A closed loading method and system for ethylene dichloride

Abstract

The invention discloses a closed loading method and system for ethylene dichloride, wherein the system comprises an ethylene dichloride storage tank, an ethylene dichloride loading pump, a pump outlet switch valve, a loading crane pipe, an oxygen meter, a vent switch valve, a recovery switch valve, a high-pressure nitrogen storage tank and a nitrogen regulating valve; the method comprises the following steps: (1) equipment connection; (2) nitrogen replacement; (3) ethylene dichloride loading: opening the recovery switch valve, starting the ethylene dichloride loading pump, starting ethylene dichloride loading, when the liquid level meter shows 0%, stopping the ethylene dichloride loading pump, opening the nitrogen regulating valve, pressing the ethylene dichloride in the pipeline into the tank car, and completing the loading of ethylene dichloride. The invention realizes the closed loading of ethylene dichloride, reduces the labor intensity of employees, and reduces environmental pollution; at the same time, it reduces the waste of vinyl chloride monomer and improves the utilization rate of vinyl chloride monomer; and avoids a series of production safety accidents such as fire and explosion caused by material aggregation.

Description

Technical field:

[0001] The invention relates to a method and system for loading ethylene dichloride, and in particular to a closed method and system for loading ethylene dichloride. Background technology:

[0002] The vinyl chloride process includes mixed dehydration, synthetic conversion, water washing, alkali washing, compression and distillation. Specifically, the crude vinyl chloride formed after mixed dehydration and synthetic conversion is demercured and then enters the three-in-one water washing combination tower, and the residual trace HCL is removed by the alkali washing tower, and then enters the VC gas cabinet or removes part of the entrained liquid through the pre-cooler, and then pressurized by the compressor, and the entrained water and oil are removed by the post-cooler, and sent to distillation. After being processed by the distillation unit in the distillation system, the high-boiling substances discharged from the bottom of the high tower are processed in the "three-distillation tower" and discharged to the dichloroethane storage tank for sale.

[0003] The synthesis of vinyl chloride by the calcium carbide process is carried out in the converter. To ensure the conversion effect of acetylene gas, the excess of hydrogen chloride needs to be controlled at 3-5%, because the excess of hydrogen chloride leads to the production of high-boiling products such as ethylene dichloride. After being distilled by the distillation unit, the ethylene dichloride discharged from the bottom of the high-boiling tower is usually sold out. At present, the method of loading ethylene dichloride for sale is to connect the ethylene dichloride storage tank with a crane pipe, and the outlet end of the crane pipe is directly inserted into the manhole of the tank truck. After nitrogen is injected into the ethylene dichloride storage tank for pressurization, the valve is opened, and ethylene dichloride flows into the tank truck under pressure. The current method of loading ethylene dichloride for sale has the following problems: 1. All employees on site operate manually, which wastes manpower; 2. The crane outlet and the tank truck manhole are openly connected, and a large amount of vinyl chloride monomer and some ethylene dichloride will enter the environment through the gap between the crane outlet and the tank truck manhole, polluting the environment; 3. There is a risk of people inhaling a large amount of vinyl chloride or ethylene dichloride and being poisoned and suffocated, and vinyl chloride monomer is wasted; 4. During the loading process, due to the volatilization of ethylene dichloride and vinyl chloride monomer, materials will accumulate, resulting in a series of production safety accidents such as fire and explosion, posing serious safety hazards. Summary of the invention:

[0004] In order to overcome the above technical problems, the first object of the present invention is to provide a closed loading system for ethylene dichloride.

[0005] The second object of the present invention is to provide a closed loading method for ethylene dichloride.

