An oil return system for dehydrating oil tanks

Abstract

The present invention belongs to the technical field of petrochemical engineering, and specifically discloses an oil return system for oil tank dehydration, which includes a storage oil tank, a dehydrator, a front dehydration pipeline and a rear dehydration pipeline. It also includes a compressed air-driven or pressurized liquid-driven oil return device that can return the oil in the dehydrator to the storage oil tank and enable the water at the bottom of the storage oil tank to completely flow into the dehydrator. The oil return device includes a buffer tank placed on the front dehydration pipeline or the rear dehydration pipeline. This oil return system uses the buffer tank to store and return the oil that enters the dehydrator during dehydration or press it into the storage oil tank through pressure. The water at the bottom of the storage oil tank can flow into the interior of the dehydrator for dehydration treatment, forming a cyclic process of oil-water exchange, which is beneficial to accelerating the removal of water at the bottom of the storage oil tank, achieving thorough dehydration and good oil return effect. In addition, it ensures that the oil content in the sewage discharged from the dehydrator meets the emission standards, effectively avoids the emission of a large amount of toxic and harmful gases into the air during dehydration, and avoids environmental pollution, and is safe and reliable to use.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical engineering, and particularly relates to an oil return system for dehydrating oil tanks. Background Art

[0002] In the prior art, there is some water in the oil stored in the commonly used storage oil tanks in the petrochemical industry. After being stored for a period of time, the water will settle to the bottom of the storage oil tank. When in use, in order to ensure the purity of the oil inside the storage oil tank, the water at the bottom of the storage oil tank must be subjected to corresponding dehydration treatment. The current dehydration technology is to directly discharge the water into the sewage pool under the storage oil tank, and then flow into the sewer for discharge. With the continuous improvement of safety and environmental protection requirements, this direct exposure dehydration method has many drawbacks. For this reason, some people have developed a dehydration treatment method of separating oil and water by connecting a dehydrator at the bottom of the storage oil tank through a pipeline to remove the water inside the storage oil tank. However, during the process of discharging water, some oil will also be mixed and cannot completely flow back into the storage oil tank inside the dehydrator. At the same time, it is very difficult for the water at the bottom of the storage oil tank to completely enter the dehydrator for dehydration. In this way, a small amount of water will still accumulate at the bottom of the storage oil tank, and the purpose of complete dehydration cannot be achieved.

[0003] Therefore, it is extremely urgent to develop an oil return system for oil tank dehydration that can smoothly return the oil in the dehydrator to the storage oil tank and ensure that the water in the storage oil tank is completely removed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art, and specifically disclose an oil return system for oil tank dehydration. The oil return system for oil tank dehydration uses a buffer tank to store and return the oil in the dehydrator or press it into the storage oil tank through pressure. The water at the bottom of the storage oil tank can flow into the dehydrator for dehydration treatment, forming a cyclic process of oil-water exchange. In this way, the water at the bottom of the storage oil tank is removed more quickly, the dehydration is complete, and the oil return effect is good. In addition, it also ensures that the oil content in the sewage discharged from the dehydrator meets the emission standards, effectively avoids the emission of a large amount of toxic and harmful gases during dehydration, does not pollute the environment, and is safe and reliable to use.

[0005] In order to achieve the above technical purpose, the present invention is implemented according to the following technical solutions:

[0006] An oil return system for oil tank dehydration according to the present invention includes a storage oil tank, a dehydrator, a front dehydration pipeline connected between the storage oil tank and the inlet end of the dehydrator through a mounting flange, and a rear dehydration pipeline between the outlet ends of the dehydrator, and further includes a compressed air-driven or pressurized liquid-driven oil return device that can return the oil in the dehydrator to the storage oil tank and the water at the bottom of the storage oil tank can completely flow into the dehydrator.

[0007] In the present invention, the compressed air-driven or pressurized liquid-driven oil return device has the following nine modes in total:

[0008] First, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. The buffer tank is communicated with the top of the front dehydration pipeline through a front buffer connecting pipe, and a compressed air area is provided in the cavity of the buffer tank.

[0009] Second, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. A first one-way valve is provided on the front buffer connecting pipe. A return oil pipeline is also provided between the buffer tank and the end of the front dehydration pipeline adjacent to the storage tank. A second one-way valve is provided on the return oil pipeline, and a compressed air area is provided in the cavity of the buffer tank.

