Device and method for purifying and recycling water generated by process for preparing aromatic hydrocarbon and low-carbon olefin from oxygen-containing compound

Abstract

The invention provides a device and a method for purifying and recycling water generated by a process for preparing aromatic hydrocarbon and low-carbon olefin from an oxygen-containing compound, and relates to the technical field of purification treatment. The purifying and recycling method comprises the following steps: washing water, olefin washing water and condensate between olefin separation sections are fed into a stripping tower after passing through a buffer tank, and concentrated water at the top of the stripping tower is fed into sump oil for recycling; purified water generated by the stripping tower is cooled by an air cooler and a heat exchanger and then is pumped into a rotational flow air flotation device for oxidation and flotation, the purified water of the stripping tower is fed into the rotational flow air flotation device, and ozone and the purified water pass through a rotational flow microbubble generator and then are fed into the rotational flow air flotation device; purified water clear liquid obtained through rotational flow air flotation is recycled, and gas-liquid-solid wastewater is fed into a gas-liquid separator to separate gas and solid-containing wastewater; liquid-solid wastewater obtained by underflow of the gas-liquid separator is fed into a filter pressing device for liquid-solid separation, recovery of a catalyst and reuse of purified water are realized, and the device and the system realize oxidation of organic matters and separation of fine particles.

Description

Technical Field

[0001] This application relates to the field of purification and treatment technology, and in particular to an apparatus and method for purifying and reusing water generated in the process of producing aromatics and low-carbon olefins from oxygen-containing compounds. Background Technology

[0002] The process of producing aromatics and low-carbon olefins from oxygen-containing compounds refers to the highly selective production of para-xylene (PX) through a catalytically coupled reaction in a fluidized bed reactor using methanol and toluene as raw materials, with byproducts such as ethylene and propylene. This process produces a large amount of complex byproduct water containing unreacted alcohols, aldehydes, and other oxygen-containing compounds, as well as various pollutants including colloidal particles, suspended solids, and recalcitrant organic matter. If this byproduct water is discharged or reused without effective treatment, it will lead to water waste, environmental pollution, and may affect the stable operation of subsequent process equipment and product quality.

[0003] Currently, common treatment methods mainly rely on deep purification technologies such as physical oil removal, chemical oxidation, and biological filters combined with reverse osmosis. However, these technologies still face a series of bottlenecks, including separation difficulties caused by oil phase emulsification, equipment blockage caused by the condensation of aldehydes and ketones, operational instability due to water quality fluctuations (such as sulfide interference and catalyst fine powder impact), difficulty in meeting the chemical oxygen demand and sulfide standards of purified water, corrosion risks in reuse systems, and the economic challenges of high-cost deep treatment processes. Therefore, developing purification technologies that can efficiently remove particulate matter, dissolved and non-dissolved organic matter is crucial to ensuring the normal operation of the process water system and achieving wastewater reuse.

[0004] Chinese patent publication number CN103755087A discloses a system and method for treating methanol aromatization process wastewater. It employs a combined system of a high-temperature stripping unit, a carbon media absorption unit, and an anion exchange system to treat the wastewater, removing organic acids. However, the feasibility of this process needs verification under large volumes of water, and the treated wastewater is unlikely to meet reuse standards. Chinese patent publication number CN104150673A discloses a system and method for treating and reusing methanol aromatization wastewater. The wastewater is first separated by a gas-liquid-solid three-phase separator, then sequentially passed through a particle removal unit, a stripping unit, an oil removal unit, and an air flotation unit, finally treated by a combined biochemical system. The final discharged wastewater meets reuse standards, and some wastewater can be reused as cooling water. However, this system is complex to control, has high energy consumption, and high equipment costs. Although it achieves partial wastewater reuse, the treatment process is complex and costly.

[0005] The utility model patent CN213803376U proposes a methanol aromatization process wastewater treatment system, which includes a stripping unit, a photocatalytic unit, an activated carbon adsorption unit, a distillation unit, and a condensation unit. It primarily removes unreacted methanol and aromatics, but does not address the problem of acidic wastewater caused by the formation of organic acids from the methanol reaction. The invention patent CN102050548B discloses a method for treating and reusing wastewater from a methanol-to-olefins process. The process includes preheating a boiler to recover heat, cooling and separating in a separation tower, stripping, homogenization and conditioning, coagulation and sedimentation, aerobic aeration, sedimentation, and flocculation. The treated wastewater COD can be reduced to 68 mg / L, but the process is long, cumbersome, and involves complex equipment, resulting in high investment costs and energy consumption.

[0006] However, the current technical solution, the process disclosed in CN118184048A, although proposing air flotation sedimentation as a deep separation method, has not effectively solved the unique problem caused by the coexistence of fine catalyst powder (1-10 μm) and easily polymerizable aldehydes and ketones in the water generated by oxygen-containing compound processes. Specifically, the fine powder is difficult to capture and recover effectively through conventional separation methods, while aldehydes and ketones, due to low mass transfer efficiency and easy polymerization in high-temperature equipment such as heat exchangers during traditional ozone oxidation, lead to system blockage and short operating cycles. Therefore, there is an urgent need to develop an integrated, anti-clogging treatment technology that can achieve efficient separation of fine particles and deep oxidation of organic matter.

[0007] Traditional treatment technologies have significant shortcomings in the production of aromatics and low-carbon olefins from oxygen-containing compounds. They are ineffective in purifying the generated water, failing to meet the oil content requirements of olefin separation stripping towers. Furthermore, existing processes are generally complex and costly. Therefore, it is necessary to provide a device and method for purifying and reusing generated water from the production of aromatics and low-carbon olefins from oxygen-containing compounds to solve these technical problems. Summary of the Invention

[0008] In view of this, the purpose of this application is to overcome the shortcomings of the prior art and provide an apparatus and method for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds. This method utilizes microbubble flotation, cavitation effect to generate hydroxyl radicals to enhance the oxidation of organic matter, and cyclone and pressure filtration to obtain purified water and solid particles, thus achieving water recovery. The apparatus of this invention, through specific tangential co-directional feeding, cyclone partitioning, and microbubble generation structure coupling, at an optimized operating temperature of 40-50℃, deeply synergizes the dynamic separation effect of the cyclone field, the cavitation oxidation effect of microbubbles, and the static flotation effect of bubbles within the same reaction space. This achieves highly efficient capture of 1-50μm fine particles (removal rate ≥93%) and effective oxidative degradation of easily polymerizable aldehydes and ketones (COD removal rate ≥80%), thereby fundamentally solving the problem of system scaling and clogging, and extending the heat exchanger cleaning cycle from 3-6 months in conventional processes to more than 2.5 years.

[0009] This application provides the following technical solution: In a first aspect, embodiments of this application provide an apparatus for purifying and reusing water generated in the process of producing aromatics and low-carbon olefins from oxygenated compounds. The purification and reuse apparatus includes a stripping tower, a cyclone flotation device, a cyclone microbubble generator, a gas-liquid cyclone separator, and a filter press. The stripping tower is used to wash the generated water produced during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds, so as to dissolve or disperse solid particles and hydrocarbon organic matter in the water. The liquid phase inlet of the cyclone flotation device is connected to the purified water outlet of the stripping tower via a pump, the gas phase inlet is connected to the mixed phase outlet of the cyclone microbubble generator, and its flotation gas-liquid-solid three-phase outlet is connected to the inlet of the gas-liquid cyclone separator. After treatment by the cyclone flotation device, suspended solids in the water are effectively removed, organic matter is oxidized and degraded, and purified clear liquid is discharged from the bottom clear liquid zone. The liquid inlet of the swirling microbubble generator is connected to the reflux liquid outlet of the swirling air flotation device. Ozone gas is introduced into the gas inlet, and the mixed phase outlet generates a gas-liquid mixture rich in ozone microbubbles, which is then transported to the swirling air flotation device. Microbubbles with a diameter of less than 50 μm are generated by high-speed shearing and cavitation effects to enhance air flotation and advanced oxidation reactions. The gas-liquid cyclone separator is used to receive the gas-liquid-solid three-phase mixture from the top of the cyclone flotation device and to achieve efficient separation of the gas phase and solid-containing wastewater. The filter press is connected to the solid wastewater outlet of the gas-liquid cyclone separator and is used to separate the concentrated sludge into solid and liquid components to obtain reusable filtrate and easily disposed solid residue.

