A high-temperature tail gas purification and waste heat recovery system

Abstract

The present invention relates to a high-temperature exhaust gas purification and waste heat recovery system, comprising an air preheater, a dust collector, a desulfurization tower, an induced draft fan, and a chimney, sequentially arranged on a boiler exhaust duct. The system also includes a primary waste heat recovery subsystem and a purification system. The primary waste heat recovery subsystem includes a waste heat recovery boiler, a steam turbine generator, and an absorption chiller. The waste heat recovery boiler is arranged between the air preheater and the dust collector, the steam outlet of the waste heat recovery boiler is connected to the steam turbine generator, which is connected to the absorption chiller, and the outlet of the absorption chiller is connected to the water inlet of the waste heat recovery boiler. The purification system includes a purification tower arranged between the desulfurization tower and the induced draft fan. The present invention has the beneficial effects of purifying exhaust gas and effectively recovering and utilizing waste heat from the exhaust gas.

Description

Technical Field

[0001] The present invention relates to a tail gas purification and waste heat recovery system, in particular to a high-temperature tail gas purification and waste heat recovery system, belonging to the technical field of boiler equipment. Background Art

[0002] Among the various heat loss indicators of thermal power plant boilers, exhaust heat loss accounts for the largest proportion of the total boiler heat loss. This is more obvious in high-parameter power plant boilers, where exhaust heat loss accounts for 40%-50% of the total boiler loss, or even higher. The higher the exhaust temperature, the greater the exhaust heat loss. During the production process of a thermal power plant, the temperature of the exhaust gas generated by boiler combustion can reach 130℃-200℃, and some can actually reach as high as 250℃-300℃. Usually, this part of the waste heat is not reused but directly discharged, resulting in a certain amount of energy waste. Therefore, the development of waste heat utilization equipment is urgent. In addition, the exhaust gas emitted by traditional boilers usually needs to be cooled, which wastes recyclable energy, and the exhaust gas purification efficiency is low and the purification is not thorough. Summary of the Invention

[0003] The present invention mainly aims at the problems of low utilization rate of waste heat of tail gas and incomplete purification of tail gas in existing thermal power plant boilers, and provides a high-temperature tail gas purification and waste heat recovery system, which can effectively purify the tail gas and effectively recover and utilize the waste heat of the tail gas.

[0004] The purpose of the present invention is mainly achieved through the following solutions:

[0005] A high-temperature exhaust gas purification and waste heat recovery system includes an air preheater, a dust collector, a desulfurization tower, an induced draft fan and a chimney arranged in sequence on the boiler exhaust duct. The system also includes a first-level waste heat recovery subsystem and a purification system; the first-level waste heat recovery subsystem includes a waste heat recovery boiler, a steam turbine generator and an absorption refrigerator. The waste heat recovery boiler is arranged between the air preheater and the dust collector, the steam outlet of the waste heat recovery boiler is connected to the steam turbine generator, the steam turbine generator is connected to the absorption refrigerator, and the outlet of the absorption refrigerator is connected to the water inlet of the waste heat recovery boiler; the purification system includes a purification tower arranged between the desulfurization tower and the induced draft fan.

[0006] By adopting the above technical solution, the exhaust gas first passes through the waste heat recovery boiler for heat exchange before dust removal, which not only realizes the waste heat recovery and utilization, but also ensures that the temperature of the exhaust gas entering the dust collector is reduced, thereby protecting the dust collector and avoiding it from being damaged by the high temperature of the exhaust gas, effectively extending the service life of the dust collector; the steam turbine generator and the absorption refrigerator form a combined device, and the absorption refrigerator uses the exhaust steam of the steam turbine generator as heating steam. The steam flowing through the absorption refrigerator is liquefied into water and then returned to the waste heat recovery boiler to realize water circulation; a purification tower is set between the desulfurization tower and the induced draft fan, which can further purify the exhaust gas after desulfurization, and can effectively purify the exhaust gas and meet the emission standards.

[0007] Preferably, the high-temperature exhaust gas purification and waste heat recovery and utilization system also includes a secondary waste heat recovery and utilization subsystem, which includes a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a condenser and a vapor-liquid separator. The cold water flows through the condenser through the second heat exchanger and the third heat exchanger and is connected to the heat user through a delivery pipe; the circulating water at the bottom of the purification tower passes through the fourth heat exchanger and the first heat exchanger in turn and flows through the vapor-liquid separator. The steam in the vapor-liquid separator flows through the condenser to form condensed water. The water in the vapor-liquid separator passes through the fourth heat exchanger and the third heat exchanger and is transported to the spray pipe at the upper end of the purification tower to form a circulation loop of the secondary waste heat recovery and utilization subsystem.

