Temperature regulation system for pulp board machine flow section based on waste liquid heat recovery of pulping

Abstract

The application provides a pulp board machine flow conveying part temperature regulation system based on pulp waste liquid waste heat recovery, and belongs to the technical field of papermaking equipment. The system comprises: a process water-acidic wastewater heat exchange unit configured to heat process water by using the waste heat of acidic wastewater generated in a pulp workshop; a white water-black liquor heat exchange unit configured to heat white water of a pulp board machine by using the waste heat of black liquor generated in the pulp workshop; and a conveying pipeline unit connected to the process water-acidic wastewater heat exchange unit and the white water-black liquor heat exchange unit respectively. The waste heat of acidic wastewater and black liquor generated in the pulp workshop is recovered by the double-path heat exchange units to heat process water and white water, replacing the traditional steam heating mode, achieving accurate temperature regulation of the pulp board machine flow conveying part, significantly reducing steam consumption and production cost, and realizing resource utilization of waste heat energy.

Description

Technical Field

[0001] This application belongs to the field of papermaking equipment technology, specifically relating to a temperature control system for the flow section of a pulping machine based on waste heat recovery from pulping waste liquor. Background Technology

[0002] In the pulp board production process, the flow section is a crucial link connecting pulping and forming. Its core task is to deliver the pulp to the headbox at a stable concentration, temperature, and flow rate. To ensure pulp fluidity, prevent fiber flocculation, and guarantee paper quality, nodes in the flow system such as the warm water tank, white water tank, and high-consistency tower typically need to be maintained at high process temperatures. Currently, the industry commonly uses direct introduction of fresh steam or heating of process water and white water through steam heat exchangers to meet this temperature requirement. However, this traditional heating method not only consumes a large amount of high-quality steam, leading to high production costs, but also results in a double waste of energy and water resources because steam condensate is often not fully recovered and reused, which does not meet the current green and low-carbon development requirements of the paper industry.

[0003] Traditional pulping machines use steam to heat process water and white water in the feed section. On the one hand, the spray water in the wire pressing section requires a large amount of steam for heating; on the other hand, the pulp temperature on the wire is relatively low, resulting in low dewatering efficiency in the wire pressing section and high moisture content in the wet paper web. This leads to the drying section consuming even more steam, creating a double high energy consumption of "front-end steam heating + back-end steam drying." At the same time, the waste heat from acidic wastewater and black liquor in the pulping workshop is not recovered, resulting in a significant waste of thermal energy.

[0004] Meanwhile, pulping workshops generate a large amount of heat-rich waste fluids during production, such as high-temperature acidic wastewater and black liquor. These waste liquids typically carry a significant amount of sensible heat, but in existing technologies, they are often simply cooled before being discharged directly into the wastewater treatment system or into the subsequent evaporation stage. The residual heat they contain is not effectively extracted and utilized, resulting in serious heat loss. Summary of the Invention

[0005] To address at least one of the technical problems existing in the background art, this application provides a temperature control system for the pulp board machine's feed section based on waste heat recovery from pulping waste liquor. This system uses dual heat exchange units to recover waste heat from acidic wastewater and black liquor in the pulping workshop to heat process water and white water, replacing the traditional steam heating method. While achieving precise temperature control in the pulp board machine's feed section, it significantly reduces steam consumption and production costs, realizing the resource utilization of waste heat energy. By recovering waste heat from acidic wastewater and black liquor in the pulping workshop, it completely replaces the steam heating of the spray water in the wire pressing section. Simultaneously, by heating the white water with waste heat, it increases the temperature of the pulp on the high-consistency tower, thereby increasing the temperature of the pulp on the headbox, enhancing the dewatering efficiency of the wire pressing section, reducing the moisture content of the wet paper web, and thus reducing steam consumption in the drying section. Ultimately, it significantly reduces the total steam consumption of the entire pulp board workshop process.

[0006] A second aspect of this application provides a temperature control method.

[0007] A third aspect of this application provides a pulp board production line.

[0008] The technical solution adopted in this application is as follows: The first aspect of this application provides a temperature control system for the flow section of a pulping machine based on waste heat recovery from pulping waste liquor, comprising: The process water-acidic wastewater heat exchange unit is configured to use the waste heat from the acidic wastewater generated in the pulping workshop to heat the process water. The white water-black liquor heat exchange unit is configured to use the waste heat of the black liquor generated in the pulping workshop to heat the white water in the pulping machine. The conveying pipeline unit is connected to the process water-acidic wastewater heat exchange unit and the white water-black liquor heat exchange unit, respectively.

[0009] According to the embodiment of the first aspect of this application, the temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor has the core working principle of constructing a closed-loop energy cascade utilization mechanism of "waste heat extraction - medium heat exchange - precise delivery": The system first transfers the sensible heat in the high-temperature acidic wastewater discharged from the pulping workshop to the low-temperature process water through the process water-acidic wastewater heat exchange unit, raising its temperature to meet the temperature range required for spraying and rinsing in the screen section and pressing section; at the same time, through the white water-black liquor heat exchange unit, the waste heat of the black liquor with high solids content and high calorific value is transferred to the circulating white water of the pulping machine, raising its temperature and using it as dilution water in the high-consistency tower to directly increase the pulp temperature; through the delivery pipeline unit, these two high-temperature media are precisely delivered to key temperature control nodes such as the warm water tank, white water tank and high-consistency tower in the pulping machine conveying section, thereby completely replacing or significantly reducing the traditional steam heating load without consuming additional high-quality steam. The system significantly improves economic efficiency. First, by replacing waste with new energy, it changes the energy consumption structure of the flow section, which relies on steam heating, and greatly reduces steam consumption and water costs during production. Second, it optimizes both environmental protection and energy efficiency, effectively recovering the heat energy that was originally discharged into the sewage system, reducing the thermal pollution load of cooling wastewater, and improving the overall thermal efficiency of the plant, meeting the needs of the paper industry for green and low-carbon transformation. Third, it enhances process stability. The dual independent heat exchangers, combined with the flow and temperature control of the conveying pipeline, can more flexibly and accurately match the temperature requirements of the pulping machine under different operating conditions, avoiding common problems of large temperature fluctuations and condensate impact in steam heating, thereby ensuring the stability of pulp flowability and improving the uniformity and quality of the final pulping product.

