Oil sludge subcritical thermal hydrolysis and oxidation process and related equipment

Abstract

The present invention discloses an oil-water-solid separation tower, comprising an upper cylinder and a lower cylinder; the diameter ratio of the upper cylinder to the lower cylinder is greater than or equal to 2; the interior of the upper cylinder forms an outer cylinder, an inner cylinder is provided within the outer cylinder, and an oil separator is provided between the outer cylinder and the inner cylinder; the wall of the oil separator partially overlaps the wall of the inner cylinder, and the wall of the oil separator is higher than the wall of the inner cylinder as a whole; the space within the inner cylinder communicates with the space within the outer cylinder through the bottom space of the oil separator; the bottom of the inner cylinder is a conical structure with a hole at the bottom; two-stage agitators are respectively provided in the inner cylinder and the lower cylinder; the oil-water-solid separation tower is further provided with an annular partition disposed between the inner cylinder and the outer cylinder to partially isolate the space within the outer cylinder from the space within the lower cylinder. The present invention also discloses an oil sludge subcritical thermal hydrolysis and oxidation process using the oil-water-solid separation tower. This solves the problems of easy clogging, coking, scaling, and secondary pollution during oil sludge treatment.

Description

Technical Field

[0001] The invention relates to a subcritical thermal hydrolysis and oxidation process for oil sludge and related equipment. Background Art

[0002] Oil production and processing generate significant amounts of sludge. As oil production increases, so does the volume of hazardous waste, including various types of sludge. This waste primarily consists of oilfield sludge, tank sludge, and refinery sludge. Furthermore, historically, due to technological limitations, some sludge has been stored. Oilfield companies, refineries, and chemical companies generate significant amounts of sludge annually.

[0003] Currently, oil sludge treatment technologies include chemical thermal cleaning, sludge thermal drying, sludge pyrolysis, sludge incineration, and biological sludge treatment. Chemical thermal cleaning primarily treats oilfield sludge, but the treated sludge has a high oil content, is a hazardous waste, and generates significant amounts of wastewater. Sludge pyrolysis and incineration technologies utilize high-temperature treatment, requiring large amounts of fuel, resulting in high energy consumption and the potential for the production of carcinogens such as dioxins. Biological sludge treatment offers inconsistent results, is subject to numerous constraints, and requires a long treatment time.

[0004] Some existing technologies have low automation levels, some pose safety risks, and some have high operating costs. Some companies also outsource their sludge treatment, but this is expensive. Therefore, all companies urgently need a safe, economical, and efficient sludge treatment technology to achieve sludge reduction, resource utilization, and harmless treatment.

[0005] Oil sludge has a complex composition. Besides mud, sand, and water, its primary pollutants are oils, including alkanes, cycloalkanes, aromatic hydrocarbons, asphalt colloids, and other substances. It also contains heavy metals and inorganic salts. Oil, water, and mud are intermingled, creating water-in-oil, oil-in-water, mud-in-oil, and oil-in-mud. Colloidal particles also form in the sludge, making it highly viscous and difficult to handle. Summary of the Invention

[0006] To overcome the above-mentioned shortcomings of the prior art, the present invention provides a subcritical thermal hydrolysis and oxidation process system and oil-water-solid separation equipment for the safe and efficient treatment of oily sludge. The process system is safe and environmentally friendly, does not produce carcinogens such as dust and dioxins, is not prone to coking and scaling, has a significant separation effect, and the oil content of the treated sludge is less than 0.3%, which can effectively reduce the difficulty of resource recovery and harmless treatment of oily sludge.

[0007] The technical solution of the present invention is summarized as follows: A subcritical thermal hydrolysis and oxidation process system for oil sludge includes an oil sludge pretreatment unit, a subcritical thermal hydrolysis unit, a subcritical thermal oxidation unit, a water-solid centrifugal separation unit, and a VOCs waste gas pretreatment unit, wherein the subcritical thermal hydrolysis unit uses an oil-water-solid separation tower. In the oil-water-solid separation tower, the oil sludge after subcritical thermal hydrolysis is transported to the inner cylinder of the separation tower through a pipeline, and larger solids will directly fall into the bottom of the outer cylinder through the bottom of the inner cylinder. Most of the oil and water will flow through the inner cylinder to the outer cylinder, and liquid separation and separation will be carried out in the outer cylinder, and the solids are mainly concentrated at the bottom of the outer cylinder.

