Method for deep dewatering and resource recycling of oily sludge and treatment device thereof

Abstract

The application discloses a kind of deep dewatering and resource recovery method of oily sludge and its processing device.The processing method provided by the application comprises the following steps: demulsifying oily sludge, standing, solid-liquid separation, to obtain oil phase, aqueous phase and solid residue;The solid residue is extruded to obtain mud cake and filtrate;The mud cake is made into ceramsite;The filtrate is subjected to secondary demulsification, and is layered after standing, to obtain oil phase and aqueous phase;After sewage treatment, the aqueous phase is discharged;After oil removal by air flotation, the oil product is collected.The application also provides a complete device for realizing the above processing method.The application realizes efficient dewatering of sludge, oil recovery and resource utilization, effectively solves the environmental pollution and resource waste problems in the treatment of oily sludge.Compared with general sludge treatment, the application has the advantages of advanced technology, high treatment efficiency, low cost, high resource recovery rate, etc., and is suitable for the treatment of various types of oily sludge.

Description

Technical Field

[0001] This invention relates to the field of oil sludge treatment technology, and in particular to a method and apparatus for deep dewatering and resource recovery of oily sludge. Background Technology

[0002] Oily sludge refers to sludge mixed with crude oil, various refined oils, residual oil, and other heavy oils. With the acceleration of industrialization, the amount of oily sludge generated is increasing daily. This type of sludge not only contains large amounts of water and oil but may also contain heavy metals, organic matter, and other harmful substances, posing a serious threat to the environment. Traditional sludge treatment methods, such as natural drying, landfilling, or incineration, suffer from low treatment efficiency, significant resource waste, and severe environmental pollution. Therefore, developing an efficient and environmentally friendly oily sludge treatment technology is particularly important.

[0003] Currently, some technologies for treating oily sludge exist in the market, but most of these technologies have shortcomings, and the treatment requirements vary depending on the source and nature of the oily sludge. Traditional methods, such as plate and frame filter presses and belt filter presses, have limited dewatering effects, often resulting in high moisture content, which is detrimental to subsequent resource utilization. Furthermore, traditional methods often fail to effectively recover the oil phase resources in the sludge, leading to resource waste.

[0004] CN117303687A discloses an efficient recycling and treatment process for oily sludge from oilfields. This process utilizes ultrasonic treatment, chemical pressing, and pyrolysis to solidify the sludge, establishing a method for comprehensive treatment and utilization of oily sludge. However, it suffers from low dehydration rates and high energy consumption. CN117003451A discloses a physicochemical thermal washing process for oily sludge, achieving low-cost and effective separation. However, this method suffers from low resource utilization rates of the solid sludge. CN118480367A discloses a switchable microemulsion, its application method, and an oily sludge treatment method. This method uses a microemulsion for oily sludge extraction, achieving good cleaning results and solving the problem of microemulsion recycling. However, the oil phase of this microemulsion consists of highly toxic and odorous organic amines, which can easily cause secondary pollution and harm the health of operators.

[0005] Currently, there are difficulties in deep dewatering and oil removal of oily sludge, especially the lack of technology to achieve deep dewatering with minimal or no chemical additives. At the same time, there are also few successful cases of systematically coordinating oil recovery and residue utilization processes. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to achieve low-pollution, high-efficiency demulsification of oily sludge, efficient dehydration without chemical additives, effective oil phase recovery, and resource utilization of residues through steps such as low-pollution, low-toxicity demulsification, ultra-high pressure pressing, high-temperature ceramsite production, secondary demulsification, and air flotation oil removal. The method provided by this invention not only improves processing efficiency and reduces processing costs but also achieves resource utilization of sludge.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for deep dewatering and resource recovery of oily sludge, comprising the following steps: S1. After pretreatment of the oily sludge, demulsification is performed, followed by settling and solid-liquid separation to obtain a liquid phase and solid residue; the liquid phase is then subjected to air flotation to remove oil, resulting in an aqueous phase and an oil phase. S2. The solid residue is squeezed to obtain mud cake and filtrate; S3. The mud cake is made into ceramsite; the filtrate is subjected to secondary demulsification and allowed to stand to separate into layers, yielding an oil phase and an aqueous phase; S4. Treat the aqueous phase obtained in step S1 and step S3 for wastewater treatment and discharge them; perform air flotation to remove oil from the oil phase obtained in step S1 and step S3 and collect the oil.

