A flue gas water heat recovery system

Abstract

The present invention discloses a flue gas water heat recovery and utilization system. The flue gas passes through the regenerator of an absorption heat pump, a desulfurization tower, a membrane condenser, the condenser of the absorption heat pump, and a chimney in sequence. After the high-temperature flue gas exchanges heat with the regenerator of the absorption heat pump, the flue gas temperature is reduced. The flue gas then passes through the desulfurization tower to form low-temperature saturated wet flue gas. The low-temperature saturated wet flue gas is dehumidified and heat-exchanged in the membrane condenser to become low-temperature unsaturated wet flue gas. The low-temperature unsaturated wet flue gas is heated and heated by the condenser of the absorption heat pump before entering the chimney and being discharged into the atmosphere. The regenerator of the absorption heat pump uses the high-temperature flue gas as a driving heat source. The refrigerant in the regenerator evaporates and enters the condenser under the heat, releasing heat to the low-temperature flue gas through the condenser. The present invention can fully utilize the waste heat of the flue gas, effectively recover the moisture and heat of the flue gas system, improve the flue gas purification efficiency, increase the exhaust temperature, and reduce the water consumption of the power plant, which is of great significance for energy conservation and emission reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial water saving and energy saving, and in particular to a flue gas water heat recovery and utilization system. Background Art

[0002] The volume fraction of water vapor in industrial flue gas after desulfurization is as high as 12%-18%, and 3%-8% of the calorific value of the fuel is also discharged into the atmosphere with the flue gas. If the water resources and waste heat resources in the industrial flue gas can be recovered with appropriate technology, it will not only effectively alleviate the water pressure of the factory, but also significantly improve energy utilization.

[0003] At present, my country often adopts the technology of first condensing and then heating to realize the recovery and utilization of water vapor after flue gas desulfurization. When using refrigerant medium to exchange heat with high-temperature flue gas, the quality of energy decays step by step, and its heat exchange efficiency is poor. If a higher heat exchange efficiency is to be achieved, huge heat exchange equipment is required, and a large amount of high-quality heat source is required for secondary heating of the flue gas. The condensed water generated in the recovery process contacts the flue gas, making its quality poor. If this part of water resources is to be fully utilized, further processing is required; resources are wasted and the equipment operating costs are high.

[0004] In view of this, there is an urgent need to provide a flue gas water heat recovery system that can solve the problems of low heat exchange efficiency, low quality of recovered water, high equipment operating costs, poor "whitening" effect and low exhaust temperature in the process of flue gas waste heat utilization. Summary of the Invention

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is to provide a flue gas water heat recovery system, comprising:

[0006] The regenerator of the absorption heat pump, the desulfurization tower, the regulating valve, the membrane condenser, the condenser of the absorption heat pump and the chimney are connected in sequence; the high-temperature flue gas exchanges heat with the regenerator, the flue gas temperature is reduced, and then passes through the desulfurization tower to form low-temperature saturated wet flue gas, and the low-temperature saturated wet flue gas passes through the membrane condenser device for dehumidification and heat exchange to form low-temperature unsaturated wet flue gas, and the low-temperature unsaturated wet flue gas enters the condenser to be heated and then enters the chimney to be discharged into the atmosphere;

[0007] The regenerator is connected to the condenser through pipes and accessories; the regenerator uses high-temperature flue gas as a driving heat source, and the refrigerant contained in the solution in the regenerator evaporates and precipitates into the condenser, condensing and releasing heat to the low-temperature flue gas that has heat exchange with the condenser.

[0008] In the above solution, the condenser is connected to the evaporator, absorber and regenerator in sequence through pipelines;

[0009] The refrigerant in the regenerator enters the condenser and releases heat to the low-temperature flue gas for condensation and then cools down. The concentrated solution in the regenerator enters the absorber. The refrigerant enters the evaporator, absorbs the heat of the cooling circulating water, and then enters the absorber, where it is absorbed by the absorbent concentrated solution.

