A method and system for treating oil-containing sludge

Abstract

The present application belongs to the field of sludge treatment, and relates to a treatment method and system for oily sludge. The treatment method comprises the following steps: S1. Pretreating the oily sludge to obtain pretreated sludge; S2. Delivering the pretreated sludge into a sealed tank, introducing supercritical carbon dioxide, and performing supercritical carbon dioxide treatment on the pretreated sludge to obtain first-stage treated sludge; S3. Delivering the first-stage treated sludge into a sealed filter chamber, heating, and continuously extracting the steam-water mixture generated in the sealed filter chamber to obtain preliminary dry sludge and oily water vapor; S4. Passing the oily water vapor through a wet three-phase separation tower and an oil-water separator in sequence to recover oil resources; and S5. Delivering the preliminary dry sludge into a rotary kiln for rotary drying treatment, and then performing carbonization treatment to obtain carbonized sludge without water, carbonized flue gas, and waste heat hot air. The treatment method provided by the present application has good treatment effect on oily sludge, and can effectively separate the oil in the sludge for resource utilization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sludge treatment, and relates to a treatment method and system for oily sludge. BACKGROUND

[0002] Oily sludge is a kind of waste or pollutant containing oil, hydrocarbon compounds and solid particles. They usually come from the following main sources:

[0003] Oil industry: waste generated in the process of oil exploration, exploitation, storage and transportation and processing, such as drilling sludge, oilfield sludge, refinery sludge, etc., containing a large amount of crude oil, petroleum products and hydrocarbon compounds.

[0004] Industrial production: many industrial processes will produce oily sludge, such as metal processing, chemical production, mechanical processing, etc., and the use of lubricating oil, lubricating grease and industrial oil in these processes may lead to waste oily sludge.

[0005] Ship and port: oil pollution of ships, waste generated by ship maintenance and cleaning, and oil pollution and pollutants in ports may form oily sludge.

[0006] Land pollution: some ground oil pollution incidents, such as oil spills, industrial accidents, etc., may also lead to the generation of oily sludge.

[0007] The amount of oily sludge generated in China is about 6 million tons per year. Oily sludge is mainly composed of petroleum hydrocarbons and some difficult-to-degrade organic matter, which is difficult to degrade and dispose, and is listed as hazardous waste by the state. However, the hydrocarbon substances contained in oily sludge have certain utilization value, and can be realized after extraction. Resource utilization.

[0008] At present, for the treatment process of sludge, for example, a sludge resource treatment process and system disclosed in CN110165587A, the treatment process comprises the following steps: S1: modification: wet sludge and sludge modifier are respectively put into a sludge modification mixer for modification; S2: dewatering: the modified sludge is transported to a sludge roller pressing deep dewatering machine for roller pressing deep dewatering; S3: vacuum drying: the sludge after roller pressing deep dewatering is transported to a sludge vacuum drying machine, and is continuously heated through a steam system, and the sludge vacuum drying machine is vacuumized through a vacuum system; S4: granulation: the dry sludge after vacuum drying treatment is transported to a granulator for granulation, and fine powder is screened out in the granulation process to obtain sludge particles; S5: dry distillation carbonization: the sludge particles are pushed into a dry distillation carbonization device for pyrolysis to obtain biochar, and the mixed gas generated in the dry distillation device can be used as a heat source of the dry distillation device or / and the steam system after treatment. The present application realizes the treatment of sludge reduction, harmlessness and resource utilization. When the oil-containing sludge is treated, there may be some problems: due to the particularity of the oil-containing sludge (the oil-containing sludge is generally composed of oil-in-water (o / w), water-in-oil (w / o) and suspended solids, and is emulsified to form a suspended emulsion system under the action of shear force in the formation process), the above process has poor drying effect on the oil-containing sludge. Moreover, the separation effect of oil in the sludge is limited, which cannot maximize the utilization of resource components in the sludge, and is also not conducive to the subsequent use of the sludge.

[0009] Therefore, it is necessary to provide a specific treatment method for oil-containing sludge. SUMMARY

[0010] The present application provides a treatment method and system for oil-containing sludge, which can effectively improve the drying effect of oil-containing sludge and improve the utilization rate of oil in the sludge.

