Process for synergistic electro-osmotic dewatering of oil-containing sludge with surfactant elution and biochar and application thereof

Abstract

This invention belongs to the field of solid waste treatment and resource utilization technology, and discloses a surfactant elution and biochar synergistic electro-osmotic dewatering process for oily sludge and its application. Addressing the problems of high water content (>96%), strong insulation due to oil film coating, and difficulties in conventional dewatering of oily sludge, this invention adopts a coupled route of "liquid phase modification - mechanical pre-dewatering - electro-osmotic deep drying". First, surfactants are used to remove the oil film on the surface of sludge particles; then, biochar is added to construct a rigid conductive framework, and the water content is reduced to 80%~85% to form a sludge cake through flocculation and mechanical pressure filtration; finally, deep dewatering is carried out under the synergistic effect of electric field and mechanical pressure. This invention uses biochar to solve the problems of high resistance and high energy consumption of oily sludge, while combining Joule heating effect to assist in viscosity reduction. The water content of the treated sludge can be reduced to below 60%, and some oil is recovered during dewatering. It features high treatment efficiency, low energy consumption, long electrode life, and high resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and resource utilization technology, specifically a surfactant elution and biochar synergistic electro-osmotic dehydration process and its application for oily sludge. Background Technology

[0002] Oily sludge is a typical hazardous waste generated during petroleum extraction, transportation, refining, and oily wastewater treatment. Due to its high content of petroleum hydrocarbons, colloidal asphaltene, and fine solid particles, it forms an extremely stable three-phase emulsion system of oil, water, and solids. Currently, oily sludge generated by the petrochemical industry typically has a water content as high as 96% to 98% and is massive in volume. Traditional treatment methods usually involve first reducing the water content to around 80% through flocculation conditioning combined with mechanical dewatering, followed by thermal drying or incineration. However, because the sludge particles are coated with a tough oil film, and due to steric hindrance, bound water is difficult to separate mechanically, making it difficult to reduce the water content below 75% with conventional mechanical dewatering. Directly feeding high-moisture sludge cake into the thermal drying or incineration unit not only results in enormous energy consumption but also easily leads to secondary pollution problems such as equipment coking and excessive exhaust gas emissions.

[0003] Electroosmotic dewatering technology utilizes the electroosmotic flow phenomenon under the action of a DC electric field to effectively remove bound water from sludge, and is considered an effective means of achieving deep sludge dewatering. However, its direct application to oily sludge faces significant technical bottlenecks: First, there is the insulation problem. The oil in oily sludge acts as a poor conductor, coating the particle surface in the form of an oil film and cutting off the current path, resulting in a sludge resistivity that is 1-2 orders of magnitude higher than that of ordinary municipal sludge, leading to extremely high processing energy consumption. Second, there is the anode passivation effect. Under the action of an electric field, negatively charged oil droplets migrate towards the anode, easily forming a dense insulating oil layer on the anode surface, causing the current density to decay rapidly and forcing the dewatering process to stop. In addition, there is the risk of loss of conductivity. As the dewatering process proceeds, the sludge cake inevitably shrinks and cracks, leading to poor electrode contact and further interrupting the conductive path, making it difficult for traditional electroosmotic technology to operate stably.

[0004] To improve the effectiveness of electro-osmotic dewatering, existing technologies mainly focus on adding chemical conditioners or performing graded physical or biological modifications. For example, CN109734269A discloses a graded conditioning method to improve the electro-osmotic dewatering performance of sludge, which first uses flocculation and mechanical dewatering, followed by biological cell disruption and physical modification to enhance the effect. However, this method has a lengthy process route (flocculation-mechanical-biological-electro-osmosis), and biological enzymes are often sensitive to the environment, making it difficult to efficiently break down the stubborn "oil-solid" coating in the complex toxic environment of oily sludge. In addition, CN106830592A proposes a sludge electro-dewatering method enhanced by conditioning salts, which reduces energy consumption by adding conditioning salts and combining them with mechanical pressurization. Although the addition of inorganic salts increases the conductivity of the liquid phase, high concentrations of salt ions under the action of an electric field can easily exacerbate the electrochemical corrosion of the anode, shorten the electrode life, and simply increasing the electrolyte concentration cannot solve the problem of poor electrode contact caused by sludge cake shrinkage during dewatering.

