OGGH flue gas reheating treatment system and control method for wet desulfurization process

Abstract

The present invention is an OGGH flue gas reheat treatment system and control method for a wet flue gas desulfurization process. The flue at the outlet of the desulfurization tower is divided into a first flue and a second flue. The first flue passes through a reheater shell and merges with the second flue. A heat exchange layer is arranged in the desulfurization tower, and its tube outlet is divided into two paths. One path passes through the reheater tube and returns to the heat exchange layer tube entrance, and the other path passes through a plate heat exchanger and returns to the heat exchange layer. The front of the reheater tube entrance is connected with the front of the plate heat exchanger entrance through a branch, and the plate heat exchanger outlet is connected with the reheater tube exit through another branch. The fluid in the above pipeline is an organic working medium. The present invention extracts the latent heat of the flue gas by taking heat after the desulfurization tower, avoids low-temperature corrosion, improves heat transfer efficiency, and prolongs the operating life of the equipment. By modifying the internal space structure of the desulfurization tower, deep cooling of the flue gas in the tower is achieved, and the PM 2.5 content of the exhaust smoke is effectively reduced. With the help of the OGGH system, a personalized heat allocation plan for the flue gas process of the power plant is realized.

Description

Technical Field

[0001] The invention belongs to the field of coal-fired thermal power generation, and also includes the fields of petrochemical industry and other fields that use wet desulfurization process to treat waste flue gas. Background Art

[0002] The wet desulfurization process is an essential part of flue gas purification in coal-fired power plants. After the flue gas exchanges heat and mass with the slurry in the desulfurization tower, its sulfur oxide content decreases, the temperature decreases, and the moisture content increases. Although there is a demister at the top of the desulfurization tower, a certain amount of slurry droplets and solid fine particles are still entrained by the flue gas and eventually discharged into the atmosphere, which is one of the components of PM 2.5.

[0003] To solve the above problems, most coal-fired power plants have begun to take flue gas deep cooling measures to further reduce the temperature of wet flue gas at the outlet of the desulfurization tower, condense the water vapor in the flue gas, promote the condensation and sedimentation of slurry droplets and solid fine particles, and improve the purity of exhaust gas.

[0004] The flue gas cryogenic process requires the introduction of a large amount of cooling water, which requires power generation companies to invest corresponding funds and resources. Some power plants can use seawater as a natural cooling source, while inland areas, especially some arid and water-scarce areas, are restricted by resource conditions and can only rely on air cooling measures.

[0005] At present, there are two main types of flue gas deep cooling processes, one is slurry cooling and the other is external cooling. Slurry cooling: First, the cooling water and the desulfurization slurry are indirectly exchanged for heat. The cooled low-temperature slurry exchanges heat and mass with the flue gas in the desulfurization tower, thereby achieving the purpose of reducing the temperature and humidity of the flue gas. This method increases the depth of heat and mass exchange between the desulfurization slurry and the flue gas, but it cannot effectively reduce the PM 2.5 content in the exhaust gas. External cooling: A flue gas condenser is set in the flue at the outlet of the desulfurization tower, and cooling water is used to exchange heat with the flue gas indirectly. This method can effectively reduce the moisture content and PM 2.5 content of the exhaust gas. However, this process has two defects: first, the flue gas condensate contains a large amount of soluble salts and solid particles, and additional transfer treatment measures are required; second, the large amount of latent heat released during the flue gas condensation process is not effectively utilized.

[0006] On the other hand, the flue gas at the outlet of the desulfurization tower has a high moisture content and low temperature, and the diffusion capacity of the pollutants after emission is poor, which will cause local accumulation of PM 2.5 in the atmospheric environment. Especially in the non-heating season, the temperature difference between the flue gas and the atmospheric environment is small, and its self-extraction ability is weak, so it must be improved through the reheating process. At present, the reheating process adopted by most power plants is MGGH formed on the basis of the previous generation of GGH. This process sets flue gas heat exchangers in the upstream and downstream flues of the desulfurization tower, uses water as the heat exchange medium, and adopts the method of taking heat in front of the tower and releasing heat after the tower to achieve flue gas heat allocation.

[0007] Heat extraction before the tower: The flue gas before the tower has not yet completed the desulfurization process. Therefore, during the heat extraction process, low-temperature corrosion (acid dew point corrosion) will inevitably occur on the heat exchange wall. Long-term operation will lead to deterioration of heat transfer, reduce heat transfer efficiency, and shorten the service life of the heat exchange equipment.

[0008] Heat extraction after the tower: The temperature of the flue gas downstream of the desulfurization tower is usually in the range of 50-60℃, and the grade is relatively low, which cannot meet the requirements of the reheating process. Summary of the invention

[0009] The technical problem solved by the present invention is to propose an OGGH flue gas reheating treatment system for a wet desulfurization process and a control method thereof.

