(143f) Equipment Cost Evaluation On Continuous Crystallization and Solid-Liquid Separation System

Crystallization operation in the chemical industry is widely used to manufacture a variety of petrochemicals, functional chemicals and fine chemicals. The purpose of crystallization operation is to produce stably crystals that have required purity, shape, and crystal size distribution (CSD). One of the primary design parameters of a crystallizer is the crystal residence time. Since this parameter impacts on the product size to be obtained, it is a deciding factor in defining the crystallizer geometric size. As a result, the residence time relates directly on the equipment cost of a given continuous crystallization system. For example, the smaller crystallizer, which is less expensive, may fail to produce crystals enough to be separated easily. The crystallization process has to accompany commonly a solid-liquid separation unit. In the crystallization process, the purpose of the solid-liquid separator (SLS) is to separate efficiently the crystals from the mother liquor in the slurry discharged from the crystallizer. The key factors of solid-liquid separation include sedimentation and filtration. Sedimentation is the method to precipitate the crystals in the slurry. Since smaller crystals are more difficult to precipitate, they need such as higher centrifugal force to separate from the mother liquor. On the other hand, filtration is the method to stay the crystals on a filter element and remove the filtrate. Since the cake of the crystals acts as a filtration resistance on the filtrate, smaller crystals need larger filtration area. As a result, smaller crystals, which might be produced in a smaller crystallizer, may require a larger SLS, which is more expensive. In this work, the crystallizer was assumed as Mixed Suspension Mixed Product Removal in order to calculate CSD using an existing crystallization kinetic model compared with the crystal residence time. For each type of SLS, a proper equipment size for the obtained CSD is designed using existing fundamental model of the solid-liquid separation. Furthermore, the equipment cost of the continuous crystallization process was tried to be optimized by the best combination of crystallizer and SLS.