Development of a vertical finned crystallizer for progressive freeze concentration process
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Date
2015
Authors
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Publisher
Universiti Teknologi Malaysia
Abstract
Freeze concentration (FC) is known as one of the methods used to concentrate solution by freezing water molecules into ice crystals so that a highly concentrated solution is left behind. In this study, progressive freeze concentration (PFC), a more convenient version of FC which forms ice crystals layer on a cooled surface was investigated focusing on the evaluation of a new developed PFC crystallizer. As a result, a vertical finned crystallizer (VFC) was successfully developed in such a way to provide a larger heat transfer area for the ice crystallization which later could enhance the productivity and efficiency of the process. In the subsequent performance analysis carried out using glucose solution, the best system efficiency portrayed by the lowest value of effective partition constant (K) and the highest value of solute recovery (Y) was obtained at intermediate coolant temperature, circulation time, and shaking speed, while higher circulation flowrate was needed in providing an efficient PFC process. The precision of the experimental data obtained through this analysis was validated by a mass balance calculation. A geometrical analysis for the VFC was carried out, in which the VFC was proven to be hydrodynamically efficient with low friction factor and total head loss to avoid high additional power requirements. The VFC also recorded a higher ice production as compared to a conventional cylindrical crystallizer. A process optimization using the Response Surface Methodology (RSM) in STATISTICA software was also successfully carried out, where the interactions between process variables and optimum conditions for each response have been identified. The optimum condition of parameters that yielded the best value of K and Y were -6.8 °C for coolant temperature, 71 minutes for circulation time, 2843 mL/min for circulation flowrate and 45 ohm for shaking speed. Finally, a mathematical heat transfer model was successfully modified to obtain the crystallization growth rate at different coolant temperatures
Description
Thesis (PhD. (Chemical Engineering))
Keywords
Refrigeration and refrigerating machinery—Research, Ice crystals, Crystals at low temperatures