Study On Application Of Membrane Distillation Process In Brine Concentration

Membrane distillation is a heat-driven separation process based on gas-liquid equilibrium combined with membrane technology.Membrane distillation is widely used in the fields of seawater desalination and recovery of water due to its simple equipment,easy operation and energy saving.In Qinghai,the salt lake is rich in resources,long in sunshine,large in evaporation,and small in precipitation.Qinghai Salt Lake Chemical Production relies on light to concentrate the brine,but the salt field has the disadvantages of large evaporation ponds,long production cycles,and water taken away by evaporation cannot be recycled.The application of membrane distillation technology to salt lake brine concentration not only solves the problem of the long production cycle of traditional salt lake brine evaporation,but also recycles water and alleviates the shortage of water resources in salt lake areas.This paper studies the effects of membrane distillation methods,operating conditions,and the addition of flotation agents on salt lake production on membrane flux and salt rejection of membrane distillation in brine systems.In the experiment,firstly,pure water and inorganic salt solution were used as the membrane distillation feed liquid to compare the membrane performance,and combined with the membrane parameters,the best membrane was selected from the four membranes;then the feed liquid temperature,feed liquid circulation rate and vacuum degree were studied.Effects on membrane distillation and comparison of the effect of different membrane distillation methods on the concentration of brine.The experimental results show that the morphology and performance of Millipore's membrane are the best when selecting membranes.Therefore,Millipore's membrane was selected as an experimental membrane.In direct contact membrane distillation,the higher the temperature,the larger the flow rate,and the larger the membrane flux,of which temperature is the main influencing factor.In vacuum membrane distillation,the greater the degree of vacuum,the greater the membrane flux.The vacuum degree has the greatest influence on the membrane performance among the flow rate,temperature and vacuum degree.Concentration effect and membrane performance of real brine treatment under different membrane distillation methods were compared.It was found that direct contact membrane distillation at 60 ? and 900 mL/min was the best membrane distillation method for treating brine,and the fresh water obtained on the permeate side was consistent with domestic water Standard.Finally,the effect of sodium dodecyl sulfonate?SDS?on membrane distillation concentrated brine was studied.The experimental results show that SDS has different effects on different inorganic salt ions,among which Mg²⁺is the most sensitive to the content of SDS.The greater the SDS concentration,the more types of inorganic salts and the greater the ionic strength.The smaller the membrane flux and salt rejection,the more severe the effect on membrane distillation.