CN211329403U - Production system provided with venturi tube and used for synthesizing adiponitrile from adipic acid - Google Patents

Abstract

The utility model provides a production system for synthesizing adiponitrile from adipic acid. The system comprises a raw material preparation kettle, a loop reactor, an external heat exchanger and a product receiving tank; the raw material preparation kettle is provided with a feed inlet and a A discharge port; the inner top of the loop reactor is provided with a Venturi injector; the loop reactor is provided with a feed port, a discharge port, an ammonia gas inlet and an ammonia gas outlet; the external heat exchanger is provided with There are material inlet and material outlet; the material outlet of the raw material preparation kettle and the feed port of the loop reactor are connected through pipelines; the material outlet of the loop reactor is respectively connected with the materials of the external heat exchanger through pipelines The inlet and the product are communicated through a pipeline receiving tank. The reaction system of the utility model has simple equipment, simple operation and low maintenance cost. The Venturi injector can make the gas-liquid two-phase mix evenly, greatly improve the mass transfer efficiency, speed up the reaction speed, and improve the synthesis efficiency of adiponitrile.

Description

A kind of production system for synthesizing adiponitrile from adipic acid with venturi tube

technical field

The utility model belongs to the field of adiponitrile synthesis, in particular to a production system for synthesizing adiponitrile from adipic acid provided with a venturi tube.

Background technique

Adipic acid amination method is an important method for preparing adiponitrile. The process flow is to send adipic acid and a large amount of ammonia gas into the adiponitrile reactor in the presence of a catalyst (usually phosphoric acid is used as a catalyst), In the temperature range of 250-300 ℃, the neutralization reaction is first performed to generate diammonium adipate, and then the dehydration reaction is performed to generate adiponitrile. In the existing nitrification reactor, the gas material is generally bubbling directly after being sent from the central pipe, and a large amount of gas flows out from the intermediate pipe, which makes the gas phase flow relatively concentrated, resulting in insufficient contact between the gas phase and the liquid phase, and the bubbling efficiency and reaction yield. rates are lower. The lower yield will further lead to the production of a large number of by-products during the reaction process, which will further cause serious coking in the reactor, reduce the mass transfer efficiency and heat transfer rate in the reactor tube, and ultimately seriously affect the operating cycle of the reactor.

Liquid-phase adipic acid-catalyzed ammoniation generally passes excess ammonia gas into molten adipic acid, and the reaction is carried out under the catalysis of phosphoric acid. The neutralization reaction of adipic acid and ammonia gas is an exothermic reaction, but the dehydration reaction of diammonium adipate is a strong endothermic reaction, so most of the patents use a tube for heating. Although high temperature is beneficial to the dehydration reaction of diammonium adipate, it will increase energy consumption, and at the same time, the liquid-gas ratio of the heating tube section of the reactor is relatively high, resulting in coking of the heating tube. In order to slow down coking, the disclosed technical measures include adding a series of bubbling pre-reaction sections (Gao Feng et al. Chemical Reaction Engineering and Technology 1992, 8(2): 194); circulating between the reactor and the subsequent separation tower liquid stream (Li Zhengyi et al. CN201210577924.9); Separation tower liquid further adopts semi-nitrile evaporator to remove tar to improve the stability of system operation (Wen Zhe et al. CN204265662u; Jiang Zezhen et al. CN204147575u). The application of the two-stage method to the ammoniation of adipic acid can partially reduce the coking in the ammoniation process (CN201210577924.9), but it will increase the decomposition of adipic acid, thereby reducing the yield of the product. In addition, both the neutralization and dehydration reactions are reversible, and the high water content in the vapor phase will seriously affect the dehydration of the intermediate by-product iminonitrile cyclopentane (ICCP) into adiponitrile (Gao et al. Chemical Reaction Engineering and Technology 1991 , 7(2):128).

Utility model content

The technical problem to be solved by the utility model is to provide an adiponitrile production system which can fully mix materials, has large contact area, fast heat exchange speed, uniform material mixing, and reduces coking and material deposition on the inner wall of the tube.

