Open evaporation absorption sewage purification system and operation method

Abstract

The present invention discloses an open evaporative absorption sewage purification system and an operating method, and relates to the technical field of sewage treatment. An air-lifting device is arranged in a heat and mass generating tower, which is divided into an upper intermediate sewage treatment zone and a lower concentrated sewage treatment zone. The intermediate sewage circulation can effectively reduce the liquid carried at the outlet of the heat and mass generating tower. Dry air enters from the bottom of the lower concentrated sewage treatment zone, and is fully in contact with the concentrated sewage with a higher temperature through the coarse-pore grid filler, so that the water in the concentrated sewage enters the air more fully; after the water-containing air enters the upper intermediate sewage treatment zone, the corrugated plate in the corrugated filler is repeatedly turned back, so that the carried concentrated sewage droplets are captured, and the water-containing air passes through a defogger to collect the entrained droplets. After being treated by the open evaporative absorption sewage purification system, the amount of liquid carried in the air entering the heat and mass absorption tower can be significantly reduced, the quality of the purified water can be improved, and the purified water can be purified into process-usable water at one time without increasing energy consumption, without the need for secondary treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an open evaporation absorption sewage purification system and an operation method thereof. Background Art

[0002] In the field of zero-discharge sewage purification, the conventional treatment process is filtration, concentration, and crystallization. Among them, most of the current process routes for the concentration part are flash condensation, multi-effect evaporation, MVR steam recompression, etc. Among them, the flash condensation system is simple, but the sewage needs to be heated, the energy consumption is high, and the quality of the purified water cannot be guaranteed because the flash tank demister does not completely remove the flash liquid; the multi-effect evaporation method has lower energy consumption, but the steam required is of higher quality, and it has low adaptability to fluctuations in processing volume, and there is also the problem of incomplete removal of flash liquid; and the MVR steam recompression technology consumes a lot of electricity and can only be used in scenarios with extremely low electricity costs, and there is also the problem of incomplete removal of flash liquid.

[0003] Therefore, in addition to the energy consumption problem, the current conventional concentration technology also has the problem of unguaranteed water quality. The exported clean water often needs to be concentrated or post-processed again before it can be used in other production processes. At present, it is urgent to develop a sewage purification system that can obtain applicable clean water in one go, while meeting the requirements of low energy consumption, strong adaptability to flow fluctuations and impurity types, and coupled with other pre- and post-treatment processes to achieve zero wastewater discharge in one go.

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

[0005] The object of the present invention is to provide an open evaporation absorption sewage purification system and an operation method, aiming to reduce energy consumption while obtaining usable clean water in one go.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides an open evaporation absorption sewage purification system, comprising a heat and mass generating tower for heat and mass transfer between sewage and air and a heat and mass absorbing tower for heat and mass transfer between water-containing air and clean water, the top of the heat and mass absorbing tower is connected to the bottom of the heat and mass generating tower, and the top of the heat and mass generating tower is connected to the bottom of the heat and mass absorbing tower, so as to realize the circulation of air between the heat and mass absorbing tower and the heat and mass generating tower;

[0008] The heat and mass generating tower is provided with an air lifting device to divide the heat and mass generating tower into an upper intermediate sewage treatment zone and a lower concentrated sewage treatment zone. The tower of the upper intermediate sewage treatment zone is filled with corrugated fillers, and the lower concentrated sewage treatment zone is filled with coarse-pore grid fillers with a pore size of 3cm-5cm. A demisting device is provided inside the top of the heat and mass generating tower;

[0009] The bottom sewage outlet of the intermediate sewage treatment area at the upper end of the heat and mass generating tower is connected to an intermediate sewage storage tank, and part of the sewage in the intermediate sewage storage tank is circulated to the upper intermediate sewage treatment area, and part enters the lower concentrated sewage treatment area; the concentrated sewage output from the bottom of the tower in the lower concentrated sewage treatment area is heated and mixed with the sewage from the intermediate sewage storage tank and returned to the lower concentrated sewage treatment area;

[0010] The clean water output from the bottom of the heat and mass absorption tower is cooled by the cooler and then returned to the top of the heat and mass absorption tower. A clean water output pipeline is arranged at the front end and / or the rear end of the cooler.

[0011] In an optional embodiment, the bottom of the heat mass absorption tower is connected to the top of the heat mass generation tower through a backwash water delivery pipeline, so as to backwash the demisting device on the heat mass generation tower.

[0012] In an optional embodiment, it also includes a pretreatment filter device for removing impurities from sewage and a preheater for heat exchange between sewage and clean water. The sewage passes through the pretreatment filter device and the preheater in sequence and then enters the intermediate sewage storage tank.

[0013] In an optional embodiment, it further comprises a heat recovery heat exchanger for heat exchange between concentrated sewage and clean water and a heater for heating concentrated sewage, the bottoms of the heat mass absorption tower and the heat mass generation tower are both connected to the heat recovery heat exchanger, the concentrated sewage outlet on the heat recovery heat exchanger is connected to the heater, and the outlet of the heater is connected to the concentrated sewage treatment area at the lower end of the heat mass generation tower;

[0014] The clean water outlet on the heat recovery exchanger is communicated with the preheater, the clean water outlet of the preheater is communicated with the cooler, and the clean water outlet of the cooler is communicated with the heat and mass absorption tower.

[0015] In an optional embodiment, the concentrated sewage output from the outlet of the heater is mixed with part of the sewage output from the intermediate sewage storage tank and then enters the top of the concentrated sewage treatment area at the lower end, and contacts with the air through spraying for heat and mass transfer;

[0016] and / or, part of the sewage output from the intermediate sewage storage tank is circulated to the top of the upper intermediate sewage treatment area, and is contacted with the air by spraying for heat and mass transfer;

[0017] And / or, the clean water outputted from the cooler enters the heat and mass absorption tower and contacts with the air through spraying for heat and mass transfer;

[0018] and / or, the heat mass absorption tower is filled with a coarse-pore grid filler with a pore size of 3 cm to 5 cm;

[0019] And / or, a demisting device is provided on the top of the thermal mass absorption tower.

[0020] In an optional embodiment, it also includes: a cyclone device, a crystallization unit and a solid-liquid separation unit, the bottom of the heat and mass generating tower is connected to the inlet of the cyclone device, the upper liquid outlet of the cyclone device is connected to the bottom of the heat and mass generating tower, the lower liquid outlet of the cyclone device is connected to the crystallization unit, the crystallization unit is connected to the solid-liquid separation unit, and the separation liquid outlet of the solid-liquid separation unit is connected to the inlet of the cyclone device.

[0021] In an optional embodiment, a steam condensate outlet is further provided on the crystallization unit, and the steam condensate outlet is connected to the top of the heat and mass generating tower so that the steam condensate can be used as backwash water for the demister.

