Wastewater concentrated liquor treatment system

Abstract

The invention discloses a wastewater concentrated liquor treatment system, which relates to the field of wastewater treatment and comprises a flue gas heat removal subsystem, a concentrated liquor concentration subsystem and a waste heat gradient utilization subsystem. Wherein in the flue gas heat removal subsystem, closed demineralized water is adopted to recover flue gas heat; in the concentrated liquor concentration subsystem, a vacuum device is adopted to apply air pressure values which are gradually reduced in a gradient manner to each concentration device, so that the boiling point of concentrated liquor to be concentrated in each concentration device is sequentially reduced, and multi-stage concentration of the concentrated liquor to be concentrated is realized while multi-effect utilization of flue gas heat is realized; and finally, the waste heat gradient utilization subsystem is used for heating steam turbine condensate water or domestic water or cold air required by combustion, so that the recovery rate of flue gas waste heat is improved to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, in particular to a wastewater concentrated liquid treatment system. BACKGROUND

[0002] Two kinds of wastewater concentrated liquid are generated in a waste incineration power plant. One is concentrated liquid generated by leachate treated by a leachate system; the other is concentrated liquid with high salt content generated after washing waste water is treated in a project with a wet deacidification tower. The waste incineration power plant generally uses lime slurry and other means to treat these two kinds of concentrated liquid. However, lime slurry may not be able to completely absorb these concentrated liquids; further treatment by means of entering the furnace and back spraying and other methods will be used in the prior art, which will cause problems such as decrease of boiler efficiency and corrosion of the boiler; for the waste incineration power plant, how to efficiently treat these two kinds of wastewater concentrated liquid is a problem to be solved.

[0003] Therefore, the waste incineration power plant has the problems of low flue gas waste heat recovery efficiency and poor wastewater concentrated liquid treatment efficiency. SUMMARY

[0004] In view of the above problems, the present application provides a wastewater concentrated liquid treatment system to efficiently treat wastewater concentrated liquid by recovered waste incineration flue gas waste heat, and to improve the flue gas heat recovery efficiency. The specific scheme is as follows:

[0005] The first aspect of the present application provides a wastewater concentrated liquid treatment system, comprising a flue gas heat extraction subsystem, a concentrated liquid concentration subsystem and a waste heat cascade utilization subsystem:

[0006] The flue gas heat extraction subsystem comprises a flue gas heat exchanger;

[0007] The concentrated liquid concentration subsystem comprises at least two concentration devices and at least two first vacuum devices; wherein one concentration device corresponds to one first vacuum device, each first vacuum device has a gradient decreasing state of the air pressure value applied to the corresponding concentration device, and the air pressure value of the concentration device closer to the flue gas heat extraction subsystem is higher;

[0008] The waste heat cascade utilization subsystem comprises a waste heat cascade utilization device;

[0009] The concentrated liquid concentration subsystem delivers closed desalination water to the flue gas heat exchanger to exchange the heat of the waste incineration high-temperature flue gas discharged into the flue gas heat exchanger by the induced draft fan, and obtains high-temperature closed desalination water;

[0010] The concentrated liquid concentration subsystem uses the high-temperature closed desalted water to heat the first concentrated liquid to be concentrated in the first concentration device to obtain first water vapor; the first water vapor is input into the second concentration device with the closest air pressure value to the first concentration device to heat the second concentrated liquid to be concentrated to obtain second water vapor; the second concentration device is used as the first concentration device, the second concentrated liquid to be concentrated is used as the first concentrated liquid to be concentrated, and the second water vapor is used as the first water vapor; the first water vapor is input into the second concentration device with the closest air pressure value to the first concentration device to heat the second concentrated liquid to be concentrated to obtain second water vapor is iteratively executed in descending order of the air pressure values.

[0011] The second water vapor is input into the waste heat cascade utilization device for at least one of steam turbine condensate heating, domestic water heating, and cold air heating required for combustion.

[0012] In a possible implementation, the concentrated liquid to be concentrated in each concentration device is first input into the concentration device with the lowest air pressure by a concentrated liquid delivery pump and is sequentially input into the concentration devices in ascending order of the air pressure gradient of each concentration device.

[0013] In a possible implementation, the waste heat cascade utilization device is a waste heat cascade utilization heat exchanger.