[0010] Third, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. An oil storage bag is directly communicated above the front dehydration pipeline. The oil storage bag is connected to the buffer tank through a front buffer connecting pipe. A first one-way valve is provided on the front buffer connecting pipe. A return oil pipeline is also provided between the buffer tank and the end of the front dehydration pipeline adjacent to the storage tank. A second one-way valve is provided on the return oil pipeline, and a compressed air area is provided in the cavity of the buffer tank.

[0011] Fourth, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. An oil storage bag is directly communicated above the front dehydration pipeline. The oil storage bag is connected to the buffer tank through a front buffer connecting pipe. A first one-way valve is provided on the front buffer connecting pipe. A return oil pipeline is also provided between the buffer tank and the end of the front dehydration pipeline adjacent to the storage tank. A second one-way valve is provided on the return oil pipeline. A compressed air inlet is provided at the top of the buffer tank. The compressed air inlet is connected to the air source of compressed air through an intake pipeline and an intake valve. A piston that can move up and down is provided inside the buffer tank.

[0012] Fifth, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. A storage oil bag is directly connected above the front dehydration pipeline. The storage oil bag and the buffer tank are connected through a front buffer connecting pipe. A first one-way valve is provided on the front buffer connecting pipe. A return oil pipeline is also provided between the buffer tank and the end of the front dehydration pipeline adjacent to the storage tank. A second one-way valve is provided on the return oil pipeline. A breathing port is provided at the top of the buffer tank. A piston that can move up and down is provided inside the buffer tank. A two-way pump is provided on the front buffer connecting pipe near the oil inlet at the bottom of the buffer tank.

[0013] Sixth, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. The buffer tank is directly connected to the front dehydration pipeline. A valve hole is provided at the oil inlet at the bottom of the buffer tank. A floating ball that can float in the oil liquid is provided above the valve hole inside the buffer tank. Several limiting rods that can limit the upward movement of the floating ball are provided inside the buffer tank. The side wall position at the bottom of the buffer tank is connected to the front dehydration pipeline through a connecting pipeline. A compressed air inlet is provided at the top of the buffer tank. The compressed air inlet is connected to the air source of the compressed air through an intake pipeline and an intake valve. A piston that can move up and down is provided inside the buffer tank.

[0014] Seventh, the compressed air-driven or pressurized liquid-driven oil return device includes a buffer tank placed on the rear dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. The buffer tank is connected to the rear dehydration pipeline through a rear buffer connecting pipe. A compressed air area is provided inside the cavity of the buffer tank.

[0015] Eighth, the compressed air-driven or pressurized liquid-driven oil return device includes a buffer tank placed on the rear dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. The buffer tank is connected to the rear dehydration pipeline through a rear buffer connecting pipe. An inlet for compressed air or pressurized liquid to enter is provided at the top of the buffer tank. The inlet for compressed air or pressurized liquid is connected to the compressed air or pressurized liquid through a pipeline and an intake valve / liquid inlet valve. A piston that can move up and down is provided inside the buffer tank.

[0016] Ninth, the compressed air-driven or pressurized liquid-driven oil return device includes a buffer tank placed on the rear dehydration pipeline, which can return the oil separated in the dehydrator or press it into the storage tank through pressure. The buffer tank is connected to the rear dehydration pipeline through a rear buffer connecting pipe. A breathing port is provided at the top of the buffer tank. A piston that can move up and down is provided inside the buffer tank. A two-way pump is provided on the rear dehydration pipeline.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) In the oil return system for oil tank dehydration of the present invention, in the above first to sixth modes, during dehydration, when the dehydration valve at the outlet end of the dehydrator is closed to stop dehydration due to excessive oil content in the water, when oil return work needs to be carried out, compressed air is introduced into the buffer tank, so that the liquid in the buffer tank flows back into the interior of the storage tank. After completely emptying the liquid in the buffer tank, the compressed air source is closed, and the compressed air in the buffer tank is drained. Under the pressure generated by the liquid level height of the storage tank, the oil above the dehydrator will enter the interior of the buffer tank. At the same time, the water at the bottom of the storage tank enters the dehydrator, and the dehydrator continues to dehydrate. When the dehydrator stops dehydration again due to excessive oil content in the water, the above process is repeated, and the dehydrator continues to dehydrate until the water in the storage tank is completely removed. The working efficiency of the dehydrator is greatly improved, and the oil content rate in the discharged sewage is greatly reduced.

