Device and method for continuously treating salt wastewater

Abstract

The invention discloses a device and a method for continuously treating salt wastewater, and relates to the field of salt wastewater concentration, the device comprises an evaporation tank and an absorption tank which are used for containing a salt solution, and a steam outlet of the evaporation tank is communicated with a steam inlet of the absorption tank; the evaporation tank is provided with a material inlet and a material outlet; a first heat exchange coil pipe is arranged in the evaporation tank and is externally connected with a heat source; an absorbent capable of absorbing water vapor is contained in the absorption tank; a condensing coil is arranged in the absorption tank and is externally connected with a cold source; the top of the evaporation tank is communicated with a negative pressure pump; and the bottom of the absorption tank is communicated with the regeneration tank through a first material pump. According to the invention, long-time continuous work of the negative pressure pump is avoided, a negative pressure environment required by negative pressure evaporation can be maintained, and salt dissolution is continuously evaporated and concentrated.

Description

Technical Field

[0001] This invention relates to the field of salt wastewater concentration, and particularly to an apparatus and method for continuous treatment of salt wastewater. Background Technology

[0002] In the kimchi industry, a large amount of salt solution is generated during the production process. The salt solution needs to be concentrated before the next step can be carried out.

[0003] The current and conventional method for concentrating salt solutions is to evaporate the water in the salt solution to increase the salt concentration. Evaporation of water in the salt solution is usually achieved by heating the salt solution using a heat exchange coil (with a high-temperature medium flowing inside the coil). However, excessively high temperatures can cause dissolved salts in the salt solution to crystallize on the walls of the heat exchange coil and the inner walls of the container holding the salt solution. Over time, this can corrode the heat exchange coil and the inner walls of the container, reducing their lifespan. Furthermore, the salt crystals on the heat exchange coil affect the heat exchange efficiency between the coil and the salt solution, increasing the energy consumed in concentrating the salt solution.

[0004] To mitigate the adverse effects of high-temperature evaporation of water from salt solutions, engineers devised a low-temperature evaporation technique. This involves controlling the solution temperature between 60°C and 80°C, combined with a negative pressure environment (where water's boiling point is lower, and liquid water easily transforms into water vapor). This allows the water in the salt solution to evaporate, thereby concentrating the solution. This operation and the corresponding apparatus are called negative pressure evaporation. Due to the continuous generation of water vapor, a negative pressure environment must be maintained for the salt solution. Current negative pressure evaporation operations or devices require a negative pressure pump (a water vapor extraction device) to continuously extract water vapor to maintain the negative pressure environment, as illustrated in CN110339584A, which discloses a low-temperature heat pump type concentration device. This necessitates a continuous supply of energy to the negative pressure pump, and the extracted water vapor can easily corrode the pump's structural components (such as blades), resulting in a shorter pump lifespan.

[0005] Therefore, a new solution is needed to address the aforementioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide an apparatus and method for continuous treatment of salt wastewater, which avoids the long-term continuous operation of the negative pressure pump, can maintain the negative pressure environment required for negative pressure evaporation, and continuously evaporates and concentrates dissolved salt.

[0007] The technical solution adopted in this invention is as follows: A device for continuous treatment of salt wastewater includes an evaporator and an absorption tank for holding a salt solution, wherein the steam outlet of the evaporator is connected to the steam inlet of the absorption tank; the evaporator has a material inlet and a material outlet; a first heat exchange coil is provided inside the evaporator, which is connected to an external heat source; the absorption tank contains an absorbent capable of absorbing water vapor; and a condensation coil is provided inside the absorption tank, which is connected to an external cold source.

[0008] Furthermore, a negative pressure pump is connected to the top of the evaporator, which provides an initial negative pressure environment inside the evaporator.

[0009] Furthermore, the bottom of the absorption tank is provided with a dilute absorbent outlet, which is connected to the dilute absorbent inlet of the regeneration tank through a first feed pump. The regeneration tank is provided with a third heat exchange coil, which is connected to an external heat source. The concentrated absorbent outlet of the regeneration tank is connected to the concentrated absorbent inlet of the absorption tank.

