The method of producing vinyl chloride and device for its implementation

 

(57) Abstract:

The vinyl chloride is obtained from the reaction mixture produced by the incomplete thermal decomposition of 1,2-dichloroethane, at elevated pressure, a temperature of from 450oC distillation of hydrogen chloride. In the first stage of distillation is distilled off hydrogen chloride, in the second stage of distillation to separate the vinyl chloride. Part of the liquefied vinyl chloride return in the second stage of distillation in the form of phlegmy. The remaining part of the selected liquefied vinyl chloride fed to the head part of the third stage distillation for evaporation of hydrogen chloride together with a part of the vinyl chloride, which then return to the first stage of distillation. In the head part of the third stage distillation deduce a part of vinyl chloride in mixture with all the number of extracted hydrogen chloride and water, which is then passed through a drying zone, which removed a significant amount of water, then return to the first stage of distillation. Apparatus for producing vinyl chloride contains a zone of expansion, the first stage of distillation for the separation of hydrogen chloride, the second stage of distillation for the removal of vinyl chloride from high-boiling components and the third stage of distillation of gliclazide with the third stage distillation install node-zone drying, which removes a significant amount of water and which is connected with the first stage of distillation. In the area of drying dehumidifiers connected in a parallel circuit and apply a dewatering means, which adsorbs water, in particular silica gel or molecular sieve. In the simplified process flow scheme of the process, and reduces the corrosion of the equipment. 2 s and 5 C.p. f-crystals, 1 Il.

The invention relates to the production of alkylhalides, more specifically to a method and apparatus for producing vinyl chloride.

A known method of producing vinyl chloride from the reaction mixture produced by the incomplete thermal decomposition of 1,2 - dichloroethane, at an elevated pressure and a temperature of from about 450oC to 650oC distillation of the hydrogen chloride in the first stage of distillation and the separation in the second stage of distillation of vinyl chloride, liquefaction, and the return of liquefied vinyl chloride in the second stage of distillation in the form of phlegmy, when applying the remaining part of the selected liquefied vinyl chloride to the head part of the third stage distillation for evaporation of hydrogen chloride with a part of the vinyl chloride and returning to the first stage distillation (see U.S. patent n 3 843 736, 1974). Device for assests is Yes, the second stage of distillation for the removal of vinyl chloride from high-boiling components and the third stage distillation for the separation of hydrogen chloride and water from vinyl chloride.

The known method has the disadvantage that the exhaust from the third stage of the distillation of vinyl chloride still contains small quantities of water. Practically this cannot be avoided; especially during the start-up and interruption of the working process inevitably are trace amounts of water. Therefore, in practice, at the third stage distillation work in such a way that these quantities of water away from the bottom of the distillation column together with hydrogen chloride, which requires the use of a column filled with sodium hydroxide. If you don't have that separation of water through the lower part of the distillation column, the water falls along with the return of the vinyl chloride in the circulating mixture and will corrode the washed parts. Such corrosion is not only harmful from an economic point of view, but above all must be addressed from the point of view of safety of the process.

The objective of the invention is to simplify the technology for the production of vinyl chloride with simultaneous exclusion of corrosion, vyzyvaet from the reaction mixture, produced by the incomplete thermal decomposition of 1,2-dichloroethane, at an elevated pressure and a temperature of from about 450oC to 650oC distillation of the hydrogen chloride in the first stage of distillation and the separation in the second stage of distillation of vinyl chloride, liquefaction, and the return of liquefied vinyl chloride in the second stage of distillation in the form of phlegmy, when applying the remaining part of the selected liquefied vinyl chloride to the head part of the third stage distillation for evaporation of hydrogen chloride with a part of the vinyl chloride and returning to the first stage of distillation, due to the fact that at the head of the third stage distillation deduce a part of vinyl chloride in mixture with all the number of extracted hydrogen chloride and water, which is then passed through a drying zone, which removed a significant amount of water, then return to the first stage of distillation, and from the lower part of the third stage select clean vinyl chloride.

In the zone of dewatering water is preferably removed using a dewatering means, which preferably is a tool that adsorbs water, for example, molecular sieve or silica gel.

The device for carrying out the Dios distillation for the removal of vinyl chloride from high-boiling components and the third stage distillation for the separation of hydrogen chloride and water from vinyl chloride, while on the line output of hydrogen chloride, water, and parts of vinyl chloride with the third stage distillation install node - zone drying, which removes a significant amount of water and which is connected with the first stage of distillation.

The drying zone preferably contains a desiccant loaded tool that physically adsorbs water.

The drying zone may contain parallel-connected dryers.

The device according to the invention is shown schematically in the drawing.

Given its position (1) to (18) denote the following sites:

(1) the decomposition zone,

(2) the first stage of distillation for the separation of hydrogen chloride,

(3) the second distillation zone to the distillation of vinyl chloride from high-boiling components,

(4) the third stage distillation for the separation of hydrogen chloride and water from vinyl chloride,

(5) the drying zone,

(6) supply of 1,2-dichloroethane to the decomposition (1),

(7) the feed line from the decomposition products to the first stage of distillation (2),

(8) line separated hydrogen chloride,

(9) the feed line from the high-boiling products in the second stage distillation (3),

(10) the feed line to the condenser (11) for stellazio (3),

(13) the line separating the high-boiling by-products,

(14) the feed line of the second partial stream of liquefied vinyl chloride to the third stage distillation (4),

(15) line from the third stage distillation (4) to the drying zone (5),

(16) the return line dried mixture of hydrogen chloride and the rest of the amount of vinyl chloride in the first stage distillation (2),

(17) line separated water,

(18) line of pure vinyl chloride.

