Desulfurization slurry flash evaporation flue gas deep waste heat supply system based on process preheating

Abstract

The utility model discloses a desulfurization slurry flash evaporation flue gas deep waste heat supply system based on process preheating, and belongs to the technical field of coal-fired boiler waste heat supply. The system consists of an original desulfurization tower subsystem and a desulfurization slurry flash evaporation and process water heating subsystem, wherein the desulfurization slurry flash evaporation and process water heating subsystem comprises a flash evaporation tank 21, a flash evaporation heater 26, a vacuum pump 18, a heat supply network return water recooling bypass valve 19 and connecting pipelines and parts. Heat supply network return water is firstly used for low-temperature heating of process water or inlet air in a plant, then fed into the flash heat exchanger and returned to the desulfurizing tower for spraying, so that the flue gas waste heat recovery rate can be greatly improved, flue gas deep waste heat supply can be realized without a heat pump, the heat supply capacity is improved, and the energy consumption is reduced. And the process operation conditions of process water and inlet air are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of based on process preheating's desulfurization slurry flash steam flue gas depth waste heat heating system, belong to coal-fired boiler waste heat heating technical field. BACKGROUND

[0002] Boiler is accompanied by a large amount of high-temperature flue gas emission in heat production process, and the waste heat recovery of flue gas can not only reduce boiler heat loss, but also reduce fuel consumption and greenhouse gas emissions and other pollutants, improve the thermal efficiency of boiler. In recent years, a new type of desulfurization slurry flash steam flue gas waste heat recovery technology appears, which gives up the usual flue gas waste heat exchanger, and uses desulfurization slurry flash evaporation + absorption type heat pump to take out the heat of flue gas from desulfurization slurry through flash tank, and send flash steam into heat pump for waste heat recovery, and heat network return water or other process water, while concentrated liquid returns to desulfurization circulating water. Its advantages are: no need to transform flue gas system, reduce the difficulty of site implementation; condensate water quality is better, convenient for recycling. But the disadvantage is also very obvious: flue gas temperature can only be reduced to 42~45℃, about half of the recovered flue gas waste heat, not deep heat recovery, only half of the project, still a lot of flue gas waste heat from flue gas, and future needs to do secondary transformation to achieve deep heat recovery. The cost of unit waste heat recovery is relatively high, and the investment recovery period is long. The fundamental reason why it cannot reduce the flue gas temperature to 30℃ level and achieve deep heat recovery is: first, desulfurization slurry flash evaporation complete equipment is a vacuum equipment, and its system integration is more complex, with high protection requirements, and the lower the flash steam temperature, the larger the specific volume, the larger the equipment size, and the higher the cost; second, a lot of SO2 and other non-condensable gases will be released during the desulfurization slurry flash evaporation process, and the flash steam is sent into the absorption type heat pump, and it is difficult to extract vacuum during the condensation and heat release process in the heat pump horizontal evaporator, and the absolute pressure can only be maintained at about 7~8kPa during actual operation, and it is difficult to further improve the vacuum degree under the existing equipment and conditions, and it cannot further improve the vacuum degree like the usual condenser, so the saturation temperature of flash steam can only be reduced to 38~40℃ level, resulting in that the flue gas temperature can only be reduced to 40~45℃ level; third, this technical method still belongs to heat pump method in nature, only the heat taking device is different, and a lot of driving steam is still needed, with high operation cost, which worsens the flexible adjustment problem of thermal power in power plant, and even sometimes seriously affects the technical and economic benefits of power plant. CONTENT OF UTILITY MODEL

[0003] The purpose and task of the utility model are to reduce the temperature of return water by using return water of heat network for process preheating, and then sending it into desulfurization slurry flash heat exchanger for low-temperature heat exchange, to build a new flue gas deep waste heat recovery integrated system, aiming at the technical limitations of various flue gas waste heat recovery systems and their influence on the economy of power plant.

