阅读说明：本技术 一种置换烟气余热的气体预热系统及方法 (Gas preheating system and method for replacing flue gas waste heat ) 是由 吴勇刚 贾双燕 王继忠 潘常宝 于 2021-06-24 设计创作，主要内容包括：本发明涉及一种置换烟气余热的气体预热系统及方法,气体预热系统包括用于连接烟气入口管路的第一塔、第二塔、气体介质输送管路以及气体介质出口管路,第一塔底部通过第一输送管路与第二塔内的第二喷淋装置连接,第二塔底部通过第二输送管路与第一塔内的第一喷淋装置连接；第二塔上连接有气体介质出口管路,气体介质输送管路分别连接第一支路和第二支路,第一支路与所述第二塔连接,所述第二支路与所述气体介质出口管路连接。本发明的气体预热系统,采取液体介质置换原湿烟气热量来预热空气,极大提高了传热效率,使脱硫、除尘效率大幅提升、并将热量传递给空气,输送到锅炉内,提高锅炉的送风温度,从而提高其工作效率,大幅降低锅炉运行成本。(The invention relates to a gas preheating system and a method for replacing flue gas waste heat, wherein the gas preheating system comprises a first tower, a second tower, a gas medium conveying pipeline and a gas medium outlet pipeline which are used for connecting a flue gas inlet pipeline, the bottom of the first tower is connected with a second spraying device in the second tower through the first conveying pipeline, and the bottom of the second tower is connected with a first spraying device in the first tower through the second conveying pipeline; and a gas medium outlet pipeline is connected to the second tower, a gas medium conveying pipeline is respectively connected with a first branch and a second branch, the first branch is connected with the second tower, and the second branch is connected with the gas medium outlet pipeline. According to the gas preheating system, the liquid medium is adopted to replace the heat of the original wet flue gas to preheat air, so that the heat transfer efficiency is greatly improved, the desulfurization and dust removal efficiency is greatly improved, the heat is transferred to the air and conveyed into the boiler, the air supply temperature of the boiler is improved, the working efficiency is improved, and the operating cost of the boiler is greatly reduced.)

1. The gas preheating system for replacing the waste heat of the flue gas is characterized by comprising a first tower (1), a second tower (2), a gas medium conveying pipeline (B1) and a gas medium outlet pipeline (B2), wherein the first tower (1) is connected with a flue gas inlet pipeline (A1), the bottom of the first tower (1) is connected with a second spraying device (6) in the second tower (2) through the first conveying pipeline, and the bottom of the second tower (2) is connected with a heat exchange device in the first tower (1) through the second conveying pipeline; the second tower (2) is connected with a gas medium outlet pipeline (B2), the gas medium conveying pipeline (B1) is respectively connected with a first branch (B11) and a second branch (B12), the first branch (B11) is connected with the second tower (2), and the second branch (B12) is connected with the gas medium outlet pipeline (B2).

2. The gas preheating system for replacing the residual heat of flue gas of claim 1, wherein a heating device (7) is connected to the second branch (B12).

3. The gas preheating system for replacing the residual heat of the flue gas according to claim 2, wherein the heating device (7) comprises a heater or/and a heat exchanger; when the heating means (7) comprise a heater, said heater is directly connected to the second branch (B12); when the heating device (7) comprises a heat exchanger, the tube side of the heat exchanger is connected with a heat exchange pipeline, and the shell side of the heat exchanger is connected with the second branch (B12).

4. The gas preheating system for replacing the waste heat of the flue gas as recited in claim 3, wherein a first branch pipeline and a second branch pipeline are connected to the first conveying pipeline, the first branch pipeline is connected to the second spraying device (6) in the second tower (2), the second branch pipeline is connected to the top of the second tower (2), and a part of the second branch pipeline is connected to the tube side of the heat exchanger as a heat exchange pipeline.

5. The gas preheating system for replacing residual heat of flue gas of claim 1, further comprising a flue gas inlet line (A1) and a flue gas outlet line (A2), wherein the flue gas inlet line (A1) is connected with the side wall of the first tower (1), and the flue gas outlet line (A2) is connected with the top of the first tower (1).

6. The gas preheating system for replacing the waste heat of flue gas as claimed in claim 1, wherein the first conveying pipeline and the second conveying pipeline are respectively connected with a conveying pump.

7. The gas preheating system for replacing the waste heat of the flue gas as recited in claim 1, wherein the heat exchanging device comprises a first spraying device (5), and the spraying liquid of the first spraying device (5) adopts clear water or alkaline solution; the particle diameter of the water mist droplets sprayed by the first spraying device (5) and the second spraying device (6) is less than 100 mu m.

