Desulfurization slurry flash evaporation flue gas deep waste heat recovery system with total heat air pre-heater

Abstract

The utility model discloses a desulfurization slurry flash evaporation flue gas deep waste heat recovery system with a total heat air pre-heater, and belongs to the technical field of coal-fired boiler waste heat heat supply. According to the system, desulfurization slurry grading flash evaporation and boiler combustion-supporting air heating and humidifying technologies are combined, flue gas deep waste heat recovery is achieved, the system is used for heating heat supply network return water and boiler inlet air, desulfurization slurry is firstly fed into a front flash evaporation tank to be subjected to primary negative pressure flash evaporation, and flash evaporation steam preheats the heat supply network return water; the first-stage concentrated slurry is sent to a final-stage flash tank for final-stage negative pressure flash evaporation, flash evaporation steam heats intermediate water, and final-stage slurry is returned to a desulfurized water system; intermediate water is fed into a total heat air pre-heater, boiler inlet air is heated, humidified and overheated and then fed into a boiler, and the content of steam in flue gas and the temperature of a desulfurization slurry outlet are increased; flash steam condensation water is used as demister washing water, desulfurization replenishing water, heat supply network replenishing water and the like in the flash tank to realize comprehensive recycling; and the condensing heat exchanger adopts a vertical tube bundle, so that a vacuumizing device can maintain a relatively high vacuum degree of a large amount of non-condensable gases such as SO2.

Description

Technical Field

[0001] The utility model relates to a desulfurized slurry flash evaporation flue gas deep waste heat recovery system with a total heat air preheater, belonging to the technical field of waste heat heating of coal-fired boilers. Background Technique

[0002] During the heat production process of boilers, a large amount of high-temperature flue gas is discharged. Recovering the waste heat of the flue gas can not only reduce the heat loss of the boiler, but also reduce the fuel consumption and pollutant emissions such as greenhouse gases, and improve the thermal efficiency of the boiler. The existing flue gas waste heat recovery systems mainly include three categories: (1) The first category is to use a wall-type heat exchanger to realize the waste heat recovery of the flue gas, that is, to use a low-temperature economizer or an economizer, etc. An exchanger with a tubular structure or the like is installed on the boiler outlet flue to recover the waste heat of the flue gas and heat the boiler feed water or the heating return water. This method has a simple system and a relatively low total cost. The disadvantage is that the waste heat recovery rate is low, and it is affected by the changes in the inlet temperature of the heated water, the flue gas temperature, etc. Usually, the actual temperature difference is only about 20-30 °C, which is about 1%-2% of the boiler heat output, and the latent heat of vaporization of the water vapor in the flue gas cannot be recovered, so deep heat recovery cannot be achieved. (2) The second category is to use the absorption heat pump flue gas deep recovery technology. The absorption heat pump is used to recover the waste heat of the flue gas and heat the network return water, etc. The flue gas temperature can be greatly reduced to about 30 °C, and the waste heat recovery amount is equivalent to 8%-15% of the boiler heat output, so deep heat recovery can be achieved. However, the absorption heat pump needs to consume high-level heat sources such as steam to drive, and a large amount of acidic condensate will be generated in the flue gas, and an anti-corrosion heat exchanger needs to be used, and the equipment investment is relatively high. (3) The third category is the total heat exchange recovery technology based on air-flue gas. By humidifying the air, the dew point temperature of the flue gas is increased, and the condensation heat of the flue gas is recovered in the tail flue. This method has a simple system structure, does not require an additional driving heat source, and has a low investment cost. In recent years, the "steam-borne boiler flue gas waste heat recovery" series of patented technologies jointly developed by Tsinghua University and Beijing Qingda Tiangong Energy Technology Research Institute (patent numbers CN104110675B, CN107166420A, CN206929794U, etc.) have been widely promoted and applied at present and have good application prospects. However, its normal-pressure flue gas waste heat spray tower usually extracts heat from the flue gas by intermediate water, and the size of the flue gas waste heat spray tower is very large, and a certain resistance will be increased on the flue gas side. If the outlet pressure margin of the original induced draft fan is insufficient, the fan needs to be replaced or a booster induced draft fan needs to be set up. The above situations will all cause an increase in cost, and sometimes the on-site conditions do not allow implementation.