[0011] The present application adopts the following technical scheme:

[0012] A treatment method for oil-containing sludge, comprising the following steps:

[0013] S1. Pre-treating the oil-containing sludge to obtain pre-treated sludge;

[0014] S2. Transporting the pre-treated sludge into a sealed tank, and introducing supercritical carbon dioxide to treat the pre-treated sludge by supercritical carbon dioxide to obtain first-stage treated sludge;

[0015] S3. Transporting the first-stage treated sludge into a sealed filter chamber, heating, and continuously extracting the steam-water mixture generated in the sealed filter chamber to maintain a vacuum in the sealed filter chamber to obtain preliminary dry sludge and oil-containing water vapor;

[0016] S4. Passing the oil-containing water vapor through a wet-type three-phase separation tower and an oil-water separator in sequence to recover oil resources;

[0017] S5. The primary dry sludge is sent into a rotary kiln for rotary drying treatment, and then treated by a carbonization device to obtain water-free carbonized sludge, carbonized flue gas and waste heat hot air, and the carbonized sludge is subjected to incineration treatment.

[0018] Preferably, in step S3, the carbon dioxide discharged in S2 is introduced into a sealed filter chamber after being pressurized and heated, and the carbon dioxide is used as a heat medium to heat the primary treated sludge.

[0019] Preferably, in step S2, the supercritical carbon dioxide treatment is performed under the conditions of a temperature of 50 to 55 ℃ and a pressure of 75 to 80 ATM.

[0020] Preferably, in step S2, the supercritical carbon dioxide treatment is performed for 1 to 1.5 h.

[0021] Preferably, in step S2, the supercritical carbon dioxide treatment is performed while low-speed stirring is performed.

[0022] Preferably, the stirring speed is 120-150 rpm.

[0023] Preferably, in step S1, the pretreatment includes adding wood fibers to the oil-containing sludge.

[0024] Preferably, in step S4, the non-condensable gas generated in the wet three-phase separation tower is maintained at a temperature of 65 ℃ or higher and sent into the smokeless device for combustion.

[0025] The present application also provides an oil-containing sludge treatment system for implementing the above treatment method.

[0026] The above treatment system comprises:

[0027] a pretreatment tank, a supercritical carbon dioxide generator, a supercritical carbon dioxide treatment sealed tank, a sealed filter chamber, a wet three-phase separation tower, an oil-water separator, a low-speed rotary kiln and a carbonization device, the pretreatment tank is connected to the supercritical carbon dioxide treatment sealed tank to deliver pretreated sludge into the supercritical carbon dioxide treatment sealed tank, the supercritical carbon dioxide treatment sealed tank is connected to the sealed filter chamber to deliver primary treated sludge into the sealed filter chamber, the sealed filter chamber is connected to the wet three-phase separation tower, the wet three-phase separation tower is connected to the oil-water separator, oil-containing water vapor is sequentially sent into the wet three-phase separation tower and the oil-water separator, the supercritical carbon dioxide generator is connected to the supercritical carbon dioxide treatment sealed tank, and the supercritical carbon dioxide treatment sealed tank is also connected to the sealed filter chamber through a connecting pipe.

[0028] By implementing the above technical solution, the present application has the following beneficial effects:

[0029] The treatment method has good treatment effect on oily sludge, and can effectively separate and utilize the oil in the sludge. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A flow chart of the treatment method provided by the present application is shown in the figure.

[0031] Figure 2 A structure schematic diagram of the treatment system provided by the present application is shown in the figure. DETAILED DESCRIPTION

[0032] The present application will be further described in detail through specific embodiments.

[0033] It should be noted that the following embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0034] A treatment method of oily sludge, comprising the following steps:

[0035] S1. Pre-treating the oily sludge to obtain pre-treated sludge;

[0036] The pre-treatment can include initial sedimentation of the oily sludge, screening of large-particle solid impurities, crushing of large pieces of oily sludge, etc., which are all conventional pre-treatment operation methods; the initial sedimentation is mainly to preliminarily increase the water content of the sludge, and to remove most of the water in the sludge for the oily sludge with excessive water content; the screening of large-particle solid impurities is mainly to screen out large-particle impurities such as large stones and metal blocks in the sludge by using a filtering method; and the crushing of large pieces of oily sludge is mainly to crush the sludge to facilitate subsequent treatment.