[0010] The technical means adopted in the present invention are as follows.

[0011] 1. An OGGH flue gas reheating treatment system for a wet flue gas desulfurization process, characterized in that the flue 12 at the outlet of the desulfurization tower 1 is divided into a first flue 121 and a second flue 122 connected in parallel, the first flue 121 merges with the second flue 122 after passing through the shell side of the reheater 5; a heat exchange layer 2 is arranged at the top of the desulfurization tower 1 and before the flue gas outlet, the tube side outlet of the heat exchange layer 2 is divided into two paths, one path passes through the tube side of the reheater 5 and returns to the tube side inlet of the heat exchange layer 2, and the other path passes through the plate heat exchanger 6 and returns to the heat exchange layer 2; the tube side inlet of the reheater 5 is connected to the inlet of the plate heat exchanger 6 through a branch road, and the outlet of the plate heat exchanger 6 is connected to the outlet of the reheater 5 tube side through another branch road, and the fluid in the pipeline connecting the tube side inlet and outlet of the heat exchange layer 2 is an organic working medium.

[0012] Preferably, the flue 12 is divided into a first flue 121 and a second flue 122 by a first three-way regulating valve FV-1, and the closing point of the first three-way regulating valve FV-1 on the second flue 122 is position A, and the closing point of the first flue 121 is position B;

[0013] The first flue 121 and the second flue 122 are joined by the second three-way regulating valve FV-2. The closing point of the second three-way regulating valve FV-2 on the second flue 122 is the C position, and the closing point on the first flue 121 is the D position.

[0014] Preferably, the outlet of the tube side of the heat exchange layer 2 is divided into a first pipeline 21 and a fifth pipeline 25; the outlet of the first pipeline 21 is connected to the inlet of the gas-liquid separator 4, the outlet of the gas-liquid separator 4 enters the inlet of the tube side of the reheater 5 through the second pipeline 22, the outlet of the tube side of the reheater 5 is connected to the liquid storage tank 7 through the third pipeline 23, the outlet of the liquid storage tank 7 is connected to the inlet of the tube side of the heat exchange layer 2 through the fourth pipeline 24; the outlet of the fifth pipeline 25 is connected to the hot side fluid inlet H1 of the plate heat exchanger 6, and the hot side fluid outlet H2 of the plate heat exchanger 6 is divided into a sixth pipeline 24. 26 and the seventh pipeline 27, the outlet of the sixth pipeline 26 is connected to the third pipeline 23, and the seventh pipeline 27 is connected to the fourth pipeline 24; the branch connected to the hot side fluid inlet H1 of the plate heat exchanger 6 before the inlet of the reheater 5 is the eighth pipeline 28; the cooling water return pipeline 30 is connected to the cold side fluid inlet L1 of the plate heat exchanger 6 after merging with the heating network return pipeline 40, and the cold side fluid outlet L2 of the plate heat exchanger 6 is divided into two routes, one is the cooling water supply pipeline 50, and the other is the heating network supply pipeline 60.

[0015] Preferably, a compressor 3 is provided on the first pipeline 21 , and a working fluid pump 9 is provided on the seventh pipeline 27 .

[0016] Preferably, a first switching valve V-1 is provided on the first pipeline 21, a second shut-off valve V-2 is provided on the second pipeline 22, a throttle valve 8 is provided on the fourth pipeline 24 and at the outlet of the liquid storage tank 7, a fifth switching valve V-5 is provided on the fifth pipeline 25, a sixth switching valve V-6 is provided on the sixth pipeline 26, a third shut-off valve V-3 is provided before the working fluid pump 9 of the seventh pipeline 27, and a seventh shut-off valve V-7 is provided after the working fluid pump 9, an eighth switching valve V-8 is provided on the eighth pipeline 28, a ninth switching valve V-9 is provided on the cooling water return pipeline 30, a tenth switching valve V-10 is provided on the heating network return pipeline 40, an eleventh switching valve V-11 is provided on the cooling water supply pipeline 50, and a twelfth switching valve V-12 is provided on the heating network supply pipeline 60.

[0017] Preferably, the flow direction of the organic working fluid is the same as the flow direction of the flue gas.

[0018] Preferably, the flue gas ducts joined by the second three-way regulating valve FV-2 are connected to the chimney 14 through the induced draft fan 13.