[0008] As one aspect of the present invention, it relates to an oil-water-solid separation tower for oil sludge subcritical thermal hydrolysis and oxidation process, comprising: an upper cylinder 1 and a lower cylinder 2; the diameter ratio of the upper cylinder 1 to the lower cylinder 2 is greater than or equal to 2; the interior of the upper cylinder 1 is surrounded by an outer cylinder 9, an inner cylinder 7 is provided inside the outer cylinder 9, and an oil separation cylinder 8 is provided between the outer cylinder 9 and the inner cylinder 7; in the vertical direction, the cylinder wall of the oil separation cylinder 8 partially overlaps with the cylinder wall of the inner cylinder 7, and the cylinder wall of the oil separation cylinder 8 is higher than the cylinder wall of the inner cylinder 7. The inner cylinder 7 is connected to the outer cylinder 9 through the bottom of the oil separator 8. The inner cylinder 7 has a conical bottom with an opening. The inner cylinder 7 and the lower cylinder 2 are each equipped with a two-stage agitator 3, which can rotate coaxially. The oil-water-solid separation tower is also equipped with an annular baffle 15, which is located between the inner cylinder 7 and the outer cylinder 9 to partially isolate the inner cylinder 9 from the inner cylinder 2. The gap between the annular baffle 15 and the outer cylinder allows solids to fall into the outer cylinder 2. In a specific embodiment, the oil separator 8 is fixedly connected to the bracket of the outer cylinder 9, the inner cylinder 7 is fixedly connected to the bracket of the oil separator 8, and the feed center pipe 6 is fixedly connected to the bracket of the inner cylinder 7.

[0009] In a specific embodiment, the oil-water-solid separation tower is further provided with a central feed pipe 6 for feeding materials into the inner cylinder 7 .

[0010] In a specific embodiment, the diameter of the inner cylinder 7 is smaller than the diameter of the lower cylinder 2 .

[0011] In a specific embodiment, an oil separation inclined plate 4 is provided on the outer cylinder 9. The oil separation inclined plate 4 is arranged in a ring below the oil outlet 10. The angle between the inclined plate and the horizontal is 30-60 degrees, which can effectively increase the oil separation effect.

[0012] In a specific embodiment, the oil-water-solid separation tower is further provided with a feed pipe port 5 , an oil outlet 10 , a water outlet 12 and a mud discharge port 13 .

[0013] As another aspect of the present invention, it relates to an oil sludge subcritical thermal hydrolysis and oxidation process system, which includes the above-mentioned oil-water-solid separation tower.

[0014] In a specific embodiment, in the above-mentioned oil sludge subcritical thermal hydrolysis and oxidation process system, the oil sludge produced by subcritical thermal hydrolysis is transported to the feed pipe port 5 of the oil-water-solid separation tower through a pipeline after pressure reduction and flash evaporation, and enters the inner cylinder 7 through the feed center pipe 6.

[0015] As another aspect of the present invention, it relates to a sludge subcritical thermal hydrolysis and oxidation process, comprising an sludge pretreatment unit, a subcritical thermal hydrolysis unit, a subcritical thermal oxidation unit, a water-solid centrifugal separation unit and a VOCs waste gas pretreatment unit, wherein the subcritical thermal hydrolysis unit uses the oil-water-solid separation tower.

[0016] According to an embodiment of the present invention, the oil sludge pretreatment unit uses a vibrating screen and a ball mill to screen out soft and large debris such as plastic bags and rags, and deeply grinds the oil sludge to avoid clogging.