[0010] In the above scheme, a second throttle valve is provided on the pipe connecting the condenser and the evaporator, a heat exchanger is connected between the absorber and the regenerator, a solution pump is provided on the inflow pipe connecting the absorber to the heat exchanger, and a first throttle valve is provided on the outflow pipe connecting the heat exchanger to the absorber.

[0011] In the above scheme, the cooling water passing through the membrane condenser exchanges heat with the flue gas and absorbs the flue gas moisture and waste heat that penetrates into the membrane, then merges with the supplementary cooling water, exchanges heat with the absorber, absorbs heat, and then enters the boiler system to replenish water.

[0012] In the above solution, regulating valves are respectively provided on the membrane condenser cooling water inlet pipe and the supplementary cooling water inlet pipe.

[0013] In the above scheme, the solution in the regenerator is a lithium bromide-water solution.

[0014] The system provided by the present invention combines the advantages of absorption heat pump technology and membrane condensation technology, can make full use of flue gas waste heat, effectively recover the heat of the flue gas system, improve the flue gas purification efficiency, increase the exhaust temperature, and reduce the water consumption of the power plant. It solves the problems of low heat exchange efficiency, low quality of recycled water, high operating costs of heating equipment, poor "whitening" effect and low exhaust temperature in the process of utilizing flue gas waste heat, and is of great significance to energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the system structure provided by the present invention;

[0016] Figure 2 A schematic structural diagram of a film condenser 9 provided by the present invention;

[0017] Figure 3 A schematic structural diagram of the diaphragm 16 provided by the present invention;

[0018] Description of reference numerals:

[0019] 1. Evaporator of absorption heat pump, 2. Absorber of absorption heat pump, 3. First throttle valve, 4. Heat exchanger, 5. Regenerator of absorption heat pump, 6. Solution pump, 7. Desulfurization tower, 8. Control valve, 9. Membrane condenser, 10. Condenser of absorption heat pump, 11. Second throttle valve, 12. Chimney, 13. Separation layer, 14. Support layer, 15. Structural layer, 16. Diaphragm. DETAILED DESCRIPTION

[0020] In the description of this utility, it should be noted that the terms "vertical," "upper," "lower," and "horizontal" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are intended only to facilitate the description of this utility and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this utility. The present invention will be described in detail below in conjunction with specific embodiments and the accompanying drawings.

[0021] like Figure 1 As shown, the present invention provides a flue gas water heat recovery and utilization system, comprising an absorption heat pump regenerator 5, a desulfurization tower 7, a regulating valve 8, a membrane condenser 9, an absorption heat pump condenser 10 and a chimney 12 connected in sequence. The high-temperature flue gas passes through the regenerator 5, the desulfurization tower 7, the membrane condenser 9, and the condenser 10 and is discharged into the atmosphere through the chimney 12. The high-temperature flue gas is cooled, desulfurized, dehumidified, and reheated and then discharged through the chimney 12; that is, the high-temperature flue gas exchanges heat with the regenerator 5 of the absorption heat pump, and the flue gas temperature is reduced. The flue gas then passes through the desulfurization tower 7 to form a low-temperature saturated wet flue gas. The low-temperature saturated wet flue gas passes through the membrane condenser 9 for dehumidification and heat exchange to form a low-temperature unsaturated wet flue gas. The low-temperature unsaturated wet flue gas is heated by the condenser 10 of the absorption heat pump and then enters the chimney 12 to be discharged into the atmosphere.

[0022] The absorption heat pump's regenerator 5 is connected to its condenser 10 via piping and accessories. The regenerator 5 utilizes high-temperature flue gas as a driving heat source. The refrigerant in the regenerator 5 evaporates upon heating and precipitates into the condenser 10, where it condenses and releases heat to the low-temperature flue gas, heating it. In this embodiment, the solution in the regenerator 5 is a lithium bromide-water solution, with lithium bromide as the absorbent and water as the refrigerant. The refrigerant in the lithium bromide-water solution is heated and precipitates into the condenser 10, where it condenses and releases heat to the low-temperature flue gas passing through the condenser 10.

