A flue gas desulfurization system using the surplus cold quantity of an intercooling tower to perform self-circulation condensation of a desulfurization tower

Abstract

This application discloses a flue gas desulfurization system that utilizes the surplus cooling capacity of an indirect cooling tower for self-circulating condensation of the desulfurization tower. The system includes a desulfurization tower and an indirect cooling tower. The desulfurization tower contains a slurry pool and a spray layer. The indirect cooling tower includes a tower cylinder, an air inlet at the bottom of the cylinder, and a radiator. The radiator includes multiple circumferentially distributed heat dissipation units. It also includes a circulating water tank and a circulating water pump. Above the spray layer, along the flue gas flow direction, a liquid collection layer and a condensation layer are sequentially arranged. The condensation layer has a medium flow channel with an inlet and an outlet. The liquid collection layer has a drain outlet. Both the outlet and drain outlet are connected to the circulating water tank via water pipes. The circulating water tank, some idle heat dissipation units, and the condensation layer are connected by a circulating water pump and water pipes to form a cooling water circulation loop. This application fully utilizes the surplus cooling capacity of idle or low-load operating modules of indirect cooling towers in power plants in Northwest China during winter, providing a cold source for cooling and condensing the desulfurized flue gas, achieving cross-system cascade transfer and efficient utilization of cooling capacity.

Description

Technical Field

[0001] This application relates to the field of energy conservation and emission reduction technology in thermal power plants, specifically to a flue gas desulfurization system that utilizes the surplus cooling capacity of an indirect cooling tower for self-circulating condensation of the desulfurization tower. Background Technology

[0002] Due to water scarcity, coal-fired power plants in Northwest China commonly employ indirect air-cooling systems as their cold-end solution. The design capacity of these indirect cooling towers must meet the heat dissipation demands during extreme summer temperatures. However, in winter, with significantly reduced ambient temperatures, their heat dissipation capacity far exceeds actual needs. To maintain circulating water temperatures above the antifreeze threshold and prevent equipment freezing damage, 40%-60% of the cooling modules in the indirect cooling towers typically need to be shut down or their operating load drastically reduced. This results in a large number of cooling units remaining idle, and their potential cooling capacity not being fully utilized.

[0003] The clean flue gas produced by wet desulfurization processes in coal-fired power plants is typically in a saturated wet state with a temperature of approximately 45-55°C. Direct discharge into the atmosphere can easily form colored plumes or gypsum rain, causing environmental problems. Therefore, further cooling and condensation of the clean flue gas is necessary to improve the chimney's corrosion resistance or recover moisture from the flue gas. Currently, the mainstream approach is to add a separate flue gas condenser after the desulfurization system, along with an additional cooling water circulation system or a more energy-intensive chilled water system. Furthermore, the large amount of condensate generated during the condensation process is discharged directly without effective utilization, further exacerbating water resource consumption.

[0004] Currently, the desulfurization flue gas condensation system and the indirect cooling tower system operate in a separate mode, which has many obvious defects and resource misallocations: (1) In the winter, the large amount of surplus cold energy in the indirect cooling tower is not effectively utilized, resulting in a huge waste of natural cold source; (2) In order to obtain the cooling capacity required for flue gas condensation, the desulfurization system has to add and operate high-energy-consuming cooling devices or consume a large amount of cooling water, which significantly increases the operating cost of the power plant, especially the energy cost and water resource cost.

[0005] (3) The flue gas condensation process itself can generate a considerable amount of water, which is a valuable supplementary water source for water-scarce areas. However, under the current model, most of this condensate is directly discharged and fails to achieve closed-loop recycling, resulting in secondary waste of water resources.

[0006] This fragmented approach places the water-scarce Northwest region under the dual pressures of water resource constraints and rising costs. Furthermore, the addition of specialized equipment increases initial investment and maintenance workload. Therefore, there is an urgent need for a new technology that can efficiently utilize existing resources within power plants (especially surplus cooling capacity in winter) to achieve flue gas condensation after desulfurization, while simultaneously reducing energy consumption, water consumption, and investment costs. Utility Model Content

[0007] This invention provides a flue gas desulfurization system that utilizes the surplus cooling capacity of the indirect cooling tower for self-circulating condensation of the desulfurization tower. This scheme fully leverages the surplus cooling capacity of the indirect cooling tower modules that are idle or operating at low load in power plants in Northwest China during winter, constructing a closed-loop cooling cycle using the desulfurization tower's own condensate as the medium. This provides a cold source for cooling and condensing the desulfurized flue gas, achieving cross-system cascade transfer and efficient utilization of cooling capacity. It significantly reduces external cooling water consumption and reliance on dedicated cooling equipment, achieving energy saving, water saving, reduced consumption, and lower investment and operating costs.

