Pulp production line and its heat energy recovery system

Abstract

The application provides a paper pulp production line and a heat energy recovery system thereof; the heat energy recovery system comprises a steam exhaust generating device, a heat exchanger and a refrigerator; the heat exchanger is communicated with a steam exhaust output pipeline of the steam exhaust generating device; the heat exchanger is used for transferring the heat of the steam exhaust to hot water, and conveying the hot water to the refrigerator; the refrigerator uses the heat in the hot water to refrigerate, and conveys the hot water after heat exchange back to the heat exchanger to be heated again, and realizes the heat utilization of the steam exhaust generated in the steam exhaust generating device through reciprocating circulation. The heat energy recovery system provided by the application has the advantages of saving energy consumption (saving original refrigeration energy consumption) to realize the purpose of reducing operation cost, realizing closed cooling of waste heat steam exhaust, reducing heat emission, reducing carbon emission, being environment-friendly, not producing new pollution emission, conforming to the national energy saving and environmental protection policy, obvious economic benefit and social benefit, and good application prospect.

Description

Technical Field

[0001] This application relates to the technical field of papermaking equipment, specifically to a pulp production line and its heat recovery system. Background Technology

[0002] In the current industrial production of chemimechanical pulp, both the APMP process used by Andritz and the BCTPM process by Valmet involve the bleaching tower emitting steam containing pulp fibers during actual production. This direct emission of steam not only wastes energy but also increases environmental pollution. Utility Model Content

[0003] The first aspect of this application provides a heat recovery system, which includes: a waste steam generating device, a heat exchanger, and a refrigerator; the heat exchanger is connected to the waste steam output pipeline of the waste steam generating device, the heat exchanger is used to transfer the heat of the waste steam to hot water, and deliver the hot water to the refrigerator, the refrigerator uses the heat in the hot water to cool, and delivers the hot water after heat exchange back to the heat exchanger for reheating, and the cycle is repeated to realize the utilization of the heat of the waste steam generated in the waste steam generating device.

[0004] In some alternative embodiments, the waste steam generating device is a bleaching tower used for pulp treatment in the papermaking process.

[0005] In some alternative embodiments, the heat exchanger is connected to the exhaust steam output pipeline via a first pipeline and a second pipeline, the first pipeline being used for air intake and the second pipeline being used for exhaust; a first valve is provided on the first pipeline, a second valve is provided on the second pipeline, and a third valve is provided on the exhaust steam output pipeline, the third valve being located between the connection points of the first pipeline and the second pipeline and the exhaust steam output pipeline.

[0006] In some alternative embodiments, a pressure detector is provided on the exhaust steam output line.

[0007] In some alternative embodiments, the cooler is a hot water type lithium bromide cooler.

[0008] In some alternative embodiments, the chilled water produced by the refrigerator is connected to a cooling device, which is connected in parallel with the electric refrigerator.

[0009] In some alternative embodiments, the heat recovery system further includes a cooling tower connected to the refrigerator for cooling the refrigerator.

[0010] In some optional embodiments, the heat recovery system further includes a waste steam condensate recovery device connected to the heat exchanger.

[0011] In some alternative embodiments, the heat exchanger plates are provided with a passivation layer or an electrochemical polishing layer.

[0012] Secondly, embodiments of this application provide a pulp production line, which includes the heat recovery system described in the above embodiments.

[0013] The heat recovery system provided in this application has the purpose of saving energy consumption (saving the original refrigeration energy consumption) to reduce operating costs. The waste heat and exhaust steam achieve closed-loop cooling, reducing heat emissions and carbon emissions. It is environmentally friendly, does not generate new pollution emissions, complies with the national energy conservation and environmental protection policies, has obvious economic and social benefits, and has good application prospects. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of an embodiment of the heat recovery system of this application;

[0016] Figure 2 This is a schematic diagram of another embodiment of the heat recovery system of this application;

[0017] Figure 3 This is a schematic diagram of another embodiment of the heat recovery system of this application;

[0018] Figure 4 This is a schematic flowchart of an embodiment of the pulp production line of this application. Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0020] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] The purpose of this patent is to provide a device unit for recovering waste steam from a bleaching tower for lithium bromide refrigeration, so as to achieve efficient energy recovery and utilization while avoiding environmental impact caused by emissions.