[0014] The waste heat cascade utilization heat exchanger uses the heat exchanged from the second water vapor for at least one of steam turbine condensate heating, domestic water heating, and cold air heating required for combustion.

[0015] In a possible implementation, the first vacuum device corresponds to each first vacuum pump of each concentration device.

[0016] Each first vacuum pump sets different air pressure values for each concentration device, so that the air pressure values of each concentration device between the flue gas heat extraction subsystem and the waste heat cascade utilization subsystem are in a gradient decrease.

[0017] In a possible implementation, the concentrated liquid concentration subsystem further includes a first water storage tank for receiving first condensate water of each concentration device.

[0018] The waste heat cascade utilization subsystem further includes a second water storage tank for receiving second condensate water of the waste heat cascade utilization device.

[0019] The first condensate water and the second condensate water are delivered to a condensate water return pipe for full-plant recycling.

[0020] In a possible implementation, a concentrated water return main pipe in communication with the concentration device with the highest air pressure is further included.

[0021] The concentrated thick liquid after the concentration treatment is recovered through the concentrated water return main pipe.

[0022] In a possible implementation, the flue gas heat extraction subsystem includes at least one flue gas heat exchanger.

[0023] When the flue gas heat exchange system includes multiple flue gas heat exchangers, the multiple heat exchangers are respectively connected with the waste incinerator arranged in parallel.

[0024] In a possible implementation, the thick liquid concentration subsystem delivers the closed desalted water into the flue gas heat exchanger, including:

[0025] The thick liquid concentration subsystem delivers the closed desalted water into the flue gas heat exchanger through a circulating water pump.

[0026] In a possible implementation, the waste heat cascade utilization subsystem further includes a second vacuum device corresponding to the waste heat cascade utilization device.

[0027] The second vacuum device is configured to reduce the air pressure value in the waste heat cascade utilization device.

[0028] In a possible implementation, the thick liquid to be concentrated includes leachate thick liquid and flue gas washing wastewater thick liquid.

[0029] According to the technical solution, the waste water thick liquid treatment system includes a flue gas heat extraction subsystem, a thick liquid concentration subsystem, and a waste heat cascade utilization subsystem. In the flue gas heat extraction subsystem, closed desalted water is used to recover flue gas heat. In the thick liquid concentration subsystem, a vacuum device is used to apply a gradient-decreasing air pressure value to each concentration device, to sequentially reduce the boiling point of the thick liquid to be concentrated in each concentration device, to realize multi-effect utilization of flue gas heat and multi-stage concentration of the thick liquid to be concentrated. Finally, the waste heat cascade utilization subsystem is used for heating steam turbine condensate, heating domestic water, or heating cold air required for combustion, to maximize the recovery rate of flue gas waste heat. BRIEF DESCRIPTION OF DRAWINGS

[0030] The above and other features, advantages, and aspects of the embodiments of the present disclosure will become more apparent as various embodiments of the present disclosure are disclosed in detail with reference to the drawings. Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. It should be understood that the drawings are schematic, and the original and elements are not necessarily drawn according to the scale.

[0031] Figure 1 A structural composition diagram of the waste water thick liquid treatment system provided by the present application is provided.

[0032] Figure 2 A structural composition example diagram of the waste water thick liquid treatment system provided by the present application is provided. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present application in conjunction with the accompanying drawings. The terms used in the implementation methods of the present application are only used to explain the specific embodiments of the present application and are not intended to limit the present application.

[0034] The embodiments of the present application are described below in conjunction with the accompanying drawings. Those skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0035] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, and this is merely a way of distinguishing the objects of the same attributes when describing them in the embodiments of the present application. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment comprising a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0036] Waste-to-energy plants generate two types of difficult-to-treat concentrated liquids. One is the concentrated liquid produced after leachate is treated in the leachate system, and the other is the high-salt concentrated liquid produced during the operation of projects equipped with wet deacidification towers after treating tobacco washing wastewater. To treat these two concentrated liquids, existing technologies generally use methods such as slaked lime pulping. However, slaked lime pulping cannot completely absorb these concentrated liquids. Another existing method for treating these concentrated liquids is to inject them back into the boiler. However, this treatment method can cause problems such as reduced boiler efficiency and corrosion.

