A system and method for treating pyrolysis water from oil sludge

Abstract

This invention discloses a treatment system and method for oily sludge pyrolysis water, belonging to the field of wastewater treatment technology. The oily sludge pyrolysis water treatment system includes, in sequence, an oil-water separation system (1), a conditioning and separation system (2), an ultrafiltration membrane system (3), a nanofiltration membrane system (4), a disc tube reverse osmosis membrane system (5), an evaporation and crystallization system (6), and a pyrolysis system (7). The oily sludge pyrolysis water treatment system provided by this invention employs a combination of oil-water separation, conditioning and demulsification, and membrane technology to effectively treat and utilize the oily sludge pyrolysis water for resource recovery.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a treatment system and method for oily sludge pyrolysis water. Background Technology

[0002] Oil extraction and processing generate large quantities of waste oily sludge. Direct discharge of this sludge into the environment without treatment poses a serious threat to environmental safety and human health. Oily sludge has an extremely complex composition, being a highly stable suspended emulsion system containing large amounts of aged crude oil, waxes, asphaltenes, colloids, suspended solids, bacteria, salts, acidic gases, corrosion products, and water treatment agents such as coagulants, corrosion inhibitors, scale inhibitors, and bactericides added during production. Common methods for treating oily sludge both domestically and internationally include: incineration, biological treatment, thermal washing, solvent extraction, chemical demulsification, solid-liquid separation, coking, oily sludge profile control, and comprehensive utilization of oily sludge.

[0003] Pyrolysis is a modified high-temperature sludge treatment method. At temperatures between 200-550℃, it distills the light oil components and decomposes the heavy oils in oily sludge into volatile low-carbon hydrocarbon fuels, liquid fuels, and solid carbon. Because no air participates in the high-temperature decomposition reaction, the process eliminates the generation of dioxins and NOx, and produces almost no H2S or SO2. In recent years, there have been increasing number of operational cases using pyrolysis technology to treat oily sludge. After pyrolysis, oily sludge mainly produces three categories of substances: recoverable oil and gas, water vapor, non-condensable combustible gas (non-condensable gas), carbon residue, and inorganic solid particles.

[0004] The water vapor produced by the pyrolysis of waste oily sludge generated during oil extraction and processing is called oily sludge pyrolysis water. Oily sludge pyrolysis water has characteristics of both coking wastewater and high-concentration organic wastewater, and is a comprehensive organic wastewater with high tar content, high COD content, high salt content, and high ammonia nitrogen content.

[0005] The existing technology, "Research and Application of Comprehensive Treatment Technology for Pyrolysis of Oily Sludge," discloses a method for treating oily sludge generated during oil and gas resource exploration and development. The pyrolysis water, after oil-water separation, is recycled as cooling water. However, because the pyrolysis water contains ammonia nitrogen, tar, and salt, directly using it as circulating water can lead to problems such as equipment corrosion and scaling. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects and shortcomings of using oily sludge pyrolysis water directly as cooling water circulation, which leads to corrosion, scaling and odor problems. This invention provides a method for treating oily sludge pyrolysis water, which adopts a combination of oil-water separation, conditioning and demulsification and membrane technology to effectively treat and utilize oily sludge pyrolysis water. The treated effluent can be reused and meets the requirements for sewage discharge, and can be discharged into the pipeline, thus avoiding the occurrence of corrosion and scaling problems in the equipment.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A treatment system for pyrolysis water of oily sludge includes an oil-water separation system, a conditioning and separation system, an ultrafiltration membrane system, a nanofiltration membrane system, a disc tube reverse osmosis membrane system, an evaporation crystallization system, and a pyrolysis system connected in sequence.

[0009] The conditioning and separation system includes a demulsification system, a flocculation system, and a solid-liquid separation system connected in sequence.

[0010] The concentrate end of the ultrafiltration membrane system is connected to the inlet end of the conditioning and separation system;

[0011] The outlet of the nanofiltration membrane system is connected to the feed end of the disc tube reverse osmosis membrane system, and the concentrate end of the nanofiltration membrane system is connected to the inlet end of the evaporation crystallization system.

[0012] The slag outlet of the evaporation crystallization system is connected to the feed outlet of the pyrolysis system, and the water outlet of the evaporation crystallization system is connected to the water inlet of the ultrafiltration membrane system.

[0013] The slag outlet of the conditioning and separation system is connected to the feed outlet of the pyrolysis system.

