A heat pump device for a paper machine and a papermaking method

Abstract

The present application relates to the technical field of heat pump, especially to a heat pump device for paper machine and a papermaking method, which solves the problem of insufficient liquid supply and unstable heat exchange of the existing heat pump device when applied to the paper machine gas hood partition recovery. The present application comprises: a partition evaporator, which comprises an upper heat exchange zone and a lower heat exchange zone; a gas-liquid separation chamber for receiving gas-liquid two-phase refrigerant flowing out from the refrigerant outlet of the upper heat exchange zone, the gas-liquid separation chamber is provided with a gas phase outlet and a liquid phase outlet; a gas phase reflux pipeline, the gas phase outlet is connected with a compressor through the gas phase reflux pipeline; a liquid phase downward pipeline, the liquid phase outlet is connected with the refrigerant inlet of the lower heat exchange zone through the liquid phase downward pipeline; an intracavity pressure detection member is arranged in the gas-liquid separation chamber; and the frequency of the one-way regulating valve, the throttling valve or the compressor is adjusted according to the pressure change in the gas-liquid separation chamber, so as to improve the adaptability of the heat pump device to the load fluctuation of the paper machine wet heat exhaust gas.

Description

Technical Field

[0001] This invention relates to the field of heat pump technology, and more particularly to a heat pump device for a paper machine and a papermaking method. Background Technology

[0002] In the papermaking process, the paper web needs to evaporate a large amount of moisture in the drying section. This humid air is usually discharged through paper machine hoods, exhaust fans, and heat recovery systems. Because the exhaust air from the paper machine hoods is characterized by high temperature, high moisture content, and high latent heat content, when the ambient temperature is low, the discharged humid air is prone to producing white fog, dripping mist, or condensation. This not only affects the factory and surrounding environment but also results in a large amount of low-grade waste heat not being fully utilized.

[0003] Chinese Patent Publication No. CN111877046A discloses a paper machine hood exhaust treatment system and method. This system utilizes a deodorizing spray device, a demisting device, a heat exchange module, a mixing and water-blocking module, and a mixture of drying and hot air to demist and remove blemishes from the paper machine hood exhaust. The aim is to reduce the temperature and moisture content of the final exhaust air, thereby improving the demisting and blemish-removing effects. This solution primarily improves upon the air-side treatment, spray deodorization, water-blocking and demisting, and air-to-air heat exchange aspects of the paper machine hood exhaust.

[0004] When heat pump evaporators are used for waste heat recovery from paper machine hood exhaust, the humidity and heat load of the paper machine hood exhaust are not completely consistent in different areas of the paper web. Usually, the exhaust humidity and latent heat load are higher in the middle area of ​​the paper web, while the exhaust humidity and heat exchange load are relatively lower in the areas on both sides of the paper web.

[0005] If the high-humidity exhaust gas and low-humidity exhaust gas are mixed and then introduced into the evaporator, the heat and moisture quality of the high-humidity exhaust gas will be diluted by the low-humidity exhaust gas, making it difficult to effectively exchange heat for different moisture loads. If an upper and lower partitioned evaporator is simply used, so that the refrigerant first exchanges heat in the upper heat exchange zone corresponding to the high-humidity exhaust gas and then enters the lower heat exchange zone corresponding to the low-humidity exhaust gas, the refrigerant is likely to form a gas-liquid two-phase state after passing through the upper heat exchange zone.

[0006] When the two-phase refrigerant directly enters the lower heat exchange zone, the large volume of the gaseous refrigerant easily occupies the effective flow area of ​​the refrigerant channel in the lower heat exchange zone, leading to uneven distribution of the liquid refrigerant, insufficient liquid supply in the lower heat exchange zone, excessive local superheat, and decreased heat exchange efficiency. On the other hand, if a large amount of the gaseous refrigerant flowing out of the upper heat exchange zone is directly returned to the compressor, a rapid pressure drop can easily occur in the gas-liquid separation chamber or intermediate cavity, causing the liquid refrigerant to lack the pressure differential required to enter the lower heat exchange zone, resulting in discontinuous liquid supply or unstable heat exchange in the lower heat exchange zone. Summary of the Invention

[0007] Therefore, there is a need to provide a heat pump device and papermaking method for paper machines to solve the problems of insufficient liquid supply and unstable heat exchange that are common when existing heat pump devices are applied to the gas hood zoning recovery of paper machines.

[0008] To achieve the above objectives, the inventors provide a heat pump device for a paper machine, comprising:

[0009] A partitioned evaporator, the partitioned evaporator comprising an upper heat exchange zone for exchanging heat with high humidity exhaust gas and a lower heat exchange zone for exchanging heat with low humidity exhaust gas.

