Ejecting heat pump flue gas waste heat recovery system for inlet air humidification, desulfurization and slurry flash evaporation

Abstract

The utility model discloses an injection heat pump flue gas waste heat recovery system for inlet air humidification, desulfurization and slurry flash evaporation, and belongs to the technical field of coal-fired boiler waste heat heat supply. Desulfurization slurry grading flash evaporation, injection pressurization and boiler combustion-supporting air heating and humidifying technologies are combined, deep flue gas waste heat recovery is achieved, the water temperature of a heat supply network is greatly increased, and the process includes the steps that desulfurization slurry is firstly fed into a front flash evaporation tank to be subjected to first-stage negative pressure flash evaporation, and flash evaporation steam conducts first-stage preheating on heat supply network return water; the first-stage concentrated slurry is sent to an injection flash tank for second-stage negative pressure flash evaporation, flash steam is sent to a negative pressure injector and is driven by heat supply steam to be pressurized into medium-pressure steam, and then second-stage large-temperature-difference heating is conducted on heat supply network return water; sending the second-stage concentrated slurry to a final-stage flash tank for final-stage negative-pressure flash evaporation, heating intermediate water by flash evaporation steam, and returning the final-stage slurry to a desulfurized water system; the intermediate water is fed into the total heat air preheater, and is fed into the boiler after heating, humidifying and overheating the inlet air of the boiler, so that the steam content of flue gas and the temperature of a desulfurization slurry outlet are increased.

Description

Technical Field

[0001] The utility model relates to an ejector heat pump flue gas waste heat recovery system for inlet air humidification and desulfurized slurry flash evaporation, 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. 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, to use a low-temperature economizer or an economizer, etc. Install a heat exchanger with a tubular structure or the like on the outlet flue of the boiler 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 and a relatively low total cost. The disadvantage is that the waste heat recovery rate is low, and it is affected by 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. The latent heat of vaporization of the water vapor contained 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. Use the absorption heat pump 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 for driving, 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-heat-carrying 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, abandoning the flue gas waste heat exchanger, extracting the heat in the flue gas from the desulfurized slurry through a flash tank, sending the flash steam into the heat pump for waste heat recovery, heating the return water of the heat network or other process water, and returning the concentrated liquid 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 into 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 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. Summary of the Invention

[0004] The purpose and task of the present invention are to construct a brand-new integrated flue gas waste heat recovery system to achieve extremely deep flue gas waste heat recovery 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.

[0005] The specific description of the present utility model is: An ejector heat pump flue gas waste heat recovery system for inlet air humidification and desulfurized slurry flash evaporation, which consists 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 humidification 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-stage flash tank 21, a pre-stage heater 26, an ejector flash tank 11, an ejector 15, an ejector heater 16, 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 humidification 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 tank of the original desulfurization tower 1 through a waste heat slurry pump 10, and is also connected to the slurry inlet of the ejector flash tank 11 through a pre-stage slurry bypass valve 24. The primary concentrated slurry outlet of the pre-stage flash tank 21 is connected to the slurry inlet of the ejector flash tank 11, and is also connected to the slurry inlet of the final-stage flash tank 31 through an ejector slurry bypass valve 34. The secondary concentrated slurry outlet of the ejector flash tank 11 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, and is also connected to the slurry inlet of the final-stage flash tank 31 through an intermediate slurry bypass valve 44. Inside the upper part of the pre-stage flash tank 21, there are a flash steam pre-stage 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, an ejector washing spray layer 13, and a final-stage washing spray layer 33, and is also communicated with the outlet pipe of the pre-stage external discharged condensate W1. Inside the upper part of the ejector flash tank 11, there are a flash steam ejector demister 12 and an ejector washing spray layer 13. Its flash steam outlet is connected to the low-pressure steam inlet pipe 15b of the ejector 15. The high-pressure steam inlet pipe 15a of the ejector 15 is communicated with the steam supply pipe of the heating steam Q through an ejector regulating valve 14. The medium-pressure exhaust pipe 15c of the ejector 15 is connected to the steam inlet of the ejector heater 16. The condensate outlet of the ejector heater 16 is connected to the inlet of an ejector condensate pump 17. The outlet of the ejector condensate pump 17 is communicated with the outlet pipe of the ejector external discharged condensate W. The low-temperature water inlet of the pre-stage heater 26 is communicated with the incoming water pipe of the heat network return water H1. The low-temperature water outlet of the pre-stage heater 26 is respectively communicated with the incoming water pipe of the heat network return water H1, the return water pipe of the heat network return water H2, and the low-temperature water inlet of the ejector heater 16 through a heat network water series-parallel valve group 28. The low-temperature water outlet of the ejector heater 16 is respectively communicated with the low-temperature water inlet of the ejector heater 16 and the return water pipe of the heat network return water H2.At the upper part inside the final flash 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 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 outlet of the intermediate water condensate pump 37 is respectively communicated with 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-condensable gas S of the preheater 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 low-pressure steam inlet pipe 15b of the ejector 15; the outlet of the ejector non-condensable gas S1 of the ejector heater 16 is 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; at the lower part of the total heat air preheater 40, there is an air inlet of the ambient air A0, and at the top of the total heat air preheater 40, there is an air outlet of the humidified air A1. The air outlet of the 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 of the superheated air A2. The air outlet of the forced draft fan 6 is communicated 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 a dust collector 7 and an 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 bottom desulfurization slurry tank of the original desulfurization tower 1 is respectively communicated with the inlet of the original slurry pump 3, the inlet pipe of the desulfurization make-up 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. The blowdown port of the bottom desulfurization slurry tank of the original desulfurization tower 1 is communicated with the drain pipe of the desulfurization wastewater P.;

