Open type absorption heat pump flue gas waste heat recovery technology based on water vapor heat-carrying circulation

Abstract

The utility model discloses an open type absorption heat pump flue gas waste heat recovery technology based on water vapor heat-carrying circulation, and belongs to the technical field of boiler flue gas waste heat supply. Aiming at the problems that flue gas waste heat recovery of an open type absorption heat pump is limited by solution heat exchange, thermodynamic cycle characteristics, equipment capacity and the like, so that the flue gas cooling amplitude is limited, and the waste heat recovery amount is too low, a secondary absorption heat exchange module is additionally arranged at the upper part of an absorption tower of a conventional open type absorption heat pump, and heat is taken by intermediate water; after boiler combustion-supporting air is heated and humidified, fuel is saved, the steam content and the enthalpy value of the flue gas are increased, and therefore the heating capacity of heat supply network return water in an absorption tower and the temperature of a dilute solution outlet are increased, and the dilute solution can generate more secondary steam after entering a generator. The concentrated solution returns to the absorption tower for continuous spraying; the heat supply network return water at the outlet of the absorption tower exchanges heat with the secondary steam, so that the temperature rise can be greatly increased, and the system waste heat return quantity can be nearly doubled.

Description

Technical Field

[0001] The utility model relates to an open absorption heat pump flue gas waste heat recovery technology based on water vapor heat-carrying cycle, belonging to the technical field of boiler flue gas waste heat heating. Background Technique

[0002] A large amount of high-temperature flue gas is discharged during the heat production process of a boiler. 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. Therefore, the development of flue gas waste heat recovery technology is an important way to help achieve the "dual carbon" strategic goal. 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 recover the waste heat of the flue gas, that is, to install a heat exchanger with a tubular structure or the like on the flue at the boiler outlet 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% - 7% 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 a good application prospect. 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 cause an increase in the cost, and sometimes the on-site conditions are not suitable for implementation.

[0003] In recent years, in the second type of flue gas waste heat recovery method, an open absorption heat pump method based on solution spraying for heat extraction has emerged. In this method, a concentrated solution is sprayed on high-humidity flue gas in the absorption tower to absorb water vapor and a large amount of latent heat of vaporization. The flue gas becomes low-humidity medium-temperature flue gas and is discharged. After the concentrated solution becomes a dilute solution, it is sent to the generator, where secondary steam is evaporated by the driving steam. After the solution concentration is increased, it continues to return to the absorption tower for circulation. The return water of the heat network is first sent to the absorption tower for preheating and then sent out after heat exchange with the secondary steam of the generator. Its advantages are as follows: The concentrated solution can easily absorb a large amount of flue gas condensate, and flue gas pollutants are further intercepted, achieving near-zero emissions; the quality of the condensate is good, which is convenient for recycling. However, the disadvantages are also very obvious: The flue gas temperature can usually only be reduced to 40-45°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. A large amount of flue gas waste heat still escapes from the flue gas in vain, and secondary transformation is still needed in the future 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. In addition, this technical method is still essentially similar to the heat pump method, except that the heat extraction device is different, but it still requires a large amount of driving steam, and the energy efficiency ratio is still low, resulting in 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 object and task of the present invention are to optimize and upgrade the conventional open absorption heat pump method by using a water vapor heat-carrying flue gas waste heat recovery method 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. A secondary absorption heat exchange module is arranged downstream of the flue gas in the absorption tower to recover the waste heat in the low-temperature section of the flue gas and send it to the total heat air preheater to heat and humidify the air entering the boiler, so as to achieve deep flue gas waste heat recovery.

