Closed loading system for low flash point shale oil

Abstract

This application relates to the field of crude oil loading and transportation technology, and discloses a closed loading system suitable for low flash point shale oil, including an oil pipeline and a gas phase balance pipeline. The oil pipeline includes an oil storage tank and an oil delivery mechanism. The oil storage tank is connected to a gas supply pipeline that keeps it under positive pressure. The gas phase balance pipeline includes a return pipeline, one end of which is connected to a gas phase loading arm. A check valve is connected to the side of the return pipeline near the venting pool to prevent gas flow back into the tank truck. A flame arrester is connected between the check valve and the gas phase loading arm. This method eliminates the need to introduce gas from the tank truck into the oil storage tank, thereby achieving fully closed loading under a slightly positive pressure state, reducing the volatilization and explosion of combustible gases and VOC emissions during loading, and eliminating the risk of personnel injury caused by frequent manual climbing to inspect observation holes.

Description

Technical Field

[0001] This application relates to the field of crude oil loading and transportation technology, specifically to a closed loading system suitable for low flash point shale oil. Background Technology

[0002] In shale oil pilot production stations, the collected shale gas needs to be temporarily stored in oil storage tanks. When the shale oil in the storage tanks needs to be transferred to other locations, the crude oil in the storage tanks needs to be loaded into tank trucks. Generally, the oil in the storage tanks is pumped into the tank trucks using an oil pump. The tank trucks are specifically designed for oil storage, so a large amount of oil and gas will remain inside the tanks. As the oil volume gradually increases, the oil and gas in the tanks are compressed, generating internal pressure, making it difficult to load crude oil. In addition, there is a possibility of oil and gas spillage. The main components of shale oil are alkanes, which are highly volatile. The flash point of the volatile gases is around 20°C, which is lower than that of ordinary oil products. Furthermore, the oil storage tanks at pilot production stations are temporary constructions, which cannot completely prevent the volatilization of shale oil. Especially since the pilot production stations are located in the field and the oil storage tanks are designed for open-air conditions, the risk of flash explosions increases, particularly in summer. During the oil extraction process, operators need to monitor the process at all times. If a flash explosion occurs due to the volatilization of shale oil, it will not only damage the surrounding facilities, but also put the monitoring personnel at great risk to their lives.

[0003] To avoid these situations, it is necessary to recover the oil and gas in the tanker. Therefore, when pumping oil, a pipeline for recovering oil and gas is now required to recover the oil and gas in the tanker.

[0004] In the traditional way, in order to maintain the air pressure balance between the oil storage tank and the tank truck, the recovered oil vapor is directly introduced into the oil tank;

[0005] Oil storage and transportation at a pilot production station constitute a complete operational process. Since oil storage tanks are typically placed outdoors, the diurnal temperature variation causes significant changes in the volatile gases within the tanks. For example, at higher temperatures, a large amount of volatile gas accumulates, leading to excessive pressure within the tank. Conversely, at lower temperatures, the volatile gases condense, causing a rapid decrease in pressure. This continuous increase in pressure can easily lead to pressure buildup in the tank, potentially resulting in oil and gas leaks. Conversely, when the pressure decreases, air can be drawn in from the outside, creating a mixture of gases within the tank and increasing the probability of a deflagration.

[0006] Therefore, a new method is now used to balance the pressure in the oil storage tank by introducing natural gas into it, maintaining a positive pressure at all times. When the pressure in the tank decreases, natural gas is added, typically at a pressure of 5 kPa. When the pressure in the tank exceeds a certain level, the venting pipe is opened, allowing the gas to be released into the venting pool at the test site. This method is used to balance the pressure in the oil storage tank.

[0007] Based on this, the traditional method of maintaining pressure balance between the storage tank and the tank truck is no longer feasible, as the pressure in the storage tank remains above 5 kPa, preventing the oil and gas in the tank truck from flowing back into the storage tank. Therefore, the tank truck loading system needs to be improved to maintain pressure balance during loading. Summary of the Invention

[0008] This application aims to provide a closed loading system suitable for low flash point shale oil, specifically for oil loading operations in storage tanks supplemented with natural gas, to achieve pressure balance during tank truck loading.

