阅读说明：本技术 一种垃圾焚烧系统烟气余热回收装置 (Waste incineration system flue gas waste heat recovery device ) 是由 凌佩武 叶龙祥 张维辉 郝琦 徐晓芳 于 2021-08-25 设计创作，主要内容包括：本发明公开了一种垃圾焚烧系统烟气余热回收装置,包括垃圾焚烧处理装置、具有喷射器的吸收塔和具有喷淋装置的溶液发生塔,溶液发生塔与吸收塔的喷射器相连通。经垃圾焚烧处理装置焚烧处理后的烟气分别进入吸收塔和溶液发生塔,喷射器喷出高浓度液体吸湿剂吸收烟气中的水蒸汽而变成低浓度溶液,低浓度溶液通过热交换装置将热量传导给热水管网；此时的低浓度溶液由溶液发生塔内的喷淋装置向下喷出,与溶液发生塔内的烟气接触换热,低浓度溶液升温蒸发掉水分而变成高浓度的液体吸湿剂,高浓度的液体吸湿剂重新进入吸收塔吸湿。本发明可充分回收烟气中的余热,并降低烟气露点温度,避免烟气结露腐蚀烟囱,可提高垃圾发电厂的热效率。(The invention discloses a flue gas waste heat recovery device of a waste incineration system, which comprises a waste incineration treatment device, an absorption tower with an ejector and a solution generation tower with a spraying device, wherein the solution generation tower is communicated with the ejector of the absorption tower. The flue gas incinerated by the garbage incineration device respectively enters an absorption tower and a solution generation tower, a high-concentration liquid hygroscopic agent is sprayed by an ejector to absorb water vapor in the flue gas and change the water vapor into a low-concentration solution, and the low-concentration solution transmits heat to a hot water pipe network through a heat exchange device; the low-concentration solution is sprayed downwards by a spraying device in the solution generating tower and contacts with the flue gas in the solution generating tower to exchange heat, the low-concentration solution is heated to evaporate water to become a high-concentration liquid moisture absorbent, and the high-concentration liquid moisture absorbent enters the absorption tower again to absorb moisture. The invention can fully recover the waste heat in the flue gas, reduce the dew point temperature of the flue gas, avoid the flue gas from dewing and corroding a chimney and improve the heat efficiency of a garbage power plant.)

1. A flue gas waste heat recovery device of a waste incineration system comprises a waste incinerator for incinerating waste, a waste heat boiler for converting the heat of flue gas into steam to generate electricity, a post-treatment device for purifying the flue gas, a hot water pipe network for providing hot water, and a heat exchange device comprising a heat supply end and a heat absorption end, wherein the heat absorption end of the heat exchange device is connected to the hot water pipe network, the flue gas waste heat recovery device is characterized by further comprising an absorption tower and a solution generation tower which are connected with the post-treatment device in parallel through pipelines, an ejector is arranged in the absorption tower, a spray device is arranged in the solution generation tower, the absorption tower is communicated with the heat supply end of the heat exchange device through a first output pipeline, the heat supply end of the heat exchange device is communicated with the spray device in the solution generation tower through a heat supply pipeline, and the solution generation tower is communicated with the ejector of the absorption tower through a second output pipeline, the working steps of the waste heat recovery device are as follows:

the method comprises the following steps that garbage is incinerated in a garbage incinerator to form high-temperature flue gas, and the high-temperature flue gas enters a waste heat boiler to release heat to generate steam for power generation;

after the flue gas is purified by the post-treatment device, one part of the flue gas enters an absorption tower, and the other part of the flue gas enters a solution generation tower;

the ejector in the absorption tower sprays high-concentration liquid moisture absorbent, the high-concentration liquid moisture absorbent absorbs water vapor and heat in the flue gas entering the absorption tower, so that the water vapor and the heat are changed into low-concentration solution with increased temperature, the low-concentration solution enters the heat supply end of the heat exchange device through the first output pipeline to emit heat, and the heat absorption end of the heat exchange device conducts the heat to the hot water pipe network to increase the temperature of the hot water pipe network;

the low concentration solution that the temperature that flows from heat exchange device becomes low gets into in the solution takes place the tower, and spout downwards through spray set, the low concentration solution that the temperature becomes low fully contacts the heat transfer with the flue gas that gets into in the solution takes place the tower, the temperature of flue gas reduces, and the low concentration solution that the temperature becomes low intensifies, moisture in the low concentration solution evaporates into water vapor, then become the liquid hygroscopic agent of high concentration, the liquid hygroscopic agent rethread second output pipeline of high concentration gets into the absorption tower, and spout downwards through the sprayer, thereby realize the circulation flow of liquid hygroscopic agent.

