Anthracite, burning

Fig. 3. Comparison of burning profiles for coals of different ranks where ( ) represents anthracite (-) semianthracite ( ) LV bituminous (° ) HV...

The fuel flows at right angles to the air flow. Only a small amount of air is fed at the front of the stoker, to keep the fuel mixture rich, but as the coal moves toward the middle of the furnace, the amount of air is increased, and most of the coal is burned by the time it gets halfway down the length of the grate. Fuel-bed depth varies from 100 to 200 mm (4 to 8 in), depending on the fuel, which can be coke breeze, anthracite, or any noncaking bituminous coal. 

The rank of coal (maturity) is an important factor that affects PAH emissions from residential combustion. PAH emission from various coals is found to have a relationship with their volatile contents, and the complete combustion of coals with a high volatile content is more difficult to achieve. Bituminous and sub-bituminous coals with high volatile content yield more PAHs when burned at low temperatures, such as residential combustion, while anthracite coal containing very little volatile matter can burn more completely and emit PAHs with a mass that is three orders of magnitude lower than bituminous coal. Smoky coal, which is burned as fuel for cooking and heating in unvented homes, produces combustion emissions composed primarily of parent PAHs and alkylated PAHs. 

Because of the small samples often generated, ultimate analysis of selected density fractions was performed with a modified Perkin-Elmer 240, C, H, N, analyzer (modification XA by Control Equipment Corp.) using a modified burn procedure which includes increasing the time of burn and the amount of 02 used in the burn. Good correlation for carbon and hydrogen (r2 = 0.98) with ASTM methods was found for a range of coals from sub-bituminous to anthracites. 

One kilogram of anthracite coal when burned evolves about 30,500 kJ. Calculate the amount of coal required to heat 4.0 kg of water from 20°C to the boiling point at 1 atm pressure, assuming no loss of heat in the process. 

Traveling-grate furnaces can also be employed. In this process, anthracite briquettes are fed to a depth of about 15 cm. After ignition by the previous charge, the coal briquettes are covered by ore/coal briquettes. The latter are dried with waste heat from the furnace. Zinc vapor evolves and burns in a combustion chamber, and the spent clinker falls into containers for removal. 

Use of petroleum coke would also require greater logistical, handling, and purchasing flexibility by a utility. With current technology, petroleum coke is burned as a blend with coal, anthracite, fuel oil or natural gas. This requires additional mixing equipment and storage space which may not be compensated for by lower petroleum coke prices. 

Bituminous and sub-bituminous coals account for the major share of all coal produced in the United States. In 2000, production of all types of coal totaled almost 1.1 billion short tons, of which about 95 percent was bituminous or sub-bituminous (Fig. 19.1). Despite its clean burning characteristics, anthracite, most of which is mined in northeastern Pennsylvania, accounts for a diminishing share of total coal production. Figure 19.2 presents data on coal consumption in the United States. 

Uses of bituminous coals as ingredients of expls are discussed under Coal Dust and Its Uses. Anthracitic (also known as hard coal) is a variety of coal contg the highest percent of fixed carbon (86 to 98%) and very little of volatile matter it is blk in color with a brilliant luster it burns with a short blue flame giving off very little smoke or odor used as household industrial fuel,... 

Lapham, D. M., Barnes, J. H., Downey, W. F., Jr., and Finkelman, R. B., 1980, Mineralogy associated with burning anthracite deposits of eastern Pennsylvania Mineral Resources Report, V. 78, p. 1-82. 

The rate of combustion is the weight of coal burned per square foot of grate per hour. It may be expressed by Rc == m /d, where d = draft between ashpit and furnace, in inches of water, and m = 17 to 32 for anthracite (increasing with the size), 80 and 60 for bituminous run-of-rniiie and slack, and 50 for run-of-mine semi-bituminous coal. 

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