Study On The Gas-liquid Mass Transfer Of The Carbon Sequestration Process By Seawater In Bubble Column And Its Pilot Scale-up

The seawater decalcification and carbon fixation process has received attention due to its ability to fix carbon dioxide while removing calcium ions in seawater,but there are still problems such as insufficient theoretical research and large consumption of alkali sources.Therefore,this subject has developed a bubble column to strengthen its gas-liquid mass transfer process and realize continuous production.Pilot-scale experimental research has been carried out to provide a theoretical basis for industrialization.First,a small bubble tower was designed and the process of seawater decalcification and carbon fixation was explored.Using the decalcification rate,carbon fixation rate,and mass transfer coefficient as indicators,under the three changing conditions of temperature,air flow,and carbon dioxide flow,explore the optimal process conditions,and explore its interior through changes in p H,HCO₃^-,and CO₃^2-dynamic changes.At the same time,the effect of crystallization time on the decalcification rate was investigated,in order to improve the decalcification rate through the crystallization process during decalcification at low temperature.The results show that under the conditions of air flow rate of 4 L/min,carbon dioxide flow rate of 60 L/h and temperature of 50?,it has high decalcification rate,carbon fixation rate and total mass transfer coefficient.The carbon fixation rate decreases with increasing temperature,the decalcification rate increases with increasing temperature,the p H of the solution decreases with increasing carbon dioxide flow,and excessive air flow is not conducive to gas-liquid absorption.Through the crystallization process,the lower initial decalcification rate can be increased to more than 90%.Based on the optimization of the process of decalcification and carbon fixation,in order to improve the quality of by-product calcium carbonate,the concentration of magnesium ion,temperature,liquid level,and sodium dodecylbenzenesulfonate(SDBS)concentration were also investigated for the purity,particle size and Morphological influence.The results show that the increase of magnesium ion concentration can promote the crystalline transformation of calcium carbonate,which is not conducive to the formation of aragonite whiskers,and it is not conducive to the decalcification reaction.With the increase of magnesium ion concentration,the carbon fixation rate increased first and then decreased.The increase in temperature can indirectly affect the purity of the product by increasing the conversion rate of magnesium oxide.On the other hand can cause agglomeration of crystals.The liquid level determines the gas-liquid contact and reaction time.High agglomerates are prone to produce large aggregates,and lower liquid levels will cause inadequate reactions.The addition of SDBS significantly agglomerated the crystals and increased the average particle size of the product.At lower concentrations,aragonite whiskers can be formed.As the concentration of SDBS increases,the aragonite whiskers gradually disappear.Finally,the pilot process was designed through material balance and the pilot experiment and economic balance were carried out.The real-time decalcification rate reached more than 80%under the conditions of air flow 120 m³/h,carbon dioxide flow 6m³/h,and 50°C and Can reach more than 90%through crystallization.After reaction at room temperature,the decalcification rate can reach more than 90%through 24 h crystallization,and pure calcium carbonate can be obtained.The results of the pilot and pilot experiments are consistent.