2. The waste incineration system flue gas waste heat recovery device according to claim 1, wherein the first output pipeline is provided with a first circulating pump.

3. The waste incineration system flue gas waste heat recovery device according to claim 1, wherein a second circulation pump is provided on the second output pipeline.

4. The waste incineration system flue gas waste heat recovery device according to claim 1, wherein the liquid desiccant is a lithium bromide solution.

5. The waste incineration system flue gas waste heat recovery device according to claim 1, wherein a flue gas valve is provided on a pipeline connecting the post-treatment device and the solution generation tower.

6. The waste incineration system flue gas waste heat recovery device according to claim 1, further comprising a condensation tower, wherein the condensation tower is communicated with the upper part of the solution generation tower through a pipeline arranged in the middle part, the condensation tower is communicated with a pipeline connecting the absorption tower and the post-treatment device through a pipeline arranged at the top part, a condensed water outlet is arranged at the bottom part of the condensation tower, and an ejector is arranged in the condensation tower;

in the step d, the flue gas and the water vapor in the solution generating tower enter a condensing tower to exchange heat with low-temperature condensed water sprayed from an injector in the condensing tower, the flue gas and part of the water vapor which is not condensed enter an absorption tower, so that the step c is continued, and the condensed water formed by condensing the water vapor is output outwards through a condensed water outlet.

7. The waste incineration system flue gas waste heat recovery device of claim 1, wherein the condensed water outlet is communicated with a heat supply end of another heat exchange device through a pipeline, and a heat absorption end of the heat exchange device is connected to a hot water pipeline network.

8. The waste incineration system flue gas waste heat recovery device according to claim 1 or 7, wherein the heat exchange device is a water-solution plate heat exchanger.

Technical Field

The invention belongs to the technical field of domestic garbage incineration flue gas treatment and waste heat recovery, and particularly relates to a flue gas waste heat recovery device of a garbage incineration system.

Background

Waste incineration has attracted much attention because of a series of advantages such as high harmless degree, large volume reduction, recoverable heat energy (power generation and heat supply), timely treatment and the like, and a plurality of cities construct waste incineration power plants to treat domestic waste. In the prior art, people usually burn the garbage in a garbage burning boiler to generate high-temperature flue gas, the high-temperature flue gas is recycled in a waste heat boiler, the flue gas with the reduced temperature enters a flue gas purification system for purification treatment, and the treated flue gas can be discharged outwards. At present, the temperature of the flue gas after purification treatment is generally between 130 and 160 ℃, and the water content in the flue gas is about 28%, that is, a large amount of residual heat exists in the flue gas at this moment, if the flue gas is directly discharged, the waste of heat energy is caused, and meanwhile, the flue gas with high water content forms a large amount of white smoke plume when being discharged. The waste heat in the purified flue gas mainly comprises two parts of flue gas sensible heat and water vapor liquefaction latent heat, and the recovery rate of the water vapor liquefaction latent heat by the existing waste heat recovery and utilization technology is extremely low. In particular, when the temperature of the flue gas is reduced below the dew point, the flue gas condensate can cause corrosion of the equipment and the chimney.

Disclosure of Invention

The invention aims to provide a flue gas waste heat recovery device of a waste incineration system, which can fully recover the waste heat in the flue gas, can reduce the dew point temperature of the flue gas, avoids the flue gas from dewing and corroding a chimney due to waste heat utilization, and effectively eliminates the generation of white smoke plume while improving the heat efficiency of a waste power plant.