[0022] In a second aspect, the present invention provides a sewage purification method, which uses the open evaporation absorption sewage purification system of any one of the aforementioned embodiments to purify sewage, comprising:

[0023] After being preheated, the sewage enters the intermediate sewage storage tank and mixes with the intermediate sewage flowing out of the upper intermediate sewage treatment area. After that, part of the sewage circulates to the upper intermediate sewage treatment area of ​​the heat and mass generating tower to use the corrugated packing to contact with the air for heat and mass transfer, and part of the sewage enters the concentrated sewage treatment area at the lower end of the heat and mass generating tower.

[0024] The concentrated sewage is output from the bottom outlet of the tower in the lower concentrated sewage treatment area for heating. The heated concentrated sewage is mixed with sewage from the intermediate sewage storage tank and returned to the lower concentrated sewage treatment area, where the coarse-pore grid filler is in contact with the air for heat and mass transfer.

[0025] The water-containing air is processed by a demisting device at the top of the heat and mass generating tower and then outputted, and enters the bottom of the heat and mass absorbing tower, where it contacts with the clean water for heat and mass transfer, so that the moisture in the water-containing air enters the clean water, and the air outputted from the top of the heat and mass absorbing tower is circulated to the bottom of the heat and mass generating tower;

[0026] The clean water output from the bottom of the heat and mass absorption tower is cooled by the cooler and then returned to the top of the heat and mass absorption tower, and the clean water is output at the front end and / or rear end of the cooler.

[0027] In an optional embodiment, the sewage first passes through a pre-treatment filter to remove impurities, and then enters an intermediate sewage storage tank after heat exchange with clean water in a preheater;

[0028] The concentrated sewage output from the bottom of the heat and mass absorption tower and the clean water output from the bottom of the heat and mass absorption tower are heat exchanged in the recuperator. The concentrated sewage heated by the recuperator is heated by the heater and then returned to the concentrated sewage treatment area at the lower end of the heat and mass generation tower. The clean water cooled by the recuperator is heat exchanged with the sewage after impurities are removed in the preheater. The clean water cooled by the heat exchanger is cooled by the cooler and then returned to the heat and mass absorption tower.

[0029] and / or, a portion of the clean water output from the bottom of the heat mass absorption tower is used as backwash water to backwash the demisting device on the heat mass generation tower;

[0030] And / or, concentrated sewage output from the outlet of the heater is mixed with part of the sewage output from the intermediate sewage storage tank and then enters the top of the concentrated sewage treatment area at the lower end, and contacts with the air through spraying to transfer heat and mass;

[0031] and / or, part of the sewage output from the intermediate sewage storage tank is circulated to the top of the upper intermediate sewage treatment area, and is contacted with the air by spraying for heat and mass transfer;

[0032] And / or, after the sewage output from the bottom of the heat and mass generating tower is treated by a cyclone device, the upper liquid of the cyclone device is returned to the bottom of the heat and mass generating tower, and the lower liquid of the cyclone device enters a crystallization unit for heating crystallization or cooling crystallization, and the crystal slurry output from the crystallization unit is subjected to solid-liquid separation, and the obtained separated liquid is returned to the cyclone device;

[0033] When heating crystallization is adopted, the secondary steam condensate produced by evaporative crystallization is used as backwash water to backwash the demisting device on the heat and mass generating tower.

[0034] In an optional embodiment, the heat source temperature t1 of the heater is controlled to be 75°C-130°C, and the cold source temperature t2 of the cooler is controlled to be 30°C-60°C;

[0035] Define the dry air ratio and sewage circulation ratio. The dry air ratio is equal to the ratio of the circulation flow of dry air to the flow of treated sewage, and the sewage circulation ratio is equal to the ratio of the circulation volume of concentrated sewage to the volume of treated sewage.

[0036] When 110≤t1≤130, the dry air ratio is controlled to 0.5-0.7 and the sewage circulation ratio is 10-17;

[0037] When 90≤t1<110, the dry air ratio is controlled to be 1.1-1.4 and the sewage circulation ratio is 12-24;

[0038] When 75≤t1<90, the dry air ratio is controlled to be 4-7 and the sewage circulation ratio is controlled to be 18-40;

[0039] The dry air ratio and sewage circulation ratio are determined according to the value of t1 and the cold source temperature. The higher the cold source temperature, the greater the dry air ratio and sewage circulation ratio.

[0040] and / or, the flow ratio of the intermediate sewage circulation volume flow rate to the concentrated sewage circulation volume flow rate is 1:(4-6);

[0041] And / or, the flow ratio of the clean water circulation volume to the concentrated sewage circulation volume is 1:(0.9-1.1).

[0042] The present invention has the following beneficial effects: an air-lifting device is arranged in the heat and mass generating tower, which is divided into an upper intermediate sewage treatment zone and a lower concentrated sewage treatment zone, generating an intermediate sewage circulation, which can effectively reduce the liquid carried at the outlet of the heat and mass generating tower. After the dry air enters from the bottom of the lower concentrated sewage treatment zone, it is fully in contact with the concentrated sewage with a higher temperature through the coarse-pore grid filler, so that the water in the concentrated sewage enters the air more fully; after the water-containing air enters the upper intermediate sewage treatment zone, the corrugated plate in the corrugated filler is repeatedly turned back, so that the carried concentrated sewage droplets are captured, and the water-containing air is further collected by the demisting device. After being treated by the open evaporation absorption sewage purification system provided by the present invention, the amount of liquid carried in the air entering the heat and mass absorption tower can be significantly reduced, the quality of the purified water can be improved, and the purified water can be purified into process-usable water at one time without increasing energy consumption, without the need for secondary treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A structural diagram of an open evaporation absorption sewage purification system provided by an embodiment of the present invention;

[0045] Figure 2 for Figure 1 The schematic diagram of the open evaporation absorption sewage purification system in the figure with the numbers deleted and the component names added;

[0046] Figure 3 This is the flow chart of triple-effect evaporation technology.

[0047] Icons: 100-open evaporative absorption sewage purification system; 110-heat and mass generating tower; 111-aeration device; 112-upper intermediate sewage treatment area; 113-lower concentrated sewage treatment area; 114-corrugated packing; 115-first coarse-pore grid packing; 116-first demister; 120-heat and mass absorption tower; 121-second coarse-pore grid packing; 122-second demister; 131-intermediate sewage storage tank; 132-cooler; 133-pretreatment filter device; 134-preheater; 135-regenerative heat exchanger; 136-heater; 141-clean water output pipeline; 142-backwash water delivery pipeline; 143-fan; 151-cyclone device; 152-crystallization unit; 153-solid-liquid separation unit. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0049] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides an open evaporation absorption sewage purification system 100, including a heat and mass generating tower 110 and a heat and mass absorbing tower 120. The heat and mass generating tower 110 performs heat and mass transfer between sewage and air, so that the water vapor generated by gasification of the sewage enters the air; the heat and mass absorbing tower 120 is used for heat and mass transfer between water-containing air and clean water, so that the moisture in the water-containing air is condensed and enters the clean water.