[0010] The gas-liquid separation chamber is used to receive the two-phase refrigerant (gas and liquid) flowing out of the refrigerant outlet of the upper heat exchange zone. The gas-liquid separation chamber is provided with a gas phase outlet and a liquid phase outlet.

[0011] A gas phase reflux pipeline is provided, wherein the gas phase outlet is connected to a compressor via the gas phase reflux pipeline, and a one-way regulating valve is provided on the gas phase reflux pipeline;

[0012] A liquid phase downfeed pipeline is provided, wherein the liquid phase outlet is connected to the refrigerant inlet of the lower heat exchange zone via the liquid phase downfeed pipeline, and a throttling valve is provided on the liquid phase downfeed pipeline. The one-way regulating valve and the throttling valve are configured to maintain the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone.

[0013] An internal pressure detection device is disposed inside the gas-liquid separation chamber;

[0014] The controller is connected to the cavity pressure detection element, the one-way regulating valve, the throttle valve, and the compressor, respectively. The controller is configured to adjust the opening of the one-way regulating valve, or the opening of the throttle valve, or adjust the compressor frequency while adjusting the opening of the one-way regulating valve, based on the change value of the cavity pressure detection element.

[0015] Furthermore, the change values ​​include positive change values ​​and negative change values;

[0016] When the change value is a positive change value, the controller is configured to: increase the opening of the one-way regulating valve, or increase the opening of the throttle valve, or increase the compressor frequency while increasing the opening of the one-way regulating valve;

[0017] When the change value is a negative change value, the controller is configured to: reduce the opening of the one-way regulating valve, or reduce the opening of the throttle valve, or reduce the compressor frequency while reducing the opening of the one-way regulating valve.

[0018] Furthermore, when the change value of the intracavity pressure detection element is continuously positive within a first set time period, the controller is configured to: increase the opening degree of the one-way regulating valve while increasing the compressor frequency;

[0019] When the change value of the intracavity pressure detection element is continuously positive within a second set time, the controller is configured to: increase the opening of the one-way regulating valve;

[0020] When the change value of the intracavity pressure detection element is continuously negative within a first set time, the controller is configured to: reduce the opening of the one-way regulating valve while reducing the compressor frequency;

[0021] When the change value of the intracavity pressure detection element is continuously negative within a second set time, the controller is configured to: reduce the opening of the one-way regulating valve;

[0022] The first set time is greater than the second set time.

[0023] Furthermore, it also includes a liquid replenishment pipeline for replenishing refrigerant to the lower heat exchange zone, a liquid replenishment throttle valve provided on the liquid replenishment pipeline, and a liquid level detection device provided in the gas-liquid separation chamber. The controller is connected to the liquid replenishment throttle valve and the liquid level detection device. The controller is configured to open the liquid replenishment throttle valve or increase the opening degree of the liquid replenishment throttle valve when the liquid level in the gas-liquid separation chamber is lower than a preset height and the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone is lower than a preset pressure difference.

[0024] Furthermore, it also includes a two-phase detection element located between the refrigerant outlet of the upper heat exchange zone and the gas-liquid separation chamber. The two-phase detection element is used to obtain the gas phase volume fraction based on the change in the dielectric properties of the gas and liquid two-phase refrigerant within the two-phase detection element.

[0025] Furthermore, the upper heat exchange zone is provided with an upper refrigerant heat exchange tube assembly, which includes multiple heat exchange sections arranged at intervals. The controller is configured to control the number of effective heat exchange sections of the upper refrigerant heat exchange tube assembly, so that the refrigerant flowing from the upper heat exchange zone into the gas-liquid separation chamber remains in a gas-liquid two-phase state.

[0026] Furthermore, the high humidity and heat exhaust is the exhaust from the paper machine hood corresponding to the middle area of ​​the paper web, and the low humidity and heat exhaust is the exhaust from the paper machine hood corresponding to the two sides of the paper web.

[0027] Furthermore, an air isolation layer is provided between the upper heat exchange zone and the lower heat exchange zone.

[0028] Furthermore, the lower heat exchange zone is provided with a lower zone pressure detection device, and the controller is connected to the lower zone pressure detection device. The controller is configured to determine the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone based on the pressure of the gas-liquid separation chamber detected by the chamber pressure detection device and the pressure of the lower heat exchange zone detected by the lower zone pressure detection device, and adjust the opening of the one-way regulating valve and / or the opening of the throttle valve according to the pressure difference.