In order to achieve the purpose, the invention adopts the following technical scheme:

a flue gas waste heat recovery device of a waste incineration system comprises a waste incinerator for incinerating waste, a waste heat boiler for converting the heat of flue gas into steam to generate electricity, a post-treatment device for purifying the flue gas, a hot water pipe network for providing hot water, and a heat exchange device comprising a heat supply end and a heat absorption end, the heat absorption end of the heat exchange device is connected with the hot water pipe network, and the heat exchange device also comprises an absorption tower and a solution generation tower which are connected with the post-treatment device in parallel through pipelines, the absorption tower is internally provided with an ejector, the solution generating tower is internally provided with a spraying device, the absorption tower is communicated with the heat supply end of the heat exchange device through a first output pipeline, the heat supply end of the heat exchange device is communicated with the spraying device in the solution generating tower through a heat supply pipeline, the solution generating tower is communicated with the ejector of the absorption tower through a second output pipeline, and the working steps of the waste heat recovery device are as follows:

a. the method comprises the following steps that garbage is incinerated in a garbage incinerator to form high-temperature flue gas, and the high-temperature flue gas enters a waste heat boiler to release heat to generate steam for power generation;

b. after the flue gas is purified by the post-treatment device, one part of the flue gas enters an absorption tower, and the other part of the flue gas enters a solution generation tower;

c. the ejector in the absorption tower sprays high-concentration liquid moisture absorbent, the high-concentration liquid moisture absorbent absorbs water vapor and heat in the flue gas entering the absorption tower, so that the water vapor and the heat are changed into low-concentration solution with increased temperature, the low-concentration solution enters the heat supply end of the heat exchange device through the first output pipeline to emit heat, and the heat absorption end of the heat exchange device conducts the heat to the hot water pipe network to increase the temperature of the hot water pipe network;

d. the low concentration solution that the temperature that flows from heat exchange device becomes low gets into in the solution takes place the tower, and spout downwards through spray set, the low concentration solution that the temperature becomes low fully contacts the heat transfer with the flue gas that gets into in the solution takes place the tower, the temperature of flue gas reduces, and the low concentration solution that the temperature becomes low intensifies, moisture in the low concentration solution evaporates into water vapor, then become the liquid hygroscopic agent of high concentration, the liquid hygroscopic agent rethread second output pipeline of high concentration gets into the absorption tower, and spout downwards through the sprayer, thereby realize the circulation flow of liquid hygroscopic agent.

It is known that a high concentration of the liquid moisture absorbent has a good dehumidifying effect, thereby becoming a low concentration of the liquid moisture absorbent. When the low-concentration liquid moisture absorbent is heated and evaporated, the low-concentration liquid moisture absorbent becomes the high-concentration liquid moisture absorbent, so that the good dehumidification effect is recovered. The invention skillfully utilizes the characteristic of the liquid moisture absorbent, firstly sprays the high-concentration liquid moisture absorbent into the absorption tower to absorb the water vapor in the flue gas entering the absorption tower, and the liquid moisture absorbent absorbing the water vapor is reduced in concentration and increased in temperature to become a low-concentration solution with increased temperature. Then the low-concentration solution transfers heat to a hot water pipe network through a heat exchange device so as to fully utilize the waste heat of the flue gas. And then, the low-concentration solution with the reduced temperature enters the solution generating tower and is sprayed downwards through the spraying device, the low-concentration solution is in full contact with the flue gas entering the solution generating tower to exchange heat, the temperature of the flue gas is reduced, the low-concentration solution is heated, at the moment, the moisture in the low-concentration solution is evaporated into water vapor, the low-concentration solution is changed into the high-concentration liquid moisture absorbent again, and the high-concentration liquid moisture absorbent enters the absorption tower again through the second output pipeline.

That is, the invention enables the liquid moisture absorbent to circularly flow between the absorption tower and the solution generating tower, thereby effectively utilizing the waste heat of the flue gas, improving the utilization rate of heat energy, effectively removing the water vapor content in the flue gas, avoiding the flue gas from dewing and corroding a chimney, and further being beneficial to eliminating the generation of white smoke plume when the flue gas is discharged outwards.

Preferably, a first circulating pump is arranged on the first output pipeline: be equipped with the second circulating pump on second delivery pipe to can promote the velocity of flow of liquid in first delivery pipe, the second delivery pipe, accelerate the efficiency that the flue gas was handled then, and can avoid liquid to appear the detention phenomenon.