[0010] According to one embodiment of this application, the process water-acidic wastewater heat exchange unit includes a shell-and-tube heat exchanger; The hot-side inlet of the shell-and-tube heat exchanger is connected to the acidic wastewater conveying pipe of the pulping workshop, and the hot-side outlet is connected to the wastewater treatment system. The cold-side inlet of the shell-and-tube heat exchanger is connected to the process water supply pump, and the cold-side outlet is connected to the inlet of the warm water tank and the inlet of the white water tank of the pulping machine through branch pipelines.

[0011] According to one embodiment of this application, each of the branch pipelines is equipped with an electric regulating valve, a flow meter, a temperature sensor, and a central control controller; The temperature sensor is used to collect the temperature signal of the heated process water in real time and transmit it to the central control controller. The flow meter is used to monitor the instantaneous flow rate and cumulative flow rate of process water flowing through the corresponding branch pipeline in real time, and to feed back the instantaneous flow rate data and cumulative flow rate data to the central control controller. The central control controller is used to dynamically adjust the opening degree of the electric regulating valve based on the process water temperature signal, the instantaneous flow rate data, and the cumulative flow rate data.

[0012] According to one embodiment of this application, the white water-black liquor heat exchange unit includes a plate heat exchanger; The hot-side inlet of the plate heat exchanger is connected to the black liquor conveying pipe in the pulping workshop, and the hot-side outlet is connected to the black liquor post-treatment system in the pulping workshop. The cold-side inlet of the plate heat exchanger is connected to the white water delivery pump of the white water tank of the slurry machine, and the cold-side outlet is connected to the dilution water inlet of the high-concentration tower of the slurry machine.

[0013] According to one embodiment of this application, an electric regulating valve, a flow meter, a temperature sensor, and a central control controller are provided on the pipeline between the cold side outlet of the plate heat exchanger and the dilution water inlet of the high concentration tower. The temperature sensor is used to collect the temperature signal of the heated white water in real time and transmit it to the central control controller. The flow meter is used to monitor the instantaneous flow rate and cumulative flow rate of white water flowing through the pipeline in real time, and feeds back the instantaneous flow rate data and cumulative flow rate data to the central control controller; The central control controller is used to dynamically adjust the opening degree of the electric regulating valve based on the white water temperature signal, the instantaneous flow rate data, and the cumulative flow rate data.

[0014] According to one embodiment of this application, the outer wall of the delivery pipeline unit is wrapped with an insulation layer.

[0015] The second aspect of this application provides a temperature control method for a pulping machine conveying section temperature control system based on pulping waste heat recovery, as described in any of the first aspects above, comprising: The process water-acidic wastewater heat exchange process is started. Acidic wastewater from the pulping workshop is introduced into the hot side of the shell-and-tube heat exchanger in the process water-acidic wastewater heat exchange unit, and ambient temperature process water is introduced into the cold side of the shell-and-tube heat exchanger for countercurrent heat exchange to obtain high temperature process water. The high-temperature process water is transported in two ways: one way is injected into the warm water tank of the pulping machine, and the other way is injected into the white water tank of the pulping machine. Start the white water-black liquor heat exchange process, introduce the white water in the white water tank of the pulping machine into the cold side of the plate heat exchanger in the white water-black liquor heat exchange unit, and introduce the black liquor from the pulping workshop into the hot side of the plate heat exchanger for countercurrent heat exchange to obtain high temperature white water. The high-temperature white water is transported to the high-concentration tower of the pulping machine as dilution water, and mixed with the pulp to increase the pulp temperature.

[0016] According to one embodiment of this application, the high-temperature process water is transported in two routes, one route being injected into the warm water tank of the pulping machine and the other route being injected into the white water tank of the pulping machine, specifically as follows: Real-time collection of temperature and flow data at each injection point; The collected temperature and flow data are compared with the preset process target temperature and target flow values, respectively. If the temperature and flow data deviate from the preset values, the opening of the electric regulating valve on the corresponding pipeline will be automatically adjusted by the central control controller.

[0017] According to one embodiment of this application, the method further includes: Real-time monitoring of the temperature and flow rate of acidic wastewater and black liquor in the pulping workshop; When the temperature of acidic wastewater or black liquor is detected to be lower than the preset heat exchange threshold, or the flow is interrupted, the central control controller immediately issues an alarm signal and controls the bypass valve on the bypass pipeline of the corresponding heat exchange unit to open, while closing the inlet and outlet valves of the heat exchange unit. Automatically switch to standby heating mode or reduce the operating load of the pulping machine.

