Open type gradient absorption generation wastewater purification system and method

Abstract

The invention discloses an open type gradient absorption generation wastewater purification system and method, and relates to the technical field of wastewater treatment. An absorption tower and a regeneration tower are divided into three stages, three-stage feeding temperature control of waste water is realized by matching a two-stage heat regeneration module with a continuous drainage water heater and a steam heater, three-stage feeding temperature control of purified water is realized by matching the two-stage heat regeneration module with a cooler, meanwhile, fillers at all stages are optimized, and efficient fillers are adopted in a low-temperature and low-speed area; the high-strength filler is adopted in the high-temperature and high-speed area, the better solution of overall resistance, efficiency and safety is achieved, and the overall heat and mass transfer efficiency can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular, to an open-gradient absorption and generation wastewater purification system and method. Background Art

[0002] At present, open absorption and generation sewage purification systems have been gradually promoted in the market. During the actual operation of open evaporation and absorption sewage purification systems, it is found that there are large temperature differences and humidity differences before and after the air circulates, resulting in uneven air flow velocity in the tower. Specifically, the heat and mass transfer efficiency of air in the low-speed area is lower than the average value, and due to the relatively large overall height, pipeline cavitation problems may occur when the heat source is unstable or in high-altitude areas.

[0003] Therefore, it is urgent to improve the open absorption and generation sewage purification system at present to achieve a better solution for overall resistance, efficiency, and safety, and avoid the risk of pipeline cavitation in case of unstable heat source or high-altitude areas.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide an open-gradient absorption and generation wastewater purification system and method, aiming to improve the overall heat and mass transfer efficiency on the premise of ensuring safety performance.

[0006] The present invention is implemented as follows:

[0007] In a first aspect, the present invention provides an open-gradient absorption and generation wastewater purification system, including:

[0008] An absorption tower for heat and mass transfer between wastewater and air, enabling the water in the wastewater to enter the air and outputting water-containing air; the absorption tower is sequentially provided with a first absorption packing layer, a second absorption packing layer, and a third absorption packing layer from bottom to top;

[0009] A regeneration tower for heat and mass transfer between the water-containing air generated by the absorption tower and purified water, enabling the water in the water-containing air to enter the purified water, and the air output by the regeneration tower is circulated to the absorption tower; the regeneration tower is sequentially provided with a first regeneration packing layer, a second regeneration packing layer, and a third regeneration packing layer from bottom to top;

[0010] A double-stage regenerative heat exchange module, the double-stage regenerative heat exchange module includes a first regenerator and a second regenerator; both the first regenerator and the second regenerator are used for heat exchange between purified water and wastewater;

[0011] Part of the wastewater output from the bottom of the absorption tower enters the second regenerator for a primary temperature increase. After the primary temperature increase, the wastewater is divided into two paths. One path enters the first absorption packing layer of the absorption tower, and the other path enters the first regenerator for a secondary temperature increase. After the secondary temperature increase, the wastewater is divided into two paths. One path enters the second absorption packing layer after being heated by the continuous drainage heater, and the other path enters the third absorption packing layer after being heated by the steam heater.

[0012] Part of the purified water output from the bottom of the regeneration tower enters the first regenerator for a primary temperature decrease. After the primary temperature decrease, the purified water is divided into two paths. One path enters the first regeneration packing layer of the regeneration tower, and the other path enters the second regenerator for a secondary temperature decrease. After the secondary temperature decrease, the purified water is divided into two paths. One path enters the second regeneration packing layer of the regeneration tower, and the other path enters the third regeneration packing layer of the regeneration tower after being cooled by the cooler.

[0013] The first regeneration packing layer and the third absorption packing layer are filled with packing having a specific surface area of 50 m 2 / m 3 -100 m 2 / m 3 The third regeneration packing layer and the first absorption packing layer are filled with packing having a specific surface area of 310 m 2 / m 3 -400 m 2 / m 3 The second regeneration packing layer and the second absorption packing layer are filled with packing having a specific surface area of 100 m 2 / m 3 -300 m 2 / m 3 of the packing.

[0014] In an alternative embodiment, the steam heater is connected to a separation tank, and the liquid output from the separation tank is input into the third absorption packing layer of the absorption tower;

[0015] Part of the wastewater output from the bottom of the absorption tower enters the concentrated water storage tank, and then secondary steam is generated after passing through the evaporation crystallization unit;

[0016] The gas output from the separation tank, the secondary steam, and the water-containing air output from the top of the absorption tower all enter the bottom of the scrubbing tower. The bottom of the scrubbing tower is connected with a circulation pipeline to circulate the liquid stored at the bottom of the scrubbing tower to the top through the circulation pipeline, spray it, and contact the packing in the scrubbing tower. The water-containing air output from the top of the scrubbing tower enters the bottom of the regeneration tower.

[0017] In an alternative embodiment, the packing on the first regeneration packing layer and the third absorption packing layer is hexagonal grid packing;

[0018] and / or, the packing on the third regeneration packing layer and the first absorption packing layer is dumped packing;

[0019] And / or, the packing on the second regeneration packing layer and the second absorption packing layer is corrugated perforated plate packing;

[0020] And / or, the packing in the scrubbing tower is a grid plate.