[0037] The pre-treatment can also preferably include adding wood fibers to the oily sludge, which is usually performed in the step before the pre-treated sludge is transported to the sealed tank after the above-mentioned pre-treatment of the oily sludge, such as initial sedimentation, screening of large-particle solid impurities, and crushing of large pieces of oily sludge.

[0038] The amount of wood fibers added is about 1 to 3 kilograms of wood fibers per 100 liters of oily sludge in terms of the volume of the sludge. The length of the fibers also affects the effect, and short fibers are preferred, which are usually within 1 millimeter, and the fiber size is preferably between 0.3 millimeters and 1 millimeter.

[0039] S2. The pretreated sludge is transported into a sealed tank, supercritical carbon dioxide is introduced into the tank, and the pretreated sludge is treated by supercritical carbon dioxide to obtain first-stage treated sludge;

[0040] When the temperature of carbon dioxide is higher than the critical temperature Tc=31.26°C and the pressure is higher than the critical pressure Pc=72.9atm, the properties of carbon dioxide change, and the carbon dioxide in this state is called supercritical carbon dioxide. In this state, the density of carbon dioxide is close to that of a liquid, the viscosity is close to that of a gas, the diffusion coefficient is about 100 times that of a liquid, and the superstrong dissolving capacity is provided.

[0041] In the present application, supercritical carbon dioxide is introduced into the sealed tank, and the temperature in the tank is maintained at 50-55°C, the pressure is maintained at 75-80 ATM, and the maintaining time is 1-1.5h, and low-speed stirring is performed at the same time. Then, the pressure in the sealed tank is changed to restore the state of carbon dioxide under normal temperature and pressure, and then the carbon dioxide is discharged. During the maintaining period, the carbon dioxide is in a supercritical state and has specific properties in this state.

[0042] The present application takes advantage of the properties of supercritical carbon dioxide to fully carry the oil in the sludge, which is more conducive to the separation of oil from the sludge and provides a basis for subsequent efficient separation.

[0043] The pretreatment in step S1 of the present application is beneficial to assisting the supercritical carbon dioxide to fully fill in the sludge, and further improves the effect of supercritical carbon dioxide.

[0044] The supercritical carbon dioxide is selected in the present application because it has the following characteristics:

[0045] (1) The critical temperature of CO2 is 31.26°C, the critical pressure is 72.9atm, and the critical condition is easy to achieve.

[0046] (2) CO2 is chemically inert, colorless, odorless, nontoxic, and safe.

[0047] (3) The price is cheap, the purity is high, and it is easy to obtain.

[0048] S3. The first-stage treated sludge is transported into a sealed filter chamber, heated, and the steam-water mixture generated in the sealed filter chamber is continuously extracted to maintain a vacuum in the sealed filter chamber, to obtain preliminary dry sludge and oil-containing steam; the water content of the preliminary dry sludge is less than 25%;

[0049] In this step, the sealed filter chamber needs to be heated, and the heating temperature is generally about 100 DEG C. In the present application, the carbon dioxide discharged in step S2 is used as a heat medium, is appropriately pressurized and heated, and is introduced into the sealed filter chamber. The high-pressure carbon dioxide forms bubbles in the preliminary dried sludge. In the drying process, the bubbles break, which is beneficial to the formation of pores in the sludge and the penetration of heat, and the gas is discharged, which can take away the water and is more beneficial to the drying of the sludge.

[0050] S4. The oil-containing water vapor is sequentially introduced into a wet three-phase separation tower and an oil-water separator, and oil resources are recovered;

[0051] The non-condensable gas generated in the wet three-phase separation tower is kept above 60 DEG C and is introduced into a smokeless device for combustion. The combustion temperature is 800 DEG C to 1000 DEG C. At this time, the flue gas meets the emission standard and can be directly discharged or recycled to S3 to heat the first-stage treated sludge and then discharged.

[0052] S5. The preliminary dried sludge is introduced into a rotary kiln for rotary drying treatment, and then is treated by a carbonization device to obtain carbonized sludge without water, carbonization flue gas and waste heat hot air, and the carbonized sludge is further incinerated.

[0053] The specific steps of the carbonized sludge include:

[0054] S51. The dried sludge is crushed into powder, an activator is added, and the mixture is stirred uniformly in a carbonization furnace at a temperature increasing rate of 50-60 DEG C per minute to 750-800 DEG C. At the same time, protective gas is introduced to carbonize the sludge. The carbonization time is 90-100 minutes.