[0018] The third aspect of this application provides a pulp board production line, including a pulping workshop, a pulp board conveying section, and a temperature control system for the pulp board conveying section based on waste heat recovery from pulping waste liquid as described in any of the first aspects embodiments above. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 A schematic diagram of the interconnected structure of the process water-acidic wastewater heat exchange unit provided in an embodiment of this application; Figure 2This is a schematic diagram of the interconnected structure of the white water-black liquor heat exchange unit provided in an embodiment of this application. Detailed Implementation

[0020] To more clearly illustrate the overall concept of this application, a detailed explanation is provided below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below. It should be noted that, unless otherwise specified, the embodiments of this application and the features thereof can be combined with each other.

[0022] Furthermore, it should be understood in the description of this application that the terms "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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 this application.

[0023] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] In this application, unless otherwise expressly specified and limited, the "above" or "below" of the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0025] like Figures 1 to 2As shown, the first aspect of this application provides a temperature control system for the conveying section of a pulping machine based on waste heat recovery from pulping waste liquor, comprising: The process water-acidic wastewater heat exchange unit is configured to use the waste heat from the acidic wastewater generated in the pulping workshop to heat the process water. The white water-black liquor heat exchange unit is configured to use the waste heat of the black liquor generated in the pulping workshop to heat the white water in the pulping machine. The pipeline unit is connected to the process water-acidic wastewater heat exchange unit and the white water-black liquor heat exchange unit, respectively.

[0026] Firstly, the process water-acidic wastewater heat exchange unit, as the first-stage heat source recovery module of the system, typically adopts a corrosion-resistant shell-and-tube heat exchanger structure. Its hot side is connected to the acidic wastewater discharge pipeline of the pulping workshop, and its cold side is connected to the plant's process water supply network. This unit utilizes the medium- and low-temperature sensible heat carried by the acidic wastewater to preheat the ambient temperature process water, raising its temperature to meet the process temperature required for the screen spraying, felt cleaning, and warm water tank replenishment of the pulping machine. While achieving wastewater cooling for easier subsequent treatment, it significantly reduces the dependence on fresh steam for process water heating. Secondly, the white water-black liquor heat exchange unit, as the second-stage high-calorific-value recovery module, is designed with high efficiency and corrosion-resistant plate heat exchangers in mind, taking into account the high viscosity, high solids content, and strong corrosiveness of pulping black liquor. The hot side introduces high-temperature black liquor, while the cold side introduces circulating white water from the pulping machine. This unit uses the countercurrent heat exchange principle to transfer the high-grade heat energy contained in the black liquor to the white water, significantly increasing the temperature of the white water. Subsequently, the white water is used as high-temperature dilution water and directly enters the high-consistency tower to mix with the pulp, raising the pulp temperature from the source to improve fiber dispersibility and prevent flocculation. Finally, the delivery pipeline unit constitutes an energy transmission network connecting the heat exchange end and the application end. This unit not only includes the main and branch pipelines connecting the outlets of the two heat exchange units to various nodes of the pulper's conveying section (such as the warm water tank, white water tank, and high-consistency tower), but also integrates insulation layers, flow regulating valves, temperature sensors, and control valves. Its function is to ensure the stable delivery of the heated high-temperature medium under low heat loss conditions, and to dynamically adjust the flow rate and temperature ratio of each medium according to the instructions of the central control system, thereby achieving refined and automated control of the overall temperature field of the pulper's conveying section, ensuring the continuity of the production process and the stability of product quality.

[0027] The above structure eliminates the need for a steam heater for the spray water in the grid pressure section, and all spray water is supplied by the process water-acidic wastewater heat exchange unit.

[0028] Specifically, after the high-temperature white water enters the high-concentration tower, the slurry temperature can be raised to 60℃~65℃, the headbox head temperature can be increased by 5℃~10℃, the dewatering capacity of the headbox pressing section can be increased by more than 10%, and the steam consumption of the drying section can be reduced by 15%~30% after the headbox temperature is increased.

[0029] According to the embodiment of the first aspect of this application, the temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor has the core working principle of constructing a closed-loop energy cascade utilization mechanism of "waste heat extraction - medium heat exchange - precise delivery": The system first transfers the sensible heat in the high-temperature acidic wastewater discharged from the pulping workshop to the low-temperature process water through the process water-acidic wastewater heat exchange unit, raising its temperature to meet the temperature range required for spraying and rinsing in the screen section and pressing section; at the same time, through the white water-black liquor heat exchange unit, the waste heat of the black liquor with high solids content and high calorific value is transferred to the circulating white water of the pulping machine, raising its temperature and using it as dilution water in the high-consistency tower to directly increase the pulp temperature; through the delivery pipeline unit, these two high-temperature media are precisely delivered to key temperature control nodes such as the warm water tank, white water tank and high-consistency tower in the pulping machine conveying section, thereby completely replacing or significantly reducing the traditional steam heating load without consuming additional high-quality steam. The system significantly improves economic efficiency. First, by replacing waste with new energy, it changes the energy consumption structure of the flow section, which relies on steam heating, and greatly reduces steam consumption and water costs during production. Second, it optimizes both environmental protection and energy efficiency, effectively recovering the heat energy that was originally discharged into the sewage system, reducing the thermal pollution load of cooling wastewater, and improving the overall thermal efficiency of the plant, meeting the needs of the paper industry for green and low-carbon transformation. Third, it enhances process stability. The dual independent heat exchangers, combined with the flow and temperature control of the conveying pipeline, can more flexibly and accurately match the temperature requirements of the pulping machine under different operating conditions, avoiding common problems of large temperature fluctuations and condensate impact in steam heating, thereby ensuring the stability of pulp flowability and improving the uniformity and quality of the final pulping product.

