Heat exchanger for production of monuron

Abstract

A heat exchanger for production of monuron relates to the field of heat exchange equipment, including main shell, heat exchange pipe and head, heat exchange pipe is arranged in main shell, heat exchange pipe is flowing with pipe fluid, the space between the outer wall of heat exchange pipe and main shell is flowing with shell fluid, pipe fluid and shell fluid are exchanged through the pipe wall of heat exchange pipe, the outside of main shell is provided with shell fluid inlet pipe and shell fluid outlet pipe;Two inlet branch pipes are arranged on the shell fluid inlet pipe, one end of the two inlet branch pipes is communicated with the shell fluid inlet pipe respectively, the other end is communicated with the internal space of main shell respectively;Two inlet branch pipes and two outlet branch pipes are arranged along the axis direction of main shell;Switch control device is arranged at the inlet branch pipe and outlet branch pipe, the switch control of each inlet branch pipe and outlet branch pipe can be realized by operating switch control device, the passing path of shell fluid in main shell is changed, so that the adjustment of heat exchange capacity is realized.

Description

Technical Field

[0001] This invention belongs to the field of heat exchange equipment, and particularly relates to a heat exchanger used in the production of metribuzin. Background Technology

[0002] Bentazon is a chemical pesticide ingredient. The production of betazon requires heat exchange with a heat exchanger. In production practice, the following problems have been found with currently used heat exchangers:

[0003] First, the large temperature difference throughout the year in northern my country causes the heat loss of the shell fluid in the heat exchanger to fluctuate greatly with the change in temperature. Under the condition of a fixed shell fluid flow rate, the heat exchanger's heat exchange capacity also fluctuates significantly, which in turn has an adverse effect on product quality.

[0004] Second, the heat exchange capacity of existing heat exchangers is not adjustable, making it difficult for the same heat exchanger to adapt to production processes with different heat exchange capacity requirements. Summary of the Invention

[0005] This invention provides a heat exchanger for use in the production of metribuzin, with the aim of improving the cleaning effect of the filter screen in the vacuum feeder.

[0006] The technical problem solved by the present invention is achieved by the following technical solution: The present invention provides a heat exchanger for the production of metribuzin, including a main shell, heat exchange tubes and end caps. The heat exchange tubes are arranged inside the main shell, and a tube fluid flows inside the heat exchange tubes. A shell fluid flows in the space between the outer wall of the heat exchange tubes and the main shell. The tube fluid and the shell fluid exchange heat through the tube wall of the heat exchange tubes. A shell fluid inlet pipe and a shell fluid outlet pipe are arranged on the outside of the main shell.

[0007] The shell fluid inlet pipe is provided with two inlet branch pipes, one end of which is connected to the shell fluid inlet pipe and the other end of which is connected to the internal space of the main shell. Similarly, the fluid outlet pipe is provided with two outlet branch pipes, one end of which is connected to the shell fluid outlet pipe and the other end of which is connected to the internal space of the main shell.

[0008] Two inlet branch pipes are connected to the outside of one end of the main shell, and two outlet branch pipes are connected to the outside of the other end of the main shell.

[0009] The two inlet branch pipes and the two outlet branch pipes are arranged along the axial direction of the main shell;

[0010] Both the inlet and outlet branches are equipped with switch control devices. By operating the switch control devices, the opening and closing of each inlet and outlet branch can be controlled, changing the flow path of the shell fluid in the main shell, thereby adjusting the heat exchange capacity.

[0011] As a preferred embodiment, the switch control device is a valve, and one of the valves is connected in series on each inlet branch pipe and outlet branch pipe.

[0012] As a preferred embodiment, the shell fluid inlet pipe and the shell fluid outlet pipe each include a horizontal pipe section, and the two horizontal pipe sections are coaxial;

[0013] The switch control device includes a dual-axis motor and two piston assemblies. Each end of the dual-axis motor is provided with a lead screw with the same pitch but opposite directions of rotation. The two piston assemblies are respectively connected to the two lead screws by threads. At the same time, the two piston assemblies are slidably installed in two horizontal pipe sections and slide in cooperation with the horizontal pipe sections.

[0014] The piston assembly includes a threaded piston, an end piston, and a connecting rod. The end piston is fixedly connected to the threaded piston via the connecting rod. The threaded piston connects the entire piston assembly to the lead screw via threads. After the dual-axis motor is started, the rotational motion of the lead screw is converted into linear motion of the entire piston assembly, thereby adjusting the position of the threaded piston and the end piston in the horizontal pipe section and realizing the on / off control of each inlet branch pipe and outlet branch pipe.

