A harmless and resourceful treatment system and method for oil-containing sludge

Abstract

The application provides a harmless and resourceful treatment system and method for oily sludge. The system comprises a reactor, a filtering device, a flash evaporator, an extractant recovery device, an oil-water separation device, a wastewater treatment device and a sludge treatment device. The oily sludge and the extractant are reacted, and the reaction product is separated, so that the crude oil can be efficiently separated from the oily sludge, and the resourceful treatment is realized. The system and method can not only realize the harmless and resourceful treatment of the oily sludge, but also have low operation cost and strong process applicability, so that the problem of the oily sludge treatment is systematically solved.

Description

Technical Field

[0001] This invention relates to the field of oily sludge treatment, and in particular to a system and method for the harmless and resource-based treatment of oily sludge. Background Technology

[0002] Oily sludge refers to sludge mixed with crude oil and refined oil. It is mainly generated in the oil field extraction and petroleum refining process. It is leaked to the ground due to improper operation, equipment and pipeline damage, etc., and mixes with mud, sand and water to form an oil, mud, sand and water mixture.

[0003] Oily sludge is extremely hazardous. The oily gases produced after the oily substances evaporate can irritate the respiratory organs, eyes, and skin of humans and animals, causing damage to mucous membranes. Contaminated soil loses its ability to support plant growth, making remediation extremely difficult and generally requiring ex-situ remediation. Therefore, oily sludge is considered one of the main pollutants from oil extraction, processing, and transportation.

[0004] Currently, various physicochemical and biological methods have been tried in China, and numerous field trials have been conducted. However, significant shortcomings remain in terms of treatment efficiency, cost, and resource recovery. For example, incineration involves sending dewatered oily sludge to an incinerator for burning. Its advantages include good harmlessness and volume reduction, but it cannot achieve resource recovery. Biological methods utilize highly efficient hydrocarbon-oxidizing bacteria and other microorganisms to degrade hydrocarbons in oily sludge. Its advantages include relatively low treatment costs, but its disadvantages include susceptibility to temperature and raw material factors affecting microbial degradation, resulting in low treatment efficiency and the risk of secondary pollution.

[0005] Therefore, it is necessary to develop a new process for the harmless and resource-based treatment of oily sludge. Summary of the Invention

[0006] The purpose of this invention is to address the problem of low resource recovery efficiency in the treatment of oily sludge in existing technologies, and to provide a system and method for the harmless and resource-based treatment of oily sludge. This objective can be achieved through the following technical solutions: A system for the harmless and resource-based treatment of oily sludge, comprising: A reactor used to mix oily sludge with an extractant to obtain a solid-liquid mixture; A filtration device is connected to the reactor and is used to filter the solid-liquid mixture formed in the reactor to obtain mud and sand and a mixed liquid. A flash evaporator, connected to a filter, is used to flash-dry a mixture to obtain extractant vapor and an oil-water mixture. The extractant recovery unit is used to liquefy the extractant vapor and send it back to the reactor; An oil-water separation device, wherein the oil-water separator is connected to a flash evaporator, is used to separate oil-water mixtures to obtain crude oil and wastewater; Wastewater treatment equipment used to treat wastewater; A mud and sand treatment device used for incinerating mud and sand.

[0007] Optionally, the reactor is a batch reactor, and the oily sludge is added to the reactor via a screw pump; Preferably, the filtration device is a filter press.

[0008] Optionally, the extractant recovery device includes a compressor, a condenser, an extractant storage tank, and a metering pump connected in sequence; the extractant vapor is compressed by the compressor and then liquefied by the condenser before entering the extractant storage tank; the extractant in the extractant storage tank enters the reactor through the metering pump.

[0009] Optionally, the condensation device may employ a tubular heat exchanger or a thin-film heat exchanger. Preferably, the oil-water separation device is a centrifugal separator or a hydrocyclone separator.

[0010] Optionally, the wastewater treatment device includes a coagulation sedimentation device, a catalytic oxidation treatment device, and a biological treatment device connected in sequence; the wastewater treatment device treats the wastewater to obtain treated wastewater and sludge, and the sludge is sent to a sludge and sand treatment device.

