Study On Limestone Calcination Process Under High CO₂ Atmosphere

CO₂ capture is a powerful measure to mitigate global warming.At present,the related research work on CO₂ capture and utilization is mostly carried out on the flue gas of coal-fired power plants;relatively speaking,the CO₂ concentration in the gaseous products of lime kiln is higher,which is more sui Tablele for capture and utilization.However,regardless of the production technology and degree of automation,or the product quality and flue gas emission concentration of China’s lime kiln production,more in-depth research work is required.This thesis focuses on the thermal decomposition of limestone and the kinetic characteristics of pyrolysis reaction in a high-concentration CO₂ atmosphere,and uses the Aspen Plus software to es Tablelish a limestone calcination process under a high-concentration CO₂ atmosphere.This thesis first uses a thermo-gravimetric analyzer to analyze the thermal decomposition characteristics of limestone samples under different carrier gas atmospheres and different heating rates.The carrier gas（CO₂ and air mixture atmosphere）is determined based on the actual limestone process and flame-proof calcination process.The CO₂volume concentration They are 25%,35%,45%,55%,65%,and the heating rates are 10℃/min,20℃/min,and 30℃/min.The experimental results show that increasing the heating rate will help speed up the reaction process,but will cause the decomposition reaction to move to the high temperature region.The effect of the carrier gas atmosphere on the decomposition reaction is obvious.As the concentration of CO₂ increases,the decomposition reaction moves to a high temperature region.In addition,the magnesium carbonate component contained in limestone helps to promote the decomposition of calcium carbonate.Based on the data of the limestone pyrolysis experiments described above,this article uses a combination of the Flynn-Wall-Ozawa method and the Coats-Redfern method to analyze the kinetic parameters of limestone thermal decomposition reaction,including apparent activation energy,pre-finger factors and mechanism functions calculation.The calculation results show that the reaction process of limestone thermal decomposition follows a random nucleation and subsequent growth model;the apparent activation energy of limestone decomposition increases with the increase of CO₂ concentration in the reaction atmosphere.Based on the above work,this thesis uses Aspen Plus software to es Tablelish a limestone muffler calcination process model based on flue gas circulation,verifies the feasibility of the limestone muffler calcination process,and obtains the key parameters of the limestone insulation flame calcination process.By analyzing the factors that affect the concentration of CO₂ in the circulating flue gas,it is found that under the same conditions,an increase in the amount of air in the calciner will reduce the volume concentration of CO₂in the circulating flue gas.The exponential growth is positive;when the limestone feed is fixed,the optimal amount of air and gas required for calcination can be obtained.In addition,when the volume concentration of carbon dioxide in the circulating flue gas is determined,the feed amount of the raw material changes proportionally.This thesis optimized the limestone muffle calcination process and designed an experimental scheme.At the same time,according to the data obtained from the above research,the lime kiln,high-temperature heat storage chamber and combustion chamber in the limestone muffled calcination system were designed,and equipment such as dust collectors and fans sui Tablele for this process were selected.The research in this writing has accumulated basic data for the limestone calcination process under a high concentration of carbon dioxide atmosphere,and has certain guiding significance for the application of the new calcination process.