Purification and rectification system for by-products in production of vinyl chloride by calcium carbide method

Abstract

The utility model provides a purification and rectification system for by-products in production of vinyl chloride by a calcium carbide method, belongs to the technical field of purification and rectification of vinyl chloride, solves the problems that purification and rectification products of by-products in production of vinyl chloride are low in purity and cannot be efficiently recovered, and comprises a dichloroethane storage tank and at least two purification units, each purification unit comprises a rectifying tower, a first cooler is arranged at the top of the rectifying tower and connected with a return tank, the return tank is connected with the rectifying tower, a reboiler is arranged at the bottom of the rectifying tower, and the first coolers of the purification units are jointly connected with a vinyl chloride gas holder; the reboiler of the previous purification unit is connected with the rectifying tower of the next purification unit, the return tank of the last purification unit is connected with a finished product tank, and the reboiler of the last purification unit is connected with a residue tank. The dichloroethane rectification system solves the problem of resource waste caused by low purity of dichloroethane removed by the traditional rectification system, realizes high-efficiency recovery and cyclic recovery, and improves the resource utilization rate.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of vinyl chloride purification rectification, and particularly relates to a purification rectification system for by-products of calcium carbide method vinyl chloride production. BACKGROUND

[0002] In the current calcium carbide method vinyl chloride production process, the calcium carbide may contain impurities such as sulfur and phosphorus in the production process. When the calcium carbide reacts with water, the impurities generate corresponding impurity gases such as hydrogen sulfide and hydrogen phosphide, which enter the vinyl chloride conversion system. At the same time, when the calcium carbide reacts with water to generate acetylene, other side reactions may also occur. The impurities in the calcium carbide react with water, or the acetylene further reacts under certain conditions to generate other organic or inorganic compounds. In addition, in the vinyl chloride synthesis stage, catalysts such as mercury chloride are used to promote the reaction of acetylene and hydrogen chloride. In addition to catalyzing the main reaction, the catalysts may also promote some side reactions to generate by-products such as dichloroethane and dichloroethane.

[0003] To ensure the purity of the vinyl chloride monomer, the production device needs to be provided with a purification device to wash the alkali, remove the inorganic substances contained in the vinyl chloride monomer, and then send the vinyl chloride monomer to a vinyl chloride gas tank for storage. Then, the vinyl chloride in the gas tank is sent to a rectification device by a compressor to remove organic compounds such as acetylene and high-boiling substances, and finally obtain the vinyl chloride monomer with qualified product purity for polymerization. The dichloroethane and other high-boiling substances removed at the end of the device need to be loaded into a truck for external sale. On the one hand, the purity of the dichloroethane removed by the traditional rectification system is relatively low, which leads to a low external sale price and causes waste of production resources. On the other hand, since dichloroethane is a flammable and explosive hazardous chemical, long-distance transportation of dichloroethane with low purity poses a great safety risk, and accidents such as explosion and fire during transportation are likely to occur, which may cause personnel injury and property loss. UTILITY MODEL CONTENTS

[0004] The utility model aims to provide a purification rectification system for by-products of calcium carbide method vinyl chloride production, to solve the problem of low purity of the purification rectification product of the vinyl chloride production by-products and the problem of inefficient recovery.

[0005] The technical scheme of the utility model is as follows: a purification rectification system for by-products of calcium carbide method vinyl chloride production, which comprises a dichloroethane storage tank and at least two purification units. The purification units are connected in series. Each purification unit comprises a rectification tower. A first cooler is arranged at the top of the rectification tower. The first cooler is connected with a reflux tank. The reflux tank is connected with the rectification tower. A reboiler is arranged at the bottom of the rectification tower. The first coolers of each purification unit are jointly connected with a vinyl chloride gas tank. The dichloroethane storage tank is connected with the first purification unit. The reboiler of the previous purification unit is connected with the rectification tower of the next purification unit. The reflux tank of the last purification unit is connected with a finished product tank. The reboiler of the last purification unit is connected with a residue tank.

[0006] As a further improvement of the present invention, a jacket is provided in the residue tank, the jacket is connected to a steam pipe, and the residue tank is connected to the distillation tower of the last purification unit through a recovery pipe.

[0007] As a further improvement of the present invention, the finished product tank outlet is connected to a second cooler, and the second cooler is connected to a dichloroethane loading crane pipe; a third cooler is connected between the residue tank and the reboiler of the last purification unit, and the residue tank outlet is connected to a residue loading crane pipe.

