Post-treatment device for DMT purification

Abstract

The post-treatment device comprises a DMT filter, and the filter comprises a filter shell, a filter element arranged in the middle of the shell, an annular stirring device, a constant-temperature condensation reflux device and an internal and external cooperative temperature control system; wherein the filter element is centrally fixed, and multiple groups of arc-shaped stirring blades are arranged in a gap between the inner wall of the shell and the filter element to avoid interference with the position of the filter element; a constant-temperature condensation reflux device is integrated at the top, specific-temperature biphenyl steam is introduced into a condensation cavity jacket, constant-temperature cooling water is introduced into a coiled pipe, a reflux branch pipe is subjected to heat tracing to reach the DMT liquid stable temperature, and a gravity straight pipe is used for guiding flow at the tail end; a heating rod is embedded in the center of the filter element, a heating outer jacket controls the temperature in three sections, and multiple groups of sensors adjust the temperature in a closed-loop mode in real time.

Description

Technical Field

[0001] This application relates to the field of regenerated DMT production technology, specifically to a post-processing device for DMT purification. Background Technology

[0002] Dimethyl terephthalate (DMT) is a key intermediate in the synthesis of polyester materials (such as PET and PBT), and its purity directly affects the performance of downstream products. In the production and recycling of DMT, post-processing such as decolorization and filtration are required to remove impurities. Among these, DMT melt decolorization and filtration are the core steps—DMT needs to be heated to a molten state above 141°C, and impurities are intercepted through filters to ensure purity.

[0003] Existing DMT filters have long been constrained by two major problems: uneven heating and DMT volatilization losses. Most existing filters use a single temperature control method with external jacket heating. When heat is transferred from the shell to the interior, the low thermal conductivity of DMT easily leads to significant temperature differences: the DMT temperature near the shell reaches 155-165℃, while the center of the filter element only reaches 135-145℃, a difference of up to 30℃. This temperature difference causes localized solidification of the central DMT when the temperature drops below 141℃, clogging the filter element, causing system pressure fluctuations, and shortening equipment lifespan. Furthermore, when the external DMT exceeds 160℃, it undergoes thermal oxidative degradation, generating acidic impurities that corrode the equipment and affect the quality of downstream products.

[0004] DMT has a boiling point of approximately 288℃, and its evaporation rate increases with temperature. Due to high external temperatures, DMT vapor is easily generated inside the filter. Existing simple venting structures (such as top vent valves) cannot recover this vapor, resulting in a 3%-5% evaporation loss per filtration cycle. Furthermore, the vapor solidifies upon condensation, clogging the pipes and requiring frequent shutdowns for cleaning. Therefore, improvements to DMT filtration equipment are urgently needed. Summary of the Invention

[0005] In view of the above problems, this application provides a post-processing device for DMT purification to solve the technical problems of uneven heating of DMT filters and DMT volatilization damage.

[0006] To achieve the above objectives, this application provides a post-processing device for DMT purification, including a DMT filter connected to the outlet of a DMT purification tank; the DMT purification tank is provided with purification packing material for purifying regenerated DMT, and the DMT filter is used to filter the purified regenerated DMT.

[0007] The DMT filter includes a filter housing, a filter element centrally located within the housing, an annular stirring device, a constant temperature condensation reflux device, and an internal and external coordinated temperature control system.

[0008] The internal and external temperature control system includes a heating rod embedded in the central skeleton of the filter element and a heating outer jacket disposed on the surface of the filter housing;

[0009] The annular stirring device includes multiple sets of arc-shaped stirring blades distributed circumferentially along the annular gap between the inner wall of the filter housing and the filter element, an annular stirring frame, and a reduction motor. The reduction motor is connected to the annular stirring frame through an eccentric transmission rod, driving the stirring frame to rotate the blades circumferentially, thereby reducing the temperature difference between the inner and outer sides of the DMT inside the housing.

[0010] The constant temperature condensation and reflux device is integrated on the top of the filter cover and includes a cylindrical sealed condensation chamber, a serpentine condenser tube, a constant temperature guide tube, and a reflux branch pipe with heat tracing. The outer wall of the condensation chamber is wrapped with an annular constant temperature jacket through which biphenyl vapor at 142-145℃ is introduced. The serpentine condenser tube is filled with constant temperature cooling water at 138-140℃, and the tube wall temperature is stabilized at 140-141℃. The outer wall of the constant temperature guide tube is wrapped with a miniature electric heating jacket with a set temperature of 141℃. The outer wall of the reflux branch pipe is wrapped with a self-regulating electric heating tape with a set temperature of 141℃, and the end of the reflux branch pipe is connected to a vertically downward gravity guide straight pipe.