[0010] Furthermore, the heat source includes a heat storage tank containing a phase change material, and an electric heating device is installed inside the heat storage tank; Or / and also includes a solar collector, wherein a fifth heat exchange coil is provided in the solar collector and a sixth heat exchange coil is provided in the heat storage tank, wherein the fifth heat exchange coil and the sixth heat exchange coil are connected end to end to form a third closed loop; a third circulation pump is provided on the third closed loop, and the third circulation pump drives the heat transfer oil in the third closed loop to circulate in the loop.

[0011] Furthermore, a fourth heat exchange coil is provided inside the heat storage tank. The fourth heat exchange coil is connected to the third heat exchange coil at the end to form a second closed loop. A second circulation pump is provided on the second closed loop, and the second circulation pump drives the heat transfer oil in the second closed loop to circulate in the loop.

[0012] Furthermore, a second heat exchange coil is provided inside the heat storage tank. The second heat exchange coil is connected to the first heat exchange coil at the end to form a first closed loop. A first circulation pump is provided on the first closed loop, and the first circulation pump drives the heat transfer oil in the first closed loop to circulate in the loop.

[0013] Furthermore, there are two heat storage tanks, and the peak temperature of the phase change material in each heat storage tank is different. Each heat storage tank is equipped with a fifth heat exchange coil, a fourth heat exchange coil, and a second heat exchange coil. All the fifth heat exchange coils are connected in parallel to a third closed loop through a three-way valve. All the fourth heat exchange coils are connected in parallel to a second closed loop through a three-way valve. All the second heat exchange coils are connected in parallel to a first closed loop through a three-way valve.

[0014] Furthermore, an intermediate oil tank is connected in series in the second closed loop, and the intermediate oil tank is located at the oil outlet of the second heat exchange tube; the oil inlet and oil outlet of the first heat exchange coil are both connected to the intermediate oil tank, and a first circulating pump is provided between the oil inlet of the first heat exchange coil and the intermediate oil tank.

[0015] Furthermore, a second material pump is provided at the material outlet.

[0016] A method for continuous treatment of saline wastewater, using the aforementioned apparatus for continuous treatment of saline wastewater, includes the following steps: S1: Start the first and second circulation pumps, and the heat transfer oil flows in the first and third heat exchange coils; S2: Start the negative pressure pump. The negative pressure pump provides an initial negative pressure environment inside the evaporator. After the vacuum level inside the evaporator drops to the set value, the negative pressure pump is turned off. S3: A salt solution is continuously supplied to the evaporator through the material inlet. The salt solution in the evaporator evaporates into water vapor after being heated by the first heat exchange coil, increasing the salt solution concentration. As the salt solution is continuously supplied to the evaporator through the material inlet, the amount of salt solution in the evaporator will continuously increase until the liquid level reaches the target position. Then, the second feed pump is started to continuously discharge the concentrated salt solution from the evaporator. The flow rate of the second feed pump is adjusted so that the amount of salt solution discharged is equal to the amount of salt solution supplied. S4: Occurs simultaneously with step S3. The water vapor generated in the evaporator enters the absorption tank. The absorbent in the absorption tank absorbs the water vapor, and the condenser coil cools the heat carried by the water vapor and further promotes the condensation of the water vapor into water droplets, so that the evaporator maintains a negative pressure environment. S5: Occurs simultaneously with step S4. The first feed pump is started, and the first feed pump draws the absorbent in the absorption tank into the regeneration tank. The absorbent in the regeneration tank evaporates into water vapor after being heated by the third heat exchange coil. The water vapor escapes to the outside, and the concentration of absorbent in the regeneration tank increases. S6: Since the absorption tank and the evaporator are connected, the inside of the absorption tank is also under negative pressure. There is a pressure difference between the inside of the absorption tank and the regeneration tank. Under the action of this pressure difference and the first feed pump delivering the absorbent, the absorbent in the regeneration tank flows back into the absorption tank to maintain the concentration of the absorbent in the absorption tank. S7: Dynamically and continuously cycle steps S3-S6 until all salt solutions are concentrated, completing the continuous treatment of salt wastewater.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention innovatively utilizes an absorbent to absorb the water vapor generated inside the evaporator, thereby maintaining a negative pressure environment inside the evaporator. This eliminates the need for a negative pressure pump to continuously extract water vapor, effectively reducing the energy consumption of the negative pressure pump and the corrosion of its internal components by water vapor, thus ensuring the service life of the negative pressure pump. 2. This invention uses phase change material to store energy and maintain a stable heating temperature by placing phase change material inside the heat storage tank. The stored energy forms a thermal buffer, which effectively reduces the impact of unstable heat obtained by the solar collector on the heat exchange of the entire device. 3. By setting up multiple heat storage tanks or intermediate oil tanks, this invention achieves the tiered utilization of thermal energy, effectively meeting the different heat requirements of the evaporator and regeneration tank, while making full use of thermal energy and reducing its waste. Attached Figure Description

