Treatment process and device for recycling of oil tanker cleaning water

Abstract

The oil tanker washing water recycling treatment process and device belong to the field of waste water treatment and recycling, and the device comprises a water tank, a water pump, a contact coagulation filter tank, a high-precision composite membrane tank, an ozone reactor and corresponding pipelines and valves connected together; the washing water is pumped from the water tank into the contact coagulation filter tank for pretreatment, and then the pretreated washing water is input into the high-precision composite membrane tank to remove emulsified oil and dissolved oil; finally, the washing water is input into the ozone membrane reactor for decolorization and odor removal. The process of the present application meets the requirements of oil removal, suspended matter removal, odor removal and color reduction by the combination of the processes of 'contact coagulation filtration + high-precision composite oil removal membrane + ozone membrane reactor'; the oil tanker washing water recycling rate is improved, the washing water discharge is reduced, no chemical agents are added, the ozone membrane reactor oxidation technology is adopted, the ozone utilization rate is close to 100%, the tail gas after reaction can return to the ozone generator, the pure oxygen consumption is reduced, and the operation cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and reuse, specifically relating to a process and apparatus for reusing tank washing water from oil tankers. Background Technology

[0002] Tank cleaning water for oil tankers refers to the wastewater generated during the cleaning of oil tanks. Its main source is the thorough cleaning required when changing the type of oil loaded into the cargo tanks, which washes away the existing oil and produces a certain amount of oily wastewater. The main pollutants in tank cleaning water are oil, silt, and rust, in addition to various chemical additives and small amounts of phenols.

[0003] Current tank cleaning wastewater treatment processes mainly employ gravity settling and coalescing filtration. Gravity settling utilizes the density difference between oil and water; oil particles in still water or relatively static conditions generate buoyancy with minimal resistance, causing them to rise and achieving oil-water separation. Coalescing filtration works by leveraging the significant difference in affinity between oil and water for the surface of a coalescing material. When oily wastewater flows through, tiny oil particles are adsorbed onto the surface or within the pores of the coalescing material. As the number of adsorbed oil particles increases, they gradually coalesce into an oil film on the surface. Once the oil film reaches a certain thickness, it forms larger oil droplets sufficient to separate from the aqueous phase and rise to the surface.

[0004] This combination of processes can remove most oil, silt, and rust, but the treated effluent has problems such as strong odor and high color, which cannot meet the requirements for tank washing and reuse. Therefore, it is necessary to develop a treatment process and device that has high oil removal efficiency and can also remove odor and color. Summary of the Invention

[0005] To address the aforementioned issues, this invention discloses a process and apparatus for reusing tanker washing water. Through a process combination of "contact coagulation filtration + high-precision composite oil removal membrane + ozone membrane reactor," the requirements for oil removal, suspended solids removal, odor removal, and color reduction can be met simultaneously.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems includes the following steps:

[0007] (1) Contact coagulation filtration: The collected tank washing water is pumped into the contact coagulation filter tank. The contact coagulation filter tank is filled with hydrophilic porous ceramic filter media, which can intercept suspended particles in the water, including silt, rust, etc., and can also play a coarsening role to remove most of the suspended oil, serving as a pretreatment step in the entire treatment process.

[0008] (2) High-precision composite membrane oil removal: After pretreatment, the tank washing water is removed by high-precision composite membrane oil removal, which can remove emulsified oil and some dissolved oil, and the oil content can be reduced to below 1 mg / L. At the same time, high-precision composite membrane oil removal can also be used as pretreatment for subsequent ozone membrane reactors, improving the treatment efficiency of ozone membrane reactors.

[0009] (3) Ozone membrane reactor: Dissolved organic matter, volatile organic matter, and other pollutants that cause high color and odor in the washing water are directly oxidized into carbon dioxide and water in the ozone membrane reactor. After treatment by the ozone membrane reactor, the effluent meets the requirements for reuse. By combining ozone and membrane contactor, ozone can be used efficiently, reducing operating costs and the footprint of the equipment.

[0010] The further optimized technical solution of this invention is as follows:

[0011] The hydrophilic porous ceramic filter media is a porous ceramic spherical granular filter media made by high-temperature sintering of alumina powder, trace rare earth raw materials, kaolin, clay, clay and other raw materials. It has a Mohs hardness greater than 5, a bulk density of 1.1-1.2 g / cm³, and a porosity of 50-60%.

[0012] The hydrophilic porous ceramic filter media expands to 100% under backwash water flow rate of 8-10 m / h.