[0011] Furthermore, the inner wall of the gravity guide tube is polished, the tube length is 50-80mm, and an umbrella-shaped anti-splash baffle is provided directly below the guide tube and on the top of the filter element. The diameter of the baffle is 1.2 times the diameter of the top of the filter element, and the edge is inclined downward at 10°.

[0012] Furthermore, the filter element is fixed by a top flange suspension and a bottom positioning groove embedded in the bottom of the housing. The positioning groove is equipped with a heat-resistant sealing gasket, and the outer wall of the filter element is wrapped with a 316L stainless steel porous protective sleeve with a pore diameter larger than the filter element's filtration accuracy.

[0013] Furthermore, the volume of the cylindrical sealed condensing chamber is 1 / 5 of the total volume of the filter. The bottom of the condensing chamber is provided with a liquid collection trough inclined at 15°-20°. The inner wall of the liquid collection trough is lined with a polytetrafluoroethylene non-stick coating. The lowest point of the liquid collection trough is connected to the constant temperature guide pipe.

[0014] Furthermore, the serpentine condenser tube has a diameter of 20mm and a cooling water flow rate of 8-10L / min. The constant temperature guide tube has a diameter of 30mm and a length of 150mm. The miniature electric heating mantle has a power of 100-150W and a temperature control accuracy of ±1℃.

[0015] Furthermore, the power of the self-regulating electric heating is 20W / m, and the outer side is wrapped with 20mm thick aluminum silicate insulation cotton.

[0016] Furthermore, the internal and external coordinated temperature control system also includes five sets of resistance temperature sensors placed on the wall of the serpentine condenser tube, inside the condenser chamber, at the outlet of the constant temperature guide tube, in the middle of the return branch tube, and at the outlet of the gravity guide straight tube. The temperature sensors are electrically connected to the central controller to form a closed-loop temperature regulation.

[0017] Furthermore, the temperature regulation logic of the central controller is as follows: when the temperature at any location is below 140°C, the heating power of the corresponding area is increased; when the temperature is above 142°C, the heating power of the corresponding area is reduced; when the temperature of the return branch pipe remains below 140°C for more than 10 seconds, an alarm is triggered and the high-temperature purging valve for introducing 150°C nitrogen gas into the end of the branch pipe is opened.

[0018] Furthermore, the top of the cylindrical sealed condensation chamber is equipped with a micro-pressure safety valve with an opening pressure of 0.12-0.15MPa, and an inert gas inlet connected to a nitrogen source, with an inert gas inlet flow rate of 0.5-1L / min.

[0019] Furthermore, the nickel-chromium alloy heating rod has a power of 500-800W, and magnesium oxide powder insulation material is filled between the outer wall of the heating rod and the central skeleton of the filter element.

[0020] Unlike existing technologies, the above-mentioned technical solution for the post-processing device of DMT purification includes a DMT filter. The filter includes a filter housing, a filter element centrally located within the housing, a ring-shaped stirring device, a constant-temperature condensation and reflux device, and an internal and external temperature control system. The filter element is centrally fixed, and multiple sets of arc-shaped stirring blades are provided between the inner wall of the housing and the filter element to avoid interference with the filter element's position. A constant-temperature condensation and reflux device is integrated at the top. The condensation chamber jacket is circulated with biphenyl vapor at a specific temperature, a serpentine tube circulates constant-temperature cooling water, and the reflux branch pipe is heated to the stable liquid temperature of DMT. The end is guided by a gravity straight pipe. A heating rod is embedded in the center of the filter element, and the outer jacket is heated with three-stage temperature control. Multiple sensors provide real-time closed-loop temperature regulation.

[0021] This technical solution effectively reduces the temperature difference between the center of the filter element and the outside of the housing by coordinating internal and external temperature control, preventing DMT from clogging the filter element due to local low temperature solidification or overheating degradation due to local high temperature; and the constant temperature condensation reflux structure can efficiently recover the volatilized DMT vapor, greatly reducing material loss, while avoiding pipeline blockage caused by vapor solidification upon condensation.

[0022] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0023] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of the present invention and other related contents, and should not be considered as limitations on this application.

