CN111003896A

CN111003896A - Multi-membrane integrated near-zero emission treatment process for MTO (methanol to olefin) high-concentration organic wastewater

Info

Publication number: CN111003896A
Application number: CN201911372250.7A
Authority: CN
Inventors: 李卫星; 周迪; 杨春胜; 冯刚; 王晓军; 赵静; 崔乃俊
Original assignee: Nanjing Tech University; Nanjing Chengzhi Clean Energy Co Ltd
Current assignee: Nanjing Tech University; Nanjing Chengzhi Clean Energy Co Ltd
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2020-04-14

Abstract

The invention discloses a multi-membrane integrated near-zero-emission treatment process for MTO high-concentration organic matter wastewater. The treatment process adopts a flow taking ozone floatation-BAF-MBR-UF-RO-CWO as a main line, so that organic matters in the high-concentration organic matter wastewater are effectively separated and oxidized and degraded, near zero emission is finally realized, and treated produced water enters a reuse water system. The method for treating the high-concentration organic wastewater from the preparation of olefin from methanol in MTO has the advantages of high and stable treatment effect, simple and convenient operation and easy maintenance.

Description

Multi-membrane integrated near-zero emission treatment process for MTO (methanol to olefin) high-concentration organic wastewater

Technical Field

The invention relates to the technical field of organic wastewater treatment in the technical field of wastewater treatment, in particular to a method for treating wastewater of a methanol-to-olefin production process in an MTO coal chemical technology.

Background

With the development of economy and society, especially the increasing demand for basic organic chemical raw materials, such as low-carbon olefins like ethylene and propylene, these low-carbon olefins are widely used in the fields of synthetic materials, organic synthesis, instrument analysis, fine chemicals, agriculture, etc., and resources such as naphtha and light diesel oil, which are the traditional raw materials of low-carbon olefins, face the situation of increasing shortage.

Under the background, people are prompted to seek a new way for further developing non-petroleum resources, and the development of coal chemical industry and natural gas chemical industry is greatly promoted. In recent years, the technology development of Methanol To Olefin (MTO) technology from coal or natural gas has become mature internationally.

The MTO reaction mechanism is that methanol is dehydrated to generate dimethyl ether, and then the dimethyl ether reacts with the methanol to be converted into low-carbon olefin mainly comprising ethylene and propylene, a small amount of saturated hydrocarbon and aromatic hydrocarbon and the like. The waste water produced in the reaction process contains organic matters such as oil substances, water, methanol, dimethyl ether, low-carbon hydrocarbons, low-carbon hydrogen and the like and fine powder of the catalyst. The wastewater contains a large amount of oxygen-containing organic matters and has high pollutant content. If the wastewater is directly discharged to a conventional sewage treatment plant for treatment without pretreatment, the requirement of the influent water quality of the sewage treatment plant cannot be met, and the normal stable operation of the sewage treatment plant and the standard-reaching requirement of discharged sewage cannot be ensured.

Chinese patent CN 103833171A discloses a method for treating organic wastewater with ultrahigh concentration in a process for preparing olefin from methanol, wherein after MTO wastewater is treated by adopting the treatment processes of demulsification primary oil removal, alcohol-ketone stripping separation, secondary demulsification oil removal and high-efficiency adsorption and corresponding conditions in sequence, COD in concentrated wastewater with ultrahigh organic content can be reduced to below 3000 mg/L from 100000 mg/L, and the removal rate is more than 97%. However, the patent only proposes a method for separating and adsorbing organic matters from MTO reaction wastewater, and does not mention how to treat the organic matters and treat hazardous waste generated in the adsorption process, and a stripping tower is also used, so that the energy consumption is high.

Chinese patent CN 102442744A discloses a method for treating high-concentration process wastewater from methanol to olefin, which adopts the treatment processes of homogeneous adjustment, oil-separation coagulating sedimentation, steam stripping, anaerobic treatment and post-precipitation and corresponding conditions to reduce the COD of the wastewater from about 50000 mg/L to below 500 mg/L, and the removal rate reaches more than 99%. The energy consumption of the stripping process used in the patent is relatively high, while the whole patent is only a pretreatment part, and is relatively complex and lengthy, and the operation cost is relatively high.

