Desulfurization slurry flash evaporation coupling water vapor heat-carrying type flue gas waste heat recovery system

Abstract

The utility model discloses a desulfurization slurry flash evaporation and steam heat-carrying coupling type flue gas waste heat recovery system, and belongs to the technical field of coal-fired boiler waste heat heat supply. In order to solve the problem that the waste heat recovery amount of a desulfurization slurry flash evaporation system is too low due to the fact that the vacuum degree is difficult to increase, a method that a secondary absorption heat exchange module is additionally arranged on the upper portion of a desulfurization tower to take heat and the heat is fed into a total heat air pre-heater to heat and humidify boiler inlet air is adopted, and deep recovery of flue gas waste heat can be achieved without a heat pump; desulfurization slurry enters the flash tank to be subjected to flash evaporation and then returns to the slurry pond, and flash steam enters the tubular heat exchanger and heats heat supply network return water. A secondary absorption heat exchange module is additionally arranged at the upper part of the desulfurization tower, a gas-liquid separator is arranged at the lower part of the desulfurization tower, flue gas penetrates through the gas-liquid separator from bottom to top and exchanges heat with low-temperature intermediate water, and the flue gas is sent out after being greatly cooled; the effluent medium water is fed into the total heat air pre-heater to release heat and then returns; the total heat air pre-heater can heat and humidify combustion-supporting air of the boiler, saves fuel, and improves the content of water vapor in flue gas and the temperature of a desulfurization slurry outlet.

Description

Technical Field

[0001] The utility model relates to a system for desulfurized slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery, belonging to the technical field of waste heat heating of coal-fired boilers. Background Technique

[0002] A large amount of high-temperature flue gas is discharged during the heat production process of boilers. Recycling 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 shell-and-tube heat exchanger to realize the waste heat recovery of the flue gas, that is, a heat 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 heating return water. This method has a simple system, but it cannot achieve deep heat recovery. (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. Therefore, deep heat recovery can be achieved. However, the absorption heat pump needs to be driven by high-level heat sources such as steam, and a large amount of acidic condensate will be generated in the flue gas, so 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. At present, it has been widely promoted and applied and has good application prospects. However, it usually uses a flue gas waste heat spray tower to extract heat from the flue gas. 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 increase the cost, and sometimes the site does not have the implementation conditions.

[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 taken out from the desulfurized slurry through a flash tank, and the flash steam is sent to the heat pump for waste heat recovery, and the return water of the heat network or other process water is heated, 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 reasons why it cannot reduce the flue gas temperature to the 30 °C level and achieve deep heat recovery are as follows: First, the complete set of desulfurized slurry flash evaporation 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 and 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 improve the vacuum degree with the existing equipment and conditions, and it is impossible to 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 even 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, in view of the respective inherent technical limitations of the above-mentioned various flue gas waste heat recovery systems and their impacts on the economy of the power plant, to use desulfurized slurry flash evaporation to extract the waste heat of the high-temperature section of the flue gas to heat the return water of the heat network, and a secondary absorption and heat exchange module is arranged in the desulfurization tower to recover the waste heat of the low-temperature section of the flue gas and send it to the total heat air preheater to heat and humidify the incoming air of the boiler, so as to achieve deep waste heat recovery of the flue gas.