[0010] In some embodiments of the first aspect, the liquid inlet and the gas-phase mixture inlet of the swirl flotation device are both tangential feeding structures with the same swirl direction to form a synergistic swirling field.

[0011] In some embodiments of the first aspect, the cyclone flotation device includes a gas-liquid-solid three-phase aggregation zone, a flotation oxidation zone, and a clear liquid zone, which are arranged sequentially from top to bottom. Wastewater and microbubbles enter tangentially and complete the flotation and oxidation reaction in the flotation oxidation zone. The gas-liquid-solid three-phase aggregation zone is used to collect the floating foam layer and entrained matter, and the clear liquid zone is used to collect the purified water and discharge it.

[0012] In some embodiments of the first aspect, the swirling microbubble generator consists of multiple swirling units arranged in parallel, with the gas phase of each swirling unit injected through a small hole in its throat, the diameter of which is no greater than 1 mm.

[0013] Secondly, embodiments of this application also provide a method for purifying and reusing water generated in a process for producing aromatics and low-carbon olefins from oxygen-containing compounds. The purification and reuse method is applied to a purification and reuse apparatus as described in any of the above embodiments, and the purification and reuse method includes: S1: The generated water produced during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds is sent to a stripping tower for washing treatment, so that the benzene series compounds, aromatic organic compounds and catalyst fine powder in the water are dissolved or dispersed in the water to obtain purified water containing pollutants. S2: The purified water is transported to the cyclone flotation device, and ozone is simultaneously introduced into the cyclone microbubble generator to generate ozone-rich micro-nano bubbles. The micro-nano bubbles are injected into the cyclone flotation device. Under the action of the cyclone field, the micro-nano bubbles come into full contact with the pollutants. The bubbles collapse to generate hydroxyl radicals, which oxidize and degrade organic matter. At the same time, fine particles adhere to the bubble surface and float to the surface for separation, realizing the advanced oxidation of organic matter and the synergistic removal of suspended solids, and obtaining a bottom clear liquid and a top gas-liquid-solid three-phase mixture. S3: The generated gas-liquid-solid three-phase mixture is introduced into a gas-liquid cyclone separator, and centrifugal force is used to achieve efficient separation of the gas phase and the liquid-solid phase, exhaust gas and obtain solid-containing concentrate. S4: The obtained solid-containing concentrate is subjected to solid-liquid separation by a filter press to obtain reusable filtrate and solid residue mainly composed of catalyst particles, thereby realizing the recycling of water resources and catalysts.

[0014] In some embodiments of the second aspect, in step S1, the obtained purified water has a petroleum content of 10 to 20 mg / L, a turbidity of 18.3 NTU, and a suspended particle size distribution within 1 to 10 μm.

[0015] In some embodiments of the second aspect, the content of petroleum substances in the clear liquid after step S2 is less than 0.5 mg / L, the turbidity is less than 1 NTU, and the residual particle size is less than 1 μm.

[0016] In some embodiments of the second aspect, in step S2, the volume of scum generated after air flotation accounts for 3% to 8% of the total volume of purified water.

[0017] In some embodiments of the second aspect, in S4, the gas phase is discharged from the overflow port of the filter press and the liquid-solid mixture is discharged from the underflow port of the filter press.

[0018] In some embodiments of the second aspect, in S1, the purified water generated after the stripping tower gas is cooled to 40 to 50 °C after air cooling and heat exchange.

[0019] The embodiments of this application have the following advantages: This invention utilizes a cyclone flotation device to perform flotation on the purified water from the stripping tower, achieving the oxidation of organic matter and the flotation of fine particles. This solves the problem of difficult treatment of pollutants in various forms. The cyclone microbubble generator uses the cavitation effect to break ozone bubbles into Wiener-scale bubbles, accompanied by the generation of hydroxyl radicals. The increased specific surface area of ​​the microbubbles enhances mass transfer, effectively removing organic matter and flotating fine particles, ultimately achieving the purpose of purifying and reusing process wastewater from the production of aromatics and low-carbon olefins from oxygen-containing compounds.

[0020] This invention employs a combination of swirling and venturi techniques to enhance microbubble generation, utilizing these microbubbles for efficient flotation of fine particulate matter and effective oxidation of organic matter. Multiple parallel swirling microbubble generators tangentially inject microbubbles into the flotation oxidation zone, forming a swirling liquid phase and a swirling gas phase. This significantly increases the contact frequency between the bubbles and contaminants, thereby simultaneously enhancing the oxidation and flotation processes and achieving highly efficient purification of the resulting water. This method offers advantages such as simple equipment structure, high processing efficiency, and low maintenance costs.

[0021] This invention treats volatile organic compounds, some alkanes, and fine particulate matter in purified water after stripping in a stripping tower. It utilizes cyclone flotation to achieve both the oxidation and removal of organic matter and the flotation of particulate matter, improving the quality of the purified water while enabling its reuse. In the cyclone flotation device, the cyclone field enhances multiphase contact, and microbubbles provide a sufficiently large specific surface area. The micro-interface enhances the removal of organic matter by ozone, while microbubbles float micron-sized particles, achieving integrated oxidation and flotation treatment, effectively improving water quality and enabling reuse.

[0022] This invention employs a multi-stage synergistic treatment process: stripping volatile organic compounds, some hydrocarbon organic compounds, and fine particles using a stripping tower; oxidizing organic compounds and flotating particulate matter using a cyclone flotation device; separating gas and liquid-solid phases using a cyclone separator; and separating liquid-solid phases using a filter press. This process effectively overcomes the shortcomings of existing technologies, enabling the reuse of purified water, reducing water waste, and providing excellent environmental and economic benefits. Furthermore, the entire treatment process is rational, easy to operate, and lower in cost. Through the synergistic effect of each unit, the reliability and stability of the purification effect are ensured. This invention provides an efficient and feasible solution for wastewater treatment in the production processes of aromatics from oxygenated compounds and low-carbon olefins.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This illustration shows a schematic diagram of the structure of a purification and reuse device according to an embodiment of this application. Figure 2 A schematic diagram illustrating the principle of a purification and reuse method according to an embodiment of this application is shown; Figure 3 A schematic flowchart of a purification and reuse method according to an embodiment of this application is shown.

[0026] Explanation of key component symbols: 1-Stripping tower; 2-Swirl flotation device; 3-Swirl microbubble generator; 31-Throat; 4-Gas-liquid cyclone separator; 5-Filtration device. Detailed Implementation

[0027] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0028] It should be noted that when an element is said to be "fixed" to another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly" on another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0029] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0031] Unless otherwise defined, 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 application belongs. The terminology used herein in the template description is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] It is important to emphasize that this application, based on extensive and in-depth research, found that the purified water produced by stripping tower 1 in the process of producing aromatics and low-carbon olefins from oxygen-containing compounds is characterized by its complex composition and susceptibility to operational problems. The purified water contains acetone, small amounts of methanol, dimethyl ether, aldehydes (such as acetaldehyde), benzene compounds, and particulate matter. These oxygen-containing organic compounds, especially aldehydes and ketones, readily undergo polymerization reactions in high-temperature equipment (such as heat exchangers and furnaces), forming hard coke lumps, leading to equipment blockage, increased pressure differential, and seriously threatening the long-term operation of the unit. Furthermore, if it is recycled, unconverted components such as acetone will penetrate the reactor bed, reducing the reaction depth and increasing byproducts. To solve this system problem, a multi-technology combination of cyclone flotation, cyclone separator, and pressure filtration is used to separate fine particulate matter and oxidized organic matter in the purified water. This method, by combining enhanced multiphase contact through cyclone flow and enhanced mass transfer through micro-interfaces, not only solves the original equipment blockage problem but also achieves integrated treatment of multiple pollutants. Compared with other multi-technology combination processes, this method has lower cost, lower energy consumption, and more reliable operation.

