An industrial waste gas waste heat recovery system and method

Abstract

The present application discloses an industrial waste gas waste heat recovery system and method. The system includes an inlet flue, a purification tower, a heat extraction liquid connection pipeline, a heat extraction liquid buffer tank, and a heat extraction liquid discharge pump; a raw flue gas heat extractor is provided in the inlet flue, and a heat extraction liquid reheater is provided above the raw flue gas heat extractor outside the inlet flue; a flue gas inlet is provided on the tower wall of the purification tower, and a flue gas outlet is provided at the top. The flue gas inlet is connected to the inlet flue. Inside the tower body between the flue gas inlet and the flue gas outlet of the purification tower, a washing liquid heat extractor, a spray washing layer, a demister, and a clean flue gas heat extractor are successively arranged from bottom to top; the clean flue gas heat extractor, the washing liquid heat extractor, and the heat extraction liquid reheater are successively connected in series, and the heat of the heat extraction liquid reheater is extracted into the raw flue gas through the raw flue gas heat extractor. The present application solves the problems of heat reuse of low-grade hot flue gas in the purification tower and uniform heat exchange within the flue gas cross-section.

Description

Technical Field

[0001] This application relates to the field of new energy and energy conservation, and specifically relates to an industrial waste gas waste heat recovery system and method. Background Art

[0002] During industrial production processes, there are various boilers and furnaces of different specifications. Part of the heat released by the fuel combustion in industrial boilers and furnaces serves as the energy source for the production process, part is dissipated through thermal radiation in the boiler system, and part of the heat is discharged into the environment along with the combustion exhaust gas. The heat dissipated by radiation and the heat of the exhaust gas are both ineffective heat. Therefore, reducing the heat dissipated by radiation and the exhaust gas temperature is beneficial to improving the boiler efficiency.

[0003] Currently, the average exhaust gas temperature of industrial boilers and furnaces is above 180°C. The exhaust gas temperature of some ordinary industrial boilers is as high as above 250°C. Even after waste heat recovery, the exhaust gas temperature of power station boilers is mostly around 130 - 180°C, and most of the waste heat in this part of the flue gas has not been reasonably recovered and utilized. The high-temperature flue gas carrying a large amount of heat is directly discharged into the air, which not only has a huge impact on the environment but also causes a great waste of energy. Taking industrial boilers as an example, generally, for every 15 - 20°C reduction in the exhaust gas temperature of the boiler tail gas, the boiler thermal efficiency increases by about 1%. In addition, among the energy expenditures of various industrial furnaces, the waste heat of the exhaust gas accounts for about 15% - 35%. The heat loss of the boiler flue gas is the largest among various heat losses, generally between 5% - 8%.

[0004] Energy conservation and emission reduction are important measures to promote the sustainable development of industry, with obvious economic and environmental benefits. Driven by both policies and market demands, the future utilization of the waste heat of flue gas emissions will have a broad market space. Especially in high-energy-consuming and high-pollution industries such as coal power, waste incineration power generation, steel, and metallurgical furnaces, it is an inevitable choice to fully recover and utilize the waste heat of flue gas. Conducting research on technologies related to flue gas waste heat is of great practical significance for fully and reasonably utilizing various flue gas waste heat resources, energy conservation and emission reduction, and improving energy utilization efficiency.

[0005] Using a heat exchanger to indirectly extract heat from industrial exhaust gas and using the extracted heat for material waste heat can effectively achieve the recovery and utilization of exhaust gas waste heat and improve the boiler efficiency. However, the following problems exist in the process of waste heat recovery of industrial exhaust gas by conventional indirect heat exchangers:

[0006] (1) In addition to containing relatively high heat, industrial tail gas also contains water vapor, nitrogen oxides, sulfur oxides, dust particles, etc. generated by fuel combustion. When the industrial tail gas is cooled by heat exchange, when the tail gas condenses to a certain temperature, sulfur oxides and water vapor condense to form sulfuric acid mist, which corrodes the heat exchanger. In order to ensure the normal and stable operation of the heat exchanger, it is often necessary to control the temperature of the tail gas after heat exchange to be higher than the critical temperature of acid mist condensation, resulting in limited heat extraction from the tail gas and unable to maximize the recovery of heat in the tail gas;

[0007] (2) Wet scrubbing processes are mostly used at the end of industrial tail gas to remove pollutants in the flue gas. The industrial tail gas after wet scrubbing is mostly saturated steam between 50°C and 65°C. The heat of the scrubbed flue gas has limited effect on raising the temperature of the heat extraction liquid in the heat exchanger, resulting in the heat extracted by the heat extraction liquid in the heat exchanger being unable to be reused;

[0008] (3) During the flow of the heat extraction liquid in the heat exchanger, the temperature of the heat exchanger wall surface in the direction of the heat extraction liquid flow continuously increases during the heat exchange process, resulting in uneven heat exchange amount and temperature of the flue gas after heat exchange in the flue gas cross-section, which is not conducive to achieving efficient heat exchange.