Chinese patent CN 105923875A discloses a treatment method of wastewater from methanol-to-olefin process, which comprises the steps of separating the wastewater into an oil phase and a water phase by a phase separation device, recycling the oil phase, and carrying out the next treatment on the water phase; rectifying the wastewater phase obtained by the first step to remove organic matters dissolved in the wastewater, wherein the COD of the wastewater is reduced to below 500 mg/L. And (3) after heat exchange of the wastewater treated in the first step by a heat exchanger, feeding the wastewater into the middle part of a rectifying tower, heating the tower bottom by a reboiler, condensing steam at the tower top by a condenser and feeding the steam into a reflux tank to obtain a mixture of an oil phase and a water phase, recovering and utilizing the oil phase, feeding the water phase back to the rectifying tower by a reflux pump, and cooling the water discharged from the tower kettle for next step treatment. However, this patent only proposes a method for separating useful components from MTO reaction wastewater and does not mention how to treat the wastewater.

It is apparent from the above published documents that the current MTO wastewater treatment approaches focus primarily on the physical separation of water from contaminants, and that the proposed point of wastewater reuse is only fundamental, and there is essentially no concern as to how the wastewater to be discharged is further treated and reused.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a multi-membrane integrated near-zero-emission treatment process for MTO high-concentration organic wastewater, which can greatly reduce the total amount of pollutants emitted to the environment in MTO production and completely oxidize and degrade the organic matters, so as to make up the defects in the prior art and finally realize the near-zero-emission target.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:

the multi-membrane integrated near-zero-emission treatment process of MTO high-concentration organic matter wastewater comprises the following steps:

firstly, adopting an ozone air floatation method, adding a collecting agent and a flocculating agent, removing fine suspended matters and micro-flocs in wastewater, and performing emulsion breaking separation on surface floating oil and micro-emulsified organic matters;

secondly, adjusting the pH value of the wastewater subjected to the ozone flotation in the first step to a corresponding value by an adjusting tank, and staying for a short time and then entering the next step;

thirdly, adopting a Biological Aerated Filter (BAF) process to remove SS and COD in the wastewater_CrAnd BOD₅；

Fourthly, the wastewater in the third step is subjected to a Membrane Bioreactor (MBR) process, so that organic matters in the wastewater are further degraded by activated sludge, and macromolecular organic matters are intercepted;

fifthly, adopting an Ultrafiltration (UF) system to further intercept organic matters and part of oil, colloid, suspended matters and particulate matters in the wastewater treated in the fourth step, and returning the generated concentrated water to the BAF process;

sixthly, enabling the wastewater filtered in the fifth step to enter a Reverse Osmosis (RO) system, almost completely intercepting organic matters in the wastewater, and enabling penetrating fluid to enter a reuse water system;

and seventhly, adopting a catalytic wet oxidation technology (CWO) to the concentrated water generated in the sixth step to almost completely degrade organic matters, and enabling the generated water to enter a reuse water system.

In the technical scheme, the collecting agent added in the ozone gas floating method is one or more of a sulfhydryl collecting agent, a hydroxyl collecting agent, an amine collecting agent, an amino acid collecting agent, an ester collecting agent, a polar collecting agent of a double-sulfide collecting agent and a non-polar collecting agent of hydrocarbon oil, and the using amount is 0.1-1 kg/t; the added flocculating agent is aluminum salt, iron salt or Polyacrylamide (PAM), and the dosage is 1-15 kg/t.

In the above technical scheme, the air floatation method adopts a micro-bubble upper floatation method, an impeller air floatation method or pressurizationOne or more of the dissolved air flotation methods, wherein the pressure of the pressurized dissolved air flotation method is 1-6 kg/cm²。

In the technical scheme, in the second step, the adjusting tank adjusts the pH of the wastewater to be 5-10, and adopts 5-10 wt.% of NaOH solution and 5-10 wt.% of dilute H₂SO₄The solution stays for 3-24 hours.

In the technical scheme, the BAF process adopts volcanic biological filter materials or similar round coal cinder as fillers, the diameter of the fillers is 1-5 mm, the height of the fillers is 0.5-2 m, and the operating temperature is 5-35 ℃.