[0019] An OGGH flue gas reheat control method for a wet flue gas desulfurization process, using the aforementioned system, is as follows:

[0020] (1) In the non-heating season, the flue gas needs to be discharged after deep cooling and reheating process: the first three-way regulating valve FV-1 is adjusted to position A, the second three-way regulating valve FV-2 is adjusted to position C, and at the same time, the first switching valve V-1, the fifth switching valve V-5, the second shut-off valve V-2, the third shut-off valve V-3, the seventh shut-off valve V-7, the throttle valve 8, the ninth switching valve V-9, and the eleventh switching valve V-11 on the organic working fluid pipeline are opened, and at the same time, the eighth switching valve V-8, the sixth switching valve V-6, the tenth switching valve V-10, and the twelfth switching valve V-12 are closed;

[0021] (2) When heating is performed at off-peak hours, the flue gas needs to be discharged directly after the cryogenic process: the first three-way regulating valve FV-1 is adjusted to position B, the second three-way regulating valve FV-2 is adjusted to position D, and at the same time, the fifth switching valve V-5, the third shut-off valve V-3, the seventh shut-off valve V-7, the tenth switching valve V-10, and the twelfth switching valve V-12 on the organic working fluid pipeline are opened, and the first switching valve V-1, the eighth switching valve V-8, the second shut-off valve V-2, the sixth switching valve V-6, the throttle valve 8, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed;

[0022] (3) When heating is performed at off-peak hours, the flue gas needs to be discharged after deep cooling and reheating: the first three-way regulating valve FV-1 is adjusted to position A, the second three-way regulating valve FV-2 is adjusted to position C, and at the same time, the valves on the organic working fluid pipeline, including the first switching valve V-1, the fifth switching valve V-5, the second shut-off valve V-2, the third shut-off valve V-3, the seventh shut-off valve V-7, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12 are opened, and the eighth switching valve V-8, the sixth switching valve V-6, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed;

[0023] (4) During peak heating, the flue gas needs to be discharged directly after the cryogenic process: the first three-way regulating valve FV-1 is adjusted to position B, the second three-way regulating valve FV-2 is adjusted to position D, and at the same time, the first switching valve V-1, the eighth switching valve V-8, the sixth switching valve V-6, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12 of the organic working fluid pipeline are opened, and the fifth switching valve V-5, the second shut-off valve V-2, the third shut-off valve V-3, the seventh shut-off valve V-7, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed;

[0024] (5) During peak heating, the flue gas is discharged after deep cooling and reheating process: the first three-way regulating valve FV-1 is adjusted to position A, and the second three-way regulating valve FV-2 is adjusted to position C. At the same time, the first switching valve V-1, the eighth switching valve V-8, the second shut-off valve V-2, the sixth switching valve V-6, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12 of the organic working fluid pipeline are opened, and the fifth switching valve V-5, the third shut-off valve V-3, the seventh shut-off valve V-7, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed.

[0025] The present invention achieves the following beneficial effects through the "organic working medium-flue gas deep cooling and reheating process" OGGH (Organic Gas Gas Heater) system.

[0026] 1. The present invention extracts the latent heat of flue gas by taking heat after the desulfurization tower, avoiding the low-temperature corrosion of the heat exchange wall surface existing in taking heat before the desulfurization tower, improving the heat transfer efficiency and extending the service life of the equipment.

[0027] 2. The present invention realizes deep cooling of flue gas in the tower by transforming the internal space structure of the desulfurization tower, that is, integrating the desulfurization and deep cooling processes, effectively reducing the PM 2.5 content in the exhaust gas, and at the same time allowing the aerosol to settle in the slurry pool at the bottom of the tower with the condensed water for centralized treatment.

[0028] 3. With the help of the OGGH system, the required valves are opened and closed according to different working conditions, and different circulation methods are adopted to realize the personalized heat allocation plan of the flue gas process of the power plant. In the non-heating season, the system can reduce the external cold source consumption of the flue gas cryogenic process of the power plant; in the heating season, it can realize clean heating and peak load regulation functions on the basis of meeting the needs of the flue gas cryogenic reheating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the present invention.

[0030] Description of the figure number:

[0031] Desulfurization tower 1, flue gas inlet 11, flue 12, first flue 121, second flue 122, first three-way regulating valve FV-1, second three-way regulating valve FV-2, induced draft fan 13, chimney 14;

[0032] Heat exchange layer 2, organic working fluid pipeline 20, first pipeline 21, first switching valve V-1, second pipeline 22, second shut-off valve V-2, third pipeline 23, fourth pipeline 24, throttle valve 8, fifth pipeline 25, fifth switching valve V-5, sixth pipeline 26, sixth switching valve V-6, seventh pipeline 27, working fluid pump 9, third shut-off valve V-3, seventh shut-off valve V-7, eighth pipeline 28, eighth switching valve V-8;

[0033] Compressor 3; gas-liquid separator 4; reheater 5;

[0034] Plate heat exchanger 6, hot side fluid inlet H1, hot side fluid outlet H2, cold side fluid inlet L1, cold side fluid outlet L2; liquid storage tank 7;

[0035] Cooling water return pipeline 30, ninth switching valve V-9, heating network return pipeline 40, tenth switching valve V-10, eleventh switching valve V-11, cooling water supply pipeline 50, heating network supply pipeline 60, twelfth switching valve V-12. DETAILED DESCRIPTION