[0006] The preheater 26, the ejector heater 16, and the intermediate water heater 36 respectively adopt a vertical tubular heat exchange structure, with a condensate hot well at the bottom and a non-condensable gas discharge port above the liquid level of the hot well.

[0007] The inside of the preflash tank 21 and the final flash tank 31 is set as a first-stage heat exchange area or an N-stage heat exchange area, where N is greater than or equal to 2. When setting the N-stage heat exchange area, the flash concentrated slurry outlet of each stage of the heat exchange area 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 ejector 15 adopts a high-efficiency wide-range negative pressure ejector structure with an approximately equal-proportion adjustment of the internal flow cross-sectional area.

[0009] The vacuum pump 18 adopts a water-ring vacuum pump, a water jet air ejector, or a Roots vacuum pump structure.

[0010] The heating steam Q is steam greater than atmospheric pressure or negative pressure steam; the outlet pipes for ejecting the externally drained condensate W and the intermediate externally drained condensate W2 are respectively communicated with the desulfurization make-up water B, the inlet of the make-up water pipe of the return water of the heat network H1, and / or the outlet pipe of the pre-positioned externally drained condensate W1.

[0011] The beneficial effects of the present utility model are as follows.

[0012] (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 low-temperature waste heat of the flue gas enters the flue gas in the form of the latent heat of vaporization of water vapor through the way of humidifying the boiler inlet air by the final flash evaporation through the intermediate water system, which increases the water vapor content, energy grade and desulfurization slurry temperature of the flue gas. Thus, the return water of the heat network can be directly heated by the first-stage flash evaporation, and the return water of the heat network can be continuously heated by the ejector heat pump composed of the ejector in the second-stage flash evaporation, so as to realize the extremely deep heat recovery of the flue gas, and the flue gas temperature can be reduced to the level of 20-30 °C, fundamentally avoiding the inherent disadvantages of the existing desulfurization slurry flash evaporation + absorption heat pump technology method, and the maximum waste heat recovery amount can reach 2-3 times.

[0013] (2) The ejector heat pump system is composed of equipment components such as an ejector flash tank 11, an ejector 15, and an ejector heater 16, which recovers a part of the waste heat of the desulfurization slurry. The ejector 15 adopts a high-efficiency wide-range negative pressure ejector structure with an internally flowing cross-sectional area adjusted in an approximately equal proportion, so that the ejector heat pump can flexibly adapt to the changes in technical conditions such as the inlet and outlet temperatures, pressures and flows on the desulfurization slurry flash evaporation side and the heat network return water heating side, and always maintain a very high system energy efficiency ratio.

[0014] (3) The waste heat of the desulfurization slurry is recovered by the direct heat exchange method to the greatest extent, and the return water of the heat network and the boiler inlet air are preheated; the ejector heat pump system can also maintain a very high energy efficiency ratio, thus greatly reducing the steam consumption of the driving steam, and its steam consumption is only a fraction of the conventional desulfurization slurry flash evaporation + absorption heat pump method. Therefore, the comprehensive energy efficiency ratio of the entire waste heat recovery system can reach 3-6 times, far higher than the conventional method.

