Liquid-phase ethylene continuous gasification conveying system in process of producing vinyl chloride from ethylene

Abstract

The utility model relates to a liquid-phase ethylene continuous gasification conveying system in a process of producing vinyl chloride from ethylene. Comprising an ethylene return tank, an ethylene precooler and an ethylene evaporator, an outlet of the ethylene return tank is connected with an inlet of the ethylene precooler and an inlet of the ethylene evaporator respectively, an outlet of the ethylene precooler and an outlet of the ethylene evaporator are connected with an inlet of a crude ethylene cooler, and an outlet of the crude ethylene cooler is connected with an inlet of an ethylene heater. An outlet of the ethylene heater is connected with a heat exchange medium pipeline inlet of the ethylene precooler, a heat exchange medium pipeline outlet of the ethylene precooler is connected with the ethylene downstream chlorination device, a heat exchange medium pipeline of the ethylene evaporator is connected with the steam heat exchange system, and a heat exchange medium pipeline of the ethylene heater is connected with the hot propylene circulating system. When the ethylene pre-cooler breaks down and cannot normally supply gas-phase ethylene, long-time, safe and stable full-load operation of a downstream VCM process is ensured through the ethylene evaporator, and cost rise and product quality reduction caused by frequent starting and stopping are effectively avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of producing polyvinyl chloride by ethylene method, and specifically relates to a liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride by ethylene. Background Art

[0002] Based on the current energy situation of "rich in coal, poor in oil, and little gas" in my country, in order to make full use of Xinjiang's abundant coal resources, coal-to-ethylene and then ethylene as raw material to prepare vinyl chloride is the development trend of the PVC industry. In the process of producing vinyl chloride from ethylene, it is very important to stably transport gaseous ethylene and ensure that the upstream and downstream processes are closely connected. In the existing process of producing vinyl chloride from ethylene, the liquid ethylene sent out from the ethylene process is recovered by the ethylene precooler, and the low-temperature gaseous ethylene after gasification is further recovered by the crude ethylene cooler, and then sent to the downstream PVC process through the ethylene heater. Usually, the ethylene heater uses a propylene refrigeration system to provide energy exchange. When the propylene refrigeration system fails or stops, the ethylene precooler will lose the product ethylene gasification function, which will affect the production and supply of product ethylene into the downstream process. Since the downstream ethylene chlorination process of producing vinyl chloride involves the production process of key controlled hazardous chemicals, the process control requirements are strict and the safety protection logic is complex, so it is very necessary to study and design how to ensure the stable transportation of ethylene during the gas-liquid phase conversion process. Summary of the invention

[0003] The purpose of the utility model is to solve the above technical problems and provide a liquid ethylene continuous gasification and transportation system in the ethylene production of vinyl chloride process, which can ensure the long-term safe and stable operation of the downstream process and effectively reduce the cost increase and quality decline caused by frequent start-up and shutdown.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] A liquid phase ethylene continuous gasification and transportation system in an ethylene production vinyl chloride process comprises an ethylene reflux tank, an ethylene precooler, an ethylene evaporator, a crude ethylene cooler and an ethylene heater, wherein the outlet of the ethylene reflux tank is respectively connected to the inlet of the ethylene precooler and the inlet of the ethylene evaporator, the outlet of the ethylene precooler and the outlet of the ethylene evaporator are connected to the inlet of the crude ethylene cooler, the outlet of the crude ethylene cooler is connected to the inlet of the ethylene heater, the outlet of the ethylene heater is connected to the inlet of a heat exchange medium pipeline of the ethylene precooler, the outlet of the heat exchange medium pipeline of the ethylene precooler is connected to an ethylene downstream chlorination device, the heat exchange medium pipeline of the ethylene evaporator is connected to a steam heat exchange system, and the heat exchange medium pipeline of the ethylene heater is connected to a hot propylene circulation system.

[0006] In the above-mentioned liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride from ethylene, a flow regulating valve is arranged on the pipeline between the outlet of the ethylene reflux tank and the inlet of the ethylene precooler and the inlet of the ethylene evaporator.

[0007] In the above-mentioned liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride from ethylene, the steam heat exchange system connected to the ethylene evaporator is a medium-pressure steam system.

[0008] The above-mentioned liquid ethylene continuous gasification and transportation system in the ethylene production of vinyl chloride process, wherein the hot propylene circulation system includes a propylene compressor, the outlet of the propylene compressor is connected to the inlet of the heat exchange medium pipeline of the ethylene heater, and the outlet of the heat exchange medium pipeline of the ethylene heater is connected to the propylene collection tank.

[0009] In the above-mentioned liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride from ethylene, the propylene compressor comprises a primary propylene compressor and a secondary propylene compressor.

[0010] In the above-mentioned liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride from ethylene, flow control valves are arranged between the outlet of the ethylene precooler and the outlet of the ethylene evaporator and the inlet of the crude ethylene cooler.