[0013] The high-precision composite membrane is composed of two polymer materials: a superhydrophilic membrane and a superoleophilic membrane. The outer superhydrophilic membrane can intercept emulsified oil droplets through the water film effect, while the inner superoleophilic membrane can adsorb and capture dissolved oil, thereby removing both emulsified and dissolved oil. The water flux of the high-precision composite membrane can reach 1200 L / m²·h.

[0014] The high-precision composite membrane adopts a frustum-shaped structure with a larger bottom and a smaller top. The bottom diameter is 100mm, the top diameter is 75mm, and the membrane length is 1100mm, which is conducive to the aggregation and floating of oil droplets.

[0015] The ozone membrane reactor consists of a membrane shell and hollow fiber membrane filaments. The hollow fiber filaments are encapsulated within the membrane shell at both ends using fluoropolymer resin. Ozone-containing gas flows inside the filaments, while the washing water flows outside. Utilizing the hydrophobic and permeable properties of the membrane material, ozone molecules in the gas can permeate and diffuse into the outside of the membrane filaments, reacting with colored and odor-causing pollutants in the water to achieve decolorization and deodorization. After the reaction, the ozone component in the ozone-containing gas has completely reacted, leaving 99% oxygen, which returns to the ozone generator's inlet as raw material gas.

[0016] During the operation of the ozone membrane reactor, the pressure on the wastewater side is controlled at 95-100 kPa, the pressure on the ozone phase side is controlled at 90-95 kPa, and the pressure loss on the ozone phase side is controlled at 3-5 kPa.

[0017] The hollow fiber membrane filaments are cross-fixed using a braided method, which increases the Reynolds number on the filament surface and promotes mass transfer of ozone molecules to the external wash tank water, resulting in near 100% ozone utilization. The hollow fiber membrane is made of one of polytetrafluoroethylene, polyvinylidene fluoride, and polydimethylsiloxane. The inner diameter of the hollow fiber membrane filaments is 0.2-0.5 mm, and the outer diameter is 0.6-0.8 mm.

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] (1) It solved the problems of high color and strong odor in the recycled tank cleaning water of oil tankers, and further improved the working environment of tank cleaning.

[0020] (2) It improved the reuse rate of tank cleaning water for oil tankers and reduced the amount of tank cleaning water discharged, thus achieving the effect of energy conservation and emission reduction.

[0021] (3) Compared with existing processing solutions, the processing flow of the present invention is simple, occupies a small area, does not require the addition of chemical agents, and significantly reduces operating costs.

[0022] (4) The ozone membrane reactor oxidation technology is adopted, and the ozone utilization rate is close to 100%. At the same time, the tail gas after the reaction can be returned to the ozone generator, reducing the amount of pure oxygen used and reducing operating costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0024] Figure 2 This is a schematic diagram of the external structure of a high-precision composite membrane.

[0025] Figure 3 This is a schematic diagram of an ozone membrane reactor.

[0026] Figure 4 This is a schematic diagram of the mass transfer principle of an ozone membrane reactor.

[0027] Figure 5 Schematic diagram of an electrolytic ozone membrane reactor;

[0028] Figure 6 Hollow fiber membrane filaments with metal mesh.

[0029] In the figure: 1. Shell, 2. Hollow fiber membrane with metal mesh, 3. Air inlet, 4. Exhaust outlet, 5. Water inlet, 6. Water outlet, 7. Graphite sleeve, 8. Micropore, 9. Power supply, 10. Metal mesh layer, 11. Hollow fiber membrane layer. Detailed Implementation Example 1

[0030] See Figure 1-4 The present invention relates to a tanker washing water reuse treatment device, which specifically includes: a water tank, a water pump, a contact coagulation filter tank, a high-precision composite membrane tank, an ozone membrane reactor, an ozone generator, and corresponding pipelines and valves.

[0031] The collected tank washing water is pumped from the water tank into a contact coagulation filter tank for pretreatment. The contact coagulation filter tank is filled with hydrophilic porous ceramic filter media, which can intercept suspended particulate matter in the water, including silt, rust, etc., and also acts as a coarse-graining agent, removing most of the suspended oil. The pretreated tank washing water is then fed into a high-precision composite membrane tank, which houses a high-precision composite membrane. This high-precision composite membrane has a frustum-shaped structure with a larger bottom and a smaller top, with a bottom diameter of 100mm, a top diameter of 75mm, and a membrane length of 1100mm, which is conducive to the aggregation and floating of oil droplets. The high-precision composite membrane is composed of two polymer materials: a superhydrophilic membrane and a superoleophilic membrane. The outer superhydrophilic membrane intercepts emulsified oil droplets through the water film effect, while the inner superoleophilic membrane adsorbs and captures dissolved oil, thereby removing both emulsified and dissolved oil. The water flux of the high-precision composite membrane can reach 1200 L / m²·h. The tanker wash water, after removing emulsified oil and some dissolved oil, is then fed into the ozone membrane reactor.