[0015] (4) A large amount of SO2 and the like are contained in the non-condensable gas of the pre-positioned heater 26 and the intermediate water heater 36. Instead of setting a special vacuum pump, it is directly extracted by the ejector 15, and a very high vacuum degree can be maintained (reduced to the absolute pressure level of 2-4 kPa when necessary). Therefore, the pre-positioned flash tank 21 and the final flash tank 31 can achieve a very high vacuum degree, which is beneficial to greatly reducing the desulfurization slurry temperature, further greatly reducing the flue gas temperature, realizing the extremely deep flue gas waste heat recovery, and recovering the flue gas waste heat to the greatest extent.

[0016] (5) The steam side pressure of the ejector heater 16 is relatively high, so the technical requirements for the vacuum pump 18 for extracting non-condensable gases are reduced; at the same time, the preheater 26, the ejector heater 16 and the intermediate water heater 36 respectively adopt a vertical tube-and-shell heat exchange structure, which is also conducive to improving the extraction of non-condensable gases by the vacuum pump 18 and maintaining a higher vacuum degree.

[0017] (6) Using the condensate of the flash steam to wash the demisters in each flash tank can maintain a higher demisting effect and supplement water to the desulfurization slurry to replace part or all of the original desulfurization make-up water B, and the make-up 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.

[0018] (7) The condensate of the flash steam can also be used as the make-up 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 condensate also correspondingly greatly reduces the consumption of water resources.

[0019] (8) This solution and system can be widely applied to the flue gas waste heat recovery and heating systems of thermal power plants and boiler houses, promoting the realization of the comprehensive technical and economic benefits of energy conservation and environmental protection integration. Brief Description of the Drawings

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

[0021] Figure 1 The numbers and names of the components in it are as follows.

[0022] 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, ejector flash tank 11, flash steam ejector demister 12, ejector washing spray layer 13, ejector regulating valve 14, ejector 15, high-pressure steam inlet pipe 15a, low-pressure steam inlet pipe 15b, medium-pressure exhaust pipe 15c, ejector heater 16, ejector condensate pump 17, vacuum pump 18, pre-stage flash tank 21, flash steam pre-stage demister 22, pre-stage washing spray layer 23, pre-stage slurry bypass valve 24, pre-stage connecting pipe 25, pre-stage heater 26, pre-stage condensate pump 27, heat network water series-parallel valve group 28, non-condensable gas regulating valve 29, final-stage flash tank 31, flash steam final-stage demister 32, final-stage washing spray layer 33, ejector slurry bypass valve 34, final-stage connecting pipe 35, intermediate water heater 36, intermediate water condensate pump 37, total heat air preheater 40, fresh air superheater 41, intermediate water pump 42, intermediate slurry bypass valve 44, ambient air A0, humidified air A1, superheated air A2, desulfurization make-up water B, heat network return water incoming H1, heat network return water discharging H2, desulfurization wastewater P, heating steam Q, pre-stage non-condensable gas S, ejector non-condensable gas S1, intermediate water non-condensable gas S2, ejector discharged condensate water W, pre-stage discharged condensate water W1, intermediate discharged condensate water W2, original flue gas Y1, clean flue gas Y2. Detailed implementation manners

[0023] Figure 1 It is a system schematic diagram and an embodiment of the present utility model.

[0024] The specific embodiments of the present utility model are as follows.