In the technical scheme, the MBR process device adopts a flat curtain-shaped immersed membrane component or a hollow fiber column-shaped immersed membrane component, wherein the organic membrane adopts one of polyolefine, polyacrylonitrile, polysulfone, aromatic, polyamide, fluorine-containing polymer, PVDF, PE or PP materials, the pore size of the membrane is 0.1-1 mu m, the procedures of anaerobic treatment, anoxic treatment and aerobic treatment are sequentially adopted, and the sludge concentration in the anaerobic treatment is 5-50 g/L; the effluent of the reactor is subjected to external circulation, and the circulation ratio is 1-20: 1; controlling the anaerobic reaction temperature at 15-50 ℃; adding N nutrient salt and P nutrient salt into the wastewater during anaerobic treatment, wherein the adding proportion is that COD is that N and P are 100-; the added P nutrient salt is one or more of trisodium phosphate, calcium superphosphate or potassium dihydrogen phosphate.

In the technical scheme, the operating pressure in the UF system is 0.1-0.8 MPa, the average pore diameter of the membrane is 0.01-0.1 μm, wherein the organic ultrafiltration membrane is cellulose, cellulose derivatives, polysulfones, polyimide, polyetherimide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride or polyolefin ultrafiltration membrane; the inorganic film is Al₂O₃、TiO₂Or ZrO₂Is a single-pass or multi-channel ceramic membrane made of main materials; the membrane component adopts the form of a hollow fiber membrane component, a tubular membrane component, a curtain type membrane component, a roll-up membrane component or a plate-and-frame type membrane component; the operation mode of the ultrafiltration system is a cross-flow filtration mode or a dead-end filtration mode.

In the technical scheme, the RO system is divided into a low-pressure section and a high-pressure section, the operating pressure is 0.5-3.5 MPa, and a cross flow operation mode is adopted.

In the technical scheme, the temperature of the CWO technology is 75-300 ℃, the operating pressure is 0.5-6 MPa, air, oxygen or ozone is used as an oxidant, and a catalyst loading element is a noble metal, a transition metal or a rare earth element, wherein the noble metal is ruthenium, rhodium, palladium, iridium or platinum, the transition metal is copper, iron, manganese or cobalt, and the rare earth element is cerium, lanthanum or praseodymium; the load mass percentage is 0.1-5 wt.%.

The invention has the following beneficial effects:

the traditional biological treatment technology provided by the invention is coupled with an advanced membrane method integration technology and a catalytic wet oxidation technology in an advanced oxidation technology, aiming at high-concentration organic matter wastewater in an MTO process, the invention not only can effectively separate organic pollutants (COD) in the wastewater, but also can effectively degrade the organic pollutants, and the thought of combining separation and separate treatment is adopted, so that the recovery utilization rate of the wastewater is improved, the aim of near zero emission of the wastewater is fulfilled, and the cost of an enterprise is greatly reduced.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

