Oily sludge resourceful treatment method based on hydrothermal technology

Abstract

The invention relates to the technical field of waste treatment, and discloses an oily sludge resourceful treatment method based on a hydrothermal technology, which comprises the following steps: step 1, transporting oily sludge to a treatment place from a tank truck, pumping the oily sludge into a closed sludge storage tank through a pipeline pump, and preparing a stirring device in the sludge storage tank to stir the sludge in the sludge storage tank; step 2, treating the stored sludge through a vibrating screen, screening out large-volume impurities in the sludge, and adding a demulsifying agent and a flocculating agent into the sludge in the sludge storage tank after the large-volume impurities are screened out; and step 3, heating the sludge to 60-80 DEG C through a steam heat exchange system. A high-temperature and high-pressure environment is arranged in the hydrothermal reaction kettle, so that an oil-water-solid three-phase interface in the oily sludge is promoted to be fully damaged, the viscosity of an oil phase is reduced, the oil-water separation efficiency is improved, and the problem of low oil-water separation efficiency in the oily sludge is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of waste treatment, and in particular to a method for resource treatment of oily sludge based on hydrothermal technology. Background Art

[0002] Oily sludge is an inevitable byproduct of the petrochemical industry, oil field development, and refining, storage, and transportation. Its main sources include oil tank cleaning, oil and gas separation equipment sediments, and sediments during pipeline transportation. Depending on the source, the composition of oily sludge is complex and varied, usually containing a large amount of oil, sediment, water, and suspended particles, and is a typical hazardous waste. Its main characteristics include high oil content, high water content, and complex composition structure, which increase the difficulty of treatment and bring great potential harm to the environment.

[0003] The rapid development of industrialization and the improvement of environmental protection requirements have put forward requirements for the treatment of oily sludge. Traditional treatment methods mainly include landfill, incineration and simple physical separation technology. However, the proposed technology has obvious limitations and cannot meet the needs of modern environmental protection and resource utilization. For example, landfilling easily leads to oil leakage and contamination of soil and groundwater; incineration will cause secondary pollution and high treatment costs; and physical separation technology cannot efficiently remove residual oil and impurities in oily sludge.

[0004] According to relevant research, the treatment of oily sludge needs to meet the requirements of harmlessness and should take into account the goal of resource utilization, that is, to recover oil, water and solid components from oily sludge and convert them into usable resources to achieve a win-win situation of economic and environmental benefits. However, traditional technologies have limited effects on the destruction and separation of the oil, water and solid three-phase interface in oily sludge, resulting in low resource utilization efficiency. At the same time, the existing treatment process has high energy consumption and expensive operating costs, which limits the promotion and application of technology.

[0005] Traditional treatment methods have limited ability to dehydrate solid sludge, resulting in high moisture content, poor fluidity, and unstable physical properties. The sludge cannot be used as a raw material for building materials or for safe landfill, which restricts the development of resource-based treatment of oily sludge.

[0006] Oily sludge from different sources has significant differences in composition and physical properties. Existing technologies cannot be flexibly adjusted when treating specific types of sludge, resulting in a narrow scope of application of the technology and insufficient process adaptability.

[0007] Therefore, those skilled in the art provide a method for resource recovery of oily sludge based on hydrothermal technology to solve the above-mentioned problems. Summary of the invention

[0008] In view of the deficiencies of the prior art, the present invention provides a method for resource processing of oily sludge based on hydrothermal technology to solve the problems raised in the above background technology.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for resource treatment of oily sludge based on hydrothermal technology, comprising:

[0010] Step 1: transport the oily sludge by tank truck to the treatment site, pump it into a closed sludge storage tank through a pipeline, and equip the sludge storage tank with a stirring device to stir the sludge in the sludge tank;

[0011] Step 2: Process the stored sludge through a vibrating screen to remove large-volume impurities in the sludge. After the large-volume impurities are removed, add a demulsifier and a flocculant to the sludge in the sludge storage tank;

[0012] Step 3, heating the sludge to 60°C to 80°C through a steam heat exchange system;