[0011] In the above-mentioned liquid phase ethylene continuous gasification and transportation system in the ethylene production vinyl chloride process, the inlet of the crude ethylene cooler heat exchange tube is connected to the water-containing ethylene pipeline, and the outlet of the crude ethylene cooler heat exchange tube is connected to the ethylene dryer.

[0012] In the above-mentioned liquid phase ethylene continuous gasification and transportation system in the ethylene production of vinyl chloride process, a bypass is arranged between the inlet and outlet of the crude ethylene cooler, and a flow control valve is arranged on the bypass. Beneficial Effects

[0013] The utility model designs an ethylene evaporator that runs in parallel with the ethylene precooler on the pipeline between the ethylene reflux tank and the crude ethylene cooler. During normal operation, the ethylene evaporator with a low flow rate is often opened to ensure the effective operation of the parallel branch. When the propylene refrigeration system fails and cannot normally supply gas-phase ethylene, the flow rate of the fully opened ethylene evaporator is used to ensure the long-term, safe, stable and full-load operation of the downstream VCM process, effectively avoiding the cost increase and product quality decline caused by frequent start and stop. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of Embodiment 1 of the present utility model;

[0015] Figure 2 It is a structural schematic diagram of Embodiment 2 of the present utility model;

[0016] Shown in the figure: 1. Ethylene reflux tank, 2. Ethylene precooler, 3. Crude ethylene cooler, 4. Ethylene heater, 5. Ethylene evaporator, 6. Flow control valve, 7. Propylene compressor, 7-1. First-stage propylene compressor, 7-2. Second-stage propylene compressor, 8. Medium-pressure steam heat exchange system, 9. Propylene collecting tank, 10. Ethylene downstream chlorination unit, 11. Ethylene dryer, 12. Water-containing ethylene pipeline. DETAILED DESCRIPTION

[0017] In order to have a clearer understanding of the technical features, purposes and effects of the present utility model, the preferred embodiments of the present utility model are now described in detail with reference to the accompanying drawings. Example

[0018] Reference Figure 1 The utility model provides a liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride from ethylene, comprising an ethylene reflux tank 1, an ethylene precooler 2, an ethylene evaporator 5, a crude ethylene cooler 3, and an ethylene heater 4. The outlet of the ethylene reflux tank 1 is respectively connected to the inlet of the ethylene precooler 2 and the inlet of the ethylene evaporator 5. A flow control valve 6 is arranged on the pipeline between the outlet of the ethylene reflux tank 1 and the inlet of the ethylene precooler 2 and the inlet of the ethylene evaporator 5. A flow control valve 6 is also arranged between the outlet of the ethylene precooler 2 and the outlet of the ethylene evaporator 5 and the inlet of the crude ethylene cooler 3. The outlet of the ethylene precooler 2 and the outlet of the ethylene evaporator 5 are connected to the inlet of the crude ethylene cooler 3. A bypass is arranged between the inlet and the outlet of the crude ethylene cooler 3, and a flow control valve 6 is arranged on the bypass. The inlet of the heat exchange pipe of the crude ethylene cooler 3 is connected to the water-containing ethylene pipeline 12, and the outlet of the heat exchange pipe of the crude ethylene cooler 3 is connected to the ethylene dryer 11. The outlet of the crude ethylene cooler 3 is connected to the inlet of the ethylene heater 4, the outlet of the ethylene heater 4 is connected to the inlet of the heat exchange medium pipeline of the ethylene precooler 2, and the outlet of the heat exchange medium pipeline of the ethylene precooler 2 is connected to the ethylene downstream chlorination device 10. The heat exchange medium pipeline of the ethylene evaporator 5 is connected to the medium-pressure steam heat exchange system 8, and the heat exchange medium pipeline of the ethylene heater 4 is connected to the hot propylene circulation system, and the hot propylene gas after heat exchange is sent to the propylene collection tank 9. The hot propylene circulation system includes a propylene compressor 7, the outlet of the propylene compressor 7 is connected to the inlet of the heat exchange medium pipeline of the ethylene heater 4, and the outlet of the heat exchange medium pipeline of the ethylene heater 4 is connected to the propylene collection tank 9. Example

[0019] Reference Figure 2 The difference between this embodiment and embodiment 1 is that the propylene compressor includes a primary propylene compressor 7-1 and a secondary propylene compressor 7-2, and the primary propylene compressor 7-1 and the secondary propylene compressor 7-2 are connected in series. Propylene is introduced into the primary propylene compressor 7-1, the outlet of the secondary propylene compressor 7-2 is connected to the inlet of the heat exchange medium pipeline of the ethylene heater 4, and the outlet of the heat exchange medium pipeline of the ethylene heater 4 is connected to the propylene collection tank 9.

