The Design of Preparation and Regeneration Process for Activated Semi-coke Catalyst in Flue Gas Desulfurization and Denitrification
|School||Ocean University of China|
|Keywords||Activated semi-coke Flue gas desulfurization and denitrification Regeneration The recycle of ammonium sulphate and ammonium nitrate|
In recent years, our country’s air pollution control methods have transferred fromSO2emission control to SO2, NOx, mercury and its compounds, and PM2.5emissioncontrol gradually. In spite of numerous FGD methods developed by other countries,they only tend to desulfurize. By contrast, flue gas desulfurization and denitrification indry method based on activated semi-coke can not only remove SO2, NOx, mercury andPM2.5in flue gas together, but recycle sulfur, nitrogen and carbon as resource as well,which is more coincident to the present and future requirements on atmosphereenvironment management in our nation. Therefore, this method has a broaddevelopment prospect.This dissertation uses Erdos semi-coke as crude material and divides thepreparation process into4steps, which includes high-pressure hydrothermal activation,nitric acid activation, impregnated with active components and high-temperaturecalcination.Then, this dissertation designs and optimizes the flue gas desulfurization anddenitrification process in fixed-bed method and moving-bed method respectively, withactivated semi-coke as absorbent and catalyst. More specifically, fixed-bed processoperates with three single columns or cascaded columns （two operating columns andone spare column）, of which the denitrification system is designed after itsdesulfurization process. Also, fixed-bed reactor uses "drawer type" modular design.Thus, when the space velocity of desulfurization is900h-1, the computed single reactorvolume of desulfurization is150m3and the pressure drop of catalyst bed is3521.5Pa.When denitrification space velocity is1000h-1, the denitrification column volume is135m3. Moreover, in the moving-bed process, flue gas desulfurization is operatingtogether with denitrification in a moving-bed reactor, which is designed to some unit modules. When the space velocity is900h-1, the volume of moving-bed reactor is180m3and bed pressure drop is1580.8Pa.As the desulfurization and denitrification reaction continues, semi-coke couldinactivate gradually and needs to be regenerated regularly. The regeneration process ofinactivated semi-coke is an innovation point in the whole design. This dissertationfirstly regenerates the inactivated semi-coke with ammonia, and then choose520%semi-coke and do a further regeneration with hot steam, which is characterized by shortregeneration time, low energy consumption, regenerating thoroughly and generating thebyproducts of ammonium sulphate or ammonium nitrate. In this process, ammoniaregeneration technology is a ammonia spray process with moving type under elevatedpressure and generating byproducts named ammonium sulphate or ammonium nitrate.The length and width of transmission steel belt is17m and3m respectively.Transmission speed is34m/min and the spray amount of ammonium is4.86m3/h. Inaddition, the thermal regeneration is designed to a heat regenerating technology withthe flue gas close-circuit cycling. when the temperature is500℃and space velocity is2000h-1, the amount of steam consumed by thermal regeneration is832.5m3/h and thecoke oven gas is1126.1m3/h.The final part of this dissertation introduces two typical evaporation andcrystallization technologies of ammonium sulphate and ammonium nitrate solution,which are referenced to the design. The evaporator is chosen to be hanging-frameevaporator, of which the heat transfer area is795.2m2and the heat transfer rate is8.101×106kJ/h, namely2250.2kW.