Efficient and energy-saving calcium carbide process vinyl chloride purification system

Abstract

The utility model provides an efficient and energy-saving calcium carbide process vinyl chloride purification system, which belongs to the technical field of vinyl chloride purification, solves the problems of poor vinyl chloride purification effect and incapability of efficiently utilizing resources, and comprises a cooler, a falling film absorber, a water scrubber and an alkaline tower which are connected in sequence, a bubble cap section and a filler layer are respectively arranged at the upper part of the water scrubber from top to bottom, the water scrubber is connected with a diluted hydrochloric acid tank and a diluted hydrochloric acid cooler, the diluted hydrochloric acid cooler is connected to the bubble cap section and the filler layer of the water scrubber, and a filler layer is arranged in the middle of the alkaline tower; the cooled crude vinyl chloride enters a falling film absorber for pre-absorption of hydrogen chloride; carrying out acid gas reaction absorption on the absorbed vinyl chloride and diluted hydrochloric acid; and the absorbed vinyl chloride reacts with alkali liquor for further absorption. According to the device disclosed by the utility model, a chloroethylene product which is relatively high in purity and meets the production requirement is obtained, the operation load of the subsequent water washing tower and the alkaline washing tower is reduced in the process, the recycling of resources is realized, and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of chloroethylene purification, and particularly relates to an efficient and energy-saving calcium carbide method chloroethylene purification system. BACKGROUND

[0002] In the current calcium carbide method chloroethylene production process, mainly scientific proportioning of acetylene and hydrogen chloride is used, and crude chloroethylene monomer is produced by the catalytic action of a mercury chloride catalyst in a converter; the crude chloroethylene monomer is sent to a polymerization kettle for production after purification, compression and rectification systems ensure that the purity of the monomer is 99.9%; a first-stage converter and a second-stage converter are usually arranged in the chloroethylene purification system to perform a chloroethylene synthesis reaction; the first-stage converter requires that the conversion index of acetylene is less than or equal to 30% and the conversion index of hydrogen chloride is less than or equal to 40%; the second-stage converter requires that the conversion index of acetylene is less than or equal to 3% and the conversion index of hydrogen chloride is less than or equal to 5%; the main purpose of arranging the chloroethylene purification system is to remove unreacted hydrogen chloride and other acidic substances in the conversion process; acetylene and other substances contained in the chloroethylene can be removed through a subsequent pressurized rectification device to ensure that the purity of the obtained chloroethylene monomer meets the requirements of the subsequent polymerization reaction.

[0003] The core of the calcium carbide method chloroethylene purification principle is to remove impurity gases in chloroethylene through a chemical reaction; in the process of producing chloroethylene by the calcium carbide method, calcium carbide reacts with water to generate acetylene, and the acetylene reacts with hydrogen chloride to generate chloroethylene; since industrial calcium carbide contains a large amount of impurities, hydrogen sulfide, phosphine and other impurity gases are generated in the hydrolysis reaction; therefore, the calcium carbide method chloroethylene purification process generally has problems such as high energy consumption, great difficulty, waste of resources that cannot be reused, high requirements for equipment, high risk of environmental pollution and the like. UTILITY MODEL CONTENTS

[0004] The utility model aims to provide an efficient and energy-saving calcium carbide method chloroethylene purification system to solve the problems of poor chloroethylene purification effect and inefficient resource utilization.

[0005] The technical scheme of the utility model is as follows: an efficient and energy-saving calcium carbide method chloroethylene purification system, which comprises, in sequence, a cooler, a falling film absorber, a water washing tower and an alkali washing tower; the falling film absorber is connected to the bottom of the water washing tower; the upper portion of the water washing tower is provided, from top to bottom, with a bubble cap section and a filler layer; the bottom of the water washing tower is sequentially connected to a dilute hydrochloric acid tank and a dilute hydrochloric acid cooler; the dilute hydrochloric acid cooler is connected to the bubble cap section and the filler layer of the water washing tower, respectively; and the alkali washing tower is provided with a filler layer in the middle portion.

[0006] As a further improvement of the utility model, the bottom of the cooler and the falling film absorber is respectively connected to a concentrated hydrochloric acid tank.

