Drying treatment desulfurization wastewater system and process flow

Abstract

The application discloses a kind of dry treatment desulfurization wastewater system and process flow, high-temperature hot flue gas of boiler induced draft fan outlet is used, dust removal is entered into evaporator coil heat exchange to realize brine concentration, and cooperate with damper to realize temperature rise in evaporator and reach crystallization temperature requirement, by concentrated liquid direct injection high-temperature air duct to carry out vapor-solid separation, then into dryer to carry out gas-solid high-temperature cyclone separation.The application is more reasonable in arrangement, has lower maintenance cost, has wider applicability in finished product production, has higher economic benefit, especially avoids chloride crystalline salt pollution ash, so that ash and chloride crystalline salt can be collected and utilized separately.

Description

Technical Field

[0001] This invention relates to the field of desulfurization wastewater treatment, and more particularly to a drying system and process flow for desulfurization wastewater. Background Technology

[0002] Currently, calcium-based limestone-gypsum wet flue gas desulfurization (FGD) is the most widely used FGD process in power plants, industrial kilns, and the chemical industry. This process generates a large amount of high-salinity wastewater, which is difficult to treat. Current wastewater treatment methods include softening pretreatment followed by ceramic ultrafiltration membrane filtration, and crystallization technology often employs multi-effect evaporators. This process is complex to implement, has high investment costs, a high failure rate and maintenance costs, and is unstable in operation, forcing companies to reduce or halt production.

[0003] To address the aforementioned issues, Chinese patent CN201710370314 discloses a zero-discharge treatment system and method for desulfurization wastewater from undersaturated flue gas concentration and crystallization. However, this system has significant drawbacks. During implementation, sulfur dioxide in the flue gas reacts with the desulfurization wastewater to form a strong acid, leading to severe corrosion of the concentration tower and pipelines. Furthermore, without oxidizing air, sulfur dioxide and desulfurization wastewater produce a large amount of calcium sulfite, preventing effective evaporation and concentration. These drawbacks result in severe corrosion of the concentration tower and easy blockage of the conveying pipelines. Additionally, the concentrated mixture can only react directly with the high-heat, untreated flue gas in the crystallization tower for crystallization; crystallization is impossible when the flue gas temperature is insufficient. This results in a large amount of ash and slag in the finished product, making it unusable for secondary use and hindering ash and slag collection and reuse.

[0004] There is currently a lack of specific solutions to the above problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a drying system and process for desulfurization wastewater that is more rational in implementation, has a low rate of blockage failure, is easy to maintain, and especially requires low temperature for gas-solid separation and produces finished crystals without ash residue.

[0006] The desulfurization wastewater drying system includes a boiler, the boiler flue gas duct is connected to a dust collector, the dust collector duct is connected to an induced draft fan, the induced draft fan is connected to a desulfurization tower through an exhaust duct, and the desulfurization tower duct is connected to a chimney.

[0007] The exhaust fan outlet, which is the front end of the exhaust pipe, is connected to the hot air duct via a three-way pipe. The hot air duct is equipped with a three-way valve, which connects the evaporator heat exchange tube and the drying tube.

[0008] The evaporator heat exchange tubes are connected to the heat exchange coils of the evaporator.

[0009] The evaporator includes a casing, an axial flow fan is mounted on the upper part of the casing, a process water spray unit is mounted below the axial flow fan, an exhaust baffle is mounted below the process water spray unit, exhaust pipes are arranged in an array on the exhaust baffle, and a water baffle cap is provided on each exhaust pipe; a high-salt wastewater nozzle is arranged in an array below the exhaust baffle, and a heat exchange coil is mounted below the high-salt wastewater nozzle;

[0010] The bottom of the evaporator's outer casing is a water tank, and the water tank pipe is connected to a high-salt wastewater conveying pipe, which is used to inject high-salt wastewater into the water tank.