[0014] The source of the oily sludge pyrolysis water of the present invention is: a large amount of waste oily sludge is generated during the oil extraction and production process. After pyrolysis at 200-550℃, the pyrolysis water is condensed from the pyrolysis water vapor. The pH of the oily sludge pyrolysis water is 5.5-8.5, the conductivity is 2000-20000 μS / cm, the COD is 5000-15000 mg / L, the ammonia nitrogen content is 100-1000 mg / L, and the oil content is 0.1-3%.

[0015] In the oil-containing sludge pyrolysis water treatment system of this invention, the oil-water separation system can achieve oil-water separation, with the purpose of removing oily substances, dust, and suspended particulate matter from the pyrolysis water. The oil-water separation system is equipped with an air flotation device and an oil skimming device, which aim to remove as much floating oil as possible from the pyrolysis water and reduce the oil content in the water. The oil phase collected by the oil-water separation system can be purified and dehydrated before being sold, realizing resource utilization.

[0016] The effluent from the oil-water separation system enters the conditioning and separation system. The purpose of the conditioning and separation system is to remove some high-molecular-weight organic matter and dissolved tar substances from the pyrolysis water through a combination of demulsification, oil removal, flocculation, and sedimentation. Specifically, the demulsification system separates dispersed oil droplets or emulsified oil from the water by adding appropriate chemical agents, while the flocculation system adds flocculants to cause residual tar and some organic matter in the water to form flocs, which then settle to the bottom of the water body.

[0017] The solid-liquid separation system in the conditioning and separation system can be one or more of the following: plate and frame filter press, horizontal centrifuge, or screw press.

[0018] Ultrafiltration membrane systems effectively achieve physical demulsification and retention of organic matter, removing organic nitrogen from water.

[0019] The role of nanofiltration membrane systems is to further remove divalent salts and some COD from water.

[0020] Disc tube reverse osmosis (DTRO) systems effectively remove ammonia nitrogen and desalinate water, achieving a permeate recovery rate of over 75%. The treated water from a disc tube DTRO system can be reused and also meets wastewater discharge requirements, allowing for proper piped discharge.

[0021] Evaporation crystallization systems can effectively concentrate materials, crystallizing waste salts and organic matter at low temperatures to maximize volume reduction in pyrolysis water treatment. Evaporation crystallization systems can employ low-temperature evaporation or mechanical vapor recompression (MVR) technology, and crystallization can be achieved using scraper crystallizers or centrifugal crystallizers.

[0022] The evaporation temperature is 35-42℃, which is beneficial for cleaning scale buildup in equipment and treating evaporating water. It maximizes the concentration of pollutants into the residue, making it easier for downstream treatment and utilization.

[0023] The outlet of the evaporation crystallization system is connected to the inlet of the ultrafiltration membrane system. Its function is to pre-treat the evaporation crystallization effluent using an ultrafiltration membrane, mainly to remove a small amount of suspended solids or floating oil, so as to ensure that the downstream processing is not affected under abnormal circumstances.

[0024] The function of the pyrolysis system is to reduce the amount of solid residue and recover any remaining oil from the residue. The evaporation system can preferentially utilize the abundant heat source of the pyrolysis itself.

[0025] Preferably, the ultrafiltration membrane system includes an organic tubular membrane with a pore size of 30-50 nm.

[0026] The tubular membrane can be made of one or more of the following materials: PVDF, PVC, PTFE, PES, or PAN.

[0027] Tubular membrane treatment has a pore size of less than 30nm, which is not conducive to equipment investment and system recovery design.

[0028] Tubular membrane treatment has a pore size greater than 50nm, which is not conducive to the removal of pollutants in the system. The quality of the effluent cannot meet the requirements of the downstream influent, affecting the stable operation of the entire system.

[0029] Preferably, the pore size of the antifouling membrane in the nanofiltration membrane system is 1–5 nm.

[0030] Nanofiltration membranes can be 8040 wide-channel antifouling membranes with a divalent salt rejection rate of ≥98%.

[0031] Preferably, the system further includes a pH adjustment system disposed between the nanofiltration membrane system and the disc tube reverse osmosis membrane system, the pH adjustment system being used to adjust the pH to 6-6.5. The purpose of adjusting the pH is to effectively remove ammonia nitrogen.

[0032] The pH value can be adjusted to 6-6.5 using dilute sulfuric acid or caustic soda flakes.

[0033] A pH value less than 5.5 is not conducive to the selection of system materials.

[0034] A pH value greater than 6.5 is not conducive to the removal and retention of ammonia nitrogen.

