Experimental Study And Numerical Simulation Of Poly-generation Technology Devices Of Entrained-flow Coupled With Fluidized-bed Coal Gasification For Fine Coal Pyrolysis

In view of shortage of large scale utilization technology of semi-char from coal pyrolysis and inefficient recycling of the synthetized gas heat from coal gasification, so the poly-generation technology of entrained-flow bed(EB) coupled with fluidized-bed(FB) coal gasification for fine coal pyrolysis(EBCFB pyrolysis technology)has been proposed. The two phase flow and transfer laws in entrained-flow bed for fine coal pyrolysis are the very important fundamental for this process design. The cold test is the effective method to study the gas-solid two phase flow process. A set of cold experimental devices for EBCFB pyrolysis technology has been setup according to the design data. The gas-solid two phase flow transfer laws in the entrained bed were studied by methods of cold test and numerical simulation.The broken corns, rape seed and wheat were used to simulate fine coal for cold test on the cold test devices. And the influences of particle circulation rate and air flow rate on pressure drop were studied on the condition of single size particles feeding and different size particles mixture feeding respectively. The results indicated that the pressure drop increased with the particle circulation rate at the same air volume, and increased with the air volume at the same particle circulation rate. The mathematical model has been established by using method of dimensional analysis, which gives a theoretical foundation for design of entrained flow bed in EBCFB pyrolysis technology. This model indicated that the main influence factors of pressure drop are particle circulation rate, air quantity, properties of material, and structure parameters of entrained flow bed, and so on.The particle velocity in EB were measured by particle image velocimetry(PIV). The result showed that the particle velocity in EB has little change with the increasing of particle circulation rate while air volume has no change, but increased with the air volume while particle circulation rate has no change, and decrease with the increasing of particle size while both of particle circulation rate and air volume have no change. Coal pyrolysis kinetics and energy conservation equation are solved by using MATLAB software, and the time for the completed pyrolysis of Shenmu fine coal in EB was obtained through this calculation, finally the height of entrained flow bed pyrolysis reactor for Shenmu fine coal has been calculated on the basis of the pyrolysis time and particle velocity in EB. The lowest height of entrained flow bed pyrolysis reactor for0-3mm Shenmu fine coal was6.28m.The particle concentration distribution in the EB system has been simulated by using Fluent software. Gambit was firstly used to plot grid of the EB system, and the system was simulated and analyzed by using the Eulerian two-fluid model in2D and3D model respectively. It was found that the particle flow properties are coincidence with core-annulus model at radial direction, and one-dimensional axial model at axial direction. The average particle concentration in the EB system is about0.01. Because of the influence of the T type forced outlet, the particle concentration on the opposite side of outlet is higher. The average particle concentration in the system of EB coupled with FB is up to about0.05, and the particle gathered phenomenon was also found.