[0005] In summary, current methods for deep dewatering oily sludge still face the challenges of "high insulation, easy passivation, and high energy consumption." There is an urgent need to develop a low-energy-consumption treatment process that can effectively disrupt the oil film insulation layer, construct stable conductive channels, and simultaneously achieve dewatering and deoiling. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing oily sludge treatment technologies, such as high power consumption due to oil film insulation, easy passivation and corrosion of the anode, and power outages due to sludge cake shrinkage in the later stages of dewatering. This invention provides a surfactant elution and biochar-assisted electro-osmotic dewatering process for oily sludge. This process aims to solve the technical problems of difficult deep dewatering of oily sludge, high energy consumption, and significant equipment wear and tear.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] According to a first aspect of the present invention, a process for surfactant elution and biochar-co-assisted electro-osmotic dewatering of oily sludge is provided, comprising the following steps:

[0009] S1. Liquid phase homogenization: Take oily sludge raw mud with a water content of 96%~98%, remove impurities, and use mechanical stirring at a speed of 100~300rpm for 10~30 minutes to homogenize and adjust it so that the solid-liquid-oil three phases are mixed evenly.

[0010] S2, Primary Interface Modification: Add surfactant to homogenized sludge and stir rapidly to disrupt the oil-water interface on the surface of sludge particles.

[0011] S3. Construction of the secondary conductive framework: Add biochar powder to the primary modified sludge, stir and mix to make the biochar evenly dispersed and construct conductive channels;

[0012] S4. Solid-liquid separation and cake making: Flocculant is added to carry out flocculation reaction, and free water is removed by mechanical dewatering to form pre-dehydrated cement cake containing biochar.

[0013] S5. Electro-osmotic deep dehydration: The pre-dehydrated cement cake is placed between the anode and cathode of the electro-osmosis device, and direct current is passed through while mechanical pressure is applied to perform deep dehydration.

[0014] Preferred:

[0015] In step S2, the surfactant is an anionic surfactant or a biosurfactant; the amount of surfactant added is 0.1% to 0.5% of the oven-dry solids mass of the sludge. More preferably, the anionic surfactant is sodium dodecylbenzenesulfonate, and the biosurfactant is rhamnolipid biosurfactant.

[0016] The speed of the rapid stirring is 200~400 rpm, and the stirring time is 5~10 minutes.

[0017] Preferred:

[0018] In step S3, the biochar is prepared by pyrolysis of biomass raw materials at a high temperature above 600℃ under anaerobic or limited oxygen conditions; the particle size of the biochar passes through a 60-100 mesh sieve; the biomass raw materials are preferably agricultural or forestry waste rich in lignocellulose (such as straw, sawdust, fruit shells, etc.); the BET specific surface area of ​​the biochar is 150-400 m² / g, and the electrical conductivity is 0.1-2.0 S / cm; the dosage of the biochar is 10%-50% of the oven-dry solids mass of the sludge. More preferably, the dosage of the biochar is 20%-30% of the oven-dry solids mass of the sludge. More preferably, the pyrolysis is carried out under the protection of an inert gas (such as nitrogen).

[0019] Preferred:

[0020] In step S4, the flocculant is cationic polyacrylamide (CPAM), and the dosage is 0.1% to 0.3% of the oven-dry solids mass of the sludge; the mechanical dewatering method is any one of plate and frame filter press, belt filter press, or vacuum filtration; through this step, the moisture content of the pre-dewatered cement cake is controlled at 80% to 85%.

[0021] Preferred:

[0022] In step S5, the mechanical pressure ranges from 100 kPa to 500 kPa; the voltage gradient of the direct current is from 10 V / cm to 40 V / cm; and the electroosmotic dehydration time is from 10 to 60 minutes.

[0023] Further preferred: During the electroosmotic deep dehydration process, the Joule heat generated by the current is used to maintain the cake temperature at 40℃-70℃, and the temperature rise is used to reduce the viscosity of the oil phase to promote dehydration and deoiling.

