N-ethyl carbazole production system

Abstract

The utility model relates to the technical field of chemical production devices, and discloses an N-ethyl carbazole production system which is characterized in that an alkylation kettle is connected with a liquid caustic soda feeding pipe and a carbazole feeding pipe; the alkylation kettle is connected with a bromoethane head tank liquid outlet and pressure balance pipe; a top outlet of the alkylation kettle is connected with a receiving tank through a first tubular condenser, and the receiving tank is connected with the alkylation kettle; the alkylation kettle is connected with a liquid caustic soda concentration kettle; a liquid outlet pipe is connected with a nitration kettle through a liquid outlet branch pipe; the top of the liquid caustic soda concentration kettle is connected with a water receiving tank through a second tube bundle condenser, and the water receiving tank is connected with a blow-down pipe and a liquid caustic soda preparation kettle; the liquid caustic soda concentration kettle is connected with a centrifugal machine, a filtrate outlet of the centrifugal machine is connected with a recovered caustic soda intermediate tank, the recovered caustic soda intermediate tank is connected with a liquid caustic soda preparation kettle, the liquid caustic soda preparation kettle is connected with a liquid caustic soda metering tank, and a bottom outlet of the liquid caustic soda metering tank is connected with an alkylation kettle. The system improves the utilization rate of bromoethane, thoroughly recovers the byproduct sodium bromide, reduces the unit consumption of sodium hydroxide, and reduces pollution.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical production equipment, in particular to a production system of a permanent violet intermediate, specifically an N-ethylcarbazole production system. Background Art

[0002] The production of permanent violet has a mature process in China. In the prior art, the preparation process of the permanent violet intermediate N-ethylcarbazole adopts a phase catalytic alkylation system. The production and use process of this system is as follows: sodium hydroxide solution, carbazole, phase transfer catalyst, and benzene are added to the reactor, and the temperature is kept at 35-40°C after stirring and mixing. Ethyl bromide is added dropwise, and after the addition is completed, the temperature is kept at 50-60°C for a certain period of time to allow a complete reaction, and then the temperature is increased to distill out the excess ethyl bromide. The distilled material is allowed to stand and separate to separate the sodium hydroxide solution at the lower layer for recycling, and the molten N-ethylcarbazole at the upper layer is transported to the next process (nitration reactor) through a pipeline.

[0003] The above production system has two problems. On the one hand, the boiling point of ethyl bromide is relatively low at 39°C, and the traditional alkylation reaction is a normal pressure reaction. During the process of adding ethyl bromide and keeping the reaction warm, ethyl bromide gas will be volatilized from the vent pipe of the reflux system. The volatilization of ethyl bromide into the air not only causes a waste of raw materials but also brings environmental pollution. Sometimes, excessive volatilization will cause incomplete reaction, which has an adverse effect on product quality. Therefore, the traditional process uses a lot of excessive ethyl bromide to achieve the purpose of complete reaction, resulting in a large amount of raw materials. Use, increase production costs. On the other hand, the sodium hydroxide solution from the alkylation layer contains a large amount of sodium bromide, which is directly used without removal. Since the sodium bromide is in a supersaturated crystalline state, it will eventually be brought into the product and seriously affect the product quality.

[0004] In summary, in the prior art, the phase-catalyzed alkylation system used in the preparation of the permanent violet intermediate N-ethylcarbazole will cause excessive use of ethyl bromide, resulting in a waste of raw materials. At the same time, the vented ethyl bromide will pollute the environment. In addition, the product contains unremoved sodium bromide, which affects the product quality. Summary of the invention

[0005] The utility model provides an N-ethylcarbazole production system to solve a series of problems such as the inability to recycle ethyl bromide in the current catalytic alkylation system, resulting in excessive use, increased raw material costs while polluting the environment, and the presence of byproduct sodium bromide in the product that cannot be completely recovered, affecting product quality.