[0004] The utility model discloses a specific description is: a kind of based on process preheating's desulfurization slurry flash steam flue gas depth waste heat heating system, by original desulfurization tower subsystem and desulfurization slurry flash and heating process water subsystem, the original desulfurization tower subsystem includes original desulfurization tower 1, original flue gas inlet smoke pipe 2 and original slurry pump 3, it is characterized in that, the desulfurization slurry flash and heating process water subsystem includes flash tank 21, flash heater 26, vacuum pump 18, hot water return cooling bypass valve 19 and connecting pipeline and component, wherein the slurry inlet of flash tank 21 is connected with the bottom desulfurization slurry pool of original desulfurization tower 1 by waste heat slurry pump 20 and waste heat slurry outlet, the concentrated slurry outlet of flash tank 21 is connected with the inlet of original slurry pump 3;Flash tank 21 is provided with flash steam demister 22, washing spray layer 23 in inside upper portion, its flash steam outlet is connected with the steam inlet of flash heater 26 by flash steam communication pipe 25, the condensate outlet of flash heater 26 is connected with the inlet of condensate pump 27, the outlet of condensate pump 27 is communicated with the inlet of washing spray layer 23 and the outlet pipe of condensate water W outside row respectively;The low temperature water inlet of flash heater 26 is connected with the water outlet of hot water return cooling bypass valve 19, the water inlet of hot water return cooling bypass valve 19 is communicated with the water inlet pipe of hot water return water H1, the low temperature water outlet of flash heater 26 is communicated with the water outlet pipe of hot water return water H2;The outlet of non-condensable gas S of flash heater 26 is connected with the gas inlet of vacuum pump 18.

[0005] The exhaust port of vacuum pump 18 is communicated with the original flue gas inlet smoke pipe 2 of original desulfurization tower 1;The upstream of original flue gas inlet smoke pipe 2 is the inlet of original flue gas Y1, downstream is the smoke inlet of original desulfurization tower 1, the top of original desulfurization tower 1 is the outlet of clean flue gas Y2;The circulating liquid outlet of the bottom desulfurization slurry pool of original desulfurization tower 1 is communicated with the inlet of original slurry pump 3, the water inlet pipe of desulfurization water B and the concentrated slurry outlet of flash tank 21 respectively, the outlet of original slurry pump 3 is connected with the circulating slurry spray inlet of original desulfurization tower 1, the blowdown of the bottom desulfurization slurry pool of original desulfurization tower 1 is communicated with the drain pipe of desulfurization wastewater P.

[0006] The water inlet of hot water return cooling bypass valve 19 is also connected with the high temperature side inlet of hot water return cooling heat exchanger 29, the water outlet of hot water return cooling bypass valve 19 is also connected with the high temperature side outlet of hot water return cooling heat exchanger 29, the low temperature side inlet of hot water return cooling heat exchanger 29 is communicated with the water inlet pipe of heated low temperature process water C1, the low temperature side outlet of hot water return cooling heat exchanger 29 is communicated with the water outlet pipe of heated low temperature process water C2.

[0007] The water inlet of the heat network backwater recooling bypass valve 19 is also connected with the high-temperature side inlet of the boiler air inlet low-temperature warm air heater 15, the high-temperature side outlet of the boiler air inlet low-temperature warm air heater 15 is connected with the water outlet of the heat network backwater recooling bypass valve 19 through the warm air heater booster pump 14, the low-temperature side inlet of the boiler air inlet low-temperature warm air heater 15 is communicated with the ambient air A0, the low-temperature side outlet of the boiler air inlet low-temperature warm air heater 15 is connected with the air inlet of the high-temperature warm air heater 10 through the communication pipe of the preheated air A1, the air outlet of the high-temperature warm air heater 10 is connected with the air inlet of the air preheater 9 of the boiler body 8 through the air blower 11, and the smoke outlet of the air preheater 9 is communicated with the original flue gas inlet pipe 2 through the dust remover 12 and the induced draft fan 13.

