Solar-driven wastewater evaporation and concentration system and method

Abstract

This invention discloses a solar-driven wastewater evaporation and concentration system and method. The system includes a concentrated brine tank, with several solar thermal collectors connected in series at the output end of the tank. These solar thermal collectors are driven by a control system. The output end of each solar thermal collector is connected to a concentrated water flash evaporator, which is connected to a condensate recovery unit, a crystallization unit, and a vacuum system. Each solar thermal collector is also connected to a heat storage medium tank, which is connected to a heat storage unit. The heat storage unit and the several solar thermal collectors connected in series form a circulation loop. The system of this invention has advantages such as high power flexibility, high output, low cost, and strong structural reliability.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a solar-driven wastewater evaporation and concentration system and method. Background Technology

[0002] Currently, water scarcity is a major global challenge. With rising economic levels, industrial production generates large amounts of high-salinity wastewater. Due to the complex composition, fluctuating volatility, and high toxicity of this wastewater, centralized collection and extensive treatment methods exacerbate these characteristics, further increasing treatment difficulty and costs. Therefore, to meet stringent environmental requirements, concentration technology, crystallization technology, and synergistic technologies combining these two are widely used to achieve zero-discharge recycling of high-salinity wastewater. The evaporation and concentration stage requires significant heat to reduce the volume of high-salinity wastewater. Currently, evaporation reduction is primarily achieved through steam thermal concentration or electrically driven membrane modules, resulting in high energy consumption and investment costs, which does not meet national energy conservation and carbon reduction requirements. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a solar-driven wastewater evaporation and concentration system and method, which has the advantages of high power flexibility, high output, low cost and strong structural reliability.

[0004] The solar-driven wastewater evaporation and concentration system proposed in this invention includes a concentrated brine tank. The output end of the concentrated brine tank is connected to several solar thermal collectors connected in series. The solar thermal collectors are driven by a control system. The output end of the solar thermal collectors is connected to a concentrated water flash tank. The concentrated water flash tank is connected to a condensate recovery unit, a crystallization unit, and a vacuum system. The solar thermal collectors are also connected to a heat storage medium tank. The heat storage medium tank is connected to a heat storage unit. The heat storage unit and the several solar thermal collectors connected in series form a circulation loop.

[0005] Preferably, the concentrated water flash tank includes a tank body, which is connected to an inlet pipe and a steam outlet pipe. A first-stage vertical baffle, a second-stage vertical baffle, and a third-stage vertical baffle are spaced apart inside the tank body to divide the tank body into a first flash zone, a second flash zone, a third flash zone, and a fourth flash zone. A horizontal baffle is provided above the first flash zone, and a salt collection tank is provided at the lower end of the second, third, and fourth flash zones.

[0006] Preferably, a wire mesh demister is also provided inside the tank, and the wire mesh demister is located below the steam outlet pipe.

[0007] Preferably, the height of the first-stage vertical baffle and the third-stage vertical baffle is 1 / 5 to 1 / 4 of the height of the horizontal baffle; the height of the second-stage vertical baffle is 1 / 3 to 4 / 5 of the height of the first-stage vertical baffle.

[0008] Preferably, the inclination angle of the sidewall of the salt collection tank is 120-145°.

[0009] Preferably, the first-stage vertical baffle, the second-stage vertical baffle, and the third-stage vertical baffle 55 are each provided with a plurality of jet holes, which are distributed in a square, inverted triangle, or equilateral triangle pattern.

[0010] Preferably, the widths of the first flash zone, the second flash zone, the third flash zone, and the fourth flash zone are the same.

[0011] Preferably, the outlet of the concentrated water flash evaporator is also connected to the inlet of the concentrated brine tank.

