Device and method for recovering aromatic hydrocarbon in washing water of methanol-to-aromatic hydrocarbon process

Abstract

The invention provides a device and a method for recovering aromatic hydrocarbon in washing water of a methanol-to-aromatic hydrocarbon process, and relates to the technical field of purification treatment. The recycling device comprises a water washing tower, a centrifugal pump, a settling tank and a micro-flow demulsification separator. The settling tank is provided with an inlet, a bottom water outlet and a top oil outlet, and the inlet of the settling tank is communicated with the tower kettle outlet of the water washing tower through a centrifugal pump. The micro-flow demulsification separator is provided with an inlet, a bottom water outlet, a backwashing gas-liquid inlet, a backwashing gas-liquid outlet and a top oil outlet, the inlet of the micro-flow demulsification separator is communicated with the bottom water outlet of the settling tank, and the top oil outlet of the micro-flow demulsification separator and the top oil outlet of the settling tank are converged to an aromatic hydrocarbon recovery pipeline. The device can effectively separate and recover the aromatic hydrocarbon product in the washing water, obviously improve the aromatic hydrocarbon yield, greatly reduce the load and treatment difficulty of a subsequent wastewater treatment unit, and realize the dual goals of resource recovery and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of purification treatment, in particular to a device and method for recovering aromatics in washing water in a methanol-to-aromatics process. BACKGROUND

[0002] Methanol-to-aromatics (MTA) is a key technology for producing aromatics from methanol. The typical process is as follows: the methanol raw material is contacted with a catalyst in a reactor to generate a mixed gas mainly composed of aromatics and a small amount of byproducts under suitable temperature and pressure. The high-temperature product after the reaction is first cooled and preliminarily separated in a quench tower, and then the gas phase at the top of the tower is further washed and purified in a water washing tower to prepare for subsequent separation and purification. The oil-containing wastewater discharged from the tower bottoms of the quench tower and the water washing tower is collected and treated in a stripping tower.

[0003] However, due to the limited separation precision of the water washing tower, the washing water discharged therefrom still contains aromatics with high concentration and difficult to be directly degraded. These substances mainly exist in the form of free oil, emulsified oil and dissolved oil, accompanied by a small amount of unconverted methanol, dimethyl ether and fine catalyst powder. This not only causes the loss of high-value aromatic products, but also leads to the problems of difficult treatment and high cost of the oil-containing wastewater. Therefore, efficient separation and recovery of the aromatic products in the washing water are of great significance for improving the economic efficiency of the process and realizing environmentally friendly operation.

[0004] For example, Chinese invention patent publications CN 119330454 A, CN 119608114 A and Chinese utility model patent CN 222266633 U all relate to a method for recovering aromatics from oil-containing wastewater by using an adsorbent. The adsorption and desorption of the adsorbent can be used to realize efficient recovery of aromatics. However, the use amount of the adsorbent is large, and the regeneration process of the adsorbent needs to be further optimized. SUMMARY

[0005] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a device and method for recovering aromatics in washing water in a methanol-to-aromatics process, which can effectively separate and recover the aromatic products in the washing water, significantly improve the yield of aromatics, and greatly reduce the load and treatment difficulty of the subsequent wastewater treatment unit, achieving the dual goals of resource recovery and environmental protection.

[0006] The present application provides the following technical solutions: In a first aspect, the present application provides a device for recovering aromatics in washing water in a methanol-to-aromatics process, which comprises a water washing tower, a centrifugal pump, a settling tank and a micro-flow demulsification separator. The settling tank is provided with an inlet, a bottom water outlet and a top oil outlet, the inlet of the settling tank is communicated with the outlet of the tower kettle of the water washing tower through the centrifugal pump; The micro-flow demulsification separator is provided with an inlet, a bottom water outlet, a backwashing gas-liquid inlet, a backwashing gas-liquid outlet and a top oil outlet, the inlet of the micro-flow demulsification separator is communicated with the bottom water outlet of the settling tank, and the top oil outlet of the micro-flow demulsification separator is gathered to the aromatic hydrocarbon recovery pipeline through the top oil outlet of the settling tank.

[0007] In some embodiments of the first aspect, the recovered device further comprises a heat exchanger, and the bottom water outlet of the micro-flow demulsification separator is communicated with the reflux inlet of the water washing tower through the heat exchanger.

[0008] In some embodiments of the first aspect, the bottom water outlet of the settling tank is further communicated with the reflux inlet of the water washing tower through the heat exchanger.

[0009] In some embodiments of the first aspect, the micro-flow demulsification separator comprises a solid phase interception module, a cyclone separation module and a coalescence enhancement module, and the solid phase interception module, the cyclone separation module and the coalescence enhancement module are sequentially arranged in the direction of water flow. The solid phase interception module is used for intercepting and removing solid particles through fluidization technology. The cyclone separation module is used for preliminarily separating and recovering free-state aromatic hydrocarbons based on the hydrocyclone centrifugal separation technology. The coalescence enhancement module is used for realizing deep separation and recovery of dispersed-state and emulsified-state aromatic hydrocarbons by promoting liquid droplet coalescence and combining gravity sedimentation.

[0010] In some embodiments of the first aspect, the solid phase interception module comprises a boiling bed and a tee joint, the inside of the boiling bed is provided with a backwashing gas inlet, the lower end of the boiling bed is provided with a backwashing water outlet, the upper end of the boiling bed is provided with the tee joint, the upper end of the tee joint is provided with a water washing water inlet and a backwashing exhaust port, the built-in pipeline of the tee joint extends to the inside of the boiling bed, and the two sides of the tee joint are respectively provided with backwashing sewage outlets.

