Oil-containing solid oil washing system and method

Abstract

The present invention relates to an oil-containing solid oil washing system and method. The technical scheme is as follows: the oil washing medium is tap water or seawater, the lower side of the dissolving and washing oil system is connected to a heating system, the top is connected to a low-temperature constant temperature cooling system through a pipeline, and a pumping system and a back pressure system are provided, the end of the low-temperature constant temperature cooling system is connected to an oil-water separation system, the tap water is heated to supercritical water by the heating system and then pumped to the dissolving and washing oil system, the oil-containing sludge in the dissolving and washing oil system is soaked, dissolved, and the oil in the oil-containing solid is extracted to form a supercritical aqueous solution of oil, and then pumped to the low-temperature constant temperature cooling system for cooling and then sent to the oil-water separation system to realize stratified separation. The beneficial effects of the present invention are: simple structure, good treatment effect, not only can the oil be recovered to the maximum extent, but also there is no secondary pollution, no need to use organic solvents, no need to add chemicals to the water, the washing water can be recycled, safe, environmentally friendly, economical and efficient.

Description

Technical Field

[0001] The invention relates to a hazardous waste treatment technology and a petroleum environmental protection technology, and in particular to an oil-containing solid oil washing system and method. Background Art

[0002] With the increasing demand for oil and the continuous development of the oil industry, the development of unconventional oil and gas resources has been expanding in breadth and depth, and the use of oil-based drilling fluids has become more and more widespread, resulting in more and more oily sludge and oily drill cuttings. In addition, various oily sludges are also produced during the conventional mining, gathering, transportation and refining of oil. Oily sludge entering the surface soil and water will cause serious pollution problems. Therefore, it is necessary to effectively separate the oil-solid from the oil-containing solid matter and reduce the oil content to an environmentally acceptable level before solid waste can be discharged into the environment.

[0003] Oily solids such as oily sludge and drill cuttings are hazardous wastes. Domestic and foreign researchers have developed and applied a variety of technologies for the treatment of oily solids, which can be generally summarized into four categories. The first category is high-temperature incineration (1200℃~1500℃). That is, the oily sludge and drill cuttings are collected first, and then incinerated in a special high-temperature incinerator. The incinerator needs to be equipped with dust removal and gas recovery devices, otherwise it will cause serious pollution to the atmosphere. The second category is the low-temperature pyrolysis process. This process is to desorb the oil substances in the oily sludge and drill cuttings by heating at low temperature (340℃), and then cool the oil and water converted to gas phase into liquid in a series of pipes with cooling water, separate the oil and water, and then separate the oil and water. This process has the following problems: washing and purification uses ammonia water, the washing volume is large, the wastewater generated is large, the subsequent wastewater treatment is complicated, and the oil-water separation treatment volume is large. The third category is the dissolution washing process. This process mainly uses an aqueous solution of a surfactant or an organic solvent to wash the oily sludge and drilling cuttings at a certain temperature and pressure, and then separates the solid and liquid and then the oil and water. This process will produce a large amount of wastewater and consume a large amount of organic solvents. The subsequent oil-water separation, wastewater treatment and waste organic solvent treatment processes are cumbersome and the operating costs are high. The fourth category is microbial treatment process technology. This technology requires the special cultivation of bacteria that can decompose oil substances and requires a complex domestication process. Microorganisms have a certain selectivity for oil products and the application conditions are relatively harsh. It is not yet mature and has not been promoted and applied industrially. In summary, except for the fourth method, which is still immature, the first three categories of process methods are relatively complicated, and the treatment process will consume more materials to varying degrees, and will cause secondary pollution to the environment.

[0004] Water is the most common and most polar inorganic solvent in nature. According to the principle of like dissolves like, highly polar water cannot be mixed with weakly polar oil. According to physical and chemical knowledge, as the temperature increases, the polarity of water decreases significantly. p -T Phase diagram, when it reaches the critical state (temperature 374.15℃, pressure reaches 22.1MPa), it becomes supercritical water, and its polarity becomes very weak, similar to organic solvents, so it can completely dissolve with oil to form a homogeneous solution. When the temperature and pressure are reduced to below the critical temperature and critical pressure of water, the difference in polarity between oil and water becomes larger, and oil and water cannot be mixed; due to the difference in density of oil and water, oil and water naturally separate. In addition, oil substances in oil-containing solids are prone to thermal desorption when the temperature exceeds 340℃, changing from an adsorbed / bound state to a free state, leaving the surface of solid pores, and are more easily miscible with high-temperature water, subcritical water, and supercritical water. Summary of the invention

[0005] The purpose of the present invention is to provide an oil-containing solid oil washing system and method in view of the above-mentioned defects in the prior art, so as to solve the problems of complex process, high material consumption and secondary pollution of the existing oil-containing solid treatment system.

