Calcium carbonate is an industrial mineral with a wide variety of applications. It is an important component of many aqueous solutions, and is often used as a food additive. It is also a sorbent, anticaking agent and an inhibitor of algal blooms.
In its natural form, calcium carbonate is a polymorphic rock and can be crystallized from aqueous solutions of calcium chloride (CaCl2) and ammonium carbonate (NH4CO3). Calcite is the major product, and aragonite is a minor one.
The chemical composition of aqueous solutions of calcite and aragonite is similar. But calcite crystallizes as a dihydrate, while aragonite is a hexahydrate. In the laboratory, calcite can be produced by placing an aqueous solution of CaCl2 in a desiccator along with ammonium carbonate, and allowing carbon dioxide to diffuse into the aqueous solution.
Pellets can be a valuable addition to a sewage treatment plant, especially for those with a limited space and a high capacity. They have a good density, a very low water absorption coefficient when crushed and high mechanical resistance.
During pelleting, the moisture content of the raw material (MC) has an effect on the density, strength and durability of the pellets. This is why it is essential to choose the right raw materials for a pelleting process. MC should be around 8-12% to prevent the high frictional forces in the compression area from being too great and to ensure the best pellet quality.