[0025] Specific description of the embodiment of the present utility model: An ejector heat pump flue gas waste heat recovery system for inlet air humidification and desulfurized slurry flash evaporation, 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 humidification 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 evaporation tank 21, a pre-stage heater 26, an ejector flash evaporation tank 11, an ejector 15, an ejector heater 16, a vacuum pump 18, a final-stage flash evaporation tank 31, an intermediate water heater 36, and connecting pipelines and components. The combustion-supporting air heating and humidification 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 evaporation tank 21 is connected to the waste heat slurry outlet of the bottom desulfurized slurry tank of the original desulfurization tower 1 through a waste heat slurry pump 10, and is connected to the slurry inlet of the ejector flash evaporation tank 11 through a pre-stage slurry bypass valve 24. The primary concentrated slurry outlet of the pre-stage flash evaporation tank 21 is connected to the slurry inlet of the ejector flash evaporation tank 11, and is connected to the slurry inlet of the final-stage flash evaporation tank 31 through an ejector slurry bypass valve 34. The secondary concentrated slurry outlet of the ejector flash evaporation tank 11 is connected to the slurry inlet of the final-stage flash evaporation tank 31. The final-stage concentrated slurry outlet of the final-stage flash evaporation tank 31 is connected to the inlet of the original slurry pump 3, and is connected to the slurry inlet of the final-stage flash evaporation tank 31 through an intermediate slurry bypass valve 44. Inside the upper part of the pre-stage flash evaporation tank 21, there are a flash steam pre-stage 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, an ejector washing spray layer 13, and a final-stage washing spray layer 33, and is communicated with the outlet pipe of the pre-stage external discharged condensate W1. Inside the upper part of the ejector flash evaporation tank 11, there are a flash steam ejector demister 12 and an ejector washing spray layer 13. Its flash steam outlet is connected to the low-pressure steam inlet pipe 15b of the ejector 15. The high-pressure steam inlet pipe 15a of the ejector 15 is communicated with the steam supply pipe of the heating steam Q through an ejector regulating valve 14. The medium-pressure exhaust pipe 15c of the ejector 15 is connected to the steam inlet of the ejector heater 16. The condensate outlet of the ejector heater 16 is connected to the inlet of an ejector condensate pump 17. The outlet of the ejector condensate pump 17 is communicated with the outlet pipe of the ejector external discharged condensate W. The low-temperature water inlet of the pre-stage heater 26 is communicated with the incoming water pipe of the return water from the heat supply network H1. The low-temperature water outlet of the pre-stage heater 26 is respectively connected to the incoming water pipe of the return water from the heat supply network H1, the return water pipe of the return water from the heat supply network H2, and the low-temperature water inlet of the ejector heater 16 through a heat supply network water series-parallel valve group 28. The low-temperature water outlet of the ejector heater 16 is respectively connected to the low-temperature water inlet of the ejector heater 16 and the return water pipe of the return water from the heat supply network H2.An upper part inside the final flash tank 31 is provided with 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 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 outlet of the intermediate water condensate pump 37 communicates with 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 respectively; 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 connected to the low-pressure steam inlet pipe 15b of the ejector 15; the outlet of the ejector non-condensable gas S1 of the ejector heater 16 is 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 of the ambient air A0 is provided at the lower part of the total heat air preheater 40, and an air outlet of the humidified air A1 is provided at the top of the total heat air preheater 40. The air outlet of the 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 of the 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 a dust collector 7 and an 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 bottom desulfurization slurry tank 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 final concentrated slurry outlet 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 bottom desulfurization slurry tank of the original desulfurization tower 1 is connected to the drain pipe of the desulfurization wastewater P.;

[0026] The pre-stage heater 26, the ejector heater 16, 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.

[0027] The inside of the pre-stage flash tank 21 and the final flash tank 31 is set as a first-stage heat exchange area or an N-stage heat exchange area, where N is greater than or equal to 2. When setting the N-stage heat exchange area, the flash concentrated slurry outlet of each stage of the heat exchange area 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.

[0028] The ejector 15 adopts a high-efficiency wide-range negative pressure ejector structure with an almost equal-proportion adjustment of the internal flow cross-sectional area.

[0029] The vacuum pump 18 adopts a water ring vacuum pump, a water jet air ejector, or a Roots vacuum pump structure.

[0030] The heating steam Q is steam greater than atmospheric pressure or negative pressure steam; the outlet pipes for ejecting the external drained condensate W and the intermediate external drained condensate W2 are respectively communicated with the desulfurization make-up water B, the inlet of the make-up water pipe of the return water from the heat network H1 and / or the outlet pipe of the pre-positioned external drained condensate W1.

[0031] It should be noted that the present utility model is based on key technologies such as multi-stage flashing of desulfurization slurry, heating and humidifying of boiler inlet air, pressurized heat exchange of flash steam by an ejector heat pump, vacuum pumping by an ejector, and using clean condensate as desulfurization make-up water to reduce the external discharge flow of desulfurization wastewater. A complete set of new integrated systems and operation strategies for extremely deep flue gas waste heat recovery by flashing desulfurization slurry are proposed. 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 simply deformed implementation manners, such as simple deformations of flash steam and heat exchangers and simple adjustments of pipelines, or simple changes in vacuum pumping methods and condensate recovery and utilization methods, etc., all fall within the protection scope of the present utility model.