[0030] Furthermore, the temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor provided in this application embodiment also achieves three levels of energy saving, specifically: Level 1 energy saving: Recovering waste heat from acidic wastewater to heat process water, completely eliminating steam heating of spray water in the grid pressure section.

[0031] Secondary energy saving: Recovering waste heat from black liquor to heat white water, increasing the headbox temperature of the high-concentration tower, and increasing the dewatering capacity of the grid pressure section by 10% to 25%.

[0032] Level 3 energy saving: The moisture content of the wet paper web at the wire pressing section is reduced, and the steam consumption of the drying section is reduced by 15% to 30% year-on-year.

[0033] Comprehensive energy saving: The total steam consumption in the pulp board workshop is reduced by 20% to 40%.

[0034] In some embodiments of this application, the process water-acidic wastewater heat exchange unit includes a shell-and-tube heat exchanger; The hot-side inlet of the shell-and-tube heat exchanger is connected to the acidic wastewater conveying pipe of the pulping workshop, and the hot-side outlet is connected to the wastewater treatment system. The cold-side inlet of the shell-and-tube heat exchanger is connected to the process water supply pump, and the cold-side outlet is connected to the inlet of the warm water tank and the white water tank of the pulping machine through branch pipes.

[0035] First, shell-and-tube heat exchangers, due to their robust structure, large flow cross-section, and strong anti-clogging capabilities, are particularly suitable for treating suspended impurities or fiber debris that may be present in acidic wastewater from pulping workshops. This effectively avoids the risk of downtime caused by blockage of the heat exchange channels. Furthermore, their corrosion-resistant materials (such as titanium or special stainless steel) can withstand the erosion of acidic wastewater for a long time, significantly extending the equipment's service life and reducing maintenance costs. Second, the design, which connects the hot-side inlet to the acidic wastewater delivery pipe and the outlet to the wastewater treatment system, achieves "online extraction" of waste heat resources. Without changing the original wastewater treatment process, it efficiently recovers the sensible heat of the originally directly discharged high-temperature wastewater. This reduces the temperature load when the wastewater enters the treatment system (beneficial for subsequent biochemical treatment) and transforms waste into a valuable high-temperature heat source. Finally, the cold-side outlet is connected to the warm water tank and the white water tank via branch pipes, achieving precise distribution and multi-functional utilization of heat energy: one branch injects high-temperature process water into the warm water tank, which can directly meet the strict water temperature requirements of the high-pressure spraying of the wire section and the cleaning of the felt, improving the dewatering efficiency; the other branch injects water into the white water tank, which raises the reference temperature of the entire white water circulation system, providing a stable heat source for the screening, dilution and rinsing processes. This dual-flow design, combined with subsequent flow control, allows the system to dynamically adjust the flow ratio of the two water sources according to different production conditions of the pulping machine (such as changes in machine speed and paper type switching), maximizing the utilization rate of waste heat while ensuring that the temperature of each hot spot meets the standard, completely replacing the traditional extensive mode of relying on separate steam heating, and significantly reducing steam consumption and operating costs.

[0036] In some embodiments of this application, each branch pipeline is equipped with an electric regulating valve, a flow meter, a temperature sensor, and a central control controller; Temperature sensors are used to collect the temperature signal of the heated process water in real time and transmit it to the central control controller; The flow meter is used to monitor the instantaneous and cumulative flow of process water flowing through the corresponding branch pipeline in real time, and to feed back the instantaneous and cumulative flow data to the central control controller. The central control controller is used to dynamically adjust the opening of the electric regulating valve based on the process water temperature signal, instantaneous flow data, and cumulative flow data.

[0037] By integrating electric regulating valves, flow meters, temperature sensors, and a central control controller into the branch pipelines, a high-precision closed-loop automatic feedback control system was constructed, significantly improving the intelligence level and process stability of temperature control in the pulping machine's flow section. First, the real-time monitoring function of the temperature sensor and flow meter eliminates the lag and blindness of traditional manual experience-based adjustments, enabling millisecond-level capture of deviations in process water temperature and flow caused by fluctuations in the heat source of pulping waste liquor or changes in pulping machine speed, ensuring the immediacy and accuracy of data feedback. Second, the central control controller, as the "brain" of the system, performs complex calculations based on the collected temperature signals and flow data, dynamically identifying the difference between current heat load demand and supply, and outputting precise control commands. Finally, the electric regulating valve executes these commands to quickly adjust its opening, achieving stepless and precise adjustment of the high-temperature process water flow rate and mixing temperature injected into the warm water tank and white water tank.

[0038] This automated control mechanism not only effectively overcomes the technical challenge of unstable waste heat source temperature, ensuring that each node in the flow section (such as wire spraying and felt cleaning) is always maintained within the optimal process temperature range, avoiding quality defects such as pulp flocculation and decreased paper uniformity caused by temperature fluctuations, but also prevents energy waste caused by overheating by optimizing heat distribution, truly realizing "unmanned" intelligent temperature control and ultimate energy efficiency management in the production process.