[0032] The top of the ozone membrane reactor is equipped with an air inlet, which is connected to the outlet of the ozone generator to allow ozone to enter the hollow fiber membrane filaments inside the reactor; the bottom of the ozone membrane reactor is equipped with an exhaust port, which is connected to the inlet of the ozone generator to input the oxygen generated in the reaction in the ozone membrane reactor into the ozone generator.

[0033] The ozone membrane reactor has an inlet at the lower left end and an outlet at the upper right end. The tank cleaning water, after being treated by a high-precision composite membrane tank, is introduced into the ozone membrane reactor through the inlet. The reactor consists of a membrane shell and hollow fiber membrane filaments. The hollow fiber filaments are encapsulated within the membrane shell using fluoropolymer resin at both ends. Ozone-containing gas flows inside the filaments, while the tank cleaning water flows outside. Utilizing the hydrophobic and permeable properties of the membrane material, ozone molecules in the gas can permeate and diffuse into the outside of the filaments, reacting with colored and odorous pollutants in the water to achieve decolorization and deodorization. After the reaction, the ozone component in the ozone-containing gas has completely reacted, leaving 99% oxygen, which returns to the inlet of the ozone generator as raw material. The treated water from the ozone generator, meeting the standards, is collected and reused through the outlet at the upper right end.

[0034] During the operation of the ozone membrane reactor, the pressure on the wastewater side is controlled at 95-100 kPa, the pressure on the ozone phase side is controlled at 90-95 kPa, and the pressure loss on the ozone phase side is controlled at 3-5 kPa.

[0035] The hollow fiber membrane filaments are cross-fixed using a braided method, which increases the Reynolds number on the filament surface and promotes mass transfer of ozone molecules to the external wash tank water, resulting in near 100% ozone utilization. The hollow fiber membrane is made of one of polytetrafluoroethylene, polyvinylidene fluoride, and polydimethylsiloxane. The inner diameter of the hollow fiber membrane filaments is 0.2-0.5 mm, and the outer diameter is 0.6-0.8 mm.

[0036] The present invention relates to a process for treating and reusing tank cleaning water from oil tankers, which is applied to a demonstration project for treating and reusing tank cleaning water from an oil tanker in Nanjing. The technical solution includes the following steps:

[0037] (1) Contact coagulation filtration: 5 m³ / h of tank washing water with an oil content of 1200 mg / L, a suspended solids content of 362 mg / L, and a color of 200 times is pumped into the contact coagulation filter tank. The contact coagulation filter tank is filled with hydrophilic porous ceramic filter media, which can intercept suspended particles in the water, including silt, rust, etc., and can also play a coarsening role to remove most of the suspended oil, serving as a pretreatment step in the entire treatment process.

[0038] (2) High-precision composite membrane oil removal: After pretreatment, the tank washing water has an oil content of 215 mg / L, a suspended solids content of 68 mg / L, and a color of 150 times. Through high-precision composite membrane oil removal, emulsified oil and some dissolved oil can be removed, reducing the oil content to 0.8 mg / L, the suspended solids content to 3.4 mg / L, and the color to 100 times. At the same time, high-precision composite membrane oil removal can also be used as a pretreatment for subsequent ozone membrane reactors, improving the treatment efficiency of ozone membrane reactors.

[0039] (3) Ozone membrane reactor: After the tank washing water is treated by the ozone membrane reactor, the pollutants such as dissolved organic matter and volatile organic matter in the water that cause high color and odor are directly oxidized into carbon dioxide and water in the ozone membrane reactor. After treatment by the ozone membrane reactor, the oil content of the effluent is not detected, and the color is reduced to 15 times, which meets the requirements for reuse. Example 2