[0009] Therefore, the existing flue gas heat extraction technology cannot achieve the maximum recovery of industrial tail gas waste heat, and the energy-saving effect is not obvious. Developing an industrial tail gas waste heat recovery technology with deep flue gas waste heat recovery and low operating cost is an inevitable trend. Summary of the Invention

[0010] In view of the above problems, the present application provides an industrial tail gas waste heat recovery system and method. By using a low-temperature heat extraction liquid to perform cascade recovery of the waste heat in the flue gas in the industrial tail gas scrubbing tower, a heat extraction liquid with a high-grade heat source is obtained, while achieving deep recovery of industrial tail gas waste heat, improving the scope of use of the recovered waste heat, and realizing the effective reuse of the waste heat in industrial tail gas emissions.

[0011] An industrial tail gas waste heat recovery system includes an inlet flue, a purification tower, a heat extraction liquid connection pipeline, a heat extraction liquid buffer tank, and a heat extraction liquid discharge pump;

[0012] A raw flue gas heat extractor is provided in the inlet flue, and a heat extraction liquid reheater is provided outside the inlet flue and above the raw flue gas heat extractor. The heat of the heat extraction liquid reheater comes from the raw flue gas heat extractor;

[0013] The purification tower is provided with a flue gas inlet on the tower wall and a flue gas outlet at the top. The flue gas inlet is connected to the inlet flue. Inside the tower body between the flue gas inlet and the flue gas outlet of the purification tower, a washing liquid heat extractor, a spray washing layer, a demister, and a clean flue gas heat extractor are successively arranged from bottom to top;

[0014] The heat extraction liquid inlet pipeline is respectively connected to the liquid inlet of the clean flue gas heat extractor and the liquid inlet of the heat extraction liquid reheater;

[0015] The liquid outlet of the clean flue gas heat extractor and the liquid inlet of the washing liquid heat extractor are connected through a pipeline.

[0016] The liquid outlet of the washing liquid heat extractor is connected to the liquid inlet of the heat extraction liquid reheater through a pipeline.

[0017] The liquid outlet of the heat extraction liquid reheater is connected to the heat extraction liquid buffer tank through a pipeline.

[0018] The inlet of the heat extraction liquid discharge pump is connected to the heat extraction liquid buffer tank through a pipeline.

[0019] The following also provides several optional ways, which are not additional limitations to the above overall solution, but only further supplements or optimizations. Without technical or logical contradictions, each optional way can be combined with the above overall solution separately, or multiple optional ways can be combined with each other.

[0020] The purification tower is a wet spray washing tower, such as a desulfurization tower, a spray dust removal tower, etc. The recovery system of the present application has advantages such as good universality.

[0021] Optionally, flow control valves are provided on the heat extraction liquid inlet pipelines connecting the liquid inlet of the clean flue gas heat extractor and the liquid inlet of the heat extraction liquid reheater.

[0022] Optionally, the clean flue gas heat extractor includes a number of gaps or channels for the vertical flow of clean flue gas and a number of cavities or pipe structures arranged horizontally for the flow of heat extraction liquid.

[0023] Optionally, the washing liquid heat extractor includes a number of gaps or channels for the vertical flow of clean flue gas and a number of cavities or pipe structures arranged horizontally for the flow of heat extraction liquid.

[0024] The present application further solves the problem of uneven heat exchange amount of flue gas in the flue gas cross-section and uneven temperature of the flue gas after heat exchange on the basis of solving the problem of deep recovery of waste heat of low-grade flue gas.

[0025] Optionally, it further includes a number of engineering heat pipes. Each heat pipe includes an evaporation section, a condensation section, and an arc-shaped elbow section connecting the evaporation section and the condensation section. Both the evaporation section and the condensation section are straight pipes, and the inside of the evaporation section, the arc-shaped elbow section, and the condensation section is a connected sealed cavity; the evaporation section of the engineering heat pipe is installed in the inlet flue to form the original flue gas heat extractor.