[0039] In some embodiments of this application, the white water-black liquor heat exchange unit includes a plate heat exchanger; The hot-side inlet of the plate heat exchanger is connected to the black liquor conveying pipe in the pulping workshop, and the hot-side outlet is connected to the black liquor post-treatment system in the pulping workshop. The cold-side inlet of the plate heat exchanger is connected to the white water transfer pump of the white water tank of the slurry machine, and the cold-side outlet is connected to the dilution water inlet of the high-concentration tower of the slurry machine.

[0040] First, plate heat exchangers possess extremely high heat transfer coefficients and compact structural designs, making them particularly suitable for heat exchange between media such as black liquor and white water, which have high viscosity or contain trace impurities. They can achieve highly efficient heat transfer with small temperature differences, maximizing the extraction of high-grade heat energy contained in the black liquor, significantly outperforming traditional shell-and-tube heat exchangers at low flow rates. Second, by directly connecting the cold-side outlet to the dilution water inlet of the high-consistency tower in the pulp mill, the pulp temperature is increased at the source: high-temperature white water is used as dilution water and directly mixed with the concentrated pulp in the high-consistency tower. Utilizing the high specific heat capacity of water, the overall pulp temperature is rapidly increased, effectively reducing pulp viscosity and improving fiber dispersion in water. This prevents fiber flocculation during subsequent flow processes from the source, providing the headbox with pulp of uniform temperature and excellent flowability, thereby significantly improving the uniformity and physical strength of the paper. Finally, this flow path utilizes the white water circulating inside the pulping machine as a refrigerant, which not only solves the problem that the white water system usually requires additional heating, but also avoids the energy waste caused by the direct discharge of black liquor heat. It realizes cross-process thermal energy coupling between the pulping workshop (heat source end) and the papermaking workshop (heat consumption end), which significantly reduces the steam consumption of the entire plant while optimizing the thermal balance of the entire production line.

[0041] In some embodiments of this application, an electric regulating valve, a flow meter, a temperature sensor, and a central control controller are installed on the pipeline between the cold side outlet of the plate heat exchanger and the dilution water inlet of the high concentration tower. The temperature sensor is used to collect the temperature signal of the heated white water in real time and transmit it to the central control controller; The flow meter is used to monitor the instantaneous and cumulative flow of white water flowing through the pipeline in real time, and feeds back the instantaneous and cumulative flow data to the central control controller. The central control unit is used to dynamically adjust the opening of the electric regulating valve based on the white water temperature signal, instantaneous flow data, and cumulative flow data.

[0042] By integrating an electric regulating valve, flow meter, temperature sensor, and central controller into the key pipeline from the cold-side outlet of the plate heat exchanger to the dilution water inlet of the high-consistency tower, a high-precision closed-loop temperature control system targeting the core temperature zone of the slurry was constructed, solving the technical problems of large temperature fluctuations and slow response under traditional open-loop control. Specifically, the temperature sensor captures the temperature of the white water after heating with black liquor in real time, enabling immediate detection of heat source disturbances caused by changes in black liquor concentration or flow fluctuations; the flow meter accurately measures the amount of dilution water entering the high-consistency tower, providing crucial material balance data for the central controller; based on these two sets of real-time data, combined with a preset target slurry temperature model, the central controller dynamically calculates and outputs commands using advanced algorithms such as PID, driving the electric regulating valve to adjust its opening in milliseconds.

[0043] This control strategy ensures that regardless of fluctuations in the black liquor heat source at the pulping end, the temperature and flow rate of the dilution water entering the high-consistency tower remain at their optimal set values, thus guaranteeing the temperature uniformity and stability of the pulp during mixing. This not only effectively avoids problems such as increased pulp viscosity, uneven fiber dispersion, and flocculation caused by excessively low temperatures, but also prevents the risk of adhesive precipitation or equipment scaling caused by excessively high temperatures. It significantly improves the flow performance of the pulp in the delivery section and the uniformity and strength of the final pulp board product. At the same time, the system achieves "on-demand supply" of dilution water heat, eliminating energy waste caused by overheating, and further improving the energy efficiency and automated operation reliability of the entire production line.

[0044] In some embodiments of this application, the outer wall of the conveying pipeline unit is wrapped with an insulation layer. The insulation layer (such as high-efficiency thermal insulation materials such as polyurethane, rock wool, or aluminum silicate fiber) constructs a thermal barrier with a low thermal conductivity, significantly reducing radial heat loss of high-temperature process water and high-temperature white water during long-distance transportation. This ensures that the temperature drop of the medium from the heat exchange unit outlet to each hot spot (warm water tank, white water tank, high-consistency tower) in the pulp mill flow section is minimized, thereby maximizing the actual utilization rate of waste heat recovery and avoiding the phenomenon of "overheating at the front end and insufficient heat at the back end" caused by pipeline heat dissipation, reducing dependence on auxiliary heating sources. Secondly, a stable conveying temperature is crucial for pulp production. The insulation measures effectively eliminate medium temperature fluctuations caused by changes in ambient temperature (such as low temperatures in winter or diurnal temperature differences), ensuring a constant temperature of process water and dilution water entering the flow system, thereby guaranteeing the uniformity of pulp viscosity, dispersibility, and paper quality. Finally, the insulation layer also serves as a safety protection and anti-condensation function: on the one hand, it reduces the temperature of the outer surface of the pipeline, preventing operators from being burned by accidental contact with the high-temperature pipe wall and improving the workshop working environment; on the other hand, in the humid papermaking workshop environment, the insulation layer can prevent condensation from forming on the outer wall of the pipeline in the low-temperature season, avoiding the adverse effects of dripping water on electrical equipment, paper surface or anti-slip floor, extending the service life of the pipeline system and improving the overall operational safety.