[0008] The outlet of the waste heat slurry pump 20 is connected with the slurry inlets of N-stage flash tanks 31, where N is greater than or equal to 2, and the inside upper part of the N-stage flash tank 31 is provided with an N-stage flash steam demister 32 and an N-stage washing spray layer 33, the flash steam outlet of the N-stage flash tank 31 is connected with the steam inlet of an N-stage flash heater 36 through an N-stage flash steam communication pipe 35, the condensate water outlet of the N-stage flash heater 36 is connected with the inlet of an N-stage condensate pump 37, and the outlet of the N-stage condensate pump 37 is communicated with the inlet of the N-stage washing spray layer 33 and the water outlet pipe of N-stage external condensate water W1 respectively; at this time, the water inlet of the heat network backwater recooling bypass valve 19 is connected with the high-temperature side inlet of the boiler air inlet low-temperature warm air heater 15 through the warm air heater bypass valve 17, the high-temperature side outlet of the boiler air inlet low-temperature warm air heater 15 is connected with the low-temperature water inlet of the N-stage flash heater 36, and the low-temperature water outlet of the N-stage flash heater 36 is communicated with the low-temperature water outlet of the flash heater 26 and the water return pipe of the heat network backwater return water H2 respectively; the slurry outlet of the N-stage flash tank 31 is connected with the spray inlet of the N-stage spray layer 4 in the original desulfurization tower 1 through an N-stage slurry pump 16, and the N-stage spray layer 4 and the lower spray layer 6 below the N-stage spray layer 4 form an N-stage desulfurization heat exchange zone 5, and the lower spray layer 6 and the inlet of the original flue gas inlet pipe 2 below the lower spray layer 6 form a lower-stage desulfurization heat exchange zone 7; the N-stage non-condensable gas S1 outlet of the N-stage flash heater 36 is connected with the gas inlet of an N-stage vacuum pump 28, and the gas outlet of the N-stage vacuum pump 28 is communicated with the tower internal desulfurization heat exchange zone of the original desulfurization tower 1.

[0009] The beneficial effects of the utility model are as follows.

[0010] (1) For the inherent problem of desulfurization slurry flash flue gas waste heat recovery technology that the efficiency is not high due to the influence of the heat supply network return water temperature on the waste heat recovery scale, flue gas temperature reduction range, etc., by using the heat supply network return water for process preheating first, i.e. as preheating boiler feed water, desalted water make-up, etc. The heat supply network return water temperature is significantly reduced, usually by 5-20℃, then the lower temperature heat supply network return water and the desulfurization slurry flash steam can be used for heat exchange without the need for a heat pump, achieving waste heat supply while significantly reducing the steam temperature and pressure of the desulfurization slurry flash, thereby significantly reducing the outlet temperature of the concentrated slurry, and then returning to the desulfurization tower for spray desulfurization, heat exchange, significantly reducing the exhaust gas temperature and significantly improving the waste heat recovery scale. Thus, deep heat recovery of flue gas can be achieved, avoiding the inherent shortcomings of the existing desulfurization slurry flash + absorption heat pump technology, and the waste heat recovery amount can be increased by 1.5-2 times.

[0011] (2) The use of fractional flash evaporation to achieve temperature grading of the concentrated slurry output, and then returning to the desulfurization tower for step-by-step spray desulfurization and step-by-step temperature reduction, is more conducive to significantly reducing the exhaust gas temperature. This is particularly suitable for scenarios where the heat supply network return water temperature is relatively high.

[0012] (3) The supporting vacuum pump can use a high vacuum model to significantly increase the working vacuum of the last stage flash tank and the flash steam heat exchanger, which is more conducive to reducing the exhaust gas temperature and improving the waste heat recovery rate.

[0013] (4) The condensate water of the flash steam can be used to wash the demister in the flash tank, maintaining a higher demisting effect and supplementing the desulfurization slurry, replacing part or all of the original desulfurization make-up B, which is often sourced from wastewater containing high chloride ions. The use of flash steam condensate water instead can help significantly reduce the discharge flow of desulfurization wastewater P and significantly reduce the secondary pollution and operation and maintenance costs caused by it, improving the operation of the desulfurization system.

[0014] (5) The condensate water of the flash steam can also be used as make-up water for the heat supply network return water, significantly reducing the amount of softened water and its cost. At the same time, the comprehensive recycling of condensate water also significantly reduces water resource consumption.

[0015] (6) The preheating of relevant low-temperature process water and boiler inlet air within the plant can be achieved, effectively saving energy and reducing emissions, and reducing coal consumption and costs.

[0016] (7) The present scheme and system can be widely used in flue gas waste heat recovery and heating systems for power plants and boiler houses, promoting the realization of energy-saving and environmental protection integrated comprehensive technology and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 、 2, 3 is the system schematic diagram of the utility model.

[0018] Figure 1 、 2 , 3 the component number and name as follows.