[0007] As a further improvement of the utility model, the alkali washing tower is connected to an alkali liquor circulation tank between the top and the bottom thereof; and the alkali liquor circulation tank is provided with an alkali adding pipeline.

[0008] As a further improvement of the present invention, the concentrated hydrochloric acid tank outlet is connected to a concentrated hydrochloric acid pipeline, the dilute hydrochloric acid tank inlet is connected to a dilute hydrochloric acid pipeline, and an external hydrochloric acid desorption system is connected between the dilute hydrochloric acid pipeline and the concentrated hydrochloric acid pipeline.

[0009] As a further improvement of the present invention, the cooler, the falling film absorber and the dilute hydrochloric acid cooler are respectively provided with a heat exchange inlet pipe and a heat exchange outlet pipe.

[0010] As a further improvement of the present invention, the outlet of the dilute hydrochloric acid cooler is connected to the falling film absorber.

[0011] As a further improvement of the present invention, a primary water replenishment pipeline is provided on the top of the water washing tower.

[0012] As a further improvement of the present invention, baffles are respectively provided in the concentrated hydrochloric acid tank and the dilute hydrochloric acid tank.

[0013] The beneficial effects of the present invention are as follows: In view of the prominent problems in the purification process of vinyl chloride by the calcium carbide method, such as high energy consumption, great difficulty, waste of resources that cannot be reused, high requirements for equipment, and high risk of environmental pollution, the present invention adopts the principle of combined utilization of a cooler, a falling film absorber, a water washing tower, and an alkali washing tower. According to the principle that the solubility of hydrogen chloride in water decreases with increasing temperature, the falling film absorber is fully utilized for pre-absorption. Then, the vinyl chloride entering through the bottom of the water washing tower is in reverse contact with the dilute hydrochloric acid entering from the top of the tower to absorb the acidic gas in the packing layer and the bubble section. Finally, a packing layer is set in the middle of the alkali washing tower for the contact reaction of vinyl chloride and alkali solution for further absorption, and finally a vinyl chloride product with high purity that meets production needs is obtained. In this process, the operating load of subsequent water washing towers and alkali washing towers is reduced, the consumption of primary water and alkali solution is reduced, the recycling and reuse of resources is realized, and the production cost is reduced.

[0014] The main function of the water washing tower provided in the utility model is to remove acidic substances. In the process of acetylene and hydrogen chloride reacting to generate vinyl chloride, a small amount of incompletely reacted hydrogen chloride and other acidic impurities may remain. Water washing can neutralize and remove these acidic substances, reduce the impact on subsequent processes, and lower the temperature. The temperature of the vinyl chloride gas generated by the reaction is relatively high, and the water washing process also plays a cooling role, which helps to control the operating conditions of the subsequent processes. At the same time, water washing can remove a part of impurities that are easily soluble in water, preparing for subsequent more refined purification steps.

[0015] The alkali washing tower is used for further removing acidic impurities, although most of the acidic substances can be removed by water washing, but some acidic impurities such as trace hydrogen chloride may still exist, the alkali washing uses alkaline solution (usually sodium hydroxide solution), can more effectively neutralize and remove these acidic residues, improve the purity of vinyl chloride; remove sulfide and other impurities, hydrogen sulfide and other harmful gases may be produced in the production process, alkali washing can effectively remove these harmful impurities, reduce the risk of equipment corrosion and environmental pollution; protect the subsequent equipment, through alkali washing, the acidic impurities can be prevented from entering the sensitive equipment such as rectifying tower, the equipment corrosion is reduced, and the service life is prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is the structure schematic view of the utility model.

[0017] In the figure: 1-cooler;2-falling film absorber;3-water washing tower;4-alkali washing tower;5-concentrated hydrochloric acid tank;6-dilute hydrochloric acid tank;7-alkali liquor circulating tank;8-dilute hydrochloric acid cooler;9-heat exchange import pipe;10-heat exchange export pipe;11-valve;12-vinyl chloride pipeline;13-acid pipeline;14-alkali pipeline;15-primary water water supply pipeline;16-concentrated hydrochloric acid pipeline;17-dilute hydrochloric acid pipeline;18-concentrated acid pump;19-dilute hydrochloric acid pump;20-alkali liquor circulating pump;21-baffle;22-alkali adding pipeline. DETAILED DESCRIPTION

[0018] The utility model makes further detailed description in combination with the drawings and specific implementation.

