A heat recovery system applied to the production process of lyocell fibers

Abstract

The application discloses a heat recovery system applied to a lyocell fiber production process and relates to the technical field of lyocell fiber production. The system comprises a cyclone plate tower, an inner circulation water tank and a heat exchanger, and a spraying assembly arranged at the top of the cyclone plate tower. The inner circulation water tank is used for collecting high-temperature inner circulation water sprayed by the spraying assembly and subjected to heat exchange with drying tail gas flowing into the bottom of the cyclone plate tower, and the high-temperature inner circulation water is transmitted to the heat exchanger. The heat exchanger is used for cooling the high-temperature inner circulation water by using collected steam condensate water generated in the lyocell fiber production process, and the steam condensate water after being heated is introduced into a raw material end of a lyocell fiber production line, and the inner circulation water after being cooled is introduced into the spraying assembly. The system realizes efficient recovery of waste heat of the drying tail gas, builds a closed loop circulation system of the steam condensate water, reduces steam consumption in the lyocell fiber production, and solves double energy waste in the drying link of the lyocell fiber.

Description

Technical Field

[0001] This application relates to the field of lyocell fiber production technology, and more particularly to a heat recovery system applied in the lyocell fiber production process. Background Technology

[0002] In the production process of lyocell fiber, the spinning workshop needs to use steam to dry the moisture in the lyocell staple fiber. However, in the process of the high-temperature gas discharged from the drying process into the atmosphere, not only is the heat of the high-temperature exhaust gas not recovered, but additional cooling is also required to cool it down, resulting in double energy waste.

[0003] Therefore, there is an urgent need for a system to recover the heat from the high-temperature exhaust gas generated during the production of lyocell fibers, in order to reduce energy consumption during the production process. Utility Model Content

[0004] In view of the above problems, this application provides a heat recovery system applied to the production process of lyocell fibers, so as to recover the heat of high-temperature exhaust gas generated during the production process and reduce energy consumption in the production process. The specific solution is as follows:

[0005] The first aspect of this application provides a heat recovery system for use in the production process of lyocell fiber, comprising: a cyclone plate tower, an internal circulating water tank and a heat exchanger, and a spray assembly disposed at the top of the cyclone plate tower;

[0006] The bottom inlet of the cyclone plate tower is connected to the drying exhaust outlet to receive the drying exhaust gas;

[0007] The internal circulating water tank is located at the bottom of the cyclone plate tower, collects the high-temperature internal circulating water sprayed by the spray assembly and after heat exchange with the drying exhaust gas, and transmits the high-temperature internal circulating water to the heat exchanger.

[0008] The inlet of the heat exchanger is connected to the steam condensate outlet of the lyocell fiber production line to collect the steam condensate generated during the lyocell fiber production process. The steam condensate is used to cool the high-temperature internal circulating water, and the heated steam condensate is introduced into the raw material end of the lyocell fiber production line. The cooled internal circulating water is then introduced into the spray assembly.

[0009] In one possible implementation, it further includes: a circulation pump disposed between the internal circulating water tank and the heat exchanger, the circulation pump being used to drive the high-temperature internal circulating water to flow to the heat exchanger.

[0010] In one possible implementation, it further includes a filter disposed between the internal circulating water tank and the heat exchanger for filtering particulate matter in the high-temperature internal circulating water.

[0011] In one possible implementation, the spray assembly is an atomizing nozzle or a variable orifice nozzle.

[0012] In one possible implementation, the spray assembly is provided with a gas composition detector and a reagent mixer;

[0013] The gas composition detector is installed at the bottom inlet of the cyclone plate tower to detect the composition of the drying tail gas.

[0014] The reagent mixer mixes the corresponding reagent into the internal circulating water to be sprayed according to the composition of the exhaust gas.

[0015] In one possible implementation, it also includes: a temperature sensor and a first regulating valve disposed at the bottom of the cyclone plate tower;

[0016] The temperature sensor is used to detect the temperature of the drying exhaust gas flowing into the cyclone plate tower and transmit the detected temperature information to the first regulating valve.

[0017] The first regulating valve is used to open the valve when the temperature information meets the preset cooling conditions, so that the spray assembly sprays the internal circulating water.

