CN110627289A

CN110627289A - Low-temperature flue gas heating wastewater concentration system

Info

Publication number: CN110627289A
Application number: CN201911034637.1A
Authority: CN
Inventors: 王争荣; 汪洋; 胡小夫; 苏军划; 夏怀鹏; 耿宣
Original assignee: China Huadian Engineering Group Co Ltd; Huadian Environmental Protection Engineering and Technology Co Ltd
Current assignee: China Huadian Engineering Group Co Ltd; Huadian Environmental Protection Engineering and Technology Co Ltd
Priority date: 2019-10-28
Filing date: 2019-10-28
Publication date: 2019-12-31
Anticipated expiration: 2039-10-28

Abstract

The invention provides a low-temperature flue gas heating wastewater concentration system.A flash tank realizes multi-stage flash by using gradient vacuum, and the concentration effect of desulfurization wastewater is increased; meanwhile, steam with different temperatures formed by multi-stage flash evaporation enters the communicated shell separation process to perform cascade heat exchange with a second heat exchange medium, so that the heat exchange effect is improved; the second heat exchanger is of a shell-and-tube structure, and a plurality of shell-divided passes are adopted, so that the condensation effect of steam is improved, the complexity of connection between the structure of the second heat exchanger and the tube passes is reduced, and the investment cost and the construction period of system equipment are reduced; the flue gas waste heat participates in the wastewater flash evaporation after the wastewater temperature is increased, is taken out along with the steam and then is recycled by a second heat exchange medium, and finally returns to the low pressure feeding system. Under the condition that the recovered heat is hardly lost, the heat application is expanded, the gradient utilization of heat energy is realized, the defect that high-quality heat energy is consumed in the conventional route utilization is overcome, and the energy consumption of a unit is reduced.

Description

Low-temperature flue gas heating wastewater concentration system

Technical Field

The invention relates to the technical field of environmental protection, in particular to a low-temperature flue gas heating wastewater concentration system.

Background

Chinese electric energy mainly uses coal resources, and sulfur dioxide becomes a main pollution source of atmosphere along with the increase of the installed capacity of thermal power. Flue Gas Desulfurization (FGD) is a main process of industrial desulfurization, and a wet limestone washing process is the most common flue gas desulfurization technology at present due to the advantages of high desulfurization efficiency, good coal adaptability, mature process and reliable operation. However, desulfurization waste water is generated in the desulfurization process, and the water quality and water quantity characteristics of the desulfurization waste water are related to a plurality of factors such as unit load, coal components, operation conditions, the quality of desulfurization process water, limestone components and the like. The desulfurization wastewater is acidic and has strong corrosivity, the possibility of high content of suspended matters, high content of chlorine roots, high content of salt and excessive heavy metal in water exists, and the wastewater is the most difficult to treat in a power plant.

At present, desulfurization wastewater is mainly treated by a three-header pretreatment, a clarification tank and a dehydrator technology: adding alkaline substances into the wastewater to neutralize the desulfurized wastewater, and adding organic sulfides to precipitate most heavy metals in the wastewater; adding flocculant to make the sediment become sludge, and making the sludge pass through a filter press to form a sludge cake. After the wastewater is treated, part of heavy metals are removed, the PH value and the concentration of suspended matters of the heavy metals reach the standard, but chloride ions cannot be removed, and the wastewater cannot be discharged.

The technologies currently under study mainly comprise deep pretreatment, concentration and decrement and evaporation drying. The deep pretreatment comprises dosing, clarification and filtration; the concentration and decrement can be realized by a thermal method and a membrane method; the evaporation drying is drying by using the waste heat of steam or smoke. The steam evaporation drying method consumes high-quality steam, and has high energy consumption, large investment and high operation requirement; the adoption of flue gas waste heat evaporation drying needs to consume high-quality flue gas waste heat, influences the flue gas temperature of the air preheater, causes the unit efficiency to be reduced, and can increase the load of the dust removal equipment. In a word, the concentration and decrement of the desulfurization wastewater needs a large amount of high-quality steam or flue gas waste heat, the energy consumption is high, the investment cost is high, the operation requirement is high, and the unit is adversely affected.

Disclosure of Invention

Therefore, the invention aims to overcome the defects of high-quality heat energy consumption and high energy consumption in the existing desulfurization wastewater concentration technology, and provides a low-temperature flue gas heating wastewater concentration system.

The technical scheme provided by the invention is as follows:

the invention provides a low-temperature flue gas heating wastewater concentration system, which comprises a dust removal unit and a desulfurization unit which are communicated, and also comprises a coal economizer and a wastewater concentration system, wherein the coal economizer is arranged between the dust removal unit and the desulfurization unit or is arranged in front of the dust removal unit along the flow direction of flue gas, the wastewater concentration system comprises,

the first heat exchanger is communicated with the economizer so that the wastewater and a first heat exchange medium from the economizer exchange heat in the first heat exchanger;

the flash evaporation tank comprises at least two flash evaporation chambers, adjacent flash evaporation chambers are communicated through overflow holes, and the liquid inlet end of the flash evaporation tank is communicated with the first heat exchanger, so that the waste water after heat exchange sequentially passes through the corresponding flash evaporation chambers and is discharged from the liquid outlet end of the flash evaporation tank;

the second heat exchanger comprises a shell and a plurality of heat exchange tubes arranged in the shell to respectively form a shell pass and a tube pass, wherein the shell pass comprises at least two sub-shell passes, the sub-shell passes and the flash chambers are in one-to-one correspondence and are communicated with each other, so that steam in the corresponding flash chambers enters the corresponding sub-shell passes to exchange heat with a second heat exchange medium in the tube pass;

the first pump is connected with the flash tank, so that the vacuum degree of each flash chamber is sequentially increased along the direction from the liquid inlet end to the liquid outlet end of the flash tank;

and the precipitation device is communicated with the liquid outlet end of the flash tank so as to send the cooled wastewater into the precipitation device for precipitation.

Further, at least one partition plate is arranged in the flash tank to divide the interior of the flash tank into at least two flash chambers; an overflow hole is formed in one side, close to the flash tank, of the partition plate, and an overflow weir is arranged at the edge of the overflow hole, so that the partition plate, the inner wall of the flash tank and the overflow weir form an accommodating tank for accommodating wastewater; at least one baffle is arranged in the second heat exchanger to divide the interior of the shell pass into at least two sub-shell passes; the two ends of the heat exchange tube are respectively an inflow end and an outflow end and are respectively communicated with the low pressure feed system, so that a second heat exchange medium in the low pressure feed system enters the tube side to exchange heat with steam in the shell side; the first pump is sequentially communicated with the second heat exchanger and the flash tank, and the shell passes and the first pump are connected in series or in parallel.

Further, relative to the axis of the flash tank, adjacent overflow holes are respectively arranged on two sides of the axis of the flash tank so as to realize staggered arrangement; preferably, the adjacent overflow holes are respectively contacted with one end of the inner wall of the flash tank and are respectively arranged at two sides of the axis of the flash tank; the area of the cross section of the overflow hole along the direction vertical to the axis of the flash tank is 1/8-1/4 of the area of the baffle plate; the height of the overflow weir is 2-30 cm; the second heat exchanger baffle is provided with holes, the number of the holes is the same as that of the heat exchange tubes, and the diameter of each hole is the same as the outer diameter of the heat exchange tube, so that the heat exchange tube penetrates through the hole; the shape of the heat exchange tube is one of spiral, linear and wave.

