Method for recovering dead steam working medium and heat and preparing low-pressure steam

Abstract

The invention discloses a method for recycling a dead steam working medium and heat and preparing low-pressure steam. The method comprises the following steps that a micro-negative pressure environment is generated through a water jet steam extractor, dead steam from a steam using point is recycled and mixed with circulating water, heat and mass transfer is achieved, and heated circulating water is formed and stored in a water collecting tank; a heat pump system is adopted, so that a refrigerant absorbs heat of circulating water in an evaporator, the heat is released to a water supply system in a condenser after the refrigerant is compressed by a compressor, and the water supply temperature is increased; feeding the heated feed water into a flash tank, and carrying out flash evaporation in a negative pressure environment to generate saturated steam and non-vaporized low-temperature feed water; after saturated steam generated by flash evaporation is separated through a steam-water separator, compression and pressure boosting are conducted through a steam compressor, and steam is obtained; and the obtained steam is conveyed to each steam using point, so that the waste dead steam is converted into the steam, the consumption of fresh steam and the water replenishing cost are reduced, the production cost is reduced, and meanwhile, energy conservation is realized.

Description

Technical Field

[0001] This invention relates to technologies in the field of energy-efficient utilization, and in particular to a method for recovering waste steam working fluid and heat to produce low-pressure steam. Background Technology

[0002] In industrial production, such as thermal power, petrochemical, textile, food, and papermaking industries, a large number of processes require the use of steam. As a commonly used energy medium, steam generates a large amount of waste steam after heat exchange is completed at steam-using points (such as printing and dyeing, papermaking, and chemical drying processes).

[0003] These exhaust steams are usually emitted directly into the air, but due to the instability or even discontinuity of exhaust steam emissions, recovery is difficult. Most of the exhaust steam can only be emitted into the air, and the water vapor working fluid contained in the exhaust steam is not recovered, and the latent heat and sensible heat of vaporization carried by the exhaust steam are directly lost, resulting in a great waste of resources and energy and thermal pollution to the environment.

[0004] Currently, the main technical challenges facing exhaust steam recovery are the dispersed emission points, low pressure (often slightly positive or atmospheric pressure), and unstable or even discontinuous flow rates. Common recovery methods include direct condensation heat exchange, which often only recovers a portion of the sensible heat, while the latent heat and all working fluid cannot be effectively recovered. Alternatively, large-scale, high-energy-consuming mechanical vapor recompression systems are used, which have high investment and operating costs and are difficult to promote and apply in small and medium-sized exhaust steam emission scenarios.

[0005] Therefore, a new technical solution needs to be researched to address the above problems. Summary of the Invention

[0006] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide a method for recovering waste steam working fluid and heat to produce low-pressure steam. This method converts waste steam into steam, reduces the consumption of fresh steam and water replenishment costs, lowers production costs, and achieves energy conservation.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for recovering waste steam working fluid and heat and producing low-pressure steam includes the following steps:

[0009] Step 1: Use a water jet steam extractor to create a slightly negative pressure environment, recover the exhaust steam from the steam consumption point, mix it with the circulating water, realize the transfer of heat and mass, form heated circulating water and store it in the water collection tank;

[0010] Step 2: A heat pump system is used to allow the refrigerant to absorb heat from the circulating water in the evaporator, and after being compressed by the compressor, the heat is released to the water supply system in the condenser to increase the water supply temperature.

[0011] Step 3: The heated feedwater is sent into the flash tank, where flash evaporation occurs under negative pressure, producing saturated steam and unvaporized low-temperature feedwater;

[0012] Step 4: After the saturated steam generated by flash evaporation is separated by a steam-water separator, it is compressed and pressurized by a steam compressor to obtain steam;

[0013] Step 5: Deliver the steam obtained in Step 4 to each steam-using point.

[0014] As a preferred embodiment, in step 1, the water jet steam extraction is achieved by injecting pressurized circulating water. By generating a micro-negative pressure environment of -10 kPa at the throat of the water jet steam extractor, the micro-pressure exhaust steam released from each steam consumption point is drawn in and mixed with the circulating water.