[0006] The first object of the present invention is implemented by the following technical scheme: a closed loading system for dichloroethane, which includes a dichloroethane storage tank, a dichloroethane loading pump, a pump outlet switch valve, a loading crane pipe, an oxygen content meter, a venting switch valve, a recovery switch valve, a high-pressure nitrogen storage tank and a nitrogen regulating valve; the outlet of the dichloroethane storage tank is connected to the inlet of the dichloroethane loading pump through a pipeline, the outlet of the dichloroethane loading pump is connected to the inlet of the pump outlet switch valve through a pipeline, the outlet of the pump outlet switch valve is connected to the inlet of the loading crane pipe through a pipeline, a quick connector is installed at the outlet of the loading crane pipe, the quick connector at the outlet of the loading crane pipe is connected to the quick connector at the inlet of the tank truck, a quick connector is installed at the recovery inlet of the loading crane pipe, and a quick connector is installed at the recovery inlet of the loading crane pipe. The connector is connected to the quick connector of the tank truck recovery port; the loading crane pipe recovery outlet is connected to the oxygen meter inlet through a pipeline, the oxygen meter outlet is respectively connected to the recovery switch valve inlet and the venting switch valve inlet through pipelines, and the recovery switch valve outlet is connected to the gas cabinet; a large amount of vinyl chloride monomer and part of ethylene dichloride volatilized during the loading process are discharged from the tank truck recovery port, and discharged into the gas cabinet for recycling through the oxygen meter and the recovery switch valve, so as to avoid the vinyl chloride monomer and part of ethylene dichloride volatilizing into the air, which is safer and more environmentally friendly, and can effectively utilize the vinyl chloride monomer; the high-pressure nitrogen storage tank outlet is connected to the nitrogen regulating valve inlet through a pipeline, and the nitrogen regulating valve outlet is connected to the pipeline connecting the ethylene dichloride loading pump outlet and the pump outlet switch valve inlet.

[0007] Furthermore, the closed dichloroethane loading system also includes a remote controller and a liquid level meter. The dichloroethane storage tank is provided with a liquid level meter. The signal output end of the liquid level meter is connected to the signal input end of the remote controller, and the signal output end of the remote controller is connected to the signal input end of the dichloroethane loading pump; the signal output end of the remote controller is respectively connected to the signal input end of the pump outlet switch valve, the signal input end of the vent switch valve, the signal input end of the recovery switch valve and the signal input end of the nitrogen regulating valve; the signal output end of the oxygen meter is connected to the signal input end of the remote controller.

[0008] Furthermore, the enclosed loading system for ethylene dichloride further includes an alarm, and the signal output end of the remote controller is connected to the signal input end of the alarm.

[0009] Furthermore, a Y-type filter is provided between the dichloroethane storage tank and the dichloroethane loading pump, the outlet of the dichloroethane storage tank is connected to the inlet of the Y-type filter through a pipeline, and the outlet of the Y-type filter is connected to the inlet of the dichloroethane loading pump through a pipeline.

[0010] Furthermore, a pressure gauge is provided at the outlet of the dichloroethane loading pump.

[0011] Furthermore, a flow meter is provided on the pipeline connecting the outlet of the dichloroethane loading pump and the inlet of the pump outlet switch valve.

[0012] Furthermore, the closed loading system for ethylene dichloride also includes a reflux pipe, one end of which is connected to the ethylene dichloride storage tank, and the other end of which is connected to a pipe connecting the outlet of the ethylene dichloride loading pump and the inlet of the pump outlet switch valve. The initial pressure of the ethylene dichloride loading pump is relatively large, and adding a reflux pipe can buffer the pressure in the pipe and ensure that the transportation of ethylene dichloride is more stable. At the same time, after the loading is completed, the residual ethylene dichloride and vinyl chloride in the pipe volatilize, which will cause the gas pressure in the pipe to increase, and adding a reflux pipe can buffer the pressure in the pipe.

[0013] The second object of the present invention is implemented by the following technical solution: a closed loading method of ethylene dichloride in a closed loading system of ethylene dichloride, comprising the following steps:

[0014] (1) Equipment connection: Connect the loading crane pipe outlet quick connector to the tank truck inlet quick connector, and connect the loading crane pipe recovery inlet quick connector to the tank truck recovery port quick connector;

[0015] (2) Nitrogen replacement: After the equipment is connected, open the pump outlet switch valve and the vent switch valve, open the nitrogen regulating valve to replace the air in the pipeline and tank truck, and observe the oxygen content in the pipeline and tank truck through the oxygen meter; when the oxygen volume percentage of the exhaust gas detected by the oxygen meter is less than 0.2%, close the nitrogen regulating valve and the vent switch valve to complete the nitrogen replacement;

[0016] (3) Ethylene dichloride loading: Open the recovery switch valve, start the ethylene dichloride loading pump, and start loading ethylene dichloride. When the liquid level meter shows 0%, stop the ethylene dichloride loading pump, open the nitrogen regulating valve, press the ethylene dichloride in the pipeline into the tank truck, close the nitrogen regulating valve, close the pump outlet switch valve and close the recovery switch valve to complete the loading of ethylene dichloride.