[0009] To achieve the above objectives, this application adopts the following technical solution: a closed loading system suitable for low flash point shale oil, including an oil pipeline and a vapor phase balance pipeline. The oil pipeline includes an oil storage tank and an oil delivery mechanism. The oil storage tank is connected to a gas supply pipeline to maintain it under positive pressure. The oil delivery mechanism includes an oil pipeline with an oil pump installed on it. One end of the oil pipeline is connected to a liquid phase loading arm, and the other end is connected to the oil storage tank. The vapor phase balance pipeline includes a return pipeline. One end of the return pipeline is connected to the vapor phase loading arm, and the other end is connected to the venting pool of the test production station. A check valve is connected to the side of the return pipeline near the venting pool to prevent gas flow back into the tank truck. A flame arrester is connected between the check valve and the vapor phase loading arm to prevent flames from the venting pool from spreading into the return pipeline.

[0010] The principle and beneficial effects of this application are as follows: In closed-loop loading, shale oil stored in the storage tank is transferred to the tanker truck's tank via a bottom loading method. A liquid phase loading arm connects the oil transfer pipeline to the tanker truck's inlet, and a gas phase loading arm connects the return pipeline to the tanker truck's gas return outlet. Because the storage tank is under a slightly positive pressure, the return pipeline is no longer connected to the storage tank; instead, it is directly introduced into the venting pool for venting. This method eliminates the need to introduce gas from the tanker truck into the storage tank, thus achieving fully closed-loop loading under slightly positive pressure operation. This reduces the risk of flammable gas volatilization and explosion, as well as VOC emissions, during loading, while also eliminating the risk of personnel injury from frequent manual inspections of observation ports.

[0011] A check valve is installed on the return pipe to prevent the gas flow from flowing back into the tanker, and a flame arrester is installed on the return pipe to prevent the venting flame from backflashing.

[0012] Furthermore, the return pipe is connected to the venting pipe on the oil storage tank via the venting riser and together they are connected to the venting pool. A venting torch is connected to the end of the venting riser.

[0013] To reduce the amount of piping required, the venting pipe and return pipe of the oil storage tank are connected by a venting riser. The combustible gas to be vented is then gathered at the venting flare outlet through the venting riser and ignited to complete the venting.

[0014] Furthermore, the closed loading system also includes a flow rate control mechanism, which includes a liquid mass flow meter and a regulating valve connected to the oil pipeline, as well as a PLC controller for automatic control. The electrical signal of the liquid mass flow meter is connected to the input terminal of the PLC controller, and the electrical signals of the regulating valve and the oil pump are connected to the output terminal of the PLC controller. The liquid mass flow meter is used to obtain the shale oil flow rate in the oil pipeline. If the PLC controller determines that the shale oil flow rate is higher than the safe flow rate range, it controls the opening of the regulating valve or controls the speed of the oil pump to reduce the shale oil flow rate and bring it within the safe flow rate range. If the flow rate is lower than the safe flow rate range, the PLC controller issues an alarm and stops the oil pump and closes the regulating valve.

[0015] The flow rate in the oil pipeline is controlled by a flow rate control mechanism to keep it within a safe flow rate range, avoiding disruption of the loading schedule caused by excessively fast flow rate, and detecting excessively slow flow rate due to valve blockage.

[0016] Furthermore, the sealed loading system also includes an electrostatic discharge (ESD) control mechanism. This mechanism includes an alarm frame equipped with an audible and visual alarm to indicate the presence of static electricity, an ESD sensor installed inside the alarm frame, and an ESD clamp attached to the oil pipeline, return pipeline, and tanker body. The ESD clamp is connected to the ESD sensor via a wire. The electrical signal from the ESD sensor is connected to the signal input terminal of the PLC controller. Upon receiving a signal indicating the presence of static electricity, the PLC controller sends an alarm signal to the audible and visual alarm, stops the oil pump, and closes the regulating valve.

[0017] The static electricity generated on the oil pipeline and tanker is detected by electrostatic clamps. When the static electricity generated exceeds the set limit, the audible and visual alarm will sound to remind personnel to evacuate. In addition, the oil pump will be stopped immediately and the regulating valve will be closed to stop the loading operation and avoid the risk of fire.

[0018] Furthermore, the sealed loading system also includes an overflow prevention mechanism, which includes a liquid level measuring frame for measuring the upper limit of the tanker's oil tank capacity. The liquid level measuring frame includes a liquid level probe inserted into the top of the tanker's oil tank. The end of the liquid level probe is provided with a sealing plug, and the tail end of the sealing plug is fixed with an installation handle. The liquid level probe is electrically connected to the signal input terminal of the PLC controller. After the PLC controller receives an overflow signal, it sends an audible and visual alarm signal to sound an alarm, stops the oil pump, and closes the regulating valve.

