Benzoic acid nitration continuous flow production system

Abstract

The utility model discloses a benzoic acid nitration continuous flow production system, which belongs to the field of dinitrobenzoic acid production, aims to solve the problems of high safety risk and high labor intensity in the production process of 3, 5-dinitrobenzoic acid, and comprises a powder treatment unit, a mixed acid pretreatment unit, a reaction unit, an aging unit and a dilution centrifugal unit, ton bag materials are lifted and transported through an electric hoist, manual unpacking is completed in a stock bin, the stock bin is evenly discharged and conveyed through a rotary valve and conveyed according to 2000 kg / h, the materials are crushed through a crusher so as to meet the feeding particle size requirement, in the benzoic acid solid feeding process, a vacuum conveying mode is adopted for feeding, personnel investment and working labor intensity are greatly reduced, and the production efficiency is improved. Compared with traditional manual feeding and long-time dropwise adding operation of nitric acid, intermittent reaction is changed into continuous reaction in the operation mode, continuous production is achieved, and the using number of operators is reduced.

Description

Technical Field

[0001] The utility model relates to the field of 3,5-dinitrobenzoic acid production, in particular to a continuous flow production system for benzoic acid nitration. Background Art

[0002] 3,5-dinitrobenzoic acid is an important organic synthesis intermediate. There are mainly two synthesis processes for 3,5-dinitrobenzoic acid: (1) directly nitrating benzoic acid with concentrated nitric acid as the nitrating agent to produce 3,5-dinitrobenzoic acid; (2) nitrating benzoic acid in one step to produce 3,5-dinitrobenzoic acid. Both processes use batch kettle reactions.

[0003] The production process of 3,5-dinitrobenzoic acid is as follows: nitration, dilution, dilution and centrifugation. In the nitration process, the feeding method is manual feeding. Workers slowly add flaky benzoic acid powder into the nitration kettle. The feeding time is more than 4 hours. The labor input is large, the labor intensity is high, and the manual feeding is uneven, which is prone to local heat release and cause spraying process accidents. The kettle reaction process time is long and the heat transfer effect of the reaction kettle is limited. If the heat exchange is not timely, it is easy to cause "temperature runaway" or "boiling over" in the kettle, and the reaction is easy to get out of control. This batch nitration process also does not meet the regulatory requirements of the state for nitration process transformation. Therefore, it is urgent to transform the process equipment, process and system. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a continuous flow production system for benzoic acid nitration, aiming to solve the problems of high safety risk and high labor intensity in the production process of 3,5-dinitrobenzoic acid in the above background art.

[0005] The utility model is implemented by the following technical solutions: A continuous flow production system for benzoic acid nitration, which includes a powder processing unit, a mixed acid pretreatment unit, a reaction unit, an aging unit, and a dilution and centrifugation unit;

[0006] The hopper outlet of the powder processing unit is connected to the inlet pipeline of the first-stage circulation reactor of the reaction unit;

[0007] The outlet of the preparation tank of the mixed acid pretreatment unit is connected to the inlet pipeline of the first-stage circulation reactor of the reaction unit;

[0008] The outlet of the fifth-stage circulation reactor of the reaction unit is connected to the inlet pipeline of the first-stage heat preservation aging kettle of the aging unit;

[0009] The outlet of the third-stage heat preservation aging kettle of the aging unit is connected to the inlet pipeline of the dilution kettle of the dilution and centrifugation unit;

[0010] The mother liquor outlet of the centrifuge of the dilution and centrifugation unit is connected to the inlet pipeline of the mother liquor tank, and the solid outlet of the centrifuge is oppositely arranged to the inlet of the product storage tank.

[0011] Further, the powder material processing unit includes a conveying device, a silo, a crusher, a vacuum loader, and a hopper. The outlet of the conveying device is arranged opposite to the inlet of the silo vertically. The outlet of the silo is connected to the inlet of the crusher through a pipeline. The outlet of the crusher is connected to the inlet of the vacuum loader through a pipeline. The outlet of the vacuum loader is connected to the inlet of the hopper through a pipeline. The outlet of the hopper is connected to the inlet of the first-stage circulation reactor through a pipeline.