[0036] The present invention protects an OGGH flue gas reheating treatment system and a control method thereof for a wet desulfurization process. Figure 1 As shown, the bottom of the desulfurization tower 1 is a flue gas inlet 11, and the top flue gas outlet of the desulfurization tower 1 is connected to a flue 12. The flue 12 is provided with a first three-way regulating valve FV-1, which divides the flue 12 into two parallel flue branches, namely, a first flue 121 and a second flue 122. When the first three-way regulating valve FV-1 is adjusted to position A, the first flue 121 forms a passage, and when the first three-way regulating valve FV-1 is adjusted to position B, the second flue 122 forms a passage. The outlets of the two flue branches are connected to the subsequent flue after converging through the second three-way regulating valve FV-2. When the second three-way regulating valve FV-2 is adjusted to position C, the first flue 121 is connected to the subsequent flue, and when the second three-way regulating valve FV-2 is adjusted to position D, the second flue 122 is connected to the subsequent flue, and different conduction modes are used to adapt to different working conditions.

[0037] It also includes a reheater 5, wherein the first flue 121 passes through the shell side of the reheater 5, the shell side fluid of the flue gas reheater 5 is flue gas, and the tube side fluid is organic working fluid.

[0038] A heat exchange layer 2 is arranged at the top of the existing structure in the desulfurization tower 1 and before the flue gas outlet. The best way is that the heat exchange layer 2 is arranged above the spray layer and below the demisting layer of the desulfurization tower 1. It adopts a shell and tube heat exchange structure, and the flue gas flow area in the tower is the shell side. An organic working fluid pipeline 20 is arranged in the heat exchange layer 2, which is the tube side of the heat exchange layer 2. The tube side fluid is an organic working fluid, which exchanges heat with the flue gas after desulfurization, and the flow direction of the organic working fluid is the same as the flow direction of the flue gas.

[0039] The system also includes a gas-liquid separator 4, a plate heat exchanger 6 and a liquid storage tank 7. The outlet of the organic working medium pipeline 20 in the heat exchange layer 2 is divided into a first pipeline 21 and a fifth pipeline 25. A compressor 3 is provided on the first pipeline 21, and the outlet of the first pipeline 21 is connected to the inlet of the gas-liquid separator 4, and the outlet of the gas-liquid separator 4 enters the pipe-side inlet of the reheater 5 through the second pipeline 22. The pipe-side outlet of the reheater 5 is connected to the inlet of the liquid storage tank 7 through the third pipeline 23, and the outlet of the liquid storage tank 7 is connected to the inlet of the organic working medium pipeline 20 in the heat exchange layer 2 through the fourth pipeline 24. The outlet of the fifth pipeline 25 is connected to the hot side fluid inlet H1 of the plate heat exchanger 6, and the hot side fluid outlet H2 of the plate heat exchanger 6 is divided into a sixth pipeline 26 and a seventh pipeline 27, and the outlet of the sixth pipeline 26 is connected to the third pipeline 23, and the seventh pipeline 27 is connected to the fourth pipeline 24. The system further comprises an eighth pipeline 28 , an inlet of which is connected to the second pipeline 22 , and an outlet of which is connected to the fifth pipeline 25 .

[0040] After the cooling water return pipeline 30 merges with the heating network return pipeline 40, the pipeline is connected to the cold side fluid inlet L1 of the plate heat exchanger 6. The cold side fluid outlet L2 of the plate heat exchanger 6 is divided into two paths, one is the cooling water supply pipeline 50, and the other is the heating network supply pipeline 60.

[0041] Each of the above pipelines is provided with a shut-off valve or an operating condition switching valve to adapt to different operating conditions through different conduction modes.

[0042] Specifically, the first pipeline 21 is provided with a first switching valve V-1, which is located after the branching point between the first pipeline 21 and the fifth pipeline 25 and before the compressor 3. The second pipeline 22 is provided with a second shut-off valve V-2, which is located after the intersection of the second pipeline 22 and the eighth pipeline 28 and before the inlet of the reheater 8. The fourth pipeline 24 is provided with a throttle valve 8, which is located after the outlet of the liquid storage tank 7 and before the intersection of the fourth pipeline 24 and the seventh pipeline 27. The fifth pipeline 25 is provided with a fifth switching valve V-5, which is located after the branching point between the first pipeline 21 and the fifth pipeline 25 and before the intersection of the fifth pipeline 25 and the eighth pipeline 28. The sixth pipeline 26 is provided with a sixth switching valve V-6. The seventh pipeline 27 is provided with a working fluid pump 9, and a third shut-off valve V-3 is provided before the inlet of the working fluid pump 9, and a seventh shut-off valve V-7 is provided after the outlet of the working fluid pump 9. The eighth pipeline 28 is provided with an eighth switching valve V-8. A ninth switching valve V-9 is provided on the cooling water return pipeline 30, a tenth switching valve V-10 is provided on the heating network return pipeline 40, an eleventh switching valve V-11 is provided on the cooling water supply pipeline 50, and a twelfth switching valve V-12 is provided on the heating network supply pipeline 60.