[0011] Optionally, the mud and sand treatment device includes a rotary kiln for incinerating mud and sand and a tail gas treatment device for treating the tail gas of the rotary kiln. The exhaust gas treatment device uses an activated carbon adsorption module.

[0012] A method for the harmless and resource-based treatment of oily sludge includes the following steps: Step 1) Mix the oily sludge with the extractant to obtain a solid-liquid mixture; Step 2) Filter the solid-liquid mixture to obtain mud and sand and a mixed liquid; Step 3) The mixture is flash-evaporated to obtain extractant vapor and oil-water mixture; the extractant vapor is liquefied and returned to Step 1); the oil-water mixture is then separated to obtain crude oil and wastewater. Step 4) The wastewater is treated by a sewage treatment device to obtain treated wastewater and sludge. The sludge and the mud and sand in Step 2) are then calcined.

[0013] Optionally, the extractant is at least one of ethane, propane, and butane.

[0014] Optionally, the weight ratio of oily sludge to extractant in step one) is 1:1 to 10:1.

[0015] Optionally, in step three), the pressure of the extractant vapor after flash evaporation is 0.5~1.5 bar and the temperature is 5~15℃; The conditions for extractant vapor liquefaction are to pressurize the extractant vapor to 8-12 bar and then liquefy it at 25-35°C. In step four), the sludge and sand are calcined at 800~1200℃ for 0.5~1.0h.

[0016] Compared with the prior art, the present invention has the following beneficial effects. This invention provides a system and method for the harmless and resource-based treatment of oily sludge. The system includes a reactor, a filtration device, a flash evaporator, an extractant recovery device, an oil-water separation device, a wastewater treatment device, and a sludge treatment device. This invention reacts oily sludge with an extractant and separates the reaction products, achieving efficient separation of crude oil from the oily sludge and realizing resource-based treatment. The extractant recovery device recovers the extractant with a recovery rate of over 95%, achieving efficient recovery and reducing treatment costs. The wastewater treatment device and sludge treatment device harmlessly treat the wastewater and sludge generated during the reaction and discharge them in compliance with standards, achieving harmless treatment. This system and method not only achieves the harmless and resource-based treatment of oily sludge but also has low operating costs and strong process applicability, thus systematically solving the problem of oily sludge treatment. Attached Figure Description

[0017] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided: Figure 1 This is a process flow diagram of the system of the present invention.

[0018] The markings in the diagram are: 1. Oily sludge; 2. Screw pump; 3. Extractant storage tank; 4. Metering pump; 5. Stirred tank reactor; 6. Fully enclosed filter press; 7. Flash evaporator; 8. Gas compressor; 9. Thin film heat exchanger; 10. Sludge; 11. Oil-water mixture; 12. Centrifugal separator; 13. Crude oil; 14. Wastewater; 15. Wastewater treatment device; 16. Treated wastewater; 17. Rotary kiln; 18. Sludge after incineration; 19. Activated carbon adsorption module. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0020] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] First, this invention proposes a system for the harmless and resource-based treatment of oily sludge, comprising: A reactor used to mix oily sludge with an extractant to obtain a solid-liquid mixture; A filtration device is connected to the reactor and is used to filter the solid-liquid mixture formed in the reactor to obtain mud and sand and a mixed liquid. A flash evaporator, connected to a filter, is used to flash-dry a mixture to obtain extractant vapor and an oil-water mixture. The extractant recovery unit is used to liquefy the extractant vapor and send it back to the reactor; An oil-water separation device, wherein the oil-water separator is connected to a flash evaporator, is used to separate oil-water mixtures to obtain crude oil and wastewater; Wastewater treatment equipment used to treat wastewater; A mud and sand treatment device used for incinerating mud and sand.

[0026] As a preferred embodiment, the reactor is a batch reactor, and the oily sludge is added to the reactor via a screw pump.

[0027] In a more preferred embodiment, the extractant is stored in an extractant tank and added to the reactor via a metering pump.

[0028] Preferably, the filtration device is a filter press.

[0029] In a more preferred embodiment, the oily sludge and extractant undergo a sequential batch reaction in a reactor, including steps such as feeding, stirring reaction and discharging, with a reaction cycle of 0.1~1.0h. The solid-liquid mixture after the reaction enters a filter press.