[0003] In recent years, in the second type of flue gas waste heat recovery method, a method of using desulfurized slurry flash evaporation + absorption heat pump has emerged. That is, instead of using a flue gas waste heat exchanger, the heat in the flue gas is extracted from the desulfurized slurry through a flash tank, and the flash steam is sent to the heat pump for waste heat recovery, heating the return water of the heat network or other process water, while the concentrated liquid returns to the desulfurized circulating water. Its advantages are: there is no need to transform the flue gas system, reducing the on-site implementation difficulty; the quality of the condensate water is good, which is convenient for recycling. However, the disadvantages are also very obvious: the flue gas temperature can usually only be reduced to 42 - 45°C, recovering about half of the flue gas waste heat, which does not belong to deep heat recovery and can only be regarded as a half-finished project. There is still a large amount of flue gas waste heat escaping from the flue gas. In the future, secondary transformation is still needed to achieve deep heat recovery. The cost calculated for the unit waste heat recovery amount is relatively high, and the investment payback period is long. The fundamental reason why it cannot reduce the flue gas temperature to the 30°C level and achieve deep heat recovery is as follows: First, the desulfurized slurry flash evaporation complete set of equipment is a vacuum equipment, its system integration is relatively complex, the guarantee requirements are high, and the lower the flash steam temperature, the larger the specific volume, the larger the equipment volume, and the higher the cost; Second, a large amount of non-condensable gases such as SO2 will escape during the desulfurized slurry flash evaporation process. The flash steam is sent to the absorption heat pump, and it is difficult to evacuate during the condensation heat release process in the horizontal evaporator of the heat pump. The absolute pressure during actual operation can only be maintained at about 7 - 8 kPa. It is very difficult to further increase the vacuum degree with the existing equipment and conditions, and it cannot further increase the vacuum degree like a normal condenser. Therefore, the saturation temperature of the flash steam can only be reduced to the 38 - 40°C level, resulting in the flue gas temperature can only be reduced to the 40 - 45°C level; Third, this technical method still belongs to the heat pump method in essence, only the heat extraction device is different. It still requires a large amount of driving steam, with high operating costs, deteriorating the thermal power flexibility adjustment problem of the power plant, and sometimes seriously affecting the technical and economic benefits of the power plant. Utility Model Content

[0004] The purpose and task of the present utility model are, aiming at the respective inherent technical limitations of the above various flue gas waste heat recovery systems and their impacts on the economy of the power plant, if the return water temperature of the heat network is relatively low, a brand-new integrated flue gas waste heat recovery system can be constructed to achieve deep flue gas waste heat recovery.