[0043] The above system can be applied to 5 different working conditions by using different control methods on the valve body.

[0044] Working condition 1: Non-heating season + deep cooling and reheating working condition (in summer, the flue gas is discharged after deep cooling and reheating process).

[0045] The first three-way regulating valve FV-1 is adjusted to position A, and the second three-way regulating valve FV-2 is adjusted to position C; the flue gas completes the cooling and condensing process in the shell side of the heat exchange layer 2, and then enters the shell side of the reheater 5 of the first flue 121 for isohypsum heating, and is finally sent to the chimney 14 for discharge through the induced draft fan 13.

[0046] The first switching valve V-1, the fifth switching valve V-5, the second shut-off valve V-2, the third shut-off valve V-3, the seventh shut-off valve V-7, the throttle valve 8, the ninth switching valve V-9, and the eleventh switching valve V-11 on the organic working fluid pipeline are opened, while the eighth switching valve V-8, the sixth switching valve V-6, the tenth switching valve V-10, and the twelfth switching valve V-12 are closed.

[0047] The organic working medium in the state of low-pressure saturated wet steam enters the tube side of the heat exchange layer 2 to evaporate and absorb heat, and becomes a low-pressure saturated dry steam state; then it is divided into two parts, one part maintains a low-pressure state, exchanges heat with cooling water in the plate heat exchanger 6 through the fifth pipeline 25, and becomes a low-pressure saturated wet steam, and then is transported by the working medium pump 9 through the seventh pipeline 27 to merge with the other part; the other part enters the compressor 3 through the first pipeline 21 for isentropic compression, and becomes a high-pressure superheated steam state, after passing through the gas-liquid separator 4, enters the tube side of the reheater 5 through the second pipeline 22 to exchange heat with the flue gas after desulfurization, and becomes a high-pressure subcooled liquid, and then enters the liquid storage tank 7 through the third pipeline 23, and finally enters the throttle valve 8 of the fourth pipeline 24 for isentropic throttling, and becomes a low-pressure saturated wet steam; the above two parts of the organic working medium in the state of saturated wet steam merge, return to the tube side of the heat exchange layer 2, and continue the next thermal cycle process.

[0048] Working condition 2: Flat-peak heating + deep-cooling direct discharge working condition (late autumn and early spring, the flue gas is directly discharged after the deep-cooling process).

[0049] The first three-way regulating valve FV-1 is adjusted to position B, and the second three-way regulating valve FV-2 is adjusted to position D; the flue gas completes the cooling and condensing process in the shell side of the heat exchange layer 2, and is then directly sent to the chimney 14 for discharge through the induced draft fan 13.

[0050] The fifth switching valve V-5, the third shut-off valve V-3, the seventh shut-off valve V-7, the tenth switching valve V-10 and the twelfth switching valve V-12 on the organic working fluid pipeline are opened, and the first switching valve V-1, the eighth switching valve V-8, the second shut-off valve V-2, the sixth switching valve V-6, the throttle valve 8, the ninth switching valve V-9 and the eleventh switching valve V-11 are closed.

[0051] The organic working fluid in the state of low-pressure saturated wet steam enters the tube side of the heat exchange layer 2 to evaporate and absorb heat, and becomes a low-pressure saturated dry steam state; then it enters the plate heat exchanger 6 through the fifth pipeline 25 to exchange heat with the circulating water of the heating network, and becomes low-pressure saturated wet steam; finally, it is transported by the working fluid pump 9 of the seventh pipeline 27 and returns to the tube side of the heat exchange layer 2 through the fourth pipeline 24 to continue the next thermal cycle process.

[0052] Operating condition three: flat-peak heating + deep cooling and reheating condition (in late autumn and early spring, the flue gas is discharged after deep cooling and reheating process).

[0053] The first three-way regulating valve FV-1 is adjusted to position A, and the second three-way regulating valve FV-2 is adjusted to position C; the flue gas completes the cooling and condensing process in the shell side of the heat exchange layer 2, and then enters the shell side of the reheater 5 for isohyperthermia, and is finally sent to the chimney 14 for discharge through the induced draft fan 13.

[0054] The valves on the organic working fluid pipeline, including the first switching valve V-1, the fifth switching valve V-5, the second shut-off valve V-2, the third shut-off valve V-3, the seventh shut-off valve V-7, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12, are opened, and the eighth switching valve V-8, the sixth switching valve V-6, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed.