[0030] The filter press performs a filter press operation on the solid-liquid mixture after the reaction. The filter press cycle is 0.5 to 2 hours. The filter cake after filter press is mud and sand, which enters the mud and sand treatment device. The filtrate is a liquid-liquid mixture of crude oil, water and extractant, which enters the flash evaporator.

[0031] Optionally, the extractant recovery device includes a compressor, a condenser, an extractant storage tank, and a metering pump connected in sequence; the extractant vapor is compressed by the compressor and then liquefied by the condenser before entering the extractant storage tank; the extractant in the extractant storage tank enters the reactor through the metering pump.

[0032] The flash evaporator can instantly reduce the pressure of the liquid-liquid mixture. Taking advantage of the low boiling point of the extractant, it can separate the extractant from the oil and water. The gas produced by flash evaporation enters the gas compressor, and the oil-water mixture enters the oil-water separation device.

[0033] As a preferred embodiment, the gas compressor can compress the low-temperature, low-pressure gas separated by flash evaporation into a high-temperature, high-pressure gas, which then enters the condensation device.

[0034] As a preferred embodiment, the heat exchanger can be a tubular heat exchanger or a thin-film heat exchanger. The high-temperature and high-pressure gas exchanges heat with the refrigerant in the heat exchanger. After the temperature drops, the gas changes from a gaseous state to a liquid state and enters the extractant storage tank, thereby realizing the recovery of the extractant. The recovery rate can reach more than 95%.

[0035] As a preferred embodiment, the oil-water separation device can be a centrifugal separator or a hydrocyclone separator. The wastewater generated by the separation enters the wastewater treatment device, and the crude oil is recovered to achieve resource utilization.

[0036] Optionally, the wastewater treatment device includes a coagulation sedimentation device, a catalytic oxidation treatment device, and a biological treatment device connected in sequence; the wastewater treatment device treats the wastewater to obtain treated wastewater and sludge, and the sludge is sent to a sludge and sand treatment device.

[0037] Optionally, the mud and sand treatment device includes a rotary kiln for incinerating mud and sand and a tail gas treatment device for treating the tail gas of the rotary kiln. The exhaust gas treatment device uses an activated carbon adsorption module.

[0038] As a preferred embodiment, the mud and sand treatment device includes a rotary kiln and a tail gas treatment device. The residual crude oil and other pollutants in the mud and sand are removed. The treated mud and sand are backfilled on-site or transported off-site for disposal. The tail gas generated by the rotary kiln combustion is treated by the tail gas treatment device and then discharged in compliance with standards.

[0039] The specific processing flow of this invention is as follows: Oily sludge and extractant are added to the reactor via screw pumps and metering pumps, respectively, for a sequencing batch reaction (SBR) process, including feeding, stirring, and discharging. The reaction product enters a fully enclosed filter press. The filter cake, a sludge, enters a sludge treatment unit. The filtrate, a liquid-liquid mixture of crude oil, water, and extractant, enters a flash evaporator. The flash evaporator separates the extractant from the liquid-liquid mixture into a gaseous form. A gas compressor then converts the low-temperature, low-pressure gas into a high-temperature, high-pressure gas. After heat exchange, the gas is converted back into a liquid and enters the extractant storage tank. The oil-water mixture from the flash evaporator is separated into crude oil and wastewater by an oil-water separator. The crude oil is recovered for resource utilization, and the wastewater is treated to meet discharge standards. The sludge generated during the treatment process, along with the sludge formed after filtration, enters the sludge treatment unit. The sludge and sand are incinerated in a rotary kiln and then either backfilled on-site or transported for disposal. The exhaust gas generated during the treatment process is treated to meet emission standards.

[0040] Based on the above system, the present invention also proposes a method for the harmless and resource-based treatment of oily sludge, comprising the following steps: Step 1) Mix the oily sludge with the extractant to obtain a solid-liquid mixture; Step 2) Filter the solid-liquid mixture to obtain mud and sand and a mixed liquid; Step 3) The mixture is flash-evaporated to obtain extractant vapor and oil-water mixture; the extractant vapor is liquefied and returned to Step 1); the oil-water mixture is then separated to obtain crude oil and wastewater. Step 4) The wastewater is treated by a sewage treatment device to obtain treated wastewater and sludge. The sludge and the mud and sand in Step 2) are then calcined.

