RU2292945C2 - Nozzle reactor for production of 1.2-dichloroethane - Google Patents

Abstract

FIELD: chemical industry; designs of the bubble-type reactors for production of 1.2-dichloroethane.

SUBSTANCE: the invention is pertaining to the design of the bubble-type reactors for production of 1.2-dichloroethane by the method of the liquid-phase chlorination of ethylene with the reaction heat removal at boiling of the working medium. As the contact device the reactor uses two layers of the metallic nozzle. The liquid 1.2-dichloroethane is fed from above to the nozzle, into the space between the layers of the nozzle feed the gaseous chlorine with nitrogen, and under the lower layer of the nozzle feed the gaseous ethylene with nitrogen, that allows to reduce the diameter of the reactor in 1.5-2 times due to the increased effectiveness of stirring and formation of the developed contact surface of the phases. At that the heat of the reaction is removed by evaporation of 1.2-dichloroethane in nitrogen. At that the temperature of the liquid is maintained below the boiling temperature. The technical result of the invention is the increased selectivity of the process, reduction of the outlet of the by-products (the highest ethane chlorides) and the decreased overall dimensions of the reactor.

EFFECT: the invention ensures the increased selectivity of the process, reduction of the outlet of the by-products (the highest ethane chlorides) and the decreased overall dimensions of the reactor.

1 ex, 4 dwg

Description

Technical field

The invention relates to a device for producing 1,2-dichloroethane by liquid-phase chlorination of ethylene with removal of the heat of reaction during boiling of the working medium.

State of the art

The closest reactor designs for producing 1,2-dichloroethane are high-temperature and low-temperature liquid-phase chlorination reactors of ethylene [1].

In a high-temperature reactor, the process is carried out at a temperature equal to the boiling temperature of the working medium (83.5-110 ° C, depending on pressure). The high-temperature process reactor is a bubble gas lift column 1 provided with an internal circulation pipe 4 (Fig. 1). The working medium is liquid 1,2-dichloroethane. The catalyst of the process is FeCl ₃ , which is in the reactor in dissolved form. To obtain a solution, gaseous chlorine through the distributor 2 is fed into the lower part of the annular space. The reaction is carried out upstream when ethylene gas is introduced into the reactor through a distributor 3. Due to the difference in the density of the media in the circulation pipe and in the annular space, liquid circulation occurs. Perforated plates 6 are installed in the upper part of the reactor, designed to intensify mixing. The heat of reaction is removed due to the evaporation of 1,2-dichloroethane during boiling. The upper part of the reactor acts as a separator to separate liquid droplets from steam. The reaction products are discharged in the form of vapors to the rectification stage through a fitting in the reactor lid. Due to its low volatility, the catalyst remains in the reactor. To maintain the liquid level, 1,2-dichloroethane is introduced into the lower part of the reactor.

An important advantage of a high-temperature reactor compared to a low-temperature one is its efficiency: the heat generated is spent on evaporation and rectification of products, there is no waste water, and the consumption of catalyst is minimal.

The disadvantage of a high-temperature reactor is the low selectivity (98.0-98.7%) associated with an increase in the rate of adverse reactions with increasing temperature. By-products - trichloroethane, trichloethylene and other higher chlorine derivatives of ethane - are formed in the reactor as a result of substitution chlorination reactions. The rate of adverse reactions decreases with decreasing temperature [2]. When 1 mole of 1,2-dichloroethane is formed, a sufficient amount of heat is released to evaporate 6 moles of 1,2-dichloroethane.

The low-temperature reactor (figure 2) is a bubble column 1, connected in the upper and lower parts with a remote shell-and-tube heat exchanger 5. The working medium in the reactor is the reaction product -1,2-dichloroethane in a liquid state. Chlorine is introduced into the bottom of the column through a distributor 2. Above ethylene is introduced into the resulting chlorine solution through a distributor 3. Due to the difference in the densities of the media in the refrigerator and the column, the circulation of the working medium with an upward flow in the column occurs. The temperature in the reactor is 65 ° C. The synthesis product is removed by gravity through the overflow. The separation of the product from the catalyst is carried out at the stage of purification. The catalyst after the purification step cannot be regenerated. The products of the process from the purification stage go to rectification.

The advantage of the low-temperature reactor is its high selectivity (99.6%), which is explained by the slowdown of the side reactions of substitution chlorination with decreasing temperature. The disadvantages of the low-temperature reactor include a large flow of wastewater at the stage of purification of the product from the catalyst, a significant consumption of catalyst per unit of production, high energy costs for cooling the reaction mass, and irrational use of the heat of reaction.