[0055] S52. The carbonized product obtained in step S51 is washed, filtered, and the solid phase is further subjected to pickling, water washing, filtering and drying to obtain carbonized sludge.

[0056] The present application also provides a treatment system for oil-containing sludge for implementing the above-mentioned treatment method.

[0057] The pre-treatment tank, the supercritical carbon dioxide generator, the supercritical carbon dioxide treatment sealed tank, the sealed filter chamber, the wet three-phase separation tower, the oil-water separator, the rotary kiln and the carbonization device are connected. The pre-treatment tank is connected to the supercritical carbon dioxide treatment sealed tank to deliver the pre-treated sludge into the supercritical carbon dioxide treatment sealed tank. The supercritical carbon dioxide treatment sealed tank is connected to the sealed filter chamber to deliver the first-stage treated sludge into the sealed filter chamber. The sealed filter chamber is connected to the wet three-phase separation tower, and the wet three-phase separation tower is connected to the oil-water separator. The oil-containing water vapor sequentially passes through the wet three-phase separation tower and the oil-water separator. The supercritical carbon dioxide generator is connected to the supercritical carbon dioxide treatment sealed tank. The supercritical carbon dioxide treatment sealed tank is also connected to the sealed filter chamber through a connecting pipe.

[0058] Embodiment 1:

[0059] A method for treating oily sludge, comprising the following steps:

[0060] S1. Pre-treating the oily sludge to obtain pre-treated sludge;

[0061] The pre-treating comprises sequentially removing large-particle solid impurities, primary settling of the oily sludge, and crushing the large oily sludge.

[0062] S2. Delivering the pre-treated sludge into a sealed tank, introducing supercritical carbon dioxide, maintaining a temperature of 50°C and a pressure of 75 ATM in the tank, and treating the pre-treated sludge with the supercritical carbon dioxide for 1 hour, while stirring at a low speed of 120 rpm; after the treatment, reducing the pressure in the tank to a value at which the carbon dioxide is out of the critical state, discharging the carbon dioxide, and obtaining primary treated sludge;

[0063] S3. Delivering the primary treated sludge into a sealed filter chamber, heating the chamber to 100°C, continuously discharging steam-water mixture generated in the chamber, and maintaining a vacuum in the chamber to obtain preliminary dry sludge and oily steam; in this step, the carbon dioxide discharged in step S2 is used as a heat medium, is appropriately pressurized and heated (to a pressure of 1 MPa and a temperature of about 50°C), and is introduced into the sealed filter chamber.

[0064] S4. Recovering oil resources from the oily steam by sequentially passing the oily steam through a wet three-phase separation tower and an oil-water separator.

[0065] Non-condensable gases generated in the wet three-phase separation tower are maintained at a temperature of 60°C or higher, are sent to a smokeless device for combustion, and the combustion temperature is 1000°C; at this time, the flue gas meets the emission standard and can be directly discharged or recycled to step S3 for heating the primary treated sludge and then discharged.

[0066] S5. Delivering the preliminary dry sludge into a rotary kiln for rotary drying treatment, then treating the dry sludge by a carbonization device to obtain carbonized sludge containing no water, carbonized flue gas, and waste heat hot air, and then incinerating the carbonized sludge.

[0067] The specific steps of the carbonized sludge include:

[0068] S51. Crushing the dry sludge into powder, stirring the powder in a carbonization furnace, heating the powder to 750°C at a heating rate of 50°C per minute, introducing a protective gas, and carbonizing the sludge for 90 minutes.

[0069] S52. Washing and filtering the carbonized product obtained in step S51, and then subjecting the solid phase to acid washing, water washing, filtering, and drying to obtain carbonized sludge.

[0070] Embodiment 2

[0071] A method for treating oily sludge, comprising the following steps:

[0072] S1. Pretreating the oily sludge to obtain pretreated sludge;

[0073] The pretreatment comprises, in sequence, screening out large-particle solid impurities, primary precipitation of the oily sludge, and crushing the bulk oily sludge.

