A waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory

Abstract

This invention relates to the field of energy recovery and reuse technology, and in particular to a waste heat recovery system for a deaerator in a cigarette factory's gas-fired boiler. The system includes a steam heat exchange loop, a bathing water heat exchange loop, and a softened water heat exchange loop. The steam heat exchange loop is sequentially equipped with a deaerator, a second valve, a first heat exchanger, a third valve, a second heat exchanger, a fifth valve, and a return water tank. The bathing water heat exchange loop and the softened water heat exchange loop form closed loops with the cold sides of the first and second heat exchangers, respectively. The system can also be supplemented with a first valve and a fourth valve, allowing for switching between series and parallel operation modes of the heat exchangers through valve on / off coordination. This invention employs a two-stage heat exchange and cascade utilization process. The series mode adapts to normal steam operating conditions to achieve deep waste heat recovery, while the parallel mode adapts to high steam load conditions to achieve heat load diversion. This enables zero secondary steam discharge from the deaerator, achieving dual recovery of heat energy and water resources.

Description

Technical Field

[0001] This invention relates to the field of energy recovery and reuse technology, and in particular to a waste heat recovery system for a deaerator in a cigarette factory's gas-fired boiler. Background Technology

[0002] The deaerator is a key piece of equipment for ensuring the safe operation of a boiler system. Its core function is to remove dissolved oxygen and other non-condensable gases from the feedwater to prevent corrosion of the boiler and its piping system. The deaerators used in cigarette factory gas-fired boilers typically operate at a temperature of 100℃-105℃ and a pressure of <0.1MPa. Existing deaerator units consist of a softened water tank, a return water tank, and the deaerator connected in sequence. This structure provides the basic circulation of deaerated water for the boiler system and is a standard configuration for cigarette factory gas-fired boilers.

[0003] Existing deaerator systems in cigarette factory gas-fired boilers, based on the aforementioned basic structure, mostly employ a combination of chemical dosing and thermal deaeration methods. Due to the characteristics of the boiler circulation system, the deaerator needs to continuously discharge secondary steam to maintain system pressure balance, and this discharged secondary steam is directly vented for a long time, becoming a long-standing energy waste problem for enterprises. Current technology lacks efficient recovery technology for deaerator secondary steam. Direct steam discharge not only causes serious waste of both heat energy and softened water, but also generates thermal and noise pollution. At the same time, the factory's hot water supply system for bathing requires additional steam to heat cold water. Boiler softened water enters the deaerator and boiler body directly after passing through the softened water tank and return water tank, without a preheating process, further increasing natural gas consumption and boiler operating costs, resulting in low overall boiler system thermal efficiency.

[0004] Currently, most waste heat recovery solutions for deaerators in industrial boilers are single-stage heat exchange structures, which can only achieve heating of a single medium, resulting in low waste heat utilization. Furthermore, some solutions require significant modifications to the existing boiler system, leading to high modification costs and poor compatibility with the original equipment. In addition, they lack flexible operating mode design, making it impossible to adapt to different steam emission conditions of the deaerator and difficult to balance waste heat recovery efficiency with boiler system operational stability. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by developing a waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory. The system employs a two-stage heat exchange and cascade utilization process. The series connection mode adapts to normal steam conditions, achieving deep waste heat recovery, while the parallel connection mode adapts to high steam load conditions, enabling heat load diversion. This achieves zero emissions of secondary steam from the deaerator, completing the dual recovery of heat energy and water resources. Furthermore, it is based on existing system modifications without altering the original equipment's temperature control characteristics, ensuring stable operation and low modification costs. It significantly reduces natural gas consumption and improves boiler thermal efficiency, combining economic and environmental benefits.

[0006] The technical solution of this invention to solve the technical problem is as follows:

[0007] This application provides a waste heat recovery system for a deaerator in a cigarette factory gas-fired boiler, including a steam heat exchange circuit, a bath water heat exchange circuit, and a softened water heat exchange circuit. The steam heat exchange circuit includes a deaerator, a first heat exchanger, a second heat exchanger, and a return water tank connected in sequence. The secondary steam outlet of the deaerator is connected to the hot side inlet of the first heat exchanger, the hot side outlet of the first heat exchanger is connected to the hot side inlet of the second heat exchanger, and the hot side outlet of the second heat exchanger is connected to the inlet of the return water tank. An vent pipe is also connected to the secondary steam outlet of the deaerator. The bathing water heat exchange circuit includes a bathing hot water tank, the outlet end of which is connected to the cold side inlet of the first heat exchanger, and the cold side outlet of the first heat exchanger is connected to the return port of the bathing hot water tank. The softened water heat exchange circuit includes a softened water tank, the outlet of which is connected to the cold side inlet of the second heat exchanger, and the cold side outlet of the second heat exchanger is connected to the return port of the softened water tank.

[0008] As an improvement to the above scheme, the steam heat exchange circuit further includes a second valve, a third valve, and a fifth valve. The secondary steam outlet of the deaerator is connected to a secondary steam outlet main pipe. The second valve is connected in series on the secondary steam outlet main pipe. The outlet end of the second valve is connected to the hot side inlet of the first heat exchanger. The hot side outlet of the first heat exchanger is connected to the inlet end of the third valve. The outlet end of the third valve is connected to the hot side inlet of the second heat exchanger. The hot side outlet of the second heat exchanger is connected in series with the fifth valve and then connected to the inlet of the return water tank.