[0050] It should be noted that "open" refers to the process of evaporation and condensation in the tower, which is a process in which the circulating air and the spray liquid are in direct contact, which is different from the partition-type contact. Among them, the circulating air is approximately equal to normal pressure, which is consistent with the external pressure.

[0051] The top of the heat and mass absorption tower 120 is connected to the bottom of the heat and mass generation tower 110, and the top of the heat and mass generation tower 110 is connected to the bottom of the heat and mass absorption tower 120 through the fan 143, so as to realize the circulation of the humid air in the heat and mass generation tower 110 and the heat and mass absorption tower 120. Specifically, the air in the heat and mass generation tower 110 contacts the sewage with a higher temperature, and the low-temperature and low-humidity air enters from the bottom of the heat and mass generation tower 110, and after contacting with the sewage for heat and mass transfer, the water generated by gasification in the sewage enters the air, and the obtained high-temperature and high-humidity air is output from the top of the heat and mass generation tower 110. The high-temperature and high-humidity air output from the top of the heat and mass generation tower 110 enters from the bottom of the heat and mass absorption tower 120, and after contacting with the clean water with a lower temperature for heat and mass transfer, the condensed water generated by the high-temperature and high-humidity air enters the clean water, and the low-temperature and low-humidity air output from the bottom of the heat and mass absorption tower 120 circulates to the bottom of the heat and mass generation tower 110, realizing the circulation of the humid air.

[0052] A gas lift device 111 is provided in the heat and mass generating tower 110 to divide the heat and mass generating tower 110 into an upper intermediate sewage treatment zone 112 and a lower concentrated sewage treatment zone 113. The tower of the upper intermediate sewage treatment zone 112 is filled with corrugated filler 114, and the lower concentrated sewage treatment zone 113 is filled with a first coarse-pore grid filler 115 with a pore size of 3cm-5cm (i.e., the diameter of the square holes of the grid is 3cm-5cm). A first demister 116 is provided inside the top of the heat and mass generating tower 110. After entering from the bottom of the concentrated sewage treatment area 113 at the lower end, the dry air passes through the first coarse-pore grid filler 115 and fully contacts with the concentrated sewage with a higher temperature, so that the water in the concentrated sewage enters the air more fully, and the concentrated sewage returns to the bottom of the tower after the amount is reduced and the temperature is lowered; after entering the upper middle sewage treatment area 112, the water-containing air is repeatedly turned back by the corrugated plates in the corrugated filler 114, so that the concentrated sewage droplets carried are captured, and the water-containing air passes through the first demister 116 to further collect the entrained droplets, thereby significantly reducing the entrained sewage in the air entering the thermal mass absorption tower 120 and improving the water quality of the purified water.

[0053] Specifically, the gas lift device 111 is a structure commonly used in tower equipment to separate two parts. The specific structure can refer to CN112169543B. The gas can pass from bottom to top, and the liquid cannot fall from top to bottom. The first coarse-pore grid filler 115 can be a commercially available filler with a pore size that meets the requirements; the corrugated filler 114 can also be a commercially available filler, and its parameters are as follows: the filler model is 125Y or 250Y, and the material is ceramic. The corrugated filler 114 has a large expansion area, and the flue gas needs to be repeatedly deflected, which is equivalent to defogger; the coarse-pore grid filler has a relatively large liquid density and is not easy to produce liquid flooding.

[0054] In some embodiments, the bottom of the heat mass absorption tower 120 is connected to the top of the heat mass generation tower 110 through a backwash water delivery pipeline 142, which is used to backwash the first demisting device 116 on the heat mass generation tower 110 to keep the demisting device clean and unobstructed. The upper intermediate sewage treatment area 112 is mainly used for initial sewage and clean water spraying, and the water quality is good, and it is not easy to introduce harmful liquid into the air.

[0055] The upper intermediate sewage treatment area 112 of the heat and mass generating tower 110 is provided with an intermediate sewage circulation, the lower concentrated sewage treatment area 113 is provided with a concentrated sewage circulation, and the heat and mass absorbing tower 120 is provided with a purified water circulation.

[0056] Intermediate sewage circulation: The bottom sewage outlet of the upper intermediate sewage treatment area 112 of the heat and mass generating tower 110 is connected to the intermediate sewage storage tank 131. Part of the sewage in the intermediate sewage storage tank 131 is circulated to the upper intermediate sewage treatment area 112, and part of the sewage enters the lower concentrated sewage treatment area 113. The use of the intermediate sewage storage tank 131 for intermediate sewage circulation can effectively reduce the liquid at the outlet of the heat and mass generating tower 110. Due to the intermittent addition of backwash clean water and the continuous addition of sewage, the intermediate sewage in the intermediate sewage circulation tank needs to be continuously discharged into the lower concentrated sewage circulation.

[0057] Concentrated sewage circulation: The concentrated sewage output from the bottom of the tower of the lower concentrated sewage treatment area 113 is heated and mixed with the sewage from the intermediate sewage storage tank 131, and then returned to the lower concentrated sewage treatment area 113. The intermediate sewage from the intermediate sewage storage tank 131 is added to the concentrated sewage circulation, and the adding point is set after the heater 136, because the intermediate sewage is basically in adiabatic contact with the air at the top of the heat and mass generating tower 110, and the temperature is the same and relatively high. If it is set before the heater 136 or at the bottom of the tower, the efficiency of the heater 136 will be reduced.

[0058] Clean water circulation: The clean water output from the bottom of the heat and mass absorption tower 120 is cooled by the cooler 132 and then returned to the top of the heat and mass absorption tower 120. A clean water output pipeline 141 is set at the front end and / or the rear end of the cooler 132. The water content of the clean water circulation is increasing. A discharge port is set after the preheater 134 or after the cooler 132 to output the clean water. Specifically, when the waste heat needs to be recycled, the clean water discharge point is placed after the cooler 132 and before the spraying; when the waste heat does not need to be recycled but needs to be dissipated, the clean water discharge point is placed after the preheater 134 and before the cooler 132.

[0059] In some embodiments, the open evaporation absorption sewage purification system 100 further includes a pretreatment filter device 133 for removing impurities from the sewage and a preheater 134 for heat exchange between the sewage and the clean water. The sewage passes through the pretreatment filter device 133 and the preheater 134 in sequence and then enters the intermediate sewage storage tank 131. The pretreatment filter device 133 can be selected according to the type of impurities in the sewage. The pretreatment filter device 133 can remove large impurities and part of the precipitated impurities, and then heat is exchanged with the clean water at a lower temperature in the preheater 134, and then enters the intermediate sewage storage tank 131.