Preferably, the liquid desiccant is a lithium bromide solution.

The high-concentration lithium bromide solution has good moisture absorption effect and low toxicity. In particular, the lithium bromide solution circulating through the inside of the absorption column and the solution generation column through the piping has a low oxygen content and is thus not highly corrosive to metals.

Preferably, a flue gas valve is arranged on a pipeline connecting the post-treatment device and the solution generating tower.

The flue gas valve can effectively control the amount of flue gas entering the solution generating tower. That is to say, according to actual needs, most of the flue gas can enter the absorption tower, and a small part of the flue gas enters the solution generation tower in a controlled manner, so that the flue gas in the two towers is balanced and matched, and the utilization efficiency of the flue gas waste heat is improved to the maximum extent.

Preferably, the device also comprises a condensing tower, wherein the condensing tower is communicated with the upper part of the solution generating tower through a pipeline arranged in the middle part, the condensing tower is communicated with a pipeline connecting the absorption tower and the post-treatment device through a pipeline arranged at the top part, a condensed water outlet is arranged at the bottom of the condensing tower, and an ejector is arranged in the condensing tower;

in the step d, the flue gas and the water vapor in the solution generating tower enter a condensing tower to exchange heat with low-temperature condensed water sprayed from an injector in the condensing tower, the flue gas and part of the water vapor which is not condensed enter an absorption tower, so that the step c is continued, and the condensed water formed by condensing the water vapor is output outwards through a condensed water outlet.

In this scheme, the flue gas that enters into in the solution takes place the tower and the vapor accessible pipeline that is formed by the evaporation of low concentration solution gets into the condensing tower in, the comdenstion water in the condensing tower passes through the sprayer and spouts downwards, then takes place fully to contact the heat transfer with flue gas and vapor, most vapor condensation becomes the comdenstion water, and the aforesaid circulation step is restarted in the absorption tower together to the vapor intercommunication flue gas that a small part of noncondensation. At the moment, the condensed water is output outwards through the condensed water outlet, so that the water vapor converted from the moisture in the flue gas is effectively eliminated, the flue gas is further prevented from being condensed to corrode a chimney, and the generation of white smoke plume when the flue gas is discharged outwards is favorably eliminated.

Preferably, the condensed water outlet is communicated with the heat supply end of another heat exchange device through a pipeline, and the heat absorption end of the heat exchange device is connected to the hot water pipe network.

It can be understood that the temperature of the low-temperature condensed water sprayed out of the condensing tower is higher than that of the original low-temperature condensed water when the low-temperature condensed water condenses steam and is formed, therefore, the invention heats the condensed water for a hot water pipe network through another heat exchange device, thereby further utilizing the waste heat of the flue gas and improving the heat efficiency. Meanwhile, the temperature of the condensed water after heat exchange is reduced, so that the condensed water becomes low-temperature condensed water of condensed water steam.

That is to say, through a heat exchange device, both can promote the make full use of flue gas waste heat effectively, can realize the cyclic reuse of comdenstion water again. Certainly, an external drainage valve may be disposed at the condensed water outlet, and when the condensed water in the condensing tower is excessive, a part of the excessive condensed water may be drained outwards through the external drainage valve, so as to ensure normal recycling of the condensing tower.

Preferably, the heat exchange device is a water-solution plate heat exchanger.

As we know, the water-solution plate heat exchanger has the advantages of high heat exchange efficiency, high temperature resistance, small occupied space, small resistance and the like, so when the water-solution plate heat exchanger is used for the heat exchanger, the utilization of the waste heat of the flue gas can be improved to the maximum extent, and the water-solution plate heat exchanger is beneficial to the rapid temperature rise of a hot water pipe network.

Therefore, the invention has the following beneficial effects: the waste heat in the flue gas can be fully recovered, and the dew point temperature of the flue gas can be reduced, so that the flue gas is prevented from dewing and corroding a chimney due to waste heat utilization, the heat efficiency of the garbage power plant is improved, and the generation of white smoke plume is effectively eliminated.

Drawings

FIG. 1 is a schematic diagram of an embodiment of the present invention.