[0040] refer to Figures 5-6 In this embodiment, Figure 1 The ozone membrane reactor in the middle was completely replaced with Figure 5 The electrolytic ozone membrane reactor comprises a shell 1, hollow fiber membrane filaments 2 with metal mesh, and a graphite sleeve 7. The hollow fiber membrane filaments 2 with metal mesh and the graphite sleeve 7 are encapsulated within the shell 1 at both ends using fluororesin. The shell 1 has an air inlet 3 at the top, an exhaust outlet 4 at the bottom, a water inlet 5 on the lower left side, and a water outlet 6 on the upper right side. The graphite sleeve 7 is cylindrical and hollow, without top or bottom surfaces, and has micropores 8. Several hollow fiber membrane filaments 2 with metal mesh are placed inside the graphite sleeve 7 within the shell 1. Each hollow fiber membrane filament 2 has a two-layer structure: an outer metal mesh layer and an inner hollow fiber membrane filament layer. The graphite sleeve 7 is connected to the positive terminal of a power supply 9, and the hollow fiber membrane filaments 2 with metal mesh are connected to the negative terminal of the power supply 9 through their outer layer. The air inlet 3 is connected to the outlet of the ozone generator, and the exhaust port 4 is connected to the inlet of the ozone generator. The water inlet 5 of the shell 1 is connected to the high-precision composite membrane tank, and the water outlet 6 of the shell 1 is used to discharge compliant recycled water. Micropores 8 are provided on the graphite sleeve 7. The graphite sleeve 7 is uniformly provided with micropores 8, which are circular holes with a diameter of 5-8 mm and a spacing of 10-15 mm between adjacent holes, facilitating the flow of the liquid to be treated into the hollow fiber membrane filaments 2 with metal mesh.

[0041] The electrolytic ozone membrane reactor has an internal submerged structure. The oxygen and ozone mixture generated by the ozone generator is introduced into the hollow fiber membrane filament 2 with a metal mesh. Figure 6 As shown, a hollow fiber membrane 2 with a metal mesh serves as the cathode, a graphite sleeve 7 serves as the anode, and the liquid to be treated serves as the electrolyte, thus constituting an electrolysis device.

[0042] A mixture of oxygen and ozone is brought into contact with the membrane layer of a hollow fiber membrane filament 2 with a metal mesh. The membrane layer is hydrophobic, and the gas diffuses through the membrane pores to the metal mesh layer (conductive layer) and comes into contact with the feed liquid. Oxygen is reduced to H2O2 at the conductive layer, which acts as the cathode. The resulting H2O2 reacts with O3 to generate ·OH. The specific equation is as follows:

[0043] ;

[0044] .

[0045] The process involves oxidizing and degrading organic matter in wastewater. Organic matter in the wastewater undergoes electrocatalytic ozone oxidation on the surface of the electrocatalytic functional layer. Specifically, when a mixture of oxygen and ozone diffuses from the center of the hollow fiber membrane filament 2 with a metal mesh to the side of the wastewater to be treated, oxygen gains electrons in the conductive layer to generate hydrogen peroxide. The hydrogen peroxide then reacts with ozone to generate ·OH. The strong oxidizing properties of ·OH allow it to undergo a rapid chain reaction with most organic pollutants, non-selectively decomposing harmful substances and recalcitrant organic matter into CO2, H2O, or mineral salts, thus treating recalcitrant wastewater.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A treatment device for recycling of tank cleaning water from a tanker, c h a r a c t e r i s e d i n that It comprises a water tank, a water pump, a contact coagulation filter tank, a high-precision composite membrane tank, an ozone membrane reactor, an ozone generator, and corresponding pipelines and valves; the tank-cleaning water is pumped from the water tank into the contact coagulation filter tank for pretreatment, and then the pretreated tank-cleaning water is input into the high-precision composite membrane tank to remove emulsified oil and dissolved oil; finally, the water is input into the ozone membrane reactor for decolorization and odor removal. The ozone membrane reactor is an electrolytic ozone membrane reactor. The contact coagulation filter tank is filled with hydrophilic porous ceramic filter material, which is a porous ceramic spherical granular filter material sintered at high temperature from alumina powder, trace rare earth raw materials, kaolin, pottery clay, and clay. The high-precision composite membrane tank is installed with high-precision composite membranes; the high-precision composite membranes have a circular truncated cone structure with a large bottom and a small top, which is beneficial to the aggregation and floating of oil droplets; the high-precision composite membranes are composed of two high-molecular materials, super-hydrophilic and super-oil-absorbing, the outer layer of super-hydrophilic membrane intercepts emulsified oil droplets through water film effect, and the inner layer of super-oil-absorbing membrane adsorbs and captures dissolved oil, thereby removing emulsified oil and dissolved oil; the water flux of the high-precision composite membrane can reach 1200 L / m2·h. The electrolytic ozone membrane reactor is composed of a shell (1), a hollow fiber membrane wire (2) with a metal screen, and a graphite sleeve (7); the hollow fiber membrane wire (2) with a metal screen and the graphite sleeve (7) are packaged in the shell (1) by fluororesin at both ends of the shell (1); the top of the shell (1) is provided with an air inlet (3), the bottom is provided with an air outlet (4), the left lower part is provided with a water inlet (5), and the right upper part is provided with a water outlet (6); the graphite sleeve (7) is a cylindrical hollow structure without upper and lower bottom surfaces, and is provided with micropores (8) thereon; in the shell (1), the hollow fiber membrane wire (2) with a metal screen is arranged in the graphite sleeve (7); the hollow fiber membrane wire (2) with a metal screen has a two-layer structure, the outer layer is a metal screen layer, and the inner layer is a hollow fiber membrane wire layer; the graphite sleeve (7) is connected to the positive electrode of a power supply (9), and the hollow fiber membrane wire (2) with a metal screen is connected to the negative electrode of the power supply (9) through the outer layer; the air inlet (3) is connected to the outlet end of an ozone generator, and the air outlet (4) is connected to the inlet end of the ozone generator; the water inlet (5) of the shell (1) is connected to the high-precision composite membrane tank, and the water outlet (6) of the shell (1) is used for discharging the standard recycled water.