[0024] In the accompanying drawings of the instruction manual:

[0025] Figure 1 This is a schematic diagram of the post-processing device for DMT purification as described in the specific embodiment;

[0026] Figure 2 This is a schematic diagram of the structure of the DMT filter described in a specific embodiment;

[0027] The reference numerals used in the above figures are explained as follows:

[0028] 1. DMT purification tank; 2. DMT filter;

[0029] 20. Filter housing; 21. Filter element; 22. Heating jacket; 23. Heating rod; 24. Arc-shaped stirring blade; 241. Gear motor; 25. Cylindrical sealed condensing chamber; 26. Serpentine condenser tube; 27. Gravity guide straight pipe; Detailed Implementation

[0030] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0031] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0032] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0033] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0034] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order between these entities or operations.

[0035] Without further limitations, the use of terms such as “comprising,” “including,” “having,” or other similar open-ended expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0036] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0037] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0038] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0039] Please see Figures 1 to 2 The post-processing device for DMT purification provided in this embodiment includes a DMT purification tank 1 and a DMT filter 2; the DMT filter 2 is connected to the outlet of the DMT purification tank 1, the DMT purification tank is provided with purification packing material (for regenerated DMT purification), and the DMT filter is used to filter the purified regenerated DMT.

[0040] The DMT filter 2 includes a filter housing 20, a centrally located filter element 21, a ring-shaped stirring device, a constant-temperature condensation reflux device, and an internal and external coordinated temperature control system. The specific structures of each component of the DMT filter 2 are as follows:

[0041] An annular stirring device is installed in the annular gap between the inner wall of the filter housing and the filter element. It includes 3-6 sets of circumferentially distributed arc-shaped stirring blades 24, an annular stirring frame, and a geared motor 241. The arc-shaped stirring blades 24 are parallel to the axis of the filter element 21, with their edges 7mm-20mm away from the outer wall of the filter element, and are fixed on the annular stirring frame. The annular stirring frame is fitted on the outside of the filter element 21 and is driven by the geared motor 241 on the outside of the housing through an eccentric transmission rod, causing the annular stirring frame to rotate circumferentially at a speed of 12r / min.

[0042] The constant-temperature condensation reflux device is integrated into the top of the filter cover and includes a cylindrical sealed condensation chamber 25, an annular constant-temperature jacket, a titanium alloy serpentine condenser tube 26 (condenser tubes of other materials and shapes can also be used), a constant-temperature guide tube, a reflux branch tube, a gravity guide straight tube 27, and an umbrella-shaped splash guard.

[0043] The cylindrical sealed condensing chamber 25 has a volume of 1 / 8 to 1 / 5 of the total filter volume. Its outer wall is wrapped with an annular thermostatic jacket (through which biphenyl vapor at approximately 143°C is introduced), and its bottom has a 15° inclined liquid collection trough (with a PTFE anti-stick coating on the inner wall, and its lowest point connected to the thermostatic guide pipe). A titanium alloy serpentine condensing tube 26, with a diameter of 20mm-40mm, is located inside the cylindrical sealed condensing chamber and is filled with thermostatic cooling water at 139°C (lower than the temperature of the annular thermostatic jacket). The thermostatic guide pipe has a diameter of 30mm and a length of 150mm, and its outer wall is wrapped with a 120W miniature electric heating jacket with a temperature control accuracy of ±1°C. One end is connected to the bottom of the cylindrical sealed condensing chamber, and the other end is connected to the return branch pipe. The outer wall of the return branch pipe is wrapped with a 20W / m self-regulating electric heating tape (heating temperature 141℃), and the end is connected to a vertically downward gravity guide pipe 27 (the inner wall is polished to Ra=0.6μm, and the pipe length is 60mm). The end of the gravity guide pipe extends to 12mm above the top of the filter element. An umbrella-shaped splash guard is located directly below the gravity guide pipe and on the top of the filter element, with a diameter 1.2 times the diameter of the top of the filter element, and the edge is inclined downward at 15°-20°.

[0044] The internal and external temperature control system includes a nickel-chromium alloy heating rod 23 (other materials can also be used, power 600-1000W), a segmented heating jacket 22, a high-temperature platinum resistance temperature sensor, and a central controller. The nickel-chromium alloy heating rod 23 is embedded in the central frame of the filter element 21, and the space between the outer wall and the frame is filled with magnesium oxide powder insulation material (2mm thick, to ensure insulation safety). The heating jacket 22 of the filter housing is a segmented heating jacket, divided into three independent heating sections: upper, middle, and lower, each equipped with an electric heating element.

