阅读说明：本技术 一种四氯乙烯生产过程中的除水方法 (Water removal method in tetrachloroethylene production process ) 是由 吴刚 周强 庄丽珍 黄波 应仲阳 袁永永 徐峰 郑辉煌 于 2020-11-04 设计创作，主要内容包括：本发明公开了一种四氯乙烯生产过程中的除水方法,将四氯乙烯粗品进入精馏塔进行共沸精馏,四氯乙烯和水经加热形成共沸物进入塔顶,从塔釜收集得到除水后的四氯乙烯产品,塔顶的共沸物经冷凝后得到非均相液体,将非均相液体分层,得到有机相和无机相,将有机相回流至精馏塔。本发明具有工艺简单,处理效率高,成本低、绿色环保的优点。(The invention discloses a water removal method in a tetrachloroethylene production process, which comprises the steps of enabling a tetrachloroethylene crude product to enter a rectifying tower for azeotropic rectification, enabling tetrachloroethylene and water to form an azeotrope through heating, enabling the azeotrope to enter the tower top, collecting a dehydrated tetrachloroethylene product from a tower kettle, condensing the azeotrope at the tower top to obtain heterogeneous liquid, layering the heterogeneous liquid to obtain an organic phase and an inorganic phase, and enabling the organic phase to flow back to the rectifying tower. The method has the advantages of simple process, high treatment efficiency, low cost and environmental protection.)

1. A water removal method in a tetrachloroethylene production process is characterized in that a tetrachloroethylene crude product enters a rectifying tower for azeotropic rectification, the tetrachloroethylene and water are heated to form an azeotrope, the azeotrope enters the tower top, a dehydrated tetrachloroethylene product is collected from a tower kettle, the azeotrope at the tower top is condensed to obtain heterogeneous liquid, the heterogeneous liquid is layered to obtain an organic phase and an inorganic phase, and the organic phase flows back to the rectifying tower.

2. The method for removing water in the production process of tetrachloroethylene according to claim 1, wherein the temperature of azeotropic distillation is 60-90 ℃ and the pressure is-10-20 kPa.

3. The method as claimed in claim 1, wherein the water content in the crude tetrachloroethylene is 200-500 ppm.

4. The method of claim 1, wherein the condensing temperature is in the range of 25 to 40 ℃.

Technical Field

The invention relates to the technical field of tetrachloroethylene, and particularly relates to a water removal method in a tetrachloroethylene production process.

Background

Tetrachloroethylene has wide application, is mainly used as a raw material for synthesizing trichloroethylene and fluorine-containing organic compounds, such as a refrigerant HFC-125, can be used as a fat extractant, a fire extinguishing agent and a smoke curtain agent, can be used as a degreasing detergent of metal, a general solvent and an organic synthesis intermediate, and can be used as a chromatographic analysis standard substance.

At present, the preparation method of tetrachloroethylene mainly comprises the following steps:

(1) ethylene process

The ethylene method can co-produce trichloroethylene and tetrachloroethylene and comprises the following two steps:

a. direct chlorination. In the presence of FeCl₃Reacting in 1, 2-dichloroethane solution of catalyst at 280-450 deg.C to obtain 1, 2-dichloroethane, further chlorinating to obtain trichloroethylene and tetrachloroethylene, distilling, and respectively using NH₃Neutralizing, washing and drying to obtain the finished product.

b. An oxychlorination process. Addition of ethylene and chlorine to produce 1, 2-dichloroethane, reaction of 1, 2-dichloroethane with chlorine and oxygen in the presence of CuCl₂KCl is used as a catalyst, and the oxychlorination reaction is carried out under the conditions of 350-500 ℃ and 138-207kPa, and the product is cooled, washed, dried and distilled to obtain the product.

(2) Hydrocarbon oxidation process

The hydrocarbon mixture containing methane, ethane, propane, propylene, etc. is chloridized and pyrolyzed at 50-500 deg.c to obtain the mixture of chlorinated hydrocarbons, which are rectified and separated into various products.

(3) Acetylene process

Heating and chlorinating acetylene and chlorine to generate 1, 1, 2, 2-tetrachloroethane, removing hydrogen chloride by using alkali to obtain trichloroethylene, generating pentachloroethane by chlorination, and removing hydrogen chloride by using alkali to obtain tetrachloroethylene. Because of the high price of acetylene, the acetylene is gradually replaced by an ethylene method and the like.

The purification and drying process for producing tetrachloroethylene in the prior art generally comprises the following steps: and cooling, washing with water or/and alkali, drying, distilling and the like.

For example, chinese patent publication No. CN106831319A discloses a tetrachloroethylene purification and drying method, which comprises the following steps: (1) putting the tetrachloroethylene crude product flowing out of the rectifying tower and alkali liquor into an alkaline washing tank for mixing reaction to obtain a mixed material; (2) conveying the mixed material to an alkaline washing phase separator through an alkaline washing mixing pump for primary separation to obtain tetrachloroethylene and alkali liquor after primary separation; (3) carrying out secondary separation on the tetrachloroethylene subjected to the primary separation by using a high-efficiency phase separator to obtain tetrachloroethylene subjected to secondary separation; (4) and drying the tetrachloroethylene subjected to secondary separation in a dryer to obtain a tetrachloroethylene finished product.