[0006] The utility model is implemented by the following technical solutions:

[0007] An N-ethylcarbazole production system comprises an alkylation kettle, wherein the top inlet of the alkylation kettle is connected with a liquid alkali feeding pipe and a carbazole feeding pipe; the top inlet and the top outlet of the alkylation kettle are respectively connected with the bottom liquid outlet and the top pressure balance pipe of the ethyl bromide high-level tank, and the top of the ethyl bromide high-level tank is connected with a storage tank through an ethyl bromide feeding pipe; the top outlet of the alkylation kettle is connected with a first tube-in-tube condenser, the outlet of the first tube-in-tube condenser is connected with a receiving tank, and the outlet of the receiving tank is connected with the top inlet of the alkylation kettle through an ethyl bromide recovery pipe; the bottom outlet of the alkylation kettle is connected with one or more parallel liquid alkali concentration kettles through a liquid outlet pipe, and the liquid outlet pipe is connected with a liquid outlet pipe. The branch pipe is connected to the nitrification kettle; a second tube condenser is installed on the top of the liquid alkali concentration kettle, the outlet of the second tube condenser is connected to the water receiving tank, the top outlet of the water receiving tank is connected to the vent pipe, and the bottom outlet of the water receiving tank is connected to the liquid alkali preparation kettle; the bottom outlet of the liquid alkali concentration kettle is connected to the centrifuge, the filter cake outlet of the centrifuge is connected to the packaging section, the filtrate outlet of the centrifuge is connected to the alkali recovery intermediate tank, the alkali recovery intermediate tank is connected to the liquid alkali preparation kettle, the top of the liquid alkali preparation kettle is provided with a caustic flake feeding port, the bottom outlet of the liquid alkali preparation kettle is connected to the liquid alkali metering tank, the top outlet of the liquid alkali metering tank is connected to the vent pipe, and the bottom outlet of the liquid alkali metering tank is connected to the alkylation kettle.

[0008] During implementation, the method comprises an alkylation kettle with a pressure of 0.05 MPa, the alkylation kettle is made of stainless steel, the bottom of the alkylation kettle is conical, which is conducive to liquid stratification, the alkylation kettle is connected with a jacket cooling water inlet pipe and a jacket cooling water outlet pipe; the alkylation kettle is connected with a jacket steam inlet pipe and a jacket steam condensate outlet pipe; the top inlet of the alkylation kettle is connected with a liquid alkali feeding pipe and a carbazole feeding pipe;

[0009] The top inlet and the top outlet of the alkylation kettle are connected to the bottom liquid outlet of the ethyl bromide header tank and the top pressure balance pipe respectively; specifically, the top inlet of the alkylation kettle is connected to the bottom liquid outlet of the ethyl bromide header tank through the ethyl bromide inlet pipe, a second valve is installed on the ethyl bromide inlet pipe, and the top of the ethyl bromide header tank is connected to the storage tank through the ethyl bromide feed pipe;

[0010] The top outlet of the alkylation kettle is connected with a first tube condenser, which is inclined to ensure the reflux height and reflux efficiency. The first tube condenser is connected with a condenser vent pipe provided with a third valve. The outlet of the first tube condenser is connected with a receiving tank, and the outlet of the receiving tank is connected with the top inlet of the alkylation kettle through an ethyl bromide recovery pipe; the ethyl bromide recovery pipe is provided with a first valve;

[0011] The bottom outlet of the alkylation kettle is connected to one or more parallel liquid alkali concentration kettles through a liquid outlet pipe, and the liquid alkali concentration kettle is connected with a jacket cooling water inlet pipe and a jacket cooling water outlet pipe to cooperate to complete the jacket cooling water circulation; the alkylation kettle is connected with a jacket steam inlet pipe and a jacket steam condensate outlet pipe to cooperate to complete the jacket steam circulation; the liquid outlet pipe is connected to the nitration kettle through a liquid outlet branch pipe, and a liquid outlet pump is installed on the liquid outlet pipe behind the liquid outlet branch pipe;

[0012] A second tube condenser is installed on the top of the liquid alkali concentration kettle, the outlet of the second tube condenser is connected to a water receiving tank, the top outlet of the water receiving tank is connected to a vent pipe, the bottom outlet of the water receiving tank is connected to a liquid alkali preparation kettle, and a jacket cooling water inlet pipe and a jacket cooling water outlet pipe are installed on the liquid alkali preparation kettle;

[0013] The bottom outlet of the liquid alkali concentration kettle is connected to the centrifuge, the filter cake outlet of the centrifuge is connected to the packaging section, the filtrate outlet of the centrifuge is connected to the alkali recovery intermediate tank, the alkali recovery intermediate tank is connected to the liquid alkali preparation kettle, the alkali recovery conveying pump is installed on the connecting pipeline between the alkali recovery intermediate tank and the liquid alkali preparation kettle, the top of the liquid alkali preparation kettle is provided with a caustic flake feeding port, the bottom outlet of the liquid alkali preparation kettle is connected to the liquid alkali metering tank, the top outlet of the liquid alkali metering tank is connected to the vent pipe, the bottom outlet of the liquid alkali metering tank is connected to the alkylation kettle, and the alkali preparation conveying pump is installed on the connecting pipeline between the liquid alkali metering tank and the alkylation kettle to complete the circulation.

