A treatment system for oily wastewater in methanol to olefins products

Abstract

The present invention provides a treatment system for oily wastewater in methanol to olefins products, the treatment system comprises an oil separator, a clarification tank, a filter, a coalescer and a clean water tank which are sequentially connected through pipelines, the oil separator is provided with a water inlet, and the clean water tank is provided with a water outlet; wherein, the inner cavity of the oil separator and the clarification tank is provided with a plurality of partitions arranged at intervals from each other, the partitions divide the inner cavity of the tank into a plurality of reaction chambers, the partitions are provided with connecting ports to connect the reaction chambers, an oil bag is provided in each cavity of the oil separator, and a dosing device is provided in the cavity of the clarification tank to add drugs thereto. In view of the characteristics of methanol to olefin oily wastewater, the present invention treats floating oil, solid attached oil, suspended matter and emulsified oil separately, and modifies the wastewater from three phases of oil, water and solid into two phases of oil and water, thereby reducing the difficulty of treating the oily wastewater and improving the treatment stability of the oily wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of preparing olefins from methanol in coal chemical industry, and relates to a comprehensive treatment system for oil-water in methanol-to-olefins products. Background Art

[0002] Methanol to olefins (MTO) refers to a chemical technology that uses methanol as raw material to produce low-carbon olefins in the form of fluidized bed reaction. The process mainly includes a reaction regeneration system (reactor and regenerator), a product purification system (quench tower, water washing tower, alkali washing tower and drying tower) and a product separation system (olefin separation device). A large amount of wastewater generated comes from the product purification system and the product separation system, including quench water at the bottom of the quench tower, oily wastewater from the gasoline tank at the bottom of the water washing tower, and oily wastewater from the skimming oily wastewater in the settling tank. The characteristics of quench water are low oil content and high solid content, but due to the fine solid particles, it is difficult to separate by gravity sedimentation and filtration; the characteristics of oily wastewater from the gasoline tank and oily wastewater from the skimming oily wastewater in the settling tank are high oil content (including emulsified oil and floating oil), and contain a small amount of catalyst, and the emulsification phenomenon is serious. For the above-mentioned wastewater, methods such as adding demulsifiers, standing, and sedimentation are generally used, but the treatment effect is not good, and it is extremely difficult to remove oil and solids. Therefore, oily and solid-containing wastewater has become a difficult problem in the MTO industry.

[0003] Patent CN103951098A discloses a method and device for desolidification and oil removal of quench water and washing water in the methanol to olefins process, which mainly includes ultrafiltration membrane separation of MTO / MTP quench water, ultrafiltration membrane concentrate entering the three-phase cyclone separator separation system to recover catalyst and oil; ultrafiltration membrane permeate is cooled back to the quench water system for recycling; MTO / MTP washing water is separated by ultrafiltration membrane, and ultrafiltration membrane concentrate enters the three-phase cyclone separator separation system to recover catalyst and oil; ultrafiltration membrane permeate is cooled back to the washing water system for recycling. Although this method can remove solids and oil, the ultrafiltration membrane is easy to clog and difficult to clean, and the emulsified oil in the treated water cannot meet the standard, and will be enriched in the system for a long time, increasing the difficulty of treatment.

[0004] Patent CN102050548A discloses a method for treating and reusing wastewater from a methanol to olefins process, which includes the following steps: 1) after the heat of the effluent from the MTO reactor is recovered by a waste heat boiler, the effluent is cooled and separated into high-concentration MTO wastewater by a separation tower; 2) the effluent from the MTO reactor is further cooled to obtain a water phase at the bottom of the separation tower and olefin gas at the top of the separation tower; the olefin gas is further purified by compression and water washing operations; 3) the water phase from the bottom of the separation tower and the bottom of the water washing tower is subjected to stripping treatment, and the water phase obtained at the bottom of the stripping tower is cooled and cooled by a bottom heat exchanger to obtain low-concentration MTO water; 4) the low-concentration MTO water is homogenized; 5) the low-concentration MTO water after homogenization is subjected to coagulation and sedimentation treatment; 6) the low-concentration MTO water after coagulation and sedimentation treatment is subjected to aerobic aeration treatment; 7) the effluent from the aerobic aeration treatment is subjected to sedimentation treatment; 8) the effluent from the sedimentation treatment is subjected to flocculation and filtration treatment. This method performs steam stripping treatment on the water phase from the bottom of the separation tower and the bottom of the water washing tower, but does not mention the pretreatment of the water phase before steam stripping. Oil and catalyst particles in the water phase may cause blockage of the stripping tower and the reboiler.