[0008] As a further improvement of the present invention, thermometers are respectively provided on the top and bottom of the distillation tower, the inlet pipe of the reflux tank, the outlets of the second cooler and the third cooler, and the residue tank.

[0009] As a further improvement of the present invention, the first cooler, the second cooler and the third cooler are respectively provided with heat exchange pipes, the heat exchange pipe on the first cooler is provided with a first regulating valve, the heat exchange pipe on the second cooler is provided with a second regulating valve, and the heat exchange pipe on the third cooler is provided with a third regulating valve; the reboiler is provided with a steam pipe, the steam pipe is provided with a fourth regulating valve; the steam pipe connected to the jacket is provided with a fifth regulating valve.

[0010] As a further improvement of the present invention, the thermometer on the inlet pipe of the reflux tank is interlocked with the first regulating valve; the thermometer at the bottom of the distillation tower is interlocked with the fourth regulating valve.

[0011] As a further improvement of the present invention, the thermometer on the outlet of the second cooler is interlocked with the second regulating valve, and the temperature index is ≤30°C; the thermometer on the outlet of the third cooler is interlocked with the third regulating valve; the thermometer on the residue tank is interlocked with the fifth regulating valve, and the temperature index is 60-75°C.

[0012] The beneficial effects of the utility model are as follows: the utility model performs purification treatment by setting up multiple purification units, each purification unit is used in conjunction with a distillation tower and a cooler, a reboiler and a reflux tank arranged thereon, the distillation tower heats the steam heated by the reboiler at the bottom of the tower in reverse contact with the condensate of the first cooler at the top of the tower in the tower, utilizes the difference in boiling point and volatility of the by-products at the end of the distillation, performs mass transfer and heat transfer on the materials, and separates the components by controlling the pressure and reflux amount, thereby purifying the dichloroethane product after the distillation of vinyl chloride, so that the purity index of dichloroethane meets the requirements. The requirements are met, and finally 99% pure ethylene dichloride is produced. It is transported to downstream pesticide and pharmaceutical intermediate production equipment as raw materials by tank trucks over short distances. This solves the problem that the low purity of ethylene dichloride removed by traditional distillation systems causes waste of production resources. Long-distance transportation of low-purity ethylene dichloride poses a major safety hazard and is very likely to cause casualties and property damage. At the same time, the utility model also achieves efficient recovery and recycling, improves resource utilization, reduces raw material costs, and enhances the market competitiveness of products, thereby bringing better economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural diagram of the present utility model.

[0014] In the figure: 1-dichloroethane storage tank; 2-distillation tower; 3-first cooler; 4-reflux tank; 5-reboiler; 6-vinyl chloride gas holder; 7-finished product tank; 8-second cooler; 9-third cooler; 10-residue tank; 101-jacket; 11-dichloroethane loading crane pipe; 12-residue loading crane pipe; 13-pressure gauge; 14-thermometer; 15-first regulating valve; 16-second regulating valve; 17-third regulating valve; 18-fourth regulating valve; 19-fifth regulating valve; 20-sixth regulating valve; 21-seventh regulating valve; 22-eighth regulating valve; 23-recovery pipeline; 24-feed pump; 25-reflux pump; 26-loading pump; 27-purification unit. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0016] like Figure 1As shown, a purification and distillation system for by-products of vinyl chloride production by the calcium carbide process includes a dichloroethane storage tank 1 and at least two purification units 27. The purification units 27 are connected in series in sequence. Each purification unit 27 includes a distillation tower 2. A first cooler 3 is provided at the top of the distillation tower 2. The first cooler 3 is connected to a reflux tank 4. The reflux tank 4 is connected to the distillation tower 2. A reboiler 5 is provided at the bottom of the distillation tower 2. The first cooler 3 of each purification unit 27 is commonly connected to a vinyl chloride gas holder 6; the dichloroethane storage tank 1 is connected to the first purification unit 27, the reboiler 5 of the previous purification unit 27 is connected to the distillation tower 2 of the next purification unit 27, the reflux tank 4 of the last purification unit 27 is connected to a finished product tank 7, and the reboiler 5 of the last purification unit 27 is connected to a residue tank 10.