The flash tank comprises a flash tank body, a flash tank inlet end, a flash tank outlet end and a flash tank outlet end, wherein the flash tank inlet end is connected with the flash tank inlet end;

the baffle comprises first baffle and second baffle, follows in the direction of the outflow end of heat exchange tube and inflow end, first baffle and second baffle arrange in proper order in the second heat exchanger and will the shell side divide into first branch shell side, second branch shell side and third branch shell side in proper order, first branch shell side with first flash chamber intercommunication, second branch shell side and second flash chamber intercommunication, third branch shell side and third flash chamber intercommunication to make the indoor steam of each flash chamber get into in the branch shell side of intercommunication and in proper order with the second heat transfer medium heat transfer in the heat exchange tube.

Further, the edge of the first partition plate abuts against the inner wall of the first flash chamber to separate the first flash chamber from the second flash chamber; the edge of the second clapboard is abutted against the inner wall of the second flash chamber so as to separate the second flash chamber from the third flash chamber; the liquid inlet end is arranged at the top of the first flash chamber, and the liquid outlet end is arranged at the bottom of the third flash chamber; the edge of the first baffle is abutted against the inner wall of the first shell-dividing pass so as to separate the first shell-dividing pass from the second shell-dividing pass; the edge of the second baffle is abutted against the inner wall of the second shell-dividing pass so as to separate the second shell-dividing pass from the third shell-dividing pass.

Furthermore, the flash tank comprises a first overflow hole, and one side of the first overflow hole, which is close to the flash tank, is arranged on the first partition plate;

the second overflow hole is arranged on the second partition plate at one side close to the flash tank, and is respectively arranged at two sides of the axis of the flash tank together with the first overflow hole so as to realize staggered arrangement;

the first steam outlet is arranged at the top or above the side wall of the first flash chamber;

the second steam outlet is arranged at one end, far away from the first overflow hole, of the inner wall of the second flash chamber close to the first partition plate;

and the third steam outlet is arranged at one end, far away from the second overflow hole, of the inner wall of the third flash chamber close to the second partition plate.

The flash tank further comprises a first demister, wherein the first demister is arranged at the top of the first flash chamber and is positioned in a region between a plane where the liquid inlet end is positioned and a plane where the first steam outlet is positioned, so that steam in the first flash chamber is demisted by the first demister and then is discharged from the first steam outlet;

the second demister is arranged close to the second steam outlet and is positioned at the lower end of the second steam outlet, so that the steam in the second flash chamber is demisted by the second demister and then is discharged from the second steam outlet;

and the third demister is arranged close to the third steam outlet and is positioned at the lower end of the third steam outlet, so that the steam in the third flash chamber is demisted by the third demister and then is discharged from the third steam outlet.

Further, the area of the horizontal section of the first demister is smaller than or equal to the area of the section of the inner wall of the first flash chamber; the area of the horizontal section of the second demister is smaller than or equal to the area of the bottom of the first partition plate; the area of the horizontal section of the third demister is smaller than or equal to the area of the bottom of the second partition plate.

Further, the first demister, the second demister and the third demister can be wire mesh demisters or baffle plate demisters.

Furthermore, a first steam inlet is arranged above the first shell side, a first condensate outlet is arranged below the first shell side, the first steam inlet is communicated with the first steam outlet of the first flash chamber, so that steam in the first flash chamber enters the first shell side for heat exchange, and the generated condensate flows into a condensate pipe from the first condensate outlet;

a second steam inlet is arranged above the second shell dividing pass, a second condensate outlet is arranged below the second shell dividing pass, the second steam inlet is communicated with a second steam outlet of the second flash chamber, so that steam in the second flash chamber enters the second shell dividing pass for heat exchange, and the generated condensate flows into a condensate pipe from the second condensate outlet;

and a third steam inlet is arranged above the third shell division pass, a third condensate outlet is arranged below the third shell division pass, the third steam inlet is communicated with a third steam outlet of the third flash chamber, so that steam in the third flash chamber enters the third shell division pass for heat exchange, and generated condensate flows into a condensate pipe from the third condensate outlet.

Further, the serial arrangement is that the first pump, the third shell-dividing pass, the second shell-dividing pass and the first shell-dividing pass are sequentially communicated so as to respectively vacuumize the third flash chamber, the second flash chamber and the first flash chamber; the vacuum pipeline which is connected in parallel and is communicated with the second heat exchanger and the first pump leads out a first vacuum branch pipe connected with the first shell side, a second vacuum branch pipe connected with the second shell side and a third vacuum branch pipe connected with the third shell side, and the first vacuum branch pipe, the second vacuum branch pipe and the third vacuum branch pipe are respectively provided with a valve so as to control the vacuum degree of the third flash chamber, the second flash chamber and the first flash chamber.

Furthermore, the condensate pipe and the vacuum pipeline are respectively arranged or combined into one pipeline; when the condensate pipe and the vacuum pipeline are respectively arranged, a condensate water collecting tank is also arranged on the condensate pipe.

Further, the precipitation device comprises a concentrated waste liquid separation unit and a dilute waste liquid storage unit, a concentrated waste water inflow port and a supernatant fluid outflow port are arranged above the concentrated waste liquid separation unit, a concentrated waste water discharge port is arranged below the concentrated waste liquid separation unit, the liquid outlet end of the flash tank is communicated with the concentrated waste water inflow port, so that the concentrated waste water after flash evaporation enters the concentrated waste liquid separation unit to be separated into supernatant fluid and concentrated waste water, and the concentrated waste water is discharged from the concentrated waste water discharge port; the dilute waste liquid storage unit is communicated with the supernatant liquid outlet.

Further, the concentrated waste liquid separation unit and the dilute waste liquid storage unit are respectively arranged or can be combined; when the concentrated waste liquid separation unit and the dilute waste liquid storage unit are respectively arranged, a fourth pump is further arranged on a pipeline between the concentrated waste liquid separation unit and the dilute waste liquid storage unit so as to send supernatant liquid into the dilute waste liquid storage unit; when the sedimentation device is combined, the sedimentation device comprises a cavity, the lower part of the cavity is conical so that concentrated wastewater is deposited at the lower part of the cavity, and the upper layer of the cavity is the supernatant and is mixed with the pretreated wastewater.

Further, the first demister and the first partition plate are arranged perpendicular to the inner wall of the first flash chamber; the second demister and the second partition plate are arranged perpendicular to the inner wall of the second flash chamber; the third demister is arranged perpendicular to the inner wall of the third flash chamber.

Further, the low-temperature flue gas heating wastewater concentration system also comprises a vacuum buffer tank, wherein the second heat exchanger, the vacuum buffer tank and the first pump are communicated in sequence;

the second pump is arranged on a pipeline between the precipitation device and the first heat exchanger so as to send the supernatant and the pretreated wastewater into the first heat exchanger;

and the third pump is arranged on the condensate pipe and used for sending the steam condensate to the desulfurization unit for supplementing water for the desulfurization unit process.

Further, the low-temperature flue gas heating wastewater concentration system further comprises a chimney, and the chimney is communicated with the desulfurization unit.

Further, the dust removal unit is an electric dust remover; the coal economizer is a low-temperature coal economizer; the desulfurization unit is a desulfurization tower.

Further, the first heat exchange medium is hot medium water, and the second heat exchange medium is low condensed water or desalted water.