[0015] As a preferred embodiment, in step 2, the refrigerant absorbs heat from the circulating water in the evaporator and evaporates. After being compressed by the compressor, it becomes a high-temperature and high-pressure gas, which is then condensed in the condenser, releasing heat to the feed water. The refrigerant, after releasing heat, is depressurized by the expansion valve and re-enters the evaporator to absorb heat.

[0016] As a preferred embodiment, in step 2, the refrigerant, after releasing heat, expands through the throttling valve and its temperature decreases before entering the evaporator to begin a secondary heat absorption cycle.

[0017] As a preferred embodiment, in step 3, the feedwater, which is first pressurized by the feedwater pump and absorbs heat in the condenser, is depressurized in the flash tank. Then, partial vaporization occurs to generate steam. Through the suction at the inlet of the steam compressor, the flash tank generates a negative pressure environment lower than the saturation pressure corresponding to the feedwater temperature. This causes the high-temperature feedwater to flash when it enters the flash tank, resulting in partial vaporization. After vaporization, the vaporized water carries droplets and enters the steam-water separator in the form of saturated steam for steam-water separation.

[0018] As a preferred embodiment, in step 3, the unvaporized feedwater first loses heat due to flash vaporization, and then, after being pressurized by the feedwater pump, it re-enters the condenser to absorb heat and participate in the cycle of step 3 again.

[0019] As a preferred embodiment, in step 4, the saturated steam containing droplets after flash evaporation is first separated by a steam-water separator to obtain saturated steam. Then, under the suction force at the inlet of the steam compressor, the saturated steam enters the steam compressor. By inputting electrical energy, the steam compressor performs mechanical work, thereby increasing the steam temperature and pressure.

[0020] As a preferred option, in step 4, the heated and pressurized steam is buffered by a pressure stabilizing tank and then transported to each steam consumption point through pipelines.

[0021] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution, it mainly creates a micro negative pressure environment by using a water jet steam ejector, which can effectively extract and recover the exhaust steam that is dispersed at steam consumption points and under low pressure. The exhaust steam is directly mixed with circulating water to achieve simultaneous heat and mass transfer. Compared with the traditional method of only condensing and recovering the working fluid, it can avoid the problem that the exhaust steam is difficult to collect due to low pressure, and greatly improve the recovery rate of water vapor working fluid in the exhaust steam.

[0022] Secondly, through the heat pump system, the low-grade heat after the exhaust steam and circulating water are mixed is absorbed by the evaporator, increased by the compressor, and released by the condenser, and converted into high-grade heat energy that can be used to heat the feed water. This fully utilizes the exhaust steam heat that was originally lost, improves the efficiency of heat recovery and utilization, and provides sufficient energy for subsequent flash steam production.

[0023] Next, the negative pressure environment inside the flash tank, combined with the heated feedwater, enables stable flash vaporization. The steam-water separator separates the liquid-containing steam, ensuring that the steam entering the steam compressor is clean saturated steam. After being pressurized by the steam compressor, low-pressure steam that meets the requirements of the steam consumption point can be produced.

[0024] Then, through the coordinated operation of each link from waste steam recovery and heat conversion to steam production and transportation, the water jet ejector continuously draws in to ensure the source of working fluid, the heat pump system stabilizes heat exchange to increase feedwater temperature, and the flash evaporation and compression links precisely control steam parameters, which can provide continuous and stable low-pressure steam to the steam consumption points, maintain stable steam production and pressure, ensure the reliable operation of steam-consuming equipment, and improve production continuity and product quality consistency.

[0025] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached diagram:

[0028] 1. Steam point 2. Water injection steam extractor

[0029] 11. Exhaust steam outlet 12. Steam inlet

[0030] 13" Mother tube

[0031] 21. Exhaust steam inlet 22. Water outlet

[0032] 23. Drive water inlet

[0033] 3. Water collection tank 4. Circulation pump

[0034] 5. Evaporator 6. Compressor

[0035] 7. Throttling valve 8. Condenser

[0036] 9. Water supply pump 10. Water supply tank

[0037] 11. Flash evaporator 12. Steam separator

[0038] 13. Steam compressor 14. Pressure stabilizing tank. Detailed Implementation

[0039] Please refer to Figure 1 As shown, it illustrates the specific structure of an embodiment of the present invention.

