| Compared with the existing technology, the oxygen-fuel method to produce calcium carbide process which use powder raw material has a very big advantage in the energy consumption, resource utilization and pollution emissions. If we can develop a suitable reactor for the oxygen-heating method to produce calcium carbide process, there could form a route to make utmost use of coal in hierarchical transformation range.In this paper, we study on the entrained-flow reactor’s performance in terms of both modeling and experiment. Based on the combined-bed reactor we design a new combined-bed reactor without distributing device, and study their performance by mathematical model.First, we study the motion of particles and temperature profile of gas-solid phase and investigate the rationality of the design parameters of the reactor by establishing mathematical model for gas-solid phase movement and heat transfer in the preheating zone. We study the heat transfer process from burning zone to the reaction zone by establishing mathematical model for materials slag layer in the reaction zone. We obtain gas phase flow field in the entrained-flow reactor by IFA300multi-channel hot film anemometer. The results suggest that:(1) The dp=28.2μm coke particles and dp=20.7μm calcium oxide particles are the minimum size of solid particles can pass through the preheating zone, these parameters can be used taken as reference to select the particle size for the entrained-flow reactor.(2) The particles and the gas phase get thermal equilibrium where the particles’displacement is more than5m, but the height of the preheating zone is10.3m, so we can reduce the height to lessen the equipment investment.(3) The residence time and heat transfer of particles have been less affected by the particles’ initial velocity.(4) The thermal resistance of materials slag layer in the reaction zone is very small, The materials slag layer doesn’t hinder the heat transfer process from burning zone to the reaction zone.(5) The gas phase flow field in the entrained-flow reactor is good for the combustion of coke and the heat-exchange in the preheating zone.Next, we study the heat transfer of larger particles countercurrent moving bed in the dense-phase zone above distributing device, then; we obtain an analytical solution and a numerical solution of the process can provide design basis for such process. We also obtain the temperature distribution of gas and solid and the mole fraction of each constituent in the gas phase along the centre axis in the tow combined-bed reactor by mathematical model. The results suggest that:(1) The heat transfer of larger particles countercurrent moving bed is controlled by three dimensionless parameters:φ,βand γ. When the particles’size is big(φ>3.3), the particle internal resistance become the control step of heat transfer between gas and solid phase, in comprehensive consideration of the bed permeability and bed pressure drop, smaller particles is a better choice. The analytical solution of temperature distribution can provide more accurate design basis to moving-bed heat exchangers.(2) From the result of the model, the combined-bed reactor concept model with distributing device can satisfy the need of oxygen-heating method to produce calcium carbide, oxygen and coke for combustion can complete combustion, carbon monoxide composition in the gas phase is also high.(3) For the reactor without distributing device, oxygen and coke for combustion can complete combustion in the combustion zone. The reactor can satisfy the oxygen-heating method well.(4) Due to the combustion inhomogeneity of the particles, we can make coke mainly distributed on the outer edge of the particles.(5) We obtain the preliminary design size of the combined-bed reactor. The reactor without distributing device is smaller than the one with it. |
PDF Full Text Request