OPERATIONAL CONDITIONS EVALUATION IN AMMONIUM BICARBONATE CRYSTALLIZATION

摘要

The fast development of the industrial crystallization and precipitation field has allowed considerable improvement in the control of products characteristics, such as the crystal size distribution, morphology and product crystallinity. One of the products obtained through this technique is the ammonium bicarbonate, NH_4HCO_3, which is of great industrial interest and, used mainly as chemical fermentation agent in the bakery products. The work had the objective to study the stage of formation of the NH_4HCO_3 seeking to understand the three-phase (gas-liquid-solid) crystallization system in order to control the crystal size and morphology, to guarantee a good quality of the final product and above all, to prevent caking. After the assembly of bench scale equipment, a standard condition was established, based on the industrial plant, and the starting operational conditions were varied, with the aim to determine an optimal region for the system operation. The studied variables were flow rate and bubbling time of CO_2, time and temperature of cooling, agitation, pressure, reactants concentration, volume of the solution in the reactor and anticaking additives. The best results obtained for the mean diameter of the crystals were a higher flow rate and bubbling time of CO_2, smaller ammonia concentration and a smaller suspension volume in the reactor. Among the tested additives, the best anti-caking found was sucrose.