[0017] According to an embodiment of the present invention, the subcritical thermal hydrolysis unit first mixes and conditions the oil sludge. After the recycled water is mixed with the oil sludge, steam produced as a byproduct of the primary flash tank is introduced through a nozzle into the conditioning tank to preheat and condition the oil sludge. The conditioned oil sludge is transported to the thermal hydrolysis reactor via a centrifugal pump. The pressure is controlled at 4.0-8.5 MPaG and the temperature is controlled at 250-300°C. Under subcritical conditions, the residence time is 1 hour, and the oil on the solid surface of the oil sludge and contained therein is extracted into the water by the subcritical water.

[0018] According to an embodiment of the present invention, the oil sludge after thermal hydrolysis is flashed and cooled, the flash by-product steam is recycled to the blending tank, and the liquid phase is transported to the oil-water-solid separation tower. Through the inner and outer cylinders and two-stage stirring, the separation of oil, water and solid is achieved. The upper layer is the oil phase, the middle part is the recycled water layer, and the bottom is a slurry of mud and water with an oil content of about 1-2%, which flows by gravity to the oxidation unit mud tank.

[0019] According to an embodiment of the present invention, the lower cylinder and the inner cylinder of the oil-water-solid separation tower are provided with an agitator with a stirring rate of 3-5 r / min; the aperture of the opening at the bottom of the conical structure at the bottom of the inner cylinder is 1 / 5 of the feed pipe; the liquid level of the inner cylinder is controlled at 1 / 3 from the top, and the residence time of the oil sludge in the separation tower is 1 hour.

[0020] According to an embodiment of the present invention, the subcritical thermal oxidation unit re-delivers the oil sludge containing 1-3% oil, and the water content after derivation is about 80-95%. The oil sludge slurry is preheated with the steam produced as a by-product of the secondary flash tank, and then transported to the subcritical thermal oxidation reactor through a centrifugal pump. The pressure is controlled at 4.0 MPaG and the temperature is controlled at 250°C. Under the subcritical state, the residence time is 0.5h. An oxidant (hydrogen peroxide or ozone) is added to the oxidation reactor, and the solid surface of the oil sludge and the oil encapsulated therein react with the oxidant (hydrogen peroxide or ozone) under the subcritical state and decompose. The macromolecular substances are decomposed into small molecular substances, and some small molecular substances are oxidized into carbon dioxide and water. The sludge after the oxidation reaction enters the secondary flash tank, the gas phase steam is reused, and the liquid phase is centrifuged.

[0021] According to an embodiment of the present invention, the slurry that has undergone subcritical oxidation is flash evaporated and decompressed and then transported to a centrifuge for dehydration. The dehydrated slurry is then transported to a storage yard via a screw conveyor, and the separated water is reused.

[0022] According to an embodiment of the present invention, the VOCs gas from the oil-water-solid separation tower and the secondary flash tank is transported to the scrubbing tower for pre-treatment, and the non-condensable gas is sent to the VOCs treatment facility for deep treatment to meet emission standards.

[0023] The present invention develops a process flow for subcritical thermal hydrolysis and oxidation of oil sludge, which solves the problems of easy clogging, coking, scaling and secondary pollution in the oil sludge treatment process.

[0024] The present invention utilizes the physical property changes of water in the subcritical state, such as the reduction of dielectric constant, polarity, viscosity and diffusion coefficient, to extract the oil phase in the sludge, thereby realizing resource utilization and harmless treatment of the sludge.

[0025] The present invention develops a new oil-water-solid separation tower, which can avoid the solid phase deposition of oil sludge while achieving efficient separation of oil and water; increasing the diameter ratio of the upper cylinder to the lower cylinder of the oil-water-solid separation tower will help to separate the oil from the sludge at the bottom of the separation tower; while ensuring the accumulation of sludge at the bottom of the separation tower, the lower the agitator speed, the better the oil separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 1. Figure 1 The invention relates to a subcritical thermal hydrolysis process system for treating oil sludge.

[0027] It includes: a. oil sludge pretreatment unit, b. subcritical thermal hydrolysis unit, c. subcritical thermal oxidation unit, d. water-solid centrifugal separation unit, e. VOCs waste gas pretreatment unit.