[0018] The present invention will be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the first embodiment of the present invention; Figure 2 This is a schematic diagram of the second embodiment of the present invention; Figure 3 This is a schematic diagram of the third embodiment of the present invention; The diagram is labeled as follows: 1-Evaporator; 11-Material Inlet; 12-Material Outlet; 13-Second Feed Pump; 14-Negative Pressure Pump; 2-Absorption Tank; 21-Condensing Coil; 22-First Feed Pump; 23-Regeneration Tank; 24-Valve; 3-First Closed Loop; 31-First Heat Exchange Coil; 32-First Circulation Pump; 33-Second Heat Exchange Coil; 4-Second Closed Loop; 41-Fourth Heat Exchange Coil; 42-Third Heat Exchange Coil; 43-Second Circulation Pump; 5-Heat Storage Tank; 51-Phase Change Material; 52-Electric Heating Device; 6-Third Closed Loop; 61-Sixth Heat Exchange Coil; 62-Third Circulation Pump; 63-Fifth Heat Exchange Coil; 7-Solar Collector; 8-Intermediate Oil Tank; 9-Three-Way Valve. Detailed Implementation

[0019] In the description of this specification, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" appear to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this specification and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this specification.

[0020] Furthermore, the use of terms such as "horizontal" or "vertical" in this specification does not imply that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0021] In the description of this specification, it should also be noted that, unless otherwise expressly specified and limited, the terms “set up,” “install,” “connect,” and “link” should be interpreted broadly. For example, a link can be a fixed link, a detachable link, or an integral link; it can be a mechanical link or an electrical link; it can be a direct link or an indirect link through an intermediate medium; it can be a connection within two components.

[0022] Example 1 like Figures 1-3 As shown, an apparatus for continuous treatment of salt wastewater includes an evaporator 1 for holding a salt solution and an absorption tank 2. The steam outlet of the evaporator 1 is connected to the steam inlet of the absorption tank 2. The evaporator 1 has a material inlet 11 and a material outlet 12. A first heat exchange coil 31 is installed inside the evaporator 1 and is connected to an external heat source. The absorption tank 2 contains an absorbent capable of absorbing water vapor. A condenser coil 21 is installed inside the absorption tank 2 and is connected to an external cold source.

[0023] In this embodiment, the evaporator 1 is in a negative pressure environment, which means that the air pressure is lower than the absolute atmospheric pressure. The water vapor generated in the evaporator 1 is absorbed by the absorbent in the absorption tank 2, thereby maintaining the negative pressure environment in the evaporator 1. To provide the initial negative pressure environment for the evaporator 1, the first embodiment can use the negative pressure pump 14 to extract the air in the evaporator 1 as described below. Therefore, the top of the evaporator 1 is connected to the negative pressure pump 14, which provides the initial negative pressure environment inside the evaporator 1. In fact, the negative pressure pump 14 is a vacuum pump, and the negative pressure pump 14 can be turned off after the air in the evaporator 1 is extracted to the set vacuum value.

[0024] The bottom of the absorption tank 2 is provided with a dilute absorbent outlet, which is connected to the dilute absorbent inlet of the regeneration tank 23 through the first feed pump 22. The regeneration tank 23 is provided with a third heat exchange coil 42, which is connected to an external heat source. The concentrated absorbent outlet of the regeneration tank 23 is connected to the concentrated absorbent inlet of the absorption tank 2. This structure realizes the circulation of absorbent and discharge of water absorbed in absorbent, maintains the concentration of absorbent, and ensures the absorbent's ability and stability to absorb water vapor.