[0006] The present invention mentions an oil-containing solid oil washing system, and its technical solution is: it includes six parts: a pumping system, a heating system, a dissolving oil washing system, a low-temperature constant temperature cooling system, a back pressure system, and an oil-water separation system. The oil washing medium is tap water. The lower side of the dissolving oil washing system is connected to the heating system, and the top is connected to the low-temperature constant temperature cooling system through a pipeline, and a pumping system and a back pressure system are provided. The end of the low-temperature constant temperature cooling system is connected to the oil-water separation system. The tap water is heated to supercritical water by the heating system and then pumped to the dissolving oil washing system. The oil-containing sludge in the dissolving oil washing system is soaked, dissolved, and the oil in the oil-containing solid is extracted to form a supercritical aqueous solution of oil, which is then pumped to the low-temperature constant temperature cooling system for cooling and then sent to the oil-water separation system to achieve stratified separation.

[0007] Preferably, the heating system uses a heater (2) for heating water to the temperature and pressure conditions of supercritical water, with a maximum heating temperature of 550° C. and a pressure resistance of 50 MPa.

[0008] Preferably, the low-temperature constant temperature cooling system comprises a condensing coil (5) and a low-temperature circulating water bath (6), which are used to cool the supercritical aqueous solution containing the oil to a temperature below the critical temperature and the critical pressure, and the temperature of the low-temperature circulating water bath (6) is adjustable between -10°C and 100°C.

[0009] Preferably, the back pressure system is composed of a back pressure valve (7), a buffer container (8) and a hand pump (9); the back pressure valve (7) is connected to the hand pump (9) via the buffer container (8) and is used to control the circulating pressure in the high temperature and high pressure container. The maximum working pressure is 50 MPa and can be pressurized by gas or liquid.

[0010] Preferably, the oil-water separation system is composed of an oil-water separation tank (10), a first pneumatic valve (11), an oil pump (12), a second pneumatic valve (13), and a water pump (14); the middle portion of the oil-water separation tank (10) is connected to the oil tank (15) via the first pneumatic valve (11) and the oil pump (12); and the lower portion of the oil-water separation tank (10) is connected to the water tank (4) via the second pneumatic valve (13) and the water pump (14).

[0011] Preferably, the above-mentioned dissolving and washing oil system adopts a high-temperature and high-pressure container (1), the inner cavity of the high-temperature and high-pressure container (1) is filled with oil-containing sludge, and is provided with a heating jacket (23) for soaking, dissolving, and extracting oil from the oil-containing sludge or rock cuttings to form a supercritical aqueous solution of oil. The high-temperature and high-pressure container used has a pressure resistance of 40 MPa, and the maximum heating temperature of the heating jacket (23) is 550°C.

[0012] Preferably, a third temperature gauge (25) is provided on the pipeline at the bottom of the high-temperature and high-pressure container (1), a four-way valve (18) is provided on the top of the high-temperature and high-pressure container (1), and a safety valve (16) and a vent valve (17) are provided on the four-way valve (18).

[0013] Preferably, the back pressure valve (7) is connected to a hand pump (9) via a buffer container (8).

[0014] Preferably, a pressure gauge (19) and a first temperature gauge (20) are provided between the condensing coil (5) and the back pressure valve (7).

[0015] The method for using the oil-containing solid oil washing system mentioned in the present invention comprises the following steps:

[0016] (i) The pumping system injects clean water into the heating system, and the heating system heats the clean water to a supercritical state;

[0017] (ii) injecting supercritical water into the oil dissolving and washing system under pumping pressure, wherein the supercritical water fully soaks, dissolves and extracts the oil in the oil-containing solid in the oil dissolving and washing system to form a supercritical aqueous solution of oil;

[0018] (iii) The supercritical aqueous solution of oil is pumped out from the dissolving and washing oil system and enters the low-temperature constant temperature cooling system. After being cooled to a temperature below the supercritical temperature, it enters the oil-water separation system through the back pressure system;

[0019] (iv) After the oil-water separation system realizes oil-water separation, the oil is recovered and the water enters the water tank, and then the next round of oil washing cycle is carried out through the pumping system until no oil is washed out and the oil content in the oily sludge and drill cuttings reaches the standard requirements for discharge into the environment.

