Analysis of a novel double-effect split mechanical vapor recompression systems for wastewater concentration

Abstract

A novel double-effect split mechanical vapor recompression (MVR) system is proposed in this paper to reduce the system operation cost together with the technical requirements for the steam compressor. Theoretical models of the novel double-effect split MVR system together with the double-stage MVR system and double-effect downstream MVR system are established by the simulation software of Aspen Plus. Performances of the three systems for the concentration of calcium chloride solution with a mass flow rate of 1000 kg/h are simulated. For a better evaluation, analysis of the energy consumption, operation cost, compressor operating parameters and gained output ratio are carried out with the simulation results. It is concluded that an optimal steam ratio exists for the smallest compressor power consumption of the double-effect split MVR system which is 0.3 for the simulated conditions. The operation cost beneficial of the novel system increases with the rise of electricity price and final mass fraction of the solute. The maximal suction volume flow and pressure ratio of the steam compressor in the novel system are both the smallest among the three MVR systems. The pressure ratio ranges from 1.2 to 1.7 which can be easily realized by mature roots compressor or centrifugal compressor. Exergy efficiency of the novel system is also the highest. Development and application of heat pump or solar energy fresh steam generator can further enhance advantages of the novel system.