[0015] As a preferred embodiment, the piston assembly typically has three locations within the horizontal pipe section:

[0016] The following stipulations are made: the two inlet branch pipes, in order from left to right, are respectively called Inlet Branch Pipe No. 1 and Inlet Branch Pipe No. 2; the two outlet branch pipes, in order from left to right, are respectively called Outlet Branch Pipe No. 1 and Outlet Branch Pipe No. 2. Then:

[0017] When in the first typical position, the No. 1 inlet branch is open, the No. 2 inlet branch is blocked by the corresponding threaded piston, the No. 1 outlet branch is blocked by the corresponding outlet branch, and the No. 2 outlet branch is open.

[0018] When in the second typical position, inlet branch pipe No. 1, inlet branch pipe No. 2, outlet branch pipe No. 1 and outlet branch pipe No. 2 are all connected;

[0019] When in the third typical position, the No. 1 inlet branch is blocked by the corresponding end piston, the No. 2 inlet branch is open, the No. 1 outlet branch is open, and the No. 2 outlet branch is blocked by the corresponding end piston.

[0020] As a preferred embodiment, the main housing is provided with baffles, which are arranged at equal intervals and staggered vertically to form a serpentine flow channel within the main housing for the passage of fluid.

[0021] As a preferred embodiment, a locking mechanism is provided at the connection between the threaded piston and the horizontal pipe section, which can lock the threaded piston onto the horizontal pipe section.

[0022] As a preferred embodiment, the outer side of the threaded piston is provided with scale lines. By observing the scale lines, the position of the threaded piston and the end piston in the horizontal pipe section can be determined, thereby determining whether each inlet branch pipe and outlet branch pipe is blocked.

[0023] As a preferred embodiment, the scale lines consist of two sets, which respectively indicate the degree to which the two inlet branch pipes are blocked by the corresponding two pistons, or the degree to which the two outlet branch pipes are blocked by the corresponding two pistons.

[0024] This invention improves upon existing technologies, resulting in the following advantages:

[0025] 1. The present invention provides two inlet branch pipes and two outlet branch pipes with different axial positions on the outside of the main shell. During operation, by opening or closing the inlet branch pipes and outlet branch pipes with different axial positions, the length of the flow path of the shell fluid in the main shell can be changed, that is, the heat exchange time between the shell fluid and the tube fluid can be changed, thereby realizing flexible adjustment of the heat exchange capacity of the heat exchanger.

[0026] 2. In this invention, the shell fluid inlet pipe and the shell fluid outlet pipe each include a horizontal pipe section, the two horizontal pipe sections are coaxial, and two piston assemblies are respectively mounted on the two lead screws at both ends of the dual-shaft motor. The piston assembly is composed of a threaded piston, a connecting rod, and an end piston. This design has the following advantages.

[0027] First, driven by the dual-axis motor, the two lead screws rotate synchronously, which in turn drives the two piston assemblies to slide synchronously, thus ensuring that the total diameter of the two inlet branch pipes and the total diameter of the two outlet branch pipes remain the same at all times.

[0028] Secondly, compared with using valves as the switching control device, using a dual-axis motor to drive two piston assemblies to move can more quickly and conveniently control the switching of two inlet branch pipes and two outlet branch pipes simultaneously, realizing multiple changes in the flow path of the shell fluid in the main shell, and greatly improving the ease of operation.

[0029] Third, the piston assembly, consisting of a threaded piston, connecting rod, and end piston, can move to individually block or open a single inlet or outlet branch pipe, simultaneously open two inlet and two outlet branch pipes, or partially open or block a single inlet and outlet branch pipe, thus providing multiple different flow paths for the shell fluid. Compared to using valves as on / off control devices, this method of changing the flow path of the shell fluid allows for more precise and flexible adjustment, thereby achieving precise and flexible adjustment of the heat exchanger's heat exchange capacity.

[0030] Fourth, the pressure from the fluid in the shell on the two threaded pistons connected to both ends of the dual-axis motor is simultaneously applied to both ends of the motor shaft of the dual-axis motor (the so-called dual-axis motor does not mean that there are two shafts, but that one shaft extends from both ends of the dual-axis motor) and cancels each other out, thus making it easier to ensure the structural strength of the dual-axis motor.

[0031] 3. By controlling the operation of the dual-axis motor through automation, the heat exchanger's heat exchange capacity can be dynamically adjusted, thereby meeting the need for dynamic adjustment of the heat exchanger's heat exchange capacity during continuous production. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the first embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of the second embodiment of the present invention.