[0012] Further, the conveying device is an electric hoist.

[0013] Further, the mixed acid pretreatment unit includes a preparation tank, a sulfuric acid metering tank, and a nitric acid metering tank. The outlets of the sulfuric acid metering tank and the nitric acid metering tank are respectively connected to the inlet of the preparation tank through pipelines. The outlet of the preparation tank is connected to the inlet of the first-stage circulation reactor through a pipeline.

[0014] Further, a cooling jacket is provided on the outer wall of the preparation tank.

[0015] Further, the reaction unit includes a first-stage circulation reactor, a second-stage circulation reactor, a third-stage circulation reactor, a fourth-stage circulation reactor, and a fifth-stage circulation reactor that are connected in sequence through pipelines. The outlet of the fifth-stage circulation reactor is connected to the inlet of the first-stage heat preservation aging kettle through a pipeline.

[0016] Further, the aging unit includes a first-stage heat preservation aging kettle, a second-stage heat preservation aging kettle, and a third-stage heat preservation aging kettle that are connected in sequence through pipelines. The outlet of the third-stage heat preservation aging kettle is connected to the inlet of the dilution kettle through a pipeline.

[0017] Further, the dilution and centrifugation unit includes a dilution kettle and a centrifuge. The outlet of the dilution kettle is connected to the inlet of the centrifuge through a pipeline. The mother liquor outlet of the centrifuge is connected to the inlet of the mother liquor tank through a pipeline. The solid outlet of the centrifuge is arranged opposite to the inlet of the product storage tank.

[0018] Further, a water jacket is fixed on the outer wall of the dilution kettle.

[0019] Advantages of the present utility model: The ton bag material is lifted and transported by an electric hoist, and manual unpacking is completed at the outlet of the silo. The silo discharges materials evenly through a rotary valve for conveying at a rate of 2000 kg / h. The crusher crushes the materials to meet the feeding particle size requirements. During the feeding process of benzoic acid solid, vacuum conveying is used for feeding, which greatly reduces the personnel input and labor intensity. Compared with the traditional manual feeding and long-time dropping operation of nitric acid, the intermittent reaction is changed to a continuous reaction in the operation mode, realizing continuous production and reducing the number of operators used.

[0020] Benzoic acid is fed by vacuum conveying, and mixed acid is fed through a metering tank. The feeding amount is controllable, ensuring that when finally entering the reaction unit, the ratio of each raw material is accurate. A microchannel reactor is used in the reaction unit. Since the total amount of materials used is greatly reduced, its safety is significantly improved compared with traditional batch reactors, reducing potential safety hazards in production and improving product quality and purity. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is a schematic structural diagram of the utility model;

[0023] In the figure: powder processing unit 1, conveying device 1.1, storage bin 1.2, crusher 1.3, vacuum feeder 1.4, hopper 1.5, mixed acid pretreatment unit 2, preparation tank 2.1, cooling jacket 2.1.1, sulfuric acid metering tank 2.2, nitric acid metering tank 2.3, reaction unit 3, primary circulation reactor 3.1, secondary circulation reactor 3.2, tertiary circulation reactor 3.3, quaternary circulation reactor 3.4, quinary circulation reactor 3.5, aging unit 4, primary heat preservation aging kettle 4.1, secondary heat preservation aging kettle 4.2, tertiary heat preservation aging kettle 4.3, dilution and centrifugation unit 5, dilution kettle 5.1, water addition pipeline 5.1.1, water jacket 5.1.2, centrifuge 5.2, mother liquor tank 5.2.1, product storage tank 5.2.2. Detailed Embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0025] As Figure 1 shown, a continuous flow production system for nitration of benzoic acid includes a powder processing unit 1, a mixed acid pretreatment unit 2, a reaction unit 3, an aging unit 4, and a dilution and centrifugation unit 5;

[0026] The outlet of the hopper 1.5 of the powder processing unit 1 is connected to the inlet pipeline of the primary circulation reactor 3.1 of the reaction unit 3;

