| The status quo of China's energy structure promotes the transition of traditional coal chemical industry to modern coal chemical industry,which takes clean coal utilization measures to make up for the energy structure defects,such as coal to liquids,coal to natual gas.But the modern coal chemical industry's high water consumption,high pollution,the reverse distribution characteristic of coal resources and water resources and the strict request of "zero discharge" of national environmental protection administation restricts the development of coal chemical industry.As the bottleneck problem of ' zero discharge'',the treatment of coal chemical brine is difficult and high cost.The treatment of crystallization of mixed salt by traditional evaporation crystallization process of brine is 3000 yuan/t,the treatment cost used to deal with the crystallization of mixed salt accounts for 60% of the total costs of coal chemical industry wastewater treatment of coal chemical industry enterprise each year.In order to further realize zero discharge requirements,promote the steady development of coal chemical industry,this research project discusses the expriment of coal chemical industrial brine's separation of industrial salt by evaporation and crystallization,carrys through on-site salt seperation test system's debugging and running.Aiming at the crystallization of the existing mixed salt in coal chemical industry,puts forward processing scheme of recycling use to explore and experiment,perform the technical and economic cost of crystallization mixed salt resource recovery process and the evaporation crystallization for salt separation process respectively.It performs the passivation-complexation pretreatment experiment by adding the reagent CaO,MgO,PAC,PAM and Na2CO3 to remove the hardness,alkalinity,activated silica and heavy metal ions in the brine based on the water quality conditions of brine,which determines the reagents optimal dosing quantity is 80 mg/L 2500 mg/L,120 mg/L,2 mg/L,70 mg/L respectively.The removal rate of Ca2+,Mg2+,alkalinity,Mn2+,Al3+,total Fe and Si were 76.07%,88.31%,44.53%,76.07% and 78.64%,25.73%,49.71% respectively,the ionic compound removal rate is 412.99%.The brine through the passivation-complexation retreatment can reduce the disk tubular nanofiltration(DTNF)unit's membrane fouling and evaporation crystallization unit'scorrosion and scaling of field salt separation test system.On account of the low removal rate of heavy metal ions by passivation-complexation process,choosing the characteristics of heavy metal ions Cu2+,total As and Ni2+in coal chemical industry brine and improving its concentration to brine water distribution experiments,exploring the brine's TDS,TOC and pH changes to the influence of removing heavy metal ions.The experiment determines the best flocculant is Fe SO4,the best intensive dosage of which is 90 mg/L.Under the condition of TDS54000mg/L,TOC 180 mg/L,pH 6-10 in concentrated brine.The best pH for the removal rate of Cu2+,Ni2+ and total As were 9.80,9.80,7.85.The removal rate were73.00%,71.25% and 46.67% respectively.According to the optimum pH,introducing Na2CO3 to further improve the removal rate of heavy metals in the experimental process,the dosage of Na2CO3 is determined for 120 mg/L.Ca2+is introduced to analyze the effect of metal hydration finally,explaining poor removal rate of heavy metal ions in passivation-complexation process.According to agentia dosage conditions by pretreatment experiment,relying on coal chemical industry brine TMC thermal membrane coupling separation technology to run and debug field salt separation test system,the process unit of which include passivation-complexation and resin pretreatment unit,DTNF unit,Hetro-Catalytic Ozonation System(HCOS)unit and evaporation crystallization unit.DTNF unit separates Cl-,SO42-respectively and forms two types of water quality,using HCOS technology unit to further remove organic matter,the TOC removal rate is steady at55.22%-61.60%,the evaporation crystallization unit crystalizes NaCl and Na2SO4 respectively,the crystallization of NaCl salt meet the wet salt level index of the industrial salt,Na2SO4 crystallization salt meet meet secondary index of industrial salt II.Through the TMC thermal membrane coupling process,the total salt recovery rate of coal chemical industry brine can reach 74.67%,Na Cl theory recovery was 86.42%,accounting for 86.42% of the total salt,Na2SO4 recovery was 91.59%,accounting for25.51% of the total salt.The theory proportion of outside mother liquor of produced water and concentrated water by evaporation crystallization were 1%,5%.Continuous discharge of mother liquid is 0.0156m3/h.The treatment method of which is crystallization,biochemical or dry processing.The thesis puts forward recycle treatment scheme on crystallization of mixed salt,dosing thick-H2SO4 in mixed salt to manufacture industrial-grade NaHSO4.According to experimental analysis,the appropriate reaction conditions were H2SO4 concentration90%-98%,dosing method 1:2.5,reaction temperature 130 ?,reaction time 30 min,dosing method of distilled water 1:1,adopting saturated NaHSO4 to wash reaction liquid,the preparation of NaHSO4 the standard of industry I class.It designs technological process and analyzes economic cost according to the processing scheme.The processing cost of mixed crystallization salt is 36.49 yuan/t.Compared with hazardons waste treatment,it has obvious technology and economy.The effect of separating salt from coal chemical industry brine by evaporation and crystallization isfavorable,the resource utilization rate of brine is high,compared with the conventional evaporation crystallization and natural evaporation process,the treatment costs of coal chemical industry brine were 50.32 yuan/t,204.35 yuan/t and234.34 yuan/t,the proportion of hazardous waste disposal costs accounted for 16.67%,84.39% and 96.78% respectively,the technological process of separating salt from coal chemical industry brine by evaporation and crystallization need low cost treatment,produces less solid waste(crisis),high resource utilization,own high resource utilization,which has obvious technical and economical advantages.This study core is the resource utilization of coal chemical industry brine,probing into the brine pretreatment experiments and the running and debugging of field salt separation test system,putting forward the resource utilization scheme of mixed crystallization salt,analyzing the technique and economy of the mixed crystallization salt and coal chemical industry brine.The treatment cost of mixed crystallization salt by resource utilization is low cost,which can fundamentally solve the treatment problem of mixed crystallization salt as hazardous waste,such as high yield,high processing cost and easy to produce secondary pollution.Coal chemical industry brine TMC thermal membrane coupling industrial salt separation technology can realize high total salt recovery rate,high purity crystal salt,little mother liquor discharge,less waste generated,high clean water recovery rate,all in all,it possesses a great prospect of engineering application. |
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