[0019] Overflow often occurs when the oil tanker reaches its maximum capacity, posing a risk of spillage. By detecting the maximum oil level in the tanker using a level probe, the oil pump should be stopped and the regulating valve closed in a timely manner to prevent overflow.

[0020] Furthermore, a shut-off valve is connected to the oil pipeline, and an emergency stop button is directly connected to the power supply circuit of the oil pump and the shut-off valve. In case of an emergency, the oil pump and the oil pipeline can be directly shut off by pressing the emergency stop button, thus eliminating the need for a PLC controller to output a signal to shut off the oil pump.

[0021] Furthermore, the cable used on the level probe is made of oil-resistant, flame-retardant soft rubber, which extends the service life of the level probe and its accessories.

[0022] Furthermore, the liquid phase loading arm is connected to a first quick connector, the gas phase loading arm is connected to a second quick connector, a first break-off valve is provided between the liquid phase loading arm and the first quick connector, and a second break-off valve is provided between the gas phase loading arm and the second quick connector.

[0023] During the tanker loading process, quick-connect couplings can be used to quickly and securely connect the tanker's oil inlet and gas return outlet. Additionally, if the coupling is not disconnected before the tanker departs, potentially causing oil leakage in the pipeline, a disconnect valve can be used to prevent such leaks.

[0024] Finally, electric heating tape was wrapped around the bends of the oil pipeline, connecting regulating valves, oil pumps, liquid phase mass flow meters, and the inlet and outlet of the liquid phase loading arm, and the heating tape was maintained at 45~55℃. Since there may still be untreated wax in the shale oil in the pilot production station, which is prone to depositing at the bends and connections of the oil pipeline, the heating of the electric heating tape ensures that the wax residue is eliminated. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a closed loading system suitable for low flash point shale oil.

[0026] Figure 2 This is a schematic diagram of the electrical control system in a closed loading system.

[0027] The reference numerals in the accompanying drawings include: oil storage tank 1; gas replenishment pipeline 11; venting pool 2; venting riser 21; check valve 22; flame arrester 23; return pipeline 3; oil transfer skid 4; gas phase loading arm 5; second breakaway valve 51; second quick connector 52; liquid phase loading arm 6; first breakaway valve 61; first quick connector 62; tanker tank 7; level probe 71; oil transfer pipeline 8; regulating valve 81; liquid phase mass flow meter 82; oil pump 83. Detailed Implementation

[0028] The following detailed description of the specific implementation method further illustrates this solution.

[0029] Example 1

[0030] like Figure 1 As shown, a closed loading system suitable for low flash point shale oil includes an oil pipeline and a vapor phase balance pipeline. The oil pipeline includes an oil storage tank 1 and an oil delivery mechanism. The oil storage tank 1 is connected to a gas supply pipeline 11 to maintain it under positive pressure. The oil delivery mechanism includes an oil delivery pipeline 8, on which an oil pump 83 is installed. One end of the oil delivery pipeline 8 is connected to a liquid phase loading arm 6, and the other end is connected to the oil storage tank 1. The vapor phase balance pipeline includes a return pipeline 3. One end of the return pipeline 3 is connected to a vapor phase loading arm 5, and the other end is connected to the venting pool 2 of the test production station. A check valve 22 is connected to the side of the return pipeline 3 near the venting pool 2 to prevent gas flow back into the tank truck. A flame arrester 23 is connected between the check valve 22 and the vapor phase loading arm 5 to prevent the flame from the venting pool from spreading into the return pipeline 3.

[0031] The return pipe 3 is connected to the venting pipe on the oil storage tank 1 through the venting riser 21 and is connected to the venting pool 2 together. The end of the venting riser 21 is connected to the venting torch.

[0032] The liquid phase loading arm 6 is connected to a first quick connector 62, and the gas phase loading arm 5 is connected to a second quick connector 52. A first break-off valve 61 is provided between the liquid phase loading arm 6 and the first quick connector 62, and a second break-off valve 51 is provided between the gas phase loading arm 5 and the second quick connector 52.

[0033] The liquid phase loading arm 6, the gas phase loading arm 5, and the connecting pipelines for oil transportation are all integrated into the oil transportation skid 4, which is installed as a whole at the tanker loading point.