[0040] A method for recovering waste steam working fluid and heat and producing low-pressure steam includes the following steps:

[0041] Step 1: A micro-negative pressure environment is generated using a water jet steam ejector 2 to recover the exhaust steam from steam consumption point 1, mix it with circulating water, realize the transfer of heat and mass, form heated circulating water, and store it in the water collection tank 3; preferably, in step 1, the water jet steam ejection is achieved by spraying pressurized circulating water, and by generating a micro-negative pressure environment of -10kPa at the throat of the water jet steam ejector 2, the micro-pressure exhaust steam released from each steam consumption point 1 is drawn in and mixed with the circulating water.

[0042] Step 2: A heat pump system is used to allow the refrigerant to absorb heat from the circulating water in the evaporator 5. After being compressed by the compressor 6, the refrigerant releases the heat to the water supply system in the condenser 8, thereby increasing the water supply temperature. Preferably, in step 2, the refrigerant, after releasing heat, expands through the throttling valve 7 and its temperature decreases before entering the evaporator 5 to begin a second cycle of heat absorption.

[0043] Preferably, in step 2, the refrigerant absorbs heat from the circulating water in the evaporator 5 and evaporates. After being compressed by the compressor 6, it becomes a high-temperature and high-pressure gas, which is then condensed in the condenser 8, releasing heat to the feed water. After releasing heat, the refrigerant is depressurized by the expansion valve 7 and re-enters the evaporator 5 to absorb heat.

[0044] Step 3: The heated feedwater is sent into the flash tank 11, where flash evaporation occurs under negative pressure, producing saturated steam and unvaporized low-temperature feedwater. Preferably, in step 3, the feedwater, which is first pressurized by the feedwater pump 9 and absorbs heat in the condenser 8, is depressurized in the flash tank 11, and then partially vaporizes to produce steam. Through the suction at the inlet of the steam compressor 13, the flash tank 11 generates a negative pressure environment lower than the saturation pressure corresponding to the feedwater temperature. This causes the high-temperature feedwater to flash evaporate when it enters the flash tank 11, resulting in partial vaporization of the feedwater. After vaporization, the vaporized feedwater carries droplets and enters the steam-water separator 12 in the form of saturated steam for steam-water separation.

[0045] Preferably, in step 3, the unvaporized feedwater initially loses heat due to flash vaporization, and after being pressurized by the feedwater pump, it re-enters the condenser to absorb heat and participate in the cycle of step 3 again.

[0046] Step 4: The saturated steam generated by flash evaporation is separated by a steam-water separator 12 and then compressed and pressurized by a steam compressor 13 to obtain steam. Preferably, in step 4, the saturated steam containing droplets after flash evaporation is first separated by the steam-water separator 12 to obtain saturated steam. Then, under the suction at the inlet of the steam compressor 13, the saturated steam enters the steam compressor 13. By inputting electrical energy, the steam compressor 13 performs mechanical work, thereby increasing the steam temperature and pressure. Preferably, in step 4, the heated and pressurized steam is buffered by a pressure stabilizing tank 14 and then transported to each steam consumption point 1 through pipelines.

[0047] Step 5: Deliver the steam obtained in Step 4 to each steam consumption point 1.

[0048] Next, a system is provided that can be used to recover the working fluid and heat of the above-mentioned waste steam and produce low-pressure steam, which includes a useful steam point 1, a water ejector 2, a water collection tank 3, an evaporator 5, a compressor 6, a condenser 8, a feed water pump 9, a flash tank 11, a steam-water separator 12, and a steam compressor 13.

[0049] A slightly negative pressure environment is established by the water jet steam ejector 2 to efficiently extract the exhaust steam from the dispersed steam consumption point 1, thereby realizing the recovery of the working fluid. The refrigeration cycle consisting of the evaporator 5, compressor 6, and condenser 8 is used to convert the low-grade heat of the exhaust steam into feedwater heat energy to provide energy for subsequent flash evaporation. The flash tank 11, combined with the steam-water separator 12 and the steam compressor 13, accurately produces and improves low-pressure steam, forming a closed loop from exhaust steam recovery to heat conversion and then to steam regeneration, which greatly improves the energy efficiency of the steam system. In typical scenarios (such as textile printing and dyeing), it can reduce the energy consumption of steam preparation.