[0012] The working method of the solar-driven wastewater evaporation and concentration system proposed in this invention includes the following steps:

[0013] S1: During the daytime sunlight, the concentrated brine in the concentrated brine tank is pumped to the solar thermal collector unit to gradually increase its temperature, and then discharged into the concentrated water flash tank for evaporation and concentration;

[0014] S2: The concentrated water after being treated in the concentrated water flash tank enters the crystallization unit for crystallization. The evaporated steam is collected or reused by the condensate recovery unit. If the concentration is not up to the design multiple, it is returned to the concentrated brine tank through the return pipe. At the same time, the heat storage medium in the heat storage medium tank enters the solar collector unit to absorb heat and store heat for later use.

[0015] S3: At night, close the valve on the pipeline between the concentrated brine tank and the solar collector unit. The concentrated brine in the concentrated brine tank enters the concentrated water flash tank for flash evaporation after heat exchange with the heat storage unit. The subsequent steps are the same as S2.

[0016] Beneficial technical effects of the present invention:

[0017] 1. The solar thermal collector unit of the present invention can adjust its own angle in a timely manner so that the concentrated brine pipe is always at the focal point of the unit, maximizing the utilization of solar energy and achieving high thermal energy conversion efficiency. The present invention realizes the modularization of the solar thermal collector unit, and can flexibly arrange the number and arrangement of solar thermal collector units according to the actual project scale and land area. It can realize large-scale industrial wastewater evaporation and concentration using a single skid-mounted module or multiple modules.

[0018] 2. The concentrated brine of the present invention is concentrated and evaporated in a concentrated water flash tank, which can realize the reduction of concentration volume, reuse of condensate, and collection of crystal precipitation, thereby improving the economic efficiency of the system. The concentrated water flash tank of the present invention utilizes the rational arrangement of baffles to achieve the mixing degree of high-salt wastewater in the flash chamber, reduce eddy current losses, and improve the heat and mass transfer intensity. On the other hand, through the different forms of openings in the baffles, segmented pressure reduction evaporation is achieved, further effectively improving the thermal energy utilization rate.

[0019] 3. This invention achieves stable and continuous operation of the wastewater evaporation and concentration system under no light or weak light conditions through the coupling of the heat storage unit, thereby increasing the system reliability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the solar-driven wastewater evaporation and concentration system proposed in this invention;

[0021] Figure 2 This is a schematic diagram of the structure of the concentrated water flash evaporator proposed in this invention;

[0022] Figure 3 This is a schematic diagram of the vertical baffle plate proposed in this invention.

[0023] In the diagram: 1-Concentrated brine tank, 2-Solar collector unit, 3-Heat storage medium tank, 4-Heat storage unit, 5-Concentrated water flash tank, 51-Inlet pipe, 52-Horizontal baffle, 53-First-stage vertical baffle, 54-Second-stage vertical baffle, 55-Third-stage vertical baffle, 56-Salt collection tank, 57-Wire mesh demister, 58-Steam outlet pipe, 59-Tank body, 6-Condensate recovery unit, 7-Crystallization unit, 8-Vacuum system, 9-Control system. Detailed Implementation

[0024] The present invention will be further explained below with reference to specific embodiments.

[0025] Reference Figure 1 The solar-driven wastewater evaporation and concentration system proposed in this invention includes a concentrated brine tank 1. The output end of the concentrated brine tank 1 is connected to several solar collector units 2 connected in series. The solar collector units 2 are driven by a control system 9. The output end of the solar collector units 2 is connected to a concentrated water flash tank 5. The concentrated water flash tank 5 is connected to a condensate recovery unit 6, a crystallization unit 7, and a vacuum system 8. The solar collector units 2 are also connected to a heat storage medium tank 3. The heat storage medium tank 3 is connected to a heat storage unit 4. The heat storage unit 4 and the several solar collector units 2 connected in series form a circulation loop. The outlet of the concentrated water flash tank 5 is also connected to the inlet of the concentrated brine tank 1.

[0026] The solar collector unit uses trough solar modules, including a parabolic reflector, absorber tube, focal point positioning ring, connecting bracket, rotating motor, and rotating shaft gear. The solar collector unit can be connected in series, parallel, or series-parallel configurations to achieve high-efficiency operation, depending on the actual engineering conditions.