[0017] Furthermore, the liquid level meter transmits the detected liquid level signal to the remote controller. When the detected liquid level exceeds >50%, the remote controller controls the alarm to sound an alarm, prompting the staff to contact the manufacturer to sell ethylene dichloride.

[0018] Further, after the equipment is connected, the on-site staff is contacted to operate the remote controller to send an opening signal to the pump outlet switch valve, the vent switch valve and the nitrogen regulating valve, and the pump outlet switch valve, the vent switch valve and the nitrogen regulating valve are opened; the oxygen meter transmits the detected oxygen volume percentage data to the remote controller, and the oxygen volume percentage setting value set by the remote controller is 0.2%. When the oxygen volume percentage detected by the oxygen meter is less than the oxygen volume percentage setting value of 0.2%, the remote controller sends an opening signal to the nitrogen regulating valve and the vent valve. The switch valve sends a closing signal, and the nitrogen regulating valve and the venting switch valve are closed; at the same time, an opening signal is sent to the recovery switch valve and the dichloroethane loading pump, the recovery switch valve is opened, and the dichloroethane loading pump is started; the liquid level meter transmits the detected liquid level signal to the remote controller. When the liquid level detected by the liquid level meter is 0%, the remote controller controls the dichloroethane loading pump to stop, and controls the nitrogen regulating valve to open. After a delay period, the remote controller controls the nitrogen regulating valve, the pump outlet switch valve and the recovery switch valve to close. The delay time is determined according to the on-site situation and is generally 2-3 minutes.

[0019] Advantages of the present invention:

[0020] 1. The closed loading of ethylene dichloride is realized, and the on-site operation is fully automated, reducing the labor intensity of employees;

[0021] 2. The tank truck and the crane pipe are connected by quick connectors to recover the large amount of vinyl chloride monomer and ethylene dichloride generated during loading to the gas cabinet, thus reducing environmental pollution;

[0022] 3. Eliminate the risk of poisoning and suffocation caused by inhaling large amounts of vinyl chloride or ethylene dichloride, while reducing the waste of vinyl chloride monomer and improving the utilization rate of vinyl chloride monomer;

[0023] 4. During the loading process, recover the volatile ethylene dichloride and vinyl chloride monomer to avoid a series of production safety accidents such as fire and explosion caused by material accumulation. Description of the drawings:

[0024] Figure 1 This is a schematic diagram of a closed loading system for ethylene dichloride.

[0025] Figure 2 This is a control schematic diagram of a closed loading system for ethylene dichloride.

[0026] Dichloroethane storage tank 1, Y-type filter 2, dichloroethane loading pump 3, pump outlet switch valve 4, loading crane pipe 5, oxygen content meter 6, venting switch valve 7, recovery switch valve 8, high-pressure nitrogen storage tank 9, nitrogen regulating valve 10, remote controller 11, alarm 12, liquid level meter 13, pressure gauge 14, flow meter 15, reflux pipe 16. Specific implementation method:

[0027] The present invention will be further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Those skilled in the art can refer to the contents of this article, and appropriate improvements in process parameters are also considered within the scope of this patent.