[0045] Five sets of high-temperature platinum resistance temperature sensors are arranged on the wall of the titanium alloy serpentine condenser tube, inside the cylindrical sealed condenser chamber, at the outlet of the constant temperature guide tube, in the middle of the return branch tube, and at the outlet of the gravity guide straight tube. All sensors are electrically connected to the central controller.

[0046] In this embodiment, the filter element adopts a fixing method of "top flange suspension + bottom positioning groove fitting": the top is fixed to the center of the filter cover by the flange, and the bottom is embedded in the positioning groove at the bottom of the filter housing (the groove is equipped with a fluororubber heat-resistant sealing gasket to prevent DMT melt leakage); the outer wall of the filter element is wrapped with a 316L stainless steel porous protective sleeve (pore diameter 10μm, which is greater than the 5μm filtration accuracy of the filter element and is used to prevent scratches).

[0047] In this embodiment, the purified DMT melt, decolorized by activated carbon, is introduced into the filter housing, with the amount introduced being 2 / 3 of the effective volume inside the filter housing. The three independent heating sections of the outer jacket of the filter housing and the nickel-chromium alloy heating rod in the center of the filter element are turned on. The target temperature of 155°C is set through the central controller, and the reduction motor of the annular stirring device is turned on at the same time.

[0048] During the filtration process, real-time temperature control is implemented. A high-temperature platinum resistance temperature sensor collects temperatures at various locations and transmits them to the central controller. If the external temperature of the filter housing exceeds 157°C and the center temperature of the filter element falls below 153°C, the central controller automatically reduces the heating power of the outer jacket and increases the power of the nickel-chromium alloy heating rod, maintaining the temperature difference between the filter element center and the outer housing within ±2°C. Simultaneously, the annular constant-temperature jacket supply of biphenyl vapor and the cooling water circulation of the titanium alloy serpentine condenser are activated, ensuring an ambient temperature of 142°C in the cylindrical sealed condensing chamber, a wall temperature of 140.5°C for the titanium alloy serpentine condenser, and stable temperatures of the return branch, constant-temperature guide pipe, and gravity guide straight pipe at 141°C. If the temperature of the return branch remains below 140°C for more than 10 seconds, the central controller triggers an alarm and opens a high-temperature purge valve at the end of the branch, introducing 150°C nitrogen gas, while simultaneously recording abnormal data.

[0049] During the filtration process, the DMT melt is propelled by the arc-shaped stirring blades of the annular stirring device, flowing uniformly along the annular gap and passing through the filter element, where impurities are trapped. The DMT vapor volatilized during filtration rises into the cylindrical sealed condensation chamber, where it condenses into liquid DMT upon contact with the titanium alloy serpentine condenser tube. This liquid flows along the bottom inclined collection trough (with a PTFE anti-stick coating to reduce adhesion) into the constant-temperature guide pipe, then drips through the return branch pipe and gravity guide straight pipe, and is uniformly mixed into the DMT melt within the filter housing under the guidance of the umbrella-shaped splash guard.

[0050] In this embodiment, the inclined liquid accumulation trough at the bottom of the cylindrical sealed condensation chamber guides the flow of liquid DMT by gravity. Combined with the PTFE anti-stick coating and the constant-temperature guide pipe's heat tracing (141°C), the liquid DMT remains unretained and does not solidify, eliminating the need for frequent shutdowns for cleaning. Simultaneously, the micro-pressure safety valve at the top of the condensation chamber (opening pressure 0.13MPa) prevents overpressure rupture within the chamber, and the inert gas inlet (nitrogen flow rate 0.8L / min) forces incompletely condensed DMT vapor towards the condenser tube, improving condensation recovery and reducing evaporation losses. Furthermore, the 20mm thick aluminum silicate insulation cotton on the outer wall of the return branch pipe prevents heat loss from the self-regulating heating cable, allowing the cable to maintain a low power of only 20W / m to stabilize the 141°C temperature. Compared to a structure without insulation, heat tracing energy consumption is reduced by more than 25%. Combined with the segmented temperature control of the outer jacket and precise heating by the nickel-chromium alloy heating rod, the overall operating cost of the equipment is significantly reduced.

