N, N-dimethylformamide synthesis device and process

Abstract

The invention discloses a device and a process for synthesizing N, N-dimethylformamide. The device comprises a reactor, a primary condenser, a secondary condenser, a circulating delivery pump A, a circulating heat exchanger, an injection pump A, a circulating delivery pump B, a CO distributor, an injection pump B and the like. Compared with the traditional process, the device disclosed by the invention has the advantages that the two symmetrical two-stage injection pumps are arranged at the bottom of the reactor, the CO distributor with the special anti-blocking spray head is adopted, and the inlet positions of the feeding and returning pipelines are flexibly arranged, so that the uncondensed raw material gas at the tower top is effectively recovered, and meanwhile, the mass transfer effect of kettle liquid is enhanced; the gas-liquid contact area is increased, and the reaction efficiency is obviously improved. In addition, the device can effectively prevent and solve the problem that the system is blocked by crystals, and stable operation of the system is ensured. The method has the remarkable advantages in the aspects of improving the reaction efficiency, reducing the energy consumption and solving the blockage problem, and an efficient and reliable solution is provided for production of N, N-dimethylformamide.

Description

Technical Field

[0001] The invention belongs to the field of N,N-dimethylformamide production, and specifically relates to an N,N-dimethylformamide synthesis device and process. Background Art

[0002] Dimethylformamide (DMF), also known as N,N-dimethylformamide, has the molecular formula C3H7NO. DMF is a highly versatile solvent and chemical raw material, primarily used in industries such as polyurethane, acrylic fibers, pharmaceuticals, pesticides, dyes, and electronics. The current DMF synthesis route is the carbon monoxide (CO) one-step process, which uses dimethylamine and CO as raw materials and sodium methoxide as a catalyst to directly synthesize DMF under a certain temperature and pressure. The (CO) one-step process actually proceeds in two steps: in the first step, methanol reacts with carbon monoxide to form methyl formate, and in the second step, methyl formate reacts with dimethylamine to form DMF. The reaction equation is as follows:

[0003] Step 1: CH3OH+CO=HCOOCH3

[0004] Step 2: HCOOCH3+(CH3)2NH=(CH3)2NCOH+CH3OH

[0005] The above two reactions are both exothermic reactions. The first step, methanol carbonylation, is a strongly exothermic reaction with a slow reaction rate, while the second step is a substitution reaction with a fast reaction rate.

[0006] The one-step CO production process offers advantages such as abundant raw material resources, low cost, a simple process flow, an anhydrous reaction process, low overall energy consumption for product separation, high product purity, and good yield, making it suitable for large-scale production. However, in practical applications, this process still faces some challenges. For example, when sodium methoxide is used as a catalyst, it easily reacts with water, oxygen, and carbon dioxide in the raw materials to form crystalline products such as sodium formate and sodium carbonate, leading to blockage of equipment and pipelines. Furthermore, during the reaction, CO cannot be fully and evenly mixed and dissolved into the reaction solution, resulting in reduced reaction efficiency and waste of raw materials.

[0007] To address these issues, patent CN 204093422U discloses a dimethylformamide reactor and supporting equipment. The patent describes a dimethylformamide reactor with a lower kettle reactor equipped with two layers of gas distributors and gas nozzles to uniformly distribute CO. The bottom of the kettle reactor is also configured with a 60-degree conical head. Patent CN113769697B discloses a dimethylformamide synthesis reactor and synthesis device, in which the bottom of the reactor is configured as a horizontal shell, with partitions installed inside the shell, and calandria-type gas distributors installed on both sides of the partition. Patent CN220531526U discloses a dimethylformamide reactor designed to prevent the accumulation of bottom crystals. The bottom of the reactor is configured as a conical head, equipped with a bottom gas distributor, and evenly staggered bottom gas nozzles.

