Thermodynamic simulation and experiment research of the solar air evaporating separation system for saline wastewater treatment with thermal collector–evaporator integrated unit

Abstract

Solar driven air evaporating separation (AES) technology has extensive application in the field of saline wastewater treatment due to its energy saving and cleanliness. However, these current systems generally utilize solar collectors to heat working fluids (air and wastewater), and then pass these heat carrying fluids into the evaporator to complete the mass transfer evaporation process, so as to realize the separation of the wastewater. This conventional process inevitably leads to the mismatch between heat and mass transfer of two working fluids in evaporator, which limits the efficient utilization of the energy. Accordingly, a novel thermal collector–evaporator integrated unit, in which the collecting process and evaporating process are carried out at the meantime and the collected heat directly supplies the latent heat consumed by this evaporation process, is designed to couple with the solar air evaporating separation system for saline wastewater treatment in this paper. Meanwhile, the system thermodynamic simulation model is established and detailed system performance experimental investigations are carried out. The results show that this system is feasible, and this special design is indeed conducive to improve the system thermal utilization (compared with the traditional system, the average irradiation utilization efficiency ηi can be increased by 21.2%). Furthermore, by comparing the experimental and simulation results, the thermodynamic model can effectively predict various system state parameters during operation (errors are all basically within ±10%). More importantly, from the system dynamic characteristic analysis results, the stored wastewater has the phenomenon of heat storage and heat release, which is beneficial to prolong the duration of maintaining high GOR, evaporation efficiency (EE) and system energy utilization efficiency (ηsys). Even under experimental conditions in winter, this system can still sustain high wastewater treatment performance and energy efficiency (When c=10%, three average indicator: GOR= 3.99, EE= 6.97 kg/kWh, ηsys=73.8%).