[0045] A second aspect of this application provides a temperature control method for a pulping machine conveying section temperature control system based on waste heat recovery from pulping waste liquor, as described in any of the embodiments of the first aspect above, comprising: Step 100: Start the process water-acidic wastewater heat exchange process. Introduce the acidic wastewater from the pulping workshop into the hot side of the shell-and-tube heat exchanger in the process water-acidic wastewater heat exchange unit, and introduce the ambient temperature process water into the cold side of the shell-and-tube heat exchanger for countercurrent heat exchange to obtain high temperature process water.

[0046] Step 200: The high-temperature process water is transported in two ways, one of which is injected into the warm water tank of the pulping machine, and the other of which is injected into the white water tank of the pulping machine.

[0047] Step 300: Start the white water-black liquor heat exchange process. Introduce the white water from the white water tank of the pulping machine into the cold side of the plate heat exchanger in the white water-black liquor heat exchange unit, and introduce the black liquor from the pulping workshop into the hot side of the plate heat exchanger for countercurrent heat exchange to obtain high-temperature white water.

[0048] Step 400: High-temperature white water is transported to the high-consistency tower of the pulping machine as dilution water, and mixed with the pulp to increase the pulp temperature.

[0049] Step 100, as the system's heat source extraction and primary heating stage, focuses on establishing an efficient heat exchange channel between acidic wastewater and process water. This step involves introducing high-temperature acidic wastewater from the pulping workshop onto the hot side of a shell-and-tube heat exchanger, utilizing its sensible heat to counter-currently heat the ambient-temperature process water input to the cold side. The counter-current heat exchange method maximizes the average temperature difference between the hot and cold fluids, thereby achieving the highest heat recovery efficiency within a limited heat exchange area and ensuring that the produced high-temperature process water consistently meets process requirements. This step not only achieves immediate capture of waste heat energy but also ensures the continuity of the flow of impurity-laden acidic wastewater through the anti-clogging characteristics of the shell-and-tube structure, providing a stable and clean high-temperature heat source for subsequent processes and directly replacing the energy consumption of traditional steam heating of process water.

[0050] Step 200 employs a multi-point precise heat energy distribution strategy to address the differentiated hot water requirements of different sections of the pulping machine. This step divides the high-temperature process water prepared in step 100 into two streams via an intelligent diversion system: one stream is injected into a warm water tank, primarily serving the high-pressure spraying of the wire section and the cleaning of the felt, utilizing the high temperature to reduce the surface tension and viscosity of the water, significantly improving dewatering efficiency and cleaning effect; the other stream is injected into a white water tank to raise the reference temperature of the entire white water circulation system, providing a preheating medium for screening, dilution, and various rinsing processes. This dual-path parallel delivery mechanism breaks through the limitations of traditional single-path heating, achieving tiered utilization and on-demand distribution of heat energy. It ensures temperature stability in key forming sections and optimizes the heat distribution in the plant's overall water balance system, avoiding the negative impact of localized overheating or undercooling on paper quality.

[0051] Step 300 constitutes the deep waste heat recovery and high-grade thermal energy conversion stage of the system, focusing on using black liquor, a high-calorific-value waste liquid, to raise the temperature of the circulating white water inside the pulp mill. This step draws white water from the white water tank into the cold side of a plate heat exchanger, where it undergoes efficient countercurrent heat exchange with the high-temperature black liquor from the pulping workshop on the hot side. Since the temperature of black liquor is typically much higher than that of acidic wastewater, this step can obtain a higher-temperature heat source, making it particularly suitable for the temperature-sensitive pulp dilution process. The high heat transfer coefficient of the plate heat exchanger ensures that a large amount of heat can be transferred even with minimal temperature differences, converting the waste heat of the black liquor, which would otherwise require cooling, into high-quality thermal energy that can be directly used for pulp temperature control. This significantly improves the overall plant's thermal energy utilization rate while reducing the cooling load of the black liquor before it enters the evaporation section.

[0052] Step 400 is the final execution of temperature control and a core process optimization step, directly determining the rheological properties of the pulp and the quality of the finished paper. In this step, the high-temperature white water prepared in step 300 is used as dilution water and directly pumped into the high-consistency tower of the pulp mill to mix with the high-concentration pulp. Utilizing the high specific heat capacity of water, the high-temperature dilution water can rapidly and uniformly raise the overall temperature of the pulp, effectively reducing pulp viscosity and improving the dispersion of fibers in the aqueous phase, preventing fiber flocculation and agglomeration from the source. This process not only ensures that the pulp entering the headbox has excellent flowability and temperature uniformity, significantly improving the stability of the basis weight and physical strength of the pulp sheet, but also completely eliminates the dependence on direct steam injection heating of the pulp, avoiding the dilution interference of steam condensate on the pulp concentration, achieving the dual goals of energy saving and consumption reduction, and product quality improvement.

[0053] In the above method, high-temperature white water is sent into a high-consistency tower to mix with the pulp, raising the pulp temperature to the target wire-connecting temperature range. This allows the pulp to maintain optimal fluidity and dewatering performance when it is wire-connected in the headbox, improving the dewatering rate of the wire pressing section and reducing the moisture content of the paper web entering the drying section, thereby reducing the steam consumption of the drying section.