[0033] The technical concept of this invention is as follows: The purified water from the stripping tower 1 is treated by a cyclone flotation device 2. Ozone is generated by a microbubble generator to oxidize organic matter and float fine particles in the purified water. Ozone and hydroxyl radicals oxidize the organic matter, and the clarified liquid, after removing particulate matter and organic matter, is reused. The solid-containing wastewater separated by flotation is sent to a cyclone separator for gas-phase and liquid-solid separation. The liquid-solid wastewater enters a filter press 5 for liquid-solid separation. This method achieves deep removal of nano- and micron-sized particulate matter and oxidation of organic matter in the purified water, completing the purification and reuse of the process water. The concentration of suspended solids in the effluent is reduced to below 5 mg / L, which can reduce the cleaning frequency of the system heat exchanger and air cooler by 90%.

[0034] like Figure 1 and Figure 2 As shown, in order to solve the above-mentioned technical problems, this application provides an apparatus for purifying and reusing water generated in the process of producing aromatics and low-carbon olefins from oxygen-containing compounds. The purification and reuse apparatus includes a stripping tower 1, a cyclone flotation device 2, a cyclone microbubble generator 3, a gas-liquid cyclone separator 4, and a filter press 5. The stripping tower 1 is used to wash the generated water produced during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds, so as to dissolve or disperse solid particles and hydrocarbon organic matter in the water. The liquid phase inlet of the cyclone flotation device 2 is connected to the purified water outlet of the stripping tower 1 via a pump, and the gas phase inlet is connected to the mixed phase outlet of the cyclone microbubble generator 3. Its flotation gas-liquid-solid three-phase outlet is connected to the inlet of the gas-liquid cyclone separator 4. After being treated by the cyclone flotation device 2, the suspended solids in the water are effectively removed, the organic matter is oxidized and degraded, and the purified clear liquid is discharged from the bottom clear liquid zone. The liquid inlet of the swirling microbubble generator 3 is connected to the reflux liquid outlet of the swirling air flotation device 2. Ozone gas is introduced into the gas inlet, and the mixed phase outlet generates a gas-liquid mixture rich in ozone microbubbles and transports it to the swirling air flotation device 2. Microbubbles with a diameter of less than 50 μm are generated by high-speed shearing and cavitation effects to enhance air flotation and advanced oxidation reactions. The gas-liquid cyclone separator 4 is used to receive the gas-liquid-solid three-phase mixture from the top of the cyclone flotation device 2 and to achieve efficient separation of the gas phase and solid-containing wastewater. The filter press 5 is connected to the solid wastewater outlet of the gas-liquid cyclone separator 4 and is used to separate the concentrated sludge into solid and liquid components to obtain reusable filtrate and easily disposed solid residue.

[0035] That is, the cyclone flotation separator connected to the stripping tower 1 for oxidizing organic matter and flotating particulate matter in purified water, the cyclone microbubble generator 3 connected to the cyclone flotation separator, the cyclone separator connected to the three-phase outlet of the cyclone flotation device, and the filter press 5 connected to the underflow port of the cyclone separator.

[0036] The cyclone flotation separator uses microbubbles to float particulate matter and utilizes ozone and hydroxyl radicals to oxidize organic matter. Both the liquid phase and the microbubble inlet are tangentially inlet with the same cyclone direction.

[0037] The bottom clear liquid is pumped tangentially into the swirling microbubble generator, where a strong swirling flow field is formed by the liquid phase swirling flow. This cuts the bubbles at the throat and further breaks them up by cavitation in the expansion section, thus obtaining micro-nano bubbles and hydroxyl radicals at the same time.

[0038] The gas-liquid-solid three-phase wastewater is fed into a hydrocyclone separator, where the gas phase is removed by the cyclone field, and particulate matter concentrate is obtained from the underflow outlet. Finally, liquid-solid separation is performed using a filter press 5.

[0039] Obviously, the apparatus and method for producing aromatics and low-carbon olefins from oxygen-containing compounds of the present invention can be extended to various heterogeneous separation situations where liquids contain fine particles and organic matter.

[0040] More specifically, this embodiment provides a device for purifying and reusing the generated water from the process of producing aromatics and low-carbon olefins from oxygenated compounds. This device treats highly polluted generated water from the stripping tower 1 or the reaction water washing unit of the process. Typical characteristics of this generated water are: COD 800–1500 mg / L, suspended solids (SS) 100–300 mg / L, oil content 50–200 mg / L, containing organic matter such as methanol, formaldehyde, and acetic acid, pH 4.5–6.0, and containing colloidal particles such as ZSM-5 catalyst fine powder.

[0041] The purification and reuse device includes a stripping tower 1, a cyclone flotation device 2, a cyclone microbubble generator 3, a gas-liquid cyclone separator 4, and a filter press 5 connected in sequence. Each unit works together to achieve efficient purification and resource recovery.

[0042] Stripping tower 1 adopts a packed structure, with the tower filled with structured ceramic packing. A spray water distributor is installed at the top of the tower, and a product water inlet and a purified water outlet are located at the bottom. Product water from the oxygen-containing compound to aromatics and low-carbon olefins processes is pumped into the top of stripping tower 1 and flows downwards. Simultaneously, low-pressure steam (or nitrogen) at a temperature of 90–110℃ is introduced at the bottom, flowing counter-currently upwards.

[0043] During the stripping process, light hydrocarbons in the water (such as unreacted methanol, dimethyl ether, and small amounts of benzene compounds) are stripped by steam / gas and discharged from the top of the tower, entering the subsequent condensation and recovery system. Simultaneously, the steam agitation fully disperses previously aggregated colloidal particles and fine suspended solids (such as ZSM-5 catalyst powder) in the water, forming a stable suspension system that facilitates subsequent air flotation separation. The effluent temperature after stripping is maintained at 80–95℃, and the suspended solids concentration increases to 200–400 mg / L, providing favorable conditions for subsequent cyclone air flotation.

[0044] The purified water outlet of stripping tower 1 is connected to the liquid phase inlet of cyclone flotation device 2 via a corrosion-resistant centrifugal pump (such as a fluoropolymer-lined pump). This device is a vertical cyclone reactor with internal spiral guide plates to form a strong shear cyclone field.

[0045] The gas phase inlet of the swirl flotation device 2 is connected to the mixed phase outlet of the swirl microbubble generator 3 via a high-pressure pipeline. Ozone-rich microbubbles are injected tangentially from the bottom and thoroughly mixed with the polluted water flow in the swirling field. The microbubbles have a diameter of 10 to 50 μm and a negatively charged surface, which can effectively adsorb positively charged colloidal particles and hydrophobic organic matter.

[0046] Under the combined action of swirling shear and microbubble buoyancy, pollutants rapidly rise to the top of the device, forming a stable scum layer, which is continuously discharged through the top overflow port, creating a gas-liquid-solid three-phase mixture flow. The bottom of the device is the clear liquid zone, where denser purified water accumulates and is discharged through the bottom outlet to enter the subsequent treatment unit.

[0047] The liquid inlet of the swirl microbubble generator 3 is connected to the reflux liquid outlet of the swirl air flotation device 2 via a reflux pipeline, for example, with a reflux ratio of 20 to 40%. The gas inlet is supplied with ozone gas at a concentration of 8 to 12 wt%, which is prepared on-site by the bubble generator.

[0048] Inside the vortex microbubble generator 3, high-pressure water (0.3 to 0.6 MPa) mixes violently with ozone gas in a high-speed rotating impeller or venturi structure, generating a strong cavitation effect. The instantaneous collapse of the cavitation bubbles generates local high temperature and pressure (>5000 K, >10 MPa), which promotes the decomposition of ozone and generates a large number of hydroxyl radicals, while simultaneously forming a uniform and stable ozone microbubble cluster.

[0049] This microbubble cluster not only serves as a flotation carrier, but also effectively degrades recalcitrant organic matter in water (such as formaldehyde, acetic acid, long-chain aldehydes and ketones) through advanced oxidation, significantly reducing COD.

[0050] The gas-liquid-solid three-phase mixture discharged from the top of the cyclone flotation device 2 enters the gas-liquid cyclone separator 4. This separator is a high-efficiency cyclone demister structure, with a conical guide cavity and a central exhaust pipe inside.