In the figure: 1. the system comprises a garbage incinerator 2, a waste heat boiler 31, a neutralization tower 32, a dust remover 4, a hot water pipe network 5, a heat exchange device 51, a heat supply end 52, a heat absorption end 6, an absorption tower 61, an ejector 62, a first output pipeline 63, a first circulating pump 7, a solution generation tower 71, a spraying device 72, a second output pipeline 73, a second circulating pump 74, a flue gas valve 8, a condensing tower 81, a condensed water outlet 9, a chimney 91 and an induced draft fan.

Detailed Description

The invention is further described with reference to the following detailed description and accompanying drawings.

As shown in fig. 1, a flue gas waste heat recovery device of a waste incineration system comprises a waste incineration device and a flue gas waste heat recovery device, wherein the waste incineration device comprises a waste incinerator 1 for incinerating waste, a waste heat boiler 2 for converting heat of flue gas into steam to generate power, and a post-treatment device for purifying the flue gas. Certainly, the invention also comprises a hot water pipe network 4 for providing hot water and a heat exchange device 5 comprising a heat supply end 51 and a heat absorption end 52, wherein the heat absorption end of the heat exchange device is connected to the hot water pipe network, the heat supply end of the heat exchange device exchanges heat between the waste heat generated by the smoke in the invention and the heat absorption end, and then the heat is transferred to the hot water pipe network through the heat absorption end of the heat exchange device, so that the hot water in the hot water pipe network is heated for downstream users to use.

In addition, the flue gas waste heat recovery device comprises an absorption tower 6 and a solution generating tower 7 which are connected with the post-treatment device in parallel through a pipeline, an ejector 61 is arranged in the absorption tower, a spraying device 71 is arranged in the solution generating tower, the absorption tower is communicated with the heat supply end of the first heat exchange device through a first output pipeline 62, the heat supply end of the heat exchange device is communicated with the spraying device in the solution generating tower through a heat supply pipeline, the solution generating tower is communicated with the ejector of the absorption tower through a second output pipeline 72,

it should be noted that the post-treatment device includes a neutralization tower 31 connected with the waste heat boiler through a pipeline, and a dust remover 32 connected with the neutralization tower through a pipeline, a slaked lime injection device is arranged in the neutralization tower, an activated carbon injection device is arranged on a pipeline connecting the neutralization tower and the dust remover, the garbage incinerator is connected with the waste heat boiler through a pipeline, the waste heat boiler is connected with the neutralization tower in the post-treatment device through a pipeline, and the flue gas waste heat recovery device of the invention is arranged behind the dust remover.

After the garbage is incinerated in the garbage incinerator and high-temperature flue gas is generated, the high-temperature flue gas flows to the waste heat boiler to generate steam for power generation, and the temperature of the flue gas is reduced. Then the flue gas enters into the neutralization tower and reacts with the powdery slaked lime sprayed by the slaked lime spraying device to eliminate the acidic pollutants in the flue gas. And then the flue gas enters the dust remover through a pipeline, and the activated carbon sprayed by the activated carbon spraying device arranged on the pipeline can absorb dioxin pollutants in the flue gas. The dust collector can then remove the dust from the flue gas entering the dust collector to purify the flue gas. At this time, the temperature of the flue gas is reduced to between 130 ℃ and 160 ℃, and the moisture content in the flue gas is about 28%.

The working steps of the invention are described in detail below:

a. the garbage is firstly burned in a garbage incinerator to form high-temperature flue gas, and the high-temperature flue gas enters a waste heat boiler to release heat to generate steam for power generation. Wherein the temperature of the high-temperature flue gas is approximately between 180 ℃ and 240 ℃;

b. the flue gas is purified by the post-treatment device and then is changed into purified flue gas, one part of the purified flue gas enters the absorption tower, and the other part of the purified flue gas enters the solution generation tower;

c. the ejector in the absorption tower sprays high-concentration liquid moisture absorbent, the high-concentration liquid moisture absorbent absorbs water vapor and heat in the flue gas entering the absorption tower, so that the water vapor and the heat are changed into low-concentration solution with increased temperature (namely the diluted liquid moisture absorbent), the low-concentration solution enters the heat supply end of the first heat exchange device through the first output pipeline to emit heat, and the heat absorption end of the first heat exchange device conducts the heat to the hot water pipe network to increase the temperature of the hot water pipe network;