The technical scheme of the invention has the following advantages:

1. according to the low-temperature flue gas heating wastewater concentration system provided by the invention, the flash tank realizes multi-stage flash by using gradient vacuum, so that the concentration of desulfurization wastewater is facilitated; meanwhile, steam with different temperatures formed by multi-stage flash evaporation enters the communicated shell separation process to perform cascade heat exchange with a second heat exchange medium, so that the heat exchange effect is improved; the second heat exchanger is of a shell-and-tube structure and adopts a plurality of shell-divided passes, so that steam in the flash chamber can enter the corresponding shell-divided passes to exchange heat with a second heat exchange medium in the tube pass, the condensation effect of the steam is improved, the complexity of the connection between the structure of the second heat exchanger and the tube pass is reduced while the efficient condensation effect is achieved, the investment cost and the construction period of system equipment are reduced, and the design is ingenious; the coal economizer is arranged to use the flue gas waste heat to improve the temperature of the wastewater, the recovered flue gas waste heat is taken out along with the steam after the wastewater is flashed, the heat contained in the steam is recovered by using a second heat exchange medium, and finally the heat returns to the low pressure heating system. Through the mode, the waste water concentration is realized, the problem of flue gas waste heat recovery of coal-fired power plants or other industries is solved, the energy consumption is low, the investment is low, the operation cost is low, the efficient energy-saving and emission-reducing environmental protection effects are achieved, and the social and economic influences are good.

2. According to the low-temperature flue gas heating wastewater concentration system provided by the invention, the first pump is sequentially communicated with the second heat exchanger and the flash evaporation chamber, each flash evaporation chamber is communicated with the corresponding shell separation process, and each shell separation process is connected with the first pump. The second heat exchanger adopts a plurality of shell passes and is respectively communicated with the first pump, so that the vacuum degree of each flash evaporation chamber can be independently controlled, and the pressure difference exists in each flash evaporation chamber.

3. According to the low-temperature flue gas heating wastewater concentration system provided by the invention, the flow direction of the second heat exchange medium in the heat exchange tube is opposite to the flow direction of steam in the shell pass, so that the heat exchange effect can be increased, and the heat recovery rate is improved; meanwhile, the number of the heat exchange tubes can be adjusted according to the condition, the heat exchange effect can be increased by the proper number, and the heat recovery rate is improved.

4. According to the low-temperature flue gas heating wastewater concentration system provided by the invention, relative to the axis of the flash tank, the adjacent overflow holes are respectively arranged on the two sides of the axis of the flash tank so as to realize staggered arrangement, so that the flow paths of wastewater and each flash chamber can be increased, the flash effect is increased, the concentration of concentrated wastewater after flash evaporation and the amount of steam are increased, the heat exchange temperature of the steam and a second heat exchange medium is increased, and the recovery effect of flue gas waste heat is finally improved.

5. According to the low-temperature flue gas heating wastewater concentration system provided by the invention, the first demister, the second demister and the third demister are arranged, so that fine wastewater liquid drops can be prevented from being brought into the second heat exchanger by steam in the steam-water separation process.

6. According to the low-temperature flue gas heating wastewater concentration system provided by the invention, the vacuum buffer tank is arranged, so that the stability of the vacuum degree of the system can be maintained, meanwhile, liquid drops brought out along with non-condensable gas can be separated, and the liquid drops are prevented from entering the first pump to cause damage to the first pump.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic structural diagram of a low-temperature flue gas heating wastewater concentration system in an embodiment of the invention;

FIG. 2 is a schematic diagram of a wastewater concentration system according to an embodiment of the present invention;

FIG. 3 is a schematic diagram showing a structure of a weir in a flash tank according to example 1 of the present invention;

FIG. 4 is a schematic view showing another structure of a weir in the flash tank in example 1 of the present invention;

FIG. 5 is a schematic diagram of a demister in the flash tank according to embodiment 1 of the present invention;

FIG. 6 is a schematic view of another configuration of a demister in the flash tank according to embodiment 1 of the present invention;

FIG. 7 is a schematic view of a structure in which vacuum pipes are arranged in series in example 1 of the present invention;

FIG. 8 is a schematic structural view of a vacuum line arrangement in parallel in example 1 of the present invention;

FIG. 9 is a schematic view of the structure in which the vacuum pipe and the condensate pipe are separately provided in embodiment 1 of the present invention;

FIG. 10 is a schematic view showing a structure in which a vacuum pipe and a condensate pipe are incorporated in embodiment 1 of the present invention;

FIG. 11 is a schematic view of a demister in embodiment 1 of the present invention;

reference numerals:

1-a dust removal unit; 2-a desulfurization unit; 3-a coal economizer; 4-a chimney; 5-low addition system; 6-a first heat exchanger; 7-a flash tank; 7-1-a first flash chamber; 7-2-a second flash chamber; 7-3-a third flash chamber; 7-4-a first separator; 7-5-a second separator; 7-6-a first overflow aperture; 7-7-a second overflow aperture; 7-8-a first steam outlet; 7-9-a second steam outlet; 7-10-a third steam outlet; 7-11-liquid inlet end; 7-12-liquid outlet end; 7-13-a first demister; 7-14-a second demister; 7-15-a third demister; 7-16-a first weir; 7-17-a second weir; 8-a second heat exchanger; 8-1-a first split shell side; 8-2-second shell side; 8-3-third split shell pass; 8-4-a first steam inlet; 8-5-a first condensate outlet; 8-6-a second steam inlet; 8-7-a second condensate outlet; 8-8-a third steam inlet; 8-9-a third condensate outlet; 8-10-heat exchange tube; 8-11-a first baffle; 8-12-a second baffle; 9-a precipitation device; 9-1-dilute waste liquid storage unit; 9-2-concentrated waste liquid separation unit; 9-3-concentrated wastewater discharge port; 10-a first pump; 11-a second pump; 12-vacuum buffer tank; 13-a third pump; 14-a fourth pump; 15-condensed water collection tank.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art. In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

The embodiment provides a low-temperature flue gas heating wastewater concentration system, as shown in fig. 1, which includes a dust removal unit 1 and a desulfurization unit 2 that are arranged in a communicating manner, and further includes an economizer 3 and a wastewater concentration system, wherein the economizer 3 is arranged between the dust removal unit 1 and the desulfurization unit 2, or is arranged in front of the dust removal unit 1 along a flue gas flowing direction; the dust removal unit 1 is an electric dust remover, the desulfurization unit 2 is a desulfurization tower, the coal economizer 3 is a low-temperature coal economizer, and the arrangement of the coal economizer 3 can improve the dust removal capacity of the dust removal unit 1.

As shown in fig. 2, the wastewater concentration system includes: the first heat exchanger 6 is communicated with the economizer 3, so that the wastewater and a first heat exchange medium from the economizer 3 exchange heat in the first heat exchanger 6; the first heat exchange medium is heat medium water;

the flash tank 7 comprises at least two flash chambers, adjacent flash chambers are communicated through overflow holes, and a liquid inlet end 7-11 of the flash tank 7 is communicated with the first heat exchanger 6, so that the waste water after heat exchange sequentially passes through the corresponding flash chambers and is discharged from a liquid outlet end 7-12 of the flash tank 7;

the second heat exchanger 8 comprises a shell and a plurality of heat exchange tubes 8-10 arranged in the shell to respectively form a shell pass and a tube pass, wherein the shell pass comprises at least two sub-shell passes, the sub-shell passes correspond to the flash chambers one by one and are communicated with each other, so that steam in the corresponding flash chambers enters the corresponding sub-shell passes to exchange heat with a second heat exchange medium in the tube pass;

the first pump 10 is connected with the flash tank 7, so that the vacuum degree of each flash chamber is sequentially increased along the direction from the liquid inlet end 7-11 to the liquid outlet end 7-12 of the flash tank;

and the precipitation device 9 is communicated with the liquid outlet end 7-12 of the flash tank 7 so as to send the cooled wastewater into the precipitation device 9 for precipitation.

