Study On The Crystallization Kinetics Of Potassium Sulfate From The Gypsum

The crystal of potassium sulfate obtained from the process hi high concentration ammonia solution and the crystal of calcium carbonate obtained from the first step of the two-step process are small. It is disadvantaged to the following step such as filtration and will influence the quality of the finished product,so the crystallization kinetics of potassium sulfate is important.In this paper,the crystallization kinetics of potassium sulfate in ammonia solution,the crystallization kinetics of calcium carbonate and the crystallization kinetics of potassium sulfate of the two-step process have been studied in a continuous MSMPR crystallizer.The results show that the decline of the temperature and the concentration of the reactants,the increase of the concentration of ammonia solution and the ratio of excess potassium chloride make for the increase of the purity of product. The optimal remaining time is abtained. The scanning electron microscope photos show that when the purity of the potassium sulfate declines,the crystal gradually turns from the mix of granule-like shape and needle-like shape to the needle-like shape and the crystal of the granule-like shape disappears.The optimum reaction conditions of the first step of the two-step process are obtained. The steady conversion of S042- and big crystal of calcium carbonate can beobtained under these conditions.The optimum reaction conditions of the second step of the two-step process are obtained. Big and uniform crystal of potassium sulfate with the excellence quality can be obtained under these conditions.In this paper,the influences of the additives are investigated by use of the batch experiment. After adding the additives,the quality of the product is better and the shape of the crystal is more regular.In the batch experiment,the crystallization process of calcium carbonate is investigated with additives. The results show the crystallization process is improved by adding the OP emulsion and the Dodecyl Benzene Sulfonic Acid Sodium Salt. The optimum dosages are obtained.