[0005] The specific description of the present utility model is: A desulfurized slurry flash evaporation flue gas deep waste heat recovery system with a total heat air preheater, which is composed of an original boiler and auxiliary machine subsystem, a desulfurized slurry staged flash evaporation and heated process water subsystem, and a combustion-supporting air heating and humidifying subsystem. The original boiler and auxiliary machine subsystem includes a boiler body 4, an air preheater 5, a forced draft fan 6, a dust collector 7, an induced draft fan 8, an original desulfurization tower 1, an original flue gas inlet pipe 2, and an original slurry pump 3. It is characterized in that the desulfurized slurry staged flash evaporation and heated process water subsystem includes a pre-flash evaporation tank 21, a pre-heater 26, a vacuum pump 18, a final flash evaporation tank 31, an intermediate water heater 36, and connecting pipelines and components. The combustion-supporting air heating and humidifying subsystem includes a total heat air preheater 40, a fresh air superheater 41, an intermediate water pump 42, and connecting pipelines and components. Among them, the slurry inlet of the pre-flash evaporation tank 21 is connected to the waste heat slurry outlet of the bottom desulfurization slurry tank of the original desulfurization tower 1 through a waste heat slurry pump 10. The primary concentrated slurry outlet of the pre-flash evaporation tank 21 is connected to the slurry inlet of the final flash evaporation tank 31. The final concentrated slurry outlet of the final flash evaporation tank 31 is connected to the inlet of the original slurry pump 3. Inside the upper part of the pre-flash evaporation tank 21, there are a pre-flash steam demister 22 and a pre-washing spray layer 23. Its flash steam outlet is connected to the steam inlet of the pre-heater 26 through a pre-connection pipe 25. The condensate outlet of the pre-heater 26 is connected to the inlet of a pre-condensate pump 27. The outlet of the pre-condensate pump 27 is respectively connected to the inlets of the pre-washing spray layer 23 and the final washing spray layer 33, and is communicated with the outlet pipe of the pre-external discharged condensate W1. The low-temperature water inlet of the pre-heater 26 is communicated with the incoming water pipe of the heat network return water H1, and is connected to the low-temperature water outlet of the pre-heater 26 through a valve. The low-temperature water outlet of the pre-heater 26 is communicated with the return water pipe of the heat network return water H2. Inside the upper part of the final flash evaporation tank 31, there are a final flash steam demister 32 and a final washing spray layer 33. Its flash steam outlet is connected to the steam inlet of the intermediate water heater 36 through a final connection pipe 35. The condensate outlet of the intermediate water heater 36 is connected to the inlet of an intermediate water condensate pump 37. The outlet of the intermediate water condensate pump 37 is respectively connected to the low-temperature water outlet of the intermediate water heater 36, the spray water inlet of the total heat air preheater 40, and the outlet pipe of the intermediate external discharged condensate W2. The low-temperature water inlet of the intermediate water heater 36 is communicated with the bottom water tank of the total heat air preheater 40 through an intermediate water pump 42. The outlet of the pre-non-condensable gas S of the pre-heater 26 is connected to the outlet of the intermediate water non-condensable gas S2 of the intermediate water heater 36 through a non-condensable gas regulating valve 29, and is connected to the air inlet of the vacuum pump 18. The exhaust outlet of the vacuum pump 18 is communicated with the original flue gas inlet pipe 2 of the original desulfurization tower 1.An air inlet for ambient air A0 is provided at the lower part of the total heat air preheater 40, and an air outlet for humidified air A1 is provided at the top of the total heat air preheater 40. The air outlet for humidified air A1 is connected to the air inlet of the fresh air superheater 41. The air outlet of the fresh air superheater 41 is connected to the air inlet of the forced draft fan 6 through a connecting pipe for superheated air A2. The air outlet of the forced draft fan 6 communicates with the furnace of the boiler body 4 through the air inlet side of the air preheater 5; the flue gas side outlet of the air preheater 5 communicates with the original flue gas inlet pipe 2 through the dust collector 7 and the induced draft fan 8. The upstream of the original flue gas inlet pipe 2 is the inlet of the original flue gas Y1, and the downstream is the flue gas inlet of the original desulfurization tower 1. The top of the original desulfurization tower 1 is the outlet of the clean flue gas Y2; the circulating liquid outlet of the desulfurization slurry tank at the bottom of the original desulfurization tower 1 communicates with the inlet of the original slurry pump 3, the water inlet pipe of the desulfurization make-up water B, and the outlet of the final-stage concentrated slurry of the final-stage flash tank 31 respectively. The outlet of the original slurry pump 3 is connected to the circulating slurry inlet of the original desulfurization tower 1. The blowdown port of the desulfurization slurry tank at the bottom of the original desulfurization tower 1 communicates with the drain pipe of the desulfurization waste water P.;

[0006] The preheater 26 and the intermediate water heater 36 respectively adopt a vertical tube heat exchange structure, with a condensate hot well provided at the bottom and a non-condensable gas discharge port provided above the liquid level of the hot well.

[0007] The interior of the pre-stage flash tank 21 and the final-stage flash tank 31 is set as a primary heat exchange zone or an N-stage heat exchange zone, where N is greater than or equal to 2. When setting the N-stage heat exchange zone, the flash concentrated slurry outlet of each stage of the heat exchange zone is connected to the slurry inlet of its next stage, and the low-temperature water inlet is connected to the low-temperature water outlet of its next stage.

[0008] The vacuum pump 18 adopts a water-ring vacuum pump, a water jet air ejector or a Roots vacuum pump structure.