If the coal economizer is installed in the original flue gas system, the flue gas system does not need to be reformed, only the pipeline of the coal economizer needs to be reformed, and the pipeline which is directly sent to the low pressure addition system 5 is cut off and is connected to a vacuum phase change wastewater concentration system; if the flue gas system is not provided with an economizer, the economizer and a vacuum phase-change wastewater concentration system are required to be added. In the low-temperature flue gas heating wastewater concentration system, flue gas passes through the economizer 3 and then exchanges heat with the first heat exchange medium, and the first heat exchange medium after being heated is sent to the first heat exchanger 6 to exchange heat with dilute wastewater; the heated dilute wastewater enters a flash tank 7 from a liquid inlet end 7-11, and the arrangement of a first pump 10 enables the vacuum degree of each flash chamber to be sequentially increased along the direction from the liquid inlet end 7-11 to a liquid outlet end 7-12 of the flash tank 7, so that when the wastewater is subjected to flash evaporation in each flash chamber in succession, the dilute wastewater is concentrated and steam is generated at the top of each flash chamber; steam enters each shell pass connected with the flash chamber of the steam generator, exchanges heat with a second heat exchange medium, and generated steam condensate water enters a condensate pipe and can be used for process water replenishing of the desulfurization unit 2; the concentrated wastewater after flash evaporation enters a precipitation device 9 for precipitation. The flash tank 7 realizes multi-stage flash by using gradient vacuum, and is beneficial to the concentration of desulfurization wastewater; meanwhile, steam with different temperatures formed by multi-stage flash evaporation enters the communicated shell separation process to perform cascade heat exchange with a second heat exchange medium, so that the heat exchange effect is improved; the second heat exchanger 8 is of a shell-and-tube structure and adopts a plurality of shell-divided passes, so that steam in the flash chamber can enter the corresponding shell-divided passes to exchange heat with a second heat exchange medium in the tube pass, the condensation effect of the steam is improved, the complexity of the connection between the structure of the second heat exchanger 8 and the tube pass is reduced while the efficient condensation effect is achieved, the investment cost and the construction period of system equipment are reduced, and the design is ingenious; the economizer 3 is arranged to use the flue gas waste heat to improve the temperature of the wastewater, the flue gas waste heat recovered after the wastewater is flashed is taken out along with the steam, the heat contained in the steam is recovered by using a second heat exchange medium, and finally the heat is returned to the low pressure heating system 5. Through the mode, the waste water concentration is realized, the problem of flue gas waste heat recovery of coal-fired power plants or other industries is solved, the energy consumption is low, the investment is low, the operation cost is low, the efficient energy-saving and emission-reducing environmental protection effects are achieved, and the social and economic influences are good.

Further, at least one partition plate is arranged in the flash tank 7 to divide the interior of the flash tank 7 into at least two flash chambers;

one side of the partition plate close to the flash tank 7 is provided with an overflow hole, and the area of the cross section of the overflow hole along the direction vertical to the axis of the flash tank 7 is 1/8-1/4 of the area of the partition plate;

the edge of the overflow hole is provided with an overflow weir, so that the partition plate, the inner wall of the flash tank 7 and the overflow weir form a containing tank for containing wastewater; the height of the overflow weir is 2-30cm and can be determined according to the circulation volume of the wastewater; in the operation process of the system, a liquid seal is formed at the overflow weir, so that the flash chambers are mutually independent, and the vacuum degrees of the flash chambers are sequentially increased along the direction from the liquid inlet end 7-11 to the liquid outlet end 7-12 of the flash tank; preferably, one end of the overflow weir, which is close to the partition plate, is provided with an extension section so as to improve the liquid seal effect;

at least one baffle is arranged in the second heat exchanger 8 to divide the interior of the shell pass into at least two sub-shell passes; two ends of each heat exchange tube 8-10 are respectively an inflow end and an outflow end and are respectively communicated with the low pressure feed system 5, so that a second heat exchange medium in the low pressure feed system 5 enters a tube side to exchange heat with steam in a shell side; the baffle is provided with holes, the number of the holes is the same as that of the heat exchange tubes 8-10, and the diameter of each hole is the same as the outer diameter of each heat exchange tube 8-10, so that the heat exchange tubes 8-10 penetrate through the holes; the shape of the heat exchange tube 8-10 is one of spiral, linear and wave; preferably, the heat exchange tubes 8-10 are spiral in shape; the number of the heat exchange tubes 8-10 can be adjusted according to the situation, and the appropriate number can increase the heat exchange effect and improve the recovery rate of heat.

The first pump 10 is sequentially communicated with the second heat exchanger 8 and the flash tank 7, and the shell passes of the respective sub-pumps are connected with the first pump 10 in series or in parallel. The second heat exchanger 8 adopts a plurality of shell-divided passes and is respectively communicated with the first pump 10, so that the vacuum degree of each flash chamber can be independently controlled, and the pressure difference exists in each flash chamber.

Further, relative to the axis of the flash tank 7, the adjacent overflow holes are respectively arranged on two sides of the axis of the flash tank 7 to realize staggered arrangement, so that the flow paths of the wastewater and each flash chamber are increased, the flash effect is increased, the concentration of the concentrated wastewater after flash evaporation and the amount of steam are increased, the heat exchange temperature of the steam and a second heat exchange medium is increased, and the recovery effect of the flue gas waste heat is finally improved; preferably, adjacent overflow holes are respectively contacted with one end of the inner wall of the flash tank 7 and are respectively arranged at two sides of the axis of the flash tank 7.

As an alternative embodiment, as shown in fig. 3, the partition plates are composed of a first partition plate 7-4 and a second partition plate 7-5, and the first partition plate 7-4 and the second partition plate 7-5 are sequentially arranged in the flash tank 7 along the direction from the liquid inlet end 7-11 to the liquid outlet end 7-12 of the flash tank 7, and divide the interior of the flash tank 7 into a first flash chamber 7-1, a second flash chamber 7-2 and a third flash chamber 7-3; as shown in fig. 7, the baffle is composed of a first baffle 8-11 and a second baffle 8-12, and in the direction of the outflow end and the inflow end of the heat exchange tube 8-10, the first baffle 8-11 and the second baffle 8-12 are sequentially arranged in the second heat exchanger 8 and divide the shell pass into a first shell pass 8-1, a second shell pass 8-2 and a third shell pass 8-3, the first shell pass 8-1 is communicated with the first flash chamber 7-1, the second shell pass 8-2 is communicated with the second flash chamber 7-2, and the third shell pass 8-3 is communicated with the third flash chamber 7-3, so that the steam in each flash chamber enters the communicated shell pass and sequentially exchanges heat with the second heat exchange medium in the heat exchange tube 8-10. The second heat exchange medium is low condensed water or desalted water. The flowing direction of the second heat exchange medium in the heat exchange tubes 8-10 is opposite to the flowing direction of the steam in the shell pass, so that the heat exchange effect can be improved, and the heat recovery rate is improved.