[0008] By adopting the above technical solution, cold water first flows through the second heat exchanger and the third heat exchanger, and exchanges heat with the exhaust gas in the purification tower and the hot water flowing through the third heat exchanger respectively. The obtained hot water is further heat-exchanged with the high-temperature steam in the condenser to obtain final hot water and provided to heat users; the water at the bottom of the purification tower flows through the fourth heat exchanger, the first heat exchanger and the vapor-liquid separator under the action of the circulation pump, and then is divided into two paths. The high-temperature steam discharged from the vapor-liquid separator enters the condenser for condensation, and the obtained condensed water is supplied to the outside world. The high-temperature water discharged from the vapor-liquid separator enters the fourth heat exchanger and the third heat exchanger for heat exchange, and then is transported to the spray pipe at the upper end of the purification tower for purifying the exhaust gas, realizing the water circulation in the secondary waste heat recovery and utilization subsystem, while recycling and utilizing the waste heat of the exhaust gas and saving water resources.

[0009] Preferably, the first heat exchanger is arranged between the dust collector and the desulfurization tower.

[0010] By adopting the above technical solution, secondary heat exchange is carried out before the desulfurization tower, which can fully utilize the waste heat of the tail gas and avoid the temperature of the tail gas dropping after entering the desulfurization tower, resulting in a decrease in the utilization rate of the waste heat of the tail gas.

[0011] Preferably, the tail gas in the purification tower exchanges heat with cold water flowing through the second heat exchanger through the second heat exchanger.

[0012] By adopting the above technical solution, the waste heat of the tail gas flowing through the purification tower is used to exchange heat with cold water, thereby fully utilizing resources.

[0013] Preferably, the desulfurization tower adopts a spray desulfurization tower, and a spray layer and a float layer are arranged at intervals inside the desulfurization tower. The bottom of the desulfurization tower is connected to a regeneration pool for treating waste liquid. The regeneration liquid in the regeneration pool is transported to the spray layer through a delivery pipe. The spray layer includes an annular spray pipe, which is connected to the delivery pipe outside the desulfurization tower. The spray layer and the float layer are both provided with 3-5 layers.

[0014] By adopting the above technical solution, the spray layer and the float layer are set at intervals, which can maximize the contact with the exhaust gas, fully adsorb substances such as dust and sulfur dioxide in the exhaust gas, and improve the exhaust gas purification and desulfurization effects; and the bottom of the desulfurization tower is connected to a regeneration pool for treating waste liquid, which regenerates the generated waste liquid and reuses the water in the desulfurization tower, effectively reducing the desulfurization cost and saving resources.

[0015] Preferably, the steam turbine generator adopts a back-pressure steam turbine generator, and the absorption refrigerator adopts a lithium bromide absorption refrigerator. The lithium bromide absorption refrigerator and the back-pressure steam turbine generator form a combined device, and the exhaust steam of the back-pressure steam turbine generator is used as the heating steam of the lithium bromide absorption refrigerator. The absorption refrigerator is connected to the cold user through a delivery pipe.

[0016] By adopting the above technical solution, the steam generated by the waste heat recovery boiler drives the steam turbine generator to generate electricity. The steam discharged from the steam turbine generator is used as heating steam for the absorption refrigerator. The absorption refrigerator is connected to the cold users through a transmission pipe to provide cold air or cold water to the cold users. The steam flowing through the absorption refrigerator is liquefied into water and then returned to the water inlet of the waste heat recovery boiler, realizing water circulation and saving resources.

[0017] Preferably, the dust collector is a bag dust collector.

[0018] By adopting the above technical solution, the bag dust collector is a dry dust filtering device with high dust removal efficiency, generally above 99%. It has a high classification efficiency for fine dust with submicron particle size, can handle a wide range of air volume, and can reduce the emission of pollutants in the exhaust gas. Compared with the electrostatic precipitator, the bag dust collector has a simple structure and is easy to maintain and operate. While ensuring the same high dust removal efficiency, the cost is also lower.

[0019] Preferably, the induced draft fan is an axial flow induced draft fan.

[0020] By adopting the above technical solution, the axial flow induced draft fan can discharge the exhaust gas in the exhaust duct at a low speed, thereby preventing the exhaust gas from being discharged too quickly in the exhaust duct and affecting the waste heat recovery and purification of the exhaust gas.