[0008] While the aforementioned patents alleviate the problems of reactor blockage and uneven CO distribution to a certain extent, they still suffer from uneven CO distribution, insufficient recycling of unreacted CO, and ineffective solutions for blockage in circulation lines or heat exchangers. To address these issues, the present invention proposes an N,N-dimethylformamide synthesis device and process, designed to address these issues. Through optimized design and process improvements, this device and process significantly improve reaction efficiency, conserve raw materials, and reduce operating costs, demonstrating promising application prospects. Summary of the Invention

[0009] In response to the above-mentioned problems, the present invention provides an N,N-dimethylformamide synthesis device and process. By arranging two symmetrical two-stage jet pumps at the bottom of the reactor, adopting a CO distributor with a special anti-clogging nozzle, and flexibly arranging the inlet positions of the feed and return feed pipelines, the uncondensed raw gas at the top of the tower can be effectively recovered, the mass transfer effect of the kettle liquid is enhanced, the gas-liquid contact area is increased, the reaction efficiency is improved, and the problem of crystallization blocking the system can be effectively prevented and solved.

[0010] The technical solution adopted by the present invention to solve the technical problem is:

[0011] An N,N-dimethylformamide production device comprises a reactor, a primary condenser, a secondary condenser, a circulating delivery pump A, a circulating heat exchanger, a jet pump A, a circulating delivery pump B, a CO distributor, and a jet pump B. The jet pump A, the CO distributor, and the jet pump B are arranged in the lower part of the reactor; the gas outlet at the top of the reactor is connected to the inlet of the primary condenser, the gas phase outlet of the primary condenser is connected to the inlet of the secondary condenser, the liquid outlet at the bottom of the reactor is connected to the inlet of the circulating delivery pump A and the inlet of the circulating delivery pump B, the outlet of the circulating delivery pump A is connected to the inlet of the circulating heat exchanger, and the outlet of the circulating heat exchanger is connected to the reactor; the outlet of the circulating delivery pump B is connected to the liquid phase inlets of the jet pump A and the jet pump B, the gas phase inlets of the jet pump A and the jet pump B are connected to the non-condensable gas outlets of the primary condenser and the secondary condenser, and the non-condensable gas outlet of the secondary condenser is also connected to a venting pipeline with a control valve.

[0012] Furthermore, the reactor consists of a lower reaction zone one and an upper reaction zone two, wherein the reaction zone one is a high-speed turbulent reaction zone, and the reaction zone two is a tower reaction zone containing tower plates or fillers, and the reaction zone one and the reaction zone two are combined into a complete reactor; wherein the outlet of the circulating heat exchanger is divided into two routes, one route is connected to the reaction zone two, and the other route is connected to the reaction zone one.

[0013] Furthermore, the reaction zone 1 is provided with an upper and lower two-layer structure, the upper layer structure is two symmetrical jet pumps A and jet pump B, and the lower layer structure is provided with 1 to 2 layers of CO distributors; wherein, when the jet pumps A and jet pumps B eject the medium, their ejection directions are staggered in different vertical planes.

[0014] Furthermore, the jet pump A and the jet pump B are both composed of two-stage Venturi, wherein the jet gas inlet of the first-stage Venturi is connected to the non-condensable gas outlet of the first-stage condenser and the second-stage condenser, the jet liquid inlet of the first-stage Venturi is connected to the outlet of the circulating delivery pump B, the outlet of the mixing chamber 1 of the first-stage Venturi is connected to the second-stage Venturi, and the outlet nozzle of the mixing chamber 1 is connected to the mixing chamber 2 of the second-stage Venturi.

[0015] Furthermore, the CO distributor is one or more of a ring tubular distributor and a tree tubular distributor, and special anti-blocking nozzles are provided on the top of the ring tubular distributor and the tree tubular distributor. The number of the special anti-blocking nozzles is not less than 5 to 30 per 10,000 tons of DMF / year of DMF production.

[0016] Furthermore, the reactor is also provided with a raw material methylamine inlet, a raw material CO inlet, a catalyst inlet and a light component return port from a downstream distillation device, wherein the raw material methylamine, raw material CO and catalyst inlets are respectively provided with 1 to 2 inlets in reaction zone 1 and reaction zone 2, and the light component return port is provided with 4 to 5 branches, 3 to 4 of which are connected to the reaction zone 2, and another branch is connected to the material inlet of the circulating heat exchanger.