[0027] The heat storage medium tank is made of corrosion-resistant materials such as carbon steel, stainless steel, or titanium. The heat storage medium can be biphenyl-biphenyl ether or silicone oil, or molten salt media such as nitrate / nitrite, carbonate, chloride, and fluoride salts.

[0028] Reference Figure 2-3 The concentrated water flash tank 5 includes a tank body 59, which is connected to an inlet pipe 51 and a steam outlet pipe 58. The tank body 59 is equipped with a first-stage vertical baffle 53, a second-stage vertical baffle 54 and a third-stage vertical baffle 55 at intervals to divide the tank body 59 into a first flash zone, a second flash zone, a third flash zone and a fourth flash zone. A horizontal baffle 52 is provided above the first flash zone, and a salt collection tank 56 is provided at the lower end of the second flash zone, the third flash zone and the fourth flash zone.

[0029] A wire mesh demister 57 is also installed inside the tank 59, located below the steam outlet pipe 58. The wire mesh demister can be supported by corrosion-resistant stainless steel wire or high-polymer corrosion-resistant organic material. The wire mesh aperture is required to be 0.1-0.3mm, preferably 0.25mm; the porosity is approximately 0.97-0.99, preferably 0.98. The wire mesh demister has mesh thicknesses of 80mm, 100mm, 150mm, and 200mm, which need to be selected appropriately according to the amount of liquid entrainment. When the amount of liquid entrainment is small, a thickness of less than 100mm is selected; when the amount of liquid entrainment is large, a thickness of more than 150mm is selected.

[0030] The heights of the first-stage vertical baffle 53 and the third-stage vertical baffle 55 are 1 / 5 to 1 / 4 of the height of the horizontal baffle 52, preferably 1 / 5; the height of the second-stage vertical baffle 54 is 1 / 3 to 4 / 5 of the height of the first-stage vertical baffle 53, preferably 1 / 3; the inclination angle of the sidewall of the salt collection tank 56 is 120-145°, preferably 120°; the first-stage vertical baffle 53, the second-stage vertical baffle 54, and the third-stage vertical baffle 55 are all provided with a number of jet holes, which are distributed in a square, inverted triangle, or equilateral triangle pattern; the widths of the first flash zone, the second flash zone, the third flash zone, and the fourth flash zone are the same.

[0031] The working principle of the concentrated wastewater flash evaporator: Heated high-salt wastewater flows into the flash chamber from the bottom through the inlet pipe, where it boils under low vacuum conditions in the space formed by the horizontal baffle and the first-stage vertical baffle. Most of the overflow enters the rear of the flash chamber, while a portion enters the rear through the jet holes of the first-stage vertical baffle, promoting mixing between liquids. The high-salt wastewater undergoes the aforementioned flash evaporation and jet boiling phenomena as it flows through the second and third-stage vertical baffles, ensuring strong vapor-liquid exchange at a relatively low superheat. After concentration, the high-salt wastewater crystallizes and flows into the salt collection tank for collection, and is periodically discharged by the rear-end conveying device. The steam generated in the flash chamber flows through the top wire mesh demister to reduce liquid entrainment before being discharged into the steam outlet pipe for utilization.

[0032] The working method of the solar-driven wastewater evaporation and concentration system of the present invention is as follows:

[0033] S1: During the daytime sunlight, the concentrated brine in the concentrated brine tank is pumped to the solar thermal collector unit to gradually increase its temperature, and then discharged into the concentrated water flash tank for evaporation and concentration;

[0034] S2: The concentrated water after being treated in the concentrated water flash tank enters the crystallization unit for crystallization. The evaporated steam is collected or reused by the condensate recovery unit. If the concentration is not up to the design multiple, it is returned to the concentrated brine tank through the return pipe. At the same time, the heat storage medium in the heat storage medium tank enters the solar collector unit to absorb heat and store heat for later use.