[0025] Specifically, since the absorption tank 2 and the evaporator 1 are connected, the absorption tank 2 is also under negative pressure. Under negative pressure, the absorbent in the absorption tank 2 will not flow out of the absorption tank 2 on its own. Therefore, a first feed pump 22 is needed to provide energy for the absorbent to flow out of the absorption tank 2. Under the action of the first feed pump 22, the absorbent enters the regeneration tank 23. The absorbent in the regeneration tank 23 evaporates into water vapor after being heated by the third heat exchange coil 42. The generated water vapor escapes from the absorption tank 2, thereby increasing the concentration of the absorbent. That is, the actual function of the regeneration tank 23 is to evaporate the water in the absorbent (with a lower concentration) from the absorption tank 2 into the external environment to form a higher concentration absorbent. The high-concentration absorbent then flows back into the absorption tank 2 to maintain the concentration of the absorbent and ensure the absorbent's ability and stability to absorb water vapor.

[0026] More specifically, regarding the high-concentration absorbent reflux from regeneration tank 23 into absorption tank 2, the main driving force comes from the fact that absorption tank 2 is also in a negative pressure environment. The pressure difference between the inside of regeneration tank 23 and absorption tank 2 provides the power for absorbent reflux.

[0027] Furthermore, the water vapor generated inside the regeneration tank 23 can escape to the outside, thus the interior of the regeneration tank 23 is actually connected to the outside, meaning that the pressure inside the regeneration tank 23 is not lower than the normal atmospheric pressure. Therefore, a safety valve can be installed at the steam outlet of the regeneration tank 23, and the opening pressure of the safety valve is not lower than the normal atmospheric pressure. And because the pressure inside the regeneration tank 23 is not lower than the normal atmospheric pressure, the temperature required for the water to evaporate and form water vapor inside the regeneration tank 23 is higher than the temperature required for the water to evaporate and form water vapor inside the evaporation tank 1.

[0028] In this embodiment, a valve 24 can be installed between the concentrated absorbent outlet of the regeneration tank 23 and the concentrated absorbent inlet of the absorption tank 2 to control the amount of absorbent replenished in the absorption tank 2.

[0029] In this embodiment, a second feed pump 13 is provided at the material outlet 12. The second feed pump 13 is provided because the evaporator 1 is in a negative pressure environment. The salt solution inside the evaporator needs the second feed pump 13 to provide power to overcome the negative pressure environment so that the salt solution can flow out of the evaporator 1. At the same time, the flow rate of the salt solution drawn by the second feed pump 13 and the flow rate of the salt solution flowing into the material inlet 11 of the evaporator 1 are controlled so that the two flow rates are equal, thereby achieving stable continuous processing.

[0030] In this embodiment, a portion of the condenser coil 21 is below the liquid surface of the absorbent, and a portion is above the liquid surface of the absorbent, so as to achieve both cooling of the absorbent and cooling of water vapor.

[0031] Example 2 Based on Example 1, further feasible implementation methods are proposed.

[0032] In one feasible implementation, a level gauge can be installed inside the evaporator 1 to monitor the liquid level of the salt solution in real time. This ensures the salt solution level is maintained at an optimal position, preventing dry burning. Furthermore, since the salt solution occupies space within the evaporator 1, the amount of salt solution is functionally related to the vacuum level of the negative pressure environment inside the evaporator 1. Controlling the salt solution level ensures the vacuum level of the negative pressure environment inside the evaporator 1 is optimal, avoiding excessive vacuum and preventing boiling over within the 60℃-80℃ range. This prevents water from converting into water vapor too quickly, thus avoiding rapid salt crystallization. Conversely, insufficient vacuum ensures a uniform rate of water vapor conversion within the 60℃-80℃ range without requiring excessively high temperatures for phase transition. It should be noted that this optimal liquid level and the initial vacuum level value of the negative pressure environment described later can be obtained from a limited number of experiments and will not be detailed here.

[0033] Example 3 Based on Examples 1-2, further feasible implementation methods are proposed.

[0034] The specific technical solutions for the heat source are as follows.

[0035] In the first embodiment, the heat source includes a heat storage tank 5, a phase change material 51 is disposed inside the heat storage tank 5, and an electric heating device 52 is disposed inside the heat storage tank 5. When the electric heating device 52 is powered on, the heat generated is absorbed by the phase change material 51. The phase change material 51 acts as a heat buffer material and a heat storage material. After absorbing heat, its temperature rises and remains relatively stable at the peak of its temperature performance. As a heat source with stable temperature, it provides stable energy for the evaporation of water in the evaporator 1 and the regeneration tank 23.

