A power plant multi-source waste heat collaborative recovery system and method based on slurry flashing

Abstract

The application discloses a power plant multi-source waste heat collaborative recovery system and method based on slurry flashing, and relates to the technical field of energy saving of thermal power plants. The system comprises a flue gas waste heat recovery unit, a deaerator exhaust waste heat recovery unit and a continuous drainage waste heat recovery unit. The flue gas waste heat recovery unit comprises a flashing tank, a slurry inlet and outlet of the flashing tank are connected with a desulfurization tower, and a steam exhaust outlet of the flashing tank is connected with a steam collecting cylinder. The deaerator exhaust waste heat recovery unit comprises a deaerator, a deaerator steam exhaust heat exchanger and a condensate tank which are connected in sequence, and the condensate tank is connected with the flashing tank. The continuous drainage waste heat recovery unit comprises a continuous drainage flashing tank and a continuous drainage multi-stage flashing tank, and a steam exhaust outlet of the continuous drainage multi-stage flashing tank is connected with the steam collecting cylinder. The application collaboratively optimizes and recovers waste heat from different sources, effectively improves the recovery efficiency of waste heat, reduces the corrosion risk of equipment, and realizes full recovery of continuous drainage.

Description

Technical Field

[0001] This invention belongs to the field of energy-saving technology for thermal power plants, specifically relating to a multi-source waste heat recovery system and method for power plants based on slurry flash evaporation. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Currently, power plants generate a large amount of waste heat during operation. This waste heat comes from various sources, such as low-temperature flue gas waste heat, deaerator exhaust waste heat, and continuous wastewater waste heat. How to efficiently utilize this waste heat to improve energy efficiency and reduce environmental pollution has become an important issue facing the power industry.

[0004] Traditional methods for utilizing waste heat from deaerator exhaust typically involve either injecting the exhaust gas or directly mixing it with cold source water. However, these methods all suffer from significant technical bottlenecks. Due to the high oxygen content in the deaerator exhaust, none of these waste heat recovery methods effectively release the oxygen, which can easily lead to corrosion of equipment and pipelines, thereby shortening the service life of the waste heat recovery system.

[0005] In terms of waste heat recovery and utilization in continuous discharge, the existing technology generally adopts the method of flash evaporation in the continuous discharge tank for waste heat recovery. This treatment method can often only recover part of the heat in the continuous discharge, and a large amount of waste heat is still not effectively utilized. In order to meet the discharge requirements, it is necessary to discharge it into the cooling pool for further cooling. At the same time, the amount of wastewater recovered is also limited, and the maximum utilization of water resources is not achieved. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-source waste heat recovery system and method for power plants based on slurry flash evaporation. By coordinating and optimizing the recovery of waste heat from different sources within the power plant, the system effectively improves the waste heat recovery efficiency, reduces the risk of equipment corrosion, and achieves full recycling of wastewater.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] In a first aspect, embodiments of the present invention provide a multi-source waste heat recovery system for power plants based on slurry flash evaporation, comprising:

[0009] The flue gas waste heat recovery unit includes a flash tank, the slurry inlet and outlet of which are connected to the desulfurization tower, and the exhaust steam outlet of which is connected to the steam collection cylinder.

[0010] A deaerator exhaust waste heat recovery unit includes a deaerator, a deaerator exhaust steam heat exchanger, and a condensate tank connected in sequence, wherein the condensate tank is connected to the flash tank.

[0011] The waste heat recovery unit for continuous drainage includes a continuous drainage flash tank and a continuous drainage multi-stage flash tank, wherein the exhaust steam outlet of the continuous drainage multi-stage flash tank is connected to the steam collection cylinder.

[0012] As a further technical solution, the multi-stage flash tank with continuous drainage is provided with multiple flash chambers, and the exhaust steam outlet of each flash chamber is connected to the steam collecting cylinder.

[0013] As a further technical solution, a vacuum regulating valve is installed at the exhaust steam outlet of each flash chamber, and the pressure of the last flash chamber is reduced to 5-8 kPa by a vacuum pump.

[0014] As a further technical solution, the steam outlet of the deaerator is connected to the deaerator exhaust steam heat exchanger, in which steam and condensate exchange heat.

