Numerical Simulation Of Gas - Solid Two - Phase Flow And Semi - Dry Flue Gas Desulfurization Reaction

With the high speed development of society nowadays, acid rain, haze and a series of environmental problems have become increasingly concerned by people, a number of measures have been taken to control the emissions of various environmental pollutants. Coal dominates the energy consumption structure of our country, the sulfur component in coal would be caused great environmental pollution, flue gas desulfurization can effectively reduce environmental pollution after the coal combustion. Powder-particle spouted bed semi-dry flue gas desulfurization technology has been successfully applied in many fields and become a great application value and promising desulfurization technology, based on its simple structure, high desulfurization efficiency, low cost.Firstly, The gas-solid two phase flow behavior in spouted bed was simulated by introducing the particle momentum source term to modify axial pressure in the annular gap area in this article. The effects of axial pressure correction on spray form, fountain height, diameter of spout, minimum spouted velocity, and distributions of the particle velocity and particle concentration of fountain area in spouted bed were explored. The simulation values of the fountain height and the particle velocity distribution of fountain area and PIV experiment results were analyzed to determine the best of axial pressure correction parameter ka value under the system. The results showed that within a certain range, with the decrease of the value of ka,the minimum spouted velocity decreases, while the fountain height and the particle velocity of fountain area increases. Under the same operating conditions, when the value of ka was 0.694, the simulation results with the experimental results were very close.In addition, the numerical simulation method was adopted to investigate the effect of operating pressure on spouted height, the distribution of gas and solid velocity, diameter of spout and the distribution of solid volume fraction within the spouted bed in this paper. The results show that with the pressure increase, the spouted height increase under the same gas velocity, while the minimum spouted velocity decreased under the same static bed height. When the gas superficial velocity was 1.2Ums, with the increase of the pressure, the diameter of spout increases, the formation of spray spouted was faster and more stable, and different pressure has certain effect on the distribution of particle axial velocity and particle concentration.Water evaporation process and desulfurization reaction process were studied in the powder-particle spouted bed semi-dry flue gas desulfurization system, on the basis of the gas-solid two-phase flow, the mathematical and physical models of water vaporization process and flue gas desulfurization reaction process have been established through reasonable hypothesis and simplification of the system. Numerical simulation method was used to simulate the water evaporation and|the desulfurization reaction process, the desulfurization efficiency of the simulation and the experiment results of Ma et al [1,2,3] were analyzed. The results showed that water vaporization rate was high in spout and annular region because of high gas temperature, high gas velocity in spout region and large gas-liquid contact area, high gas flow rate, long water retention time in annular region. The main area where flue gas desulfurization reaction occurs was annular area. Desulfurization products were mainly concentrated in the annulus region and gas outlet. Under the same conditions, the desulfurization efficiency of simulation value is less than the experimental values, indicating that improving optimization model to realize the more accurate calculation of the process.