Claims

1. An induced heat pump flue gas waste heat recovery system for air intake humidification desulfurization slurry flash evaporation, comprising an original boiler and auxiliary machine subsystem, a desulfurization slurry graded flash evaporation and heating process water subsystem and a combustion 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), an ejector flash tank (11), an ejector (15), an ejector heater (16), 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 is connected to the slurry inlet of the ejector flash tank (11) through a pre-slurry bypass valve (24). The first concentrated slurry outlet of the pre-flash tank (21) is connected to the slurry inlet of the ejector flash tank (11), and is connected to the slurry inlet of the final flash tank (31) through the ejector slurry bypass valve (34); the second concentrated slurry outlet of the ejector flash tank (11) is connected to the slurry inlet of the final flash tank (31); the final concentrated slurry outlet of the final flash tank (31) is connected to the inlet of the raw slurry pump (3), and is connected to the slurry inlet of the final flash tank (31) through the intermediate slurry bypass valve (44); a flash steam pre-demister (22) and a pre-washing spray layer (23) are provided at the upper part of the interior of the pre-flash tank (21); the flash steam outlet thereof is connected to the steam of the pre-heater (26) through the 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), the ejector washing spray layer (13) and the final-stage washing spray layer (33), and is communicated with the outlet pipe of the pre-exhaust condensate (W1); the upper part of the ejector flash tank (11) is provided with a flash steam ejector demister (12) and an ejector washing spray layer (13); the flash steam outlet is connected to the low-pressure steam inlet pipe (15b) of the ejector (15); the high-pressure steam inlet pipe (15a) of the ejector (15) is communicated with the steam supply pipe of the heating steam (Q) via the ejector regulating valve (14); the medium-pressure steam exhaust pipe (15c) of the ejector (15) is connected to the steam supply pipe of the heating steam (Q) via the ejector regulating valve (14); The preheater (26) is connected to the steam inlet of the ejector heater (16); the condensate outlet of the ejector heater (16) is connected to the inlet of the ejector condensate pump (17); the outlet of the ejector condensate pump (17) is connected to the outlet pipe of the ejector condensate (W); the low-temperature water inlet of the preheater (26) is connected to the water inlet pipe of the return water (H1) of the heating network; the low-temperature water outlet of the preheater (26) is respectively connected to the water inlet pipe of the return water (H1) of the heating network, the water return pipe of the return water (H2) of the heating network and the low-temperature water inlet of the ejector heater (16) through the hot water series-parallel valve group (28); the low-temperature water outlet of the ejector heater (16) is respectively connected to the low-temperature water inlet of the ejector heater (16) and the water return pipe of the return water (H2) of the heating network;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), wherein 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), and 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 full heat air preheater (40) and the outlet pipe of the intermediate external condensate water (W2); the low-temperature water of the intermediate water heater (36) is connected to the inlet of the intermediate water condensate pump (37). The inlet is connected to the water pool at the bottom of the full-heat air preheater (40) through the intermediate water pump (42); the outlet of the preheater (26) of the preheater (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 low-pressure steam inlet pipe (15b) of the ejector (15); the outlet of the ejector heater (16) of the ejector non-condensable gas (S1) is connected to the air inlet of the vacuum pump (18), and 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 full-heat air preheater (40 ) is provided with an air inlet for ambient air (A0) at the bottom, 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). 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 upstream of the 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. The exhaust heat recovery system of flue gas with ejector heat pump for flash evaporation of air-intake humidification desulfurization slurry as claimed in claim 1, characterized in that The preheater (26), the ejector heater (16) and the intermediate water heater (36) respectively adopt a vertical tube-in-tube heat exchange structure, a condensate water hot well is arranged at the bottom, and a non-condensable gas discharge port is arranged above the hot well liquid surface.

3. The exhaust heat recovery system of flue gas with ejector heat pump for flash evaporation of air-intake humidified desulfurized slurry 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. The exhaust heat recovery system of flue gas with ejector heat pump for flash evaporation of air-intake humidified desulfurized slurry as claimed in claim 1, characterized in that The ejector (15) adopts a high-efficiency wide-range negative pressure ejector structure in which the internal flow cross-sectional area is adjusted in nearly equal proportion.

5. The exhaust heat recovery system of flue gas with ejector heat pump for flash evaporation of air-intake humidification desulfurization slurry 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.

6. The exhaust heat recovery system of flue gas with ejector heat pump for flash evaporation of air-intake humidified desulfurized slurry as claimed in claim 1, characterized in that The heating steam (Q) is steam with a pressure greater than normal pressure or negative pressure steam; the outlet pipes of the induced external condensate (W) and the intermediate external condensate (W2) are respectively connected to the feed pipe inlet of the desulfurization feed water (B), the heat network return water (H1) and / or the outlet pipe of the front external condensate (W1).

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