[0029] A papermaking method, employing the aforementioned heat pump device for a paper machine, includes the following steps:

[0030] S1. Use a paper machine to dry the paper web and collect the high-humidity heat exhaust and low-humidity heat exhaust generated during the paper machine drying process;

[0031] S2. The high-humidity and high-heat exhaust gas is introduced into the upper heat exchange zone of the partitioned evaporator, and the low-humidity and high-heat exhaust gas is introduced into the lower heat exchange zone of the partitioned evaporator.

[0032] S3. The refrigerant first flows through the upper heat exchange zone and exchanges heat with the high humidity and heat exhaust gas, so that the gas-liquid two-phase refrigerant flowing out of the refrigerant outlet of the upper heat exchange zone enters the gas-liquid separation chamber.

[0033] S4. The gas-liquid two-phase refrigerant is separated in the gas-liquid separation chamber, so that the separated gas phase refrigerant flows to the compressor through the gas phase outlet and the gas phase return pipeline, and the separated liquid phase refrigerant flows to the lower heat exchange zone through the liquid phase outlet and the liquid phase downfeed pipeline.

[0034] S5. Obtain the pressure change value of the gas-liquid separation chamber by means of the chamber pressure detection device provided in the gas-liquid separation chamber;

[0035] S6. The controller adjusts the opening of the one-way regulating valve on the gas phase return pipeline, or the opening of the throttle valve on the liquid phase downflow pipeline, or adjusts the compressor frequency while adjusting the opening of the one-way regulating valve, according to the pressure change value, so as to maintain the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone, so that the liquid refrigerant in the gas-liquid separation chamber enters the lower heat exchange zone and exchanges heat with the low-humidity and high-temperature exhaust gas.

[0036] Unlike existing technologies, the above technical solution has the following advantages:

[0037] This invention divides the paper machine exhaust into high-humidity exhaust and low-humidity exhaust, and introduces them into the upper and lower heat exchange zones of the partitioned evaporator, respectively. This allows the high-humidity exhaust to preferentially exchange heat with the refrigerant, thus fully recovering the sensible and latent heat carried by the high-humidity exhaust in the paper machine hood.

[0038] Meanwhile, after passing through the upper heat exchange zone, the refrigerant forms a two-phase gas-liquid refrigerant and enters the gas-liquid separation chamber for gas-liquid separation. The gas phase refrigerant returns to the compressor through the gas phase return pipeline, while the liquid phase refrigerant enters the lower heat exchange zone through the liquid phase downfeed pipeline to continue heat exchange. This can reduce the gas resistance, uneven distribution, and decreased heat exchange efficiency caused by the gas phase refrigerant entering the lower heat exchange zone.

[0039] By installing a one-way regulating valve on the gas phase return pipeline and a throttling valve on the liquid phase delivery pipeline, and adjusting the one-way regulating valve, throttling valve, or compressor frequency according to the pressure changes in the gas-liquid separation chamber, the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone can be maintained. This allows the liquid refrigerant in the gas-liquid separation chamber to stably enter the lower heat exchange zone, thereby ensuring the continuous heat exchange capacity of the lower heat exchange zone and improving the adaptability of the heat pump unit to fluctuations in the wet and hot exhaust load of the paper machine.

[0040] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0041] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of the present invention and other related contents, and should not be considered as limitations on this application.

[0042] In the accompanying drawings of the instruction manual:

[0043] Figure 1 This is a schematic diagram of the connection structure of each component of the heat pump device in this embodiment.

[0044] The reference numerals used in the above figures are explained as follows:

[0045] 1. Zoned evaporator; 11. Upper heat exchange zone; 12. Lower heat exchange zone; 13. Air isolation layer; 14. Heat exchange section;

[0046] 2. Gas-liquid separation chamber; 21. Gas phase outlet; 22. Liquid phase outlet;

[0047] 3. Gas phase reflux pipeline; 31. One-way regulating valve;

[0048] 4. Liquid phase feed line; 41. Throttling valve;

[0049] 5. Compressor;

[0050] 6. Replenishment pipeline; 61. Replenishment throttle valve;

[0051] 7. Two-phase testing components. Detailed Implementation

[0052] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0053] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0054] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0055] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0056] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0057] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0058] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0059] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0060] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0061] Example 1: Please refer to Figure 1 This embodiment provides a heat pump device for a paper machine, used to recover heat from the humid and hot air discharged from the paper machine's hood. The heat pump device includes a partitioned evaporator 1, a gas-liquid separation chamber 2, a gas phase reflux pipeline 3, a liquid phase downflow pipeline 4, a compressor 5, and a controller (not shown in the figure).