[0035] This invention also protects a method for treating pyrolysis water containing oily sludge, comprising the following steps:

[0036] S1. Oil-water separation: Oil-water separation is used to treat the pyrolysis water of oily sludge.

[0037] S2. Conditioning and Separation: The aqueous phase after the oil-water separation treatment in S1 is subjected to demulsification treatment with demulsifier, flocculation treatment with flocculant, and solid-liquid separation treatment to obtain slag phase and aqueous phase;

[0038] S3. Ultrafiltration membrane treatment: The aqueous phase obtained after the above S2 treatment is treated with an ultrafiltration membrane; the concentrate after the S3 ultrafiltration membrane treatment is returned to the S2 conditioning and separation treatment.

[0039] S4. Nanofiltration membrane treatment: The aqueous phase obtained after the above S3 treatment is treated with a nanofiltration membrane;

[0040] S5. Disc tube reverse osmosis membrane treatment: The aqueous phase obtained after the above S4 treatment is treated by a disc tube reverse osmosis membrane.

[0041] S6. Evaporation and Crystallization Treatment: The concentrate after treatment with S4 nanofiltration membrane and S5 disc tube reverse osmosis membrane is evaporated and crystallized; the aqueous phase after treatment with S4 nanofiltration membrane and S5 disc tube reverse osmosis membrane is returned to S3 ultrafiltration membrane treatment.

[0042] S7. Pyrolysis treatment: The slag phase after S6 evaporation and crystallization and the slag phase after S2 conditioning and separation are pyrolyzed.

[0043] Preferably, in step S2, the demulsifier is one or more of polyaluminum chloride, lime, nonylphenol polyoxyethylene ether, or sodium carbonate, and the mass ratio of the demulsifier to the aqueous phase after oil-water separation in step S1 is (0.6–2.0):1000. The demulsifier works by separating oil from water through charge neutralization and flocculation, with the main purpose of purifying the water.

[0044] Preferably, in S2, the flocculant is polyacrylamide, and the mass ratio of the flocculant to the aqueous phase after oil-water separation in S1 is (0.1-0.8):1000.

[0045] Preferably, in S3, the ultrafiltration membrane operating pressure is 0.2-0.6 MPa.

[0046] The operating pressure of ultrafiltration membrane treatment is less than 0.2 MPa, which is not conducive to the retention of pollutants. Low-pressure operation is very likely to clog the membrane pores, affecting the system recovery rate and causing unstable equipment operation.

[0047] Operating pressures greater than 0.6 MPa in ultrafiltration membrane treatment are not conducive to long-term operation of the ultrafiltration membrane and can easily lead to membrane module damage and turbidity in the produced water.

[0048] Before the S3 ultrafiltration membrane treatment, there is also a filtration process, with the filter having a pore size of 20mm-120mm. The purpose of the filtration process is to remove a certain size of suspended particulate matter and some organic matter adsorbed in the particulate matter from the oily sludge pyrolysis water, ensuring the stable operation of the ultrafiltration membrane system.

[0049] Preferably, in S4, the operating pressure of the nanofiltration membrane is 0.8-2.5 MPa.

[0050] If the operating pressure of the nanofiltration membrane is too low, it will not meet the requirements for the recovery rate of the treated water.

[0051] Excessive operating pressure on nanofiltration membranes is detrimental to the long-term stable operation of the equipment.

[0052] Prior to the S4 nanofiltration membrane treatment, a filtration process is also included, with the filter having a pore size of 5 μm.

[0053] Preferably, the pyrolysis water of the oily sludge has a pH of 5.5 to 8.5, an electrical conductivity of 2000 to 20000 μS / cm, a COD of 5000 to 15000 mg / L, an ammonia nitrogen content of 100 to 1000 mg / L, and an oil content of 0.1% to 3%.

[0054] Compared with the prior art, the beneficial effects of the present invention are:

[0055] This invention discloses a treatment system for oily sludge pyrolysis water, employing a combination of oil-water separation, conditioning and demulsification, and membrane technology to effectively treat and utilize oily sludge pyrolysis water for resource recovery. The system separates oil, water, and sludge from the oily sludge pyrolysis water, enabling full resource utilization and treatment of the oily sludge pyrolysis water.