[0034] Example 2

[0035] like Figure 1 and Figure 2As shown, the closed loading system also includes a flow rate control mechanism, which includes a liquid mass flow meter 82 and a regulating valve 81 connected to the oil pipeline 8, as well as a PLC controller for automatic control. The electrical signal of the liquid mass flow meter 82 is connected to the input terminal of the PLC controller, and the electrical signals of the drivers of the regulating valve 81 and the oil pump 83 are connected to the output terminal of the PLC controller. The liquid mass flow meter 82 is used to obtain the shale oil flow rate in the oil pipeline 8. If the PLC controller determines that the shale oil flow rate is higher than the safe flow rate range, it controls the opening of the regulating valve 81 and the rotation speed of the oil pump 83, thereby reducing the shale oil flow rate and keeping it within the safe flow rate range. If the flow rate is lower than the safe flow rate range, the PLC controller issues an alarm and stops the oil pump 83 and closes the regulating valve 81.

[0036] The flow rate in the oil pipeline 8 is controlled by a flow rate control mechanism to keep it within a safe flow rate range, avoiding the disruption of the loading rhythm caused by excessively fast flow rate, and detecting excessively slow flow rate due to valve blockage.

[0037] The sealed loading system also includes an electrostatic discharge (ESD) control mechanism, which includes an alarm frame equipped with an audible and visual alarm to indicate the presence of static electricity, an ESD sensor installed inside the alarm frame, and ESD clamps attached to the oil pipeline, return pipeline, and tank car body. The ESD clamps are connected to the ESD sensor via wires, and the electrical signal from the ESD sensor is connected to the signal input terminal of the PLC controller. After receiving a signal indicating the presence of static electricity, the PLC controller sends an alarm signal to the audible and visual alarm, stops the oil pump 83, and closes the regulating valve 81.

[0038] The sealed loading system also includes an overflow prevention mechanism, which comprises a hydraulic measuring frame for measuring the upper limit of the tanker's oil tank 7 capacity. The measuring frame includes a level probe 71 inserted into the top of the tanker's oil tank. A sealing plug is located at the end of the level probe 71, and an installation handle is fixed to the tail end of the sealing plug. The level probe 71 is electrically connected to the signal input terminal of the PLC controller. Upon receiving an overflow signal, the PLC controller sends an alarm signal to the audible and visual alarm, stops the oil pump 83, and closes the regulating valve 81. The cable used on the level probe 71 is an oil-resistant, flame-retardant soft rubber cable, which extends the service life of the level probe and its accessories.

[0039] The oil pipeline 8 is also connected to a shut-off valve, and an emergency stop button is directly connected to the power supply circuit of the oil pump and the shut-off valve. In case of an emergency, the oil pump and the oil pipeline can be directly shut off by pressing the emergency stop button, thus eliminating the need to output a signal from the controller to shut off the oil pump.

[0040] Electric heating tape is wrapped around the bends of oil pipeline 8, the inlet and outlet of the connecting regulating valve, oil pump, liquid phase mass flow meter and liquid phase loading arm, and the electric heating tape is maintained at 45~55℃.

[0041] The oil storage tank is equipped with a pressure sensor that measures the internal air pressure. The electrical signal of the pressure sensor is connected to the input terminal of the PLC controller. When the pressure sensor detects that the air pressure in the oil storage tank is lower than 2 kPa, the PLC controller outputs a pump stop command to stop the oil pump from supplying oil.

[0042] Gas sensors are installed in the tanker loading area to detect oil and gas leaks. If the amount of oil and gas in the loading area exceeds a threshold, the PLC controller will output a pump stop command and issue an alarm command to stop the oil pump from supplying oil and remind relevant personnel to evacuate the site.

[0043] In this embodiment, the PLC controller used is a Siemens S7-200, with external explosion-proof measures added. The explosion-proof level meets ExdIIBT4, and the protection level meets IP65. The oil pump is a servo oil pump with a driver. The electrostatic sensor is a customized sensor that simultaneously measures overflow and static electricity, specifically the ET-BLS anti-overflow and anti-static sensor. The liquid phase mass flow meter is a Micro Motion mass flow meter with an explosion-proof level meeting ExdIIBT4. The liquid level probe is an LMT300 series magnetostrictive liquid level gauge, the regulating valve is a pneumatic V-type regulating valve, and the shut-off valve is a G4070 pneumatic two-stage shut-off ball valve.