[0055] The organic working medium in the state of low-pressure saturated wet steam enters the tube side of the heat exchange layer 2 to evaporate and absorb heat, and becomes a low-pressure saturated dry steam state; then it is divided into two parts, one part maintains a low-pressure state, enters the plate heat exchanger 6 through the fifth pipeline 25 to exchange heat with the circulating water of the heating network, and becomes a low-pressure saturated wet steam, and then is transported by the working medium pump 9 of the seventh pipeline 27 to merge with the other part; the other part enters the compressor 3 through the first pipeline 21 for isentropic compression, and becomes a high-pressure superheated steam state, after passing through the gas-liquid separator 4, enters the tube side of the reheater 5 through the second pipeline 22 to exchange heat with the flue gas after desulfurization, and becomes a high-pressure subcooled liquid, and then enters the liquid storage tank 7 through the third pipeline 23, and finally enters the throttle valve 8 of the fourth pipeline 24 for isentropic throttling, and becomes a low-pressure saturated wet steam; the above two parts of the organic working medium in the state of saturated wet steam merge, enter the tube side of the heat exchange layer 2 in the fourth pipeline 24, and continue the next thermal cycle process.

[0056] Operating condition 4: Peak heating + deep cooling direct discharge condition (in winter, the flue gas is directly discharged after the deep cooling process).

[0057] The first three-way regulating valve FV-1 is adjusted to position B, and the second three-way regulating valve FV-2 is adjusted to position D; the flue gas completes the cooling and condensing process in the shell side of the heat exchange layer 2, and is then sent to the chimney 14 through the second flue 122 by the induced draft fan 13 for discharge.

[0058] The first switching valve V-1, the eighth switching valve V-8, the sixth switching valve V-6, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12 of the organic working fluid pipeline are opened, and the fifth switching valve V-5, the second shut-off valve V-2, the third shut-off valve V-3, the seventh shut-off valve V-7, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed.

[0059] The organic working medium in the state of low-pressure saturated wet steam enters the tube side of the heat exchange layer 2 to evaporate and absorb heat, and becomes a low-pressure saturated dry steam state; then it enters the compressor 3 through the first pipeline 21 for isentropic compression and becomes a high-pressure superheated steam state, passes through the gas-liquid separator 4, enters the fifth pipeline 25 through the eighth pipeline 28, and then enters the plate heat exchanger 6 to exchange heat with the circulating water of the heating network, and becomes a high-pressure subcooled liquid, and then enters the third pipeline 23 through the sixth pipeline 26 and then enters the liquid storage tank 7. The organic working medium coming out of the liquid storage tank 7 enters the throttle valve 8 for isentropic throttling and becomes a low-pressure saturated wet steam; finally, the organic working medium returns to the tube side of the heat exchange layer 2 through the fourth pipeline 24 to continue the next thermal cycle process.

[0060] Operating condition five: Peak heating + deep cooling and reheating condition (in winter, the flue gas is discharged after deep cooling and reheating process).

[0061] The first three-way regulating valve FV-1 is adjusted to position A, and the second three-way regulating valve FV-2 is adjusted to position C; the flue gas completes the cooling and condensing process in the shell side of the heat exchange layer 2, and then enters the shell side of the reheater 5 of the first flue 121 for isohypsum heating, and is finally sent to the chimney 14 for discharge through the induced draft fan 13.

[0062] The first switching valve V-1, the eighth switching valve V-8, the second shut-off valve V-2, the sixth switching valve V-6, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12 of the organic working fluid pipeline are opened, and the fifth switching valve V-5, the third shut-off valve V-3, the seventh shut-off valve V-7, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed.

[0063] The organic working medium in the state of low-pressure saturated wet steam enters the tube side of the heat exchange layer 2 to evaporate and absorb heat, and becomes a low-pressure saturated dry steam state; then it enters the compressor 3 through the first pipeline 21 for isentropic compression and becomes a high-pressure superheated steam state; then it is divided into two parts, one part enters the reheater 5 through the second pipeline 22 to exchange heat with the flue gas and becomes a high-pressure subcooled liquid and enters the third pipeline 23; the other part enters the fifth pipeline 25 through the eighth pipeline 28 and then enters the plate heat exchanger 6 to exchange heat with the circulating water of the heating network, and finally becomes a high-pressure subcooled liquid and enters the third pipeline 23 through the sixth pipeline 26; the two parts of high-pressure subcooled liquid organic working medium merge and enter the liquid storage tank 7, and the organic working medium coming out of the liquid storage tank 7 completes the isentropic throttling process through the throttle valve 8 and becomes a low-pressure saturated wet steam state; finally, the organic working medium returns to the tube side of the heat exchange layer 2 through the fourth pipeline to continue the next thermal cycle process.

[0064] A specific embodiment of the fifth working condition is given below.

[0065] The first three-way regulating valve FV-1 is adjusted to position A, and the second three-way regulating valve FV-2 is adjusted to position C. The flue gas at 55°C completes the cooling and condensing process to 45°C in the shell side of the heat exchange layer 2, and then enters the shell side of the reheater 5 for isohumidification heating to 80°C, and is finally sent to the chimney 14 for discharge through the induced draft fan 10.