[0017] A process for producing an N,N-dimethylformamide device comprises the following process steps:

[0018] Step 1: Methylamine from the upstream section enters the reaction zone 1 through the feed pipeline. After reaching a certain liquid level, the circulating delivery pump A is started. After the reaction liquid circulates normally, the primary condenser, secondary condenser and circulating heat exchanger are opened. The catalyst is added in proportion at the same time as the raw material liquid enters the reaction zone 1, and finally the raw gas CO is fed;

[0019] Step 2: After carbon monoxide is introduced for reaction, the reaction system pressure is controlled to 1.5-3.0 MPaG through the top condenser and the vent line, and the reaction system temperature is controlled to 70-130°C by regulating the temperature of the material at the outlet of the circulating heat exchanger;

[0020] Step 3: Start the circulation pump B, the jet pump A and the jet pump B while maintaining the reactor pressure stable;

[0021] Step 4: After the reaction temperature and pressure reach a stable state, the feed line of methylamine and catalyst into the reaction zone 2 is opened; when the light component of the downstream distillation unit is returned, the light component of the returned material is opened to enter the return line of the reaction zone 2 or the feed side pipeline of the circulating heat exchanger;

[0022] Step 5: After a certain reaction time, when the product DMF concentration reaches approximately the target concentration, open the circulation delivery pump A and the branch pipeline to discharge the crude product to the downstream section.

[0023] Furthermore, the process of the N,N-dimethylformamide production device is characterized in that the non-condensable gas that is not condensed at the top of the reactor is returned to the reactor through jet pump A and jet pump B.

[0024] Furthermore, the process of the N,N-dimethylformamide production device is characterized in that the temperature of the medium used to cool the circulating heat exchanger cannot be lower than 50°C.

[0025] Furthermore, the process of the N,N-dimethylformamide production device is characterized in that when there is blockage in the reaction zone 2 or the circulating heat exchanger in the reactor, the return port is opened to flush the corresponding pipeline.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) In the above-mentioned N,N-dimethylformamide production device and process, a jet pump and a CO distributor in an upper and lower combination are used to enhance CO distribution. Fresh CO is introduced into the lower CO distributor, and CO recovered from the top of the reactor is introduced into the upper jet pump and returned to the reactor. This can not only recover unreacted raw materials, but also fully disperse the CO, thereby improving reaction efficiency.

[0028] 2) A jet pump is used in conjunction with two venturi stages. The first stage venturi uses the circulating liquid delivered by the circulating delivery pump B as the ejection medium to suck the uncondensed gas at the top of the tower. The second stage venturi uses the gas-liquid mixture at the outlet of the first stage venturi as the ejection medium to suck the gas material in the gas phase space in the reactor, thereby enhancing the mixing effect of the reactor liquid and further improving the reaction efficiency.

[0029] 3) Special anti-clogging nozzles are installed on the top of the ring tube and tree tube of the CO distributor to effectively prevent crystals in the reaction liquid from clogging the nozzles;

[0030] 4) By flexibly setting multiple branches of the light component return port, for example, connecting 3 to 4 branches to the reaction zone 2 and another branch to the material inlet of the circulating heat exchanger, when the reaction zone 2 or the circulating heat exchanger is blocked, the material at the return port can be used as a flushing liquid due to its high temperature to flush the blocked area, thereby improving the system patency and clearing the blockage;

[0031] 5) Methylamine and catalyst feed inlets are set in reaction zone 1 and reaction zone 2 respectively to further enhance material mixing.

[0032] In summary, compared with the existing technology, the present technical solution has obvious advantages in terms of equipment investment, operating costs, reaction efficiency, etc., and can produce N,N-dimethylformamide more efficiently and energy-savingly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of an N,N-dimethylformamide synthesis device and process flow of the present invention;

[0034] Figure 2 A top view and a side view of a CO distributor of an N,N-dimethylformamide synthesis device and process of the present invention;

[0035] Figure 3 A jet pump for an N,N-dimethylformamide synthesis device and process of the present invention;

[0036] Figure 4 This is a schematic diagram of the structure of the CO distributor of the present invention arranged in the lower part of the reactor;

[0037] In the figure: 1-reactor, 2-first-stage condenser, 3-secondary condenser, 4-circulating delivery pump A, 5-circulating heat exchanger, 6-jet pump A, 7-circulating delivery pump B, 8-CO distributor, 9-jet pump B, 601-injection gas inlet of the first-stage Venturi, 602-injection liquid inlet of the first-stage Venturi, 603-mixing chamber 1, 604-mixing chamber 2, 801-ring tubular distributor, 802-tree tubular distributor, 803-special anti-blocking nozzle. DETAILED DESCRIPTION