[0021] In an alternative embodiment, a first demister is provided at the top of the regeneration tower, and a second demister is provided at the top of the scrubbing tower;

[0022] And / or, in the first absorption packing layer, the second absorption packing layer, and the third absorption packing layer, the wastewater is sprayed from the top and then falls into the packing to contact the air;

[0023] And / or, in the first regeneration packing layer, the second regeneration packing layer, and the third regeneration packing layer, the purified water is sprayed from the top and then falls into the packing to contact the water-containing air.

[0024] In an alternative embodiment, a preheater is further included. A part of the purified water output from the bottom of the regeneration tower enters the preheater to exchange heat with the desulfurized wastewater, the cooled purified water is output, and the heated wastewater enters the second absorption packing layer.

[0025] In an alternative embodiment, a gas-lifting device is provided between the second regeneration packing layer and the first regeneration packing layer of the regeneration tower;

[0026] The bottom of the second regeneration packing layer is connected with a water delivery pipeline to deliver the purified water at the bottom of the second regeneration packing layer to the first regeneration packing layer through the water delivery pipeline.

[0027] In a second aspect, the present invention provides an open-gradient absorption and generation wastewater purification method, which is processed by using the open-gradient absorption and generation wastewater purification system in any one of the foregoing embodiments, including: heat and mass transfer occur between the wastewater and the air in the absorption tower, so that the water in the wastewater enters the air, and the water-containing air is output at the top of the absorption tower;

[0028] The water-containing air undergoes heat and mass transfer with the purified water in the regeneration tower, so that the water in the water-containing air enters the purified water, and the air is output at the top of the regeneration tower and circulated to the bottom of the absorption tower;

[0029] Wherein, a double-stage regenerative heat exchange module formed by the first regenerator and the second regenerator exchanges heat between the purified water and the wastewater. A part of the wastewater output from the bottom of the absorption tower enters the second regenerator for a first temperature rise. After the first temperature rise, the wastewater is divided into two paths. One path enters the first absorption packing layer of the absorption tower, and the other path enters the first regenerator for a second temperature rise; after the second temperature rise, the wastewater is divided into two paths. One path is heated by the continuous drainage heater and then enters the second absorption packing layer, and the other path is heated by the steam heater and then enters the third absorption packing layer;

[0030] Part of the purified water output from the bottom of the regeneration tower enters the first recuperator for a primary temperature reduction. After the primary temperature reduction, the purified water is divided into two paths. One path enters the first regeneration packing layer of the regeneration tower, and the other path enters the second recuperator for a secondary temperature reduction. After the secondary temperature reduction, the purified water is divided into two paths. One path enters the second regeneration packing layer of the regeneration tower, and the other path enters the third regeneration packing layer of the regeneration tower after being cooled by a cooler.

[0031] In an alternative embodiment, the air feed temperature at the bottom of the absorption tower is 43°C - 48°C, the air discharge temperature at the top of the absorption tower is 85°C - 90°C, and then it enters the regeneration tower at a temperature of 88°C - 92°C after being treated by the scrubbing tower. The air discharge temperature at the top of the regeneration tower is 43°C - 48°C;

[0032] And / or, the temperature of the wastewater output from the bottom of the absorption tower is 48°C - 52°C;

[0033] And / or, the temperature of the purified water output from the bottom of the regeneration tower is 82°C - 88°C.

[0034] In an alternative embodiment, the purified water feed temperature of the first regeneration packing layer of the regeneration tower is 65°C - 70°C, the purified water feed temperature of the second regeneration packing layer is 55°C - 60°C, and the purified water feed temperature of the third regeneration packing layer is 35°C - 40°C;

[0035] And / or, the wastewater feed temperature of the first absorption packing layer of the absorption tower is 63°C - 67°C, the wastewater feed temperature of the second absorption packing layer is 88°C - 92°C, and the wastewater feed temperature of the third absorption packing layer is 93°C - 98°C.

[0036] In an alternative embodiment, the temperature of the desulfurized wastewater after being preheated by the preheater is 78°C - 82°C;

[0037] And / or, the temperature of the wastewater entering the continuous blowdown heater and the steam heater is 78°C - 82°C.

[0038] The present invention has the following beneficial effects: The present invention divides the absorption tower and the regeneration tower into three stages, uses a double-stage recuperation module in cooperation with a continuous blowdown heater and a steam heater to achieve three-stage feed temperature control of the wastewater, uses a double-stage recuperation module in cooperation with a cooler to achieve three-stage feed temperature control of the purified water, and optimizes each stage of packing. High-efficiency packing is used in the low-temperature and low-speed area, and high-strength packing is used in the high-temperature and high-speed area, achieving a better solution for the overall resistance, efficiency, and safety, and can significantly improve the overall heat and mass transfer efficiency.

[0039] In a preferred embodiment, by reasonably utilizing a separator and a scrubber, the risk of pipeline cavitation that may occur due to unstable heat sources or high-altitude areas is avoided. The improvement of this system is more adaptable to situations that are sensitive to heat transfer efficiency (such as limited space where equipment must be reduced), and is also more adaptable to operating conditions in high-altitude areas or with unstable heat sources. It can be preferentially selected for the zero-discharge operation of desulfurized wastewater in some power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0041] Figure 1 Structural diagram of the open-gradient absorption and generation wastewater purification system provided by the present invention;

[0042] Figure 2 is Figure 1 Schematic diagram of the structural diagram after deleting the reference numerals and adding the device names;

[0043] Figure 3 Structural diagram of the double-stage regenerative heat module;

[0044] Figure 4 is Figure 3 Schematic diagram of the double-stage regenerative heat module after deleting the reference numerals and adding the device names.