[0024] Preferred:

[0025] In step S5, the anode of the electroosmosis device is a dimensionally stable anode (DSA) or a titanium-coated ruthenium-iridium electrode, and the cathode is a stainless steel mesh or a conductive filter cloth; and a filter paper or an insulating and permeable layer (preferably non-woven fabric or polypropylene membrane) is provided on the surface of the cathode filter cloth to prevent electrode short circuits caused by excessive biochar.

[0026] According to a second aspect of the present invention, the above-described process is provided for use in treating petroleum industry waste, wherein the petroleum industry waste is oily sludge;

[0027] The oily sludge is oily bottom mud or scum generated during oil extraction, transportation, refining or wastewater treatment; after the process described, the moisture content of the final sludge cake is reduced to below 60%.

[0028] The core mechanism of this invention is:

[0029] S1 (Interface Modification Elution): Utilizing the amphiphilic properties of surfactants, it targets and adsorbs onto the "oil-solid" interface. By reducing interfacial tension, it peels off the insulating oil film that has been wrapped around the surface of sludge particles due to long-term aging, significantly reducing the contact resistance between sludge particles and eliminating the insulation barrier of electroosmosis.

[0030] S2 (Conductive Framework Construction): Utilizing the porous structure and excellent conductivity (high-temperature pyrolysis carbonization) of biochar, a three-dimensional rigid framework is constructed between the sludge flocs. This framework supports the sludge cake to prevent pore closure and maintain water seepage channels. On the other hand, in the later stages of dewatering, when the reduced water content leads to a decrease in ionic conductivity, the biochar particles come into contact with each other to form an electronic conduction network, replacing water molecules to maintain the current path and prevent circuit breakage.

[0031] S3 (Electro-thermal-mechanical coupling): While the DC electric field drives the electroosmotic migration of water, the Joule heating effect generated by the current through the biochar skeleton effectively reduces the viscosity of crude oil. Combined with mechanical pressing force, it achieves efficient separation of water, oil and solids.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] Overcoming the oil film barrier and significantly reducing energy consumption: By pre-washing away the insulating oil film with surfactants and combining it with low-resistance channels constructed with biochar, the problem of excessively high resistivity of oily sludge is solved, allowing electrical energy to be mainly used to drive water migration rather than heat loss, thus significantly improving current efficiency.

[0034] Solving the problems of electrode corrosion and short lifespan: This process abandons the lengthy traditional route or high-concentration inorganic chloride salt conditioning, and uses non-corrosive biochar and surfactants, combined with corrosion-resistant DSA electrodes, which greatly extends the service life of the equipment and reduces maintenance costs.

[0035] Overcoming dehydration stagnation caused by cake shrinkage: Addressing the industry pain point of cake shrinkage and poor contact with electrodes in the later stages of electroosmosis, the biochar framework introduced in this invention can still maintain good electrical contact during cake drying and shrinkage, ensuring that the dehydration process can continue until the moisture content is below 60%.

[0036] Resource-oriented, with no secondary pollution: The biochar used is derived from biomass, which is green and environmentally friendly. The biochar remaining in the dried mud has a high calorific value, which is beneficial for subsequent incineration or pyrolysis to produce gas. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the application of this method to treat oily sludge in an embodiment of the present invention. Detailed Implementation

[0038] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0039] Preliminary Note: To clarify the technical solution and data indicators of this invention, in the following embodiments and comparative examples, the "moisture content," "oil content," and "solid content" of the raw mud and dewatered cake are calculated based on a "wet basis" (i.e., the total mass of the material at this stage). Furthermore, under any condition, the sum of the moisture content, oil content, and solid content of the material is strictly equal to 100%. Regarding the unit dewatering energy consumption of the electro-osmotic dewatering stage... (kWh / t, calculated after removing moisture per ton), using the standard formula: ;in The applied DC voltage (V). The average current (A) during the dehydration process. The energizing time (h) is the duration of operation. The mass (t) of water removed during this stage.