[0005] In the process of olefin production, how to recycle and utilize oil- and solid-containing wastewater is of great significance to the development of coal-to-olefin or methanol-to-olefin industries, and is conducive to promoting the application of comprehensive wastewater treatment and reuse in olefin production. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, the present invention provides a treatment system for methanol to olefins quench water and water washing water. According to the characteristics of methanol to olefins oily wastewater, the wastewater is modified from three phases of oil, water and solid to two phases of oil and water, thereby reducing the difficulty of treating the oily wastewater and improving the treatment stability of the oily wastewater.

[0007] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a treatment system for oily wastewater in methanol-to-olefin products, the treatment system comprising an oil separator, a clarification tank, a filter, a coalescer and a clean water tank which are sequentially connected through pipelines, the oil separator is provided with a water inlet for conveying wastewater to the treatment system, and the clean water tank is provided with a water outlet for discharging clear liquid;

[0009] The inner cavity of the oil separator tank is provided with a plurality of partitions arranged at intervals from each other, and the plurality of partitions divide the inner cavity of the tank into a primary oil separator chamber, a secondary oil separator chamber and a clean water chamber I in sequence, and a connecting port is provided on the partition, and a primary oil bag and a secondary oil bag are respectively provided on the top of the primary oil separator chamber and the secondary oil separator chamber;

[0010] The inner cavity of the clarification tank is provided with a plurality of partitions arranged at intervals from each other, and the plurality of partitions divide the inner cavity of the tank into reaction chamber I, reaction chamber II, reaction chamber III and clean water chamber II in sequence, the partition is provided with a connecting port, the reaction chamber III and the clean water chamber II are also connected by a connecting pipe, and a mud discharge pipe is provided at the bottom of the reaction chamber III; a dosing device I is provided at the top of the reaction chamber I, and a dosing device II is provided at the top of the reaction chamber II;

[0011] The inner cavity of the coalescer is divided into a primary oil separator chamber and a secondary oil separator chamber by a partition plate, and the tops of the primary oil separator chamber and the secondary oil separator chamber are provided with a primary oil bag and a secondary oil bag of the coalescer respectively;

[0012] The treatment system also includes a sludge tank and an oil product buffer tank, and the bottom of the reaction chamber III and the sewage outlet of the filter are connected to the inlet of the sludge tank;

[0013] The primary oil bag, the secondary oil bag, the coalescer primary oil bag and the coalescer secondary oil bag are connected to the inlet of the oil product buffer tank through pipelines.

[0014] In a specific embodiment of the treatment system of the present invention, the connecting port is provided at the bottom of the partition between the primary oil-water separator and the secondary oil-water separator in the oil-water separator tank; the connecting port is provided at the top of the partition between the secondary oil-water separator and the clean water chamber I.

[0015] In the clarification tank, the communicating port is provided at the bottom of the partition between reaction chamber I and reaction chamber II; the communicating port is provided at the top of the partition between reaction chamber II and reaction chamber III; and the communicating port is provided at the top of the partition between reaction chamber III and clean water chamber II.

[0016] In a specific embodiment of the treatment system of the present invention, an inclined plate assembly is obliquely arranged in the reaction chamber III, and a plurality of passage openings are opened on the inclined plate assembly; in some specific embodiments, the inclined plate assembly can be formed by splicing a plurality of folded plates, and passage openings are formed between the folded plates after splicing, and the shape of the passage openings can be hexagonal, square or circular, etc. The inclined plate assembly is arranged obliquely with respect to the horizontal plane in the chamber of the reaction chamber III, and in some preferred embodiments, the inclination angle is 30° to 45°.

