CN211035579U - Vacuum phase-change wastewater concentration and flue gas waste heat recovery system - Google Patents
Vacuum phase-change wastewater concentration and flue gas waste heat recovery system Download PDFInfo
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- CN211035579U CN211035579U CN201921825434.XU CN201921825434U CN211035579U CN 211035579 U CN211035579 U CN 211035579U CN 201921825434 U CN201921825434 U CN 201921825434U CN 211035579 U CN211035579 U CN 211035579U
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Abstract
The utility model provides a vacuum phase change wastewater concentration and flue gas waste heat recovery system, wherein flue gas exchanges heat with a first heat exchange medium after passing through an economizer, and a flash tank realizes multi-stage flash evaporation by utilizing gradient vacuum, thereby being beneficial to the concentration of desulfurization wastewater; meanwhile, steam with different temperatures can be formed by multi-stage flash evaporation, and after entering the heat exchange assembly, the steam and a second heat exchange medium perform cascade heat exchange, so that the heat exchange effect is improved; the coal economizer is arranged to enable the flue gas waste heat to be used for improving the temperature of the waste water, the flue gas waste heat recovered after the waste water is subjected to flash evaporation is taken out along with the steam, the second heat exchange medium recovers the heat contained in the steam, 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 a coal-fired power plant or other industries is solved, and the method has good social and economic influences.
Description
Technical Field
The utility model relates to an environmental protection technology field, concretely relates to vacuum phase transition waste water is concentrated and flue gas waste heat recovery system, in particular to be used for thermal power factory flue gas waste heat recovery in coordination with waste water concentrated 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.
SUMMERY OF THE UTILITY MODEL
Therefore, the to-be-solved technical problem of the utility model lies in overcoming the concentrated technique of current desulfurization waste water and having the high-quality heat energy of consumption, and the defect that the energy consumption is high to a vacuum phase transition waste water is concentrated and flue gas waste heat recovery system is provided.
The utility model provides a technical scheme as follows:
the utility model provides a vacuum phase change wastewater concentration and flue gas waste heat recovery system, which comprises a dust removal unit and a desulfurization unit which are communicated, and also comprises an economizer and a wastewater concentration system, wherein the economizer is arranged between the dust removal unit and the desulfurization unit or is arranged in front of the dust removal unit along the flue gas circulation direction, 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 heat exchange assembly comprises at least two heat exchange units, the heat exchange units 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 heat exchange units for heat exchange;
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; the first pump is communicated with the heat exchange assembly and the flash tank in sequence, and each heat exchange unit is connected with the first pump 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 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 heat exchange assembly consists of a first heat exchange unit, a second heat exchange unit and a third heat exchange unit, the first heat exchange unit is communicated with the first flash chamber, the second heat exchange unit is communicated with the second flash chamber, and the third flash chamber is communicated with the third heat exchange unit;
the vacuum phase change wastewater concentration and flue gas waste heat recovery system further comprises a low pressure feeding system which is sequentially connected with the third heat exchange unit, the second heat exchange unit and the first heat exchange unit in series, so that a second heat exchange medium sequentially passes through the third heat exchange unit, the second heat exchange unit and the first heat exchange unit and exchanges heat with corresponding steam.
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.
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 heat exchange unit, a first condensate outlet is arranged below the first heat exchange unit, 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 heat exchange unit for heat exchange, and the generated condensate flows into a condensate pipe from the first condensate outlet;
a second steam inlet is formed in the upper part of the second heat exchange unit, a second condensate outlet is formed in the lower part of the second heat exchange unit, the second steam inlet is communicated with the second steam outlet of the second flash chamber, so that steam in the second flash chamber enters the second heat exchange unit for heat exchange, and the generated condensate flows into a condensate pipe from the second condensate outlet;
and a third steam inlet is formed in the upper part of the third heat exchange unit, a third condensate outlet is formed in the lower part of the third heat exchange unit, the third steam inlet is communicated with the third steam outlet of the third flash chamber, so that steam in the third flash chamber enters the third heat exchange unit for heat exchange, and generated condensate flows into the condensate pipe from the third condensate outlet.
Further, the serial arrangement is that the first pump, the third heat exchange unit, the second heat exchange unit and the first heat exchange unit 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 heat exchange assembly and the first pump leads out a first vacuum branch pipe connected with the first heat exchange unit, a second vacuum branch pipe connected with the second heat exchange unit and a third vacuum branch pipe connected with the third heat exchange unit, 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, vacuum phase transition waste water is concentrated and flue gas waste heat recovery system still includes, the vacuum buffer tank, heat exchange assembly, vacuum buffer tank, first pump communicate in proper order.