8. An air preheating method for replacing flue gas waste heat is characterized by comprising the following steps:

s1, conveying the desulfurized flue gas into the first tower (1), directly contacting with a heat exchange device in the first tower (1), absorbing heat of the flue gas by a heat exchange medium in the heat exchange device, allowing a condensate in the flue gas to fall to the bottom of the first tower (1), conveying the condensate and the heat exchange medium in the heat exchange device into the second tower (2) through a second conveying pipeline as heat exchange liquid respectively, and discharging the heat-exchanged flue gas from the first tower (1);

s2, enabling the gas medium to enter a second tower (2) through a first branch (B11) of a gas medium conveying pipeline (B1), enabling the gas medium to directly contact with heat exchange liquid sprayed by a second spraying device (6) for heat exchange to obtain first gas and liquid medium which are heated and humidified, and conveying the liquid medium to a heat exchange device in the first tower (1) through a second conveying pipeline to serve as heat exchange medium;

s3, the second gas conveyed by the second branch (B12) of the gas medium conveying pipeline (B1) is merged with the first gas in the gas medium outlet pipeline (B2) on the second tower (2) and is used.

9. The air preheating method for replacing the residual heat of flue gas as claimed in claim 8, wherein in S3, the heating device (7) is a heater, the gas medium is connected with the heater through a second branch (B12) of the gas medium conveying pipeline (B1), and the gas in the second branch (B12) is heated by the heater; or, the heating device (7) is a heat exchanger, the gas medium is connected with the shell side of the heat exchanger through a second branch (B12) of a gas medium conveying pipeline (B1), the tube side of the heat exchanger is connected with a heat exchange pipeline, and the gas in the second branch (B12) is heated through the heat exchange pipeline; or, the heating device (7) comprises a heater and a heat exchanger, and the gas in the second branch (B12) is heated simultaneously through the heater and the heat exchanger.

10. The air preheating method for replacing the waste heat of the flue gas as recited in claim 8, wherein the heat exchanging device comprises a first spraying device (5); in S1, the desulfurized flue gas is conveyed into the first tower (1) and directly contacts with the liquid medium sprayed by the first spraying device (5), the heat of the flue gas is absorbed by the liquid medium, and the condensate in the flue gas is converged with the liquid medium and falls into the bottom of the first tower (1) to form heat exchange liquid.

Technical Field

The invention relates to the technical field of wet flue gas desulfurization, in particular to the technical fields of waste heat utilization, environmental protection and water saving, and particularly relates to a gas preheating system and a gas preheating method for replacing flue gas waste heat.

Background

The coal-fired flue gas desulfurization process commonly used at present mainly comprises a limestone-gypsum wet flue gas desulfurization process (gypsum method for short) which accounts for about 95 percent, and for example, the limestone-gypsum wet flue gas desulfurization process comprises other wet processes such as an alkali method/double alkali method, an ammonia method, a magnesium method and the like, and accounts for more than 99 percent of the flue gas desulfurization process. The clean flue gas at the outlet of the wet desulphurization process is low-temperature saturated flue gas, and a large amount of water vapor has a large amount of latent heat but lacks an effective means for recycling due to too low temperature. In addition, a large amount of water vapor is contained in the saturated flue gas and is discharged into the air, so that the waste of water sources is caused.

For the recovery of the part of heat, waste heat recovery is generally performed at the front end of the flue gas desulfurization, for example, a low-temperature economizer is additionally arranged, or MGGH is adopted to heat saturated clean flue gas at a desulfurization outlet, and the like.

Due to the limitation of economic conditions and technical conditions, especially the existence of the difficult problem of corrosion of front-end raw flue gas to heat exchange equipment, the realization of waste heat utilization at a desulfurization flue gas purification end is always a research focus. However, because the temperature of the clean flue gas is too low, the quality of the recovered waste heat is too low, the quality of the recovered heat is generally improved by adopting a heat pump, the investment and operation cost is high, and the economic efficiency and the popularization value are difficult to achieve.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art and provides a gas preheating system and a gas preheating method for replacing flue gas waste heat.

The technical scheme for solving the technical problems is as follows: a gas preheating system for replacing flue gas waste heat comprises a first tower, a second tower, a gas medium conveying pipeline and a gas medium outlet pipeline, wherein the first tower, the second tower, the gas medium conveying pipeline and the gas medium outlet pipeline are connected with a flue gas inlet pipeline; the second tower is connected with a gas medium outlet pipeline, the gas medium conveying pipeline is respectively connected with a first branch and a second branch, the first branch is connected with the second tower, and the second branch is connected with the gas medium outlet pipeline.