[0014] When in use, sodium hydroxide solution is added to the stirred alkylation kettle through the liquid alkali feeding pipe, carbazole and phase transfer catalyst are added through the liquid carbazole feeding pipe, the whole reaction system is sealed, and the refrigerated circulating water on the first tube condenser is opened, ethyl bromide flows by gravity through the second valve through the ethyl bromide high-level tank and is added dropwise within a specified time, the molar ratio of carbazole to ethyl bromide is 1:1.025-1.050, and the reaction is continued for 2 hours after the addition is completed. When adding dropwise, the third valve is closed, the condenser vent pipe is closed, and the cooling circulating water on the jacket of the alkylation kettle is opened, that is, the jacket cooling water inlet pipe and the jacket cooling water outlet pipe on the alkylation kettle are opened to circulate the cooling water, and the reaction temperature in the alkylation kettle is maintained at 30-35°C. The ethyl bromide volatilized during the reaction will be condensed by the first tube condenser and flow to the receiving tank, and the first valve is opened after the receiving tank has liquid.

[0015] After the reaction is completed, the reflux state is switched to the distillation state, the first valve and the second valve are closed, the cooling circulating water on the jacket of the alkylation kettle is closed, the third valve is opened, and the steam circulation on the jacket of the alkylation kettle is opened, that is, the jacket steam inlet pipe and the jacket steam condensate outlet pipe on the alkylation kettle are opened for steam circulation, so that the temperature in the alkylation kettle is heated to 90°C to distill ethyl bromide into the receiving tank, and the ethyl bromide in the receiving tank is used for the next batch. After reaching the reaction end point, it is allowed to stand for 10 minutes, and the liquid is separated into layers. The sodium hydroxide solution containing sodium bromide in the lower layer is first pumped to the liquid alkali concentration kettle through the liquid outlet pipe by the liquid outlet pump, and then the molten N-ethylcarbazole on the upper layer of the liquid surface is transported to the nitration kettle through the liquid outlet branch pipe for subsequent processing. In the liquid alkali concentration kettle, the sodium hydroxide solution containing sodium bromide is concentrated, and the gas phase is condensed into the water receiving tank through the second tube condenser, and then leads to the liquid alkali preparation kettle. The liquid phase sodium bromide solution is cooled and crystallized, and then centrifuged and filtered in the centrifuge. The filter cake after centrifugation obtains sodium bromide, which is packaged in the packaging section and sold outside. The filtrate after centrifugation flows by gravity to the alkali recovery intermediate tank for enrichment. The sodium hydroxide solution in the alkali recovery intermediate tank is pumped into the liquid alkali preparation kettle through the alkali recovery delivery pump, and alkali flakes and quantitative water are added to the liquid alkali preparation kettle through the alkali flake feeding port. After the solution is prepared to the specified concentration, it is pumped into the liquid alkali metering tank, and then pumped into the alkylation kettle through the alkali preparation delivery pump for subsequent circulation.

[0016] Compared with the prior art, the utility model has the following beneficial effects:

[0017] The utility model provides an N-ethylcarbazole production system, which improves the production system by using a closed pressure process, fully improves the utilization rate of ethyl bromide, reduces the unit consumption of ethyl bromide to a minimum, and reduces the consumption of raw materials. Compared with the prior art, the use of solvents is avoided, thereby improving the production environment. The byproduct sodium bromide is completely recovered, and the infinite circulation of sodium hydroxide solution is realized, the unit consumption of sodium hydroxide is reduced, and no wastewater and waste liquid are generated, thereby reducing the pressure of sewage discharge.