[0036] In the second embodiment, the heat source includes a heat storage tank 5, which contains a phase change material 51, and a solar collector 7. The solar collector 7 contains a fifth heat exchange coil 63, and the heat storage tank 5 contains a sixth heat exchange coil 61. The fifth heat exchange coil 63 and the sixth heat exchange coil 61 are connected end to end to form a third closed loop 6. A third circulation pump 62 is installed on the third closed loop 6, which drives the heat transfer oil in the third closed loop 6 to circulate in the loop. The heat transfer oil flowing in the third closed loop 6 carries the heat in the solar collector 7 to the heat storage tank 5 and supplies it to the phase change material 51.

[0037] As described above, the first implementation method uses pure electrical energy to provide energy; the second implementation method uses only solar energy as the energy supply, which has greater instability; therefore, the third implementation method includes a heat storage tank 5, which contains a phase change material 51, a solar collector 7, and an electric heating device 52. Solar energy and electric energy work together as the energy supply, with solar energy as the main energy supply and electric energy as the auxiliary energy supply. That is, electric energy can supplement energy when solar energy is insufficient. In this way, the phase change material 51 can obtain a stable energy supply, and electric energy can be saved, thereby saving energy cost expenditure.

[0038] In this embodiment, the specific structures of the electric heating device 52 and the solar collector 7 are structures known to those skilled in the art, and will not be described in detail here.

[0039] In this embodiment, the phase change material 51 can be paraffin.

[0040] In one feasible implementation, a fourth heat exchange coil 41 is provided inside the heat storage tank 5. The fourth heat exchange coil 41 is connected to the third heat exchange coil 42 at their ends to form a second closed loop 4. A second circulation pump 43 is provided on the second closed loop 4. The second circulation pump 43 drives the heat transfer oil in the second closed loop 4 to circulate in the loop. The heat transfer oil flowing in the second closed loop 4 transfers the heat in the heat storage tank 5 to the regeneration tank 23, so that the water in the absorbent in the regeneration tank 23 is heated and evaporated.

[0041] Regarding evaporator 1, based on the description of the heat energy supply of regeneration tank 23, several implementation schemes for the heat supply of evaporator 1 are further proposed.

[0042] like Figure 1 As shown in Embodiment A, a second heat exchange coil 33 is provided inside the heat storage tank 5. The second heat exchange coil 33 is connected to the first heat exchange coil 31 at both ends to form a first closed loop 3. A first circulation pump 32 is provided on the first closed loop 3. The first circulation pump 32 drives the heat transfer oil in the first closed loop 3 to circulate in the loop. The heat transfer oil flowing in the first closed loop 3 transfers the heat in the heat storage tank 5 to the evaporator 1, so that the water in the salt solution in the evaporator 1 is heated and evaporated.

[0043] As described in Example 2, the temperature required for water evaporation in the regeneration tank 23 is higher than that required for water evaporation in the evaporation tank 1. In fact, the temperature required for water evaporation in the regeneration tank 23 is not lower than 100°C, while the temperature required for water evaporation in the evaporation tank 1 is between 60°C and 80°C. Therefore, if only one heat storage tank 5 is used, with the structure described in Embodiment A above, the heat source temperatures of the regeneration tank 23 and the evaporation tank 1 can only be matched with one of them. If the regeneration tank 23 and the evaporation tank 1 are independently equipped with the heat source as described above, at least two sets of electric heating devices 52 and solar collectors 7 are required. To resolve the contradiction between the required temperatures of the regeneration tank 23 and the evaporation tank 1, and to reduce the cost of the equipment, the following embodiments are further proposed.

[0044] like Figure 2 As shown in Embodiment B, there are two heat storage tanks 5. The phase change material 51 in each heat storage tank 5 is a dual-peak phase change material 51, such as a phase change material 51 composed of paraffin and fatty acid. This phase change material 51 has two peaks, 80°C and 130°C. Each heat storage tank 5 is equipped with a sixth heat exchange coil 61, a fourth heat exchange coil 41, and a second heat exchange coil 33. All the sixth heat exchange coils 61 are connected in parallel to the third closed loop 6 through a three-way valve 9. All the fourth heat exchange coils 41 are connected in parallel to the second closed loop 4 through a three-way valve 9. All the second heat exchange coils 33 are connected in parallel to the first closed loop 3 through a three-way valve 9.