[0041] Furthermore, the extractant is at least one of ethane, propane, and butane.

[0042] Optionally, the weight ratio of oily sludge to extractant in step one) is 1:1 to 10:1.

[0043] Optionally, in step three), the pressure of the extractant vapor after flash evaporation is 0.5~1.5 bar and the temperature is 5~15℃; The conditions for extractant vapor liquefaction are to pressurize the extractant vapor to 8-12 bar and then liquefy it at 25-35°C. In step four), the sludge and sand are calcined at 800~1200℃ for 0.5~1.0h.

[0044] Example 1 This embodiment proposes a system for the harmless and resource-based treatment of oily sludge, such as... Figure 1 As shown, the system includes: The reactor is used to mix and react oily sludge 1 with an extractant to obtain a solid-liquid mixture; A filtration device is connected to the reactor and is used to filter the solid-liquid mixture formed in the reactor to obtain mud and sand 10 and a mixed liquid. Flash evaporator 7, which is connected to a filter, is used to flash-evaporate the mixture to obtain extractant vapor and oil-water mixture 11; The extractant recovery unit is used to liquefy the extractant vapor and send it back to the reactor; An oil-water separation device, wherein the oil-water separator is connected to a flash evaporator, is used to separate an oil-water mixture to obtain crude oil 13 and wastewater 14; Wastewater treatment device 15 is used to treat wastewater 14; A mud and sand treatment device is used to incinerate mud and sand 10.

[0045] Specifically, such as Figure 1 As shown, in this invention, the reactor is a batch reactor 5, and the oily sludge 1 is added to the batch reactor 5 via a screw pump 2. The filtration device is a fully enclosed filter press 6, and the filter cake after filtration is mud and sand, which enters the mud and sand treatment device; the filtrate is a liquid-liquid mixture of crude oil, water and extractant, which enters the flash evaporator 7.

[0046] The extractant recovery device includes a gas compressor 8, a thin-film heat exchanger 9 (condenser), an extractant storage tank 3, and a metering pump 4 connected in sequence. The extractant vapor is compressed by the gas compressor 8 and then liquefied in the thin-film heat exchanger 9 before entering the extractant storage tank 3. The extractant in the extractant storage tank 3 enters the batch reactor 5 through the metering pump 4.

[0047] The oil-water separation device uses a centrifugal separator 12, and the wastewater generated by the separation enters the wastewater treatment device 15.

[0048] The wastewater treatment device 15 includes a coagulation sedimentation device, a catalytic oxidation treatment device, and a biological treatment device connected in sequence; the wastewater treatment device 15 treats the wastewater to obtain treated wastewater 16 and sludge, and the sludge is sent to the mud and sand treatment device.

[0049] Optionally, the mud and sand treatment device includes a rotary kiln 17 for incinerating mud and sand and a tail gas treatment device for treating the tail gas from the rotary kiln; the tail gas treatment device employs an activated carbon adsorption module 19. The incinerated mud and sand 18 produced by the rotary kiln 17 can be directly used for backfilling.

[0050] The specific process for the above system to treat oily sludge is as follows: Step 1: The oily sludge is mixed with the extractant to obtain a solid-liquid mixture. Oily sludge 1 is a mixture of mud, sand, oil, and water, with mass percentages of 30%–80%, 5%–50%, and 10%–30%, respectively. Oily sludge 1 and the extractant are added to a batch reactor 5 via a screw pump 2 and a metering pump 4, respectively, for a sequencing batch reaction (SBR) process, including feeding, stirring, and discharging steps. The reaction cycle is 0.2–1.0 h, with a feeding time of 2–15 min, a stirring time of 5–30 min, and a discharging time of 5–15 min. To ensure complete separation of crude oil from oily sludge 1, the ratio of extractant to oily sludge 1 can be controlled between 1:1 and 10:1, based on the characteristics of oily sludge 1. The extractant is an alkane (specifically a mixture of propane and butane, with a propane to butane mass ratio of 3:1). A solid-liquid mixture is then formed.