[0035] S3: At night, close the valve on the pipeline between the concentrated brine tank and the solar collector unit. The concentrated brine in the concentrated brine tank enters the concentrated water flash tank for flash evaporation after heat exchange with the heat storage unit. The subsequent steps are the same as S2.

Claims

1. A solar-powered wastewater evaporation and concentration system, characterized in that, The system includes a concentrated brine tank (1), the output end of which is connected to several solar thermal collectors (2) connected in series. The solar thermal collectors (2) are driven by a control system (9). The output end of the solar thermal collectors (2) is connected to a concentrated water flash evaporator (5). The concentrated water flash evaporator (5) is connected to a condensate recovery unit (6), a crystallization unit (7), and a vacuum system (8). The solar thermal collectors (2) are also connected to a heat storage medium tank (3). The heat storage medium tank (3) is connected to a heat storage unit (4). The heat storage unit (4) and the several solar thermal collectors (2) connected in series form a circulation loop. The concentrated water flash tank (5) includes a tank body (59), which is connected to an inlet pipe (51) and a steam outlet pipe (58). The tank body (59) is provided with a first-stage vertical baffle (53), a second-stage vertical baffle (54) and a third-stage vertical baffle (55) at intervals to divide the tank body (59) into a first flash zone, a second flash zone, a third flash zone and a fourth flash zone. A horizontal baffle (52) is provided above the first flash zone, and a salt collection tank (56) is provided at the lower end of the second, third and fourth flash zones.

2. The solar-driven wastewater evaporation and concentration system according to claim 1, characterized in that, The tank (59) is also equipped with a wire mesh demister (57), which is located below the steam outlet pipe (58).

3. The solar-driven wastewater evaporation and concentration system according to claim 1, characterized in that, The heights of the first-stage vertical baffle (53) and the third-stage vertical baffle (55) are 1 / 5 to 1 / 4 of the height of the horizontal baffle (52); the height of the second-stage vertical baffle (54) is 1 / 3 to 4 / 5 of the height of the first-stage vertical baffle (53).

4. The solar-driven wastewater evaporation and concentration system according to claim 1, characterized in that, The inclination angle of the sidewall of the salt collection tank (56) is 120-145°.

5. The solar-driven wastewater evaporation and concentration system according to claim 1, characterized in that, The first-stage vertical baffle (53), the second-stage vertical baffle (54) and the third-stage vertical baffle (55) are each provided with a number of jet holes, which are distributed in a square, inverted triangle or equilateral triangle pattern.

6. The solar-driven wastewater evaporation and concentration system according to claim 1, characterized in that, The widths of the first flash zone, the second flash zone, the third flash zone, and the fourth flash zone are the same.

7. The solar-driven wastewater evaporation and concentration system according to claim 1, characterized in that, The outlet of the concentrated water flash tank (5) is also connected to the inlet of the concentrated brine tank (1).

8. The operating method of the solar-driven wastewater evaporation and concentration system as described in any one of claims 1-7, characterized in that, The steps are as follows: S1: During the daytime sunlight, the concentrated brine in the concentrated brine tank is pumped to the solar thermal collector unit to gradually increase its temperature, and then discharged into the concentrated water flash tank for evaporation and concentration; S2: The concentrated water after being treated in the concentrated water flash tank enters the crystallization unit for crystallization. The evaporated steam is collected or reused by the condensate recovery unit. If the concentration is not up to the design multiple, it is returned to the concentrated brine tank through the return pipe. At the same time, the heat storage medium in the heat storage medium tank enters the solar collector unit to absorb heat and store heat for later use. S3: At night, close the valve on the pipeline between the concentrated brine tank and the solar collector unit. The concentrated brine in the concentrated brine tank enters the concentrated water flash tank for flash evaporation after heat exchange with the heat storage unit. The subsequent steps are the same as S2.

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