The design of a unit sweeping gas membrane distillation: experimental study on a membrane and operating parameters

Abstract

The paper presents the focuses of application in membrane processes for the desalination of brackish water or salt water using the sweeping gas membrane distillation (SGMD); at first, it is the least used configuration of MD, and the design of this system is arduous and very expensive, and it is used to treat solutions containing non-volatile compounds, such us salts which is totally rejected, and high purity of water was recuperated. Vapor transfer is an important thermally induced phenomenon in the membrane-by-membrane (MD) evaporation and condensation. Our SGMD distillation system was simulated using MATLAB programmers on heat and mass transfer aspects. In our research, we found that heat and mass transfer in the SGMD is determined by the evaporation temperature of the gas and the sweep rate. The operational parameter (fluid velocity) is influenced across the layer on both sides of the membrane, because it is the source of the transfer of heat and mass in many membrane processes.

The Application of Open Capillary Modules for Sweeping Gas Membrane Distillation

“…Such a case is called direct contact MD (DCMD) [2,3]. In the MD process, porous membranes made of hydrophobic polymers with a low thermal conductivity coefficient are used [4][5][6]. However, due to the small thickness of the membranes (e.g., 100 µm), it does not eliminate the heat conduction from the feed to the permeate side and, as a result, heat losses in the DCMD process may exceed 50% [2,7].…”

“…This inconvenience was limited by separating the membrane from the cold distillate with a gas layer (Air Gap MD) [8]. In another variant of the MD process, a gas stream flows on the permeate side [1,5]. A flowing gas is used to sweep the vapour out of the membrane permeate side, and this variant is called sweeping gas MD (SGMD) [1,[3][4][5][6].…”

“…In another variant of the MD process, a gas stream flows on the permeate side [1,5]. A flowing gas is used to sweep the vapour out of the membrane permeate side, and this variant is called sweeping gas MD (SGMD) [1,[3][4][5][6]. The gaseous layer increases the resistance to heat transfer which decreases the heat loss by conduction.…”

“…The driving force for mass transport in the MD process is the difference in vapour pressure [2,9]. In the case of SGMD, it results from the vapour pressure at the evaporation Energies 2022, 15, 1454 2 of 17 surface in the pores of the membrane and the water vapour content in the gas [1,5]. Mass and heat transfer causes both the concentration and temperature in the membrane adjacent layers to differ from those in the bulk (polarization effects), which reduces the driving force [2,5,9].…”

“…In the case of SGMD, it results from the vapour pressure at the evaporation Energies 2022, 15, 1454 2 of 17 surface in the pores of the membrane and the water vapour content in the gas [1,5]. Mass and heat transfer causes both the concentration and temperature in the membrane adjacent layers to differ from those in the bulk (polarization effects), which reduces the driving force [2,5,9]. It has been reported that increasing the turbulence flow of the stream usually allows to limit the influence of polarization phenomena [10,13,14].…”