[0062] The partitioned evaporator 1 includes an upper heat exchange zone 11 and a lower heat exchange zone 12. The upper heat exchange zone 11 is used for heat exchange with high-humidity exhaust gas, and the lower heat exchange zone 12 is used for heat exchange with low-humidity exhaust gas. Specifically, the high-humidity exhaust gas can be the exhaust gas in the paper machine hood corresponding to the middle region of the paper web, and the low-humidity exhaust gas can be the exhaust gas in the paper machine hood corresponding to the two sides of the paper web. Since the middle region of the paper web usually has a higher moisture content, the corresponding exhaust gas has a higher humidity and a higher latent heat load, so this part of the high-humidity exhaust gas is introduced into the upper heat exchange zone 11; the exhaust gas corresponding to the two sides of the paper web has a relatively lower humidity, so this part of the low-humidity exhaust gas is introduced into the lower heat exchange zone 12.

[0063] An air isolation layer 13 is provided between the upper heat exchange zone 11 and the lower heat exchange zone 12. The air isolation layer 13 is used to restrict the heat exchange of high-humidity exhaust gas and low-humidity exhaust gas in the partitioned evaporator 1, which would cause uneven local heat exchange and frost formation. The air isolation layer 13 is used to restrict the heat exchange of high-humidity exhaust gas and low-humidity exhaust gas in the partitioned evaporator 1, which would cause uneven heat exchange in the lower heat exchange zone 12. This can prevent the high-humidity exhaust gas from being diluted by the low-humidity exhaust gas, and can also prevent the heat exchange load of the lower heat exchange zone 12 from changing abruptly due to the intrusion of high-humidity airflow.

[0064] The upper heat exchange zone 11 is equipped with an upper refrigerant heat exchange tube assembly; the upper refrigerant heat exchange tube assembly includes multiple heat exchange sections 14 arranged at intervals. A non-heat exchange transition space can be formed between two adjacent heat exchange sections 14. The multiple heat exchange sections 14 do not cover the entire upper heat exchange zone 11, but are arranged in sections to control the effective heat exchange area of ​​the upper heat exchange zone 11; the controller can adjust the heat exchange intensity of the upper heat exchange zone 11 by controlling the number of heat exchange sections 14 participating in the heat exchange, so that the refrigerant flowing out of the upper heat exchange zone 11 remains in a gas-liquid two-phase state, and the refrigerant is prevented from being completely evaporated in the upper heat exchange zone 11. The reason for designing the upper refrigerant heat exchanger tube assembly as multiple spaced heat exchange sections 14 is as follows: due to the short-term fluctuations in the moisture content and latent heat load of the high-humidity exhaust gas from the paper machine hood, the upper heat exchange zone 11 adopts multiple spaced heat exchange sections to disperse the condensation load of the high-humidity exhaust gas, avoid excessive local cooling and excessive refrigerant evaporation in the upper heat exchange zone 11, and prevent the concentrated generation of condensate when the tube wall temperature of the upper refrigerant heat exchanger tube assembly is below the freezing point, thereby reducing the risk of condensate frosting or freezing.

[0065] The gas-liquid separation chamber 2 is used to receive the gas-liquid two-phase refrigerant flowing out of the refrigerant outlet of the upper heat exchange zone 11. The gas-liquid separation chamber 2 has a gas phase outlet 21 and a liquid phase outlet 22. The gas phase outlet 21 is located in the upper part of the gas-liquid separation chamber 2, and the liquid phase outlet 22 is located in the lower part of the gas-liquid separation chamber 2. After the gas-liquid two-phase refrigerant enters the gas-liquid separation chamber 2, the gas phase refrigerant accumulates in the upper part of the gas-liquid separation chamber 2, and the liquid phase refrigerant accumulates in the lower part of the gas-liquid separation chamber 2, thereby achieving gas-liquid separation.

[0066] The gas phase outlet 21 is connected to the compressor 5 through the gas phase return pipeline 3. A one-way regulating valve 31 is installed on the gas phase return pipeline 3. The one-way regulating valve 31 is used to allow the gas phase refrigerant in the gas-liquid separation chamber 2 to flow towards the compressor 5 and to restrict the refrigerant on the compressor 5 side from flowing back into the gas-liquid separation chamber 2. The one-way regulating valve 31 can also regulate the discharge amount of the gas phase refrigerant to prevent the pressure in the gas-liquid separation chamber 2 from dropping rapidly due to the gas phase refrigerant being discharged too quickly.

[0067] The liquid phase outlet 22 is connected to the refrigerant inlet of the lower heat exchange zone 12 through the liquid phase downfeed pipeline 4. A throttle valve 41 is installed on the liquid phase downfeed pipeline 4. The throttle valve 41 is used to regulate the flow rate of liquid refrigerant entering the lower heat exchange zone 12 from the gas-liquid separation chamber 2. The one-way regulating valve 31 and the throttle valve 41 cooperate to maintain a certain pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12, so that the liquid refrigerant in the gas-liquid separation chamber 2 can enter the lower heat exchange zone 12 under the action of the pressure difference and continue to evaporate and absorb heat in the lower heat exchange zone 12.