[0013] Step 4, the oily sludge heated by the preheating device in step 3 is pumped from the sludge storage tank into the hydrothermal reactor through the conveying pipeline. In the hydrothermal reactor, the sludge is maintained in an environment of 180° C. to 250° C. and 2 MPa to 10 MPa for 30 to 120 minutes, and is stirred again by means of a stirring device for full contact. After the reaction is completed, the sludge mixture in the hydrothermal reactor will contain a portion of free oil phase, water phase and mud residue;

[0014] Step 5: After the product of the hydrothermal reaction flows out of the hydrothermal reactor, it enters a horizontal screw centrifuge for solid-liquid separation. The horizontal screw centrifuge separates the reaction product into solid sludge and a liquid mixture through centrifugal force, and the separated sludge is transported to a drying device;

[0015] Step 6: The liquid mixture in the solid-liquid separation of step 5 enters the oil-water separation equipment through a pipeline, and the oil phase and the water phase are separated by gravity sedimentation and membrane separation technology. The oil phase is stored separately after separation, and the water phase is transported to the subsequent water treatment unit;

[0016] Step 7: The separated oil phase is transported to a refining device and a fuel utilization device, and is used as an industrial raw material and fuel after purification;

[0017] Step 8, dehydrating the solid sludge in the solid-liquid separation in step 5 through a drying device, and using the dehydrated solid sludge for producing building materials and safe landfill;

[0018] Step 9: Reuse the water phase treated by the water treatment unit in step 6 in the conditioning and reaction stages, and discharge the unreused portion into the external water body and treatment system after meeting the discharge standards, thus completing the resource recovery process.

[0019] Preferably, the demulsifier added in step 2 is a nonionic demulsifier, the flocculant is polyacrylamide, the addition ratio of the demulsifier is controlled at 1% to 3% according to the oil content of the sludge, and the addition ratio of the flocculant is controlled at 1% to 2%.

[0020] Preferably, when the oily sludge is heated by the preheating device in step 3, the steam pressure is controlled at 0.4 MPa to 0.6 MPa, and the preheating time is adjusted to 10 minutes to 30 minutes according to the initial temperature of the sludge.

[0021] Preferably, the inner wall of the hydrothermal reactor in step 4 is coated with a corrosion-resistant material, the material comprising a nickel-based alloy and high-temperature resistant stainless steel, to prevent corrosion and wear of the reactor wall during the high-temperature and high-pressure reaction process;

[0022] The stirring device in step 4 is an axial flow stirrer, and the stirring speed is controlled at 50 r / min to 200 r / min.

[0023] Preferably, the centrifugal speed range of the horizontal screw centrifuge in step 5 is controlled at 2000r / min to 4000r / min, and the centrifugal time range is controlled at 1min to 10min to adapt to sludge with different solid contents and reduce the moisture content of the solid sludge to 50% to 60%.

[0024] Preferably, the oil-water separation equipment in step 6 adopts a combination of gravity sedimentation and ultrafiltration membrane separation, wherein the pore size of the ultrafiltration membrane is 0.01 micron to 0.1 micron;

[0025] When the water phase separated in step 6 enters the subsequent water treatment unit, it is first subjected to coagulation and sedimentation treatment, then passes through a biological filter to degrade organic matter, and finally passes through an ultrafiltration membrane for deep treatment, so that the water quality reaches the standard for recycling or qualified discharge.

[0026] Preferably, the time t used for gravity sedimentation in step 6 satisfies the formula:

[0027]

[0028] Where t is the gravity sedimentation time, μ is the dynamic viscosity of the liquid, g is the gravitational acceleration, and ρ s is the density of the oil droplet, ρ w is the density of water, d is the diameter of the oil droplet;

[0029] The gravity sedimentation process needs to be optimized in time according to the density and diameter of the oil droplets in the oily sludge to improve the separation efficiency.

