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Solid Circulation and Gas Bypassing in an Internally Circulating Fluidied Bed with an Orifice-Type Draft Tube

Hong-Sik Ahn¹ Woon-Jae Lee¹ Sang-Done Kim¹ Byung-Ho Song^{1 2}

¹Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, Taejon, Korea ²Department of Chemical Engineering, Kunsan National University, Kunsan, Korea

Korean Journal of Chemical Engineering, September 1999, 16(5), 618-623(6), 10.1007/BF02708141

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Abstract

The effects of orifice diameter in the draft tube, particle size, gas velocities and bed height on the circulation rate of solids and gas bypassing between the draft tube and annulus have been determined in an internally circulating fluidized bed(i.d., 0.3 m ; height, 2.5 m) with an orifice-type draft tube. Aconical shape gas separator has been employed above the draft tube to facilitate the separation of gases from the two beds. The circulation rate of solids and the quantity of gas bypass from the annulus to draft tube show their minimums when the static bed height is around the bottom of the separator. The circulation rate of solids increases with an increase in orifice diameter in the draft tube. At fixed aeration to the annulus, gas bypassing from the draft tube to annulus sections decreases, whereas reverse gas bypassing from the annulus to the draft tube increases with increasing the inlet gas velocity to the draft tube. The obtained solids circulation rate has been correlated by a relationship developed for the cocurrent flow of gas and solid through the orifice

Keywords

Circulating Fluidized Bed Draft Tube Orifice Gas Bypass Solids Circulation Rate

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