[0068] An internal pressure detection device (not shown in the figure) is installed in the gas-liquid separation chamber 2. The internal pressure detection device is used to detect the pressure in the gas-liquid separation chamber 2. The controller is connected to the internal pressure detection device, the one-way regulating valve 31, the throttle valve 41 and the compressor 5 respectively. The controller adjusts the opening of the one-way regulating valve 31, or the opening of the throttle valve 41, or adjusts the frequency of the compressor 5 at the same time as adjusting the opening of the one-way regulating valve 31, based on the pressure change value detected by the internal pressure detection device within a set time.

[0069] Specifically, the pressure change values ​​include positive and negative values. A positive change value indicates that the pressure inside the gas-liquid separation chamber 2 is increasing, while a negative change value indicates that the pressure inside the gas-liquid separation chamber 2 is decreasing.

[0070] When the pressure change is a positive change, the controller can increase the opening of the one-way regulating valve 31 to increase the return flow of gaseous refrigerant to the compressor 5; it can also increase the opening of the throttle valve 41 to increase the delivery of liquid refrigerant to the lower heat exchange zone 12; and it can also increase the frequency of the compressor 5 while increasing the opening of the one-way regulating valve 31 to enhance the refrigerant circulation capacity.

[0071] When the pressure change is negative, the controller can reduce the opening of the one-way regulating valve 31 to reduce the amount of gaseous refrigerant discharged and prevent the gas-liquid separation chamber 2 from depressurizing rapidly; it can also reduce the opening of the throttle valve 41 to reduce the amount of liquid refrigerant flowing out; it can also reduce the frequency of the compressor 5 while reducing the opening of the one-way regulating valve 31 to reduce the suction effect of the compressor 5 on the gaseous refrigerant.

[0072] Specifically, when the pressure sensor in the cavity continuously changes positively within a first set time (e.g., 30 seconds), it indicates that the amount of gaseous refrigerant flowing into the gas-liquid separation chamber 2 has increased. This means that the heat exchange capacity of the upper heat exchange zone 11 is insufficient due to factors such as increased humidity in the middle of the paper web or adjustments to paper machine parameters. The controller then increases the opening of the one-way regulating valve 31 and increases the frequency of the compressor 5. When the pressure sensor in the cavity continuously changes positively within a second set time (e.g., 5 seconds), it indicates that the air pressure in the lower heat exchange zone 12 has increased. This means that the heat exchange efficiency of the lower heat exchange zone 12 is insufficient. The controller then increases the opening of the throttle valve 41 to increase the refrigerant flow rate in the lower heat exchange zone 12. Simultaneously, since the one-way regulating valve 31 and the throttle valve 41 are configured to maintain the pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12, the opening of the throttle valve 41 is increased while the opening of the one-way regulating valve 31 is decreased to maintain the air pressure in the cavity.

[0073] Specifically, when the pressure sensor in the cavity continuously changes negatively within a first set time (e.g., 30 seconds), it indicates that the liquid phase refrigerant in the gas-liquid two-phase refrigerant flowing into the gas-liquid separation chamber 2 has increased. This means that the heat exchange capacity of the upper heat exchange zone 11 is excessive due to factors such as increased humidity in the middle of the paper web or adjustments to paper machine parameters. The controller then reduces the opening of the one-way regulating valve 31 and decreases the frequency of the compressor 5. When the pressure sensor continuously changes negatively within a second set time (e.g., 5 seconds), it indicates that the air pressure in the lower heat exchange zone 12 has decreased. This means that the heat exchange efficiency of the lower heat exchange zone 12 is excessive. The controller only reduces the opening of the throttle valve 41, and the one-way regulating valve 31 reduces its opening to maintain the air pressure in the cavity. Therefore, for short-term pressure fluctuations, the one-way regulating valve 31 can be used for rapid adjustment; for continuous pressure fluctuations, the frequency of the compressor 5 can be further adjusted to improve system stability.

[0074] The first set time is longer than the second set time.

[0075] Specifically, when the change value of the pressure detection element in the cavity continues to exceed the set change value within a first set time (e.g., 30s), the heat exchange intensity adjustment of the upper heat exchange zone 11 exceeds the adjustment range of the gas-liquid separation chamber 2. The controller adjusts the heat exchange intensity of the upper heat exchange zone 11 by controlling the number of heat exchange sections 14 participating in the heat exchange, so that the refrigerant flowing out of the upper heat exchange zone 11 remains in a gas-liquid two-phase state.