[0037] Furthermore, heat lost from flue gas emissions from waste incineration power plants is a significant component of overall plant heat loss. Conventional technologies utilize a five-step flue gas treatment process: "SNCR (Selective Non-Catalytic Reduction) + semi-dry + dry + activated carbon + bag filter." The temperature of the treated flue gas is between 130° and 180°C. Direct discharge results in significant heat loss and environmental pollution. To minimize environmental pollution, conventional technologies utilize a five-step process to treat the flue gas generated during waste incineration. This involves directly connecting a flue gas-water heat exchanger to the tail end of the flue gas exhaust duct, with the cold water in the flue gas-water heat exchanger exchanging heat directly with the flue gas to be discharged. However, this flue gas waste heat recovery method has low heat recovery efficiency.

[0038] In summary, waste incineration plants currently have two problems that need to be solved urgently: low flue gas waste heat recovery efficiency and poor wastewater concentrate treatment efficiency.

[0039] In order to solve the above problems, the present application provides a wastewater concentrate treatment system. The applicant thought that the temperature of the waste incineration flue gas in the waste incineration power plant is relatively high, and direct discharge will cause a large amount of heat loss. Then the high-temperature flue gas from the waste incineration can be used as a heat source to further concentrate the wastewater concentrate and then use it to heat the steam turbine condensate and / or domestic water and / or the cold air required for combustion. That is, the wastewater concentrate treatment system provided by the present application couples the waste heat recovery in the waste incineration flue gas and the concentration of the wastewater concentrate, and simultaneously achieves the reduction of the wastewater concentrate and the heating of the steam turbine condensate and / or domestic water and / or the cold air required for combustion, achieving the two goals of flue gas waste heat recovery and wastewater concentrate treatment, thereby increasing the power generation of the entire waste incineration power plant.

[0040] Optional, see Figure 1 , the composition structure diagram of the wastewater concentrate treatment system provided in this application.

[0041] like Figure 1 As shown in the figure, the wastewater concentrate treatment system includes three subsystems: flue gas heat extraction subsystem, concentrate concentration subsystem and waste heat cascade utilization subsystem.

[0042] The flue gas heat extraction subsystem includes a flue gas heat exchanger. The concentrate concentration subsystem uses a circulating water pump to input closed desalted water into the flue gas heat exchanger in exchange for heat in the high-temperature flue gas from the waste incineration. The heat in the high-temperature flue gas from the waste incineration is used as a heat source to heat the concentrate to be concentrated in the concentration device of the concentrate concentration subsystem, and the water in the concentrate to be concentrated is evaporated to complete the treatment of the wastewater concentrate. The water vapor generated by evaporation is input into the waste heat cascade utilization subsystem to heat at least one of the steam turbine condensate cooling water, domestic water cooling water, and cold air required for combustion.

[0043] Next, the structure of each subsystem and the operating principle of each subsystem are introduced in detail.

[0044] The high-temperature flue gas from garbage incineration is discharged into the flue gas heat exchanger through the induced draft fan.

[0045] Specifically, the induced draft fan discharges the waste incineration high-temperature hot gas into the metal tube wall of the flue gas heat exchanger, the waste incineration high-temperature hot gas flows in the metal tube wall, and the heat is transferred from the flue gas to the tube wall through heat conduction; the concentrated liquid concentration device uses a circulating water pump to input the closed desalted water into the flue gas heat exchanger, the closed desalted water circulates in the tube or shell side of the flue gas heat exchanger, absorbs the heat outside the tube wall through convection heat exchange, and its temperature rises, the flue gas and the salt water do not directly contact, but are separated by the metal wall. The flue gas flows through the tube, and the salt water flows through the shell, and the heat exchange is realized through the tube wall. This design avoids mixing of the media and is suitable for scenarios where the salt water needs to be kept pure or the flue gas contains corrosive components.

[0046] The advantages of using closed desalted water for heat transfer are as follows:

[0047] 1. Reliable source:

[0048] Waste incineration power plants generally have a desalted water treatment system, so the supply of closed desalted water can be guaranteed.

[0049] 2. Recyclable:

[0050] Closed desalted water can be recycled with almost no loss.

[0051] 3. Good water quality and high heat exchange efficiency:

[0052] The water quality of closed desalted water is good, and it almost does not corrode the tube bundle or cause fouling problems. Moreover, as a heat transfer medium, desalted water has high specific heat capacity and no fouling, and the heat exchange efficiency is high.

[0053] Based on the above advantages, closed desalted water is used for heat transfer in this application.