[0019] In the above seventh to ninth modes, since a buffer tank is provided on the post-dehydration pipeline, which is used to store the water at the bottom of the dehydrator, under the action of the external force of compressed air or pressurized liquid, the water in the buffer tank can be better pressed into the dehydrator from the bottom of the dehydrator, and the water level inside the dehydrator will rise. In this way, the rising water level enables the oil floating on the upper layer of the dehydrator to flow back to the bottom of the storage tank along the pre-dehydration pipeline; after draining the compressed air or pressurized liquid in the buffer tank, under the action of the oil tank pressure, the water in the dehydrator enters the buffer tank, and the water at the bottom of the storage tank enters the dehydrator to continue dehydration. After multiple cycles, the oil in the dehydrator can also be completely returned to the storage tank, with high oil return efficiency, and the water at the bottom of the storage tank can be completely removed until the water in the storage tank is completely removed. The working efficiency of the dehydrator is greatly improved, and the oil loss rate is greatly reduced;

[0020] (2) In the oil return system for oil tank dehydration of the present invention, since the oil recovery rate is greatly improved, the oil content in the pipeline after dehydration by the dehydrator is small, so that the oil content in the finally discharged sewage reaches the discharge standard, effectively avoiding the emission of a large amount of toxic and harmful gases into the air during dehydration and not causing pollution to the environment, and being safe and reliable in use.

[0021] (3) The oil return system for oil tank dehydration of the present invention can solve the technical problems of difficult dehydration and oil return for petrochemical enterprises, bring good economic and environmental benefits to petrochemical enterprises, and has strong practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be described in detail below with reference to the drawings and specific embodiments:

[0023] Figure 1 It is a schematic structural diagram of the oil return system for oil tank dehydration according to Embodiment 1 of the present invention;

[0024] Figure 2 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 2 of the present invention;

[0025] Figure 3 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 3 of the present invention;

[0026] Figure 4 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 4 of the present invention;

[0027] Figure 5 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 5 of the present invention;

[0028] Figure 6 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 6 of the present invention;

[0029] Figure 7 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 7 of the present invention;

[0030] Figure 8 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 8 of the present invention;

[0031] Figure 9 It is a schematic structural diagram of the oil return system for oil tank dehydration described in Embodiment 9 of the present invention. Detailed implementation manners

[0032] Embodiment 1:

[0033] As Figure 1 shown, the oil return system for oil tank dehydration described in the present invention includes a storage oil tank 1, a dehydrator 2, a front dehydration pipeline 5 connected between the storage oil tank 1 and the dehydrator 2 through a mounting flange 3, and a rear dehydration pipeline 30 disposed between the outlet ends of the dehydrator 2. It further includes a compressed air-driven oil return device that can return the oil in the dehydrator 2 to the storage oil tank 1 and enable the water at the bottom of the storage oil tank 1 to completely flow into the dehydrator 2. The compressed air-driven oil return device includes a buffer tank 6 disposed on the front dehydration pipeline 5 that can return or press the oil separated in the dehydrator 2 into the interior of the storage oil tank 1. A tank root valve 8 is provided on the mounting flange 3, and a dehydration valve 9 is provided at the outlet end of the dehydrator 2.

[0034] The buffer tank 6 is communicated with the front dehydration pipeline 5 through a front buffer connection pipe 4, and a compressed air area 7 is provided in the cavity of the buffer tank 6.

[0035] The following specifically describes the working process of the oil return system for oil tank dehydration described in this embodiment:

[0036] (1) First, open the root valve 8 at the bottom outlet of the storage oil tank 1. The water at the bottom of the storage oil tank enters the buffer tank 6 and the dehydrator 2, and the dehydrator 2 starts to dehydrate. The water at the bottom of the storage oil tank 1 gradually decreases. When the oil in the storage oil tank 1 enters the dehydrator 2, the dehydrator 2 closes the dehydration valve 9 at the outlet end and stops dehydrating. By introducing compressed air into the buffer tank 6, the liquid in the buffer tank 6 is driven to flow back into the interior of the storage oil tank 1;

[0037] (2) Then, after the interior of the buffer tank 6 is completely emptied, the compressed air in the buffer tank 6 is drained. Under the pressure of the storage oil tank 1, the oil inside the dehydrator 2 will enter the buffer oil tank 6, and at the same time, the water at the bottom of the storage oil tank 1 will enter the dehydrator 2, and the dehydrator 2 continues to dehydrate;

[0038] (3) The above processes of dehydration and oil return can be cycled multiple times until the water at the bottom of the storage oil tank 1 is completely dehydrated.

