Combustion characteristics of dry coal slime powders in a fluidized bed

Aiming at exploring new techniques for coal slime combustion, the combustion kinetics of Dry Coal Slime Powders (DCSP) was firstly investigated by a thermogravimetric analyzer.Then, the combustion characteristics of the DCSP was further measured in a fluidized bed with a height of 2 000 mm and an inside diameter of 100 mm.The results showed that the combustion of DCSP can be well correlated by a first-order reaction kinetics.At the bed temperature 900℃ with 40 mesh quartz sand as the bed material, the axial temperature profile and the CO, SO₂, NO_x concentrations fluctuate significantly when u/u_mf>6, because the residence time of DCSP in the bed is too short to allow the complete combustion to be achieved at higher gas velocities.At lower gas velocities (u/u_mf<2) the fluidization quality is poor, the flammable fine coal slime powders accumulated in bed bottom lead to sudden and explosive combustions, causing the bed temperature to rise sharply.When u/u_mf is between 2 and 6, the CO, SO₂, NO_x all increase with the increase of u/u_mf.Experimental data also revealed that at the same Ca/S molar ratio, the SO₂ removal efficiency by in-bed limestone increase with the decrease of gas velocity, which is resulted from the increased residence time at lower gas velocities.