The invention has the beneficial effects that: the gas preheating system comprises two modules (a first tower, a second tower and related parts) which take liquid as a medium to absorb and release heat, wherein the liquid medium absorbs the heat in hot and high-temperature wet flue gas through the first module, the temperature of the liquid medium is increased, the liquid medium with the increased temperature enters the second module and is in direct contact with gas entering the second module to transfer the heat in the liquid medium to the gas, so that the temperature of the gas is increased, and the purpose of replacing the waste heat of the flue gas is achieved. In the first heat replacement process, the temperature of high-temperature wet flue gas is reduced, and due to condensation, water vapor in the wet flue gas is condensed into water and collected into a liquid medium to play a role in recovering water, so that the content of the water vapor in the flue gas is obviously reduced, the aim of weakening white smoke plume is fulfilled, and the emission of the flue gas is facilitated; in the second heat replacement process, the gas is heated by direct heat exchange, and meanwhile, a path of indirect heat exchange bypass is additionally arranged to mix hot dry gas with the gas subjected to direct heat exchange, so that the saturated damp and hot gas is prevented from being condensed by water drops, and the heated gas can be utilized by other systems; the function of utilizing the waste heat of the flue gas is completed through the heat replacement process of the two modules. The low-temperature low-quality waste heat at the clean flue gas side is transferred to the gas side by using the liquid medium, so that the gas preheating is completed, and the heat recovery process is realized; adopt liquid medium replacement former wet flue gas heat to preheat gas, greatly improved heat transfer efficiency, make desulfurization, dust collection efficiency promote by a wide margin and give gas with heat transfer, gas can be carried in the boiler, improves the air supply temperature of boiler to improve its work efficiency, reduce boiler running cost by a wide margin.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, a heating device is connected to the second branch.

The beneficial effect of adopting the further scheme is that: the second gas subjected to heat exchange in the second tower can be connected with external equipment through a gas medium outlet pipeline, the second gas heated by the heating device converges to the gas medium outlet pipeline through a second branch, and the unsaturated high-temperature gas obtained after the two second gases in different states are mixed enters the external equipment for utilization.

Further, the heating device comprises a heater or/and a heat exchanger; when the heating device comprises a heater, the heater is directly connected with the second branch circuit; when the heating device comprises a heat exchanger, the tube side of the heat exchanger is connected with a heat exchange pipeline, and the shell side of the heat exchanger is connected with the second branch.

The beneficial effect of adopting the further scheme is that: the second branch can be directly heated by electric heating or other heating methods. The heat exchanger can also be used for carrying out heat exchange on the second branch, and the heat source of the heat exchanger is from the heat exchange pipeline. Or simultaneously heating by the heater and heat exchange.

Furthermore, a first branch pipeline and a second branch pipeline are connected to the first conveying pipeline, the first branch pipeline is connected with a second spraying device in the second tower, the second branch pipeline is connected with the top of the second tower, and one part of the second branch pipeline is connected with the tube side of the heat exchanger as a heat exchange pipeline.

The beneficial effect of adopting the further scheme is that: the second branch pipe can be heated by connecting the middle section of the second branch pipe serving as a heat exchange pipe with the pipe side of the heat exchanger, namely, the gas of the second branch pipe is heated by adopting the high-temperature heat exchange liquid at the bottom of the first tower through heat exchange.

Further, still include flue gas inlet pipeline and flue gas outlet pipeline, the flue gas inlet pipeline with first tower lateral wall is connected, the flue gas outlet pipeline with the top of first tower is connected.

The beneficial effect of adopting the further scheme is that: can let in into first tower through flue gas inlet pipeline with the high temperature flue gas through desulfurization, can export first tower through the flue gas outlet pipeline with the flue gas through spraying cooling and further desulfurization.

Further, the first conveying pipeline and the second conveying pipeline are respectively connected with a conveying pump.

The beneficial effect of adopting the further scheme is that: the heat exchange liquid at the bottom of the first tower and the spraying liquid at the bottom of the second tower can be conveyed by the conveying pump.

Further, the heat exchange device comprises a first spraying device, and the spraying liquid of the first spraying device adopts clear water or alkaline solution; the particle size of the water mist liquid drops sprayed by the first spraying device and the second spraying device is less than 100 mu m.

The beneficial effect of adopting the further scheme is that: the particle size of the water mist droplets sprayed by the first spraying device and the second spraying device is less than 100 mu m, and the water mist droplets have a very large heat transfer coefficient, so that the heat in the flue gas can be absorbed in a very short time (the time for the flue gas to enter the first tower through the inlet pipeline), and the temperature of the flue gas is reduced. Meanwhile, the liquid drops contact residual sulfur dioxide in the flue gas, and can absorb the sulfur dioxide in the flue gas and enter the spraying liquid, so that the content of the sulfur dioxide in the flue gas is further reduced; meanwhile, as the temperature of the original wet flue gas is reduced, water vapor contained in the flue gas is partially condensed to form condensate, and the condensate is mixed in the spray liquid; the spraying liquid further contacts the micro-dust contained in the flue gas, so that the micro-dust is adsorbed on the liquid drops of the condensate, and the content of the micro-dust in the flue gas is reduced.