[0051] Under centrifugal force, the denser solid-containing wastewater is thrown against the wall of the separator and flows downward along the spiral channel, exiting from the bottom solid-containing wastewater outlet; while the less dense gas phase (containing unreacted ozone and stripped hydrocarbons) gathers towards the center and is discharged through the top exhaust port, which can be connected to a tail gas treatment system (such as activated carbon adsorption or catalytic combustion). This separator can achieve highly efficient separation of the gas phase and solid-containing wastewater, with a separation efficiency of ≥95%, avoiding gas entrainment from affecting subsequent pressure filtration operations.

[0052] The solid wastewater outlet of the gas-liquid cyclone separator 4 is connected to the filter press 5 via a sludge pump. The filter press 5 is a plate and frame or chamber filter press, equipped with acid and alkali resistant filter cloth (such as polypropylene).

[0053] The concentrated solid wastewater is subjected to solid-liquid separation under a pressure of 0.6 to 1.0 MPa to obtain solid residues with a water content of less than 60% (mainly catalyst fine powder, colloidal polymers, etc.), which can be safely disposed of or utilized as industrial solid waste; the filtrate is clear and can be directly reused in stripping tower 1 or used as makeup water for circulating cooling water.

[0054] The purification and reuse device provided in this embodiment achieves the following technical effects through an integrated process of "stripping—cyclone flotation—microbubble oxidation—cyclone separation—pressure filtration": Steam stripping removes volatile organic compounds (VOCs), while cyclone flotation combined with microbubbles achieves efficient separation of colloids and suspended solids. Utilizing cavitation, hydroxyl radicals are generated in situ, synergistically with ozone oxidation, significantly improving the removal rate of recalcitrant organic compounds. The cyclone equipment has no easily clogged structure, is highly resistant to water quality fluctuations, and is suitable for the complex water quality of process water generated from oxygenated compounds in the production of aromatics and low-carbon olefins. The purified water can be reused in the process system, reducing solid residue and lowering operating costs and environmental risks.

[0055] In some embodiments, the liquid inlet and the gas-phase mixture inlet of the swirl flotation device 2 are both tangential feeding structures with the same swirl direction to form a synergistic swirling field.

[0056] In these embodiments, this embodiment further optimizes the feeding structure of the swirl flotation device 2 to enhance the swirl intensity and gas-liquid mixing efficiency.

[0057] The liquid phase inlet and the gas phase mixed liquid inlet (i.e. the mixed phase inlet from the swirling microbubble generator 3) of the swirling air flotation device 2 are both set as tangential feeding structures, and the rotation directions of the two feed streams are consistent, forming a synergistically enhanced swirling field.

[0058] Specifically, the liquid inlet is located on the lower side wall of the device body, and is tangentially connected in a direction perpendicular to the axis of the body. For example, the tangential angle is 80° to 90°. The gas phase mixture inlet is also tangentially connected, located above the liquid phase inlet, and its tangential direction is exactly the same as that of the liquid phase inlet, ensuring that the ozone microbubble mixture and the pollutant-containing water flow enter the reaction zone in the same direction of rotation.

[0059] When two tangential feed streams simultaneously enter the vortex flotation device 2, the water flow forms a stable spiral upward flow field inside the device, and a low-pressure reflux zone is formed in the central region, which is conducive to the microbubbles carrying pollutants to the surface. Since the liquid phase and gas phase inlet vortexes are in the same direction, the flow field disturbance and energy loss caused by traditional opposing feeds are avoided, and the vortex shear force and bubble distribution uniformity are significantly enhanced.

[0060] In other words, the bottom clear liquid is pumped tangentially into the swirling microbubble generator, where a strong swirling flow field is formed by the liquid phase swirling flow, cutting the bubbles at the throat, and further breaking the bubbles by cavitation in the expansion section, thereby obtaining micro-nano bubbles and hydroxyl radicals at the same time.

[0061] Preferably, the gas-liquid-solid three-phase wastewater is fed into a hydrocyclone separator, where the gas phase is removed by the cyclone field, and a particulate concentrate is obtained from the underflow outlet. Finally, a filter press 5 is used for liquid-solid separation.

[0062] By adopting a tangential feeding structure, the tangential velocity of the fluid inside the device is increased, the residence time of microbubbles is extended, the collision and adhesion efficiency between bubbles and particles is significantly improved, the removal rate of suspended solids is increased, and the removal rate of COD is improved.

[0063] In addition, the synergistic swirling field helps reduce dead zones inside the unit, prevents solid particles such as catalyst powder from depositing at the bottom, and improves operational stability. It is especially suitable for treating process water generated in the production of aromatics and low-carbon olefins from oxygen-containing compounds containing high concentrations of colloidal particles.

[0064] In some embodiments, the cyclone flotation device 2 includes a gas-liquid-solid three-phase aggregation zone, an air flotation oxidation zone, and a clear liquid zone, which are arranged sequentially from top to bottom. Wastewater and microbubbles enter tangentially and complete the flotation and oxidation reaction in the air flotation oxidation zone. The gas-liquid-solid three-phase aggregation zone is used to collect the floating foam layer and entrained matter, and the clear liquid zone is used to collect the purified water and discharge it.

[0065] In these embodiments, the cyclone flotation separation device consists of three zones: an oxidation flotation zone, a gas-liquid-solid three-phase aggregation zone, and a clear liquid zone. During normal operation, purified water enters the device through the liquid phase inlet. The clear liquid, used to shear bubbles, is pumped into the cyclone microbubble generator 3. After microbubbles are generated by the cyclone microbubble generator 3, they enter the cyclone flotation device through the gas-liquid mixing inlet. In the flotation oxidation zone, the cyclone field is used to enhance the gas-liquid-solid three-phase contact. The microbubbles entering tangentially have a longer residence time, which enhances flotation and gas-liquid contact, enhances mass transfer, and promotes the oxidation of organic matter by the ozone and hydroxyl radicals carried by the microbubbles. The clear liquid, after removing the solid phase and organic matter, enters the clear liquid zone after passing through the isolation device at the bottom. It is discharged through the clear liquid outlet for reuse. The gas-liquid-solid phase after bubble flotation enters the three-phase mixing zone and is discharged through the mixed phase outlet before entering the subsequent cyclone separation section for further processing.

[0066] More specifically, this embodiment further optimizes the internal structure of the swirl flotation device 2, dividing it along the axial direction into three functionally distinct regions: a gas-liquid-solid three-phase aggregation region, a flotation oxidation region, and a clear liquid region. These three regions are arranged sequentially from top to bottom to form an efficient multiphase separation and reaction space.

[0067] The device is a vertical cylindrical pressure vessel with no central shaft or stirring components inside. It achieves self-sustaining flow by relying on the swirling flow formed by tangential feeding.

[0068] Air flotation oxidation zone: Wastewater and ozone microbubble mixture from cyclone microbubble generator 3 simultaneously enter the central area of ​​the device—the air flotation oxidation zone—through the tangential feed inlet. This zone is the main area where flotation and advanced oxidation reactions occur.

[0069] Under the influence of the synergistic swirling flow field, the water flows in a spiral upward motion. During the ascent, microbubbles (10–50 μm in diameter) collide and adhere with suspended particles, colloids, and hydrophobic organic matter (such as oil droplets and polymers) in the water, forming "bubble-particle" aggregates. At the same time, the cavitation effect on the surface of the microbubbles continuously generates hydroxyl radicals, which oxidize and degrade organic matter (such as formaldehyde, acetic acid, and aldehyde-ketone condensates), achieving synergistic removal by physical flotation and chemical oxidation.

[0070] The gas-liquid-solid three-phase aggregation zone is located above the air flotation oxidation zone. This zone has an expanded diameter or slow-flow structure, with a diameter slightly larger than the lower reaction zone, in order to reduce the upward flow velocity and prevent foam breakage or entrainment of droplets.

[0071] Under the combined action of the swirling uplift force and the buoyancy of the bubbles, the "bubble-particle" aggregates carrying pollutants continuously rise into this area, forming a stable foam layer where they accumulate. The foam layer contains pollutants such as oils, colloids, some recalcitrant organic matter, and fine catalyst powder. These pollutants are continuously discharged through the annular overflow weir or skimmer at the top, forming concentrated sludge, which is then sent to the subsequent gas-liquid cyclone separator 4 for further gas-liquid-solid separation. The design of this area effectively prevents foam backmixing, improving flotation efficiency and the stability of the effluent quality.

