Abstract

Lignite and brown coal are intermediate between peat and bituminous coal. These coals are high in moisture content, low in density, and frequently low in sulfur, and tend toward spontaneous ignition in air. The brown coals are geologically younger than the firmer, fibrous lignite. Deposits, from 2–60 million years old, are found mainly in Russia, central Europe, Australia, and the United States. Proved reserves, about 300 billion metric tons, represent close to a 290 year supply at 1990 production rates.

Most lignite and brown coal is burned for electric power generation and mines are usually close to utilization sites for both economic and safety reasons. Lignite briquettes are also used for domestic heating in various parts of the world. Processes for lignite and brown coal conversion to synthesis gas for feedstock utilization, to both gaseous and liquid fuels, and to materials for use as soil conditioners, wax, and so on, are described.