[0011] An air vent is provided on the outer casing of the machine body above the water tank;

[0012] The lower part of the water tank is equipped with a high saline circulation pipe, which is connected to the circulation delivery pipe through a three-way pipe. A circulation pump is installed on one of the circulation delivery pipes, and the circulation pump pipe is connected to a high saline wastewater nozzle.

[0013] A conveying pump is installed on another pipeline of the circulating conveying pipe. The conveying pump pipeline is connected to the concentrated liquid spraying module, and the concentrated liquid spraying module is installed inside the drying pipe. The drying pipe pipeline is connected to the drying separator, and the drying separator pipeline is connected to the second dust collector. The second dust collector is equipped with a waste heat flue gas pipeline, and the waste heat flue gas pipeline is connected to the evaporator heat exchange tube through a three-way pipeline.

[0014] The second dust collector has a finished product outlet at its lower part.

[0015] An exhaust duct is provided on the outer casing of the evaporator below the heat exchange coil. A second exhaust fan is installed on the exhaust duct, and the exhaust fan is connected to the exhaust duct.

[0016] Furthermore, the process water spray unit is configured in the following manner:

[0017] Inside the outer casing of the evaporator, a double-layer demister is installed below the axial flow fan, and two layers of process water spray modules are installed between and below the double-layer demister.

[0018] The process water spray module is connected to the process water tank via piping.

[0019] The lower part of the process water spray unit is also provided with a cooling water circulation spray module, which is configured in the following manner:

[0020] On the outer casing of the evaporator, a condensate drain pipe is provided on the upper part of the exhaust baffle, and the condensate drain pipe is connected to a water storage tank; the water storage tank is connected to a condensate spray device through a water pump pipe, and the condensate spray device consists of nozzles arranged in an array at the lower part of the process water spray unit.

[0021] Furthermore, a high-density brine buffer tank is provided at the bottom of the water tank, and the high-density brine buffer tank is connected to a drying conveying pipeline.

[0022] The high-density brine buffer tank is also equipped with a stirring device.

[0023] The effect achieved is that once the brine density in the water tank reaches the standard, it can be pre-filled into a high-density brine buffer tank, and high-salt wastewater can be continuously injected into the water tank, thereby achieving the purpose of continuous production.

[0024] Furthermore, the water tank pipe is connected to a high-salt wastewater buffer tank, the high-salt wastewater buffer tank pipe is connected to a circulation pump, and the high-salt wastewater nozzle is connected through the circulation pump pipe.

[0025] The high-salt wastewater conveying pipe is equipped with a three-way valve, and one end of the three-way valve is connected to the water tank, while the other end is connected to the high-salt wastewater buffer tank.

[0026] The high-salt wastewater buffer tank still contains a stirring device.

[0027] The effect achieved is that the high-salt wastewater buffer tank temporarily stores the brine.

[0028] Furthermore, a three-way valve is installed on the pipeline between the circulating pump and the high-salt wastewater nozzle, and the backup preparation system is connected through the three-way valve pipeline;

[0029] The backup preparation system includes a material conveying pipe, which is connected to the pipeline between the circulating pump and the high-salt wastewater nozzle via a three-way valve; the material conveying pipe is connected to a thickener, and the thickener is connected to a centrifuge.

[0030] In other words, when the chloride crystallization salt production system involved in the evaporator is under maintenance, production can continue through the backup preparation system, thus avoiding the impact of shutdown on production.

[0031] The aforementioned drying process for desulfurization wastewater includes the following steps;

[0032] 1. After the boiler flue gas is cleaned by the dust collector, the hot air (referring to hot air at 120-130℃ that is free of ash and slag) is delivered by the induced draft fan to the desulfurization tower and the hot air duct respectively.

[0033] The hot air duct delivers hot air to the evaporator heat exchange tubes and drying tubes;

[0034] The heat exchange coils inside the evaporator deliver hot air for heat exchange via the evaporator heat exchange tubes.

[0035] 2. High-salt wastewater flows into the water tank of the evaporator through the high-salt wastewater conveying pipe. The high-salt wastewater in the water tank is then sprayed onto the heat exchange coils through the high-salt wastewater spray nozzles via the circulating conveying pipe and circulating pump.