[0019] As Figure 1 Indicated, a kind of high-efficiency energy-saving chlor-alkali purification system of calcium carbide method, including the cooler 1 of connection in proper order, falling film absorber 2, water washing tower 3 and alkali washing tower 4, falling film absorber 2 is connected with the bottom of water washing tower 3, and water washing tower 3 upper portion is equipped with bubble cap section and filler layer from top to bottom respectively, and water washing tower 3 bottom is sequentially connected with dilute hydrochloric acid tank 6 and dilute hydrochloric acid cooler 8, and dilute hydrochloric acid cooler 8 is connected to bubble cap section and filler layer of water washing tower 3 respectively, and alkali washing tower 4 middle part is equipped with filler layer.

[0020] Cooler 1 and falling film absorber 2 bottom are respectively connected with concentrated hydrochloric acid tank 5;Alkali washing tower 4 top and bottom are connected with alkali liquor circulating tank 7, and alkali liquor circulating tank 7 is equipped with alkali adding pipeline 22;Concentrated hydrochloric acid tank 5 outlet is connected with concentrated hydrochloric acid pipeline 16, and dilute hydrochloric acid tank 6 import is connected with dilute hydrochloric acid pipeline 17, and dilute hydrochloric acid pipeline 17 and concentrated hydrochloric acid pipeline 16 are connected with external hydrochloric acid desorption system;Cooler 1, falling film absorber 2 and dilute hydrochloric acid cooler 8 are respectively equipped with heat exchange import pipe 9 and heat exchange export pipe 10;Dilute hydrochloric acid cooler 8 outlet is connected with falling film absorber 2;Water washing tower 3 top is equipped with primary water water supply pipeline 15;Concentrated hydrochloric acid tank 5 and dilute hydrochloric acid tank 6 are respectively equipped with baffle 21.

[0021] Example 1,

[0022] The cooler 1 is arranged at the front end of the system, and the cooler 1 is designed as a graphite column tube heat exchanger. A vinyl chloride pipeline 12 is arranged at the top of the cooler 1, and a heat exchange inlet pipe 9 and a heat exchange outlet pipe 10 are arranged in the shell side of the cooler 1 to form a heat exchange pipeline, which is connected to 5°C water for heat exchange. A U-shaped acid sealing pipeline is arranged at the bottom of the cooler 1, which is designed to cool the vinyl chloride before entering the purification device according to the principle that the solubility of hydrogen chloride in water decreases with the increase of temperature, so as to ensure that the hydrogen chloride and acid gas contained in the vinyl chloride are fully absorbed in the purification process. During the operation of the device, the circulating amount of 5°C cooling water in the shell side of the cooler 1 is required to be controlled by adjusting the valve, so as to ensure that the temperature of the material at the outlet of the cooler 1 is ≤15°C, which is convenient for subsequent production.

[0023] The crude vinyl chloride from the conversion system is sent to the cooler 1 through the vinyl chloride pipeline 12, and is indirectly cooled by heat exchange with 5°C cooling water in the heat exchange pipeline of the shell side of the cooler 1, so as to reduce the temperature of the crude vinyl chloride from the conversion, which is convenient for subsequent absorption of the falling film absorber 2. The acid pipeline 13 is arranged at the bottom of the cooler 1, and the condensed acid in the tube side of the cooler 1 is discharged to the concentrated hydrochloric acid tank 5 for collection and utilization. The vinyl chloride pipeline 12 is arranged at the gas phase outlet of the cooler 1, and the cooled vinyl chloride is sent to the falling film absorber 2. The acid pipeline 13 is arranged at the bottom of the falling film absorber 2, and the absorbed concentrated hydrochloric acid is discharged to the concentrated hydrochloric acid tank 5 through the pipeline according to gravity flow for secondary utilization.