[0019] The original desulfurization tower 1, the original flue gas into the smoke pipe 2, the original slurry pump 3, the N level spray layer 4, the lower spray layer 6, the N level desulfurization heat exchange zone 5, the lower spray layer 6, the lower level desulfurization heat exchange zone 7, the boiler body 8, the air preheater 9, the high-temperature warm air heater 10, the air blower 11, the dust remover 12, the induced draft fan 13, the warm air heater booster pump 14, the boiler air inlet low-temperature warm air heater 15, the N level slurry pump 16, the warm air heater bypass valve 17, the vacuum pump 18, the heat network return water recooling bypass valve 19, the waste heat slurry pump 20, the flash tank 21, the flash steam demister 22, the washing spray layer 23, the flash steam communication pipe 25, the flash heater 26, the condensation pump 27, the N level vacuum pump 28, the heat network return water recooling heat exchanger 29, the N level flash tank 31, the N level flash steam demister 32, the N level washing spray layer 33, the N level flash steam communication pipe 35, the N level flash heater 36, the N level condensation pump 37, the ambient air A0, the preheated air A1, the desulfurization makeup water B, the heated low-temperature process inlet water C1, the heated low-temperature process outlet water C2, the heat network return water inlet water H1, the heat network return water outlet water H2, the desulfurization waste water P, the non-condensable gas S, the N level non-condensable gas S1, the external discharge condensate water W, the N level external discharge condensate water W1, the original flue gas Y1, the clean flue gas Y2. DETAILED DESCRIPTION

[0020] Figure 1 、 2 , 3 is the system schematic diagram and embodiment of the utility model.

[0021] The specific embodiment of the utility model is as follows.

[0022] The system schematic diagram of embodiment 1 of the utility model is as follows Figure 1As shown, its specific description is: a kind of deep waste heat heating system of desulfurization slurry flash gas based on process preheating, by original desulfurization tower subsystem and desulfurization slurry flash and heating process water subsystem, the original desulfurization tower subsystem includes original desulfurization tower 1, original flue gas inlet smoke pipe 2 and original slurry pump 3, it is characterized in that, the desulfurization slurry flash and heating process water subsystem includes flash tank 21, flash heater 26, vacuum pump 18, hot water return cooling bypass valve 19 and connecting pipeline and component, wherein the slurry inlet of the flash tank 21 is connected with the waste heat slurry outlet of the bottom desulfurization slurry pool of original desulfurization tower 1 by waste heat slurry pump 20, and the concentrated slurry outlet of flash tank 21 is connected with the inlet of original slurry pump 3;Flash tank 21 is provided with flash steam demister 22, washing spray layer 23 in the inside upper portion, and the steam outlet of flash steam is connected with the steam inlet of flash heater 26 by flash steam communication pipe 25, the condensate water outlet of flash heater 26 is connected with the inlet of condensate pump 27, and the outlet of condensate pump 27 is communicated with the inlet of washing spray layer 23 and the outlet pipe of condensate water W for external discharge respectively;The low-temperature water inlet of flash heater 26 is connected with the water outlet of hot water return cooling bypass valve 19, the water inlet of hot water return cooling bypass valve 19 is communicated with the water inlet pipe of hot water return water H1, and the low-temperature water outlet of flash heater 26 is communicated with the water outlet pipe of hot water return water H2;The outlet of non-condensable gas S of flash heater 26 is connected with the gas inlet of vacuum pump 18.

[0023] The exhaust port of vacuum pump 18 is communicated with the original flue gas inlet smoke pipe 2 of original desulfurization tower 1;The upstream of original flue gas inlet smoke pipe 2 is the inlet of original flue gas Y1, and the downstream is the smoke inlet of original desulfurization tower 1, and the top of original desulfurization tower 1 is the outlet of clean flue gas Y2;The circulating liquid outlet of the bottom desulfurization slurry pool of original desulfurization tower 1 is communicated with the inlet of original slurry pump 3, the water inlet pipe of desulfurization water B and the concentrated slurry outlet of flash tank 21 respectively, the outlet of original slurry pump 3 is connected with the circulating slurry spray inlet of original desulfurization tower 1, and the blowdown port of the bottom desulfurization slurry pool of original desulfurization tower 1 is communicated with the drain pipe of desulfurization wastewater P.

[0024] The water inlet of hot water return cooling bypass valve 19 is also connected with the high-temperature side inlet of hot water return cooling heat exchanger 29, the water outlet of hot water return cooling bypass valve 19 is also connected with the high-temperature side outlet of hot water return cooling heat exchanger 29, the low-temperature side inlet of hot water return cooling heat exchanger 29 is communicated with the water inlet pipe of heated low-temperature process water C1, and the low-temperature side outlet of hot water return cooling heat exchanger 29 is communicated with the water outlet pipe of heated low-temperature process water C2.