[0026] Optionally, a certain volume of low-boiling-point liquid heat extraction agent is contained in the sealed cavity of the engineering heat pipe; a liquid distributor is provided at the connection between the cavity of the arc-shaped elbow section and the cavity of the evaporation section of the engineering heat pipe.

[0027] Using a heat pipe as a heat extractor, during the heat exchange process between the heat extractor and the flue gas, the low-boiling heat extraction agent is heated and evaporated, ensuring that the temperature of the evaporation section tube wall always remains near the boiling point temperature of the heat extraction agent, improving the uniformity of the heat extraction device wall temperature and the uniformity of the flue gas heat exchange and cooling, preventing uneven heat extraction and cooling of the flue gas, and preventing excessive condensation of part of the flue gas to form acid mist that corrodes equipment such as the heat extractor.

[0028] Optionally, the evaporation sections of several engineering heat pipes are installed in parallel on a cross-section perpendicular to the flue gas flow direction in the inlet flue, and the evaporation sections of the engineering heat pipes are vertically installed in the inlet flue; the tube wall of the evaporation section is provided with a metal fin structure.

[0029] Optionally, the heat extraction liquid reheater includes a shell, a heat extraction liquid sprayer, and the condensation section of the engineering heat pipe; the shell of the heat extraction liquid reheater is provided with a heat extraction liquid reheater inlet and a heat extraction liquid reheater outlet; the heat extraction liquid sprayer is arranged in the shell, and the inlet of the heat extraction liquid sprayer is connected to the heat extraction liquid reheater inlet; the condensation section of the engineering heat pipe extends obliquely upward into the shell at a certain inclination angle and is located below the heat extraction liquid sprayer; the outer wall of the condensation section of the engineering heat pipe is a smooth tube structure.

[0030] Optionally, the heat extraction liquid can be selected from hot water, process water, or other heat extraction media according to the production hot water demand. When heat needs to be supplemented for the boiler deaerator, pure water is used as the heat extraction liquid, and the heat extraction liquid output pump is connected to the boiler deaerator. It is used as a deaeration heat source to reduce the energy consumption of the deaerator.

[0031] The present application also provides an industrial waste gas waste heat recovery method, preferably implemented using the recovery system of the present application, including the following steps:

[0032] (a) High-temperature industrial waste gas carrying a large amount of discharged waste heat and air pollutants enters the purification tower from the inlet flue and flows upward; in the inlet flue, the high-temperature flue gas contacts the finned tube outside the straight pipe section of the engineering heat pipe in the original flue gas heat extractor, heating the liquid heat extraction agent in the engineering heat pipe to complete the primary heat extraction; the flue gas after the primary heat extraction enters the purification tower and successively flows through the washing liquid heat extractor and the washing spray layer, and the pollutants in the flue gas are washed and purified, and at the same time, the washing liquid is heated and exchanged in temperature to complete the secondary heat extraction of the industrial flue gas; the flue gas that has completed washing and purification and secondary heat extraction enters the clean flue gas heat extractor for contact and heat exchange to complete the tertiary heat extraction of the industrial flue gas, and the low-temperature clean flue gas after the tertiary heat extraction is discharged from the purification tower flue gas outlet;

[0033] (b) The low-temperature hot water for heat extraction is sent into the clean flue gas heat extractor through the heat extraction liquid pipeline, and the heat of the clean flue gas is recovered through the clean flue gas heat extractor to achieve primary waste heat recovery; the hot water for heat extraction that has completed primary waste heat recovery enters the washing liquid heat extractor from the outlet pipeline of the clean flue gas heat extractor, and exchanges heat with the high-temperature washing liquid flowing downward on the surface of the washing liquid heat extractor to recover the heat in the washing liquid and achieve secondary waste heat recovery; the hot water for heat extraction that has completed secondary waste heat recovery is sent into the heat extraction liquid reheater through the pipeline from the outlet of the washing slurry heat extractor, atomized into droplets by the sprayer in the heat extraction liquid reheater and evenly distributed on the surface of the condensation section of the engineering heat pipe, exchanges heat with the heat extraction agent steam in the condensation section to increase the temperature, and performs tertiary waste heat recovery. The high-temperature hot water for heat extraction that has completed tertiary waste heat recovery is sent into the heat extraction liquid buffer tank through the pipeline from the outlet of the heat extraction liquid reheater for standby;

[0034] (c) When the temperature of the heat extraction liquid at the outlet of the washing liquid heat extractor is high, resulting in limited heat extraction of the raw flue gas heat extractor, control the flow control valve on the heat extraction liquid inlet pipeline connected to the liquid inlets of the heat extraction liquid reheater and the clean flue gas heat extractor, increase the flow rate of the low-temperature heat extraction liquid to reduce the inlet temperature of the heat extraction liquid entering the heat extraction liquid reheater, and increase the heat extraction amount of the raw flue gas heat extractor.