[0023] In addition, in this embodiment, the porous membrane of the membrane condenser 9 is provided with low-temperature saturated wet flue gas flowing outside and cooling water flowing inside. Figure 2 As shown, the membrane condenser 9 is a ceramic membrane condenser, which is composed of a plurality of membranes 16 in series, wherein the inside of the membrane 16 is flowing cooling water and the outside is flue gas, as shown in FIG. Figure 3 As shown, the membrane structure is divided into three layers: a separation layer 13, a support layer 14, and a structural layer 15. When high-humidity flue gas passes through the membrane surface, water and heat recovery are achieved through the capillary condensation mechanism and surface diffusion mass transfer characteristics.

[0024] Cooling water flows evenly in the porous membrane channel, and a certain negative pressure value is maintained in the porous membrane. When the low-temperature saturated wet flue gas passes through the surface of the separation layer 13 (flue gas side), the water vapor in the flue gas condenses when it encounters the lower temperature membrane, and on the other hand, it condenses into tiny droplets in the channel through capillary condensation through the tiny pores on the membrane surface. Due to the high water permeability of the membrane and the existence of negative pressure inside the membrane, the surface droplets quickly pass through the inside of the permeate membrane. As condensation continues to occur, the micropores on the membrane surface are gradually filled with condensate and continuously transferred to the support layer 14 and the structural layer 15 (permeate side). As water transfers from the flue gas side to the permeate side, part of the heat in the flue gas is also transferred to the cooling water on the permeate side through heat and mass exchange, thereby realizing water heat recovery. Since the condensable gas water vapor in the flue gas fills the porous channel during the transmission process, it prevents the passage of non-condensable gases and maintains good recovered water quality.

[0025] This embodiment uses high-temperature flue gas as the driving heat source for the regenerator 5 of the absorption heat pump to heat the lithium bromide-water solution, and utilizes the heat released by the condenser to heat the low-temperature flue gas. After being heated in the regenerator, the absorbent precipitates and enters the condenser 10, releasing heat to the low-temperature flue gas exchanging heat with the condenser 10, fully and efficiently utilizing the waste heat of the flue gas itself, thereby improving energy utilization efficiency.

[0026] In addition, the membrane condensation system can effectively recover the moisture in the flue gas. The recovered water is relatively clean and can be fully recycled. By increasing the flue gas temperature and reducing the moisture content in the flue gas at the point of entry into the chimney, the metal corrosion problem inside the chimney can be effectively reduced.

[0027] In this embodiment, the condenser 10 is also connected to the evaporator 1, the absorber 2 and the regenerator 5 in sequence through pipelines; wherein,

[0028] The refrigerant in the regenerator 5 is cooled after condensing and releasing heat to the low-temperature flue gas in the condenser 10, and then enters the evaporator 1. After absorbing the heat of the cooling circulating water in the evaporator 1, it enters the absorber 2. In the absorber 2, the refrigerant is absorbed by the absorbent concentrated solution, and heat is released in this process; after entering the regenerator 5, the solution in the regenerator 5 absorbs the heat of the flue gas, and the refrigerant absorbs heat and evaporates and enters the condenser 10, while the absorbent concentrated solution enters the absorber 2, and the cycle is repeated. In this embodiment, the waste heat of the flue gas itself is fully and efficiently utilized to form a complementary cycle, completing the cyclic process of the heat pump system absorbing heat in the high-temperature flue gas and releasing heat in the low-temperature flue gas, thereby improving the energy utilization efficiency and realizing the cascade utilization of high-temperature flue gas energy.

