| The chelating resin is used to treat secondary brine in chlor-alkali plant.It regenerates with acid when chelating resin saturation and produced high-salinity waste water that is difficult to treat.This paper deals with the treatment of high-salinity waste water from the resin regenerated by vacuum membrane distillation.The influence of various factors on the permeation flux was discussed.A mathematical model and a visual software interface were set up and the process was analyzed.A good result had been obtained.First the heat transfer coefficient of the membrane module was determined by pure water experiment.On this basis,the permeation flux prediction model was established by combining the physical parameters of pure water and NaCl solution.The results showed that the error range of the simulated value and the experimental value was within 5%,indicating that the heat transfer equation had good applicability in the vacuum membrane distillation experiment,and the mathematical model in this paper was also verified by the diffusion and adhesion of the Knudsen.In the simulated wastewater treatment experiment,the effects of feed temperature,feed flow rate and permeat vacuum on permeation flux were studied.The results showed that increasing the operation conditions can effectively increase the permeation flux,and the temperature and vacuum have the greatest influence on the flux.The model had been used to predict the permeation flux.The results showed that the error range of the experimental and simulated values is within 8%,indicating that the model still had good applicability in the wastewater.At the same time,the temperature difference polarization coefficient and concentration polarization coefficient were estimated by this model.It was found that the increase of temperature and vacuum can enhance the polarization and increase the heat and mass transfer resistance,and the increase of velocity can effectively weaken the influence of polarization.The influence of the change of salinity on the permeation flux in the long run experiment was studied.According to the results,the change of permeate flux could be divided into two stages:the decline stage and the sharp decline stage.The simulation of these two stages showed that the simulated data and experimental data could be well fitted only in the down stage.In the sharp decline stage,the flux decreased sharply due to the aggravation of membrane fouling.The main pollution was found to be salt crystallization by SEM.The conductivity of the effluent was measured.The results show that the average conductivity was about 4.98 ?S/cm,and the rejection rate was more than 99.99%.The transfer resistance in the long run experiment was estimated.The results showed that the membrane fouling resistance in the transfer resistance began to increase rapidly after the salinity of 23.5%,and the selection of the optimal concentration point was 23.5%.In the continuous running experiment,the flux of the membrane was stable at about 15 L/(m2·h)at 0.048 m/s of continuous feed velocity and 0.035 m/s of discharge velocity,and the yield of pure water is 59.87 g/h.The concentration of wastewater was treated by spray drying,and the rate of salt product was 38.97 g/h,which realized the continuous zero discharge operation of high salt wastewater treatment by vacuum membrane distillation. |
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