[0009] As an improvement to the above solution, a first pressurized water pump is connected in series on the pipe connecting the outlet end of the hot water tank to the cold side inlet of the first heat exchanger.

[0010] As an improvement to the above solution, a second booster pump is connected in series on the pipe connecting the outlet end of the softened water tank to the cold side inlet of the second heat exchanger.

[0011] As an improvement to the above scheme, it also includes a first valve and a fourth valve. The inlet end of the first valve is connected to the main pipeline of the secondary steam outlet of the deaerator, and the outlet end is connected to the hot side inlet of the second heat exchanger. The inlet end of the fourth valve is connected to the hot side outlet of the first heat exchanger, and the outlet end is connected to the inlet of the return water tank. Through the on-off coordination of the first valve, the fourth valve, the second valve, the third valve, and the fifth valve, the series and parallel connection modes of the first heat exchanger and the second heat exchanger can be switched.

[0012] As an improvement to the above solution, a steam flow meter is installed at the secondary steam outlet of the deaerator.

[0013] As an improvement to the above solution, a condensate meter is installed at the inlet of the return water tank.

[0014] As an improvement to the above solution, thermometers and pressure gauges are installed on the pipes of the bath water heat exchange circuit and the softened water heat exchange circuit to monitor the temperature and pressure of the medium before and after heat exchange in the corresponding circuit in real time.

[0015] As an improvement to the above solution, a shut-off valve is connected in series on the venting pipe.

[0016] This invention also provides a method for waste heat recovery from a deaerator in a cigarette factory's gas-fired boiler, applicable to any of the aforementioned waste heat recovery systems for cigarette factory gas-fired boilers. The method includes two operating modes: series operation and parallel operation, and can switch between the two modes. The specific steps are as follows: Serial operation mode: Step 1.1: Valve status control, open the second, third and fifth valves, close the first and fourth valves, and construct a series operation path for three closed-loop heat exchange circuits; Step 1.2: The steam heat exchange circuit is started. The secondary steam generated by the deaerator enters the hot side of the first heat exchanger through the secondary steam outlet main pipe and the second valve to complete the first heat exchange. The steam condenses into high-temperature condensate. The high-temperature condensate enters the hot side of the second heat exchanger through the third valve to complete the second heat exchange. After the condensate cools down, it flows into the return water tank through the fifth valve. Step 1.3: The heat exchange loop operates synchronously. The first pressurized water pump is started, and the cold water in the hot water tank flows back to the hot water tank after exchanging heat with the steam on the cold and hot sides of the first heat exchanger, forming a closed-loop heat exchange for the bathing water. The second pressurized water pump is started, and the softened water in the softened water tank flows back to the softened water tank after exchanging heat with the high-temperature condensate on the cold and hot sides of the second heat exchanger, forming a closed-loop heat exchange for the softened water. Parallel operation mode: Step 2.1: Valve status control, open the first valve, the second valve, the fourth valve and the fifth valve, close the third valve, and construct a parallel operation path for three closed-loop heat exchange circuits; Step 2.2: Start-up of steam heat exchange circuit and heat load diversion. The secondary steam generated by the deaerator is divided into two paths. The first path enters the hot side of the first heat exchanger through the second valve and then the condensate flows into the return water tank through the fourth valve. The second path enters the hot side of the second heat exchanger through the first valve and then the condensate flows into the return water tank through the fifth valve. Step 2.3: The heat exchange circuit operates synchronously. Start the first pressurized water pump. The cold water in the hot water tank returns to the hot water tank after heat exchange on the cold side of the first heat exchanger. Start the second pressurized water pump. The softened water in the softened water tank returns to the softened water tank after heat exchange on the cold side of the second heat exchanger. Operating mode switching: Once the temperature and flow rate of the secondary steam in the deaerator return to normal operating conditions from high-load conditions, close the first and fourth valves and open the third valve to switch the system from parallel operation mode to series operation mode.

[0017] Compared with existing technologies, the above solution has the following advantages or beneficial effects: 1. The secondary steam of the deaerator is condensed and recovered throughout the entire process through cascade heat exchange, achieving zero discharge of secondary steam. The recovered condensate is returned to the return water tank for recycling, which completely solves the problem of heat and water waste caused by direct steam discharge. At the same time, it eliminates the thermal and noise pollution caused by direct steam discharge, resulting in significant environmental benefits.

[0018] 2. High-grade steam waste heat is prioritized for heating bath water, replacing the original method of additionally consuming steam to heat bath water. Low-grade waste heat is used to preheat softened water, realizing the precise utilization of heat energy in stages. After the preheated softened water enters the boiler body, it effectively reduces boiler heating energy consumption, significantly reduces natural gas consumption, and improves the overall thermal efficiency of the boiler system.