[0045] Main element symbol description: 110 - absorption tower; 111 - first absorption packing layer; 112 - second absorption packing layer; 113 - third absorption packing layer; 120 - regeneration tower; 121 - first regeneration packing layer; 122 - second regeneration packing layer; 123 - third regeneration packing layer; 124 - first demister; 125 - gas-lifting device; 126 - water pipeline; 130 - double-stage regenerative heat module; 131 - first regenerator; 132 - second regenerator; 141 - continuous drainage heater; 142 - steam heater; 143 - cooler; 144 - separation tank; 145 - concentrated water storage tank; 146 - evaporation and crystallization unit; 150 - scrubber; 151 - second demister; 160 - preheater. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0047] As Figure 1 and Figure 2 shown, an open-gradient absorption-generated wastewater purification system provided by an embodiment of the present invention includes an absorption tower 110, a regeneration tower 120, and a two-stage regenerative heat exchange module 130. A three-stage gradient layout design inside the towers is carried out for the absorption tower 110 and the regeneration tower 120. By using the two-stage regenerative heat exchange module 130 in cooperation with other heating and cooling devices to achieve temperature control at each stage, and in cooperation with the improvement of packing at each stage, simultaneous optimization of the overall resistance, efficiency, and safety can be achieved.

[0048] The absorption tower 110 is used for heat and mass transfer between high-temperature wastewater and air. The circulating air enters from the bottom of the tower and contacts the high-temperature wastewater countercurrently, causing the water in the high-temperature wastewater to enter the air, and high-temperature and high-humidity air is output from the top of the tower. The regeneration tower 120 is used for heat and mass transfer between the water-containing air generated by the absorption tower 110 and purified water. The water-containing air enters from the bottom of the regeneration tower 120 and contacts the low-temperature purified water countercurrently, causing the water in the water-containing air to enter the purified water. The low-temperature and low-humidity air output from the regeneration tower 120 is circulated to the absorption tower 110.

[0049] The absorption tower 110 is sequentially provided with a first absorption packing layer 111, a second absorption packing layer 112, and a third absorption packing layer 113 from bottom to top, forming a three-stage temperature gradient. The temperature of the wastewater flowing into from the lower first absorption packing layer 111 to the upper third absorption packing layer 113 gradually increases. Similarly, the regeneration tower 120 is sequentially provided with a first regeneration packing layer 121, a second regeneration packing layer 122, and a third regeneration packing layer 123 from bottom to top, also forming a three-stage temperature gradient. The temperature of the purified water flowing into from the lower first regeneration packing layer 121 to the upper third regeneration packing layer 123 gradually decreases. The first absorption packing layer 111, the second absorption packing layer 112, and the third absorption packing layer 113 all spray the wastewater from the top and then let it fall into the packing to contact the air; the first regeneration packing layer 121, the second regeneration packing layer 122, and the third regeneration packing layer 123 all spray the purified water from the top and then let it fall into the packing to contact the water-containing air.

[0050] Further, the first regeneration packing layer 121 and the third absorption packing layer 113 are filled with packing (i.e., packing A1 and packing B3) with a specific surface area of 50 m 2 / m 3 -100 m 2 / m 3 . The specific specific surface area can be 50 m 2 / m 3 , 60 m 2 / m 3 , 70 m 2 / m 3 , 80 m 2 / m 3, 90 m 2 / m 3 , 95 m 2 / m 3 , 100 m 2 / m 3 etc. The air flow rate faced by the first regeneration packing layer 121 and the third absorption packing layer 113 is relatively large (high temperature, high humidity), the flow velocity is relatively high, and the temperature is relatively high. It is preferably a hexagonal grid packing with a specific surface area < 100 m 2 / m 3 . The advantage of this type of packing is that the resistance factor is small, the strength of the same material is high, and it is less likely to soften at high temperatures; the disadvantage is that the specific surface area is low and the mass transfer capacity is poor. Considering the characteristics of the hexagonal grid packing with a specific surface area < 100 m 2 / m 3 , it is more suitable for application in the first regeneration packing layer 121 and the third absorption packing layer 113.

[0051] Furthermore, the third regeneration packing layer 123 and the first absorption packing layer 111 are filled with packing with a specific surface area of 310 m 2 / m 3 -400 m 2 / m 3 (i.e., packing A3, packing B1). The specific specific surface area can be 310 m 2 / m 3 , 320 m 2 / m 3 , 330 m 2 / m 3 , 340 m 2 / m 3 , 350 m 2 / m 3 , 360 m 2 / m 3 , 370 m 2 / m 3 , 380 m 2 / m 3 , 390 m 2 / m 3 , 400 m 2 / m 3 etc. The third regeneration packing layer 123 and the first absorption packing layer 111 are in the low-temperature and low-humidity range, with a low air flow velocity. It is preferably a dumped packing with a specific surface area greater than 300 m 2 / m 3 . The advantage of this type of packing is strong mass transfer capacity, and the disadvantage is that the resistance factor is small and the high-temperature resistance property is poor. This type of packing is more suitable for placement in the low-temperature and low-humidity section.