[0018] In one possible implementation, it further includes: a gas flow sensor disposed at the bottom of the cyclone plate tower, used to detect the flow rate of the drying tail gas flowing into the cyclone plate tower, and to transmit the detected flow information to the first regulating valve;

[0019] The first regulating valve adjusts the valve opening according to the flow information to adjust the amount of internal circulating water sprayed by the spray assembly.

[0020] In one possible implementation, the internal circulating water tank includes: a liquid level sensor and a second regulating valve;

[0021] The liquid level sensor is used to detect the water level in the internal circulating water tank and transmit the water level in the internal circulating water tank to the second regulating valve;

[0022] The second regulating valve is used to open the valve when the water level in the internal circulating water tank reaches the replenishment water level, so as to replenish water to the internal circulating water tank until the water level in the internal circulating water tank reaches the full water level.

[0023] In one possible implementation, the second regulating valve is an electronic regulating valve or a solenoid valve.

[0024] In one possible implementation, the heat exchanger is a plate heat exchanger.

[0025] By employing the above technical solution, the heat recovery system provided in this application for the production process of lyocell fiber significantly reduces the temperature of the exhaust gas and ensures its safe emission through direct heat exchange between the internal circulating water sprayed inside the cyclone plate tower and the high-temperature drying exhaust gas. Simultaneously, the waste heat captured from the drying exhaust gas is used through a heat exchanger to heat the steam condensate generated during the lyocell fiber production process. The heated steam condensate is directly returned to the raw material end of the lyocell fiber production line to participate in the next round of fiber production, while the internal circulating water, after releasing heat, returns to the spray assembly for the next round of spraying.

[0026] This system replaces the additional cooling capacity with steam condensate from the lyocell fiber production process, enabling the captured heat to be reused and achieving efficient recovery of waste heat from the drying exhaust. At the same time, it constructs a closed-loop circulation system for steam condensate, reducing steam consumption in lyocell fiber production and solving the dual energy waste in the lyocell fiber drying process. Attached Figure Description

[0027] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0028] Figure 1 A schematic diagram of a heat recovery system applied in the production process of lyocell fiber is provided as an embodiment of this application;

[0029] Figure 2 An example diagram illustrating the application of PCL water is provided in an embodiment of this application;

[0030] Figure 3 This is an example diagram illustrating another application of PCL water provided in an embodiment of this application.

[0031] Figure label:

[0032] A - Steam condensate outlet of the lyocell fiber production line; B - Raw material end of the lyocell fiber production line; P - Circulation pump; P1 - Steam-driven feed water pump; P2 - Electric feed water pump; T - Temperature sensor. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. In the description of the present utility model, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," 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 the present utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model. For those skilled in the art, the specific meaning of the above terms in the present utility model can be understood according to the specific circumstances. Multiple technical solutions in the same embodiment, as well as multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions that do not contradict or conflict, all of which are within the scope of protection claimed by the present utility model.

[0034] This application can be applied to the field of lyocell fiber production. The following is an example of a heat recovery system for lyocell fiber production, which is used to recover heat in the lyocell fiber production process and utilize the recovered heat.

[0035] Reference Figure 1 The present application provides a schematic diagram of a heat recovery system applied to the production process of lyocell fiber. The heat recovery system applied to the production process of lyocell fiber includes: a cyclone plate tower, an internal circulating water tank and a heat exchanger, and a spray assembly disposed at the top of the cyclone plate tower.

[0036] The bottom inlet of the cyclone plate tower is connected to the drying exhaust outlet to receive the drying exhaust gas; the internal circulating water tank is set at the bottom of the cyclone plate tower to collect the high-temperature internal circulating water sprayed by the spraying components and after heat exchange with the drying exhaust gas.

[0037] Inside the cyclone separator, the drying exhaust gas generated during the lyocell fiber production process enters from the bottom, forming a high-speed rotating upward airflow. Its initial temperature is typically above 60°C, and it may also carry a large amount of sensible heat and small amounts of dust, volatile organic compounds, and other impurities. Simultaneously, cooled internal circulating water falls from the top of the cyclone separator through a spray system; the temperature of the cooled internal circulating water is generally around 30°C.