Detailed Description

Example 1

The method comprises the following steps of firstly carrying out ozone air floatation process treatment on MTO high-concentration organic wastewater generated by a certain coal chemical industry enterprise, wherein the air floatation process adopts a micro-bubble upward floatation method, 0.5 kg/t of sulfydryl collecting agent is added, and then, 7.5 kg/t of aluminum salt (polyaluminium chloride) flocculating agent is added to remove fine suspended matters and micro-flocs in the wastewater and simultaneously carry out emulsion breaking separation on surface floating oil and micro-emulsified organic matters; the wastewater then enters a conditioning tank to adjust the pH using 7 wt.% NaOH solution or 7 wt.% dilute H₂SO₄The pH value of the wastewater is adjusted to 7 by the solution, and the wastewater stays for 12 hours; then entering a BAF treatment process, wherein the filler is a volcanic biological filter material, the diameter of the filler is 3 mm, the height of the filler is 1.5 m, and the operation temperature is controlled at 25 ℃ to remove SS and COD in the wastewater_CrAnd BOD₅(ii) a Then the membrane enters the MBR treatment process, adopts a flat plate type curtain-shaped immersed membrane component and is assembledThe method is characterized in that a centralized organic membrane is made of polyacrylonitrile, the membrane aperture is 0.5 mu m, the process of anaerobic → anoxic → aerobic sequence is adopted, wherein the sludge concentration in the anaerobic treatment is 25 g/L, the effluent of a reactor is subjected to external circulation, the circulation ratio is 10:1, the anaerobic reaction temperature is controlled at 25 ℃, N nutrient salt and P nutrient salt are required to be added during the anaerobic treatment, the adding ratio is COD (chemical oxygen demand), N is 500: P is 7:3, the N nutrient salt is urea, the P nutrient salt is trisodium phosphate, organic matters in the wastewater are further degraded, and macromolecular organic matters and activated sludge are intercepted; then entering a UF system, adopting a hollow fiber membrane component, operating pressure of 0.5 MPa, average pore diameter of the membrane of 0.05 μm, adopting cellulose and cellulose derivative materials as an organic ultrafiltration membrane, adopting a cross-flow filtration mode as a system operation mode, and further intercepting partial oil, colloid, suspended matters and particulate matters in the wastewater to generate concentrated water which flows back to a BAF process, and adopting an RO system for water production; the operating pressure of a low-pressure section in the RO system is 1MPa, the operating pressure of a high-pressure section in the RO system is 3 MPa, a cross flow operation mode is adopted to almost completely intercept organic matters in the wastewater, penetrating fluid enters a reuse water system, and RO concentrated water enters a CWO treatment process; the reaction temperature in the CWO process is 200 ℃, the operation pressure is 4 MPa, ozone is used as an oxidant, auxiliary elements in catalyst load are ruthenium and palladium, the load mass percentage is 2.5 wt.%, organic matters are almost completely degraded, and water produced enters a reuse water system.

Example 2

MTO high-concentration organic wastewater generated by a certain coal chemical industry enterprise is firstly treated by an ozone air floatation process, wherein the air floatation process adopts a pressurized dissolved air floatation method, and the pressure is 3 kg/cm²Adding 0.1 kg/t of double sulfide collecting agent, then adding 15 kg/t of ferric salt (polyferric chloride) flocculant to remove fine suspended matters and micro-flocs in the wastewater, and simultaneously performing emulsion breaking separation on the surface floating oil and micro-emulsified organic matters; the wastewater then enters a conditioning tank to adjust the pH using either 5wt.% NaOH solution or 5wt.% dilute H₂SO₄The pH value of the wastewater is adjusted to 7 by the solution, and the wastewater stays for 24 hours; then enters a BAF treatment process, the filler is a volcanic biological filter material, and the diameter of the filler is 1mm, the height of the filler is 2m, and the operation temperature is controlled at 35 ℃ so as to remove SS and COD of the wastewater_CrAnd BOD₅(ii) a Then, an MBR treatment process is carried out, a hollow fiber columnar immersed membrane component is adopted, an organic membrane in the device is made of polysulfone materials, the membrane aperture is 0.1 mu m, the sequence of anaerobic → anoxic → aerobic is adopted, the sludge concentration in the anaerobic treatment is 50 g/L, the effluent of the reactor is subjected to external circulation, the circulation ratio is 15:1, the anaerobic reaction temperature is controlled at 25 ℃, N nutrient salt and P nutrient salt are required to be added in the anaerobic treatment, the adding proportion is that COD (chemical oxygen demand) is that N: P is 1000:5:1, the N nutrient salt is ammonium chloride, the P nutrient salt is calcium superphosphate, organic matters in the wastewater are further degraded, and macromolecular organic matters and activated sludge are intercepted; then entering a UF system, adopting a curtain type membrane component, wherein the operation pressure is 0.1 MPa, the average pore diameter of the membrane is 0.1 mu m, and the inorganic ultrafiltration membrane adopts Al₂O₃The system is a multi-channel ceramic membrane made of main materials, the system operation mode is a cross-flow filtration mode and is used for intercepting part of oil, colloid, suspended matters and particulate matters in the wastewater and further intercepting organic matters, the generated concentrated water flows back to the BAF process, and the water is produced by an RO system; the operating pressure of a low-pressure section in the RO system is 0.5 MPa, the operating pressure of a high-pressure section in the RO system is 3.5MPa, a cross flow operation mode is adopted to almost completely intercept organic matters in the wastewater, penetrating fluid enters a reuse water system, and RO concentrated water enters a CWO treatment process; the reaction temperature in the CWO process is 300 ℃, the operation pressure is 0.5 MPa, air is used as an oxidant, auxiliary elements in the catalyst load are manganese and cobalt, the load mass percentage is 0.1 wt.%, the organic matters are almost completely degraded, and the produced water enters a reuse water system.