An air preheating method for replacing flue gas waste heat comprises the following steps:

s1, conveying the desulfurized flue gas into a first tower, directly contacting with a heat exchange device in the first tower, absorbing heat of the flue gas by a heat exchange medium in the heat exchange device, allowing a condensate in the flue gas to fall to the bottom of the first tower, conveying the condensate and the heat exchange medium in the heat exchange device into a second tower through a second conveying pipeline as heat exchange liquid respectively, and discharging the heat-exchanged flue gas from the first tower;

s2, enabling the gas medium to enter a second tower through a first branch of a gas medium conveying pipeline, enabling the gas medium to directly contact with heat exchange liquid sprayed by a second spraying device for heat exchange to obtain first gas and a liquid medium which are heated and humidified, and conveying the liquid medium to a heat exchange device in the first tower through a second conveying pipeline to serve as a heat exchange medium;

and S3, merging and mixing the second gas conveyed by the second branch of the gas medium conveying pipeline and the first gas in the gas medium outlet pipeline on the second tower for utilization.

The invention has the beneficial effects that: according to the air preheating method, the liquid medium is utilized to transfer the low-temperature low-quality waste heat at the clean smoke side to the air side, so that gas preheating is completed, and the heat recovery process is realized. Adopt liquid medium replacement former wet flue gas heat to preheat the air, greatly improved heat transfer efficiency, make desulfurization, dust collection efficiency promote by a wide margin and with heat transfer for the air, carry in the boiler, improve the air supply temperature of boiler to improve its work efficiency, reduce boiler running cost by a wide margin.

Further, in S3, the heating device is a heater, the gas medium is connected to the heater through a second branch of the gas medium conveying pipeline, and the gas in the second branch is heated by the heater; or, the heating device is a heat exchanger, the gas medium is connected with the shell side of the heat exchanger through a second branch of the gas medium conveying pipeline, the tube side of the heat exchanger is connected with the heat exchange pipeline, and the gas in the second branch is heated through the heat exchange pipeline; or the heating device comprises a heater and a heat exchanger, and the gas in the second branch is heated by the heater and the heat exchanger simultaneously.

The beneficial effect of adopting the further scheme is that: the gas of the second branch can be heated by adopting a heat exchange pipeline, preferably, a pipeline where high-temperature heat exchange liquid which is subjected to heat exchange at the bottom of the first tower is located is used as the heat exchange pipeline to heat the gas of the second branch, the gas of the second branch can be directly heated by utilizing a heater, and the heat exchange liquid heating and the heater heating can be simultaneously adopted.

Further, the heat exchange device comprises a first spraying device; in S1, the desulfurized flue gas is conveyed into the first tower and is in direct contact with the liquid medium sprayed by the first spraying device, the heat of the flue gas is absorbed by the liquid medium, and the condensate in the flue gas is converged with the liquid medium and falls into the bottom of the first tower to form the heat exchange liquid.

The beneficial effect of adopting the further scheme is that: the first spraying device is adopted to spray the liquid medium, so that the heat exchange efficiency with the flue gas can be improved.

Drawings

Fig. 1 is a schematic structural diagram of a gas preheating system for replacing flue gas waste heat according to the present invention.

In the drawings, the components represented by the respective reference numerals are listed below:

a1, a flue gas inlet pipeline; a2, a flue gas outlet pipeline; b1, a gas medium conveying pipeline; b11, a first branch pipe; b12, a second branch pipe; b2, a gas medium outlet pipeline;

1. a first tower; 2. a second tower; 3. a first delivery pump; 4. a second delivery pump; 5. a first spraying device; 6. a second spraying device; 7. a heating device.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

Example 1

As shown in fig. 1, the gas preheating system for replacing flue gas waste heat of this embodiment includes a first tower 1, a second tower 2, a gas medium conveying pipeline B1 and a gas medium outlet pipeline B2, which are used for connecting a flue gas inlet pipeline a1, the bottom of the first tower 1 is connected to a second spraying device 6 in the second tower 2 through a first conveying pipeline, and the bottom of the second tower 2 is connected to a heat exchange device in the first tower 1 through a second conveying pipeline; the second tower 2 is connected with a gas medium outlet pipeline B2, the gas medium conveying pipeline B1 is respectively connected with a first branch B11 and a second branch B12, the first branch B11 is connected with the second tower B12, and the second branch B12 is connected with the gas medium outlet pipeline B2.

Wherein, the indirect heat transfer mode of heat exchanger can be selected to the heat transfer device of this embodiment, also can select the mode of spraying to carry out direct heat transfer. Preferably, the heat exchange device comprises a first spraying device 5.

In this embodiment, the second branch B12 delivers the dry high temperature gas to mix with the high temperature wet gas output from the gas medium outlet line B2 to obtain an unsaturated gas. The second branch B12 can deliver the dry high temperature gas directly from the upstream high temperature gas, or can be heated by a heating device to obtain the dry high temperature gas, see example 2 specifically.

