This paper introduces the new trend of coal chemical industry environmental protection policy, analyzes the pollution sources of coal chemical industry wastewater, discusses the modern coal chemical industry wastewater treatment process in detail, and briefly describes the whole process control concept of coal chemical industry wastewater treatment.

1, the new trend of environmental protection policy

The revision of the Law of the People's Republic of China on Water Pollution Prevention has lowered the barriers to public participation, tightened supervision (such as not allowing transboundary drainage and intensifying penalties, etc.), promoted the pilot of sewage permits, and increased the joint and several liability of the EIA agencies. The "National List of Hazardous Wastes" was also revised, the "list" of waste types were adjusted, and a clear list of coal chemical-related hazardous wastes was made.

2, coal chemical wastewater pollution sources analysis

Coal gasification wastewater mainly comes from pressurized gasification wastewater and some slag pool wastewater; catalytic wastewater is a typical source of coal-to-liquid wastewater; hydrotreating and cracking are also sources of high-concentration coal-to-oil wastewater; although the amount of Fischer-Tropsch wastewater Small, but difficult to handle; MTO wastewater and a small amount of waste lye is a coal-to-olefin increase than other processes of wastewater pollution sources; public works, auxiliary works and other wastewater is also the sewage link.

3, the status of modern coal chemical wastewater treatment

Coal chemical wastewater treatment process can be roughly divided into wastewater pretreatment, biochemical treatment, salty wastewater reuse, high salt water treatment four process units.

3.1 Wastewater pretreatment unit

Fixed bed gasification wastewater is typical of coal chemical project wastewater, usually using gas-water separation, phenol ammonia recovery as a pre-treatment means. At present, the main use of "first deamidation and then extraction," the technical transformation, the next step is to optimize the optimization of space optimization and equipment selection.

3.2 biochemical treatment unit

Fixed bed gasification commonly used anaerobic, aerobic combination of biological treatment, the key is to improve the biodegradability of wastewater, entrained gasification using conventional biochemical treatment technology can be achieved. At present, the domestic technology basically meets the requirements for reuse. The next step is to optimize the technical integration and reduce the operating costs.

3.3 salty wastewater reuse unit

The basic double membrane to ultrafiltration, reverse osmosis-based treatment process. The difference is mainly reflected in the rate of wastewater recovery. The next step is to optimize the space mainly organic matter, the hardness of the membrane system, maximize recovery.

3.4 high concentration brine treatment unit

One is to send evaporation ponds, the use of the environment itself, the evaporation capacity of evaporation of water; one is the use of evaporation crystallization technology to further recover water, producing crystalline salt. At present, no enterprise really crystallizes the concentrated sodium sulfate and sodium chloride in the coal chemical's high-concentration brine through evaporative crystallization process. The key task for the next step is to screen the core technologies, optimize integration based on experimental verification, and explore new ways of reducing and reusing salt.

3.5 non-normal status of wastewater treatment status

Downtime and maintenance and other non-normal operating conditions of process equipment, water drainage imbalance will make the treatment of recycled water recycling standards can not be fully recycled. Unreasonable setting of temporary wastewater pool for individual projects can not guarantee the reuse of most of the water. Once the temporary storage tank is full, the wastewater can not be fully reused. Enterprises will be forced to stop for overhaul and more frequent parking will cause pollution.

At present, Shenhua Coal Oil, Datang Duolun, Keqi, Qinghua, etc. have been put into operation evaporation ponds are high liquid level operation.

4 modern coal chemical wastewater treatment process control

The whole process of control concepts include: selection of environmentally friendly production process, process design reform, flood management system, a reasonable direction to determine the sewage and overcome the pollution disposal problems of five parts. The whole process control theory is applied to the treatment of coal chemical wastewater. The design of the process will change from taking COD removal as the main line to gradually reducing the importance of reducing TDS. TDS reduction will be the main line to separate and classify concentrated brine. The whole process control theory applied to coal chemical water-saving emission reduction, the use of "water pinch" step by step the use of water quality, rational allocation of water sources and water wells, from the system perspective to consider the effective use of water, make the whole plant water balance.

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