[0035] The heat extraction liquid after heat exchange through the three-stage heat extractor is used as the deaeration heat source of the boiler deaerator, reducing the energy consumption of the boiler deaerator.

[0036] Compared with the prior art, the present application has at least the following beneficial effects:

[0037] (1) The present application provides a solution for cascaded recovery of flue gas waste heat. Based on the industrial tail gas wet scrubbing and purification system, a low-temperature heat extraction medium is used to sequentially extract heat from the clean flue gas, the spray washing liquid, and the raw flue gas, and a heat extraction medium with high temperature and high heat source is obtained, increasing the waste heat reuse path while improving the efficiency of industrial tail gas waste heat recovery;

[0038] (2) The present application provides a solution for improving the recovery rate of industrial tail gas waste heat. The evaporation section and the condensation section of the engineering heat pipe are connected by a bent pipe. The evaporation section is placed in the original flue as the flue gas heat extractor, and the condensation section is placed outside the flue as the heat extraction liquid reheater. By spraying and distributing the heat extraction liquid and forming a dynamic liquid film on the outer surface of the light pipe in the condensation section, the heat transfer efficiency of the heat pipe is improved. By setting the condensation section obliquely, the heat transfer area and contact time of the heat extraction liquid on the light pipe surface are increased, improving the heat transfer amount;

[0039] (3) The present application provides a solution for the reuse of industrial tail gas discharge waste heat. Different heat extraction liquids are used as the heat extraction medium according to production needs, and the removed high-temperature heat extraction liquid is used to provide heat source for the production process, reducing the operating energy consumption in the industrial production process. Brief Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of the device of the present application;

[0041] Figure 2 It is a structural schematic diagram of a single heat pipe heater.

[0042] Figure 3 For Figure 2 It is an enlarged structural schematic diagram of the liquid redistributor in

[0043] Figure 4 For Figure 1 It is a structural schematic diagram of the purified flue gas heater and the washing liquid heater in

[0044] The reference numerals shown in the figure are as follows:

[0045] 1 - Purification tower 2 - Washing liquid heater 3 - Washing spray layer

[0046] 4 - Demister 5 - Clean flue gas heater 6 - Flue gas outlet

[0047] 7 - Inlet flue 8 - Engineering heat pipe 9 - Shell

[0048] 10 - Heat extraction liquid sprayer 11 - Heat extraction liquid inlet pipeline 12 - Heat extraction liquid control valve

[0049] 13 - Bypass control valve 14 - Heat extraction liquid buffer tank 15 - Heat extraction liquid discharge pump

[0050] 21 - Heat extraction liquid flow pipeline 22 - Flue gas flow channel

[0051] 81 - Evaporation section 82 - Arc elbow section 83 - Condensation section

[0052] 84 - Liquid distributor 85 - Insertion part Detailed implementation manners

[0053] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0054] To better describe and illustrate the embodiments of the present application, one or more accompanying drawings may be referred to, but the additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of any one of the invention creations, the currently described embodiments or the preferred modes of the present application.

[0055] It should be noted that when a component is referred to as being "connected" to another component, it can be directly connected to the other component or there may be an intermediate component. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component at the same time.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0057] As Figure 1 shown, an industrial waste gas waste heat recovery system includes a purification tower 1, an inlet flue 7, a heat extraction liquid buffer tank 14, a heat extraction liquid discharge pump 5, and each heat extraction liquid connection pipeline.