[0038] When the high-temperature drying exhaust gas from the bottom up and the low-temperature internal circulating water from the top down come into countercurrent contact within the tower, the heat in the drying exhaust gas is rapidly transferred to the surface of the liquid droplets in the internal circulating water through forced convection and phase change heat transfer. This causes the liquid temperature to rise sharply to near the temperature at the inlet of the drying exhaust gas within a short contact time, while the temperature of the drying exhaust gas drops significantly due to heat exchange. During this process, the centrifugal force generated by the cyclone plate throws the liquid in the internal circulating water against the tower wall, forming a liquid film, which prolongs the gas-liquid contact time and enhances the heat exchange efficiency. Furthermore, the components in the drying exhaust gas can be captured by the liquid droplets in the internal circulating water, and some volatile substances in the drying exhaust gas are absorbed or condensed, ultimately achieving heat recovery, gas cooling, and preliminary purification of the drying exhaust gas.

[0039] The dried exhaust gas, cooled down after heat exchange, is discharged from the top of the cyclone plate tower, while the heated internal circulating water (high-temperature internal circulating water) flows along the tower wall into the internal circulating water tank at the bottom of the cyclone plate tower.

[0040] The outlet of the internal circulating water tank is connected to the inlet of the heat exchanger to transfer high-temperature internal circulating water to the heat exchanger. The inlet of the heat exchanger is connected to the outlet A of the steam condensate of the lyocell fiber production line to collect the steam condensate generated during the lyocell fiber production process. The steam condensate is used to cool the high-temperature internal circulating water, and the heated steam condensate is introduced into the raw material end B of the lyocell fiber production line. The cooled internal circulating water is then introduced into the spray assembly.

[0041] The outlet of the internal circulating water tank is directly connected to the inlet of the heat exchanger via a pipeline, continuously supplying the high-temperature internal circulating water, after absorbing heat, to the interior of the heat exchanger. Simultaneously, the condensate from the steam generated by the lyocell fiber production line flows into the inlet of the heat exchanger through a separate pipeline, forming a counter-current contact with the high-temperature internal circulating water. In one possible implementation, the heat exchanger is a plate heat exchanger, with the outlet of the internal circulating water tank and the steam condensate outlet connected to the inlets on both sides of the heat exchanger, allowing the hot and cold fluids to enter the gaps between the plates on both sides of the heat exchanger and exchange heat through the plate surfaces.

[0042] Inside the heat exchanger, the relatively low-temperature steam condensate acts as a cooling medium, absorbing heat from the high-temperature internal circulating water. This reduces the internal circulating water temperature to the spray temperature required by the process. The cooled internal circulating water is then transported through pipelines to the spray assembly, which can use atomizing nozzles or variable-aperture nozzles. The cooled internal circulating water is then used as the medium mentioned above for cooling the drying exhaust gas in the cyclone plate tower, exchanging heat with the drying exhaust gas again. Meanwhile, the steam condensate, after absorbing heat and heating up, is reintroduced into the raw material end of the lyocell fiber production line through the heat exchanger outlet to participate in subsequent fiber spinning. This forms a closed-loop system of internal circulating water and condensate circulation, achieving closed-loop utilization of the heat carried by the drying exhaust gas and the cold energy carried by the steam condensate, improving the efficient use of resources in the lyocell fiber production process and reducing resource waste.

[0043] In summary, the heat recovery system provided in this application for the production process of lyocell fiber significantly reduces the temperature of the exhaust gas and ensures its safe emission through direct contact heat exchange between the internal circulating water sprayed in the cyclone plate tower and the high-temperature drying exhaust gas. Simultaneously, the waste heat captured from the drying exhaust gas is used to heat the steam condensate generated during the lyocell fiber production process via a heat exchanger. The heated steam condensate is then directly returned to the raw material end of the lyocell fiber production line to participate in the next round of fiber production, while the internal circulating water, after releasing heat, returns to the spray assembly for the next round of spraying. This system replaces the additional cold energy introduced by using steam condensate from the lyocell fiber production process, enabling the capture heat to be reused and achieving efficient recovery of waste heat from the drying exhaust gas. It also constructs a closed-loop circulation system for the steam condensate, reducing steam consumption in lyocell fiber production and solving the dual energy waste in the lyocell fiber drying process.