The gas preheating system of this embodiment may be used to preheat air, nitrogen, or other gases that need to be preheated. The system comprises 3 heat transfer modules which take water (other liquid media can be adopted) as liquid media, namely a first tower 1 as a high-temperature wet flue gas heat release module, a second tower 2 as a gas heat absorption module and a second branch B12 as a gas bypass. The media are conveyed among the heat transfer modules through pipelines and the like, a first branch B11 of the gas media conveying pipeline B1 is used as a direct heat exchange air pipeline, and a second branch B12 is used as an indirect heat exchange air pipeline. The specific heat transfer process is as follows: the wet flue gas of high temperature after the desulfurization enters into first tower 1 from the well lower part of first tower 1, and the heat transfer process is accomplished in first tower 1 with the spray solution that first spray set 5 sprayed direct contact, and the heat of the wet flue gas of high temperature is absorbed by the spray solution, and the temperature reduces, and the condensate in the wet flue gas of high temperature converges with the spray solution, falls into first tower 1 bottom and forms heat exchange liquid, and the clean flue gas after the cooling is discharged from first tower 1. Wherein, gas enters into the second tower 2 from the middle-lower part of the second tower 2 through the first branch of the gas medium conveying pipeline B1, and is directly contacted with the heat-exchange liquid which is conveyed into the second tower 2 from the first tower 1 and is sprayed by the second spraying device 6, the heat of the heat-exchange liquid is absorbed by the gas, the gas temperature is increased, the temperature of the heat-exchange liquid falls into the bottom of the second tower 2 after being reduced, and the sprayed liquid is conveyed back to the first spraying device in the first tower 1 for spraying again. The gas flows out of the second tower 2 after being heated and humidified in the second tower. The gas supplied from the second branch B12 of the gas medium supply line B1 is mixed with the hot and humid gas flowing out of the second column 2 to form an unsaturated hot gas, and the unsaturated hot gas is supplied to an external device for use, for example, a boiler or other device requiring the use of a hot gas.

In this embodiment, first tower 1 is the vertical or horizontal heat transfer device that spray liquid and wet flue gas of high temperature formed, and spray liquid and wet flue gas of high temperature direct contact heat transfer in first tower 1, and first tower 1 adopts the dead space structure, or also can not adopt the dead space structure and set up the filler. The second tower is a vertical or horizontal heat exchange device formed by heat exchange liquid and gas, the heat exchange liquid and the gas are in direct contact heat exchange, and the second tower 2 adopts a hollow section structure or can be provided with fillers without adopting the hollow section structure.

As shown in fig. 1, a specific solution of this embodiment is that the gas preheating system further includes a flue gas inlet pipeline a1 and a flue gas outlet pipeline a2, the flue gas inlet pipeline a1 is connected to the side wall of the first tower 1, and the flue gas outlet pipeline a2 is connected to the top of the first tower 1. Can let in into first tower through flue gas inlet pipeline with the high temperature flue gas through desulfurization, can export first tower through the flue gas outlet pipeline with the flue gas through spraying cooling and further desulfurization.

As shown in fig. 1, the first conveying pipeline and the second conveying pipeline of this embodiment are respectively connected with a conveying pump. As shown in fig. 1, a first delivery pump 3 is connected to the first delivery pipeline, and the gas is subjected to heat exchange by contacting the gas with a heat exchange liquid driven by the first delivery pump 3; and a second conveying pump 4 is connected to the second conveying pipeline, the second conveying pump 4 drives the spraying liquid to contact with the high-temperature clean flue gas, the heat in the original wet flue gas is absorbed, and the temperature of the high-temperature clean flue gas is reduced. Can carry the heat exchange liquid of first tower bottom and the spray liquid of second tower bottom through the delivery pump, the circulation heat transfer effect in first tower and the second tower can be increased to the delivery pump. In the process of condensing and heat exchanging between the spraying liquid and the high-temperature clean flue gas, the high-temperature clean flue gas is further washed, and SO in the clean flue gas₂Dust, condensable particulates, and the likeThe contaminants are further removed. The high-temperature clean flue gas reduces the temperature, the partial pressure of saturated steam is reduced, a large amount of condensed water is recovered, water for other equipment is supplemented, and the water consumption is reduced. The moisture content of the high-temperature clean flue gas is reduced, and the phenomenon of white smoke plume of the clean flue gas can be reduced or eliminated. The first transfer pump 3 transfers the heat exchange liquid containing the heat source to the second tower, and the heat exchange liquid is contacted with the gas in the second tower, and the gas absorbs the heat brought by the heat exchange liquid in the second tower, so that the temperature rise is completed.

