Performance analysis of a vacuum membrane distillation system coupled with heat pump for sulfuric acid solution treatment

This paper proposed a vacuum membrane distillation system coupled with heat pump (VMD-HP) for the treatment of sulfuric acid solution, in which the evaporator was employed to cool secondary vapor from the VMD process while the condenser was used to heat feed sulfuric acid solution. Mathematical models were first established in view of mass and energy conservation principles, and then validated through a conventional VMD experimental system with polytetrafluoroethylene (PTFE) membrane material. Furthermore, the effects of operating parameters on system performance were investigated comprehensively. The results showed that the combined system could achieve the evaporation process with lower temperature of 318.15 K-333.15 K. Decreasing feed concentration or increasing feed temperature, feed velocity and permeate side pressure, was effective to reduce the specific heating energy consumption (SHEC) and elevate the performance coefficient (COP). Taking the treatment concentration of 20% for instance, feed temperature, feed flow rate and evaporation rate were fixed at 333.15 K, 2 t center dot h- 1and 1 t center dot h-1, respectively. The SHEC and COP for the VMD-HP system were 181.47 kWh center dot t- 1 and 3.44, respectively. The specifics evaporation cost was found to be 15.56 $center dot t- 1, with a reduction amplitude of 58.74% than that of conventional VMD system.