[0023] Energy recovery and utilization: The heat from the exhaust steam of the bleaching tower is recycled back to the lithium bromide refrigeration system, achieving efficient energy recovery and utilization, reducing energy consumption in chemical pulp production, and improving economic efficiency.

[0024] Environmentally friendly and energy-saving: It reduces direct emissions of exhaust steam, thus lowering the environmental impact. Furthermore, lithium bromide refrigeration technology itself has advantages such as energy saving and environmental friendliness, further improving the system's environmental performance.

[0025] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an embodiment of the heat recovery system of this application. The heat recovery system 10 in this embodiment includes, but is not limited to, the following structures: exhaust steam generating device 100, heat exchanger 200, and cooler 300.

[0026] Specifically, the heat exchanger 200 is connected to the exhaust steam output pipeline 110 of the exhaust steam generating device 100. The heat exchanger 200 is used to transfer the heat of the exhaust steam to the hot water and deliver the hot water to the cooler 300. The cooler 300 uses the heat in the hot water to cool it and delivers the hot water after heat exchange back to the heat exchanger 200 for reheating. This cycle is repeated to realize the utilization of the heat of the exhaust steam generated in the exhaust steam generating device 100.

[0027] Optionally, the waste steam generating device 100 in this embodiment can be a bleaching tower used for pulp treatment in the papermaking process. In a specific embodiment, it can be used to utilize the waste heat of the waste steam from the chemimechanical pulp bleaching tower. After filtration, this steam is heated to 90°C by a heat exchanger 200 (a plate heat exchanger) and then enters a chiller 300 for cooling, producing 7°C cold water which is sent to a cooling device 400 (specifically, it can be sent to the pulp mill's chilled water network to replace electric air conditioning for cooling; after cooling and heat exchange, the cold water is returned to the chiller for further cooling). Replacing "waste heat" with cooling capacity to replace electric chillers saves electricity and achieves energy conservation, emission reduction, and carbon reduction. This not only brings economic benefits from energy conservation but also serves as a model for industrial carbon reduction, contributing to national carbon neutrality.

[0028] Optionally, the refrigerator in this embodiment can be a hot water type lithium bromide refrigerator. The refrigeration process of the hot water type lithium bromide refrigerator mainly includes the following steps:

[0029] 1. Heating dilute solution: Low-energy hot water from the device flows through the heat transfer tube of the generator, heating the dilute lithium bromide solution outside the tube, causing it to produce refrigerant vapor, and the solution is concentrated into a concentrated solution.

[0030] 2. Condensing refrigerant vapor: Refrigerant vapor from the generator enters the condenser and is condensed into refrigerant water by the cooling water flowing through the heat transfer tubes of the condenser. The heat is carried into the cooling water system.

[0031] 3. Evaporative Refrigerant Water: After being throttled through a U-shaped tube, the refrigerant water enters the evaporator. It flashes and cools down inside the evaporator before flowing into the evaporator refrigerant water pan. The refrigerant water entering the evaporative refrigerant water pan is then pumped out by the refrigerant pump and sprayed onto the surface of the evaporator heat transfer tubes. It absorbs heat from the cold water flowing through the heat transfer tubes and boils, evaporating into refrigerant vapor.

[0032] 4. Absorption of refrigerant vapor: The generated refrigerant vapor enters the absorber and is absorbed by the concentrated solution returning to the absorber. The heat released during the absorption process is carried away by the cooling water flowing through the heat transfer tubes of the absorber and is then carried into the cooling water system.

[0033] 5. Cooling water: After the heat is carried away by the refrigerant water, the temperature of the cooling water decreases, and it flows out of the unit and into the cooling water system.

[0034] The cycle process: After absorbing the refrigerant vapor, the concentration of the concentrated solution decreases, becoming a dilute solution, which is then pumped back to the generator for heating and concentration.