[0011] In some embodiments of the first aspect, the cyclone separation module comprises a cyclone group and a liquid guide pipe, the cyclone group is communicated with the purified water outlet of the boiling bed of the solid phase interception module through the liquid guide pipe, a first oil bag is arranged on the upper part of the overflow port of the cyclone group, the cyclone group is provided with a flushing port, and the top oil outlet of the micro-flow demulsification separator and the oil outlet of the first oil bag are communicated.

[0012] In some embodiments of the first aspect, the coalescence intensification module comprises a fiber coalescer, an inlet of the fiber coalescer being in communication with the underflow outlet of the cyclone group, a back end of the fiber coalescer being provided with a settling section, an upper end of the fiber coalescer being provided with a second oil pocket, an inlet of the second oil pocket being in communication with an upper end of the settling section, the settling section being provided with a flushing outlet, a lower end of the settling section being provided with a water washing water outlet, a top oil outlet of the micro-flow demulsification separator being in communication with an oil outlet of the second oil pocket.

[0013] In a second aspect, the embodiments of the present application further provide a method for recovering aromatic hydrocarbons in washing water in a methanol-to-aromatics process, the recovery method being applied to the recovery device as described in any of the above embodiments, and the recovery method comprising: S1: pumping the aromatic hydrocarbon-containing washing water from the water washing tower into a settling tank to achieve preliminary oil-water separation and liquid-solid separation through static settling; S2: sending the water outlet of the settling tank into a micro-flow demulsification separator to simultaneously separate a plurality of forms of aromatic hydrocarbon products by using the micro-flow demulsification separator; S3: recovering the separated aromatic hydrocarbon products; S4: returning the treated water generated by the settling tank and the micro-flow demulsification separator to the water washing tower after adjusting the temperature of the treated water by a heat exchanger for recycling.

[0014] In some embodiments of the second aspect, the flow rate of the washing water in the settling tank is not greater than 0.3 m / h.

[0015] In some embodiments of the second aspect, the flow rate of the washing water in the micro-flow demulsification separator is 10-15 m / h.

[0016] The embodiments of the present application have the following advantages: The recovery device recovers aromatic hydrocarbons efficiently through a multi-stage cooperative separation mechanism. The oil-containing sewage discharged from the tower bottom of the water washing tower is first delivered to the settling tank by a centrifugal pump. Under the action of gravity, the free oil droplets and solid particles (such as catalyst powder) with relatively large densities in the sewage gradually float or sink, achieving preliminary separation of oil, water, and solids. The aromatic hydrocarbon oil phase enriched at the top is discharged through the top oil outlet, and the sewage containing emulsified oil and dissolved oil after preliminary purification is discharged through the bottom water outlet. The water outlet at the bottom of the settling tank enters the micro-flow demulsification separator, which realizes efficient demulsification and separation of the emulsified oil and dissolved oil through the following mechanisms: Micro-flow shearing effect: the fluid generates high-frequency shearing action in the micro-channel with a specific structure, which destroys the interface film of the emulsified oil droplets and promotes the coalescence of the oil droplets; Gas-liquid backwashing reinforcement: gas (such as nitrogen or steam) is injected through the backwashing gas-liquid inlet to backflush the particle bed; Density differential separation: The coalesced oil droplets float to the top under the action of gravity, and are discharged through the top oil outlet, while the purified water phase is discharged from the bottom water outlet.

[0017] The top oil outlet of the micro-flow demulsification separator and the top oil outlet of the settling tank are connected to the aromatic recovery pipeline, ensuring that all separated aromatic products are recovered uniformly. The backwash gas liquid outlet can be connected to the waste gas treatment system to avoid secondary pollution.

[0018] Therefore, by combining the pre-treatment by settling and the micro-flow demulsification technology, the free oil, emulsified oil and dissolved oil are effectively separated, the aromatic recovery rate is significantly improved, the product waste is reduced, and the economic benefit is directly improved. The oil content in the water after deep demulsification separation is very low, significantly reducing the pollutant load of the subsequent wastewater treatment unit (such as a stripping tower), reducing the treatment difficulty and operation cost. The micro-flow demulsification separator has excellent treatment effect on high-concentration and difficult-to-degrade emulsified oil, is suitable for the characteristics of complex composition and high emulsification degree of the washing water in the methanol-to-aromatics process, and has strong anti-fluctuation ability. The device structure is compact, the process is simple, no chemical demulsifier needs to be added, new pollutants are avoided, the backwash gas liquid can be recycled or treated harmlessly, and green operation is realized. While improving the aromatic yield, the source reduction and pre-treatment of wastewater are realized, which meets the requirements of sustainable development, and has the values of resource recovery and environmental protection.

[0019] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 A structural schematic diagram of one view of a device for recovery provided by an embodiment of the present application is shown; Figure 2 A structural schematic diagram of one view of a device for recovery provided by another embodiment of the present application is shown; Figure 3 A structural schematic diagram of one view of a micro-flow demulsification separator provided by an embodiment of the present application is shown; Figure 4 A flowchart of a method for recovery provided by an embodiment of the present application is shown.

[0022] Main element symbol explanation: 1-Microflow demulsifier; 2-Settling tank; 3-Water washing tower; 4-Heat exchanger; Ⅰ-Solid phase interception module; 11-Fluidized bed; 12-Three-way valve; 13-Backwash exhaust port; 14-Backwash drain port; 15-Wash water inlet; 16-Built-in piping; II-Cyclone separation module; 17-Liquid guide pipe; 18-Cyclone separator group; 19-First oil tank; Ⅲ-Coalescing reinforcement module; 20-Fiber coalescer; 21-Second oil pack; 22-Wash water outlet. Detailed Implementation

[0023] like Figure 1 and Figure 3 As shown, in order to solve the above-mentioned technical problems, this application provides an apparatus for recovering aromatics from washing water in a methanol-to-aromatics process. The recovery apparatus includes a water washing tower 3, a centrifugal pump, a settling tank 2, and a micro-flow demulsifier 1. The settling tank 2 is provided with an inlet, a bottom water outlet and a top oil outlet. The inlet of the settling tank 2 is connected to the bottom outlet of the water washing tower 3 through the centrifugal pump. The micro-flow demulsifier 1 is provided with an inlet, a bottom water outlet, a backwash gas-liquid inlet, a backwash gas-liquid outlet, and a top oil outlet. The inlet of the micro-flow demulsifier 1 is connected to the bottom water outlet of the settling tank 2, and the top oil outlet of the micro-flow demulsifier 1 and the top oil outlet of the settling tank 2 converge to the aromatics recovery pipeline.