Further, the edge of the first clapboard 7-4 is abutted against the inner wall of the first flash chamber 7-1 so as to separate the first flash chamber 7-1 from the second flash chamber 7-2; the edge of the second clapboard 7-5 is abutted against the inner wall of the second flash chamber 7-2 so as to separate the second flash chamber 7-2 from the third flash chamber 7-3; the liquid inlet end 7-11 is arranged at the top of the first flash chamber 7-1, and the liquid outlet end 7-12 is arranged at the bottom of the third flash chamber 7-3; the first clapboard 7-4 is arranged vertical to the inner wall of the first flash chamber 7-1, and the second clapboard 7-5 is arranged vertical to the inner wall of the second flash chamber 7-2.

Furthermore, the edge of the first baffle plate 8-11 is abutted against the inner wall of the first shell-dividing pass 8-1 so as to separate the first shell-dividing pass 8-1 from the second shell-dividing pass 8-2; the edge of the second baffle 8-12 is abutted against the inner wall of the second shell-dividing pass 8-2 to separate the second shell-dividing pass 8-2 from the third shell-dividing pass 8-3; the first baffle 8-11 is arranged vertical to the inner wall of the first flash chamber 7-1, and the second baffle 8-12 is arranged vertical to the inner wall of the second flash chamber 7-2.

In the embodiment, the flash tank 7 comprises a first overflow hole 7-6, and one side close to the flash tank 7 is arranged on the first partition plate 7-4; the second overflow hole 7-7 is arranged on the second partition plate 7-5 at one side close to the flash tank 7, and is arranged at two sides of the axis of the flash tank 7 with the first overflow hole 7-6 to realize staggered arrangement; a first steam outlet 7-8 arranged at the top or above the side wall of the first flash chamber 7-1; a second steam outlet 7-9 which is close to the first clapboard 7-4 and is arranged at one end of the inner wall of the second flash chamber 7-2 far away from the first overflow hole 7-6; and a third steam outlet 7-10 is arranged at one end of the inner wall of the third flash chamber 7-3 far away from the second overflow hole 7-7, close to the second clapboard 7-5. A first overflow weir 7-16 is arranged at the edge of the first overflow hole 7-6, and a second overflow weir 7-17 is arranged at the edge of the second overflow hole 7-7; the heights of the first overflow weir 7-16 and the second overflow weir 7-17 are 2-30cm and can be determined according to the circulating amount of wastewater; as shown in FIG. 3, the first overflow weir 7-16 is connected to the first partition 7-4 at an end adjacent to the first partition 7-4, and the second overflow weir 7-17 is connected to the second partition 7-5 at an end adjacent to the second partition 7-5; as an alternative embodiment, as shown in FIG. 4, an extension is provided at an end of the first overflow weir 7-16 adjacent to the first partition 7-4, and an extension is provided at an end of the second overflow weir 7-17 adjacent to the second partition 7-5.

Further, as shown in fig. 5-6, the flash tank 7 further comprises a first demister 7-13 disposed at the top of the first flash chamber 7-1 and located in a region between the plane of the liquid inlet end 7-11 and the plane of the first steam outlet 7-8, so that the steam in the first flash chamber 7-1 is demisted by the first demister 7-13 and then discharged from the first steam outlet 7-8; the second demister 7-14 is arranged close to the second steam outlet 7-9 and is positioned at the lower end of the second steam outlet 7-9, so that the steam in the second flash chamber 7-2 is demisted by the second demister 7-14 and then is discharged from the second steam outlet 7-9; the third demister 7-15 is arranged close to the third steam outlet 7-10 and is positioned at the lower end of the third steam outlet 7-10, so that the steam in the third flash chamber 7-3 is demisted by the third demister 7-15 and then discharged from the third steam outlet 7-10; the first demister 7-13 is arranged perpendicular to the inner wall of the first flash chamber 7-1; the second demister 7-14 is arranged perpendicular to the inner wall of the second flash chamber 7-2; the third demister 7-15 is arranged perpendicular to the inner wall of the third flash chamber 7-3. The first demister 7-13, the second demister 7-14 and the third demister 7-15 are arranged, so that fine waste water droplets brought into the second heat exchanger 8 by steam in the steam-water separation process can be avoided.

Further, the area of the horizontal section of the first demister 7-13 is smaller than or equal to the area of the section of the inner wall of the first flash chamber 7-1; the area of the horizontal section of the second demister 7-14 is smaller than or equal to the area of the bottom of the first partition plate 7-4; the area of the horizontal section of the third demister 7-15 is less than or equal to the area of the bottom of the second partition plate 7-5; as an embodiment, as shown in FIG. 5, the area of the horizontal section of the first demister 7-13 is smaller than the area of the section of the inner wall of the first flash chamber 7-1; the area of the horizontal section of the second demister 7-14 is smaller than the area of the bottom of the first partition plate 7-4; the area of the horizontal section of the third demister 7-15 is smaller than the area of the bottom of the second clapboard 7-5; as an alternative embodiment, as shown in FIG. 6, the area of the horizontal section of the first demister 7-13 is equal to the area of the section of the inner wall of the first flash chamber 7-1; the area of the horizontal section of the second demister 7-14 is equal to the area of the bottom of the first partition plate 7-4; the area of the horizontal section of the third demister 7-15 is equal to the area of the bottom of the second partition plate 7-5; further, as shown in fig. 11, the first demister 7-13, the second demister 7-14, and the third demister 7-15 may be wire mesh demisters or baffle demisters.

In the embodiment, a first steam inlet 8-4 is arranged above the first shell-dividing pass 8-1, a first condensate outlet 8-5 is arranged below the first shell-dividing pass 8-1, the first steam inlet 8-4 is communicated with the first steam outlet 7-8, so that steam in the first flash chamber 7-1 enters the first shell-dividing pass 8-1 for heat exchange, and the generated condensate flows into a condensate pipe from the first condensate outlet 8-5; a second steam inlet 8-6 is arranged above the second shell division pass 8-2, a second condensate outlet 8-7 is arranged below the second shell division pass 8-2, the second steam inlet 8-6 is communicated with the second steam outlet 7-9, so that steam in the second flash chamber 7-2 enters the second shell division pass 8-2 for heat exchange, and the generated condensate flows into a condensate pipe from the second condensate outlet 8-7; a third steam inlet 8-8 is arranged above the third shell division 8-3, a third condensate outlet 8-9 is arranged below the third shell division 8-3, the third steam inlet 8-8 is communicated with a third steam outlet 7-10, so that steam in the third flash chamber 7-3 enters the third shell division 8-3 for heat exchange, and the generated condensate flows into a condensate pipe from the third condensate outlet 8-9.

As an optional embodiment, the third sub-shell pass 8-3, the second sub-shell pass 8-2, the first sub-shell pass 8-1 and the first pump 10 are connected in series or in parallel. As shown in fig. 7, the first pump 10, the third shell-dividing pass 8-3, the second shell-dividing pass 8-2, and the first shell-dividing pass 8-1 are connected in series, and are sequentially communicated to respectively vacuumize the third flash chamber 7-3, the second flash chamber 7-2, and the first flash chamber 7-1; as shown in FIG. 8, a vacuum pipeline connected in parallel, that is, communicating the second heat exchanger 8 with the first pump 10, leads out a first vacuum branch pipe connected with the first shell side 8-1, a second vacuum branch pipe connected with the second shell side 8-2, and a third vacuum branch pipe connected with the third shell side 8-3, and the first vacuum branch pipe, the second vacuum branch pipe, and the third vacuum branch pipe are respectively provided with a valve to control the vacuum degree of the third flash chamber 7-3, the second flash chamber 7-2, and the first flash chamber 7-1.