[0020] The beneficial effects of the present invention are as follows: the pumping system of the present invention injects clean water into the heater to make the water reach a supercritical state, and then injects it into the dissolving and washing oil system, in which the supercritical water fully soaks, dissolves, and extracts the oil in the oil-containing solid to form a supercritical aqueous solution of oil, and then pumps it out from the upper outlet pipeline of the dissolving and washing oil system, enters a low-temperature constant temperature cooling system, and after being cooled to a temperature lower than the supercritical temperature, passes through a back pressure system, enters an oil-water separation system to achieve oil-water separation, and then the oil is recovered, and the water enters a water tank, and then the next round of oil washing circulation is carried out through the pumping system until no oil is washed out and the oil content in the oil-containing sludge and drill cuttings reaches the standard requirement for being discharged into the environment;

[0021] The structure and process flow of the invention are simple, and the treatment effect is good. Not only can the oil be recovered to the greatest extent, but there is no secondary pollution, and no organic solvents need to be used, and no chemical agents need to be added to the water. The washing water can be recycled, and it is safe, environmentally friendly, economical, and efficient. It can provide technical means for the harmless treatment of oily sludge and cuttings, the oil washing treatment of oil layer cores, and the research on improving the recovery rate of miscible phase drive. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Attached Figure 1 It is a schematic diagram of the structure of the present invention;

[0023] In the above figure: high temperature and high pressure container 1, heater 2, horizontal flow pump 3, water tank 4, condensing coil 5, low temperature circulating water bath 6, back pressure valve 7, buffer container 8, hand pump 9, oil-water separation tank 10, first pneumatic valve 11, oil pump 12, second pneumatic valve 13, water pump 14, oil tank 15, safety valve 16, vent valve 17, four-way valve 18, pressure gauge 19, first thermometer 20, pressure gauge 21, three-way valve 22, heating jacket 23, second thermometer 24, third thermometer 25, temperature controller 26. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0025] Example 1, refer to the attached Figure 1The present invention mentions an oil-containing solid oil washing system, which includes six parts: a pumping system, a heating system, a dissolving oil washing system, a low-temperature constant temperature cooling system, a back pressure system, and an oil-water separation system. The oil washing medium is tap water. The lower side of the dissolving oil washing system is connected to the heating system, and the top is connected to the low-temperature constant temperature cooling system through a pipeline, and is provided with a pumping system and a back pressure system. The end of the low-temperature constant temperature cooling system is connected to the oil-water separation system. The tap water is heated to supercritical water by the heating system and then pumped to the dissolving oil washing system. The oil-containing sludge in the dissolving oil washing system is soaked, dissolved, and the oil in the oil-containing solid is extracted to form a supercritical aqueous solution of oil, which is then pumped to the low-temperature constant temperature cooling system for cooling and then sent to the oil-water separation system to achieve stratified separation.

[0026] The heating system uses a heater 2, which is used to heat water to the temperature and pressure conditions of supercritical water, with a maximum heating temperature of 550°C and a pressure resistance of 50MPa; the above-mentioned low-temperature constant temperature cooling system includes a condensing coil 5 and a low-temperature circulating water bath 6, which are used to cool the supercritical aqueous solution containing oil to below the critical temperature and critical pressure, and the temperature of the low-temperature circulating water bath 6 is adjustable between -10°C and 100°C. The above-mentioned back pressure system is composed of a back pressure valve 7, a buffer container 8 and a hand pump 9. The back pressure valve 7 is connected to the hand pump 9 through the buffer container 8, which is used to control the circulating pressure in the high-temperature and high-pressure container, with a maximum working pressure of 50MPa, and can be pressurized by gas or liquid.

