Characteristics Of CO₂ Circulating Absorption By Sodium Humate/Carbonate

Dry CO₂ capture with alkali metal absorbent is one of the promising technologies in carbon capture technology.However,after multiple cycles,the main active substances in the absorbent continue to decrease,which affects the industrial application of alkali metal based absorbent in carbon capture technology.In this paper,sodium humate was used as additive to compound K₂CO₃ absorbent.The preparation method,absorption reaction characteristics and regeneration cycle reaction characteristics of HA-Na/KHCO₃ absorbent were studied.The mechanism of sodium humate modified K₂CO₃ absorbent was discussed by establishing the reaction model of absorbent.In this paper,the advantages and disadvantages of two preparation methods of K₂CO₃ absorbent,physical doping method and impregnation method,as well as the influence of calcination temperature and calcination time in the preparation conditions of the absorbent were studied.The sodium humate modified absorbent was prepared by selecting the best preparation method and the best conditions in the preparation process.The effects of carbonation temperature,carbonation time,CO₂ concentration in carbonation atmosphere,water vapor concentration and doping amount on the carbonation performance of sodium humate modified absorbent were studied in a self-made reactor.Through the regeneration carbonation reaction of the absorbent under the optimal reaction conditions,the effects of the final temperature of regeneration reaction,heating rate of regeneration reaction,water vapor concentration and cycle reaction times on the regeneration performance of the modified absorbent were studied.Combined with XRD,SEM,BET and particle size test analysis,the micro characteristics of the modified absorbent and the modification process were explored The modification mechanism of absorbent.Study on preparation method and carbonation performance of modified absorbent.The effects of physical doping method and impregnation method on the carbonation performance of modified absorbent were investigated.The results showed that the carbonation performance of sodium humate modified absorbent prepared by impregnation method was better than that by physical doping method.Compared with the physical doping method,it is only the absorption and mixing between particles,which can not stimulate the effect of sodium humate.The modified K₂CO₃ absorbent prepared by impregnation method changes the structure of K₂CO₃to a certain extent,which not only improves the carbonation conversion of the absorbent,but also improves the cyclic reaction performance of the absorbent.It is found that the calcination temperature of the modified absorbent is 200℃and the calcination time is 3 h,which is an ideal condition for the calcination reaction time.Study on the absorption reaction characteristics of K₂CO₃ modified by sodium humate.Firstly,the optimal reaction conditions of carbonation reaction process were investigated through experiments:the influence of different factors in the preparation stage of absorbent（200℃,3h,100%N₂）cyclic carbonation reaction process.The results showed that the optimal reaction conditions of cyclic carbonation reaction were as follows:carbonation reaction stage（80℃,20min,15%CO₂,20%H₂O,65%N₂）,and the optimal doping amount of K₂CO₃ loaded sodium humate is 30%.It is found that the addition of sodium humate improves the surface structure of K₂CO₃ crystal,increases the specific surface area,pore volume and pore size of K₂CO₃,decreases the particle size of K₂CO₃,and improves the carbonation performance of K₂CO₃.Study on the absorption reaction characteristics of K₂CO₃ modified by sodium humate.Firstly,the optimal regeneration conditions of carbonation reaction process were investigated through experiments:regeneration reaction stage（30min,200℃,40%N₂,60%H₂O）,and the number of cycles was 10.After modification by sodium humate,the specific surface area of HA-3 can reach 33.111m²/g,which indicates that the specific surface area of K₂CO₃ is greatly affected by the addition of sodium humate,which increases the specific surface area.After 10 cycles of reaction,the specific surface area of HA-3 can still reach 19.236m²/g after the 10th cycle of reaction,and it decreases to 6.034 after the 13th cycle of reaction After the 13th calcination reaction,the pore volume and pore size decreased,which affected the structural stability of K₂CO₃.The cross-linking and fusion between particles easily occurred,which reduced the reaction stability of the absorbent.Study on absorption mechanism of HA-Na/KHCO3 absorbent.Firstly,the particle model was established,and the mechanism of CO₂ absorption by HA-Na/KHCO3particles was analyzed.According to the chemical reaction characteristics of K₂CO₃and CO₂,the reaction type of the model was determined,the shrinking core model was established,and the differential equation of the model was described.Through the experiment,the absorbent particle size and carbonation reaction efficiency were obtained,and the key parameters of the model were determined by fitting the data.Finally,the HA Na/KHCO₃ particle model with different K₂CO₃ particle size and CO₂concentration is analyzed by using the established particle model,and the simulation results are basically consistent with the actual absorption effect for HA Na/KHCO₃particle model,which indicates that the established model is reasonable.