Experimental and numerical study on thermodynamic characteristics of a vacuum membrane distillation system based on mechanical vapor recompression for sulfuric acid waste

Abstract

Energy conservation and emission reduction in the field of industrial wastewater treatment have attracted worldwide attention. This study focused on the concentration and recovery of industrial sulfuric acid waste by a vacuum membrane distillation system based on mechanical vapor recompression (VMD-MVR). Mathematical models were built considering the mass and energy conservation principles and relevant thermal equilibrium theory, and an experimental platform, which was suitable for sulfuric acid solution, with excellent corrosion resistance was also constructed. Initially, the performance of VMD-MVR from the energetic and exergetic standpoints was evaluated based on the experimental data. Furthermore, the effects of critical parameters on compression and condensation heat transfer in VMD-MVR were simulated and revealed, and exergy destruction analysis was conducted using various selected parameters. The obtained experimental results indicated that VMD-MVR exhibited a membrane flux of 1.7 kg·m−2·h−1, separation efficiency of 99.9%, and performance coefficient (COP) of 7.88 under the following conditions: feed concentration: 5%; feed temperature: 353.0 K; feed velocity: 1.6 m·s−1; permeate side pressure: 45 kPa; heat transfer temperature difference (ΔThex): 2 K; and compressor frequency: 40 Hz. The exergy input, exergy destruction, exergy output, and exergy efficiency were 4.95 kW, 4.691 kW, 0.259 kW, and 5.24%, respectively. Moreover, according to the numerical simulation results, with a decrease in the feed concentration and ΔThex or with an increase in the feed temperature, feed velocity, and permeate side pressure, the compression ratio and exergy destruction in VMD-MVR decreased, whereas the COP increased.