[0008] A flue gas desulfurization system that utilizes the surplus cooling capacity of an indirect cooling tower for self-circulating condensation of the desulfurization tower includes a desulfurization tower and an indirect cooling tower. The desulfurization tower has a slurry pool and a spray layer. The indirect cooling tower includes a tower cylinder and an air inlet and a radiator disposed at the bottom of the tower cylinder. The radiator includes multiple sets of circumferentially distributed heat dissipation units. It also includes a circulating water tank and a circulating water pump; above the spray layer, along the flue gas flow direction, a liquid collection layer and a condensation layer are arranged in sequence to collect condensate in the flue gas and use it as circulating cooling water; the condensation layer has a medium flow channel with an inlet and an outlet, and the liquid collection layer has a drain outlet; both the outlet and the drain outlet are connected to the circulating water tank through water pipes; the circulating water tank, the partially idle heat dissipation unit, and the condensation layer are connected by the circulating water pump and water pipes to form a cooling water circulation loop, driving the cooling water to circulate among the condensation layer, the circulating water tank, and the partially idle heat dissipation unit.

[0009] As one possible connection method for the cooling water circulation loop, the drain outlet of the circulating water tank is connected to the inlet of a partially unused heat dissipation unit via a water pipe, the outlet of the corresponding heat dissipation unit is connected to the inlet of the circulating water pump via a water pipe, and the outlet of the circulating water pump is connected to the inlet of the condensate medium flow channel via a water pipe, thus forming a closed cooling water circulation loop.

[0010] The condensate generated in the desulfurization tower's condensate layer is collected by the liquid collection layer and flows into the circulating water tank as a cooling medium. The circulating water pump transports the condensate, which serves as the cooling medium, through pipelines to the idle heat dissipation module of the indirect cooling tower. The natural wind in the low-temperature environment carries away the heat of the condensate, lowering its temperature before it is transported to the desulfurization tower's condensate layer. As a cold source, it cools and condenses the saturated flue gas after desulfurization. The newly generated condensate absorbs heat, raising its own temperature. After completing the heat exchange, the cooling water flows back into the circulating water tank, forming a closed cooling water circulation loop.

[0011] Indirect cooling towers utilize the density difference between the air inside and outside the tower to generate self-adsorption, thereby driving air convection: cold air enters from the bottom of the tower, exchanges heat with the heat dissipation unit to form humid, warm air, and then exits from the top, thus achieving continuous air circulation. Indirect cooling towers have two operating modes: summer and winter. This application mainly applies to the winter operating mode. In summer, with natural wind temperatures of 30-40℃, the inlet water temperature of the heat dissipation unit is 50-63℃, and the outlet water temperature after cooling is 35-45℃, operating at full load. In winter, with natural wind temperatures of -15-5℃, the inlet water temperature of the heat dissipation unit is 30-45℃, and the outlet water temperature after cooling is 5-15℃, operating at low load, with some heat dissipation units idle. This application connects the desulfurization system's condensate circulation loop to the idle heat dissipation units, enabling efficient recovery and utilization of the surplus cooling resources of the indirect cooling tower. A circulating water pump provides the power for the circulating water transport.

[0012] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0013] Optionally, the heat dissipation unit is a finned tube heat dissipation unit.

[0014] Optionally, a switching valve is installed on the inlet and outlet water pipes of the heat dissipation unit. This valve is used to direct the circulating water that needs cooling to a selected heat dissipation unit that is idle or operating at low load.

[0015] Optionally, the circulating water tank is positioned higher than the corresponding heat dissipation unit.

[0016] Optionally, the circulating water tank is further equipped with a water inlet and an overflow outlet. These are used to maintain a stable system water level and for necessary drainage. Water replenishment should prioritize the excess condensate generated by the system itself; if necessary, a small amount of demineralized water or treated industrial water can be added.

[0017] Optionally, the condensation layer may employ a bare tube heat exchanger.

[0018] Optionally, the liquid collection layer adopts several strip-shaped guide channels arranged at intervals and with a certain slope, and the gap between adjacent strip-shaped guide channels serves as a flue gas channel.

[0019] Optionally, 40%-60% of the total heat dissipation units are left unused.

