This paper was prepared for the Eastern Regional Meeting to be held in Columbus, Ohio, November 8–9, 1972. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.
The future of coal usage to alleviate the energy shortage depends on our ability to burn coal cleanly and to convert it to gaseous and liquid products. This paper discusses the state-of-the-art of coal conversion and reviews briefly by simplified flow sheets the major gasification and liquefaction processes. At present technology has not advanced beyond pilot plant or demonstration stages; even the optimistic experts predict that commercial operations will not be realized before the 1980's. Hence, a large and concerted effort is needed now to implement conversion of coal to gas and oil.
Rapid depletion of our oil and gas resources has focused attention on our vast reserves of coal as a source of clean, gaseous and liquid fuels. Several coal gasification and liquefaction processes are currently in various stages of development and it remains to be seen which will reach commercial operation first and which will prove to be most economical. Familiarity with this field is increasing rapidly, but a broadening front of developments makes it difficult to keep up. This paper discusses the fundamentals of coal gasification and liquefaction and reviews the current status of processes now under active development.
Coal is a rock composed mostly of organic matter (carbon, hydrogen, oxygen, sulfur acid nitrogen) and some mineral species. In order to convert coal to gas or liquid fuels, either carbon must be removed or hydrogen must be added to the coal molecule; precursors of pollutants, such as sulfur, must be converted to removable pollutants, such as sulfur, must be converted to removable compounds, and undesirable inorganic matter separated. As the fuel type changes from coal to liquid to gas, the C/H weight ratio decreases. For example, as given in Figure 1, in approximate terms, coal has a carbon-to-hydrogen weight ratio (C/H) of 16; crude oil, 7; fuel oil, 6; gasoline, 5; and natural gas, 4.
The aim of conversion processes usually is to add hydrogen to convert coal to a gaseous or liquid feedstock. Conversion of coal by removing carbon, such as by pyrolysis, will decrease the C/H ratio, but these processes are less efficient and non-selective. processes are less efficient and non-selective. In the United States, there are seven major processes to convert coal to pipeline quality gas and five processes to convert coal to liquid fuels (table 1). Simplified flow-sheets for these processes depict the essential features of each and the significant differences between them. In each case, the status of the project, whether laboratory, pilot plant or semi-commercial (demonstration), is pilot plant or semi-commercial (demonstration), is indicated.
In addition to these seven processes, there are several consortiums and partnerships of power, coal, oil, gas and earlier companies being formed to investigate fixed-bed, fluid-bed and entrained-bed coal conversion processes. processes.
