Gasified coal

Benfield process Removal of carbon dioxide from fuel gases, such as those obtained by gasifying coal in the Lurgi process, by countercurrent scrubbing of the gases by hot potassium carbonate solution. 

In 1984, the Ube Ammonia Industry Co. began operating the largest Texaco coal gasification complex to date. This faciUty is located in Ube City, Japan, and has a rated gasification capacity of 1500 t/day of coal, and production capacity of 1000 t/day of ammonia. The plant has successfully gasified coals from Canada, AustraUa, South Africa, and China. At the present time the plant uses a mixture of petroleum coke and coal (43). 

Ammonia (NHj) is produced from atmospheric nitrogen and hydrogen from a hydrocarbon source. Natural gas is the most commonly used hydrocarbon feedstock for new plants other feedstocks that have been used include naphtha, oil, and gasified coal. Natural gas is favored over the other feedstocks from an environmental perspective. 

Many chemicals are produced from synthesis gas. This is a consequence of the high reactivity associated with hydrogen and carhon monoxide gases, the two constituents of synthesis gas. The reactivity of this mixture was demonstrated during World War II, when it was used to produce alternative hydrocarbon fuels using Fischer Tropsch technology. The synthesis gas mixture was produced then hy gasifying coal. Fischer Tropsch synthesis of hydrocarbons is discussed in Chapter 4. 

In a gasifier, coal (solid carbon) is converted to syngas by the following gasification reactions ... 

In the gasifier, coal is fed along with calcium oxide, steam, and oxygen. The excess steam in the gasifier drives the following reaction toward the formation of H2 ... 

CGCC [Coal Gasification, Combined Cycle] A general name for processes that both gasify coal and produce electricity. One such process has been operated by Louisiana Gasification Technology, at Plaquemine, LA, since 1987. See also APAC. 

KR [Kellogg-Rust] A fluidized-bed process for gasifying coal, initially developed by the Westinghouse Corporation. 

KRW Figure 2.5 illustrates key features of this gasifier. Coal and limestone, crushed to below 1/4," are transferred from feed storage to the KRW fluidized-bed gasifier via a lock hopper system. Gasification takes place by mixing steam and... 

Transport Reactor Gasifier Coal (sub-bituminous), KY and IL No. 6, coke breeze LHV IGCC 26.8-64... 

The addition of H2O and CO2 to the fuel gas modifies the equilibrium gas composition so that the formation of CH4 is not favored. Carbon deposition can be reduced by increasing the partial pressure of H2O in the gas stream. The measurements (20) on 10 cm x 10 cm cells at 650°C using simulated gasified coal GF-1 (38% H2/56% CO/6% CO2) at 10 atm showed that only a small amount of CH4 is formed. At open circuit, 1.4 vol% CH4 (dry gas basis) was detected, and at fuel utilizations of 50 to 85%, 1.2 to 0.5% CH4 was measured. The experiments with a high CO fuel gas (GF-1) at 10 atmospheres and humidified at 163°C showed no indication of carbon deposition in a subscale MCFC. These studies indicated that CH4 formation and carbon deposition at the anodes in an MCFC operating on coal-derived fuels can be controlled, and under these conditions, the side reactions would have little influence on power plant efficiency. 

Gasified coal is expected to be the major source of fuel gas for MCFCs, but because coal contains many contaminants in a wide range of concentrations, fuel derived from this source also contains a considerable number of contaminants. A critical concern with these contaminants is the concentration levels that can be tolerated by MCFCs without suffering significant degradation in... 

Steam generated in the bottoming cycle is utilized in a reheat turbine to produce 118 MWe, as well as to supply the steam required by the air separation unit (ASU) and the gasifier coal slurry heater. The cycle exhaust exits the heat recovery steam generator at 126°C (259°F) and 0.98 atmospheres. 

The product hydrogen is about 2.8 MPa, with a purity higher than 97.5%. It is more efficient to gasify coal at elevated pressures. 

R D on Hydrogen Purification from Gasified Coal (EAGLE). The objectives of the EAGLE project are development of an optimum coal gasifier for fuel cells and establishment of a gas clean-up system for purification of coal gas to the acceptable level for utilization for MCFC and SOFC. The budget allocations for 2000-2003 total 4.6 billion the 2003 allocation is 1,000 million. Work is sponsored by METI and the Electric Power Development Co., Ltd. 

When the gasified coal is to be used for synthesis of methane methanol, or hydrogen, part or all of it is subjected to the water-gas shift reaction, converting CO and water to CO2 and H2. Sulfur must be removed completely. The acid gases H2S and CO2 are first extracted from the gas before or after the shift conversion these acid gases may be processed in a second step in a Claus unit. The acid gas composition depends on each part of the sequence preceding the Claus unit. 

COS usually constitutes about 5 percent of total sulfur in the gasified coal. Passing over the complex problem of extractiig COS from the gas, its conversion to sulfur in the Claus unit requires some attention. It is best hydrolyzed to H2S, then converted to sulfur. Alumina Claus catalyst is effective for hydrolysis at above 650°F, and promoted catalysts are said to be effective at still lower temperatures. 

Gasifier - [COAL CONVERSION PROCESSES - GASIFICATION] (Void) - [COALCONVERSIONPROCESSES - GASIFICATION] (Void) - [COALCONVERSIONPROCESSES - GASIFICATION] (Void) - [COALCONVERSIONPROCESSES - GASIFICATION] (Void) - [COALCONVERSIONPROCESSES - GASIFICATION] (Void) - [COALCONVERSIONPROCESSES - GASIFICATION] (Void)... 

Figure 11.24 Facilitated transport of hydrogen sulfide through an immobilized carbon-ate/bicarbonate solution [26]. Reprinted with permission from S.L. Matson, C.S. Herrick and W.J. Ward III, Progress on the Selective Removal of H2S from Gasified Coal Using an Immobilized Liquid Membrane, Ind. Eng. Chem., Prod. Res. Dev. 16, 370. Copyright 1977, American Chemical Society and American Pharmaceutical Association...

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