[0074] S2. Delivering the pretreated sludge into a sealed tank, introducing supercritical carbon dioxide, maintaining a temperature of 52°C and a pressure of 80 ATM in the tank, and treating the pretreated sludge with the supercritical carbon dioxide for 1 hour, while stirring at a low speed of 130 rpm; after the treatment, reducing the pressure in the tank and discharging the carbon dioxide to obtain first-stage treated sludge;

[0075] S3. Delivering the first-stage treated sludge into a sealed filter chamber, heating at 100°C, continuously discharging the steam-water mixture generated in the filter chamber, and maintaining a vacuum in the filter chamber to obtain preliminary dry sludge and oily steam; the carbon dioxide discharged in step S2 is used as a heat medium, is appropriately pressurized and heated (to 1 MPa and about 50°C), and is introduced into the filter chamber.

[0076] S4. Recovering oil resources from the oily steam by sequentially passing the oily steam through a wet-type three-phase separation tower and an oil-water separator;

[0077] Non-condensable gases generated in the wet-type three-phase separation tower are maintained at a temperature of 60°C or higher and are sent to a smokeless device for combustion at a temperature of 1000°C; at this time, the flue gas meets the emission standard and can be directly discharged or recycled to step S3 for heating the first-stage treated sludge and then discharged.

[0078] S5. Delivering the preliminary dry sludge into a rotary kiln for rotary drying treatment, then treating the dry sludge in a carbonization device to obtain carbonized sludge containing no water, carbonized flue gas, and waste heat hot air, and then incinerating the carbonized sludge.

[0079] The specific steps of the carbonized sludge include:

[0080] S51. Crushing the dry sludge into powder, stirring the powder in a carbonization furnace, heating at a rate of 50-60°C per minute to 800°C, and introducing a protective gas to carbonize the sludge; the carbonization time is 90 minutes.

[0081] S52. Washing and filtering the carbonized product obtained in step S51, and then subjecting the solid phase to acid pickling, water washing, filtering, and drying to obtain carbonized sludge.

[0082] Embodiment 3:

[0083] A method for treating oily sludge, comprising the following steps:

[0084] S1. Pretreating the oily sludge to obtain pretreated sludge;

[0085] The pretreatment comprises, in sequence, screening out large-particle solid impurities, primary precipitation of the oily sludge, and crushing the bulk oily sludge.

[0086] S2. Delivering the pretreated sludge into a sealed tank, introducing supercritical carbon dioxide, maintaining the temperature at 55°C and the pressure at 75 ATM in the tank, and treating the pretreated sludge with the supercritical carbon dioxide for 1.5 hours, while stirring at a low speed of 150 rpm; after the treatment, reducing the temperature in the tank to room temperature (below 30°C), discharging the carbon dioxide, and obtaining primary treated sludge;

[0087] S3. Delivering the primary treated sludge into a sealed filter chamber, heating at 100°C, continuously discharging the steam-water mixture generated in the filter chamber, and maintaining a vacuum in the filter chamber, to obtain preliminary dry sludge and oily steam; in this step, the carbon dioxide discharged in step S2 is used as a heat medium, and is introduced into the filter chamber after being appropriately pressurized and heated (to 1 MPa and about 50°C).

[0088] S4. Recovering oil resources from the oily steam by sequentially passing the oily steam through a wet three-phase separation tower and an oil-water separator.

[0089] The non-condensable gas generated in the wet three-phase separation tower is maintained at a temperature above 60°C and is sent to a smokeless device for combustion at a temperature of 1000°C; at this time, the flue gas meets the emission standard and can be directly discharged or recycled to step S3 for heating the primary treated sludge and then discharged.

[0090] S5. Delivering the preliminary dry sludge into a rotary kiln for rotary drying treatment, then treating the dry sludge in a carbonization device to obtain carbonized sludge containing no water, carbonized flue gas, and waste heat hot air, and then incinerating the carbonized sludge.

[0091] The specific steps of the carbonized sludge include:

[0092] S51. Crushing the dry sludge into powder, stirring the powder in a carbonization furnace, heating at a rate of 50°C per minute to 800°C, introducing a protective gas, and carbonizing the sludge for 100 minutes.

[0093] S52. Washing and filtering the carbonized product obtained in step S51, and then subjecting the solid phase to acid pickling, water washing, filtering, and drying to obtain carbonized sludge.

