Combustion of coal in fluidized bed

V SUMMARY Master Thesis COMBUSTION OF COAL IN FLUIDIZED BED Neslihan DEVECİ Fırat University Graduate School of Natural and Applied Sciences Department of Chemical Engineering 1994, Page : 80 Studies aimed making profitable use of less valuable coals for producing cheaper energy has increased. Fluidized-beds which could burn wastes containing up to 85 % inert material, has been accepted the most suitable burning systems. The most important advantages of fluidized-beds are easier controlling of atmosferic pollutants in the flue gas and easy and rapid heat transfer in the bed. Studies on fluidized-bed combustion has included subjects such as releasing and burning of volalities, determining tha mechanisms controlling the combustion of remainder char. In this study, vol ali ties and carbon combustion times of single partic les, which ranged in size between 1,70-15 mm, of Şırnak-Cizre lignite, Tuncbilek lignite and Zonguldak bituminous coal were determined in a fixedu ?/I bed and a fluidized bed of sand particles whose density was 2,638 g/cm3. Moreover the change of carbon combustion time with bed temperature and air velocity was investigated. In the second part of the study, combustion rates of carbon which was continueously fed in the fluidized bed were estimated, and these were com pared with rates computed numerically by using double resistance theory. In addition to the experimantal studies, carbon combustion times have been calculated using a mathematical model for the same conditions, in order to describe the mechanism of combustion (by diffusional kinetic, che mical kinetic or both of them). in the study it has been found that volalities combustion was controlled by chemical kinetic whereas carbon combustion was controlled by diffusio nal kinetic. It has been shown that change of bed temperature hasn't effec ted the burning time of coals which undergo swelling when heated, but the burning time of coals which retain their original size has decreased with the bed temperature. Air velocity did'nt effect the burning times of coals appreciably. Besides these it has been concluded that the ash contents of coals did greatly effect combustion times. Thus burning times of lignite char partic les, which might be expected to burn faster due to higher reactivity, could increase with the quantity of ash.