[0024] It should be noted that the aromatic hydrocarbon content in the washing water is below 30,000 ppm, the working environment does not exceed 120 ℃, and the aromatic hydrocarbons include free, dispersed, and emulsified states. The main aromatic hydrocarbon species is p-xylene, and the flow rate is 300 m³ / h. 3 / h.

[0025] This application provides an apparatus for recovering aromatics from wash water in a methanol-to-aromatics process. The apparatus is integrated into a typical methanol-to-aromatics process system, located downstream of the water washing tower 3, and is used to treat the oily wash water discharged from the water washing tower 3, achieving efficient separation and recovery of aromatic products.

[0026] The recycling equipment mainly includes a water washing tower 3, a centrifugal pump, a settling tank 2, and a micro-flow demulsifier 1.

[0027] For example, the water washing tower 3 is a gas-liquid countercurrent contact tower, and its bottom outlet is connected to the subsequent processing unit via a pipeline. In the methanol-to-aromatics process, the high-temperature mixed gas from the quench tower enters the water washing tower 3, where it comes into contact with circulating washing water to remove impurities such as catalyst dust, methanol, and dimethyl ether. The purified gas after washing is discharged from the top of the tower and enters the subsequent separation unit; while the oily washing water, which has absorbed aromatic organic matter (including free oil droplets, emulsified oil, and a small amount of dissolved oil), catalyst powder, methanol, and dimethyl ether, is discharged from the bottom of the tower.

[0028] A centrifugal pump is installed after the outlet of the bottom of the washing tower 3 to pressurize and transport the oily wash water to the settling tank 2. This pump is corrosion-resistant to withstand wash water environments containing trace amounts of acidic or alkaline impurities. Its flow rate and head are selected based on the process water volume and system resistance to ensure a continuous and stable liquid supply.

[0029] Settling tank 2 is a cylindrical container with an inlet, a bottom water outlet, and a top oil outlet. Oily wash water, pressurized by a centrifugal pump, enters the inner cavity of settling tank 2 tangentially through the inlet, forming a swirling flow for initial separation, and then settles under gravity. Because aromatic organic matter is less dense than water, after a period of time, most of the free oil phase floats to the top of the tank, forming an oil-rich layer; while the relatively clean water phase sinks to the bottom. The top oil outlet continuously or intermittently discharges the floating crude aromatic product into the aromatic recovery pipeline. The bottom water outlet leads out the partially de-oiled water phase and transports it to the next processing unit. Settling tank 2 can be equipped with a level gauge and an automatic control valve to maintain a stable oil-water interface.

[0030] The micro-flow demulsifier 1 is the core high-efficiency separation unit of this device. This separator has an inlet, a bottom water outlet, a backwash gas-liquid inlet, a backwash gas-liquid outlet, and a top oil outlet. The inlet is connected to the bottom water outlet of the settling tank 2 via a pipe, receiving the aqueous phase that has undergone preliminary settling treatment but still contains emulsified and dissolved oil.

[0031] The micro-flow demulsifier 1 features an internal microchannel or porous media structure, capable of generating strong shearing and turbulent effects at low flow rates, disrupting the stability of the oil-water emulsion system. Simultaneously, air or an inert gas (such as nitrogen) is periodically or continuously injected through the backwash gas-liquid inlet to backwash the particle layer. The backwashing process also effectively prevents clogging of the porous media, maintaining long-term operational efficiency. The treated purified water is discharged from the bottom outlet and can be returned to the water washing system for recycling or enter the biochemical treatment unit. The gas-liquid mixture generated during backwashing is discharged from the backwash gas-liquid outlet; after gas-liquid separation, the gas can be recycled, and the liquid is returned to the treatment process.

[0032] Specifically, the top oil outlet of the microflow demulsifier 1 and the top oil outlet of the settling tank 2 converge to the same aromatics recovery pipeline, combining the recovered aromatics from both streams and transporting them to a storage tank or distillation unit for further purification. This achieves multi-stage synergistic separation, significantly improving the total aromatics recovery rate.

[0033] In one embodiment, the recovery device further includes an online oil content monitor (not shown in the figure), installed at the bottom outlet of the micro-flow demulsifier 1, for real-time monitoring of the effluent water quality. When the oil content in the water exceeds a set threshold (e.g., 10 mg / L), the system automatically triggers an increase in backwash frequency or adjusts operating parameters to ensure that the effluent consistently meets the standards.

[0034] For ease of understanding, the operating process is as follows: Oily wash water discharged from the water washing tower 3 in the methanol-to-aromatics process is pressurized by a centrifugal pump and transported to settling tank 2. Gravity settling occurs in settling tank 2, causing most of the free oil to float and be recovered through the top oil outlet. The preliminarily purified aqueous phase is discharged from the bottom water outlet. The resulting aqueous phase is introduced into a micro-flow demulsifier 1. Under micro-flow conditions, combined with air flotation backwashing, the emulsified state is further broken down, and residual emulsified oil and dissolved oil are separated. The resulting oil phase is recovered through the top oil outlet, and the purified water is discharged from the bottom water outlet. The aromatic products recovered from settling tank 2 and micro-flow demulsifier 1 are combined and transported to the aromatics recovery pipeline to achieve resource recovery.