[0029] In this embodiment, a second throttle valve 11 is provided on the pipe connecting the condenser 10 and the evaporator 1, a heat exchanger 4 is connected between the absorber 2 and the regenerator 5, a solution pump 6 is provided on the inlet pipe connecting the absorber 2 to the heat exchanger 4, and a first throttle valve 3 is provided on the outflow pipe connecting the heat exchanger 4 to the absorber 2; the refrigerant in the lithium bromide-water solution is heated and precipitated into the condenser 10, where it condenses and releases heat to the low-temperature flue gas and is cooled, and then enters the evaporator 1 after throttling and reducing the pressure through the second throttle valve 11, absorbs the heat of the cooling circulating water in the evaporator 1, and enters the absorber 2, where the refrigerant is absorbed by the absorbent concentrated solution. In this process Heat is released in the absorber 2; the lithium bromide-water solution is pumped by the solution pump 6 through the heat exchanger 4 and then enters the regenerator 5. After the lithium bromide-water solution in the regenerator 5 is heated, the absorbent absorbs heat and evaporates and enters the condenser 10. After the absorbent concentrated solution passes through the heat exchanger 4, it is reduced in pressure by the throttle valve 3 and then enters the absorber 2. In this embodiment, through the effective cooperation between the second throttle valve 11, the solution pump 6 and the first throttle valve 3, the flow rate of the lithium bromide-water solution in the entire circulation system can be flexibly adjusted according to the requirement of the condenser 10 for increasing the flue gas temperature, thereby adjusting the amount of heat absorbed by the regenerator 5 and the amount of heat released by the condenser 10, thereby achieving the goal of adjusting the temperature of the flue gas entering the desulfurization tower 7.

[0030] In this embodiment, regulating valves 8 are respectively provided on the cooling water inlet pipe and the supplementary cooling water inlet pipe of the membrane condenser 9. The cooling water passing through the membrane condenser 9 absorbs the moisture and waste heat that penetrates into the inside of the diaphragm from the flue gas, and then merges with the supplementary cooling water. After heat exchange with the absorber 2 and absorbing heat, it enters the boiler system to replenish water. In this embodiment, the amount of water for heat exchange with the generator 2 can be adjusted according to the amount of cooling water and supplementary cooling water entering the membrane condenser, which can fully recover the latent heat of water vapor in the flue gas, greatly improve the efficiency of the boiler, and achieve energy saving and emission reduction effects.

[0031] After the cooling water in the evaporator 1 exchanges heat with the evaporator 1 and is cooled, it enters the cooling tower device for heat exchange; the evaporator 1 uses the cooling water as a low-temperature heat source for heat exchange.

[0032] This embodiment provides a high-efficiency flue gas water and heat recovery and utilization system that utilizes a combination of first-class absorption heat pump technology and membrane condensation technology to achieve the recovery and utilization of flue gas moisture and waste heat. In the system, evaporator 1 uses circulating cooling water as a low-temperature heat exchange source, with a cooling water temperature of 25-40°C. Regenerator 5 uses medium- and high-temperature flue gas as a driving heat source, with a flue gas temperature of 110-150°C. Low-temperature unsaturated wet flue gas is heated using condenser 10 as a heating source, and the flue gas temperature is raised to an unsaturated state of 60-90°C after heat exchange. Absorber 2 is used as a heating source for the cooling water and supplementary cooling water after the flue gas moisture is recovered by membrane condenser 9.

[0033] The membrane condenser 9 is composed of multiple diaphragms 16, and each diaphragm is connected in series. During the flue gas recovery process, the inside of the diaphragm is the water side, with circulating cooling water flowing, and a vacuum degree of 0.01-0.1Mpa exists on the water side. The diaphragm structure is divided into a structural layer, a support layer and a separation layer. The separation layer is the key to achieving the water collection function, and the pore size of the separation layer is 10-200nm. The outside of the diaphragm is flue gas, and through the capillary condensation and surface diffusion principle on the membrane surface, under the action of the pressure difference between the inside and outside of the membrane, liquid and vapor separation is achieved, and finally the sensible heat of the flue gas and the latent heat of water in the flue gas are recovered.