[0019] 3. By coordinating the on and off of valves, the heat exchanger can be flexibly switched between series and parallel operation modes. The series mode is suitable for the normal steam discharge condition and realizes deep waste heat recovery; the parallel mode is suitable for the high steam discharge condition and realizes the uniform distribution of heat load, avoiding overload of a single heat exchanger. It takes into account the waste heat recovery efficiency and system operation safety under different operating conditions, and the mode switching operation is simple and the response is fast.

[0020] 4. After heat exchange, the temperature rise of the softened water is only about 5°C. When the condensate is returned to the return water tank, the temperature drops to about 20°C. This does not change the temperature control characteristics of the original softened water tank and return water tank, ensuring the operational stability of the boiler inlet water system and the overall circulation system. The three closed-loop heat exchange loops work together and operate independently, with no medium mixing or discharge losses, further improving the reliability of the system operation.

[0021] 5. The system is based on the existing gas boiler deaerator system of the cigarette factory. It makes full use of the original deaerator, hot water tank for bathing, softened water tank, return water tank and other equipment. Only the core heat exchange components and supporting accessories are added. There is no need to occupy additional production space. The modification is simple and the investment cost is controllable. In addition, the new heat exchanger is small in size, has high heat exchange efficiency and is easy to maintain in the later stage.

[0022] In summary, this invention employs a process path of two-stage heat exchange and cascade utilization. The series mode is adapted to the conventional steam operating conditions to achieve deep waste heat recovery, while the parallel mode is adapted to the high steam load operating conditions to achieve heat load diversion. It can achieve zero emission of secondary steam from the deaerator, complete the dual recovery of heat energy and water resources, and is based on the modification of the existing system without changing the temperature control characteristics of the original equipment. It is stable in operation, has low modification cost, significantly reduces natural gas consumption and improves boiler thermal efficiency, and has both economic and environmental benefits. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0024] Figure 1 This is a schematic diagram of the existing deaerator system in a cigarette factory's gas-fired boiler.

[0025] Figure 2 This is a schematic diagram of the waste heat recovery system of the deaerator of the cigarette factory gas boiler in Embodiment 1.

[0026] Figure 3 This is a schematic diagram of the flow structure of the waste heat recovery system of the deaerator of the cigarette factory gas boiler in the series mode of Embodiment 2.

[0027] In the diagram, 100 is the deaerator; 200 is the softened water tank; 300 is the return water tank; 1 is the deaerator; 2 is the first heat exchanger; 3 is the second heat exchanger; 4 is the hot water tank for bathing; 5 is the softened water tank; 6 is the return water tank; 7 is the first booster pump; 8 is the second booster pump; 9 is the first valve; 10 is the second valve; 11 is the third valve; 12 is the fourth valve; 13 is the fifth valve; 14 is the main secondary steam outlet pipe; and 15 is the vent pipe. Detailed Implementation

[0028] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure of the invention, components and arrangements of specific examples are described below. Furthermore, reference numerals and / or letters may be repeated in different examples. This repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. It should be noted that the components illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and processes are omitted to avoid unnecessarily limiting the invention. Terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] Example 1 See Figure 2 The waste heat recovery system for the deaerator of a gas-fired boiler in a cigarette factory provided in this embodiment achieves zero emissions of secondary steam and efficient recovery of heat and water resources through a process path of two heat exchanges and cascade utilization, combined with three closed-loop heat exchange circuits and a series-parallel dual operation mode. This system is a modification of the existing deaerator system of the gas-fired boiler in the cigarette factory, achieving synergistic effects of various technical features through specific structural connections, component selection, and operating condition control.

[0030] The system in this embodiment includes a steam heat exchange circuit, a bath water heat exchange circuit, and a softened water heat exchange circuit.

[0031] The steam heat exchange circuit is sequentially connected to deaerator 1, first heat exchanger 2, second heat exchanger 3, and return water tank 6, and is equipped with second valve 10, third valve 11, and fifth valve 13 to form a complete steam heat exchange path. The secondary steam outlet of deaerator 1 is connected to a secondary steam outlet main pipe 14. The second valve 10 is connected in series on the secondary steam outlet main pipe 14. The outlet end of the second valve 10 is connected to the hot side inlet of the first heat exchanger 2. The hot side outlet of the first heat exchanger 2 is connected to the hot side inlet of the second heat exchanger 3 in series with the third valve 11. The hot side outlet of the second heat exchanger 3 is connected to the inlet of the return water tank 6 in series with the fifth valve 13.

[0032] The bathing water heat exchange circuit includes a bathing hot water tank 4. The outlet end of the bathing hot water tank 4 is connected to the cold side inlet of the first heat exchanger 2 through the first pressurized water pump 7. The cold side outlet of the first heat exchanger 2 is connected to the return port of the bathing hot water tank 4.

[0033] The softened water heat exchange circuit includes a softened water tank 5. The outlet of the softened water tank 5 is connected to the cold side inlet of the second heat exchanger 3 through a second pressurized water pump 8. The cold side outlet of the second heat exchanger 3 is connected to the return port of the softened water tank 5.