[0028] 2. Figure 2 It is a structural schematic diagram of an oil-water-solid separation tower of the present invention.

[0029] In the figure, 1. upper cylinder, 2. lower cylinder, 3. two-stage agitator, 4. oil separation inclined plate, 5. feed pipe mouth, 6. feed center pipe, 7. inner cylinder, 8. oil separation cylinder, 9. outer cylinder, 10. oil outlet, 11. oil-water outlet, 12. water outlet, 13. mud discharge port, 14. VOCs discharge port, 15. annular partition. DETAILED DESCRIPTION

[0030] Example 1

[0031] See also Figure 1 This embodiment discloses a subcritical thermal hydrolysis process system for treating oil sludge, including an oil sludge pretreatment unit a, a subcritical thermal hydrolysis unit b, a subcritical thermal oxidation unit c, a water-solid centrifugal separation unit d, and a VOCs waste gas pretreatment unit e.

[0032] The sludge pretreatment unit (a) uses a vibrating screen to initially screen and sort the incoming sludge, removing larger, harder debris like rocks and steel pipes and softer debris like plastic bags and rags to prevent clogging. The screened sludge is then fed into a ball mill, where recycled water is added for wet grinding and refining, reducing the particle size to less than 0.1mm. The sludge is then fed into a blending tank, where recycled water is added to adjust the sludge slurry concentration to approximately 80-95% water content.

[0033] Subcritical thermal hydrolysis unit b first mixes and conditions the oil sludge. After the recycled water is mixed with the oil sludge, steam from the byproduct of the first-stage flash tank is introduced through a nozzle into the conditioning tank to preheat and condition the oil sludge. This not only heats the oil sludge but also prevents it from depositing on the heating pipe. The conditioned oil sludge is transported to the thermal hydrolysis reactor via a centrifugal pump. The pressure is controlled at 4.0 MPaG and the temperature is controlled at 250°C. Under subcritical conditions for a residence time of 1 hour, the oil on the surface of the oil sludge solids and contained therein is extracted into the water by the subcritical water, reducing the oil content in the oil sludge solids. The oily sludge after thermal hydrolysis enters the first-stage flash tank for pressure reduction and flash evaporation. The by-product steam is recycled to the blending tank to recover the heat. The liquid phase is transported to the oil-water-solid separation tower. Through the inner and outer cylinders and two-stage stirring, the oil, water and solid separation is efficiently achieved. The upper layer is the oil phase, the middle is the recycled water layer, and the bottom is the mud water slurry with an oil content of about 2%, which flows by gravity to the oxidation unit mud tank.

[0034] See also Figure 2This embodiment discloses an oil-water solid separation tower. After the oil sludge passes through a subcritical thermal hydrolysis reactor, the surface of the sludge solids and the oil contained therein are extracted into the aqueous phase. After pressure reduction and flash evaporation, the sludge is transported to the feed pipe 5 of the oil-water solid separation tower through a pipeline. The sludge discharge port 13 is closed. When oil is discharged from the oil outlet 10, the sludge discharge port 13 is opened and the sludge enters the inner cylinder 7 through the feed center pipe 6. Most of the solids fall into the lower cylinder 2 through the opening at the bottom of the inner cylinder 7. The oil and water phases flow through the gap between the inner cylinder 7 and the oil separator 8, forming a plug flow overflow into the outer cylinder 9. A small amount of solids in the oil and water can fall into the lower cylinder 2 through the gap between the bottom of the annular partition 15 and the outer cylinder 9. Because the upper cylinder 1 is much larger in diameter than the lower cylinder 2, and under the obstruction of the oil separator 8 and the annular partition 15, the stirred slurry has little effect on the oil and water in the outer cylinder 9. The oil and water in the outer cylinder 9 are relatively static, creating good conditions for oil-water separation. The outer cylinder 9 is not provided with an oil separation inclined plate 4, which can further promote oil-water separation. The oil phase overflows from the oil outlet 10, the water phase is discharged from the water outlet 12, the solid phase is discharged from the mud discharge port 13, and the gas phase is discharged from the VOCs discharge port.