[0050] The steam consumption point 1 is provided with a waste steam outlet 11" and a steam inlet 12"; the water jet ejector 2 is provided with a waste steam inlet 21, a water outlet 22 and a driving water inlet 23; the evaporator 5 is provided with a cooled side inlet and a cooled side outlet; the condenser 8 is provided with a refrigerant inlet and a refrigerant outlet; and the outlet of the water collection tank 3 is connected to the cooled side inlet of the evaporator 5.

[0051] The exhaust steam outlet 11" of the steam consumption point 1 is connected to the exhaust steam inlet 21 of the water jet steam ejector 2 via a main pipe 13". Preferably, multiple sets of steam consumption points 1 are provided, and all sets of steam consumption points 1 are connected to the exhaust steam inlet 21 of the water jet steam ejector 2 via a main pipe 13". For example, there are multiple sets of steam consumption points 1 in an industrial plant area (such as a textile industrial park) (such as multiple dryers and setting machines in a dyeing and printing workshop). The dispersed exhaust steam (with different pressures and flow rates) is collected by the main pipe 13" and sent to the water jet steam ejector 2. The working fluid and heat can be recovered in a centralized manner, avoiding the high cost (equipment investment and operation and maintenance) of individual equipment recovery (such as each unit being equipped with a small condenser 8).

[0052] The outlet of the water collection tank 3 is connected to the inlet of the evaporator 5 on the cooled side via the circulation pump 4; preferably, the water collection tank 3 is provided with a water supply pipe, an overflow pipe and a water discharge pipe, and the outlet of the water collection tank 3 is connected to the inlet of the circulation pump 4 via the water supply pipe; when the volume of water in the water collection tank 3 exceeds the interface of the overflow pipe, the water in the water collection tank 3 automatically overflows.

[0053] To ensure stable drive water circulation, the water collection tank 3 serves as the drive water storage and distribution unit. The water supply pipe replenishes water lost from the system (such as leakage from the water jet ejector 2 or indirect water loss during flash evaporation), ensuring sufficient water supply at the inlet of the circulating pump 4. This prevents a decrease in the suction capacity of the water jet ejector 2 due to water shortage (resulting in the inability to establish a slight negative pressure and a sharp reduction in the amount of waste steam recovered). The overflow pipe and drain pipe work together to control the liquid level in the water collection tank 3, preventing overflow caused by excessive water supply (such as a malfunction of the automatic water supply valve) or water quality issues due to long-term accumulation of impurities (regular water draining and cleaning). During industrial steam consumption, the amount of waste steam at steam consumption point 1 fluctuates with the load (such as changes in the speed of the paper machine). The water supply pipe can flexibly replenish water to maintain the liquid level in the water collection tank 3. The overflow pipe automatically drains excess water to balance the increase in water volume caused by sudden changes in the amount of waste steam (such as simultaneous exhaust from multiple devices).

[0054] The cooled side outlet of the evaporator 5 is connected to the drive water inlet 23 of the water ejector 2; the refrigerant outlet of the evaporator 5 is connected to the inlet of the compressor 6. The high-temperature and high-pressure refrigerant gas from the heat pump compressor flows in the tube side (or shell side) of the condenser, releasing heat to the feed water flowing in the shell side (or tube side). The refrigerant itself condenses into a liquid due to cooling, while the feed water is heated to a higher temperature (usually 40-50°C, reaching close to or exceeding 100°C).

[0055] Preferably, the refrigerant outlet of the condenser 8 is connected to the refrigerant inlet of the evaporator 5 via a throttling valve. This valve efficiently transfers the low-grade heat extracted from the exhaust vapor by the evaporator, compressor, condenser, and throttling valve to the flash tank through the refrigerant condensation heat release process. During the refrigeration cycle, the high-pressure refrigerant discharged from the condenser 8 is depressurized and cooled by the throttling valve, becoming a low-temperature, low-pressure liquid. This liquid then enters the evaporator 5 to more efficiently absorb heat from the driving water. Compared to a direct-flow system without a throttling valve, the throttling valve allows the refrigerant to absorb heat more fully in the evaporator 5. The improved refrigeration cycle efficiency indirectly enhances the heating capacity of the condenser 8 for feedwater, providing more heat for the flash evaporation stage. Secondly, by adjusting the opening of the throttle valve, the refrigerant flow rate and the evaporation temperature of the evaporator 5 can be controlled. When the demand of steam point 1 changes (such as the steam pressure needs to be adjusted from 0.3MPa to 0.25MPa), the throttle valve is adjusted in conjunction with the condenser 8 to change the heat release power, adapting to the demand of flash tank 11 for feedwater temperature and heat, so that the low-pressure steam parameters (pressure and temperature) can be adjusted as needed to meet the process requirements of steam point 1.