[0054] It should be noted that the flue gas heat extraction subsystem includes at least one flue gas heat exchanger; when the flue gas heat exchange system includes multiple flue gas heat exchangers, the multiple heat exchangers are connected to the parallelly arranged waste incinerators respectively.

[0055] The concentrated liquid concentration device includes at least two concentration devices and at least two first vacuum devices. Each concentration device has a corresponding vacuum device. The vacuum device can be a vacuum pump, which mainly applies a negative pressure value to the corresponding concentration device; each concentration device is arranged between the flue gas heat extraction subsystem and the waste heat cascade utilization subsystem, and each first vacuum pump applies a negative pressure value to the corresponding concentration device in a gradient decreasing state, i.e. the closer to the flue gas heat extraction subsystem, the higher the pressure value of the concentration device, and the closer to the waste heat cascade utilization subsystem, the lower the pressure value of the concentration device. Correspondingly, the boiling point of the concentrated liquid to be concentrated in the concentration device with high pressure value is high, and the boiling point of the concentrated liquid to be concentrated in the concentration device with low pressure value is low.

[0056] In the present application, a vacuum pump is used to reduce the air pressure in each concentration device, so that the air pressure value in the concentration device is in a gradient decreasing state, thereby reducing the boiling point of the concentrated liquid to be concentrated in the concentration device, and reducing the quality requirement of the concentrated liquid to be concentrated in each concentration device for the heating heat source. A lower temperature heat source can be used to achieve the boiling and evaporation of the wastewater concentrate. The principle is as follows:

[0057] When the pressure is reduced, the boiling point of water decreases, at this time the pressure difference between the liquid surface vapor and the environment increases, the evaporation driving force is enhanced, and the evaporation rate will also be accelerated even if the temperature is not significantly increased; under low pressure, the density difference between liquid and vapor increases, which strengthens the convective heat transfer. For example, in vacuum distillation, the heat transfer temperature difference is expanded due to the reduction of boiling point, and the heat transferred per unit time is increased, thereby accelerating evaporation.

[0058] In summary, the concentrate concentration subsystem provided in the present application utilizes low pressure to gradually reduce the boiling point of the concentrated liquid to be concentrated, and the secondary steam is reused, thereby achieving significant energy saving effect.

[0059] Optionally, the operation process of the concentrate concentration subsystem is as follows:

[0060] The concentrate concentration subsystem uses high-temperature closed desalted water to heat the first concentrated liquid to be concentrated in the first concentration device to obtain first water vapor; the first water vapor is input into the second concentration device with the air pressure value closest to that of the first concentration device to heat the second concentrated liquid to be concentrated to obtain second water vapor; the second concentration device is used as the first concentration device, the second concentrated liquid to be concentrated is used as the first concentrated liquid to be concentrated, and the second water vapor is used as the first water vapor; according to the descending order of the air pressure values, the iteration of inputting the first water vapor into the second concentration device with the air pressure value closest to that of the first concentration device to heat the second concentrated liquid to be concentrated to obtain the second water vapor is performed, and the second water vapor is output from the concentrate concentration device.

[0061] Illustratively, the heating method for heating the concentrated liquid to be concentrated using the heat of the waste incineration high-temperature gas in the concentrate concentration subsystem can be referred to as segmented heating.

[0062] First segment: The waste incineration high-temperature flue gas heats the closed desalted water, which can heat the closed desalted water to about 115°C. The 115°C closed desalted water enters the first concentration device of the concentrate concentration subsystem (the one closest to the flue gas heat extraction subsystem side, which is also the concentration device with the highest air pressure value among all the concentration devices; the first concentration device can also be referred to as the first-stage heating tank), accelerates the tube bundle to heat the concentrated liquid to be concentrated, and at the same time adjusts the air pressure value in the concentration device through vacuum pumping by the vacuum pump corresponding to the first concentration device to control the temperature of the water vapor evaporated from the concentrated liquid to be concentrated in the heating tank to be 100°C. From this, the first-stage heating is completed, that is, the evaporation reduction of the concentrated liquid to be concentrated in the first-stage heating tank is completed.

[0063] The second stage: the 100℃ water vapor evaporated in the first stage heating tank enters the heating pipe bundle in the second stage evaporation tank, and the air pressure value in the tank is adjusted by the vacuum pump corresponding to the second stage evaporation tank to control the water vapor temperature evaporated from the concentrated solution to be concentrated in the heating tank to be 80℃, and thus the second stage heating is completed.