[0018] According to actual production statistics, the reaction yield of this system can reach more than 99.5% during production; the by-product sodium bromide is recovered to the maximum extent, and 600 kg of sodium bromide can be recovered for every ton of N-ethylcarbazole produced, generating an economic benefit of 6,000 yuan / ton; the recycling of the acid-binding agent sodium hydroxide is realized, reducing the consumption of sodium hydroxide by 500 kg / ton; the closed pressurized reaction is used to reduce the volatilization of ethyl bromide, and the unit consumption of ethyl bromide is reduced from the existing 700 kg / ton product to 570 kg / ton product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The schematic diagram of the structure of the utility model is shown.

[0020] In the figure: 1-alkylation kettle, 2-bromoethane high-level tank, 3-first tube condenser, 4-receiving tank, 5-liquid alkali concentration kettle, 6-liquid discharge pump, 7-nitration kettle, 8-second tube condenser, 9-water receiving tank, 10-liquid alkali preparation kettle, 1001-flaked alkali feeding port, 11-centrifuge, 12-alkali recovery intermediate tank, 13-liquid alkali metering tank, 14-preparation alkali delivery pump, 15-recovery alkali delivery pump, 16-first valve, 17-second valve, 18-third valve;

[0021] L1- bromoethane inlet pipe, L2- condenser vent pipe, L3- liquid alkali feeding pipe, L4- bromoethane recovery pipe, L5- bromoethane feed pipe, L6- carbazole feeding pipe, L7- liquid outlet pipe, L8- liquid outlet branch pipe, L9- vent pipe, L10- jacket cooling water inlet pipe, L11- jacket cooling water outlet pipe, L12- jacket steam inlet pipe, L13- jacket steam condensate outlet pipe. DETAILED DESCRIPTION

[0022] The specific embodiments of the present utility model are described below in conjunction with the accompanying drawings.

[0023] A system for producing N-ethylcarbazole, such as Figure 1 As shown: it includes an alkylation kettle 1 with a pressure of 0.05MPa, the alkylation kettle 1 is made of stainless steel, and is connected to a jacket cooling water inlet pipe L10 and a jacket cooling water outlet pipe L11; the alkylation kettle 1 is connected to a jacket steam inlet pipe L12 and a jacket steam condensate outlet pipe L13; the top inlet of the alkylation kettle 1 is connected to a liquid alkali feeding pipe L3 and a carbazole feeding pipe L6;

[0024] The top inlet and the top outlet of the alkylation kettle 1 are connected to the bottom liquid outlet and the top pressure balance pipe of the ethyl bromide header tank 2 respectively; specifically, the top inlet of the alkylation kettle 1 is connected to the bottom liquid outlet of the ethyl bromide header tank 2 through the ethyl bromide inlet pipe L1, and the second valve 17 is installed on the ethyl bromide inlet pipe L1. The top of the ethyl bromide header tank 2 is connected to the storage tank through the ethyl bromide feed pipe L5, which serves as the feed source of ethyl bromide;

[0025] The top outlet of the alkylation kettle 1 is connected to a first tube-and-tube condenser 3, which is inclined to ensure the reflux height and reflux efficiency. The first tube-and-tube condenser 3 is connected to a condenser vent pipe L2 provided with a third valve 18, and the outlet of the first tube-and-tube condenser 3 is connected to a receiving tank 4, and the outlet of the receiving tank 4 is connected to the top inlet of the alkylation kettle 1 through an ethyl bromide recovery pipe L4; the ethyl bromide recovery pipe L4 is provided with a first valve 16;

[0026] The bottom outlet of the alkylation kettle 1 is connected to one or more parallel liquid alkali concentration kettles 5 through a liquid outlet pipe L7, and the liquid alkali concentration kettle 5 is connected to a jacket cooling water inlet pipe L10 and a jacket cooling water outlet pipe L11, which cooperate to complete the jacket cooling water circulation; the alkylation kettle 1 is connected to a jacket steam inlet pipe L12 and a jacket steam condensate outlet pipe L13, which cooperate to complete the jacket steam circulation; the liquid outlet pipe L7 is connected to the nitration kettle 7 through a liquid outlet branch pipe L8, and a liquid outlet pump 6 is installed on the liquid outlet pipe L7 behind the liquid outlet branch pipe L8;

[0027] A second tube condenser 8 is installed on the top of the liquid alkali concentration kettle 5, the outlet of the second tube condenser 8 is connected to a water receiving tank 9, the top outlet of the water receiving tank is connected to a vent pipe L9, the bottom outlet of the water receiving tank 9 is connected to a liquid alkali preparation kettle 10, and a jacket cooling water inlet pipe L10 and a jacket cooling water outlet pipe L11 are installed on the liquid alkali preparation kettle 10;