[0040] Application Example 1

[0041] Taking the oily sludge produced by a joint station in a domestic oilfield as an example, its water content was measured to be 96.0%, oil content to be 2.0%, and oven-dry solids mass to be 20g (solids content 2.0%). The method provided in this invention was used to perform deep dehydration and oil removal treatment. The treatment process includes: liquid phase homogenization, primary interface modification with surfactants, secondary framework construction with biochar, flocculation and mechanical pre-dehydration, and deep electroosmotic dehydration, specifically as follows:

[0042] S1. Take 1 kg of oily sludge raw mud, remove large particles of sand and impurities, and then use mechanical stirring at 200 rpm for 15 minutes to homogenize and adjust the sludge.

[0043] S2. Add sodium dodecylbenzenesulfonate, an anionic surfactant, to the homogenized sludge. The amount added is 0.3% (0.06g) of the oven-dry solid mass. Adjust the stirring speed to 300rpm and stir rapidly for 8 minutes. Use the surfactant to wash off the oil film on the surface of the particles into the liquid phase to form an emulsion.

[0044] S3. Add wheat straw biochar powder to the system after step S2. The biochar is obtained by pyrolysis at 600℃ under nitrogen protection and passed through an 80-mesh sieve. Its BET specific surface area is 285m² / g and its electrical conductivity is 1.2S / cm. The amount added is 30% of the dry solid mass (i.e., 6.0g). Continue stirring for 5 minutes to make the biochar evenly dispersed.

[0045] S4. A cationic polyacrylamide solution containing 0.2% (by weight of oven-dry solids) was added for flocculation, followed by mechanical dehydration using a vacuum filtration device. Due to the effective elution of the surfactant, a large amount of free oil was removed along with the free water by filtration, resulting in a pre-dehydrated cake with a water content of 83%. During the mechanical pressure filtration (S4) stage, the filtrate discharged from the vacuum filtration was collected and subjected to centrifugation after settling. The actual measured mass of the discharged free oil was 12.0 g.

[0046] S5. Place the pre-dehydrated cake in an electroosmotic dewatering device (anode is a DSA electrode, cathode is a stainless steel mesh), and provide an insulating and permeable layer (such as a polypropylene diaphragm) on the cathode surface to prevent biochar particles in the cake from penetrating the filter cloth and causing a short circuit in the electrode. Apply a mechanical pressure of 300 kPa, and simultaneously connect a DC power supply, setting the voltage gradient to 25 V / cm. Under the coupling effect of the electric field and pressure, react for 35 minutes. During this period, monitor the temperature using an infrared thermometer, maintaining the center temperature of the cake at 55℃~60℃.

[0047] The above steps can achieve deep dewatering and simultaneous oil removal of oily sludge.

[0048] Results: After dehydration, a dried mud cake with a total mass of approximately 63.2 g was obtained. Calculations showed that the moisture content of the mud cake decreased to 56.0%, and it contained approximately 26.0 g of solid phase (41.1% solids content). The original mud contained 20.0 g of oil; after dehydration, only about 1.8 g of oil remained in the mud cake. Over 90% of the oil was discharged with the electroosmotic filtrate and collected after settling and stratification, achieving efficient resource recovery of crude oil. Furthermore, using the aforementioned energy consumption formula, the unit dehydration energy consumption of the electroosmotic dehydration stage (removing approximately 131 g of water, with an average current of approximately 0.19 A) in this embodiment was approximately 42.3 kWh / t. Compared to the traditional thermal drying process, which typically consumes 800-1000 kWh / t, this represents an energy saving of over 90%.

[0049] The specific calculation process for the unit dehydration energy consumption in Application Example 1 is as follows:

[0050] I. Calculation of the actual mass of water removed during the electroosmosis stage (S5)

[0051] 1. The state of the pre-removed cement cake (at the end of S4).

[0052] According to Example 1, the raw sludge contained 20g of absolutely dry solids, and 6g of biochar was added, resulting in a total solids content of 26g in the sludge cake. During the mechanical pressure filtration (S4) stage, due to the elution effect of the surfactant, a large amount of free water and most of the desorbed free oil were filtered out together. Actual measurements of the mechanically dehydrated filtrate from the S4 stage showed that approximately 60% of the free oil, or 12g, was removed, leaving approximately 8g of oil bound by capillary action in the sludge cake. At this point, the total non-aqueous matter (solids + oil) mass of the pre-dehydrated sludge cake was 26g + 8g = 34g. Example 1 recorded a pre-dehydrated sludge cake with a water content of 83%, indicating a non-aqueous matter content of 17%. Therefore, the total mass of the pre-dehydrated sludge cake was 34g ÷ 17% = 200g. Before electroosmosis, the water content in the sludge cake was 200g × 83% = 166g.

