologies are most likely.
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From page 59... ...
Presented at the EPRI/Gasification Technologies Council Technology Conference, Grand Hyatt Hotel, San Francisco, California, October 4-7, 1998.
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From page 60... ...
Presented at the EPRI/Gasification Technology Council, Gasification Technologies Conference, Grand Hyatt Hotel, San Francisco, California, October 4-7, 1998. Williams, M.C.
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