[0058] A flue gas inlet is provided on the tower wall of the purification tower 1, and a flue gas outlet 6 is provided at the top. The flue gas inlet is connected to the inlet flue 7. A washing spray layer 3 is provided in the middle of the purification tower 1. Inside the purification tower 1, an entrainer 4 and a clean flue gas heat extractor 5 are sequentially provided above the washing spray layer 3, and a washing liquid heat extractor 2 is provided below the washing spray layer 3. The washing liquid heat extractor 2 is located above the flue gas inlet, that is, in the washing tower and between the flue gas inlet and the flue gas outlet, the washing liquid heat extractor 2, the washing spray layer 3, the entrainer 4, and the clean flue gas heat extractor 5 are sequentially provided from bottom to top. A raw flue gas heat extractor is provided in the inlet flue 7, and a heat extraction liquid reheater is provided outside the inlet flue and above the raw flue gas heat extractor. The clean flue gas heat extractor 5, the washing liquid heat extractor 2, and the heat extraction liquid reheater are sequentially connected in series through water pipes. The heat of the heat extraction liquid reheater comes from the clean flue gas heat extractor. One way of the heat extraction liquid inlet pipeline 11 is connected to the liquid inlet of the clean flue gas heat extractor 5, and the other way is connected to the liquid inlet of the heat extraction liquid reheater; the liquid outlet of the clean flue gas heat extractor 5 is connected to the liquid inlet of the washing liquid heat extractor 2 through a pipeline; the liquid outlet of the washing liquid heat extractor is connected to the liquid inlet of the heat extraction liquid reheater through a pipeline; the liquid outlet of the heat extraction liquid reheater is connected to the heat extraction liquid buffer tank 14, and the heat extraction liquid buffer tank 14 is connected to the heat extraction liquid discharge pump 15.

[0059] The purification tower is a wet spray washing tower, such as a desulfurization tower, a spray dust removal tower, etc. In this application, it is a spray desulfurization tower. Both the washing spray layer 3 and the entrainer 4 adopt conventional components in the wet spray tower.

[0060] The clean flue gas heat extractor 5 and the washing liquid heat extractor 2 can adopt the same heat extractor structure. In one implementation, the structures of the clean flue gas heat extractor 5 and the washing liquid heat extractor 2 both include: a number of horizontally arranged cavities or pipe structures for circulating the heat extraction liquid; vertically connected gaps or channels for circulating the flue gas. In a specific implementation, a specific implementation of the clean flue gas heat extractor 5 and the washing liquid heat extractor 2, such asFigure 4 As shown in the figure, it includes a heat-taking liquid circulation pipe 21 arranged horizontally, and the gap between adjacent heat-taking liquid circulation pipes is a flue gas circulation channel 22.

[0061] A number of engineering heat pipes 8 are arranged at the inlet flue. The structure of a single engineering heat pipe 8 is as Figure 2 shown. The engineering heat pipe 8 includes an evaporation section 81 and a condensation section 83. Both the evaporation section 81 and the condensation section 83 are straight pipe structures. The evaporation section and the condensation section are connected by an arc-shaped elbow section 82, so that the evaporation section and the condensation section of the engineering heat pipe form a certain angle, and this angle is an obtuse angle. When the evaporation section is vertical, the condensation section is inclined obliquely upward. The evaporation section, the arc-shaped elbow section and the condensation section are internally a connected sealed cavity, and a certain volume of low-boiling liquid heat-taking agent is contained in the sealed cavity; the evaporation section is used to absorb heat from the raw flue gas, and the condensation section is used to transfer the heat from the raw flue gas to the heat-taking liquid. The outside of the evaporation section is a fin structure, and the condensation section is a smooth pipe structure.

[0062] A liquid distributor 84 is provided at the connection between the cavity of the arc-shaped elbow section and the cavity of the evaporation section. The function of the liquid distributor is to evenly guide the liquid condensed in the condensation section to the inner wall of the heating section. The condensed liquid drops along the pipe wall of the heating section, so as to better achieve the equal wall temperature effect of the pipe wall of the heating section. One implementation of the liquid distributor is as Figure 3 shown, adopting a hollow frustum-shaped structure. The outer side surface of the frustum structure is an inwardly concave arc surface, which guides the condensed water to the wall surface, and the hollow cavity is a steam rising channel.

[0063] To facilitate the installation of the heat pipe in the inlet flue, a plug-in part 85 is provided on the bottom end surface of the heat pipe, and a matching plug-in groove is provided on the inner wall of the inlet flue. The plug-in part and the plug-in groove cooperate to realize the relative fixed installation of the heat pipe and the inner wall of the inlet flue.

[0064] As an installation method of the engineering heat pipe, the evaporation sections of a number of engineering heat pipes are installed in parallel on the radial section in the inlet flue 7. All the evaporation sections are installed vertically and cover the entire radial section. The gap between adjacent fins of the heating section is a flue gas channel, and the condensation sections of all the engineering heat pipes extend in the same direction. The evaporation sections arranged in parallel in the inlet flue 7 form a raw flue gas heat extractor.