[0064] In addition, the concentrated solution evaporated in the first stage heating tank (i.e. the first concentration device) can also be used to preheat the concentrated solution to be concentrated about to enter the first stage heating tank. Specifically, the heat exchanger arranged can be used to preheat the concentrated solution to be concentrated, thereby further increasing the waste heat utilization rate and realizing the evaporation reduction of the concentrated solution to be concentrated in the first stage heating tank. Similarly, the concentrated solution at the outlet of the second stage heating tank is used to heat the concentrated solution to be concentrated at the inlet of the second stage heating tank, and the concentrated solution to be concentrated about to enter the heating tank is preheated in the same way in each stage of heating tank, thereby realizing the cascade utilization of the waste heat energy in the concentrated solution.

[0065] For example, the 100℃ concentrated solution evaporated in the first stage heating tank is used to preheat the concentrated solution to be concentrated about to enter the first stage heating tank, thereby realizing the evaporation reduction of the concentrated solution to be concentrated in the first stage heating tank. Similarly, the 80℃ concentrated solution at the outlet of the second stage heating tank is used to heat the concentrated solution to be concentrated at the inlet of the second stage heating tank, and through this step-by-step heating mode, the cascade utilization of the waste heat energy of the concentrated solution at the outlet of each stage of heating tank is realized.

[0066] During the operation of the concentrated solution concentration subsystem, the 140℃ flue gas is used to heat the high-temperature closed desalted water to 115℃; the 115℃ high-temperature closed desalted water is used to provide heat for the first stage heating tank to obtain 100℃ water vapor and 100℃ concentrated solution, and the 100℃ concentrated solution at the outlet of the first stage heating tank is used to preheat the concentrated solution to be concentrated about to enter the inlet of the first stage heating tank; the 100℃ water vapor is used to provide heat for the second stage heating tank to obtain 80℃ water vapor and 80℃ concentrated solution, and the 80℃ water vapor is used to provide heat for the third stage heating tank to obtain 60℃ water vapor and 60℃ concentrated solution, and the 80℃ concentrated solution at the outlet of the second stage heating tank is used to preheat the concentrated solution to be concentrated about to enter the inlet of the second stage heating tank; finally, the 60℃ water vapor and 60℃ concentrated solution are delivered to the heat exchanger to indirectly heat the condensate water of the steam turbine, thereby completing the cascade utilization and coupled utilization of the waste heat of the garbage flue gas.

[0067] In summary, in the concentrated liquid concentration subsystem, the closed desalted water at 115°C is obtained by heat exchange from the flue gas at 140°C, the concentrated liquid to be concentrated in the first-stage heating tank is further heated by the closed desalted water at 115°C to obtain water vapor at 100°C and concentrated liquid, the concentrated liquid at 100°C is used to preheat the concentrated liquid to be concentrated in the second-stage heating tank, the concentrated liquid to be concentrated in the second-stage heating tank is heated by the water vapor at 100°C, and finally water vapor at 80°C and concentrated liquid are obtained. Subsequently, a gradient utilization device can be further added to generate water vapor at 60 / 40°C or even lower temperature for utilization.

[0068] Finally, the waste water concentrated liquid treatment system is introduced, and the waste heat cascade utilization subsystem in the waste water concentrated liquid treatment system includes a waste heat cascade utilization device. Specifically, the waste heat cascade utilization device can be a waste heat cascade utilization heat exchanger; the waste heat cascade utilization heat exchanger uses the heat obtained from the second water vapor to heat at least one of condenser water, domestic water, and cold air required for combustion.

[0069] In addition, the waste heat cascade utilization subsystem further includes a second vacuum device corresponding to the waste heat cascade utilization device; the second vacuum device is used to reduce the air pressure value in the waste heat cascade utilization device and accelerate the heat exchange between the water vapor and the condenser water or the domestic water or the cold air required for combustion.

[0070] It should be noted that the concentrated liquid to be concentrated mentioned above is the leachate concentrated liquid and the waste water concentrated liquid.

[0071] The concentrated liquid to be concentrated is first transported to the concentrated device with the lowest air pressure by the concentrated liquid conveying pump and is sequentially input into each concentrated device in the order of increasing air pressure values of each concentrated device. Finally, the concentrated liquid is recovered through the concentrated water return pipe.