For example, chinese patent publication No. CN109265312A discloses an apparatus and method for preparing tetrachloroethylene by connecting reactors in series, the apparatus comprising a first fixed bed reactor, a second fixed bed reactor, a condenser, a gas-liquid separator, a first phase separator, a distillation column, a rectification column, a dryer, a filter, a heat insulating plate and a second phase separator, the first fixed bed reactor is provided with a first raw material inlet, the second fixed bed reactor is provided with a second raw material inlet, the middle part of the second fixed bed reactor is provided with the heat insulating plate, a gas-liquid separator gas phase outlet is connected with the dryer, the filter and the first raw material inlet, a gas-liquid separator bottom outlet is connected with the distillation column, a distillation column bottom outlet is connected with the rectification column, a distillation column top outlet is connected with the second phase separator, and a second recycle outlet is connected with the second raw material inlet.

Tetrachloroethylene is used as a raw material for producing the refrigerant HFC-125, has strict requirements on moisture, and the moisture content must be 0-50 ppm.

At present, the drying methods adopted in the industrial production of tetrachloroethylene mainly comprise the following steps: calcium chloride drying method, solvent adsorption method, permeation membrane method and rectification method. The calcium chloride drying method needs to replace calcium chloride regularly every month, so that the replacement operation intensity is high, the operation cost is high, and the difficulty and the cost of post-treatment of the replaced calcium chloride as solid waste are high; the problems of mixing and dissolving, separation and the like of tetrachloroethylene and a solvent exist after water is removed by a solvent adsorption method; the membrane in the permeation membrane method is not resistant to acid conditions and part of organic solvents; the common rectification separation method is to carry out rectification separation according to the difference between the boiling points of substances, has large investment and high operation cost, has low economy for trace moisture separation, and easily causes the acidolysis of the tetrachloroethylene due to high temperature of a tower kettle.

Disclosure of Invention

The invention aims to solve the defects of the prior art and provides the green and environment-friendly water removal method in the tetrachloroethylene production process, which has the advantages of simple process, good treatment effect and low cost.

In order to achieve the purpose, the invention adopts the technical scheme that: a method for removing water in the production process of tetrachloroethylene comprises the steps of enabling a tetrachloroethylene crude product to enter a rectifying tower for azeotropic rectification, enabling tetrachloroethylene and water to form an azeotrope through heating, enabling the azeotrope to enter the tower top, collecting a dehydrated tetrachloroethylene product from a tower kettle, condensing the azeotrope at the tower top to obtain heterogeneous liquid, layering the heterogeneous liquid to obtain an organic phase and an inorganic phase, and enabling the organic phase to flow back to the rectifying tower.

In a preferred embodiment of the invention, the temperature of the azeotropic distillation is 60-90 ℃ and the pressure is-10-20 kPa.

As a preferred embodiment of the present invention, the water content in the crude tetrachloroethylene is 200-500 ppm.

As a preferred embodiment of the present invention, the condensation temperature is 25 to 40 ℃.

The invention utilizes the principle that tetrachloroethylene and water are immiscible and can form a binary heterogeneous azeotrope, the tetrachloroethylene and the water have an azeotropic point, the solubility of the water in the tetrachloroethylene is 105ppm, and the aim of dehydration and drying in the production process of the tetrachloroethylene is achieved by applying the azeotropic rectification principle on the premise of not introducing an azeotropic agent. The water content of the dehydrated tetrachloroethylene product is below 28ppm, and the tetrachloroethylene product meets the requirements of raw materials for producing the refrigerant HFC-125.

Compared with the prior art, the invention has the advantages that:

1. the process flow is simple, the operation is convenient, the azeotropic distillation technology can effectively remove the moisture in the tetrachloroethylene, the requirements of the tetrachloroethylene as the raw material for producing the refrigerant HFC-125 are met, the process has high operation flexibility, the continuous production can be realized, and the drying process in the production process of the tetrachloroethylene is obviously simplified;

2. the water removal effect is good, and the water content in the tetrachloroethylene product obtained after treatment is below 28 ppm;

3. the method is green and environment-friendly, and the water and the tetrachloroethylene form an azeotrope through azeotropic dehydration, so that the azeotropic distillation separation is carried out, the water of the tetrachloroethylene product can be effectively removed, and the generation amount of solid waste and the production cost are obviously reduced.

The method has high product purity, and the azeotropic distillation separation is carried out by utilizing the characteristic that water and tetrachloroethylene form an azeotrope, so that an entrainer is not used, and the pollution to the product caused by introducing extra impurities is avoided.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

In the figure, 1 is a rectifying tower, 2 is a condenser, 3 is a layering tank, 4 is a reboiler, 5 is a reflux pump, and 6 is a product pump.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the present invention is not limited to these specific examples. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.