[0045] Specifically, only one of the two thermal storage tanks 5 can obtain thermal energy from the electric heating device 52 and / or the solar collector 7. The two thermal storage tanks 5 are tank number one and tank number two. For the phase change material 51 in tank number one and tank number two, when the phase change material 51 in tank number one (tank number two) heats up to the peak of 130°C, the three-way valve 9 in the third closed loop 6 adjusts the flow direction of the heat transfer oil, so that the heat transfer oil flows to the sixth heat exchange coil 61 in tank number two (tank number one). At the same time, the electric heating device 52 is activated as needed, and the phase change material 51 in tank number two (tank number one) is heated and gradually heats up. Simultaneously, the three-way valve 9 in the second closed loop 4 adjusts the flow direction of the heat transfer oil, causing the heat transfer oil to flow into the fourth heat exchange coil 41 in the first tank (second tank), to obtain the heat from the 130°C phase change material 51 in the first tank (second tank), and transfer the heat to the regeneration tank 23 for evaporating the water in the regeneration tank 23; the heat of the phase change material 51 in the first tank (second tank) gradually dissipates and the temperature decreases until the temperature of the phase change material 51 in the first tank (second tank) drops to the peak of 80°C. At this time, the phase change material 51 in the second tank (first tank) is heated and the temperature rises to almost the peak of 130°C. The three-way valve 9 in the second closed loop 4 is adjusted to cause the heat transfer oil to flow into the fourth heat exchange coil 41 in the second tank (first tank), to obtain the heat from the phase change material 51 in the second tank (first tank); Meanwhile, after the temperature of the phase change material 51 in the No. 1 tank (No. 2 tank) drops to the peak of 80°C, the three-way valve 9 in the first closed loop 3 adjusts the flow direction of the heat transfer oil, so that the heat transfer oil flows to the second heat exchange coil 33 in the No. 1 tank (No. 2 tank) to obtain the heat of the phase change material 51 in the No. 1 tank (No. 2 tank) and transfer the heat to the evaporator 1 for evaporating the water in the evaporator 1; In summary, the three-way valve 9 in each closed loop is continuously adjusted to adapt each closed loop to its own requirements.

[0046] like Figure 3 As shown in embodiment C, there can be only one heat storage tank 5, and the phase change material 51 can be a single-peak phase change material 51 with a peak temperature of 130°C, such as paraffin wax; however, an intermediate oil tank 8 needs to be connected in series on the second closed loop 4, and the intermediate oil tank 8 is located at the oil outlet of the second heat exchange tube; the oil inlet and outlet of the first heat exchange coil 31 are both connected to the intermediate oil tank 8, and a first circulation pump 32 is provided between the oil inlet of the first heat exchange coil 31 and the intermediate oil tank 8; specifically, after the fourth heat exchange coil 41 in the second closed loop 4 obtains energy from the heat storage tank 5, it transports the heat under the carrying of the heat transfer oil. Upon reaching the regeneration tank 23, the heat is released by the third heat exchange coil 42 for water evaporation. After exiting the third heat exchange coil 42, the temperature of the heat transfer oil drops to approximately 110°C, and it is then pumped into the intermediate oil tank 8 by the second circulation pump 43. Simultaneously, the heat transfer oil (below 80°C) flowing from the outlet of the first heat exchange tube also enters the intermediate oil tank 8. The heat transfer oils in the two closed loops mix in the intermediate oil tank 8, forming heat transfer oil at approximately 80°C. The first circulation pump 32 in the first closed loop 3 draws this heat transfer oil at approximately 80°C from the intermediate oil tank 8 for evaporating the water in the evaporator 1. This method achieves stepped energy utilization, effectively resolving the temperature conflict between the regeneration tank 23 and the evaporator 1, reducing equipment costs, and fully utilizing thermal energy.

[0047] It should be noted that, for implementation method C, valves 24 can be added to the first closed loop 3 and the second closed loop 4 to control the flow ratio of the two closed loops, thereby stabilizing the temperature of the heat transfer oil in the intermediate oil tank 8 at about 80°C; or the circulation pumps on the first closed loop 3 and the second closed loop 4 can be variable pumps.

