High-salinity wastewater concentration and reduction system and method

Abstract

The invention discloses a high-salinity wastewater concentration reduction system and method. The system comprises a raw water tank, a concentration circulating pump, a resin bed, a buffer water tank and a wastewater discharge pump. The raw water tank conveys high-salinity wastewater to the resin bed through a concentration circulating pump, a concentration water inlet valve is arranged between the concentration circulating pump and the resin bed, after water is absorbed by the resin bed, the substandard concentrated wastewater returns to the raw water tank through a first pipeline, the standard concentrated wastewater flows to the buffer water tank through a second pipeline, and a concentration water outlet valve is arranged at a liquid phase outlet of the resin bed. The first pipeline is provided with a concentrated water return valve, the second pipeline is provided with a drain valve, a dry gas inlet valve is arranged between the dry gas inlet and the resin bed, and the buffer water tank is connected with a subsequent treatment device through a wastewater discharge pump. Resin infiltration water absorption and drying gas water removal are utilized for circular treatment, high-salinity wastewater concentration reduction is achieved, the requirement for an external heat source is greatly reduced, operation can be conducted under the working condition far lower than the boiling point of a solution or at the room temperature, and system scaling can be avoided to the maximum extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-salt wastewater treatment, and specifically relates to a high-salt wastewater concentration and reduction system and method, which can be widely used in zero-emission treatment of high-salt wastewater at the end of industrial production such as coal-fired power plants, chemical pharmaceuticals, mining and smelting. Background Art

[0002] High-salt wastewater usually refers to wastewater with a total salt content (TDS) of at least 10,000 mg / L. Coal-fired power plants, mining and smelting, chemical and pharmaceutical industries all produce such high-salt wastewater, which not only contains many high-concentration organic pollutants, but also is accompanied by a large amount of calcium, sodium, chloride, sulfate and other ions. If discharged into the environment indiscriminately, it will cause serious harm. Therefore, it is necessary for the industry to reduce the wastewater through the concentration and reduction process to reduce the terminal treatment cost.

[0003] At present, wastewater concentration processes are mainly divided into membrane concentration and reduction and thermal concentration and reduction. The membrane concentration process is a separation technology based on the principle of semi-permeable membranes. It separates and concentrates different substances through pressure drive. However, this process has high requirements on the quality of influent water and requires pre-treatment such as softening, which results in high investment and operation costs for the entire system. In addition, the membrane is at risk of contamination and blockage and needs to be cleaned or replaced frequently, resulting in a limited service life. Thermal concentration and reduction mainly utilizes the difference between the boiling points of substances. By evenly applying the wastewater solution to be evaporated onto the heat exchange tubes and plates, heating it to the boiling point or near the boiling point to evaporate the water, the wastewater is concentrated and reduced. However, its system is relatively complex, with a high energy consumption-output ratio, and the heat exchanger is prone to scaling.

[0004] Therefore, it is necessary to develop a new high-salt wastewater concentration and reduction system and process to avoid the problems of high energy consumption, low flux and scaling and clogging to the greatest extent. It can not only treat high-salt wastewater thoroughly and efficiently, but also greatly reduce cost investment, which has important practical significance. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the present invention provides a novel high-salt wastewater concentration and reduction system and method. The system uses resin to absorb water through penetration, and then uses dry gas to quickly evaporate and regenerate the resin, so as to achieve rapid concentration of high-salt wastewater at low temperature through the water absorption / evaporation cycle operation between the two.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A high-salinity wastewater concentration and reduction system comprises a raw water tank, a concentration circulation pump, a resin bed, a buffer water tank, and a wastewater efflux pump. The raw water tank outlet pipe is connected to the liquid phase inlet of the resin bed, and a concentration circulation pump is arranged on the connecting pipeline. The liquid phase outlet pipeline of the resin bed is divided into a first pipeline and a second pipeline. The first pipeline is connected to the raw water tank, and the second pipeline is connected to the buffer water tank. A wastewater efflux pump is arranged on the outlet pipeline of the buffer water tank, and the wastewater efflux pump is connected to a subsequent treatment device; the gas phase inlet of the resin bed is connected to the dry gas inlet channel, and the gas phase outlet of the resin bed is connected to the wet gas exhaust channel. A high-salinity wastewater inlet pipeline is connected to the top of the raw water tank.