[0020] How it works:

[0021] When the system is operating normally, the liquid ethylene from the ethylene reflux tank 1 is sent to the crude ethylene cooler 3 in two ways, one of which is sent to the crude ethylene cooler 3 after recovering cold through the ethylene precooler 2. The ethylene precooler 2 uses the propylene refrigeration system 7 to provide heat. The ethylene precooler 2 is used to cool and liquefy the crude ethylene. The other way is sent to the crude ethylene cooler 3 after recovering cold through the ethylene evaporator 5. The flow rate of liquid ethylene sent to the ethylene evaporator 5 is equal to 5% of the total amount of the outlet of the ethylene reflux tank 1. A small amount of ethylene enters the ethylene evaporator 5 and is heated by steam to achieve the hot standby of the ethylene evaporator 5 and ensure that the product ethylene is completely gasified. The temperature of the material after the ethylene precooler 2 and the ethylene evaporator 5 recover cold is controlled at -38°C. The gaseous ethylene recovered by the ethylene precooler 2 and the ethylene evaporator 5 is sent to the crude ethylene cooler 3 to further recover cold, and is sent to the ethylene heater 4 after heat exchange; the material sent to the ethylene heater 4 is heat-exchanged with the high-temperature gas-phase hot propylene gas to control the temperature of the ethylene product at 22°C, and the gasified ethylene product is sent to the downstream of the ethylene.

[0022] When the propylene refrigeration system fails or stops, the ethylene precooler will lose its function of gasifying the product ethylene. If the downstream device requires the maintenance of ethylene supply, all the liquid ethylene can be cut into the evaporator to complete the gasification of all ethylene by steam and heat it to a qualified temperature before sending it to the downstream PVC process. When the heat exchange medium of the ethylene precooler cannot be supplied normally, close the flow control valve 6 of the inlet branch of the ethylene precooler 2, and fully open the flow control valve 6 of the inlet branch of the ethylene evaporator 5, so that all the liquid ethylene from the ethylene reflux tank 1 is sent to the ethylene evaporator 5, and the gaseous ethylene recovered by the ethylene evaporator 5 is sent to the crude ethylene cooler 3, and the material is sent to the ethylene heater 4 after heat exchange; the material sent to the ethylene heater 4 is heat exchanged with the hot propylene gas, and the gasified qualified ethylene product is sent to the downstream of the ethylene.

[0023] The utility model designs an ethylene evaporator that runs in parallel with the ethylene precooler on the pipeline between the ethylene reflux tank and the crude ethylene cooler. During normal operation, the ethylene evaporator with a low flow rate is often opened to ensure the effective operation of the parallel branch. When the ethylene precooler fails to supply gas-phase ethylene normally, the flow rate of the ethylene evaporator is fully opened to ensure the long-term, safe, stable and full-load operation of the downstream VCM process, effectively avoiding the cost increase and product quality reduction caused by frequent start and stop.

[0024] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several changes and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A liquid phase ethylene continuous gasification and transportation system in the process of producing vinyl chloride from ethylene, characterized in that: The invention comprises an ethylene reflux tank, an ethylene precooler, an ethylene evaporator, a crude ethylene cooler and an ethylene heater. The outlet of the ethylene reflux tank is respectively connected to the inlet of the ethylene precooler and the inlet of the ethylene evaporator. The outlet of the ethylene precooler and the outlet of the ethylene evaporator are connected to the inlet of the crude ethylene cooler. The outlet of the crude ethylene cooler is connected to the inlet of the ethylene heater. The outlet of the ethylene heater is connected to the inlet of the heat exchange medium pipeline of the ethylene precooler. The outlet of the heat exchange medium pipeline of the ethylene precooler is connected to the downstream chlorination device of ethylene. The heat exchange medium pipeline of the ethylene evaporator is connected to the steam heat exchange system. The heat exchange medium pipeline of the ethylene heater is connected to the hot propylene circulation system.

2. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 1, characterized in that: A flow regulating valve is arranged on the pipeline between the outlet of the ethylene reflux tank and the inlet of the ethylene precooler and the inlet of the ethylene evaporator.

3. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 1, characterized in that: The steam heat exchange system connected to the ethylene evaporator is a medium-pressure steam system.

4. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 1, characterized in that: The hot propylene circulation system comprises a propylene compressor, the outlet of the propylene compressor is connected to the inlet of the heat exchange medium pipeline of the ethylene heater, and the outlet of the heat exchange medium pipeline of the ethylene heater is connected to the propylene collection tank.

5. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 4, characterized in that: The propylene compressor includes a primary propylene compressor and a secondary propylene compressor.

6. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 1, characterized in that: A flow control valve is arranged between the outlet of the ethylene precooler, the outlet of the ethylene evaporator and the inlet of the crude ethylene cooler.

7. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 1, characterized in that: The inlet of the heat exchange pipe of the crude ethylene cooler is connected to the water-containing ethylene pipeline, and the outlet of the heat exchange pipe of the crude ethylene cooler is connected to the ethylene dryer.

8. The continuous gasification and transportation system for liquid ethylene in the process of producing vinyl chloride from ethylene according to claim 1, characterized in that: A bypass is arranged between the inlet and the outlet of the crude ethylene cooler, and a flow control valve is arranged on the bypass.

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