[0015] As a further technical solution, the steam outlet of the continuous flash tank is connected to the deaerator.

[0016] As a further technical solution, the steam collecting cylinder is connected to a lithium bromide heat pump, and the lithium bromide heat pump is connected to a vacuum pump.

[0017] As a further technical solution, the flash tank is provided with an upper spray layer and a lower spray layer. The upper spray layer is connected to the condensate tank, and the lower spray layer is connected to the slurry outlet of the desulfurization tower.

[0018] Secondly, embodiments of the present invention provide a method for the coordinated recovery of multi-source waste heat in power plants based on slurry flash evaporation, comprising the following steps:

[0019] The slurry in the flash tank enters the desulfurization tower to recover the waste heat of the flue gas. After recovering the waste heat, the slurry enters the flash tank for flash evaporation. The exhaust steam generated by flash evaporation enters the steam collection cylinder.

[0020] The exhaust gas discharged from the deaerator is heated by the deaerator exhaust steam heat exchanger and condensed into condensate water which enters the condensate tank. The condensate water in the condensate tank is pumped into the upper spray layer of the flash tank for spraying. After the oxygen in the condensate water is released, it is discharged through the vacuum pump.

[0021] Boiler wastewater enters a continuous flash tank for initial flashing. After flashing, the wastewater enters a multi-stage flash tank for multi-stage flashing. The steam generated by each stage of flashing enters a steam collection cylinder, and the steam in the steam collection cylinder enters a lithium bromide heat pump for heat release.

[0022] As a further technical solution, the temperature of the condensate generated by the deaerator exhaust steam heat exchanger is controlled at 40-50℃.

[0023] As a further technical solution, the continuous drainage temperature after the initial flash evaporation is 100-120℃, and the continuous drainage temperature after multi-stage flash evaporation is 32-42℃.

[0024] The beneficial effects of the above embodiments of the present invention are as follows:

[0025] The multi-source waste heat recovery system for power plants based on slurry flash evaporation provided by this invention deeply integrates slurry flash evaporation flue gas waste heat recovery technology with deaerator exhaust waste heat and continuous discharge waste heat. One system realizes the comprehensive recovery of three types of waste heat in power plants, significantly improving energy utilization efficiency and reducing energy waste; it achieves efficient synergistic recovery of multi-source waste heat, making full use of flue gas waste heat, deaerator exhaust waste heat and continuous discharge waste heat.

[0026] Traditional methods for recovering waste heat from deaerator exhaust gas suffer from the problem of oxygen not being released from the exhaust gas, leading to equipment and pipeline corrosion. This invention innovatively pumps the high-oxygen condensate from the deaerator exhaust steam heat exchange into the flash tank of a slurry flash evaporation system. Utilizing the negative pressure environment within the flash tank, oxygen is released into the atmosphere, effectively reducing the oxygen content in the water, preventing equipment corrosion, extending equipment lifespan, and simultaneously achieving the harmless recovery of water resources.

[0027] Existing continuous discharge systems still have a large amount of unutilized waste heat after flash evaporation in the continuous discharge tank, and the discharge volume is also large. This invention utilizes the vacuum system of the slurry flash evaporation system to perform multi-stage flash evaporation on the continuous discharge, further improving the waste heat recovery efficiency. Simultaneously, the flash evaporation exhaust steam is introduced into the absorption heat pump of the slurry flash evaporation system for waste heat recovery, increasing the superheat of the slurry flash evaporation exhaust steam, and recovering clean water resources from the continuous discharge through flash evaporation.

[0028] This invention utilizes a multi-stage flash tank for continuous drainage to further flash the cooled continuous drainage. The flashed exhaust steam is mixed with the slurry flash exhaust steam from the flash tank via a steam collecting cylinder and then enters a lithium bromide heat pump for heat release. This process achieves deep recovery of waste heat and water resources from the continuous drainage. In addition, a vacuum regulating valve is installed at the steam outlet of each flash chamber, which can adjust the pressure of different flash chambers in the multi-stage flash tank according to the operating conditions, thereby improving the flashing efficiency. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1The present invention is a multi-source waste heat recovery system for power plants based on slurry flash evaporation.

[0031] The diagram is for illustrative purposes only.

