The Flow And Heat Transfer Performance Of The Combined-Bed Reactor For Oxygen-Heating Calcium Carbide Production

Calcium carbide is one of the most important fundamental chemical raw material. Calcium carbide and its down-stream industry are very important in China. Traditional electro-thermal furnace costs too much energy and brings pollution. To solve this problem, a new oxygen-heating calcium carbide production process has been presented by professor Liu Zheng Yu. Different kinds of conceptual reactor models for this new process has been developed. This paper concentrates on the combine-bed reactor model and explores performance of the distributing device in the reactor and the flow and heat transfer performance of the reactor with some experiment and numerical simulation.First we set up a cold model of the reactor and designed different distributing devices. Then we did some experiment on particle flowing and distributing performance in different operating conditions. The results suggest that:(1)The average mass flux of particles is controlled by the shape of open-hole of distributing device, increases with the opening of the fan-shaped opening distributing device, and changes little with the rotor speeds of distributing devices and static bed height. The changing ratio of average mass flux of particles is not completely the same as the changing ratio of the open-hole number of the distributing device.(2)The particle radial distribution shows an M-shaped distribution when using the fan-shaped opening distributing device, and is nearly uniform when using rectangle opening distributing device. The distribution changes insignificantly at varying rotor speeds of the distributing devices, bed height and open-hole of distributing devices.(3)The coefficient of variation changes insignificantly at varying rotor speeds of the distributing devices, bed height and open-hole of distributing devices. The coefficient of variation of fan-shaped opening distributing device is about1.0-1.1while the coefficient of variation of rectangle opening distributing device is about0.4-0.5.(4)Properties of particles have little influence on the distribution features of distributing devices.Second, we built a viscous flow model to describe particle flow in simple moving bed. Also we did some experiment to verify the model and confirmed the undetermined viscosity coefficient in the model. After substituting the viscosity coefficient, we simulated particle flow passing different distributing device in the dense-phase zone of combined-bed. The results shows that:(1)Comparing experiment and simulation results, we confirmed the undetermined viscosity coefficient μs=0.03Pa·s, and proved the correction of viscous flow model.(2)The particle flow of moving-bed is uniform and the flow pattern is piston flow; at the bottom of moving bed, the flow pattern is convergence flow.(3) At most upper part of bed, the flow pattern is piston flow; at the bottom part of bed, distribution of axial velocity on radial direction shows an W-shaped distribution.Finally, in order to describe the pre-designed combine-bed model, we simulated heat exchange performance of the dense-phase zone of combined-bed and flow and heat transfer performance of the whole combined-bed. The results shows that:(1)The length of thermo-osmosis part of dense-phase zone increase with time. Particle with temperature gradient also increase with time until reaching a stable value. After heating110minutes, the whole dense-phase zone was heated. Preheat rate of dense-phase zone is about106kg/min.(2) The length of thermo-osmosis part of dense-phase zone increase and bed temperature increase with inlet velocity and Bed porosity.(3)In dilute-phase section the pressure distribution is uniform while in dense-phase section the pressure drop is high.(4)Velocity field at injection nozzle is complex while the left parts get almost the same velocity distribution.(5)At the bottom of burning zone, the temperature is about2300K-2700K and completely satisfies the temperature of calcium carbide production. After leaving the burning zone, temperature gets lower to about2200K-1300K in dilute-phase section. In dense-phase section the temperature is about 1300K-400K.(6)Particles get very short but nearly the same settling time. Particle temperature changes little in the whole dilute-phase section.