[0072] In addition, a water storage tank is configured for each concentrated device in the concentrated liquid concentration subsystem, and each water storage tank is used to recover the condensed water of the corresponding concentrated device; a water storage tank is also configured for the waste heat cascade utilization heat exchanger in the waste heat cascade utilization subsystem, which is used to recover the condensed water generated by the heat exchange between the second water vapor and the condenser water and / or the domestic water, and each water storage tank is in communication with the condensed water return pipe for full-plant recycling.

[0073] The wastewater concentrate treatment system provided in this specific embodiment can also be called a waste incineration flue gas waste heat coupled wastewater concentrate treatment system, which uses the waste heat in the flue gas to heat the leachate concentrate or the tobacco washing wastewater concentrate, evaporates the water in the concentrate, and completes the wastewater concentrate treatment. The water vapor generated by evaporation contains a large amount of waste heat, which is reused in the waste heat cascade utilization device, such as heating steam turbine condensate, domestic water, cold air required for combustion, etc., to achieve waste heat cascade utilization while treating the wastewater concentrate with flue gas waste heat. The patent of this invention can effectively recover the heat in the flue gas, reduce the cost and difficulty of wastewater concentrate treatment, and at the same time use the steam generated by the evaporation of the wastewater concentrate to heat the heat medium, realizing the dual utilization of flue gas waste heat recovery.

[0074] In summary, the wastewater concentrate treatment system provided by this application includes a flue gas heat extraction subsystem, a concentrate concentration subsystem, and a waste heat cascade utilization subsystem. The flue gas heat extraction subsystem uses closed demineralized water to recover flue gas heat; the concentrate concentration subsystem uses a vacuum device to apply a gradient-decreasing air pressure to each concentrator, sequentially lowering the boiling point of the concentrate to be concentrated in each concentrator, achieving multi-effect utilization of flue gas heat while simultaneously achieving multi-stage concentration of the concentrate to be concentrated; finally, the waste heat cascade utilization subsystem is used to heat turbine condensate, domestic water, or cold air required for combustion, thereby maximizing the recovery rate of flue gas waste heat.

[0075] Optional, see Figure 2 , an example diagram of the structural composition of the wastewater concentrate treatment system provided in this application.

[0076] like Figure 2 As shown, the wastewater concentrate treatment system includes a WGGH (Water Media Gas-Gas Heater), concentrators 1 and N, a waste heat cascade heat exchanger, a water storage tank 1 corresponding to concentrator N, a water storage tank N corresponding to the waste heat cascade heat exchanger, vacuum pumps 1 and N, a concentrate return main pipe, and a condensate return main pipe.

[0077] An induced draft fan is used to introduce high-temperature flue gas into the flue gas heat exchanger, and the flue gas is discharged through the chimney after heat exchange. The concentration device sends WGGH cold water to the flue gas heat exchanger through a circulating water pump, and then the WGGH hot water is heated by the heat of the high-temperature flue gas in the flue gas heat exchanger to provide heat for the evaporation and concentration of the leachate and / or tobacco washing wastewater in the concentration device 1.

[0078] It should also be noted that, in the wastewater treatment system, the flue gas heat exchanger can be arranged in parallel with the waste incinerator.

[0079] The vacuum pump 1 adjusts the pressure in the concentration device 1 by vacuumizing, and the vacuum pump N adjusts the pressure in the concentration device N by vacuumizing. It should be noted that the pressures in the concentration device 1 and the concentration device N are different, and the pressure in the concentration device 1 is higher than the pressure in the concentration device N, that is, the saturation temperatures (boiling points) of water in the concentration device 1 and the concentration device N are different.

[0080] For example, assuming that the vacuum pump 1 adjusts the pressure in the concentration device 1 to 0.02 MPa, the saturation temperature of water in the device is 60°C, and the temperature of the water vapor evaporated into the concentration device N is 60°C. This part of the water vapor is used to evaporate the leachate and / or the flue gas washing wastewater in the concentration device N. The pressure in the concentration device N can be adjusted to 0.01 MPa, and the saturation temperature of water in the device is 45.8°C.