[0035] The diameter ratio of the upper cylinder 1 and the lower cylinder 2 of the oil-water-solid separation tower is 2; the lower cylinder 2 and the inner cylinder 7 are provided with a stirrer with a stirring rate of 5r / min; the bottom of the inner cylinder 7 is a conical structure, and the aperture of the bottom opening is 1 / 5 of the diameter of the feed pipe opening 5; an annular partition 15 is provided on the outer side of the bottom of the inner cylinder 7 to reduce the influence of the two-stage stirrer 3 on oil separation; the liquid level of the feed center pipe 6 is controlled at 1 / 3 of the distance from the top, and the residence time of the oil sludge in the oil-water-solid separation tower is about 1h.

[0036] Hot produced water is added to the mud tank of the subcritical thermal oxidation unit C, and the 3% oil-containing sludge discharged from the bottom of the oil-water-solid separation tower is redistributed. After redistribution, the water content is about 80-95%. The oil sludge slurry is preheated with the steam produced as a by-product of the secondary flash tank and then transported to the subcritical thermal oxidation reactor through a centrifugal pump. A heating pipe is set up in the oxidation reactor, which can not only heat the mud but also prevent the mud from being deposited on the heating pipe. The heating medium is high-pressure steam or heat-conducting oil heat medium. The pressure is controlled at 4.0MPaG and the temperature is controlled at 250℃. Under subcritical state, the residence time is 0.5h. An oxidant (hydrogen peroxide or ozone) is added to the oxidation reactor. The solid surface of the sludge and the oil wrapped therein react with the oxidant (hydrogen peroxide or ozone) under subcritical state and decompose. The macromolecular substances are decomposed into small molecular substances, and some small molecular substances are oxidized into carbon dioxide and water, further reducing the oil content of the sludge. The sludge after the oxidation reaction enters the secondary flash tank, the gas phase steam is reused, and the liquid phase is centrifuged.

[0037] In the water-solid separation unit d, the slurry after subcritical oxidation is flashed and decompressed and then transported to the centrifuge for dehydration. The separated solid material has a moisture content of about 75% and an oil content of about 0.3%. The dehydrated slurry is sent to the storage yard through a screw conveyor, and the separated water is reused.

[0038] In the VOCs waste gas pretreatment unit e, the VOCs gas from the oil-water-solid separation tower and the secondary flash tank is transported to the washing tower for pretreatment, and the non-condensable gas is sent to the VOCs treatment facility for deep treatment to meet the emission standards.

[0039] Example 2

[0040] Based on the subcritical thermal hydrolysis process system for treating oil sludge and the oil-water-solid separation tower of Example 1, the process operating parameters and the structural design of the oil-water-solid separation tower of Example 1 were adjusted.

[0041] The sludge pretreatment unit a is described in the above embodiment 1.

[0042] In the subcritical thermal hydrolysis unit b, the operating pressure of the thermal hydrolysis reactor was gradually increased to 8.5 MPa, the temperature was controlled at 300°C, and the residence time was 1 h in the subcritical state.

[0043] The oil sludge after thermal hydrolysis enters the first-stage flash tank for pressure reduction and flash evaporation. The by-product steam is recycled to the blending tank to recover the heat. The liquid phase is transported to the oil-water-solid separation tower, and the separation of oil, water and solid is achieved through the inner and outer cylinders and two-stage stirring.

[0044] In Example 2, the diameter ratio of the upper cylinder 1 to the lower cylinder 2 of the oil-water-solid separation tower is 4. The lower cylinder 2 and inner cylinder 7 are equipped with a stirrer at a stirring rate of 3 r / min. The bottom of the inner cylinder 7 has a conical structure, and the bottom opening has an aperture diameter that is 1 / 5 of the diameter of the feed pipe 5. An annular baffle 15 is installed on the outer side of the bottom of the inner cylinder 7 to reduce the impact of the two-stage agitator 3 on oil separation. The liquid level of the central feed pipe 6 is controlled at 1 / 3 of the distance from the top. The residence time of the oil-sludge slurry in the oil-water-solid separation tower is approximately 1 hour. The upper layer of the oil-water-solid separation tower is the oil phase, the middle layer is the recycled water layer, and the bottom layer is the mud slurry with an oil content of approximately 1%, which flows by gravity to the slurry tank of the oxidation unit.

