System and method for recycling water vapor in exhaust smoke of power station boiler

Abstract

According to the system and method for recycling the water vapor in the exhaust smoke of the power station boiler, the low-temperature smoke heat exchanger integrated at the inlet of the flue and the low-temperature power circulation system with the organic working medium as the core work cooperatively, so that the low-temperature smoke exchanges heat with the working medium in the heat exchanger to be cooled to be below the dew point; meanwhile, the working medium absorbs the waste heat of the flue gas and then drives the expansion machine to do work; according to the system, power generated by the expansion machine is directly used for driving the smoke exhaust fan, a self-generating and self-using closed loop of waste heat recovery, water resource extraction and smoke exhaust power supply is achieved, finally, purified water is effectively recovered, the overall heat efficiency of the system is improved, and meanwhile the energy consumption is reduced. The problem of high cost caused by the use of high-price corrosion-resistant materials and the consumption of extra electric energy in the traditional scheme is avoided, and the unification of energy conservation, water conservation and low-cost operation is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power generation system, in particular to a system and method for recovering water vapor in flue gas of power plant boiler. BACKGROUND

[0002] Coal-fired units have been developed for many years, and energy utilization efficiency is continuously improved. Most of the waste heat, waste energy, especially high-temperature waste heat, has been utilized. However, due to the limitation of current technical conditions and the influence of cost control, most of the waste heat utilization forms adopt direct heat exchange. High-temperature waste heat can be used to heat boiler feed water, while low-temperature waste heat, especially low-temperature waste heat of scattered equipment, if used to heat boiler feed water, the heat is small and the temperature is low, so the yield is not high. Therefore, the low-temperature waste heat generated by many auxiliary equipment in power plants has not been collected and utilized, or simply used to heat domestic hot water.

[0003] At the same time, the proportion of water consumed in flue gas in coal-fired power plants cannot be ignored, especially in water-deficient areas. If this part of water resources can be recovered, it is beneficial to energy saving and emission reduction or saving water resources.

[0004] However, there are several difficulties in recovering water from flue gas in coal-fired power plants at present. 1. The flue gas contains acid gases. If the water vapor in the flue gas condenses, it is likely to cause damage to ordinary heat exchanger equipment, pipes, etc. Therefore, special material pipes or heat exchangers, such as PTFE material or high-grade stainless steel, need to be used, which will increase the cost of the system. The second reason is that the exhaust gas height will be affected after the flue gas temperature is reduced. In addition to ensuring the exhaust gas temperature, the exhaust gas can also be ensured by increasing the air pressure, but this will also increase the power consumption. In addition, a certain amount of low-temperature heat will be released during the flue gas cooling process. Usually, these low-temperature heat can only be used for waste heat air or feed water. Therefore, extracting water from flue gas will increase the cost, but the benefit is less. Unless in very water-deficient areas, otherwise it is less used. SUMMARY

[0005] The first aspect of the present disclosure provides a system for recovering water vapor in flue gas of power plant boiler, comprising a flue gas system and a low-temperature power cycle system. The flue gas system comprises a flue gas duct 11, a fan 12 arranged on the flue gas duct 11, and a waste water collection tank 13 for collecting condensed water. The low-temperature power cycle system comprises a low-temperature power cycle expander 21, a condenser 22, a liquid tank 23, a liquid pump 24, and a low-temperature flue gas heat exchanger 25. The low-temperature flue gas heat exchanger 25 is arranged at the inlet of the flue gas duct 11, and is used for heat exchange between the flue gas and the low-temperature organic working medium. The outlet of the low-temperature power cycle expander 21 is connected to the inlet of the condenser 22, the outlet of the condenser 22 is connected to the inlet of the liquid tank 23, the outlet of the liquid tank 23 is connected to the working medium side inlet of the low-temperature flue gas heat exchanger 25 through the liquid pump 24, and the working medium side outlet of the low-temperature flue gas heat exchanger 25 is connected to the inlet of the low-temperature power cycle expander 21, thereby forming an organic working medium cycle loop.

[0006] In combination with the first aspect, the output shaft of the low-temperature power cycle expander 21 is connected to the driving shaft of the fan 12, for directly driving the fan 12 to operate.