[0027] In addition, the above-mentioned oil-water separation system is composed of an oil-water separation tank 10, a first pneumatic valve 11, an oil pump 12, a second pneumatic valve 13, and a water pump 14. The middle part of the oil-water separation tank 10 is connected to the oil tank 15 through the first pneumatic valve 11 and the oil pump 12, and the lower part of the oil-water separation tank 10 is connected to the water tank 4 through the second pneumatic valve 13 and the water pump 14.

[0028] Furthermore, the dissolving and washing oil system adopts a high-temperature and high-pressure container 1, the inner cavity of which is filled with oily sludge and is provided with a heating jacket 23 for soaking, dissolving, and extracting oil from the oily sludge or rock cuttings to form a supercritical aqueous solution of oil. The high-temperature and high-pressure container used has a pressure resistance of 40 MPa, and the maximum heating temperature of the heating jacket 23 is 550°C.

[0029] In addition, a third thermometer 25 is provided on the pipeline at the bottom of the high-temperature and high-pressure container 1, a four-way valve 18 is provided on the top of the high-temperature and high-pressure container 1, and a safety valve 16 and a vent valve 17 are provided on the four-way valve 18; the back-pressure valve 7 is connected to the hand pump 9 through the buffer container 8; a pressure gauge 19 and a first thermometer 20 are provided between the condensing coil 5 and the back-pressure valve 7.

[0030] A further specific description is as follows. The present invention includes a high-temperature and high-pressure container 1, a heater 2, a horizontal flow pump 3, a water tank 4, a condensing coil 5, a low-temperature circulating water bath 6, a back pressure valve 7, an oil-water separation tank 10, a first pneumatic valve 11, an oil pump 12, a second pneumatic valve 13, a water pump 14, and an oil tank 15. The inner cavity of the high-temperature and high-pressure container 1 is filled with oily sludge and is provided with a heating jacket 23. The bottom is connected to the heater 2 through a pipeline, and the heater 2 is connected to the water tank 4 through the horizontal flow pump 3; the top of the high-temperature and high-pressure container 1 is connected to the condensing coil 5 through a pipeline, and the condensing coil 5 is arranged in the inner cavity of the low-temperature circulating water bath 6. The condensing coil 5 is then connected to the oil-water separation tank 10 through the back pressure valve 7. The middle part of the oil-water separation tank 10 is connected to the oil tank 15 through the first pneumatic valve 11 and the oil pump 12, and the lower part of the oil-water separation tank 10 is connected to the water tank 4 through the second pneumatic valve 13 and the water pump 14.

[0031] The working principle of the present invention is: the pumping system injects clean water into the heater to make the water reach a supercritical state, and then injects it into the dissolving and washing oil system. In the dissolving and washing oil system, supercritical water fully soaks, dissolves, and extracts the oil in the oil-containing solid to form a supercritical aqueous solution of oil, and then pumps it out from the upper outlet pipeline of the dissolving and washing oil system, enters the low-temperature constant temperature cooling system, and passes through the back pressure system after cooling to below the supercritical temperature, enters the oil-water separation system to achieve oil-water separation, oil recovery, water enters the water tank, and then the next round of oil washing cycle is carried out through the pumping system until no oil is washed out and the oil content in the oil-containing sludge and drill cuttings reaches the standard requirements for discharge to the environment. The working pressure of this device is normal pressure ~ 40MPa, and the working temperature is room temperature ~ 500℃. The technical principle of this device is to first heat ordinary water to a supercritical state, and use the principle of supercritical water and oil miscibility to achieve the purpose of cleaning oil-containing solids. The temperature is lower than the critical temperature, and the oil and water are naturally separated to achieve the effect of oil-water separation. There is no need to use organic solvents or add chemicals to the water, and the washing water can be recycled. The system and method are safe, environmentally friendly, economical, and efficient, and do not produce secondary pollution. They provide technical means for the harmless treatment of oily sludge and cuttings, oil washing treatment of oil layer cores, and research on improving the recovery rate of miscible phase drive.