[0053] 2. The state of the cement cake after deep dewatering (at the end of S5).

[0054] In Example 1, the final total mass of the mud cake was approximately 63.2g, with a moisture content of 56.0%. After electroosmosis, the residual water content in the mud cake was approximately 35.4g (63.2g × 56.0%).

[0055] 3. Water removal volume during the electroosmosis stage

[0056] =166g−35.4g=130.6g=0.000131t.

[0057] II. Confirming Electric Field Parameters

[0058] 1. Apply voltage

[0059] In Example 1, the voltage gradient was set to 25V / cm. The initial thickness of the mud cake (plate spacing) in this stage of a conventional plate-and-frame dewatering mold was set to 2cm. Therefore, the actual applied constant DC voltage U = 25V / cm × 2cm = 50V.

[0060] 2. Power-on time

[0061] In Example 1, the reaction time was 35 minutes, i.e., t = 35 ÷ 60 = 0.5833 h (hours).

[0062] 3. Average current

[0063] Under a constant voltage of 50V, the addition of 30% highly conductive wheat straw biochar (conductivity 1.2S / cm) maintained a good conductive path during the dehydration process. According to the experimental records, the average current throughout the process was approximately 0.19A.

[0064] III. Substituting into the energy consumption formula for calculation

[0065] Substituting the above parameters into the unit dehydration energy consumption formula: ≈42.3kWh / t

[0066] Application Example 2

[0067] Taking the scum sludge produced by a wastewater treatment plant in a domestic oil refinery as an example, its moisture content is 96.0%, oil content is 2.5%, and oven-dry solids mass is 15g (solids content 1.5%). Due to the high degree of emulsification of this sludge, the following parameters are used for treatment:

[0068] S1. Take 1 kg of the above-mentioned oily sludge raw mud, remove impurities, and then use mechanical stirring at 250 rpm for 20 minutes to homogenize and adjust.

[0069] S2. Add rhamnolipin biosurfactant to the homogenized sludge at a rate of 0.2% (0.03g) of the oven-dry solids mass. Adjust the stirring speed to 400 rpm and stir rapidly for 5 minutes to break down the stubborn oil-water interface.

[0070] S3. Add pine wood biochar powder to the system. The biochar is obtained by pyrolysis at 600℃ under nitrogen protection and passed through an 80-mesh sieve. The BET specific surface area of ​​the biochar is measured to be 320m² / g and the electrical conductivity is 1.5S / cm. The amount added is 20% of the oven-dry solid mass (i.e., 3.0g). Stir and mix for 10 minutes to build a conductive channel.

[0071] S4. 0.15% cationic polyacrylamide solution (by oven-dry solids mass) was added for flocculation, followed by mechanical dewatering using a belt filter press to obtain a pre-dehydrated cake with a water content of 81%. During the mechanical filtration (S4) stage, the filtrate discharged from the filter press was collected and tested for oil-water separation. The actual measured mass of free oil discharged in this stage was 16.0g.

[0072] S5. Place the sludge cake in an electroosmotic dehydration device, using a titanium-coated ruthenium-iridium electrode as the anode and a conductive filter cloth as the cathode. An insulating and permeable layer (such as a polypropylene diaphragm) is provided on the cathode surface to prevent biochar particles in the sludge cake from penetrating the filter cloth and causing a short circuit in the electrode. Apply a mechanical pressure of 400 kPa, pass a direct current, and set the voltage gradient to 35 V / cm, reacting for 20 minutes. During the reaction, the Joule heating effect raises the center temperature of the sludge cake to approximately 65°C, significantly reducing the viscosity of the crude oil and promoting the discharge of deep-bound oil with the electroosmotic flow.

