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A pulverized coal-fired boiler is an industrial or utility boiler that generates thermal energy by burning pulverized coal (also known as powdered coal or coal dust since it is as fine as face powder in cosmetic makeup) that is blown into the firebox. The basic idea of a firing system using pulverised fuel is to use the whole volume of the furnace for the combustion of solid fuels. Coal is ground to the size of a fine grain, mixed with air and burned in the flue gas flow. Biomass and other materials can also be added to the mixture. Coal contains mineral matter which is converted to ash during combustion. The ash is removed as bottom ash and fly ash. The bottom ash is removed at the furnace bottom. This type of boiler dominates the electric power industry, providing steam to drive large turbines. Pulverized coal provides the thermal energy which produces about 50% of the world's electric supply. ==History== Prior to the developments leading to the use of pulverized coal most boilers utilized grate firing where the fuel was mechanically distributed onto a moving grate at the bottom of the firebox in a partially crushed gravel like form. Air for combustion was blown upward through the grate carrying the lighter ash and smaller particles of unburned coal up with it, some of which would adhere to the sides of the firebox. In 1918 The Milwaukee Electric Railway and Light Company, later Wisconsin Electric, conducted tests in the use of pulverized coal at its Oneida Street power plant. These experiments helped Fred L. Dornbrook to develop methods of controlling the pulverized coal's tarry ash residues with boiler feed water tube jackets that served to reduce the surface temperature of the firebox walls and allowed the ash deposits be easily removed. This plant became the first central power station in the United States to use pulverized fuel. The Oneida Street power plant near Milwaukee's City Hall was subsequently decommissioned and renovated in 1987. It is now the site of the Milwaukee Repertory Theatre. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pulverized coal-fired boiler」の詳細全文を読む スポンサード リンク
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