[0056] This invention discloses a method for treating pyrolysis water from oily sludge. This method can treat pyrolysis water from oily sludge with a pH of 5.5–8.5, conductivity of 2000–20000 μS / cm, COD of 5000–15000 mg / L, ammonia nitrogen content of 100–1000 mg / L, and oil content of 0.1–3%. The collected oil phase after treatment can be purified and dehydrated for sale, achieving resource utilization. Pollutants are concentrated in the residue for easier downstream disposal and utilization. The treated effluent has a pH of 6.5–7.5, conductivity of 100–300 μS / cm, COD of 40–120 mg / L, ammonia nitrogen content of 1–20 mg / L, and oil content <1 ppm. The treated effluent can be reused and meets wastewater discharge requirements, allowing for piped discharge and preventing equipment corrosion and scaling. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the structure of the oily sludge pyrolysis water treatment system in Example 1. In the figure, 1-oil-water separation system, 2-conditioning and separation system, 3-ultrafiltration membrane system, 4-nanofiltration membrane system, 5-disc tube reverse osmosis membrane system, 6-evaporation crystallization system, and 7-pyrolysis system. Detailed Implementation

[0058] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0059] Example 1

[0060] like Figure 1 As shown, a treatment system for pyrolysis water of oily sludge includes an oil-water separation system 1, a conditioning and separation system 2, an ultrafiltration membrane system 3, a nanofiltration membrane system 4, a disc tube reverse osmosis membrane system 5, an evaporation and crystallization system 6, and a pyrolysis system 7 connected in sequence.

[0061] The conditioning and separation system 2 includes a demulsification system, a flocculation system and a solid-liquid separation system connected in sequence;

[0062] The concentrate end of the ultrafiltration membrane system 3 is connected to the inlet end of the conditioning and separation system 2;

[0063] The outlet of the nanofiltration membrane system 4 is connected to the feed end of the disc tube reverse osmosis membrane system 5, and the concentrate end of the nanofiltration membrane system 4 is connected to the inlet end of the evaporation crystallization system 6.

[0064] The slag outlet of the evaporation crystallization system 6 is connected to the feed outlet of the pyrolysis system 7, and the water outlet of the evaporation crystallization system 6 is connected to the water inlet of the ultrafiltration membrane system 3.

[0065] The slag outlet of the conditioning and separation system 2 is connected to the feed outlet of the pyrolysis system 7.

[0066] The oil-water separation system 1 is equipped with an air flotation device and an oil skimming device. The oil phase collected by the oil-water separation system 1 can be purified and dehydrated before being sold, realizing resource utilization.

[0067] Among them, the solid-liquid separation system in conditioning and separation system 2 is a plate and frame filter press.

[0068] The effluent from the disc tube reverse osmosis membrane system can be reused and also meets the requirements for wastewater discharge, allowing for pipe discharge.

[0069] The evaporation crystallization system 6 can employ low-temperature evaporation or mechanical vapor recompression (MVR) technology, and crystallization can be carried out using scraper crystallization equipment or centrifugal crystallization equipment.

[0070] The evaporation temperature is 38℃, which concentrates pollutants into the residue, making it easier for downstream disposal and utilization.

[0071] The ultrafiltration membrane system 3 includes a tubular membrane with a pore size of 40 nm.

[0072] The tubular membrane is made of PVDF.

[0073] The antifouling membrane in nanofiltration membrane system 4 has a pore size of 2 nm.

[0074] Nanofiltration membranes can be 8040 wide-channel antifouling membranes.

[0075] It also includes a pH adjustment system located between the nanofiltration membrane system 4 and the disc tube reverse osmosis membrane system 5, which is used to adjust the pH to 6.

[0076] Adjust the pH to 6 using dilute sulfuric acid or caustic soda.

[0077] A method for treating pyrolysis water containing oily sludge includes the following steps:

[0078] S1. Oil-water separation: Oil-water separation is used to treat the pyrolysis water of oily sludge.

[0079] S2. Conditioning and Separation: The aqueous phase after the oil-water separation treatment in S1 is subjected to demulsification treatment with demulsifier, flocculation treatment with flocculant, and solid-liquid separation treatment to obtain slag phase and aqueous phase;

[0080] S3. Ultrafiltration membrane treatment: The aqueous phase obtained after the above S2 treatment is treated with an ultrafiltration membrane; the concentrate after the S3 ultrafiltration membrane treatment is returned to the S2 conditioning and separation treatment.

[0081] S4. Nanofiltration membrane treatment: The aqueous phase obtained after the above S3 treatment is treated with a nanofiltration membrane;

[0082] S5. Disc tube reverse osmosis membrane treatment: The aqueous phase obtained after the above S4 treatment is treated by a disc tube reverse osmosis membrane.