Example 3

MTO high-concentration organic wastewater generated by a certain coal chemical industry enterprise is firstly treated by an ozone air floatation process, wherein the air floatation process adopts a pressurized dissolved air floatation method, and the pressure is 1 kg/cm²Adding 1 kg/t of hydroxyl collecting agent, then adding 1 kg/t of PAM (polyacrylamide) flocculating agent to remove fine suspended matters and micro-flocs in the wastewater, and simultaneously performing emulsion breaking separation on the surface floating oil and micro-emulsified organic matters; then the wastewater enters an adjusting tank to adjust the pH valueUsing 10 wt.% NaOH solution or 10 wt.% dilute H₂SO₄The pH value of the wastewater is adjusted to 10 by the solution, and the wastewater stays for 3 hours; then entering BAF treatment process, wherein the filler is volcanic biological filter material, the diameter of the filler is 5mm, the height of the filler is 0.5 m, and the operation temperature is controlled at 5 ℃ to remove SS and COD in the wastewater_CrAnd BOD₅(ii) a Then, an MBR treatment process is carried out, a hollow fiber cylindrical immersed membrane component is adopted, an organic membrane in the device is made of PVDF material, the membrane aperture is 1 micrometer, the sequence of anaerobic → anoxic → aerobic is adopted, wherein the sludge concentration in the anaerobic treatment is 5 g/L, the effluent of the reactor is subjected to external circulation, the circulation ratio is 1:1, the anaerobic reaction temperature is controlled at 50 ℃, N nutrient salt and P nutrient salt are required to be added during the anaerobic treatment, the adding ratio is COD, N: P is 100:10:5, the N nutrient salt is ammonium chloride, the P nutrient salt is potassium dihydrogen phosphate, and the organic matter in the wastewater is further degraded, and macromolecular organic matter and active sludge are intercepted; then entering a UF system, adopting a tubular membrane component, operating pressure of 0.8 MPa, average pore diameter of the membrane of 0.01 mu m, and ZrO as an inorganic ultrafiltration membrane₂The system is a single-channel ceramic membrane made of main materials, the system operation mode is a dead-end filtration mode, and the single-channel ceramic membrane is used for intercepting part of oil, colloid, suspended matters and particulate matters in wastewater and further intercepting organic matters, generated concentrated water flows back to a BAF process, and water is produced by an RO system; the operating pressure of a low-pressure section in the RO system is 0.8 MPa, the operating pressure of a high-pressure section in the RO system is 3.1 MPa, a cross flow operation mode is adopted to almost completely intercept organic matters in the wastewater, penetrating fluid enters a reuse water system, and RO concentrated water enters a CWO treatment process; the reaction temperature in the CWO process is 75 ℃, the operation pressure is 6 MPa, air is used as an oxidant, auxiliary elements in the catalyst load are cerium and lanthanum, the load mass percentage is 5wt.%, organic matters are almost completely degraded, and the produced water enters a reuse water system.