[0024] The vinyl chloride is cooled by the cooler 1 and then enters the falling film absorber 2 for pre-absorption of hydrogen chloride. The falling film absorber 2 has the advantages of high absorption efficiency, good heat management ability and operation flexibility, and is suitable for absorption of high-concentration and strong-corrosion gas. The design adopts a vertical installation column tube structure, each column tube is equivalent to a small wet wall tower, and a jacket is arranged outside to form a heat exchange pipeline by arranging a heat exchange inlet pipe 9 and a heat exchange outlet pipe 10. The heat exchange pipeline is connected to 5°C water for cooling circulation, and the absorption temperature is reduced by indirect heat exchange to remove the heat released in the absorption process. A distributor or a film distributor is arranged at the top of the column tube for uniformly distributing the absorption liquid (usually water) to the inner wall of the column tube to form a continuous liquid film. The gas inlet is located at the upper part of the falling film absorber 2, and the contact absorption of hydrogen chloride in dilute hydrochloric acid is carried out in a parallel flow operation mode. The design principle of the jacket cooling is also based on the principle that the solubility of hydrogen chloride in water decreases with the increase of temperature. It is required to control the gas phase outlet temperature of the falling film absorber 2 to be ≤10°C during the operation.

[0025] Chloroethylene pipeline 12 is arranged at the gas phase outlet of falling film absorber 2 to send the chloroethylene absorbed by falling film absorber 2 to the inlet of water washing tower 3. Dilute hydrochloric acid tank 6 is arranged at the bottom of water washing tower 3. Dilute hydrochloric acid pump 19 is arranged at the bottom. Acid pipeline 13 is arranged at the outlet of dilute hydrochloric acid pump 19. After being cooled by dilute hydrochloric acid cooler 8, the dilute hydrochloric acid is sent to the bubble cap section and the packing section of water washing tower 3 through two valves 11. Three-way connecting pipeline is arranged on the pipeline. Part of the dilute hydrochloric acid is sent to falling film absorber 2 as absorption liquid by using valve 11. The dilute hydrochloric acid absorbed in the tower continues to flow to dilute hydrochloric acid tank 6 for recycling. Primary water supplement pipeline 15 is arranged at the top of water washing tower 3 for water supplement. Valve 11 for water supplement control is arranged on primary water supplement pipeline 15.

[0026] Water washing tower 3 is a combined absorption tower. The tower body requires glass steel material. The heavy metal structure in the tower needs to be designed for corrosion protection. Other structures in the tower are made of corrosion-resistant materials. Water washing tower 3 is designed to have two sections. The upper part of the tower is provided with a bubble cap section for absorbing hydrogen chloride. The lower part of the tower is provided with a corrugated plate packing layer to realize the absorption of hydrogen chloride. Chloroethylene enters from the bottom of water washing tower 3 and flows out from the top of water washing tower 3. Primary water supplement pipeline 15 is arranged at the top of water washing tower 3 for water supplement. Dilute hydrochloric acid tank 6 is arranged at the bottom of water washing tower 3. Before the system is operated, primary water is introduced into water washing tower 3 from the top of water washing tower 3 and then flows into dilute hydrochloric acid tank 6. Dilute hydrochloric acid cooler 8 is a graphite tube heat exchanger. The shell side is provided with heat exchange pipeline to cool the circulating dilute hydrochloric acid to ensure the absorption effect in water washing tower 3. The purpose of arranging dilute hydrochloric acid cooler 8 is to reduce the temperature of dilute hydrochloric acid by using the principle that the solubility of hydrogen chloride in water decreases with the increase of temperature. The main function of primary water supplement pipeline 15 arranged at the top of water washing tower 3 is to use water at a lower temperature to reduce the temperature of the gas to prevent corrosion of the cold exchange equipment and ensure the mass transfer efficiency through water flow distribution. The effective operation of primary water supplement pipeline at the top of water washing tower 3 is ensured, and the efficiency and safety of the equipment are improved. Before the design of water washing tower 3, the system flux needs to be calculated. Pressure monitoring and temperature monitoring are arranged at the top and bottom of the tower respectively. The pressure difference of the tower is required to be ≤3Kpa, and the temperature difference between the inlet temperature and the outlet temperature is required to be ≤5℃ during the operation.