[0017] In the clarification tank of the treatment system of the present invention, the dosing device I is used to add a modifier and a flocculant into the reaction chamber I; the modifier is selected from the quench water containing the catalyst, for example, the quench water can be selected from the quench water produced by methanol to olefins, wherein the content of the catalyst is 100mg / L to 1000mg / L, for example, 200mg / L, 500mg / L, 800mg / L. In some preferred embodiments, the modifier is the quench water discharged from the methanol to olefins device; in some specific embodiments, the addition ratio of the modifier to the oily wastewater is (0.1 to 0.5):1, for example, 0.2:1, 0.3:1, 0.4:1.

[0018] In some specific embodiments, the added amount of the flocculant is 50-200 mg / l, and the flocculant is selected from one or more of polyaluminum sulfate, aluminum chloride, polyaluminum chloride, ferric sulfate, ferrous sulfate or ferric chloride.

[0019] In the clarification tank of the treatment system of the present invention, a coagulant is added to the reaction chamber II through the dosing device II, and the amount of the coagulant added is 3 to 20 mg / l, which can be specifically selected from one or more of polyacrylic acid, sodium polyacrylate, calcium polyacrylate, polyacrylamide, styrene sulfonate, wood sulfonate, acrylic acid or methacrylic acid.

[0020] In the treatment system of the present invention, filter material is filled in the filter, and the particle size of the filter material is 0.2-0.5 mm; the filter material can be specifically selected from one or more of quartz sand, river sand, sea sand, ceramsite, anthracite, activated carbon, diatomaceous earth, manganese sand, iron sand or zeolite.

[0021] The coalescer in the treatment system of the present invention uses a coalescing filter element to separate oil from water. The coalescing filter element uses one or more of metal wire mesh, synthetic fiber, non-woven fabric or glass fiber.

[0022] In the treatment system of the present invention, a part of the clear liquid discharged from the clear water tank is returned to the filter as backwash water, and the other part is discharged from the system.

[0023] The above technical solution has the following technical effects:

[0024] According to the characteristics of oily wastewater from methanol to olefins, the present invention treats floating oil, solid attached oil, suspended matter and emulsified oil separately, and modifies the wastewater from three phases of oil, water and solid to two phases of oil and water, thereby reducing the difficulty of treating the oily wastewater and improving the treatment stability of the oily wastewater.

[0025] After being treated by the treatment system provided by the present invention, the petroleum content in the water is lower than 50 mg / l, and the water can be used as water for gasification and coal grinding, thus realizing the comprehensive utilization of waste water.

[0026] The treatment system of the present invention uses the quench water discharged from the methanol to olefins device as a modifier to modify the oily wastewater. The raw materials are easily available and waste is treated with waste, which greatly reduces the operating cost. At the same time, the waste oil products in the oily wastewater are recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : An embodiment of the system for treating oily wastewater in methanol to olefins products of the present invention;

[0028] Figure 2 : Figure 1 Structural diagram of the intermediate oil tank;

[0029] Figure 3 : Figure 1 Schematic diagram of the structure of the intermediate clarification tank;

[0030] Figure 4 : Figure 1 A partial enlarged view of the middle inclined plate assembly;

[0031] Figure 5 : Figure 1 Schematic diagram of the structure of the middle coalescer;

[0032] Among them, 1. oil separator, 2. clarification tank, 3. sludge tank, 4. filter, 5. coalescer, 6. clean water tank, 7. oil buffer tank, 8. dosing device I, 9. dosing device II, 10. primary oil separator, 11. primary oil bag, 12. secondary oil bag, 13. secondary oil separator, 14. clean water chamber I, 15. reaction chamber I, 16. reaction chamber II, 17. reaction chamber III, 18. clean water chamber II, 19. connecting port, 20. coalescing filter element filler, 21. primary oil bag of coalescer, 22. secondary oil bag of coalescer, 23. inclined plate assembly, 24. channel port, 25. connecting pipe, 26. sludge discharge pipe. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0034] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0035] Example 1

[0036] This embodiment uses oily wastewater produced by a methanol to olefins system as feed, wherein the petroleum content is 28695 mg / l.

[0037] The above-mentioned oily wastewater is transported to the oil separator tank 1 through the water inlet on the oil separator tank 1, and the floating oil in the wastewater slowly aggregates in the primary oil separator chamber 10 and floats to the primary oil bag 11, and then the oily wastewater further enters the secondary oil separator chamber 13 and floats to the secondary oil bag 12, and the floating oil in the primary oil bag 11 and the secondary oil bag 12 is discharged to the oil buffer tank 7 for collection; the oily wastewater after the floating oil is removed enters the clean water chamber Ⅰ14, and is sent to the clarification tank 2 through its outlet.