[0008] In this invention, in step S1, the pretreatment refers to sending the oily sludge into a centrifugal screening device via an elevator for preliminary sorting to remove large impurities such as sand and gravel larger than 4mm, and then crushing it by a pulverizer.

[0009] In this invention, in step S1, the reagents used for the demulsification treatment are octane- and decacarbon-mixed fatty acid methyl esters and biosurfactants.

[0010] The amount of the octane-decacarbon mixed fatty acid methyl ester used is 0.01% to 0.1% of the total mass of the oily sludge.

[0011] The biosurfactant is selected from one or more of lipopeptides, glycolipids, and rhamnolipids. The amount of the biosurfactant used is 0.005% to 0.05% of the total mass of the oily sludge. The mass ratio of the octane- and decacarbon-mixed fatty acid methyl ester to the biosurfactant is 2:1.

[0012] In this invention, in step S2, the extrusion is performed using pulsed parallel extrusion, divided into three stages: low pressure, medium pressure, and high pressure. The extrusion process yields a clay cake with a moisture content of less than 60%. Specifically, controlling the moisture content of the clay cake within the range of 20% to 60% facilitates shaping and reduces firing difficulty, effectively avoiding prolonged firing time and the tendency for the ceramsite to crack, thus ensuring the granulation effect and the density, strength, and other properties of the ceramsite.

[0013] The low-pressure conditions are: pressure of 0.3MPa~0.5MPa, time of 10~20min; The conditions for the medium pressure are: pressure of 1.0 MPa to 2.0 MPa, and time of 10 to 20 minutes; The conditions for high pressure are: pressure of 5MPa to 7MPa and time of 10 to 20 minutes.

[0014] Preferably, the low pressure, medium pressure, and high pressure are 0.4 MPa, 1.5 MPa, and 6 MPa, respectively, at which point the moisture content can be reduced to below 50% and the volume reduction rate to above 70%.

[0015] In this invention, step S3 involves the following steps for preparing the ceramsite: mixing mud cake with fly ash, clay, and zeolite powder, and then sintering the resulting material to obtain ceramsite. Specifically, in the mixture, the mass fraction of the mud cake is 30%-80%, the mass fraction of the fly ash is 10%-30%, the mass fraction of the clay is 10%-40%, and the mass fraction of the zeolite powder is 1%-10%.

[0016] In one embodiment, the mixture comprises 50% mud cake, 20% fly ash, 20% clay, and 10% zeolite powder by mass fraction.

[0017] The ceramsite produced by this invention has a particle size of 5-20 mm and can be sieved as needed to obtain a specific particle size distribution; its bulk density is 600-800 kg / m³. 3 Between; water absorption rate between 5% and 20%; cylinder compressive strength between 1.5 and 7.0 MPa.

[0018] The escape material obtained by this invention can be used as a building material, a soil conditioner in landscaping, and a biological filter material in sewage treatment.

[0019] In this invention, the sintering process is as follows: the material is preheated at 300~400℃ for 15~60min, and then sintered at 1100℃~1300℃ for 10~20min.

[0020] In this invention, the demulsifier and surfactant used for the second demulsification are the same as those used in step S1.

[0021] In this invention, in step S4, the air flotation oil removal is carried out as follows: air is drawn into a high-pressure dissolved air tank by a dissolved air pump, so that the air dissolves in water, and then released by a dissolved air release device under reduced pressure to form microbubbles, so that oil particles in the oil phase adhere to the bubbles and float to the water surface with the bubbles to form scum, thereby achieving oil-water separation. The conditions for air flotation oil removal are: dissolved air pressure of 0.32-0.50 MPa and processing time of 10-30 min.