Example 4

The MTO high-concentration organic wastewater produced by a certain coal chemical industry enterprise is firstly treated by an ozone air floatation process, wherein the air floatation process adopts an impeller air floatation process, 0.8 kg/t of hydroxyl collecting agent is added, and 8 kg/t of PAM (polyacrylamide) flocculating agent is added to remove the wastewaterMedium and fine suspended matters and micro flocs, and simultaneously performing emulsion breaking and separation on the surface floating oil and micro-emulsified organic matters; the wastewater then enters a conditioning tank to adjust the pH using 6 wt.% NaOH solution or 6 wt.% dilute H₂SO₄The pH value of the wastewater is adjusted to 9 by the solution, and the wastewater stays for 20 hours; then entering a BAF treatment process, wherein the filler is similar round coal slag, the diameter of the filler is 4mm, the height of the filler is 1.2 m, and the operation temperature is controlled at 20 ℃ to remove SS and COD in the wastewater_CrAnd BOD₅(ii) a Then, an MBR treatment process is carried out, a hollow fiber columnar immersed membrane component is adopted, an organic membrane in the device is made of polyamide materials, the membrane aperture is 0.8 mu m, the sequence of anaerobic → anoxic → aerobic is adopted, wherein the sludge concentration in the anaerobic treatment is 40 g/L, the effluent of the reactor is subjected to external circulation, the circulation ratio is 7:1, the anaerobic reaction temperature is controlled at 15 ℃, N nutrient salt and P nutrient salt are required to be added during the anaerobic treatment, the adding ratio is COD, N, P is 800:8:3, the N nutrient salt is urea, the P nutrient salt is potassium dihydrogen phosphate, and the biological wastewater is used for further degrading organic matters in the wastewater and intercepting macromolecular organic matters and active sludge; then entering a UF system, adopting a roll-type membrane module, wherein the operating pressure is 0.7 MPa, the average pore diameter of the membrane is 0.08 mu m, the organic ultrafiltration membrane is made of polyether imide materials, the system operation mode is a cross-flow filtration mode, the system is used for further intercepting partial oil, colloid, suspended matters and particulate matters in the wastewater, the generated concentrated water flows back to a BAF process, and the water is produced by an RO system; the operating pressure of a low-pressure section in the RO system is 0.9 MPa, the operating pressure of a high-pressure section in the RO system is 3.4 MPa, a cross flow operation mode is adopted to almost completely intercept organic matters in the wastewater, penetrating fluid enters a reuse water system, and RO concentrated water enters a CWO treatment process; the reaction temperature in the CWO process is 250 ℃, the operation pressure is 5MPa, air is used as an oxidant, the auxiliary elements in the catalyst load are copper and iron, the load mass percentage is 4 wt.%, the organic matters are almost completely degraded, and the produced water enters a reuse water system.

Example 5

MTO high-concentration organic wastewater generated by a certain coal chemical industry enterprise is firstly treated by an ozone floatation process, wherein the floatation process adopts a micro-bubble upward floatation process,adding 1 kg/t of amino acid collecting agent, then adding 13 kg/t of ferric salt (polyferric chloride) flocculant to remove fine suspended matters and micro-flocs in the wastewater, and simultaneously performing emulsion breaking separation on the surface floating oil and micro-emulsified organic matters; the wastewater then enters a conditioning tank to adjust the pH using 9 wt.% NaOH solution or 9 wt.% dilute H₂SO₄The pH value of the wastewater is adjusted to 6 by the solution, and the wastewater stays for 10 hours; then entering a BAF treatment process, wherein the filler is similar circular coal slag, the diameter of the filler is 2mm, the height of the filler is 0.8 m, and the operation temperature is controlled at 30 ℃ to remove SS and COD in the wastewater_CrAnd BOD₅(ii) a Then, performing MBR treatment process, adopting a flat curtain-shaped immersed membrane component, wherein an organic membrane in the device is made of PP material, the membrane aperture is 0.4 mu m, and adopting the procedures of anaerobic → anoxic → aerobic sequence, wherein the sludge concentration in the anaerobic treatment is 20 g/L, the effluent of the reactor is subjected to external circulation, the circulation ratio is 20:1, the anaerobic reaction temperature is controlled at 45 ℃, N nutrient salt and P nutrient salt are required to be added during the anaerobic treatment, the adding ratio of COD, N, P, N nutrient salt and P is 400:9:4, the N nutrient salt is urea, the P nutrient salt is trisodium phosphate, and the organic matter in the wastewater is further degraded, and macromolecular organic matter and activated sludge are intercepted; then entering a UF system, adopting a roll-type membrane component, wherein the operating pressure is 0.5 MPa, the average pore diameter of the membrane is 0.05 mu m, the organic ultrafiltration membrane is made of polyvinylidene fluoride materials, the system operation mode is a cross-flow filtration mode, the cross-flow filtration mode is used for further intercepting partial oil, colloid, suspended matters and particulate matters in the wastewater, the generated concentrated water flows back to a BAF process, and the water is produced by an RO system; the operating pressure of a low-pressure section in the RO system is 1.5 MPa, the operating pressure of a high-pressure section in the RO system is 3 MPa, a cross flow operation mode is adopted to almost completely intercept organic matters in the wastewater, penetrating fluid enters a reuse water system, and RO concentrated water enters a CWO treatment process; the reaction temperature in the CWO process is 200 ℃, the operation pressure is 4.5 MPa, air is used as an oxidant, the auxiliary elements in the catalyst load are copper and iron, the load mass percentage is 3.5 wt.%, the organic matter is almost completely degraded, and the produced water enters a reuse water system.

