Hydration-doping Compound Modification Process And Activation Mechanism Of Calcium Based Absorbent

Limestone natural calcium-based absorbent has the advantages of high theoretical adsorption capacity,high-temperature flue gas treatment,low trapping cost,and convenient transportation and storage.However,in the actual cyclic calcination/carbonation process,the carbon capture efficiency of the unmodified calcium-based absorbent will drop sharply in a short period of time.At present,the related modification research is mostly focused on the development of new preparation methods based on chemical raw materials and the stability of high adsorption performance.The potentially high cost is not conducive to the wide application of calcium-based absorbents.Therefore,using natural limestone as raw material to explore a more practical and efficient pore structure reconstruction and cycle stable modification process still has important theoretical significance and practical reference value.In this paper,natural limestone was used as the calcium source,ethanol as the dispersant,MgO,Zn O,Ti O₂,and Al₂O₃ as the dopants,combined with various characterization methods such as SEM,EDS,XRD,BET,and TGA.Firstly,the calcium-based absorber with adsorption capacity close to the theoretical value was obtained by calcination hydration synergistic treatment method,and the preheated hydration structure regulation mechanism was determined.Based on this,anti-sintering substances were dispersed and introduced to discuss the influence law of each metal oxide on the carbonation kinetics and cyclic stability of the absorber.Further,the water vapor reactivation process and reactivation mechanism of the deactivated calcium-based absorbers were studied.The results are as follows:（1）Using 80-100 mesh natural limestone as raw material,preheated and calcined at1100°C for 1 hour,hydrated for 1 hour at a volume ratio of ethanol to water of 8:2,and calcined at 900°C for 30 minutes.The particles have interconnected pores and well-developed pores.The specific surface area can reach 32.74 m²/g.The first absorption efficiency of calcium-based absorbent reaches 90.7%,which is 38.5%higher than that of unmodified calcium-based absorbent.（2）Ultrasonic dispersion introduces MgO with a mass ratio of 8:1 to CaO in ethanol medium.After 30 cycles of calcination/carbonation,the carbonation conversion rate of MgO-doped calcium-based absorbent can reach 54.6%,which is higher than that of non-doped MgO.The impurity sample is increased by 175%,and the CaO particle size is maintained at 400-600nm.（3）The calcium-based absorbent after 30 cycles is activated in a 90%humidity water vapor environment.The water absorption and weight gain rates of MgO and Zn O modified calcium-based absorbents can reach 155%and 145%,respectively,and the corresponding reactivation The first absorption efficiency of the calcium-based absorbent can reach 76%and 75%,the specific surface area is 30.3 m²/g and 28.4 m²/g,the grain size is about 200-500 nm,and the carbonation conversion rate can still reach 55% after 30 cycles.