d. the low-concentration solution with the lowered temperature flowing out of the first heat exchange device enters the solution generating tower and is sprayed downwards through the spraying device, the low-concentration solution with the lowered temperature is in full contact with the flue gas entering the solution generating tower to exchange heat, the temperature of the flue gas is lowered, the temperature of the low-concentration solution with the lowered temperature is raised, at the moment, moisture in the low-concentration solution is evaporated into water vapor, correspondingly, the low-concentration solution is dehydrated to become a high-concentration liquid moisture absorbent, and the high-concentration liquid moisture absorbent enters the absorption tower through the second output pipeline and is sprayed downwards through the sprayer, so that the circulating flow of the liquid moisture absorbent is realized.

It is known that a high concentration of the liquid moisture absorbent has a good dehumidifying effect, thereby becoming a low concentration of the liquid moisture absorbent. When the low-concentration liquid moisture absorbent is heated and evaporated, the low-concentration liquid moisture absorbent becomes the high-concentration liquid moisture absorbent, so that the good dehumidification effect is recovered. The invention skillfully utilizes the characteristic of the liquid moisture absorbent, firstly sprays the high-concentration liquid moisture absorbent into the absorption tower to absorb the water vapor in the flue gas entering the absorption tower, and the liquid moisture absorbent absorbing the water vapor is reduced in concentration and increased in temperature to become a low-concentration solution with increased temperature. Then the low-concentration solution transfers heat to a hot water pipe network through a heat exchange device so as to fully utilize the waste heat of the flue gas. And then, the low-concentration solution with the reduced temperature enters the solution generating tower and is sprayed downwards through the spraying device, the low-concentration solution is in full contact with the flue gas entering the solution generating tower to exchange heat, the temperature of the flue gas is reduced, the low-concentration solution is heated, at the moment, the moisture in the low-concentration solution is evaporated into water vapor, the low-concentration solution is changed into the high-concentration liquid moisture absorbent again, and the high-concentration liquid moisture absorbent enters the absorption tower again through the second output pipeline.

That is, the invention enables the liquid moisture absorbent to circularly flow between the absorption tower and the solution generating tower, thereby effectively utilizing the waste heat of the flue gas, improving the utilization rate of heat energy, effectively removing the water vapor content in the flue gas, avoiding the flue gas from dewing and corroding a chimney, and further being beneficial to eliminating the generation of white smoke plume when the flue gas is discharged outwards.

It should be noted that a second heat exchange device may be further disposed between the absorption tower and the solution generation tower, a heat supply end of the second heat exchange device is disposed on the second output pipeline, and a heat absorption end of the second heat exchange device is disposed on a pipeline connecting the heat supply end of the first heat exchange device and the spray device. Therefore, the low-concentration solution subjected to heat exchange and temperature reduction through the first heat exchange device can exchange heat with the high-concentration liquid moisture absorbent flowing in the second output pipeline at a higher temperature to increase the temperature of the low-concentration solution in advance, so that the low-concentration solution and the solution are heated in the solution generation tower to evaporate moisture in the solution.

Preferably, the liquid desiccant is a lithium bromide solution. It is known that a high-concentration lithium bromide solution has a good hygroscopic effect and the lithium bromide solution has low toxicity. In particular, since the lithium bromide solution circulating through the absorption tower and the solution generation tower via the pipeline has a low oxygen content, it is not highly corrosive to metals and is useful for a long period of time.

Further, we can also set a first circulation pump 63 on the first output pipe: set up second circulating pump 73 on second output pipeline to can promote the velocity of flow of liquid in first output pipeline, the second output pipeline, the low concentration solution of being convenient for is the downward blowout of atomizing form from spray set, is favorable to the abundant contact of low concentration solution and flue gas, accelerates the efficiency that the flue gas was handled then, and can avoid liquid to appear the detention phenomenon.

