Research On Molding Process Of Catalyst For Sulfite Oxidationand Poisoning Mechanism

The flue gas emitted by small and medium-sized industrial boilers has become the most important source of SO₂.The wet magnesium flue gas desulfurization process has been widely used in small and medium-sized industrial boilers because of its small footprint,low operating cost,and simple system.However,the by-product of magnesium desulfurization-magnesium sulfite is difficult to oxidize in a high-concentration sulfate environment,resulting in excessive energy consumption for subsequent magnesium sulfate recovery,which can only be discarded for disposal,resulting in a large amount of desulfurized yellow mud solid waste（the main component is magnesium sulfite）,which has a huge impact on the environment.Therefore,increasing the oxidation rate of magnesium sulfite to realize the recycling of desulfurization by-products has become a bottleneck problem in the promotion of wet magnesium flue gas desulfurization technology.This article aims to develop a highly efficient,stable,and low-cost industrialized molding catalyst.The cobalt-based supported catalyst is prepared by the impregnation method with molecular sieve as the carrier and cobalt nitrate as the active component.Through orthogonal analysis experiments,the influence of five factors such as impregnation concentration,impregnation time,and roasting temperature on the oxidation rate of the catalyst was studied,and the optimal catalyst preparation scheme was obtained.The solid-phase catalyst was characterized and analyzed by BET,SEM,XRD,XRF and methods,and the composition,morphology and structure of the catalyst as well as the existence form and content of the active components in the catalyst were investigated,and the effect of the catalyst on the oxidation of magnesium sulfite was proved.Mechanism.Simulating the actual working conditions of desulfurization wastewater,the catalyst heavy metal poisoning mechanism was studied.By changing the solid-phase catalyst mass concentration,gas flow rate,heavy metal ion type and concentration,the influence of various factors on the catalytic performance of the catalyst was determined.Combining XRD,BET,SEM and other characterization methods,the As poisoning mechanism of the catalyst was determined,and it was confirmed that As₂O₃blocked the mesoporous pores of the catalyst,resulting in a decrease in catalytic oxidation activity.Co-MS-F was molded by extrusion molding method to obtain Co-MS-F.The effects of binder SB powder,peptizer HNO₃,and water-to-powder ratio on the extrusion molding of the molding catalyst were studied.The molding process was studied through orthogonal experiments.Each component influences each other and the best ratio,and the best molding process conditions are:25%of SB powder,8%of nitric acid,and water-to-powder ratio of 1.0.Using a bubbling reaction device,the kinetics of MgSO₃ catalytic oxidation was studied,and the effects of p H,temperature T,initial MgSO₃ concentration,catalyst concentration,etc.on the rate of MgSO₃ oxidation reaction were obtained,and the optimal catalytic oxidation conditions were obtained.Through laboratory-scale and pilot-scale experimental equipment,the Co-MS-F catalytic oxidation of magnesium sulfite-recovery of magnesium sulfate process has been studied,and it is found that Co-MS-F not only significantly increases the MgSO₃ oxidation rate,but also greatly reduces the energy.It is proved that the shaped catalyst can meet the actual demand of magnesium sulfite resource recycling process,which provides an important reference for the promotion of the new magnesium flue gas desulfurization process.