Further, as shown in fig. 9 to 10, the condensate pipe and the vacuum pipe are separately provided or combined into one pipe; as shown in fig. 9, when the condensate pipe and the vacuum pipe are separately provided, a condensate collecting tank 15 is further provided on the condensate pipe.

In the present embodiment, the precipitation device 9 includes a concentrated waste liquid separation unit 9-2 and a dilute waste liquid storage unit 9-1; a concentrated wastewater inflow port and a supernatant outflow port are arranged above the concentrated waste liquid separation unit 9-2, a concentrated wastewater discharge port 9-3 is arranged below the concentrated waste liquid separation unit, and a liquid outlet end 7-12 of the flash tank 7 is communicated with the concentrated waste water inflow port, so that the concentrated waste water after flash evaporation enters the concentrated waste liquid separation unit 9-2 to be separated into supernatant and concentrated waste water, and the concentrated waste water is discharged from the concentrated waste water discharge port 9-3; the dilute waste liquid storage unit 9-1 is communicated with the supernatant liquid outlet.

Further, the concentrated waste liquid separation unit 9-2 and the dilute waste liquid storage unit 9-1 are respectively arranged or can be combined; when the concentrated waste liquid separation unit 9-2 and the dilute waste liquid storage unit 9-1 are respectively arranged, a fourth pump 14 is further arranged on a pipeline between the concentrated waste liquid separation unit 9-2 and the dilute waste liquid storage unit 9-1 so as to send supernatant liquid into the dilute waste liquid storage unit 9-1; when combined, the settling device 9 comprises a tapered lower chamber for settling the concentrated wastewater in the lower chamber, and an upper chamber supernatant for mixing with the pretreated wastewater.

Furthermore, the low-temperature flue gas heating wastewater concentration system also comprises a vacuum buffer tank 12, the second heat exchanger 8, the vacuum buffer tank 12 and the first pump 10 are sequentially communicated, so that the stability of the vacuum degree of the low-temperature flash system is maintained, meanwhile, liquid drops brought out along with non-condensable gas can be separated, and the liquid drops are prevented from entering the first pump and causing damage to the first pump; the second pump 11 is arranged on a pipeline between the precipitation device 9 and the first heat exchanger 6 so as to send the supernatant and the pretreated wastewater into the first heat exchanger 6; and the third pump 13 is arranged on the condensate pipe to send the steam condensate to the desulfurization unit 2 for supplementing the process water of the desulfurization unit 2.

Further, the low-temperature flue gas heating wastewater concentration system also comprises a chimney 4 which is communicated with the desulfurization unit 2.

Example 2

As shown in fig. 1, the embodiment provides a low-temperature flue gas heating wastewater concentration system, which includes a dust removal unit 1, a desulfurization unit 2, a chimney 4, an economizer 3 and a wastewater concentration system, where the economizer 3 is disposed between the dust removal unit 1 and the desulfurization unit 2; the dust removal unit 1 is an electric dust remover, the desulfurization unit 2 is a desulfurization tower, and the economizer 3 is a low-temperature economizer; the wastewater concentration system comprises:

the first heat exchanger 6 is communicated with the economizer 3, so that the wastewater and a first heat exchange medium from the economizer 3 exchange heat in the first heat exchanger 6;

as shown in fig. 9, the flash tank 7 is internally provided with a first partition plate 7-4 and a second partition plate 7-5, the first partition plate 7-4 and the second partition plate 7-5 are sequentially arranged in the flash tank 7 along the direction from the liquid inlet end 7-11 to the liquid outlet end 7-12 of the flash tank 7, the flash tank 7 is internally divided into a first flash chamber 7-1, a second flash chamber 7-2 and a third flash chamber 7-3 in sequence, and adjacent flash chambers are communicated through overflow holes; a liquid inlet end 7-11 of the flash tank 7 is arranged at the top of the first flash chamber 7-1 and is communicated with the first heat exchanger 6; the liquid outlet end 7-12 of the flash tank 7 is arranged at the bottom of the third flash chamber 7-3;

the second heat exchanger 8 comprises a shell and a plurality of heat exchange tubes 8-10 arranged in the shell to respectively form a shell pass and a tube pass, and two ends of each heat exchange tube 8-10 are respectively an inflow end and an outflow end and are respectively communicated with the low pressure feed system 5, so that a second heat exchange medium in the low pressure feed system 5 enters the tube pass to exchange heat with steam in the shell pass; a first baffle 8-11 and a second baffle 8-12 are arranged in the second heat exchanger 8, the first baffle 8-11 and the second baffle 8-12 are sequentially distributed in the second heat exchanger 8 along the direction of the outflow end and the inflow end of the heat exchange tube 8-10, the shell pass is sequentially divided into a first shell pass 8-1, a second shell pass 8-2 and a third shell pass 8-3, the first shell pass 8-1 is communicated with the first flash chamber 7-1, the second shell pass 8-2 is communicated with the second flash chamber 7-2, and the third shell pass 8-3 is communicated with the third flash chamber 7-3, so that steam in each flash chamber enters the communicated shell pass and sequentially exchanges heat with a second heat exchange medium in the heat exchange tube 8-10; holes are formed in the first baffle 8-11 and the second baffle 8-12, the number of the holes is the same as that of the heat exchange tubes 8-10, and the diameter of each hole is the same as that of the outer diameter of each heat exchange tube 8-10, so that the heat exchange tubes 8-10 penetrate through the holes; the heat exchange tubes 8-10 are spiral in shape; the second heat exchange medium is low condensed water or desalted water;

the first pump 10 is connected with the flash evaporation chamber 7 so as to sequentially increase the vacuum degrees of the first flash evaporation chamber 7-1, the second flash evaporation chamber 7-2 and the third flash evaporation chamber 7-3;

the precipitation device 9 comprises a concentrated waste liquid separation unit 9-2 and a dilute waste liquid storage unit 9-1; a concentrated wastewater inflow port and a supernatant outflow port are arranged above the concentrated waste liquid separation unit 9-2, a concentrated wastewater discharge port 9-3 is arranged below the concentrated waste liquid separation unit, and a liquid outlet end 7-12 of the flash tank 7 is communicated with the concentrated waste water inflow port, so that the concentrated waste water after flash evaporation enters the concentrated waste liquid separation unit 9-2 to be separated into supernatant and concentrated waste water, and the concentrated waste water is discharged from the concentrated waste water discharge port 9-3; the dilute waste liquid storage unit 9-1 is communicated with the supernatant liquid outlet so that the supernatant liquid enters the dilute waste liquid storage unit 9-1; the concentrated waste liquid separation unit 9-2 and the dilute waste liquid storage unit 9-1 are respectively arranged, and a fourth pump 14 is further arranged on a pipeline between the concentrated waste liquid separation unit 9-2 and the dilute waste liquid storage unit 9-1.