[0028] Embodiment 1: A closed loading system for ethylene dichloride, comprising an ethylene dichloride storage tank 1, a Y-type filter 2, an ethylene dichloride loading pump 3, a pump outlet switch valve 4, a loading crane pipe 5, an oxygen content meter 6, a venting switch valve 7, a recovery switch valve 8, a high-pressure nitrogen storage tank 9, a nitrogen regulating valve 10, a remote controller 11, an alarm 12 and a liquid level meter 13; the outlet of the ethylene dichloride storage tank 1 is connected to the inlet of the Y-type filter 2 through a pipeline, the outlet of the Y-type filter 2 is connected to the inlet of the ethylene dichloride loading pump 3 through a pipeline, the outlet of the ethylene dichloride loading pump 3 is connected to the inlet of the pump outlet switch valve 4 through a pipeline, and a pressure gauge 14 is provided at the outlet of the ethylene dichloride loading pump 3; a flow meter 15 is provided on the pipeline connecting the outlet of the ethylene dichloride loading pump 3 and the inlet of the pump outlet switch valve 4. The outlet of the pump outlet switch valve 4 is connected to the inlet of the loading crane pipe 5 through a pipeline, a quick connector is installed at the outlet of the loading crane pipe 5, the quick connector at the outlet of the loading crane pipe 5 is connected to the quick connector at the inlet of the tank truck, a quick connector is installed at the recovery inlet of the loading crane pipe 5, and the quick connector at the recovery inlet of the loading crane pipe 5 is connected to the quick connector at the recovery port of the tank truck; the recovery outlet of the loading crane pipe 5 is connected to the inlet of the oxygen meter 6 through a pipeline, the outlet of the oxygen meter 6 is respectively connected to the inlet of the recovery switch valve 8 and the inlet of the venting switch valve 7 through pipelines, and the outlet of the recovery switch valve 8 is connected to the gas cabinet; a large amount of vinyl chloride monomer and part of dichloroethane volatilized during the loading process are discharged from the recovery port of the tank truck, and discharged into the gas cabinet for recycling through the oxygen meter 6 and the recovery switch valve 8, so as to avoid the volatilization of vinyl chloride monomer and part of dichloroethane into the air, which is safer and more environmentally friendly, and can effectively utilize vinyl chloride monomer; the outlet of the high-pressure nitrogen storage tank 9 is connected to the inlet of the nitrogen regulating valve 10 through a pipeline, and the outlet of the nitrogen regulating valve 10 is connected to the pipeline connecting the outlet of the dichloroethane loading pump 3 and the inlet of the pump outlet switch valve 4.

[0029] The dichloroethane storage tank 1 is provided with a liquid level meter 13, the signal output end of the liquid level meter 13 is connected to the signal input end of the remote controller 11, and the signal output end of the remote controller 11 is connected to the signal input end of the dichloroethane loading pump 3; the signal output end of the remote controller 11 is respectively connected to the signal input end of the pump outlet switch valve 4, the signal input end of the vent switch valve 7, the signal input end of the recovery switch valve 8 and the signal input end of the nitrogen regulating valve 10; the signal output end of the oxygen meter 6 is connected to the signal input end of the remote controller 11; the signal output end of the remote controller 11 is connected to the signal input end of the alarm 12.

[0030] The closed loading system of ethylene dichloride in this embodiment also includes a reflux pipe 16, one end of which is connected to the ethylene dichloride storage tank 1, and the other end of which is connected to the pipe connecting the outlet of the ethylene dichloride loading pump 3 and the inlet of the pump outlet switch valve 4. The initial pressure of the ethylene dichloride loading pump 3 is relatively large, and the addition of the reflux pipe 16 can buffer the pressure in the pipe, ensuring that the transportation of ethylene dichloride is more stable. At the same time, after the loading is completed, the residual ethylene dichloride and vinyl chloride in the pipe volatilize, which will cause the gas pressure in the pipe to increase, and the addition of the reflux pipe 16 can buffer the pressure in the pipe.

[0031] Example 2: The closed loading method of ethylene dichloride is completed by using the system of Example 1, which includes the following steps: First, the liquid level meter 13 transmits the detected liquid level signal to the remote controller 11. When it is detected that the liquid level of the ethylene dichloride storage tank 1 exceeds >50%, the remote controller 11 controls the alarm 12 to sound an alarm, prompting the staff to contact the manufacturer to sell ethylene dichloride. The specific loading steps are:

[0032] (1) Equipment connection: Connect the loading crane pipe 5 outlet quick connector to the tank truck inlet quick connector, and connect the loading crane pipe 5 recovery inlet quick connector to the tank truck recovery port quick connector;