[0052] Further, the second regenerated packing layer 122 and the second absorption packing layer 112 are filled with packing materials (i.e., packing A2 and packing B2) having a specific surface area of 100 m 2 / m 3 -300 m 2 / m 3 . Specifically, the specific surface area can be 100 m 2 / m 3 , 130 m 2 / m 3 , 150 m 2 / m 3 , 180 m 2 / m 3 , 200 m 2 / m 3 , 230 m 2 / m 3 , 250 m 2 / m 3 , 280 m 2 / m 3 , 300 m 2 / m 3 etc. The second regenerated packing layer 122 and the second absorption packing layer 112 face medium flue gas flow rate and temperature. Preferably, corrugated perforated plate packing with a specific surface area of 100 m 2 / m 3 -300 m 2 / m 3 is used. Its strength, mass transfer capacity, and resistance are all at a medium level, suitable for being placed in the middle position of the tower.

[0053] It should be noted that by using the double-stage regenerative heat exchange module 130 in cooperation with other heating and cooling devices to achieve temperature control at each stage, and in cooperation with the improvement of packing at each stage, the overall resistance can be reduced, and high-specific-surface-area packing can be applied as much as possible to increase the system processing capacity. At the same time, the tower diameter can be reduced during the design stage, thereby reducing the system floor area.

[0054] Please refer to Figure 3 and Figure 4 . The double-stage regenerative heat exchange module 130 includes a first regenerator 131 and a second regenerator 132. Both the first regenerator 131 and the second regenerator 132 are used for heat exchange between purified water and wastewater to output purified water and wastewater at different temperatures. The double-stage regenerative heat exchange module 130 is essentially two regenerators connected in series, and a path of wastewater / purified water is taken from the middle of the two-stage heat exchange to be sprayed at the bottom of the corresponding tower. By using the double-stage regenerative heat exchange module 130, part of the solution between the two-stage regenerative heat exchange is used to spray the gas for the first time, achieving a shorter heat path for regenerative heat exchange. At the same time, a temperature gradient difference can be created, which is beneficial to the full utilization of the packing.

[0055] Specifically, a part of the wastewater output from the bottom of the absorption tower 110 enters the second regenerator 132 for a first temperature rise. After the first temperature rise, the wastewater is divided into two paths. One path enters the first absorption packing layer 111 (i.e., the bottom spray layer of the absorption tower) of the absorption tower 110, and the other path enters the first regenerator 131 for a second temperature rise. After the second temperature rise, the wastewater is divided into two paths. One path enters the second absorption packing layer 112 after being heated by the continuous blowdown heater 141, and the other path enters the third absorption packing layer 113 after being heated by the steam heater 142. By utilizing the temperature difference between the continuous blowdown heater 141 and the steam heater 142, there is a significant temperature difference in the temperature of the heated wastewater, meeting the temperature difference requirements of the second absorption packing layer 112 and the third absorption packing layer 113, and also completing the concentrated water circulation. A multi-stage gradient spray design is adopted, using two heat sources, namely the continuous blowdown of the boiler and steam, to exchange heat between different air temperatures and the corresponding concentrated water or purified water, shortening the heat transfer process and enabling the full utilization of the packing.

[0056] Specifically, the continuous blowdown heater is a device that uses the continuous blowdown from the boiler continuous blowdown flash tank to heat the sewage. The continuous blowdown of the boiler would be directly discharged after passing through the flash tank. Therefore, this device can achieve the recovery of the waste heat of the continuous blowdown. The steam heater is a device that uses water vapor as the heat source, using external steam as the heat source and generating steam condensate after cooling.

[0057] Further, a part of the purified water output from the bottom of the regeneration tower 120 enters the first regenerator 131 for a first temperature drop. After the first temperature drop, the purified water is divided into two paths. One path enters the first regeneration packing layer 121 (i.e., the bottom spray layer of the regeneration tower) of the regeneration tower 120, and the other path enters the second regenerator 132 for a second temperature drop. After the second temperature drop, the purified water is divided into two paths. One path enters the second regeneration packing layer 122 (i.e., the middle spray layer of the regeneration tower) of the regeneration tower 120, and the other path enters the third regeneration packing layer 123 of the regeneration tower 120 after being cooled by the cooler 143. In this way, the purified water entering the regeneration tower 120 is divided into three levels, meeting the temperature gradient requirements of the three spray layers and also completing the purified water circulation. Specifically, the cold source of the cooler can be low-temperature demineralized water, but it is not limited to this.

[0058] In some embodiments, the steam heater 142 is connected to the separation tank 144. The wastewater heated by the steam heater 142 enters the separation tank for gas-liquid separation. The separated liquid phase enters the third absorption packing layer 113 of the absorption tower, and the small amount of flash steam generated after separation enters the bottom of the scrubbing tower 150. Adding the separation tank 144 after the concentrated water is heated to a high temperature can effectively prevent pipeline cavitation and avoid the risk of pipeline cavitation that may occur in the case of unstable heat sources or high-altitude areas. Moreover, the steam generated by local vaporization can be directly discharged into the circulating air without going through the concentrated water evaporation process in the absorption tower, and a part of the packing can also be saved.