[0028] The bottom outlet of the liquid alkali concentration kettle 5 is connected to the centrifuge 11, the filter cake outlet of the centrifuge 11 is connected to the packaging section, the filtrate outlet of the centrifuge 11 is connected to the alkali recovery intermediate tank 12, the alkali recovery intermediate tank 12 is connected to the liquid alkali preparation kettle 10, and the connecting pipeline between the alkali recovery intermediate tank 12 and the liquid alkali preparation kettle 10 is installed with a alkali recovery delivery pump 15. The top of the liquid alkali preparation kettle 10 is provided with a caustic soda flake feeding port 1001, the bottom outlet of the liquid alkali preparation kettle 10 is connected to the liquid alkali metering tank 13, the top outlet of the liquid alkali metering tank 13 is connected to the vent pipe L9, the bottom outlet of the liquid alkali metering tank 13 is connected to the alkylation kettle 1, and the connecting pipeline between the liquid alkali metering tank and the alkylation kettle 1 is installed with a prepared alkali delivery pump 14 to complete the circulation.

[0029] When in use, sodium hydroxide solution is added to the stirred alkylation kettle 1 through the liquid alkali feeding pipe L3, carbazole and phase transfer catalyst are added through the liquid carbazole feeding pipe L6, the whole reaction system is sealed, and the refrigerated circulating water on the first tube condenser 3 is opened, ethyl bromide flows by gravity through the second valve 17 through the ethyl bromide header tank 2 and is added dropwise within a specified time, the molar ratio of carbazole to ethyl bromide is 1:1.025-1.050, and the reaction is continued for 2 hours after the addition is completed. When the addition is completed, the third valve 18 is closed, the condenser vent pipe L9 is closed, and the cooling circulating water on the jacket of the alkylation kettle 1 is opened, that is, the jacket cooling water inlet pipe L10 and the jacket cooling water outlet pipe L11 on the alkylation kettle 1 are opened to circulate the cooling water, and the reaction temperature in the alkylation kettle 1 is maintained at 30-35°C. The volatilized ethyl bromide during the reaction will be condensed by the first tube condenser 3 and flow to the receiving tank 4. After the receiving tank 4 stores liquid, the first valve 16 is opened.

[0030] After the reaction is finished, the state is switched from reflux to distillation, the first valve 16 and the second valve 17 are closed, the cooling circulating water on the jacket of the alkylation kettle 1 is closed, the third valve 18 is opened, the steam circulation on the jacket of the alkylation kettle is opened, that is, the jacket steam inlet pipe L12 and the jacket steam condensate outlet pipe L13 on the alkylation kettle 1 are opened to carry out steam circulation, so that the temperature in the alkylation kettle 1 is heated to 90°C to distill ethyl bromide to the receiving tank 4, and the ethyl bromide in the receiving tank 4 is used for the next batch. After reaching the end point of the reaction, it is allowed to stand for 10 minutes, and the liquid is separated into layers. The sodium hydroxide solution containing sodium bromide in the lower layer is first pumped to the liquid alkali concentration kettle 5 through the liquid outlet pipe L7 by the liquid outlet pump 6, and then the molten N-ethylcarbazole on the upper layer of the liquid surface is transported to the nitration kettle 7 through the liquid outlet branch pipe L8 for subsequent processing. In the liquid alkali concentration kettle 5, the sodium hydroxide solution containing sodium bromide is concentrated, and the gas phase is condensed into the water receiving tank 9 through the second tube condenser 8, and then leads to the liquid alkali preparation kettle 10. The liquid phase sodium bromide solution is cooled and crystallized, and then centrifuged and filtered in the centrifuge 11. The filter cake after centrifugation obtains sodium bromide, which enters the packaging section for packaging and then is sold. The filtrate after centrifugation flows by gravity to the alkali recovery intermediate tank 12 for enrichment. The sodium hydroxide solution in the alkali recovery intermediate tank 12 is pumped into the liquid alkali preparation kettle 10 through the alkali recovery delivery pump 15, and alkali flakes and a certain amount of water are added to the liquid alkali preparation kettle 10 through the alkali flake feeding port 1001. After the solution is prepared to a specified concentration, it is pumped into the liquid alkali metering tank 13, and then pumped into the alkylation kettle 1 through the alkali preparation delivery pump 14 for subsequent circulation.