[0007] In combination with the first aspect, the flue gas side contact surface of the low-temperature flue gas heat exchanger 25 is made of a corrosion-resistant material, including a PP+PE plastic layer.

[0008] In combination with the first aspect, the water outlet of the wastewater collection tank 13 is connected to a power plant water treatment system, for purifying the recovered wastewater.

[0009] In combination with the first aspect, the organic working medium used in the low-temperature power cycle system includes R245fa or R123.

[0010] The second aspect of the present disclosure provides a method for recovering water vapor in flue gas discharged from a power plant boiler, including the following steps: The low-temperature flue gas discharged from the boiler enters the flue gas duct 11 in which the low-temperature flue gas heat exchanger 25 is arranged; The flue gas exchanges heat with the low-temperature organic working medium in the low-temperature flue gas heat exchanger 25, and the temperature is reduced to below the dew point, wherein the water vapor condenses into water and is collected into the wastewater collection tank 13, and the non-condensable gas is discharged from the flue by the fan 12; Meanwhile, in the low-temperature power cycle system, the low-temperature organic working medium vaporizes after absorbing the waste heat of the flue gas in the low-temperature flue gas heat exchanger 25, the gaseous working medium formed enters the low-temperature power cycle expander 21 to do work, the working medium after doing work enters the condenser 22 to condense into liquid, and is stored in the liquid tank 23, and is then pressurized by the liquid pump 24 to be sent back to the low-temperature flue gas heat exchanger 25 to complete the cycle.

[0011] In combination with the second aspect, the power generated by the low-temperature power cycle expander 21 is directly used to drive the fan 12, to provide power for flue gas discharge.

[0012] In combination with the second aspect, the wastewater collected in the wastewater collection tank 13 is transported to a power plant water treatment system to remove acidic components and impurities.

[0013] The third aspect of the present disclosure provides an electronic device, including: one or more processors; A storage unit configured to store one or more programs that, when executed by the one or more processors, cause the one or more processors to implement the method for recovering water vapor in flue gas of a power plant boiler.

[0014] In a fourth aspect, the present disclosure provides a computer-readable storage medium having stored thereon a computer program, wherein the computer program, when executed by a processor, causes the method for recovering water vapor in flue gas of a power plant boiler to be implemented.

[0015] Beneficial effects: The method and system for recovering water vapor in flue gas of a power plant boiler provided by the present disclosure, through the cooperation of the low-temperature flue gas heat exchanger integrated at the flue inlet and the low-temperature power cycle system taking organic working medium as the core, the low-temperature flue gas is heat-exchanged with the working medium in the heat exchanger to be cooled below the dew point, thereby efficiently condensing and recovering water, and the working medium absorbs the waste heat of the flue gas to drive the expander to work; the power generated by the expander is directly used to drive the flue gas fan, realizing a self-generating and self-using closed loop of waste heat recovery, water resource extraction and flue gas emission power supply, finally effectively recovering clean water and improving the overall thermal efficiency of the system while avoiding the high cost problem caused by the need to use high-priced corrosion-resistant materials and consume additional electric energy in the traditional scheme, achieving the unity of energy saving, water saving and low-cost operation. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 FIG. 1 is a structural schematic diagram of a system for recovering water vapor in flue gas of a power plant boiler according to an embodiment of the present disclosure; Figure 2 FIG. 2 is a flowchart of a method for recovering water vapor in flue gas of a power plant boiler according to an embodiment of the present disclosure; Figure 3 The electronic device according to the embodiment of the present disclosure. DETAILED DESCRIPTION

[0017] The exemplary embodiments will be described in detail herein below with reference to the drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the embodiments of the present disclosure.

[0018] The terms used in the embodiments of the present disclosure are merely used to describe particular embodiments, and are not intended to limit the embodiments of the present disclosure. The singular forms "a," "an," and "the" used in the embodiments of the present disclosure and the appended claims are intended to include the plural forms, unless the context clearly indicates otherwise. It will be further understood that the term "and / or" used herein includes any or all possible combinations of one or more associated listed items.