[0072] The clear liquid zone, located at the bottom of the device, is a relatively static settling and collection area. After sufficient reaction and flotation separation in the air flotation oxidation zone, the denser purified water gathers towards the central area of ​​the device under the action of centrifugal force and gravity, and then sinks into the clear liquid zone.

[0073] The area is equipped with a central water collection pipe or a ring-shaped water collection tank, which continuously discharges the purified water from the bottom outlet to subsequent units or for direct reuse.

[0074] The bottom of the clear liquid zone is slightly conical, which facilitates the accumulation of small amounts of sediment towards the center. This sediment can be discharged periodically through the sludge discharge valve to prevent sludge accumulation during long-term operation.

[0075] Clearly, the flotation oxidation zone achieves efficient flotation and in-situ oxidation. The three-phase aggregation zone stably collects foam and prevents entrainment. The clear liquid zone ensures clear effluent and improves system stability. This partitioned design significantly enhances the device's pollutant removal efficiency and resistance to shock loads, making it particularly suitable for the continuous treatment of complex multiphase pollutants in the water generated by processes producing aromatics from oxygenated compounds and low-carbon olefins.

[0076] In some embodiments, the swirling microbubble generator 3 is composed of multiple swirling units arranged in parallel, and the gas phase of each swirling unit is injected through a small hole in the throat 31, the diameter of which is no greater than 1 mm.

[0077] In these embodiments, the microbubble generator is mainly divided into a gas-liquid mixed phase outlet, an expansion section, an injection port, a swirl column section, a liquid inlet, a contraction section, and a throat. During normal operation, the clarified liquid enters the device tangentially from the liquid phase inlet, and the gas phase is injected from the small hole in the throat 31 of the throat section. After being cut by the swirl, the large bubbles are sheared into multiple small bubbles. After entering the expansion section, the small bubbles are broken into microbubbles due to the cavitation effect. The generated bubbles are injected tangentially into the swirl flotation device from the gas-liquid mixed phase outlet.

[0078] In these embodiments, the internal structure of the swirling microbubble generator 3 is optimized to improve the uniformity, stability, and system processing capacity of microbubble generation.

[0079] The swirling microbubble generator 3 consists of multiple swirling units arranged in parallel, preferably 3–6 swirling sub-modules with the same structure integrated in parallel within the same housing. Each swirling unit operates independently without interfering with others, forming a modular and scalable microbubble generation system as a whole.

[0080] The gas phase of each swirl unit is injected through a small orifice in the throat 31. The orifice is a precision-machined circular nozzle with a diameter of no more than 1 mm, preferably 0.2-0.8 mm. The axis of the orifice is perpendicular to the liquid flow direction or at an angle of 15°-30° to facilitate gas breakup.

[0081] When the high-pressure water flow (pressure 0.3–0.6 MPa) passes through throat 31, the flow velocity increases significantly, the local pressure decreases, and a negative pressure zone is formed. Under the action of pressure difference, ozone gas is injected into the high-speed liquid flow through the small hole, where it is strongly sheared and stretched, and rapidly broken into microbubbles with a diameter of less than 50 μm, which then enter the downstream mixed phase outlet with the swirling flow.

[0082] Due to the extremely small orifice diameter, gas is injected in the form of a microjet, which greatly enhances the gas-liquid interface renewal rate and significantly improves bubble dispersion and ozone mass transfer efficiency (increasing kLa value by 40–60%). At the same time, the orifice structure is not easily clogged under high-speed fluid scouring, resulting in good operational stability.

[0083] The system employs a parallel design with multiple cyclone units, allowing for adaptation to different scales of oxygen-containing compound-to-aromatics and low-carbon olefin processes (e.g., 50–500 m³ / h throughput) by adjusting the number of units. Some units can be shut down at low loads, saving energy and reducing consumption. A single unit failure does not affect overall operation, facilitating maintenance. Each unit generates bubbles independently, avoiding the bubble aggregation phenomenon common in traditional single-channel systems.

[0084] With the structure of this embodiment, the average diameter of microbubbles can be controlled within the range of 20–40 μm, the number density of bubbles is increased by more than 3 times, the amount of hydroxyl radicals generated is increased, and the removal rate of formaldehyde, acetic acid and other recalcitrant organic compounds is significantly improved.

[0085] like Figure 3 As shown, in some embodiments, this application also provides a method for purifying and reusing water generated in a process for producing aromatics and low-carbon olefins from oxygen-containing compounds. The purification and reuse method is applied to a purification and reuse apparatus as described in any of the above embodiments, and the purification and reuse method includes: S1: The generated water produced during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds is sent to stripping tower 1 for washing treatment, so that the benzene series compounds, aromatic organic compounds and catalyst fine powder in the water are dissolved or dispersed in the water, and purified water containing pollutants is obtained.

[0086] This step involves stripping and washing. Product water from the process water washing unit of the oxygen-containing compound to aromatics and low-carbon olefins process is pumped to stripping tower 1.

[0087] Inside stripping tower 1, low-pressure steam (or nitrogen) at a temperature of 95–105℃ is used to purge the water countercurrently from bottom to top. The steam strips away residual light volatile organic compounds (such as methanol, dimethyl ether, benzene, toluene, etc.) in the water and condenses and recovers them from the top of the tower; at the same time, the steam agitation fully disperses the originally aggregated catalyst fine powder and colloidal particles in the water, forming a stable suspension system.

[0088] After stripping, the effluent temperature is 85–95℃, and the suspended solids concentration is increased to 250–350 mg / L, creating favorable conditions for subsequent air flotation separation. This step mainly achieves the recovery of hydrocarbons and the uniform dispersion of solid particles.

[0089] S2: The purified water is transported to the cyclone flotation device 2, and ozone is simultaneously introduced into the cyclone microbubble generator 3 to generate ozone-rich micro-nano bubbles. The micro-nano bubbles are injected into the cyclone flotation device 2. Under the action of the cyclone field, the micro-nano bubbles come into full contact with the pollutants. The bubbles collapse to generate hydroxyl radicals, which oxidize and degrade organic matter. At the same time, fine particles adhere to the bubble surface and float to the surface for separation, realizing the advanced oxidation of organic matter and the synergistic removal of suspended solids, and obtaining a bottom clear liquid and a top gas-liquid-solid three-phase mixture.

[0090] This step involves the synergistic treatment of cyclone flotation and advanced oxidation. The purified water containing contaminants after stripping is pumped to the liquid phase inlet of the cyclone flotation unit 2 via a corrosion-resistant pump, while the cyclone microbubble generator 3 is started simultaneously.

[0091] The specific operation is as follows: The return liquid (purified water from the clear liquid zone at the bottom of the vortex flotation device 2) enters the vortex microbubble generator 3. Ozone gas is injected into the high-speed water flow through a small hole with a diameter of 0.5 mm in the throat 31, forming ozone-rich micro-nano bubbles (10–50 μm in diameter) in the multi-unit parallel vortex chamber; the micro-nano bubble mixture is injected into the vortex flotation device 2 through the tangential inlet, forming a co-current vortex field with the incoming water in the flotation oxidation zone.

[0092] Under the action of strong shear swirling, micro-nano bubbles collide and adhere efficiently with suspended particles, colloids and hydrophobic organic matter in the water, forming "bubble-particle" aggregates that float to the top gas-liquid-solid three-phase aggregation zone, forming a foam layer and continuously overflowing.

[0093] Meanwhile, under the cavitation effect generated at the moment of microbubble collapse, ozone decomposes to generate a large number of hydroxyl radicals, which carry out advanced oxidative degradation of recalcitrant organic matter (such as formaldehyde, acetic acid, and aldehyde-ketone condensates), and the COD removal rate can reach 70-90%.

[0094] This step achieves synergistic purification through the removal of suspended solids (>90%), oil removal (>85%), and oxidation of organic matter, resulting in a purified liquid at the bottom and a gas-liquid-solid three-phase mixture at the top.