[0030] Preferably, the flux J of the ultrafiltration membrane separation process in step 6 satisfies the formula:

[0031] Where J is the water flux of the ultrafiltration membrane, ΔP is the pressure difference on the opposite sides of the membrane, Δπ is the osmotic pressure difference on the opposite sides of the membrane, u is the dynamic viscosity of water, and R is the total resistance of the membrane;

[0032] The membrane flux control range is 0.001m 3 / m 2 s to 0.01m 3 / m 2 ·s.

[0033] Preferably, the dehydration efficiency E of the solid sludge in step 5 satisfies the formula:

[0034]

[0035] Where E is the dehydration efficiency, W i is the mass of solid sludge before entering the drying device, W f It is the mass of solid sludge after being processed by the solid sludge drying device;

[0036] The drying efficiency needs to be controlled at 50% to 70% to ensure the resource utilization performance of the sludge.

[0037] Preferably, the recycling ratio R of the water phase in step 9 satisfies the formula:

[0038]

[0039] Among them, R is the reuse ratio of the water phase, Q r Q is the amount of water used in the conditioning and reaction process. t The total amount of water output from the water treatment unit;

[0040] The recycling ratio needs to be controlled between 80% and 90%.

[0041] The present invention provides a method for resource treatment of oily sludge based on hydrothermal technology. It has the following beneficial effects:

[0042] 1. The present invention sets a high temperature and high pressure environment in the hydrothermal reactor to fully destroy the oil, water and solid three-phase interface in the oily sludge, reduce the viscosity of the oil phase, and improve the oil-water separation efficiency, thereby effectively solving the problem of low oil-water separation efficiency in the oily sludge.

[0043] 2. The present invention separates solid and liquid through hydrothermal reaction combined with a horizontal screw centrifuge, so that the residual oil content in the solid sludge is significantly reduced, achieving the goal of significantly reducing the oil content of the sludge, and solving the problem that the solid sludge has a high residual oil content and cannot meet environmental protection requirements.

[0044] 3. The present invention adopts a water treatment unit technology that combines coagulation sedimentation, biodegradation and ultrafiltration membrane deep treatment to effectively remove suspended matter, organic matter and residual oil in the water phase, achieve water quality standards and recycling, and solve the problems of incomplete wastewater treatment and low recycling rate.

[0045] 4. The present invention reduces the moisture content of solid sludge through a drying device, so that the sludge has physical stability and is suitable as a raw material for building materials or for safe landfill, thereby realizing resource utilization of solid sludge and solving the problem that solid sludge cannot be utilized as a resource in traditional processes.

[0046] 5. The present invention realizes the effective recovery and treatment of pollutants through a fully closed system combined with oil-water separation, solid-liquid separation and supporting waste gas and wastewater treatment technologies, thereby solving the serious problem of secondary pollution in traditional treatment processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0048] In order to make the technical personnel in the technical field understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in combination with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a partial embodiment of the present invention, not a complete embodiment. Based on the embodiment of the present invention, other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present invention.

[0049] The present invention is described in detail below in conjunction with the accompanying drawings:

[0050] Example:

[0051] Please see attached Figure 1 The embodiment of the present invention provides a method for resource treatment of oily sludge based on hydrothermal technology, comprising:

[0052] Step 1: transport the oily sludge by tank truck to the treatment site, pump it into a closed sludge storage tank through a pipeline, and equip the sludge storage tank with a stirring device to stir the sludge in the sludge tank;

[0053] Step 2: Process the stored sludge through a vibrating screen to remove large-volume impurities in the sludge. After the large-volume impurities are removed, add a demulsifier and a flocculant to the sludge in the sludge storage tank;

[0054] Step 3, heating the sludge to 60°C to 80°C through a steam heat exchange system;

[0055] Step 4, the oily sludge heated by the preheating device in step 3 is pumped from the sludge storage tank into the hydrothermal reactor through the conveying pipeline. In the hydrothermal reactor, the sludge is maintained in an environment of 180° C. to 250° C. and 2 MPa to 10 MPa for 30 to 120 minutes, and is stirred again by means of a stirring device for full contact. After the reaction is completed, the sludge mixture in the hydrothermal reactor will contain a portion of free oil phase, water phase and mud residue;