[0019] Figure 1 A structural schematic diagram of a system for recovering water vapor in flue gas of a power plant boiler according to an embodiment of the present disclosure, comprising: a flue gas system and a low-temperature power cycle system; The flue gas system comprises a flue gas duct 11, a fan 12 arranged on the flue gas duct 11, and a wastewater collection tank 13 for collecting condensed water; The low-temperature power cycle system comprises a low-temperature power cycle expander 21, a condenser 22, a liquid tank 23, a liquid pump 24, and a low-temperature flue gas heat exchanger 25; The low-temperature flue gas heat exchanger 25 is arranged at the inlet of the flue gas duct 11, for heat exchange between the flue gas and the low-temperature organic working medium; The outlet of the low-temperature power cycle expander 21 is connected to the inlet of the condenser 22, the outlet of the condenser 22 is connected to the inlet of the liquid tank 23, the outlet of the liquid tank 23 is connected to the working medium side inlet of the low-temperature flue gas heat exchanger 25 through the liquid pump 24, and the working medium side outlet of the low-temperature flue gas heat exchanger 25 is connected to the inlet of the low-temperature power cycle expander 21, thereby forming an organic working medium circulation loop.

[0020] The output shaft of the low-temperature power cycle expander 21 is connected to the driving shaft of the fan 12, for directly driving the fan 12 to operate.

[0021] The flue gas side contact surface of the low-temperature flue gas heat exchanger 25 is made of corrosion-resistant material, including a PP+PE plastic layer.

[0022] The water outlet of the wastewater collection tank 13 is connected to a power plant water treatment system, for purifying the recovered wastewater.

[0023] The organic working medium used in the low-temperature power cycle system comprises R245fa or R123.

[0024] The flue gas system is responsible for treating the low-temperature flue gas discharged by the boiler. Its process starts from the flue gas duct 11, and the key heat exchange equipment is arranged at the inlet of the duct. A fan 12 is arranged on the duct, for providing power for the flue gas flow. A wastewater collection tank 13 is arranged at the bottom of the system, for collecting the condensed liquid water in the whole process.

[0025] The low-temperature power cycle system is a closed organic working medium cycle, and its core function is to convert the low-temperature waste heat in the flue gas into mechanical energy. The system contains all the necessary components for completing the cycle: a low-temperature power cycle expander 21, a condenser 22, a liquid tank 23, a liquid pump 24, and a low-temperature flue gas heat exchanger 25.

[0026] The system's interconnections form a complete working loop. The cryogenic flue gas heat exchanger 25 is strategically positioned at the inlet of the flue gas duct 11, serving as the site for energy exchange between the flue gas and the circulating working fluid. Within the circulating system, the working fluid flows as follows: the working fluid exiting the expander 21 enters the condenser 22 for cooling, then flows into the liquid tank 23 for storage, is pressurized by the liquid pump 24 and transported to the cryogenic flue gas heat exchanger 25 to absorb heat, and finally returns to the expander 21 to complete a full cycle.

[0027] The key design feature lies in the direct utilization of power. The output shaft of the cryogenic power cycle expander 21 is mechanically connected to the drive shaft of the fan 12 in the flue gas system. This design allows the mechanical work generated by the expander's waste heat to be directly used to drive the fan, providing emission power for the cooled flue gas, thus forming a highly efficient self-utilizing energy closed loop.

[0028] To address the potential corrosion issues caused by acidic components in the flue gas, the system incorporates special considerations in material selection. The flue gas side contact surface of the low-temperature flue gas heat exchanger 25 is protected with corrosion-resistant materials such as a PP+PE plastic layer, significantly improving the equipment's service life in acidic condensate environments.

[0029] The system also includes a downstream treatment channel for the recycled water. The outlet of the wastewater collection tank 13 is connected to the power plant's water treatment system, allowing the collected condensate to be further purified to remove acidic components and impurities, thereby achieving water recycling.

[0030] In terms of working fluid selection, the cryogenic power cycle system uses organic working fluids such as R245fa or R123, which are suitable for low-temperature heat source power generation. These working fluids have good thermophysical properties and can operate efficiently under the relatively low temperature heat source provided by flue gas, ensuring the operating efficiency of the entire power cycle system.