[0035] Through the above-described embodiments, the recovery device of this application can effectively solve the problems of high residual aromatic hydrocarbons and difficult wastewater treatment in the existing technology. Using this device, simultaneous separation of multiple forms of aromatic hydrocarbon products can be achieved, with strong separation capabilities for free, dispersed, and emulsified aromatic hydrocarbon products. The total removal rate of aromatic hydrocarbons in the washing water can reach over 98%, significantly improving the yield of aromatic hydrocarbon products and greatly reducing the COD load of subsequent wastewater treatment units, achieving a balance between economic and environmental benefits. Furthermore, this application also simultaneously removes residual catalysts from the washing water through the micro-flow demulsifier 1, achieving a removal accuracy of over 85% for the residual catalysts in the washing water, with most of the removed particle sizes being above 3μm. In particular, this application effectively solves the problems of product waste and difficult treatment of oily wastewater caused by the low separation accuracy of the washing tower 3 in existing processes, which results in a large amount of aromatic hydrocarbon products remaining in the washing water.

[0036] It should be noted that the microflow demulsifier 1 contains a separation unit composed of porous media. This porous media not only has micron-level channels to generate a microflow effect, disrupting the stability of the oil-water emulsion system, but also functions as a precision filter. The porous media can be a ceramic membrane, sintered metal fibers, or porous polymer materials. This pore size design can efficiently trap residual catalyst particles with a particle size greater than 3 μm, achieving synergistic oil-water separation and solid-liquid separation.

[0037] The recovered aromatics contain no more than 1000 ppm of water, allowing them to proceed to subsequent processing stages in the aromatics production process. Furthermore, the effluent from the micro-flow demulsifier 1 contains no more than 500 ppm of aromatics, with a separation efficiency exceeding 95%.

[0038] In some embodiments, a backwashing process is incorporated within the microflow demulsifier 1, extending the system's operating cycle. Air or an inert gas (such as nitrogen) is periodically or continuously injected through the backwash gas-liquid inlet, forming fine bubbles under microflow conditions. These bubbles carry tiny oil droplets to the liquid surface via flotation, forming a thin oil layer at the top, which is then discharged through the top oil outlet. The backwashing process not only removes oil adhering to the medium surface, preventing membrane fouling, but also loosens and washes away trapped catalyst particles, discharging them from the backwash gas-liquid outlet, thus achieving online regeneration and long-term stable operation of the separation unit. The treated purified water is discharged from the bottom outlet.

[0039] Optionally, the gas-liquid ratio used in the backwashing process is 1.5:1 to 5:1, and the backwashing time is 15 to 30 minutes.

[0040] In some embodiments, the recovery device further includes a heat exchanger 4, and the bottom outlet of the microflow demulsifier 1 is connected to the reflux port of the water washing tower 3 via the heat exchanger 4.

[0041] The hot-side inlet of heat exchanger 4 is connected to the bottom outlet of microflow demulsifier 1, while the cold-side outlet is connected to the return port of water washing tower 3. The purified water discharged from microflow demulsifier 1 still carries a certain amount of heat (typically 40–60°C), which is recovered by exchanging heat with external low-temperature makeup water or circulating water system through heat exchanger 4. After being cooled by heat exchanger 4, the temperature of the purified water decreases (e.g., to 30–40°C), meeting the reuse requirements, and is then transported back to water washing tower 3 for recycling. This design effectively reduces the heating energy consumption of makeup water in water washing tower 3 and improves the energy efficiency of the entire MTA process system.

[0042] Specifically, the top oil outlet of the microflow demulsifier 1 and the top oil outlet of the settling tank 2 converge to the same aromatics recovery pipeline, combining the recovered aromatics from both streams and transporting them to a storage tank or distillation unit for further purification. This achieves multi-stage synergistic separation, significantly improving the total aromatics recovery rate.

[0043] like Figure 2 As shown, in some embodiments, the bottom outlet of the settling tank 2 is also connected to the return port of the water washing tower 3 through the heat exchanger 4.

[0044] In these embodiments, the bottom outlet of the settling tank 2 and the bottom outlet of the micro-flow demulsifier 1, either separately or in combination, are connected to the reflux port of the water washing tower 3 through the heat exchanger 4.

[0045] Implementation method 1 (parallel): The bottom outlet of the settling tank 2 and the bottom outlet of the micro-flow demulsifier 1 are respectively connected to two independent hot-side channels of the heat exchanger 4. The two water streams exchange heat independently in the heat exchanger 4, and the cooled water streams are then merged or returned to the water washing tower 3 respectively.

[0046] Implementation Method 2 (Series): The purified water (usually cleaner) discharged from the micro-flow demulsifier 1 can be used as a cooling medium to first exchange heat with the water discharged from the settling tank 2, which is at a higher temperature and contains a small amount of oil, to achieve preliminary cooling, and then enter the external heat exchanger 4 to exchange heat with the system makeup water.

[0047] Implementation Method 3 (Heat Exchange After Merging): The water flow from the bottom outlet of the settling tank 2 and the bottom outlet of the micro-flow demulsifier 1 merges in the pipeline and then enters the heat exchanger 4 together for heat recovery. The cooled mixed purified water is returned to the washing tower 3 for recycling as washing water.

[0048] Regardless of the connection method used, the core function of heat exchanger 4 is to recover the waste heat from the purified water in settling tank 2 and / or micro-flow demulsifier 1, which is used to preheat the makeup water or circulating water entering water washing tower 3, thereby reducing the heating energy consumption of water washing tower 3. The temperature of the purified water cooled by heat exchanger 4 is reduced (for example, to 30 to 40°C), meeting the requirements for reuse.