[0005] The specific description of the present utility model is: an open absorption heat pump flue gas waste heat recovery technology based on water vapor heat-carrying cycle, which consists of a boiler and flue gas treatment equipment subsystem, an open absorption heat pump 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, an original desulfurization tower 10, a forced draft fan 11, a dust collector 12, and an induced draft fan 13. It is characterized in that the open absorption heat pump subsystem includes an absorption tower 1, a generator 2, a secondary steam heater 3 and its connecting pipes and components. The total heat air preheater flue gas waste heat recovery subsystem includes a total heat air preheater 16, a fresh air superheater 17, a secondary absorption heat exchange module 4 and connecting pipelines and components. The lower part of the absorption tower 1, where the inlet of the high-humidity medium-temperature flue gas Y1 is connected to the flue gas outlet of the original desulfurization tower 10. The upper part of the absorption tower 1 is provided with a concentrated solution spraying device. After the high-humidity flue gas passes upward through the concentrated solution spraying device, it is transformed into a low-humidity medium-temperature flue gas Y2. The upper flue gas outlet of the absorption tower 1 is communicated with the lower flue gas inlet of the secondary absorption heat exchange module 4. After the clean flue gas Y2 at the lower part of the secondary absorption heat exchange module 4 passes upward through the intermediate water spraying area sprayed by the intermediate water spraying device, the upper outlet is the dry and cold flue gas Y3. The outlet of the dilute solution at the bottom of the absorption tower 1 is connected to the inlet of the pollutant treatment device 18. The outlet of the pollutant treatment device 18 is connected to the inlet of the dilute solution pump 19. The outlet of the dilute solution pump 19 is connected to the dilute solution inlet of the generator 2. The concentrated solution outlet of the generator 2 is connected to the inlet of the concentrated solution pump 15. The outlet of the concentrated solution pump 15 is connected to the liquid inlet of the concentrated solution spraying device of the absorption tower 1. The regeneration heat source inlet of the generator 2 is communicated with the steam supply pipe of the driving steam Q1. The regeneration heat source outlet of the generator 2 is communicated with the condensate drain pipe of the driving condensate C1. The outlet of the secondary steam Q2 of the generator 2 is connected to the steam inlet of the secondary steam heater 3. The outlet of the secondary condensate C2 of the secondary steam heater 3 is communicated with the condensate drain pipe of the secondary condensate. The inlet of the heated water in the middle of the absorption tower 1 is communicated with the water supply pipe of the heat network return water H1. The outlet of the heated water at the upper part of the absorption tower 1 is connected to the inlet of the heated water of the secondary steam heater 3. The outlet of the heated water of the secondary steam heater 3 is communicated with the condensate drain pipe of the heat network return water H2. The outlet of the bottom water tank of the secondary absorption heat exchange module 4 is connected to the inlet of the intermediate water pump 7. The outlet of the intermediate water pump 7 is connected to the inlet of the spraying device of the total heat air preheater 16. The outlet of the bottom water tank of the total heat air preheater 16 is connected to the inlet of the low-temperature water pump 14. The outlet of the low-temperature water pump 14 is connected to the inlet of the spraying device of the secondary absorption heat exchange module 4. The side of the lower part of the total heat air preheater 16 is provided with an air inlet of the ambient air A0. The top is provided with an air outlet of the saturated humid air A1. The air outlet of the saturated humid 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.

[0006] The secondary absorption heat exchange module 4 is arranged at the top of the absorption tower 1. The two form an integral structure and are separated by a gas-liquid separator 6. There are N ventilation devices 5 arranged on the gas-liquid separator 6, where N is greater than or equal to 1. The clean flue gas Y2 at the upper part of the absorption tower 1 enters upward from the lower inlet of the ventilation device 5 on the gas-liquid separator 6 and flows out from the upper ventilation opening of the ventilation device 5. After passing through the intermediate water spray area sprayed by the intermediate water spray device, it is the outlet of the ultra-clean flue gas Y3 upward; the intermediate water sprayed by the intermediate water spray device falls into the water tank of the gas-liquid separator 6, and its outlet is connected to the inlet of the intermediate water pump 7.

[0007] The spray heat exchange area of the secondary absorption heat exchange module 4 and the total heat air preheater 16 adopts a packing structure or an empty tower spray structure.

[0008] The solution circulating between the absorption tower 1 and the generator 2 adopts lithium bromide solution, lithium chloride solution, calcium chloride solution or other highly hygroscopic non-toxic salt solutions.

[0009] The innovation points and beneficial effects of the present utility model are as follows.