[0005] The specific description of the present utility model is: A system for desulfurized slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery, which consists of a boiler and flue gas treatment equipment subsystem, a desulfurized slurry flash evaporation heating subsystem, and a total heat air preheater flue gas waste heat recovery subsystem. The boiler and flue gas treatment equipment subsystem includes a boiler body 8, an air preheater 9, a forced draft fan 11, a dust collector 12, an induced draft fan 13, an integral two-stage desulfurization absorption tower 1, a raw flue gas inlet pipe 2, and a raw slurry pump 3. It is characterized in that the integral two-stage desulfurization absorption tower 1 is divided into upper and lower zones. The lower part is a conventional desulfurization spray reaction zone, and the upper part is a secondary absorption heat exchange module 4. A gas-liquid separator 6 is arranged between the two zones, and N ventilation devices 5 are arranged on the gas-liquid separator 6, where N is greater than or equal to 1. The flue gas inlet of the integral two-stage desulfurization absorption tower 1 is communicated with the flue gas outlet pipe of the raw flue gas Y1 from the outlet of the induced draft fan 13 through the raw flue gas inlet pipe 2. The upper part of the flue gas inlet of the integral two-stage desulfurization absorption tower 1 is the conventional desulfurization spray reaction zone, where the flue gas flows from bottom to top, and the desulfurized slurry sprayed by the upper desulfurization slurry spraying device flows downward. The flue gas above the desulfurization slurry spraying device is converted into clean flue gas Y2, and the clean flue gas Y2 enters from the lower inlet of the ventilation device 5 on the gas-liquid separator 6 upward, flows out from the upper ventilation opening of the ventilation device 5, and then passes through the intermediate water spraying area sprayed by the intermediate water spraying device and then upward to the outlet of the ultra-clean flue gas Y3. The circulating liquid outlet of the desulfurization slurry pool at the bottom of the integral two-stage desulfurization absorption tower 1 is respectively communicated with the inlet of the raw slurry pump 3, the water inlet pipe of the desulfurization makeup water B, and the concentrated slurry outlet of the pre-flash tank 21. The outlet of the raw slurry pump 3 is connected to the inlet of the circulating slurry spraying device of the integral two-stage desulfurization absorption tower 1. The blowdown port of the desulfurization slurry pool at the bottom of the integral two-stage desulfurization absorption tower 1 is communicated with the drain pipe of the desulfurization wastewater P. The desulfurized slurry flash evaporation heating subsystem includes a pre-flash tank 21, a pre-heater 26, a vacuum pump 18, and connecting pipelines and components. 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 integral two-stage desulfurization absorption tower 1 through a waste heat slurry pump 10, and the concentrated slurry outlet of the pre-flash tank 21 is connected to the inlet of the raw slurry pump 3 or the desulfurization slurry pool. The flash steam outlet of the pre-flash tank 21 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 the pre-condensate pump 27. The outlet of the pre-condensate pump 27 is communicated with the outlet pipe of the pre-external discharged condensate W1. The outlet of the pre-non-condensable gas S of the pre-heater 26 is connected to the air inlet of the vacuum pump 18, and the exhaust port of the vacuum pump 18 is communicated with the raw flue gas inlet pipe 2 of the integral two-stage desulfurization absorption tower 1.The flue gas waste heat recovery subsystem of the total heat air preheater includes a total heat air preheater 16, a fresh air superheater 17, and connecting pipelines and components. Among them, the spray water inlet of the total heat air preheater 16 is connected to the bottom intermediate water outlet of the gas-liquid separator 6 through an intermediate water pump 7. The bottom water outlet of the total heat air preheater 16 is connected to the spray device inlet of the secondary absorption heat exchange module 4 through a low-temperature water pump 14. An air inlet for ambient air A0 is provided laterally at the lower part of the total heat air preheater 16, and an air outlet for saturated wet air A1 is provided at the top. The air outlet of the saturated wet air A1 is connected to the air inlet of the fresh air superheater 17. The fresh air superheater 17 is also provided with an air outlet for superheated air A2 and inlets and outlets for a high-temperature heat source. Among them, the air outlet of the superheated air A2 is connected to the air inlet of the forced draft fan 11; the low-temperature water inlet of the preheater 26 is communicated with the water supply pipe of the heat network return water H1, and the low-temperature water outlet of the preheater 26 is communicated with the drain pipe of the heat network return water H2.;

[0006] The preheater 26 adopts a vertical tube heat exchange structure or a horizontal tube heat exchange structure. When adopting the vertical tube heat exchange structure, a condensate hot well is provided at the bottom, and a non-condensable gas discharge port is provided above the liquid level of the hot well; when adopting the horizontal tube heat exchange structure, a non-condensable gas discharge port is provided at the upper part of one end on the condensate outlet side.

[0007] The vacuum pump 18 adopts a water ring vacuum pump, a water jet air ejector or a Roots vacuum pump structure.

[0008] The interior of the total heat air preheater 16 adopts a packed spray or empty tower spray structure.

[0009] The outlet pipe of the prefrontal external discharged condensate W1 is respectively communicated with the desulfurization make-up water B and the make-up water inlet pipe of the heat network return water H1.

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

[0011] (1) The flue gas waste heat recovery is divided into two processes: a high-temperature section and a low-temperature section. Among them, the high-temperature section of the flue gas waste heat adopts the desulfurization slurry flashing method, and the flash steam heats the heat network return water in a shell and tube heat exchanger for the first stage; while the low-temperature section of the flue gas waste heat adopts the method of adding a secondary absorption heat exchange module to heat the intermediate water and send it to a heat pump for waste heat recovery, which is used for the second stage of heating the heat network return water. In this way, the inherent problem that it is difficult to greatly improve the vacuum degree during the desulfurization slurry flashing is avoided, and the waste heat recovery amount can be increased by more than 1 time at most.