[0049] Clearly, the above-described structure enables the micro-flow demulsifier 1 to partially process the effluent from the settling tank 2, thus achieving long-term operation under different working conditions. For example, this applies when the volume of washing water exceeds the processing capacity of the micro-flow demulsifier 1.

[0050] In one embodiment, the recovery device further includes an online oil content monitor and a particulate matter concentration detector (not shown in the figure), which are respectively installed at the bottom outlet of the micro-flow demulsifier 1 for real-time monitoring of the effluent water quality. When the oil content in the water exceeds the set threshold or the particulate matter concentration rises abnormally, the system automatically triggers an increase in backwashing frequency or adjusts operating parameters to ensure that the effluent consistently meets the standards.

[0051] In some embodiments, the microfluidic demulsifier 1 includes a solid-phase interception module, a cyclone separation module, and a coalescence enhancement module, which are connected in series in the direction of water flow. The solid-phase interception module is used to trap and remove solid particles using fluidization technology. The cyclone separation module is used for the preliminary separation and recovery of free aromatics based on hydrocyclone centrifugation technology. The coalescence enhancement module is used to achieve deep separation and recovery of dispersed and emulsified aromatics by promoting droplet coalescence combined with gravity sedimentation.

[0052] In these embodiments, the microflow demulsifier 1 adopts a modular design, including a solid phase interception module, a cyclone separation module, and a coalescence enhancement module. These three modules are connected in series in the water flow direction to form a multi-stage synergistic separation process, capable of efficiently treating different forms of contaminants (solid particles, free oil, emulsified oil) in the washing water in a step-by-step manner.

[0053] Oily wash water first enters the solid-phase interception module through the inlet. This module is filled with a porous medium or particle bed with a high specific surface area (such as quartz sand, activated carbon, or ceramic microspheres) and is designed with a water distribution structure to achieve uniform water flow. The solid-phase interception module is used to trap and remove solid particles through fluidization technology. Specifically, the water flows upward through the bed at a suitable velocity, slightly fluidizing the medium particles. This effectively traps residual catalyst particles larger than 3 μm (such as molecular sieve particles and metal oxide dust), preventing them from clogging subsequent modules. The micro-disturbance caused by fluidization also reduces oil adhesion to the medium surface, maintaining a longer operating cycle. The trapped solid particles are discharged from the backwash gas-liquid outlet with the periodic backwash water flow.

[0054] After solid-phase interception, the water flow enters the cyclone separation module. This module contains a micro-cyclone tube array or a spiral flow channel structure. The cyclone separation module is used for the preliminary separation and recovery of free aromatics based on hydrocyclone centrifugation technology. The water flows at high speed within the micro-cyclone unit, generating a strong centrifugal force field. Because aromatic organic compounds are less dense than water, the resulting free oil droplets are thrown towards the outer wall of the flow channel under centrifugal force, converging upwards along the wall and finally exiting from the top oil outlet. The denser aqueous phase, however, gathers towards the center and flows downwards from the bottom, entering the next module. This module exhibits extremely high separation efficiency for free oil droplets larger than 10 μm.

[0055] Finally, the water flows into the coalescence enhancement module. This module contains oleophilic coalescing materials (such as modified polypropylene fibers, coalescing plates, or microporous polymer membranes) and is designed with gentle flow channels to extend the residence time. The coalescence enhancement module is used to achieve deep separation and recovery of dispersed and emulsified aromatics by promoting droplet coalescence combined with gravity settling. When water containing tiny oil droplets (1 to 10 μm) passes through the coalescing material, the droplets collide and merge on the material surface, forming larger droplets. These larger droplets rapidly rise to the surface in the subsequent gravity settling zone (such as an enlarged chamber) due to buoyancy, eventually merging with the oil phase produced by the cyclone separation module and being discharged from the top oil outlet. This module is key to achieving high aromatic recovery rates.

[0056] The backwash system (not labeled in the diagram) is connected to the backwash gas-liquid inlet and the backwash gas-liquid outlet. It can periodically inject air or clean water into each module to achieve online backwashing, remove trapped solids and oil, and restore separation performance.

[0057] Specifically, the top oil outlet of the micro-flow demulsifier 1 and the top oil outlet of the settling tank 2 are connected to the same aromatic hydrocarbon recovery pipeline, and the aromatic hydrocarbon products recovered from the two pipelines are combined and transported to a storage tank or distillation unit for further purification.

[0058] The heat exchanger 4 is connected as described in the aforementioned embodiments. The effluent from the settling tank 2 and / or the micro-flow demulsifier 1 is cooled by the heat exchanger 4 and then returned to the water washing tower 3.

[0059] The aqueous phase obtained in step S2 is introduced into the microfluidic demulsifier 1 and passes through the following sequentially: The solid-phase interception module uses fluidization technology to trap and remove solid particles such as residual catalysts. The cyclone separation module is based on cyclone centrifugation technology to perform preliminary separation and recovery of free aromatics; The coalescence enhancement module promotes droplet coalescence and combines it with gravity sedimentation to achieve deep separation and recovery of dispersed and emulsified aromatics; the resulting oil phase is recovered through the top oil outlet, and the purified water is discharged from the bottom water outlet.

[0060] The water phase discharged from the bottom outlet of the settling tank 2 in step S2 and / or the purified water discharged from the bottom outlet of the micro-flow demulsifier 1 in step S3 are heat-recovered through the heat exchanger 4, and the cooled water is returned to the water washing tower 3 for recycling as washing water.

[0061] Through the above-described embodiments, the recovery device of this application achieves efficient synergistic recovery of aromatics and catalyst from the washing water of the methanol-to-aromatics process. The removal accuracy of residual catalyst can reach over 85% (mainly removing particles larger than 3 μm), and the total aromatic recovery rate is ≥98%. Waste heat is recovered through heat exchanger 4, significantly reducing system energy consumption. This application not only improves resource utilization but also greatly reduces the pressure of subsequent environmental treatment, demonstrating significant economic and environmental benefits.