[0044] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A closed loading system suitable for low flash point shale oil, comprising an oil pipeline and a vapor phase balance pipeline, wherein the oil pipeline includes an oil storage tank and an oil delivery mechanism, characterized in that: The oil storage tank is connected to a gas supply pipeline that keeps it under positive pressure. The oil delivery mechanism includes an oil delivery pipeline with an oil pump installed on it. One end of the oil delivery pipeline is connected to a liquid phase loading arm, and the other end is connected to the oil storage tank. The gas phase balance pipeline includes a return pipeline. One end of the return pipeline is connected to a gas phase loading arm, and the other end is connected to the venting pool of the test production station. A check valve is connected to the side of the return pipeline near the venting pool to prevent gas flow from flowing back into the tank truck. A flame arrester is connected between the check valve and the gas phase loading arm to prevent the flame from the venting pool from spreading into the return pipeline.

2. The closed loading system for low flash point shale oil according to claim 1, characterized in that: The return pipe is connected to the venting pipe on the oil storage tank through the venting riser and together they are connected to the venting pool. A venting torch is connected to the end of the venting riser.

3. The closed loading system for low flash point shale oil according to claim 1, characterized in that: It also includes a flow rate control mechanism, which comprises a liquid mass flow meter and a regulating valve connected to the oil pipeline, as well as a PLC controller for automatic control. The electrical signal of the liquid mass flow meter is connected to the input terminal of the PLC controller, and the electrical signals of the regulating valve and the oil pump are connected to the output terminal of the PLC controller. The liquid mass flow meter is used to obtain the shale oil flow rate in the oil pipeline. If the PLC controller determines that the shale oil flow rate is higher than the safe flow rate range, it controls the opening of the regulating valve or controls the speed of the oil pump to reduce the shale oil flow rate and bring it within the safe flow rate range. If the flow rate is lower than the safe flow rate range, the PLC controller issues an alarm and stops the oil pump and closes the regulating valve.

4. The closed loading system for low flash point shale oil according to claim 3, characterized in that: It also includes an electrostatic discharge (ESD) control mechanism, which includes an alarm frame equipped with an audible and visual alarm to indicate the presence of static electricity, an ESD sensor installed inside the alarm frame, and an ESD clamp clamped onto the oil pipeline, return pipeline, and tanker body. The ESD clamp is connected to the ESD sensor via a wire, and the electrical signal from the ESD sensor is connected to the signal input terminal of the PLC controller. After receiving a signal indicating the presence of static electricity, the PLC controller sends an alarm signal to the audible and visual alarm, stops the oil pump, and closes the regulating valve.

5. The closed loading system for low flash point shale oil according to claim 4, characterized in that: It also includes an overflow prevention mechanism, which includes a liquid level measuring frame for measuring the upper limit of the tanker's oil tank capacity. The liquid level measuring frame includes a liquid level probe inserted into the top of the tanker's oil tank. The end of the liquid level probe is provided with a sealing plug, and the tail end of the sealing plug is fixed with an installation handle. The liquid level probe is electrically connected to the signal input terminal of the PLC controller. After the PLC controller receives an overflow signal, it sends an alarm signal to the audible and visual alarm, stops the oil pump, and closes the regulating valve.

6. The closed loading system for low flash point shale oil according to claim 5, characterized in that: The oil pipeline is also connected to a shut-off valve, and an emergency stop button is directly connected to the power supply circuit of the oil pump and the shut-off valve.

7. The closed loading system for low flash point shale oil according to claim 5, characterized in that: The cable used on the liquid level probe is an oil-resistant, flame-retardant soft rubber cable.

8. The closed loading system for low flash point shale oil according to claim 7, characterized in that: The liquid phase loading arm is connected to a first quick connector, and the gas phase loading arm is connected to a second quick connector. A first break-off valve is provided between the liquid phase loading arm and the first quick connector, and a second break-off valve is provided between the gas phase loading arm and the second quick connector.

9. The closed loading system for low flash point shale oil according to claim 8, characterized in that: Electric heating tape is wrapped around the bends of the oil pipeline, the inlet and outlet of the connecting regulating valve, oil pump, liquid phase mass flow meter, and liquid phase loading arm. The electric heating tape is maintained at 45~55℃.

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