[0056] The outlet of the compressor 6 is connected to the refrigerant inlet of the condenser 8, and the refrigerant outlet of the condenser 8 is connected to the refrigerant inlet of the evaporator 5; the heated water outlet of the condenser 8 is connected to the water supply inlet of the flash tank 11; the water supply pump 9 provides pressure for the unvaporized water coming out of the flash tank, overcomes the resistance of pipelines, valves and equipment, and delivers it to the higher-positioned flash tank, ensuring that the water entering the flash tank has sufficient pressure.

[0057] Preferably, the unvaporized water outlet of the flash tank 11 is connected to the water supply pump 9 through a connecting pipe, so that the unvaporized water is sent back into the flash tank 11 after passing through the water supply pump 9, forming a circulation loop. Inside the flash tank 11, during the flash evaporation of high-temperature feedwater under negative pressure, there is unvaporized feedwater (still containing a large amount of sensible heat). This unvaporized feedwater is connected to the feedwater pump 9 through the unvaporized feedwater outlet, allowing it to re-participate in heat exchange and preventing heat from being idle. For example, after flash evaporation of 100°C feedwater, the temperature of the unvaporized water is about 90°C. It can be recycled to continue absorbing heat from the condenser 8 (such as raising the temperature to 100°C), improving flash evaporation efficiency. The circulating flow makes the water temperature and level in the flash tank 11 more uniform, reducing local overcooling or overheating. When the load of the steam consumption point 1 fluctuates (such as the start and stop of the dyeing machine), and the feedwater flow and temperature change, the circulation loop can buffer and adjust to ensure the stability of the negative pressure flash evaporation environment in the flash tank 11, avoiding large fluctuations in steam output and quality, and ensuring a continuous and stable supply of low-pressure steam to the steam consumption point 1.

[0058] The top steam outlet of the flash tank 11 is connected to the inlet of the steam-water separator 12, the steam outlet of the steam-water separator 12 is connected to the inlet of the steam compressor 13, and the outlet of the steam compressor 13 is connected to the steam inlet 12″ of the steam point 1 through a steam delivery pipeline.

[0059] Preferably, the outlet of the steam compressor 13 is connected to a pressure stabilizing tank 14, and the outlet of the pressure stabilizing tank 14 is connected to the steam inlet 12" of the steam consumption point 1 via a steam delivery pipeline. The pressure stabilizing tank 14 acts as a pressure buffer, and its internal air chamber can absorb fluctuating pressure, allowing the pressure in the steam delivery pipeline to change smoothly.

[0060] Preferably, the system for recovering waste steam working fluid and heat to produce low-pressure steam further includes a water replenishment tank 10. The outlet of the water replenishment tank 10 is connected to the feed water pump 9 via a connecting pipe. During flash evaporation, the feed water turns into steam, which leads to a reduction in the system water volume (e.g., 1 t of water flashes to produce 0.1 t of steam, resulting in a water loss of 0.1 t). The water replenishment tank 10 is directly connected to the feed water pump 9, which can replenish this water in real time to maintain the water level and temperature in the flash tank 11. For example, in a continuous chemical reaction process, the water replenishment tank 10 replenishes water according to the water loss rate to ensure continuous steam production in the flash tank 11, avoiding flash evaporation interruption and steam pressure drop due to water shortage, thus stabilizing the operating conditions of the steam consumption point 1 (e.g., reactor heating) and improving product quality consistency.