[0032] The components include: 1. Desulfurization tower; 2. Slurry circulation pump; 3. Flash tank; 4. Slurry reflux pump; 5. Steam collection cylinder; 6. Lithium bromide heat pump; 7. Vacuum pump; 8. Continuous discharge flash tank; 9. Continuous drainage multi-stage flash tank; 10. Continuous drainage discharge pump; 11. Vacuum regulating valve; 12. Deaerator; 13. Deaerator exhaust steam heat exchanger; 14. Condensate tank; 15. Condensate discharge pump. Detailed Implementation

[0033] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] Example 1

[0035] In a typical embodiment of the present invention, such as Figure 1 As shown, a multi-source waste heat recovery system for power plants based on slurry flash evaporation is provided, comprising:

[0036] The flue gas waste heat recovery unit includes a flash tank 3, the slurry inlet and outlet of the flash tank 3 are connected to the desulfurization tower 1, and the exhaust steam outlet of the flash tank 3 is connected to the steam collection cylinder 5.

[0037] The deaerator exhaust waste heat recovery unit includes a deaerator 12, a deaerator exhaust steam heat exchanger 13 and a condensate tank 14 connected in sequence, wherein the condensate tank 14 is connected to the flash tank 3.

[0038] The waste heat recovery unit for continuous drainage includes a continuous drainage flash tank 8 and a continuous drainage multi-stage flash tank 9, wherein the exhaust steam outlet of the continuous drainage multi-stage flash tank 9 is connected to the steam collection cylinder 5.

[0039] Specifically, the slurry inlet of flash tank 3 is connected to the slurry outlet at the bottom of desulfurization tower 1, and a slurry circulation pump 2 is installed on the connected pipeline. Under the action of slurry circulation pump 2, the slurry after recovering the waste heat of flue gas enters flash tank 3 for flash evaporation. The slurry outlet of flash tank 3 is connected to the slurry inlet at the top of desulfurization tower, and a slurry return pump 4 is installed on the connected pipeline. Under the action of slurry return pump 4, the flash-evaporated slurry re-enters desulfurization tower 1 to recover waste heat from the flue gas.

[0040] In this embodiment, the steam outlet of the continuous flash tank 8 is connected to the deaerator. The steam generated after flashing is discharged through the top of the continuous flash tank 8 to the deaerator for use. After flashing, the temperature of the continuous drainage water is reduced to 100-120°C. The cooled continuous drainage water enters the continuous drainage multi-stage flash tank 9 for further flashing.

[0041] In this embodiment, the continuous drainage multi-stage flash tank 9 is provided with multiple flash chambers. The exhaust steam outlet of each flash chamber is connected to the steam collecting cylinder 5. A vacuum regulating valve 11 is provided at the exhaust steam outlet of each flash chamber. The continuous drainage enters the first flash chamber at the top of the continuous drainage multi-stage flash tank 9 for flashing, and then enters the next flash chamber in sequence for flashing. The pressure in each flash chamber is controlled by the opening of the vacuum regulating valve 11. Through the flashing of multiple chambers in the continuous drainage multi-stage flash tank 9, the pressure in the last flash chamber is reduced to 5-8 kPa by the vacuum pump 7.

[0042] In this embodiment, the steam outlet of the deaerator 12 is connected to the deaerator exhaust steam heat exchanger 13. In the deaerator exhaust steam heat exchanger, steam and condensate exchange heat. The steam condenses into condensate and enters the condensate tank 14. The condensate tank 14 is connected to the flash tank through the condensate discharge pump 15. The condensate enters the flash tank for flash evaporation.

[0043] Furthermore, the flash tank 3 is provided with an upper spray layer and a lower spray layer. The upper spray layer is connected to the condensate tank 14, and the lower spray layer is connected to the slurry outlet of the desulfurization tower 1.

[0044] In this embodiment, the steam collecting cylinder 5 is connected to the lithium bromide heat pump 6, which is connected to the vacuum pump 7. The vacuum pump 7 periodically removes non-condensable gases to maintain a high vacuum environment in the lithium bromide heat pump system, ensuring that the working fluid (water) evaporates at low temperatures and maintaining the normal operation of the refrigeration cycle. Since the lithium bromide heat pump 6 is connected to the flash tank 3 and the continuous-drainage multi-stage flash tank 9 through the steam collecting cylinder, the vacuum pump 7 can maintain the negative pressure required for flashing in the flash tank 3 and the continuous-drainage multi-stage flash tank 9.

