Simulation on thermodynamic state of ammonia carbonation at low temperature and low pressure

Design and Optimization of the Preparation of Calcium Carbonate from Calcium Sulfate and Ammonium Bicarbonate

Simulation on single factor effect was used for the design and optimization of the preparation of calcium carbonate from calcium sulfate (DH) and ammonium bicarbonate. This study shows that simulation on single factor effect is effective because the experimental results are close to predicted results. Furthermore, response surface method based on a central composite design was used to determine the range of parameters to achieve a highly efficient conversion of DH. The results indicate that the significant parameters that affected the conversion of DH were ratio of carbon to sulfur, temperature, concentration of ammonium bicarbonate, and stirring speed. The strength order of factors is as follows: ratio of carbon to sulfur > concentration of ammonium bicarbonate > stirring speed > temperature. A quadratic polynomial equation was established using multiple regression analysis. The optimum parameters were determined as follows: 2.10 for ratio of carbon to sulfur, 320.35 K for temperature, 337.31 rpm for the stirring speed, and 1.75 mol · L−1 for bicarbonate concentration. The corresponding conversion rate of the experimental result was 99.7%, which was highly consistent with the predicted value of 99.9%. Based on model and the optimum parameters, products of vaterite, with ammonium sulfate crystal of grade A, can be obtained. Equipotential lines of conversional rate and desired process conditions were provided as well.