[0027] The outlet of the preparation tank 2.1 of the mixed acid pretreatment unit 2 is connected to the inlet pipeline of the first-stage circulation reactor 3.1 of the reaction unit 3;

[0028] The outlet of the fifth-stage circulation reactor 3.5 of the reaction unit 3 is connected to the inlet pipeline of the first-stage heat preservation aging kettle 4.1 of the aging unit 4;

[0029] The outlet of the third-stage heat preservation aging kettle 4.3 of the aging unit 4 is connected to the inlet pipeline of the dilution kettle 5.1 of the dilution and centrifugation unit 5;

[0030] The mother liquor outlet of the centrifuge 5.2 of the dilution and centrifugation unit 5 is connected to the inlet pipeline of the mother liquor tank 5.2.1, and the solid outlet of the centrifuge 5.2 is arranged opposite to the inlet of the product storage tank 5.2.2.

[0031] The powder processing unit 1 includes a conveying device 1.1, a bin 1.2, a crusher 1.3, a vacuum feeding machine 1.4, and a hopper 1.5. The outlet of the conveying device 1.1 is arranged vertically opposite to the inlet of the bin 1.2. The outlet of the bin 1.2 is connected to the inlet pipeline of the crusher 1.3. The outlet of the crusher 1.3 is connected to the inlet pipeline of the vacuum feeding machine 1.4. The outlet of the vacuum feeding machine 1.4 is connected to the inlet pipeline of the hopper 1.5. The outlet of the hopper 1.5 is connected to the inlet pipeline of the first-stage circulation reactor 3.1. The conveying device 1.1 is an electric hoist. The ton bag material is lifted and transported by the electric hoist. Workers complete unpacking at the outlet of the bin 1.2. The bin 1.2 discharges materials evenly through a rotary valve and conveys at a rate of 2000 kg / h. The crusher 1.3 crushes the materials to meet the feeding particle size requirements. During the feeding process of benzoic acid solid, vacuum conveying is used for feeding, which greatly reduces the personnel input and labor intensity. Compared with the traditional manual feeding and long-time dropping operation of nitric acid, the intermittent reaction is changed to a continuous reaction in the operation mode, realizing continuous production and reducing the number of operators used.

[0032] The mixed acid pretreatment unit 2 includes a preparation tank 2.1, a sulfuric acid metering tank 2.2, and a nitric acid metering tank 2.3. The outlets of the sulfuric acid metering tank 2.2 and the nitric acid metering tank 2.3 are respectively connected to the inlet pipeline of the preparation tank 2.1. The outlets of the sulfuric acid metering tank 2.2 and the nitric acid metering tank 2.3 accurately measure the discharged liquid through metering pumps. The outlet of the preparation tank 2.1 is connected to the inlet pipeline of the first-stage circulation reactor 3.1. A cooling jacket 2.1.1 is provided on the outer wall of the preparation tank 2.1. Chilled brine is introduced into the inlet of the cooling jacket 2.1.1 and discharged from the outlet of the cooling jacket 2.1.1. The heat generated during the preparation process of the preparation tank 2.1 is exchanged by the chilled brine. During the preparation of the mixed acid, the mixed acid in the preparation tank 2.1 is timely heat-exchanged through the cooling jacket 2.1.1 to control the temperature of the mixed acid within a certain range, and then enters the first-stage circulation reactor 3.1 for reaction together with benzoic acid.