[0076] The heat pump device also includes a liquid replenishment line 6, which is used to replenish refrigerant to the lower heat exchange zone 12. A liquid replenishment throttling valve 61 is installed on the liquid replenishment line 6. A liquid level detection device (not shown in the figure) is also installed in the gas-liquid separation chamber 2. The controller is connected to the liquid replenishment throttling valve 61 and the liquid level detection device respectively. When the liquid level detection device detects that the liquid level in the gas-liquid separation chamber 2 is lower than a preset height, and the pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12 is lower than a preset pressure difference, the controller opens the liquid replenishment throttling valve 61 or increases the opening degree of the liquid replenishment throttling valve 61, allowing external liquid refrigerant to enter the lower heat exchange zone 12 through the liquid replenishment line 6, thus preventing liquid shortage in the lower heat exchange zone 12.

[0077] A two-phase detection element 7 is installed between the refrigerant outlet of the upper heat exchange zone 11 and the gas-liquid separation chamber 2. The two-phase detection element 7 is used to obtain the gas phase volume fraction based on the change in the dielectric properties of the gas and liquid refrigerants inside. Since the dielectric properties of gaseous refrigerant and liquid refrigerant are different, the detection signal of the two-phase detection element 7 changes when the gas-liquid ratio changes. The controller can determine the gas phase volume fraction before entering the gas-liquid separation chamber 2 based on the detection signal. This allows the controller to determine whether the heat exchange intensity of the upper heat exchange zone 11 is appropriate, avoiding an excessively low gas phase ratio of refrigerant entering the gas-liquid separation chamber 2, which would make it difficult to maintain the pressure, and also avoiding an excessively high gas phase ratio, which would lead to insufficient liquid refrigerant.

[0078] In this embodiment, the two-phase detection element 7 can be a capacitive two-phase flow detector known in the art. In other embodiments, the two-phase detection element 7 can also be a microwave, radio frequency, ultrasonic, differential pressure, density, or sight liquid two-phase flow detector. The above-mentioned detection instruments are all conventional detection methods in the art for obtaining the porosity, gas phase volume fraction, or dryness of gas-liquid two-phase flow, and will not be described in detail here.

[0079] In this embodiment, the lower heat exchange zone 12 is also provided with a lower zone pressure detection element (not shown in the figure). The lower zone pressure detection element is used to detect the pressure of the lower heat exchange zone 12. The controller is connected to the lower zone pressure detection element and determines the pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12 based on the pressure detected by the internal pressure detection element and the pressure detected by the lower zone pressure detection element. The controller adjusts the one-way regulating valve 31 and / or the throttle valve 41 according to the pressure difference, so that the pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12 is suitable for liquid refrigerant delivery.

[0080] In other preferred embodiments, the lower zone pressure detection element may not be provided. Since the refrigerant outlet of the lower heat exchange zone 12 is connected to the suction side of the compressor 5, and the lower heat exchange zone 12 is located on the low-pressure evaporation side of the heat pump system, the controller can use the suction side pressure of the compressor 5, the low-pressure side pressure of the system, or the preset lower zone evaporation pressure as the equivalent value of the pressure in the lower heat exchange zone 12. Based on the pressure in the gas-liquid separation chamber 2 detected by the intracavity pressure detection element and the equivalent value, the controller determines or estimates the pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12, and adjusts the opening of the one-way regulating valve 31 and / or the throttle valve 41 accordingly. When the pressure difference between the gas-liquid separation chamber 2 and the equivalent value is lower than the preset pressure difference, the controller reduces the opening of the one-way regulating valve 31 to limit the rapid backflow of gaseous refrigerant and maintain the pressure inside the gas-liquid separation chamber 2; or reduces the opening of the throttle valve 41 to reduce the outflow of liquid refrigerant; when the pressure difference between the gas-liquid separation chamber 2 and the equivalent value is higher than the preset pressure difference, the controller increases the opening of the one-way regulating valve 31 and / or increases the opening of the throttle valve 41 to avoid excessive pressure in the gas-liquid separation chamber 2.

[0081] The controller can be a programmable logic controller, a microcontroller, an industrial control computer, an embedded control module, or the main control board integrated into the heat pump unit. The controller includes a signal acquisition terminal, a processing unit, and an execution output terminal. The signal acquisition terminal receives detection signals from the pressure detection device, liquid level detection device, two-phase detection device 7, and lower zone pressure detection device. The processing unit determines the pressure change value, liquid level state, gas phase volume fraction, and pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12 based on the detection signals. The execution output terminal outputs control signals to the one-way regulating valve 31, the throttle valve 41, the liquid replenishment throttle valve 61, and the compressor 5.

