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Additionally, specific physical and mechanical properties of coal and particular carbonization properties The calorific value Q of coal [kJ/kg] is the heat liberated by its complete combustion with oxygen. Q is a complex function of the elemental composition of the coal [citation needed]. Q can be determined experimentally using calorimeters.
The raw coal is then fed into the pulverizer along with air heated to about 650 °F (340 °C) from the boiler. As the coal gets crushed by the rolling action, the hot air dries it and blows out the usable fine coal powder to be used as fuel. The powdered coal from the pulverizer is directly blown to a burner in the boiler.
The Coldry Process is applied to brown coal with a typical moisture content of 60 per cent by weight and transforms the coal into a densified coal product of equal or better calorific value (5,800 kcal/kg) to typical export quality black coal, with less ash and sulfur content. Black coal equivalent derived from brown coal is ostensibly a ...
The rank of coal is correlated with its geologic history, as described in Hilt's law. In the ASTM system, any coal with more than 69% fixed carbon is classified by its content of carbon and volatiles. Coal with less than 69% fixed carbon is classified by its heating value. Volatiles and carbon are on a dry mineral free base; heating value is ...
The products from the air cycle contain non-calorific nitrogen and are exhausted out the stack while the products of the steam cycle are kept as blue water gas. This gas is composed almost entirely of CO and H 2, and burns with a pale blue flame similar to natural gas. BWG has a calorific value of 11 MJ/m 3 (300 BTU/cu ft).
An anthracite pile in Trevorton, Pennsylvania. Anthracite derives from the Greek anthrakítēs (ἀνθρακίτης), literally "coal-like". [9] Other terms which refer to anthracite are black coal, hard coal, stone coal, [10] [11] dark coal, coffee coal, blind coal (in Scotland), [7] Kilkenny coal (in Ireland), [10] crow coal or craw coal, and black diamond.
Young coals (brown coal, lignite) are not black. The two main black coals are bituminous, which is more abundant, and anthracite. The % carbon in coal follows the order anthracite > bituminous > lignite > brown coal. The fuel value of coal varies in the same order. Some anthracite deposits contain pure carbon in the form of graphite.
Thus methane has an HHV (Higher heating value) of 55.50 MJ/kg, the highest value of common fuels. Diesel fuel has an HHV value of 44.80 MJ/kg and anthracite coal a value of 32.50 MJ/kg. Moisture and ash-free firewood has a lower value of 21.70 MJ/kg while dry peat has the lowest value of all common fuels of about 15.00 MJ/kg.