[0051] Step 2: The reacted solid-liquid mixture enters a fully enclosed filter press 6 for filtration. The filtration cycle is 0.5~2 hours, including feeding, filtration, and discharging operations. The feeding time is 10~30 minutes, the filtration time is 15~60 minutes, and the discharge time is 5~30 minutes. The filter cake after filtration is mud and sand 10, which enters the mud and sand treatment unit. The filtrate is a mixture of crude oil, water, and extractant, which enters the flash evaporator.

[0052] Step 3: After the mixture enters the flash evaporator 7, the flash evaporator 7 can instantly reduce the pressure of the oil-water mixture 11. Utilizing the low boiling point of the extractant, the extractant is separated in gaseous form. After flash evaporation, the pressure of the extractant vapor is 0.5~1.5 bar and the temperature is 5~15℃. Then, the low-temperature, low-pressure gas is converted into a high-pressure gas by the gas compressor 8. After compression, the pressure is 8~12 bar and the temperature rises to 25~35℃. The high-pressure gas exchanges heat with the refrigerant in the thin-film heat exchanger 9. After the pressure drops to 5~7 bar, it changes from a gaseous state to a liquid state and enters the extractant storage tank 3, thereby realizing the recovery of the extractant. The recovery rate can reach over 95%. The oil-water mixture 11 from the flash evaporator 7 passes through the centrifuge separator 12 to separate the crude oil 13 and wastewater 14. The crude oil 13 is recovered and utilized as a resource, while the wastewater 14 generated from the separation enters the wastewater treatment device 15.

[0053] Step 4: The wastewater is treated by a wastewater treatment device to obtain treated wastewater and sludge. The sludge and the mud and sand from Step 2 are then calcined. Wastewater treatment device 15 includes coagulation sedimentation, catalytic oxidation, and biological treatment devices. The total reaction time is 2 hours, with coagulation sedimentation taking 30 minutes, catalytic oxidation taking 30 minutes, and biological treatment taking 60 minutes. Pollutants in wastewater 14 are degraded, resulting in treated wastewater 16 and sludge. Treated wastewater 16 is discharged directly after meeting standards, while the generated sludge enters a mud and sand treatment device for treatment together with mud and sand 10. The mud and sand treatment device includes a rotary kiln 17 and a tail gas treatment device, wherein the tail gas treatment device uses an activated carbon adsorption module 19. Sludge and sand 10 are calcined at 800~1200℃ for 0.5~1.0h. Through the high-temperature combustion of the rotary kiln, the residual crude oil and other pollutants in the sand 10 are removed. After incineration, the sand 18 is backfilled on-site or transported off-site for disposal. The exhaust gas generated by the rotary kiln incineration is treated by the activated carbon adsorption module 19 to obtain qualified exhaust gas.

[0054] Example 2 This embodiment presents a specific process for treating oily sludge using the system described in Example 1: 1 ton of oily sludge containing 25% crude oil and 30% water is treated using the method described in Example 1, with a mixture of propane and butane (mass ratio 3:1) as the extractant. The process includes the following steps: Step 1: Oily sludge and extractant are added to a batch reactor via screw pump and metering pump, respectively, for a sequencing batch reaction (SBR). This process includes feeding, stirring, and discharging, with a reaction cycle of 0.5 hours. The feeding time is 5 minutes, the stirring time is 15 minutes, and the discharging time is 10 minutes. To ensure complete separation of crude oil from the oily sludge, the ratio of extractant to oily sludge is controlled at 5:1, based on the characteristics of the oily sludge.

[0055] Step 2: The reacted solid-liquid mixture is fed into a fully enclosed filter press for filtration. The filtration cycle is 1 hour, including feeding, filtration, and discharging. The feeding time is 15 minutes, the filtration time is 30 minutes, and the discharge time is 15 minutes. The filter cake after filtration is mud and sand, which enters the mud and sand treatment unit. The filtrate is a mixture of crude oil, water, and extractant, which enters the flash evaporator.

[0056] Step 3: The flash evaporator separates the extractant in gaseous form. After flash evaporation, the extractant vapor has a pressure of 1 bar and a temperature of 10°C. Then, a gas compressor converts the low-temperature, low-pressure gas into a high-pressure gas, which is compressed to 10 bar and reaches a temperature of 30°C. This high-pressure gas exchanges heat with the refrigerant in a thin-film heat exchanger, reducing the pressure to 6 bar before changing from a gaseous state to a liquid state and entering the extractant storage tank, thus achieving extractant recovery with a recovery rate exceeding 95%. The oil-water mixture from flash evaporator 7 is then separated into crude oil and wastewater by a centrifugal separator. The recovered crude oil is utilized as a resource, while the wastewater generated during separation is sent to a wastewater treatment plant.