[0034] The deaerator 1 is installed at the original location of the boiler system. The secondary steam outlet is split into two branches through the secondary steam outlet main pipeline 14. One branch is connected to the inlet of the second valve 10, and the other branch is connected to the inlet of the first valve 9, providing a waste heat steam source for the system. The operating temperature is maintained at 100℃-105℃ and the pressure is <0.1MPa. As the core component for generating waste heat, it ensures the deaeration effect of the boiler and provides a stable steam source for subsequent heat exchange by precisely controlling the steam output. This avoids deaeration failure and insufficient waste heat recovery caused by excessive steam discharge or insufficient steam output.

[0035] The system in this embodiment also includes a first valve 9 and a fourth valve 12. The inlet end of the first valve 9 is connected to the secondary steam outlet main pipe 14 of the deaerator 1, and the outlet end is connected to the hot side inlet of the second heat exchanger 3. The inlet end of the fourth valve 12 is connected to the hot side outlet of the first heat exchanger 2, and the outlet end is connected to the inlet of the return water tank 6. By coordinating the opening and closing of the first valve 9, the fourth valve 12, the second valve 10, the third valve 11, and the fifth valve 13, the series and parallel connection modes of the first heat exchanger 2 and the second heat exchanger 3 can be switched.

[0036] The first heat exchanger 2 is a plate heat exchanger, installed on the platform above the deaerator 1. Its hot-side inlet is connected to the outlet of the second valve 10, and its hot-side outlet is split into two paths: one path connects to the hot-side inlet of the second heat exchanger 3 via the third valve 11, and the other path connects to the inlet of the return water tank 6 via the fourth valve 12. The cold-side inlet of the first heat exchanger 2 is connected to the outlet of the hot water tank 4 via the first pressurized water pump 7, and its cold-side outlet is directly connected to the return port of the hot water tank 4, forming a closed-loop heat exchange system for bathing water. The plates of the first heat exchanger 2 are made of 316L stainless steel, which is corrosion-resistant and has high heat exchange efficiency. As the core component of the primary heat exchanger, it prioritizes the use of high-grade steam heat energy to heat the bathing water, meeting the plant's domestic hot water needs and replacing the previous method of additionally consuming steam to heat the bathing water, thus significantly reducing natural gas consumption.

[0037] The second heat exchanger 3 is also a plate heat exchanger, installed on the platform above the deaerator 1 along with the first heat exchanger 2, forming a series layout. The hot-side inlet has two branches: one connects to the hot-side outlet of the first heat exchanger 2 via the third valve 11, and the other connects to the secondary steam outlet main pipeline 14 of the deaerator 1 via the first valve 9. The hot-side outlet connects to the inlet of the return water tank 6 via the fifth valve 13. The cold-side inlet connects to the outlet of the softened water tank 5 via the second pressurized water pump 8, and the cold-side outlet directly connects to the return port of the softened water tank 5, forming a closed-loop heat exchange system for softened water. The second heat exchanger 3 also uses 316L stainless steel plates as the core component of the secondary heat exchange, recovering the low-grade waste heat of the steam after the primary heat exchange to preheat the softened water, achieving cascade utilization of thermal energy. Furthermore, the temperature rise of the softened water is only about 5°C, which does not change the original temperature control characteristics of the softened water tank 5, ensuring the stability of the boiler feedwater system.

[0038] The first valve 9 is installed on the branch from the secondary steam outlet of the deaerator 1 to the hot-side inlet of the second heat exchanger 3. It is the on / off and flow control component of this branch. Its core function is to realize the independent steam supply to the second heat exchanger 3, and to complete the switching between series and parallel modes in conjunction with other valves. Under parallel operation, it distributes the steam heat load to the second heat exchanger 3 to avoid overload of a single heat exchanger. At the same time, by adjusting the opening degree, it can accurately control the steam flow of this branch to ensure the heat load balance of the two heat exchangers under parallel operation.

[0039] The second valve 10 is the steam branch switching component from deaerator 1 to the first heat exchanger 2; the third valve 11 is the steam branch switching component for the first heat exchanger 2 and the second heat exchanger 3 connected in series; the fourth valve 12 is the condensate branch switching component from the first heat exchanger 2 to the return water tank 6; and the fifth valve 13 is the condensate branch switching component from the second heat exchanger 3 to the return water tank 6. By combining with the first valve 9, the series and parallel connection modes of the heat exchangers can be switched to adapt to different steam discharge conditions of deaerator 1.

[0040] A flow regulating valve is installed between the outlet of the hot water tank 4 and the first pressurized water pump 7, and between the outlet of the softened water tank 5 and the second pressurized water pump 8, respectively. These valves are used to precisely regulate the flow of the medium, match the amount of steam waste heat release, and ensure stable heating / preheating temperature.

[0041] The return water tank 6 is an existing piece of equipment in the plant. Its inlet is connected to the outlet of the fourth valve 12 and the fifth valve 13, respectively. It is used to recover steam condensate after one or two heat exchanges. The temperature of the recovered condensate drops to about 20°C, which will not disturb the temperature field of the return water tank 6. This achieves full recovery and recycling of water resources and solves the problem of water waste caused by direct steam discharge.

