Research On Preparation And Hcl Removal Performance Of Modified Hydrotalcite-Like Adsorbent

Waste incineration is one of the main methods of municipal solid waste treatment.The HCl gas in the flue gas in the waste incineration causes high temperature corrosion of the metal heating surfaces such as superheater and strengthens the re-synthesis reaction of dioxins.Therefore,investigations on the HCl removal in the exhaust gas of waste incineration are necessary.The hydrotalcite-like adsorbents can effectively remove acid gases such as HCl and have potential application prospects.However,current research shows that when the hydrotalcite-like adsorbents are used to remove HCl gas at high temperature,there are still problems such as rapid alkali failure and insufficient adsorption capacity,and the efficiency of HCl removal needs to be further improved.In this paper,the preparation of modified hydrotalcite-like adsorbents and the performance of removing HCl were studied.The Ca Mg Al hydrotalcite-like adsorbents were modified by potassium carbonate or intercalated by organic anions.The effects of modified parameters,reaction temperature and HCl concentration on the HCl removal performance of modified hydrotalcite-like adsorbents were studied.Some characterization methods such as X-ray powder diffraction（XRD）,scanning electron microscopy（SEM）,specific surface area test（BET）and thermogravimetric analysis（TG）were used to characterize the modified hydrotalcite-like adsorbents.The adsorption kinetics method was used to study the adsorption mechanism of the removal of HCl by modified hydrotalcite-like adsorbents.The main research contents and results are as follows:（1）The potassium carbonate modification method was used to modify the hydrotalcite-like adsorbent.The effects of the loading ratio of potassium carbonate,reaction temperature,HCl concentration and CO₂ concentration on the HCl removal performance of potassium carbonate modified hydrotalcite-like adsorbent（K/Ca Mg Al-LDO）were studied.The K/Ca Mg Al-LDO was characterized by XRD,BET,TG and other methods.The results showed that the HCl removal performance of the hydrotalcite-like adsorbents modified by potassium carbonate were significantly improved,and the HCl removal performance of K/Ca Mg Al-LDO with potassium carbonate loading ratio of 30%was best.The HCl adsorption capacity of30%K/Ca Mg Al-LDO was highest when the reaction temperature was 600℃.The HCl adsorption capacity of 30%K/Ca Mg Al-LDO remained stable under different HCl concentrations.The HCl removal efficiency of 30%K/Ca Mg Al-LDO decreased with the increase of CO₂ concentration.The thermal stability of the hydrotalcite-like adsorbents modified by potassium carbonate were enhanced.（2）The organic anion intercalation method was used to modify the hydrotalcite-like adsorbents.The effects of the type of anion,reaction temperature,HCl concentration and inlet gas velocity on the HCl removal performance of organic anion intercalation modified hydrotalcite-like adsorbent（C/Ca Mg Al-LDO）were studied.The C/Ca Mg Al-LDO was characterized by XRD,BET,SEM and other methods.The results showed that the HCl removal performance of organic anion intercalated hydrotalcite-like adsorbents were better than that of carbonate intercalated hydrotalcite-like adsorbent,and the HCl adsorption capacity of octanoate intercalated hydrotalcite-like adsorbent（C8/Ca Mg Al-LDO）was highest.The HCl removal performance of C8/Ca Mg Al-LDO was best when the reaction temperature was 600℃.In the range of 300-1200ppm HCl concentration,the HCl adsorption capacity of C8/Ca Mg Al-LDO increased slightly with the increase of HCl concentration.The penetration time of C8/Ca Mg Al-LDO was shortened and the HCl adsorption capacity was reduced with the increase of inlet gas velocity.The specific surface area and pore volume of the hydrotalcite-like adsorbents modified by organic anion intercalation were increased significantly.（3）The apparent adsorption kinetic model was used to fit the HCl adsorption curve of the modified hydrotalcite-like adsorbents.The mechanism of the adsorption process was studied.The results show that the imitative effect of the whole process of HCl adsorption by Bangham model was best,and the fitting result for the middle and later stages of the adsorption process by pseudo-second-order kinetic model was good.The process of HCl adsorbed by modified hydrotalcite-like adsorbents included physical adsorption and chemical adsorption.The adsorption process was simultaneously controlled by multiple mechanisms such as gas film diffusion,intra-particle diffusion,and surface reaction.