[0034] Figure 3 yes Figure 2 A schematic diagram showing the position of the piston assembly in the shell fluid inlet pipe and the shell fluid outlet pipe.

[0035] Figure 4 This is a schematic diagram of the second position of the piston assembly in the shell fluid inlet pipe and the shell fluid outlet pipe.

[0036] Figure 5 This is a schematic diagram of the third position of the piston assembly in the shell fluid inlet pipe and the shell fluid outlet pipe.

[0037] In the diagram, 1. End cap, 2. No. 1 inlet branch pipe, 3. Main shell, 4. Shell fluid inlet pipe, 5. No. 1 outlet branch pipe, 6. Shell fluid outlet pipe, 7. Heat exchange tube, 8. Baffle plate, 9. End piston, 10. Connecting rod, 11. Threaded piston, 12. Lead screw, 13. Dual-shaft motor, 14. Horizontal pipe section, 15. No. 2 inlet branch pipe, 16. No. 2 outlet branch pipe. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings:

[0039] First embodiment

[0040] like Figure 1As shown, this embodiment includes a main shell 3, a heat exchange tube 7, and a head 1. The heat exchange tube 7 is disposed inside the main shell 3, and a tube fluid flows inside the heat exchange tube 7. A shell fluid flows in the space between the outer wall of the heat exchange tube 7 and the main shell 3. The tube fluid and the shell fluid exchange heat through the tube wall of the heat exchange tube 7. Specifically, the heat exchange tube 7 is connected to the head 1 and communicates with the internal space of the head 1. A tube fluid inlet pipe and a tube fluid outlet pipe are provided on the outer side of the head 1 for the tube fluid to enter and exit. A shell fluid inlet pipe 4 and a shell fluid outlet pipe 6 are provided on the outer side of the main shell 3. The above structure is mature prior art, so it will not be described in detail here.

[0041] like Figure 1 As shown, in this embodiment, the shell fluid inlet pipe 4 is provided with two inlet branch pipes, one end of each inlet branch pipe is connected to the shell fluid inlet pipe 4, and the other end is connected to the internal space of the main shell 3. Similarly, the fluid outlet pipe is provided with two outlet branch pipes, one end of each outlet branch pipe is connected to the shell fluid outlet pipe 6, and the other end is connected to the internal space of the main shell 3. The two inlet branch pipes are connected to the outside of one end of the main shell 3, and the two outlet branch pipes are connected to the outside of the other end of the main shell 3.

[0042] By setting two inlet branch pipes and two outlet branch pipes, and arranging each branch pipe along the axial direction of the main shell 3, the length of the flow path of the shell fluid in the main shell 3 can be changed by opening or closing the inlet and outlet branch pipes at different axial positions during operation. This changes the heat exchange time between the shell fluid and the tube fluid, thereby enabling flexible adjustment of the heat exchanger's heat exchange capacity.

[0043] like Figure 1 As shown in this embodiment, both the inlet branch pipe and the outlet branch pipe are equipped with switch control devices. By operating the switch control devices, the switching control of each inlet branch pipe and the outlet branch pipe can be realized, thereby opening or closing each inlet branch pipe and each outlet branch pipe as needed.

[0044] like Figure 1 As shown, in this embodiment, the switch control device is a traditional valve, with one valve connected in series on each inlet branch pipe and outlet branch pipe. By changing the valve's opening and closing state, the following functions can be achieved:

[0045] First, by changing the opening and closing state of the valves, the length of the shell fluid flow path can be adjusted. The longer the flow path, the longer the contact time between the shell fluid and the outer wall of the heat exchange tube 7, and the stronger the heat exchanger's heat exchange capacity. For example, when the shell fluid enters the main shell 3 from the first inlet branch pipe 2 and then flows out from the second outlet branch pipe 16, the flow path of the shell fluid is the longest, and the heat exchanger's heat exchange capacity is the strongest. When the shell fluid enters the main shell 3 from the second inlet branch pipe 15 and then flows out from the first outlet branch pipe 5, the flow path of the shell fluid is the shortest, and the heat exchanger's heat exchange capacity is the weakest.

[0046] Secondly, by changing the valve's on / off state, the shell fluid can flow in simultaneously from both inlet branch pipes. This dual-channel inflow method can, to some extent, break the turbulence in the shell fluid flow, promote heat exchange inside the shell fluid, and thus improve heat exchange efficiency.