[0009] The outlet pipe of the intermediate external discharge condensate W2 communicates with the desulfurization make-up water B, the inlet of the make-up water pipe of the return water of the heat supply network H1 and / or the outlet pipe of the pre-stage external discharge condensate W1 respectively.

[0010] The beneficial effects of the present utility model are as follows.

[0011] (1) Heat is taken from the desulfurization slurry without adding a flue gas waste heat exchanger and its flue gas resistance; at the same time, the waste heat in the low-temperature section of the flue gas enters the flue gas in the form of the latent heat of vaporization of water vapor through the final-stage flash and humidifies the boiler inlet air through the intermediate water system, improving the water vapor content, energy grade and desulfurization slurry temperature of the flue gas. Therefore, on the premise of a relatively low return water temperature of the heat supply network, the return water of the heat supply network can be directly heated through a single-stage flash, so that the flue gas can be extremely deeply heat recovered, and the flue gas temperature can be reduced to the 30°C level, fundamentally avoiding the inherent disadvantages of the existing desulfurization slurry flash + absorption heat pump technology method, and the maximum waste heat recovery amount can reach 2 to 3 times.

[0012] (2) Recover the waste heat of the desulfurization slurry by direct heat exchange to the greatest extent, and preheat the return water of the heat network and the boiler inlet air; deep waste heat recovery of flue gas can be achieved without using an absorption heat pump and consuming a large amount of driving energy.

[0013] (3) The preheater 26 and the intermediate water heater 36 adopt a vertical tube bundle heat exchange structure. Although a large amount of SO2 and other substances are contained in the non-condensable gas, a large amount of non-condensable gas can still be pumped out by the vacuum pump 18 and the pressure of the flash tank can be effectively reduced, thereby effectively reducing the flue gas temperature.

[0014] (4) Wash the demister in each flash tank with the condensate of the flash steam, which can maintain a higher demisting effect and make up water for the desulfurization slurry to replace part or all of the original desulfurization makeup water B. The makeup water source of the latter is often wastewater with a very high chloride content. After replacing it with the condensate of the flash steam, it can help significantly reduce the discharge flow of the desulfurization wastewater P and greatly reduce the secondary pollution and operation and maintenance costs caused by it, and improve the operation effect of the desulfurization system.

[0015] (5) The condensate of the flash steam can also be used as the makeup water for the return water of the heat network, which helps to significantly reduce the production volume and cost of softened water; at the same time, the comprehensive recovery and utilization of the condensate also correspondingly greatly reduces the consumption of water resources.

[0016] (6) This solution and system can be widely applied to the flue gas waste heat recovery heating system of thermal power plants and boiler houses, promoting the realization of comprehensive technical and economic benefits of energy conservation and environmental protection integration. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the system of the present utility model.

[0018] Figure 1 The numbers and names of each component in it are as follows.

[0019] Original desulfurization tower 1, original flue gas inlet pipe 2, original slurry pump 3, boiler body 4, air preheater 5, forced draft fan 6, dust collector 7, induced draft fan 8, waste heat slurry pump 10, vacuum pump 18, pre-flash tank 21, flash steam pre-demister 22, pre-washing spray layer 23, pre-connection pipe 25, preheater 26, pre-condensate pump 27, non-condensable gas regulating valve 29, final flash tank 31, flash steam final demister 32, final washing spray layer 33, final connection pipe 35, intermediate water heater 36, intermediate water condensate pump 37, total heat air preheater 40, fresh air superheater 41, intermediate water pump 42, ambient air A0, humidified air A1, superheated air A2, desulfurization makeup water B, return water of heat network H1, return water of heat network discharged H2, desulfurization wastewater P, heating steam Q, pre-non-condensable gas S, intermediate water non-condensable gas S2, pre-discharged condensate W1, intermediate discharged condensate W2, original flue gas Y1, clean flue gas Y2. Detailed implementation mode

[0020] Figure 1 It is a system schematic diagram and an embodiment of the present utility model.

[0021] The specific embodiments of the present utility model are as follows.