[0051] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A post-processing apparatus for DMT purification, characterized in that, The device includes a DMT filter connected to the outlet of a DMT purification tank. The DMT purification tank is filled with purification packing material for purifying regenerated DMT, and the DMT filter is used to filter the purified regenerated DMT. The DMT filter includes a filter housing, a filter element centrally located within the housing, an annular stirring device, a constant temperature condensation reflux device, and an internal and external coordinated temperature control system. The internal and external temperature control system includes a heating rod embedded in the central skeleton of the filter element and a heating outer jacket disposed on the surface of the filter housing; The annular stirring device includes multiple sets of arc-shaped stirring blades distributed circumferentially along the annular gap between the inner wall of the filter housing and the filter element, an annular stirring frame, and a reduction motor. The reduction motor is connected to the annular stirring frame through an eccentric transmission rod, driving the stirring frame to rotate the blades circumferentially, thereby reducing the temperature difference between the inner and outer sides of the DMT inside the housing. The constant temperature condensation and reflux device is integrated on the top of the filter cover and includes a cylindrical sealed condensation chamber, a serpentine condenser tube, a constant temperature guide tube, and a reflux branch pipe with heat tracing. The outer wall of the condensation chamber is wrapped with an annular constant temperature jacket through which biphenyl vapor at 142-145℃ is introduced. The serpentine condenser tube is filled with constant temperature cooling water at 138-140℃, and the tube wall temperature is stabilized at 140-141℃. The outer wall of the constant temperature guide tube is wrapped with a miniature electric heating jacket with a set temperature of 141℃. The outer wall of the reflux branch pipe is wrapped with a self-regulating electric heating tape with a set temperature of 141℃, and the end of the reflux branch pipe is connected to a vertically downward gravity guide straight pipe.

2. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The inner wall of the gravity guide tube is polished, and the tube length is 50-80mm. An umbrella-shaped anti-splash baffle is provided directly below the guide tube and on the top of the filter element. The diameter of the baffle is 1.2 times the diameter of the top of the filter element, and the edge is inclined downward at 10°.

3. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The filter element is fixed by a top flange suspension and a bottom positioning groove embedded in the bottom of the housing. The positioning groove is equipped with a heat-resistant sealing gasket, and the outer wall of the filter element is wrapped with a 316L stainless steel porous protective sleeve with a pore size larger than the filter element's filtration accuracy.

4. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The volume of the cylindrical sealed condensing chamber is 1 / 5 of the total volume of the filter. The bottom of the condensing chamber is provided with a liquid collection tank with an inclination of 15°-20°. The inner wall of the liquid collection tank is lined with a polytetrafluoroethylene non-stick coating. The lowest point of the liquid collection tank is connected to the constant temperature guide pipe.

5. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The serpentine condenser tube has a diameter of 20mm and a cooling water flow rate of 8-10L / min. The constant temperature guide tube has a diameter of 30mm and a length of 150mm. The miniature electric heating mantle has a power of 100-150W and a temperature control accuracy of ±1℃.

6. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The self-regulating electric heating has a power of 20W / m and is wrapped with 20mm thick aluminum silicate insulation cotton on the outside.

7. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The internal and external coordinated temperature control system also includes five sets of resistance temperature sensors placed on the wall of the serpentine condenser tube, inside the condenser chamber, at the outlet of the constant temperature guide tube, in the middle of the return branch tube, and at the outlet of the gravity guide straight tube. The temperature sensors are electrically connected to the central controller to form a closed-loop temperature regulation.

8. The post-processing apparatus for DMT purification according to claim 7, characterized in that, The temperature regulation logic of the central controller is as follows: when the temperature at any location is below 140℃, the heating power of the corresponding area is increased; when the temperature is above 142℃, the heating power of the corresponding area is reduced; when the temperature of the return branch pipe remains below 140℃ for more than 10 seconds, an alarm is triggered and the high-temperature purging valve that introduces 150℃ nitrogen gas into the end of the branch pipe is opened.

9. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The top of the cylindrical sealed condensation chamber is equipped with a micro-pressure safety valve with an opening pressure of 0.12-0.15MPa and an inert gas inlet connected to a nitrogen source, with an inert gas inlet flow rate of 0.5-1L / min.

10. The post-processing apparatus for DMT purification according to claim 1, characterized in that, The nickel-chromium alloy heating rod has a power of 500-800W, and magnesium oxide powder insulation material is filled between the outer wall of the heating rod and the central skeleton of the filter element.

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