[0022] Preferably, the dissolved gas pressure is 0.36 MPa, which provides the best separation effect.

[0023] The oily sludge described in this invention refers to sludge with an oil content between 3% and 10% and a water content exceeding 90%.

[0024] The present invention also provides a processing apparatus for implementing the above-mentioned processing method, comprising a conditioning and demulsification unit, a solid slag extrusion unit, and a mud cake ceramsite making unit connected in sequence; The filtrate outlet of the solid residue extrusion unit is connected to the secondary demulsification unit; The oil phase outlet of the conditioning and demulsification unit and the oil phase outlet of the secondary demulsification unit are both connected to the air flotation oil removal unit, which is connected to the oil recovery device. The aqueous phase outlet of the conditioning and demulsification unit and the aqueous phase outlet of the secondary demulsification unit are both connected to the wastewater treatment unit.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention are: This invention discloses a systematic method for deep dewatering and resource recovery of oily sludge. Through preliminary demulsification, efficient ultra-high pressure pressing, an innovative high-temperature ceramsite production process, and subsequent secondary demulsification, air flotation oil removal, and wastewater treatment, it achieves comprehensive treatment and resource utilization of oily sludge. Compared to traditional sludge treatment methods, the treatment method provided by this invention exhibits several significant advantages, as follows: In terms of dehydration efficiency, the ultra-high pressure pressing technology adopted by this invention on the basis of the previous demulsification treatment can significantly reduce the water content of sludge, making the treated sludge drier and easier to store, transport and further process. At the same time, through the high temperature ceramsite production process, the pressed sludge cake is transformed into ceramsite products with multiple uses, which not only solves the problem of sludge disposal, but also creates new economic benefits for enterprises.

[0026] In terms of resource recycling, this invention achieves high-purity separation of oil through secondary demulsification and air flotation oil removal technologies. The recovered oil can be reused, reducing resource waste. Furthermore, the wastewater treatment step ensures that the wastewater generated during the treatment process meets discharge standards, avoiding secondary pollution and protecting the ecological environment.

[0027] In summary, the treatment apparatus and method provided by this invention not only significantly reduce the moisture content of sludge but also successfully recover oil resources, while avoiding the environmental pollution problems associated with traditional treatment methods. Furthermore, the high-temperature ceramsite production process opens up new avenues for the secondary utilization of sludge, creating additional economic value. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the method for deep dewatering and resource recovery of oily sludge in oil fields according to the present invention.

[0029] Figure 2 This is a curve showing the change in moisture content of oily sludge. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, all reagents, materials, instruments, etc. used in the following examples are commercially available.

[0033] The reagents used in the following examples: Methyl ester of mixed octane and decacarbon fatty acids, CAS number 67762-39-4.

[0034] Example Taking an oily scum with a water content of 92% processed by a petrochemical company in Xinjiang as an example, the device and method provided by this invention are used for deep dehydration and resource recovery. The process flow diagram is as follows: Figure 1 As shown, the process includes: systematic demulsification treatment of sludge, ultra-high pressure pressing, high-temperature ceramsite production, secondary demulsification, air flotation oil removal, and wastewater treatment. Through these steps, efficient dewatering of sludge, oil recovery, and resource utilization can be achieved.

[0035] The processing device includes a conditioning and demulsification unit, a solid slag extrusion unit, and a mud cake ceramsite production unit connected in sequence. The filtrate outlet of the solid residue extrusion unit is connected to the secondary demulsification unit; The oil phase outlet of the conditioning and demulsification unit and the oil phase outlet of the secondary demulsification unit are both connected to the air flotation oil removal unit, which is connected to the oil recovery device. The aqueous phase outlet of the conditioning and demulsification unit and the aqueous phase outlet of the secondary demulsification unit are both connected to the wastewater treatment unit.