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 externally connected with the heat exchange assembly and arranged on the condensate pipe so as to convey the steam condensate to the desulfurization unit for process water supplement of the desulfurization unit.
Further, the vacuum phase-change wastewater concentration and flue gas waste heat recovery 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 exchanger, the first heat exchange unit, the second heat exchange unit and the third heat exchange unit can adopt plate heat exchangers or shell-and-tube heat exchangers; preferably, the first heat exchanger, the first heat exchange unit, the second heat exchange unit and the third heat exchange unit all adopt plate heat exchangers.
Further, the first heat exchange medium is hot medium water, and the second heat exchange medium is low condensed water or desalted water.
The utility model discloses technical scheme has following advantage:
1. the utility model provides a vacuum phase transition waste water concentration and flue gas waste heat recovery system, the flue gas exchanges heat with first heat transfer medium after passing through the economizer, the first heat transfer medium after rising the temperature is sent to the first heat exchanger and exchanges heat with rare waste water; the heated dilute wastewater enters a flash evaporation tank from a liquid inlet end, and the arrangement of a first pump enables the vacuum degree of each flash evaporation chamber to be sequentially increased along the direction from the liquid inlet end to the liquid outlet end of the flash evaporation tank, so that when the wastewater is subjected to flash evaporation in succession in each flash evaporation chamber, the dilute wastewater is concentrated and steam is generated at the top of each flash evaporation chamber; steam enters each heat exchange unit connected with the flash chamber of the steam generator to exchange heat with a second heat exchange medium, and the generated steam condensate water enters a condensate pipe and can be used for process water replenishing of a desulfurization system; and (4) the flash-evaporated concentrated wastewater enters a precipitation device for precipitation. The flash tank realizes multi-stage flash by using gradient vacuum, and is favorable for concentrating the desulfurization wastewater; meanwhile, steam with different temperatures can be formed by multi-stage flash evaporation, and after entering the heat exchange assembly, the steam and a second heat exchange medium perform cascade heat exchange, so that the heat exchange effect is improved; 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. The utility model provides a concentrated and flue gas waste heat recovery system of vacuum phase transition waste water, for the axis of flash tank, adjacent overflow hole branch is located the axis both sides of flash tank are in order to realize crisscross setting, can increase the flow path of waste water and each flash chamber to increase the flash distillation effect, and then the concentration of the thick waste water of increase flash distillation back and the volume of steam, increased the heat transfer temperature of steam and second heat transfer medium then, finally improved the recovery effect of flue gas waste heat.
3. The utility model provides a concentrated and flue gas waste heat recovery system of vacuum phase transition waste water through setting up first defroster, second defroster and third defroster, can avoid steam-water separation process steam to bring tiny waste water liquid drop into heat exchange assemblies.
4. The utility model provides a concentrated and flue gas waste heat recovery system of vacuum phase transition waste water, the setting of vacuum buffer tank can maintain the system vacuum stable, can avoid the liquid drop to advance first pump and cause the injury to first pump along with the liquid drop separation that noncondensable gas took out simultaneously.
5. The utility model provides a concentrated and flue gas waste heat recovery system of vacuum phase transition waste water, the dust collection ability of dust removal unit can be improved in the setting of economizer.
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 embodiments or the technical solutions in 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 for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a vacuum phase-change wastewater concentration and flue gas waste heat recovery system in an embodiment of the present 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 structural diagram of an overflow weir in the flash tank according to embodiment 1 of the present invention;
FIG. 4 is another schematic structural diagram of an overflow weir in the flash tank according to embodiment 1 of the present invention;
fig. 5 is a schematic structural view of a vacuum pipeline arranged in series in embodiment 1 of the present invention;
fig. 6 is a schematic structural view of the vacuum pipes arranged in parallel in embodiment 1 of the present invention;
FIG. 7 is a schematic structural view showing the vacuum pipe and the condensate pipe separately provided in embodiment 1 of the present invention;
FIG. 8 is a schematic structural view of the embodiment 1 of the present invention in which a vacuum pipe and a condensate pipe are combined;
fig. 9 is a schematic structural view of a demister according to embodiment 1 of the present invention;
fig. 10 is a schematic structural diagram of a demister in the flash tank according to embodiment 1 of the present invention;
fig. 11 is another schematic structural diagram of a demister in the flash tank according to 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 heat exchange assembly; 8-1-a first heat exchange unit; 8-2-a second heat exchange unit; 8-3-a third heat exchange unit; 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; 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 solution of the present invention will be described clearly and completely with reference to the accompanying drawings, and obviously, the described embodiments are some, but not all embodiments of the present invention. The following examples are provided for better understanding of the present invention, and are not limited to the best mode, and do not limit the scope and content of the present invention, and any product that is the same or similar to the present invention, which is obtained by combining the features of the present invention with other prior art or the present invention, falls within the 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", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific 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 is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; 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 meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art. Furthermore, the technical features mentioned in the different embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.