[0044] In one possible implementation, the steam condensate could be PCL water (containing trace amounts of NMMO solvent) regenerated from the ion exchange beds in the spinning and scouring workshop of a lyocell fiber production line. Its temperature is relatively low, and it would require heating for reuse, as described above. Figure 2 The present application provides an example diagram of the application of PCL water, which is heated by steam condensate (such as pure water).

[0045] In this process, the steam condensate is used in the boiler feedwater stage of lyocell fiber production. An electric deaerator uses steam to heat the steam condensate to saturation temperature, and then provides high-pressure feedwater to the boiler via steam-driven feedwater pump P1 and electric feedwater pump P2. However, due to heat exchange between the steam condensate and the PCL water, the temperature of the steam condensate entering the boiler feedwater process is relatively low. For example, the original 80°C steam condensate only reaches 40°C after heat exchange with the PCL water. After the temperature sensor T in the boiler feedwater stage detects this temperature, it requires even more steam to reheat the steam condensate.

[0046] Therefore, the heat recovery system provided in this application for the production of lyocell fibers is introduced into the lyocell fiber production process, referring to... Figure 3 The embodiment of this application provides another example of PCL water application. The PCL water is heated using heat absorbed from the drying exhaust gas, and then flows into the spinning workshop, achieving PCL water recycling. Furthermore, compared to the original PCL water heat exchange method, the heat of the steam condensate is recovered, increasing the temperature of the steam condensate sent to the power plant deaerator. For example, if it flows into the power plant deaerator at 80°C before heat exchange, the steam energy consumption of the power plant deaerator is reduced. Simultaneously, the heat exchanger used for heat exchange between the steam condensate and PCL water is eliminated.

[0047] Optionally, the heat exchanger used for heat exchange between steam condensate and PCL water can also be kept as a backup. When the cyclone plate tower fails or other unexpected situations occur, the heat exchanger can be put back into use to maintain the circulation of PCL water.

[0048] Next, through the following embodiments, other possible implementations of a heat recovery system applied to the lyocell fiber production process provided in this application will be described.

[0049] In one possible implementation, refer to Figure 3 The heat recovery system applied to the lyocell fiber production process also includes: a circulation pump P located between the internal circulating water tank and the heat exchanger, which drives the high-temperature internal circulating water to the heat exchanger.

[0050] A circulating pump drives liquid to circulate in a closed system. In this embodiment, the circulating pump is positioned between the inner circulating water tank and the heat exchanger to drive the high-temperature internal circulating water output from the inner circulating water tank to the heat exchanger. It is understood that while the inner circulating water tank is located at the bottom of the cyclone separator and has a certain liquid level, the heat exchanger is positioned high enough to directly deliver the heat-exchanged internal circulating water to the spray assembly at the top of the tower. The liquid level in the inner circulating water tank is insufficient to drive the water flow to the heat exchanger inlet. Therefore, this embodiment provides a circulating pump to provide kinetic energy for the internal circulating water flow to the heat exchanger, promoting water circulation in the system.

[0051] In one possible implementation, the heat recovery system applied to the lyocell fiber production process also includes a filter located between the internal circulating water tank and the heat exchanger for filtering particulate matter from the high-temperature internal circulating water.

[0052] It is understandable that during the heat exchange process between the internal circulating water and the high-temperature drying position, the internal circulating water also adsorbs impurities such as dust in the drying exhaust gas. Filters, such as Y-type filters, angle filters, and automatic backwash filters, are installed on the pipeline connecting the outlet of the internal circulating water tank and the inlet of the heat exchanger to filter out impurities in the high-temperature internal circulating water, thereby protecting the heat exchanger and subsequent process equipment.

[0053] In one possible implementation, in a heat recovery system applied to the production process of lyocell fibers, the spray assembly is equipped with a gas composition detector and a reagent mixer; the gas composition detector is located at the bottom inlet of the cyclone plate tower to detect the composition of the drying exhaust gas; the reagent mixer mixes the corresponding reagent into the internal circulating water to be sprayed according to the composition of the exhaust gas.