[0017] A jacket 101 is provided in the residue tank 10, and the jacket 101 is connected to a steam pipe. The residue tank 10 is connected to the distillation tower 2 of the last purification unit 27 through a recovery pipe 23; the outlet of the finished product tank 7 is connected to a second cooler 8, and the second cooler 8 is connected to a dichloroethane loading crane pipe 11; a third cooler 9 is connected between the residue tank 10 and the reboiler 5 of the last purification unit 27, and the outlet of the residue tank 10 is connected to a residue loading crane pipe 12; thermometers 14 are respectively provided at the top and bottom of the distillation tower 2, the inlet pipe of the reflux tank 4, the outlets of the second cooler 8 and the third cooler 9, and the residue tank 10.

[0018] The first cooler 3, the second cooler 8 and the third cooler 9 are respectively provided with heat exchange pipes. The heat exchange pipe on the first cooler 3 is provided with a first regulating valve 15, the heat exchange pipe on the second cooler 8 is provided with a second regulating valve 16, and the heat exchange pipe on the third cooler 9 is provided with a third regulating valve 17; the reboiler 5 is provided with a steam pipe, and the steam pipe is provided with a fourth regulating valve 18; the steam pipe connected to the jacket 101 is provided with a fifth regulating valve 19.

[0019] The thermometer 14 on the inlet pipe of the reflux tank 4 is interlocked with the first regulating valve 15; the thermometer 14 at the bottom of the distillation tower 2 is interlocked with the fourth regulating valve 18; the thermometer 14 on the outlet of the second cooler 8 is interlocked with the second regulating valve 16, and the temperature index is ≤30°C; the thermometer 14 on the outlet of the third cooler 9 is interlocked with the third regulating valve 17; the thermometer 14 on the residue tank 10 is interlocked with the fifth regulating valve 19, and the temperature index is 60-75°C.

[0020] Example 1

[0021] Taking the setting of two purification units 27 as an example, the distillation tower 2 in the device used in the present invention is a vertically oriented sieve plate tower, which utilizes the principle that substances of different components have different vapor partial pressures, and uses the reverse contact heat exchange of the bottom heating steam and the top condensate in the tower to achieve separation, which has the characteristic of high efficiency. Therefore, in this embodiment, two distillation towers 2 are set to meet production needs. Pressure gauges 13 are also provided at the top and bottom of the distillation tower 2 for monitoring during operation to ensure normal operation.

[0022] The front end of the system is equipped with a stainless steel storage tank for the dichloroethane storage tank 1. A feed pipe is set on the top of the dichloroethane storage tank 1 to send the dichloroethane after distillation to the dichloroethane storage tank 1 for temporary storage. An outlet pipe is set at the bottom of the dichloroethane storage tank 1 to connect the feed pump 24. The dichloroethane is pumped to the previous purification unit 27 for purification. The top of the distillation tower 2 of the purification unit 27 is connected to the first cooler 3 through a pipe. The shell side of the first cooler 3 is heat-exchanged by a heat exchange pipe with 5°C water. The heat exchange pipe is provided with a first regulating valve 1. 5 for regulating heat exchange. The bottom of the first cooler 3 is connected to the reflux tank 4 through a pipeline. A thermometer 14 is provided on the inlet pipeline of the reflux tank 4 and is interlocked with the first regulating valve 15. A pipeline is provided at the bottom of the reflux tank 4 and is connected to a reflux pump 25 to send the vinyl chloride in the reflux tank 4 to the distillation tower 2 for further heat exchange. The reboiler 5 provided at the bottom of the distillation tower 2 is fed with steam through the shell side of the steam pipeline. A fourth regulating valve 18 is provided on the steam pipeline. The fourth regulating valve 18 is interlocked with the thermometer 14 at the bottom of the distillation tower 2 for temperature regulation.

[0023] The latter purification unit 27 is provided with a distillation tower 2, a first cooler 3, a reflux tank 4, a reboiler 5, a first regulating valve 15, a fourth regulating valve 18 and a reflux pump 25 with the same connection relationship and working principle as the former purification unit 27. Similarly, a thermometer 14 is provided on the inlet pipe of the reflux tank 4 of the purification unit 27. The distillation tower 2 of the purification unit 27 is interlocked with the first regulating valve 15 provided on the first cooler 3. The thermometer 14 at the bottom of the distillation tower 2 is interlocked with the fourth regulating valve 18 on the reboiler 5 connected thereto for temperature adjustment. The uncondensed gas phase in the first cooler 3 on the distillation tower 2 is transported to the vinyl chloride gas holder 6 through a pipeline. On the pipelines connecting the first coolers 3 of the two purification units 27 to the vinyl chloride gas holder 6, seventh regulating valves 21 are respectively provided for control and adjustment. The system is in a fully open state during operation.