[0022] Specific description of an embodiment of the present utility model: A desulfurized slurry flash evaporation flue gas deep waste heat recovery system with a total heat air preheater, which consists of an original boiler and auxiliary machine subsystem, a desulfurized slurry staged flash evaporation and heating process water subsystem, and a combustion-supporting air heating and humidifying subsystem. The original boiler and auxiliary machine subsystem includes a boiler body 4, an air preheater 5, a forced draft fan 6, a dust collector 7, an induced draft fan 8, an original desulfurization tower 1, an original flue gas inlet pipe 2, and an original slurry pump 3. It is characterized in that the desulfurized slurry staged flash evaporation and heating process water subsystem includes a pre-stage flash tank 21, a pre-stage heater 26, a vacuum pump 18, a final-stage flash tank 31, an intermediate water heater 36, and connecting pipelines and components. The combustion-supporting air heating and humidifying subsystem includes a total heat air preheater 40, a fresh air superheater 41, an intermediate water pump 42, and connecting pipelines and components. Among them, the slurry inlet of the pre-stage flash tank 21 is connected to the waste heat slurry outlet of the bottom desulfurization slurry pool of the original desulfurization tower 1 through a waste heat slurry pump 10. The primary concentrated slurry outlet of the pre-stage flash tank 21 is connected to the slurry inlet of the final-stage flash tank 31. The final-stage concentrated slurry outlet of the final-stage flash tank 31 is connected to the inlet of the original slurry pump 3. Inside the upper part of the pre-stage flash tank 21, there are a pre-stage flash steam demister 22 and a pre-stage washing spray layer 23. Its flash steam outlet is connected to the steam inlet of the pre-stage heater 26 through a pre-stage connecting pipe 25. The condensate outlet of the pre-stage heater 26 is connected to the inlet of a pre-stage condensate pump 27. The outlet of the pre-stage condensate pump 27 is respectively connected to the inlets of the pre-stage washing spray layer 23 and the final-stage washing spray layer 33, and is also connected to the outlet pipe of the pre-stage external discharged condensate W1. The low-temperature water inlet of the pre-stage heater 26 is connected to the incoming water pipe of the heat network return water H1 and is connected to the low-temperature water outlet of the pre-stage heater 26 through a valve. The low-temperature water outlet of the pre-stage heater 26 is connected to the return water pipe of the heat network return water H2. Inside the upper part of the final-stage flash tank 31, there are a final-stage flash steam demister 32 and a final-stage washing spray layer 33. Its flash steam outlet is connected to the steam inlet of the intermediate water heater 36 through a final-stage connecting pipe 35. The condensate outlet of the intermediate water heater 36 is connected to the inlet of an intermediate water condensate pump 37. The outlet of the intermediate water condensate pump 37 is respectively connected to the low-temperature water outlet of the intermediate water heater 36, the spray water inlet of the total heat air preheater 40, and the outlet pipe of the intermediate external discharged condensate W2. The low-temperature water inlet of the intermediate water heater 36 is connected to the bottom water tank of the total heat air preheater 40 through an intermediate water pump 42. The outlet of the pre-stage non-condensable gas S of the pre-stage heater 26 is connected to the outlet of the intermediate water non-condensable gas S2 of the intermediate water heater 36 through a non-condensable gas regulating valve 29 and is also connected to the air inlet of the vacuum pump 18. The exhaust outlet of the vacuum pump 18 is connected to the original flue gas inlet pipe 2 of the original desulfurization tower 1.An air inlet for ambient air A0 is provided at the lower part of the total heat air preheater 40, and an air outlet for humidified air A1 is provided at the top of the total heat air preheater 40. The air outlet for humidified air A1 is connected to the air inlet of the fresh air superheater 41. The air outlet of the fresh air superheater 41 is connected to the air inlet of the forced draft fan 6 through a connecting pipe for superheated air A2. The air outlet of the forced draft fan 6 communicates with the furnace of the boiler body 4 through the air inlet side of the air preheater 5; the flue gas outlet on the smoke exhaust side of the air preheater 5 is connected to the original flue gas inlet pipe 2 through the dust collector 7 and the induced draft fan 8. The upstream of the original flue gas inlet pipe 2 is the inlet of the original flue gas Y1, and the downstream is the flue gas inlet of the original desulfurization tower 1. The top of the original desulfurization tower 1 is the outlet of the clean flue gas Y2; the circulating liquid outlet of the desulfurization slurry pool at the bottom of the original desulfurization tower 1 communicates with the inlet of the original slurry pump 3, the water inlet pipe of the desulfurization make-up water B, and the outlet of the final concentrated slurry of the final flash tank 31 respectively. The outlet of the original slurry pump 3 is connected to the circulating slurry inlet of the original desulfurization tower 1. The blowdown port of the desulfurization slurry pool at the bottom of the original desulfurization tower 1 communicates with the drain pipe of the desulfurization wastewater P.;

