Synthetic fuels conversion

Synthetic Fuel. Solvent extraction has many appHcations in synthetic fuel technology such as the extraction of the Athabasca tar sands (qv) and Irish peat using / -pentane [109-66-0] (238) and a process for treating coal (qv) using a solvent under hydrogen (qv) (239). In the latter case, coal reacts with a minimum amount of hydrogen so that the solvent extracts valuable feedstock components before the soHd residue is burned. Solvent extraction is used in coal Hquefaction processes (240) and synthetic fuel refining (see Coal conversion processes Fuels, synthetic). 

Coal is used ia industry both as a fuel and ia much lower volume as a source of chemicals. In this respect it is like petroleum and natural gas whose consumption also is heavily dominated by fuel use. Coal was once the principal feedstock for chemical production, but ia the 1950s it became more economical to obtain most industrial chemicals from petroleum and gas. Nevertheless, certain chemicals continue to be obtained from coal by traditional routes, and an interest in coal-based chemicals has been maintained in academic and industrial research laboratories. Much of the recent activity in coal conversion has been focused on production of synthetic fuels, but significant progress also has been made on use of coal as a chemical feedstock (see Coal CONVERSION processes). 

In 1991, the relatively old and small synthetic fuel production faciHties at Sasol One began a transformation to a higher value chemical production facihty (38). This move came as a result of declining economics for synthetic fuel production from synthesis gas at this location. The new faciHties installed in this conversion will expand production of high value Arge waxes and paraffins to 123,000 t/yr in 1993. Also, a new faciHty for production of 240,00 t/yr of ammonia will be added. The complex will continue to produce ethylene and process feedstock from other Sasol plants to produce alcohols and higher phenols. 

In Germany, large-scale production of synthetic fuels from coal began in 1910 and necessitated the conversion of coal to carbon monoxide and hydrogen. 

Liquid Fuels. Liquid fuels can be obtained as by-products of low temperature carbonization by pyrolysis, solvent refining, or extraction and gasification followed by catalytic conversion of either the coal or the products from the coal. A continuing iaterest ia Hquid fuels has produced activity ia each of these areas (44—46). However, because cmde oil prices have historically remained below the price at which synthetic fuels can be produced, commercialization awaits an economic reversal. 

Petroleum refining, also called petroleum processing, is the recovery and/or generation of usable or salable fractions and products from cmde oil, either by distillation or by chemical reaction of the cmde oil constituents under the effects of heat and pressure. Synthetic cmde oil, produced from tar sand (oil sand) bitumen, and heavier oils are also used as feedstocks in some refineries. Heavy oil conversion (1), as practiced in many refineries, does not fall into the category of synthetic fuels (syncmde) production. In terms of Hquid fuels from coal and other carbonaceous feedstocks, such as oil shale (qv), the concept of a synthetic fuels industry has diminished over the past several years as being uneconomical in light of current petroleum prices. 

Goal Processing to Synthetic Fuels and Other Products. The primary approaches to coal processing or coal conversion are thermal decomposition, including pyrolysis or carbonization (5,6), gasification (6), and Hquefaction by hydrogenation (6). The hydrogenation of coal is not currently practiced commercially. 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

After 1973 the United States invested heavily in synthetic fuel research and development, hoping synthetics could sciwc as economical substitutes for crude oil. However, coal conversion is not profitable unless the price of crude oil is over 50 per barrel, which is why the processes developed were mothballed when world crude oil prices fell in the 1980s. 

The reason for the poor conversion efficiency to synthetic fuels is the high energy cost in liberating hydrogen from water (thermal dissociation, electroly-... 

The process will adversely affect air quality by releasing nitrogen oxides, sulfur oxides, carbon monoxides and other particulates into the atmosphere. Better control of the conversion conditions and better control of emissions can make the process cleaner, yet technology cannot do anything to curb carbon emissions. Since much of the carbon in coal is converted to carbon dioxide in the synthesis process, and is not part of the synthetic fuel itself, the amount of carbon dioxide that will be released to the environment during combustion is 50 to 100 percent more than coal, and around three times more than natural gas. 

South African coals differ from most Northern Hemisphere coals in their geological age, unusual petrology and their high mineral matter content. If these coals are to be used for conversion to synthetic fuels then criteria must be found to enable predictions of their behaviour under liquefaction conditions to be determined. This paper describes the hydrogenation of a number of South African coals using two different techniques, to ascertain whether well known coal properties can be used to predict their hydrogenation behaviour. 

Second-generation biofuel technologies make use of a much wider range of biomass feedstock (e.g., forest residues, biomass waste, wood, woodchips, grasses and short rotation crops, etc.) for the production of ethanol biofuels based on the fermentation of lignocellulosic material, while other routes include thermo-chemical processes such as biomass gasification followed by a transformation from gas to liquid (e.g., synthesis) to obtain synthetic fuels similar to diesel. The conversion processes for these routes have been available for decades, but none of them have yet reached a high scale commercial level. 

Del Bel, E, Friedman, S. and Yavorsky, P.M., "Economic Feasibility of the Conversion of Organic Waste to Fuel Oil and Pipeline Gas", in "Synthetic Fuels Processing Comparative Economics", A.H. Pelofsky (Ed.), Chap. XX, 443-459,... 

The importance of sulfur as an industrial chemical is discussed and forecasts of projected sulfur demand in the U.S. are given. Three processes for conversion of coal and oil shale to synthetic fuels are examined in some detail to show how the sulfur in the original feedstock material is recovered as elemental by-product sulfur. Three synthetic fuel scenarios are examined and their potential impact on sulfur availability with current and projected markets to the year 2000 are examined. 

The projected synthetic fuels program involving conversion of coal and shale may have a profound effect on available supplies of sulfur and supply patterns. Desulfurization of intermediate process streams to hydrogen sulfide will be required to meet environmental standards. Conversion of intermediate hydrogen sulfide to elemental sulfur will be carried out as in the case of crude oil desulfurization. Elemental sulfur represents the preferred sulfur... 

By the process of carbonisation of biomass and subsequent gasification of the volatile products from carbonisation, a portion of carbon element in biomass is stabilised as solid carbon, and the remaining portion of carbon is converted by gasification and conversion process to synthetic fuels, which can replace fossil fuels for energy supply. 

FIGURE 9 Biomass conversion processes. [Reprinted with permission from Probstein, R. F., and Hicks, R. E. (1990). Synthetic Fuels, pH Press, Cambridge, MA.]... 

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