[0054] In some embodiments of this application, the high-temperature process water is delivered in two routes: one route is injected into the warm water tank of the pulping machine, and the other route is injected into the white water tank of the pulping machine. Specifically: Real-time collection of temperature and flow data at each injection point; The collected temperature and flow data are compared with the preset process target temperature and target flow values, respectively. If the temperature and flow data deviate from the preset values, the opening of the electric regulating valve on the corresponding pipeline will be automatically adjusted by the central control controller.

[0055] The process of delivering high-temperature process water through two channels and injecting it into the warm water tank and white water tank of the pulping machine is specifically refined into a dynamic closed-loop control mechanism based on real-time data feedback. This mechanism first uses a high-precision sensor network to collect temperature and flow data from the two branches injected into the warm water tank and white water tank in milliseconds, establishing a comprehensive understanding of the heating status. Then, the central control controller performs high-frequency comparison calculations between the collected real-time data and preset process target temperature and flow values ​​to accurately identify the deviation between the current heat supply and actual demand. Once a deviation from the preset allowable range is detected (such as temperature / flow anomalies caused by heat source fluctuations or changes in production load), the central control controller immediately outputs a correction command, driving the electric regulating valve on the corresponding pipeline to perform stepless opening adjustment. This automated control strategy of "monitoring-comparison-execution" not only eliminates the lag and error of manual adjustment, ensuring that the warm water tank and white water tank are always maintained in the optimal process temperature range, guaranteeing the stability of the dewatering efficiency of the screen section and the thermal balance of the white water system, but also realizes the precise allocation of thermal energy resources on demand, effectively avoiding energy waste caused by excessive heating or quality defects caused by insufficient heating, and significantly improving the intelligence level and robustness of the temperature control of the pulper's flow section.

[0056] In some embodiments of this application, the method further includes: Real-time monitoring of the temperature and flow rate of acidic wastewater and black liquor in the pulping workshop; When the temperature of acidic wastewater or black liquor is detected to be lower than the preset heat exchange threshold, or the flow is interrupted, the central control controller immediately issues an alarm signal and controls the bypass valve on the bypass pipeline of the corresponding heat exchange unit to open, while closing the inlet and outlet valves of the heat exchange unit. Automatically switch to standby heating mode or reduce the operating load of the pulping machine.

[0057] This method further introduces a heat source anomaly monitoring and emergency protection mechanism, significantly improving the reliability and safety of system operation. This mechanism constructs a 24 / 7 monitoring network for heat source stability by real-time monitoring of the temperature and flow rate of acidic wastewater and black liquor in the pulping workshop. Once the heat source temperature is detected to be below the preset heat exchange threshold (leading to failure to meet process requirements) or a flow interruption occurs (potentially causing the heat exchanger to burn out or the refrigerant to become too cold), the central control controller will immediately trigger a multi-level response: first, it will issue an audible and visual alarm signal to prompt operator intervention; simultaneously, it will quickly execute valve switching actions, opening the bypass valve on the bypass pipeline and closing the inlet and outlet valves of the heat exchange unit, allowing the medium to bypass the faulty heat exchanger and flow directly, preventing the low-temperature medium from impacting downstream processes or damaging equipment. Next, the system automatically executes the contingency plan, seamlessly switching to the backup steam heating mode to maintain production continuity, or intelligently reducing the pulping machine's operating load to match the current heat supply level when backup capacity is insufficient. This series of automated protection measures effectively avoids the risks of pulp temperature runaway, fiber flocculation and equipment thermal shock caused by heat source fluctuations, ensuring that the pulp board production line can still operate safely and orderly under extreme conditions, minimizing unplanned downtime and product quality loss.

[0058] The third aspect of this application provides a pulp board production line, including a pulping workshop, a pulp board conveying section, and a temperature control system for the pulp board conveying section based on waste heat recovery from pulping waste liquid, as described in any of the first aspects above.

[0059] According to the pulp board production line provided in the third aspect of this application, a cross-process thermal energy coupling and closed-loop ecological production system is constructed by deeply integrating the pulping workshop, the pulp board machine conveying section, and the aforementioned waste heat recovery temperature control system. This process line breaks through the energy utilization barriers in the traditional pulping and papermaking process, transforming the high-temperature acidic wastewater and black liquor that the pulping workshop originally bore the burden of cooling treatment into a high-quality heat source urgently needed by the pulp board machine conveying section. Specifically, the waste liquid discharge outlet of the pulping workshop is directly connected to the heat exchange unit of the temperature control system. After being cooled by heat exchange, the waste liquid enters the subsequent treatment system, reducing the heat load of wastewater treatment. The released heat is precisely injected into the warm water tank, white water tank, and high-consistency tower of the pulp board machine conveying section, completely replacing or significantly reducing the dependence on external fresh steam. This integrated design not only enables the tiered utilization and internal circulation of heat energy throughout the plant, significantly reducing steam consumption per ton of paper and operating costs, but also optimizes the temperature field of the pulp in the flow section through a stable waste heat supply, improving fiber dispersion and paper uniformity. At the same time, the process line has a high degree of automation and robustness, and can adapt to fluctuations in different paper types and production loads, creating a modern pulp board production demonstration line for paper manufacturing enterprises that integrates green and low-carbon, energy-saving and efficient, and stable quality.

[0060] For any parts not mentioned in this application, existing technologies may be used or referenced.