[0061] The workflow of this embodiment is described in detail below:

[0062] Step 1: Using a water jet ejector, the discharged low-pressure exhaust steam is recovered. The exhaust steam released from each steam point 1 is collected through the main pipe and then connected to the water jet ejector 2. Utilizing the Venturi principle, the circulating water, pressurized by the circulating pump 4 and releasing heat in the evaporator 5, is injected into the water jet ejector 2 with residual pressure, creating a slight negative pressure environment of about -10 kPa at the throat. The low-pressure exhaust steam released from the steam point 1 enters the water jet ejector 2 through the main pipe under the action of slight negative pressure, achieving heat and mass mixing with the circulating water, thus realizing the purpose of recovering the working fluid and heat of the exhaust steam. After the circulating water and exhaust steam undergo heat and mass transfer and mixing, the temperature rises (about 10°C) and is stored in the water collection tank 3 as the heat source in Step 2.

[0063] Step 2: Using heat pump technology (also referring to a heat pump system), the heat from the heated circulating water in Step 1 is transferred to the water supply system (this also refers to the refrigerant absorbing heat from the circulating water in the evaporator and evaporating, then being compressed into a high-temperature, high-pressure gas by the compressor, and subsequently condensing in the condenser, releasing heat to the water supply), thus increasing the water temperature of the water supply system (by 5-10°C, which can raise the temperature of the relative heat source by 40-50°C). This step achieves heat transfer and temperature increase through the circulation of refrigerant; specifically, firstly, the refrigerant absorbs heat from the heated circulating water in the evaporator 5, increasing its temperature. Then, the compressor 6 compresses the refrigerant, further increasing its temperature. Subsequently, the refrigerant releases heat in the condenser 8 to the water supply, which has been pressurized by the water supply pump 9. After releasing heat, the refrigerant expands through the expansion valve 7, decreasing its temperature, and then enters the evaporator 5 to begin the second cycle of heat absorption.

[0064] Step 3: Flash evaporation technology is used, utilizing the principle that the boiling point of water decreases as pressure decreases. The feedwater, pressurized by the feedwater pump 9 and absorbing heat in the condenser 8, experiences a pressure reduction in the flash tank 11, resulting in partial vaporization and the generation of steam. The suction at the inlet of the steam compressor 13 creates a negative pressure environment in the flash tank 11 that is lower than the saturation pressure corresponding to the feedwater temperature (the saturation temperature corresponding to this pressure is 5-10℃ lower than the feedwater temperature). When the high-temperature feedwater enters the flash tank 11, due to the pressure reduction, the temperature of the feedwater is higher than the saturation temperature corresponding to the pressure inside the flash tank, causing flash evaporation. Part of the feedwater vaporizes and, carrying droplets, enters the steam-water separator 12 in the form of saturated steam for steam-water separation. The remaining unvaporized feedwater cools down due to the heat carried away by flash vaporization and continues to be pressurized by the feedwater pump 9 to begin the second cycle of heat absorption. The water lost due to the steam generated by flash evaporation is replenished through the water supply tank 10.

[0065] Step 4: Employing steam compression technology, the saturated steam is heated and pressurized using steam compressor 13. After flash evaporation, the saturated steam containing droplets is separated by steam-water separator 12, resulting in saturated steam with higher dryness. Under the suction at the inlet of steam compressor 13, the saturated steam enters steam compressor 13. By inputting electrical energy, the steam compressor 13 performs mechanical work, thereby increasing the steam temperature and pressure to meet the steam quality requirements of the production process.

[0066] Step 5: After being heated and pressurized, the steam is buffered by the pressure stabilizing tank 14 and then transported to each steam consumption point 1 through pipelines.

[0067] The key design feature of this invention is that it creates a micro-negative pressure environment by using a water jet steam extractor, which can effectively extract and recover exhaust steam that is dispersed at steam consumption points and under low pressure. The exhaust steam is directly mixed with circulating water to achieve simultaneous heat and mass transfer. Compared with the traditional method of only condensing and recovering the working fluid, it can avoid the problem of exhaust steam being difficult to collect due to low pressure, and significantly improve the recovery rate of water vapor working fluid in the exhaust steam.