The spraying liquid of the first spraying device 5 in this embodiment is a liquid heat absorbing medium, absorbs heat from high-temperature wet flue gas, and the temperature of the spraying liquid is raised, and the spraying liquid may be clear water or an alkaline solution, and the alkaline solution may be a calcium hydroxide solution, a sodium carbonate solution, or other alkaline solutions. The sprayed liquid absorbs heat and is heated up and then is conveyed into the second tower 2 as heat exchange liquid. The heat exchange liquid is used as a liquid heat release medium in the second tower 2, heat is directly transferred to gas, and the temperature of the gas is reduced. Spraying liquid and heat exchange liquid are respectively sprayed by a first spraying device 5 and a second spraying device 6 under certain pressure to form fine particles to complete the heat replacement process, and the first spraying device 5 and the second spraying device 6 can adopt nozzles or other spraying modes.

The particle diameter of the water mist droplets sprayed by the first spraying device 5 and the second spraying device 6 of the present embodiment is less than 100 μm. The diameters of the water mist droplets sprayed by the first spraying device 5 and the second spraying device 6 are less than 100 micrometers, and the water mist droplets have a very large heat transfer coefficient, so that the heat in the flue gas can be absorbed in a very short time (the time for the flue gas to enter the first tower through the inlet pipeline), and the temperature of the flue gas can be reduced. Meanwhile, the liquid drops contact residual sulfur dioxide in the flue gas, and can absorb the sulfur dioxide in the flue gas and enter the spraying liquid, so that the content of the sulfur dioxide in the flue gas is further reduced; meanwhile, as the temperature of the original wet flue gas is reduced, water vapor contained in the flue gas is partially condensed to form condensate, and the condensate is mixed in the spray liquid; the spraying liquid further contacts the micro-dust contained in the flue gas, so that the micro-dust is adsorbed on the liquid drops of the condensate, and the content of the micro-dust in the flue gas is reduced.

The gas preheating system of this embodiment, including using liquid to absorb, release two modules of heat (first tower, second tower and relevant part) as the medium, through first module, liquid medium absorbs the heat in the wet flue gas of hot high temperature, and the liquid medium temperature risees, and the liquid medium after the rising temperature enters into second module, and with the gaseous direct contact who enters into the second module, gives gas with the heat transfer in the liquid medium to gas temperature obtains promoting, reaches the purpose of replacement flue gas waste heat. In the first heat replacement process, the temperature of high-temperature wet flue gas is reduced, and due to condensation, water vapor in the wet flue gas is condensed into water and collected into a liquid medium to play a role in recovering water, so that the content of the water vapor in the flue gas is obviously reduced, the aim of weakening white smoke plume is fulfilled, and the emission of the flue gas is facilitated; in the second heat replacement process, the gas is heated by direct heat exchange, and meanwhile, a path of indirect heat exchange bypass is additionally arranged to mix hot dry gas with the gas subjected to direct heat exchange, so that the saturated damp and hot gas is prevented from being condensed by water drops, and the heated gas can be utilized by other systems; the function of utilizing the waste heat of the flue gas is completed through the heat replacement process of the two modules. The embodiment utilizes the liquid medium to transfer the low-temperature low-quality waste heat of the clean flue gas side to the gas side, completes gas preheating and realizes the heat recovery process. This embodiment uses dalton vapor partial pressure theory as the basis, adopts the cold source to absorb wet saturated flue gas heat, then gives the technical measure of cold gas with the heat special delivery, realize former saturated flue gas cooling, vapor is appeared, release latent heat of vaporization simultaneously, absorb surplus sulfur dioxide and dust particle in the former flue gas, make desulfurization, dust collection efficiency promote by a wide margin, and give gas with heat transfer, carry the boiler in, improve the air supply temperature of boiler, thereby improve its efficiency, thereby reduce boiler running cost by a wide margin.

Example 2

On the basis of embodiment 1, the gas preheating system of the present embodiment further includes a heating device 7. The second gas after heat exchange in the second tower 2 can be connected with external equipment through a gas medium outlet pipeline B2, the second gas heated by the heating device 7 can be converged to a gas medium outlet pipeline B2 through a second branch B12, and the two second gases in different states are mixed to obtain unsaturated high-temperature gas which enters the external equipment for utilization.

The heating device 7 may only adopt a heater, may only adopt a heat exchanger, and may adopt both a heater and a heat exchanger. When the heater is used to heat the second branch B12, the heater may be electric heating, electromagnetic heating, steam heating, or the like. When the heat exchanger is used for heating the second branch B12, the tube side of the heat exchanger may be connected to the heat exchange pipeline, and the shell side of the heat exchanger may be connected to the second branch. In the embodiment, the second branch B12 of the gas medium conveying pipeline B1 is used as an indirect heat exchanger for heating by gas bypass, the gas is not in direct contact with the heating medium, the humidity of the heated gas is not increased, the heat source of the heat exchanger may be the heat exchange liquid conveyed from the first tower 1, and the heat source of the heat exchanger may also be other heat sources.