[0056] Step 5: After the product of the hydrothermal reaction flows out of the hydrothermal reactor, it enters a horizontal screw centrifuge for solid-liquid separation. The horizontal screw centrifuge separates the reaction product into solid sludge and a liquid mixture through centrifugal force, and the separated sludge is transported to a drying device;

[0057] Step 6: The liquid mixture in the solid-liquid separation of step 5 enters the oil-water separation equipment through a pipeline, and the oil phase and the water phase are separated by gravity sedimentation and membrane separation technology. The oil phase is stored separately after separation, and the water phase is transported to the subsequent water treatment unit;

[0058] Step 7: The separated oil phase is transported to a refining device and a fuel utilization device, and is used as an industrial raw material and fuel after purification;

[0059] Step 8, dehydrating the solid sludge in the solid-liquid separation in step 5 through a drying device, and using the dehydrated solid sludge for producing building materials and safe landfill;

[0060] Step 9: Reuse the water phase treated by the water treatment unit in step 6 in the conditioning and reaction stages, and discharge the unreused portion into the external water body and treatment system after meeting the discharge standards, thus completing the resource recovery process.

[0061] Benefits of step 1: By setting up a closed sludge storage tank and a stirring device, the uniformity of the oily sludge during storage and preliminary treatment is ensured, the leakage and secondary pollution of volatile organic compounds are effectively prevented, and sludge raw materials are provided for subsequent treatment links;

[0062] Benefits of step 2: Remove large-volume impurities through the vibrating screen to avoid damage to the equipment and improve equipment operation efficiency; add demulsifiers and flocculants to initially destroy the oil-water-solid three-phase interface structure to provide conditions for subsequent oil-water separation;

[0063] Benefits of step 3: Using the steam heat exchange system to heat the sludge to 60°C to 80°C effectively reduces the viscosity of the sludge, improves fluidity, enhances the oil-water separation effect, and creates temperature conditions for subsequent hydrothermal reactions;

[0064] Benefits of step 4: By setting a high temperature and high pressure environment in the hydrothermal reactor, the interface structure of the oil, water and solid phases is destroyed, the viscosity of the oil phase is significantly reduced and the release of the oil phase is promoted, so that the oil, water and solid phases are fully separated and the overall separation efficiency is improved;

[0065] Benefits of step 5: The reaction products are separated into solid and liquid by a horizontal screw centrifuge. The effective separation of solid sludge and liquid mixture provides a good basis for subsequent treatment; the solid sludge is transported to the drying device separately, which is convenient for resource utilization;

[0066] Benefits of step 6: Use gravity sedimentation and membrane separation technology to efficiently separate the oil phase and water phase in the liquid mixture, ensuring the purity of the oil phase and the standard treatment of the water phase, providing guarantee for resource utilization and environmentally friendly treatment;

[0067] Benefits of step 7: The separated oil phase is refined and processed as industrial raw materials and fuel, maximizing resource recycling, increasing economic value, and reducing the impact of waste oil on the environment;

[0068] Benefits of step 8: The moisture content of the solid sludge is reduced by the drying device, so that the solid sludge has good physical stability, which is convenient for use as a building material or for safe landfill, realizing the resource utilization of solid waste and reducing the processing cost;

[0069] Benefits of Step 9: After the water phase is deeply treated by the water treatment unit, part of it is reused in the conditioning and reaction stages, and the unreused part is discharged after meeting the standards, thereby reducing the use of fresh water, reducing the impact of wastewater on the environment, and achieving efficient recycling of water resources.

[0070] In summary, the present invention combines hydrothermal technology and a variety of physical and chemical separation technologies to achieve efficient separation and resource utilization of oil, water and solid phases in oily sludge. Each step is closely linked in the process to solve the technical problems of low efficiency, high residual oil and heavy pollution in the treatment of oily sludge, and significantly reduce operating costs and environmental risks through resource utilization and closed-loop process design, providing a technical solution for the harmless, reduced and resource-based treatment of oily sludge.