[0038] The dosing device Ⅰ8 opened on the top of the reaction chamber Ⅰ15 in the clarification tank 2 is used to add a modifier and a flocculant into the reaction chamber Ⅰ15 for modification, wherein the modifier is selected from the quenching water of the quenching tower in the methanol to olefin process (the solid content of the quenching water, i.e., the catalyst content, is 500 mg / l, and the ratio of the quenching water addition to the oily wastewater is 0.5:1), and the flocculant is selected from polyaluminum sulfate (the addition amount is 50 mg / l); the modified oily water is continuously sent to the reaction chamber Ⅱ16 through the connecting port 19 at the bottom of the partition. A dosing device II9 is ​​provided on the top of the reaction chamber II16 for adding a coagulant aid (polyacrylamide, the addition amount is 3 mg / l) thereto. In the process, the solids in the oily water adhere to the oil and slowly form flocs, which are then sent to the reaction chamber III17 for natural sedimentation. The sludge formed at the bottom is sent to the sludge tank 3 through the sludge discharge pipe 26. The clear liquid in the upper part overflows upward through the channel port 24 on the inclined plate assembly 23, and enters the clean water chamber II18 through the connecting pipe 25. The treated water in the clean water chamber II18 is further filtered through the lifting pump filter 4 (the filter material is quartz sand and manganese sand).

[0039] The treated water after filtration is continuously sent to the coalescer 5 (the coalescing filter element filler 20 is a metal wire mesh), and the petroleum content in the treated water is 16.8 mg / l. The floating oil in the treated water slowly coalesces in the chamber of the coalescer 5 and floats to the first-level oil bag 21 and the second-level oil bag 22 of the coalescer, and the floating oil in the above-mentioned oil bags is then discharged to the oil buffer tank 7 for collection. The floating oil discharged from the oil separator 1 and the floating oil discharged from the coalescer 5 are collected in the oil buffer tank 7 and sent out as waste oil.

[0040] The treated water from the coalescer 5 is sent to the clean water tank 6. Part of the water in the clean water tank 6 is sent to the filter 4 via a lift pump as backwash water, and the other part of the water is discharged as treated water for gasification coal grinding.

[0041] Example 2

[0042] The difference between this embodiment and embodiment 1 is that the solid content of the quench water added to the reaction chamber Ⅰ15 is 1000 mg / l, the ratio of the quench water added to the oily wastewater is 0.1:1, and the petroleum in the effluent water after treatment is 6.3 mg / l.

[0043] Example 3

[0044] The difference between this embodiment and embodiment 1 is that the amount of polyaluminium sulfate added to the reaction chamber Ⅰ15 is 200 mg / l, and the petroleum in the effluent after treatment is 10.5 mg / l.

[0045] Example 4

[0046] The difference between this embodiment and embodiment 1 is that the flocculant in the reaction chamber Ⅰ15 is ferric sulfate, the addition amount of which is 200 mg / l, and the petroleum in the effluent after treatment is 7.8 mg / l.

[0047] Example 5

[0048] The difference between this embodiment and embodiment 1 is that the flocculant in the reaction chamber Ⅰ15 is polyaluminium chloride, the addition amount of which is 200 mg / l, and the petroleum in the effluent after treatment is 8.8 mg / l.

[0049] Comparative Example

[0050] The difference between this comparative example and Example 1 is that only flocculant is added to the oily wastewater in the reaction chamber Ⅰ15 of the clarification tank 2, and no modifier is added. The upper clear liquid obtained from the reaction chamber Ⅲ17 enters the clean water chamber Ⅱ18 and is then pumped to the filter 4. The solid attached oil causes the filter 4 to be blocked and cannot be regenerated.