[0039] Embodiment Two:

[0040] This embodiment is basically the same as the above Embodiment One, and the difference is that: as Figure 2 shown, a first one-way valve 11 is provided on the front buffer connection pipe 4, and an oil return pipeline 12 is further provided between the buffer tank 6 and the end of the front dehydration pipeline 5 adjacent to the storage oil tank 1. A second one-way valve 13 is provided on the oil return pipeline 12, and a compressed air area 7 is provided in the cavity of the buffer tank 6.

[0041] Compared with Embodiment One, in this embodiment, through the setting of the oil return branch 12, the first one-way valve 11 and the second one-way valve 13, the oil inside the dehydrator 2 can better enter the buffer tank 6 through the first one-way valve 11. The oil level in the buffer tank 6 rises to the highest level, and then compressed air is introduced into the buffer tank 6, and then the oil inside the buffer tank 6 is forced to flow back to the storage liquid tank 1 through the oil return branch 12. The opening and closing of the first one-way valve 11 and the second one-way valve 13 enable the oil in the dehydrator 2 and the front dehydration pipeline 5 to have a fast oil return circulation speed, good oil return effect, and thorough dehydration.

[0042] Embodiment Three:

[0043] This embodiment is basically the same as the above Embodiment Two, and the difference is that: as Figure 3 shown, a storage oil bag 20 is directly connected above the front dehydration pipeline 5, and the storage oil bag 20 is connected to the buffer tank 6 through the front buffer connection pipe 4.

[0044] The similarities are: a first one-way valve 11 is provided on the front buffer connection pipe 4, and an oil return branch 12 is further provided between the buffer tank 6 and the end of the front dehydration pipeline 5 adjacent to the storage oil tank 1. A second one-way valve 13 is provided on the oil return branch 12, and a compressed air area 7 is provided in the cavity of the buffer tank 6.

[0045] In this embodiment, through the setting of the return oil branch 12, the first one-way valve 11 and the second one-way valve 13, the oil inside the dehydrator 2 can be better passed through the oil storage bag 20, the front cache connecting pipe 4, and the first one-way valve 11 into the cache tank 6. The oil level in the cache tank 6 rises to the highest height, and then compressed air is introduced into the cache tank 6, forcing the oil inside the cache tank 6 to flow back to the liquid storage tank 1 through the return oil branch 12. The oil in the dehydrator 2 and the front dehydration pipeline 5 can achieve a faster oil return cycle through the opening and closing of the first one-way valve 11 and the second one-way valve 13, and the oil return effect is good. At the same time, due to the setting of the oil storage bag 20, the amount of oil returned each time is increased, the oil return efficiency is greatly improved, and the dehydration of the liquid storage tank 1 is also faster.

[0046] Embodiment 4:

[0047] This embodiment is basically the same as the above-mentioned embodiment 2. Figure 4 As shown, the front dehydration pipeline 5 is directly connected to an oil storage bag 20 above, and the oil storage bag 20 is connected to the cache tank 6 through a front cache connecting pipe 4. The front cache connecting pipe 4 is provided with a first one-way valve 11, and an oil return branch 12 is also provided between the cache tank 6 and the end of the front dehydration pipeline 5 on the side adjacent to the oil storage tank 1, and the oil return branch 12 is provided with a second one-way valve 13.

[0048] The difference lies in that a compressed air inlet 61 is provided on the top of the cache tank 6, and the compressed air inlet 61 is connected to the compressed air source through an intake pipe 14 and an intake valve 15, and a piston 16 that can move up and down is provided inside the cache tank 6.