[0036] The specific processing steps are as follows: A. Pretreatment: The oily sludge is fed into a centrifugal screening device by an elevator for preliminary sorting to remove large impurities such as sand and gravel larger than 4mm, and then crushed by a crusher; B. Demulsification and solid-liquid separation: The pretreated oily sludge from step A is fed into a conditioning tank. Octa- and deca-carboxylic acid mixed methyl esters and biosurfactant lipopeptides are added to the tank for demulsification. The mixture is then stirred and homogenized using a mechanical propeller-type stirring system. After treatment, the solid and liquid phases are separated. The amount of octa- and deca-carboxylic acid mixed methyl esters used is 0.05% of the total mass of the oily sludge, and the amount of lipopeptides used is 0.025% of the total mass of the oily sludge.

[0037] C. Ultra-high pressure pressing: The solid residue separated in step B is fed into an ultra-high pressure pressing device and subjected to pulse-type parallel pressing, which is divided into three stages. The pressures of low pressure, medium pressure and high pressure are 0.4MPa, 1.5MPa and 6MPa respectively, to complete deep dewatering and reduce the moisture content of the sludge to about 50%. During this process, the capillary water in the filter cake can be further discharged by hot air blowing. Through a three-stage pressing process, the moisture content of the oily sludge gradually decreased from 92% to 82%, 66%, and 48%. For example... Figure 2 As shown.

[0038] D. High-temperature ceramsite production: The pressed mud cake from step C is processed into ceramsite using a wet granulation-sintering process at high temperature, thereby realizing resource utilization. The wet granulation-sintering process described in step D requires the following: the moisture content of the granulated cake is less than 60%, and fly ash, clay, and zeolite powder are added. By mass fraction, the mixture comprises 50% granulated cake, 20% fly ash, 20% clay, and 10% zeolite powder. The mixture is preheated at 300℃ for 30 minutes, and the sintering temperature is between 1100℃ and 1300℃ for approximately 15 minutes. E. Secondary demulsification: The filtrate produced by ultra-high pressure pressing in step C is subjected to secondary demulsification. The demulsifier and activator are the same as in step B to ensure more thorough separation of the oil phase and water phase. F. Air flotation for oil removal: The oil-water mixture generated in steps B and E is subjected to air flotation for oil removal. Air is drawn into a high-pressure dissolved air tank by a dissolved air pump, allowing the air to fully dissolve in the water. Then, the dissolved air is released under reduced pressure by a dissolved air release device to form microbubbles. The dissolved air pressure is controlled at 0.36 MPa to ensure that the dissolved air effect is within a good range. G. Oil phase collection: The oil phase separated in step F is collected, with a floating oil recovery rate of 82%. It is then transported to an oil separator or a special tank for collection and storage for reuse.

[0039] H. Aqueous phase treatment: The aqueous phase separated in step F is treated with wastewater, such as by deep filtration and activated carbon adsorption, to improve the quality of the effluent so that it meets the discharge standards before being discharged.

[0040] Comparative Example Similarly, oily sludge with a water content of 92% was selected from a petrochemical company in Xinjiang as the treatment target. After treatment using the traditional plate and frame pressing method, the water content of the sludge was reduced to 65%, and the crude oil recovery rate was 62%.

[0041] Results of the investigation into process factors: 1. Effects of demulsifiers The demulsifier, a mixture of octane- and deca-carboxylic fatty acid methyl esters, in the above embodiments was replaced with commercially available demulsifiers A and B, and the demulsification time was adjusted. The results are as follows.

[0042] Demulsifier A is NALCO EC6443A produced by Dow Chemical, whose main components are high molecular polymers (such as modified polyethers and polyacrylates) or composite surfactants; Demulsifier B is BASF LutensolTO 8 produced by BASF in Germany, whose main component is alkylphenol polyoxyethylene ether.

[0043] Table 1 Effects of different demulsifiers

[0044] As shown in Table 1, the octane-decacarbon mixed fatty acid methyl ester selected in this invention can significantly reduce the water content of sludge in a relatively short time.

