Full-membrane zero-emission treatment system for circulating water and sewage in thermal power plants

Wet-cooled thermal power plant’s circulating water and sewage accounts for 70% to 80% of the total wastewater in the plant. The circulating water system is the system with the greatest water-saving potential in the plant.

Therefore, the reuse of circulating water and sewage from thermal power plants has good environmental and economic benefits, and is in line with national water-saving and environmental protection policies.

The quality of circulating water and sewage is complex, and its salt content, suspended solids, alkalinity, and hardness are high. According to the characteristics of circulating water and sewage, the more common circulating water and sewage treatment systems at this stage are:

Coagulation clarification-ultrafiltration-reverse osmosis, electroflocculation-precipitation-ultrafiltration-reverse osmosis, etc., but the existing treatment system has poor operation stability, serious fouling of membrane system, and the recovery rate of the system is generally between 50% and 75%. During the period, the recovery rate is low, the salt content of the reverse osmosis concentrated water is high, and the water volume is too large, which cannot meet the water quality requirements for reuse in the desulfurization system.

For power plants whose sewage permit requires that the wastewater cannot be discharged, most of the power plants currently combine the reverse osmosis concentrated water with the terminal wastewater in the circulating water sewage treatment system, resulting in high investment and operating costs, and at the same time, the circulating water sewage cannot be realized. zero emission.

The purpose of the utility model is to overcome the shortcomings of the above-mentioned prior art, and to provide a full-film zero-discharge treatment system for circulating water and sewage in thermal power plants.

The system can realize zero discharge of circulating water sewage, meet the environmental protection requirements of thermal power plants for water saving and emission reduction, and has low treatment costs.

In order to achieve the above-mentioned purpose, the thermal power plant circulating water and sewage full-membrane method zero-discharge treatment system includes a conditioning pool, a dual-alkali method combined softening-coagulation clarification treatment system, a multi-media filter, an ultrafiltration treatment system, Nanofiltration treatment system and reverse osmosis treatment system.

The outlet of the regulating pool is communicated with the inlet of the combined softening-coagulation-clarification treatment system by the dual-alkali method, and the outlet of the combined softening-coagulation-clarification treatment system by the dual-alkali method is communicated with the inlet of the multi-media filter.

The outlet of the multi-media filter is connected with the nanofiltration treatment system through the ultrafiltration treatment system, the produced water outlet of the nanofiltration treatment system is connected with the reverse osmosis treatment system, and the concentrated water outlet of the nanofiltration treatment system is connected with the process water tank of the external desulfurization system connected.

The double-alkali method combined softening-coagulation clarification treatment system includes a high-efficiency clarifier, a coagulant dosing device, a sodium carbonate dosing device, a sodium hydroxide dosing device, a coagulant dosing device, a hydrochloric acid dosing device and an intermediate pool. The outlet of the conditioning tank is communicated with the inlet of the high-efficiency clarifier.

The interior of the high-efficiency clarifier is divided into successively connected coagulation zone, flocculation zone and clarification zone. The outlet of the coagulant dosing device and the outlet of the sodium carbonate dosing device are communicated with the coagulation zone.

The outlet of the sodium hydroxide dosing device and the outlet of the coagulant dosing device are communicated with the flocculation zone, and the outlet of the clarification zone and the outlet of the hydrochloric acid dosing device are communicated with the inlet of the intermediate pool.

The outlet of the regulating tank is connected with the high-efficiency clarifier through the lift pump.

The water outlet of the intermediate pool is connected with the water inlet of the multi-media filter through the filter feed pump, the water outlet of the multi-media filter is connected with the water inlet of the clean water tank, and the outlet of the clean water tank is connected with the ultrafiltration treatment system.

The ultrafiltration treatment system includes an ultrafiltration feed pump, an ultrafiltration device and an ultrafiltration water production tank that are connected in sequence, wherein the water outlet of the multi-media filter is communicated with the inlet of the ultrafiltration feed pump.

The outlet of the ultrafiltration water production tank is communicated with the nanofiltration treatment system.

The nanofiltration treatment system includes a scale inhibitor dosing device, a reducing agent dosing device, a nanofiltration feed pump, a security filter, a nanofiltration high-pressure pump, a nanofiltration device and a nanofiltration production water tank;

The outlet of the ultrafiltration treatment system, the outlet of the scale inhibitor dosing device and the outlet of the reducing agent dosing device are connected with the inlet of the security filter through the nanofiltration feed pump through the pipeline.

The outlet of the security filter is connected with the inlet of the nanofiltration device through the nanofiltration high-pressure pump, the water production outlet of the nanofiltration device is connected with the inlet of the nanofiltration production water tank, and the concentrated water outlet of the nanofiltration device is connected with the process water tank of the external desulfurization system. The outlet of the nanofiltration water production tank is connected with the reverse osmosis treatment system.

The reverse osmosis treatment system includes reverse osmosis high pressure pump, reverse osmosis device, fresh water tank and fresh water pump.

The outlet of the nanofiltration treatment system is connected to the inlet of the reverse osmosis device through the reverse osmosis high-pressure pump, the fresh water outlet of the reverse osmosis device is connected to the inlet of the fresh water tank, and the outlet of the fresh water tank is connected to the external circulating water through the fresh water pump. The system is connected, and the concentrated water outlet of the reverse osmosis device is connected with the ash and slag humidification water system.

It also includes a sludge treatment system, which includes a sludge discharge pump, a sludge buffer tank, a sludge feed pump, a plate and frame filter press, a mud hopper, a filtrate water tank and a filtrate water pump.

The sludge discharge port at the bottom of the high-efficiency clarifier is connected with the inlet of the sludge buffer tank through the sludge discharge pump, and the sludge outlet at the bottom of the sludge buffer tank is connected with the inlet of the plate and frame filter press.

The sludge outlet of the plate and frame filter press is communicated with the inlet of the mud hopper, the filtrate outlet of the plate and frame filter press is communicated with the inlet of the filtrate water tank, and the outlet of the filtrate water tank is communicated with the regulating pool through the filtrate water pump.

The top outlet of the sludge buffer tank, the backwash water outlet of the multi-media filter, and the backwash water outlet of the ultrafiltration device are connected to the inlet of the waste water recovery pool, and the water outlet of the waste water recovery pool is connected to the inlet of the adjustment pool through the waste water pump. Pass.

The utility model has the following beneficial effects:

During the specific operation of the full-film zero-discharge treatment system for circulating water and sewage in a thermal power plant, the dual-alkali method combined softening-coagulation and clarification treatment system is used to treat Ca2+, Mg2+, suspended solids and total in the circulating water and sewage. Phosphorus is removed, and the removal rate is ≥90%.

Then enter the multi-media filter and ultrafiltration treatment system to remove suspended impurities and colloidal substances, and then use the nanofiltration treatment system to further remove divalent ions and organic substances such as Ca2+, Ba2+, Sr2+ and SO42-.

Among them, the recovery rate of nanofiltration reaches more than 80%. Among them, the concentrated water output by the nanofiltration system is recycled into the process water tank of the external desulfurization system, and the produced water output by the nanofiltration system is subjected to reverse osmosis treatment by the reverse osmosis treatment system. In the circulating water system, the reverse osmosis recovery rate is 90%.

The reverse osmosis concentrated water output by the reverse osmosis treatment system is consumed by mixing dry ash to wet, so as to achieve zero discharge of circulating water and sewage, meet the environmental protection requirements of thermal power plants for water saving and emission reduction, and at the same time, the treatment cost is low.

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