[0033] The reaction unit 3 includes a first-stage circulation reactor 3.1, a second-stage circulation reactor 3.2, a third-stage circulation reactor 3.3, a fourth-stage circulation reactor 3.4, and a fifth-stage circulation reactor 3.5 that are connected in sequence by pipelines. The outlet of the fifth-stage circulation reactor 3.5 is connected to the inlet pipeline of the first-stage heat-insulated aging kettle 4.1. The first-stage circulation reactor 3.1, the second-stage circulation reactor 3.2, the third-stage circulation reactor 3.3, the fourth-stage circulation reactor 3.4, and the fifth-stage circulation reactor 3.5 are specifically microchannel reactors. The microchannel reactors increase the two-phase contact area through millimeter-level process channels and the local eddy current collision formed by diffusion and structural design, enabling the fluid to fully contact, mix, and mass transfer, improving the reaction efficiency. For strongly exothermic reactions, the reaction heat can be removed in a timely manner, effectively avoiding safety accidents such as kettle runaway temperature caused by a large amount of reaction heat release; the liquid discharged from the first-stage circulation reactor 3.1 enters the second-stage, third-stage, fourth-stage, and fifth-stage circulation reactors in sequence for cyclic reaction until the reaction is complete, optimizing the production process of the continuous nitration reaction equipment, and having a low total liquid holdup. The total liquid holdup of the overall equipment is less than 10 L. Considering the risks of dangerous chemicals such as nitration raw materials, products, and nitrating agents, since the total material consumption is greatly reduced, its safety is significantly improved compared with traditional batch kettles, reducing safety hazards in production, improving product quality and purity, making it reach the domestic first-class standard, and further enhancing the production efficiency of this industry.

[0034] The aging unit 4 includes a first-stage heat-insulated aging kettle 4.1, a second-stage heat-insulated aging kettle 4.2, and a third-stage heat-insulated aging kettle 4.3 that are connected in sequence by pipelines. The outlet of the third-stage heat-insulated aging kettle 4.3 is connected to the inlet pipeline of the dilution kettle 5.1. Then, the third-stage heat-insulated aging kettle 4.3 is set up. Through staged heat insulation and aging and the method of pumping materials for complete mixing, the materials meet the requirements of purity and content indicators, ensuring the continuity of production.

[0035] The dilution and centrifugation unit 5 includes a dilution kettle 5.1 and a centrifuge 5.2. The outlet of the dilution kettle 5.1 is connected to the inlet pipeline of the centrifuge 5.2. The mother liquor outlet of the centrifuge 5.2 is connected to the inlet pipeline of the mother liquor tank 5.2.1. The solid outlet of the centrifuge 5.2 is arranged opposite to the inlet of the product storage tank 5.2.2. A water pipeline 5.1.1 is provided at the top of the dilution kettle 5.1 to add water to dilute the product, reduce the acidity of the waste acid, and reduce the solubility of the final reaction product in the waste acid for stratification, realizing the separation of the final product and the waste acid. Finally, under the action of the centrifuge 5.2, the waste acid mother liquor and the solid product are separated. A water jacket 5.1.2 is fixed on the outer wall of the dilution kettle 5.1, and chilled brine is introduced into the water jacket 5.1.2 to cool the reaction product to below 30 degrees Celsius, and then the material can be discharged.

[0036] The specific operation process of this embodiment:

[0037] The tonnage of bulk materials is lifted and transported by an electric hoist. Workers unpack the materials at the outlet of the storage bin 1.2. The storage bin 1.2 discharges materials evenly through a rotary valve and is transported at a rate of 2000 kg / h. The crusher 1.3 crushes the materials to meet the feeding particle size requirements. During the feeding process of solid benzoic acid, vacuum conveying is used for feeding.

[0038] Nitric acid and sulfuric acid are sent into the preparation tank 2.1 through the nitric acid metering tank 2.3 and the sulfuric acid metering tank 2.2. During the preparation process, heat exchange is carried out using the cooling jacket 2.1.1 to ensure the reaction temperature.

[0039] Then, the mixed acid and benzoic acid powder are sent into the reaction unit 3. The liquid discharged from the first-stage circulation reactor 3.1 enters the second-stage, third-stage, fourth-stage, and fifth-stage circulation reactors in sequence for circulation reaction until the reaction is complete. Then, a third-stage heat preservation aging kettle 4.3 is set up. Through hierarchical heat preservation and the method of pumping materials, the mixing is complete, so that the materials meet the requirements of purity and content indicators.