[0048] Example 4 A method for continuous treatment of saline wastewater, using the apparatus for continuous treatment of saline wastewater described in any one of Examples 1-3, includes the following steps: S1: Start the first circulation pump 32 and the second circulation pump 43, and heat transfer oil flows in the first heat exchange coil 31 and the third heat exchange coil 42; S2: Start the negative pressure pump 14. The negative pressure pump 14 provides an initial negative pressure environment inside the evaporator 1. After the vacuum level inside the evaporator 1 drops to the set value, the negative pressure pump 14 is turned off. S3: A salt solution is continuously supplied to the evaporator 1 through the material inlet 11. The salt solution in the evaporator 1 evaporates into water vapor after being heated by the first heat exchange coil 31, and the salt solution concentration increases. As the salt solution is continuously supplied to the evaporator 1 through the material inlet 11, the amount of salt solution in the evaporator 1 will continue to increase until the liquid level reaches the target position. Then, the second feed pump 13 is started to continuously discharge the concentrated salt solution from the evaporator 1. The flow rate of the second feed pump 13 is adjusted so that the amount of salt solution discharged is equal to the amount of salt solution supplied. S4: Occurs simultaneously with step S3. The water vapor generated in evaporator 1 enters absorber 2. The absorbent in absorber 2 absorbs the water vapor, and condenser coil 21 cools the heat carried by the water vapor and further promotes the condensation of water vapor into water droplets, so that the evaporator 1 maintains a negative pressure environment. S5: Occurs simultaneously with step S4. The first feed pump 22 is started. The first feed pump 22 draws the absorbent in the absorption tank 2 into the regeneration tank 23. The absorbent in the regeneration tank 23 evaporates into water vapor after being heated by the third heat exchange coil 42. The water vapor escapes to the outside, and the concentration of absorbent in the regeneration tank 23 increases. S6: Since the absorption tank 2 is connected to the evaporator 1, the inside of the absorption tank 2 is also under negative pressure. There is a pressure difference between the inside of the absorption tank 2 and the regeneration tank 23. Under the action of this pressure difference and the first feed pump 22 delivering the absorbent, the absorbent in the regeneration tank 23 flows back to the absorption tank 2, maintaining the concentration of the absorbent in the absorption tank 2. S7: Dynamically and continuously cycle steps S3-S6 until all salt solutions are concentrated, completing the continuous treatment of salt wastewater.

[0049] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. An apparatus for continuous treatment of saline wastewater, characterized in that: The system includes an evaporator (1) for holding a salt solution and an absorption tank (2), with the steam outlet of the evaporator (1) connected to the steam inlet of the absorption tank (2); the evaporator (1) has a material inlet (11) and a material outlet (12); a first heat exchange coil (31) is installed inside the evaporator (1), which is connected to an external heat source; the absorption tank (2) contains an absorbent capable of absorbing water vapor; and a condenser coil (21) is installed inside the absorption tank (2), which is connected to an external cold source. The top of the evaporator (1) is connected to a negative pressure pump (14), which provides an initial negative pressure environment inside the evaporator (1); the bottom of the absorption tank (2) is provided with a dilute absorbent outlet, which is connected to the dilute absorbent inlet of the regeneration tank (23) through a first feed pump (22); a third heat exchange coil (42) is provided inside the regeneration tank (23), which is connected to an external heat source; the concentrated absorbent outlet of the regeneration tank (23) is connected to the concentrated absorbent inlet of the absorption tank (2).

2. The apparatus according to claim 1, characterized in that: A level gauge is installed inside the evaporation tube (1).

3. The apparatus according to claim 1, characterized in that: The heat source includes a heat storage tank (5) containing a phase change material (51). The heat storage tank (5) is equipped with an electric heating device (52) and / or a solar collector (7). The solar collector (7) is equipped with a fifth heat exchange coil (63). The heat storage tank (5) is equipped with a sixth heat exchange coil (61). The fifth heat exchange coil (63) and the sixth heat exchange coil (61) are connected end to end to form a third closed loop (6). A third circulation pump (62) is installed on the third closed loop (6). The third circulation pump (62) drives the heat transfer oil in the third closed loop (6) to circulate in the loop.