[0045] The working process of the power plant multi-source waste heat synergistic recovery system based on slurry flash evaporation provided in this embodiment is as follows:

[0046] The power plant desulfurization tower 1 generally adopts a limestone wet desulfurization system. The temperature of the desulfurization slurry is generally between 50-55℃. The desulfurization slurry at the bottom of the desulfurization tower is pumped to the lower spray layer inside the flash tank 3 by the slurry circulation pump 2 for spraying. The internal pressure of the flash tank is maintained between 5-8 kPa by the vacuum pump 7. The desulfurization slurry is flashed under negative pressure in the flash tank. The exhaust steam generated by the flash desulfurization slurry is mixed with the continuous drainage flash exhaust steam generated from the continuous drainage multi-stage flash tank 9 through the exhaust port at the top of the flash tank 3 and the steam collection cylinder 5. After mixing, they enter the evaporator inside the lithium bromide heat pump 6 to release heat. Driven by steam, the lithium bromide heat pump 6 absorbs the heat of the flash exhaust steam and transfers the heat to the heating network water or other cold source water.

[0047] Boiler wastewater undergoes initial flash evaporation in a flash evaporator 8. The steam generated after flash evaporation is discharged through the top of the flash evaporator 8 to the deaerator for utilization. After flash evaporation, the temperature of the wastewater decreases to 100-120℃. The cooled wastewater then enters a multi-stage flash evaporator 9 for further flash evaporation. The multi-stage flash evaporator 9 can be designed with multiple flash chambers. The wastewater enters the first flash chamber at the top of the multi-stage flash evaporator 9 for flash evaporation, and then sequentially enters the next stage flash chamber for flash evaporation. The pressure in each stage flash chamber is controlled by the opening of the vacuum regulating valve 11, so that the vacuum level in the multiple flash chambers gradually increases from top to bottom, and the temperature gradually decreases. Multi-stage flash evaporation is mainly to increase the flash evaporation effect and obtain more exhaust steam. The pressure in the last stage flash chamber is reduced to 5-8 kPa by the vacuum pump 7, and the wastewater temperature is reduced to between 32-42℃. The wastewater after the last stage flash evaporation is discharged through the wastewater discharge pump 10. The exhaust steam from the continuous drainage multi-stage flash tank 9 is mixed with the slurry flash steam from the flash tank 3 through the steam collection cylinder 5 and then enters the lithium bromide heat pump 6 to release heat. This process realizes the deep recovery of waste heat and water resources from the continuous drainage.

[0048] The exhaust gas from deaerator 12 is condensed after exchanging heat with cold source water through deaerator exhaust steam heat exchanger 13. The condensate temperature is controlled between 40-50℃. The condensate from the deaerator exhaust steam flows by gravity into condensate tank 14 and is pumped to the upper spray layer of flash tank 3 by condensate discharge pump 15. Due to the sudden pressure drop inside the flash tank, the oxygen contained in the condensate is released instantly. The released oxygen is discharged to the atmosphere through lithium bromide heat pump and then through vacuum pump 7. The condensate is further cooled by flash evaporation and then pumped to the desulfurization tower together with the desulfurization slurry for desulfurization. The heat of this part of the condensate can be deeply recovered. The recovered condensate can be used as makeup water for desulfurization slurry, thereby reducing the amount of makeup water used for desulfurization slurry and realizing the recycling of condensate.

[0049] Example 2

[0050] In a typical embodiment of the present invention, a method for synergistic recovery of multi-source waste heat from power plants based on slurry flash evaporation is provided, comprising the following steps:

[0051] The slurry in the flash tank enters the desulfurization tower to recover the waste heat of the flue gas. After recovering the waste heat, the slurry enters the flash tank for flash evaporation. The exhaust steam generated by flash evaporation enters the steam collection cylinder.