[0073] Results: A hard, dry, blocky mud cake with a final mass of approximately 41.1 g was obtained. The moisture content of the mud cake was reduced to 52.0%, and the solids content was 43.8%. The initial oil content in the raw mud was 25.0 g, and the residual oil content in the final mud cake was approximately 1.7 g, with an oil recovery rate exceeding 93%. The unit dehydration energy consumption of this process was approximately 48.5 kWh / t (removal of approximately 93.7 g of water, average current of approximately 0.39 A), which is more than 90% energy-efficient compared to traditional thermal drying processes. This example further demonstrates that this process still exhibits excellent low-energy dehydration and deoiling performance under conditions of high oil content, high voltage gradient, and short time.

[0074] The specific calculation process for unit dehydration energy consumption in Application Example 2 is as follows:

[0075] I. Calculation of the actual mass of water removed during the electroosmosis stage (S5)

[0076] 1. The state of the pre-removed cement cake (at the end of S4).

[0077] The original sludge contained 15g of absolute dry solids, and 3g of added biochar, resulting in a total solids content of 18g in the sludge cake. During the mechanical pressure filtration (S4) stage, the mechanically dewatered filtrate was measured, and approximately 64% of the free oil, or 16g, was removed. About 9g of oil remained in the sludge cake due to emulsification. At this point, the total non-aqueous matter (solids + oil) mass of the pre-dewatered sludge cake was 18g + 9g = 27g. The S4 pre-dewatered sludge cake had a water content of 81% and a non-aqueous matter content of 19%. Therefore, the total mass of the pre-dewatered sludge cake was approximately 27g ÷ 19% ≈ 142.1g. Before electroosmosis, the water content in the sludge cake was approximately 142.1g × 81% ≈ 115.1g.

[0078] 2. The state of the cement cake after deep dewatering (at the end of S5).

[0079] Example 2 describes the final mud cake mass as approximately 41.1g with a moisture content of 52.0%. After electroosmosis, the residual water content in the mud cake is approximately 21.4g (41.1g × 52.0%).

[0080] 3. Water removal volume during the electroosmosis stage

[0081] =115.1g−21.4g=93.7g=0.0000937t.

[0082] II. Confirming Electric Field Parameters

[0083] 1. Apply voltage

[0084] In Example 2, the voltage gradient was set to 35V / cm. The plate-and-frame electroosmotic dehydration mold used in this experiment had an initial mud chamber thickness (electrode spacing) of 1cm. Therefore, the actual applied constant DC voltage U = 35V / cm × 1cm = 35V.

[0085] 2. Power-on time

[0086] In Example 2, the reaction time was 20 minutes, i.e., t = 20 ÷ 60 = 0.3333 h.

[0087] 3. Average current

[0088] In the constant-voltage electroosmosis experiment, the current changes dynamically as the mud cakes and the resistance increases. During this stage, the average current recorded by the DC power supply throughout the dehydration process is approximately 0.39 A.

[0089] III. Substituting into the energy consumption formula for calculation

[0090] Substituting the above parameters into the unit dehydration energy consumption formula: ≈48.5kWh / t

[0091] Comparative Example 1 (Default Biochar)

[0092] To verify the role of biochar as a conductive framework, Comparative Example 1 was set up. The treatment objects and steps were basically the same as in Application Example 1, except that biochar was not added in step S3, while the remaining steps and process parameters remained the same.

[0093] Results: When the electroosmotic dehydration reaction had proceeded for approximately 15 minutes, the resistance increased sharply due to the gradual drying and shrinkage of the sludge cake and the lack of a rigid conductive framework for support. The current density rapidly decreased to near zero, forcing the dehydration process to terminate prematurely. Upon disassembly, an insulating oil film was found adhering to the anode surface, indicating severe passivation of the electrode plates. Ultimately, the moisture content of the sludge cake only decreased to 73%, and the energy consumption per unit of dehydration reached a high of 115 kWh / t, as most of it was converted into ineffective resistance heat. This comparative example demonstrates the irreplaceable role of biochar in maintaining the current path and preventing electrode passivation.

[0094] Comparative Example 2 (default surfactant)

[0095] To verify the effect of surfactant on interfacial modification, Comparative Example 2 was set up. The treatment objects and steps were basically the same as in Application Example 1, except that no surfactant was added in step S2, while the remaining steps and process parameters remained the same.