[0036] 3. After repeated concentration in the evaporator to above 1300 kg / m3, the damper and axial flow fan are closed, and circulation convection is carried out to raise the temperature inside the evaporator to the crystallization temperature of saturated brine. The high-density brine in the water tank is pumped into the drying tube through the circulation conveying pipe, the conveying pump, and the spray gun module to achieve vapor-solid separation and directly form chloride crystal salt.

[0037] 4. The material inside the drying tube passes through the drying separator to achieve gas-solid separation, and then passes through the second dust collector to form a finished product free of ash and slag.

[0038] The beneficial effects of this invention are: the layout of this invention is more reasonable, the maintenance cost is lower, the applicability of the finished product is wider, and the economic benefits are higher. Compared with the existing desulfurization wastewater drying treatment process, more specifically, this application solves the following problems:

[0039] 1. Low-temperature drying and crystallization of desulfurization wastewater has been achieved.

[0040] 2. It avoids the problem of sulfur dioxide in flue gas reacting with desulfurization wastewater to form strong acid, which would lead to severe corrosion of the concentration tower and pipelines;

[0041] This avoids the problem of flue gas mixing with desulfurization wastewater, which would cause a large amount of calcium sulfite to be generated in the concentration tower, preventing effective evaporation and concentration, and causing material to clog pipes and flues.

[0042] 3. To avoid contamination of ash residue by chloride crystallization salts, a low-temperature drying crystallization process is used to spray the concentrated liquid into a filtered low-temperature hot air environment to achieve gas-solid separation. This avoids spraying the concentrated liquid into a high-temperature flue gas environment, allowing the ash residue and chloride crystallization salts to be collected and utilized separately. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the implementation of a drying system and process flow for desulfurization wastewater as described in this invention.

[0044] Figure 2 yes Figure 1 A magnified view of a portion of the image;

[0045] Figure label:

[0046] 1-Boiler 2-Dust Collector 3-Induced Draft Fan 4-Drying Separator 5-Secondary Dust Collector 6-Evaporator 7-Desulfurization Tower 8-Chimney 9-Water Storage Tank 10-Process Water Tank 11-Thickening Tank 12-Centrifuge 13-Water Tank 14-Exhaust Pipe 15-High-Salinity Wastewater Transfer Pipe 16-Transfer Pump 17-Circulation Pump 18-High-Salinity Circulation Pipe 19-Condensate Discharge Pipe 20-Secondary Induced Draft Fan

[0047] 61-Axial flow fan 62-Double-layer demister 63-Process water spray module 64-Condensate spray device 65-Water baffle 66-Exhaust pipe 67-High-salt wastewater nozzle 68-Damper 69-Heat exchange coil

[0048] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0049] Reference Figure 1 , Figure 2 The present invention provides a drying system for desulfurization wastewater, which includes a boiler 1, a flue gas duct of the boiler 1 connected to a dust collector 2, a duct of the dust collector 2 connected to an induced draft fan 3, an induced draft fan 3 connected to a desulfurization tower 7 via an exhaust pipe 14, and a duct of the desulfurization tower 7 connected to a chimney 8.

[0050] The outlet end of the induced draft fan 3, that is, the front end of the exhaust pipe 14, is connected to the hot air pipe through a three-way pipe. The hot air pipe is equipped with a three-way valve and is connected to the heat exchange tube of the evaporator 6 and the drying tube through the three-way valve.

[0051] In other words, the flue gas from boiler 1 is removed by dust collector 2, and hot air without ash and slag is introduced into heat exchange tubes and drying tubes of evaporator 6 by induced draft fan 3, and a hot air environment of not less than 120°C is formed in the drying tube.

[0052] The heat exchange tubes of the evaporator 6 are connected to the heat exchange coils 69 of the evaporator 6.