[0082] The controller can receive signals from various sensors via analog input interfaces, digital input interfaces, or communication interfaces, and control the opening degree of the one-way regulating valve 31, throttle valve 41, and replenishing throttle valve 61, as well as the operating frequency of the compressor 5, via analog output interfaces, digital output interfaces, pulse output interfaces, or communication interfaces. The communication interface can be an RS485 interface, CAN interface, Ethernet interface, or other industrial communication interface.

[0083] Example 2: This example provides a papermaking method using the heat pump device for paper machines described in Example 1. The papermaking method includes the following steps.

[0084] S1. The paper web is dried using a paper machine. During the paper web drying process, the paper machine hood collects the humid and hot air evaporated from the paper web and discharges it as exhaust from the paper machine hood. Based on the humidity differences in different transverse areas of the paper web, the exhaust generated during the paper machine drying process is divided into high-humidity exhaust and low-humidity exhaust. Among them, the high-humidity exhaust is the exhaust from the paper machine hood corresponding to the middle area of ​​the paper web, and the low-humidity exhaust is the exhaust from the paper machine hood corresponding to the two sides of the paper web.

[0085] S2. High-humidity exhaust gas is introduced into the upper heat exchange zone 11 of the partitioned evaporator 1, and low-humidity exhaust gas is introduced into the lower heat exchange zone 12 of the partitioned evaporator 1. The upper heat exchange zone 11 and the lower heat exchange zone 12 are separated by an air isolation layer 13, so that the high-humidity exhaust gas and the low-humidity exhaust gas flow through the corresponding heat exchange zones respectively, reducing airflow mixing.

[0086] S3. The refrigerant first flows through the upper heat exchange zone 11 and exchanges heat with the high humidity and heat exhaust gas. Due to the high humidity and heat exhaust gas having a high latent heat load, the refrigerant absorbs heat from the high humidity and heat exhaust gas in the upper heat exchange zone 11 and forms a gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flowing out of the refrigerant outlet of the upper heat exchange zone 11 enters the gas-liquid separation chamber 2.

[0087] S4. In the gas-liquid separation chamber 2, the gas-liquid two-phase refrigerant is separated into gas and liquid phases. The separated gas phase refrigerant enters the gas phase return pipeline 3 through the gas phase outlet 21 and flows to the compressor 5 through the one-way regulating valve 31. The separated liquid phase refrigerant enters the liquid phase downfeed pipeline 4 through the liquid phase outlet 22 and flows to the lower heat exchange zone 12 through the throttling valve 41.

[0088] S5. In the above process, the pressure change value of the gas-liquid separation chamber 2 is obtained by a chamber pressure detection device installed in the gas-liquid separation chamber 2. The controller adjusts the opening of the one-way regulating valve 31 on the gas phase return pipeline 3, or the opening of the throttle valve 41 on the liquid phase downflow pipeline 4, or adjusts the frequency of the compressor 5 while adjusting the opening of the one-way regulating valve 31, to maintain the pressure difference between the gas-liquid separation chamber 2 and the lower heat exchange zone 12. As a result, the liquid refrigerant in the gas-liquid separation chamber 2 can stably enter the lower heat exchange zone 12 under the action of the pressure difference, and exchange heat with the low-humidity and high-temperature exhaust gas in the lower heat exchange zone 12.

[0089] S6. The controller adjusts the opening of the one-way regulating valve on the gas phase return pipeline, or the opening of the throttle valve on the liquid phase downflow pipeline, or adjusts the compressor frequency while adjusting the opening of the one-way regulating valve, according to the pressure change value, so as to maintain the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone, so that the liquid refrigerant in the gas-liquid separation chamber enters the lower heat exchange zone and exchanges heat with the low-humidity and high-temperature exhaust gas.