[0032] The present invention provides a method for comprehensive treatment and recovery of oil-containing solids, comprising the following steps:

[0033] (1) In accordance with Figure 1 As shown, connect all systems, pipelines, tees, crosses, valves, and switches, and test the pressure with tap water to ensure airtightness;

[0034] (2) Place the oily sludge containing 4.6% oil into the sample chamber of the high-temperature and high-pressure container, tighten the upper and lower covers, connect the inlet and outlet pipelines and valves, fill the water tank and cooling water bath with water, and fill the containers and pipelines of each system, and remove the air in the pipelines, containers, and valves along the way;

[0035] (3) Turn on the heater power switch to heat the water. As the temperature rises, the pressure also increases accordingly;

[0036] (4) Turn on the heating power switch of the high-temperature and high-pressure container to heat the high-temperature and high-pressure container and keep the temperature not lower than 380°C;

[0037] (5) When the water temperature in the heater is higher than 400°C and the pressure is higher than 25 MPa, open the switch, three-way, four-way and valve in sequence to allow the high-temperature and high-pressure supercritical water to fully soak, dissolve and extract the oil in the oil-containing solid in the sample chamber of the high-temperature and high-pressure container to form a supercritical aqueous solution of oil;

[0038] (6) The oil-water miscible solution then flows out from the outlet pipeline on the upper part of the high-temperature and high-pressure container and enters the low-temperature constant-temperature cooling water bath. After being cooled to a temperature below the critical temperature, it passes through the back-pressure valve and enters the oil-water separation pipe.

[0039] (7) In the oil-water separation pipe, oil and water are naturally separated due to density difference, the oil is recovered, and the water enters the water tank;

[0040] (8) The recovered water in the water tank is pumped through a horizontal flow pump for the next round of oil washing cycle until no oil is washed out and the oil content in the oily sludge is 0.08%.

[0041] Embodiment 2: An oil-containing solid oil washing system mentioned in the present invention comprises six parts: a pumping system, a heating system, a dissolving oil washing system, a low-temperature constant temperature cooling system, a back pressure system and an oil-water separation system. The oil washing medium is seawater. The lower side of the dissolving oil washing system is connected to the heating system, and the top is connected to the low-temperature constant temperature cooling system through a pipeline. A pumping system and a back pressure system are provided. The end of the low-temperature constant temperature cooling system is connected to the oil-water separation system. Tap water is heated to supercritical water by the heating system and then pumped to the dissolving oil washing system. The oil-containing drill cuttings in the dissolving oil washing system are soaked, dissolved and the oil in the oil-containing drill cuttings is extracted to form a supercritical aqueous solution of oil, which is then pumped to the low-temperature constant temperature cooling system for cooling and then sent to the oil-water separation system to achieve stratified separation.

[0042] The present invention provides a method for comprehensive treatment and recovery of oil-containing solids, comprising the following steps:

[0043] (1) In accordance with Figure 1 As shown, connect all systems, pipelines, tees, crosses, valves, and switches, and test the pressure with seawater to ensure airtightness;

[0044] (2) Load the oil-containing drill cuttings with an oil content of 4.8% into the sample chamber of the high-temperature and high-pressure container, tighten the upper and lower covers, connect the inlet and outlet pipelines and valves, fill the water tank and cooling water bath with seawater and fill the containers and pipelines of each system, and remove the air in the pipelines, containers, and valves along the way;

[0045] (3) Turn on the heater power switch to heat the seawater. As the temperature rises, the pressure also increases accordingly;

[0046] (4) Turn on the heating power switch of the high-temperature and high-pressure container to heat the high-temperature and high-pressure container and keep the temperature not lower than 380°C;

[0047] (5) When the water temperature in the heater is higher than 400°C and the pressure is higher than 25 MPa, open the switch, three-way, four-way and valve in sequence to allow the high-temperature and high-pressure supercritical water to fully soak, dissolve and extract the oil in the oil-containing solid in the sample chamber of the high-temperature and high-pressure container to form a supercritical aqueous solution of oil;

[0048] (6) The oil-water miscible solution then flows out from the outlet pipeline on the upper part of the high-temperature and high-pressure container and enters the low-temperature constant-temperature cooling water bath. After being cooled to a temperature below the critical temperature, it passes through the back-pressure valve and enters the oil-water separation pipe.

[0049] (7) In the oil-water separation pipe, oil and water are naturally separated due to density difference, the oil is recovered, and the water enters the water tank;

[0050] (8) The recovered water in the water tank is pumped through a horizontal flow pump for the next round of oil washing cycle until no oil is washed out and the oil content in the oily sludge is 0.07%.