[0052] The exhaust gas discharged from the deaerator is heated by the deaerator exhaust steam heat exchanger and condensed into condensate water which enters the condensate tank. The condensate water in the condensate tank is pumped into the upper spray layer of the flash tank for spraying. After the oxygen in the condensate water is released, it is discharged through the vacuum pump.

[0053] Boiler wastewater enters a continuous flash tank for initial flashing. After flashing, the wastewater enters a multi-stage flash tank for multi-stage flashing. The steam generated by each stage of flashing enters a steam collection cylinder, and the steam in the steam collection cylinder enters a lithium bromide heat pump for heat release.

[0054] Furthermore, the temperature of the condensate generated by the exhaust steam heat exchanger of the deaerator is controlled at 40-50℃.

[0055] Furthermore, the continuous drainage temperature after the initial flash evaporation is 100-120℃, and the continuous drainage temperature after multi-stage flash evaporation is 32-42℃.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-source waste heat co-recovery system based on slurry flashing for power plants, characterized in that, include: The flue gas waste heat recovery unit includes a first flash tank, the slurry inlet and outlet of the first flash tank are connected to the desulfurization tower, and the exhaust steam outlet of the first flash tank is connected to the steam collection cylinder. The deaerator exhaust waste heat recovery unit includes a deaerator, a deaerator exhaust steam heat exchanger and a condensate tank connected in sequence. The condensate tank is connected to the first flash tank. The high-oxygen condensate after the deaerator exhaust steam heat exchange is pumped into the first flash tank, and oxygen is released to the atmosphere by utilizing the negative pressure environment in the first flash tank. The waste heat recovery unit for continuous drainage includes a continuous drainage flash tank and a continuous drainage multi-stage flash tank. The exhaust steam outlet of the continuous drainage multi-stage flash tank is connected to the steam collection cylinder. The steam outlet of the continuous drainage flash tank is connected to the deaerator. The steam generated after flashing is discharged through the top of the continuous drainage flash tank to the deaerator for utilization. Multi-source waste heat recovery methods in power plants include: The slurry in the first flash tank enters the desulfurization tower to recover the waste heat of the flue gas. After recovering the waste heat, the slurry enters the first flash tank for flash evaporation. The exhaust steam generated by flash evaporation enters the steam collection cylinder. The exhaust steam discharged from the deaerator is heat-exchanged through the deaerator exhaust steam heat exchanger and condensed into condensate water which enters the condensate tank. The condensate water in the condensate tank is pumped into the upper spray layer of the first flash tank for spraying. After the oxygen in the condensate water is released, it is discharged through a vacuum pump. Boiler wastewater enters a continuous flash tank for initial flash evaporation. After flash evaporation, the wastewater enters a multi-stage flash tank for multi-stage flash evaporation. The steam generated by each stage of flash evaporation enters a steam collection cylinder. The steam in the steam collection cylinder enters a lithium bromide heat pump for heat release. The steam collection cylinder is connected to the lithium bromide heat pump, which is connected to a vacuum pump. The temperature of the condensate produced by the waste steam heat exchanger of the deaerator is controlled at 40-50℃. The continuous drainage temperature after the initial flash evaporation is 100-120℃, and the continuous drainage temperature after multi-stage flash evaporation is 32-42℃.

2. The slurry flash-based power plant multi-source waste heat cogeneration system of claim 1, wherein, The multi-stage flash tank with continuous drainage is equipped with multiple flash chambers, and the exhaust steam outlet of each flash chamber is connected to the steam collection cylinder.

3. The slurry flash-based power plant multi-source waste heat cogeneration system of claim 2, wherein, Each flash chamber is equipped with a vacuum regulating valve at the exhaust steam outlet, and the pressure in the last flash chamber is reduced to 5-8 kPa by a vacuum pump.

4. The slurry flash-based power plant multi-source waste heat cogeneration system of claim 1, wherein, The exhaust steam outlet of the deaerator is connected to the exhaust steam heat exchanger of the deaerator, in which the exhaust steam exchanges heat with the cold source water.

5. The slurry flash-based power plant multi-source waste heat cogeneration system of claim 1, wherein, The first flash tank is provided with an upper spray layer and a lower spray layer. The upper spray layer is connected to the condensate tank, and the lower spray layer is connected to the slurry outlet of the desulfurization tower.

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