Abstract

Underground coal gasification appears to be one of the most attractive sources of feedstock to produce synfuels from coal because the process can produce methanol and substitute natural gas at prices competitive with existing energy sources. Savings in the form of reduced oil and gas imports from the first year of commercial operations would pay for the entire R&D budget necessary to perfect the underground coal gasification process.

The technical feasibility of underground coal gasification has been well established by 21 small scale field tests carried out in the U.S. since 1973. Cost estimates based on the resultant data are encouraging. Methanol is estimated to cost $0.52/gal (without tax) and SNG is estimated to cost $5.19/10⁶ Btu, all in 1982 dollars. The environmental effects associated with the technology appear to be acceptable. Successful commercialization of the process would probably triple the proven reserves of U.S. coal, which would be sufficient to last for hundreds of years.

At this stage of development, underground coal gasification is a high risk technology and will remain so until large scale field tests are successfully carried out. These tests are recommended by the Gas Research Institute and by the American Institute of Chemical Engineers. A seven year program costing about $200 million would permit initial commercial production in ten years.

A recent small scale field test, the Centralia Partial Seam CRIP test, was very successful. Steam and oxygen was employed to gasify 2000 tons of coal over a 30 day period, producing 250 Btu/scf gas. A larger scale test is presently being planned for Centralia, Washington, involving the U.S. DOE and an industrial consortium led by the Gas Research Institute.

This underground coal gasification review is based in part on a recent status report (Stephens et al, 1985). We thank the publishers of Mineral Processing and Technology Review for granting permission to reproduce portions of that article.