Coal Energy for the Future (1995) / Chapter Skim
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6 CLEAN FUELS AND SPECIALTY PRODUCTS FROM COAL
6 CLEAN FUELS AND SPECIALTY PRODUCTS FROM COAL
Pages 85-112
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From page 85... ...
As natural gas prices increase, substitution of gas from coal in natural gas-fired power generation plants may become economic. Advanced combined-cycle and fuel cell power generation technologies will also require the conversion of coal to clean gaseous fuels.
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From page 86... ...
Today's emphasis on increased power generation efficiency, and the availability of high-performance gas turbines and fuel cells, have created a strong incentive for development of high-efficiency gasification systems specifically designed to provide fuel for power generation. These systems can differ from systems optimized to produce highly purified synthesis gas for catalytic conversion to chemicals and clean fuels in that dilution by methane and nitrogen is acceptable and a higher level of impurities can be tolerated.
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From page 87... ...
, CCT British Gas Lurgi (high pressure, 1,000 psi) DOE-Sirrine Advanced Moving Bed (U.S.)
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From page 88... ...
Because the temperatures on exiting the gasifies are well matched to the requirements for hot gas cleanup systems, fluidized-bed gasifiers offer overall efficiency advantages relative to higher-temperature entrained-flow systems that require gas cooling prior to cleanup. Relative to moving bed gasifiers, fluidized-bed units offer higher coal throughput rates, which reduce unit size and cost.
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From page 89... ...
gas turbines, increases in efficiency to the 45 percent level projected for second-generation systems depend on the use of hot gas cleanup systems plus improvements in gasifier performance and optimized systems integration. In addition to the method of contacting coal and oxidant (entrained-flow, fluidized-bed, or moving fixed-bed)
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From page 90... ...
· For the air-blown systems, use of hot gas cleanup rather than cold gas entrained-flow system operates at 1480 °C to 1650 °C (2700 to 3000 °F) and produces a molten slag.
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From page 91... ...
, the production of hydrogen, clean low- and mediumBtu gaseous fuels for industrial and utility use, and synthesis of liquid fuels and chemicals are expected to be major potential applications for coal gasification. For both power generation and fuels production, greenhouse gas concerns are expected to greatly increase the emphasis on improved efficiency.
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From page 92... ...
As previously discussed (Table 6-2) , the loss in power generation efficiency for oxygen-blown versus air-blown systems is about 1 percent for the KRW fluidized-bed system provided that hot gas cleanup is successful, and this small difference can likely be reduced by further research and optimization.
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From page 93... ...
Of the seven programs, five plan to use the currently experimental hot gas cleanup-one on a 10 percent slipstream. Use of cold gas cleanup reduces efficiency by approximately two percentage points (see Table 6-2~.
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From page 94... ...
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From page 95... ...
This system appears to have potential for efficient integration with hot gas cleanup in a power generation system. However, because it is air-blown it would not be a good choice for coproduction of clean gaseous or liquid fuels.
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From page 96... ...
If pure hydrogen could be obtained economically as a coproduct from the coal-derived fuel gas supplied for electric power generation, it might be used for high-efficiency fuel cell operation, hydrogenation of by-product coal pyrolysis
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From page 97... ...
SNG is also produced in South Africa, and China plans to build a $220 million plant in Henan province to produce 40 Mcf/day of SNG, with over 20 percent of the coal gas destined for use as petrochemical feedstock (Oil and Gas Journal, 1994~. The Great Plains plant uses 14 Lurgi dry bottom gasifiers followed by cold gas cleanup to reduce sulfur content to less than 1.0 ppm.
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From page 98... ...
Substitution of coal-generated low- and medium-Btu gas for natural gas for power generation and industrial use could make additional supplies of natural gas available for domestic and commercial consumers. Thus, the need for major dedicated SNG manufacture could well be delayed beyond the year 2021.
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From page 99... ...
Natural gas at current prices is by far the lowest-cost feed, but at a delivered natural gas price of greater than $4 to $5/Mcf, coal gasification was judged to be competitive. Methanol-Derived Fuels There has been extensive industrial R&D, in the United States and overseas, on processes to convert methanol to gasoline, olefins, and diesel fuel (NRC, 19901.
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From page 100... ...
Even when domestic natural gas prices rise to a level where dedicated production from coal could compete economically, natural gas is expected to remain the lowest-cost syngas source for methanol production due to the large overseas supply of very low cost natural gas. However, as discussed later in the section ore coal refineries and coproduct systems, coproduction with gasification combined-cycle power generation might be competitive with imported methanol.
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From page 101... ...
For production of both methanol and hydrocarbons, the slurry process has been a focus of DOE research since it can accept the low-hydrogen/carbon monoxide synthesis gas produced from coal without the additional step of shifting the ratio required by the traditional fixed-bed systems. Success of this DOE approach has been demonstrated in a large-scale pilot plant at LaPorte, Texas, with joint DOE/ industry funding.
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From page 102... ...
State of the Art Products of direct coal liquefaction can be refined to meet all current specifications for transportation fuels derived from petroleum. Major products are likely to be gasoline, propane, butane, and diesel fuel.
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From page 103... ...
Current Programs U.S. research into direct coal liquefaction continued after the big pilot plants were abandoned in the 1980s, but both industrial and DOE activities have steadily decreased with time.
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From page 104... ...
, the equivalent crude price was approximately $33/bbl, compared to estimates of $44/bbl prepared for an earlier study (NRC, 1990~. This cost reduction results from the incorporation of more recent results from the DOE Wilsonville plant, improved gasification, and from inclusion of 3 percent inflation in the DOE-sponsored estimates.
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From page 105... ...
. Integration of direct coal liquefaction with an existing petroleum refinery could take advantage of existing facilities and ease the transition between petroleum and coal feedstock.
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From page 106... ...
When made from low-sulfur coal, pyrolysis liquids have limited potential as a substitute without refining for petroleum fuel oil, and an ongoing CCT program (ENCOAL Mild Coal Gasification project) is aimed at this market.
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From page 107... ...
With today's emphasis on increased generation efficiency and the availability of high-performance gas turbines and fuel cells, an incentive for development of high-efficiency gasification systems specifically designed to provide fuel for power generation has been established. As discussed earlier, these systems can differ from systems optimized to produce highly purified synthesis gas for conversion to chemicals and clean fuels in that dilution by methane and nitrogen is acceptable; a higher level of impurities can also be tolerated.
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From page 108... ...
As in the case of advanced power generation technologies, early market entry would likely require some federal cost sharing (see Chapter 81. Direct Liquefaction Coproduction of coal liquids and electric power based on IGCC systems offers additional opportunities for cost reduction in the production of hydrogen, which could be used for direct liquefaction.
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From page 109... ...
2. The expected major future use of coal gasification in power generation has stimulated industrial R&D for gasification systems tailored to high-efficiency power generation requirements.
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From page 110... ...
5. The air-blown fixed-bed gasifier scheduled for development at the DOE Gasification Product Improvement Facility may be competitive for use in a hot gas cleanup combined-cycle power generation system.
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From page 111... ...
2. Coproduction with electricity has the potential to reduce indirect coal liquefaction costs by $6/bbl or more, indicating that pioneer production of liquids may become economically attractive in the timeframe projected for widespread construction of advanced gasification power generation facilities.
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From page 112... ...
1993. Indirect Coal Liquefaction via Fischer-Tropsch Technology for the Baseload IGCC Plant.
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