[0095] S3: The generated gas-liquid-solid three-phase mixture is introduced into the gas-liquid cyclone separator 4, and the gas phase and liquid-solid phase are efficiently separated by centrifugal force. The exhaust gas is discharged and a solid-containing concentrate is obtained.

[0096] In these embodiments, the gas-liquid-solid three-phase mixture discharged from the top of the cyclone flotation device 2 is introduced into the gas-liquid cyclone separator 4.

[0097] Under centrifugal force, the denser solid wastewater is thrown against the wall of the container and flows downward along the spiral channel, and is discharged from the bottom outlet, forming a solid concentrate; while the less dense gas phase (containing unreacted ozone, stripped hydrocarbons and water vapor) gathers towards the center, is discharged through the top exhaust port, and is sent to the tail gas treatment system (such as activated carbon adsorption or catalytic combustion device) for harmless treatment.

[0098] This step achieves efficient separation of the gas phase and the liquid-solid two phases, avoiding gas entrainment from affecting subsequent pressure filtration operations.

[0099] S4: The obtained solid-containing concentrate is subjected to solid-liquid separation by a filter press 5 to obtain reusable filtrate and solid residue mainly composed of catalyst particles, thereby realizing the recycling of water resources and catalyst.

[0100] This step involves solid-liquid separation and resource recovery via filtration. The solid-containing concentrate is pumped into a filter press (such as a plate and frame filter press) 5 for solid-liquid separation at a pressure of 0.6–1.0 MPa.

[0101] The resulting filtrate is clear and transparent, with COD < 50 mg / L, SS < 5 mg / L, and pH 6.8–7.8. It can be directly reused as makeup water for stripping tower 1 or as makeup water for circulating cooling water. The resulting solid residue mainly consists of ZSM-5 molecular sieve catalyst fine powder, polymer colloids, and a small amount of carbonaceous sediments. It can be collected and returned to the fluidized bed reactor as catalyst replenishment, or disposed of safely as industrial solid waste.

[0102] It should be noted that in these embodiments, the generated water is fed into stripping tower 1, and the purified water and concentrate obtained after stripping in stripping tower 1 are sent to the subsequent processing section.

[0103] The purified water treated by stripping tower 1 contains ketones, aldehydes, hydrocarbons, benzene-based organic compounds, fine particulate matter, etc. The purified water is sent to a cyclone flotation device, where micro-nano bubbles generated by a microbubble generator are used to oxidize organic matter and float particulate matter to obtain gas-liquid-solid wastewater and clear liquid.

[0104] Solid wastewater is sent to a hydrocyclone separator, with particulate concentrate discharged from the underflow outlet and gas phase discharged from the overflow outlet.

[0105] The concentrated particulate liquid from the underflow outlet of the hydrocyclone separator is sent to the filter press 5 to achieve liquid-solid separation.

[0106] The solid particles generated in the water are fine powders of catalysts used in the production of aromatics and low-carbon olefins from oxygen-containing compounds, typically crushed ZSM-5 molecular sieves.

[0107] The purification methods include four types: particle flotation separation and organic matter oxidation removal, hydrocyclone liquid-solid separation, and pressure filtration. By combining multiple separation methods in series, the oxidation of organic matter and the separation of particulate matter in the purified water can be achieved.

[0108] After being separated by a cyclone flotation device, the purified water achieves a suspended solids removal rate of over 90% and a COD removal rate of 70-90% in the clarified liquid.

[0109] The hydrocyclone separator has a separation accuracy of 1.7 μm and a pressure loss of 0.15-0.30 MPa.

[0110] Using the method provided in this application, in a cyclone flotation system with an ozone concentration of 60-80 mg / L and a microbubble generation system pressure of 0.3-0.5 MPa, the COD removal rate is over 80%, and the volumetric mass transfer coefficient is [not specified]. K L a ≥ 0.45 min -1 During the cyclone separation stage, the system pressure drop is 0.15-0.30 MPa, the solid content of the obtained clear liquid is less than 5 mg / L, the suspended solids removal rate exceeds 85%, and the turbidity is ≤5 NTU. In summary, after cyclone flotation and cyclone separation, SS drops to about 1 mg / L, and COD removal rate reaches more than 80%.

[0111] In some embodiments, in step S1, the purified water has a petroleum content of 10 to 20 mg / L, a turbidity of 18.3 NTU, and a suspended particle size distribution within 1 to 10 μm.

[0112] In step S1, after washing in stripping tower 1, light hydrocarbons in the generated water are effectively stripped and recovered, while solid particles such as catalyst powder are fully dispersed to form a stable suspension system. This process not only removes volatile organic compounds but also provides uniform and treatable influent conditions for subsequent cyclone flotation.

[0113] The water quality of the purified water obtained in step S1 was tested and found to be as follows: Petroleum-related substance content: 10–20 mg / L (determined by infrared spectrophotometry, GB / T 16488–1996); Turbidity: 18.3 NTU (measured using a Hach 2100P turbidimeter at 25°C); Suspended particle size distribution: Measured by a laser particle size analyzer (such as Malvern Mastersizer 3000), more than 95% of the particles are distributed in the range of 1 to 10 μm, with an average particle size of about 5.2 μm.

[0114] The particle size distribution characteristics indicate that the ZSM-5 catalyst fine powder (typical particle size 2 to 8 μm) has been effectively dispersed during the stripping process without serious agglomeration, which is beneficial for subsequent efficient microbubble capture and flotation separation.

[0115] The petroleum content (10 to 20 mg / L) indicates that deep oil removal is still needed, highlighting the necessity of air flotation and oxidation in S2; Turbidity (18.3 NTU) and particle size distribution (e.g., 1 to 10 μm) directly support the ability of the cyclone flotation device 2 to capture fine particles, especially the size matching of microbubbles (e.g., 10 to 50 μm) and particles (e.g., 1 to 10 μm), which is conducive to collision adhesion.

[0116] Compared to existing technologies that often suffer from particle agglomeration (greater than 20μm) or difficulty in demulsifying emulsified oil, this process achieves uniform particle dispersion through stripping agitation, which is a prerequisite for achieving efficient air flotation and reflects technological progress.

[0117] In some embodiments, the content of petroleum-based substances in the clear liquid after step S2 is less than 0.5 mg / L, the turbidity is less than 1 NTU, and the residual particle size is less than 1 μm.

[0118] In step S2, after synergistic treatment by the cyclone flotation device 2, pollutants in the purified water are efficiently removed. To verify the treatment effect, samples of the clarified liquid discharged from the bottom clarified liquid zone C of the cyclone flotation device 2 were taken and analyzed. The results are as follows: Petroleum-based substance content: less than 0.5 mg / L (using infrared spectrophotometry, GB / T 16488–1996); Turbidity: less than 1 NTU (using a Hach 2100P turbidimeter, 25°C); Residual particle size: Measured by an ultrafine laser particle size analyzer or dynamic light scattering (DLS) technology, all detectable particles have a size of less than 1 μm, mainly distributed in the range of 0.1 to 0.8 μm, and the concentration is extremely low.

[0119] The achievement of the above-mentioned excellent water output indicators is attributed to the synergistic mechanism of the device of the present invention: High-efficiency microbubble capture: Ozone micro-nano bubbles (10 to 50 μm in diameter) generated by the swirling microbubble generator 3 collide and adhere efficiently with suspended particles and oil droplets of 1 to 10 μm in the swirling field, forming "bubble-particle" aggregates that float and separate, resulting in a high removal rate.

[0120] Advanced oxidative degradation of oils: The hydroxyl radicals generated by the collapse of microbubbles oxidize and break down trace amounts of hydrocarbons (such as benzene compounds and long-chain alkanes) in emulsion or dissolved states in water, converting them into small-molecule organic acids and further mineralizing them, significantly reducing the residue of petroleum substances.

[0121] Synergistic swirling flow field enhances separation: the liquid and gas phase mixtures are fed in the same direction and tangentially to form a stable spiral flow field, avoiding turbulent disturbances, which is conducive to the smooth floating of light aggregates. At the same time, the clear liquid zone is kept in a low disturbance state to prevent the separated particles from being back-mixed.

[0122] The zoned structure ensures the quality of the effluent: the air flotation oxidation zone completes the reaction, the three-phase aggregation zone stably collects foam, and the clear liquid zone achieves static sedimentation and water collection. The three zones work together to ensure a high degree of purification of the bottom effluent.

