Gasification technologies

The world production of coal is projected to rise from 2772 Mtoe in 2004 to 2818 Mtoe in 2010 and 3779 Mtoe in 2030. Much of this coal will be used for electricity generation. In future, rather than employing conventional boilers, coal will probably be converted to a gaseous fuel that will power gas turbines as part of an IGCC scheme. Compared with conventional power plants that are fired with pulverized coal, IGCC offers the following advantages  

Gasification technology is being driven primarily by the first two of these applications. 

There are three basic designs of coal gasifier  

2 Pyrolysis/Thermal Degradation (Thermal Cracking of Polymers in Inert Atmospheres) 

Pyrolysis is a synonym for cracking and is the process of thermally degrading a material in the absence of O2. Specifically, the use of the term pyrolysis refers to plastic-to-fuel (PTF) technologies that handle scrap plastic through a process of thermal 

It has been investigated as a viable recycling route by a number of researchers [14] for PSW treatment [31], or other waste including biomass [32, 33] and rubber [34-36]. 

Parameters Conventional pyrolysis Fast pyrolysis Flash pyrolysis 

Reproduced with permission from R.P. Singh, V.V. Tyagi, M. Tanu Allen, H. Ihrahim and R. Kothari, Renewable and Sustainable Energy Reviews, 2011, 15, 4797. 2011, Elsevier [16]  

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Produced from Co l. Estimates of the cost of producing methanol from coal have been made by the U.S. Department of Energy (DOE) (12,17) and they are more uncertain than those using natural gas. Experience in coal-to-methanol faciUties of the type and size that would offer the most competitive product is limited. The projected costs of coal-derived methanol are considerably higher than those of methanol produced from natural gas. The cost of the production faciUty accounts for most of the increase (11). Coal-derived methanol is not expected to compete with gasoline unless oil prices exceed 0.31/L ( 50/bbl). Successful development of lower cost entrained gasification technologies could reduce the cost so as to make coal-derived methanol competitive at oil prices as low as 0.25/L ( 40/bbl) (17) (see Coal conversion processes). 

Alternative feedstocks for petrochemicals have been the subject of much research and study over the past several decades, but have not yet become economically attractive. Chemical producers are expected to continue to use fossil fuels for energy and feedstock needs for the next 75 years. The most promising sources which have received the most attention include coal, tar sands, oil shale, and biomass. Near-term advances ia coal-gasification technology offer the greatest potential to replace oil- and gas-based feedstocks ia selected appHcations (10) (see Feedstocks, coal chemicals). 

Gasification technologies for the production of high heat-value gas do not all depend entirely on catalytic methanation, that is, the direct addition of hydrogen to coal under pressure to form methane. 

The means by which synthetic gaseous fuels could be produced from a variety of biomass sources are variable and many of the known gasification technologies can be appHed to the problem (70,71,76—82). For example, the Lurgi circulatory fluidized-bed gasifier is available for the production of gaseous products from biomass feedstocks as well as from coal (83,84). 

Coal gasification technology dates to the early nineteenth century but has been largely replaced by natural gas and oil. A more hydrogen-rich synthesis gas is produced at a lower capital investment. Steam reforming of natural gas is appHed widely on an iadustrial scale (9,10) and ia particular for the production of hydrogen (qv). 

This process is one of the three commercially practiced processes for the production of acetic anhydride. The other two are the oxidation of acetaldehyde [75-07-0] and the carbonylation of methyl acetate [79-20-9] in the presence of a rhodium catalyst (coal gasification technology, Halcon process) (77). The latter process was put into operation by Tennessee Eastman in 1983. In the United States the total acetic anhydride production has been reported to be in the order of 1000 metric tons. 

J. P. Henly, Development and Commercialisation of the Dow Coal Gasification Technology, presented iu Japan and China by Dow Chemical, Sept. 1986. 

The indirect liquefaction basehne design is for a plant of similar size. Unhke the direct hquefaction basehne, the design focuses on producing refined transportation fuels by use of Sheh gasification technology. Table 27-17 shows that the crude oil equivalent price is approximately 216/m ( 34/bbl). Additional technological advances in the production of synthesis gas, the Fischer-Tropsch synthesis, and product refining have the potential to reduce the cost to 171/m ( 27/bbl) (1993 US dollars), as shown in the second column of Table 27-17. 

For over 40 years Texaco has been commercially involved in gasification. For regular feedstock, the Texaco gasification technology has proven its reliability and flexibility in over 100 plants throughout the world. 

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