[0047] Third, by changing the opening degree of the valve, the distribution ratio of the shell fluid between the two inlet branches can be adjusted, thereby allowing the heat exchanger's heat exchange capacity to be continuously adjusted between the "strongest" and "weakest" mentioned in the first point above (as opposed to discrete adjustment), thus ensuring the accuracy of adjusting the heat exchanger's heat exchange capacity.

[0048] like Figure 1 As shown in this embodiment, the main shell 3 is provided with baffles 8. The baffles 8 are arranged at equal intervals and staggered vertically, thereby forming a serpentine flow channel in the main shell 3 for the shell fluid to pass through. This can prolong the residence time of the shell fluid in the main shell 3 and improve the heat exchange efficiency.

[0049] like Figure 1 As shown in this embodiment, a locking mechanism is provided at the connection between the threaded piston 11 and the horizontal pipe section 14. After the position of the piston assembly in the horizontal pipe section 14 is adjusted, the threaded piston 11 can be locked on the horizontal pipe section 14 by the locking mechanism, so that the position of the piston assembly remains stable after adjustment.

[0050] Second embodiment

[0051] like Figure 2 As shown, the difference between this embodiment and the first embodiment is that the first embodiment uses a valve as the switch control device at the inlet branch pipe and the outlet branch pipe, while this embodiment provides another switch control device.

[0052] like Figure 2 As shown, in this embodiment, the shell fluid inlet pipe 4 and the shell fluid outlet pipe 6 each include a horizontal pipe section 14, and the two horizontal pipe sections 14 are coaxial.

[0053] like Figure 2As shown, in this embodiment, the switch control device includes a dual-axis motor 13 and two piston assemblies. Each end of the dual-axis motor 13 is provided with a lead screw 12 with the same pitch but opposite directions of rotation. The two piston assemblies are respectively threaded onto the two lead screws 12. Simultaneously, the two piston assemblies are slidably installed within two horizontal pipe sections 14 and are in sliding engagement with the horizontal pipe sections 14. In use, driven by the dual-axis motor 13, the two lead screws 12 with the same pitch but opposite directions of rotation rotate synchronously, thereby driving the two piston assemblies to slide synchronously.

[0054] like Figure 2 As shown, in this embodiment, the piston assembly includes a threaded piston 11, an end piston 9, and a connecting rod 10. The threaded piston 11 connects the entire piston assembly to the lead screw 12 via threads. The end piston 9 is fixedly connected to the threaded piston 11 via the connecting rod 10 so that it moves synchronously with the threaded piston 11. After the dual-axis motor 13 is started, the rotational motion of the lead screw 12 is converted into linear motion of the entire piston assembly, thereby adjusting the position of the threaded piston 11 and the end piston 9 in the horizontal pipe section 14, realizing the on / off control of each inlet branch pipe and outlet branch pipe.

[0055] In this embodiment, in order to reduce the obstruction of the connecting rod 10 to the flow of the shell fluid, the connecting rod 10 can be replaced with a tubular structure. The tubular structure has the following structural features: 1) The two ends of the tubular structure are fixedly connected to the threaded piston and the end piston, respectively, to realize its connection function; 2) The outer wall of the tubular structure slides (tolerance fit) with the inner wall of the horizontal pipe section 14 to minimize its obstruction to the shell fluid; 3) The side of the tubular structure has a sufficiently large window to ensure that the shell fluid can flow through its interior along the field during the sliding of the piston assembly.

[0056] During implementation, attention should be paid to the fit between the various parts of the piston assembly and the horizontal pipe section 14. For example... Figure 3 , 4 As shown in Figure 5, in this embodiment, a sealing ring is installed on the inner side of the horizontal pipe section 14. The threaded piston 11 in the piston assembly achieves a sealing fit with the horizontal pipe section 14 through this sealing ring, thereby preventing the shell fluid from leaking to the outside of the horizontal pipe section 14. At the same time, sealing rings are not provided at the sealing points of the threaded piston 11 and the end piston 9 for each branch pipe. There are two reasons for this: first, sealing is sufficient and strict sealing is not required; second, after sealing, the piston assembly will be unable to move to the required position due to pressure buildup.

[0057] like Figure 3-5 As shown, in this embodiment, when adjusting the conduction state of each inlet branch pipe and outlet branch pipe, the piston assembly has three typical positions within the horizontal pipe section 14:

[0058] In the first typical position, inlet branch 2 is open, inlet branch 15 is blocked by the corresponding threaded piston 11, outlet branch 5 is blocked by the corresponding outlet branch, and outlet branch 16 is open. Figure 3 As shown in the diagram, at this point, the distance between the inlet and outlet branch pipes is at its maximum, and the heat exchanger's heat exchange capacity is at its strongest.