[0071] The demulsifier added in step 2 is a non-ionic demulsifier, and the flocculant is polyacrylamide. The addition ratio of the demulsifier is controlled at 1% to 3% according to the oil content of the sludge, and the addition ratio of the flocculant is controlled at 1% to 2%.

[0072] Non-ionic demulsifiers have a mild effect on the oil-water interface in sludge, can effectively destroy the oil-water interface structure, reduce the interfacial tension between oil droplets, enhance the dispersibility of the oil phase, and facilitate subsequent oil-water separation. Non-ionic demulsifiers are suitable for oily sludge with high oil content or complex components, while ensuring the separation effect, avoiding excessive chemical pollution to the water quality.

[0073] Polyacrylamide is a highly efficient flocculant that can quickly settle solid particles in mud-water mixtures by adsorbing suspended particles and forming flocs, thereby clarifying the liquid phase, providing processing conditions for subsequent solid-liquid separation, and reducing the load on centrifugal equipment.

[0074] The addition ratio of demulsifier and flocculant is controlled according to the oil content of sludge to avoid waste of resources and increase of treatment cost caused by excessive dosage of agents, while ensuring the stability of treatment effect. The ratio of demulsifier is between 1% and 3%, which meets the needs of sludge with different oil content; the ratio of flocculant is between 1% and 2%, which ensures the flocculation and separation of suspended particles.

[0075] When the oily sludge is heated by the preheating device in step 3, the steam pressure is controlled at 0.4 MPa to 0.6 MPa, and the preheating time is adjusted to 10 minutes to 30 minutes according to the initial temperature of the sludge.

[0076] Precise control of the steam pressure range ensures that the preheating device can efficiently transfer heat and quickly heat the oily sludge to the target temperature. It can stably supply heat and avoid equipment loss and safety risks caused by excessive pressure, thereby improving preheating efficiency and extending equipment service life.

[0077] Dynamically adjusting the preheating time according to the initial sludge temperature helps avoid energy waste while ensuring that the sludge achieves appropriate fluidity and uniform heating. Rapid preheating in a short period of time reduces sludge viscosity, making the oil phase easy to release and providing temperature and flow conditions for subsequent hydrothermal reactions.

[0078] The reasonable range design of steam pressure and preheating time avoids excessive energy use, while ensuring the effect of sludge preheating, reducing the steam demand per unit processing volume, and thus achieving efficient energy utilization and reduced operating costs.

[0079] In step 4, the inner wall of the hydrothermal reactor is coated with corrosion-resistant materials, including nickel-based alloys and high-temperature resistant stainless steel, to prevent corrosion and wear of the reactor wall during the high-temperature and high-pressure reaction process;

[0080] In step 4, the stirring device is an axial flow stirrer, and the stirring speed is controlled at 50 r / min to 200 r / min.

[0081] In step 4, the inner wall of the hydrothermal reactor is coated with corrosion-resistant materials and an axial flow agitator is installed to improve the durability of the equipment and the reaction efficiency. The corrosion-resistant material effectively prevents corrosion and wear of the reactor wall under high temperature and high pressure conditions, prolongs the service life of the equipment and reduces maintenance costs; the axial flow agitator ensures the full mixing and efficient reaction of the sludge and hydrothermal medium by flexibly adjusting the stirring speed, improves the safety and stability of the reactor, and provides protection for the resource treatment of oily sludge.

[0082] In step 5, the centrifugal speed range of the horizontal screw centrifuge is controlled at 2000r / min to 4000r / min, and the centrifugal time range is controlled at 1min to 10min to adapt to sludge with different solid contents and reduce the moisture content of the solid sludge to 50% to 60%.

[0083] The dehydration efficiency E of the solid sludge in step 5 satisfies the formula:

[0084]

[0085] Where E is the dehydration efficiency, W i is the mass of solid sludge before entering the drying device, W f It is the mass of solid sludge after being processed by the solid sludge drying device;

[0086] The drying efficiency needs to be controlled between 50% and 70% to ensure the resource utilization of the sludge.