[0020] A desulfurization tower self-circulation condensation method utilizing the surplus cooling capacity of an indirect cooling tower includes a desulfurization tower and an indirect cooling tower. The desulfurization tower has a slurry pool and a spray layer. After being washed and condensed in the desulfurization tower, the flue gas is discharged from the flue gas outlet at the top. The indirect cooling tower includes a tower cylinder and a radiator disposed at the bottom of the tower cylinder. The radiator includes multiple sets of circumferentially distributed heat dissipation units. Above the spray layer, along the flue gas flow direction, a liquid collection layer and a condensation layer are arranged in sequence; the condensation layer has a medium flow channel for circulating cooling water, and the condensation layer exchanges heat with the flue gas after spray washing at a temperature of 45-52℃ to reduce the exhaust gas temperature, while capturing condensate in the flue gas; the liquid collection layer collects the condensate falling from the condensation layer and discharges it. In low-temperature winter environments, some of the heat dissipation units inside the indirect cooling tower are idle. The condensate collected in the liquid collection layer is discharged to the circulating water tank and then sent to the idle heat dissipation units of the indirect cooling tower. In the heat dissipation units, the condensate undergoes indirect heat exchange with the natural air entering the heat dissipation units at a temperature of -15 to 5°C. After heat exchange, the condensate is heated to 5 to 15°C and then sent to the condensation layer by the circulating water pump as the cooling water for the condensation layer. After heat exchange in the condensation layer, the cooling water is heated to 25 to 30°C and then flows into the circulating water tank, where it mixes with the condensate to form a closed cooling water circulation loop.

[0021] Optionally, the temperature of the condensate is 30-35℃; the temperature of the condensate and cooling water after mixing in the circulating water tank is 30±2℃.

[0022] Optionally, the idle heat dissipation units account for 40%-60% of the total heat dissipation units.

[0023] Optionally, the flow rate of the cooling water in the heat dissipation unit is 1.5-2.0 m / s.

[0024] Compared with the prior art, this application has the following beneficial effects: (1) This application provides a solution for efficiently utilizing the idle cold energy of the intercooling tower in winter. By calling on the idle cold energy of the intercooling tower in winter to drive the cooling of the condensate layer of the desulfurization tower, the exhaust temperature and pollutant emission intensity are significantly reduced, the dependence on external cooling devices is reduced, and the overall energy consumption of the system is reduced.

[0025] (2) This application provides a closed-loop condensate recycling scheme. In winter, the condensate from the desulfurization tower is collected as a circulating medium and the cooling capacity is transferred to the desulfurization condensation link through the heat exchange system, which greatly reduces the cooling water consumption of the desulfurization process and effectively alleviates the water resource pressure in water-scarce areas.

[0026] (3) This application provides a solution to effectively suppress the emission of “white smoke”. In response to the low temperature and dry winter environment in Northwest China, the excess cold energy of the intercooling tower is used to deeply cool the desulfurization flue gas, reduce the flue gas temperature, eliminate the apparent temperature difference between the flue gas and the ambient air, and suppress the generation of “white smoke” from the source.

[0027] (4) This application provides a scheme for the cascade utilization of cold energy across systems. The condensate of the desulfurization tower is used as the cooling medium to transfer cold energy between the cooling tower and the condensation layer of the desulfurization tower, thereby realizing the cascade utilization of cold energy, reducing the system operation and maintenance costs, and improving the overall economic efficiency and resource utilization efficiency of the process.

[0028] This application couples the desulfurization tower with the indirect cooling tower, making full and efficient use of the existing resources inside the power plant, especially the surplus cooling capacity in winter, to achieve desulfurization flue gas condensation, while reducing energy consumption, water consumption and investment costs. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system structure of this application.

[0030] The reference numerals in the figure are as follows: 1-Desulfurization tower, 2-Circulating water tank, 3-Circulating water pump, 4-Cooling tower; 11-Slurry tank, 12-Smoke inlet, 13-Slurry collection layer, 14-Condensation layer, 15-Spray layer, 16-Smoke outlet, 17-Slurry circulation pump; 21 - First import; 22 - Second import; 41-Heat dissipation unit, 42-Tower, 43-Hot water inlet pipe, 44-Cold water outlet pipe. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] like Figure 1 As shown, a flue gas desulfurization system that utilizes the surplus cooling capacity of an indirect cooling tower for self-circulating condensation of the desulfurization tower includes a desulfurization tower 1, a circulating water tank 2, a circulating water pump 3, and an indirect cooling tower 4.