[0031] like Figure 2 The diagram shown is a flowchart illustrating a method for recovering water vapor from flue gas from a power plant boiler, according to an embodiment of this disclosure. The method includes: S1: Allow the low-temperature flue gas discharged from the boiler to enter the flue gas duct 11, which is equipped with a low-temperature flue gas heat exchanger 25. S2: Flue gas exchanges heat with low-temperature organic working fluid in low-temperature flue gas heat exchanger 25, and the temperature drops below the dew point. The water vapor in it condenses into water and is collected in wastewater collection tank 13. Non-condensable gas is driven by fan 12 to be discharged from the flue. S3: In the low-temperature power cycle system, the low-temperature organic working fluid vaporizes after absorbing the waste heat of the flue gas in the low-temperature flue gas heat exchanger 25, and the gaseous working fluid enters the low-temperature power cycle expander 21 to do work. The working fluid after doing work enters the condenser 22 to condense into a liquid, and is stored in the liquid tank 23. The liquid pump 24 pressurizes and sends the liquid working fluid back to the low-temperature flue gas heat exchanger 25 to complete the cycle.

[0032] Further, the power generated by the low-temperature power cycle expander 21 is directly used to drive the fan 12 to provide power for flue gas discharge. The wastewater collected in the wastewater collection tank 13 is transported to the power plant water treatment system to remove acidic components and impurities.

[0033] The method starts from step S1, in which the low-temperature flue gas discharged from the boiler enters the flue gas duct 11. The inlet section of the duct is integrally arranged with a low-temperature flue gas heat exchanger 25, which provides a place for subsequent heat and mass exchange processes.

[0034] Subsequently, in step S2, the core heat exchange and condensation process occurs. The flue gas flows through the low-temperature flue gas heat exchanger 25 and exchanges heat with the low-temperature organic working fluid inside. The temperature of the flue gas thus drops below the dew point, causing the water vapor contained therein to undergo a phase change and condense into liquid water. These condensed water is diverted and collected into the wastewater collection tank 13. At the same time, the non-condensable gases such as nitrogen and carbon dioxide in the flue gas are continuously pushed by the fan 12 and finally discharged from the top of the flue.

[0035] Simultaneous with the flue gas treatment process is step S3, the low-temperature power cycle. In the low-temperature flue gas heat exchanger 25, the liquid organic working fluid vaporizes after absorbing the low-temperature waste heat of the flue gas, and changes into a high-temperature gas. This high-pressure working fluid is then introduced into the low-temperature power cycle expander 21 to expand and do work, converting thermal energy into mechanical energy. The spent gas after doing work enters the condenser 22 and is condensed by the cooling medium (such as ambient air or cooling water) to recover to a liquid state and temporarily stored in the liquid tank 23. Finally, the liquid pump 24 pressurizes the liquid working fluid and pumps it back into the low-temperature flue gas heat exchanger 25, completing a complete closed cycle.

[0036] The key innovation of this method is to achieve direct on-site utilization of energy. The mechanical power generated by the low-temperature power cycle expander 21 is directly used to drive the operation of the fan 12 through mechanical transmission devices such as shaft couplings. This provides the required power to overcome system resistance and discharge the cooled flue gas to a sufficient height, forming a self-sufficient power supply closed loop that does not rely on external power grids, significantly reducing the operating energy consumption of the system.

[0037] Furthermore, this method forms a complete resource recycling chain. The wastewater collected in wastewater collection tank 13, being acidic due to its potential absorption of acidic oxides from flue gas, is transported to the power plant's dedicated water treatment system. There, the wastewater undergoes neutralization and purification processes to remove acidic components and suspended impurities, ultimately becoming high-quality water that can be reused in the power plant's cycle. This avoids the environmental problems that could be caused by direct discharge, achieving water resource recycling and combining environmental and economic benefits.

[0038] Electronic device 300 can be a desktop computer, laptop, handheld computer, cloud server, or other electronic device. Electronic device 300 may include, but is not limited to, processor 301 and memory 302. Those skilled in the art will understand that... Figure 3 This is merely an example of electronic device 300 and does not constitute a limitation on electronic device 300. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device may also include input / output devices, network access devices, buses, etc.