[0087] By controlling the centrifugal speed and time interval, the horizontal screw centrifuge can be flexibly adjusted for sludge with different solid contents to ensure maximum separation effect, meet the treatment needs of various types of oily sludge, and improve the applicability and flexibility of the process.

[0088] The centrifugal force at high speed can quickly separate the solid particles and liquid mixture in the sludge, shorten the separation time, improve the processing efficiency, and reduce the energy consumption and load of the subsequent drying process.

[0089] The moisture content of the solid sludge after centrifugal separation is reduced to 50% to 60%, which provides good conditions for the dehydration treatment of the subsequent drying device, reduces energy consumption, and improves the resource utilization value of the sludge.

[0090] By quantifying the dehydration efficiency and clarifying the control range, the physical stability and resource utilization performance of the sludge in subsequent treatment are guaranteed, while providing a basis for the production of building materials or safe landfill.

[0091] After the solid sludge is dehydrated to a moisture content of 50% to 60%, the drying efficiency is controlled at 50% to 70%, thereby increasing the dryness of the sludge. Therefore, the solid sludge can be used as a raw material for producing building materials, meeting the environmental requirements for safe landfill.

[0092] By controlling the moisture content and drying efficiency of the sludge, the transportation cost and resource consumption can be reduced, and the economic and environmental benefits of sludge resource processing can be achieved.

[0093] In step 6, the oil-water separation equipment uses a combination of gravity sedimentation and ultrafiltration membrane separation, wherein the pore size of the ultrafiltration membrane is 0.01 micron to 0.1 micron;

[0094] When the separated water phase in step 6 enters the subsequent water treatment unit, it is first subjected to coagulation and sedimentation treatment, then passes through a biological filter to degrade organic matter, and finally passes through an ultrafiltration membrane for deep treatment, so that the water quality reaches the standard for recycling or qualified discharge.

[0095] The time t used for gravity settling in step 6 satisfies the formula:

[0096]

[0097] Where t is the gravity sedimentation time, μ is the dynamic viscosity of the liquid, g is the gravitational acceleration, and ρ s is the density of the oil droplet, ρ w is the density of water, d is the diameter of the oil droplet;

[0098] The gravity sedimentation process needs to be optimized according to the density and diameter of the oil droplets in the oily sludge to improve the separation efficiency.

[0099] The flux J of the ultrafiltration membrane separation process in step 6 satisfies the formula:

[0100] Where J is the water flux of the ultrafiltration membrane, ΔP is the pressure difference on the opposite sides of the membrane, Δπ is the osmotic pressure difference on the opposite sides of the membrane, u is the dynamic viscosity of water, and R is the total resistance of the membrane;

[0101] The membrane flux control range is 0.001m 3 / m 2 s to 0.01m 3 / m 2 ·s.

[0102] Coagulation and sedimentation: By adding coagulants, the suspended particles and residual oil droplets in the water phase form floccules and precipitate, which greatly reduces the turbidity and provides a good foundation for subsequent treatment.

[0103] Biological filter: Use microorganisms to degrade organic matter in the water phase, reduce chemical oxygen demand and biochemical oxygen demand, and achieve biological purification of water quality.

[0104] Ultrafiltration membrane deep treatment: fine filtration of the effluent from the biofilter to remove tiny particles and organic residues to ensure that the effluent quality meets the reuse or discharge standards.

[0105] Optimize gravity sedimentation time: By optimizing the parameters of density difference and oil droplet size, the oil droplet separation time can be shortened, the oil-water separation efficiency can be improved, and the residual oil content can be reduced.

[0106] Enhance water purification: Comprehensively adopt physical separation (ultrafiltration membrane), chemical treatment (coagulation and sedimentation) and biodegradation (filter tank) technologies to ensure excellent effluent quality and meet recycling or discharge requirements.

