Experimental Study And Numerical Simulation Of The Flue Gas Desulfurization By Activated Carbon

Coal-consumption caused severe environmental problems in China. SO2emission was the main issue for China government. It is urgent task to develop the technology of SO2control. Promising development of activated carbon desulfurization technology in China has great development potential. Firstly, it is as a dry desulphurization technology, which can save freshwater resources. Secondly, this technology is a comprehensive purification technology, which can remove SO2, NOx, dioxins or other pollutants simultaneously. In addition, H2SO4is the main by-product, which can serve as the nutrient for industry.Systematic study of the activated carbon desulfurization technology to work as follows:(1) Investigation activated carbon desulfurization method and the reaction mechanism: activated carbon flue gas desulfurization method is highly efficient, no secondary pollution and by-product can be recycled. The adsorption process is divided into three stages:firstly, SO2, O2and H2O transfer to the surface of the activated carbon granules; secondly, they continue to spread to the internal pore of the particles from the surface until the active sites; ultimately, the molecules on the surface are adsorbed, catalytic oxidized and sulphated.(2) Carry out lab-scale desulfurization experiment to examine various factors influencing the activated carbon desulfurization efficiency:The factors including pretreatment method, water vapor content, adsorbing temperature, initial SO2concentration and flue gas flow rate. Pickling removed nearly10%of the ash of raw activated carbon and thus improving desulfurization efficiency. Increasing water vapor content in flue gas increased desulfurization efficiency to a point but then decreased at the optimal water vapor content of8%. The influence of temperature was similar with the impact of water vapor, and the optimal temperature was60℃. The efficiency was reduced with increasing velocity of flue gas. The desulfurization efficiency was about99%in10min when the velocity was0.24m/s. Desulfurization efficiency within the first15min were maintained at above90%, and penetrating time was more than40mins at optimal conditions, the adsorption capacity for37mg SO2per gram.(3) Computational Fluid Dynamics simulation methodology was employed to simulate the adsorption bed with reference to the experimental conditions, and the distribution of SO3concentration in flow field, gas velocity and adsorbing temperature were investigated. Reaction zone was moving from entrance to outlet with prolonging operation, and reaction zone accounted for more than70%of the field. The velocity of flue gas gradually declined when the gas entered adsorption bed. The temperature of the middle of the adsorption bed was the highest, and boundary region was lower. By changing the inlet velocity, adsorption temperature and the initial SO2concentration of the simulation mode, the changes of SO3concentration can be observed in the simulated adsorption bed. The following conclusions were drawn:(a) the smaller the speed was, the more SO3generated, which was consistent with the experimental results;(b) the higher adsorption temperature was, the higher SO3concentration;(c) SO3was increasing generated with increasing initial concentration. These results were consistent with experimental ones.