[0057] Step Four: The wastewater treatment unit includes coagulation sedimentation, catalytic oxidation, and biological treatment. The total reaction time is 2 hours, with coagulation sedimentation taking 30 minutes, catalytic oxidation taking 30 minutes, and biological treatment taking 60 minutes. Pollutants in the wastewater are degraded, resulting in treated wastewater and sludge. The treated wastewater meets discharge standards directly, while the generated sludge enters the sludge and sand treatment unit for further treatment. The sludge and sand treatment unit includes a rotary kiln and a tail gas treatment unit, with the tail gas treatment unit using activated carbon adsorption modules. The sludge and sand are calcined at 1000℃ for 0.6 hours. Through the high-temperature combustion in the rotary kiln, residual crude oil and other pollutants in the sludge and sand are removed. After incineration, the sludge and sand are backfilled on-site or transported for disposal. The tail gas generated from the rotary kiln incineration is treated by the activated carbon adsorption module to obtain compliant tail gas.

[0058] The crude oil recovery rate was 98%, and the extractant consumption was 2 kg. The pollutant indicators in the discharged wastewater met the "Water Quality Standard for Wastewater Discharge into Urban Sewerage Systems" (GB / T 31962-2015).

[0059] Example 3 This embodiment presents a specific process for treating oily sludge using the system described in Example 1: 1 ton of oily sludge containing 25% crude oil and 30% water is treated using the method described in Example 1, with a mixture of propane and butane (mass ratio 3:1) as the extractant. The process includes the following steps: Step 1: Oily sludge and extractant are added to a batch reactor via screw pump and metering pump, respectively, for a sequencing batch reaction (SBR). This process includes feeding, stirring, and discharging, with a reaction cycle of 1.0 hour. The feeding time is 15 minutes, the stirring time is 30 minutes, and the discharging time is 15 minutes. The ratio of extractant to oily sludge can be controlled at 3:1 to form a solid-liquid mixture.

[0060] Step Two: The reacted solid-liquid mixture is fed into a fully enclosed filter press for filtration. The filtration cycle is 2 hours, including feeding, filtration, and discharging. The feeding time is 30 minutes, the filtration time is 60 minutes, and the discharge time is 30 minutes. The filter cake after filtration is mud and sand, which enters a mud and sand treatment unit. The filtrate is a mixture of crude oil, water, and extractant, which enters a flash evaporator.

[0061] Step 3: After the mixture enters the flash evaporator, the flash evaporator instantly reduces the pressure of the oil-water mixture. Utilizing the low boiling point of the extractant, the extractant is separated in gaseous form. After flash evaporation, the extractant vapor has a pressure of 1.5 bar and a temperature of 15°C. Then, the low-temperature, low-pressure gas is converted into a high-pressure gas by a gas compressor. After compression, the pressure reaches 12 bar and the temperature rises to 35°C. The high-pressure gas exchanges heat with the refrigerant in a thin-film heat exchanger. After the pressure drops to 7 bar, it changes from a gaseous state to a liquid state and enters the extractant storage tank, thus achieving extractant recovery. The oil-water mixture from the flash evaporator is then separated into crude oil and wastewater by a centrifugal separator. The recovered crude oil is utilized as a resource, while the wastewater generated during separation enters a wastewater treatment plant.

[0062] Step 4: The wastewater is treated by a wastewater treatment device to obtain treated wastewater and sludge. The sludge and the mud and sand from Step 2 are then calcined. The wastewater treatment device includes coagulation sedimentation, catalytic oxidation, and biological treatment devices. The total reaction time is 2 hours, with coagulation sedimentation taking 30 minutes, catalytic oxidation taking 30 minutes, and biological treatment taking 60 minutes. Pollutants in the wastewater are degraded, resulting in treated wastewater and sludge. The treated wastewater is discharged directly after meeting standards, while the generated sludge enters the mud and sand treatment device for treatment together with the mud and sand. The mud and sand treatment device includes a rotary kiln and a tail gas treatment device, with the tail gas treatment device using an activated carbon adsorption module. The sludge and mud and sand are calcined at 1200℃ for 0.5 hours. Through the high-temperature combustion in the rotary kiln, residual crude oil and other pollutants in the mud and sand are removed. After incineration, the mud and sand are backfilled on-site or transported for disposal. The tail gas generated by the rotary kiln incineration is treated by the activated carbon adsorption module to obtain tail gas that meets standards. The crude oil recovery rate was 97%.