[0094] Example 4:

[0095] The difference from Example 1 is that the pretreatment in step S1 further comprises: before the pretreated sludge is transported into the sealed tank, wood fiber is added into the oily sludge while stirring. The amount of wood fiber added is about 1 kg per 100 liters of oily sludge in volume. The fiber size is between 0.3 mm and 1 mm.

[0096] Example 5:

[0097] The difference from Example 1 is that the pretreatment in step S1 further comprises: before the pretreated sludge is transported into the sealed tank, wood fiber is added into the oily sludge, and the amount of wood fiber added is about 2.5 kg per 100 liters of oily sludge in volume. The fiber size is between 0.3 mm and 1 mm.

[0098] Example 6:

[0099] The difference from Example 1 is that the pretreatment in step S1 further comprises: before the pretreated sludge is transported into the sealed tank, wood fiber is added into the oily sludge, and the amount of wood fiber added is about 5 kg per 100 liters of oily sludge in volume. The fiber size is between 0.3 mm and 1 mm.

[0100] Example 7:

[0101] The difference from Example 1 is that the pretreatment in step S1 further comprises: before the pretreated sludge is transported into the sealed tank, wood fiber is added into the oily sludge, and the amount of wood fiber added is about 2.5 kg per 100 liters of oily sludge in volume. The fiber size is between 2 mm and 3 mm.

[0102] Comparative Example 1:

[0103] The difference from Example 1 is that step S2 is not performed. The treatment method comprises:

[0104] S1. Pretreating the oily sludge to obtain pretreated sludge;

[0105] The pretreatment comprises sequentially performing screening of large particle solid impurities, primary sedimentation of the oily sludge, and crushing of the large oily sludge.

[0106] S2. Transporting the pretreated sludge into a sealed filter chamber, heating at 100°C while continuously withdrawing the steam-water mixture generated in the sealed filter chamber, maintaining a vacuum in the sealed filter chamber, and obtaining primary dry sludge and oily steam;

[0107] S3. Passing the oily steam through a wet three-phase separation tower and an oil-water separator in sequence to recover oil resources;

[0108] The non-condensable gas generated in the wet three-phase separation tower is kept above 60°C and sent to a smokeless device for combustion at a temperature of 1000°C. The smoke at this time meets the emission standard and can be directly discharged or recycled to S3 to heat the first-stage treated sludge before being discharged.

[0109] S4. The primary dry sludge is sent to a rotary kiln for rotary drying treatment, and then treated by a carbonization device to obtain water-free carbonized sludge, carbonized smoke, and waste heat hot air. The carbonized sludge is then incinerated.

[0110] The specific steps of carbonizing the sludge include:

[0111] S41. The dried sludge is crushed into powder and stirred uniformly in a carbonization furnace. The temperature is raised to 750°C at a rate of 50°C per minute, and protective gas is introduced at the same time. The sludge is carbonized for 90 minutes.

[0112] S42. The carbonized product obtained in step S41 is washed and filtered. The solid phase is further subjected to acid washing, water washing, filtering, and drying to obtain carbonized sludge.

[0113] Comparative Example 2:

[0114] The difference from Example 4 is that step S2 is not performed. The treatment method includes:

[0115] S1. The oil-containing sludge is pretreated to obtain pretreated sludge.

[0116] The pretreatment includes the following steps in sequence: screening out large particle solid impurities, primary sedimentation of oil-containing sludge, crushing of large oil-containing sludge, and adding wood fibers. The amount of wood fibers added is about 1 kg per 100 liters of oil-containing sludge. The fiber size is between 0.3 mm and 1 mm.

[0117] S2. The pretreated sludge is transported into a sealed filter chamber and heated at 100°C. The steam-water mixture generated in the sealed filter chamber is continuously extracted to maintain a vacuum in the sealed filter chamber, obtaining primary dry sludge and oil-containing steam.

[0118] S3. The oil-containing steam is sequentially passed through a wet three-phase separation tower and an oil-water separator to recover oil resources.

[0119] The non-condensable gas generated in the wet three-phase separation tower is kept above 60°C and sent to a smokeless device for combustion at a temperature of 1000°C. The smoke at this time meets the emission standard and can be directly discharged or recycled to S3 to heat the first-stage treated sludge before being discharged.