[0049] Compared with the third embodiment, this embodiment mainly adopts the coordinated arrangement of the compressed air inlet 61 at the top of the buffer tank 6 and the piston 16 arranged inside the cavity. When in use, the air inlet valve 15 is opened to deliver compressed air to the buffer tank 6, and the piston 16 of the buffer tank 6 moves downward, driving the oil in the tank to smoothly flow back to the bottom of the oil storage tank 1 through the oil return branch, thereby realizing the oil return process conveniently and quickly.

[0050] Embodiment five:

[0051] This embodiment is basically the same as the fourth embodiment, except that: Figure 5 As shown, a breathing port 10 is provided on the top of the cache tank, and a two-way pump 17 is provided on the front cache connecting pipe 4 at the bottom of the cache tank 6 adjacent to the oil inlet.

[0052] In this embodiment, by setting up the two-way pump 17, the flow rate of the oil inside the dehydrator 2 input into the buffer tank 6 and the flow rate of the oil in the buffer tank 6 returning to the oil storage tank 1 through the oil return branch 12 are increased, and the working efficiency is greatly improved.

[0053] Example VI:

[0054] This example is basically the same as Example IV above. As Figure 6 shown, a compressed air inlet 61 is provided at the top of the buffer tank 6. The compressed air inlet 61 is connected to the compressed air source through an intake pipeline 14 and an intake valve 15. A piston 16 that can move up and down is provided inside the buffer tank 6.

[0055] The difference lies in that: as Figure 6 shown, the buffer tank 6 is directly connected to the front dehydration pipeline 5. A valve hole 62 is provided at the bottom oil inlet of the buffer tank 6. Above the valve hole 62 inside the buffer tank 6, there is a floating ball 18 that can float in the liquid. Inside the buffer tank 6, there are several limiting rods 19 that can limit the upward movement of the floating ball 18. The bottom side wall of the buffer tank 6 is connected to the front dehydration pipeline 5 through an oil return branch 12.

[0056] When the oil inside the dehydrator 2 enters the buffer tank 6, the oil pressure will push open the floating ball 18, and the oil will enter the buffer tank 6. The setting of the limiting rods 19 limits the height position of the floating ball 18 rising, playing a good limiting role. When the intake valve 15 is opened, the compressed gas enters the buffer tank 6 and drives the piston 16 to move downward, causing the liquid level inside the buffer tank 6 to drop. At this time, the floating ball 18 falls until it blocks the valve hole 62, forcing the oil inside the buffer tank 6 to flow back to the storage tank 1 through the oil return branch 12, thus completing the oil return process.

[0057] Example VII:

[0058] The difference between this example and Example I above lies in that: as Figure 7 shown, the compressed air-driven or pressurized liquid-driven oil return device includes a buffer tank 6 placed on the rear dehydration pipeline 30 that can return the oil separated from the dehydrator 2 or press it into the storage tank 1 through pressure. The buffer tank 6 is connected to the rear dehydration pipeline 30 through a rear buffer connection pipe 40. At this time, the buffer tank 6 is connected to the bottom of the dehydrator 2 and is used to hold water. A compressed air area is provided inside the cavity of the buffer tank 6.

[0059] The working process of this example is specifically described as follows:

[0060] (1) First, open the tank root valve 8 at the bottom outlet of the storage tank 1, and close the dehydration valve 9 at the outlet end of the dehydrator 2. The oil-water mixture at the bottom of the storage tank 1 flows into the dehydrator 2 through the front dehydration pipeline 5 for dehydration. At this time, the oil and water inside the dehydrator 2 are separated, and the water placed at the bottom of the dehydrator 2 will enter the inside of the buffer tank 6 through the rear buffer connection pipe 40;

[0061] (2) Next, after the compressed air in the compressed air area 7 inside the buffer tank 6 is further squeezed by the rising water, the air pressure in the buffer tank 6 increases. Then, the water inside the buffer tank 6 and the post-dehydration pipeline 30 flows back reversely into the interior of the dehydrator 2, so that the water level inside the dehydrator 2 will rise, and thus the oil floating on the upper layer of the dehydrator 2 can flow back along the pre-dehydration pipeline 5 to the bottom position of the oil storage tank 1;

[0062] (3) The above process of dehydration and oil return can be cycled multiple times until the oil separated by the dehydrator 2 completely flows back into the oil storage tank 1.