[0066] The first switching valve V-1, the eighth switching valve V-8, the second shut-off valve V-2, the sixth switching valve V-6, the throttle valve 8, the tenth switching valve V-10, and the twelfth switching valve V-12 of the organic working fluid pipeline are opened, and the fifth switching valve V-5, the third shut-off valve V-3, the seventh shut-off valve V-7, the ninth switching valve V-9, and the eleventh switching valve V-11 are closed.

[0067] The organic working medium in the state of low-pressure saturated wet steam with a temperature of 40°C, a pressure of 0.15MPa, and a dryness of 23% enters the tube pass of the heat exchange layer 2 to evaporate and absorb heat, and becomes a low-pressure saturated dry steam state with a temperature of 40°C and a pressure of 0.15MPa. Then it enters the compressor 3 for isentropic compression and becomes a high-pressure superheated steam state with a temperature of 90°C and a pressure of 0.35MPa. Then it is divided into two parts, one part enters the tube pass of the reheater 5 to exchange heat with the flue gas, and the other part enters the plate heat exchanger 6 to exchange heat with the circulating water of the heating network, and finally both become a high-pressure subcooled liquid with a temperature of 52°C and a pressure of 0.35MPa. The two parts of high-pressure subcooled liquid organic working medium converge in the liquid storage tank 7, and then complete the isentropic throttling process through the throttle valve 8, and become a low-pressure saturated wet steam state with a temperature of 40°C and a pressure of 0.15MPa. Finally, the organic working medium returns to the tube pass of the heat exchange layer 2 to continue the next thermodynamic cycle process.

Claims

1. An OGGH flue gas reheating treatment system for a wet flue gas desulfurization process, characterized in that: The flue (12) at the outlet of the desulfurization tower (1) is divided into a first flue (121) and a second flue (122) connected in parallel, and the first flue (121) merges with the second flue (122) after passing through the shell side of the reheater (5); A heat exchange layer (2) is arranged at the top of the desulfurization tower (1) and before the flue gas outlet. The tube outlet of the heat exchange layer (2) is divided into two paths, one path passes through the tube of the reheater (5) and then returns to the tube inlet of the heat exchange layer (2), and the other path passes through the plate heat exchanger (6) and then returns to the heat exchange layer (2); The inlet of the tube side of the reheater (5) is connected to the inlet of the plate heat exchanger (6) through a branch line, and the outlet of the plate heat exchanger (6) is connected to the outlet of the tube side of the reheater (5) through another branch line. The fluid in the pipeline connecting the inlet and outlet of the tube side of the heat exchange layer (2) is an organic working medium. The flue (12) is divided into a first flue (121) and a second flue (122) by a first three-way regulating valve (FV-1), wherein the closing point of the first three-way regulating valve (FV-1) on the second flue (122) is position A, and the closing point of the first three-way regulating valve (FV-1) on the first flue (121) is position B; The first flue (121) and the second flue (122) are joined by a second three-way regulating valve (FV-2), wherein the closing point of the second three-way regulating valve (FV-2) on the second flue (122) is position C, and the closing point of the second three-way regulating valve (FV-2) on the first flue (121) is position D; The pipe outlet of the heat exchange layer (2) is divided into a first pipe (21) and a fifth pipe (25); The outlet of the first pipeline (21) is connected to the inlet of the gas-liquid separator (4), the outlet of the gas-liquid separator (4) enters the inlet of the tube side of the reheater (5) through the second pipeline (22), the outlet of the tube side of the reheater (5) is connected to the liquid storage tank (7) through the third pipeline (23), and the outlet of the liquid storage tank (7) is connected to the inlet of the tube side of the heat exchange layer (2) through the fourth pipeline (24); The outlet of the fifth pipeline (25) is connected to the hot side fluid inlet (H1) of the plate heat exchanger (6); the hot side fluid outlet (H2) of the plate heat exchanger (6) is divided into a sixth pipeline (26) and a seventh pipeline (27); the outlet of the sixth pipeline (26) is connected to the third pipeline (23), and the seventh pipeline (27) is connected to the fourth pipeline (24); The branch line connected before the inlet of the tube side of the reheater (5) and before the inlet (H1) of the hot side fluid of the plate heat exchanger (6) is the eighth pipeline (28); After the cooling water return pipeline (30) and the heating network return pipeline (40) are merged, the pipeline is connected to the cold side fluid inlet (L1) of the plate heat exchanger (6); the cold side fluid outlet (L2) of the plate heat exchanger (6) is divided into two paths, one is the cooling water supply pipeline (50), and the other is the heating network supply pipeline (60); The first pipeline (21) is provided with a compressor (3), and the seventh pipeline (27) is provided with a working fluid pump (9); A first switching valve (V-1) is provided on the first pipeline (21), a second shut-off valve (V-2) is provided on the second pipeline (22), a throttle valve (8) is provided on the fourth pipeline (24) and at the outlet of the liquid storage tank (7), a fifth switching valve (V-5) is provided on the fifth pipeline (25), a sixth switching valve (V-6) is provided on the sixth pipeline (26), a third shut-off valve (V-3) is provided before the working fluid pump (9) of the seventh pipeline (27), and a seventh shut-off valve (V-7) is provided after the working fluid pump (9), an eighth switching valve (V-8) is provided on the eighth pipeline (28), a ninth switching valve (V-9) is provided on the cooling water return pipeline (30), a tenth switching valve (V-10) is provided on the heating network return pipeline (40), an eleventh switching valve (V-11) is provided on the cooling water supply pipeline (50), and a twelfth switching valve (V-12) is provided on the heating network supply pipeline (60).

