Among the sources of water pollution, industrial wastewater is more difficult to handle and harms than domestic sewage. As one of the main sources of industrial wastewater, coal chemical industry wastewater also faces some problems and some restrictive factors. This article briefly discusses. 1 coal chemical wastewater treatment problems Coal chemical wastewater discharge intensity, combined with high concentration, strong toxicity, volatility and other characteristics, resulting in easy collapse of biochemical systems, contaminated difficult to remove a stable depth; the same time, lack of safe disposal of concentrated brine technology, coal chemical wastewater "zero emissions" lack of Corresponding technical support. The requirement of "zero discharge" of waste water makes the original less important part is very important, such as inorganic salt in water. Therefore, the choice of wastewater treatment technology and production processes have the same importance, must be stable and reliable. However, at present, there are some problems in the treatment of coal chemical wastewater and it is difficult to meet the environmental protection needs of enterprises. Different quality of coal, and different conversion process will cause the fluctuation of wastewater quality; the engineering design of extraction selectivity, biochemical treatment process, deep purification process, internal structure of evaporative crystallization equipment can not be well combined; the types of characteristic pollutants and Biological toxicity, the relationship between organic pollutants and the membrane, the impact of organic pollutants on the crystalline form and crystal growth is not clear, mainly based on experience to design, lack of theoretical guidance. Phenol ammonia recovery unit of the oil removal rate is low, the presence of oil and coke powder easily lead to block ammonia distillation tower, the pieces scaling. Biochemical treatment system instability, effluent COD concentration of 200 ~ 400 mg / L, ammonia nitrogen concentration of 5 ~ 80 mg / L. The depth of pollutant removal is not enough. The COD concentration in the effluent is 80 ~ 200 mg / L. The new pollutants such as cyanide, benzopyrene and polycyclic compounds are lack of relevant emission standards. Membrane flux decreased too fast, requiring large amounts of agents to wash it frequently, resulting in the cleaning agent in wastewater without a proper "zero discharge" system. If the biochemical system can not be stable, impact-resistant operation, zero discharge of waste water will be difficult to achieve. In the process of evaporation and crystallization, there are some problems such as flying material, corrosion of equipment and no export of mixed salt. 2 coal chemical wastewater "zero emissions" constraints Wastewater "zero discharge" requires a lot of energy, chemicals, capital investment, the three-effect evaporation, for example, 1 t water evaporation energy consumption of about 400 kg steam; salt environment safety of the product is unknown, resulting in salt products The way out to be determined; residual mixed salt safe disposal no reliable method of disposal. Zero-emission technology should be strengthened, management, engineering and other aspects of work. 3 solution ideas Through in-depth analysis of the sources of coal chemical wastewater, and life cycle analysis of pollutants, considering the feasibility of harmless disposal of pollutants and its impact on the environment, and then from the raw materials, production and decontamination treatment , The whole process of pollution control, and ultimately to minimize the overall cost. 4 coal chemical waste water treatment Organic matter degradation is difficult to harmless chemical and chemical waste water treatment the biggest problem. There are many kinds of organic chemicals contained in coal chemical wastewater, and there are thousands of organic compounds. Their concentration, toxicity, biodegradability and physico-chemical properties vary greatly. The pollutant concentration also has an important influence on the cost of different treatment technologies. The pre-treatment of coal chemical wastewater is mainly for the detoxification and recovery of valuable resources, the latter part of the depth of treatment is mainly to achieve discharge or near-zero emissions, and the whole process is interrelated and needs to be considered from the perspective of the whole process. 5 wastewater treatment technology applications For refractory organic matter content is high, biological toxicity of the waste water to strengthen the pretreatment of the medium concentration of wastewater biodegradation as the core, strengthen biological treatment; for low concentration of wastewater, strengthen the depth of removal and reuse. This will not only realize the recovery of resources, but also protect the pollutants from harmless treatment. Below the multi-year work of our team as an example, introduce the whole process of wastewater treatment technology. 5.1 gas purification residue pretreatment For the high concentration of gas purification (desulfurization) generated residue, the composition of the complex wastewater, COD concentration and high salt content, the use of normal temperature catalytic conversion technology for pre-removal, which remove the COD, sulfide, cyanide. 5.2 extraction and purification coke powder technology Aiming at the problem of tar and coke powder in coal chemical industry, a new extraction agent was developed by molecular design and strengthening the function of organic molecules and surface functional groups of coke powder. The coke powder was removed from the wastewater and the ammonia distillation tower Plug and extract the middle layer. 5.3 phenol oil synergistic extraction technology Development of new extractant to reduce its solubility in water and avoid the recovery of energy extraction process; in the recovery of phenol at the same time, the synergistic removal of the tar, thereby enhancing the biodegradability of wastewater. 5.4 distillation ammonia distillation technology Through global optimization and control of ammonia nitrogen removal efficiency, the development of high-efficiency tower internals, combined with process control, to achieve the ammonia nitrogen content reduced to 50mg / L or less, while recovery of more than 16% concentrated ammonia or ammonium salt. We use the above technology in the Yima gasification plant scale 1m3 / h pilot test, the main process is the first extraction degreasing phenol, ammonia de-ammonia after. The current operating results are good, COD concentration from 15 000 to 25 000 mg / L down to 2 500 mg / L below the ammonia concentration can be reduced to 50 mg / L or less. 5.5 biological strengthening treatment The core of biological treatment is to solve its operational stability issues. The main factors affecting the stable operation of biochemical systems are whether the organic matter contained in wastewater is easily degraded, the toxicity of organic compounds, the competition between autotrophic bacteria and heterotrophic bacteria and the concentration of organic compounds. Engineering hope to improve the stability of the biochemical system at the same time, reduce energy consumption, cost savings, to avoid the second settling tank. Compared with the mixed liquor refluxing process, the microbial flora in the activated sludge of the supernatant refluxing process is more significantly different in different stages, which is more conducive to efficient degradation of different types of pollutants in stages. 5.6 based on total cyanide / organic matter efficient removal of coagulant and technology In order to solve the problem of total cyanide, chroma and COD in biochemical effluent, we designed and produced a new type of high efficient coagulation decyanation agent to achieve synergistic removal of multiple pollutants. C
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