[0053] The evaporator 6 includes a housing, with an axial flow fan 61 mounted on the upper part of the housing; a process water spray unit is mounted below the axial flow fan 61, and an exhaust baffle is mounted below the process water spray unit. Exhaust pipes 66 are arranged in an array on the exhaust baffle, and each exhaust pipe 66 is covered with a water baffle cap 65; high-salt wastewater nozzles 67 are arranged in an array below the exhaust baffle, and heat exchange coils 69 are mounted below the high-salt wastewater nozzles 67.

[0054] Preferably, the inner cavity of the outer shell of the machine body is provided with a ceramic anti-corrosion layer.

[0055] The bottom of the outer casing of the evaporator 6 is a water tank 13. The water tank 13 is connected to a high-salt wastewater conveying pipe 15, which is used to inject high-salt wastewater into the water tank 13.

[0056] An air vent 68 is provided on the outer casing of the machine body above the water tank 13;

[0057] Preferably, the damper 68 is in the form of louvered guide vanes, which are arranged in a uniform array around the evaporator 6.

[0058] The lower part of the water tank 13 is provided with a high saline circulation pipe 18, which is connected to the circulation conveying pipe through a three-way pipe. A circulation pump 17 is provided on one of the circulation conveying pipes, and the circulation pump 17 is connected to a high saline wastewater nozzle 67.

[0059] In other words, high-salt wastewater is injected into the water tank 13 through the high-salt wastewater conveying pipe 15, and sprayed onto the heat exchange coil 69 through the high-salt wastewater nozzle 67 via the circulating pump 17, thereby generating hot steam, which enters the upper part of the evaporator 6 shell through the exhaust pipe 66, and is cooled by the process water spraying unit.

[0060] The opening and closing of the damper 68 can regulate the internal temperature of the evaporator 6, especially by closing the damper 68 and the axial fan 61, so that the internal temperature of the evaporator 6 rises to the crystallization temperature of saturated brine, which is above 80°C.

[0061] Furthermore, compared to existing technologies, the circulating spray concentration process used in this system can avoid direct contact between high saline water and sulfur dioxide in flue gas, which would otherwise produce calcium sulfite and strong acid, leading to equipment corrosion and blockage, and would also prevent effective evaporation and concentration.

[0062] A conveying pump 16 is installed on another pipeline of the circulating conveying pipe. The conveying pump 16 is connected to the concentrated liquid spraying module, and the concentrated liquid spraying module is installed inside the drying pipe. The drying pipe is connected to the drying separator 4, and the drying separator 4 is connected to the second dust collector 5. The second dust collector 5 is equipped with a waste heat flue gas pipeline, and the waste heat flue gas pipeline is connected to the heat exchange tube of the evaporator 6 through a three-way pipeline.

[0063] Preferably, the drying separator 4 is a cyclone dust collector 2 in the prior art.

[0064] Preferably, the inner wall of the drying tube is provided with a ceramic anti-corrosion layer.

[0065] The second dust collector 5 has a finished product outlet at its lower part.

[0066] In other words, the delivery pump 16 and the concentrated liquid spraying module are used to control the concentrated liquid to be sprayed evenly into the inner cavity of the drying tube, and to perform vapor-solid separation with hot flue gas at a temperature of not less than 120°C.

[0067] The flue gas mixture generated after steam-solid separation enters the dryer separator 4 for gas-solid rotary separation. The generated high-temperature gas enters the flue before the tube bundle of the evaporator 6 to continue heating the heat exchange coil 69 of the evaporator 6. The generated chloride crystal salt part of the flue gas enters the dust collector 2 for collection.

[0068] The generated chloride crystal salts are partially collected by the flue gas after entering the dust collector 2 through bag filter, and then stored and packaged in the silo.

[0069] An exhaust duct is provided on the outer casing of the evaporator 6 at the lower part of the heat exchange coil 69. A second exhaust fan 20 is provided on the exhaust duct, and the second exhaust fan 20 is connected to the exhaust duct 14.

[0070] The purpose of the second induced draft fan 20 is to ensure sufficient flue gas volume in this system.