[0010] (1) The flue gas waste heat recovery is divided into two processes: a high-humidity section and a low-humidity section. In the high-humidity section, the flue gas waste heat adopts an open absorption heat pump method to perform the first-stage heating on the return water of the heat network; while in the low-humidity section, 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 the total heat air preheater for waste heat recovery. By humidifying, the water vapor content of the flue gas is increased, the amount of water vapor absorbed in the absorption tower and the preheat amount of the return water of the heat network are increased, and the waste heat recovery amount of the entire system can be increased by more than 1 time at most.

[0011] (2) The direct heat exchange method is adopted to recover the waste heat of the desulfurization slurry to the greatest extent, the capacity of the heat pump is greatly reduced, and the energy efficiency ratio of the entire system is greatly improved. The waste heat recovery ratio of the conventional open absorption heat pump system is about 0.85, while this patent can be increased to 1.2 - 1.7.

[0012] (3) The condensation water amount of the flash steam can also be increased by about 1 time, which can be used as the makeup water for the return water of the heat network, helping to greatly reduce the water production amount 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

[0013] Figure 1 is the system schematic diagram of the present utility model.

[0014] Figure 1 The numbers and names of each component in

[0015] Absorption tower 1, generator 2, secondary steam heater 3, secondary absorption heat exchange module 4, ventilation device 5, gas-liquid separator 6, intermediate water pump 7, boiler body 8, air preheater 9, original desulfurization tower 10, forced draft fan 11, dust collector 12, induced draft fan 13, low temperature water pump 14, concentrated solution pump 15, total heat air preheater 16, fresh air superheater 17, pollutant treatment device 18, dilute solution pump 19, ambient air A0, saturated humid air A1, superheated air A2, driving condensate C1, secondary condensate C2, return water from heat supply network H1, return water discharged from heat supply network H2, driving steam Q1, secondary steam Q2, high humidity medium temperature flue gas Y1, low humidity medium temperature flue gas Y2, dry and cold flue gas Y3. Specific embodiments

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

[0017] The specific embodiments of the present utility model are as follows.

[0018] Specific description of the embodiments of the present utility model: The open absorption heat pump flue gas waste heat recovery technology based on the water vapor heat-carrying cycle consists of a boiler and flue gas treatment equipment subsystem, an open absorption heat pump 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, an original desulfurization tower 10, a forced draft fan 11, a dust collector 12, and an induced draft fan 13. It is characterized in that the open absorption heat pump subsystem includes an absorption tower 1, a generator 2, a secondary steam heater 3, and their connecting pipes and components. The total heat air preheater flue gas waste heat recovery subsystem includes a total heat air preheater 16, a fresh air superheater 17, a secondary absorption heat exchange module 4, and connecting pipelines and components. The lower part of the absorption tower 1, where the inlet of the high-humidity medium-temperature flue gas Y1 is connected to the flue gas outlet of the original desulfurization tower 10. The upper part of the absorption tower 1 is provided with a concentrated solution spraying device. After the high-humidity flue gas passes upward through the concentrated solution spraying device, it is transformed into a low-humidity medium-temperature flue gas Y2. The upper flue gas outlet of the absorption tower 1 is communicated with the lower flue gas inlet of the secondary absorption heat exchange module 4. After the clean flue gas Y2 at the lower part of the secondary absorption heat exchange module 4 passes upward through the intermediate water spraying area sprayed by the intermediate water spraying device, the outlet of the dry and cold flue gas Y3 is upward. The outlet of the dilute solution at the bottom of the absorption tower 1 is connected to the inlet of the pollutant treatment device 18. The outlet of the pollutant treatment device 18 is connected to the inlet of the dilute solution pump 19. The outlet of the dilute solution pump 19 is connected to the dilute solution inlet of the generator 2. The concentrated solution outlet of the generator 2 is connected to the inlet of the concentrated solution pump 15. The outlet of the concentrated solution pump 15 is connected to the liquid inlet of the concentrated solution spraying device of the absorption tower 1. The regeneration heat source inlet of the generator 2 is communicated with the steam pipe of the driving steam Q1. The regeneration heat source outlet of the generator 2 is communicated with the drain pipe of the driving condensate C1. The outlet of the secondary steam Q2 of the generator 2 is connected to the steam inlet of the secondary steam heater 3. The outlet of the secondary condensate C2 of the secondary steam heater 3 is communicated with the drain pipe of the secondary condensate. The inlet of the heated water in the middle of the absorption tower 1 is communicated with the water supply pipe of the heat network return water H1. The outlet of the heated water at the upper part of the absorption tower 1 is connected to the inlet of the heated water of the secondary steam heater 3. The outlet of the heated water of the secondary steam heater 3 is communicated with the drain pipe of the heat network return water drain H2. The outlet of the bottom water tank of the secondary absorption heat exchange module 4 is connected to the inlet of the intermediate water pump 7. The outlet of the intermediate water pump 7 is connected to the inlet of the spraying device of the total heat air preheater 16. The outlet of the bottom water tank of the total heat air preheater 16 is connected to the inlet of the low-temperature water pump 14. The outlet of the low-temperature water pump 14 is connected to the inlet of the spraying device of the secondary absorption heat exchange module 4. The side of the lower part of the total heat air preheater 16 is provided with an air inlet for the ambient air A0, and the top is provided with an air outlet for the saturated humid air A1. The air outlet of the saturated humid 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 the superheated air A2 and the inlet and outlet of the high-temperature heat source. The air outlet of the superheated air A2 is connected to the air inlet of the forced draft fan 11.

