| The state requires to achieve the goal of "zero liquid discharge" in the waste water of new coal chemical projects,while the concentrated brine treatment is the last key.Under this background,it is of great significance for the development of coal chemical industry to explore the new technology of the utilization of concentrated brine.There are many kinds of heavy metals in coal chemical brine,and the problems such as difficult data collection and poor removal effect of heavy metals restrict the resource utilization of mixed salt.In the experiment,heavy metals were removed by using the recapture agent combined with the enhanced coagulation technology.At the same time,the optimal type and dosage of recapture agent,the optimal flocculant type and dosage and the optimal coagulant dosage were determined step by step by using the single factor method.Compared with traditional chemical precipitation method,using recapture agent was more efficient in removing heavy metals.Meanwhile,the influences of different water quality?such as water temperature,p H,salinity and organic matter,etc.?on the removal of heavy metals were investigated.The experimental design of orthogonal rotation combination of 4 factors and 2 times was adopted.The initial heavy metal concentration,the amount of retargeting agent TMT-18 B,the amount of flocculant and the amount of coagulant were taken as independent variables,and the total arsenic concentration of effluent was taken as the dependent variable,and the regression equation was obtained:Y =0.1165 +0.04187x1-0.01829x3+0.00941x22 +0.0116x32-0.00719 x2 x3.The missing fitting term of the regression equation was not significant,while the regression equation reached the extremely significant level,indicating that the model was practical and could be used to predict the total arsenic concentration in effluent water.In order to further realize the resource utilization of concentrated brine,this paper proposed to use bipolar membrane electrodialysis coal chemical concentrated brine to produce acid and base,using them back to the resin regeneration process in the boiler feed water technology,so as to realize clean production and recycling economy.The effects of different operating conditions?voltage,salt content and flow rate,etc.?and the initial conditions?water temperature and p H?of concentrated brine on the concentration of base and the performance of the membrane reactor were investigated by using a threecompartment bipolar membrane electrodialysis device with nanofiltration fresh water and concentrated water as raw materials.The results showed that the operating voltage was 17.5V,the total salinity of the concentrated brine was 6.472%,the flow rate of the polar chamber was 60L/h,and the flow rate of the other chambers was 100L/h.Under these conditions,the concentration of acid and base was 3.13% and 3.26% respectively,the conversion rate was 61.71%,and the energy consumption was 4.94 k Wh·kg-1.The optimal operating voltage for bipolar membrane electrodialysis nanofiltration was 20 V,and the concentration of acid and base was 4.96% and 4.29% respectively.Finally,the experimental results of bipolar membrane method were analyzed.The acid was mixed acid,while the purity of alkali was higher,reaching more than 98%.The acid and base used for resin regeneration could realize the utilization of resources.Economic comparison and evaluation were made between the process and the evaporative crystallization MVR process.Although the investment and operation cost of bipolar membrane electrodialysis process was higher than that of MVR process,the economic benefits of bipolar membrane electrodialysis process were more considerable,with the annual benefits reaching 846.5 million yuan/year,while the annual benefits of MVR process were only 392.53 million yuan/year,indicating that bipolar membrane electrodialysis process had a certain market potential. |
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