Example 6

MTO height produced by certain coal chemical industry enterpriseThe method comprises the following steps of firstly, carrying out ozone air floatation process treatment on the concentrated organic matter wastewater, wherein the air floatation process adopts a micro-bubble upward floatation process, adding 0.8 kg/t ester collecting agent, then adding 8 kg/t ferric salt (polyferric chloride) flocculating agent to remove fine suspended matters and micro-flocs in the wastewater, and simultaneously carrying out emulsion breaking separation on surface floating oil and micro-emulsified organic matters; the wastewater then enters a conditioning tank to adjust the pH using 7 wt.% NaOH solution or 7 wt.% dilute H₂SO₄The pH value of the wastewater is adjusted to 5 by the solution, and the wastewater stays for 18 hours; then entering a BAF treatment process, wherein the filler is similar round coal slag, the diameter of the filler is 5mm, the height of the filler is 1.5 m, and the operation temperature is controlled at 15 ℃ so as to remove SS and COD in the wastewater_CrAnd BOD₅(ii) a Then, an MBR treatment process is carried out, a hollow fiber columnar immersed membrane component is adopted, an organic membrane in the device is made of PE material, the membrane aperture is 1 mu m, the sequence of anaerobic → anoxic → aerobic is adopted, wherein the sludge concentration in the anaerobic treatment is 15 g/L, the effluent of the reactor is subjected to external circulation, the circulation ratio is 7:1, the anaerobic reaction temperature is controlled at 35 ℃, N nutrient salt and P nutrient salt are required to be added during the anaerobic treatment, the adding ratio is COD, N: P is 600:7:2, the N nutrient salt is ammonium chloride, the P nutrient salt is potassium dihydrogen phosphate, and the nitrogen nutrient salt is used for further degrading organic matters in the wastewater and intercepting macromolecular organic matters and activated sludge; then entering a UF system, adopting a plate-frame type membrane assembly, wherein the operation pressure is 0.5 MPa, the average pore diameter of the membrane is 0.1 mu m, the organic ultrafiltration membrane is made of polyacrylonitrile materials, the system operation mode is a cross-flow filtration mode, the system is used for further intercepting partial oil, colloid, suspended matters and particulate matters in the wastewater, the generated concentrated water flows back to a BAF process, and the water is produced by an RO system; the operating pressure of a low-pressure section in the RO system is 0.5 MPa, the operating pressure of a high-pressure section in the RO system is 2.5 MPa, a cross flow operation mode is adopted to almost completely intercept organic matters in the wastewater, penetrating fluid enters a reuse water system, and RO concentrated water enters a CWO treatment process; the reaction temperature in the CWO process is 150 ℃, the operation pressure is 2.5 MPa, air is used as an oxidant, the auxiliary elements in the catalyst load are copper and iron, the load mass percentage is 0.5 wt.%, the organic matters are almost completely degraded, and the produced water enters a reuse water system.

Claims

The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic matter wastewater is characterized by comprising the following steps of:

firstly, adopting an ozone air floatation method, adding a collecting agent and a flocculating agent, removing fine suspended matters and micro-flocs in wastewater, and performing emulsion breaking separation on surface floating oil and micro-emulsified organic matters;

secondly, adjusting the pH value of the wastewater subjected to the ozone flotation in the first step to a corresponding value by an adjusting tank, and staying for a short time and then entering the next step;

thirdly, adopting a Biological Aerated Filter (BAF) process to remove SS and COD in the wastewater_CrAnd BOD₅；