[0045] Subcritical thermal oxidation unit c, see the description of the above embodiment 1.

[0046] Water-solid separation unit d, referring to the description of the above embodiment 1, the separated solid material has a water content of about 75% and an oil content of about 0.2%. After subcritical thermal hydrolysis, oil-water-solid separation and subcritical thermal oxidation treatment, the solid oil content is better than that of Example 1.

[0047] For the VOCs waste gas pretreatment unit e, see the description of the above embodiment 1.

[0048] Example 3

[0049] Based on the subcritical thermal hydrolysis process system for treating oil sludge and the oil-water-solid separation tower of Example 1, the process operating parameters and the structural design of the oil-water-solid separation tower of Example 1 were adjusted.

[0050] The sludge pretreatment unit a is described in the above embodiment 1.

[0051] Subcritical thermal hydrolysis unit b: the operating pressure of the thermal hydrolysis reactor is 4.0 MPa, the temperature is controlled at 250°C, and the residence time is 1 hour in the subcritical state.

[0052] The oil sludge after thermal hydrolysis enters the first-stage flash tank for pressure reduction and flash evaporation. The by-product steam is recycled to the blending tank to recover the heat. The liquid phase is transported to the oil-water-solid separation tower, and the separation of oil, water and solid is achieved through the inner and outer cylinders and two-stage stirring.

[0053] In Example 3, the diameter ratio of the upper cylinder 1 to the lower cylinder 2 of the oil-water-solid separation tower is 1.2. The lower cylinder 2 and inner cylinder 7 are equipped with a stirrer at a stirring rate of 5 r / min. The bottom of the inner cylinder 7 is a tapered structure, and the bottom opening diameter is 1 / 5 of the diameter of the feed pipe 5. An annular baffle 15 is installed on the outer side of the bottom of the inner cylinder 7 to reduce the impact of the two-stage agitator 3 on oil separation. The liquid level of the feed center pipe 6 is controlled at 1 / 3 of the distance from the top. The residence time of the oil-sludge slurry in the oil-water-solid separation tower is approximately 1 hour. The upper layer of the oil-water-solid separation tower is the oil phase, the middle layer is the recycled water layer, and the bottom layer is the mud slurry with an oil content of approximately 5%. The oil separation effect is significantly less than that of Example 1. The mud at the bottom of the separation tower flows by gravity to the oxidation unit mud tank.

[0054] Subcritical thermal oxidation unit c, see the description of the above embodiment 1.

[0055] Water-solid separation unit d, referring to the description of the above embodiment 1, the separated solid material has a water content of about 75% and an oil content of about 0.8%. After subcritical thermal hydrolysis, oil-water-solid separation and subcritical thermal oxidation treatment, the solid oil content cannot meet the requirements of the industrial solid waste landfill pollution control standard and needs to be reprocessed.

[0056] For the VOCs waste gas pretreatment unit e, see the description of the above embodiment 1.

[0057] It should be further noted that the above embodiments are intended to illustrate the technical solutions of the present invention and are not intended to be limiting. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the technical concept and scope of the technical solutions of the present invention and should be encompassed by the claims of the present invention.