The technical scheme adopted by the utility model to solve the above-mentioned technical problems is:

The utility model provides a production system for synthesizing adiponitrile from adipic acid. The system comprises a raw material preparation kettle, a loop reactor, an external heat exchanger and a product receiving tank; the raw material preparation kettle is provided with a feed inlet and a material outlet; the inner top of the loop reactor is provided with a venturi injector; the loop reactor is provided with a feed port, a material outlet, a material circulation port, an ammonia gas inlet and an ammonia gas outlet; the external type The heat exchanger is provided with a material inlet and a material outlet; the outlet of the raw material preparation kettle and the inlet of the loop reactor are connected through pipelines; the outlet of the loop reactor is respectively connected with the external heat exchanger through pipelines. The material inlet of the exchanger is communicated with the product receiving tank; the material outlet of the external heat exchanger is communicated with the material circulation port of the loop reactor.

Based on the above technical solutions, preferably, the outer walls of the raw material preparation kettle and the shell of the loop reactor are provided with an external thermal insulation jacket, and the thermal insulation jacket contains heat transfer oil, and the raw material preparation kettle and the loop are realized through the circulation of the heat transfer oil. Control of reactor temperature.

Based on the above technical solutions, preferably, the production system further includes an external heat exchanger including three parts: a circulation machine, a heater, and a cooler. The external heat exchanger includes a material circulation pipeline and a heat transfer oil circulation pipeline. , The heat transfer oil circulation pipeline is used to realize the temperature control of the whole system.

Based on the above technical solutions, preferably, the raw material preparation tank is provided with a stirring part.

Based on the above technical solutions, preferably, the feed port of the raw material preparation kettle includes a catalyst feed port, an adipic acid feed port and an adiponitrile feed port. Adipic acid, adiponitrile and catalyst phosphoric acid are mixed uniformly in the raw material preparation tank, and then transported to the loop reactor through the feed pump. The loop reactor is provided with an ammonia gas inlet and an outlet to realize the continuous introduction of ammonia gas into the reactor. The liquid that has been reacted in the reactor is transported to the product receiving tank by the circulating pump.

Based on the above technical solutions, preferably, the venturi injector includes a gas inlet, a liquid inlet, a nozzle, a gas suction cavity, a liquid jet zone, a mixed impact zone, a diffusion zone and a draft tube; the gas inlet and the ammonia of the loop reactor are composed. The gas sample inlet is communicated with, and the liquid inlet is communicated with the material circulation port of the loop reactor; the material outlet of the external heat exchanger is communicated with the material circulation port of the loop reactor. The raw material pump transports the material in the raw material preparation tank to the loop reactor through the feed port of the loop reactor, and the material in the loop reactor is transported to the external heat exchanger through the circulating pump for heat exchange, and the material passing through the external heat exchanger The outlet and the circulating material port of the loop reactor enter into the Venturi injector of the loop reactor, and the material is transported to the nozzle through the liquid inlet of the Venturi injector, and a fast jet flow is formed through the nozzle. Evenly disperse on the tube wall, and then fully mix with the gas. The turbulent flow formed by the collision of the two makes the foam well diffuse in the diffusion zone. After passing through the drainage tube, at the bottom of the diffuser, the mixture leaves the mixing ejector and is in the loop reactor. implement the cycle.

Based on the above technical solutions, preferably, the loop reactor is provided with a gas phase temperature monitoring port and a liquid phase temperature monitoring port.

Based on the above technical solutions, preferably, a raw material feeding pump is provided between the raw material preparation kettle and the loop reactor; a circulating pump is provided between the loop reactor and the product receiving tank or the external heat exchanger, and the loop reaction The reaction material in the vessel is controlled by a circulating pump to circulate and flow.

Based on the above technical solutions, preferably, a sampling port is provided on the pipelines of the loop reactor and the product receiving tank.

Based on the above technical solutions, preferably, the pipelines entering the raw material preparation kettle, the loop reactor, the external heat exchanger and the product receiving tank are all provided with cut-off valves, wherein the circulating pump and the external heat exchanger are provided with stop valves. There is a stop valve I; there is a stop valve II between the circulating pump and the product receiving tank. When the reaction material needs to be circulated and reacted in the loop reactor and the external heat exchanger, close the stop valve II and open the stop valve I. When it is necessary to stop the reaction and receive the product, close the stop valve I and open the stop valve II.

beneficial effect

(1) The reaction system of the present invention is simple in equipment, simple in operation and low in maintenance cost. The Venturi injector can make the gas-liquid two-phase mix evenly, greatly improve the mass transfer efficiency, speed up the reaction speed, and improve the synthesis efficiency of adiponitrile.