[0061] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0062] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A temperature control system for the conveying section of a pulping machine based on waste heat recovery from pulping waste liquor, characterized in that, include: The process water-acidic wastewater heat exchange unit is configured to use the waste heat from the acidic wastewater generated in the pulping workshop to heat the process water. The white water-black liquor heat exchange unit is configured to use the waste heat of the black liquor generated in the pulping workshop to heat the white water in the pulping machine. The conveying pipeline unit is connected to the process water-acidic wastewater heat exchange unit and the white water-black liquor heat exchange unit, respectively.

2. The temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor according to claim 1, characterized in that, The process water-acidic wastewater heat exchange unit includes a shell-and-tube heat exchanger. The hot-side inlet of the shell-and-tube heat exchanger is connected to the acidic wastewater conveying pipe of the pulping workshop, and the hot-side outlet is connected to the wastewater treatment system. The cold-side inlet of the shell-and-tube heat exchanger is connected to the process water supply pump, and the cold-side outlet is connected to the inlet of the warm water tank and the inlet of the white water tank of the pulping machine through branch pipelines.

3. The temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor according to claim 2, characterized in that, Each branch pipeline is equipped with an electric regulating valve, a flow meter, a temperature sensor, and a central control controller; The temperature sensor is used to collect the temperature signal of the heated process water in real time and transmit it to the central control controller. The flow meter is used to monitor the instantaneous flow rate and cumulative flow rate of process water flowing through the corresponding branch pipeline in real time, and to feed back the instantaneous flow rate data and cumulative flow rate data to the central control controller. The central control controller is used to dynamically adjust the opening degree of the electric regulating valve based on the process water temperature signal, the instantaneous flow rate data, and the cumulative flow rate data.

4. The temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor according to claim 1, characterized in that, The white water-black liquor heat exchange unit includes a plate heat exchanger; The hot-side inlet of the plate heat exchanger is connected to the black liquor conveying pipe in the pulping workshop, and the hot-side outlet is connected to the black liquor post-treatment system in the pulping workshop. The cold-side inlet of the plate heat exchanger is connected to the white water delivery pump of the white water tank of the slurry machine, and the cold-side outlet is connected to the dilution water inlet of the high-concentration tower of the slurry machine.

5. The temperature control system for the pulping machine conveying section based on waste heat recovery from pulping waste liquor according to claim 4, characterized in that, An electric regulating valve, a flow meter, a temperature sensor, and a central control controller are installed on the pipeline between the cold side outlet of the plate heat exchanger and the dilution water inlet of the high concentration tower. The temperature sensor is used to collect the temperature signal of the heated white water in real time and transmit it to the central control controller. The flow meter is used to monitor the instantaneous flow rate and cumulative flow rate of white water flowing through the pipeline in real time, and feeds back the instantaneous flow rate data and cumulative flow rate data to the central control controller; The central control controller is used to dynamically adjust the opening degree of the electric regulating valve based on the white water temperature signal, the instantaneous flow rate data, and the cumulative flow rate data.

6. The temperature control system for the conveying section of a pulping machine based on waste heat recovery from pulping waste liquor according to any one of claims 1 to 5, characterized in that, The outer wall of the delivery pipeline unit is covered with an insulation layer.

7. A temperature control method for a pulping machine conveying section temperature control system based on waste heat recovery from pulping waste liquor, as described in any one of claims 1 to 6, characterized in that, include: The process water-acidic wastewater heat exchange process is started. Acidic wastewater from the pulping workshop is introduced into the hot side of the shell-and-tube heat exchanger in the process water-acidic wastewater heat exchange unit, and ambient temperature process water is introduced into the cold side of the shell-and-tube heat exchanger for countercurrent heat exchange to obtain high temperature process water. The high-temperature process water is transported in two ways: one way is injected into the warm water tank of the pulping machine, and the other way is injected into the white water tank of the pulping machine. Start the white water-black liquor heat exchange process, introduce the white water in the white water tank of the pulping machine into the cold side of the plate heat exchanger in the white water-black liquor heat exchange unit, and introduce the black liquor from the pulping workshop into the hot side of the plate heat exchanger for countercurrent heat exchange to obtain high temperature white water. The high-temperature white water is transported to the high-concentration tower of the pulping machine as dilution water, and mixed with the pulp to increase the pulp temperature.

8. The temperature control method according to claim 7, characterized in that, The high-temperature process water is transported in two routes: one route is injected into the warm water tank of the pulping machine, and the other route is injected into the white water tank of the pulping machine. Specifically: Real-time collection of temperature and flow data at each injection point; The collected temperature and flow data are compared with the preset process target temperature and target flow values, respectively. If the temperature and flow data deviate from the preset values, the opening of the electric regulating valve on the corresponding pipeline will be automatically adjusted by the central control controller.

9. The temperature control method according to claim 7, characterized in that, The method also includes: Real-time monitoring of the temperature and flow rate of acidic wastewater and black liquor in the pulping workshop; When the temperature of acidic wastewater or black liquor is detected to be lower than the preset heat exchange threshold, or the flow is interrupted, the central control controller immediately issues an alarm signal and controls the bypass valve on the bypass pipeline of the corresponding heat exchange unit to open, while closing the inlet and outlet valves of the heat exchange unit. Automatically switch to standby heating mode or reduce the operating load of the pulping machine.

10. A pulp board production line, characterized in that, It includes a pulping workshop, a pulping machine conveying section, and a pulping machine conveying section temperature control system based on waste heat recovery from pulping waste liquid as described in any one of claims 1 to 6.

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