[0040] Water is added to the final reaction product to dilute the product, reduce the acidity of the waste acid, and make the solubility of the final reaction product in the waste acid decrease and stratify. The outer wall of the dilution kettle 5.1 is fixed with a water jacket 5.1.2. Refrigerated brine is introduced into the water jacket 5.1.2 to cool the reaction product to below 30 degrees Celsius, and then the material can be discharged. Under the action of the centrifuge 5.2, the waste acid mother liquor and the solid product are separated. The mother liquor outlet of the centrifuge 5.2 is connected to the inlet pipeline of the mother liquor tank 5.2.1, and the solid outlet of the centrifuge 5.2 is oppositely arranged with the inlet of the product storage tank 5.2.2.

[0041] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A continuous flow production system for the nitration of benzoic acid, characterized in that, It includes a powder processing unit, a mixed acid pretreatment unit, a reaction unit, an aging unit, and a dilution and centrifugation unit; The hopper outlet of the powder processing unit is connected to the inlet pipeline of the primary circulation reactor of the reaction unit; The outlet of the preparation tank of the mixed acid pretreatment unit is connected to the inlet pipeline of the primary circulation reactor of the reaction unit; The outlet of the fifth-stage circulation reactor of the reaction unit is connected to the inlet pipeline of the primary heat preservation aging kettle of the aging unit; The outlet of the third-stage heat preservation aging kettle of the aging unit is connected to the inlet pipeline of the dilution kettle of the dilution and centrifugation unit; The mother liquor outlet of the centrifuge of the dilution and centrifugation unit is connected to the inlet pipeline of the mother liquor tank, and the solid outlet of the centrifuge is arranged opposite to the inlet of the product storage tank.

2. The continuous flow production system for nitration of benzoic acid according to claim 1, wherein The powder processing unit includes a conveying device, a silo, a crusher, a vacuum feeder, and a hopper. The outlet of the conveying device is arranged vertically opposite to the inlet of the silo. The outlet of the silo is connected to the inlet pipeline of the crusher. The outlet of the crusher is connected to the inlet pipeline of the vacuum feeder. The outlet of the vacuum feeder is connected to the inlet pipeline of the hopper. The outlet of the hopper is connected to the inlet pipeline of the primary circulation reactor.

3. The continuous flow production system for nitration of benzoic acid according to claim 2, wherein The conveying device is an electric hoist.

4. The continuous flow production system for nitration of benzoic acid according to claim 1, wherein The mixed acid pretreatment unit includes a preparation tank, a sulfuric acid metering tank, and a nitric acid metering tank. The outlets of the sulfuric acid metering tank and the nitric acid metering tank are respectively connected to the inlet pipeline of the preparation tank. The outlet of the preparation tank is connected to the inlet pipeline of the primary circulation reactor.

5. The continuous flow production system for nitrating benzoic acid according to claim 4, wherein The outer wall of the preparation tank is provided with a cooling jacket.

6. The continuous flow production system for nitrating benzoic acid according to claim 1, wherein The reaction unit includes a primary circulation reactor, a secondary circulation reactor, a tertiary circulation reactor, a quaternary circulation reactor, and a fifth-stage circulation reactor connected in sequence by pipelines. The outlet of the fifth-stage circulation reactor is connected to the inlet pipeline of the primary heat preservation aging kettle.

7. The continuous flow production system for nitration of benzoic acid according to claim 1, characterized in that, The aging unit includes a primary heat preservation aging kettle, a secondary heat preservation aging kettle, and a third-stage heat preservation aging kettle connected in sequence by pipelines. The outlet of the third-stage heat preservation aging kettle is connected to the inlet pipeline of the dilution kettle.

8. The continuous flow production system for nitration of benzoic acid according to claim 1, characterized in that, The dilution and centrifugation unit includes a dilution kettle and a centrifuge. The outlet of the dilution kettle is connected to the inlet pipeline of the centrifuge. The mother liquor outlet of the centrifuge is connected to the inlet pipeline of the mother liquor tank. The solid outlet of the centrifuge is arranged opposite to the inlet of the product storage tank.

9. The continuous flow production system for nitrating benzoic acid according to claim 8, wherein The outer wall of the dilution kettle is fixedly provided with a water jacket.

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