[0019] The secondary absorption heat exchange module 4 is arranged at the top of the absorption tower 1. The two form an integral structure and are separated by a gas-liquid separator 6. There are N ventilation devices 5 arranged on the gas-liquid separator 6, where N is greater than or equal to 1. The clean flue gas Y2 in the upper part of the absorption tower 1 enters upward from the lower inlet of the ventilation device 5 on the gas-liquid separator 6 and flows out from the upper ventilation opening of the ventilation device 5. After passing through the intermediate water spray area sprayed by the intermediate water spray device, the outlet of the super-clean flue gas Y3 is upward; the intermediate water sprayed by the intermediate water spray device falls into the water tank of the gas-liquid separator 6, and the outlet is connected to the inlet of the intermediate water pump 7.

[0020] The spray heat exchange areas of the secondary absorption heat exchange module 4 and the total heat air preheater 16 adopt a packing structure or an empty tower spray structure.

[0021] The solution circulating between the absorption tower 1 and the generator 2 adopts a lithium bromide solution, a lithium chloride solution, a calcium chloride solution or other highly hygroscopic non-toxic salt solutions.

[0022] It should be noted that based on the open absorption heat pump technology, the key technologies such as heat extraction by the secondary absorption heat exchange module and heating and humidifying by the total heat air preheater, the present utility model proposes a complete set of new open absorption heat pump flue gas deep waste heat recovery integration system based on the water vapor heat-carrying cycle. 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 just one of them. Any other similar simple deformation implementation manners, such as changing the structure or position, number of stages, combination mode of the secondary absorption heat exchange module, simple deformation of the relevant spray heat exchange device and simple adjustment of the relevant pipeline, etc., all fall within the protection scope of the present utility model.

