| Modern coal chemical wastewater and coal-fired power plant wastewater will produce a large amount of high-salt wastewater during treatment.Most companies use traditional concentrated crystallization methods to separate out miscellaneous salts.The miscellaneous salts obtained after treatment is extremely expensive as a hazardous waste,and it is also easy to cause secondary pollution.It has become one of the key environmental protection issues that restrict the development of related industries.This article focuses on the treatment of high-salt wastewater and the utilization of miscellaneous salt resources.The research objects are the crushed coal pressurized gasification wastewater of a coal-to-natural gas enterprise and the desulfurization wastewater of a coal-fired power plant.According to their composition and composition characteristics,researches on the process of hetero-salt nanofiltration separation and waste water hardening pretreatment are carried out to purify the hetero-salt to the standard of saleable industrial salt to achieve the purpose of resource utilization.This paper aims at crushed coal pressurized gasification waste water,through the analysis of the existing miscellaneous salt and the water quality of the evaporator inlet and outlet water,the process plan for the treatment of high-salt wastewater and the resource utilization of miscellaneous salt is determined:The ozone oxidation method is used to perform advanced oxidation pretreatment on the evaporator inlet water to reduce TOC,and then the divalent ions such as Ca2+,Mg2+and SO42-are intercepted and separated by nanofiltration to improve the purity of sodium chloride in the evaporator inlet water.The research focused on the influence of different process operating conditions on the salt separation results of nanofiltration,and determined the best process parameters.The 50 kg/h evaporative crystallization experiment was further carried out,and the influence of steam temperature and secondary steam temperature on the purity of crystalline salt NaCl was explored,and the best crystallization purification process for miscellaneous salts were proposed.This process realizes the high-efficiency separation and purification of miscellaneous salts without waste water.The obtained crystalline salt product has been evaluated by the industry’s authoritative testing organization and has reached the standard of industrial first-class salt,and has realized the utilization of resources.In this paper,based on the desulfurization wastewater of coal-fired power plants,according to different subsequent treatment processes in actual production,different pretreatment processes for hardening removal are determined.In the nanofiltration salt evaporation crystallization process,due to the requirement to reduce the hardness of the wastewater as much as possible.Therefore,by adjusting the dosing method,sequence and amount of lime,sodium carbonate and sodium sulfate,this paper determines the best dosing method for desulfurization wastewater pretreatment of the power plant.By adjusting the mixing time and mixing speed,the effect of the process conditions on the softening and hardening of desulfurization wastewater was studied.The research results were verified by salt separation by nanofiltration membrane.In the evaporative crystallization process of the gypsum seeding method,by adjusting the dosage ratio of lime and calcium sulfate,the process enters the aqueous solution n(Ca2+):n(SO42-)=1:1.The optimal dosage of desulfurization wastewater for the coal-fired power plant was determined and verified in the pilot plant.In this paper,a new idea for the treatment of industrial high-salt wastewater and the resource utilization of high-salt wastewater was provided by studying the processes of nanofiltration separation of the wastewater from the pressurized gasification of crushed coal in modern coal chemical industry and the pretreatment of the wastewater from desulfurization in coal-fired power plants. |
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