[0083] S6. Evaporation and Crystallization Treatment: The concentrate after treatment with S4 nanofiltration membrane and S5 disc tube reverse osmosis membrane is evaporated and crystallized; the aqueous phase after treatment with S4 nanofiltration membrane and S5 disc tube reverse osmosis membrane is returned to S3 ultrafiltration membrane treatment.

[0084] S7. Pyrolysis treatment: The slag phase after S6 evaporation and crystallization and the slag phase after S2 conditioning and separation are pyrolyzed.

[0085] In S2, the demulsifier is polyaluminum chloride, and the mass ratio of the demulsifier to the aqueous phase after oil-water separation treatment in S1 is 1.0:1000.

[0086] In S2, the flocculant is polyacrylamide, and the mass ratio of the flocculant to the aqueous phase after oil-water separation treatment in S1 is 0.2:1000.

[0087] In S3, the ultrafiltration membrane operates at a pressure of 0.5 MPa.

[0088] Prior to the S3 ultrafiltration membrane treatment, there is also a filtration process with a pore size of 100 mm.

[0089] In S4, the nanofiltration membrane operates at a pressure of 1.5 MPa.

[0090] Prior to the S4 nanofiltration membrane treatment, a filtration process is also included, with the filter having a pore size of 5 μm.

[0091] Example 2

[0092] A treatment system for pyrolysis water containing oily sludge is basically the same as that in Example 1.

[0093] The method for treating oily sludge pyrolysis water differs from that in Example 1 in that:

[0094] The mass ratio of the demulsifier to the aqueous phase after S1 oil-water separation treatment is 3:1000.

[0095] The rest is the same as in Example 1, and will not be repeated here.

[0096] Example 3

[0097] A treatment system for pyrolysis water containing oily sludge is basically the same as that in Example 1.

[0098] The method for treating oily sludge pyrolysis water differs from that in Example 1 in that:

[0099] The mass ratio of flocculant to the aqueous phase after S1 oil-water separation treatment is 1:1000.

[0100] The rest is the same as in Example 1, and will not be repeated here.

[0101] Example 4

[0102] A treatment system for pyrolysis water containing oily sludge is basically the same as that in Example 1.

[0103] The method for treating oily sludge pyrolysis water differs from that in Example 1 in that:

[0104] In S3, the ultrafiltration membrane operates at a pressure of 0.7 MPa.

[0105] The rest is the same as in Example 1, and will not be repeated here.

[0106] Example 5

[0107] A treatment system for pyrolysis water containing oily sludge is basically the same as that in Example 1.

[0108] The method for treating oily sludge pyrolysis water differs from that in Example 1 in that:

[0109] In S4, the nanofiltration membrane operates at a pressure of 2.6 MPa.

[0110] The rest is the same as in Example 1, and will not be repeated here.

[0111] Comparative Example 1

[0112] A treatment system for pyrolysis water containing oily sludge is basically the same as that in Example 1.

[0113] Unlike Example 1, this example does not include a conditioning and separation system.

[0114] The rest is the same as in Example 1, and will not be repeated here.

[0115] Comparative Example 2

[0116] A treatment system for oily sludge pyrolysis water has basically the same steps as in Example 1.

[0117] Unlike Example 1, the conditioning and separation system only includes a demulsification system and a solid-liquid separation system, but does not include a flocculation system.

[0118] The rest is the same as in Example 1, and will not be repeated here.

[0119] Result detection

[0120] The methods for treating oily sludge pyrolysis water in the above embodiments and comparative examples were tested using the following performance testing methods:

[0121] COD testing method: The potassium dichromate standard method is used for testing.

[0122] Ammonia nitrogen test method: Nessler's reagent colorimetric method.

[0123] Method for testing oil content in water: Infrared spectrophotometry.

[0124] The specific test results are shown in Table 3 below:

[0125]

[0126]

[0127] As can be seen from the above data, the method for treating oily sludge pyrolysis water of the present invention, through ultrafiltration membrane, reverse osmosis, and RO or biochemical treatment, can reduce the concentration of salt, COD and ammonia nitrogen in the effluent, so that the oily sludge pyrolysis water meets the discharge standards.

[0128] As can be seen from the examples and Comparative Example 1, without the conditioning and separation system, direct ultrafiltration demulsification results in a deterioration of the effluent quality in each stage, and the final effluent cannot meet the water quality requirements for reuse.