[0062] In some embodiments, the solid-phase interception module includes a fluidized bed 11 and a three-way valve 12. The fluidized bed 11 is provided with a backwash air inlet inside, a backwash water inlet at the lower end of the fluidized bed 11, and a three-way valve 12 at the upper end of the fluidized bed 11. The three-way valve 12 is provided with a wash water inlet 15 and a backwash exhaust port 13 at the upper end. The internal pipe 16 of the three-way valve 12 extends into the fluidized bed 11, and backwash drain ports 14 are provided on both sides of the three-way valve 12.

[0063] In some more specific embodiments, the solid-phase interception module includes a fluidized bed 11 and a three-way valve 12.

[0064] The fluidized bed 11 is a horizontal container filled with solid media particles (such as quartz sand, ceramsite, or activated carbon) to form a filter bed. A backwash air inlet is located at the bottom of the fluidized bed 11 for introducing compressed air or inert gas during the backwash cycle. A backwash water inlet is located at the lower end of the fluidized bed 11 for receiving backwash water. Under normal filtration conditions, oily wash water enters through the three-way valve 12 and flows upward through the fluidized bed 11, keeping the solid media particles in a fixed state and trapping residual catalyst particles in the water. During backwashing, gas and water are simultaneously or alternately injected through the backwash air inlet and backwash water inlet, causing violent agitation and a "boiling" phenomenon in the media particles, effectively removing attached oil and solid impurities and restoring filtration performance.

[0065] The three-way valve 12 is located at the upper end of the fluidized bed 11. The upper end of the three-way valve 12 has a wash water inlet 15 and a backwash vent 13. The wash water inlet 15 is connected to the bottom outlet of the settling tank 2 and is used to introduce the oily wash water to be treated. The backwash vent 13 is used to discharge gas from the bed during backwashing, ensuring sufficient backwash water entry. The built-in pipe 16 of the three-way valve 12 extends downwards into the fluidized bed 11, evenly distributing the introduced water flow to the bottom of the bed. Backwash drain ports 14 are located on both sides of the three-way valve 12. During backwashing, the mixture containing oil and solid impurities, loosened and washed down, is discharged from the upper part of the fluidized bed 11 through the backwash drain ports 14 of the three-way valve 12, and finally exits through the backwash gas-liquid outlet of the micro-flow demulsifier 1. The backwash drain ports 14 can be equipped with a control valve to achieve periodic drainage.

[0066] After being processed by the solid-phase interception module, the water flows into the cyclone separation module. This module contains a micro-cyclone tube array or a spiral flow channel structure. The cyclone separation module is used for the preliminary separation and recovery of free aromatics based on hydrocyclone centrifugation technology. The water flows at high speed within the micro-cyclone unit, generating a strong centrifugal force field. Because aromatic organic compounds are less dense than water, the resulting free oil droplets are thrown towards the outer wall of the flow channel under centrifugal force and converge upwards along the wall, eventually exiting from the top oil outlet. The denser aqueous phase, however, gathers towards the center and flows downwards from the bottom, entering the next module. This module exhibits extremely high separation efficiency for free oil droplets larger than 10 μm. Finally, the water flows into the coalescence enhancement module.

[0067] The backwashing system is connected to the backwash gas-liquid inlet and the backwash gas-liquid outlet. It can periodically inject air or clean water into each module to achieve online backwashing, remove trapped solids and oil, and restore separation performance.

[0068] Specifically, the top oil outlet of the microflow demulsifier 1 and the top oil outlet of the settling tank 2 are connected to the same aromatic hydrocarbon recovery pipeline, and the aromatic hydrocarbon products recovered from the two pipelines are combined and transported to a storage tank or distillation unit for further purification.

[0069] Water flows through the wash water inlet 15 into the three-way valve 12, and then through the built-in pipe 16 into the bottom of the fluidized bed 11. In the fluidized bed 11, solid particles such as residual catalyst are trapped by the medium bed layer. During the backwash cycle, a gas-water mixture is injected through the backwash air inlet and backwash water inlet to make the bed “boil”. Impurities are discharged from the backwash drain outlet 14, and gas is discharged from the backwash exhaust outlet 13.

[0070] In some embodiments, the hydrocyclone separation module includes a hydrocyclone group 18 and a liquid guide pipe 17. The hydrocyclone group 18 is connected to the purified water outlet of the boiling bed 11 of the solid phase interception module through the liquid guide pipe 17. A first oil pack 19 is provided above the overflow port of the hydrocyclone group 18. The hydrocyclone group 18 is provided with a flushing port. The top oil outlet of the micro-flow demulsifier 1 is connected to the oil outlet of the first oil pack 19.

[0071] In these embodiments, the hydrocyclone separation module includes a hydrocyclone assembly 18 and a liquid guide pipe 17. The hydrocyclone assembly 18 consists of multiple micro-hydrocyclones connected in parallel to improve processing capacity. The hydrocyclone assembly 18 is connected to the purified water outlet of the fluidized bed 11 of the solid phase interception module via the liquid guide pipe 17, and receives the pre-purified water from the fluidized bed 11.

[0072] A first oil reservoir 19 is provided above the overflow port (i.e., the central gas core outlet) of the hydrocyclone assembly 18. When the oil-containing water flows at high speed within the hydrocyclone assembly 18, the less dense free aromatic oil droplets gather towards the central axis under centrifugal force and move upward with the fluid in the central low-pressure zone. After being discharged from the overflow port, they enter the first oil reservoir 19 for enrichment. The first oil reservoir 19 is used to temporarily store the separated oil phase and is equipped with an oil drain port.