Example 1
The embodiment provides a vacuum phase-change wastewater concentration and flue gas waste heat recovery system, which comprises a dust removal unit 1 and a desulfurization unit 2 which are communicated with each other, and further comprises 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 the 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 exchanger 6 can adopt a plate type heat exchanger or a shell-and-tube type heat exchanger; preferably, the first heat exchanger 6 is a plate heat exchanger; 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 heat exchange assembly 8 comprises at least two heat exchange units, the heat exchange units correspond to the flash chambers one by one and are communicated with each other, so that steam in the corresponding flash chambers 7 enters the corresponding heat exchange units for heat exchange;
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 economizer 3 is installed in the original flue gas system, the flue gas system does not need to be reformed, only the pipeline of the economizer 3 needs to be reformed, and the pipeline which is directly sent to the low pressure addition system 5 is cut off and connected to a vacuum phase change wastewater concentration system; if the economizer 3 is not arranged in the flue gas system, the economizer 3 and a vacuum phase-change wastewater concentration system need to be additionally arranged. In the vacuum phase change wastewater concentration and flue gas waste heat recovery 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 the flash evaporation tank 7 from the liquid inlet end, and the arrangement of the first pump 10 enables the vacuum degree of each flash evaporation chamber to be sequentially increased along the direction from the liquid inlet end to the liquid outlet end of the flash evaporation tank 7, so that when the wastewater is subjected to flash evaporation in succession in each flash evaporation chamber, the dilute wastewater is concentrated and steam is generated at the top of each flash evaporation chamber; steam enters each heat exchange unit connected with the flash chamber of the steam generator to exchange heat with a second heat exchange medium, and the generated steam condensate water enters a condensate pipe and can be used for process water replenishing of a desulfurization system; and (4) the flash-evaporated concentrated wastewater enters a precipitation device 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 can be formed by multi-stage flash evaporation, and after entering the heat exchange assembly, the steam and a second heat exchange medium perform cascade heat exchange, so that the heat exchange effect is improved; 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. 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;
the first pump 10 is sequentially communicated with the heat exchange assembly 8 and the flash tank 7, and the heat exchange units are connected with the first pump 10 in series or in parallel.
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. 5, the heat exchange assembly 8 is composed of a first heat exchange unit 8-1, a second heat exchange unit 8-2 and a third heat exchange unit 8-3, the first heat exchange unit 8-1 is communicated with the first flash chamber 7-1, the second heat exchange unit 8-2 is communicated with the second flash chamber 7-2, and the third flash chamber 7-3 is communicated with the third heat exchange unit 8-3; the first heat exchange unit 8-1, the second heat exchange unit 8-2 and the third heat exchange unit 8-3 can adopt plate heat exchangers or shell-and-tube heat exchangers; preferably, the first heat exchange unit 8-1, the second heat exchange unit 8-2 and the third heat exchange unit 8-3 all adopt plate heat exchangers.
Further, the vacuum phase change wastewater concentration and flue gas waste heat recovery system also comprises a low pressure feeding system 5 which is sequentially connected with a third heat exchange unit 8-3, a second heat exchange unit 8-2 and a first heat exchange unit 8-1 in series, so that a second heat exchange medium sequentially passes through the third heat exchange unit 8-3, the second heat exchange unit 8-2 and the first heat exchange unit 8-1 and exchanges heat with corresponding steam; the second heat exchange medium is low condensed water or desalted water.
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.
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 is arranged on the second partition plate 7-5 at one side close to the flash tank 7 and is respectively arranged at two sides of the axis of the flash tank 7 together with the first overflow hole 7-6 so as 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. 3-4, 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 steam generated in the steam-water separation process can be prevented from bringing fine waste water droplets into the heat exchange assembly 8.