[0059] Part of the wastewater output from the bottom of the absorption tower 110 enters the concentrated water storage tank 145, and then undergoes evaporation and crystallization in the evaporation and crystallization unit 146 to produce salt, secondary steam, and steam condensate. The gas output from the separation tank 144, the secondary steam generated by the evaporation and crystallization unit 146, and the water-containing air output from the top of the absorption tower 110 all enter the bottom of the scrubbing tower 150. A circulation pipeline is connected to the bottom of the scrubbing tower 150 to circulate the liquid stored at the bottom of the scrubbing tower 150 to the top through the circulation pipeline, and after spraying, it contacts the packing in the scrubbing tower 150. The water-containing air output from the top of the scrubbing tower 150 enters the bottom of the regeneration tower 120. The scrubbing tower 150 operates continuously, and the water at the bottom is continuously pumped to the top for circulating spraying, but there is no heat exchange involved, so very little new liquid water is generated. The total volume of water inside it only increases continuously with the small droplets collected during the scrubbing process. The arrow of the water supply pipeline from the scrubbing tower to the absorption tower 110 indicates that when the water quality of the scrubbing tower 150 is poor, the water is discharged into the sewage tower, and this process is intermittent. Since the scrubbing tower 150 has no obvious heat exchange requirements, a grid plate can be used as the packing, which mainly plays a rectifying effect on the gas and liquid.

[0060] It should be noted that adding the secondary steam generated during the evaporation and crystallization process and the partial vaporization steam generated by heating the concentrated water to a higher temperature by steam to the scrubbing tower 150 can, on the one hand, wash the water vapor to remove entrained liquid; on the other hand, the three streams of gas converge in the tower device, which can ensure stability without generating pipeline vibration and save a steam drum.

[0061] In some embodiments, a first demister 124 is provided at the top of the regeneration tower 120, and a second demister 151 is provided at the top of the scrubbing tower 150. The demister can effectively separate the liquid droplets or mist entrained in the gas.

[0062] In some embodiments, the open-gradient absorption wastewater purification system further includes a preheater 160. Part of the purified water output from the bottom of the regeneration tower 120 enters the preheater 160 to exchange heat with the desulfurization wastewater. The cooled purified water is output, and the heated wastewater enters the second absorption packing layer 112 to contact the air countercurrently. By using the preheater 160 to raise the temperature of the wastewater and lower the temperature of the purified water at the same time, this part of the heat is fully utilized. The temperature of the wastewater after heating is not much different from the temperature range of the second absorption packing layer 112, and it can be directly introduced into the second absorption packing layer 112.

[0063] Furthermore, a gas-lifting device 125 is provided between the second regeneration packing layer 122 and the first regeneration packing layer 121 of the regeneration tower 120. That is to say, the gas-lifting device 125 is located at the bottom of the second regeneration packing layer 122 and can prevent the purified water in the second regeneration packing layer 122 from directly falling into the first regeneration packing layer 121. The gas-lifting device 125 is only provided above the spray layer corresponding to the first regeneration packing layer 121, and its purpose is to intercept the falling of the upper liquid. In this way, in the lower section of the regeneration tower with a large air flow, the water flow is less, which can effectively prevent the flooding phenomenon of the packing. At the same time, this also enables the tower diameter to be smaller, which is beneficial to saving equipment costs. The bottom of the second regeneration packing layer 122 is connected with a water pipeline 126, and through the water pipeline 126, the purified water at the bottom of the second regeneration packing layer 122 can be transported to the first regeneration packing layer 121, and the liquid stored in the lower part of the second regeneration packing layer 122 can be continuously discharged to the first regeneration packing layer 121.

[0064] The embodiment of the present invention also provides an open-gradient absorption-generated wastewater purification method, including: the wastewater and air perform heat and mass transfer in the absorption tower 110, so that the water in the wastewater enters the air, and the water-containing air is output at the top of the absorption tower 110; the water-containing air performs heat and mass transfer with the purified water in the regeneration tower 120, so that the water in the water-containing air enters the purified water, and the air is output at the top of the regeneration tower 120 and circulated to the bottom of the absorption tower 110.

[0065] Among them, the double-stage regenerative heat exchange module 130 formed by the first regenerator 131 and the second regenerator 132 exchanges heat between the purified water and the wastewater. A part of the wastewater output from the bottom of the absorption tower 110 enters the second regenerator 132 for a first temperature rise. After the first temperature rise, the wastewater is divided into two paths. One path enters the first absorption packing layer 111 of the absorption tower 110, and the other path enters the first regenerator 131 for a second temperature rise; after the second temperature rise, the wastewater is divided into two paths. One path enters the second absorption packing layer 112 after being heated by the continuous drainage heater 141, and the other path enters the third absorption packing layer 113 after being heated by the steam heater 142.

[0066] A part of the purified water output from the bottom of the regeneration tower 120 enters the first regenerator 131 for a first temperature drop. After the first temperature drop, the purified water is divided into two paths. One path enters the first regeneration packing layer 121 of the regeneration tower 120, and the other path enters the second regenerator 132 for a second temperature drop; after the second temperature drop, the purified water is divided into two paths. One path enters the second regeneration packing layer 122 of the regeneration tower 120, and the other path enters the third regeneration packing layer 123 of the regeneration tower 120 after being cooled by the cooler 143.