[0035] This process is repeated continuously, and the evaporator continuously produces cold water at the required temperature. The hot water type lithium bromide refrigerator is a commonly used device in this field. This patent does not involve improvements to this device, and its detailed structure is within the understanding of those skilled in the art, so it will not be described further here.

[0036] The heat exchanger 200 is connected to the exhaust steam output pipeline 110 via a first pipeline 210 and a second pipeline 220. The first pipeline 210 is used for air intake, and the second pipeline 220 is used for exhaust. A first valve 201 (Z1 in the figure) is provided on the first pipeline 210, a second valve 202 (Z2 in the figure) is provided on the second pipeline 220, and a third valve 103 (Z3 in the figure) is provided on the exhaust steam output pipeline 110. The third valve 103 is located between the connection point of the first pipeline 210, the second pipeline 220 and the exhaust steam output pipeline 110.

[0037] A waste heat recovery device (heat exchanger 200) is added to the bypass exhaust steam pipeline. The heat exchanger 200 is installed on the newly built bypass exhaust steam pipeline. Once the heat exchanger 200 and related exhaust steam pipelines are installed, a hole is drilled to connect the bypass exhaust steam pipeline to the existing exhaust steam pipeline at a later time. A control valve (third valve 103) is added to the original main exhaust steam pipeline, thus minimizing the impact on production during the entire installation process. During normal operation, control valve Z3 on the main exhaust steam pipeline is closed, while Z1 and Z2 are open. The exhaust steam from the top of the bleaching tower passes through valve Z1, then sequentially through the waste heat recovery device and Z2, achieving cooling and condensation. The condensate is discharged back to the wood chip washing system. Z3 is used for switching during system failures or maintenance. In this embodiment, the (plate) heat exchanger 200 uses a cold-side hot water temperature control to regulate the exhaust gas pressure, ensuring that the original system process is not affected.

[0038] Optionally, since the exhaust steam from the bleaching tower contains fibers and some chemicals, the heat exchanger 200 in this embodiment can be a plate contact heat exchanger with stainless steel plates. Stainless steel has good corrosion resistance and can resist the erosion of pulp fibers, steam, and trace amounts of acids and alkalis by the plates, ensuring the service life of the heat exchanger. The plate surface is provided with a passivation layer or an electrochemical polishing layer to reduce surface roughness, decrease the friction between the fibers and the plates, and thus reduce the adhesion and bonding of pulp fibers to the plates, reducing clogging problems. The equipment is equipped with a spray device, and the spray frequency and spray time are determined according to the clogging situation of the plates. This application mainly improves the surface and material of the plates. Detailed structural features of the plate contact heat exchanger are common knowledge in the art and will not be elaborated here.

[0039] In addition, the heat recovery system in this embodiment may also include a control device and a control system. The system is equipped with a microcomputer intelligent control system, capable of stepless adjustment of the load from 20% to 100% according to load changes, with the system outlet temperature fed back to the control system in real time. Control methods: Both local control and remote monitoring can be used. Local control is adopted during commissioning and communication failure phases, while centralized monitoring is implemented in the DCS control room during normal operation. Automation level of the control system: With the assistance of a small number of on-site inspection personnel, operators can monitor and operate the system from the control room via a remote transmission system, enabling monitoring and adjustment of system equipment startup, shutdown, and normal operation, as well as handling system anomalies and accidents. Fault alarm: The control system monitors unit alarm faults in real time and can store past faults, including fault type, occurrence time, recovery time, pump running time, etc.

[0040] The heat recovery system provided in this application has the purpose of saving energy consumption (saving the original refrigeration energy consumption) to reduce operating costs. The waste heat and exhaust steam achieve closed-loop cooling, reducing heat emissions and carbon emissions. It is environmentally friendly, does not generate new pollution emissions, complies with the national energy conservation and environmental protection policies, has obvious economic and social benefits, and has good application prospects.

