Lignite production

Goal Production. In 1860 world coal production was 122 x 10 t/yr. Production increased to 1140 x 10 t in 1913, giving a 4.2% aimual average rate of increase. The rate has slowed and been erratic since that time. Statistical data on world coal production from 1860 to 1960 is given in Reference 81. World coal and lignite production rose to about 4.7 x 10 t in 1988 (1). 

The extent of lignite production is generally not proportional either lo total resources or to know n economic reserves. Lack of energy alternatives is a strong motive to developments in lignite production. 

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

Hydrocarbon resources can be classified as organic materials which are either mobile such as cmde oil or natural gas, or immobile materials including coal, lignite, oil shales, and tar sands. Most hydrocarbon resources occur as immobile organic materials which have a low hydrogen-to-carbon ratio. However, most hydrocarbon products in demand have a H C higher than 1.0. 

Worldwide production of lignite was over 1.13 x 10 tons in 1990 (U.S. production was 8 x 10 t). U.S. production has risen at ca 2% yr in the early 1990s. The world s proved lignite reserves can be recovered under local economic conditions with existing available technology, and were over 3.8 x 10 t in 1990, representing almost 300 years of production in 1990 terms (3,4). 

The tar yield is usually higher for lignite than for more mature coals. Tar yields are important in determining selection for carbonization and for Hquid fuel production by pyrolysis. 

Rates of production of lignite have continued to increase since 1960. In 1980 374 x 10 tons of coal equivalent (tee) were produced. One tee is the amount of energy available from combustion of a metric ton of coal having a heat content of 29.3 GJ, ie, 29.3 MJ/kg (12, 600 Btu/lb) (3). In 1989 this figure had risen to 460 x 10 tee. This 23% increase is somewhat less than the 28% increase in hard coal production during this period (see Coal). In 1990 the 1130 X 10 metric tons of lignite produced worldwide represented 24% of the total coal production. 

When energy alternatives are available, a compromise between cost and quaHty is often realized. Blending of coals can be used to achieve more desirable quaHties. For example, lignite from the former Yugoslavia has been blended with, and even substituted for, the highly caking Rasa coal used for coke production in the iron (qv) and steel (qv) industries. 

Hard coal is more important ia most of the western European countries with the exception of Austria and Italy. No lignitic coal production was iadicated ia 1989 for the Netherlands, Denmark, Belgium, Sweden, Norway, and the United Kingdom (24). 

North America.. In the United States, lignite deposits are located in the northern Great Plains and in the Gulf states. Subbituminous coal is found along the Rocky Mountains. The western half of North Dakota has about 74% of the nation s resources, Montana 23%, Texas 2%, and Alabama and South Dakota about 0.5% each. The lignite resources to 914 m represent 28% of the total toimage of all coal deposits in the United States. The lower cost and low sulfur content have contributed to rapid growth in production. 

The lignite deposits of North Dakota and Montana extend into Canada as far as Saskatchewan. Canadian deposits are also located in Alberta, Yukon, the Northwest Territories, Ontario, and Manitoba. Production by open-cast mining, ca3.5 x 10 t in 1975, was 10.8 x 10 t in 1989. 

The price of lignite pet mined ton or pet heat unit is lower than that for higher rank coals. The market for all coals is primarily as boilet fuel for electric power production. Prices ate generally estabUshed by contracts between utiUty and suppHet before mining begins. 

Plants for briquette production exist in the eastern part of Germany, AustraHa, and India. German transport costs pet unit of heating value ate about 40% less for briquettes than for lignite. 

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