Disclosure of invention

The objective of the invention is to increase the selectivity of the process due to the development of a new type of reactor - a packed reactor of liquid-phase chlorination of ethylene (figure 4). As a nozzle, you can use any well-known modern type of nozzle: Rashig and Pale rings, regular types of nozzles. The material for the nozzle is carbon steel. This contributes to a uniform temperature distribution in the liquid film. A stream of liquid dichloroethane with a dissolved catalyst is fed from above to the nozzle layer, and the liquid is distributed by film over the nozzle surface. Two layers of packing are placed in the reactor. The top layer of the nozzle is designed for absorption of chlorine by a stream of 1,2-dichloroethane, and the lower layer of the nozzle is used for chemisorption of ethylene with a chlorine solution. In the space between the layers of the nozzle, a gaseous mixture of chlorine and nitrogen is supplied. The resulting chlorine solution flows onto the lower layer of the nozzle, from the bottom of which a gaseous mixture of ethylene and nitrogen is supplied. The heat of reaction is removed by the evaporation of 1,2-dichloroethane into a stream of nitrogen, while the temperature of the liquid is maintained below the boiling point.

When implementing the invention, the following results can be obtained:

1. Reducing the diameter of the reactor compared to prototypes. To carry out the process in a bubbling mode with an average volumetric gas content of the medium of 20-30%, a large amount of liquid 1,2-dichloroethane is required. This explains the large diameter of the bubble reactor. In a packed reactor, the process is carried out by contacting a liquid film with chlorine, ethylene and nitrogen. In this case, a large amount of 1,2-dichloroethane is not required. 1,2-dichloroethane is fed to the packed reactor in an amount necessary to remove the reaction by evaporation. An industrial bubbler reactor with a chlorine load of 3000 m ³ / h has a diameter of 3600 mm. Calculations show that a packed reactor with the same load has a diameter of 2000 mm.

2. Increased selectivity. Chlorine mixed with nitrogen is fed to the packed reactor. As a result, the concentration of chlorine in the gas phase will be lower than in a bubble reactor. This will lead to a decrease in the equilibrium concentration of chlorine in the liquid phase in accordance with Henry's law [3].

As a result of a decrease in the concentration of chlorine in 1,2-dichloroethane, the rate of adverse reactions will decrease. This follows from [4], which shows that an increase in the concentration of dissolved chlorine in the reaction mass leads to an increase in the rate of formation of by-products, in accordance with the equation for the rate of formation of by-products.

In addition, due to the evaporative cooling of 1,2-dichloroethane to nitrogen, the temperature in the reactor will be lower than the boiling point of 1,2-dichloroethane (Fig. 3). The graph of figure 3. built on the basis of the material, heat balance of the packed reactor for the following regime: chlorine consumption 300 nm ³ / hour, ethylene consumption 315 nm ³ / hour, nitrogen consumption 300 nm ³ / hour, the initial concentration of chlorine in the liquid is 0.1 kmol / m ³ , the final concentration of chlorine in the liquid is 0.005 kmol / m ³ , the specific surface of the nozzle is 400 m ² / m ³ , the volumetric flow rate of the liquid is 134 m ³ / h, the inner diameter of the reactor is 1.36 m. From FIG. 3. it can be seen that, as it moves downward, the working fluid first heats up due to the released heat of reaction, and then begins to cool with nitrogen moving from the bottom up. The average temperature of the working fluid is 77 ° C. Thus, the temperature in the packed reactor is less than the boiling point in the bubble reactor. It is known [2] that, with decreasing temperature, the rate of adverse reactions decreases, which will increase the selectivity of the process carried out in a packed reactor. Thus, the selectivity in a packed reactor will be higher than in a high-temperature bubble reactor, in which the temperature of the working medium is 83.5–110 ° С and the selectivity of the process is 98.0–98.7% [5].

Thus, in the packed reactor of liquid-phase chlorination of ethylene, more favorable conditions for the process are created than in a reactor with a bubble inlet of reagents.

Brief Description of the Drawings

List of figures:

figure 1. Bubble gas lift reactor of high temperature liquid phase chlorination of ethylene;

figure 2. Low temperature ethylene chlorination bubbler reactor;

figure 3. Distribution of liquid temperature along the height of the packed reactor;

figure 4. Packed reactor to produce 1,2-dichloroethane.

In Fig.1 and Fig.2 describes analogues of the invention. Figure 3 shows the dependence, allowing to determine the temperature of the working fluid in any section of the reactor. Figure 4 describes the device and the principle of operation of the reactor, in which the invention can be implemented.

The implementation of the invention

The nozzle reactor (Fig. 4) for producing 1,2-dichloroethane operates in the following mode: consumption of chlorine 300 nm ³ / hour, ethylene consumption 315 nm ³ / hour, nitrogen consumption 300 nm ³ / hour, initial concentration of chlorine in liquid 0, 1 kmol / m ³ , the final concentration of chlorine in the liquid is 0.005 kmol / m ³ , the mass transfer coefficient in the liquid is 0.4 m / h, the specific surface of the nozzle is 400 m ² / m ³ , the volumetric flow rate of the liquid is 134 m ³ / h, the inner diameter of the reactor 1.36 m. The height of the nozzle layer under these conditions was 3.12 m. Rashig rings are used as the nozzle. The material for the nozzle is carbon steel, this will contribute to a uniform temperature distribution in the liquid film. The nozzle is placed in two layers.