[0054] In the production of lyocell fibers, the drying exhaust gas is the waste gas generated during the fiber drying stage. It mainly contains residual organic solvents, dust, volatile organic compounds, moisture, and a small amount of inorganic impurities. The combined effect of these impurities and water can accelerate the corrosion of equipment in the system and also affect emissions. Therefore, in this embodiment, a gas composition detector is installed at the bottom of the cyclone plate tower to detect the impurity components in the drying exhaust gas flowing into the tower. The reagent mixer can be installed in the spray assembly at the top of the cyclone plate tower, which can mix the corresponding dosage of reagent into the internal circulating water to be sprayed according to the detected gas composition to neutralize the impurity components in the drying exhaust gas.

[0055] In one possible implementation, the heat recovery system applied to the lyocell fiber production process further includes: a temperature sensor and a first regulating valve disposed at the bottom of the cyclone tower; the temperature sensor is used to detect the temperature of the drying exhaust gas flowing into the cyclone tower and transmit the detected temperature information to the first regulating valve; the first regulating valve is used to open the valve when the temperature information meets the preset cooling conditions, so that the spray assembly sprays the internal circulating water.

[0056] The production process of lyocell fiber involves several stages that require the emission of gases, such as solvent recovery, fiber drying, chemical treatment, and combustion. These stages can all be vented through a cyclone separator. However, the temperatures of the exhaust gases produced at different stages vary. If the exhaust gas introduced into the cyclone separator is of low temperature, indiscriminately triggering heat exchange will result in unnecessary energy consumption by the heat recovery system.

[0057] Therefore, to reduce energy consumption, this embodiment of the application installs a temperature sensor at the inlet at the bottom of the cyclone separator to detect the temperature of the exhaust gas flowing into the cyclone separator and transmits the temperature information to the first regulating valve. The first regulating valve compares the detected temperature with a preset temperature threshold. When the detected exhaust gas temperature reaches the valve opening temperature, the valve of the first regulating valve is opened, causing the spray assembly to spray internal circulating water to cool the exhaust gas.

[0058] In another possible implementation, the heat recovery system applied to the lyocell fiber production process further includes: a gas flow sensor installed at the bottom of the cyclone tower to detect the flow rate of the drying exhaust gas flowing into the cyclone tower and transmit the detected flow information to a first regulating valve; the first regulating valve adjusts the valve opening according to the flow information to adjust the amount of internal circulating water sprayed by the spray assembly.

[0059] A gas flow sensor is added to the bottom of the cyclone plate tower to detect the flow rate of the drying tail gas flowing into the tower in real time and transmit the flow data to the first regulating valve. The first regulating valve acts as a dynamic control unit, comparing the detected flow rate with a threshold value. When the flow rate fluctuates, the first regulating valve automatically adjusts its opening (range 0-100%) to precisely control the spray volume of the internal circulating water in the spray group. For example, when the flow rate increases compared to the threshold, the valve is opened wider to increase the spray water volume to 5-15 m³ / h, ensuring sufficient gas-liquid contact area.

[0060] In one possible implementation, a heat recovery system applied to the lyocell fiber production process includes an internal circulating water tank comprising: a level sensor and a second regulating valve; the level sensor is used to detect the water level in the internal circulating water tank and transmit the water level to the second regulating valve; the second regulating valve is used to open the valve to replenish water to the internal circulating water tank when the water level in the internal circulating water tank reaches the replenishment water level, until the water level in the internal circulating water tank reaches the full water level.

[0061] The internal circulating water tank establishes a precise automatic water replenishment control closed loop through a level sensor and a second regulating valve. The level sensor, which can employ a high-precision piezoelectric or float-type detection element, monitors the water level in the internal circulating water tank in real time and transmits the data to the second regulating valve. The second regulating valve compares the detected real-time water level with a preset water replenishment threshold. When the water level drops to the threshold, such as 30% of the total height of the internal circulating water tank, the second regulating valve opens fully or proportionally, connecting to an external water replenishment pipeline to inject internal circulating water (such as low-temperature softened water) into the internal circulating water tank. During the water replenishment process, the level sensor continuously feeds back the real-time water level to the second regulating valve. When the water level rises to the full water level threshold (such as 90% of the total tank height), the second regulating valve closes. In this embodiment, the use of a level sensor and a second regulating valve automates the control, reducing the frequency of manual water replenishment and significantly improving the stability and economy of the heat recovery system applied in the lyocell fiber production process.