In order to reasonably adjust the ratio of the flue gas entering the absorption tower and the solution generating tower, a flue gas valve 74 can be arranged on a pipeline connecting the post-treatment device and the solution generating tower so as to accurately control the amount of the flue gas entering the solution generating tower, and then adjust the ratio of the flue gas entering the absorption tower and the solution generating tower. It can be understood that most of the flue gas enters the absorption tower and a small part of the flue gas enters the solution generation tower in a controlled manner according to actual needs, so that the flue gas in the two towers is balanced and matched, and the utilization efficiency of the flue gas waste heat is improved to the maximum extent.

As a preferable scheme, the invention also comprises a condensing tower 8, wherein the condensing tower is communicated with the upper part of the solution generating tower through a pipeline arranged at the middle part, and the condensing tower is communicated with a pipeline connecting the absorption tower and the post-treatment device through a pipeline arranged at the top part. Further, a condensed water outlet 81 is provided at the bottom of the condensing tower, and an ejector for ejecting low-temperature condensed water is provided in the condensing tower.

Thus, in the step d, the flue gas and the water vapor in the solution generation tower enter the condensation tower to exchange heat with the low-temperature condensed water sprayed from the sprayer in the condensation tower, at the moment, most of the water vapor in the flue gas is condensed to form condensed water, the condensed water formed by the condensation of the water vapor is output outwards through a condensed water outlet, and the water vapor and the flue gas which are not condensed in the flue gas enter the absorption tower, so that the step c is continued.

In this scheme, the flue gas that enters into in the solution takes place the tower and pass through in the pipeline gets into the condensing tower by the steam that low concentration solution evaporation formed, and the comdenstion water in the condensing tower passes through the sprayer and spouts downwards, then takes place fully to contact the heat transfer with flue gas and steam, and most steam condensation becomes the comdenstion water, and the aforesaid circulation step is restarted in the absorption tower together to the steam intercommunication flue gas that a small part of noncondensation. At the moment, the condensed water is output outwards through the condensed water outlet, so that the water vapor converted from the moisture in the flue gas is effectively eliminated, the flue gas is further prevented from being condensed to corrode a chimney, and the generation of white smoke plume when the flue gas is discharged outwards is favorably eliminated.

Furthermore, the condensed water outlet is communicated with the heat supply end of the third heat exchange device through a pipeline, and the heat absorption end of the third heat exchange device is connected to the hot water pipe network.

It can be understood that when the low-temperature condensed water sprayed out of the condensing tower condenses steam and forms condensed water, the temperature of the condensed water is increased compared with the temperature of the original low-temperature condensed water, therefore, the invention heats the condensed water for a hot water pipe network through the third heat exchange device, thereby further utilizing the waste heat of the flue gas and improving the heat efficiency. Meanwhile, the temperature of the condensed water after heat exchange with the third heat exchange device is reduced, so that the condensed water becomes low-temperature condensed water of condensed water steam, and the recycling of the condensed water is realized.

That is to say, through third heat exchange device, both can promote the make full use of flue gas waste heat effectively, can realize the cyclic utilization of comdenstion water again. Certainly, an external drainage valve may be disposed at the condensed water outlet, and when the condensed water in the condensing tower is excessive, a part of the excessive condensed water may be drained outwards through the external drainage valve, so as to ensure normal recycling of the condensing tower. In addition, a circulating pump can be arranged on a pipeline connecting the condensed water outlet and the heat supply end of the third heat exchange device.

It should be noted that the heat exchange device in the present invention may be a water-solution plate heat exchanger. Because the water-solution plate heat exchanger has the advantages of high heat exchange efficiency, high temperature resistance, small occupied space, small resistance and the like, when the water-solution plate heat exchanger is used for the heat exchanger, the utilization of the waste heat of the flue gas can be improved to the maximum extent, and the quick temperature rise of a hot water pipe network is facilitated.

Finally, a pipeline communicated with the chimney 9 is arranged at the upper part of the absorption tower, and an induced draft fan 91 is arranged on the pipeline, and can convey the cooled and dehumidified flue gas to the chimney and discharge the flue gas outwards through the chimney. Certainly, the pipeline that is connected with aftertreatment device should set up in the lower part of absorption tower, and the flue gas that is convenient for to get into the absorption tower on the one hand carries out abundant contact with liquid hygroscopic agent, and on the other hand, avoids just getting into the flue gas of absorption tower and directly being carried the chimney by the draught fan and outwards discharging.