(2) The loop reactor of the system of the utility model makes the material contact area larger, the heat exchange speed is fast, the heat exchange is more uniform, and the coking and material deposition on the inner wall of the tube can be reduced.

Description of drawings

Fig. 1 is the structural representation of the utility model system;

Fig. 2 is the structural representation of the venturi jet mixer of the utility model system;

Among them: 1. Raw material preparation kettle; 2. Loop reactor; 3. External heat exchanger; 4. Product receiving tank; 5. Feeding pump; 6. Circulating pump; 7. Insulation jacket; 8. Sampling port; 1-I, adipic acid and adiponitrile feed port; 1-II, catalyst feed port; 2-I, Venturi injector; 2-II, liquid phase temperature monitoring port; 2-III, gas phase temperature monitoring port ;2-IV, ammonia gas inlet; 2-V, ammonia gas flowmeter; 2-VI, feed port; 2-VII, material outlet; 2-VIII, material circulation port; 2-Ⅰ-a, liquid inlet ; 2-I-b, gas inlet; 2-I-c, nozzle; 2-I-d, gas suction cavity; 2-I-e, liquid jet; 2-I-f, mixed impact zone; 2-I -g, diffusion zone; 2-I-h, drainage tube.

Detailed ways

The adiponitrile production system of the method adopts a loop reactor, and the production system consists of a raw material preparation kettle 1, a feed pump 5, a loop reactor 2, an external heat exchange 3, a circulating pump 6, and a product receiving tank 4. The described The production system also includes a gas system, the gas system is an ammonia conveying system, and the preheated ammonia is conveyed to the ammonia inlet 2-IV of the loop reactor 2 through the ammonia flow meter 2-V. Adipic acid and adiponitrile enter the raw material preparation kettle 1 through the adipic acid and adiponitrile feed port 1-I; the catalyst phosphoric acid enters the raw material preparation kettle 1 through the catalyst feed port 1-II, and the materials in the raw material preparation kettle 1 pass through the feed port 1-II. The feed pump 5 is transported to the loop reactor through the feed port 2-VI of the loop reactor; there is a venturi injector 2-I at the top of the loop reactor, and the venturi injector adopts the structure of upper narrow and lower width. Using the negative pressure formed by the ammonia gas at the venturi ejector, the liquid raw materials such as adiponitrile entering through the material circulation port 2-Ⅷ are inhaled, so that the gas and liquid materials are fully mixed and dispersed, and then sprayed into the reaction tank. Through the circulating pump, the synthesis reaction of adiponitrile can be carried out safely and continuously. The outer side of the tank body of the loop reactor 2 and the raw material preparation tank 1 is provided with a thermal insulation jacket 7, and the thermal insulation jacket 7 is provided with heat-conducting oil for temperature control; the tank body of the loop reactor 2 is also provided with a gas phase temperature monitoring port 2-III and liquid phase temperature monitoring port 2-II; the input end of the circulating pump 6 is connected with the discharge port 2-VII of the loop reactor; the output end of the circulating pump passes through the discharge port 2-VII of the external heat exchanger It is connected to the material circulation port at the top of the loop reactor, and the liquid and gas inlets are connected to the Venturi injector. After the liquid is sprayed, the gas is carried, and the reaction system is continuously operated by the circulating pump. After the reaction is completed, the product is collected into the product receiving tank for subsequent product separation. The product from the loop reactor outlet is provided with a sampling port 8 on the pipeline before entering the product receiving tank for sampling and testing.

Embodiment 1

First, 100kg/h of adipic acid, 200kg/h of adiponitrile and 0.5kg/h of phosphoric acid catalyst were added to the pre-mixing tank and preheated to 170°C. After reaching the temperature, the material was added to the loop reactor, the circulating pump was turned on, and ammonia gas was introduced from the ammonia gas inlet, wherein the flow rate of the ammonia gas was 100 kg/h. Using the negative pressure formed by the material circulation at the nozzle of the venturi ejector, the mixed raw material liquid and gas can be uniformly introduced and dispersed well. During the reaction, an external heat exchanger was used to control the temperature of the loop reactor to be 260°C. The device can continuously and uniformly feed raw materials in proportion, and the finished products can be continuously taken out from the pipe mouth. The raw materials were continuously fed into the loop reactor at a rate of 1 L/min to ensure that the residence time of the materials in the reactor was 60 min. The analysis results of gas chromatography showed that the yield of the final product adiponitrile was 85%, the dehydration rate of adipic acid was 89.6%, and the carbon deposition amount was 0.39%.