[0042] The first booster pump 7 and the second booster pump 8 are respectively installed at the outlet of the hot water tank 4 and the softened water tank 5 to provide power for the circulation and heat exchange of bathing water and softened water, ensure the stable flow rate of the medium in the closed loop, and ensure uniform and efficient heat exchange.

[0043] A steam flow meter is installed on the secondary steam outlet main pipeline 14 of deaerator 1, and a condensate meter is installed on the main pipeline at the inlet of return water tank 6 to monitor the steam discharge and condensate recovery respectively.

[0044] Thermometers and pressure gauges are distributed in the pipes of the steam heat exchange circuit, the bath water circuit, and the softened water heat exchange circuit, i.e., on the pipes before and after each heat exchange, to monitor the temperature and pressure of the medium before and after heat exchange in real time. All instruments enable visualization of operating data, providing a basis for system parameter optimization. With the help of valve adjustment, the temperature of deaerator 1 can be stabilized within a reasonable range, balancing deaeration effect and waste heat recovery efficiency.

[0045] The aforementioned secondary steam outlet main pipeline 14 is also connected to an venting pipeline 15, which is also connected in series with a shut-off valve. The venting pipeline 15 serves as an emergency pressure relief structure for the deaerator 1 system. When the system malfunctions and cannot perform waste heat recovery and heat exchange normally, or when the internal pressure of the deaerator 1 rises abnormally beyond the normal operating range, the secondary steam can be directly vented through the venting pipeline 15 to quickly release the internal pressure of the deaerator 1, preventing equipment damage due to excessive pressure and ensuring the safe operation of the deaerator 1 and the entire boiler system. During normal waste heat recovery operation, the venting pipeline 15 is in a closed state to ensure that all secondary steam enters the heat exchange circuit to achieve waste heat recovery.

[0046] This embodiment adopts a modification design adapted to existing equipment, only adding core heat exchange components and supporting accessories, without occupying additional production space, making the modification difficult and cost controllable; the three closed-loop heat exchange circuits work together and operate independently, with no medium mixing or external discharge loss, and the series and parallel dual modes can flexibly adapt to different operating conditions, achieving both efficient recovery of waste heat and water resources and stable system operation.

[0047] Example 2 See Figure 2 and 3 This embodiment provides a waste heat recovery system for a deaerator in a cigarette factory's gas-fired boiler, applied to the system described in Embodiment 1 above. Specifically, it is a series operation mode waste heat cascade recovery method, which is also the conventional operation method for waste heat recovery in deaerator 1 of the cigarette factory's gas-fired boiler. It is suitable for the conventional discharge and temperature conditions of secondary steam in deaerator 1, and can achieve cascaded deep recovery of steam waste heat. The specific steps are as follows: Step 1: Valve status control Open the second valve 10, the third valve 11, and the fifth valve 13, and close the first valve 9 and the fourth valve 12, so that the first heat exchanger 2 and the second heat exchanger 3 form a series layout, and construct a series operation path for three closed-loop heat exchange circuits: steam, bath water, and softened water.

[0048] Step 2: Start-up of the steam heat exchange circuit The secondary steam (100℃-105℃, pressure <0.1MPa) generated by deaerator 1 flows out through the secondary steam outlet and enters the hot side of the first heat exchanger 2 through the second valve 10. After completing the first heat exchange with the cold side bath water, the steam condenses into high-temperature condensate at 60-70℃. The high-temperature condensate flows out from the hot side outlet of the first heat exchanger 2 and enters the hot side of the second heat exchanger 3 through the third valve 11. It completes the second heat exchange with the cold side softened water, and the condensate temperature drops to about 20℃. Finally, the cooled condensate flows into the return water tank 6 through the fifth valve 13, completing the full-process condensation of steam and water resource recovery, and achieving "zero discharge" of secondary steam.

[0049] Step 3: Synchronous operation of the heat exchange circuit The heat exchange loop for bathing water operates synchronously: the first pressurized water pump 7 at the outlet of the hot water tank 4 is started to pressurize the cold water in the tank and send it to the cold side of the first heat exchanger 2 to exchange heat with the secondary steam on the hot side. After absorbing the high-grade heat energy of the steam, the temperature of the cold water rises to 45℃-50℃, which meets the requirements for hot water use in the factory area. The heated hot water flows out from the cold side outlet of the first heat exchanger 2 and flows back directly to the hot water tank 4, forming a closed loop of bathing water circulation. No additional steam is required to heat the cold water throughout the process.

[0050] The softened water heat exchange loop operates synchronously: the second pressurized water pump 8 at the outlet of the softened water tank 5 is started to pressurize the softened water in the tank and send it to the cold side of the second heat exchanger 3, where it exchanges heat with the high-temperature condensate water at 60-70℃ on the hot side. After absorbing low-grade waste heat, the temperature of the softened water rises by about 5℃. The preheated softened water flows out from the cold side outlet of the second heat exchanger 3 and flows directly back to the softened water tank 5, forming a closed-loop circulation of softened water. After the preheated softened water enters the boiler system, it can reduce the heating energy consumption of the boiler body and improve the boiler thermal efficiency.