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. 10, 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. 11, 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. 9, 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 heat exchange unit 8-1, a first condensed water outlet 8-5 is arranged below the first heat exchange unit 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 heat exchange unit 8-1 for heat exchange, and the generated condensed water flows into a condensed water pipe from the first condensed water outlet 8-5; a second steam inlet 8-6 is arranged above the second heat exchange unit 8-2, a second condensate outlet 8-7 is arranged below the second heat exchange unit 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 heat exchange unit 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 heat exchange unit 8-3, a third condensate outlet 8-9 is arranged below the third heat exchange unit 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 heat exchange unit 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 heat exchange unit 8-3, the second heat exchange unit 8-2, the first heat exchange unit 8-1 and the first pump 10 are connected in series or in parallel. As shown in fig. 5, the first pump 10, the third heat exchange unit 8-3, the second heat exchange unit 8-2, and the first heat exchange unit 8-1 are connected in series, that is, communicated in sequence, 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. 6, a vacuum pipeline connected in parallel, i.e., communicating the heat exchange assembly with the first pump, leads out a first vacuum branch pipe connected with the first heat exchange unit 8-1, a second vacuum branch pipe connected with the second heat exchange unit 8-2, and a third vacuum branch pipe connected with the third heat exchange unit 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. 7 to 8, the condensate pipe and the vacuum pipe are separately provided or combined into one pipe; as shown in fig. 7, 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.
Further, the vacuum phase-change wastewater concentration and flue gas waste heat recovery system also comprises a vacuum buffer tank 12, wherein the heat exchange assembly 8, the vacuum buffer tank 12 and the first pump 10 are sequentially communicated so as to maintain the stability of the vacuum degree of the low-temperature flash evaporation system, and simultaneously, liquid drops brought out along with non-condensable gas can be separated, so that the liquid drops are prevented from entering the first pump to cause 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 externally connected with the heat exchange assembly and arranged on the condensate pipe so as to send the steam condensate to the desulfurization unit 2 for process water supplement of the desulfurization unit 2.
Further, the vacuum phase-change wastewater concentration and flue gas waste heat recovery system further comprises a chimney 4 communicated with the desulfurization unit 2.
Example 2
As shown in fig. 1, the present embodiment provides a vacuum phase change wastewater concentration and flue gas waste heat recovery 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. 7, 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 heat exchange assembly 8 comprises a first heat exchange unit 8-1, a second heat exchange unit 8-2 and a third heat exchange unit 8-3, the first heat exchange unit 8-1 is communicated with the first flash chamber 7-1, the second heat exchange unit 8-2 is communicated with the second flash chamber 7-2, and the third flash chamber 7-3 is communicated with the third heat exchange unit 8-3, so that steam in the corresponding flash chamber enters the corresponding heat exchange unit for heat exchange; specifically, the first heat exchange unit 8-1, the second heat exchange unit 8-2 and the third heat exchange unit 8-3 are plate heat exchangers;
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 also arranged on a pipeline between the concentrated waste liquid separation unit 9-2 and the dilute waste liquid storage unit 9-1;
the low pressure feed system 5 is sequentially connected with the third heat exchange unit 8-3, the second heat exchange unit 8-2 and the first heat exchange unit 8-1 in series, so that a second heat exchange medium sequentially passes through the third heat exchange unit 8-3, the second heat exchange unit 8-2 and the first heat exchange unit 8-1 and exchanges heat with corresponding steam; the second heat exchange medium is low condensed water or desalted water.
Further, the first pump 10 is sequentially communicated with the heat exchange assembly 8 and the flash tank 7, and the heat exchange units are connected in series with the first pump 10, that is, the first pump 10, the third heat exchange unit 8-3, the second heat exchange unit 8-2 and the first heat exchange unit 8-1 are sequentially communicated in series, so as to respectively vacuumize the third flash chamber 7-3, the second flash chamber 7-2 and the first flash 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 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.
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. 7, 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. 7, 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 heat exchange assembly 8 comprises a first heat exchange unit 8-1, a first steam inlet 8-4 is formed in the upper portion of the first heat exchange unit, a first condensate outlet 8-5 is formed in the lower portion of the first heat exchange unit, 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 heat exchange unit 8-1 for heat exchange, and generated condensate flows into a condensate pipe from the first condensate outlet 8-5; the second heat exchange unit 8-2 is provided with a second steam inlet 8-6 at the upper part and a second condensate outlet 8-7 at the lower part, 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 heat exchange unit 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 formed in the upper part of the third heat exchange unit 8-3, a third condensate outlet 8-9 is formed in the lower part of the third heat exchange unit 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 heat exchange unit 8-3 for heat exchange, and 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.