[0024] A three-way connecting pipe is provided at the bottom of the reboiler 5 of the front purification unit 27, which is connected to the distillation tower 2 of the rear purification unit 27. A sixth regulating valve 20 is provided on the connecting pipe and is interlocked with the bottom liquid level gauge of the front distillation tower 2 to control the bottom liquid level index to be 60%-80%. By opening the sixth regulating valve 20, the dichloroethane purified in the front distillation tower 2 is continuously transported to the rear distillation tower 2 for further processing. The designed bottom temperature index range of the distillation tower 2 of the first purification unit 27 during operation is 80-90°C, the bottom pressure index is 0.12-0.2MPa, the top temperature index is ≤60°C, and the top pressure index is 0.1-0.18MPa; the designed bottom temperature index range of the distillation tower 2 of the second purification unit 27 during operation is 62-75°C, the bottom pressure index is 0-0.04MPa, the top temperature index is 62-75°C, and the top pressure index is 0-0.05MPa. The interlocking settings of various valves and thermometers can improve safety, reduce energy waste, enhance automatic control and improve production efficiency.

[0025] The reboiler 5 is a shell-and-tube heat exchanger, the tube side of which is connected to the bottom of the distillation tower 2 via a pipeline. The feed pump 24 delivers ethylene dichloride from the top of the distillation tower 2 of the previous purification unit 27 into the tower. It exchanges heat with the rising airflow generated by the heating of the reboiler 5 in the reverse direction, achieving heat exchange separation. The first cooler 3 is a shell-and-tube heat exchanger, and the shell side is controlled by a 5°C water heat exchange pipeline through the first regulating valve 15 to control the condensation temperature. The steam flowing out of the top of the tower is cooled by the first cooler 3, and the uncondensed gas is sent to the vinyl chloride gas holder 6 for recycling. The condensed liquid flows to the reflux tank 4 through the bottom pipeline of the first cooler 3. The reflux tank 4 is connected to the reflux pump 25 via the bottom pipeline, and the liquid phase in the reflux tank 4 is sent to the previous distillation tower 2 for further purification. The function of the reflux device of the previous distillation tower 2 is to reflux part of the condensate, adjust the liquid phase composition in the tower, maintain the concentration gradient of the distillation section in the tower, and improve the separation efficiency.

[0026] The inlet pipe of the reflux tank 4 of the rear purification unit 27 is equipped with a three-way pipe to transport part of the liquid dichloroethane to the finished product tank 7 for storage. The eighth regulating valve 22 is installed on the delivery pipe for regulation and control. The outlet of the finished product tank 7 is connected to the loading pump 26 through the pipe of the loading pump 26. The outlet pipe of the loading pump 26 is connected to the second cooler 8 to cool the dichloroethane in the finished product tank 7 before loading, ensuring the safety of low-temperature loading. The shell side of the second cooler 8 is equipped with a 5°C water pipe, and a second regulating valve 16 is installed on the pipe. A thermometer 14 is installed on the material outlet pipe of the second cooler 8 and is interlocked with the second regulating valve 16. The temperature index is required to be ≤30°C. The cooled dichloroethane can be loaded and transported through the dichloroethane loading crane 11. The main benefits of using the loading crane include improved safety, reduced environmental pollution, and improved loading and unloading efficiency and flexibility.

[0027] A three-way pipe is installed at the bottom of the reboiler 5 of the second purification unit 27 to transport the bottom residue of the second distillation tower 2 to the residue tank 10 via the third cooler 9. A sixth regulating valve 20 is installed on this pipe, interlocked with the liquid level at the bottom of the second distillation tower 2, to control the liquid level between 60% and 80%. The shell side of the third cooler 9 is cooled by a 5°C water heat exchange pipe. The 5°C water pipe is equipped with a third regulating valve 17. A thermometer 14 is installed on the outlet pipe of the third cooler 9, interlocked with the third regulating valve 17, and the cooled residue is transported to the residue tank 10 for storage.