Packaged reactor liquid-phase chlorination of ethylene (figure 4) works as follows. From above, 1,2-dichloroethane is supplied in an amount necessary for carrying out the reaction and cooling the reaction mixture as a result of evaporative cooling. 1,2-dichloroethane film flows down the surface of the nozzle. Two layers of packing are placed in the reactor. The top layer of the nozzle is designed for absorption of chlorine by a stream of 1,2-dichloroethane, and the lower layer of the nozzle is used for chemisorption of ethylene with a chlorine solution. A gaseous mixture of chlorine and nitrogen is fed into the space between the layers of the nozzle through the distributor 2. The resulting chlorine solution from the upper layer of the nozzle flows to the lower layer of the nozzle. Under the lower layer of the nozzle through the distributor 3 is fed a gaseous mixture of ethylene with nitrogen. The gas and liquid phases move countercurrently. The upper part of the reactor acts as a separator to separate liquid droplets from steam. The drop eliminator also contributes to this 8. As a nozzle 7, it was decided to use a metal nozzle for a more uniform temperature distribution in the liquid film. Nitrogen and excess ethylene from the top of the reactor after condensation of the vapor in the condenser 5 are separated from the liquid 1,2-dichloroethane in the gas-liquid separator 10 and returned by the compressor 9 to the reactor. The condensate after the gas-liquid separator 10 enters the distribution unit 11, part of the condensate is returned to the reactor by the pump 12, and the rest in the form of the finished product is discharged into the collection tanks. The heat of reaction is removed by evaporation of 1,2-dichloroethane into nitrogen. The method of heat removal during evaporative cooling is effective. In this packed reactor, due to the evaporative cooling of 1,2-dichloroethane to nitrogen, the temperature in the reactor will be lower than the boiling point of 1,2-dichloroethane, as shown in FIG. 3. The graph of figure 3. built on the basis of the material, thermal balance of the packed reactor. As evidence of the fact that the selectivity in the packed reactor will be higher than in the prototype (bubble high-temperature reactor), you can use the graph (figure 3). In accordance with these data, the average temperature of the working medium in the reactor will be equal to 77 ° C. As is known from [2], a decrease in temperature in the reactor will reduce the rate of side reactions, as a result, the selectivity of the process will be higher than in a high-temperature bubble reactor (Fig. 1). In a bubbler high-temperature reactor, the temperature of the working medium is 83.5-110 ° C, and the heat of reaction is removed due to the boiling of the working medium. Moreover, the selectivity of the process in a high-temperature reactor is 98.0-98.7% [5].

The nozzle reactor can be controlled by controlling the flow rate of the working fluid, the flow of nitrogen and the initial temperature of the working fluid. A decrease in the initial temperature of the working fluid will increase the selectivity of the process, however, this will require an increase in nitrogen consumption and, as a consequence, an increase in the height of the nozzle layer. Increasing the flow rate of the working fluid will reduce the average temperature in the nozzle layer, but this will also lead to the need to increase the height of the nozzle layer. Due to the increase in nitrogen flow, the temperature of the working fluid can be reduced, but due to a decrease in the concentration of ethylene and the driving force of mass transfer, an increase in the required height of the nozzle layer will occur.

Literature

1. Lebedev N.N. Chemistry and technology of basic organic and petrochemical synthesis. Ed. 2nd, per. M., "Chemistry", 1975 - 736 p.

2. Avetyan M.G., Sonin E.V., Zaydman O.A. et al. Investigation of the process of direct chlorination of ethylene in an industrial environment. // Chemical industry, 1991, No. 12, S. 710-713.

3. Ramm V.M. Gas absorption. M., High School, 1975.

4. Rozhkov V.I., Zaydman O.A., Sonin E.V., Krishtal N.F., Avetyan M.G., Treger Yu.A., Kharitonov V.I., Perevalov A.F., Mubarakov R.G. Patterns of liquid-phase chlorination of ethylene. // Chem. prom 1991. No. 7. S.398.

5. Mubarakov R. G. Hydraulics and mass transfer in a bubble reactor of ethylene chlorination. - Diss. for the degree of Cand. tech. sciences. - Angarsk, 1998.132 s.

Claims (1)

A bubble-type reactor for producing 1,2-dichloroethane by liquid-phase chlorination of ethylene with removal of the reaction heat during boiling of the working medium, characterized in that two layers of a metal nozzle are placed in the reactor, liquid 1,2-dichloroethane is fed to the nozzle from above, into the space between the layers the nozzles supply gaseous chlorine with nitrogen, and ethylene gas with nitrogen is supplied under the bottom layer of the nozzle, the heat of reaction being removed by evaporation of 1,2-dichloroethane into nitrogen and the liquid temperature is kept below the boiling point.

Images