54 THE FIVE-YEAR OUTLOOK 



Conversion from oil and natural gas to coal as a source 

 of electricity or industrial process heat would be facili- 

 tated by technologies that bum coal more efficiently and 

 leave behind fewer solid and gaseous wastes. Fluidized- 

 bed combustion, in which coal mixed with limestone (to 

 absorb sulfur) is burned while being suspended by com- 

 pressed air above the floor of the furnace, is practically a 

 commercial option today. In this process coal is burned at 

 a substantially lower temperature than in conventional 

 combustion systems, thus reducing considerably the 

 emission of oxides of nitrogen. Promising research into 

 the physical and chemical processes occurring in coal 

 combustion should permit considerable improvements in 

 the fluidized-bed process after commercialization. Re- 

 search of this type is also expected to facilitate the de- 

 velopment and commercialization of other advanced coal 

 burning systems (ENERGY). 



SYNTHETIC FUELS 



The capitalization costs for new synthetic fuels industries 

 will be enormous. Thus, the rate at which synthetic fuel 

 production from coal penetrates the market will depend 

 critically upon the projected prices for alternative and 

 gaseous liquid fuels — i.e. , natural gas, petroleum deriva- 

 tives, and fuels from heavy oils, tar sands, and shales. 

 Sometime during the late 1980s, as processes for convert- 

 ing coal into gaseous and liquid fuels are commercialized, 

 coal in these forms may begin to replace oil and natural 

 gas in many applications. 



The need for synthetic fuels made from coal has been 

 felt in the past. Production of coal gas by reaction with 

 steam became important in Europe and the United States 

 after 1861. Germany built a number of coal liquefaction 

 plants before World War II, and small-scale coal liquefac- 

 tion feasibility studies were carried out in the United 

 States during the 1930s and, again, in the late 1940s. The 

 discovery of new, easily exploitable reserves of natural gas 

 and petroleum, with consequent price reductions for the 

 fuels derived from them, precluded large-scale develop- 

 ment of these pilot synthetic fuels efforts. But they 

 provided a scientific and technological base for further 

 development . If there were no economic or environmental 

 constraints, the United States could produce enough syn- 

 thetic fuels to eliminate almost all imports, slow the 

 consumption of domestic oil, and develop a substantial 

 synthetic fuel export trade. Indeed, the availability of 

 these fuels would be a crucial factor in helping Western 

 Europe and Japan reduce their own petroleum imports. 

 However, there are financial and environmental con- 

 straints, and science and technology will have to provide 

 means for overcoming them. A primary need during the 

 present decade is to learn more about different processes 

 for producing synthetic fuels and about how to use dif- 

 ferent types of synthetic fuels in a variety of applications 

 so that a range of viable alternatives will be available when 



large-scale commercialization becomes feasible 

 (NRC-15). 



The basic chemistry that underlies synthetic fuel pro- 

 duction from coal is relatively simple. Coals are com- 

 posed primarily of carbon and hydrogen, with smaller 

 amounts of oxygen and other inorganic elements , depend- 

 ing on the type of coal. A number of chemical reactions 

 occur when coal is raised to a sufficiently high tempera- 

 ture, including reactions that produce gaseous and liquid 

 hydrocarbons (carbon-hydrogen compounds) that are usa- 

 ble as fuels. However, straightforward heating of coal also 

 yields (in addition to solid char) a wide range of other 

 gaseous and liquid compounds, most of which have too 

 low a ratio of carbon to hydrogen to serve as good fuels. 

 Efficient production of crude gases or liquids from which 

 usable synthetic fuels can be refined requires, therefore, 

 that additional hydrogen be available in the process. This 

 hydrogen can be supplied in its pure, gaseous form. 

 Alternatively, hydrogen can be extracted from water in the 

 production process, in which case compounds containing 

 oxygen as well as hydrocarbon compounds are produced. 

 The same basic processes can be used to make synthetic 

 fuels from peat or wood. 



Commercially demonstrated processes are now avail- 

 able for producing usable synthetic gas from coal, and 

 planned research and development efforts should demon- 

 strate, within the next 5 years, improved process in terms 

 of efficiency, reliability, and environmental acceptability 

 (NRC-15; ENERGY). The first step in all these processes 

 is to combine coal with steam (as a source of hydrogen) 

 and either pure oxygen or air to yield a mixture of carbon 

 monoxide, hydrogen, small amounts of methane, nitro- 

 gen (if air is used instead of oxygen) and some other 

 contaminants — primarily compounds of nitrogen and sul- 

 fur If the nitrogen and contaminants are removed, the 

 resultant gas can be used directly as a fuel. Since the 

 heating value of this gas is considerably less than that of 

 natural gas and its transportation costs higher, its use for 

 such purposes is expected to be limited. Gasified coal is, 

 however, expected to be important for other applications: 

 as a source of hydrogen for coal liquefaction; for con- 

 version to methane (equivalent to natural gas); for the 

 production of alcohol, particularly methanol; and, per- 

 haps, for synthesis into gasoline and diesel fuel, and as a 

 source of petrochemical feedstocks. Since conversion of 

 coal to such usable end products by means of gasification 

 involves multiple steps, efficiency can be increased con- 

 siderably by carrying out several steps at the same vessel. 

 Increased efficiencies of this sort appear to be possible. 

 Their implementation will depend to a large degree on the 

 markets for the output of first-generation gasification 

 plants (NRC-15). 



The commercialization of direct coal liquefaction is 

 less advanced than coal gasification. However, large pilot 

 plant programs are under way which, given sufficient 