[0027] Chloroethylene entering from the bottom of water washing tower 3 is in reverse contact with dilute hydrochloric acid entering from the top of the tower. After the absorption of acidic gas in the packing layer and the bubble cap section, chloroethylene absorbed by water washing tower 3 is sent to caustic washing tower 4 for further absorption through chloroethylene pipeline 12 arranged at the top of water washing tower 3. Caustic washing tower 4 is designed by using the principle of packing tower absorption. The main function is to remove other acidic gases contained in chloroethylene which is not absorbed by water washing tower 3 for further absorption. Sodium hydroxide is used to adjust the PH value of chloroethylene so that the PH value of chloroethylene after water and alkali washing is controlled between 7-9 to ensure the quality of polymerization products.

[0028] The alkali washing tower 4 is provided with a foam catcher at the top, and the overall flux design of the tower body needs to meet the process production requirements. The alkali washing tower 4 is provided with a tank and a feed inlet at the bottom, a packing layer is arranged in the middle of the alkali washing tower 4 for the contact reaction of vinyl chloride and alkali liquor, the packing layer is provided with alkali liquor spraying and liquid distributor at the top to realize the uniform distribution of alkali liquor, and a catcher is arranged at the top of the alkali washing tower 4 to separate the alkali liquor foam carried by the gaseous vinyl chloride in the flowing process and prevent the alkali liquor from entering the subsequent process.

[0029] An alkali liquor circulating tank 7 is arranged at the bottom of the alkali washing tower 4, an alkali liquor circulating pump 20 is arranged at the outlet of the alkali liquor circulating tank 7, and an alkali pipe 14 is arranged at the outlet of the alkali liquor circulating pump 20 to deliver the alkali liquor to the top of the alkali washing tower 4. Through the action of spraying and liquid distributor, the alkali liquor is reversely contacted with the vinyl chloride entering from the bottom of the alkali washing tower 4 through the liquid distributor and the packing at the top of the alkali washing tower 4, the reacted vinyl chloride is sent to the subsequent process through the vinyl chloride pipe 12 at the top of the alkali washing tower 4, the alkali liquor in the alkali washing tower 4 is self-flowed to the alkali liquor circulating tank 7 through the alkali pipe 14 at the bottom of the alkali washing tower 4 through gravity for repeated circulation, the alkali liquor circulating tank 7 is provided with an alkali adding pipe 22 at the top, a valve 11 is arranged on the alkali adding pipe 22 for control, and external addition of alkali liquor is facilitated. The alkali concentration of the alkali liquor circulating tank 7 is required to be 10%-15%, and the alkali liquor needs to be replaced in time when the alkali concentration exceeds or deviates from the index. The vinyl chloride temperature at the outlet of the alkali washing tower 4 is required to be ≤30℃.

[0030] The hydrochloric acid produced by the cooler 1 and the falling film absorber 2 has a high concentration, and baffles 21 are arranged in the concentrated hydrochloric acid tank 5 and the dilute hydrochloric acid tank 6. The main function of the baffles 21 arranged in the hydrochloric acid tank is to prevent the volatilization of hydrochloric acid and to play a heat preservation role, so as to realize the full mixing of the concentrated hydrochloric acid in the circulating tank. A concentrated acid pump 18 is arranged at the bottom of the concentrated hydrochloric acid tank 5, and a concentrated hydrochloric acid pipe 16 is arranged at the outlet of the concentrated acid pump 18 to deliver the concentrated hydrochloric acid to the externally connected hydrochloric acid desorption system. The desorbed dilute hydrochloric acid is returned to the dilute hydrochloric acid tank 6 through the dilute hydrochloric acid pipe 17 for repeated use.

[0031] During the operation of the device, the dynamic flow balance of the concentrated hydrochloric acid pipe 16, the dilute hydrochloric acid pipe 17 and the primary water supplement pipe 15 is required. The dilute hydrochloric acid in the dilute hydrochloric acid tank 6 is supplemented by the primary water added at the top of the water washing tower 3. During the operation of the device, the primary water needs to be added to adjust and control the liquid level balance of the concentrated hydrochloric acid tank 5 and the dilute hydrochloric acid tank 6 to be stable.