[0031] The scope of protection claimed by the present invention is not limited to the above specific implementation methods. For those skilled in the art, the present invention may have various deformations and changes. Any modification, improvement and equivalent substitution made within the concept and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for producing N-ethylcarbazole, characterized in that: It comprises an alkylation kettle (1), wherein the top inlet of the alkylation kettle (1) is connected to a liquid alkali feeding pipe (L3) and a carbazole feeding pipe (L6); The top inlet and the top outlet of the alkylation kettle (1) are respectively connected to the bottom liquid outlet and the top pressure balance pipe of the ethyl bromide high-level tank (2), and the top of the ethyl bromide high-level tank (2) is connected to the storage tank via the ethyl bromide feed pipe (L5); The top outlet of the alkylation kettle (1) is connected to a first tube-in-tube condenser (3), the outlet of the first tube-in-tube condenser (3) is connected to a receiving tank (4), and the outlet of the receiving tank (4) is connected to the top inlet of the alkylation kettle (1) via an ethyl bromide recovery pipe (L4); The bottom outlet of the alkylation kettle (1) is connected to one or more parallel liquid alkali concentration kettles (5) via a liquid outlet pipe (L7), and the liquid outlet pipe (L7) is connected to a nitration kettle (7) via a liquid outlet branch pipe (L8); A second tube condenser (8) is installed on the top of the liquid caustic soda concentration kettle (5), the outlet of the second tube condenser (8) is connected to a water receiving tank (9), the top outlet of the water receiving tank is connected to a vent pipe (L9), and the bottom outlet of the water receiving tank (9) is connected to a liquid caustic soda preparation kettle (10); The bottom outlet of the liquid alkali concentration kettle (5) is connected to a centrifuge (11), the filter cake outlet of the centrifuge (11) is connected to a packaging section, the filtrate outlet of the centrifuge (11) is connected to an intermediate alkali recovery tank (12), the intermediate alkali recovery tank (12) is connected to a liquid alkali preparation kettle (10), the top of the liquid alkali preparation kettle (10) is provided with a caustic soda flake feeding port (1001), the bottom outlet of the liquid alkali preparation kettle (10) is connected to a liquid alkali metering tank (13), the top outlet of the liquid alkali metering tank (13) is connected to a venting pipe (L9), and the bottom outlet of the liquid alkali metering tank (13) is connected to an alkylation kettle (1).

2. The N-ethylcarbazole production system according to claim 1, characterized in that: The bottom of the alkylation kettle (1) is conical, and the top inlet of the alkylation kettle (1) is connected to the bottom liquid outlet of the ethyl bromide high-level tank (2) through an ethyl bromide liquid inlet pipe (L1), and a second valve (17) is installed on the ethyl bromide liquid inlet pipe (L1).

3. The N-ethylcarbazole production system according to claim 1, characterized in that: The ethyl bromide recovery pipe (L4) is provided with a first valve (16).

4. The N-ethylcarbazole production system according to claim 1, characterized in that: A liquid outlet pump (6) is installed on the liquid outlet pipe (L7) behind the liquid outlet branch pipe (L8).

5. The N-ethylcarbazole production system according to claim 1, characterized in that: A recovery alkali delivery pump (15) is installed on the connecting pipeline between the recovery alkali intermediate tank (12) and the liquid alkali preparation kettle (10).

6. The N-ethylcarbazole production system according to claim 1, characterized in that: A prepared alkali delivery pump (14) is installed on the connecting pipeline between the liquid alkali metering tank and the alkylation kettle (1).

7. The N-ethylcarbazole production system according to claim 1, characterized in that: The alkylation kettle (1) and the liquid alkali concentration kettle (5) are both connected to a jacket cooling water inlet pipe (L10) and a jacket cooling water outlet pipe (L11); the alkylation kettle (1) is connected to a jacket steam inlet pipe (L12) and a jacket steam condensate outlet pipe (L13).

8. The N-ethylcarbazole production system according to claim 1, characterized in that: The liquid caustic soda preparation kettle (10) is provided with a jacket cooling water inlet pipe (L10) and a jacket cooling water outlet pipe (L11).

9. The N-ethylcarbazole production system according to claim 1, characterized in that: The first tube condenser (3) is connected to a condenser vent pipe (L2) provided with a third valve (18).

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