| In view of the fact that the city wastewater treatment plants of our country have an increasing output of sewage sludge and enlarging disposal pressure, adsorbent which is prepared using sewage sludge applied in flue gas desulphurization process is of high performance compared to cost. It can not only find a new way for sewage sludge disposal, but also provide a new path for flue gas desulphurization and recover sulfur. Therefore, this technology has a broad developing prospect.The research was aimed to remove SO2 from flue gas using absorbent prepared by sewage sludge of suojin village wastewater treatment plant of Nanjing. The influence of absorbent particle size, gas velocity, fixed-bed reactor temperature, SO2 concentration, O2 concentration and water vapor concentration on the desulphurization properties of sewage sludge absorbent were systematically studied. The results indicated when SO2 inlet concentration was 2000ppm, the absorbent diameter was between 20 mesh and 30 mesh, the flow velocity of simulated flue gas was 3m·min-1, reactor temperature was 60℃, O2 concentration was 12% and water vapor concentration was 14%, the sulfur capacity reached the best value. In contrast to desulphurization properties of sewage sludge adsorbent and commodity activated coke, it was known that the sulfur capacity of sewage sludge absorbent was 65.3% of activated coke's, but they had equal desulphurization efficiency which was above 95% in the first 30 minutes.The desulphurization process kinetics of sewage sludge absorbent were studied, the adsorption kinetics equation was established. Isotherm adsorption equation was determined by experiments, the isothermal adsorption process could be described by Freundlich Model. The fixed-bed adsorption model was established, simulated values and experimental values were tallied preferably.The influence of regeneration temperature and time on the regeneration rate of sewage sludge absorbent was studied. The results indicated that the regeneration rate increased with the increasing of regeneration temperature and time. Heating around 60 minutes, the SO2 that could be desorbed would be desorbed completely at the corresponding regeneration temperature. At 400℃which is the actual regeneration temperature of power plants, the regeneration rate of sewage sludge absorbent was about 75%.The influence of adsorption-regeneration cycle times on the sulfur capacity and desulphurization efficiency of the same sewage sludge absorbent was studied according to the circulation experiments. The results indicated that the sulfur capacity of the second adsorption process reached maximum value in the five adsorption-regeneration cycle experiments, then the sulfur capacity reduced along with cycle times. The desulphurization efficiency could still maintain above 90% in the beginning 20 minutes after five circulations.The unused, adsorbed and regenerated sewage sludge absorbent samples' surface properties were analyzed by SEM and FTIR. The results indicated that the developed pore structure and various surface functional groups played an important role in the desulphurization process. Heating regeneration process improved sewage sludge absorbent's pore structure which is more suitable for SO2 removal. |
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