The crude tetrachloroethylene in the examples is obtained from the rectification step in the process of producing tetrachloroethylene by hydrocarbon oxidation.

Example 1

The method comprises the steps of enabling a tetrachloroethylene crude product with the water content of 350ppm to enter a rectifying tower for azeotropic distillation, enabling a reboiler at a tower bottom of the rectifying tower to supply heat through steam stripping, controlling the temperature at the tower top to be 60 ℃ through the rectifying tower, enabling the tetrachloroethylene and water to form an azeotrope through heating and enter the tower top, condensing with circulating water at 32 ℃ through a tower top condenser to obtain heterogeneous liquid, enabling the heterogeneous liquid to enter a layering tank, enabling an upper layer to obtain a water phase after layering, enabling a lower layer to obtain an organic phase mainly containing tetrachloroethylene, enabling the organic phase at the lower layer to flow back to the rectifying tower through a reflux pump, collecting and uniformly processing the water phase at the upper layer in a wastewater form, enabling a tetrachloroethylene product obtained at the tower bottom of the rectifying tower after dehydration to be sent into a product tank through a product pump, sampling.

Example 2

The method comprises the steps of enabling a tetrachloroethylene crude product with the water content of 281ppm to enter a rectifying tower for azeotropic distillation, enabling a reboiler at a tower bottom of the rectifying tower to supply heat through steam stripping, controlling the temperature at the tower top to be 70 ℃ through the rectifying tower, enabling the tetrachloroethylene and water to form an azeotrope through heating and enter the tower top, condensing through a tower top condenser with circulating water of 30 ℃ to obtain heterogeneous liquid, enabling the heterogeneous liquid to enter a layering tank, enabling an upper layer to obtain a water phase after layering, enabling a lower layer to obtain an organic phase mainly containing tetrachloroethylene, enabling the organic phase at the lower layer to flow back to the rectifying tower through a reflux pump, collecting and uniformly processing the water phase at the upper layer in a wastewater form, enabling a tetrachloroethylene product obtained at the tower bottom of the rectifying tower after dehydration to be sent into a product tank through a product pump, sampling.

Example 3

The method comprises the steps of enabling a tetrachloroethylene crude product with the water content of 310ppm to enter a rectifying tower for azeotropic distillation, enabling a reboiler at a tower bottom of the rectifying tower to supply heat through steam stripping, controlling the temperature at the top of the rectifying tower to be 80 ℃ and the pressure to be 5kPa, enabling tetrachloroethylene and water to form an azeotrope through heating and enter the top of the rectifying tower, condensing with circulating water at 35 ℃ through a tower top condenser to obtain heterogeneous liquid, enabling the heterogeneous liquid to enter a layering tank, enabling an upper layer to obtain a water phase after layering, enabling a lower layer to obtain an organic phase mainly containing tetrachloroethylene, enabling the lower layer organic phase to flow back to the rectifying tower through a reflux pump, collecting and uniformly processing the upper layer water phase in a wastewater form, enabling a tetrachloroethylene product obtained at the bottom of the rectifying tower after dehydration to be sent into a product tank through a.

Example 4

The method comprises the steps of enabling a tetrachloroethylene crude product with the water content of 296ppm to enter a rectifying tower for azeotropic rectification, enabling a reboiler at a tower bottom of the rectifying tower to supply heat through steam stripping, controlling the temperature at the top of the rectifying tower to be 85 ℃ and the pressure to be 10kPa, enabling tetrachloroethylene and water to form an azeotrope through heating and enter the top of the rectifying tower, condensing circulating water at 28 ℃ through a tower top condenser to obtain heterogeneous liquid, enabling the heterogeneous liquid to enter a layering tank, enabling an upper layer to obtain a water phase after layering, enabling a lower layer to obtain an organic phase mainly containing tetrachloroethylene, enabling the lower layer organic phase to flow back to the rectifying tower through a reflux pump, collecting and uniformly processing the upper layer water phase in a wastewater form, enabling the tetrachloroethylene product obtained at the bottom of the rectifying tower after dehydration to be sent into a product tank through a product.

Example 5

The method comprises the steps of enabling a tetrachloroethylene crude product with the water content of 316ppm to enter a rectifying tower for azeotropic distillation, enabling a reboiler at a tower bottom of the rectifying tower to supply heat through steam stripping, controlling the temperature at the top of the rectifying tower to be 90 ℃ and the pressure to be 20kPa, enabling tetrachloroethylene and water to form an azeotrope through heating and enter the top of the rectifying tower, condensing with circulating water at 32 ℃ through a tower top condenser to obtain heterogeneous liquid, enabling the heterogeneous liquid to enter a layering tank, enabling an upper layer to obtain a water phase after layering, enabling a lower layer to obtain an organic phase mainly containing tetrachloroethylene, enabling the lower layer organic phase to flow back to the rectifying tower through a reflux pump, collecting and uniformly processing the upper layer water phase in a wastewater form, enabling the tetrachloroethylene product obtained at the bottom of the rectifying tower after dehydration to be sent into a product tank through a.