[0038] The following examples clearly and completely describe the technical solutions of the present invention. It is obvious that the described examples are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] 11. Such as Figure 1 As shown, an N,N-dimethylformamide production device is composed of a reactor 1, a primary condenser 2, a secondary condenser 3, a circulating pump A4, a circulating heat exchanger 5, a jet pump A6, a circulating pump B7, a CO distributor 8, a jet pump B9, etc. The gas outlet at the top of the reactor 1 is connected to the primary condenser 2, the gas phase outlet of the primary condenser 2 is connected to the inlet of the secondary condenser 3, the liquid outlet at the bottom of the reactor 1 is connected to the outlet of the circulating pump A4 and the outlet of the circulating pump B7, the outlet of the circulating pump A4 is connected to the inlet of the circulating heat exchanger 5, one end of the outlet of the circulating heat exchanger 5 is connected to the reaction zone 2 of the reactor 1, and the other end of the inlet is connected to the reaction zone 1; the inlet of the circulating pump B7 is connected to the liquid phase inlet of the jet pump A6 and the jet pump B9, the gas phase inlet of the jet pump A6 and the jet pump B9 is connected to the non-condensable gas outlet of the primary condenser 2 and the secondary condenser 3, and the non-condensable gas outlet of the secondary condenser 3 is also connected to a vent line with a control valve.

[0040] Based on the two-step reaction characteristics of the N,N-dimethylformamide synthesis production process, the reaction device is divided into two upper and lower zones, reaction zone one and reaction zone two, respectively for the two reactions in the synthesis process. Reaction zone one is a high-speed turbulent reaction zone, which mainly reacts with CO and methanol to produce methyl formate in a slow reaction. Reaction zone two is a tower reaction zone, which mainly provides a reaction site for the reaction between methyl formate and dimethylamine, which is a fast reaction.

[0041] Reaction Zone 1 is constructed as a two-tiered structure. The upper tier houses two symmetrical jet pumps A6 and B9, while the lower tier features one or two layers of CO distributors 8. The two upper jet pumps primarily recover unreacted CO and non-condensable gases such as methylamine from the tower overhead, while the lower CO distributor distributes freshly fed CO. Jet pumps A6 and B9 spray media in staggered directions within different vertical planes, eliminating blind spots in the spray process.

[0042] like Figure 2-Figure 3 Jet Pump A 6 and Jet Pump B 9 are both constructed as two-stage Venturi systems. The jet gas inlet 601 of the first-stage Venturi is connected to the non-condensable gas outlets of the primary condenser 2 and the secondary condenser 3, extracting uncondensed non-condensable gases from the tower top, such as CO and dimethylamine. The jet liquid inlet 602 of the first-stage Venturi is connected to the outlet of circulating pump B 7, which delivers reactor liquid as the ejection medium for the first-stage Venturi. The outlet of mixing chamber 1 603 of the first-stage Venturi is connected to the second-stage Venturi, and the outlet nozzle of mixing chamber 1 603 is connected to mixing chamber 2 604 of the second-stage Venturi. The gas-liquid mixture at the outlet of mixing chamber 1 of the first-stage Venturi enters mixing chamber 2 604 of the second-stage Venturi, serving as the ejection medium for the second-stage Venturi. The gas-phase suction port of the second-stage Venturi draws gas from the gas phase, thereby enhancing mixing.

[0043] like Figure 4 A CO distributor 8 is installed at the bottom of the reaction zone 1. The main pipeline of the CO distributor 8 can be set as one or more of a ring tubular distributor 801 or a tree tubular distributor 802 as required. A special anti-blocking nozzle 803 is installed on the main pipeline of the distributor. The number of special anti-blocking nozzles 803 installed is not less than 5 to 30 per 10,000 tons / year of DMF production.