Further, a first pump 10 is sequentially communicated with a second heat exchanger 8 and a flash evaporation chamber 7, and each sub-shell pass is connected with the first pump 10 in series, namely the first pump 10, a third sub-shell pass 8-3, a second sub-shell pass 8-2 and a first sub-shell pass 8-1 are sequentially communicated in series, so as to respectively vacuumize the third flash evaporation chamber 7-3, the second flash evaporation chamber 7-2 and the first flash evaporation chamber 7-1;

furthermore, the edge of the first clapboard 7-4 is abutted against the inner wall of the first flash chamber 7-1, and the edge of the second clapboard 7-5 is abutted against the inner wall of the second flash chamber 7-2 so as to separate the second flash chamber 7-2 from the third flash chamber 7-3; the first partition plate 7-4 is arranged vertical to the inner wall of the first flash chamber 7-1, and the second partition plate 7-5 is arranged vertical to the inner wall of the second flash chamber 7-2; the edge of the first baffle 8-11 is abutted against the inner wall of the first shell-dividing pass 8-1 so as to separate the first shell-dividing pass 8-1 from the second shell-dividing pass 8-2; the edge of the second baffle 8-12 is abutted against the inner wall of the second shell-dividing pass 8-2 to separate the second shell-dividing pass 8-2 from the third shell-dividing pass 8-3; the first baffle 8-11 is arranged vertical to the inner wall of the first flash chamber 7-1, and the second baffle 8-12 is arranged vertical to the inner wall of the second flash chamber 7-2.

Further, the first overflow hole 7-6 is arranged on the first partition plate 7-4 and is contacted with one end of the inner wall of the flash tank 7, and the area of the cross section of the first overflow hole 7-6 along the direction vertical to the axis of the flash tank 7 is 1/8-1/4 of the area of the first partition plate 7-4; the second overflow hole 7-7 is arranged on the second partition plate 7-5 and is contacted with one end of the inner wall of the flash tank 7, and the area of the cross section of the second overflow hole 7-7 along the direction vertical to the axis of the flash tank 7 is 1/8-1/4 of the area of the second partition plate 7-5; the first overflow hole 7-6 and the second overflow hole 7-7 are respectively arranged at two sides of the axis of the flash tank 7 so as to realize staggered arrangement.

Further, as shown in FIG. 9, a first overflow weir 7-16 is provided at the edge of the first overflow hole 7-6, and a second overflow weir 7-17 is provided at the edge of the second overflow hole 7-7; the heights of the first overflow weir 7-16 and the second overflow weir 7-17 are 2-30cm and can be determined according to the circulating amount of wastewater; the first overflow weir 7-16 is connected to the first partition 7-4 at an end adjacent to the first partition 7-4, and the second overflow weir 7-17 is connected to the second partition 7-5 at an end adjacent to the second partition 7-5.

Further, the flash tank 7 comprises a first steam outlet 7-8 arranged above the top or side wall of the first flash chamber 7-1; a second steam outlet 7-9 which is close to the first clapboard 7-4 and is arranged at one end of the inner wall of the second flash chamber 7-2 far away from the first overflow hole 7-6; and a third steam outlet 7-10 is arranged at one end of the inner wall of the third flash chamber 7-3 far away from the second overflow hole 7-7, close to the second clapboard 7-5.

Furthermore, the flash tank 7 also comprises a first demister 7-13 which is arranged at the top of the first flash chamber 7-1 and is positioned in a region between the plane of the liquid inlet end 7-11 and the plane of the first steam outlet 7-8, so that the steam in the first flash chamber 7-1 is demisted by the first demister 7-13 and then is discharged from the first steam outlet 7-8; the second demister 7-14 is arranged close to the second steam outlet 7-9 and is positioned at the lower end of the second steam outlet 7-9, so that the steam in the second flash chamber 7-2 is demisted by the second demister 7-14 and then is discharged from the second steam outlet 7-9; the third demister 7-15 is arranged close to the third steam outlet 7-10 and is positioned at the lower end of the third steam outlet 7-10, so that the steam in the third flash chamber 7-3 is demisted by the third demister 7-15 and then discharged from the third steam outlet 7-10; the first demister 7-13 is arranged perpendicular to the inner wall of the first flash chamber 7-1; the second demister 7-14 is arranged perpendicular to the inner wall of the second flash chamber 7-2; the third demister 7-15 is arranged perpendicular to the inner wall of the third flash chamber 7-3.

Further, as shown in fig. 9, the area of the horizontal section of the first demister 7-13 is smaller than the area of the section of the inner wall of the first flash chamber 7-1; the area of the horizontal section of the second demister 7-14 is smaller than the area of the bottom of the first partition plate 7-4; the area of the horizontal section of the third demister 7-15 is smaller than the area of the bottom of the second clapboard 7-5; the first demister 7-13, the second demister 7-14 and the third demister 7-15 may be wire mesh demisters or baffle plate demisters.

Further, the second heat exchanger 8 comprises a first shell-dividing pass 8-1, a first steam inlet 8-4 is arranged above the first shell-dividing pass, a first condensate outlet 8-5 is arranged below the first shell-dividing pass, the first steam inlet 8-4 is communicated with a first steam outlet 7-8 of the first flash chamber 7-1, so that steam in the first flash chamber 7-1 enters the first shell-dividing pass 8-1 for heat exchange, and the generated condensate flows into a condensate pipe from the first condensate outlet 8-5; a second steam inlet 8-6 is arranged above the second shell division side 8-2, a second condensate outlet 8-7 is arranged below the second shell division side 8-2, the second steam inlet 8-6 is communicated with a second steam outlet 7-9 of the second flash chamber 7-2, so that steam in the second flash chamber 7-2 enters the second shell division side 8-2 for heat exchange, and the generated condensate flows into a condensate pipe from the second condensate outlet 8-7; and a third steam inlet 8-8 is arranged above the third shell division 8-3, a third condensate outlet 8-9 is arranged below the third shell division 8-3, the third steam inlet 8-8 is communicated with a third steam outlet 7-10 of the third flash chamber 7-3, so that steam in the third flash chamber 7-3 enters the third shell division 8-3 for heat exchange, and the generated condensate flows into a condensate pipe from the third condensate outlet 8-9.

Furthermore, a condensate pipe and a vacuum pipeline are respectively arranged, and a condensate water collecting tank 15 is also arranged on the condensate pipe.

Furthermore, the low-temperature flue gas heating wastewater concentration system also comprises a vacuum buffer tank 12, a second heat exchanger 8, the vacuum buffer tank 12 and a first pump 10 which are sequentially communicated, so that the stability of the vacuum degree of the low-temperature flash system is maintained, meanwhile, liquid drops brought out along with non-condensable gas can be separated, and the liquid drops are prevented from entering the first pump and causing damage to the first pump; the second pump 11 is arranged on a pipeline between the dilute waste liquid storage unit 9-1 and the first heat exchanger 6 so as to send the supernatant and the pretreated waste water into the first heat exchanger 6; and the third pump 13 is arranged on the condensate pipe to send the steam condensate to the desulfurization unit 2 for supplementing the process water of the desulfurization unit 2.