Example 2

First, 100kg/h of adipic acid, 200kg/h of adiponitrile and 0.5kg/h of phosphoric acid catalyst were added to the raw material preparation kettle, and the raw material preparation kettle was preheated to 180°C. After reaching the temperature, the material was added to the loop reactor, the circulating pump was turned on, and ammonia gas was introduced from the ammonia gas inlet, wherein the flow rate of the ammonia gas was 100 kg/h. Using the negative pressure formed by the material circulation at the nozzle of the venturi injector, the liquid and gas can be uniformly introduced and dispersed well. During the reaction, an external heat exchanger was used to control the temperature of the reactor to 280°C. The device can continuously and uniformly feed raw materials in proportion, and the finished products can be continuously taken out from the pipe mouth. The raw materials were continuously fed into the loop reactor at a rate of 1 L/min to ensure that the residence time of the materials in the reactor was 60 min. The analysis results of gas chromatography showed that the yield of the final product adiponitrile was 90%, the dehydration rate of adipic acid was 93.5%, and the carbon content of the reactor surface area was 0.31%.

Comparative Example 1

First, 100kg/h of adipic acid, 200kg/h of adiponitrile and 0.5kg/h of phosphoric acid catalyst are premixed through a mixer, and sent to the nitrification reactor through a feed pump to be mixed with fresh ammonia (ammonia The flow rate of gas is 100kg/h) reaction, the material is reacted at 280°C, and adipic acid is dehydrated to form adiponitrile under this temperature adjustment. The reaction time should be added this time, otherwise it will be difficult to compare. The reaction was carried out at 280°C for 60 min, and the product was then analyzed by gas chromatography. The analysis results showed that the yield of the final product adiponitrile was 81.2%, the dehydration rate of adipic acid was 85.8%, and the carbon deposition amount was 0.74%.

Claims (10)

1. A production system for synthesizing adiponitrile by using adipic acid is characterized by comprising a raw material preparation kettle, a loop reactor, an external heat exchanger and a product receiving tank; the raw material preparation kettle is provided with a feeding hole and a discharging hole; a Venturi ejector is arranged at the top end inside the loop reactor; the loop reactor is provided with a feed inlet, a discharge outlet, a material circulation port, an ammonia inlet and an ammonia outlet; the external heat exchanger is provided with a material inlet and a material outlet; the discharge hole of the raw material preparation kettle is communicated with the feed inlet of the loop reactor through a pipeline; the discharge hole of the loop reactor is respectively communicated with the material inlet of the external heat exchanger and the product receiving tank through pipelines; and a discharge hole of the external heat exchanger is communicated with a material circulation hole of the loop reactor.

2. The production system according to claim 1, wherein: the external heat-insulating jacket is arranged on the outer wall of the shell of the raw material preparation kettle and the shell of the loop reactor, the heat-insulating jacket contains heat-conducting oil, and the temperature of the raw material preparation kettle and the temperature of the loop reactor are controlled through circulation of the heat-conducting oil of the external heat exchanger.

3. The production system of claim 2, further comprising an external heat exchanger comprising a circulator, a heater, and a cooler.

4. The production system of claim 1, wherein the raw material compounding kettle is provided with a stirring member.

5. The production system of claim 1, wherein the feedstock preparation kettle feed ports comprise a catalyst feed port, an adipic acid feed port, and an adiponitrile feed port.

6. The production system of claim 1, wherein the venturi ejector comprises a gas inlet, a liquid inlet, a nozzle, a gas suction chamber, a liquid jet zone, a mixing impingement zone, a diffusion zone, and a draft tube; the gas inlet is communicated with an ammonia gas injection port of the loop reactor, and the liquid inlet is communicated with a material circulation port of the loop reactor.

7. The production system of claim 1, wherein the loop reactor is provided with a gas phase temperature monitoring port and a liquid phase temperature monitoring port.

8. The production system of claim 1, wherein a feed pump is disposed between the feed preparation tank and the loop reactor; a circulating pump is arranged between the loop reactor and the product receiving tank or the external heat exchanger.

9. The production system of claim 1, wherein the piping of the loop reactor and the product receiving tank are provided with sampling ports.

10. The production system of claim 8, wherein a stop valve I is arranged between the circulating pump and the external heat exchanger; and a stop valve II is arranged between the circulating pump and the product receiving tank.

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