[0034] The desulfurization tower 1 includes a tower body, with a slurry pool 11 at the bottom of the tower body. A flue gas inlet 12 is located on the tower wall above the slurry pool. A spray layer 15 is installed above the flue gas inlet, and the spray layer is connected to the slurry pool via a slurry circulation pump 17. A liquid collection layer 13 is installed above the spray layer 15, and a condensation layer 14 is installed above the liquid collection layer. A flue gas outlet 16 is located at the top of the tower body. The condensation layer 14 has a medium flow channel with an inlet and an outlet, and the liquid collection layer 13 has a drain outlet.

[0035] The indirect cooling tower 4 includes a tower cylinder 42, which can be a hyperbolic tower cylinder. The top of the tower cylinder is an air outlet, and the bottom of the tower cylinder is arranged with radiators and air inlets (not shown in the figure) around the circumference. The radiators are located adjacent to the air inlets and inside the air inlets. The air inlets can be louvered air inlets. The radiators include multiple sets of heat dissipation units 41 distributed around the bottom of the tower cylinder 42. The heat dissipation units are finned tube heat dissipation units, and the multiple sets of heat dissipation units can be connected in series or in parallel.

[0036] Indirect cooling towers utilize the density difference between the air inside and outside the tower to generate self-adsorption, thereby driving air convection: cold air enters from the bottom of the tower, exchanges heat with the heat dissipation unit to form humid, warm air, and then exits from the top, thus achieving continuous air circulation. Indirect cooling towers have two operating modes: summer and winter. This application mainly applies to the winter operating mode. In summer, the natural wind temperature is 30-40℃, the inlet water temperature of the heat dissipation unit is 50-63℃, and the outlet water temperature after cooling is 35-45℃, operating at full load; in winter, the natural wind temperature is -15-5℃, the inlet water temperature of the heat dissipation unit is 30-45℃, and the outlet water temperature after cooling is 5-15℃, operating at low load, with some heat dissipation units idle.

[0037] In winter operation mode, the drain outlet of the liquid collection layer 13 in the desulfurization tower is connected to the second inlet 22 of the circulating water tank 2 through a water pipe; the drain outlet of the circulating water tank 2 is connected to the inlet of the idle heat dissipation unit 41 of the intercooling tower through a water pipe; the outlet of the corresponding heat dissipation unit is connected to the inlet of the circulating water pump 3 through a water pipe; the outlet of the circulating water pump 3 is connected to the inlet of the condensation layer 14 in the desulfurization tower through a water pipe; and the outlet of the condensation layer 14 is connected to the first inlet 21 of the circulating water tank 2 through a water pipe, forming a closed cooling water circulation loop. The circulating water pump provides the power for transporting circulating water, connecting the desulfurization system's condensate circulation loop to idle heat dissipation units. This efficiently recovers and utilizes the surplus cooling resources of the indirect cooling tower without affecting the normal operation of other heat dissipation units within the indirect cooling tower. Circulating water tank 2 is positioned higher than the corresponding heat dissipation unit. The gravity of the cooling water within the tank also serves as auxiliary power for its entry into the idle heat dissipation unit. The circulating water tank is also equipped with a water inlet and an overflow / drain outlet (not shown in the diagram). Water replenishment prioritizes the surplus condensate generated by the system itself; if necessary, a small amount of demineralized water or treated industrial water can be added.

[0038] At the bottom of the indirect cooling tower, multiple finned steel tube heat exchangers are vertically arranged along the tower, forming cooling units circumferentially. These units can be connected in series or in parallel to form heat dissipation zones. Cold air enters the tower through the air inlet and flows through the finned steel tube heat exchangers in the heat dissipation zone, exchanging heat with the high-temperature water flowing through the tubes. To facilitate the connection of the desulfurization system's condensate circulation loop, a switching valve (not shown in the figure) is added to the inlet and outlet water pipes of each heat dissipation unit to direct the circulating water requiring cooling to a selected idle or low-load operating cooling module.

[0039] In some implementations, the finned steel tubes of the heat dissipation unit are made of galvanized steel with corrosion resistance, an outer diameter of 42mm, and a wall thickness of 2.0mm. The condensation layer uses a bare tube heat exchanger made of corrosion-resistant stainless steel, with circulating cooling water as the medium inside the tube. The liquid collection layer mainly adopts a strip-shaped guide channel structure with a slight guide slope (1-2°) on the surface, made of corrosion-resistant FRP (fiberglass reinforced plastic). Several strip-shaped guide channels are spaced apart, with flue gas passages between adjacent strip-shaped guide channels. The strip-shaped guide channels converge at their lower ends into a drainage trough, which has a drain outlet.