[0060] In some embodiments, the open evaporative absorption wastewater purification system 100 further includes a heat recovery heat exchanger 135 for heat exchange between concentrated wastewater and clean water and a heater 136 for heating concentrated wastewater. The bottoms of the heat and mass absorption tower 120 and the heat and mass generation tower 110 are both connected to the heat recovery heat exchanger 135, and the high-temperature clean water transfers heat to the concentrated wastewater in the heat recovery heat exchanger 135. The concentrated wastewater outlet on the heat recovery heat exchanger 135 is connected to the heater 136, so that the concentrated wastewater is further heated in the heater 136, and the outlet of the heater 136 is connected to the concentrated wastewater treatment area 113 at the lower end of the heat and mass generation tower 110, so as to return the heated concentrated wastewater to the concentrated wastewater treatment area 113 at the lower end to continue to contact the air for mass and heat transfer.

[0061] Furthermore, the clean water outlet on the heat exchanger 135 is connected to the preheater 134, and the sewage is heated in the preheater 134. The clean water outlet of the preheater 134 is connected to the cooler 132, so that the clean water is further cooled and then enters the heat and mass absorption tower 120 from the clean water outlet of the cooler 132 to contact with the air.

[0062] In order to further enhance the effect of heat and mass transfer, the concentrated sewage output from the outlet of the heater 136 is mixed with part of the sewage output from the intermediate sewage storage tank 131 and then enters the top of the lower concentrated sewage treatment area 113, where it contacts with the air for heat and mass transfer by spraying; similarly, part of the sewage output from the intermediate sewage storage tank 131 is circulated to the top of the upper intermediate sewage treatment area 112, where it contacts with the air for heat and mass transfer by spraying. That is, nozzles are set at the tops of the lower concentrated sewage treatment area 113 and the upper intermediate sewage treatment area 112 for spray washing, and large liquid drops or trough-type liquid distribution can be used for circulating spray washing of the intermediate sewage; conventional dripping can be used for spraying in the lower concentrated sewage treatment area 113.

[0063] Similarly, the clean water output by the cooler 132 enters the heat and mass absorption tower 120, contacts the air by spraying, and conducts heat and mass transfer through the second coarse-pore grid filler 121 with a pore size of 3cm-5cm, cooling the hot and humid air, and the condensed water generated by the cooling of the hot and humid air is added to the clean water cycle. The concentrated sewage treatment area 113 at the lower end of the heat and mass generation tower 110 and the heat and mass absorption tower 120 use dripping instead of atomization, while avoiding more upper airflow droplet entrainment and ensuring the heat exchange capacity as much as possible; the upper part of the heat and mass absorption tower 120 uses large liquid droplets or trough-type liquid distribution to minimize the upper airflow droplet entrainment.

[0064] In some embodiments, a second demister 122 is disposed on the top of the heat and mass absorption tower 120 , and the second demister 122 can remove liquid droplets carried in the dry air.

[0065] In some embodiments, the open evaporation absorption wastewater purification system 100 further includes: a cyclone device 151, a crystallization unit 152 and a solid-liquid separation unit 153. The bottom of the heat and mass generating tower 110 is connected to the inlet of the cyclone device 151. A portion of the concentrated wastewater is selected to enter the cyclone device 151, and the cyclone device 151 is used to separate the concentrated wastewater into an upper clear liquid and a lower solid-liquid mixture. The upper liquid outlet of the cyclone device 151 is connected to the bottom of the heat and mass generating tower 110, so that the upper clear liquid returns to the bottom of the heat and mass generating tower 110; the lower liquid outlet of the cyclone device 151 is connected to the crystallization unit 152, so that the lower solid-liquid mixture enters the crystallization unit 152, and evaporation crystallization or cooling crystallization is selected according to the ion properties. The crystallization unit 152 is connected to the solid-liquid separation unit 153, and the separated liquid outlet of the solid-liquid separation unit 153 is connected to the inlet of the cyclone device 151. The crystal slurry output from the crystallization unit 152 is separated into crystal components and separation liquid in the solid-liquid separation unit 153. The separation liquid returns to the position before the cyclone device 151, and the crystals are output as products or solid wastes according to the type of sewage ions.

[0066] If evaporative crystallization is adopted, a steam condensate outlet is also provided on the crystallization unit 152, and the steam condensate outlet is connected to the top of the heat and mass generating tower 110, so that the secondary steam condensate is returned to the intermediate sewage circulation as the backwash water of the first demisting device 116, and the crystal slurry goes to the solid-liquid separation unit 153. If cooling crystallization is adopted, the crystal slurry goes directly to the solid-liquid separation unit 153.

[0067] It should be noted that in the crystallization unit 152, if the solute solubility corresponding to the internal ion decreases significantly as the temperature decreases (such as sodium sulfate), the cooling crystallization method is adopted, and a cold source needs to be introduced; if the solubility of the solute corresponding to the internal ion does not change significantly as the temperature decreases (such as sodium chloride) or increases (such as calcium hydroxide), the evaporation crystallization method is adopted, and a heat source needs to be introduced, and a cold source is required to cool the secondary steam.

[0068] It should be noted that the flushing water of the first demisting device 116 is selected according to the actual process. If the crystallization method is evaporation crystallization and the amount of secondary condensed water is large, the backwash water pump of the bottom clean water of the thermal mass absorption tower 120 can be partially turned on or not turned on as an emergency spraying measure. If the crystallization method is cooling crystallization, the bottom clean water of the thermal mass absorption tower 120 is used as the backwash water.

[0069] Specifically, the cyclone device 151 may be a conventional impeller, and the crystallization unit 152 may be a general evaporative crystallizer.

[0070] The embodiment of the present invention further provides a sewage purification method, which uses the open evaporation absorption sewage purification system 100 provided by the embodiment of the present invention to purify sewage, including the following steps:

[0071] Process of the upper intermediate sewage treatment area 112: After being preheated, the sewage enters the intermediate sewage storage tank 131 and is mixed with the intermediate sewage flowing out of the upper intermediate sewage treatment area 112. Then, part of the sewage in the intermediate sewage storage tank 131 is circulated to the upper intermediate sewage treatment area 112 of the heat and mass generating tower 110 and uses the corrugated packing 114 to contact with the air for heat and mass transfer. Part of the sewage in the intermediate sewage storage tank 131 enters the lower concentrated sewage treatment area 113 of the heat and mass generating tower 110.

