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Theoretical and Experimental Investigation of Micro Feeding Technology on a Drop Tube Furnace

Coal particles are supplied to drop tube furnace (DTF) with a designed shaftless screw micro feeder. The condition of individual particles in furnace, which demands small particles size (102μm) and low flow rate for micro feeder，is desired to reaction mechanisms research. When particle size is less than 1mm, the interparticle forces such as van der Waals interactions have enormous effect on flow behavior of particles, so it is difficult to provide continuous and steady particles flow at low flow rate. In this paper, the micro feeder uses shaftless spring as its feeding element. To simulate dispersed particles flow, the feeding rate of coal particles should be decided by feeding coefficient M and is controlled by variable rotation speed of screw. The corresponding simplified model of feeding rate is presented, and interparticle forces are evaluated by the velocity coefficient . A vibrating metal rod is inserted into the middle of the shaftless screw to avoid particles agglomeration, and particle flow stability is also effectively improved. The given results show good linearity and stability of micro feeder. Moreover, the influences of the particle properties such as particle size and particle moisture content on the feeding rate are also investigated.