[0090] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A heat pump device for a paper machine, characterized in that, include: A partitioned evaporator, the partitioned evaporator comprising an upper heat exchange zone for exchanging heat with high humidity exhaust gas and a lower heat exchange zone for exchanging heat with low humidity exhaust gas. The gas-liquid separation chamber is used to receive the two-phase refrigerant (gas and liquid) flowing out of the refrigerant outlet of the upper heat exchange zone. The gas-liquid separation chamber is provided with a gas phase outlet and a liquid phase outlet. A gas phase reflux pipeline is provided, wherein the gas phase outlet is connected to a compressor via the gas phase reflux pipeline, and a one-way regulating valve is provided on the gas phase reflux pipeline; A liquid phase downfeed pipeline is provided, wherein the liquid phase outlet is connected to the refrigerant inlet of the lower heat exchange zone via the liquid phase downfeed pipeline, and a throttling valve is provided on the liquid phase downfeed pipeline. The one-way regulating valve and the throttling valve are configured to maintain the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone. An internal pressure detection device is disposed inside the gas-liquid separation chamber; The controller is connected to the cavity pressure detection device, the one-way regulating valve, the throttle valve, and the compressor, respectively. The controller is configured to adjust the opening of the one-way regulating valve, or adjust the opening of the throttle valve, or adjust the compressor frequency while adjusting the opening of the one-way regulating valve, based on the change value of the cavity pressure detection device. And a two-phase detection element is provided between the refrigerant outlet of the upper heat exchange zone and the gas-liquid separation chamber. The two-phase detection element is used to obtain the gas phase volume fraction based on the change in dielectric properties of the gas-liquid two-phase refrigerant in the two-phase detection element. The upper heat exchange zone is provided with an upper refrigerant heat exchange tube assembly, which includes multiple heat exchange sections arranged at intervals. The controller is configured to control the number of effective heat exchange sections of the upper refrigerant heat exchange tube assembly, so that the refrigerant flowing from the upper heat exchange zone into the gas-liquid separation chamber remains in a gas-liquid two-phase state. The high humidity and heat exhaust is the exhaust from the paper machine hood corresponding to the middle area of ​​the paper web, and the low humidity and heat exhaust is the exhaust from the paper machine hood corresponding to the two sides of the paper web.

2. A heat pump device for a paper machine according to claim 1, characterized in that: The change values ​​include positive change values ​​and negative change values; When the change value is a positive change value, the controller is configured to: increase the opening of the one-way regulating valve, or increase the opening of the throttle valve, or increase the compressor frequency while increasing the opening of the one-way regulating valve; When the change value is a negative change value, the controller is configured to: reduce the opening of the one-way regulating valve, or reduce the opening of the throttle valve, or reduce the compressor frequency while reducing the opening of the one-way regulating valve.

3. A heat pump device for a paper machine according to claim 1, characterized in that: It also includes a refrigerant supply line for replenishing refrigerant to the lower heat exchange zone, a refrigerant supply throttle valve on the refrigerant supply line, and a liquid level detection device in the gas-liquid separation chamber. The controller is connected to the refrigerant supply throttle valve and the liquid level detection device. The controller is configured to open the refrigerant supply throttle valve or increase the opening degree of the refrigerant supply throttle valve when the liquid level in the gas-liquid separation chamber is lower than a preset height and the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone is lower than a preset pressure difference.

4. A heat pump device for a paper machine according to claim 1, characterized in that: An air isolation layer is provided between the upper heat exchange zone and the lower heat exchange zone.

5. A heat pump device for a paper machine according to claim 1, characterized in that: The lower heat exchange zone is equipped with a lower zone pressure detection device. The controller is connected to the lower zone pressure detection device. The controller is configured to determine the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone based on the pressure of the gas-liquid separation chamber detected by the chamber pressure detection device and the pressure of the lower heat exchange zone detected by the lower zone pressure detection device, and adjust the opening of the one-way regulating valve and / or the opening of the throttle valve based on the pressure difference.

6. A papermaking method, employing a heat pump device for a paper machine as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Use a paper machine to dry the paper web and collect the high-humidity heat exhaust and low-humidity heat exhaust generated during the paper machine drying process; S2. The high-humidity and high-heat exhaust gas is introduced into the upper heat exchange zone of the partitioned evaporator, and the low-humidity and high-heat exhaust gas is introduced into the lower heat exchange zone of the partitioned evaporator. S3. The refrigerant first flows through the upper heat exchange zone and exchanges heat with the high humidity and heat exhaust gas, so that the gas-liquid two-phase refrigerant flowing out of the refrigerant outlet of the upper heat exchange zone enters the gas-liquid separation chamber. S4. The gas-liquid two-phase refrigerant is separated in the gas-liquid separation chamber, so that the separated gas phase refrigerant flows to the compressor through the gas phase outlet and the gas phase return pipeline, and the separated liquid phase refrigerant flows to the lower heat exchange zone through the liquid phase outlet and the liquid phase downfeed pipeline. S5. Obtain the pressure change value of the gas-liquid separation chamber by means of the chamber pressure detection device provided in the gas-liquid separation chamber; S6. The controller adjusts the opening of the one-way regulating valve on the gas phase return pipeline, or the opening of the throttle valve on the liquid phase downflow pipeline, or adjusts the compressor frequency while adjusting the opening of the one-way regulating valve, according to the pressure change value, so as to maintain the pressure difference between the gas-liquid separation chamber and the lower heat exchange zone, so that the liquid refrigerant in the gas-liquid separation chamber enters the lower heat exchange zone and exchanges heat with the low-humidity and high-temperature exhaust gas.

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