Claims

1. An oil-water-solid separation tower for oil sludge subcritical thermal hydrolysis and oxidation process, characterized in that: include: An upper cylinder 1 and a lower cylinder 2; the diameter ratio of the upper cylinder 1 to the lower cylinder 2 is greater than or equal to 2; the interior of the upper cylinder 1 is surrounded by an outer cylinder 9, an inner cylinder 7 is provided inside the outer cylinder 9, and an oil separator 8 is provided between the outer cylinder 9 and the inner cylinder 7; the wall of the oil separator 8 partially overlaps with the wall of the inner cylinder 7, and the wall of the oil separator 8 is higher than the wall of the inner cylinder 7 as a whole; the space inside the inner cylinder 7 is connected with the space inside the outer cylinder 9 through the bottom space of the oil separator 8; the bottom of the inner cylinder 7 is a conical structure with an opening at the bottom; a two-stage agitator 3 is respectively provided in the inner cylinder 7 and the lower cylinder 2; the oil-water-solid separation tower is also provided with an annular partition 15, which is provided between the inner cylinder 7 and the outer cylinder 9 to partially isolate the space inside the outer cylinder 9 from the space inside the lower cylinder 2.

2. The oil-water-solid separation tower according to claim 1, characterized in that: A central feed pipe 6 is also provided for feeding materials into the inner cylinder 7 .

3. The oil-water-solid separation tower according to claim 1, characterized in that: The diameter of the inner cylinder 7 is smaller than the diameter of the lower cylinder 2 .

4. The oil-water-solid separation tower according to claim 1, characterized in that: The outer cylinder 9 is provided with an oil separation inclined plate 4 .

5. The oil-water-solid separation tower according to claim 1, characterized in that: The oil-water-solid separation tower is further provided with a feed pipe port 5 , an oil outlet 10 , a water outlet 12 and a mud discharge port 13 .

6. A subcritical thermal hydrolysis and oxidation process system for oil sludge, characterized in that: It comprises the oil-water-solid separation tower described in any one of claims 1-5.

7. The oil sludge subcritical thermal hydrolysis and oxidation process system according to claim 6, characterized in that: The oil sludge produced by subcritical thermal hydrolysis is transported to the feed pipe port 5 of the oil-water-solid separation tower through a pipeline after pressure reduction and flash evaporation, and enters the inner cylinder 7 through the feed central pipe 6.

8. A subcritical thermal hydrolysis and oxidation process for oil sludge, characterized in that: The method comprises an oil sludge pretreatment unit, a subcritical thermal hydrolysis unit, a subcritical thermal oxidation unit, a water-solid centrifugal separation unit and a VOCs waste gas pretreatment unit, wherein the subcritical thermal hydrolysis unit uses the oil-water-solid separation tower according to any one of claims 1 to 5.

9. The oil sludge subcritical thermal hydrolysis and oxidation process according to claim 8, characterized in that: The oil sludge pretreatment unit uses a vibrating screen and a ball mill to screen out soft and large debris such as plastic bags and rags, and deeply grinds the oil sludge to avoid clogging.

10. The oil sludge subcritical thermal hydrolysis and oxidation process according to claim 8, characterized in that: The subcritical thermal hydrolysis unit first mixes and conditions the oil sludge, and the conditioned oil sludge is transported to the thermal hydrolysis reactor through a centrifugal pump. The pressure is controlled at 4.0-8.5 MPaG, the temperature is controlled at 250-300°C, and the residence time is 1 hour in the subcritical state.

11. The oil sludge subcritical thermal hydrolysis and oxidation process according to claim 10, characterized in that: The oil sludge after thermal hydrolysis is flashed and cooled, and the liquid phase is transported to the oil-water-solid separation tower to achieve oil-water-solid separation. The upper layer is the oil phase, the middle layer is the recycled water layer, and the bottom is the mud and water sludge.

12. The oil sludge subcritical thermal hydrolysis and oxidation process according to claim 11, characterized in that: The stirring speed of the stirrers of the lower cylinder and the inner cylinder of the oil-water-solid separation tower is 3-5 r / min.

13. The oil sludge subcritical thermal hydrolysis and oxidation process according to claim 8, characterized in that: In the subcritical thermal oxidation unit, the pressure of the subcritical thermal oxidation reactor is controlled at 4.0 MPaG, the temperature is controlled at 250° C., the residence time is 0.5 h in the subcritical state, and an oxidant is added into the subcritical thermal oxidation reactor.

Images