[0067] It should be noted that the three-stage feed temperature control of the wastewater is achieved by using the double-stage regenerative module in combination with the continuous drainage heater and the steam heater, and the three-stage feed temperature control of the purified water is achieved by using the double-stage regenerative module in combination with the cooler. At the same time, the fillers at all levels are optimized. High-efficiency fillers are used in the low-temperature and low-speed areas, and high-strength fillers are used in the high-temperature and high-speed areas to achieve a better solution for the overall resistance, efficiency, and safety, which can significantly improve the overall heat and mass transfer efficiency.

[0068] Figure 1 The working principles of other structures are not repeated here. To further improve the heat and mass transfer efficiency, the inventor has optimized the operating parameters of each link:

[0069] The bottom air feed temperature of the absorption tower 110 is 43°C - 48°C, and the top air discharge temperature of the absorption tower 110 is 85°C - 90°C. After being treated by the scrubbing tower 150, the temperature reaches 88°C - 92°C and then enters the regeneration tower 120. The top air discharge temperature of the regeneration tower 120 is 43°C - 48°C. It is appropriate to control the air temperature in each link within the above range to improve the wastewater treatment effect.

[0070] Furthermore, the feed temperature of the purified water in the first regeneration packing layer 121 of the regeneration tower 120 is 65°C - 70°C, the feed temperature of the purified water in the second regeneration packing layer 122 is 55°C - 60°C, and the feed temperature of the purified water in the third regeneration packing layer 123 is 35°C - 40°C. The temperature of the wastewater output from the bottom of the absorption tower 110 is 48°C - 52°C, and the temperature of the purified water output from the bottom of the regeneration tower 120 is 82°C - 88°C. The feed temperature of the wastewater in the first absorption packing layer 111 of the absorption tower 110 is 63°C - 67°C, the feed temperature of the wastewater in the second absorption packing layer 112 is 88°C - 92°C, and the feed temperature of the wastewater in the third absorption packing layer 113 is 93°C - 98°C. By regulating the three-stage operating temperatures of the absorption tower 110 and the regeneration tower 120, the heat and mass transfer effect can be improved, enabling the water in the wastewater to be fully recovered into the purified water and achieving zero wastewater discharge.

[0071] Furthermore, the temperature of the desulfurized wastewater after being preheated by the preheater 160 is 78°C - 82°C, and this temperature range is close to the temperature of the second absorption packing layer. The temperature of the wastewater entering the continuous drainage heater 141 and the steam heater 142 is 78°C - 82°C, that is, the temperatures after being processed by the two regenerators in the double-stage regenerative module meet the above requirements. After being further heated by the continuous drainage heater 141 and the steam heater 142, it meets the temperature requirements of the second absorption packing layer 112 and the third absorption packing layer 113.

[0072] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0073] Example 1

[0074] This embodiment provides an open-gradient absorption-generated wastewater purification method, which is processed by an open-gradient absorption-generated wastewater purification system Figures 1-4 . The specific steps and parameters of each link are as follows: Figures 1-4 The desulfurized wastewater at 40°C enters the preheater at a flow rate of 3 t / h and exchanges heat with the purified water (85°C) output from the bottom of the regeneration tower 120. The purified water is cooled to 42°C and output at a flow rate of 2.7 t / h; the wastewater temperature rises to 80°C and enters the second absorption packing layer 112 of the absorption tower 110.

[0075] The desulfurized wastewater at 40°C enters the preheater at a flow rate of 3 t / h and exchanges heat with the purified water (85°C) output from the bottom of the regeneration tower 120. The purified water is cooled to 42°C and output at a flow rate of 2.7 t / h; the wastewater temperature rises to 80°C and enters the second absorption packing layer 112 of the absorption tower 110.

[0076] Air at 45°C and 2400 Nm³ / h enters the bottom of the absorption tower 110, passes through the first absorption packing layer 111, the second absorption packing layer 112, and the third absorption packing layer 113 in sequence, and then is output from the top of the tower as high-temperature and high-humidity air (temperature is 88°C), enters the scrubbing tower 150, and the temperature of the air leaving the scrubbing tower 150 is 90°C. Then, it enters the bottom of the regeneration tower 120 at a flow rate of 5800 Nm³ / h, passes through the first regeneration packing layer 121, the second regeneration packing layer 122, and the third regeneration packing layer 123 in sequence, and is output from the top of the tower at a temperature of 45°C and recycled to the bottom of the absorption tower 110.

[0077] Part of the wastewater (50°C, 60 t / h) output from the bottom of the absorption tower 110 enters the second recuperator 132 for a first temperature rise. After the first temperature rise, the wastewater is divided into two paths. One path (the temperature of this part of the wastewater is 65°C, 20 t / h) enters the first absorption packing layer 111 of the absorption tower 110, and the other path (the temperature of this part of the wastewater is 65°C, 40 t / h) enters the first recuperator 131 for a second temperature rise; after the second temperature rise, the wastewater temperature reaches 80°C and is divided into two paths. One path (flow rate is 20 t / h) is heated to 90°C by the continuous drainage heater 141 and then enters the second absorption packing layer 112, and the other path (flow rate is 20 t / h) is heated to 95°C by the steam heater 142 and then enters the third absorption packing layer 113.