[0032] All the regulating valves in the device must meet the requirements of AN3I / FCI70-2 in terms of accuracy, and the regulating accuracy is ±1%; the device is designed to recover flammable and explosive media, and must meet the requirements of chemical fire and explosion prevention during installation. Nitrogen must be used for replacement before operation.

[0033] The device is running before all open system associated valve 11, access to nitrogen test pressure test, test pressure 1.02 pa qualified; using nitrogen on the whole system for replacement, multiple sampling, oxygen content ≤0.2%; open cooler 1, falling film absorber 2 and dilute hydrochloric acid cooler 8 on the heat pipe; open valve 11 using the first water water washing tower 3 by water to join the dilute hydrochloric acid tank 6, dilute hydrochloric acid tank 6 liquid level 70%-80%, close valve 11; open alkali circulation tank 7 top add alkali pipe 22 on the valve 11, alkali circulation tank 7 for alkali replenishment, the alkali concentration is 10%-15%, liquid level to 70%-80% when the valve 11 is closed; to open dilute hydrochloric acid pump 19 and water washing tower 3 to establish circulation, open alkali circulation pump 20 and alkali washing tower 4 to establish circulation; open cooler 1 to alkali washing tower 4 between vinyl chloride pipe 12 on all the valve 11, open tee acid pipe 13 on the valve 11 to falling film absorber 2 to join the absorption liquid; when the liquid level of concentrated hydrochloric acid tank 5 to 70%-80%, open concentrated acid pump 18 to send concentrated hydrochloric acid through the concentrated hydrochloric acid pipe 16 to the hydrochloric acid desorption system, until the desorption of dilute hydrochloric acid through the dilute hydrochloric acid pipe 17 back to dilute hydrochloric acid tank 6 repeated absorption utilization; system running in dilute hydrochloric acid tank 6 liquid level drop, need to open the valve 11 in time, ensure the liquid level of acid circulation system stable.

Claims

1. A highly efficient and energy-saving calcium carbide-based vinyl chloride purification system, characterized by: The invention comprises a cooler (1), a falling film absorber (2), a water washing tower (3) and an alkali washing tower (4) connected in sequence, wherein the falling film absorber (2) is connected to the bottom of the water washing tower (3), the upper part of the water washing tower (3) is provided with a bubble section and a packing layer from top to bottom, the bottom of the water washing tower (3) is connected in sequence with a dilute hydrochloric acid tank (6) and a dilute hydrochloric acid cooler (8), the dilute hydrochloric acid cooler (8) is connected to the bubble section and the packing layer of the water washing tower (3), and the middle part of the alkali washing tower (4) is provided with a packing layer.

2. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 1, characterized in that: The bottoms of the cooler (1) and the falling film absorber (2) are respectively connected to concentrated hydrochloric acid tanks (5).

3. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 2, characterized in that: An alkali liquid circulation tank (7) is connected between the top and the bottom of the alkali washing tower (4), and an alkali adding pipeline (22) is provided on the alkali liquid circulation tank (7).

4. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 3, characterized in that: The outlet of the concentrated hydrochloric acid tank (5) is connected to a concentrated hydrochloric acid pipeline (16), the inlet of the dilute hydrochloric acid tank (6) is connected to a dilute hydrochloric acid pipeline (17), and an external hydrochloric acid desorption system is connected between the dilute hydrochloric acid pipeline (17) and the concentrated hydrochloric acid pipeline (16).

5. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 4 is characterized in that: The cooler (1), the falling film absorber (2) and the dilute hydrochloric acid cooler (8) are respectively provided with a heat exchange inlet pipe (9) and a heat exchange outlet pipe (10).

6. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 5, characterized in that: The outlet of the dilute hydrochloric acid cooler (8) is connected to the falling film absorber (2).

7. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 6, characterized in that: A primary water replenishment pipeline (15) is provided on the top of the water washing tower (3).

8. The high-efficiency and energy-saving calcium carbide-based vinyl chloride purification system according to claim 7, characterized in that: Baffles (21) are respectively provided in the concentrated hydrochloric acid tank (5) and the dilute hydrochloric acid tank (6).

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