Further, the vacuum phase-change wastewater concentration and flue gas waste heat recovery system also comprises a vacuum buffer tank 12, wherein the heat exchange assembly 8, the vacuum buffer tank 12 and the first pump 10 are sequentially communicated so as to maintain the stability of the vacuum degree of the low-temperature flash evaporation system, and simultaneously, liquid drops brought out along with non-condensable gas can be separated, so that the liquid drops are prevented from entering the first pump to cause 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 externally connected with the heat exchange assembly and arranged on the condensate pipe so as to send the steam condensate to the desulfurization unit 2 for process water supplement of the desulfurization unit 2.
The working principle of the vacuum phase-change wastewater concentration and flue gas waste heat recovery 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 heat exchange unit to exchange heat with a second heat exchange medium subjected to heat exchange by a second heat exchange unit, the generated steam condensate water enters a condensate pipe from the condensate pipe, and the flashed 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, steam generated at the top of the second flash chamber is demisted by a second demister and then enters a second heat exchange unit to exchange heat with a second heat exchange medium after heat exchange of a third heat exchange unit, the generated steam condensate water enters a condensate pipe through the condensate pipe, and the wastewater after flash evaporation enters the 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 heat exchange unit to exchange heat with a second heat exchange medium, 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 can be made without departing from the scope of the invention.
Claims (10)
1. A vacuum phase-change wastewater concentration and flue gas waste heat recovery system comprises a dust removal unit and a desulfurization unit which are communicated, and is characterized by also comprising 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 flue gas circulation direction, 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 heat exchange assembly comprises at least two heat exchange units, the heat exchange units 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 heat exchange units for heat exchange;
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.
2. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system of 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;
the first pump is communicated with the heat exchange assembly and the flash tank in sequence, and each heat exchange unit is connected with the first pump in series or in parallel.
3. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system according to claim 2, wherein adjacent overflow holes are respectively arranged on two sides of the axis of the flash tank so as to realize staggered arrangement relative to 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.
4. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system of claim 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;
the heat exchange assembly consists of a first heat exchange unit, a second heat exchange unit and a third heat exchange unit, the first heat exchange unit is communicated with the first flash chamber, the second heat exchange unit is communicated with the second flash chamber, and the third flash chamber is communicated with the third heat exchange unit;
the low pressure heater is characterized by further comprising a low pressure heating system which is sequentially connected with the third heat exchange unit, the second heat exchange unit and the first heat exchange unit in series, so that a second heat exchange medium sequentially passes through the third heat exchange unit, the second heat exchange unit and the first heat exchange unit and exchanges heat with corresponding steam.
5. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system 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.
6. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system of claim 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;
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.
7. The vacuum phase-change wastewater concentration and flue gas waste heat recovery 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;
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.
8. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system of claim 6 or 7,
a first steam inlet is formed above the first heat exchange unit, a first condensate outlet is formed below the first heat exchange unit, 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 heat exchange unit for heat exchange, and the generated condensate flows out of the first condensate outlet;
a second steam inlet is formed above the second heat exchange unit, a second condensate outlet is formed below the second heat exchange unit, the second steam inlet is communicated with the second steam outlet of the second flash chamber, so that steam in the second flash chamber enters the second heat exchange unit for heat exchange, and the generated condensate flows out of the second condensate outlet;
and a third steam inlet is arranged above the third heat exchange unit, a third condensate outlet is arranged below the third heat exchange unit, the third steam inlet is communicated with the third steam outlet of the third flash chamber, so that steam in the third flash chamber enters the third heat exchange unit for heat exchange, and generated condensate flows out from the third condensate outlet.
9. The vacuum phase-change wastewater concentration and flue gas waste heat recovery system according to claim 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 vacuum phase-change wastewater concentration and flue gas waste heat recovery system of claim 9, further comprising,
the heat exchange assembly, 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.
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| CN110642444A (en) * | 2019-10-28 | 2020-01-03 | 中国华电科工集团有限公司 | Vacuum phase-change wastewater concentration and flue gas waste heat recovery system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110642444A (en) * | 2019-10-28 | 2020-01-03 | 中国华电科工集团有限公司 | Vacuum phase-change wastewater concentration and flue gas waste heat recovery system |
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