When the water separation according to the invention in the drying zone comes highly corrosive mixture of vinyl chloride, hydrogen chloride and water. Under these conditions may occur in a known manner, the polymerization of vinyl chloride (catalysis by trace metals). However, in an unexpected way, even if a very long period of work in metal equipment were not observed deposition of polyvinyl chloride.

The removal of significant quantities of water according to the invention can be carried out in a known for acidic liquids. This can be accomplished by condensation of water, preferably, however, the drying, for example, with the means that cause chemical transformations, for example, liquid desiccants, such as concentrated sulfuric acid, or darurat water, such as molecular sieves and especially silica gel.

The drying zone consists mainly of two parallel-connected dryers, and through one desiccant served slurry return the mixture, while the other desiccant (other driers) recycled (regenerated) or re-loaded (loaded). Of course that can be incorporated into the work of several dehumidifiers in the series. Allocated during the regeneration of valuable substances, vinyl chloride and hydrogen chloride, can be returned to the process.

In a preferred embodiment of the invention, the dryers can be connected so that they can be in the regeneration heat and flushed with an inert gas, such as carbon dioxide, inert gases, or preferably nitrogen. Suitable are, for example, tubular heat exchangers or tanks located inside the coils.

According to the invention can be dried leaving the head part of the third stage of the distillation gases flow or condensing head product and condensate to pass preferably through the desiccant.

It is advisable to position the dryer as close to the third stage of distillation, pocket to carry out the drying gas phase. In this case, the desiccant can be placed at the beginning of the line evaporation.

The invention is illustrated by the following examples.

Example 1. The flow of vinyl chloride with an average water content of 29.5 million shares passed with a speed of 39 kg/HR (inlet pressure 16 bar) through a tube (length 200 mm, diameter 80 mm), filled with the metal cloth with density of cells 125 μm, loaded 740 g of silica gel (trade name "Blaugel", temporily, a particle size of from 1 to 3 mm). After 21 hours the silica gel was adsorbing 15,45 g of water, which corresponds to the saturation of 2.1%. The water content in the output stream of vinyl chloride is 7.1 million shares.

For desorption through the apparatus miss low pressure steam. After 180 minutes, the residual content in the silica gel is < 0,3%.

Example 2. Industrial plant flow vinyl chloride is passed with a speed of 39 kg/hour for 19 hours through the cylindrical tube described in example 1. After 19 hours, the saturation of the silica gel is of 3.07 wt.%. The water content in the dried vinyl chloride is 6.5 million shares.

For the regeneration vessel is heated to about 120oC (internal temperature), and through it pass the thread I the th installation of the flow of vinyl chloride with an average water content of 30 million share miss with a speed of 34 kg/h through a tube (length 200 mm, diameter 80 mm) filled with molecular sieve (trade name "Wessalith US 330", manufacturer Degussa AG, Hanau, Germany), the inlet pressure of 16 bar. After 88 hours molecular sieve was adsorbing 738 g of water, which corresponds to the saturation of 31.9% in the calculation of the adsorbent. 23 hours desorption at 250oC the residual content is about 13 wt.%.

Example 4. Part of the flow head part of the third stage of distillation, containing 0,37 kg of vinyl chloride with about 4 grams (1,000 million shares) of hydrogen chloride and about 6 mg (16 million shares) of water in gaseous form, assign and pass through the desiccant. The drier consists of a tube length of 200 mm and a diameter of 15 mm, It is filled with 35 g of silica gel (trade name "Blaugel", temporily, a particle size of from 1 to 3 mm). After passing 100 l of a specified gas flow through the desiccant, silica gel was adsorbing to 12.8 wt.% water. The average water content of the output gas flow of 0.5 million shares.

1. The method of producing vinyl chloride from the reaction mixture produced by the incomplete thermal decomposition of 1,2-dichloroethane, at an elevated pressure and a temperature of from about 450oWith up to 650oInishmore, its liquefaction and the return of liquefied vinyl chloride in the second stage of distillation in the form of phlegmy, when applying the remaining part of the selected liquefied vinyl chloride to the head part of the third stage distillation for evaporation of hydrogen chloride with a part of the vinyl chloride and returning to the first stage of distillation, characterized in that the head part of the third stage distillation deduce a part of vinyl chloride in mixture with all the number of extracted hydrogen chloride and water, which is then passed through a drying zone, which removed a significant amount of water, then return to the first stage of distillation, and from the lower part of the third stage select clean vinyl chloride.

2. The method according to p. 1, characterized in that in the zone of drying to remove the water using a dewatering means.

3. The method according to p. 2, characterized in that in the zone of drying use drying agent, which adsorbs the water.

4. The method according to p. 3, characterized in that in the zone of drying as drying means used molecular sieve or silica gel.

5. Apparatus for producing vinyl chloride, containing an area of decay, the first stage of distillation for the separation of hydrogen chloride, the second article is of hydrogen chloride and water from vinyl chloride, characterized in that the line output of hydrogen chloride, water, and parts of vinyl chloride with the third stage distillation install node-zone drying, which removes a significant amount of water and which is connected with the first stage of distillation.

6. The device under item 5, characterized in that in the zone of drying it contains a desiccant loaded tool that physically adsorbs water.

7. The device under item 5 or 6, characterized in that in the zone of drying it contains parallel-connected dryers.

 

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