Fourthly, the wastewater in the third step is subjected to a Membrane Bioreactor (MBR) process, so that organic matters in the wastewater are further degraded by activated sludge, and macromolecular organic matters and activated sludge are intercepted;

fifthly, adopting a UF system to further intercept organic matters and part of oil, colloid, suspended matters and particulate matters in the wastewater treated in the fourth step, and refluxing the generated concentrated water to the BAF process;

sixthly, enabling the wastewater filtered in the fifth step to enter a Reverse Osmosis (RO) system, almost completely intercepting organic matters in the wastewater, and enabling penetrating fluid to enter a reuse water system;

and seventhly, adopting a catalytic wet oxidation technology (CWO) to the concentrated water generated in the sixth step to almost completely degrade organic matters, and enabling the generated water to enter a reuse water system.
2. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: collecting agents added in the ozone gas floating method are one or more of a mercapto-group collecting agent, a hydroxyl-group collecting agent, an amine collecting agent, an amino acid collecting agent, an ester collecting agent, a double-sulfide collecting agent and a non-polar collecting agent of hydrocarbon oil, and the using amount is 0.1-1 kg/t; the added flocculating agent is aluminum salt, iron salt or PAM (polyacrylamide), and the dosage is 1-15 kg/t.
3. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: the air floating method adopts one or more of micro-bubble floating method, impeller air floating method or pressurized dissolved air floating method, wherein the pressure of the pressurized dissolved air floating method is 1-6 kg/cm²。
4. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: in the second step, the pH value of the wastewater is adjusted to 5-10 by an adjusting tank, and 5-10 wt.% of NaOH solution and 5-10 wt.% of dilute H are adopted₂SO₄The solution stays for 3-24 h.
5. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: the BAF process adopts volcanic biological filter material or similar round coal slag as filler, the diameter of the filler is 1-5 mm, the height of the filler is 0.5-2 m, and the operating temperature is 5-35 ℃.
6. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: the MBR process device adopts a flat curtain-shaped immersed membrane component or a hollow fiber column-shaped immersed membrane component, wherein the organic membrane adopts one of polyolefine, polyacrylonitrile, polysulfone, aromatic, polyamide, fluorine-containing polymer, PVDF, PE or PP material, the pore size of the membrane is 0.1-1 μm, the procedures of anaerobic treatment, anoxic treatment and aerobic treatment are sequentially adopted, and the sludge concentration in the anaerobic treatment is 5-50 g/L; the effluent of the reactor is subjected to external circulation, and the circulation ratio is 1-20: 1; controlling the anaerobic reaction temperature at 15-50 ℃; adding N nutrient salt and P nutrient salt into the wastewater during anaerobic treatment, wherein the adding proportion is that COD is that N and P are 100-; the added P nutrient salt is one or more of trisodium phosphate, calcium superphosphate or potassium dihydrogen phosphate.
7. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic matter wastewater according to claim 1, which is characterized in that: the operating pressure in the UF system is 0.1-0.8 MPa, the average pore diameter of the membrane is 0.01-0.1 μm, wherein the organic ultrafiltration membrane is cellulose or cellulose derivatives, polysulfones, polyimide, polyetherimide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride or polyolefin ultrafiltration membrane; the inorganic film is Al₂O₃、TiO₂Or ZrO₂Is a single-pass or multi-channel ceramic membrane made of main materials; the membrane component adopts the form of a hollow fiber membrane component, a tubular membrane component, a curtain type membrane component, a roll-up membrane component or a plate-and-frame type membrane component; the operation mode of the ultrafiltration system is a cross-flow filtration mode or a dead-end filtration mode.
8. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: the RO system is divided into a low-pressure section and a high-pressure section, the operation pressure is 0.5-3.5 MPa, and a cross flow operation mode is adopted.
9. The multi-membrane integrated near-zero emission treatment process of MTO high-concentration organic wastewater according to claim 1, which is characterized in that: the CWO technology has the temperature of 75-300 ℃, the operating pressure of 0.5-6 MPa, air, oxygen or ozone is used as an oxidant, and a catalyst load element is a noble metal, a transition metal or a rare earth element, wherein the noble metal is ruthenium, rhodium, palladium, iridium or platinum, the transition metal is copper, iron, manganese or cobalt, and the rare earth element is cerium, lanthanum or praseodymium; the load mass percentage is 0.1-5 wt.%.