[0044] In addition, the reactor 1 is also provided with an inlet for raw material methylamine, an inlet for raw material CO, an inlet for catalyst, and a return port for light components from a downstream distillation device. The inlets for raw material methylamine, raw material CO, and catalyst are provided in reaction zone one and reaction zone two, respectively, with 1 to 2 each. The return port for light components is provided with 4 to 5 branches, 3 to 4 of which are connected to the reaction zone two, and the other branch is connected to the material inlet of the circulating heat exchanger 5. The main purpose is to ensure uniform feeding. When the internal structure of the reaction zone two or the circulating heat exchanger 5 is blocked, the light component return from the downstream distillation device can be used as a flushing agent due to its high temperature to flush the blocked area. The components of the downstream return material are mainly methanol and dimethylamine, which are reaction raw materials and recycled raw materials. In addition, this medium can be used to flush and dissolve solid blockages.

[0045] The production process of the above-mentioned N,N-dimethylformamide production device specifically includes the following steps:

[0046] Step 1: Methylamine from the upstream process enters the reaction zone 1 through the feed pipeline. After reaching a certain liquid level, the circulating delivery pump A4 is started. After the reaction liquid circulates normally, the cooling / heating medium of the primary condenser 2, the secondary condenser 3 and the circulating heat exchanger 5 are turned on. At the same time as the raw material liquid enters the reaction zone 1, a catalyst (the catalyst can be a sodium salt, such as sodium methoxide) is added in proportion. Finally, the raw gas CO is fed;

[0047] Step 2: After carbon monoxide is introduced for reaction, the pressure of the reaction system is controlled to be 1.5-3.0 MPaG through the top condenser and the vent line, and the temperature of the reaction system is controlled to be 70-130° C. through the outlet temperature of the circulating heat exchanger 5;

[0048] Step 3: Start the circulation pump B 7, the jet pump A 6 and the jet pump B 9 while maintaining the reactor pressure stable.

[0049] Step 4: After the reaction temperature and pressure reach a stable state, the feed line for methylamine and catalyst to enter the reaction zone 2 is opened. When the light component of the downstream distillation unit is returned, the light component return line to the reaction zone 2 or the feed side line of the circulating heat exchanger 5 is opened.

[0050] Step 5: After a certain reaction time, when the concentration of the product DMF reaches about 90% wt, the circulating delivery pump A4 is turned on to discharge the crude product to the downstream section through the branch pipeline.

[0051] The non-condensable gas at the top of the reactor that is not condensed is returned to the reactor through jet pump A 6 and jet pump B 9.

[0052] During the above process, the temperature of the heat-releasing cooling medium in the circulating heat exchanger 5 must not be lower than 50°C, otherwise it will easily cause crystallization of the material and block the pipeline or heat exchanger. Once blockage occurs, open the return port to flush the corresponding pipeline.

Claims

1. A device for producing N,N-dimethylformamide, characterized in that: The invention comprises a reactor (1), a primary condenser (2), a secondary condenser (3), a circulating delivery pump A (4), a circulating heat exchanger (5), a jet pump A (6), a circulating delivery pump B (7), a CO distributor (8), and a jet pump B (9), wherein the jet pump A (6), the CO distributor (8), and the jet pump B (9) are arranged in the lower part of the reactor (1), the gas outlet at the top of the reactor (1) is connected to the inlet of the primary condenser (2), the gas phase outlet of the primary condenser (2) is connected to the inlet of the secondary condenser (3), and the liquid outlet at the bottom of the reactor (1) is connected to the inlet of the secondary condenser (3). The outlet of the circulating pump (4) is connected to the inlet of the circulating pump A (4) and the inlet of the circulating pump B (7), the outlet of the circulating pump A (4) is connected to the inlet of the circulating heat exchanger (5), and the outlet of the circulating heat exchanger (5) is connected to the reactor (1); the outlet of the circulating pump B (7) is connected to the liquid phase inlet of the jet pump A (6) and the jet pump B (9), the gas phase inlet of the jet pump A (6) and the jet pump B (9) is connected to the non-condensable gas outlet of the first condenser (2) and the second condenser (3), and the non-condensable gas outlet of the second condenser (3) is also connected to a vent line with a control valve.

2. The N,N-dimethylformamide production device according to claim 1, characterized in that: The reactor (1) consists of a lower reaction zone 1 and an upper reaction zone 2, wherein the reaction zone 1 is a high-speed turbulent reaction zone, and the reaction zone 2 is a tower reaction zone containing tower plates or fillers, and the reaction zone 1 and the reaction zone 2 are combined to form a complete reactor; wherein the outlet of the circulating heat exchanger (5) is divided into two paths, one path is connected to the reaction zone 2, and the other path is connected to the reaction zone 1.