[0041] Please see Figure 2 , Figure 2 This is a schematic diagram of another embodiment of the heat recovery system of this application. The heat recovery system 10 in this embodiment includes, but is not limited to, the following structures: exhaust steam generating device 100, heat exchanger 200, and cooler 300.

[0042] Specifically, the heat exchanger 200 is connected to the exhaust steam output pipeline 110 of the exhaust steam generating device 100. The heat exchanger 200 is used to transfer the heat of the exhaust steam to the hot water and deliver the hot water to the cooler 300. The cooler 300 uses the heat in the hot water to cool it and delivers the hot water after heat exchange back to the heat exchanger 200 for reheating. This cycle is repeated to realize the utilization of the heat of the exhaust steam generated in the exhaust steam generating device 100.

[0043] Optionally, the waste steam generating device 100 in this embodiment can be a bleaching tower used for pulp treatment in the papermaking process. In a specific embodiment, it can be used to utilize the waste heat of the waste steam from the chemimechanical pulp bleaching tower. After filtration, this steam is heated to 90°C by a heat exchanger 200 (a plate heat exchanger) and then enters a chiller 300 for cooling, producing 7°C cold water which is sent to a cooling device 400 (specifically, it can be sent to the pulp mill's chilled water network to replace electric air conditioning for cooling; after cooling and heat exchange, the cold water is returned to the chiller for further cooling). Replacing "waste heat" with cooling capacity to replace electric chillers saves electricity and achieves energy conservation, emission reduction, and carbon reduction. This not only brings economic benefits from energy conservation but also serves as a model for industrial carbon reduction, contributing to national carbon neutrality.

[0044] Optionally, the refrigerator in this embodiment can be a hot water type lithium bromide refrigerator. The refrigeration process of the hot water type lithium bromide refrigerator mainly includes the following steps:

[0045] 1. Heating dilute solution: Low-energy hot water from the device flows through the heat transfer tube of the generator, heating the dilute lithium bromide solution outside the tube, causing it to produce refrigerant vapor, and the solution is concentrated into a concentrated solution.

[0046] 2. Condensing refrigerant vapor: Refrigerant vapor from the generator enters the condenser and is condensed into refrigerant water by the cooling water flowing through the heat transfer tubes of the condenser. The heat is carried into the cooling water system.

[0047] 3. Evaporative Refrigerant Water: After being throttled through a U-shaped tube, the refrigerant water enters the evaporator. It flashes and cools down inside the evaporator before flowing into the evaporator refrigerant water pan. The refrigerant water entering the evaporative refrigerant water pan is then pumped out by the refrigerant pump and sprayed onto the surface of the evaporator heat transfer tubes. It absorbs heat from the cold water flowing through the heat transfer tubes and boils, evaporating into refrigerant vapor.

[0048] 4. Absorption of refrigerant vapor: The generated refrigerant vapor enters the absorber and is absorbed by the concentrated solution returning to the absorber. The heat released during the absorption process is carried away by the cooling water flowing through the heat transfer tubes of the absorber and is then carried into the cooling water system.

[0049] 5. Cooling water: After the heat is carried away by the refrigerant water, the temperature of the cooling water decreases, and it flows out of the unit and into the cooling water system.

[0050] The cycle process: After absorbing the refrigerant vapor, the concentration of the concentrated solution decreases, becoming a dilute solution, which is then pumped back to the generator for heating and concentration.

[0051] This process is repeated continuously, and the evaporator continuously produces cold water at the required temperature. The hot water type lithium bromide refrigerator is a commonly used device in this field. This patent does not involve improvements to this device, and its detailed structure is within the understanding of those skilled in the art, so it will not be described further here.

[0052] The heat exchanger 200 is connected to the exhaust steam output pipeline 110 via a first pipeline 210 and a second pipeline 220. The first pipeline 210 is used for air intake, and the second pipeline 220 is used for exhaust. A first valve 201 (Z1 in the figure) is provided on the first pipeline 210, a second valve 202 (Z2 in the figure) is provided on the second pipeline 220, and a third valve 103 (Z3 in the figure) is provided on the exhaust steam output pipeline 110. The third valve 103 is located between the connection point of the first pipeline 210, the second pipeline 220 and the exhaust steam output pipeline 110.