[0059] In the second typical position, inlet branch 2, inlet branch 15, outlet branch 5, and outlet branch 16 are all conductive, such as Figure 4 As shown in the figure. At this point, the heat exchanger's heat exchange capacity is moderate.

[0060] In the third typical position, inlet branch 2 is blocked by the corresponding end piston 9, inlet branch 15 is open, outlet branch 5 is open, and outlet branch 16 is blocked by the corresponding end piston 9. Figure 5 As shown in the diagram, at this point, the distance between the inlet and outlet branches is the smallest, and the heat exchanger's heat exchange capacity is the weakest.

[0061] In this embodiment, the outer side of the threaded piston 11 is provided with scale lines. By observing the scale lines, the positions of the threaded piston 11 and the end piston 9 within the horizontal pipe section 14 can be determined on-site, thereby judging whether each inlet branch pipe and outlet branch pipe is blocked. In this embodiment, there are two sets of scale lines. The two sets of scale lines respectively show the degree to which the two inlet branch pipes are blocked by the corresponding two pistons, or the degree to which the two outlet branch pipes are blocked by the corresponding two pistons (threaded piston 11 and end piston 9). For example, when a branch pipe (inlet branch pipe and outlet branch pipe) is just completely blocked, the scale value of that branch pipe is displayed as zero. If the flow area of ​​the branch pipe gradually increases as the piston moves, then for every unit increase in flow area, the scale value increases by one value.

[0062] In implementation, in addition to the two sets of scale lines mentioned above, a third scale line can be set, with heat exchange efficiency as the unit of measurement. Under fixed environmental conditions such as temperature and flow rate, regardless of the sealing status of each inlet and outlet branch pipe, each point corresponds to a specific heat exchange efficiency value. Through calibration, the correspondence between each point of the piston assembly in the horizontal pipe section (corresponding to different sealing states) and the heat exchange efficiency value can be calibrated, and the calibrated heat exchange efficiency value is reflected on the third scale line.

[0063] Compared with the first embodiment, the advantages of the technical solution described in this embodiment are:

[0064] In the first embodiment, four valves are required, and each valve needs to be operated and controlled individually, which is cumbersome. In addition, the opening degree of ordinary valves is difficult to quantify, resulting in poor control accuracy.

[0065] In this embodiment, a switch control device with a special structure is used, which produces the following effects:

[0066] First, driven by the dual-axis motor 13, the two lead screws 12 rotate synchronously, which in turn drives the two piston assemblies to slide synchronously, thereby ensuring that the total diameter of the two inlet branch pipes and the total diameter of the two outlet branch pipes remain the same at all times.

[0067] Secondly, compared with using valves as the switching control device, using a dual-axis motor 13 to drive two piston assemblies to move can more quickly and conveniently control the switching of two inlet branch pipes and two outlet branch pipes at the same time, realizing multiple changes in the flow path of the shell fluid in the main shell 3, and greatly improving the ease of operation.

[0068] Third, after the piston assembly, consisting of the threaded piston 11, connecting rod 10, and end piston 9, moves, it can either individually block or open a single inlet branch or outlet branch, or simultaneously open two inlet branches and two outlet branches. It can also partially open or block a single inlet branch and outlet branch, thus providing multiple different flow paths for the shell fluid. Compared to using valves as on / off control devices, changing the flow path of the shell fluid in this way allows for more precise and flexible adjustment of the flow path, thereby achieving precise and flexible adjustment of the heat exchanger's heat exchange capacity.

[0069] Fourth, the pressure from the shell fluid on the two threaded pistons 11 connected to both ends of the dual-axis motor 13 is simultaneously applied to both ends of the motor shaft of the dual-axis motor 13 (the so-called dual-axis motor 13 does not mean that there are two shafts, but that one shaft extends from both ends of the dual-axis motor 13) and cancels each other out, thus making it easier to ensure the structural strength of the dual-axis motor 13.