[0129] As can be seen from the examples and Comparative Example 2, the conditioning and separation system only includes a demulsification system and a solid-liquid separation system, but does not include a flocculation system. The failure of the conditioning and separation system affects the downstream, and the final effluent cannot meet the requirements for reuse.

[0130] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A treatment system for pyrolysis water containing oily sludge, characterized in that, It includes an oil-water separation system (1), a conditioning and separation system (2), an ultrafiltration membrane system (3), a nanofiltration membrane system (4), a disc tube reverse osmosis membrane system (5), an evaporation and crystallization system (6), and a pyrolysis system (7) connected in sequence. Among them, the conditioning and separation system (2) includes a demulsification system, a flocculation system and a solid-liquid separation system connected in sequence; The concentrate end of the ultrafiltration membrane system (3) is connected to the inlet end of the conditioning and separation system (2); The outlet of the nanofiltration membrane system (4) is connected to the feed end of the disc tube reverse osmosis membrane system (5), and the concentrate end of the nanofiltration membrane system (4) is connected to the inlet end of the evaporation crystallization system (6). The slag outlet of the evaporation crystallization system (6) is connected to the feed outlet of the pyrolysis system (7), and the water outlet of the evaporation crystallization system (6) is connected to the water inlet of the ultrafiltration membrane system (3). The slag outlet of the conditioning and separation system (2) is connected to the feed outlet of the pyrolysis system (7); The ultrafiltration membrane system (3) includes a tubular membrane with a pore size of 30-50 nm and an ultrafiltration membrane operating pressure of 0.2-0.6 MPa. The operating pressure of nanofiltration membranes is 0.8-2.5 MPa; The pyrolysis water containing oily sludge has a pH of 5.5-8.5, an electrical conductivity of 2000-20000 μS / cm, a COD of 5000-15000 mg / L, an ammonia nitrogen content of 100-1000 mg / L, and an oil content of 0.1-3%.

2. The treatment system for oily sludge pyrolysis water as described in claim 1, characterized in that, The antifouling membrane in the nanofiltration membrane system (4) has a pore size of 1~5nm.

3. The treatment system for oily sludge pyrolysis water as described in claim 1, characterized in that, It also includes a pH adjustment system disposed between the nanofiltration membrane system (4) and the disc tube reverse osmosis membrane system (5), the pH adjustment system being used to adjust the pH to 6 to 6.

5.

4. A method for treating pyrolysis water from oily sludge, characterized in that, The treatment of oily sludge pyrolysis water using the treatment system described in any one of claims 1 to 3 includes the following steps: S1. Oil-water separation: Oil-water separation treatment is used to treat pyrolysis water containing oily sludge; S2. Conditioning and Separation: The aqueous phase after the oil-water separation treatment in S1 is subjected to demulsification treatment with demulsifier, flocculation treatment with flocculant, and solid-liquid separation treatment to obtain slag phase and aqueous phase; S3. Ultrafiltration membrane treatment: The aqueous phase obtained after the above S2 treatment is treated with an ultrafiltration membrane; the concentrate after the S3 ultrafiltration membrane treatment is returned to the S2 conditioning and separation treatment. S4. Nanofiltration membrane treatment: The aqueous phase obtained after the above S3 treatment is treated through a nanofiltration membrane; S5. Disc tube reverse osmosis membrane treatment: The aqueous phase obtained after the above S4 treatment is treated by a disc tube reverse osmosis membrane. S6. Evaporation and Crystallization Treatment: The concentrated solution after S4. Nanofiltration membrane treatment and the concentrated solution after S5. Disc Tube Reverse Osmosis Membrane treatment are evaporated and crystallized. The aqueous phases treated by S4 nanofiltration membrane and S5 disc tube reverse osmosis membrane are returned to S3 ultrafiltration membrane for further treatment. S7. Pyrolysis treatment: The slag phase after evaporation and crystallization of S6 and the slag phase after conditioning and separation of S2 are subjected to pyrolysis treatment.

5. The method for treating oily sludge pyrolysis water as described in claim 4, characterized in that, In S2, the demulsifier is one or more of polyaluminum chloride, lime, nonylphenol polyoxyethylene ether, or sodium carbonate, and the mass ratio of the demulsifier to the aqueous phase after oil-water separation treatment in S1 is (0.6~2.0):1000.

6. The method for treating oily sludge pyrolysis water as described in claim 4, characterized in that, In S2, the flocculant is polyacrylamide, and the mass ratio of the flocculant to the aqueous phase after oil-water separation treatment in S1 is (0.1~0.8):1000.

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