[0123] In some embodiments, in step S2, the volume of scum generated after air flotation accounts for 3% to 8% of the total volume of purified water.

[0124] In step S2, after being treated by the cyclone flotation device 2, the pollutants are enriched in the top gas-liquid-solid three-phase aggregation zone A in the form of a gas-liquid-solid three-phase foam layer, and are continuously discharged through the overflow weir or the foam scraping mechanism to form scum.

[0125] The volume of scum generated during continuous operation was measured, and the results showed that: The volume of scum entering the cyclone flotation device 2 accounts for 3% to 8% of the total volume of purified water, with a typical value of about 5.5%. The scum is dark brown and viscous, with a density of approximately 1.02 to 1.08 g / cm³ and a moisture content of approximately 92% to 96%. The main components are: emulsified oil, polymer colloid, ZSM-5 catalyst fine powder, partially oxidized intermediate products and adsorbed microbubbles.

[0126] The scum is then transported to a gas-liquid cyclone separator 4 for further degassing and concentration into solid-containing wastewater, which finally enters a filter press 5 for deep dewatering.

[0127] In some embodiments, in S4, the gas phase is discharged from the overflow port of the filter press 5, and the liquid-solid mixture is discharged from the underflow port of the filter press 5.

[0128] In step S3, after separation by the gas-liquid cyclone separator 4, the concentrated liquid containing solids may still contain a small amount of microbubbles or dissolved gases. If it is directly fed into the filter press 5, it will result in: Air pockets form inside the filter chamber, affecting pressure transmission; Uneven filter cake reduces dehydration efficiency; The filter press cycle is prolonged, and the operation is unstable.

[0129] Therefore, in some embodiments, the solid-containing concentrate first enters a filter press feed buffer tank (or "deaeration tank"), which has an exhaust port at the top and an underflow outlet at the bottom.

[0130] In some embodiments, in step S1, the purified water generated after stripping in stripping tower 1 is cooled to 40 to 50 °C by air cooling and heat exchange.

[0131] In step S1, the outlet water temperature of stripping tower 1 is relatively high, typically 85 to 95°C. If it directly enters the subsequent cyclone flotation unit 2, the following problems arise: High temperatures reduce the solubility of ozone in water, affecting the efficiency of microbubble oxidation. High temperatures exacerbate the risk of equipment corrosion, especially in environments containing organic acids (such as acetic acid); High temperatures may cause aldehydes to condense, increasing the risk of scaling. This is not conducive to the long-term stable operation of non-metallic materials such as filter cloth in subsequent pressure filters.

[0132] Therefore, in some embodiments, the purified water effluent from the stripping tower 1 needs to be cooled before entering the cyclone flotation device 2.

[0133] The purified water discharged from the bottom of the stripping tower 1 first passes through a waste heat recovery heat exchanger, where it exchanges heat with the low-temperature filtrate or fresh makeup water from the filter press 5. Part of the heat is recovered and used to preheat the feed water, thus achieving energy saving. Subsequently, the water, after preliminary heat exchange, enters an air cooler (such as a finned tube air cooler), where forced convection cooling is performed using ambient air. The cooling intensity is controlled by adjusting the speed of the air-cooled fan or the opening of the louvers, so that the final outlet water temperature is stabilized at 40 to 50°C, preferably 45°C.

[0134] This temperature range offers the following advantages: At 40 to 50°C, the ozone half-life is moderate, which avoids the reaction being too slow at low temperatures and prevents rapid decomposition at high temperatures. It effectively reduces the condensation rate of aldehydes such as formaldehyde and acetaldehyde, and reduces the formation of colloids and sludge. Suitable for conventional corrosion-resistant pumps, pipelines (such as PP, PVDF) and cyclone equipment.

[0135] In summary, the method of the present invention utilizes the cyclone flotation device 2 to perform flotation on the purified water of the stripping tower 1, realizing the oxidation of organic matter and the flotation of fine particles, solving the problem of difficult treatment of pollutants of various forms. The cyclone microbubble generator 3 utilizes the cavitation effect to break ozone bubbles into Wiener-scale bubbles, accompanied by the generation of hydroxyl radicals. The specific surface area of ​​the micro-nano bubbles increases, enhancing mass transfer and effectively removing organic matter and flotation fine particles, thus realizing the purification and reuse of the water generated by the stripping tower 1.

[0136] The method of this invention utilizes a combination of swirling and venturi techniques to enhance the generation of microbubbles, thereby efficiently purifying the generated water by using microbubbles to float fine particles and oxidize organic matter.

[0137] The method of this invention utilizes multiple swirling microbubble generators connected in parallel to inject microbubbles tangentially into the flotation oxidation zone. The swirling liquid and gas phases increase the contact frequency between the bubbles and organic matter and fine particles, enhancing oxidation and flotation, and achieving preliminary water purification. This method features simple equipment, high efficiency, and low maintenance costs.

[0138] This invention treats volatile organic compounds, some alkanes, and fine particulate matter in the purified water after stripping in stripping tower 1. It utilizes cyclone flotation to achieve the oxidation removal of organic matter and the flotation of particulate matter, improving the quality of the purified water while enabling its reuse. In the cyclone flotation device, the cyclone field enhances multiphase contact, and microbubbles provide a sufficiently large specific surface area. The micro-interface enhances the removal of organic matter by ozone, while microbubbles float micron-sized particles, achieving integrated oxidation and flotation treatment, effectively improving water quality and enabling reuse.

[0139] This invention employs a multi-stage synergistic treatment process: a stripping tower 1 strips volatile organic compounds, some hydrocarbon organic compounds, and fine particles; a cyclone flotation device 2 oxidizes organic compounds and floats particles; a cyclone separator separates gas and liquid-solid mixtures; and a filter press separates liquid and solid mixtures. This process effectively overcomes the shortcomings of existing technologies, enables the reuse of purified water, reduces water waste, and offers significant environmental and economic benefits. Furthermore, the entire treatment process is rational, easy to operate, and lower in cost. Through the synergistic effect of each unit, the reliability and stability of the purification effect are ensured. This provides an efficient and feasible solution for wastewater treatment in the production processes of aromatics from oxygenated compounds and low-carbon olefins.

[0140] Example 1 (Best Implementation of the Invention) An apparatus and method for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds.

[0141] Water treatment capacity: 300 m³ / h.

[0142] Raw water quality (before entering this system): COD 1500 mg / L, suspended solids (SS) 280 mg / L, petroleum hydrocarbons 180 mg / L, ZSM-5 catalyst fine powder average particle size 5.5 μm.

[0143] Step S1 (Stripping and Cooling): Stripping tower temperature: 95℃.

[0144] The effluent quality after steam exchange and heat exchange is as follows: COD 1450 mg / L, SS 320 mg / L, petroleum hydrocarbons 15 mg / L, turbidity 18.3 NTU, and temperature 45±2℃.

[0145] Step S2 (Swirl flotation-oxidation co-treatment): The tangential flow velocity at the liquid inlet of the cyclone flotation device is 2.5 m / s; the gas inlet is fed in the same cyclone direction.

[0146] Swirl microbubble generator: number of parallel swirling units: 4; throat orifice diameter: 0.6 mm (screened and confirmed to be the optimal size for this specific water quality); ozone dosage concentration: 80 mg / L; system operating pressure: 0.45 MPa.

[0147] The internal operating temperature of the swirl flotation device is 45±2℃ (as guaranteed by the preceding cooling steps).

[0148] The treated effluent quality (bottom clear liquid of S2) is as follows: COD 150 mg / L (removal rate 90%), SS 8 mg / L (removal rate 97.5%), petroleum <0.5 mg / L, turbidity <1 NTU. Scum yield: 5% (volume).

[0149] Regarding the recovery rate of 1-10 μm catalyst fine powder: Analysis of scum and filter press solids showed an overall recovery rate of 93%.

[0150] Steps S3 and S4 (Deep Separation and Reuse): SS concentration of underflow concentrate from gas-liquid cyclone separator: 15,000 mg / L.

[0151] The filtrate quality after pressure filtration is: COD < 40 mg / L, SS < 2 mg / L, meeting the standard for direct reuse.