[0012] (2) The desulfurization slurry waste heat is recovered by the direct heat exchange method to the greatest extent, the capacity of the heat pump is greatly reduced, and the energy efficiency ratio of the whole system is greatly improved.

[0013] (3) The preheater 26 adopts a vertical tube bundle heat exchange structure. Although the non-condensable gas contains a large amount of SO2, etc., a large amount of non-condensable gas can still be extracted by the vacuum pump 18, effectively reducing the pressure of the flash tank, and then effectively reducing the flue gas temperature.

[0014] (4) The requirement for vacuum extraction is reduced, reducing the complexity of the system and its operation and maintenance.

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

[0016] Figure 1 is a schematic diagram of the system of the present utility model.

[0017] Figure 1 The numbers and names of the components in it are as follows.

[0018] Integral two-stage desulfurization absorption tower 1, raw flue gas inlet pipe 2, raw slurry pump 3, secondary absorption heat exchange module 4, ventilation device 5, gas-liquid separator 6, intermediate water pump 7, boiler body 8, air preheater 9, waste heat slurry pump 10, forced draft fan 11, dust collector 12, induced draft fan 13, low-temperature water pump 14, total heat air preheater 16, fresh air superheater 17, vacuum pump 18, preflash tank 21, preconnection pipe 25, preheater 26, precondensation pump 27, desulfurization makeup water B, heat network return water incoming water H1, heat network return water outgoing water H2, desulfurization wastewater P, pre non-condensable gas S, pre external discharged condensed water W1, raw flue gas Y1, clean flue gas Y2, ultra-clean flue gas Y3. Specific Embodiments

[0019] Figure 1 is a schematic diagram of the system and an embodiment of the present utility model.

[0020] The specific embodiments of the present utility model are as follows.

[0021] Specific description of the embodiments of the present utility model: A system for desulfurized slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery, which consists of a boiler and flue gas treatment equipment subsystem, a desulfurized slurry flash evaporation heating subsystem, and a total heat air preheater flue gas waste heat recovery subsystem. The boiler and flue gas treatment equipment subsystem includes a boiler body 8, an air preheater 9, a forced draft fan 11, a dust collector 12, an induced draft fan 13, an integral two-stage desulfurization absorption tower 1, a raw flue gas inlet pipe 2, and a raw slurry pump 3. It is characterized in that the integral two-stage desulfurization absorption tower 1 is divided into upper and lower areas. The lower part is a conventional desulfurization spray reaction area, and the upper part is a secondary absorption heat exchange module 4. A gas-liquid separator 6 is arranged between the two areas, and N ventilation devices 5 are arranged on the gas-liquid separator 6, where N is greater than or equal to 1. The flue gas inlet of the integral two-stage desulfurization absorption tower 1 is communicated with the flue gas outlet pipe of the raw flue gas Y1 from the outlet of the induced draft fan 13 through the raw flue gas inlet pipe 2. The upper part of the flue gas inlet of the integral two-stage desulfurization absorption tower 1 is the conventional desulfurization spray reaction area, where the flue gas flows from bottom to top, and the desulfurized slurry sprayed by the upper desulfurization slurry spraying device flows downward. The flue gas above the desulfurization slurry spraying device is converted into clean flue gas Y2, and the clean flue gas Y2 enters from the lower inlet of the ventilation device 5 on the gas-liquid separator 6 upward, flows out from the upper ventilation opening of the ventilation device 5, and then passes through the intermediate water spraying area sprayed by the intermediate water spraying device, and then upward is the outlet of the ultra-clean flue gas Y3. The circulating liquid outlet of the desulfurization slurry pool at the bottom of the integral two-stage desulfurization absorption tower 1 is respectively communicated with the inlet of the raw slurry pump 3, the water inlet pipe of the desulfurization make-up water B, and the concentrated slurry outlet of the pre-flash tank 21. The outlet of the raw slurry pump 3 is connected to the inlet of the circulating slurry spraying device of the integral two-stage desulfurization absorption tower 1. The sewage outlet of the desulfurization slurry pool at the bottom of the integral two-stage desulfurization absorption tower 1 is communicated with the drain pipe of the desulfurization wastewater P. The desulfurized slurry flash evaporation heating subsystem includes a pre-flash tank 21, a pre-heater 26, a vacuum pump 18, and connecting pipelines and components. 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 integral two-stage desulfurization absorption tower 1 through a waste heat slurry pump 10, and the concentrated slurry outlet of the pre-flash tank 21 is connected to the inlet of the raw slurry pump 3 or the desulfurization slurry pool. The flash steam outlet of the pre-flash tank 21 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 the pre-condensate pump 27. The outlet of the pre-condensate pump 27 is communicated with the outlet pipe of the pre-external discharged condensate W1. The outlet of the pre-non-condensable gas S of the pre-heater 26 is connected to the air inlet of the vacuum pump 18, and the exhaust outlet of the vacuum pump 18 is communicated with the raw flue gas inlet pipe 2 of the integral two-stage desulfurization absorption tower 1.The flue gas waste heat recovery subsystem of the total heat air preheater includes a total heat air preheater 16, a fresh air superheater 17 and connecting pipelines and components. Among them, the spray water inlet of the total heat air preheater 16 is connected to the bottom intermediate water outlet of the gas-liquid separator 6 through an intermediate water pump 7, and the bottom water outlet of the total heat air preheater 16 is connected to the spray device inlet of the secondary absorption heat exchange module 4 through a low-temperature water pump 14. An air inlet for ambient air A0 is provided laterally at the lower part of the total heat air preheater 16, and an air outlet for saturated wet air A1 is provided at the top. The air outlet of the saturated wet air A1 is connected to the air inlet of the fresh air superheater 17. The fresh air superheater 17 is also provided with an air outlet for superheated air A2 and inlets and outlets for a high-temperature heat source. Among them, the air outlet of the superheated air A2 is connected to the air inlet of the forced draft fan 11; the low-temperature water inlet of the preheater 26 is communicated with the water supply pipe of the heat network return water H1, and the low-temperature water outlet of the preheater 26 is communicated with the drain pipe of the heat network return water H2.;