[0078] Part of the purified water (85°C, 75 t / h) output from the bottom of the regeneration tower 120 enters the first recuperator 131 for a first temperature drop. After the first temperature drop, the purified water is divided into two paths. One path (the temperature of this part of the purified water is 77°C, 25 t / h) enters the first regeneration packing layer 121 of the regeneration tower 120, and the other path enters the second recuperator 132 for a second temperature drop; after the second temperature drop, the purified water temperature is 58°C and is divided into two paths. One path (flow rate is 25 t / h) enters the second regeneration packing layer 122 of the regeneration tower 120, and the other path (flow rate is 25 t / h) is cooled to 38°C by the cooler 143 and then enters the third regeneration packing layer 123 of the regeneration tower 120.

[0079] The continuous blowdown water at 145°C enters the continuous blowdown heater 141 at a flow rate of 4 t / h, and the outlet temperature of the continuous blowdown water is 90°C. The steam flow rate entering the steam heater 142 is 0.6 t / h, generating 0.6 t / h of steam condensate. After the wastewater heated by the steam heater 142 is separated in the separation tank 144, 0.1 t / h of exhaust steam is generated and enters the scrubbing tower 150. The flow rate of desalted makeup water entering the cooler 143 is 50 t / h and the temperature is 35°C, and the makeup water outlet temperature from the cooler 143 is 50°C.

[0080] The concentrated water at 50°C output from the bottom of the absorption tower 110 enters the concentrated water storage tank 145 at a flow rate of 0.3 t / h, and then undergoes evaporation and crystallization in the evaporation and crystallization unit 146 to produce salt (0.1 t / h), secondary steam (0.2 t / h), and steam condensate (0.2 t / h). The steam flow rate entering the evaporation and crystallization unit 146 is 0.2 t / h.

[0081] The packing A1 and packing B3 adopt hexagonal grid packings with a specific surface area of 80 m 2 / m 3 , made of reinforced PP, with a packing height of 1 m; the packing A2 and packing B2 adopt 125X corrugated hole plate packings with a specific surface area of 125 m 2 / m 3 , made of reinforced PP, with a packing height of 1 m; the packing A3 and packing B1 adopt polyhedral hollow sphere random packings with a specific surface area of 400 m 2 / m 3 , made of PP, with a packing height of 1 m. The washing tower packing C adopts hexagonal grid packings with a specific surface area of 80 m 2 / m 3 , made of reinforced PP, with a packing height of 0.4 m.

[0082] Finally, in this embodiment, 0.8 t / h of steam (steam heater 142 plus evaporation and crystallization unit 146) can be utilized to achieve zero discharge of 3 t / h of desulfurized wastewater, producing 0.1 t / h of salt and 2.9 t / h of purified water, with a tower diameter of 1.2 m.

[0083] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An open-gradient absorption-generated wastewater purification system, characterized in that, Comprising: An absorption tower for heat and mass transfer between wastewater and air, enabling the water in the wastewater to enter the air and outputting water-containing air; The absorption tower is successively provided with a first absorption packing layer, a second absorption packing layer, and a third absorption packing layer from bottom to top; A regeneration tower for heat and mass transfer between the water-containing air generated by the absorption tower and purified water, enabling the water in the water-containing air to enter the purified water, and the air output by the regeneration tower is circulated to the absorption tower; The regeneration tower is successively provided with a first regeneration packing layer, a second regeneration packing layer, and a third regeneration packing layer from bottom to top; A two-stage regenerative heat exchange module, the two-stage regenerative heat exchange module includes a first regenerator and a second regenerator; both the first regenerator and the second regenerator are used for heat exchange between purified water and wastewater; Part of the wastewater output from the bottom of the absorption tower enters the second regenerator for a first temperature rise. After the first temperature rise, the wastewater is divided into two paths. One path enters the first absorption packing layer of the absorption tower, and the other path enters the first regenerator for a second temperature rise. After the second temperature rise, the wastewater is divided into two paths. One path enters the second absorption packing layer after being heated by a continuous drainage heater, and the other path enters the third absorption packing layer after being heated by a steam heater; Part of the purified water output from the bottom of the regeneration tower enters the first regenerator for a first temperature drop. After the first temperature drop, the purified water is divided into two paths. One path enters the first regeneration packing layer of the regeneration tower, and the other path enters the second regenerator for a second temperature drop. After the second temperature drop, the purified water is divided into two paths. One path enters the second regeneration packing layer of the regeneration tower, and the other path enters the third regeneration packing layer of the regeneration tower after being cooled by a cooler; The first regenerative packing layer and the third absorption packing layer are filled with packing having a specific surface area of 50 m 2 / m 3 -100 m 2 / m 3 The third regenerative packing layer and the first absorption packing layer are filled with packing having a specific surface area of 310 m 2 / m 3 -400 m 2 / m 3 The second regenerative packing layer and the second absorption packing layer are filled with packing having a specific surface area of 100 m 2 / m 3 -300 m 2 / m 3 of the packing.