[0033] (2) Nitrogen replacement: After the equipment is connected, contact the on-site staff to operate the remote controller 11, send an opening signal to the pump outlet switch valve 4, the vent switch valve 7 and the nitrogen regulating valve 10, and the pump outlet switch valve 4, the vent switch valve 7 and the nitrogen regulating valve 10 are opened, and the high-pressure nitrogen replaces the reflux pipeline 16; the pipeline connecting the outlet of the dichloroethane loading pump 3 and the inlet of the pump outlet switch valve 4; the pipeline connecting the outlet of the pump outlet switch valve 4 and the inlet of the loading crane pipe 5; the loading crane pipe 5; the pipeline connecting the recovery outlet of the loading crane pipe 5 and the inlet of the oxygen meter 6; the pipeline connecting the outlet of the oxygen meter 6 and the inlet of the recovery switch valve 8; and the air in the tank truck, the air is emptied through the exhaust pipe. During the nitrogen replacement process, the volume percentage of oxygen in the pipeline and the tank truck gradually decreases; the oxygen meter 6 transmits the detected oxygen volume percentage data to the remote controller 11, and the remote controller 11 sets the oxygen volume percentage setting value to 0.2%. When the oxygen volume percentage detected by the oxygen meter 6 is less than the oxygen volume percentage setting value of 0.2%, the remote controller 11 sends a closing signal to the nitrogen regulating valve 10 and the vent switch valve 7, and the nitrogen regulating valve 10 and the vent switch valve 7 are closed, completing the nitrogen replacement;

[0034] (3) Ethylene dichloride loading: When the volume percentage of oxygen detected by the oxygen meter 6 is less than the set value of 0.2% of the volume percentage of oxygen, the remote controller 11 simultaneously sends an opening signal to the recovery switch valve 8 and the ethylene dichloride loading pump 3, the recovery switch valve 8 opens, the ethylene dichloride loading pump 3 starts, and the ethylene dichloride loading begins. During the loading process, a large amount of vinyl chloride monomer and part of the ethylene dichloride are discharged from the tank truck recovery port, and discharged into the gas cabinet for recycling through the oxygen meter 6 and the recovery switch valve 8, thereby avoiding the evaporation of vinyl chloride monomer and part of the ethylene dichloride. to the air, which is safer and more environmentally friendly, and can effectively utilize vinyl chloride monomer; when the liquid level meter 13 detects that the liquid level of the dichloroethane storage tank 1 is 0%, the remote controller 11 controls the dichloroethane loading pump 3 to stop, and at the same time controls the nitrogen regulating valve 10 to open, and uses high-pressure nitrogen to press the dichloroethane in the pipeline into the tank truck; after a delay period, the remote controller 11 controls the nitrogen regulating valve 10, the pump outlet switch valve 4 and the recovery switch valve 8 to close, and the dichloroethane loading is completed. The delay time is determined according to the on-site situation, generally 2-3 minutes.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A closed loading system for ethylene dichloride, It is characterized in that The invention comprises a dichloroethane storage tank, a dichloroethane loading pump, a pump outlet switch valve, a loading crane pipe, an oxygen meter, a venting switch valve, a recovery switch valve, a high-pressure nitrogen storage tank and a nitrogen regulating valve; the outlet of the dichloroethane storage tank is connected to the inlet of the dichloroethane loading pump through a pipeline, the outlet of the dichloroethane loading pump is connected to the inlet of the pump outlet switch valve through a pipeline, the outlet of the pump outlet switch valve is connected to the inlet of the loading crane pipe through a pipeline, a quick connector is installed at the outlet of the loading crane pipe, and the quick connector at the outlet of the loading crane pipe is connected to the quick connector at the inlet of the tank truck. The loading crane pipe recovery inlet is connected by a quick connector, and the loading crane pipe recovery inlet quick connector is connected to the tank truck recovery port quick connector; the loading crane pipe recovery outlet is connected to the oxygen meter inlet through a pipeline, and the oxygen meter outlet is respectively connected to the recovery switch valve inlet and the venting switch valve inlet through pipelines, and the recovery switch valve outlet is connected to the gas cabinet; the high-pressure nitrogen storage tank outlet is connected to the nitrogen regulating valve inlet through a pipeline, and the nitrogen regulating valve outlet is connected to the pipeline connecting the dichloroethane loading pump outlet and the pump outlet switch valve inlet.

2. A closed loading system for ethylene dichloride according to claim 1, It is characterized in that It also includes a remote controller and a liquid level meter. The dichloroethane storage tank is provided with a liquid level meter. The signal output end of the liquid level meter is connected to the signal input end of the remote controller, and the signal output end of the remote controller is connected to the signal input end of the dichloroethane loading pump; the signal output end of the remote controller is respectively connected to the signal input end of the pump outlet switch valve, the signal input end of the vent switch valve, the signal input end of the recovery switch valve and the signal input end of the nitrogen regulating valve; the signal output end of the oxygen meter is connected to the signal input end of the remote controller.