[0051] Step 4: Real-time adjustment of operating parameters The temperature and pressure of the medium before and after heat exchange are monitored in real time by thermometers and pressure gauges in each circuit. The circulation flow of bath water and softened water is adjusted by flow regulating valves to match the amount of waste heat released by steam and ensure stable heat exchange effect. The steam output of deaerator 1 is monitored by steam flow meter and the opening degree of second valve 10 is finely adjusted to stabilize the operating temperature in deaerator 1 at 100℃-105℃, ensuring the deaeration effect of boiler and avoiding boiler pipe corrosion problems caused by temperature fluctuations.

[0052] In this embodiment, the three closed-loop heat exchange circuits operate synchronously and independently, enabling the tiered utilization of high-grade steam heat energy to prioritize domestic hot water and low-grade heat energy to deeply preheat production water, maximizing waste heat recovery efficiency. Moreover, the recovery process does not change the temperature control characteristics of the original softened water tank 5 and return water tank 6, ensuring the overall operational stability of the boiler system.

[0053] Example 3 This embodiment provides a waste heat recovery system for a deaerator in a cigarette factory's gas-fired boiler, applied to the system described in Embodiment 1 above. Specifically, it is a waste heat recovery method in parallel operation mode, and also a high-load emergency operation method for waste heat recovery from deaerator 1 in the cigarette factory's gas-fired boiler. It is suitable for conditions where the secondary steam temperature of deaerator 1 increases, the flow rate increases, and the steam heat exceeds the single-stage heat exchange load of the first heat exchanger 2. It can achieve heat load diversion and avoid overload of a single heat exchanger. The specific steps are as follows: Step 1: Valve status control Open the first valve 9, the second valve 10, the fourth valve 12, and the fifth valve 13, and close the third valve 11 to form a parallel layout between the first heat exchanger 2 and the second heat exchanger 3, thus constructing a parallel operation path for three closed-loop heat exchange circuits: steam, bath water, and softened water.

[0054] Step 2: Start-up of steam heat exchange loop and heat load diversion The high-temperature, high-flow-rate secondary steam generated by deaerator 1 flows out through the secondary steam outlet and is divided into two hot streams at the main secondary steam outlet pipe 14. The first stream enters the hot side of the first heat exchanger 2 through the second valve 10, and the second stream enters the hot side of the second heat exchanger 3 through the first valve 9. The two streams of steam exchange heat simultaneously. The first stream of steam condenses into high-temperature water after heat exchange in the first heat exchanger 2 and flows directly into the return water tank 6 through the fourth valve 12. The second stream of steam condenses into warm water after heat exchange in the second heat exchanger 3 and flows into the return water tank 6 through the fifth valve 13. The two streams of condensate are combined in the return water tank 6 to complete the recovery, thus achieving a uniform distribution of steam heat load.

[0055] The opening degree of the first valve 9 and the second valve 10 is adjusted to reasonably distribute the flow rate of the two steam lines according to the heat exchange load capacity of the two heat exchangers, so as to ensure the heat load balance of the first heat exchanger 2 and the second heat exchanger 3 and avoid problems such as overload and reduced heat exchange efficiency of a single device due to excessive steam flow.

[0056] Step 3: Synchronous operation of the heat exchange circuit The heat exchange circuit for bathing water operates synchronously: the steps are the same as in the series operation mode. The first pressurized water pump 7 at the outlet of the hot water tank 4 is started, so that the cold water is heated and flows back after completing the heat exchange with the steam on the cold side of the first heat exchanger 2, ensuring the normal and stable supply of hot water for bathing in the plant area, which is not affected by changes in steam flow.

[0057] Synchronous operation of the softened water heat exchange circuit: The steps are the same as those of the series operation mode. Start the second pressurized water pump 8 at the outlet of the softened water tank 5 so that the softened water is preheated and returned after completing heat exchange with the steam on the cold side and hot side of the second heat exchanger 3. This achieves full recovery of low-grade waste heat and reduces boiler heating energy consumption.

[0058] Step 4: Monitoring and Controlling Operating Parameters The temperature of the inlet water in the return water tank 6 is monitored by a thermometer. Even if the inlet water temperature rises slightly to about 60°C, the return water tank 6 can withstand it normally without additional adjustment. The circulation flow rate of bath water and softened water is finely adjusted by the flow regulating valve to match the steam waste heat release of the corresponding heat exchanger, ensuring stable heating and preheating temperatures.

[0059] Step 5: Mode switching after operating conditions are restored Once the temperature and flow rate of the secondary steam in deaerator 1 return to normal operating conditions, immediately close the first valve 9 and the fourth valve 12, and open the third valve 11. The system quickly switches to the series operation mode of the above-mentioned embodiment 2, restoring the cascade deep recovery of steam waste heat.

[0060] This embodiment achieves heat load diversion through a parallel heat exchanger layout, adapting to the high-load steam discharge conditions of deaerator 1, ensuring fault-free system operation, and mode switching is completed only by valve opening and closing, which is simple to operate and has a fast response, taking into account both waste heat recovery efficiency and system operation safety under high load conditions.