[0107] In summary, step 6 combines gravity sedimentation and ultrafiltration membrane separation technology, and optimizes sedimentation time and membrane flux to achieve efficient oil-water separation and water phase purification. At the same time, the subsequent water treatment unit ensures that the effluent meets the standards for reuse or discharge through a multi-stage treatment process. The formulaic design clarifies the parameters of oil droplet sedimentation time and membrane separation efficiency, making the separation process highly controllable, improving separation efficiency, reducing pollutant emissions, and significantly enhancing the ability to recycle resources, providing support for the environmentally friendly treatment and economic application of oily sludge.

[0108] The reuse ratio R of the water phase in step 9 satisfies the formula:

[0109]

[0110] Among them, R is the reuse ratio of the water phase, Q r Q is the amount of water used in the conditioning and reaction process. t The total amount of water output from the water treatment unit;

[0111] The recycling ratio needs to be controlled between 80% and 90%.

[0112] By reusing 80% to 90% of the treated water for conditioning and hydrothermal reaction, the demand for external fresh water resources can be greatly reduced, the cost of industrial water use can be reduced, and the pressure of water resource shortage can be alleviated.

[0113] Most of the treated water is reused, and a small part is required to meet discharge standards, which significantly reduces the total amount of discharged wastewater, reduces the operating load of the wastewater treatment unit, and extends the service life of the treatment facilities.

[0114] A high proportion of water phase reuse reduces the amount of discharged water and the spread of pollutants, reduces environmental pressure, and at the same time reduces the operating costs of wastewater treatment chemicals and equipment energy consumption, achieving the unity of economic and environmental benefits.

[0115] In summary, step 9 controls the water phase reuse ratio at 80% to 90%, achieving efficient recycling of water resources while ensuring process requirements. By optimizing the design of the reuse water volume, the consumption of fresh water is reduced, the wastewater discharge and treatment burden are significantly reduced, and the dual goals of energy saving and environmental protection are achieved. Formulated reuse ratio control enables precise use of water resources and provides a guarantee for the sustainability of the oily sludge treatment process.

[0116] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recycling oily sludge based on hydrothermal technology, characterized in that: include: Step 1: transport the oily sludge by tank truck to the treatment site, pump it into a closed sludge storage tank through a pipeline, and equip the sludge storage tank with a stirring device to stir the sludge in the sludge tank; Step 2: Process the stored sludge through a vibrating screen to remove large-volume impurities in the sludge. After the large-volume impurities are removed, add a demulsifier and a flocculant to the sludge in the sludge storage tank; Step 3, heating the sludge to 60°C to 80°C through a steam heat exchange system; Step 4, the oily sludge heated by the preheating device in step 3 is pumped from the sludge storage tank into the hydrothermal reactor through the conveying pipeline. In the hydrothermal reactor, the sludge is maintained in an environment of 180° C. to 250° C. and 2 MPa to 10 MPa for 30 to 120 minutes, and is stirred again by means of a stirring device for full contact. After the reaction is completed, the sludge mixture in the hydrothermal reactor will contain a portion of free oil phase, water phase and mud residue; Step 5: After the product of the hydrothermal reaction flows out of the hydrothermal reactor, it enters a horizontal screw centrifuge for solid-liquid separation. The horizontal screw centrifuge separates the reaction product into solid sludge and a liquid mixture through centrifugal force, and the separated sludge is transported to a drying device; Step 6: The liquid mixture in the solid-liquid separation of step 5 enters the oil-water separation equipment through a pipeline, and the oil phase and the water phase are separated by gravity sedimentation and membrane separation technology. The oil phase is stored separately after separation, and the water phase is transported to the subsequent water treatment unit; Step 7: The separated oil phase is transported to a refining device and a fuel utilization device, and is used as an industrial raw material and fuel after purification; Step 8, dehydrating the solid sludge in the solid-liquid separation in step 5 through a drying device, and using the dehydrated solid sludge for producing building materials and safe landfill; Step 9: Reuse the water phase treated by the water treatment unit in step 6 in the conditioning and reaction stages, and discharge the unreused portion into the external water body and treatment system after meeting the discharge standards, thus completing the resource recovery process.