[0007] A concentrated water inlet valve is arranged on the pipeline at the liquid phase inlet of the resin bed, and the concentrated water inlet valve is located between the concentrated circulation pump and the resin bed; a concentrated water outlet valve is arranged on the pipeline at the liquid phase outlet of the resin bed, and a dry air inlet valve is arranged on the pipeline at the gas phase inlet of the resin bed; a concentrated water return valve is arranged on the first pipeline, and a drain valve is arranged on the second pipeline.

[0008] The raw water tank transports high-salt wastewater to the resin bed through a concentration circulation pump. A concentration water inlet valve is provided between the concentration circulation pump and the resin bed. After the resin bed absorbs water, the concentrated wastewater that does not meet the standards returns to the raw water tank through the first pipeline, and the concentrated wastewater that meets the standards goes to the cache water tank through the second pipeline. A concentration water outlet valve is provided at the resin bed outlet, and a dry air inlet valve is provided between the dry gas inlet and the resin bed. The cache water tank is connected to the subsequent treatment device through a wastewater discharge pump.

[0009] Furthermore, the resin bed is filled with macroporous ion exchange resin, the wetted resin pore size is 100-500 nm, the resin filling rate in the bed is 30-50%, and an interception net is provided in the reactor to prevent the resin from being carried out and lost.

[0010] Furthermore, a high-salt wastewater inlet pipeline is connected to the top of the raw water tank, the outlet pipe of the raw water tank is maintained at no less than 300 mm from the bottom, and a sedimentation and slag discharge pipeline and a slag discharge valve are provided at the bottom of the raw water tank. The pretreated or concentrated sediment produced in the raw water tank is regularly discharged to the subsequent treatment device.

[0011] Furthermore, the humid air formed by the water-absorbing resin bed can be condensed, dehumidified and dried, and after heat exchange can be re-entered into the water-absorbing resin bed as dry air for dehumidification, and the condensed water can be recovered and reused.

[0012] The present invention also provides a method for concentrating and reducing high-salinity wastewater, which is based on the high-salinity wastewater concentrating and reducing system as described above and comprises the following steps: 1) After the high-salinity wastewater is pre-treated by initial precipitation in the raw water tank, it is transported to the resin bed through a concentration circulation pump for water absorption; 2) The concentrated wastewater after the resin bed absorbs water is transported from the liquid phase outlet of the resin bed through the first pipeline back to the raw water tank, and at the same time, an empty resin bed after water absorption is obtained; 3) Dry gas is transported to the empty resin bed after water absorption. The saturated water-absorbing resin bed is fully in contact with the dry gas, which draws heat from the dry gas and uses the humidity difference to drive the evaporation of water, while achieving dry regeneration of the resin bed; 4) After fully contacting with the resin bed, moist gas is generated, which is discharged from the gas phase outlet on the top of the resin bed to the moist gas exhaust channel, undergoes a condensation dehumidification process and is dried. After heat exchange, it enters the dry gas inlet channel as dry gas again to dehumidify the water-absorbing resin bed, and the condensed water is recovered and reused; 5) Repeat steps 1) to 4) until the concentrated wastewater reaches a predetermined concentration, and then transfer it to the buffer water tank through the second pipeline and discharge it to the subsequent treatment device through the wastewater discharge pump.

[0013] Furthermore, in step 1), the TDS of the high-salt wastewater raw water is 10000~200000 mg / L, and the solution contains Na + , Cl - , Ca 2+ 、SO 4 2- Ions, pH adjusted to 4~10.

[0014] Furthermore, in step 2), the resin bed water absorption operation conditions are as follows: a temperature of 20-40° C., a wastewater / resin configuration mass ratio of 0.1-1, and a wastewater retention time of 10-30 min.

[0015] Furthermore, in step 3), the temperature of the drying gas is 35-80° C., the relative humidity is 0-40%, the drying gas-ion exchange resin empty bed residence time is 0.10-0.40 seconds, and the empty bed gas velocity is 2-5 m / s.

[0016] Furthermore, in step 4), the humid air temperature is 20-50° C. and the relative humidity is 70-100%.