[0071] Furthermore, the process water spray unit is configured in the following manner:

[0072] Inside the outer casing of the evaporator 6, a double-layer demister 62 is provided below the axial flow fan 61, and two layers of process water spray modules 63 are provided between and below the double-layer demister 62.

[0073] The process water spray module 63 is connected to the process water tank 10 via a pipeline;

[0074] Preferably, the two-layer process water spray modules 63 are respectively connected to the process water tank 10 by pipes;

[0075] The lower part of the process water spray unit is also provided with a cooling water circulation spray module, which is configured in the following manner:

[0076] On the outer casing of the evaporator 6, a condensate drain pipe 19 is provided on the upper part of the exhaust baffle, and the condensate drain pipe 19 is connected to the water storage tank 9; the water storage tank 9 is connected to the condensate spray device 64 through a water pump pipe, and the condensate spray device 64 is an array of nozzles arranged at the lower part of the process water spray unit.

[0077] Preferably, the water storage tank 9 is equipped with a desulfurization water output pipeline. The purpose of this is to make full use of the condensate water for production in other sections.

[0078] The effect achieved is to improve the condensate collection efficiency, reduce steam discharge, and form a water recycling system, thereby making full use of water resources and avoiding water waste.

[0079] Furthermore, a high-density brine buffer tank is provided at the bottom of the water tank 13, and the high-density brine buffer tank is connected to the drying conveying pipeline.

[0080] The high-density brine buffer tank is also equipped with a stirring device.

[0081] The effect achieved is that after the brine density in the water tank 13 reaches the standard, it can be pre-filled into the high-density brine buffer tank, and high-salt wastewater can be continuously injected into the water tank 13, thereby achieving the purpose of continuous production.

[0082] Furthermore, the water tank 13 is connected to a high-salt wastewater buffer tank, the high-salt wastewater buffer tank is connected to a circulation pump 17, and the high-salt wastewater nozzle 67 is connected to the circulation pump 17.

[0083] The high-salt wastewater conveying pipe 15 is equipped with a three-way valve, and one of the three-way valves is connected to the water tank 13, and the other is connected to the high-salt wastewater buffer tank.

[0084] The high-salt wastewater buffer tank still contains a stirring device.

[0085] The effect achieved is that the high-salt wastewater buffer tank temporarily stores the brine.

[0086] Furthermore, a three-way valve is installed on the pipeline between the circulating pump 17 and the high-salt wastewater nozzle 67, and the backup preparation system is connected through the three-way valve pipeline.

[0087] The backup preparation system includes a material conveying pipe, which is connected to the pipeline between the circulating pump 17 and the high-salt wastewater nozzle 67 via a three-way valve; the material conveying pipe is connected to a thickener 11, and the thickener 11 is connected to a centrifuge 12.

[0088] In other words, during the maintenance and repair of the chloride crystallization salt production system involved in evaporator 6, continuous production can be achieved through the backup preparation system, thus avoiding the impact of shutdown on production.

[0089] Preferably, a flow meter is installed on the high-salt wastewater conveying pipe 15;

[0090] The water tank 13, the high-density brine buffer tank, and the high-salt wastewater buffer tank are respectively equipped with a thermometer, a level gauge, and a density meter;

[0091] The evaporator 6 has an exhaust thermometer, a demister differential pressure gauge, a level gauge, and a thermometer arranged sequentially from top to bottom on the outer shell.

[0092] Flow meters are installed on the condensate drain pipe 19, the water pump output pipe, and the process water tank 10 output pipe, respectively.

[0093] The aforementioned drying process for desulfurization wastewater includes the following steps;

[0094] 1. After the hot flue gas from boiler 1 is purged by dust collector 2, it is then blown by induced draft fan 3 into hot air. The hot air referred to here is hot air within 120-130℃ that does not contain ash or slag; and is respectively delivered to desulfurization tower 7 and hot air duct.

[0095] The hot air duct delivers hot air to the heat exchange tubes and drying tubes of the evaporator 6.

[0096] The heat exchange coil 69 inside the evaporator 6 delivers hot air for heat exchange through the heat exchange tubes of the evaporator 6.