[0081] It should be further noted that a plurality of combinations of concentration devices and vacuum pumps can also be provided between the concentration device 1 and the concentration device N, each vacuum pump providing a different vacuum degree for the corresponding concentration device, so that the pressures in the concentration devices from 1 to N are gradiently decreased, the boiling points of the wastewater concentrate are sequentially lowered, the requirements of the leachate and / or the flue gas washing wastewater in each concentration device for the temperature of the heat source are lowered, the applicability of the entire wastewater concentrate treatment system is improved, more waste heat in the flue gas is recovered, multi-stage utilization of heat is achieved, and the operation efficiency of the entire system is improved.

[0082] For example, the heat transfer of the entire wastewater treatment system is generally as follows:

[0083] Assuming that the input heat of the WGGH is 1 MW, after passing through the concentration device 1, most of the heat 0.95 MW is transferred to the water vapor, which then enters the concentration device 2. At this time, the water vapor serves as the heat source of the concentration device 2, and the same is true for the subsequent concentration devices. The water vapor generated by the evaporation and concentration of the previous concentration device serves as the heat source for the evaporation and concentration of the current concentration device, and so on.

[0084] The water vapor generated by the evaporation and concentration of the last concentration device is input into the waste heat cascade utilization heat exchanger, and is used to heat at least one of the condenser water of the steam turbine, the cold water for domestic use, and the cold air required for combustion. Again, the waste heat in the water vapor generated by the evaporation of the concentration device is utilized, and the treatment of the wastewater concentrate by the flue gas waste heat is achieved while the cascade utilization of the waste heat is achieved.

[0085] The condensed water generated by the evaporation and concentration of each concentration device enters the corresponding water storage tank, and is collected into the condenser water return pipe for full-plant recycling, achieving the recycling of water resources.

[0086] The leachate / flue gas washing wastewater is input into each concentration device in reverse order from the concentration device N, and finally is evaporated and concentrated in the concentration device 1 and then is discharged through the concentrated water return main pipe.

[0087] As Figure 2 shown, the waste water concentrated liquid treatment system provided by the embodiment adopts indirect segmented heating for heating the leachate concentrated liquid / waste water for washing smoke by using the waste heat of flue gas: the first segment high-temperature flue gas exchanges heat with the high-pressure circulating water at about 0.2 MPa, and the circulating water is heated to about 115°C. The circulating water at 115°C enters the first-stage heating tank (concentration device 1) to accelerate the heating of the leachate by the pipe bundle, and at the same time, the vacuum pump is used for vacuum adjustment to control the evaporation temperature of the leachate in the tank to be 100°C, so that the evaporation reduction of the leachate in the first-stage heating tank is realized. After the first-stage concentration device, the total amount of waste heat is divided into two parts, which are respectively used for 100°C steam and 100°C leachate concentrated liquid. The 100°C steam evaporated from the first-stage tank enters the heating pipe bundle in the second-stage evaporation tank, and at the same time, the vacuum pump is used for vacuum adjustment to control the evaporation temperature of the leachate in the second-stage tank to be 80°C. Similarly, the same can be synchronized to the Nth-stage concentration device (concentration device N), so that the cascade utilization of the waste heat energy in the steam is realized.

[0088] In summary, the waste water concentrated liquid treatment system provided by the present application uses the waste heat in the high-temperature flue gas generated by waste incineration to heat the leachate concentrated liquid or the waste water concentrated liquid for washing smoke, evaporates the water in the concentrated liquid, and completes the waste water concentrated liquid treatment. The water vapor generated by evaporation contains a large amount of waste heat, which is used again in the waste heat cascade utilization device, such as heating the condensate of a steam turbine, domestic water, etc., so that the waste heat of flue gas is used to treat the waste water concentrated liquid, and at the same time, the waste heat cascade utilization is realized (double functions of flue gas waste heat utilization and waste water concentrated liquid treatment). The present application can effectively recover the heat in the flue gas, reduce the cost and difficulty of waste water concentrated liquid treatment, and at the same time, use the steam generated by the evaporation of the waste water concentrated liquid to heat the heat medium, so that the double utilization of flue gas waste heat recovery is realized.

[0089] In addition, the entire waste water treatment system has low energy consumption. Only the circulating water pump and the vacuum pump need to consume electricity in the system, and the rest of the equipment can realize heat recovery and utilization and waste liquid treatment without external heat source. Compared with the existing technology of flue gas injection or steam distillation process, the present system has no adverse effect on the power generation capacity of the entire plant, and the overall energy consumption is low.