[0017] Furthermore, in step 5), the concentration ratio of the high-salt wastewater is 2 to 10 times.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Different from the existing membrane concentration process, this system utilizes the water absorption and salt resistance characteristics of the resin. There is no physical membrane in the system. The interface between the resin and water can act as a membrane. The osmotic pressure inside the resin is extremely high. The forward osmosis principle causes water to penetrate from the solution into the resin to achieve wastewater concentration. (2) Unlike the existing high-temperature thermal concentration process that operates at or near the boiling point, this system is different from the existing high-temperature thermal concentration process that operates at or near the boiling point. After absorbing water, the resin in this system comes into contact with the dry gas. The system uses the difference in relative humidity sensitivity to evaporate the water in the resin into the dry gas through aerodynamics. The latent heat of water evaporation is almost entirely provided by unsaturated air, thereby reducing or eliminating the need for other external heat sources. The system can operate at a condition far below the boiling point of the solution or at room temperature. (3) In this system, resin is used as a water absorbent. The resin has a very high concentration of covalently bound functional groups and carries a fixed positive or negative charge. Due to the existence of the Gibbs-Donnan effect, electrolyte ions, especially divalent ions, will be strongly repelled, which can maximize the avoidance of scaling problems. (4) This system achieves continuous concentration of high-salinity wastewater through the circulation of water absorption by the main resin and moisture carried by dry air. It has small equipment investment, low energy consumption, simple operation and flexible equipment layout. Compared with natural evaporation methods such as evaporation ponds, it has a larger mass transfer area per unit volume and a relatively fast evaporation concentration speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the high-salt wastewater concentration and reduction system of the present invention.

[0020] In the figure: 1. Raw water tank; 2. Resin bed; 3. Buffer water tank; 4. Concentration circulation pump; 5. Wastewater discharge pump; 6. Concentration water inlet valve; 7. Dry air inlet valve; 8. Concentration water outlet valve; 9. Drain valve; 10. Concentration return valve; 11. First pipeline; 12. Second pipeline; 13. Slag discharge valve. DETAILED DESCRIPTION

[0021] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. Example 1

[0022] like Figure 1As shown, a high-salinity wastewater concentration and reduction system includes a raw water tank 1, a resin bed 2, a buffer water tank 3, a concentration circulation pump 4, and a wastewater efflux pump 5. The outlet pipe of the raw water tank 1 is connected to the liquid phase inlet of the resin bed 2, and the concentration circulation pump 4 is arranged on the connecting pipeline. The liquid phase outlet pipeline of the resin bed 2 is divided into a first pipeline 11 and a second pipeline 12. The first pipeline 11 is connected to the raw water tank 1, and the second pipeline 12 is connected to the buffer water tank 3. The outlet pipeline of the buffer water tank 3 is provided with a wastewater efflux pump 5, and the wastewater efflux pump 5 is connected to a subsequent treatment device; the gas phase inlet of the resin bed 2 is connected to the dry gas inlet channel, and the gas phase outlet of the resin bed 2 is connected to the wet gas exhaust channel. The high-salinity wastewater inlet pipeline is connected to the top of the raw water tank 1.

[0023] A concentrated water inlet valve 6 is provided on the pipeline at the liquid phase inlet of the resin bed 2, and the concentrated water inlet valve 6 is located between the concentrated circulation pump 4 and the resin bed 2; a concentrated water outlet valve 8 is provided on the pipeline at the liquid phase outlet of the resin bed 2; a dry air inlet valve 7 is provided on the pipeline at the gas phase inlet of the resin bed 2; a concentrated water return valve 10 is provided on the first pipeline 11, and a drain valve 9 is provided on the second pipeline 12.

[0024] The raw water tank 1 transports the high-salt wastewater to the resin bed 2 via the concentration circulation pump 4. A concentration water inlet valve 6 is provided between the concentration circulation pump 4 and the resin bed 2. After the resin bed 2 absorbs water, the concentrated wastewater that does not meet the standards returns to the raw water tank 1 via the first pipeline 11. After several cycles, the concentrated wastewater that meets the standards goes to the cache water tank 3 via the second pipeline 12. A dry air inlet valve 7 is provided between the dry air inlet and the resin bed 2. The cache water tank 3 is connected to the subsequent treatment device via the wastewater discharge pump 5. The top of the raw water tank 1 is connected to a high-salt wastewater inlet pipeline, the outlet pipe of the raw water tank 1 is kept at least 300 mm from the bottom, and a sedimentation and slag discharge pipeline and a slag discharge valve 13 are provided at the bottom of the raw water tank 1. The pre-treated or concentrated sediment produced in the raw water tank 1 is regularly discharged to the subsequent treatment device.