[0072] Process of lower concentrated sewage treatment area 113: concentrated sewage is output from the bottom outlet of the tower of the lower concentrated sewage treatment area 113 for heating. The heated concentrated sewage is mixed with sewage from the intermediate sewage storage tank 131 and returned to the lower concentrated sewage treatment area 113. Coarse-pore grid filler is contacted with air for heat and mass transfer, so that water vapor in the concentrated sewage with higher temperature enters the air.

[0073] Heat and mass absorption tower 120 process: the water-containing air is processed by the first demisting device 116 at the top of the heat and mass generating tower 110 and then output, and enters the bottom of the heat and mass absorption tower 120, where it contacts with clean water for heat and mass transfer, so that the moisture in the water-containing air enters the clean water, and the air output from the top of the heat and mass absorption tower 120 circulates to the bottom of the heat and mass generating tower 110; the clean water output from the bottom of the heat and mass absorption tower 120 is cooled by the cooler 132 and then returned to the top of the heat and mass absorption tower 120, and the clean water is output at the front end and / or rear end of the cooler 132.

[0074] In some embodiments, the sewage first passes through a pretreatment filter device 133 to remove impurities, and then enters the intermediate sewage storage tank 131 after heat exchange with clean water in a preheater 134; the concentrated sewage output from the bottom of the heat and mass absorption tower 120 and the clean water output from the bottom of the heat and mass absorption tower 120 are heat exchanged in a heat exchanger 135, and the concentrated sewage heated by the heat exchanger 135 is heated by a heater 136 and then returned to the concentrated sewage treatment area 113 at the lower end of the heat and mass generation tower 110, and the clean water cooled by the heat exchanger 135 is heat exchanged with the sewage after impurities are removed in a preheater 134, and the clean water cooled by the heat exchanger is then cooled by a cooler 132 and then returned to the heat and mass absorption tower 120.

[0075] It should be noted that the open evaporative absorption sewage purification system 100 provided in the embodiment of the present invention divides sewage into concentrated sewage and clean water. The fundamental source of its power is the thermal grade difference between the heat source and the cold source. The greater the temperature difference between the two and the higher the overall temperature point, the higher the overall efficiency, and the smaller the corresponding circulating air volume and water volume. At the same time, since the system as a whole maintains normal pressure, in order to avoid boiling of concentrated sewage, the temperature of the heat source does not need to be too high, and 0.2Mpa.a steam or other forms of heat sources with the same grade can be used.

[0076] In order to further ensure the quality of purified water while reducing energy consumption, the inventor optimized the operating parameters of the process. The key point of the unit operation is to determine the air flow and spray circulation volume according to the quality of the cold and heat sources. Define two key parameters: dry air ratio and sewage circulation ratio. The dry air ratio is equal to the ratio of the circulation flow of dry air to the flow of treated sewage, and the sewage circulation ratio is equal to the ratio of the circulation volume of concentrated sewage to the volume of treated sewage. After comprehensively considering the difficulty of equipment manufacturing process and heat balance, the specific values ​​of the two key parameters are controlled according to the quality of the cold source and the quality of the heat source according to the following conditions:

[0077] The heat source temperature t1 of the heater 136 is controlled to be 75°C-130°C, and the cold source temperature t2 of the cooler 132 is controlled to be 30°C-60°C; the dry air ratio and the sewage circulation ratio are determined according to the value of t1 and the cold source temperature. The higher the cold source temperature, the greater the dry air ratio and the sewage circulation ratio.

[0078] When 110≤t1≤130, the dry air ratio is controlled to be 0.5-0.7 (such as 0.5, 0.6, 0.7, etc.), and the sewage circulation ratio is 10-17 (such as 10, 11, 12, 13, 14, 15, 16, 17, etc.);

[0079] When 90≤t1<110, the dry air ratio is controlled to be 1.1-1.4 (such as 1.1, 1.2, 1.3, 1.4, etc.), and the sewage circulation ratio is 12-24 (such as 12, 15, 18, 20, 22, 24, etc.);

[0080] When 75≤t1<90, the dry air ratio is controlled to be 4-7 (such as 4, 5, 6, 7, etc.), and the sewage circulation ratio is controlled to be 18-40 (such as 18, 20, 25, 30, 35, 40, etc.).

[0081] In some embodiments, two key parameters are selected as shown in Table 1 and Table 2 below:

[0082] Table 1 Dry air ratio selection

[0083]

[0084] Table 2 Selection of sewage circulation ratio

[0085]

[0086] It should be noted that after determining the above two key parameters, the circulating air volume and concentrated sewage circulation volume can be calculated:

[0087] Circulating air volume (dry basis) = sewage treatment volume × dry-air ratio;

[0088] Concentrated sewage circulation volume = sewage treatment volume × sewage circulation ratio.

[0089] In some embodiments, the flow ratio of the intermediate sewage circulation volume flow rate to the concentrated sewage circulation volume is 1:(4-6), such as 1:4, 1:5, 1:6, etc.; the flow ratio of the clean water circulation volume to the concentrated sewage circulation volume is 1:(0.9-1.1), such as 1:0.9, 1:1.0, 1:1.1, etc.

[0090] According to the above selection method, a control system is set up according to the actual flow fluctuation of incoming sewage, and automatic gradient frequency conversion is used to adjust the concentrated sewage circulation pump, clean water circulation pump, and circulation fan to adapt to different sewage treatment volumes.

[0091] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0092] It should be noted that the wastewater treated in the following examples is as follows: 40 t / h of power plant wastewater is treated, and the main solute is 3% sodium chloride reverse osmosis concentrated water wastewater.

[0093] Example 1

[0094] This embodiment provides a sewage purification method using Figure 1 and Figure 2 The open evaporation absorption sewage purification system 100 is used to purify sewage, and the specific process is as follows:

[0095] (1) Wastewater Process

[0096] The sewage first passes through the pre-treatment filter device 133 to remove large impurities and some precipitated impurities, then enters the preheater 134 for heat exchange with clean water, and then enters the intermediate sewage storage tank 131, where it is sprayed and washed (sprayed with large liquid drops) with the wet air on the top of the heat and mass generating tower 110 along with the intermediate sewage circulation.

[0097] During the concentrated sewage circulation, the sewage is pumped out from the bottom of the tower, passes through the heat recovery heat exchanger 135 and the heater 136, and is mixed with the intermediate sewage from the intermediate sewage storage tank 131, and then enters the lower part of the heat generating tower 110 for spraying (the spraying adopts conventional dripping). After the coarse-pore grid filler and the air are heat-exchanged, part of the water evaporates into the air, and the heat is used to heat the air. The concentrated sewage is reduced in volume and cooled down and then returns to the bottom of the tower.