[0152] Key performance indicators (long-term operation data): Heat exchanger / air cooler cleaning cycle: After the unit has been running continuously for 30 months (2.5 years), no obvious blockage caused by aldehyde and ketone polymers was found in the relevant heat exchange equipment, and the pressure difference was stable. Compared with the "conventional air flotation + ozone oxidation tower" process of similar units, which requires cleaning every 3 months, the cleaning cycle has been extended by more than 90%.

[0153] Comparative Example 1: The raw water that was exactly the same as in Example 1 was treated using a conventional combination process of "dissolved air flotation (DAF) + ozone contact oxidation tower".

[0154] DAF effluent performance: SS reduced to 80 mg / L (removal rate 75%), petroleum hydrocarbons reduced to 10 mg / L, and removal rate of 1-10 μm fine powder approximately 60%.

[0155] Ozone contact oxidation tower (water temperature 45℃) treatment: COD removal rate is only 55%, final effluent COD > 650 mg / L, and due to low ozone mass transfer efficiency, ozonation utilization rate is less than 40%.

[0156] Overall effluent turbidity: 8 NTU, significantly higher than that of this invention.

[0157] Operational Issues: Due to incomplete ozone oxidation, easily polymerizable aldehyde and ketone intermediates gradually polymerize within the system's heat exchanger, leading to a significant decrease in heat exchange efficiency after six months of operation, necessitating a shutdown for cleaning. Simultaneously, a large amount of fine catalyst powder was not effectively recovered.

[0158] Comparative Example 2 (Separation comparison of components of the present invention: only cyclone enhancement, no microbubble oxidation synergy) The raw water is treated using only a "cyclone separator" with a structure similar to that of this invention, while removing the cyclone microbubble generator and ozone addition.

[0159] Treatment effect: Relying on pure cyclone centrifugal force separation, the effluent SS is 110 mg / L, the separation efficiency for 1-10 μm fine particles is only 62%, and there is basically no COD removal capacity (<5%). It cannot solve the scaling problem caused by organic matter.

[0160] In all examples shown and described herein, any specific values ​​should be interpreted as merely exemplary and not as limitations; therefore, other examples of exemplary embodiments may have different values.

[0161] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0162] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A device for purifying and reusing water generated during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds, characterized in that, The purification and reuse device includes a stripping tower, a cyclone flotation device (2), a cyclone microbubble generator (3), a gas-liquid cyclone separator (4), and a filter press (5). The stripping tower is used to wash the generated water produced during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds, so as to dissolve or disperse solid particles and hydrocarbon organic matter in the water. The liquid phase inlet of the cyclone flotation device (2) is connected to the purified water outlet of the stripping tower via a pump, and the gas phase inlet is connected to the mixed phase outlet of the cyclone microbubble generator (3). The flotation gas-liquid-solid three-phase outlet of the cyclone flotation device is connected to the inlet of the gas-liquid cyclone separator (4). After being treated by the cyclone flotation device, the suspended solids in the water are effectively removed and the organic matter is oxidized and degraded. The liquid inlet of the swirling microbubble generator (3) is connected to the reflux liquid outlet of the swirling air flotation device (2), ozone gas is introduced into the gas phase inlet, and the mixed phase outlet generates a gas-liquid mixture rich in ozone microbubbles and is transported to the swirling air flotation device (2). Microbubbles with a diameter of less than 50 μm are generated by high-speed shearing and cavitation effects. The gas-liquid cyclone separator (4) is used to receive the gas-liquid-solid three-phase mixture from the top of the cyclone flotation device (2) and to achieve efficient separation of the gas phase and solid-containing wastewater. The filter press (5) is connected to the solid wastewater outlet of the gas-liquid cyclone separator (4) for solid-liquid separation of concentrated sludge; The liquid inlet and the gas-phase mixture inlet of the cyclone flotation device (4) are both tangential feeds with the same cyclone direction, so as to form a synergistic cyclone field in the cyclone flotation device (4); the cyclone microbubble generator (3) is composed of multiple cyclone units arranged in parallel, and the gas phase of each cyclone unit is injected through a small hole with a throat diameter ≤1 mm, and each cyclone unit operates independently and can be started and stopped individually.

2. The apparatus for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 1, characterized in that, The swirling air flotation device (4) and the swirling microbubble generator (3) constitute an integrated processing unit with enhanced internal flow field. The micro-nano bubbles generated by the swirling microbubble generator (3) swirl and rise in the swirling air flotation device (4), simultaneously realizing the advanced oxidation process of hydroxyl radicals generated by cavitation effect and ozone oxidation, which deeply degrades phenols, aldehydes and ketones, which are difficult to biodegrade organic compounds, and the enhanced flotation separation process of suspended solids such as catalytic fine powder based on the efficient collision and adhesion of microbubble microparticles. The gas-liquid swirling separator (5) performs online and rapid gas-liquid-solid separation of the gas-liquid-solid three-phase mixture separated by flotation.

3. The apparatus for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 1, characterized in that, The cyclone flotation device includes a gas-liquid-solid three-phase aggregation zone, an air flotation oxidation zone, and a clear liquid zone, which are arranged sequentially from top to bottom. Wastewater and microbubbles enter tangentially and complete the flotation and oxidation reactions in the air flotation oxidation zone. The gas-liquid-solid three-phase aggregation zone is used to collect the floating foam layer and entrained matter, and the clear liquid zone is used to collect the purified water and discharge it.

4. The apparatus for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 1, characterized in that, The swirling microbubble generator operates at a pressure ≥0.3MPa and produces nanobubble concentrations ≥10. 7 per mL.

5. A method for purifying and reusing water generated during the production of aromatics and low-carbon olefins from oxygen-containing compounds, characterized in that, The purification and reuse method is applied to the purification and reuse apparatus as described in any one of claims 1 to 4, and the purification and reuse method includes: S1: The generated water produced during the process of producing aromatics and low-carbon olefins from oxygen-containing compounds is sent to a stripping tower for washing treatment, so that the benzene series, aromatic organics and catalyst fine powder are dissolved or dispersed in the water to obtain purified water containing pollutants. The purified water generated after the gas in the stripping tower is cooled by air and heat exchange to reduce the temperature to 40 to 50°C. S2: The purified water is transported to the cyclone flotation device (2), and ozone is introduced into the cyclone microbubble generator (3) to generate ozone-rich micro-nano bubbles. The micro-nano bubbles are injected into the cyclone flotation device (2). In the synergistic cyclone field formed by tangential and unidirectional feeding, the micro-nano bubbles come into full contact with the pollutants. The bubbles collapse to generate hydroxyl radicals, which oxidize and degrade organic matter. At the same time, fine particles adhere to the bubble surface and float to the surface to separate, thereby achieving advanced oxidation of organic matter and synergistic removal of suspended matter, and obtaining a bottom clear liquid and a top gas-liquid-solid three-phase mixture. S3: The generated gas-liquid-solid three-phase mixture is introduced into a gas-liquid cyclone separator (4) to achieve efficient separation of the gas phase and the liquid-solid phase by using centrifugal force, and the tail gas is discharged and a solid-containing concentrate is obtained. S4: The obtained solid-containing concentrate is subjected to solid-liquid separation by a filter press (5) to obtain reusable filtrate and solid residue mainly composed of catalyst particles, thereby realizing the recycling of water resources and catalysts.

6. The method for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 5, characterized in that, In step S1, the purified water has a petroleum content of 10–20 mg / L, a turbidity of 18.3 NTU, and a suspended particle size distribution within 1 to 10 μm.

7. The method for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 5, characterized in that, The petroleum-based substances in the clear liquid after step S2 are less than 0.5 mg / L, the turbidity is less than 1 NTU, and the residual particle size is less than 1 μm.

8. The method for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 5, characterized in that, In S2, the volume of scum generated after air flotation accounts for 3% to 8% of the total volume of purified water.

9. The method for purifying and reusing water generated from the process of producing aromatics and low-carbon olefins from oxygen-containing compounds according to claim 5, characterized in that, In S4, the gas phase is discharged from the overflow port of the filter press (5), and the liquid-solid mixture is discharged from the underflow port of the filter press (5).

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