[0061] Example 4 This embodiment provides a commissioning and parameter optimization method for a waste heat recovery system based on a deaerator in a cigarette factory's gas-fired boiler. Specifically, it is a commissioning and parameter optimization method to achieve normalized and efficient operation after the system in Embodiment 1 is installed. Through full-process data monitoring and periodic reviews, the operating parameters are optimized to ensure that the system in Embodiment 1 achieves the designed recovery effect. The specific steps are as follows: Step 1: Basic Post-Installation Testing After the system is installed, air tightness tests are performed on all connecting pipes, and water pressure tests are conducted on the first heat exchanger 2 and the second heat exchanger 3 to check for pipe leaks and equipment pressure drops. All valves, pressurized water pumps, and monitoring instruments are tested under no-load conditions to ensure that valves can be opened and closed flexibly, opening degree can be adjusted precisely, water pumps can operate without abnormal noise, and instrument data can be displayed accurately.

[0062] Step 2: Trial Run Startup The system is switched to the series operation mode of the above method embodiment 2. Each heat exchange circuit is started according to the series operation steps. The initial operating parameters of the bath water circulation flow rate, softened water circulation flow rate and the steam output of deaerator 1 are set. The trial operation period is 1 month.

[0063] Step 3: Weekly Data Monitoring and Recording A designated person is assigned to record the system's operational data weekly, including: the cumulative steam discharge from the steam flow meter, the cumulative condensate recovery from the condensate meter; the operating temperature of deaerator 1, the inlet and outlet temperatures of hot water tank 4, the inlet and outlet temperatures of softened water tank 5, and the inlet temperature of return water tank 6; the operating power of each booster pump, and the opening degree of each valve; at the same time, troubleshooting equipment malfunctions, including pipe leaks, heat exchanger scaling, valve jamming, etc., and promptly maintaining any problems found.

[0064] Step 4: Monthly performance review and parameter optimization (1) Summarize the weekly monitoring data, calculate the core indicators such as waste heat recovery efficiency, condensate recovery rate, and natural gas savings, and verify whether the system meets the design requirements; (2) Based on the actual usage of hot water for bathing in the factory area, fine-tune the flow regulating valve of the heat exchange circuit for bathing water, optimize the circulation flow of bathing water, and stabilize the temperature of hot water for bathing in the optimal range of 45℃-50℃. (3) Based on the actual operating characteristics of deaerator 1, fine-tune the steam output to stabilize the operating temperature of deaerator 1 in the optimal deoxygenation range of 102℃-105℃, taking into account both deoxygenation effect and waste heat recovery efficiency. (4) Targeted optimizations were made for problems that occurred during the trial operation. For example, if the heat exchanger had slight scaling, physical cleaning was carried out. If the pipeline pressure drop was too large, the pipeline layout was optimized. If the valve was stuck, lubrication and maintenance were carried out to ensure the valve adjustment accuracy.

[0065] Step 5: Solidify routine operating parameters After a month of trial operation and parameter optimization, the optimal operating parameters (including the flow rate of each circuit, the opening degree of each valve, the steam output of deaerator 1, etc.) were solidified, and the system was officially put into normal operation. At the same time, a weekly data monitoring mechanism was maintained, and a comprehensive monthly performance review was conducted every 6 months. The parameters were fine-tuned in a timely manner according to changes in the plant's production conditions to ensure the long-term efficient operation of the system.

[0066] This embodiment uses a full-process debugging and optimization method of "basic testing - trial operation - weekly monitoring - monthly review" to achieve precise control of system operating parameters, ensure a high degree of compatibility between the waste heat recovery system and the original boiler system, ensure that the system is in a long-term efficient and stable operating state, and maximize the effects of energy saving, water saving and cost reduction.

[0067] Although the specific embodiments of the invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the invention. Based on the technical solutions of the invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the invention.

Claims

1. A waste heat recovery system for a deaerator in a cigarette factory's gas-fired boiler, characterized in that: This includes steam heat exchange circuits, bath water heat exchange circuits, and softened water heat exchange circuits; The steam heat exchange circuit includes a deaerator (1), a first heat exchanger (2), a second heat exchanger (3), and a return water tank (6) connected in sequence. The secondary steam outlet of the deaerator (1) is connected to the hot side inlet of the first heat exchanger (2), the hot side outlet of the first heat exchanger (2) is connected to the hot side inlet of the second heat exchanger (3), and the hot side outlet of the second heat exchanger (3) is connected to the inlet of the return water tank (6). An vent pipe (15) is also connected to the secondary steam outlet of the deaerator (1). The bathing water heat exchange circuit includes a bathing hot water tank (4), the outlet end of the bathing hot water tank (4) is connected to the cold side inlet of the first heat exchanger (2), and the cold side outlet of the first heat exchanger (2) is connected to the return port of the bathing hot water tank (4). The softened water heat exchange circuit includes a softened water tank (5), the outlet of which is connected to the cold side inlet of the second heat exchanger (3), and the cold side outlet of the second heat exchanger (3) is connected to the return port of the softened water tank (5).