[0096] Results: Due to the failure to effectively remove the insulating oil film from the surface of the sludge particles, the initial resistance of the system was extremely high. Under the same voltage gradient of 25 V / cm, the electroosmotic flow rate was very slow. After 35 minutes of reaction, the final moisture content of the sludge cake only decreased to 68%, while the oil content remained as high as 4.6%, indicating a weak oil removal effect and a unit dehydration energy consumption of 85 kWh / t. This comparative example demonstrates the crucial role of surfactants in primary interface modification for overcoming the oil film insulation barrier and improving dehydration and oil removal efficiency.

[0097] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A surfactant elution and biochar synergistic electro-osmotic dewatering process for oily sludge, characterized in that, Includes the following steps: S1. Liquid phase homogenization: Take oily sludge raw mud with a water content of 96%~98%, remove impurities, and use mechanical stirring at a speed of 100~300rpm for 10~30 minutes to homogenize and adjust it so that the solid-liquid-oil three phases are mixed evenly. S2, Primary Interface Modification: Add surfactant to homogenized sludge and stir rapidly to disrupt the oil-water interface on the surface of sludge particles. S3. Construction of the secondary conductive framework: Add biochar powder to the primary modified sludge, stir and mix to make the biochar evenly dispersed and construct conductive channels; S4. Solid-liquid separation and cake making: Flocculant is added to carry out flocculation reaction, and free water is removed by mechanical dewatering to form pre-dehydrated cement cake containing biochar. S5. Electro-osmotic deep dehydration: The pre-dehydrated cement cake is placed between the anode and cathode of the electro-osmosis device, and direct current is passed through while mechanical pressure is applied to perform deep dehydration.

2. The process according to claim 1, characterized in that: In step S2, the surfactant is an anionic surfactant or a biosurfactant; The surfactant is added at a rate of 0.1% to 0.5% of the oven-dry solids mass of the sludge. The speed of the rapid stirring is 200~400 rpm, and the stirring time is 5~10 minutes.

3. The process according to claim 1, characterized in that: In step S3, the biochar is prepared by pyrolysis of biomass raw materials at a high temperature above 600°C under anaerobic or limited oxygen conditions. The biochar has a particle size that passes through a 60-100 mesh sieve; The biochar has a BET specific surface area of ​​150~400m² / g and an electrical conductivity of 0.1~2.0S / cm; The amount of biochar added is 10% to 50% of the oven-dry solids mass of the sludge.

4. The process according to claim 1, characterized in that: In step S4, the flocculant is cationic polyacrylamide (CPAM), and the dosage is 0.1% to 0.3% of the oven-dry solids mass of the sludge. The mechanical dewatering method is any one of plate and frame filter press, belt filter press, or vacuum filtration. The moisture content of the pre-dehydrated cement cake is controlled at 80%~85%.

5. The process according to claim 1, characterized in that: In step S5, the mechanical pressure ranges from 100 kPa to 500 kPa; The voltage gradient of the direct current is 10V / cm to 40V / cm; The electroosmotic dehydration time is 10-60 minutes.

6. The process according to claim 5, characterized in that: During the deep dehydration process of electroosmosis, the Joule heat generated by the current is used to maintain the temperature of the mud cake at 40℃~70℃, and the temperature rise is used to reduce the viscosity of the oil phase to promote dehydration and deoiling.

7. The process according to claim 1, characterized in that: In step S5, the anode of the electroosmosis device is a size-stabilized anode (DSA) or a titanium-coated ruthenium-iridium electrode, and the cathode is a stainless steel mesh or a conductive filter cloth; and a filter paper or an insulating and permeable layer is provided on the surface of the cathode filter cloth to prevent electrode short circuits caused by excessive biochar.

8. The application of the process according to any one of claims 1-7 in the treatment of petroleum industry waste, characterized in that: The waste from the petroleum industry is oily sludge; The oily sludge is oily bottom mud or scum generated during oil extraction, transportation, refining or wastewater treatment; after the process described, the moisture content of the final sludge cake is reduced to below 60%.

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