[0045] 2. The effect of high pressure during extrusion Table 2 Effects of different high-pressure conditions

[0046] As shown in Table 2, with the increase of pressure and extrusion time, the moisture content of the cake decreases and the oil recovery rate increases. When the pressure exceeds 7 MPa, the moisture content of the cake continues to decrease, but the oil recovery rate also decreases.

[0047] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for deep dewatering and resource recovery of oily sludge, comprising the following steps: S1. After pretreatment of oily sludge, demulsification is performed, followed by settling and solid-liquid separation to obtain liquid phase and solid residue. The liquid phase is subjected to air flotation to remove oil, resulting in an aqueous phase and an oil phase; In step S1, the reagents used in the demulsification treatment are octane- and decacarbon-mixed fatty acid methyl esters and biosurfactants. The amount of the octadecto- and deca-carboxylic acid mixed fatty acid methyl ester used is 0.01% to 0.1% of the total mass of the oily sludge; The amount of the biosurfactant used is 0.005% to 0.05% of the total mass of the oily sludge; The mass ratio of the octane- and deca-carbon mixed fatty acid methyl ester to the biosurfactant is 2:1; S2. The solid residue is squeezed to obtain mud cake and filtrate; In step S2, the extrusion is performed using pulsed parallel extrusion, which is divided into three stages: low pressure, medium pressure, and high pressure. The low-pressure conditions are: pressure of 0.3MPa~0.5MPa, time of 10~20min; The conditions for the medium pressure are: pressure of 1.0 MPa to 2.0 MPa, and time of 10 to 20 minutes; The conditions for the high pressure are: pressure of 5MPa to 7MPa and time of 10 to 20 minutes. S3. The mud cake is made into ceramsite; the filtrate is subjected to secondary demulsification and allowed to stand to separate into layers, yielding an oil phase and an aqueous phase; S4. Treat the aqueous phase obtained in step S1 and step S3 for wastewater treatment and discharge them; perform air flotation to remove oil from the oil phase obtained in step S1 and step S3 and collect the oil.

2. The processing method according to claim 1, characterized in that, The biosurfactant is selected from one or more of lipopeptides, glycolipids, and rhamnolipids.

3. The processing method according to claim 1, characterized in that, In step S3, the preparation of the ceramsite is carried out according to the following operation: the mud cake is mixed with fly ash, clay and zeolite powder, and sintered to obtain ceramsite; In the mixture, the mass fraction of the mud cake is 30%-50%, the mass fraction of the fly ash is 10%-30%, the mass fraction of the clay is 10%-40%, and the mass fraction of the zeolite powder is 1%-10%.

4. The processing method according to claim 3, characterized in that, The sintering process is as follows: the material is preheated at 300~400℃ for 15~60min, and then sintered at 1100℃~1300℃ for 10~20min.

5. The processing method according to any one of claims 1-4, characterized in that, In step S4, the air flotation oil removal is carried out as follows: air is drawn into the high-pressure dissolved air tank by a dissolved air pump, so that the air dissolves in the water, and then released by a dissolved air release device under reduced pressure to form microbubbles, so that oil particles in the oil phase adhere to the bubbles and float to the water surface with the bubbles to form scum, thereby achieving oil-water separation. The conditions for air flotation oil removal are: dissolved air pressure of 0.32-0.50 MPa and processing time of 10-30 min.

6. The processing method according to any one of claims 1-4, characterized in that, The processing device used in the processing method includes a conditioning and demulsification unit, a solid slag extrusion unit, and a mud cake ceramsite production unit connected in sequence. The filtrate outlet of the solid residue extrusion unit is connected to the secondary demulsification unit; The oil phase outlet of the conditioning and demulsification unit and the oil phase outlet of the secondary demulsification unit are both connected to the air flotation oil removal unit, which is connected to the oil recovery device. The aqueous phase outlet of the conditioning and demulsification unit and the aqueous phase outlet of the secondary demulsification unit are both connected to the wastewater treatment unit.

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