4. The apparatus according to claim 3, characterized in that: The heat storage tank (5) is equipped with a fourth heat exchange coil (41), which is connected to the third heat exchange coil (42) to form a second closed loop (4). A second circulation pump (43) is installed on the second closed loop (4), and the second circulation pump (43) drives the heat transfer oil in the second closed loop (4) to circulate in the loop.

5. The apparatus according to claim 4, characterized in that: The heat storage tank (5) is equipped with a second heat exchange coil (33), which is connected to the first heat exchange coil (31) to form a first closed loop (3). A first circulation pump (32) is provided on the first closed loop (3), and the first circulation pump (32) drives the heat transfer oil in the first closed loop (3) to circulate in the loop.

6. The apparatus according to claim 5, characterized in that: There are two heat storage tanks (5). The phase change material (51) in each heat storage tank (5) is a double-peak phase change material (51). Each heat storage tank (5) is equipped with a sixth heat exchange coil (61), a fourth heat exchange coil (41) and a second heat exchange coil (33). All the sixth heat exchange coils (61) are connected in parallel to the third closed loop (6) through a three-way valve (9). All the fourth heat exchange coils (41) are connected in parallel to the second closed loop (4) through a three-way valve (9). All the second heat exchange coils (33) are connected in parallel to the first closed loop (3) through a three-way valve (9).

7. The apparatus according to claim 4, characterized in that: The second closed loop (4) is connected in series with an intermediate oil tank (8), and the intermediate oil tank (8) is located at the oil outlet of the second heat exchange tube; the oil inlet and oil outlet of the first heat exchange coil (31) are connected to the intermediate oil tank (8), and a first circulating pump (32) is provided between the oil inlet of the first heat exchange coil (31) and the intermediate oil tank (8).

8. The apparatus according to claim 1, characterized in that: A second material pump (13) is provided at the material outlet (12).

9. A method for continuous treatment of saline wastewater, characterized in that: An apparatus for continuous treatment of saline wastewater according to any one of claims 1-8 comprises the following steps: S1: Start the first circulation pump (32) and the second circulation pump (43), and heat transfer oil flows in the first heat exchange coil (31) and the third heat exchange coil (42); S2: Start the negative pressure pump (14). The negative pressure pump (14) provides an initial negative pressure environment inside the evaporator (1). After the vacuum level inside the evaporator (1) drops to the set value, the negative pressure pump (14) is turned off. S3: A salt solution is continuously supplied to the evaporator (1) through the material inlet (11). The salt solution in the evaporator (1) evaporates into water vapor after being heated by the first heat exchange coil (31), and the salt solution concentration increases. As the salt solution is continuously supplied to the evaporator (1) through the material inlet (11), the amount of salt solution in the evaporator (1) will continue to increase until the liquid level reaches the target position. Then the second feed pump (13) is started to continuously discharge the concentrated salt solution in the evaporator (1). The flow rate of the second feed pump (13) is adjusted so that the amount of salt solution discharged is equal to the amount of salt solution supplied. S4: Occurs simultaneously with step S3. The water vapor generated in the evaporator (1) enters the absorption tank (2). The absorbent in the absorption tank (2) absorbs the water vapor, and the condenser coil (21) cools the heat carried by the water vapor and further promotes the water vapor to condense into water droplets, so that the evaporator (1) maintains a negative pressure environment. S5: Occurs simultaneously with step S4. The first feed pump (22) is started. The first feed pump (22) draws the absorbent in the absorption tank (2) into the regeneration tank (23). The absorbent in the regeneration tank (23) evaporates into water vapor after being heated by the third heat exchange coil (42). The water vapor escapes to the outside, and the concentration of absorbent in the regeneration tank (23) increases. S6: Since the absorption tank (2) is connected to the evaporator (1), the inside of the absorption tank (2) is also in a negative pressure environment. There is a pressure difference between the inside of the absorption tank (2) and the regeneration tank (23). Under the action of the pressure difference and the first feed pump (22) delivering the absorbent, the absorbent in the regeneration tank (23) flows back to the absorption tank (2) to maintain the concentration of the absorbent in the absorption tank (2). S7: Dynamically and continuously cycle steps S3-S6 until all salt solutions are concentrated, completing the continuous treatment of salt wastewater.

Images