3. An N,N-dimethylformamide production device according to claim 2, characterized in that, The reaction zone 1 is provided with an upper and lower two-layer structure, the upper layer structure is provided with two symmetrical jet pumps A (6) and jet pump B (9), and the lower layer structure is provided with 1-2 layers of CO distributors (8); wherein, when the jet pumps A (6) and jet pumps B (9) eject the medium, the ejection directions of the two are staggered in different vertical planes.

4. An N,N-dimethylformamide production device according to claim 1 or 3, characterized in that, The jet pump A (6) and the jet pump B (9) are both composed of two-stage venturi, wherein the jet gas inlet (601) of the first-stage venturi is connected to the non-condensable gas outlet of the first-stage condenser (2) and the second-stage condenser (3), the jet liquid inlet (602) of the first-stage venturi is connected to the outlet of the circulation delivery pump B (7), the outlet of the mixing chamber 1 (603) of the first-stage venturi is connected to the second-stage venturi, and the outlet nozzle of the mixing chamber 1 (603) is connected to the mixing chamber 2 (604) of the second-stage venturi.

5. The N,N-dimethylformamide production device according to claim 3, characterized in that: The CO distributor (8) is one or more of a ring-shaped tubular distributor (801) and a tree-shaped tubular distributor (802), and special anti-blocking nozzles (803) are provided on the tops of the ring-shaped tubular distributor (801) and the tree-shaped tubular distributor (802). The number of the special anti-blocking nozzles (803) is not less than 5 to 30 per 10,000 tons of DMF per year of DMF production.

6. The N,N-dimethylformamide production device according to claim 2, characterized in that: The reactor (1) is further provided with a raw material methylamine inlet, a raw material CO inlet, a catalyst inlet and a light component return port from a downstream distillation device, wherein the raw material methylamine, raw material CO and catalyst inlets are provided with 1 to 2 inlets in reaction zone 1 and reaction zone 2 respectively, and the light component return port is provided with 4 to 5 branches, 3 to 4 of which are connected to the reaction zone 2, and another branch is connected to the material inlet of the circulating heat exchanger (5).

7. The process of the N,N-dimethylformamide production device according to any one of claims 1 to 6, characterized in that: The process steps include: Step 1: Methylamine from the upstream section enters the reaction zone 1 through the feed pipeline. After reaching a certain liquid level, the circulating delivery pump A (4) is started. After the reaction liquid circulates normally, the first condenser (2), the second condenser (3) and the circulating heat exchanger (5) are opened. When the raw material liquid enters the reaction zone 1, the catalyst is added in proportion. Finally, the raw material gas CO is fed in. Step 2: After the carbon monoxide is introduced for reaction, the pressure of the reaction system is controlled to be 1.5-3.0 MPaG through the top condenser and the vent line, and the temperature of the reaction system is controlled to be 70-130°C by regulating the outlet temperature of the circulating heat exchanger (5); Step 3: Start the circulation pump B (7), the jet pump A (6) and the jet pump B (9), while maintaining the reactor pressure stable; Step 4: After the reaction temperature and pressure reach a stable state, open the feed line of methylamine and catalyst to the reaction zone 2; when the light component of the downstream distillation unit is returned, open the return line of the light component to the reaction zone 2 or the feed side line of the circulating heat exchanger (5); Step 5: After a certain reaction time, when the product DMF concentration reaches approximately the target concentration, open the circulation delivery pump A (4) and the branch pipeline behind the pump to discharge the crude product to the downstream section.

8. The process of an N,N-dimethylformamide production device according to claim 7, characterized in that: The non-condensable gas at the top of the reactor that is not condensed is returned to the reactor through jet pump A (6) and jet pump B (9).

9. The process of an N,N-dimethylformamide production device according to claim 7, characterized in that: The temperature of the medium used to cool the circulating heat exchanger (5) cannot be lower than 50°C.

10. The process of an N,N-dimethylformamide production device according to claim 7, characterized in that: When there is a blockage in the reaction zone 2 or the circulating heat exchanger (5) in the reactor, the corresponding pipeline is flushed by opening the return port.

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