[0098] A portion of the concentrated sewage at the bottom of the heat and mass generating tower 110 is selected to enter the cyclone device 151, the clear liquid at the top of the cyclone device 151 returns to the bottom of the tower, and the solid-liquid mixture at the bottom enters the crystallization unit 152 for evaporation and crystallization, and the secondary steam condensed water is used as the demister backwash water to return to the intermediate sewage circulation, and the crystal slurry goes to the solid-liquid separation unit 153. The crystal slurry is divided into crystal products and separation liquid in the solid-liquid separation unit 153, and the separation liquid returns to the position before the cyclone device 151, and the crystals are output as products.

[0099] (2) Water purification process:

[0100] The clean water is mainly sprayed and circulated in the heat mass absorption tower 120. The clean water at the bottom of the tower is cooled by the heat recovery heat exchanger 135, and then heated by the preheater 134 to cool the sewage inlet water again. After that, a part of the clean water is discharged from the system as output, and the remaining clean water is further cooled by the cooler 132 and enters the heat mass absorption tower 120, where it comes into direct contact with the hot and humid air through the coarse-pore grid filler to cool the hot and humid air. The condensed water generated by the cooling of the hot and humid air is added to the clean water circulation.

[0101] (3) Air flow:

[0102] After the air enters the lower part of the heat and mass generating tower 110, it directly exchanges heat and mass with the concentrated sewage sprayed down, and the temperature and water content increase. After that, it enters the intermediate sewage circulation through the gas lifting device 111, and is washed by the intermediate sewage with relatively low concentration in a nearly adiabatic process, and then is discharged after passing through the first demisting device 116 at the top of the heat and mass generating tower 110. After that, the air enters the lower part of the heat and mass absorbing tower 120 through the fan 143, and after being sprayed by the clean water circulation, the temperature and water content decrease. After being demisted by the second demisting device 122 at the top of the heat and mass absorbing tower 120, the air returns to the lower part of the heat and mass generating tower 110, and the cycle repeats.

[0103] The specific operating parameters are as follows:

[0104] The heat source of heater 136 adopts 100°C exhaust steam that originally needs to enter the low-pressure heater, and the cold source of cooler 132 adopts 35°C steam turbine condensate condensed by the condenser.

[0105] The solubility of sodium chloride is about 35% to 40%. In this embodiment, the sodium chloride is concentrated to 30% by concentrated sewage before entering the cyclone device 151.

[0106] The turbine condensate is heated to 60°C. According to the table with 100°C heat source and 60°C cold source, the dry air ratio is 1.4 and the sewage circulation ratio is 24. The sewage treatment capacity is 40t / h, the air dry basis circulation capacity is 40×1.4=56t / h, and the sewage circulation capacity is 24×40=960t / h. The density of sodium chloride solution after concentration is about 1.2g / cm 3 , then the sewage circulation volume flow rate is 800m 3 / h, the clean water circulation volume flow rate is 800m 3 / h, the clean water density is considered to be 1, and the clean water circulation volume is 800t / h. The intermediate sewage circulation density is also approximately equal to 1, and the intermediate sewage circulation volume flow rate is 800×1 / 5=160m 3 / h, and the intermediate sewage circulation volume is 160t / h.

[0107] According to heat balance calculation, the heater needs to consume about 8MW of heat.

[0108] About 10t / h of sodium chloride is taken from the bottom sewage of the heat and mass generating tower 110, and after cyclone, 6t / h of sodium chloride solution returns to the bottom of the heat and mass generating tower 110, and 4t / h of solution goes to the crystallization unit 152. The evaporation crystallization method consumes about 2MW of heat to crystallize sodium chloride, produces 1.2t / h of crystals, and the remaining 2.8t / h of separated liquid returns to the cyclone device.

[0109] The system inputs 8+2=10MW of heat in total, which can be used to heat turbine condensate, and can heat 320t / h, 35℃ turbine condensate to 60℃.

[0110] According to the method and parameters of this embodiment, the heat is not wasted. On the basis of sewage purification, the system realizes the separation of salt and clean water, produces 1.2t / h of crystals with sodium chloride as the main component, and about 38.8t / h of clean water. In terms of heat, except for a small part of the heat of the exhaust steam that is taken away with the clean water, most of it is given to the condensate of the steam turbine, exercising part of the function of the low-pressure heater, and there is essentially no waste.

[0111] Example 2

[0112] The only difference from Example 1 is that it is no longer used to heat the turbine condensate, but the heat is dissipated through the cooling tower, and the temperature of the cold source is 30°C. The dry air ratio is 1.1 and the sewage circulation ratio is 12. The sewage treatment capacity is 40t / h, the air dry basis circulation capacity is 40×1.1=44t / h, and the sewage circulation capacity is 12×40=480t / h. The density of the sodium chloride solution after concentration is about 1.2g / cm 3 , then the sewage circulation volume flow rate is 400m3 / h, and the clean water circulation volume flow rate is 400m 3 / h, the clean water density is considered to be 1, and the clean water circulation volume is 400t / h. The intermediate sewage circulation density is also approximately equal to 1, and the intermediate sewage circulation volume flow rate is 400×1 / 5=80m 3 / h, and the intermediate sewage circulation volume is 80t / h.

[0113] At this time, according to the heat balance calculation, the heater needs to consume about 6MW of heat. This is because the temperature difference between the cold source and the heat source is widened, and the proportion of the heat exchange end difference at each stage to the total temperature change range of the working fluid is reduced. A higher proportion of heat can be recycled internally through the regenerator, so the heat consumption will also be reduced.

[0114] About 10t / h of sodium chloride is taken from the bottom sewage of the heat and mass generating tower 110, and after cyclone, 6t / h of sodium chloride solution returns to the bottom of the heat and mass generating tower 110, and 4t / h of solution goes to the crystallization unit 152. The evaporation crystallization method consumes about 2MW of heat to crystallize sodium chloride, produces 1.2t / h of crystals, and the remaining 2.8t / h of separated liquid returns to the cyclone device.

[0115] The system inputs 6+2=8MW of heat in total, of which 6MW of heat is dissipated into the cooling tower at a thermal grade of 30℃, and the other 2MW of heat from the crystallization unit is discharged in the form of secondary steam. Since its grade is relatively high, generally around 80℃, it can be recycled to heat the turbine condensate or other working fluids. Therefore, a total of 6MW of heat is actually consumed to achieve the concentration and crystallization process.

[0116] The difference from Example 1 is that there is 6MW of heat waste, but due to the decrease in dry air ratio and circulation volume, the electricity cost will be saved. In actual application, the electricity cost and heat cost can be comprehensively considered for selection.

[0117] Comparative Example 1

[0118] This comparative example provides a conventional sewage purification method, which is as follows:

[0119] The triple-effect evaporation technology is used to treat 40t / h of power plant wastewater, with the main solute being 3% sodium chloride in the reverse osmosis concentrated water.