Claims

1. An open absorption heat pump flue gas waste heat recovery technology based on a water vapor heat transfer cycle, comprising a boiler and flue gas treatment equipment subsystem, an open absorption heat pump subsystem and a full heat air preheater flue gas waste heat recovery subsystem, wherein the boiler and flue gas treatment equipment subsystem comprises a boiler body (8), an air preheater (9), an original desulfurization tower (10), a blower (11), a dust collector (12) and an induced draft fan (13), characterized in that: The open absorption heat pump subsystem comprises an absorption tower (1), a generator (2), a secondary steam heater (3) and connecting pipes and components thereof; the full-heat air preheater flue gas waste heat recovery subsystem comprises a full-heat air preheater (16), a fresh air superheater (17), a secondary absorption heat exchange module (4) and connecting pipes and components; wherein the inlet of the high-humidity and medium-temperature flue gas (Y1) at the lower part of the absorption tower (1) is connected to the flue gas outlet of the original desulfurization tower (10); a concentrated solution spraying device is arranged at the upper part of the absorption tower (1); the high-humidity flue gas passes upward through the concentrated solution spraying device and is converted into low-humidity and medium-temperature flue gas (Y2); the upper flue gas outlet of the absorption tower (1) is connected to the lower flue gas inlet of the secondary absorption heat exchange module (4); The clean flue gas (Y2) at the bottom of the first-stage absorption heat exchange module (4) is upwardly directed through the intermediate water spraying area sprayed by the intermediate water spraying device, and then the outlet of the dry cold flue gas (Y3) is upwardly directed; the dilute solution outlet at the bottom of the absorption tower (1) is connected to the inlet of the pollutant treatment device (18), the outlet of the pollutant treatment device (18) is connected to the inlet of the dilute solution pump (19), the outlet of the dilute solution pump (19) is connected to the dilute solution inlet of the generator (2), the concentrated solution outlet of the generator (2) is connected to the inlet of the concentrated solution pump (15), the outlet of the concentrated solution pump (15) is connected to the feed liquid inlet of the concentrated solution spraying device of the absorption tower (1), the regeneration heat source inlet of the generator (2) is connected to the steam transmission pipe of the driving steam (Q1), and the generator The outlet of the regenerative heat source of the generator (2) is connected to the return pipe of the driving condensate (C1), the outlet of the secondary steam (Q2) of the generator (2) is connected to the steam inlet of the secondary steam heater (3), and the outlet of the secondary condensate (C2) of the secondary steam heater (3) is connected to the return pipe of the secondary condensate; the inlet of the heated water in the middle of the absorption tower (1) is connected to the water pipe of the return water (H1) of the heat network, the outlet of the heated water in the upper part of the absorption tower (1) is connected to the inlet of the heated water of the secondary steam heater (3), and the outlet of the heated water of the secondary steam heater (3) is connected to the return pipe of the heat network return water (H2); the outlet of the water pool at the bottom of the secondary absorption heat exchange module (4) is connected to the inlet of the intermediate water pump (7). The outlet of the intermediate water pump (7) is connected to the inlet of the spray device of the full-heat air preheater (16), the outlet of the water pool at the bottom of the full-heat air preheater (16) is connected to the inlet of the low-temperature water pump (14), and the outlet of the low-temperature water pump (14) is connected to the inlet of the spray device of the secondary absorption heat exchange module (4); the lower side of the full-heat air preheater (16) is provided with an air inlet for ambient air (A0), and the top is provided with an air outlet for saturated humid air (A1), the air outlet of the saturated humid air (A1) is connected to the air inlet of the fresh air superheater (17), and the fresh air superheater (17) is also provided with an air outlet for superheated air (A2) and an inlet and outlet of a high-temperature heat source, wherein the air outlet of the superheated air (A2) is connected to the air inlet of the blower (11).

2. The open absorption heat pump flue gas waste heat recovery technology based on water vapor heat transfer cycle according to claim 1 is characterized in that The secondary absorption heat exchange module (4) is arranged on the top of the absorption tower (1), and the two form an integral structure and are separated by a gas-liquid separator (6), wherein N ventilation devices (5) are arranged on the gas-liquid separator (6), wherein N is greater than or equal to 1, wherein the upper clean flue gas (Y2) of the absorption tower (1) enters upward from the lower inlet of the ventilation device (5) on the gas-liquid separator (6), flows out from the upper vent of the ventilation device (5), and then passes through the intermediate water spraying area sprayed by the intermediate water spraying device, and then flows upward to the outlet of the dry cold flue gas (Y3); the intermediate water sprayed by the intermediate water spraying device falls into the water pool of the gas-liquid separator (6), and the water outlet is connected to the inlet of the intermediate water pump (7).

3. The open absorption heat pump flue gas waste heat recovery technology based on water vapor heat transfer cycle according to claim 1 is characterized in that The spray heat exchange zone of the secondary absorption heat exchange module (4) and the full-heat air preheater (16) adopts a packing structure or an empty tower spray structure.

4. The open absorption heat pump flue gas waste heat recovery technology based on water vapor heat transfer cycle according to claim 1 is characterized in that The solution circulating between the absorption tower (1) and the generator (2) is a lithium bromide solution, a lithium chloride solution or a calcium chloride solution.

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