| The rapid development of coal chemical industry has brought about serious environmental problems,especially water environment and water resources,which have become one of the important bottlenecks restricting its development.With the strengthening of environmental protection and the deepening of the concept of sustainable development,the realization of "zero" emission of coal chemical wastewater has become the external requirements and their own needs for the development of coal chemical industry.However,the previous salt separation technology has many problems,such as high energy consumption,unstable equipment operation,substandard finished salt purity and large proportion of mixed salt.For this reason,this paper has carried out the research on salt separation crystallization technology of coal chemical high-salt wastewater,and the main achievements are as follows:Firstly,ozone oxidation was used to treat the high salt wastewater of coal chemical industry after the pretreatment of activated carbon,so as to reduce the COD content in the high salt wastewater,reduce its pollution to the membrane equipment and improve the quality of subsequent salt separation.The results showed that the suitable conditions for the degradation of high-salt wastewater by ozonation were pH=9,the oxidation time was 20 min,the ozone flow rate was 150 L/h and the ozone concentration was 60%.Under these conditions,the COD content in high-salt wastewater decreased from 279 mg/L to 46.76 mg/L.This paper designs and optimizes a device for the separation and concentration of high salt wastewater.Reducing the pH value of wastewater and increasing the ion concentration in wastewater are conducive to improving the efficiency of high salinity,while the increase of ion concentration can reduce the membrane flux.Increasing the influent concentration and pressure of nanofiltration can increase the flux of the membrane,but it is not conducive to salt separation.The optimized nanofiltration salt separation condition is pH of 7,the total dissolved solid content is 38-40 g/L,the inlet flow is 520-560 L/h,and the operating pressure is 1.6 Mpa.The total soluble solid content of the nanofiltration water with sodium sulfate as the main component and a small amount of sodium chloride was 50-52 g/L,and the total soluble solid content of the nanofiltration water with sodium chloride as the main component was 15-16 g/L,the salt to salt ratio was 35-40,and the TDS could reach 38-40 g/L after reverse osmosis concentration.In order to obtain sodium chloride and sodium sulfate products with high purity,large particle size and uniform distribution,which can meet the requirements of industrial salt,and realize the recovery and utilization of salt in coal chemical wastewater,the separation crystallization technology of high salt wastewater was studied.According to the chemical characteristics of high salt waste water COD,stirring speed,time,seed crystal and decoloring conditions on the influence of sodium sulfate and sodium chloride crystallization process and the quality of the product,respectively,are the crystallization of sodium sulfate and sodium chloride optimized process for sodium sulfate purity of the product accord with GB/T 6009-2014 ? class grade a standard,a purity of 98.0%or more,the average particle size of 238.5 microns;The purity of sodium chloride product GB/T 5462-2016 refined industrial salt level standard,purity?98.5%,average particle size 58.5 micron. |
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