The working principle of the low-temperature flue gas heating wastewater concentration system of the embodiment is as follows:

the pretreated dilute wastewater enters a dilute waste liquid storage unit and is conveyed to a first heat exchanger by a second pump, and the temperature of the dilute wastewater is about 35 ℃; the flue gas passes through the economizer and then exchanges heat with a first heat exchange medium, the temperature of the first heat exchange medium is generally more than 70 ℃, in order to utilize the waste heat of the flue gas as much as possible and prevent low-temperature corrosion, the temperature of the middle first heat exchange medium is selected to be 70 ℃, and the temperature of the middle first heat exchange medium is raised to about 95 ℃ after the heat exchange with the flue gas; the first heat exchange medium after temperature rise is sent to a first heat exchanger to exchange heat with dilute waste water from a dilute waste liquid storage unit, and the temperature of the dilute waste water rises to 65-85 ℃;

the heated dilute wastewater enters a first flash chamber from a liquid inlet end for negative pressure flash evaporation, the dilute wastewater is subjected to gas-liquid separation after entering because the negative pressure of the first flash chamber is lower than the saturated vapor pressure of the dilute wastewater, steam generated at the top of the first flash chamber is demisted by a first demister and then enters a first shell pass to exchange heat with a second heat exchange medium in a heat exchange tube after being subjected to heat exchange by a second shell pass, the generated steam condensate water enters a condensate pipe from the condensate pipe, and the flash evaporated wastewater enters a second flash chamber along a first overflow hole; because the negative pressure of the second flash chamber is lower than the saturated vapor pressure of the flowing dilute wastewater, gas-liquid separation occurs after the dilute wastewater enters, the steam generated at the top of the second flash chamber is demisted by a second demister and then enters a second sub-shell pass to exchange heat with a second heat exchange medium in the heat exchange tube after heat exchange of the third sub-shell pass, the generated steam condensate water enters a condensate pipe through the condensate pipe, and the flashed wastewater enters a third flash chamber along a second overflow hole; because the negative pressure of the third flash chamber is lower than the saturated vapor pressure of the flowing dilute wastewater, gas-liquid separation occurs after the dilute wastewater enters, the steam generated at the top of the third flash chamber is demisted by a third demister and then enters a third shell separation process to exchange heat with a second heat exchange medium from a low pressure feed system, and the generated steam condensate water enters a condensate pipe through the condensate pipe; the steam condensate in the condensate pipe can be sent to the desulfurization unit by a third pump for supplementing water for the desulfurization unit process; the concentrated wastewater after being flashed by the three-stage flash tank enters a concentrated waste liquid separation unit, is subjected to fractional precipitation by the concentrated waste liquid separation unit, and the supernatant is pumped into a dilute waste liquid storage unit by a fourth pump to be mixed with the dilute waste water, and then is sent to the first heat exchanger for heat exchange again for cyclic concentration; discharging the concentrated wastewater from a concentrated wastewater discharge port to obtain concentrated wastewater; and returning the heated second heat exchange medium to the low pressure heating system to complete the recovery of the flue gas waste heat. The vacuum of the first flash chamber, the vacuum of the second flash chamber and the vacuum of the third flash chamber are all provided by the first pump, and the vacuum degrees are sequentially increased, so that the step evaporation is formed.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims

1. A low-temperature flue gas heating wastewater concentration system comprises a dust removal unit and a desulfurization unit which are communicated, and is characterized by also comprising an economizer and a wastewater concentration system, wherein the economizer is arranged between the dust removal unit and the desulfurization unit or in front of the dust removal unit along the flue gas circulation direction,

2. The low-temperature flue gas heating wastewater concentration system according to claim 1,

at least one partition plate is arranged in the flash tank to divide the interior of the flash tank into at least two flash chambers;

an overflow hole is formed in one side, close to the flash tank, of the partition plate, and an overflow weir is arranged at the edge of the overflow hole, so that the partition plate, the inner wall of the flash tank and the overflow weir form an accommodating tank for accommodating wastewater;

at least one baffle is arranged in the second heat exchanger to divide the interior of the shell pass into at least two sub-shell passes;

the two ends of the heat exchange tube are respectively an inflow end and an outflow end and are respectively communicated with the low pressure feed system, so that a second heat exchange medium in the low pressure feed system enters the tube side to exchange heat with steam in the shell side;

the first pump is sequentially communicated with the second heat exchanger and the flash tank, and the shell passes and the first pump are connected in series or in parallel.

3. The system for concentrating wastewater through heating by low-temperature flue gas of claim 2, wherein, relative to the axis of the flash tank, adjacent overflow holes are respectively arranged on two sides of the axis of the flash tank so as to realize staggered arrangement;

the area of the cross section of the overflow hole along the direction vertical to the axis of the flash tank is 1/8-1/4 of the area of the baffle plate;

the height of the overflow weir is 2-30 cm;

the second heat exchanger baffle is provided with holes, the number of the holes is the same as that of the heat exchange tubes, and the diameter of each hole is the same as the outer diameter of the heat exchange tube, so that the heat exchange tube penetrates through the hole;

the shape of the heat exchange tube is one of spiral, linear and wave.

4. The low-temperature flue gas heating wastewater concentration system according to claim 2 or 3,

the partition plates consist of a first partition plate and a second partition plate, and the first partition plate and the second partition plate are sequentially distributed in the flash tank along the direction from the liquid inlet end to the liquid outlet end of the flash tank and divide the interior of the flash tank into a first flash chamber, a second flash chamber and a third flash chamber in sequence;

5. The system for concentrating wastewater by heating with low temperature flue gas according to claim 4, wherein the edge of the first partition plate abuts against the inner wall of the first flash chamber to separate the first flash chamber from the second flash chamber;

the edge of the second clapboard is abutted against the inner wall of the second flash chamber so as to separate the second flash chamber from the third flash chamber;

the liquid inlet end is arranged at the top of the first flash chamber, and the liquid outlet end is arranged at the bottom of the third flash chamber;

the edge of the first baffle is abutted against the inner wall of the first shell-dividing pass so as to separate the first shell-dividing pass from the second shell-dividing pass;

the edge of the second baffle is abutted against the inner wall of the second shell-dividing pass so as to separate the second shell-dividing pass from the third shell-dividing pass.

6. The low temperature flue gas heated wastewater concentration system of claim 4 or 5, wherein the flash tank comprises,

the first overflow hole is arranged on the first partition plate at one side close to the flash tank;

7. The low temperature flue gas heated wastewater concentration system of claim 6, wherein the flash tank further comprises,

the first demister is arranged at the top of the first flash chamber and is positioned in a region between the plane where the liquid inlet end is positioned and the plane where the first steam outlet is positioned, so that the steam in the first flash chamber is demisted by the first demister and then is discharged from the first steam outlet;

8. The low-temperature flue gas heating wastewater concentration system according to claim 6 or 7,

a first steam inlet is arranged above the first sub-shell pass, a first condensate outlet is arranged below the first sub-shell pass, the first steam inlet is communicated with the first steam outlet of the first flash chamber, so that steam in the first flash chamber enters the first sub-shell pass for heat exchange, and the generated condensate flows into a condensate pipe from the first condensate outlet;

9. The low temperature flue gas heating wastewater concentration system of any one of claims 1 to 8, wherein the precipitation device comprises,

a concentrated waste liquid separation unit, wherein a concentrated waste water inflow port and a supernatant fluid outflow port are arranged above the concentrated waste liquid separation unit, a concentrated waste water discharge port is arranged below the concentrated waste liquid separation unit, and a liquid outlet end of the flash tank is communicated with the concentrated waste water inflow port, so that the concentrated waste water after flash evaporation enters the concentrated waste liquid separation unit to be separated into supernatant fluid and concentrated waste water, and the concentrated waste water is discharged from the concentrated waste water discharge port;

and the dilute waste liquid storage unit is communicated with the supernatant liquid outlet so that the supernatant liquid enters the dilute waste liquid storage unit.

10. The low temperature flue gas heating wastewater concentration system according to any one of claims 1 to 9, further comprising,

the second heat exchanger, the vacuum buffer tank and the first pump are communicated in sequence;

the second pump is arranged on a pipeline between the precipitation device and the first heat exchanger;

and the third pump is externally connected with the heat exchange assembly to send the steam condensate to the desulfurization unit for process water supplement of the desulfurization unit.