[0028] Before the residue tank 10 is loaded onto a truck, the dichloroethane inside needs to be recovered again. Therefore, a jacket 101 is provided in the residue tank 10, and steam is introduced to heat the residue tank 10 before the residue is loaded onto a truck to recover the dichloroethane. A fifth regulating valve 19 is provided on its steam pipe to be interlocked with a thermometer 14 at the top of the residue tank 10. The recovery temperature index is 60-75°C and the loading temperature is ≤40°C. A recovery pipe 23 is provided at the top of the residue tank 10 to continue to send the recovered dichloroethane to the subsequent distillation tower 2 for processing. A loading pump 26 is provided at the bottom of the residue tank 10, and the residue is loaded and transported using a residue loading crane 12.

[0029] The pumps used in this utility model are all shielded pumps, and the design requirements are in accordance with the explosion-proof grade of vinyl chloride; the control valve accuracy must meet the requirements of ANSI / FCI70-2, and the adjustment accuracy is ±1%; this utility model has a device for recovering flammable and explosive media, and the design and installation must comply with the chemical fire and explosion protection requirements, and the system must be replaced with nitrogen before operation.

Claims

1. A purification and distillation system for by-products of vinyl chloride production by the calcium carbide process, characterized in that: The invention comprises a dichloroethane storage tank (1) and at least two purification units (27), wherein the purification units (27) are sequentially connected in series, and each purification unit (27) comprises a distillation tower (2), a first cooler (3) is provided at the top of the distillation tower (2), the first cooler (3) is connected to a reflux tank (4), the reflux tank (4) is connected to the distillation tower (2), a reboiler (5) is provided at the bottom of the distillation tower (2), and the first cooler (3) of each purification unit (27) is commonly connected to a vinyl chloride gas holder (6); the dichloroethane storage tank (1) is connected to the first purification unit (27), the reboiler (5) of the first purification unit (27) is connected to the distillation tower (2) of the next purification unit (27), the reflux tank (4) of the last purification unit (27) is connected to a finished product tank (7), and the reboiler (5) of the last purification unit (27) is connected to a residue tank (10).

2. The purification and distillation system for by-products of vinyl chloride production by the calcium carbide process according to claim 1, characterized in that: The residue tank (10) is provided with a jacket (101), the jacket (101) is connected to a steam pipeline, and the residue tank (10) is connected to the distillation tower (2) of the last purification unit (27) through a recovery pipeline (23).

3. The purification and distillation system for by-products of vinyl chloride production by the calcium carbide process according to claim 2, characterized in that: The outlet of the finished product tank (7) is connected to a second cooler (8), and the second cooler (8) is connected to a dichloroethane loading crane (11); a third cooler (9) is connected between the residue tank (10) and the reboiler (5) of the last purification unit (27), and the outlet of the residue tank (10) is connected to a residue loading crane (12).

4. The purification and distillation system for by-products of vinyl chloride production by the calcium carbide process according to claim 3, characterized in that: Thermometers (14) are respectively provided on the top and bottom of the distillation tower (2), the inlet pipe of the reflux tank (4), the outlets of the second cooler (8) and the third cooler (9), and the residue tank (10).

5. The purification and distillation system for by-products of vinyl chloride production by the calcium carbide process according to claim 4, characterized in that: The first cooler (3), the second cooler (8) and the third cooler (9) are respectively provided with heat exchange pipes, the heat exchange pipe on the first cooler (3) is provided with a first regulating valve (15), the heat exchange pipe on the second cooler (8) is provided with a second regulating valve (16), and the heat exchange pipe on the third cooler (9) is provided with a third regulating valve (17); the reboiler (5) is provided with a steam pipe, and the steam pipe is provided with a fourth regulating valve (18); the steam pipe connected to the jacket (101) is provided with a fifth regulating valve (19).

6. The purification and distillation system for by-products of vinyl chloride production by the calcium carbide process according to claim 5, characterized in that: The thermometer (14) on the inlet pipe of the reflux tank (4) is interlocked with the first regulating valve (15); the thermometer (14) at the bottom of the distillation tower (2) is interlocked with the fourth regulating valve (18).

7. The purification and distillation system for by-products of vinyl chloride production by the calcium carbide process according to claim 6, characterized in that: The thermometer (14) on the outlet of the second cooler (8) is interlocked with the second regulating valve (16), and the temperature index is ≤30°C; the thermometer (14) on the outlet of the third cooler (9) is interlocked with the third regulating valve (17); the thermometer (14) on the residue tank (10) is interlocked with the fifth regulating valve (19), and the temperature index is 60-75°C.

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