Claims

1. A system for treating oily wastewater in methanol to olefins products, characterized in that: The treatment system comprises an oil separator tank, a clarification tank, a filter, a coalescer and a clean water tank which are sequentially connected through pipelines, the oil separator tank is provided with a water inlet for conveying wastewater to the treatment system, and the clean water tank is provided with a water outlet for discharging clear liquid; The inner cavity of the oil separator tank is provided with a plurality of partitions arranged at intervals from each other, and the plurality of partitions divide the inner cavity of the tank into a primary oil separator chamber, a secondary oil separator chamber and a clean water chamber I in sequence, and a connecting port is provided on the partition, and a primary oil bag and a secondary oil bag are respectively provided on the top of the primary oil separator chamber and the secondary oil separator chamber; The inner cavity of the clarification tank is provided with a plurality of partitions arranged at intervals from each other, and the plurality of partitions divide the inner cavity of the tank into reaction chamber I, reaction chamber II, reaction chamber III and clean water chamber II in sequence. A connecting port is provided on the partition, and a connecting pipe is provided between the reaction chamber III and the clean water chamber II, and a mud discharge pipe is provided at the bottom of the reaction chamber III; a dosing device I is provided on the top of the reaction chamber I, and a dosing device II is provided on the top of the reaction chamber II; the dosing device I is used to add a modifier and a flocculant into the reaction chamber I; the dosing device II is used to add a coagulant aid into the reaction chamber II; the modifier is selected from quench water containing a catalyst, wherein the content of the catalyst is 100 mg / L to 1000 mg / L; The inner cavity of the coalescer is divided into a primary oil separator chamber and a secondary oil separator chamber by a partition plate, and the tops of the primary oil separator chamber and the secondary oil separator chamber are provided with a primary oil bag and a secondary oil bag of the coalescer respectively; The treatment system also includes a sludge tank and an oil product buffer tank, and the bottom of the reaction chamber III and the sewage outlet of the filter are connected to the inlet of the sludge tank; The primary oil bag, the secondary oil bag, the coalescer primary oil bag and the coalescer secondary oil bag are connected to the inlet of the oil product buffer tank through pipelines.

2. The processing system according to claim 1, characterized in that In the oil separator tank, the communicating port is provided at the bottom of the partition between the primary oil separator chamber and the secondary oil separator chamber; The communicating port is arranged on the top of the partition plate between the secondary oil-separating chamber and the clean water chamber I.

3. The processing system according to claim 1 or 2, characterized in that: In the clarification tank, the bottom of the partition between the reaction chamber I and the reaction chamber II is provided with the communication port; The communicating port is provided at the top of the partition between the reaction chamber II and the reaction chamber III; The communicating port is arranged on the top of the partition plate between the reaction chamber III and the clean water chamber II.

4. The processing system according to claim 3, characterized in that An inclined plate assembly is obliquely arranged in the reaction chamber III, and a plurality of channel openings are opened on the inclined plate assembly.

5. The processing system according to claim 4, characterized in that The inclination angle of the inclined plate assembly is 30° to 45°.

6. The processing system according to claim 4, characterized in that The modifier is quench water discharged from a methanol to olefins unit; The addition ratio of the modifier to the oily wastewater is (0.1-0.5):1; The added amount of the flocculant is 50-200 mg / l, and the flocculant is selected from one or more of polyaluminium sulfate, aluminium chloride, polyaluminium chloride, ferric sulfate, ferrous sulfate and ferric chloride.

7. The processing system according to claim 4, characterized in that The added amount of the coagulant is 3-20 mg / l, and the coagulant is selected from one or more of polyacrylic acid, sodium polyacrylate, calcium polyacrylate, polyacrylamide, styrene sulfonate, wood sulfonate, acrylic acid, and methacrylic acid.

8. The processing system according to any one of claims 1, 2, 4 to 7, characterized in that: The filter is filled with filter material, and the particle size of the filter material is 0.2-0.5 mm; The filter material is selected from one or more of quartz sand, river sand, sea sand, ceramsite, anthracite, activated carbon, diatomaceous earth, manganese sand, iron sand, and zeolite.

9. The processing system according to claim 8, characterized in that The coalescing filter element is used in the coalescer to separate oil and water. The coalescing filter element is made of one or more of metal wire mesh, synthetic fiber, non-woven fabric, and glass fiber.

10. The processing system according to any one of claims 1, 2, 4 to 7, and 9, characterized in that: A portion of the clear liquid discharged from the clear water tank is returned to the filter as backwash water, and the other portion is discharged externally.

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