[0034] The cooling water flowing through the membrane condenser absorbs the moisture and waste heat separated from the flue gas, then undergoes heat exchange with generator 2. After absorbing the heat released by generator 2, it undergoes simple treatment and enters the boiler as feed water. The amount of water heat exchanged with generator 2 can be adjusted based on the amount of cooling water entering the membrane condenser and the amount of feed cooling water. After passing through membrane condenser 9 and absorber 2, the cooling water temperature rises by 5-10°C, meeting the temperature and flow requirements for feed water to the boiler. The cooling water temperature drops by 5-20°C after passing through evaporator 1.

[0035] In this embodiment, taking a 600MW coal-fired unit as an example, the hourly flue gas volume is 1.7×10 6 m 3 / h. After passing through the desulfurization tower, the saturated flue gas at 55°C passes through the membrane condenser 9, and the moisture content is reduced by 50%. The effective water recovery rate is about 98.2t / h, and the waste heat recovered is about 22684MJ. After the flue gas is heated by the condenser 10, the flue gas temperature is calculated to be raised to 70°C, which can save the external heat source for secondary heating of the flue gas by about 8.52×10 5 MJ.

[0036] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone should be aware that any structural changes made under the inspiration of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the scope of protection of the present invention.

Claims

1. A flue gas water heat recovery system, characterized in that: include: The regenerator (5) of the absorption heat pump, the desulfurization tower (7), the membrane condenser (9), the condenser (10) of the absorption heat pump and the chimney (12) are connected in sequence; the high-temperature flue gas exchanges heat with the regenerator (5), the flue gas temperature is reduced, and then passes through the desulfurization tower (7) to form low-temperature saturated wet flue gas, and the low-temperature saturated wet flue gas passes through the membrane condenser (9) for dehumidification and heat exchange to form low-temperature unsaturated wet flue gas, and the low-temperature unsaturated wet flue gas enters the condenser (10), is heated, and then enters the chimney (12) and is discharged into the atmosphere; A regulating valve (8) is provided on the cooling water inlet pipe of the film condenser (9); The regenerator (5) is connected to the condenser (10) through a pipeline and accessories; the regenerator (5) uses high-temperature flue gas as a driving heat source, and the refrigerant contained in the solution in the regenerator (5) evaporates and precipitates into the condenser (10), condensing and releasing heat to the low-temperature flue gas passing through the condenser (10); The condenser (10) is connected to the evaporator (1), the absorber (2) and the regenerator (5) in sequence through pipelines; The refrigerant in the regenerator (5) is heated and precipitated into the condenser (10), and condenses and releases heat to the low-temperature flue gas and then cools down. The absorbent concentrated solution in the regenerator (5) enters the absorber (2), and the refrigerant enters the evaporator (1), absorbs the heat of the cooling circulating water, and then enters the absorber (2), where it is absorbed by the absorbent concentrated solution and releases heat. The cooling water passing through the membrane condenser (9) passes through the water and waste heat inside the permeate membrane and then merges with the supplementary cooling water. After heat exchange with the absorber (2), it absorbs heat and then enters the boiler system to make up water. The solution in the regenerator (5) is a lithium bromide-water solution.

2. The system according to claim 1, wherein A second throttle valve (11) is provided on the pipe connecting the condenser (10) and the evaporator (1), a heat exchanger (4) is connected between the absorber (2) and the regenerator (5), a solution pump (6) is provided on the inflow pipe connecting the absorber (2) to the heat exchanger (4), and a first throttle valve (3) is provided on the outflow pipe connecting the heat exchanger (4) to the absorber (2).

3. The system according to claim 1, wherein: A regulating valve (8) is provided on the supplementary cooling water inlet pipe.

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