[0025] In the embodiment 2 of the utility model, system schematic diagram refers to Figure 2As shown in the figure, the specific description is: its basic system flow is consistent with that of embodiment 1, but the object of the heat network backwater process preheating is changed from the heated low-temperature process water C1 to the preheated boiler air A0, so the water inlet of the heat network backwater cooling bypass valve 19 is connected with the high-temperature side inlet of the boiler air low-temperature air heater 15 through the air heater bypass valve 17, the high-temperature side outlet of the boiler air low-temperature air heater 15 is connected with the low-temperature water inlet of the N-stage flash evaporation heater 36, and the low-temperature water outlet of the N-stage flash evaporation heater 36 is connected with the low-temperature water outlet of the flash evaporation heater 26 and the backwater pipe of the heat network backwater H2.

[0026] The system schematic diagram of the embodiment 3 of the utility model is shown in the figure Figure 3 As shown in the figure, the specific description is: its basic system flow is consistent with that of embodiment 1, but the object of the heat network backwater process preheating is changed from the heated low-temperature process water C1 to the preheated boiler air A0, so the water inlet of the heat network backwater cooling bypass valve 19 is connected with the high-temperature side inlet of the boiler air low-temperature air heater 15 through the air heater bypass valve 17, the high-temperature side outlet of the boiler air low-temperature air heater 15 is connected with the low-temperature water inlet of the N-stage flash evaporation heater 36, and the low-temperature water outlet of the N-stage flash evaporation heater 36 is connected with the low-temperature water outlet of the flash evaporation heater 26 and the backwater pipe of the heat network backwater H2.

[0027] It needs to be explained that, based on the desulfurization slurry flash evaporation + hot water depth recooling combined mode, a whole new desulfurization slurry flash evaporation integrated system and operation strategy without heat pump can be used for flue gas deep flue gas waste heat recovery, and according to the overall solution, different specific implementation measures and different structure of the specific implementation device can be used, the above specific implementation mode is only a few of them, any other similar simple transformation implementation mode, for example, simple transformation of flash steam and heat exchanger, simple adjustment of pipeline, or simple change of vacuum extraction mode, condensate recovery mode, etc., all fall within the protection scope of the utility model.

Claims

1. A deep waste heat supply system for desulfurization slurry flash evaporation flue gas based on process preheating, comprising an original desulfurization tower subsystem and a desulfurization slurry flash evaporation and heating process water subsystem, wherein the original desulfurization tower subsystem includes an original desulfurization tower (1), an original flue gas inlet pipe (2), and an original slurry pump (3), characterized in that, The desulfurization slurry flash evaporation and heating process water subsystem includes a flash tank (21), a flash heater (26), a vacuum pump (18), a heat network return water recooling bypass valve (19), and connecting pipelines and components. The slurry inlet of the flash tank (21) is connected to the waste heat slurry outlet of the bottom desulfurization slurry pool of the original desulfurization tower (1) via a waste heat slurry pump (20), and the concentrated slurry outlet of the flash tank (21) is connected to the inlet of the original slurry pump (3). A flash steam demister (22) and a washing spray layer (23) are installed in the upper part of the flash tank (21), and its flash steam outlet is connected to the steam outlet of the flash heater (26) via a flash steam connecting pipe (25). The condensate outlet of the flash heater (26) is connected to the inlet of the condensate pump (27), and the outlet of the condensate pump (27) is connected to the inlet of the washing spray layer (23) and the outlet of the condensate (W) respectively; the low temperature water inlet of the flash heater (26) is connected to the outlet of the heat network return water recooling bypass valve (19), the inlet of the heat network return water recooling bypass valve (19) is connected to the inlet of the heat network return water (H1), and the low temperature water outlet of the flash heater (26) is connected to the outlet of the heat network return water return (H2); the non-condensable gas (S) outlet of the flash heater (26) is connected to the inlet of the vacuum pump (18).