[0062] In this embodiment, the first regulating valve provided at the spray assembly and the second regulating valve installed in the internal circulating water tank can be electronic regulating valves or solenoid valves, etc., and are not limited to a single type in this example.

[0063] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A heat recovery system applied in the production process of lyocell fiber, characterized in that, include: The cyclone plate tower, the internal circulating water tank and the heat exchanger, and the spray assembly installed at the top of the cyclone plate tower; The bottom inlet of the cyclone plate tower is connected to the drying exhaust outlet to receive the drying exhaust gas; The internal circulating water tank is located at the bottom of the cyclone plate tower, collects the high-temperature internal circulating water sprayed by the spray assembly and after heat exchange with the drying exhaust gas, and transmits the high-temperature internal circulating water to the heat exchanger. The inlet of the heat exchanger is connected to the steam condensate outlet of the lyocell fiber production line to collect the steam condensate generated during the lyocell fiber production process. The steam condensate is used to cool the high-temperature internal circulating water, and the heated steam condensate is introduced into the raw material end of the lyocell fiber production line. The cooled internal circulating water is then introduced into the spray assembly.

2. The heat recovery system applied to the lyocell fiber production process according to claim 1, characterized in that, Also includes: A circulation pump is installed between the internal circulating water tank and the heat exchanger, and the circulation pump is used to drive the high-temperature internal circulating water to flow to the heat exchanger.

3. The heat recovery system applied to the lyocell fiber production process according to any one of claims 1-2, characterized in that, Also includes: A filter installed between the internal circulating water tank and the heat exchanger is used to filter particulate matter in the high-temperature internal circulating water.

4. The heat recovery system applied to the lyocell fiber production process according to claim 1, characterized in that, The spraying assembly is an atomizing nozzle or a variable aperture nozzle.

5. The heat recovery system applied to the lyocell fiber production process according to claim 1, characterized in that, The spray assembly is equipped with a gas composition detector and a reagent mixer; The gas composition detector is installed at the bottom inlet of the cyclone plate tower to detect the composition of the drying tail gas. The reagent mixer mixes the corresponding reagent into the internal circulating water to be sprayed according to the composition of the exhaust gas.

6. The heat recovery system applied to the lyocell fiber production process according to claim 1, characterized in that, Also includes: A temperature sensor and a first regulating valve are installed at the bottom of the cyclone plate tower; The temperature sensor is used to detect the temperature of the drying exhaust gas flowing into the cyclone plate tower and transmit the detected temperature information to the first regulating valve. The first regulating valve is used to open the valve when the temperature information meets the preset cooling conditions, so that the spray assembly sprays the internal circulating water.

7. The heat recovery system applied to the lyocell fiber production process according to claim 6, characterized in that, Also includes: A gas flow sensor installed at the bottom of the cyclone plate tower is used to detect the flow rate of the drying tail gas flowing into the cyclone plate tower and transmit the detected flow information to the first regulating valve. The first regulating valve adjusts the valve opening according to the flow information to adjust the amount of internal circulating water sprayed by the spray assembly.

8. The heat recovery system applied to the lyocell fiber production process according to claim 1, characterized in that, The internal circulating water tank includes: a liquid level sensor and a second regulating valve; The liquid level sensor is used to detect the water level in the internal circulating water tank and transmit the water level in the internal circulating water tank to the second regulating valve; The second regulating valve is used to open the valve when the water level in the internal circulating water tank reaches the replenishment water level, so as to replenish water to the internal circulating water tank until the water level in the internal circulating water tank reaches the full water level.

9. The heat recovery system applied to the lyocell fiber production process according to claim 8, characterized in that, The second regulating valve is either an electronic regulating valve or a solenoid valve.

10. The heat recovery system applied to the lyocell fiber production process according to claim 1, characterized in that, The heat exchanger is a plate heat exchanger.

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