3. A closed loading system for ethylene dichloride according to claim 2, It is characterized in that It also includes an alarm, and the signal output end of the remote controller is connected to the signal input end of the alarm.

4. A closed loading system for ethylene dichloride according to claim 1, It is characterized in that A Y-type filter is provided between the dichloroethane storage tank and the dichloroethane loading pump, the outlet of the dichloroethane storage tank is connected to the inlet of the Y-type filter through a pipeline, and the outlet of the Y-type filter is connected to the inlet of the dichloroethane loading pump through a pipeline.

5. A closed loading system for ethylene dichloride according to claim 1, It is characterized in that A pressure gauge is provided at the outlet of the dichloroethane loading pump.

6. A closed loading system for ethylene dichloride according to claim 1, It is characterized in that A flow meter is provided on the pipeline connecting the outlet of the dichloroethane loading pump and the inlet of the pump outlet switch valve.

7. A closed loading system for ethylene dichloride according to claim 1, It is characterized in that It also includes a reflux pipeline, one end of which is connected to the dichloroethane storage tank, and the other end of which is connected to a pipeline connecting the outlet of the dichloroethane loading pump and the inlet of the pump outlet switch valve.

8. A method for enclosed loading of ethylene dichloride using the enclosed loading system for ethylene dichloride according to any one of claims 1 to 7, It is characterized in that It includes the following steps: (1) Equipment connection: Connect the loading crane pipe outlet quick connector to the tank truck inlet quick connector, and connect the loading crane pipe recovery inlet quick connector to the tank truck recovery port quick connector; (2) Nitrogen replacement: After the equipment is connected, open the pump outlet switch valve and the vent switch valve, open the nitrogen regulating valve to replace the air in the pipeline and tank truck, and observe the oxygen content in the pipeline and tank truck through the oxygen meter; when the oxygen volume percentage of the exhaust gas detected by the oxygen meter is less than 0.2%, close the nitrogen regulating valve and the vent switch valve to complete the nitrogen replacement; (3) Ethylene dichloride loading: Open the recovery switch valve, start the ethylene dichloride loading pump, and start loading ethylene dichloride. When the liquid level gauge shows 0%, stop the ethylene dichloride loading pump, open the nitrogen regulating valve, press the ethylene dichloride in the pipeline into the tank truck, close the nitrogen regulating valve, close the pump outlet switch valve, and close the recovery switch valve to complete the loading of ethylene dichloride.

9. A closed loading method for ethylene dichloride according to claim 8, It is characterized in that The liquid level meter transmits the detected liquid level signal to the remote controller. When the detected liquid level exceeds >50%, the remote controller controls the alarm to sound, prompting the staff to contact the manufacturer to sell ethylene dichloride.

10. A closed loading method for ethylene dichloride according to claim 8, It is characterized in that After the equipment is connected, the on-site staff is contacted to operate the remote controller, and an opening signal is sent to the pump outlet switch valve, the vent switch valve and the nitrogen regulating valve, and the pump outlet switch valve, the vent switch valve and the nitrogen regulating valve are opened; the oxygen meter transmits the detected oxygen volume percentage data to the remote controller, and the oxygen volume percentage setting value set by the remote controller is 0.2%. When the oxygen volume percentage detected by the oxygen meter is less than the oxygen volume percentage setting value of 0.2%, the remote controller sends a closing signal to the nitrogen regulating valve and the vent switch valve, and the nitrogen regulating valve and the vent switch valve are closed; at the same time, an opening signal is sent to the recovery switch valve and the dichloroethane loading pump, the recovery switch valve is opened, and the dichloroethane loading pump is started; the liquid level meter transmits the detected liquid level signal to the remote controller. When the liquid level detected by the liquid level meter is 0%, the remote controller controls the dichloroethane loading pump to stop, and controls the nitrogen regulating valve to open at the same time. After a delay, the remote controller controls the nitrogen regulating valve, the pump outlet switch valve and the recovery switch valve to close.

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