A preferred scheme of this embodiment is that the first delivery line is connected with a first branch line and a second branch line, the first branch line is connected with a second spraying device 6 in the second tower 2, the second branch line is connected with the top of the second tower 2, and the middle part of the second branch line is connected with the tube side of the heat exchanger as a heat exchange line. The second branch pipe can be heated by connecting the middle section of the second branch pipe serving as a heat exchange pipe with the pipe side of the heat exchanger, namely, the gas of the second branch pipe is heated by adopting the high-temperature heat exchange liquid at the bottom of the first tower through heat exchange. The gas in the gas medium outlet line B2 is a mixture of the hot humid gas flowing out through the second tower 2 and the gas heated by the heating device 7, and is an unsaturated gas. The tube side of the heat exchanger is connected with the second branch pipeline, the heat exchanger heats gas by using heat exchange liquid subjected to heat exchange in the first tower 1, and the heat exchange liquid subjected to heat exchange with the gas flows back into the second tower 2 to be used as spraying liquid to be conveyed into the first tower 1.

The gas is heated in the second tower and divided into two parts, and one part is directly contacted with the liquid medium in the second tower to finish the heating process; the other part is heated by a heating device to finish the temperature rise process. In the second tower, in the process of heating up a part of gas, the heat exchange liquid medium volatilizes into the air to enable the gas to reach a saturated state; the other part of the dry heating gas is mixed with the saturated gas discharged by the second tower to form unsaturated gas, so that the gas humidity is reduced, liquid drops are prevented from being condensed, and the safety requirements of dewing prevention and operation processes of equipment, pipelines and the like in the heating gas conveying process are met.

Example 3

The air preheating method for replacing the flue gas waste heat comprises the following steps:

s1, conveying the desulfurized flue gas into the first tower 1, directly contacting with a heat exchange device in the first tower 1, absorbing heat of the flue gas by a heat exchange medium in the heat exchange device, allowing a condensate in the flue gas to fall to the bottom of the first tower 1, conveying the condensate and the heat exchange medium in the heat exchange device into the second tower 2 as heat exchange liquids through a second conveying pipeline respectively, and discharging the heat-exchanged flue gas from the first tower 1;

s2, enabling the gas medium to enter the second tower 2 through a first branch B11 of the gas medium conveying pipeline B1, enabling the gas medium to directly contact with heat exchange liquid sprayed by the second spraying device 6 for heat exchange to obtain first gas and a liquid medium which are heated and humidified, and conveying the liquid medium to a heat exchange device in the first tower 1 through a second conveying pipeline to serve as a heat exchange medium;

and S3, merging and mixing the second gas conveyed by the second branch B12 of the gas medium conveying pipeline B1 with the first gas in the gas medium outlet pipeline on the second tower for utilization.

The heat exchange device of this embodiment can select the indirect heat transfer mode of heat exchanger, also can select the mode of spraying to carry out direct heat transfer. Preferably, the heat exchange device comprises a first spraying device 5; in S1, the desulfurized flue gas is conveyed into the first tower 1 and directly contacts with the liquid medium sprayed by the first spraying device 5, the heat of the flue gas is absorbed by the liquid medium, and the condensate in the flue gas is converged with the liquid medium and falls into the bottom of the first tower 1 to form the heat exchange liquid. The liquid medium sprayed by the first spraying device 5 is the spraying liquid described in the embodiments 1 and 2.

The second branch B12 of this embodiment can directly deliver the dry high temperature gas to mix with the high temperature wet gas output from the gaseous medium outlet line B2 to obtain the unsaturated gas.

The air preheating method of the embodiment comprises two modules (a first tower, a second tower and related parts) which take liquid as a medium to absorb and release heat, wherein the liquid medium absorbs the heat in hot and high-temperature wet flue gas through the first module, the temperature of the liquid medium is increased, the liquid medium with the increased temperature enters the second module and is in direct contact with gas entering the second module to transfer the heat in the liquid medium to the gas, so that the temperature of the gas is increased, and the purpose of replacing the waste heat of the flue gas is achieved. In the first heat replacement process, the temperature of high-temperature wet flue gas is reduced, and due to condensation, water vapor in the wet flue gas is condensed into water and collected into a liquid medium to play a role in recovering water, so that the content of the water vapor in the flue gas is obviously reduced, the aim of weakening white smoke plume is fulfilled, and the emission of the flue gas is facilitated; in the second heat replacement process, the gas is heated by direct heat exchange, and meanwhile, a path of indirect heat exchange bypass is additionally arranged to mix hot dry gas with the gas subjected to direct heat exchange, so that the saturated damp and hot gas is prevented from being condensed by water drops, and the heated gas can be utilized by other systems; the function of utilizing the waste heat of the flue gas is completed through the heat replacement process of the two modules. This embodiment uses dalton vapor partial pressure theory as the basis, adopts the cold source to absorb wet saturated flue gas heat, then gives the technical measure of cold gas with the heat special delivery, realize former saturated flue gas cooling, vapor is appeared, release latent heat of vaporization simultaneously, absorb surplus sulfur dioxide and dust particle in the former flue gas, make desulfurization, dust collection efficiency promote by a wide margin, and give gas with heat transfer, carry the boiler in, improve the air supply temperature of boiler, thereby improve its efficiency, thereby reduce boiler running cost by a wide margin.

