Theoretical Analyses of Energy Saving in Indirect Contact Evaporative Crystallization by Using Combined Cycle of Vapor Recompression Heat Pump and Throttling Valve

The installation of heat pumps in different chemical processes is considered as an important and prospective approach for energy saving. Various crystallization processes such as counter current crystallization, direct and indirect contact crystallization, evaporative crystallization and fractional crystallization from melts are used to be a promising chemical processes where heat pumps can be introduced for the purpose of energy saving. Usually in such processes, two zones are present; a cooling zone, where heat must be removed from the process and a heating zone, where heat must be added to the process. This work presents a theoretical analysis of the technical feasibility and the potential of heat pumps to be used in the process of indirect contact evaporative crystallization. Principle schemes of the process with heat pump and in combination with throttling valve are proposed and the corresponding calculations are performed. The Effect of temperature and initial feed concentration on the energy saving factor are investigated. The average value of this factor was estimated to be 49.6 % when a cooled feed solution enters (T =25 C) to the crystallizer. This factor was found to be increased to 70.4 % when the feed solution inters at its boiling point (T=125 C).The installation of throttling valve at the outlet of the condensate produces (based on feed conditions) an additional amount of vapor and as a result the saving factor increases from 17 % to 22 % .