[0023] The preheater 26 and the intermediate water heater 36 respectively adopt a vertical tube heat exchange structure, with a condensate hot well provided at the bottom and a non-condensable gas discharge port provided above the liquid level of the hot well.

[0024] The interiors of the preflash tank 21 and the final flash tank 31 are set as a primary heat exchange zone or an N-stage heat exchange zone, where N is greater than or equal to 2. When an N-stage heat exchange zone is set, the flash concentrated slurry outlet of each stage of the heat exchange zone is connected to the slurry inlet of its next stage, and the low-temperature water inlet is connected to the low-temperature water outlet of its next stage.

[0025] The vacuum pump 18 adopts a water-ring vacuum pump, a water jet air ejector or a roots vacuum pump structure.

[0026] The outlet pipe of the intermediate external drained condensate W2 communicates with the desulfurization make-up water B, the inlet of the make-up water pipe of the return water H1 from the heat network and / or the outlet pipe of the pre-external drained condensate W1 respectively.

[0027] It should be noted that the present utility model is based on key technologies such as multi-stage flash evaporation of desulfurization slurry, heating and humidifying of boiler inlet air, and using clean condensate as desulfurization make-up water to reduce the external discharge flow of desulfurization wastewater, and proposes a complete set of new integrated systems and operation strategies for flash evaporation of desulfurization slurry for extremely deep flue gas waste heat recovery. According to this overall solution, there can be different specific implementation measures and specific implementation devices with different structures. The above specific implementation manners are only one of them. Any other similar simple deformed implementation manners, such as simple deformations of flash steam and heat exchangers and simple adjustments of pipelines, or simple changes in the vacuum pumping method and the condensate recovery and utilization method, etc., all fall within the protection scope of the present utility model.

