Study On Three-phase Reaction Of Gas-liquid Solid In The Production Process Of Fine Calcium Carbonate Particles

As a kind of important chemical materials, calcium carbonate is being used more and more widely .In this paper, we have a study on the kinetics and the crystallization process of its production. This study has not only important theoretical value but also important practical value. Because there is chemical reaction and mass transfer among three phases in the production process of fine calcium carbonate particles, many factors can have influence on it. Although researchers had thoroughly study the kinetics of gas- liquid reaction, the study on the kinetics of gas-liquid-solid reaction is not enough. There is not a good kinetics model that is based on theory and is tested by experiment. On the base of other researchers, we had studied the kinetics of gas-liquid-solid and got a kinetic model that is improved by us. In this model, we considered not only the mass transfer between gas and liquid the mass transfer between solid and liquid and the chemical reaction but also the influence of the particles in the membrane between gas and liquid on the gas diffusion rate and on the virtual volume of the membrane where chemical reaction occurred. Furthermore, we use the method of quasilinearization and difference approximation to solve the model equation. In order to test the carbonization reaction kinetics model ,we use a carbonization reactor with plane gas-liquid interface to have carbonization reaction kinetics experiment. In the experiment ,we measured the absorption rate of carbon dioxide by slurry in different stirring rate. The absorption rate by experiment was accord with the absorption rate which is got by kinetics model. It proved that our model is rational. The experiment result also showed the influence degree of the stirring rate and the concentration of slurry on the absorption rate of carbon dioxide. In order to understand the formation process of calcium carbonate, we studied 111 the formation process of calcium carbonate by observing the change of the conductance and the PH of the slurry and by observing the microcosmic form of the solid particle. The result approved that non-crystal calcium carbonate that only could exit briefly was created in the formation process of calcium carbonate. We also verified that some wirelike substance was created in the formation process of calcium carbonate and these wirelike substance was formed by calcium hydroxide and calcium carbonate. At the end of carbonization reaction, these wirelike substance was disappeared .All of them is changed into calcium carbonate with some kind of shape and size . Moreover, because many factors may have influence on the shape and size of calcium carbonate, we also studied the influence of the stirring speed .~ the carbonization reaction temperature~. the concentration of calcium hydroxide slurry and the time when additive was added on the shape and size of calcium carbonate that was produced.