[0022] The preheater 26 adopts a vertical tube type heat exchange structure or a horizontal tube type heat exchange structure. Among them, when adopting the vertical tube type heat exchange structure, a condensate hot well is provided at the bottom, and a non-condensable gas discharge port is provided above the liquid level of the hot well; when adopting the horizontal tube type heat exchange structure, a non-condensable gas discharge port is provided at the upper part of one end on the condensate outlet side.

[0023] The vacuum pump 18 adopts a water ring type vacuum pump, a water jet air ejector or a roots vacuum pump structure.

[0024] The interior of the total heat air preheater 16 adopts a packed spray or an empty tower spray structure.

[0025] The outlet pipe of the prefrontal external discharged condensate W1 is respectively communicated with the desulfurization make-up water B and the make-up water inlet pipe of the heat network return water H1.

[0026] It should be noted that the present invention is based on key technologies such as desulfurization slurry flash evaporation heat extraction, secondary absorption heat exchange module heat extraction, and total heat air preheater heating and humidification, and proposes a complete set of new integrated systems for desulfurization slurry flash evaporation, direct heater and secondary absorption heat exchange module heat extraction and cascade heating by heat pumps to recover the deep flue gas waste heat of flue gas. 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 changing the type, number of stages, and combination method of the compressor, simple deformation of the relevant flash steam and heat exchanger, and simple adjustment of the relevant 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 invention.