Example 4

In addition to example 3, in S3, the gas in the second branch B12 may be heated to a dry high-temperature gas by the heating device 7, and the temperature of the gas in the second branch B12 may be increased. The second gas after heat exchange in the second tower 2 can be connected with external equipment through a gas medium outlet pipeline B2, the second gas heated by the heating device 7 can be converged to a gas medium outlet pipeline B2 through a second branch B12, and the two second gases in different states are mixed to obtain unsaturated high-temperature gas which enters the external equipment for utilization.

The heating device 7 may only adopt a heater, may only adopt a heat exchanger, and may adopt both a heater and a heat exchanger. When the heater is used to heat the second branch B12, the heater may be electric heating, electromagnetic heating, steam heating, or the like. When the heat exchanger is used for heating the second branch B12, the tube side of the heat exchanger may be connected to the heat exchange pipeline, and the shell side of the heat exchanger may be connected to the second branch. In the embodiment, the second branch B12 of the gas medium conveying pipeline B1 is used as an indirect heat exchanger for heating by gas bypass, the gas is not in direct contact with the heating medium, the humidity of the heated gas is not increased, the heat source of the heat exchanger may be the heat exchange liquid conveyed from the first tower 1, and the heat source of the heat exchanger may also be other heat sources.

A preferred scheme of this embodiment is that the first delivery line is connected with a first branch line and a second branch line, the first branch line is connected with a second spraying device 6 in the second tower 2, the second branch line is connected with the top of the second tower 2, and the middle part of the second branch line is connected with the tube side of the heat exchanger as a heat exchange line. The second branch pipe can be heated by connecting the middle section of the second branch pipe serving as a heat exchange pipe with the pipe side of the heat exchanger, namely, the gas of the second branch pipe is heated by adopting the high-temperature heat exchange liquid at the bottom of the first tower through heat exchange. The gas in the gas medium outlet line B2 is a mixture of the hot humid gas flowing out through the second tower 2 and the gas heated by the heating device 7, and is an unsaturated gas. The tube side of the heat exchanger is connected with the second branch pipeline, the heat exchanger heats gas by using heat exchange liquid subjected to heat exchange in the first tower 1, and the heat exchange liquid subjected to heat exchange with the gas flows back into the second tower 2 to be used as spraying liquid to be conveyed into the first tower 1.

By adopting the gas preheating system and the gas preheating method provided by the embodiment of the invention, the gas in the flue gas can be absorbed70 percent of waste heat is recycled, the final temperature of the flue gas is reduced to be below 30 ℃, the content of water vapor in the flue gas is reduced to be below 5 percent, and the content of sulfur dioxide is reduced to be 10mg/m³The dust content is reduced to 3mg/m³The following.

At a flue gas flow rate of 100 ten thousand Nm³The conventional coal-fired flue gas is exemplified by about 7% of water vapor, which is mainly derived from the water attached to the coal, the evaporation of crystal water, and the combustion products of hydrogen elements in the coal, and the water vapor contained in the combustion air.

The cold air is preheated by the second tower, the preheated air participates in the change caused by the combustion of the boiler, and the heat transfer process is reflected through the water vapor content and the temperature change. Specifically, the cold air is preheated by the second tower from 0 ℃ to 34.48 ℃, and the total flow rate of the preheated air is 984554Nm³The water vapor content in the air is increased by 3.05 percent from 0.6 percent, so that the total amount of the water vapor in the air is increased by 2.44 percent, and the water content in the coal-fired flue gas is increased from 7 percent to 9.71 percent after the water vapor participates in combustion; further causing the net flue gas discharge temperature of the wet desulphurization system to rise from 48.82 ℃ to 52.63 ℃, and correspondingly, the water vapor content rises from 11.34% to 13.69%;

the second tower recovers heat to be used for preheating air, the energy consumption of the preheated air is 9.1MW, namely the energy consumption of a corresponding air heater is saved by 9.1 MW; under the condition of low-humidity air, the energy consumption of the air heater is not considered, and the temperature of the preheated air rises, so that the smoke exhaust temperature of the smoke side of the air preheater rises from 120 ℃ to 138.31 ℃; the rise in the exhaust gas temperature causes 6.7MW of heat to be emitted; meanwhile, the temperature rise process of water vapor in the preheated air causes 1.4MW heat emission; the heat supplement quantity in the whole circulation is 9.1MW, so that the subsequent discharged heat quantity is 8.1MW, wherein 1.0MW is actually utilized;

if the positive influence of the preheated air on the improvement of the combustion efficiency of the boiler is considered, the heat utilization effect and the unit coal consumption reduction effect are better.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.