[0025] The resin bed 2 is filled with macroporous ion exchange resin, the wet resin pore size is 100-500 nm, the resin filling rate in the bed is 30-50%, and an interception net is set in the reactor of the resin bed 2 to prevent the resin from being taken out and lost. The humid gas formed by the water-absorbing resin bed is condensed, dehumidified and dried, and after heat exchange, it enters the water-absorbing resin bed as dry gas for dehumidification, and the condensed water is recovered and reused. The dry gas passes through the water-absorbing resin, and the two exchange water to form humid gas and dried resin. Example 2

[0026] This embodiment provides a method for concentrating and reducing high-salinity wastewater, comprising the following steps: 1) The high-salinity wastewater comes from the desulfurization wastewater of a coal-fired power plant. The TDS of the wastewater is 27000 mg / L (including Cl - Content 15000 mg / L, Ca2+ Content 2200 mg / L, Mg 2+ content 1200 mg / L, pH 6.5), the wastewater flow rate is 500 kg / h, the wastewater is pre-treated by preliminary precipitation in the raw water tank 1, and is transported to the resin bed 2 for water absorption through the concentration circulation pump 4; 2) The operating conditions for water absorption of resin bed 2 are as follows: temperature of 30°C, wastewater / resin mass ratio of 0.8, macroporous strong alkaline anion exchange resin, wastewater retention time of 10 min, and concentrated wastewater (TDS of 38450 mg / L) formed by sufficient water absorption by resin bed 2 is transported back to raw water tank 1 through the first pipeline from the outlet of resin bed 2, and an empty resin bed after water absorption is obtained at the same time; 3) Dry air after heat exchange with low-temperature flue gas is used as drying gas (temperature of 50°C, relative humidity of 10%) and transported to the empty resin bed after water absorption. The residence time of drying gas-ion exchange resin empty bed is 0.15 seconds, the empty bed gas velocity is 3 m / s, and the saturated water-absorbing resin bed 2 is fully contacted with the drying gas for 40 minutes. Heat is drawn from the drying gas and the humidity difference is used to drive the evaporation of water, thereby realizing the dry regeneration of the resin bed 2. 4) After being fully in contact with the resin bed 2, moist air (temperature is 35°C, relative humidity is 80%) is generated, and the moist air is discharged from the top outlet of the resin bed 2, enters the condensation system for dehumidification and heat exchange drying (temperature is 50°C, relative humidity is 10%), and then enters the water-absorbing resin bed as dry air again, and the condensed water is recovered; 5) After repeating steps 1) to 4) twice, the concentrated wastewater is tested to reach a predetermined concentration (the TDS concentration of the concentrated wastewater is 136400 mg / L), and can be transferred to the buffer water tank 2 through the second pipeline 12, and discharged to the subsequent treatment device through the wastewater discharge pump 5. During this period, about 400 kg / h of water vapor is transferred, and 100 kg / h of concentrated wastewater remains, and the concentration ratio is 5 times.

[0027] The present invention utilizes resin infiltration to absorb water and dry gas to remove water for cyclic treatment, thereby achieving concentration and reduction of high-salt wastewater, greatly reducing the demand for external heat sources, and can operate at conditions far below the boiling point of the solution or at room temperature, and can maximize the avoidance of system scaling.

[0028] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A high-salinity wastewater concentration and reduction system, characterized in that: The invention comprises a raw water tank (1), a resin bed (2) and a buffer water tank (3), wherein a water outlet pipe of the raw water tank (1) is connected to a liquid phase inlet of the resin bed (2), a concentration circulation pump (4) is arranged on the connecting pipeline, a liquid phase outlet pipeline of the resin bed (2) is divided into a first pipeline (11) and a second pipeline (12), the first pipeline (11) is connected to the raw water tank (1), the second pipeline (12) is connected to the buffer water tank (3), a wastewater efflux pump (5) is arranged on the outlet pipeline of the buffer water tank (3), and the wastewater efflux pump (5) is connected to a subsequent treatment device; a gas phase inlet of the resin bed (2) is connected to a dry gas inlet channel, a gas phase outlet of the resin bed (2) is connected to a wet gas exhaust channel, and a high-salt wastewater inlet pipeline is connected to the top of the raw water tank (1).