Claims

1. A system for desulfurization slurry flash evaporation coupled with flue gas waste heat recovery using steam as heat carrier, which is composed of a boiler and flue gas treatment equipment subsystem, a desulfurization slurry flash evaporation heating subsystem, and a total heat air preheater flue gas waste heat recovery subsystem. The boiler and flue gas treatment equipment subsystem includes a boiler body (8), an air preheater (9), a forced draft fan (11), a dust collector (12), an induced draft fan (13), an integral two-stage desulfurization absorption tower (1), a raw flue gas inlet pipe (2), and a raw slurry pump (3), and is characterized in that, The integral two-stage desulfurization absorption tower (1) is divided into upper and lower zones. The lower zone is a conventional desulfurization spray reaction zone, and the upper zone is a two-stage absorption heat exchange module (4). A gas-liquid separator (6) is arranged between the two zones, and N ventilation devices (5) are arranged on the gas-liquid separator (6), where N is greater than or equal to 1. The flue gas inlet of the integral two-stage desulfurization absorption tower (1) is communicated with the flue gas outlet pipe of the raw flue gas (Y1) from the outlet of the induced draft fan (13) through the raw flue gas inlet pipe (2). The upper part of the flue gas inlet of the integral two-stage desulfurization absorption tower (1) is the conventional desulfurization spray reaction zone, where the flue gas flows from bottom to top, and the desulfurization slurry sprayed by the upper desulfurization slurry spraying device flows downward. The flue gas in the upper part of the desulfurization slurry spraying device is converted into clean flue gas (Y2). The clean flue gas (Y2) enters from the lower inlet of the ventilation device (5) on the gas-liquid separator (6) upward, flows out from the upper ventilation opening of the ventilation device (5), and then passes through the intermediate water spraying area sprayed by the intermediate water spraying device. The outlet of the ultra-clean flue gas (Y3) is upward. The circulating liquid outlets of the bottom desulfurization slurry tank of the integral two-stage desulfurization absorption tower (1) are respectively communicated with the inlet of the original slurry pump (3), the water inlet pipe of the desulfurization make-up water (B), and the concentrated slurry outlet of the pre-flash tank (21). The outlet of the original slurry pump (3) is connected to the inlet of the circulating slurry spraying device of the integral two-stage desulfurization absorption tower (1). The sewage outlet of the bottom desulfurization slurry tank of the integral two-stage desulfurization absorption tower (1) is communicated with the drain pipe of the desulfurization wastewater (P); the desulfurization slurry flash heating subsystem includes a pre-flash tank (21), a pre-heater (26), a vacuum pump (18) and connecting pipelines and components. Among them, the slurry inlet of the pre-flash tank (21) is connected to the waste heat slurry outlet of the bottom desulfurization slurry tank of the integral two-stage desulfurization absorption tower (1) through a waste heat slurry pump (10), and the concentrated slurry outlet of the pre-flash tank (21) is connected to the inlet of the original slurry pump (3) or the desulfurization slurry tank; the flash steam outlet of the pre-flash tank (21) 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 the pre-condensate pump (27). The outlet of the pre-condensate pump (27) is communicated with the outlet pipe of the pre-discharged condensate water (W1); the outlet of the pre-non-condensable gas (S) of the pre-heater (26) is connected to the air inlet of the vacuum pump (18), and the exhaust outlet of the vacuum pump (18) is communicated with the original flue gas inlet pipe (2) of the integral two-stage desulfurization absorption tower (1); the total heat air preheater flue gas waste heat recovery subsystem includes a total heat air preheater (16), a fresh air superheater (17) and connecting pipelines and components. Among them, the spraying water inlet of the total heat air preheater (16) is connected to the bottom intermediate water outlet of the gas-liquid separator (6) through an intermediate water pump (7). The bottom water outlet of the total heat air preheater (16) is connected to the inlet of the spraying device of the secondary absorption heat exchange module (4) through a low-temperature water pump (14). An air inlet of the ambient air (A0) is arranged on the lower side of the total heat air preheater (16), and an air outlet of the saturated wet air (A1) is arranged on the top. The air outlet of the saturated wet air (A1) is connected to the air inlet of the fresh air superheater (17). The fresh air superheater (17) is also provided with an air outlet of the superheated air (A2) and the inlet and outlet of the high-temperature heat source. Among them, the air outlet of the superheated air (A2) is connected to the air inlet of the forced draft fan (11); 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 the low-temperature water outlet of the pre-heater (26) is communicated with the return water pipe of the heat network return water (H2).

2. The system for desulfurization slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery according to claim 1, characterized in that The pre-heater (26) adopts a vertical tube heat exchange structure or a horizontal tube heat exchange structure. When adopting the vertical tube heat exchange structure, a condensate heat well is arranged at the bottom, and a non-condensable gas discharge port is arranged above the liquid level of the heat well; when adopting the horizontal tube heat exchange structure, a non-condensable gas discharge port is arranged at the upper part of one end of the condensate outlet side.

3. The system for desulfurization slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery according to claim 1, characterized in that The vacuum pump (18) adopts a water ring vacuum pump, a water jet air ejector or a Roots vacuum pump structure.

4. The system for desulfurization slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery according to claim 1, characterized in that The interior of the total heat air preheater (16) adopts a packing spray or an empty tower spray structure.

5. The system for desulfurized slurry flash evaporation coupled with water vapor heat-carrying flue gas waste heat recovery according to claim 1, wherein The outlet pipes of the pre-positioned externally drained condensate (W1) are respectively communicated with the inlets of the make-up water pipes for desulfurization make-up water (B) and return water from the heat network (H1).

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