[0065] The heat extraction liquid reheater includes a housing 9, a heat extraction liquid sprayer 10 and the condensation sections of all engineering heat pipes 8. An inlet and an outlet are provided on the housing 9. The heat extraction liquid sprayer 10 is arranged inside the housing and includes a heat extraction liquid flow pipe and a number of nozzles distributed on the heat extraction liquid flow pipe. The nozzles are arranged with the spraying direction downward. The inlet of the heat extraction liquid sprayer 10 is connected to the inlet of the housing 9. The condensation sections 83 of all engineering heat pipes extend obliquely upward at a certain angle into the space below the heat extraction liquid sprayer 10 inside the housing 9. In a preferred embodiment, the inclination angle of the condensation section is 15° - 50°. The pipeline connecting the outlet of the washing liquid heat extractor is communicated with the inlet of the housing of the heat extraction liquid reheater, and the outlet on the housing is connected to the heat extraction liquid buffer tank 14 through a heat extraction liquid discharge pipeline. The water in the heat extraction liquid buffer tank 14 can be sent to the boiler deaerator through a heat extraction liquid discharge pump 15 as the heat source of the boiler deaerator.

[0066] Inside the engineering heat pipe, the low-boiling-point solution in the evaporation section absorbs the waste heat of the flue gas and evaporates into steam. The steam flows upward into the condensation section, where it undergoes falling film heat exchange with the heat extraction liquid sprayed by the heat extraction liquid sprayer. The heat absorbed from the flue gas is released to the heat extraction liquid, and the steam is condensed. The condensed liquid slides down along the inner wall of the pipe, is evenly distributed by the liquid distributor 84, and then slides down along the inner wall of the evaporation section to absorb the waste heat of the flue gas again, and the cycle continues. The sliding of the condensed liquid along the inner wall makes the wall temperature of each part of the evaporation section uniform. By adjusting the temperature and flow rate of the heat extraction liquid, the pressure inside the engineering heat pipe can be adjusted, thereby adjusting the boiling point of the solution inside the heat pipe, and further adjusting the wall temperature of the heating section to achieve isothermal wall heat exchange. Under the isothermal wall effect of the engineering heat pipe, the uniformity of the flue gas temperature upstream and downstream of the heat exchanger is good.

[0067] In another embodiment, while ensuring the recovery of low-grade waste heat, the heat exchange efficiency of the original flue gas heat extractor and the heat extraction liquid reheater is further improved. The specific implementation method is as follows: The heat extraction liquid inlet pipeline 11 is divided into two paths. One path is connected to the inlet of the clean flue gas heat extractor 5, and a heat extraction liquid control valve 12 is provided on this path; the other path is connected to the condensation sprayer 10 of the heat extraction liquid reheater, and a bypass control valve 13 is provided on this path.

[0068] Under this embodiment, the control valves on both branch paths can be opened simultaneously. When the temperature of the heat extraction liquid at the outlet of the washing liquid heat extractor is high, resulting in limited heat extraction of the original flue gas heat extractor, the flow control valve on the heat extraction liquid inlet pipeline connected to the inlet of the heat extraction liquid reheater is controlled to increase the flow rate of the low-temperature heat extraction liquid and reduce the inlet temperature of the heat extraction liquid entering the heat extraction liquid reheater, thereby increasing the heat extraction of the original flue gas heat extractor.

[0069] It is also possible to only open the heat extraction liquid control valve 12. When only the heat extraction liquid control valve 12 is opened, the heat extraction liquid sequentially passes through the clean flue gas heat exchanger 5, the washing liquid heat exchanger 2, and the heat extraction liquid reheater to gradually recover the low-grade heat of the flue gas in the purification tower. It is also possible to only bypass the control valve 13. When only the bypass control valve 13 is opened, the heat extraction liquid only extracts heat from the raw flue gas in the inlet flue through the heat extraction liquid reheater. The temperature of the inlet flue gas is 130-150°C, and the heat extraction liquid after heat exchange can meet the requirements of industrial reuse.