2. A high-salinity wastewater concentration and reduction system according to claim 1, characterized in that: A concentrated water inlet valve (6) is provided on the pipeline at the liquid phase inlet of the resin bed (2), a concentrated water outlet valve (8) is provided on the pipeline at the liquid phase outlet of the resin bed (2), and a dry air inlet valve (7) is provided on the pipeline at the gas phase inlet of the resin bed (2); a concentrated water return valve (10) is provided on the first pipeline (11), and a drain valve (9) is provided on the second pipeline (12).

3. A high-salinity wastewater concentration and reduction system according to claim 1, characterized in that: The resin bed (2) is filled with macroporous ion exchange resin, the resin pore size is 100-500 nm, the resin filling rate in the resin bed (2) is 30-50%, and an interception net is arranged in the reactor of the resin bed (2) to prevent the resin from being carried out and lost.

4. A high-salinity wastewater concentration and reduction system according to claim 1, characterized in that: The outlet pipe of the raw water tank (1) is maintained at a distance of not less than 300 mm from the bottom. A sedimentation and slag discharge pipeline and a slag discharge valve (13) are provided at the bottom of the raw water tank (1). Pre-treated or concentrated sediment produced in the raw water tank (1) is regularly discharged to a subsequent treatment device.

5. A method for concentrating and reducing high-salinity wastewater, using the concentrating and reducing system according to any one of claims 1 to 4, characterized in that: The process steps include: 1) After the high-salinity wastewater is pre-treated by initial precipitation in the raw water tank (1), the high-salinity wastewater is transported to the resin bed (2) through the concentration circulation pump (4) for water absorption; 2) After the resin bed (2) absorbs water, the concentrated wastewater is transported from the liquid phase outlet of the resin bed (2) through the first pipeline (11) back to the raw water tank (1), and an empty resin bed after water absorption is obtained at the same time; 3) Drying gas is transported to the empty resin bed after water absorption. The saturated water-absorbing resin bed and the drying gas are fully in contact, and heat is drawn from the drying gas and the humidity difference is used to drive the evaporation of water, thereby achieving the drying regeneration of the resin bed (2). 4) After being fully in contact with the resin bed (2), moist gas is generated, and the moist gas is discharged from the gas phase outlet at the top of the resin bed (2) to the moist gas exhaust passage, undergoes a condensation and dehumidification process and is dried, and after heat exchange, enters the dry gas inlet passage as dry gas again to dehumidify the water-absorbing resin bed (2), and the condensed water is recovered and reused; 5) Repeat steps 1) to 4) until the concentrated wastewater reaches a predetermined concentration, and then transfer the concentrated wastewater to the buffer water tank (3) through the second pipeline (12), and discharge the concentrated wastewater to a subsequent treatment device through the wastewater discharge pump (5).

6. A method for concentrating and reducing high-salinity wastewater according to claim 5, characterized in that: In step 2), the resin bed (2) absorbs water under the following operating conditions: a temperature of 20-40° C., a wastewater / resin mass ratio of 0.1-1, and a wastewater retention time of 10-30 min.

7. A method for concentrating and reducing high-salinity wastewater according to claim 5, characterized in that: In step 3), the temperature of the drying gas is 35-80°C, the relative humidity is 0-40%, and purified low-temperature flue gas or dry air can be used. The empty bed residence time of the drying gas-ion exchange resin is 0.10-0.40 seconds, and the empty bed gas velocity is 2-5 m / s.

8. The method for concentrating and reducing high-salinity wastewater according to claim 5, characterized in that: In step 4), the humid air temperature is 20~50℃ and the relative humidity is 70~100%.

9. The method for concentrating and reducing high-salinity wastewater according to claim 5, characterized in that: In step 5), the wastewater concentration ratio is 2 to 10 times.

10. The method for concentrating and reducing high-salinity wastewater according to claim 5, characterized in that: Step 1) The TDS of medium- and high-salt wastewater is 10,000-200,000 mg / L, and the solution contains Na + , Cl - , Ca 2+ , SO4 2- Ions, pH adjusted to 4~10.

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