[0068] Secondly, through the heat pump system, the low-grade heat after the exhaust steam and circulating water are mixed is absorbed by the evaporator, increased by the compressor, and released by the condenser, and converted into high-grade heat energy that can be used to heat the feed water. This fully utilizes the exhaust steam heat that was originally lost, improves the efficiency of heat recovery and utilization, and provides sufficient energy for subsequent flash steam production.

[0069] Next, the negative pressure environment inside the flash tank, combined with the heated feedwater, enables stable flash vaporization. The steam-water separator separates the liquid-containing steam, ensuring that the steam entering the steam compressor is clean saturated steam. After being pressurized by the steam compressor, low-pressure steam that meets the requirements of the steam consumption point can be produced.

[0070] Then, through the coordinated operation of each link from waste steam recovery and heat conversion to steam production and transportation, the water jet ejector continuously draws in to ensure the source of working fluid, the heat pump system stabilizes heat exchange to increase feedwater temperature, and the flash evaporation and compression links precisely control steam parameters, which can provide continuous and stable low-pressure steam to the steam consumption points, maintain stable steam production and pressure, ensure the reliable operation of steam-consuming equipment, and improve production continuity and product quality consistency.

[0071] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for recovering waste steam working fluid and heat and producing low-pressure steam, characterized in that: The steps include the following: Step 1: Use a water jet steam extractor to create a slightly negative pressure environment, recover the exhaust steam from the steam consumption point, mix it with the circulating water, realize the transfer of heat and mass, form heated circulating water and store it in the water collection tank; Step 2: A heat pump system is used to allow the refrigerant to absorb heat from the circulating water in the evaporator, and after being compressed by the compressor, the heat is released to the water supply system in the condenser to increase the water supply temperature. Step 3: The heated feedwater is sent into the flash tank, where flash evaporation occurs under negative pressure, producing saturated steam and unvaporized low-temperature feedwater; Step 4: After the saturated steam generated by flash evaporation is separated by a steam-water separator, it is compressed and pressurized by a steam compressor to obtain steam; Step 5: Deliver the steam obtained in Step 4 to each steam-using point.

2. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 1, characterized in that: In step 1, the water jet steam extraction is achieved by injecting pressurized circulating water. By creating a micro-negative pressure environment of -10 kPa at the throat of the water jet steam extractor, the micro-pressure exhaust steam released from each steam consumption point is drawn in and mixed with the circulating water.

3. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 1, characterized in that: In step 2, the refrigerant absorbs heat from the circulating water and evaporates in the evaporator. After being compressed by the compressor, it becomes a high-temperature and high-pressure gas, which is then condensed in the condenser, releasing heat to the feed water. After releasing heat, the refrigerant is depressurized by the expansion valve and re-enters the evaporator to absorb heat.

4. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 3, characterized in that: In step 2, the refrigerant, after releasing heat, expands through the expansion valve and its temperature decreases, then enters the evaporator to begin a second cycle of heat absorption.

5. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 1, characterized in that: In step 3, the feedwater, which is first pressurized by the feedwater pump and absorbs heat in the condenser, is depressurized in the flash tank. Then, partial vaporization occurs to generate steam. Through the suction at the inlet of the steam compressor, the flash tank is made to generate a negative pressure environment lower than the saturation pressure corresponding to the feedwater temperature. When the high-temperature feedwater enters the flash tank, flash evaporation occurs, causing partial vaporization of the feedwater. Then, after vaporization, the liquid droplets are carried into the steam-water separator in the form of saturated steam for steam-water separation.

6. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 5, characterized in that: In step 3, the unvaporized feedwater first loses heat due to flash vaporization, and then, after being pressurized by the feedwater pump, it re-enters the condenser to absorb heat and participate in the cycle of step 3 again.

7. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 1, characterized in that: In step 4, the saturated steam containing droplets after flash evaporation is first separated by a steam-water separator to obtain saturated steam. Then, under the suction force at the inlet of the steam compressor, the saturated steam enters the steam compressor. By inputting electrical energy, the steam compressor performs mechanical work, thereby increasing the steam temperature and pressure.

8. The method for recovering waste steam working fluid and heat and producing low-pressure steam according to claim 7, characterized in that: In step 4, the heated and pressurized steam is buffered by a pressure stabilizing tank and then transported to each steam consumption point through pipelines.

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