2. The waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory according to claim 1, characterized in that: The steam heat exchange circuit also includes a second valve (10), a third valve (11) and a fifth valve (13). The secondary steam outlet of the deaerator (1) is connected to a secondary steam outlet main pipe (14). The second valve (10) is connected in series on the secondary steam outlet main pipe (14). The outlet end of the second valve (10) is connected to the hot side inlet of the first heat exchanger (2). The hot side outlet of the first heat exchanger (2) is connected to the inlet end of the third valve (11). The outlet end of the third valve (11) is connected to the hot side inlet of the second heat exchanger (3). The hot side outlet of the second heat exchanger (3) is connected in series with the fifth valve (13) and then connected to the inlet of the return water tank (6).

3. The waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory according to claim 1, characterized in that: A first pressurized water pump (7) is connected in series on the pipe connecting the outlet end of the hot water tank (4) to the cold side inlet of the first heat exchanger (2).

4. The waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory according to claim 1, characterized in that: A second pressurized water pump (8) is connected in series on the pipe connecting the outlet end of the softened water tank (5) to the cold side inlet of the second heat exchanger (3).

5. A waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory according to claim 2, characterized in that: It also includes a first valve (9) and a fourth valve (12). The inlet end of the first valve (9) is connected to the secondary steam outlet main pipe (14) of the deaerator (1), and the outlet end is connected to the hot side inlet of the second heat exchanger (3). The inlet end of the fourth valve (12) is connected to the hot side outlet of the first heat exchanger (2), and the outlet end is connected to the inlet of the return water tank (6). Through the on-off coordination of the first valve (9), the fourth valve (12), the second valve (10), the third valve (11), and the fifth valve (13), the series and parallel connection modes of the first heat exchanger (2) and the second heat exchanger (3) can be switched.

6. A waste heat recovery system for a deaerator in a cigarette factory's gas-fired boiler according to claim 1 or 2, characterized in that: A steam flow meter is installed at the secondary steam outlet of the deaerator (1).

7. The waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory according to claim 1, characterized in that: A condensate meter is installed at the inlet of the return water tank (6).

8. The waste heat recovery system for a gas-fired boiler deaerator in a cigarette factory according to claim 1, characterized in that: The thermometers and pressure gauges are installed on the pipes of the bath water heat exchange circuit and the softened water heat exchange circuit to monitor the temperature and pressure of the medium before and after heat exchange in the corresponding circuit in real time.

9. The waste heat recovery system for the deaerator of a cigarette factory gas boiler according to claim 1, characterized in that, A shut-off valve is connected in series on the venting pipe (15).

10. A method for waste heat recovery from a deaerator (1) of a gas-fired boiler in a cigarette factory, applied to the waste heat recovery system of a deaerator in a gas-fired boiler in a cigarette factory as described in any one of claims 1-9, characterized in that, It includes two operating modes: series operation mode and parallel operation mode, and can switch between the two modes. The specific steps are as follows: Serial operation mode: Step 1.1: Valve status control, open the second valve (10), the third valve (11) and the fifth valve (13), close the first valve (9) and the fourth valve (12) to construct a series operation path of three closed-loop heat exchange circuits; Step 1.2: The steam heat exchange circuit is started. The secondary steam generated by the deaerator (1) enters the first heat exchanger (2) through the secondary steam outlet main pipe (14) and the second valve (10) to complete the first heat exchange on the hot side. The steam condenses into condensate. The condensate enters the second heat exchanger (3) through the third valve (11) to complete the second heat exchange on the hot side. After the condensate cools down, it flows into the return water tank (6) through the fifth valve (13). Step 1.3: The heat exchange loop operates synchronously. Start the first pressurized water pump (7). The cold water in the hot water tank (4) flows back to the hot water tank (4) after exchanging heat with the steam on the cold side of the first heat exchanger (2), forming a closed-loop heat exchange for the bathing water. Start the second pressurized water pump (8). The softened water in the softened water tank (5) flows back to the softened water tank (5) after exchanging heat with the condensate on the cold side of the second heat exchanger (3), forming a closed-loop heat exchange for the softened water. Parallel operation mode: Step 2.1: Valve status control, open the first valve (9), the second valve (10), the fourth valve (12) and the fifth valve (13), close the third valve (11) to construct the parallel operation path of three closed-loop heat exchange circuits; Step 2.2: Start-up of steam heat exchange circuit and heat load diversion. The secondary steam generated by the deaerator (1) is divided into two paths. The first path enters the first heat exchanger (2) through the second valve (10) and after heat exchange on the hot side, the condensate flows into the return water tank (6) through the fourth valve (12). The second path enters the second heat exchanger (3) through the first valve (9) and after heat exchange on the hot side, the condensate flows into the return water tank (6) through the fifth valve (13). Step 2.3: The heat exchange circuit operates synchronously. Start the first pressurized water pump (7). The cold water in the hot water tank (4) flows back to the hot water tank (4) after heat exchange on the cold side of the first heat exchanger (2). Start the second pressurized water pump (8). The softened water in the softened water tank (5) flows back to the softened water tank (5) after heat exchange on the cold side of the second heat exchanger (3). Operating mode switching: When the temperature and flow rate of the secondary steam in the deaerator (1) return to normal operating conditions from high load conditions, close the first valve (9) and the fourth valve (12), open the third valve (11), and switch the system from parallel operation mode to series operation mode.

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