[0053] A waste heat recovery device (heat exchanger 200) is added to the bypass exhaust steam pipeline. The heat exchanger 200 is installed on the newly built bypass exhaust steam pipeline. Once the heat exchanger 200 and related exhaust steam pipelines are installed, a hole is drilled to connect the bypass exhaust steam pipeline to the existing exhaust steam pipeline at a later time. A control valve (third valve 103) is added to the original main exhaust steam pipeline, thus minimizing the impact on production during the entire installation process. During normal operation, control valve Z3 on the main exhaust steam pipeline is closed, while Z1 and Z2 are open. The exhaust steam from the top of the bleaching tower passes through valve Z1, then sequentially through the waste heat recovery device and Z2, achieving cooling and condensation. The condensate is discharged back to the wood chip washing system. Z3 is used for switching during system failures or maintenance. In this embodiment, the (plate) heat exchanger 200 uses a cold-side hot water temperature control to regulate the exhaust gas pressure, ensuring that the original system process is not affected.

[0054] Optionally, since the exhaust steam from the bleaching tower contains fibers and some chemicals, the heat exchanger 200 in this embodiment can be a plate contact heat exchanger with stainless steel plates. Stainless steel has good corrosion resistance and can resist the erosion of pulp fibers, steam, and trace amounts of acids and alkalis by the plates, ensuring the service life of the heat exchanger. The plate surface is provided with a passivation layer or an electrochemical polishing layer to reduce surface roughness, decrease the friction between the fibers and the plates, and thus reduce the adhesion and bonding of pulp fibers to the plates, reducing clogging problems. The equipment is equipped with a spray device, and the spray frequency and spray time are determined according to the clogging situation of the plates. This application mainly improves the surface and material of the plates. Detailed structural features of the plate contact heat exchanger are common knowledge in the art and will not be elaborated here.

[0055] In addition, the heat recovery system in this embodiment may also include a control device and a control system. The system is equipped with a microcomputer intelligent control system, capable of stepless adjustment of the load from 20% to 100% according to load changes, with the system outlet temperature fed back to the control system in real time. Control methods: Both local control and remote monitoring can be used. Local control is adopted during commissioning and communication failure phases, while centralized monitoring is implemented in the DCS control room during normal operation. Automation level of the control system: With the assistance of a small number of on-site inspection personnel, operators can monitor and operate the system from the control room via a remote transmission system, enabling monitoring and adjustment of system equipment startup, shutdown, and normal operation, as well as handling system anomalies and accidents. Fault alarm: The control system monitors unit alarm faults in real time and can store past faults, including fault type, occurrence time, recovery time, pump running time, etc.

[0056] Unlike the previous embodiments, the heat recovery system in this embodiment also includes a cooling tower 500, which is connected to the chiller 300 and used to cool the chiller 300. Cooling water flow: Utilizing the existing cooling tower in the chemical machinery and pulp workshop, the 32°C circulating cooling water, after being cooled by the cooling tower, is sent to the chiller unit to remove heat and raise its temperature, then returns to the cooling tower to cool down, and so on.

[0057] In addition, in this embodiment, the heat recovery system is equipped with a pressure detector 800 (marked as PT in the figure) on the main exhaust steam pipeline (exhaust steam output pipeline 110) to measure the pressure of the exhaust steam pipeline. When the waste heat recovery equipment is put into operation, the hot water temperature is controlled by the cold side regulating valve. While the exhaust steam is condensed, the pressure at the connection between the main pipeline and the bypass pipeline is the same as the pressure before the waste heat recovery equipment was used, maintaining the original state inside the bleaching tower.

[0058] Please see Figure 3 , Figure 3 This is a schematic diagram of another embodiment of the heat recovery system of this application. Unlike the previous embodiment, the heat recovery system in this embodiment also includes a waste steam condensate recovery device 600, which is connected to the heat exchanger 200 and is used to recover steam condensate.