2. The open-gradient absorption wastewater purification system according to claim 1, wherein, The steam heater is communicated with a separation tank, and the liquid output by the separation tank is input into the third absorption packing layer of the absorption tower; Part of the wastewater output from the bottom of the absorption tower enters a concentrated water storage tank, and then secondary steam is generated after passing through an evaporation crystallization unit; The gas output by the separation tank, the secondary steam, and the water-containing air output from the top of the absorption tower all enter the bottom of a scrubbing tower. The bottom of the scrubbing tower is connected with a circulation pipeline to circulate the liquid stored at the bottom of the scrubbing tower to the top through the circulation pipeline, spray it, and contact the packing in the scrubbing tower. The water-containing air output from the top of the scrubbing tower enters the bottom of the regeneration tower.

3. The open-gradient absorption-occurring wastewater purification system according to claim 2, wherein The packing on the first regeneration packing layer and the third absorption packing layer is hexagonal grid packing; And / or, the packing on the third regeneration packing layer and the first absorption packing layer is dumped packing; And / or, the packing on the second regeneration packing layer and the second absorption packing layer is corrugated perforated plate packing; And / or, the packing in the scrubbing tower is a grid plate.

4. The open-gradient absorption wastewater purification system according to claim 2, characterized in that, A first demister is arranged at the top of the regeneration tower, and a second demister is arranged at the top of the scrubbing tower; And / or, the first absorption packing layer, the second absorption packing layer, and the third absorption packing layer all spray the wastewater from the top and then let it fall into the packing to contact the air; And / or, the first regeneration packing layer, the second regeneration packing layer, and the third regeneration packing layer all spray the purified water from the top and then let it fall into the packing to contact the water-containing air.

5. The open-gradient absorption wastewater purification system according to claim 2, characterized in that, It further includes a preheater. Part of the purified water output from the bottom of the regeneration tower enters the preheater to exchange heat with the desulfurized wastewater, and the cooled purified water is output, while the heated wastewater enters the second absorption packing layer.

6. The open-gradient absorption wastewater purification system according to claim 1, characterized in that, An air-lifting device is arranged between the second regeneration packing layer and the first regeneration packing layer of the regeneration tower; The bottom of the second regeneration packing layer is connected with a water delivery pipeline to deliver the purified water at the bottom of the second regeneration packing layer to the first regeneration packing layer through the water delivery pipeline.

7. An open-gradient absorption and generation wastewater purification method, characterized in that, Using the open-gradient absorption and wastewater purification system according to any one of claims 1-6 for wastewater treatment, includes: the wastewater and air perform heat and mass transfer in the absorption tower, so that the water in the wastewater enters the air, and the water-containing air is output at the top of the absorption tower; The water-containing air performs heat and mass transfer with the purified water in the regeneration tower, so that the water in the water-containing air enters the purified water, and the air is output at the top of the regeneration tower and recycled to the bottom of the absorption tower; Wherein, a double-stage regenerative heat exchange module formed by the first regenerator and the second regenerator exchanges heat between the purified water and the wastewater. Part of the wastewater output from the bottom of the absorption tower enters the second regenerator for a first temperature rise. After the first temperature rise, the wastewater is divided into two paths. One path enters the first absorption packing layer of the absorption tower, and the other path enters the first regenerator for a second temperature rise; after the second temperature rise, the wastewater is divided into two paths. One path enters the second absorption packing layer after being heated by the continuous drainage heater, and the other path enters the third absorption packing layer after being heated by the steam heater; Part of the purified water output from the bottom of the regeneration tower enters the first regenerator for a first temperature drop. After the first temperature drop, the purified water is divided into two paths. One path enters the first regeneration packing layer of the regeneration tower, and the other path enters the second regenerator for a second temperature drop; after the second temperature drop, the purified water is divided into two paths. One path enters the second regeneration packing layer of the regeneration tower, and the other path enters the third regeneration packing layer of the regeneration tower after being cooled by a cooler.

8. The open-gradient absorption wastewater purification method according to claim 7, characterized in that, The air feed temperature at the bottom of the absorption tower is 43°C - 48°C, the air discharge temperature at the top of the absorption tower is 85°C - 90°C, and then it enters the regeneration tower at a temperature of 88°C - 92°C after being treated by the scrubbing tower. The air discharge temperature at the top of the regeneration tower is 43°C - 48°C; And / or, the temperature of the wastewater output from the bottom of the absorption tower is 48°C - 52°C; And / or, the temperature of the purified water output from the bottom of the regeneration tower is 82°C - 88°C.

9. The open-gradient absorption wastewater purification method according to claim 8, wherein The purified water feed temperature of the first regeneration packing layer of the regeneration tower is 65°C - 70°C, the purified water feed temperature of the second regeneration packing layer is 55°C - 60°C, and the purified water feed temperature of the third regeneration packing layer is 35°C - 40°C; And / or, the wastewater feed temperature of the first absorption packing layer of the absorption tower is 63°C - 67°C, the wastewater feed temperature of the second absorption packing layer is 88°C - 92°C, and the wastewater feed temperature of the third absorption packing layer is 93°C - 98°C.

10. The open-gradient absorption wastewater purification method according to claim 8, characterized in that, The temperature of the desulfurized wastewater after being preheated by the preheater is 78°C - 82°C; And / or, the temperature of the wastewater entering the continuous drainage heater and the steam heater is 78°C - 82°C.

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