[0090] The above is only an embodiment of the present application and is not used to limit the present application. The present application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of claims of the present application.

Claims

1. A wastewater concentrate treatment system, characterized in that: It includes the flue gas heat extraction subsystem, the concentrated liquid concentration subsystem and the waste heat cascade utilization subsystem: The flue gas heat extraction subsystem includes a flue gas heat exchanger; The concentrate concentration subsystem includes at least two concentration devices and at least two first vacuum devices; wherein, one concentration device corresponds to one first vacuum device, and the air pressure value applied by each first vacuum device to the corresponding concentration device is in a gradient decreasing state, and the air pressure value of the concentration device closer to the flue gas heat extraction subsystem is higher; The waste heat cascade utilization subsystem includes a waste heat cascade utilization device; The concentrate concentration subsystem transports the closed demineralized water to the flue gas heat exchanger in exchange for heat from the high-temperature waste incineration flue gas discharged into the flue gas heat exchanger through the induced draft fan, thereby obtaining high-temperature closed demineralized water; The concentrate concentrating subsystem uses the high-temperature closed desalted water to heat the first concentrate to be concentrated in the first concentrating device to obtain first water vapor; inputs the first water vapor into the second concentrating device having the closest pressure value to that of the first concentrating device to heat the second concentrate to be concentrated to obtain second water vapor; uses the second concentrating device as the first concentrating device, the second concentrate to be concentrated as the first concentrate to be concentrated, and the second water vapor as the first water vapor; and iteratively executes, in descending order of pressure values, inputting the first water vapor into the second concentrating device having the closest pressure value to that of the first concentrating device to heat the second concentrate to be concentrated to obtain second water vapor; The second steam is input into the waste heat cascade utilization device to be used for at least one of heating turbine condensate, heating domestic water, and heating cold air required for combustion.

2. The wastewater concentrate treatment system according to claim 1, characterized in that: The concentrate to be concentrated in each concentrating device is first transported to the concentrating device with the lowest air pressure by a concentrate transport pump, and is then input into each concentrating device in the order of increasing air pressure values ​​of the concentrating devices.

3. The wastewater concentrate treatment system according to claim 1, characterized in that: The waste heat cascade utilization device is a waste heat cascade utilization heat exchanger; The waste heat stage utilizes a heat exchanger to exchange heat from the second steam for at least one of heating turbine condensate, heating domestic water, and heating cold air required for combustion.

4. The wastewater concentrate treatment system according to claim 1, characterized in that: The first vacuum device is a first vacuum pump corresponding to each concentration device; The first vacuum pumps set different air pressure values ​​for the concentrating devices, so that the air pressure values ​​of the concentrating devices between the flue gas heat extraction subsystem and the waste heat cascade utilization subsystem decrease gradually.

5. The wastewater concentrate treatment system according to claim 1, characterized in that: The concentrate concentration subsystem further includes a first water storage tank for receiving the first condensed water of each concentration device; The waste heat cascade utilization subsystem further includes a second water storage tank for receiving the second condensed water of the waste heat cascade utilization device; The first condensed water and the second condensed water are transported to the condensate return pipe for reuse throughout the plant.

6. The wastewater concentrate treatment system according to claim 1, characterized in that: It also includes a concentrated water return main pipe connected to the concentrator with the highest air pressure; The concentrated solution is recovered through the concentrated water return main pipe.

7. The wastewater concentrate treatment system according to claim 1, characterized in that: The flue gas heat extraction subsystem includes at least one flue gas heat exchanger; When the flue gas heat exchange system includes a plurality of flue gas heat exchangers, the plurality of heat exchangers are respectively connected to the waste incinerators arranged in parallel.

8. The wastewater concentrate treatment system according to claim 1, characterized in that: The concentrate concentration subsystem transports closed desalted water to the flue gas heat exchanger, including: The concentrate concentration subsystem transports the closed desalted water to the flue gas heat exchanger through a circulating water pump.

9. The wastewater concentrate treatment system according to claim 1, characterized in that: The waste heat cascade utilization subsystem further includes a second vacuum device corresponding to the waste heat cascade utilization device; The second vacuum device is used to reduce the air pressure value in the waste heat cascade utilization device.

10. The wastewater concentrate treatment system according to claim 1, characterized in that: The concentrated solution to be concentrated includes leachate concentrate and tobacco washing wastewater concentrate.

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