[0073] The hydrocyclone assembly 18 is also equipped with a flushing port, which is used to connect high-pressure water or cleaning agent when the equipment is shut down or during regular maintenance to flush the inner wall of the hydrocyclone tube, remove any oil or solid residue that may be attached, and ensure separation efficiency.

[0074] Specifically, the top oil outlet of the microflow demulsifier 1 is connected to the oil outlet of the first oil tank 19. The oil phase enriched in the first oil tank 19 can flow by gravity or through a small booster pump into the top oil outlet, and is finally transported to the aromatics recovery pipeline along with the aromatics products recovered by other modules.

[0075] Finally, the water flows out from the underflow port of the hydrocyclone group 18 and enters the coalescence enhancement module.

[0076] Purified water enters the hydrocyclone assembly 18 via the liquid guide pipe 17. Under the action of centrifugal force, free aromatic oil droplets gather towards the center and enter the first oil tank 19 from the overflow port for enrichment. If necessary, internal flushing is performed through the flushing port. The oil phase in the first oil tank 19 enters the top oil outlet via the connecting pipeline.

[0077] In some embodiments, the coalescence enhancement module includes a fiber coalescer 20, the inlet of which is connected to the underflow port of the hydrocyclone group 18, a settling section at the rear end of the fiber coalescer 20, a second oil pack 21 at the upper end of the fiber coalescer 20, the inlet of the second oil pack 21 being connected to the upper end of the settling section, a flushing port in the settling section, a wash water outlet 22 below the settling section, and the top oil outlet of the micro-flow demulsifier 1 and the oil outlet of the second oil pack 21 being connected.

[0078] In these embodiments, the coalescence enhancement module is used for deep separation of dispersed and emulsified aromatics remaining after the first two stages of processing. In some embodiments, the coalescence enhancement module includes a fiber coalescer 20.

[0079] The inlet of the fiber coalescer 20 is connected to the underflow port of the hydrocyclone assembly 18 to receive the water flow after hydrocyclone separation. The fiber coalescer 20 is filled with oleophilic fiber material (such as modified polypropylene fiber bundles or coalescing filter cartridges). When water flows through, tiny oil droplets collide, adsorb, and coalesce into larger oil droplets on the fiber surface.

[0080] The fiber coalescer 20 has a settling section at its rear end. Large oil droplets formed after coalescence enter the settling section with the water flow. In this area, the flow velocity decreases, and the oil droplets accelerate upward under the action of buoyancy, thus achieving oil-water separation.

[0081] A second oil reservoir 21 is provided at the upper end of the fiber coalescer 20. The inlet of the second oil reservoir 21 is connected to the upper end of the settling section, and is used to receive and enrich the oil phase floating from the settling section.

[0082] The settling section is equipped with a flushing port for flushing the settling area during maintenance to remove any impurities that may have accumulated.

[0083] A wash water outlet 22 is provided below the settling section for discharging the deeply purified water phase. This outlet is the bottom outlet of the micro-flow demulsifier 1.

[0084] Specifically, the top oil outlet of the microflow demulsifier 1 is connected to the oil outlet of the first oil pack 19 and the oil outlet of the second oil pack 21. The oil phase enriched in the first oil pack 19 and the second oil pack 21 can flow by gravity or through a small booster pump into the top oil outlet, and finally be transported to the aromatics recovery pipeline along with the aromatics products recovered by other modules.

[0085] Water flows into the fiber coalescer 20 from the underflow port of the hydrocyclone assembly 18, where tiny oil droplets coalesce and grow on the fiber surface. The coalesced oil-water mixture enters the settling section, while larger oil droplets float to the second oil tank 21. The oil phase in the second oil tank 21 enters the top oil outlet via a connecting pipeline. Deeply purified water is discharged from the wash water outlet 22.

[0086] If necessary, the settling section is flushed through the flushing port; the resulting oil phase is recovered through the top oil outlet, and the purified water is discharged from the bottom water outlet.

[0087] like Figure 4 As shown, in some embodiments, this application also provides a method for recovering aromatics from washing water in a methanol-to-aromatics process. The recovery method is applied to the recovery apparatus as described in any of the above embodiments, and the recovery method includes: S1: The aromatic-containing washing water from the water washing tower 3 is pumped into the settling tank 2, and preliminary oil-water separation and liquid-solid separation are achieved through static settling.

[0088] In this step, most of the free aromatic oil phase floats to the surface to form a rich oil layer, which is recovered through the top oil outlet of settling tank 2; the denser residual catalyst particles settle to the bottom of the tank and are discharged with the bottom water flow or periodically discharged as slag; the preliminarily purified water phase is discharged from the bottom water outlet.

[0089] S2: The effluent from the settling tank 2 is sent to the micro-flow demulsifier 1, and multiple forms of aromatic hydrocarbon products are separated simultaneously using the micro-flow demulsifier 1.

[0090] Solid phase interception module: Through the fluidization technology of the boiling bed 11, it further intercepts and removes solid particles such as residual catalyst; Cyclone separation module: Through the centrifugal separation action of the cyclone separator group 18, the free aromatic hydrocarbons are initially separated and the oil phase enters the first oil pack 19; Coagulation enhancement module: Through the coalescence effect of fiber coalescer 20 and gravity sedimentation in the settling section, the dispersed and emulsified aromatics are deeply separated, and the oil phase enters the second oil pack 21.

[0091] S3: Recover the separated aromatic products.

[0092] The crude aromatics recovered from the top outlet of settling tank 2 are combined with the deeply separated aromatics (from the first oil pack 19 and the second oil pack 21) recovered from the top outlet of microflow demulsifier 1, and then transported to the storage tank or distillation unit for further purification through the aromatics recovery pipeline.