[0063] Embodiment Eight:

[0064] This embodiment is basically the same as the above Embodiment Seven. As Figure 8 shown, the buffer tank 6' is connected to the post-dehydration pipeline 30 through the post-buffer connection pipe 40. The difference is that the top of the buffer tank 6' is provided with an inlet 61' for compressed air or pressurized liquid to enter. The inlet 61' of the compressed air or pressurized liquid is connected to the compressed air or pressurized liquid through the pipeline 14' and the air inlet valve / liquid inlet valve 15'. A piston 16' that can move up and down is provided inside the buffer tank 6'. Its working principle is the same as that of the above Embodiment Seven. The difference is that the water inside the buffer tank 6' is squeezed into the interior of the dehydrator 2 by compressed air or pressurized liquid, thereby increasing the flow rate of the oil separated on the upper layer of the dehydrator 2 flowing back into the interior of the oil storage tank 1, and the working efficiency is greatly improved.

[0065] Embodiment Nine:

[0066] This embodiment is basically the same as the above Embodiment Eight. The buffer tank 6' is connected to the post-dehydration pipeline 30 through the post-buffer connection pipe 40. As Figure 9 shown, the difference is that: a breathing port 10' is provided at the top of the buffer tank, the piston that can move up and down, and a two-way pump is provided on the post-dehydration pipeline. Due to the addition of the two-way pump 17' in this embodiment, the process of dehydration and oil return can be completed more quickly and thoroughly, and the working efficiency is greatly improved.

[0067] The present invention is not limited to the above embodiments. Any modifications or variations of the present invention that do not depart from the spirit and scope of the present invention, provided that these modifications and variations fall within the scope of the claims of the present invention and equivalent technical scope, then the present invention also means including these modifications and variations.

Claims

1. An oil return system for dehydrating oil tanks, characterized in that: it includes an oil storage tank, a dehydrator, a front dehydration pipeline connected between the oil storage tank and the inlet end of the dehydrator through a mounting flange, and a rear dehydration pipeline placed at the outlet end of the dehydrator, and also includes a compressed air-driven oil return device or a pressurized liquid-driven oil return device that can return the oil in the dehydrator to the oil storage tank and enable the water at the bottom of the oil storage tank to completely flow into the dehydrator; The compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline that can return or press the oil separated in the dehydrator into the interior of the oil storage tank through pressure. A storage oil bag is directly connected above the front dehydration pipeline. The storage oil bag is connected to the buffer tank through a front buffer connection pipe. A first one-way valve is provided on the front buffer connection pipe. A return oil pipeline is also provided between the buffer tank and the end of the front dehydration pipeline adjacent to the oil storage tank. A second one-way valve is provided on the return oil pipeline. The top of the buffer tank is provided with a compressed air inlet. The compressed air inlet is connected to the air source of the compressed air through an intake pipeline and an intake valve. A piston that can move up and down is provided inside the buffer tank; Or, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline that can return or press the oil separated in the dehydrator into the interior of the oil storage tank through pressure. A storage oil bag is directly connected above the front dehydration pipeline. The storage oil bag is connected to the buffer tank through a front buffer connection pipe. A first one-way valve is provided on the front buffer connection pipe. A return oil pipeline is also provided between the buffer tank and the end of the front dehydration pipeline adjacent to the oil storage tank. A second one-way valve is provided on the return oil pipeline. The top of the buffer tank is provided with a breathing port. A piston that can move up and down is provided inside the buffer tank. A two-way pump is provided on the front buffer connection pipe near the oil inlet at the bottom of the buffer tank; Or, the compressed air-driven oil return device includes a buffer tank placed at the top of the front dehydration pipeline that can return or press the oil separated in the dehydrator into the interior of the oil storage tank through pressure. The buffer tank is directly connected to the front dehydration pipeline. A valve hole is provided at the oil inlet at the bottom of the buffer tank. A floating ball that can float in the oil liquid is provided above the valve hole inside the buffer tank. A number of limiting rods that can limit the upward movement of the floating ball are provided inside the buffer tank. The side wall position at the bottom of the buffer tank is connected to the front dehydration pipeline through a connecting pipeline. The top of the buffer tank is provided with a compressed air inlet. The compressed air inlet is connected to the air source of the compressed air through an intake pipeline and an intake valve. A piston that can move up and down is provided inside the buffer tank.

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