[0120] The flow chart of triple effect evaporation technology is as follows Figure 3 As shown: after the sewage enters the system, it first passes through the first-stage preheater to exchange heat with the concentrated sewage and heat it up, then passes through the second-stage preheater to exchange heat with the second and third-effect condensate and heat it up, then passes through the third-stage preheater to exchange heat with the driving steam condensate and heat it up, then enters the first-effect evaporator, is heated by the driving steam to generate part of the secondary steam, and the steam-water mixture enters the first-effect separator; after the sewage is reduced in pressure, it continues to enter the second-effect evaporator, and the first-effect secondary steam serves as the driving steam of the second-effect evaporator to further evaporate the sewage; thereafter, the steam-water mixture enters the second-effect separator, the sewage at the bottom of the second-effect separator continues to reduce in pressure and goes to the three-effect evaporator, and the second-effect secondary steam at the top of the second-effect separator serves as the driving steam of the three-effect evaporator to further evaporate the sewage, and then the steam-water mixture enters the three-effect separator, the concentrated sewage at the bottom of the separator is discharged after passing through the concentrated water pump and the first-stage preheater, and the three-effect secondary steam enters the condenser and is condensed by cooling water.

[0121] The normal pressure of the last effect of the three-effect evaporation is about 7kPa, and the condensation temperature is about 40, which is not enough to heat the condensate of the steam turbine and can only be released through the cooling tower.

[0122] If the heat source quality is the same as that in Example 1, that is, a 100-degree heat source, then after calculation, the process consumes 15 t / h of initial driving steam, and each effect of the three-effect evaporation produces about 12 t / h of secondary steam, a total of 36 t / h of steam condensate is generated, and 10.5 MW of heat is consumed.

[0123] If crystallization is required later, another crystallization unit will be added, which consumes 2MW of heat. This heat will eventually be discharged in the form of secondary steam from the crystallizer. Since its quality is relatively high, generally around 80°C, it can be recycled to heat the turbine condensate.

[0124] Therefore, to achieve the same effect, the commonly used strategy on the market is a three-effect evaporation + crystallization unit, which consumes a total of 12.5MW of heat, of which 10.5MW cannot be recycled, resulting in a large waste.

[0125] The embodiments of the present invention provide an open evaporative absorption sewage purification system and an operating method, which have the following advantages:

[0126] (1) Through the reasonable setting of heat absorption tower, heat generation tower, crystallization unit and other equipment, zero wastewater discharge is achieved. At the same time, in some scenarios, heat can be discharged at a higher temperature of 60°C and used for other cold sources that need to be heated on site, so that heat will not be wasted.

[0127] (2) The heat and mass generating tower in which the concentrated sewage is circulated is graded by an air lifting device to produce an intermediate sewage circulation, which can effectively reduce the liquid at the outlet of the heat and mass generating tower.

[0128] There are several main reasons: ① The droplets of concentrated sewage carried by the gas will be repeatedly turned back through the corrugated plate in the intermediate sewage cycle and eventually captured. ② Since the intermediate sewage does not bear the heat exchange function, the circulation volume can be very small, generally 1 / 5 of the concentrated sewage circulation volume in the lower part, so the density of the spray liquid is low, and larger droplets can be used for dripping or trough-type liquid distribution in a water flow state. Compared with atomization or small droplets, there is rarely any entrainment of liquid by gas on the upper part of the spray layer. ③ The replenishment water for the intermediate sewage cycle mainly comes from clean backwash water and imported initial sewage, so its water quality is better than that of the imported initial sewage, and is far better than the water quality of the concentrated sewage cycle. Therefore, even if droplet entrainment occurs, its concentration is very low. ④ There is also a high-efficiency demisting device on the upper part of the intermediate sewage cycle, which is regularly flushed with clean water to further collect the entrained droplets.

[0129] In summary, the intermediate sewage cycle can capture the droplets entrained by the concentrated sewage cycle with the air, and the droplets themselves are large in diameter and rarely carried out, and there is an efficient demisting device on the top to capture the droplets again. At the same time, because its water quality is much better than that of the concentrated sewage cycle, the harm of a very small amount of liquid is also reduced to the minimum. Therefore, the above design can fully improve the quality of the purified water, purify the purified water into water that can be used in the process at one time, without the need for secondary treatment.

[0130] (3) Calorie consumption is minimized for the following reasons:

[0131] ① By reasonably setting up the heat recovery unit and preheating unit, the heat can be fully recycled.

[0132] ② The intermediate sewage in the intermediate sewage storage tank is added to the concentrated sewage circulation, and the adding point is set after the heater, which is beneficial to ensure the efficiency of the heater.

[0133] ③ The discharge point of purified water can be placed after the cooler and before the spraying, or after the preheater and before the cooler, depending on whether the waste heat needs to be recycled. This can preheat the sewage water as much as possible without wasting the cold source and achieving optimal heat configuration.

[0134] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An open evaporation absorption sewage purification system, It is characterized in that It comprises a heat and mass generating tower for heat and mass transfer between sewage and air and a heat and mass absorbing tower for heat and mass transfer between water-containing air and clean water, the top of the heat and mass absorbing tower is connected with the bottom of the heat and mass generating tower, and the top of the heat and mass generating tower is connected with the bottom of the heat and mass absorbing tower, so as to realize the circulation of air between the heat and mass absorbing tower and the heat and mass generating tower; The heat and mass generating tower is provided with an air lifting device to divide the heat and mass generating tower into an upper intermediate sewage treatment zone and a lower concentrated sewage treatment zone. The tower of the upper intermediate sewage treatment zone is filled with corrugated fillers, and the lower concentrated sewage treatment zone is filled with coarse-pore grid fillers with a pore size of 3 cm to 5 cm. A demisting device is provided inside the top of the heat and mass generating tower; The bottom sewage outlet of the upper intermediate sewage treatment area of ​​the heat and mass generating tower is connected to an intermediate sewage storage tank, and part of the sewage in the intermediate sewage storage tank is circulated to the upper intermediate sewage treatment area, and part enters the lower concentrated sewage treatment area; the concentrated sewage output from the bottom of the tower of the lower concentrated sewage treatment area is heated and mixed with the sewage from the intermediate sewage storage tank and returned to the lower concentrated sewage treatment area; The clean water output from the bottom of the heat and mass absorption tower is cooled by a cooler and then returned to the top of the heat and mass absorption tower, and a clean water output pipeline is arranged at the front end and / or the rear end of the cooler; The bottom of the heat and mass absorption tower is connected to the top of the heat and mass generation tower through a backwash water delivery pipeline, so as to backwash the demisting device on the heat and mass generation tower; It also includes a pre-treatment filter device for removing impurities from sewage and a preheater for heat exchange between sewage and clean water. The sewage enters the intermediate sewage storage tank after passing through the pre-treatment filter device and the preheater in sequence. It also includes a heat recovery heat exchanger for heat exchange between concentrated sewage and clean water and a heater for heating concentrated sewage, the bottoms of the heat and mass absorption tower and the heat and mass generation tower are both connected to the heat recovery heat exchanger, the concentrated sewage outlet on the heat recovery heat exchanger is connected to the heater, and the outlet of the heater is connected to the concentrated sewage treatment area at the lower end of the heat and mass generation tower; The clean water outlet on the heat recovery exchanger is communicated with the preheater, the clean water outlet of the preheater is communicated with the cooler, and the clean water outlet of the cooler is communicated with the heat and mass absorption tower.