[0070] An industrial waste gas waste heat recovery method is carried out using the above system, including:

[0071] (a) High-temperature industrial waste gas carrying a large amount of discharged waste heat and air pollutants enters the purification tower from the inlet flue and flows upward; in the inlet flue, the high-temperature flue gas contacts the finned tubes outside the evaporation section of the engineering heat pipe in the raw flue gas heat exchanger to heat the liquid heat extraction agent in the engineering heat pipe and complete the first-stage heat extraction; the flue gas after the first-stage heat extraction enters the purification tower and sequentially flows through the washing liquid heat exchanger and the washing spray layer. The pollutants in the flue gas are washed and purified, and at the same time, the washing liquid is heated and exchanged to complete the second-stage heat extraction of the industrial flue gas; the flue gas that has completed washing and purification and the second-stage heat extraction enters the clean flue gas heat exchanger after passing through the demister for contact and heat exchange to complete the third-stage heat extraction of the industrial flue gas. The low-temperature clean flue gas after the third-stage heat extraction is discharged from the flue gas outlet of the purification tower;

[0072] (b) The low-temperature heat extraction water is sent into the clean flue gas heat exchanger through the heat extraction liquid pipeline, and the heat of the clean flue gas is recovered through the clean flue gas heat exchanger to achieve the first-stage waste heat recovery; the heat extraction water that has completed the first-stage waste heat recovery enters the washing liquid heat exchanger from the outlet pipeline of the clean flue gas heat exchanger and performs film-forming heat exchange with the high-temperature washing liquid flowing downward on the surface of the washing liquid heat exchanger to recover the heat in the washing liquid and achieve the second-stage waste heat recovery; the heat extraction water that has completed the second-stage waste heat recovery is sent from the outlet of the washing slurry heat exchanger to the heat extraction liquid reheater through the pipeline, atomized into droplets by the sprayer in the heat extraction liquid reheater and evenly distributed on the surface of the condensation section of the engineering heat pipe, and exchanges heat with the heat extraction agent steam in the condensation section to increase the temperature, performing the third-stage waste heat recovery. The high-temperature heat extraction water that has completed the third-stage waste heat recovery is sent from the outlet of the heat extraction liquid reheater to the heat extraction liquid buffer tank for standby through the pipeline;

[0073] (c) When the temperature of the heat extraction liquid at the outlet of the washing liquid heat exchanger is high, resulting in limited heat extraction of the raw flue gas heat exchanger, control the flow control valve on the heat extraction liquid inlet pipeline connected to the inlet of the heat extraction liquid reheater and the clean flue gas heat exchanger to increase the flow rate of the low-temperature heat extraction liquid and reduce the inlet temperature of the heat extraction liquid entering the heat extraction liquid reheater, thereby increasing the heat extraction of the raw flue gas heat exchanger.

[0074] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0075] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An industrial waste heat recovery system, characterized in that: It includes an inlet flue, a purification tower, a heat extraction liquid connection pipeline, a heat extraction liquid buffer tank and a heat extraction liquid discharge pump; A raw flue gas heat extractor is provided in the inlet flue, and a heat extraction liquid reheater is provided outside the inlet flue and above the raw flue gas heat extractor. The heat of the heat extraction liquid reheater comes from the raw flue gas heat extractor. A flue gas inlet is provided on the tower wall of the purification tower, and a flue gas outlet is provided at the top. The flue gas inlet is connected to the inlet flue. Inside the tower body between the flue gas inlet and the flue gas outlet of the purification tower, a washing liquid heat extractor, a spray washing layer, a demister and a clean flue gas heat extractor are sequentially arranged from bottom to top; The heat extraction liquid inlet pipeline is respectively communicated with the liquid inlet of the clean flue gas heat extractor and the liquid inlet of the heat extraction liquid reheater; The liquid outlet of the clean flue gas heat extractor and the liquid inlet of the washing liquid heat extractor are communicated through a pipeline; The liquid outlet of the washing liquid heat extractor is communicated with the liquid inlet of the heat extraction liquid reheater through a pipeline; The liquid outlet of the heat extraction liquid reheater is communicated with the heat extraction liquid buffer tank through a pipeline; The inlet of the heat extraction liquid discharge pump is communicated with the heat extraction liquid buffer tank through a pipeline; It also includes a number of engineering heat pipes. Each heat pipe includes an evaporation section, a condensation section and an arc-shaped elbow section connecting the evaporation section and the condensation section. The evaporation section and the condensation section are both straight pipes, and the inside of the evaporation section, the arc-shaped elbow section and the condensation section is a connected sealed cavity. A liquid distributor is provided at the connection between the cavity of the arc-shaped elbow section and the cavity of the evaporation section. The evaporation section of the engineering heat pipe is installed in the inlet flue to form the raw flue gas heat extractor, and the condensation section extends obliquely upward into the heat extraction liquid reheater in an inclined shape.

2. The industrial waste gas waste heat recovery system according to claim 1, wherein: Flow control valves are provided on the heat extraction liquid inlet pipelines connecting the liquid inlet of the clean flue gas heat extractor and the liquid inlet of the heat extraction liquid reheater.