[0051] The above are only some preferred embodiments of the present invention. Any person skilled in the art may modify the above technical solutions or modify them into equivalent technical solutions. Therefore, any simple modification or equivalent replacement made according to the technical solution of the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. An oil-containing solid oil washing system, characterized by: It includes six parts: a pumping system, a heating system, a dissolving and washing oil system, a low-temperature constant temperature cooling system, a back pressure system, and an oil-water separation system. The oil washing medium is tap water or seawater. The lower side of the dissolving and washing oil system is connected to the heating system, and the top is connected to the low-temperature constant temperature cooling system through a pipeline. The system is also provided with a pumping system and a back pressure system. The end of the low-temperature constant temperature cooling system is connected to the oil-water separation system. The tap water or seawater is heated to supercritical water by the heating system and then pumped to the dissolving and washing oil system. The oil-containing sludge in the dissolving and washing oil system is soaked, dissolved, and the oil in the oil-containing solid is extracted to form a supercritical water solution of oil, which is then pumped to the low-temperature constant temperature cooling system for cooling and then sent to the oil-water separation system to achieve stratified separation. The heating system uses a heater (2) for heating water to the temperature and pressure conditions of supercritical water, with a maximum heating temperature of 550° C. and a pressure resistance of 50 MPa; The low-temperature constant temperature cooling system comprises a condensing coil (5) and a low-temperature circulating water bath (6), which is used to cool the supercritical aqueous solution containing oil to a temperature below the critical temperature and the critical pressure, and the temperature of the low-temperature circulating water bath (6) is adjustable between -10°C and 100°C; The back pressure system is composed of a back pressure valve (7), a buffer container (8) and a hand pump (9). The back pressure valve (7) is connected to the hand pump (9) via the buffer container (8) and is used to control the circulation pressure in the high temperature and high pressure container. The maximum working pressure is 50 MPa and can be pressurized by gas or liquid. The oil-water separation system is composed of an oil-water separation tank (10), a first pneumatic valve (11), an oil pump (12), a second pneumatic valve (13), and a water pump (14); the middle portion of the oil-water separation tank (10) is connected to the oil tank (15) via the first pneumatic valve (11) and the oil pump (12); and the lower portion of the oil-water separation tank (10) is connected to the water tank (4) via the second pneumatic valve (13) and the water pump (14); The dissolving and washing oil system adopts a high-temperature and high-pressure container (1), the inner cavity of which is filled with oily sludge and provided with a heating jacket (23) for soaking, dissolving, and extracting oil from the oily sludge or rock cuttings to form a supercritical aqueous solution of oil. The high-temperature and high-pressure container has a pressure resistance of 40 MPa, and the maximum heating temperature of the heating jacket (23) is 550°C.

2. The oil-containing solid oil washing system according to claim 1 is characterized in that: A third temperature gauge (25) is provided on the pipeline at the bottom of the high-temperature and high-pressure container (1), a four-way valve (18) is provided on the top of the high-temperature and high-pressure container (1), and a safety valve (16) and a vent valve (17) are provided on the four-way valve (18).

3. The oil-containing solid oil washing system according to claim 1 is characterized in that: The back pressure valve (7) is connected to a hand pump (9) via a buffer container (8).

4. The oil-containing solid oil washing system according to claim 1 is characterized in that: A pressure gauge (19) and a first temperature gauge (20) are provided between the condensing coil (5) and the back pressure valve (7).

5. A method for using the oil-containing solid oil washing system according to any one of claims 1 to 4, characterized in that: The process includes: (i) The pumping system injects clean water into the heating system, and the heating system heats the clean water to a supercritical state; (ii) injecting supercritical water into the oil dissolving and washing system under pumping pressure, wherein the supercritical water fully soaks, dissolves and extracts the oil in the oil-containing solid in the oil dissolving and washing system to form a supercritical aqueous solution of oil; (iii) The supercritical aqueous solution of oil is pumped out from the dissolving and washing oil system and enters the low-temperature constant temperature cooling system. After being cooled to a temperature below the supercritical temperature, it enters the oil-water separation system through the back pressure system; (iv) After the oil-water separation system realizes oil-water separation, the oil is recovered and the water enters the water tank, and then the next round of oil washing cycle is carried out through the pumping system until no oil is washed out and the oil content in the oily sludge and drill cuttings reaches the standard requirements for discharge into the environment.

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