Numerical Simulation And Experimental Studies Of The Coarse-fine Particle Composite Desulfurization

SO2pollution is one of the main "culprit" of air pollution. As a major source of SO2emission, coal-fired power plants have been responsible for the emission reduction task tomeet the increasingly stringent emission control of air pollution. Limestone-gypsum wet fluegas desulfurization(FGD) was widely used in most power plants with the technology ofmaturity and stability etc. However, this system has disadvantages of high operating costs andlarger areas. How to improve the desulfurization efficiency, while reducing energyconsumption has become a directions of system optimization. This paper presents coarse/fineparticle composite wet flue gas desulfurization(FGD) methods. Through numerical simulationand experimental analyses, validation of the method were studied and analyzed.Through analyzed the process of SO2absorption reaction in the spray tower ofLimestone-gypsum wet FGD systems, the effects of operating parameters and structuralparameters on desulfurization efficiency was studied. On this basis, a coarse/fine particlecomposite desulfurization method was proposed. The method combined the coarse spray ofmechanical nozzles (set A, B, C layer) and the fine spray of novel two-fluid nozzles (set Dlayer), the contact area of gas-liquid reaction got increased; novel two-fluid nozzles werearranged tangentially, and fine particles can form a swirl flow, the strength of flow fluidturbulence was increased, mass transfer process was promoted, desulfurization efficiency canbe improved overall. Meanwhile, the fine particle layer have advantages of a smaller numberof spray nozzles and slurry pump power, which can reduce the energy consumption ofdesulfurization system.Based on the actual situation of Spray tower of a power plant, the coarse/fine particlecomposite desulfurization method got numerical simulation and analyses by FLUENTsoftware. Comparisons were taken among spray combinations of ABC, ABCD and ABD, gasflow velocity and turbulent kinetic energy intensity of the flow fluid were analvsed. Resultsshowed that the swirl functions of the fine spray layer on the flow field can uniformdistribution of flue gas and strengthen turbulent kinetic energy.On this basis, through design and installation, coarse/fine particle compositedesulfurization industrial trials were taken. Firstly, identified optimum working pressures ofthe novel two-fluid nozzle; secondly, spray combinations of ABC, ABCD, ABD, ACD weretests; once more, the desulfurization stability of ABD mode were verified. The results showedthat, under the best working pressure, pH set5.45, The average desulfurization efficiency of ABC mode was90.1%, ABD’s was93.3%, and ACD’s was92.5%; when ABCD mode, theaverage desulfurization efficiency was93%with pH was5.16, and98%with pH was5.7.Above all, The ABCD mode has the best desulfurization characteristics with higherenergy consumption, while three layers modes, ABD and ACD were superior to the existingpower plant ABC mode, and ABD mode had better desulfurization characteristics. Wherein,the slurry pumpof the D layer has less power consumption, ABD and ACD mode had lessenergy consumption than the original plantABC mode.Through the researches above, under certain conditions, the coarse/fine particledesulfurization method is possible to improve the desulfurization efficiency and reduce theenergy consumption. With further optimization, this method is expected to widely used in fluegas desulfurization systems.