Claims

1. A desulfurization slurry flash flue gas deep waste heat recovery system with a full-heat air preheater, comprising an original boiler and auxiliary machine subsystem, a desulfurization slurry graded flash evaporation and heating process water subsystem and a combustion-supporting air heating and humidification subsystem, wherein the original boiler and auxiliary machine subsystem comprises a boiler body (4), an air preheater (5), a blower (6), a dust collector (7), an induced draft fan (8), an original desulfurization tower (1), an original flue gas inlet pipe (2) and an original slurry pump (3), characterized in that: The desulfurization slurry graded flash evaporation and heating process water subsystem comprises a pre-flash tank (21), a pre-heater (26), a vacuum pump (18), a final flash tank (31), an intermediate water heater (36) and connecting pipelines and components; the combustion air heating and humidification subsystem comprises a full-heat air preheater (40), a fresh air superheater (41), an intermediate water pump (42) and connecting pipelines and components, wherein the slurry inlet of the pre-flash tank (21) is connected to the waste heat slurry outlet of the desulfurization slurry pool at the bottom of the original desulfurization tower (1) through a waste heat slurry pump (10), and the first-stage concentrated slurry outlet of the pre-flash tank (21) is connected to the final flash tank ( The slurry inlet of the final stage flash tank (31) is connected, and the final concentrated slurry outlet of the final stage flash tank (31) is connected to the inlet of the raw slurry pump (3); the upper part of the interior of the pre-flash tank (21) is provided with a flash steam pre-demister (22) and a pre-washing spray layer (23), the flash steam outlet of which is connected to the steam inlet of the pre-heater (26) through a pre-connecting pipe (25), the condensate outlet of the pre-heater (26) is connected to the inlet of the pre-condensate pump (27), the outlet of the pre-condensate pump (27) is respectively connected to the inlets of the pre-washing spray layer (23) and the final stage washing spray layer (33), and is connected to the outlet pipe of the pre-exhaust condensate (W1) The low-temperature water inlet of the preheater (26) is connected to the water inlet pipe of the heat network return water (H1), and is connected to the low-temperature water outlet of the preheater (26) through a valve. The low-temperature water outlet of the preheater (26) is connected to the return water pipe of the heat network return water (H2). The upper part of the inner part of the final flash tank (31) is provided with a flash steam final demister (32) and a final washing spray layer (33). The flash steam outlet is connected to the steam inlet of the intermediate water heater (36) through the final connecting pipe (35). The condensate outlet of the intermediate water heater (36) is connected to the inlet of the intermediate water condensate pump (37). The intermediate water condensate pump (37) is connected to the inlet of the intermediate water condensate pump (37). The outlet of the intermediate water heater (7) is respectively connected to the low-temperature water outlet of the intermediate water heater (36), the spray water inlet of the full-heat air preheater (40) and the outlet pipe of the intermediate external condensate water (W2); the low-temperature water inlet of the intermediate water heater (36) is connected to the bottom water pool of the full-heat air preheater (40) through the intermediate water pump (42); the outlet of the pre-heater (26) is connected to the outlet of the intermediate water non-condensable gas (S2) of the intermediate water heater (36) through the non-condensable gas regulating valve (29), and is connected to the air inlet of the vacuum pump (18); the exhaust port of the vacuum pump (18) is connected to the original flue gas inlet pipe (2) of the original desulfurization tower (1);An air inlet for ambient air (A0) is provided at the bottom of the full-heat air preheater (40), and an air outlet for humidified air (A1) is provided at the top of the full-heat air preheater (40). The air outlet of the humidified air (A1) is connected to the air inlet of the fresh air superheater (41), and the air outlet of the fresh air superheater (41) is connected to the air inlet of the blower (6) through a connecting pipe for superheated air (A2). The air outlet of the blower (6) is connected to the furnace of the boiler body (4) through the air inlet side of the air preheater (5); the exhaust side outlet of the air preheater (5) is connected to the original flue gas inlet pipe (2) through a dust collector (7) and an induced draft fan (8). The original flue gas inlet pipe (2) is connected to the original flue gas (Y1), 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 desulfurization slurry pool at the bottom of the original desulfurization tower (1) is respectively connected to the inlet of the original slurry pump (3), the water inlet pipe of the desulfurization makeup water (B) and the final concentrated slurry outlet of the final flash tank (31), the outlet of the original slurry pump (3) is connected to the circulating slurry inlet of the original desulfurization tower (1), and the sewage outlet of the desulfurization slurry pool at the bottom of the original desulfurization tower (1) is connected to the drainage pipe of the desulfurization wastewater (P).

2. A desulfurization slurry flash flue gas deep waste heat recovery system with full heat air preheater as claimed in claim 1, characterized in that The front heater (26) and the intermediate water heater (36) respectively adopt a vertical tube-in-tube heat exchange structure, a condensate water hot well is provided at the bottom, and a non-condensable gas discharge port is provided above the hot well liquid surface.

3. A desulfurization slurry flash flue gas deep waste heat recovery system with full heat air preheater as claimed in claim 1, characterized in that The interior of the pre-flash tank (21) and the final flash tank (31) is configured as a first-stage heat exchange zone or an N-stage heat exchange zone, wherein N is greater than or equal to 2. When N-stage heat exchange zones are configured, the flash concentrated slurry outlet of each stage heat exchange zone is connected to the slurry inlet of the next stage heat exchange zone, and the low-temperature water inlet is connected to the low-temperature water outlet of the next stage heat exchange zone.

4. A desulfurization slurry flash flue gas deep waste heat recovery system with full heat air preheater as claimed in claim 1, characterized in that The vacuum pump (18) adopts a water ring vacuum pump, a water jet steam extractor or a Roots vacuum pump structure.

5. A desulfurization slurry flash flue gas deep waste heat recovery system with full heat air preheater as claimed in claim 1, characterized in that The outlet pipe of the intermediate external condensate water (W2) is respectively connected to the inlet of the make-up water pipe of the desulfurization make-up water (B), the return water of the heating network (H1) and / or the outlet pipe of the front external condensate water (W1).

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