[0059] In this embodiment, the heat recovery system also includes an electric chiller 700. The cooling device 400 is connected in parallel with the electric chiller 700. Under normal working conditions, the cooling device 400 uses the waste steam recovery and utilization equipment (heat exchanger 200 and chiller 300) for cooling. If the waste steam recovery and utilization equipment is damaged or shut down, the electric chiller 700 can be used for emergency use to ensure that the cooling device 400 always has a stable cold source.

[0060] Additionally, this application also provides a pulp production line; please refer to [link to relevant documentation]. Figure 4 , Figure 4 This is a schematic flow chart of an embodiment of the pulp production line of this application. The pulp production line first performs wood chip washing (401), followed by impregnation (402), high-consistency refining (403), fiber centrifugation (404), and a medium-consistency bleaching tower (405). The heat recovery system 10 in this embodiment mainly recovers and reuses the exhaust steam generated in the medium-consistency bleaching tower (405). For detailed structure of the heat recovery system 10, please refer to the relevant description in the foregoing embodiment.

[0061] In addition, the pulp production line also includes a No. 1 two-roll washing machine 406, a high-consistency bleaching machine 407, a pulp washing machine 408, a low-consistency refining machine 409, a screening machine 410, a thickener 411, and a pulp storage tower 412. The specific structure and process of each station of the pulp production line are within the understanding of those skilled in the art and will not be described in detail here.

[0062] The pulp production line in this embodiment saves energy consumption (saving the original refrigeration energy consumption) to reduce operating costs. Waste heat and exhaust steam are cooled in a closed loop, reducing heat emissions and carbon emissions. It is environmentally friendly, does not generate new pollution emissions, complies with the national energy conservation and environmental protection policies, and has significant economic and social benefits, with good application prospects.

[0063] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or direct or indirect application in other related technical fields, are similarly included in the patent protection scope of this application.

Claims

1. A heat energy recovery system, characterized in that, The heat recovery system includes: a waste steam generating device, a heat exchanger, and a refrigerator; the heat exchanger is connected to the waste steam output pipeline of the waste steam generating device, the heat exchanger is used to transfer the heat of the waste steam to hot water, and deliver the hot water to the refrigerator, the refrigerator uses the heat in the hot water to cool, and delivers the hot water after heat exchange back to the heat exchanger for reheating, and the cycle is repeated to realize the utilization of the heat of the waste steam generated in the waste steam generating device.

2. The heat recovery system according to claim 1, characterized in that, The exhaust steam generating device is a bleaching tower used for pulp treatment in the papermaking process.

3. The heat recovery system according to claim 1, characterized in that, The heat exchanger is connected to the exhaust steam output pipeline via a first pipeline and a second pipeline. The first pipeline is used for air intake, and the second pipeline is used for exhaust. A first valve is provided on the first pipeline, a second valve is provided on the second pipeline, and a third valve is provided on the exhaust steam output pipeline. The third valve is located between the connection point of the first pipeline and the second pipeline with the exhaust steam output pipeline.

4. The heat recovery system according to claim 3, characterized in that, A pressure detector is installed on the exhaust steam output pipeline.

5. The heat recovery system according to claim 1, characterized in that, The cooler is a hot water type lithium bromide cooler.

6. The heat recovery system according to claim 5, characterized in that, The cold water produced by the refrigerator is connected to the cooling device, which is connected in parallel with the electric refrigerator.

7. The heat recovery system according to claim 5, characterized in that, The heat recovery system also includes a cooling tower, which is connected to the refrigerator and is used to cool the refrigerator.

8. The heat recovery system according to claim 1, characterized in that, The heat recovery system also includes a waste steam condensate recovery device, which is connected to the heat exchanger.

9. The heat recovery system according to claim 1, characterized in that, The heat exchanger plates are provided with a passivation layer or an electrochemical polishing layer.

10. A pulp production line, characterized in that, The pulp production line includes the heat recovery system as described in any one of claims 1-9.

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