3. The industrial waste gas waste heat recovery system according to claim 1, wherein: The clean flue gas heat extractor includes a number of gaps or channels for the vertical flow of clean flue gas and a number of cavity or pipe structures for the horizontal flow of heat extraction liquid.

4. The industrial waste gas waste heat recovery system according to claim 1, characterized in that: The washing liquid heat extractor includes a number of gaps or channels for the vertical flow of clean flue gas and a number of cavity or pipe structures for the horizontal flow of heat extraction liquid.

5. The industrial waste gas waste heat recovery system according to claim 1, characterized in that: The evaporation sections of a number of engineering heat pipes are installed in parallel on the cross-section of the inlet flue perpendicular to the flue gas flow direction, and the evaporation sections of the engineering heat pipes are vertically installed in the inlet flue. The pipe wall of the evaporation section is provided with a metal fin structure.

6. The industrial waste gas waste heat recovery system according to claim 1, wherein: The heat extraction liquid reheater includes a shell, a heat extraction liquid sprayer and the condensation section of the engineering heat pipe. The shell of the heat extraction liquid reheater is provided with a heat extraction liquid reheater liquid inlet and a heat extraction liquid reheater liquid outlet. The heat extraction liquid sprayer is arranged inside the shell, and the liquid inlet of the heat extraction liquid sprayer is connected to the heat extraction liquid reheater liquid inlet. The condensation section of the engineering heat pipe extends obliquely upward into the shell at a certain inclination angle and is located below the heat extraction liquid sprayer. The outer wall of the condensation section of the engineering heat pipe is a smooth pipe structure.

7. The industrial waste gas waste heat recovery system according to claim 1, characterized in that: A certain volume of low-boiling-point liquid heat extraction agent is contained in the sealed cavity of the engineering heat pipe.

8. An industrial waste gas waste heat recovery method, characterized in that: It is completed by using the industrial waste gas waste heat recovery system described in claim 1, including the following steps: (a)High-temperature industrial tail gas carries a large amount of discharged waste heat and air pollutants and enters the purification tower from the inlet flue and flows upward; in the inlet flue, the high-temperature flue gas contacts the finned tubes outside the evaporation section of the engineering heat pipe in the primary flue gas recuperator, heating the liquid heat extraction agent in the engineering heat pipe to complete the first-stage heat extraction; the flue gas after the first-stage heat extraction enters the purification tower and flows through the washing liquid recuperator and the washing spray layer in sequence. The pollutants in the flue gas are washed and purified, and at the same time, the washing liquid is heated by heat exchange to complete the second-stage heat extraction of the industrial flue gas; the flue gas that has completed washing and purification and the second-stage heat extraction enters the clean flue gas recuperator after demisting by the demister to complete the third-stage heat extraction of the industrial flue gas. The low-temperature clean flue gas after the third-stage heat extraction is discharged from the flue gas outlet of the purification tower. (b)Low-temperature heat extraction water is sent to the clean flue gas recuperator through the heat extraction liquid pipeline, and the heat of the clean flue gas is recovered through the clean flue gas recuperator to achieve the first-stage waste heat recovery; the heat extraction water that has completed the first-stage waste heat recovery enters the washing liquid recuperator from the outlet pipeline of the clean flue gas recuperator and exchanges heat with the high-temperature washing liquid flowing downward on the surface of the washing liquid recuperator to recover the heat in the washing liquid and achieve the second-stage waste heat recovery; the heat extraction water that has completed the second-stage waste heat recovery is sent from the outlet of the washing slurry recuperator to the heat extraction liquid reheater through the pipeline, and is atomized into droplets by the sprayer in the heat extraction liquid reheater and evenly distributed on the surface of the condensation section of the engineering heat pipe, and exchanges heat with the heat extraction agent steam in the condensation section to increase the temperature, performing the third-stage waste heat recovery. The high-temperature heat extraction water that has completed the third-stage waste heat recovery is sent from the outlet of the heat extraction liquid reheater to the heat extraction liquid buffer tank through the pipeline for standby. (c)When the temperature of the heat extraction liquid at the outlet of the washing liquid recuperator is high, resulting in limited heat extraction of the primary flue gas recuperator, control the flow control valve on the heat extraction liquid inlet pipeline connected to the inlet of the heat extraction liquid reheater and the clean flue gas recuperator to increase the flow rate of the low-temperature heat extraction liquid and reduce the inlet temperature of the heat extraction liquid entering the heat extraction liquid reheater, so as to increase the heat extraction of the primary flue gas recuperator.

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