[0097] 2. High-salt wastewater flows into the water tank 13 of the evaporator 6 through the high-salt wastewater conveying pipe 15. The high-salt wastewater in the water tank 13 is then sprayed onto the heat exchange coil 69 through the high-salt wastewater nozzle 67 via the circulating conveying pipe and the circulating pump 17.

[0098] 3. After repeated concentration in evaporator 6 to above 1300 kg / m3, the damper 68 and axial fan 61 are closed to carry out circulating convection heating, raising the temperature inside evaporator 6 to the crystallization temperature of saturated brine. The high-density brine in water tank 13 is sprayed into drying tube through the circulating conveying pipe, conveying pump 16, and spray gun module to achieve vapor-solid separation and directly form chloride crystal salt.

[0099] 4. The material in the drying tube passes through the drying separator 4 to achieve gas-solid separation, and then passes through the second dust collector 5 to form a finished material free of ash and slag.

[0100] Example 1:

[0101] This embodiment uses the actual production situation at Shandong Lutai Thermal Power Co., Ltd. on October 8, 2022 as an example to explain the process method of the present invention, and does not limit the present invention in any way.

[0102] See Figure 1 , Figure 2 :

[0103] Once the boiler load is stable and there are no major operations, and all equipment in the system has passed commissioning, start the induced draft fan to put the system into operation.

[0104] 1. Transport the supernatant of the desulfurization high-salt wastewater to the water tank at the bottom of the evaporator or the high-salt wastewater buffer tank, start the circulation pump to transport it to the spray layer at the top of the evaporator for spraying, and exchange heat with the heat exchange coils in the evaporator for evaporation and concentration.

[0105] 2. Concentrate to 1300 kg / m3, close the louvers between the evaporator and the water tank to allow for circulating convection and heating until the temperature reaches above 80°C. Then, introduce the high-density brine into the high-density brine buffer tank, which is equipped with a stirrer and an electric heating device to ensure that the brine does not settle and that the temperature is maintained at 80°C.

[0106] 3. Using a delivery pump and a concentrated liquid spraying module, the concentrated liquid is evenly sprayed into the drying pipe to separate the vapor and solid components with the 120°C hot flue gas.

[0107] 4. The flue gas mixture generated after steam-solid separation enters the dryer separator for gas-solid rotary separation, and the high-temperature gas enters the flue before the evaporator tube bundle to continue heating the evaporator.

[0108] 5. The generated chloride crystal salts are partially collected in the second dust collector; the generated chloride crystal salts are partially collected by bag filter and then stored and packaged in the silo.

[0109] This experiment demonstrates that when the boiler flue gas reaches a temperature above 120℃, the concentrated brine density is above 1300 kg / m³, and the concentrated brine temperature is above 80℃, a chloride crystalline salt with relatively uniform crystals can be obtained.