[0021] Preferably, the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger are all heat pipe heat exchangers.

[0022] By adopting the above technical solution, the first heat exchange tube and the second heat exchanger adopt gas-liquid heat pipe heat exchangers, and the third heat exchanger and the fourth heat exchanger adopt liquid-liquid heat pipe heat exchangers. The heat pipe is a heat transfer component with high thermal conductivity and high isothermal properties. The heat exchanger with heat pipe as the heat transfer element has the advantages of high heat transfer efficiency, compact structure and low fluid resistance loss. It can avoid heat loss during the heat exchange process and improve the utilization rate of exhaust waste heat.

[0023] Therefore, the present invention has the following advantages:

[0024] (1) The present invention can perform multi-stage waste heat recovery and reasonable waste heat diversion of boiler tail gas, fully utilizing the waste heat of boiler tail gas, reducing exhaust heat loss, improving boiler thermal efficiency, and achieving the purpose of saving energy and reducing costs;

[0025] (2) The present invention can effectively purify boiler tail gas in multiple stages. The desulfurization tower fully absorbs dust and sulfur dioxide and other substances in the tail gas, thereby improving the effect of tail gas purification and desulfurization. The purification tower further purifies the tail gas in depth, with high purification efficiency and thorough purification, thereby reducing air pollution.

[0026] (3) The present invention has a scientific and reasonable structure, is safe and convenient to use, reduces operating costs and increases economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention;

[0028] Figure 2 It is a structural diagram of the secondary waste heat recovery subsystem of the present invention;

[0029] Figure 3 It is a structural diagram of the primary waste heat recovery and utilization subsystem of the present invention;

[0030] Figure 4 It is a structural schematic diagram of the desulfurization tower of the present invention.

[0031] Illustration: 1- boiler, 2- air preheater, 3- dust collector, 4- desulfurization tower, 5- induced draft fan, 6- chimney, 7- waste heat recovery boiler, 8- steam turbine generator, 9- absorption chiller, 10- steam outlet, 11- water inlet, 12- purification tower, 13- first heat exchanger, 14- second heat exchanger, 15- third heat exchanger, 16- fourth heat exchanger, 17- condenser, 18- vapor-liquid separator, 19- cold water, 20- hot user, 21- spray pipe, 22- spray layer, 23- floating ball layer, 24- regeneration tank, 25- cold user. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0033] like Figure 1 As shown, the present invention provides a technical solution, a high-temperature exhaust gas purification and waste heat recovery system, including an air preheater 2, a waste heat recovery boiler 7, a dust collector 3, a first heat exchanger 13, a desulfurization tower 4, a purification tower 12, an induced draft fan 5 and a chimney 6, which are sequentially arranged on the exhaust pipe of the boiler 1.

[0034] like Figure 3 As shown, the high-temperature exhaust gas purification and waste heat recovery system also includes a first-level waste heat recovery subsystem; the first-level waste heat recovery subsystem includes a waste heat recovery boiler 7, a steam turbine generator 8 and an absorption refrigerator 9. The waste heat recovery boiler 7 is arranged between the air preheater 2 and the dust collector 3. The steam outlet 10 of the waste heat recovery boiler 7 is connected to the steam turbine generator 8, the steam turbine generator 8 is connected to the absorption refrigerator 9, and the outlet of the absorption refrigerator 9 is connected to the water inlet 11 of the waste heat recovery boiler 7. The steam flowing through the absorption refrigerator 9 is liquefied into water and then returns to the waste heat recovery boiler 7 to realize water circulation; the steam turbine generator 8 adopts a back-pressure steam turbine generator, and the absorption refrigerator 9 adopts a lithium bromide absorption refrigerator. The lithium bromide absorption refrigerator and the back-pressure steam turbine generator form a combined device, and the exhaust steam of the back-pressure steam turbine generator is used as the heating steam of the lithium bromide absorption refrigerator. The absorption refrigerator 9 is connected to the cold user 25 through a delivery pipe.