[0063] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A system for the harmless and resource-based treatment of oily sludge, characterized in that, include: A reactor used to mix oily sludge with an extractant to obtain a solid-liquid mixture; A filtration device is connected to the reactor and is used to filter the solid-liquid mixture formed in the reactor to obtain mud and sand and a mixed liquid. A flash evaporator, connected to a flow device, is used to flash-evaporate a mixture to obtain extractant vapor and an oil-water mixture. The extractant recovery unit is used to liquefy the extractant vapor and send it back to the reactor; An oil-water separation device, wherein the oil-water separator is connected to a flash evaporator, is used to separate oil-water mixtures to obtain crude oil and wastewater; Wastewater treatment equipment used to treat wastewater; A mud and sand treatment device used for incinerating mud and sand.

2. The system for the harmless and resource-based treatment of oily sludge according to claim 1, characterized in that, The reactor is a batch reactor, and oily sludge is added to the reactor via a screw pump; Preferably, the filtration device is a filter press.

3. The system for the harmless and resource-based treatment of oily sludge according to claim 1, characterized in that, The extractant recovery device includes a compressor, a condenser, an extractant storage tank, and a metering pump connected in sequence; the extractant vapor is compressed by the compressor and then liquefied by the condenser, and then enters the extractant storage tank; the extractant in the extractant storage tank enters the reactor through the metering pump.

4. The system for the harmless and resource-based treatment of oily sludge according to claim 3, characterized in that, The condensation device employs a tubular heat exchanger or a thin-film heat exchanger. Preferably, the oil-water separation device is a centrifugal separator or a hydrocyclone separator.

5. The system for the harmless and resource-based treatment of oily sludge according to claim 1, characterized in that, The wastewater treatment device includes a coagulation sedimentation device, a catalytic oxidation treatment device, and a biological treatment device connected in sequence; the wastewater treatment device treats wastewater to obtain treated wastewater and sludge, and the sludge is sent to a mud and sand treatment device.

6. The system for the harmless and resource-based treatment of oily sludge according to claim 1, characterized in that, The mud and sand treatment device includes a rotary kiln for incinerating mud and sand and a tail gas treatment device for treating the tail gas of the rotary kiln. The exhaust gas treatment device uses an activated carbon adsorption module.

7. A method for the harmless and resource-based treatment of oily sludge, characterized in that, The system for treating oily sludge according to any one of claims 1 to 6 comprises the following steps: Step 1) Mix the oily sludge with the extractant to obtain a solid-liquid mixture; Step 2) Filter the solid-liquid mixture to obtain mud and sand and a mixed liquid; Step 3) The mixture is flash-evaporated to obtain extractant vapor and oil-water mixture; the extractant vapor is liquefied and returned to Step 1); the oil-water mixture is then separated to obtain crude oil and wastewater. Step 4) The wastewater is treated by a sewage treatment device to obtain treated wastewater and sludge; the sludge and the mud and sand in Step 2) are then calcined.

8. The method for harmless and resource-based treatment of oily sludge according to claim 7, characterized in that, The extractant is at least one of ethane, propane, and butane.

9. The method for harmless and resource-based treatment of oily sludge according to claim 7, characterized in that, In step one), the weight ratio of oily sludge to extractant is 1:1 to 10:

1.

10. The method for harmless and resource-based treatment of oily sludge according to claim 7, characterized in that, In step three), the pressure of the extractant vapor after flash evaporation is 0.5~1.5 bar and the temperature is 5~15℃. The conditions for extractant vapor liquefaction are to pressurize the extractant vapor to 8-12 bar and then liquefy it at 25-35°C. In step four), the sludge and sand are calcined at 800~1200℃ for 0.5~1.0h.

Images