2. The OGGH flue gas reheating treatment system for wet desulfurization process according to claim 1, characterized in that: The flow direction of the organic working fluid is the same as that of the flue gas.

3. The OGGH flue gas reheating treatment system for wet desulfurization process according to claim 1, characterized in that: The flue gas ducts that are joined by the second three-way regulating valve (FV-2) are connected to the chimney (14) via the induced draft fan (13).

4. An OGGH flue gas reheat control method for a wet flue gas desulfurization process, using the system as described in any one of claims 1 to 3, characterized in that: Here’s how: (1) During the non-heating season, the flue gas needs to be discharged after deep cooling and reheating process: the first three-way regulating valve (FV-1) is adjusted to position A, the second three-way regulating valve (FV-2) is adjusted to position C, and at the same time, the first switching valve (V-1), the fifth switching valve (V-5), the second shut-off valve (V-2), the third shut-off valve (V-3), the seventh shut-off valve (V-7), the throttle valve (8), the ninth switching valve (V-9), and the eleventh switching valve (V-11) on the organic working fluid pipeline are opened, and at the same time, the eighth switching valve (V-8), the sixth switching valve (V-6), the tenth switching valve (V-10), and the twelfth switching valve (V-12) are closed; (2) When heating is performed at off-peak hours, the flue gas needs to be discharged directly after the deep cooling process: the first three-way regulating valve (FV-1) is adjusted to position B, the second three-way regulating valve (FV-2) is adjusted to position D, and at the same time, the fifth switching valve (V-5), the third shut-off valve (V-3), the seventh shut-off valve (V-7), the tenth switching valve (V-10), and the twelfth switching valve (V-12) on the organic working fluid pipeline are opened, and the first switching valve (V-1), the eighth switching valve (V-8), the second shut-off valve (V-2), the sixth switching valve (V-6), the throttle valve (8), the ninth switching valve (V-9), and the eleventh switching valve (V-11) are closed; (3) When heating is performed at off-peak hours, the flue gas needs to be discharged after deep cooling and reheating: the first three-way regulating valve (FV-1) is adjusted to position A, the second three-way regulating valve (FV-2) is adjusted to position C, and at the same time, the valves on the organic working fluid pipeline, including the first switching valve (V-1), the fifth switching valve (V-5), the second shut-off valve (V-2), the third shut-off valve (V-3), the seventh shut-off valve (V-7), the throttle valve (8), the tenth switching valve (V-10), and the twelfth switching valve (V-12), are opened, and the eighth switching valve (V-8), the sixth switching valve (V-6), the ninth switching valve (V-9), and the eleventh switching valve (V-11) are closed; (4) During peak heating, the flue gas needs to be discharged directly after the deep cooling process: the first three-way regulating valve (FV-1) is adjusted to position B, the second three-way regulating valve (FV-2) is adjusted to position D, and at the same time, the first switching valve (V-1), the eighth switching valve (V-8), the sixth switching valve (V-6), the throttle valve (8), the tenth switching valve (V-10), and the twelfth switching valve (V-12) of the organic working fluid pipeline are opened, and the fifth switching valve (V-5), the second shut-off valve (V-2), the third shut-off valve (V-3), the seventh shut-off valve (V-7), the ninth switching valve (V-9), and the eleventh switching valve (V-11) are closed; (5) During peak heating, the flue gas is discharged after deep cooling and reheating process: the first three-way regulating valve (FV-1) is adjusted to position A, the second three-way regulating valve (FV-2) is adjusted to position C, and at the same time, the first switching valve (V-1), the eighth switching valve (V-8), the second shut-off valve (V-2), the sixth switching valve (V-6), the throttle valve (8), the tenth switching valve (V-10), and the twelfth switching valve (V-12) of the organic working fluid pipeline are opened, and the fifth switching valve (V-5), the third shut-off valve (V-3), the seventh shut-off valve (V-7), the ninth switching valve (V-9), and the eleventh switching valve (V-11) are closed.

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