2. The deep waste heat supply system for desulfurization slurry flash evaporation flue gas based on process preheating as described in claim 1, characterized in that... The exhaust port of the vacuum pump (18) is connected to the original flue gas inlet pipe (2) of the original desulfurization tower (1); the upstream of the original flue gas inlet pipe (2) is the inlet of the original flue gas (Y1), the downstream is the inlet of the original desulfurization tower (1), and the top of the original desulfurization tower (1) is the outlet of the clean flue gas (Y2); the circulating liquid outlet of the bottom desulfurization slurry pool of the original desulfurization tower (1) is connected to the inlet of the original slurry pump (3), the water inlet pipe of the desulfurization makeup water (B) and the concentrated slurry outlet of the flash tank (21), respectively; the outlet of the original slurry pump (3) is connected to the circulating slurry spray inlet of the original desulfurization tower (1); and the sewage outlet of the bottom desulfurization slurry pool of the original desulfurization tower (1) is connected to the drainage pipe of the desulfurization wastewater (P).

3. A deep waste heat supply system for desulfurization slurry flash evaporation flue gas based on process preheating as described in claim 1, characterized in that... The inlet of the heat network return water recooling bypass valve (19) is also connected to the high-temperature side inlet of the heat network return water recooling heat exchanger (29), and the outlet of the heat network return water recooling bypass valve (19) is also connected to the high-temperature side outlet of the heat network return water recooling heat exchanger (29). The low-temperature side inlet of the heat network return water recooling heat exchanger (29) is connected to the inlet pipe of the heated low-temperature process water (C1), and the low-temperature side outlet of the heat network return water recooling heat exchanger (29) is connected to the outlet pipe of the heated low-temperature process return water (C2).

4. A deep waste heat supply system for desulfurization slurry flash flue gas based on process preheating as described in claim 1, characterized in that... The inlet of the heat network return water recooling bypass valve (19) is also connected to the high-temperature side inlet of the boiler air inlet low-temperature warm air blower (15). The high-temperature side outlet of the boiler air inlet low-temperature warm air blower (15) is connected to the outlet of the heat network return water recooling bypass valve (19) via the warm air blower booster pump (14). The low-temperature side inlet of the boiler air inlet low-temperature warm air blower (15) is connected to the ambient air (A0). The low-temperature side outlet of the boiler air inlet low-temperature warm air blower (15) is connected to the air inlet of the high-temperature warm air blower (10) via the preheated air (A1) connecting pipe. The air outlet of the high-temperature warm air blower (10) is connected to the air inlet of the air preheater (9) of the boiler body (8) via the blower (11). The exhaust port of the air preheater (9) is connected to the original flue gas inlet pipe (2) via the dust collector (12) and the induced draft fan (13).

5. A deep waste heat supply system for desulfurization slurry flash flue gas based on process preheating as described in claim 4, characterized in that... The outlet of the waste heat slurry pump (20) is connected to the slurry inlet of the flash tank (21) and the slurry inlet of the N-stage flash tank (31), where N is greater than or equal to 2. The upper part of the interior of the N-stage flash tank (31) is equipped with an N-stage flash steam demister (32) and an N-stage washing spray layer (33). Its flash steam outlet is connected to the steam inlet of the N-stage flash heater (36) via the N-stage flash steam connecting pipe (35). The condensate outlet of the N-stage flash heater (36) is connected to the inlet of the N-stage condensate pump (37). The outlet of the N-stage condensate pump (37) is connected to the inlet of the N-stage washing spray layer (33) and the outlet pipe of the N-stage external condensate (W1) respectively. At this time, the inlet of the heat network return water recooling bypass valve (19) is connected to the high-temperature side inlet of the boiler air inlet low-temperature warm air heater (15) via the warm air heater bypass valve (17). The high-temperature outlet of the heater (15) is connected to the low-temperature water inlet of the N-stage flash heater (36), and the low-temperature water outlet of the N-stage flash heater (36) is connected to the low-temperature water outlet of the flash heater (26) and the return water pipe of the heat network (H2); the slurry outlet of the N-stage flash tank (31) is connected to the spray inlet of the N-stage spray layer (4) inside the original desulfurization tower (1) through the N-stage slurry pump (16), and the N-stage spray layer (4) is connected to the return water pipe of the heat network (H2). The N-stage desulfurization heat exchange zone (5) is between the spray layer (4) and the lower spray layer (6) below it, and the lower spray layer (6) is between the inlet of the original flue gas inlet pipe (2) below it, and the lower desulfurization heat exchange zone (7); the outlet of the N-stage non-condensable gas (S1) of the N-stage flash heater (36) is connected to the inlet of the N-stage vacuum pump (28), and the exhaust port of the N-stage vacuum pump (28) is connected to the desulfurization heat exchange zone inside the original desulfurization tower (1).

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