[0035] like Figure 2 As shown, the high-temperature exhaust gas purification and waste heat recovery system also includes a secondary waste heat recovery subsystem, which includes a first heat exchanger 13, a second heat exchanger 14, a third heat exchanger 15, a fourth heat exchanger 16, a condenser 17 and a vapor-liquid separator 18. The cold water 19 passes through the second heat exchanger 14 and the third heat exchanger 15 and flows through the condenser 17 and is connected to the heat user 20 through a delivery pipe. The exhaust in the purification tower 12 exchanges heat with the cold water 19 flowing through the second heat exchanger 14 through the second heat exchanger 14; the circulating water at the bottom of the purification tower 12 passes through the fourth heat exchanger 16 and the first heat exchanger 13 in sequence and flows through the vapor-liquid separator 18. The steam in the vapor-liquid separator 18 flows through the condenser 17 to form condensed water. The water in the vapor-liquid separator 18 passes through the fourth heat exchanger 16 and the third heat exchanger 15 and is transported to the spray pipe 21 at the upper end of the purification tower 12, forming a circulation loop of the secondary waste heat recovery subsystem.

[0036] like Figure 4As shown, the desulfurization tower 4 adopts a spray desulfurization tower, and a spray layer 22 and a float layer 23 are arranged at intervals inside the desulfurization tower 4. The bottom of the desulfurization tower 4 is connected to a regeneration pool 24 for treating waste liquid. The regenerated liquid in the regeneration pool 24 is transported to the spray layer 22 through a delivery pipe. The spray layer 22 includes an annular spray pipe, which is connected to the delivery pipe outside the desulfurization tower 4. The spray layer 22 and the float layer 23 are both provided with 3 layers. The water mist sprayed from the annular spray pipe is combined with dust, sulfur dioxide and other substances in the exhaust gas, and then falls to the bottom of the desulfurization tower 4 after combination. The floats in the float layer 23 can contact with the exhaust gas to the maximum extent, fully adsorb dust, sulfur dioxide and other substances in the exhaust gas, and improve the exhaust gas purification and desulfurization effect; and the bottom of the desulfurization tower 4 is connected to a regeneration pool 24 for treating waste liquid, which regenerates the generated waste liquid, so that the water in the desulfurization tower 4 is reused, effectively reducing the desulfurization cost and saving resources.

[0037] In this embodiment, the dust collector 3 is a bag dust collector, the induced draft fan 5 is an axial flow induced draft fan, the first heat exchanger 13 and the second heat exchanger 14 are gas-liquid heat pipe heat exchangers, and the third heat exchanger and the fourth heat exchanger are liquid-liquid heat pipe heat exchangers.

[0038] The specific working process of the present invention is as follows: first, the induced draft fan 5 leads the boiler tail gas with a temperature of up to 200°C to the smoke exhaust pipe, the tail gas passes through the air preheater 2 to preheat the air entering the boiler 1, and then enters the waste heat recovery boiler 7, the tail gas discharged from the waste heat recovery boiler 7 enters the dust collector 3 for preliminary dust removal, and the tail gas after preliminary dust removal enters the first heat exchanger 3 for heat exchange under the action of the induced draft fan 5, and the tail gas coming out of the first heat exchanger 13 enters the desulfurization tower 4 for desulfurization, and the desulfurized tail gas enters the purification tower 12 for deep purification, and then is discharged from the chimney 6 to the atmosphere under the action of the induced draft fan 5; the waste heat recovery boiler 7 uses the heat contained in the tail gas to generate high-temperature and high-pressure steam, and the high-temperature and high-pressure steam enters the steam turbine generator 8 through the steam outlet 10 for power generation and the absorption refrigerator 9 for refrigeration, and the air flowing through the absorption refrigerator 9 is discharged from the exhaust gas. The steam is liquefied into water and returns to the waste heat recovery boiler 7; the cold water 19 flows through the second heat exchanger 14 and the third heat exchanger 15, and exchanges heat with the exhaust gas in the purification tower 12 and the hot water in the third heat exchanger 15 respectively. The obtained hot water is further heat-exchanged with the high-temperature steam in the condenser 17, and the hot water finally obtained is provided to the heat user 20 through the delivery pipe. The water at the bottom of the purification tower 12 flows through the fourth heat exchanger 16, the first heat exchanger 13 and the vapor-liquid separator 18 under the action of the circulation pump, and then is divided into two paths. The high-temperature steam discharged from the vapor-liquid separator 18 enters the condenser 17 for condensation, and the obtained condensed water is used by the outside world. The high-temperature water discharged from the vapor-liquid separator 18 enters the fourth heat exchanger 16 and the third heat exchanger 15 for heat exchange, and then is transported to the spray pipe 21 at the upper end of the purification tower 12 for purifying the exhaust gas and realizing water circulation.