[0040] The above desulfurization system operates as follows: The heat dissipation units of the indirect cooling tower are connected in series. In winter operation mode, the natural wind temperature is -15 to 5℃, the inlet water temperature of the heat dissipation unit is 30 to 45℃, and the outlet water temperature after cooling is 5 to 15℃. During low-load operation, some heat dissipation units are connected in series through a switching valve to cool the original hot water, while the remaining heat dissipation units are idle.

[0041] The desulfurization slurry in the desulfurization tower slurry pool has a temperature of 55℃. A slurry circulation pump draws it out from one side of the pool and transports it to the spray layer to desulfurize the rising high-temperature flue gas inside the tower. After spray desulfurization, the flue gas temperature inside the desulfurization tower is 45-52℃. Upon entering the condensation layer, it exchanges heat with the cooling water flowing within. The circulating cooling water, at 5-15℃, flows inside the pipes. The heat from the desulfurized flue gas is transferred to the cooling water through the pipe walls, achieving flue gas cooling and pollutant condensation. The cooled flue gas temperature is 30-35℃, and the cooling water absorbs heat and heats up to 25-30℃. The flue gas is discharged after heat exchange and cooling, while the cooling water, after heat exchange and heating, is sent to the circulating water tank through the first inlet. The condensate produced during the condensation process has a temperature of 30-35℃ and flows into the circulating water tank through the second inlet, mixing with the circulating water to maintain the tank temperature at approximately 30℃. The return water at around 30℃ is connected to the idle heat dissipation unit through the switching valve, and exchanges heat with the natural wind at -15 to 5℃. After the heat exchange and cooling, the water at 5 to 15℃ is sent into the condensation layer by the circulating water pump.

[0042] In winter operation mode, some heat dissipation units connected in series continue to cool the original hot water, which is supplied through the hot water inlet pipe 43 and discharged through the cold water outlet pipe 44 after heat exchange. Some heat dissipation units connected in series are used to cool the condensate of the desulfurization system, which does not affect the operation of the indirect cooling tower and also utilizes its surplus cooling capacity.

[0043] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A flue gas desulfurization system utilizing the surplus cooling capacity of an indirect cooling tower for self-circulating condensation in a desulfurization tower, comprising a desulfurization tower and an indirect cooling tower, wherein the desulfurization tower has a slurry pool and a spray layer; the indirect cooling tower includes a tower cylinder and an air inlet and a radiator disposed at the bottom of the tower cylinder, wherein the radiator includes multiple sets of circumferentially distributed heat dissipation units; characterized in that, It also includes a circulating water tank and a circulating water pump; above the spray layer, along the flue gas flow direction, a liquid collection layer and a condensation layer are arranged in sequence to collect condensate in the flue gas and use it as circulating cooling water; the condensation layer has a medium flow channel with an inlet and an outlet, and the liquid collection layer has a drain outlet; both the outlet and the drain outlet are connected to the circulating water tank through water pipes; the circulating water tank, the partially idle heat dissipation unit, and the condensation layer are connected by the circulating water pump and water pipes to form a cooling water circulation loop, driving the cooling water to circulate among the condensation layer, the circulating water tank, and the partially idle heat dissipation unit.

2. The flue gas desulfurization system according to claim 1, characterized in that, The drain outlet of the circulating water tank is connected to the inlet of a partially unused heat dissipation unit via a water pipe. The outlet of the corresponding heat dissipation unit is connected to the inlet of the circulating water pump via a water pipe. The outlet of the circulating water pump is connected to the inlet of the condensate medium flow channel via a water pipe, forming a closed cooling water circulation loop.

3. The flue gas desulfurization system according to claim 1, characterized in that, The heat dissipation unit is a finned tube heat dissipation unit.

4. The flue gas desulfurization system according to claim 3, characterized in that, A switching valve is installed on the inlet and outlet water pipes of the heat dissipation unit.

5. The flue gas desulfurization system according to claim 1, characterized in that, The circulating water tank is positioned higher than the corresponding heat dissipation unit.

6. The flue gas desulfurization system according to claim 1, characterized in that, The circulating water tank is also equipped with a water inlet and an overflow outlet.

7. The flue gas desulfurization system according to claim 1, characterized in that, The condensation layer uses a bare tube heat exchanger.

8. The flue gas desulfurization system according to claim 1, characterized in that, The liquid collection layer is composed of several spaced strip-shaped guide channels with a certain slope, and the gap between adjacent strip-shaped guide channels serves as flue gas channels.

9. The flue gas desulfurization system according to claim 1, characterized in that, Idle heat dissipation units account for 40%-60% of the total heat dissipation units.

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