2. The open evaporation absorption sewage purification system according to claim 1, It is characterized in that The concentrated sewage output from the outlet of the heater is mixed with part of the sewage output from the intermediate sewage storage tank and then enters the top of the lower concentrated sewage treatment area, where it contacts with the air through spraying to transfer heat and mass; And / or, part of the sewage output from the intermediate sewage storage tank is circulated to the top of the upper intermediate sewage treatment area, and is contacted with the air by spraying for heat and mass transfer; And / or, the clean water outputted by the cooler enters the heat and mass absorption tower and contacts with the air through spraying to transfer heat and mass; And / or, the heat mass absorption tower is filled with a coarse-pore grid filler with a pore size of 3 cm to 5 cm; And / or, a demisting device is provided on the top of the thermal mass absorption tower.

3. The open evaporation absorption sewage purification system according to claim 1, It is characterized in that Also includes: A cyclone device, a crystallization unit and a solid-liquid separation unit, the bottom of the heat and mass generating tower is connected to the inlet of the cyclone device, the upper liquid outlet of the cyclone device is connected to the bottom of the heat and mass generating tower, the lower liquid outlet of the cyclone device is connected to the crystallization unit, the crystallization unit is connected to the solid-liquid separation unit, and the separation liquid outlet of the solid-liquid separation unit is connected to the inlet of the cyclone device.

4. The open evaporation absorption sewage purification system according to claim 3, It is characterized in that The crystallization unit is also provided with a steam condensate outlet, which is communicated with the top of the heat and mass generating tower so that the steam condensate can be used as backwash water for the demister.

5. An operating method of an open evaporation absorption sewage purification system according to any one of claims 1 to 4, It is characterized in that include: After being preheated, the sewage enters the intermediate sewage storage tank and mixes with the intermediate sewage flowing out of the upper intermediate sewage treatment area. Then, part of the sewage circulates to the upper intermediate sewage treatment area of ​​the heat and mass generating tower to transfer heat and mass by contacting the corrugated packing with the air, and part of the sewage enters the lower concentrated sewage treatment area of ​​the heat and mass generating tower. The concentrated sewage is output from the bottom outlet of the tower of the lower concentrated sewage treatment zone for heating, and the heated concentrated sewage is mixed with sewage from the intermediate sewage storage tank and returned to the lower concentrated sewage treatment zone, and heat and mass transfer is carried out by contact between the coarse-pore grid filler and the air; The water-containing air is processed by a demisting device at the top of the heat and mass generating tower and then output, and enters the bottom of the heat and mass absorbing tower, and contacts with the clean water in the heat and mass absorbing tower for heat and mass transfer, so that the moisture in the water-containing air enters the clean water, and the air output from the top of the heat and mass absorbing tower is circulated to the bottom of the heat and mass generating tower; The clean water output from the bottom of the heat and mass absorption tower is cooled by a cooler and then returned to the top of the heat and mass absorption tower, and the clean water is output at the front end and / or rear end of the cooler.

6. The operating method according to claim 5, It is characterized in that The sewage first passes through a pre-treatment filter to remove impurities, and then enters the intermediate sewage storage tank after heat exchange with clean water in a preheater; The concentrated sewage output from the bottom of the heat and mass absorption tower and the clean water output from the bottom of the heat and mass absorption tower are heat exchanged in a regenerative heat exchanger, the concentrated sewage heated by the regenerative heat exchanger is heated by a heater and then returned to the concentrated sewage treatment area at the lower end of the heat and mass generation tower, the clean water cooled by the regenerative heat exchanger and the impurity-removed sewage are heat exchanged in the preheater, and the clean water cooled by the heat exchanger is cooled by the cooler and then returned to the heat and mass absorption tower; and / or, using part of the clean water output from the bottom of the heat mass absorption tower as backwash water to backwash the demisting device on the heat mass generation tower; And / or, concentrated sewage output from the outlet of the heater is mixed with part of the sewage output from the intermediate sewage storage tank and then enters the top of the lower concentrated sewage treatment area, and contacts with the air through spraying to transfer heat and mass; And / or, part of the sewage output from the intermediate sewage storage tank is circulated to the top of the upper intermediate sewage treatment area, and is contacted with the air by spraying for heat and mass transfer; And / or, after the sewage output from the bottom of the heat and mass generating tower is treated by a cyclone device, the upper liquid of the cyclone device is returned to the bottom of the heat and mass generating tower, and the lower liquid of the cyclone device enters a crystallization unit for heating crystallization or cooling crystallization, the crystal slurry output from the crystallization unit is subjected to solid-liquid separation, and the obtained separated liquid is returned to the cyclone device; When heating crystallization is adopted, the secondary steam condensate produced by evaporative crystallization is used as backwash water to backwash the demisting device on the heat and mass generating tower.

7. The operating method according to claim 6, It is characterized in that Control the heat source temperature t1 of the heater to be 75°C-130°C, and the cold source temperature t2 of the cooler to be 30°C-60°C; Define the dry air ratio and sewage circulation ratio. The dry air ratio is equal to the ratio of the circulation flow of dry air to the flow of treated sewage, and the sewage circulation ratio is equal to the ratio of the circulation volume of concentrated sewage to the volume of treated sewage. When 110≤t1≤130, the dry air ratio is controlled to 0.5-0.7 and the sewage circulation ratio is 10-17; When 90≤t1<110, the dry air ratio is controlled to be 1.1-1.4 and the sewage circulation ratio is 12-24; When 75≤t1<90, the dry air ratio is controlled to be 4-7 and the sewage circulation ratio is controlled to be 18-40; The dry air ratio and sewage circulation ratio are determined according to the value of t1 and the cold source temperature. The higher the cold source temperature, the greater the dry air ratio and sewage circulation ratio. and / or, the flow ratio of the intermediate sewage circulation volume flow rate to the concentrated sewage circulation volume flow rate is 1:(4-6); And / or, the flow ratio of the clean water circulation volume to the concentrated sewage circulation volume is 1:(0.9-1.1).

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