2. The tanker wash water reuse treatment apparatus according to claim 1, characterized in that: The porous ceramic spherical granular filter material has a Mohs hardness greater than 5, a bulk density of 1.1-1.2 g / cm3, and a porosity of 50-60%.

3. The tanker wash water reuse treatment apparatus according to claim 1, characterized by: The graphite sleeve (7) is uniformly provided with micropores (8), the micropores (8) are circular holes with a diameter of 5-8 mm, and the spacing between adjacent circular holes is 10-15 mm, which is beneficial to the flow of the to-be-treated liquid to the hollow fiber membrane wire (2) with a metal screen.

4. The treatment apparatus for reusing the tank washing water of a tanker according to claim 2, characterized by: The method comprises the following steps:

5. A process for recycling of oil tanker washing water using the oil tanker washing water recycling treatment apparatus according to any one of claims 1 to 4, characterized by, S1. Contact coagulation filtration: the collected tank-cleaning water is pumped into the contact coagulation filter tank, which is filled with hydrophilic porous ceramic filter material for intercepting suspended particles in water and also playing a role of coarse granulation to remove most of the suspended oil. ​ S2. High-precision composite membrane oil removal: the washing water is pretreated by contact coagulation filtration, and then is treated by high-precision composite membrane oil removal to remove emulsified oil and part of dissolved oil, so that the oil content is reduced to below 1 mg / L; S3. Ozone membrane reactor: the washing water treated by high-precision composite membrane oil removal is input into the ozone membrane reactor; the pollutants of high colority and peculiar smell caused by dissolved organic matter and volatile organic matter in the washing water are directly oxidized into carbon dioxide and water in the ozone membrane reactor, and the effluent treated by the ozone membrane reactor meets the requirements of reuse.

6. The process for the re-use of tank cleaning water according to claim 5, characterized in that: The step S3 ozone membrane reactor is an electrolytic ozone membrane reactor, the hollow fiber membrane wire (2) with a metal wire mesh is used as a cathode, the graphite sleeve (7) is used as an anode, and the to-be-treated liquid is used as an electrolyte to form an electrolysis device; the hollow fiber membrane wire (2) with a metal wire mesh has a two-layer structure, the outer layer is a metal wire mesh layer, and the inner layer is a hollow fiber membrane wire layer; the graphite sleeve (7) is connected to the positive electrode of the power supply (9), and the hollow fiber membrane wire (2) with a metal wire mesh is connected to the negative electrode of the power supply (9) through the outer layer; the mixed gas of oxygen and ozone contacts the membrane wire layer of the hollow fiber membrane wire (2) with a metal wire mesh, the membrane wire layer is a hydrophobic layer, the gas diffuses to the metal wire mesh layer through the membrane holes and contacts the liquid, the oxygen is reduced to obtain H2O2 at the metal wire mesh layer, and the obtained H2O2 reacts with O3 to generate ·OH.

7. The process for the re-use of tank cleaning water from an oil tanker according to claim 6, characterized in that: The ·OH has strong oxidizing property and can rapidly react with most organic pollutants in a chain reaction, and has no selectivity to decompose harmful substances and difficult-to-biodegrade organic matter into CO2, H2O or mineral salts, so that the treatment of difficult-to-biodegrade wastewater is realized.

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