[0039] Processor 301 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0040] The memory 302 can be an internal storage unit of the electronic device 300, such as a hard disk or RAM of the electronic device 300. The memory 302 can also be an external storage device of the electronic device 300, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the electronic device 300. Furthermore, the memory 302 can include both internal and external storage units of the electronic device 300. The memory 302 is used to store the computer program 303 and other programs and data required by the electronic device. The memory 302 can also be used to temporarily store data that has been output or will be output.

[0041] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure, and should all be included within the protection scope of this disclosure.

Claims

1. A system for recovering water vapor from flue gas of a power plant boiler, characterized in that, The system comprises a flue gas system and a low-temperature power cycle system; The flue gas system comprises a flue gas duct (11), a fan (12) arranged on the flue gas duct (11), and a wastewater collection tank (13) for collecting condensed water; The low-temperature power cycle system comprises a low-temperature power cycle expander (21), a condenser (22), a liquid tank (23), a liquid pump (24), and a low-temperature flue gas heat exchanger (25); The low-temperature flue gas heat exchanger (25) is arranged at the inlet of the flue gas duct (11) and used for heat exchange between the flue gas and the low-temperature organic working medium; The outlet of the low-temperature power cycle expander (21) is connected to the inlet of the condenser (22), the outlet of the condenser (22) is connected to the inlet of the liquid tank (23), the outlet of the liquid tank (23) is connected to the working medium side inlet of the low-temperature flue gas heat exchanger (25) through the liquid pump (24), and the working medium side outlet of the low-temperature flue gas heat exchanger (25) is connected to the inlet of the low-temperature power cycle expander (21), thereby forming an organic working medium cycle loop.

2. The system of claim 1, wherein, The output shaft of the low-temperature power cycle expander (21) is connected to the driving shaft of the fan (12) and used for directly driving the fan (12) to operate.

3. The system of claim 1, wherein, The flue gas side contact surface of the low-temperature flue gas heat exchanger (25) is made of a corrosion-resistant material and comprises a PP+PE plastic layer.

4. The system of claim 1, wherein, The outlet of the wastewater collection tank (13) is connected to a power plant water treatment system and used for purifying the recovered wastewater.

5. The system of claim 1, wherein, The organic working medium used in the low-temperature power cycle system comprises R245fa or R123.

6. A method of recovering water vapour from flue gas of a boiler of a power plant based on the system of claim 1, characterized by, The method comprises the following steps: The low-temperature flue gas discharged from a boiler enters the flue gas duct (11) in which the low-temperature flue gas heat exchanger (25) is arranged; The flue gas exchanges heat with the low-temperature organic working medium in the low-temperature flue gas heat exchanger (25) and the temperature is reduced to below the dew point, the water vapor in the flue gas condenses into water and is collected into the wastewater collection tank (13), and the non-condensable gas is discharged from the flue duct by the fan (12); Meanwhile, in the low-temperature power cycle system, the low-temperature organic working medium absorbs the waste heat of the flue gas in the low-temperature flue gas heat exchanger (25), vaporizes, and forms gaseous working medium which enters the low-temperature power cycle expander (21) to do work, the working medium after doing work enters the condenser (22) to condense into liquid and is stored in the liquid tank (23), and then is pressurized by the liquid pump (24) and sent back to the low-temperature flue gas heat exchanger (25) to complete the cycle.

7. The method of claim 6, wherein, The power generated by the low-temperature power cycle expander (21) is directly used for driving the fan (12) to provide power for flue gas discharge.

8. The method of claim 6, wherein, The wastewater collected in the wastewater collection tank (13) is transported to a power plant water treatment system to remove acidic components and impurities.

9. An electronic device, comprising: The system comprises: one or more processors; a storage unit for storing one or more programs, which, when executed by the one or more processors, enable the one or more processors to implement the method for recovering water vapor in flue gas discharged from a boiler of a power plant according to claims 6-8.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program, when executed by a processor, can implement the method for recovering water vapor in flue gas discharged from a boiler of a power plant according to claims 6-8.

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