[0110] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0111] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A drying system for desulfurization wastewater, comprising a boiler, wherein the boiler flue gas duct is connected to a dust collector, the dust collector duct is connected to an induced draft fan, the induced draft fan is connected to a desulfurization tower via an exhaust duct, and the desulfurization tower duct is connected to a chimney, characterized in that: The outlet end of the induced draft fan is connected to the hot air duct through a three-way pipe. The hot air duct is equipped with a three-way valve and is connected to the evaporator heat exchange tube and the drying tube through the three-way valve. The evaporator heat exchange tubes are connected to the heat exchange coils of the evaporator. The evaporator includes a casing, an axial flow fan is mounted on the upper part of the casing, a process water spray unit is mounted below the axial flow fan, an exhaust baffle is mounted below the process water spray unit, exhaust pipes are arranged in an array on the exhaust baffle, and a water baffle cap is provided on each exhaust pipe; a high-salt wastewater nozzle is arranged in an array below the exhaust baffle, and a heat exchange coil is mounted below the high-salt wastewater nozzle; The bottom of the evaporator's outer casing is a water tank, and the water tank pipe is connected to a high-salt wastewater conveying pipe. An air vent is provided on the outer casing of the machine body above the water tank; The lower part of the water tank is equipped with a high saline circulation pipe, which is connected to the circulation delivery pipe through a three-way pipe. A circulation pump is installed on one of the circulation delivery pipes, and the circulation pump pipe is connected to a high saline wastewater nozzle. A conveying pump is installed on another pipeline of the circulating conveying pipe. The conveying pump pipeline is connected to the concentrated liquid spraying module, and the concentrated liquid spraying module is installed inside the drying pipe. The drying pipe pipeline is connected to the drying separator, and the drying separator pipeline is connected to the second dust collector. The second dust collector is equipped with a waste heat flue gas pipeline, and the waste heat flue gas pipeline is connected to the evaporator heat exchange tube through a three-way pipeline. The second dust collector has a finished product outlet at its lower part; An exhaust duct is provided on the outer casing of the evaporator below the heat exchange coil. A second exhaust fan is installed on the exhaust duct, and the exhaust fan duct is connected to the exhaust duct. A high-density brine buffer tank is installed at the bottom of the water tank, and the high-density brine buffer tank is connected to a drying and conveying pipeline. The high-density brine buffer tank is also equipped with a stirring device; The water tank pipe is connected to a high-salt wastewater buffer tank, the high-salt wastewater buffer tank pipe is connected to a circulation pump, and the high-salt wastewater nozzle is connected through the circulation pump pipe. The high-salt wastewater conveying pipe is equipped with a three-way valve, and one end of the three-way valve is connected to the water tank, while the other end is connected to the high-salt wastewater buffer tank. The high-salt wastewater buffer tank is also equipped with a stirring device. A three-way valve is installed on the pipeline between the circulating pump and the high-salt wastewater nozzle, and the backup preparation system is connected through the three-way valve pipeline; The backup preparation system includes a material conveying pipe, which is connected to the pipeline between the circulating pump and the high-salt wastewater nozzle via a three-way valve; the material conveying pipe is connected to a thickener, and the thickener is connected to a centrifuge.

2. The desulfurization wastewater drying system according to claim 1, characterized in that: The process water spray unit is configured in the following manner: Inside the outer casing of the evaporator, a double-layer demister is installed below the axial flow fan, and two layers of process water spray modules are installed between and below the double-layer demister. The process water spray module is connected to the process water tank via piping. The lower part of the process water spray unit is also provided with a cooling water circulation spray module, which is configured in the following manner: On the outer casing of the evaporator, a condensate drain pipe is provided on the upper part of the exhaust baffle, and the condensate drain pipe is connected to a water storage tank; the water storage tank is connected to a condensate spray device through a water pump pipe, and the condensate spray device consists of nozzles arranged in an array at the lower part of the process water spray unit.

3. The drying system for desulfurization wastewater according to claim 1, characterized in that: Its process flow Includes the following steps; 1. After the boiler flue gas is cleaned by the dust collector, the hot air (referring to hot air at 120-130℃ that is free of ash and slag) is delivered by the induced draft fan to the desulfurization tower and the hot air duct respectively. The hot air duct delivers hot air to the evaporator heat exchange tubes and drying tubes; The heat exchange coils inside the evaporator deliver hot air for heat exchange via the evaporator heat exchange tubes.

2. High-salt wastewater flows into the water tank of the evaporator through the high-salt wastewater conveying pipe. The high-salt wastewater in the water tank is then sprayed onto the heat exchange coils through the high-salt wastewater spray nozzles via the circulating conveying pipe and circulating pump.

3. After repeated concentration in the evaporator to above 1300 kg / m3, the damper and axial flow fan are closed, and circulating convection is carried out to raise the temperature inside the evaporator to the crystallization temperature of saturated brine. The high-density brine in the water tank is pumped into the drying tube through the circulating conveying pipe, conveying pump, and spray gun module to achieve vapor-solid separation and directly form chloride crystal salt.

4. The material inside the drying tube passes through the drying separator to achieve gas-solid separation, and then passes through the second dust collector to form a finished product free of ash and slag.

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