[0039] The present invention has a scientific and reasonable structure and is safe and convenient to use. The multi-stage waste heat recovery and reasonable waste heat diversion of boiler tail gas can fully utilize the waste heat of boiler tail gas, reduce exhaust heat loss, improve boiler thermal efficiency, and achieve the purpose of saving energy and reducing costs. The boiler tail gas is effectively purified at multiple stages. The desulfurization tower fully absorbs dust, sulfur dioxide and other substances in the tail gas, improving the effect of tail gas purification and desulfurization. The purification tower further deeply purifies the tail gas with high purification efficiency and thorough purification, reducing air pollution, lowering operating costs, and increasing economic benefits.

[0040] It should be understood that this embodiment is only used to illustrate the present invention and is not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

Claims

1. A high-temperature tail gas purification and waste heat recovery system, comprising an air preheater (2), a dust collector (3), a desulfurization tower (4), an induced draft fan (5) and a chimney (6) arranged in sequence on the exhaust pipe of a boiler (1), characterized in that: The system further comprises a primary waste heat recovery subsystem and a purification system; the primary waste heat recovery subsystem comprises a waste heat recovery boiler (7), a steam turbine generator (8) and an absorption refrigerator (9); the waste heat recovery boiler (7) is arranged between the air preheater (2) and the dust collector (3); the steam outlet (10) of the waste heat recovery boiler (7) is connected to the steam turbine generator (8), the steam turbine generator (8) is connected to the absorption refrigerator (9), and the outlet of the absorption refrigerator (9) is connected to the water inlet (11) of the waste heat recovery boiler (7); the purification system comprises a purification tower (12) arranged between the desulfurization tower (4) and the induced draft fan (5); The high-temperature tail gas purification and waste heat recovery and utilization system also includes a secondary waste heat recovery and utilization subsystem, which includes a first heat exchanger (13), a second heat exchanger (14), a third heat exchanger (15), a fourth heat exchanger (16), a condenser (17) and a vapor-liquid separator (18). Cold water (19) flows through the second heat exchanger (14) and the third heat exchanger (15), passes through the condenser (17), and is connected to the heat user (20) through a delivery pipe; the circulating water at the bottom of the purification tower (12) passes through the fourth heat exchanger (16) and the first heat exchanger (13) in sequence and flows through the vapor-liquid separator (18); the steam in the vapor-liquid separator (18) flows through the condenser (17) to form condensed water; the water in the vapor-liquid separator (18) passes through the fourth heat exchanger (16) and the third heat exchanger (15) and is transported to the spray pipe (21) at the upper end of the purification tower (12), forming a circulation loop of the secondary waste heat recovery and utilization subsystem; The desulfurization tower (4) is a spray desulfurization tower. A spray layer (22) and a float layer (23) are provided inside the desulfurization tower (4). A regeneration pool (24) for treating waste liquid is connected to the bottom of the desulfurization tower (4). The regeneration liquid in the regeneration pool (24) is transported to the spray layer (22) through a transport pipe. The steam turbine generator (8) is a back-pressure steam turbine generator, and the absorption refrigerator (9) is a lithium bromide absorption refrigerator. The lithium bromide absorption refrigerator and the back-pressure steam turbine generator form a combined device, and the exhaust steam of the back-pressure steam turbine generator is used as heating steam for the lithium bromide absorption refrigerator. The absorption refrigerator (9) is connected to the cold user (25) through a delivery pipe; The first heat exchanger (13), the second heat exchanger (14), the third heat exchanger (15), and the fourth heat exchanger (16) are all heat pipe heat exchangers; The spray layer (22) includes an annular spray pipe connected to a delivery pipe outside the desulfurization tower (4). The spray layer (22) and the floating ball layer (23) are both provided with 3-5 layers.

2. A high-temperature tail gas purification and waste heat recovery system according to claim 1, characterized in that: The first heat exchanger (13) is arranged between the dust collector (3) and the desulfurization tower (4).

3. A high-temperature tail gas purification and waste heat recovery system according to claim 2, characterized in that: The tail gas in the purification tower (12) exchanges heat with the cold water flowing through the second heat exchanger (14) through the second heat exchanger (14).

4. The high-temperature tail gas purification and waste heat recovery system according to claim 1, characterized in that: The dust collector (3) is a bag type dust collector.

5. The high-temperature tail gas purification and waste heat recovery system according to claim 1, characterized in that: The induced draft fan (5) is an axial flow induced draft fan.

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