2. The method for recycling oily sludge based on hydrothermal technology according to claim 1 is characterized in that: The demulsifier added in step 2 is a nonionic demulsifier, and the flocculant is polyacrylamide. The addition ratio of the demulsifier is controlled at 1% to 3% according to the oil content of the sludge, and the addition ratio of the flocculant is controlled at 1% to 2%.

3. The method for recycling oily sludge based on hydrothermal technology according to claim 1 is characterized in that: When the oily sludge is heated by the preheating device in step 3, the steam pressure is controlled at 0.4 MPa to 0.6 MPa, and the preheating time is adjusted to 10 minutes to 30 minutes according to the initial temperature of the sludge.

4. The method for recycling oily sludge based on hydrothermal technology according to claim 1 is characterized in that: In step 4, the inner wall of the hydrothermal reactor is coated with corrosion-resistant materials, including nickel-based alloys and high-temperature resistant stainless steel, to prevent corrosion and wear of the reactor wall during the high-temperature and high-pressure reaction process; The stirring device in step 4 is an axial flow stirrer, and the stirring speed is controlled at 50 r / min to 200 r / min.

5. The method for recycling oily sludge based on hydrothermal technology according to claim 1 is characterized in that: In step 5, the centrifugal speed range of the horizontal screw centrifuge is controlled within 2000r / min to 4000r / min, and the centrifugal time range is controlled within 1min to 10min to adapt to sludge with different solid contents and reduce the moisture content of the solid sludge to 50% to 60%.

6. The method for recycling oily sludge based on hydrothermal technology according to claim 1 is characterized in that: The oil-water separation equipment in step 6 adopts a combination of gravity sedimentation and ultrafiltration membrane separation, wherein the pore size of the ultrafiltration membrane is 0.01 micron to 0.1 micron; When the water phase separated in step 6 enters the subsequent water treatment unit, it is first subjected to coagulation and sedimentation treatment, then passes through a biological filter to degrade organic matter, and finally passes through an ultrafiltration membrane for deep treatment, so that the water quality reaches the standard for recycling or qualified discharge.

7. The method for recycling oily sludge based on hydrothermal technology according to claim 6 is characterized in that: The time t used for gravity sedimentation in step 6 satisfies the formula: Where t is the gravity sedimentation time, μ is the dynamic viscosity of the liquid, g is the gravitational acceleration, and ρ s is the density of the oil droplet, ρ w is the density of water, d is the diameter of the oil droplet; The gravity sedimentation process needs to be optimized in time according to the density and diameter of the oil droplets in the oily sludge to improve the separation efficiency.

8. The method for recycling oily sludge based on hydrothermal technology according to claim 7 is characterized in that: The flux J of the ultrafiltration membrane separation process in step 6 satisfies the formula: Where J is the water flux of the ultrafiltration membrane, ΔP is the pressure difference on the opposite sides of the membrane, Δπ is the osmotic pressure difference on the opposite sides of the membrane, u is the dynamic viscosity of water, and R is the total resistance of the membrane; The membrane flux control range is 0.001m 3 / m 2 s to 0.01m 3 / m 2 ·s.

9. The method for recycling oily sludge based on hydrothermal technology according to claim 5 is characterized in that: The dehydration efficiency E of the solid sludge in step 5 satisfies the formula: Where E is the dehydration efficiency, W i is the mass of solid sludge before entering the drying device, W f It is the mass of solid sludge after being treated by the solid sludge drying device; The drying efficiency needs to be controlled at 50% to 70% to ensure the resource utilization performance of the sludge.

10. The method for recycling oily sludge based on hydrothermal technology according to claim 1, characterized in that: The recycling ratio R of the water phase in step 9 satisfies the formula: Among them, R is the reuse ratio of the water phase, Q r Q is the amount of water used in the conditioning and reaction process. t The total amount of water output from the water treatment unit; The recycling ratio needs to be controlled between 80% and 90%.

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