Preparation Of Spherical Calcium Carbonate In Rotator-Stator Reactor

The preparation method of calcium carbonate generally includes double decomposition method,carbonization method,thermal decomposition method,etc.,wherein the carbonization method is widely used in the industrial field due to simple operation,environmental friendliness,and high reaction efficiency.However,the spherical calcium carbonate prepared by this method has poor polydispersity,wide particle size distributions and irregular morphology,which affects the product performance and quality.There are often emission problems and cost when using the crystal modifier to prepare high sphericity products.In this research,combined with rotor-stator reactor(RSR),spherical calcium carbonate with good dispersion and narrow particle size distribution was prepared.The results of research are as follows:(1)The lysine system is selected for carbonization,and the effects of temperature,lysine-calcium concentration,rotating speed of RSR,CO2 gas velocity,circulating fluid volume and lysine dosage on the morphology and particle size of calcium carbonate were studied by a single variable method.By observing the surface of crystal,the effects of various operating parameters on the particle size,dispersion and crystal form of the product were studied.The optimal preparation conditions of the spherical calcium carbonate product were determined.The results show that the particle size of calcium carbonate is greatly improved in the preparation of the RSR.The temperature,lysine dosage and rotating speed of RSR play an important role in the crystallization.As the increases of CO2 gas velocity,circulating fluid volume,the rotating speed,the system concentration,the product particle size is shown down.Finally,spherical and micron-sized calcium carbonate were prepared,and the particle size was mainly distributed in 2～3μm.(2)The growth of calcium carbonate in lysine solution under different pH conditions was studied by the crystal form and solution conductivity of different products under different pH conditions and the morphology of spherical calcium carbonate prepared under optimal pH conditions.The results showed that the different alkalinity of lysine solution had a great influence on the crystal form of the product.When the pH value of the system was 8.5,with the longest crystallization induction time and crystal growth time,and the highest vaterite content among such condition.The different dissociation forms of lysine have a great influence on the reaction product,and the degree of dissociation of a-NH2 is positively correlated with the stability of vaterite.(3)In order to recycle the amino acids in the filtrate and reduce emissions and costs,this paper innovatively proposed a method for regenerating lysine solution.The effects of pH condition and calcium ion content on product morphology and solution storage stability were studied..The lysine concentration loss in the circulating mother liquor is low,the solution storage time is long,the oxalic acid consumption is low,and it can be reused many times.This process greatly reduces the consumption of additives in the preparation of spherical calcium carbonate,and can be used to prepare spherical calcium carbonate under high concentration conditions.In this paper,spherical calcium carbonate is prepared based on the carbonization method.The process has the following advantages:The spherical calcium carbonate with good dispersion,good morphology and high dispersion was prepared by the fixed-rotor reactor,and the product quality was greatly improved compared with other carbonization products;By adding oxalic acid to regenerate the lysine solution,the lysine solution can be recycled under high concentration operating conditions,and no excessive cost is incurred except for a small amount of lysine loss and oxalic acid loss.The process route has the advantages of low emission,environmental friendliness,low cost,large production capacity,excellent product performance and easy realization of industrial production,and provides a feasible way for industrial preparation of spherical calcium carbonate.