Claims

1. A heat exchanger for use in the production of metribuzin, comprising a main shell (3), heat exchange tubes (7), and end caps (1), wherein the heat exchange tubes (7) are disposed inside the main shell (3), a tube fluid flows inside the heat exchange tubes (7), and a shell fluid flows in the space between the outer wall of the heat exchange tubes (7) and the main shell (3), and the tube fluid and the shell fluid exchange heat through the tube wall of the heat exchange tubes (7), and a shell fluid inlet pipe (4) and a shell fluid outlet pipe (6) are disposed on the outer side of the main shell (3), characterized in that: The shell fluid inlet pipe (4) is provided with two inlet branch pipes. One end of each of the two inlet branch pipes is connected to the shell fluid inlet pipe (4), and the other end is connected to the internal space of the main shell (3). The fluid outlet pipe is provided with two outlet branch pipes. One end of each of the two outlet branch pipes is connected to the shell fluid outlet pipe (6), and the other end is connected to the internal space of the main shell (3). Two inlet branch pipes are connected to the outside of one end of the main shell (3), and two outlet branch pipes are connected to the outside of the other end of the main shell (3); The two inlet branch pipes and the two outlet branch pipes are arranged along the axial direction of the main shell (3); Both the inlet and outlet branches are equipped with switch control devices. By operating the switch control devices, the switch control of each inlet and outlet branch can be realized, thereby changing the flow path of the shell fluid in the main shell (3) and thus adjusting the heat exchange capacity. The shell fluid inlet pipe (4) and the shell fluid outlet pipe (6) each include a horizontal pipe section (14), and the two horizontal pipe sections (14) are coaxial; The switch control device includes a dual-axis motor (13) and two piston assemblies. Each end of the dual-axis motor (13) is provided with a lead screw (12) with the same pitch but opposite direction of rotation. The two piston assemblies are respectively connected to the two lead screws (12) by threads. At the same time, the two piston assemblies are respectively slidably installed in two horizontal pipe sections (14) and slidably cooperate with the horizontal pipe sections (14). The piston assembly includes a threaded piston (11), an end piston (9), and a connecting rod (10). The end piston (9) is fixedly connected to the threaded piston (11) via the connecting rod (10). The threaded piston (11) connects the entire piston assembly to the lead screw (12) via threads. After the dual-axis motor (13) is started, the rotational motion of the lead screw (12) is converted into linear motion of the entire piston assembly, thereby adjusting the position of the threaded piston (11) and the end piston (9) in the horizontal pipe section (14) to realize the on / off control of each inlet branch pipe and outlet branch pipe.

2. A heat exchanger for use in the production of metribuzin according to claim 1, characterized in that: The piston assembly typically has three locations within the horizontal tube section (14): The following stipulations are made: the two inlet branch pipes are referred to as inlet branch pipe No. 1 (2) and inlet branch pipe No. 2 (15) from left to right, and the two outlet branch pipes are referred to as outlet branch pipe No. 1 (5) and outlet branch pipe No. 2 (16) from left to right. Then: When in the first typical position, the No. 1 inlet branch (2) is open, the No. 2 inlet branch (15) is blocked by the corresponding threaded piston (11), the No. 1 outlet branch (5) is blocked by the corresponding outlet branch, and the No. 2 outlet branch (16) is open. When in the second typical position, the No. 1 inlet branch (2), the No. 2 inlet branch (15), the No. 1 outlet branch (5) and the No. 2 outlet branch (16) are all connected; When in the third typical position, the No. 1 inlet branch (2) is blocked by the corresponding end piston (9), the No. 2 inlet branch (15) is open, the No. 1 outlet branch (5) is open, and the No. 2 outlet branch (16) is blocked by the corresponding end piston (9).

3. A heat exchanger for use in the production of metribuzin according to claim 1, characterized in that: The main shell (3) is provided with baffles (8), which are arranged at equal intervals and staggered vertically to form a serpentine flow channel in the main shell (3) for the passage of fluid.

4. A heat exchanger for use in the production of metribuzin according to claim 1, characterized in that: A locking mechanism is provided at the connection between the threaded piston (11) and the horizontal pipe section (14), which can lock the threaded piston (11) onto the horizontal pipe section (14).

5. A heat exchanger for use in the production of metribuzin according to claim 1, characterized in that: The threaded piston (11) has scale lines on its outer side. By observing the scale lines, the position of the threaded piston (11) and the end piston (9) in the horizontal pipe section (14) can be determined, and then it can be determined whether each inlet branch pipe and outlet branch pipe is blocked.

6. A heat exchanger for use in the production of metribuzin according to claim 5, characterized in that: There are two sets of scale lines. The two sets of scale lines show the degree to which the two inlet branch pipes are blocked by the corresponding two pistons, or the degree to which the two outlet branch pipes are blocked by the corresponding two pistons.

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