[0093] S4: The treated water generated by the settling tank 2 and the micro-flow demulsifier 1 is returned to the water washing tower 3 for recycling after the temperature is adjusted by the heat exchanger 4.

[0094] The purified water discharged from the bottom outlet of settling tank 2 and / or the bottom outlet of micro-flow demulsifier 1 still carries a certain amount of heat. It exchanges heat with low-temperature makeup water or circulating cooling water through heat exchanger 4 to recover waste heat and reduce the heating energy consumption of water washing tower 3. The cooled purified water is at a suitable temperature and can be directly returned to water washing tower 3 for recycling, achieving closed-loop utilization of water resources.

[0095] In some embodiments, the flow rate of the washing water in the settling tank 2 is no greater than 0.3 m / h.

[0096] In these embodiments, the flow rate of the washing water in the settling tank 2 is controlled to be no greater than 0.3 m / h to ensure a sufficiently long residence time.

[0097] In some embodiments, the flow rate of the washing water in the microflow demulsifier 1 is 10 to 15 m / h.

[0098] In these embodiments, the flow rate of the wash water within the microflow demulsifier 1 is controlled to be 10 to 15 m / h. This flow rate range is optimized to balance separation efficiency and processing capacity. Lower limit (10 m / h): Ensure that the water flow has sufficient kinetic energy to drive slight disturbances in the fluidized bed, reduce the adhesion of oil on the medium surface, and provide the necessary centrifugal force field for the cyclone separation module to ensure effective separation of free oil droplets.

[0099] Upper limit (15 m / h): To avoid excessively high flow rates leading to overly vigorous fluidization, causing wear on media particles or re-entrainment of solid particles, and to prevent impact damage to the fiber material of the coalescing reinforcement module. This flow rate can be achieved by adjusting the inlet water pressure, controlling the valve opening, or designing a reasonable internal flow channel cross-sectional area.

Claims

1. An apparatus for recovering aromatics from washing water in a methanol-to-aromatics process, characterized in that, The recycling apparatus includes a water washing tower, a centrifugal pump, a settling tank, and a micro-flow demulsifier. The settling tank is provided with an inlet, a bottom water outlet and a top oil outlet. The inlet of the settling tank is connected to the bottom outlet of the water washing tower through the centrifugal pump. The micro-flow demulsifier is provided with an inlet, a bottom water outlet, a backwash gas-liquid inlet, a backwash gas-liquid outlet, and a top oil outlet. The inlet of the micro-flow demulsifier is connected to the bottom water outlet of the settling tank, and the top oil outlet of the micro-flow demulsifier and the top oil outlet of the settling tank converge to the aromatics recovery pipeline. The microflow demulsifier includes a solid phase interception module, a swirling separation module, and a coalescence enhancement module, which are connected in series in the direction of water flow. The solid-phase interception module is used to intercept and remove solid particles through fluidization technology; The cyclone separation module is used for the preliminary separation and recovery of free aromatic hydrocarbons based on cyclone centrifugation separation technology. The coalescence enhancement module is used to achieve deep separation and recovery of dispersed and emulsified aromatics by promoting droplet coalescence and combining it with gravity sedimentation.

2. The apparatus for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 1, characterized in that, The recovery device also includes a heat exchanger, and the bottom outlet of the microflow demulsifier is connected to the reflux port of the water washing tower via the heat exchanger.

3. The apparatus for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 2, characterized in that, The bottom outlet of the settling tank is also connected to the return outlet of the washing tower through the heat exchanger.

4. The apparatus for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 1, characterized in that, The solid-phase interception module includes a fluidized bed and a three-way valve. The fluidized bed is provided with a backwash air inlet and a backwash water inlet at its lower end. The three-way valve is provided at its upper end, with a wash water inlet and a backwash exhaust outlet at its upper end. The internal pipe of the three-way valve extends into the fluidized bed, and backwash drain outlets are provided on both sides of the three-way valve.

5. The apparatus for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 1, characterized in that, The hydrocyclone separation module includes a hydrocyclone group and a liquid guide pipe. The hydrocyclone group is connected to the purified water outlet of the boiling bed of the solid phase interception module through the liquid guide pipe. A first oil pack is provided above the overflow port of the hydrocyclone group. The hydrocyclone group is provided with a flushing port. The top oil outlet of the micro-flow demulsifier is connected to the oil discharge port of the first oil pack.

6. The apparatus for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 1, characterized in that, The coalescence enhancement module includes a fiber coalescer, the inlet of which is connected to the underflow port of the hydrocyclone group, a settling section at the rear end of the fiber coalescer, a second oil pack at the upper end of the fiber coalescer, the inlet of the second oil pack being connected to the upper end of the settling section, the settling section having a flushing port, a wash water outlet at the bottom of the settling section, and the top oil outlet of the micro-flow demulsifier being connected to the oil outlet of the second oil pack.

7. A method for recovering aromatics from washing water in a methanol-to-aromatics process, characterized in that, The recycling method is applied to the recycling apparatus as described in any one of claims 1 to 6, the recycling method comprising: S1: The aromatic-containing wash water from the water washing tower is pumped into the settling tank, and preliminary oil-water separation and liquid-solid separation are achieved through static settling. S2: The effluent from the settling tank is sent to a micro-flow demulsifier to simultaneously separate multiple forms of aromatic hydrocarbon products. S3: Recover the separated aromatic products; S4: The treated water generated by the settling tank and micro-flow demulsifier is returned to the water washing tower for recycling after the temperature is adjusted by the heat exchanger.

8. The method for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 7, characterized in that, The flow rate of the washing water in the settling tank shall not exceed 0.3 m / h.

9. The method for recovering aromatics from washing water in the methanol-to-aromatics process according to claim 7, characterized in that, The flow rate of the washing water in the micro-flow demulsifier is 10 to 15 m / h.

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