Carbonation And Regeneration Characteristics Of Potassium-Based Sorbents Supported By Coal Fired Fly Ash For CO₂Capture

The essences of removing CO2by using regenerable alkali metal sorbents is to use alkialicarbonate salts mixed with CO2in the flue gas, and react to form alkiali bicarbonate salts, the saltswill decompose to regenerate for releasing CO2under certain conditions, which to achieve theseparation of CO2and flue gas. Compared with removeing CO2by chemisorptions, the dry CO2absorption by using regenerable alkali metal sorbents with the advantages of low energyconsumption, high recycling efficiency, no corrosion to equipment and no secondary pollution hasbecome a research hotspot. This paper focuses on studying carbonation reaction and regenerationreaction characteristics characteristics of KHCO3-based sorbents supported by coal fired fly ashfor CO2Capture in a fluidized-bed.The K2CO3with structure of hexagonal crystal is selected as the active components ofpotassium based fly ash sorbents by comparing specific surface area, pore diameter and volume ofthe hexagonal crystal K2CO3with the monoclinic crystal K2CO3, which is obtained from calcinedof KHCO3. The power plant coal fly ash is selected as the carrier material of sorbents through tothe carrier material abrasion resistance, particle shape and smoothness, particle size distribution,porosity and cost aspects. Compared particle size distribution of the Jiangsu jiangyinligang powerplant coal fly ash and Shanghai minhang power plant coal fly ash, Shanghai minhang power plantcoal fly ash is choosed as the carrier material of dry CO2sorbents. The potassium based coal flyash sorbents is mainly composed of active components, the carrier material and adhesive, etc. Andthe active components is KHCO3the carrier material is Shanghai minhang power plant coal flyash, the adhesive is liquid sodium silicate. The preparation of sorbents includes grinding, mixing,drying and calcination etc.By studying the influence on the reaction of carbonation,such as the loading rate, temperature,the atmosphere of carbonation, steam pretreatment time and so on, obtained optimal conditions ofcarbonation reaction of potassium-based coal fly ash sorbents in a fluidized bed optimalconditions. The results showed that the increase of the loading rate will promote reaction, enhancethe CO2absorption performance, to extend the time of CO2penetrate, but limited by KHCO3loading rate is difficult to ascend, and considering the wear resistance of the absorbent, theappropriate loading rate is between30%~40%; Potassium sorbents after joining steampretreatment can lead to more fully reaction with the CO2, CO2penetrate the time better than nowater pretreatment increased0.4min, water pretreatment for10miniutes, steam pretreatmentthrough time was1.53min; Carbonate reaction may affect the effect of reaction temperature,reaction temperature is too low will reduce the reaction rate, but as a result of carbonate of thereaction is an exothermic reaction process, the temperature too high could suppress reaction, andthe best reaction temperature of60℃;Introducing the higher initial concentration of CO2, CO2penetrate the shorter the time. By studying the loading rate, heating rate, final temperature and atmospheric conditionsaffect the regeneration of the absorbent reaction, potassium-based sorbents obtained optimumregeneration reaction conditions, while strike absorbent regeneration reaction kinetic parametersunder different circumstances, and analyze its properties. The results showed that regenerationreactio of absorbents began at100℃reaction, the reaction is completed in about210℃, in thevicinity of170℃most rapid response; when loading rate is35%, the maximum conversion rate isthe max, and decomposition activation energy is110.5kJ/mol, this time absorbing most easilybiodegradable, renewable best performance; little response relationship between regeneration andheating rate, when the heating rate reached10℃/min or more, the CO2concentration curverelatively close; when the temperature reaches150℃, the absorbent can fully decomposed, themaximum conversion rate of over95%; regeneration greatly influenced by the temperature of thereaction at temperatures below200℃, the temperature is higher than200℃, the final temperatureeffect of the regeneration reaction is weakened; when introduced into the reaction atmosphereH2O, the reaction efficiency was significantly reduced, the more the fed amount of H2O, thereaction worse the effect, which is because the regeneration process of KHCO3potassium basedadsorbents will break down generate CO2and H2O, and the decomposition reaction is a dynamicequilibrium process, when the regeneration atmosphere for H2O, the reaction will decomposeKHCO3direction to the reverse reaction, is not conducive to the regeneration of potassium-basedsorbents.