[0120] S4. The preliminary dry sludge is sent into a rotary kiln for rotary drying treatment, and then treated by a carbonization device to obtain water-free carbonized sludge, carbonized flue gas and waste heat hot air, and the carbonized sludge is further incinerated.

[0121] The specific steps of carbonizing the sludge include:

[0122] S41. The dried sludge is crushed into powder and stirred uniformly in a carbonization furnace, and heated to 750℃ at a heating rate of 50℃ per minute while protective gas is introduced, to carbonize the sludge, with a carbonization time of 90 minutes.

[0123] S42. The carbonized product obtained in step S41 is washed and filtered, and the solid phase is further subjected to acid washing, water washing, filtering and drying to obtain carbonized sludge.

[0124] The treatment system used in the above examples and comparative examples is described in Figure 2 , which includes a pretreatment tank 100, a supercritical carbon dioxide generator 200, a supercritical carbon dioxide treatment sealed tank 300, a sealed filter chamber 400, a wet-type three-phase separation tower 500, an oil-water separator 600, a rotary kiln 700 and a carbonization device 800. The pretreatment tank is connected to the supercritical carbon dioxide treatment sealed tank, and the pretreated sludge is delivered into the supercritical carbon dioxide treatment sealed tank. The supercritical carbon dioxide treatment sealed tank is connected to the sealed filter chamber, and the first-stage treated sludge is delivered into the sealed filter chamber. The sealed filter chamber is connected to the wet-type three-phase separation tower, and the wet-type three-phase separation tower is connected to the oil-water separator. The oil-containing water vapor passes through the wet-type three-phase separation tower and the oil-water separator in sequence. The supercritical carbon dioxide generator is connected to the supercritical carbon dioxide treatment sealed tank. The supercritical carbon dioxide treatment sealed tank is also connected to the sealed filter chamber through a connecting pipe.

[0125] The same batch of oil-containing sludge (oilfield sludge, with an oil content of 36%) is treated by the method of the above examples and comparative examples, and the oil content in the preliminary dry sludge after treatment is determined. The determination method is described in "Study on Determination Method of Oil Content in Oil Sand Sludge", Xu Xiuqiang et al., Chemical Industry and Engineering Technology, 2008, 16(4): 1-4", and the determination results are shown in Table 1 below.

[0126]

Claims

1. A method for treating oil-containing sludge, characterized by, The method comprises the following steps: S1. Pretreating the oily sludge to obtain pretreated sludge, comprising adding wood fiber to the oily sludge; S2. Transporting the pretreated sludge into a sealed tank, introducing supercritical carbon dioxide, and performing supercritical carbon dioxide treatment on the pretreated sludge to obtain first-stage treated sludge; S3. Transporting the first-stage treated sludge into a sealed filter chamber, heating, continuously extracting steam-water mixture generated in the sealed filter chamber, and maintaining vacuum in the sealed filter chamber to obtain preliminary dry sludge and oily water vapor; S4. Passing the oily water vapor through a wet three-phase separation tower and an oil-water separator in sequence to recover oil resources; S5. Transporting the preliminary dry sludge into a rotary kiln, performing rotary drying treatment, and then performing treatment through a carbonization device to obtain carbonized sludge.

2. The method for treating oil-containing sludge according to claim 1, characterized by, In step S3, the carbon dioxide discharged in S2 is introduced into the sealed filter chamber after being pressurized and heated, and the supercritical carbon dioxide is used as a heat medium to heat the first-stage treated sludge.

3. The method of treating oil-containing sludge according to claim 1, characterized in that, In step S2, the supercritical carbon dioxide treatment is performed at a temperature of 50-55℃ and a pressure of 75-80 ATM.

4. The method of treating oil-containing sludge according to claim 3, characterized in that, In step S2, the supercritical carbon dioxide treatment is performed for 1-1.5 h.

5. The method of treating oil-containing sludge according to claim 1, characterized by, In step S2, the supercritical carbon dioxide treatment is performed while stirring.

6. The method of treating oil-containing sludge according to claim 5, characterized in that, The stirring speed is 120-150 rpm.

7. The method of treating oil-containing sludge according to claim 1, wherein In step S4, the non-condensable gas generated in the wet three-phase separation tower is maintained at a temperature of 65℃ or higher and is introduced into a smokeless device for combustion.

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