RU2821462C1 - Method for deep purification of flushing water used in process of converting methanol into olefins - Google Patents

Abstract

FIELD: technology of water and air purification.

SUBSTANCE: disclosed is a method for deep purification of flushing water used in the process of converting methanol to olefins. Method employs a device for deep purification of flushing water, comprising a cooling column, a water washing column, a fluidised bed separator, fibrous coagulator and buffer settling tank. Proposed method includes steps of: setting pressure drop on filter and time of regeneration operation for separator; providing normal operation of the device, in which flushing water is supplied from the water washing column to the upper part of the separator, directing into the granular layer, wherein after separation of washing water by granular layer, it is supplied for purification into fibrous coagulator, and waste oil is discharged into buffer settling tank, wherein the pressure drop in the separator is controlled in real time during normal operation of the device; starting the regeneration operation when determining the set pressure drop on the filter, at that, the flow of flushing water into the separator is changed so that it is passed through the granular layer from the bottom up with the separator cleaning and regeneration; and when the specified time of regeneration operation is reached, the flow of flushing water into the separator is changed so that the device continues to operate normally.

EFFECT: invention enables to create a device for deep purification of flushing water used in the process of converting methanol to olefins, which has a long continuous working cycle and provides higher effect of separation of catalyst particles and paraffin-oil substances in flushing water.

9 cl, 6 dwg, 2 tbl

Description

TECHNICAL FIELD

The present invention relates to the field of comprehensive purification from environmental pollution and relates to a device for deep purification of wash water used in the process of converting methanol into olefins, a purification method using the said purification device, and a comprehensive purification method for extracting waste liquid and waste gas generated during regeneration said cleaning device, and recovering residual heat in the purified rinsing water.

BACKGROUND OF THE ART

The production of olefins from methanol, called MTO (methanol to olefins conversion), refers to the process of producing low carbon olefins through a catalytic reaction using methanol as a feed. The reaction is usually carried out in a fluidized bed reactor, and the catalyst currently used is a SAPO-34 molecular sieve. The high temperature reaction gas in the reactor passes through a three-stage cyclone separator to recover catalyst particles. The reaction gas from which the catalyst has been recovered is sent to a cooling column for cooling. Due to the limited accuracy of the cyclone separator, a small amount of fine powder catalyst with a particle size of less than 10 µm or less than 5 µm is not separated and carried away by the reaction gas. After washing in the cooling column, most of

fine powder catalyst remains in the cooling column, and a small part is sent to the water-washing column. Meanwhile, unreacted methanol, dimethyl ether and other oxygen-containing organic compounds, as well as a small amount of reaction by-products such as aromatic hydrocarbons and alkanes, enter the cooling column and the washing water column along with the reaction gas. Due to the high operating temperature in the cooling column and the short contact time between the reaction gas and the cooling water, most of the oxygen-containing organic compounds and hydrocarbons enter the wash water.

As a result, the wash water typically contains catalyst powder, oxygen-containing organic compounds such as methanol and dimethyl ether, and paraffino-oil substances such as aromatic hydrocarbons and alkanes. To ensure proper operation of the water system, catalyst and wax-oil substances must be effectively removed from the wash water. Paraffino-oil substances in the wash water are mainly heavy components such as aromatic hydrocarbons and alkanes. Depending on the size of the oil droplets, these substances are mainly present in the form of free oil, dispersed oil and emulsified oil.

At present, common methods for removing solids and oil from waste water mainly include physical methods, chemical methods, physicochemical methods and biological methods. Physical methods mainly include gravity method, centrifugal separation method, precision filtration method, membrane separation method, etc. The gravity method has low separation error and cannot remove emulsified oil from the wash water. The separation effect is weak when the centrifugal separation method is used to separate oil droplets or submicron particles. Since particles having a small particle size and small amounts of paraffino-oil substances present in the wash water used in the methanol to olefins conversion process can easily enter the filter element channels of the precision filtration device, they block the channels and are practically not removed by real-time backwash. Membrane separation method has been widely used in recent years due to its excellent separation effect, but it has the disadvantages of easy clogging, high maintenance and high cost due to the high solids content and oil content of the washing water used in the process of converting methanol to olefins. Chemical methods mainly include flocculation method, oxidation method, electrochemical method, etc. The flocculation method has little effect on emulsified oil and fine particles. In addition, treatment reagents are expensive and secondary pollution is easily caused. Chemical oxidizers such as ozone, Fenton's reagent, etc. can be used to decompose organic matter in waste water to improve biodegradability, but the treatment cost is high. The electroflocculation method requires the consumption of large amounts of auxiliary salt reagents and electricity, and the operating costs are high. Physicochemical methods mainly include air flotation method, adsorption method, coagulation method, etc. The air flotation process requires chemical consumption and a large footprint. The adsorbent used in the adsorption method has limited adsorption capacity and high cost, and its regeneration is difficult. The coagulation method is easy to operate and does not require a large area, but it is necessary to add a coagulant, and its cost is high. Although the biochemical method has a low cost, it requires only little input and does not involve secondary pollution and requires a large area to perform. In addition, the waste water produced from the conversion of methanol to olefins contains a high concentration of contaminants and a large amount of organic components, which will affect the normal operation of the biochemical reservoir.

Chinese Patent Application No. 103951098 A proposes the use of a superfiltration membrane for the separation and purification of wash water and cooling water, and the regeneration of catalyst and oil using a three-phase separator. In this application, membrane separation technology is used to purify the wash water. Fine cleaning is achieved for fine particles, but a large flow of high oil content washing water may cause the pressure drop to increase during cleaning, and therefore the cleaning efficiency is low. In addition, the filtration unit consists of a series of filter membranes. During backwashing, due to the high solids and oil content in the concentrate, the sequential filter membranes increase the pressure drop, which does not contribute to the stable and continuous flow of the high-flow processing process.

Chinese patent applications CN 102093153 A and CN 101352621 A propose the use of microcyclone technology to perform microcyclone separation of cooling water and wash water used in the methanol to olefins conversion process to remove trapped catalyst particles. Microcyclone separator has the advantages of good adaptability, low cost, easy maintenance, etc., but the efficiency of separating fine particles less than 3 μm in washing water is limited. In addition, the wash water contains a large amount of oxygen-containing compounds and paraffin-oil substances, and therefore the microcyclone separator does not separate the oil fraction well.

Chinese patent application CN 104649446 A discloses a method and apparatus for liquid-solid separation of cooling water and wash water used in the process of converting methanol to olefins. The method involves the use of three or more filters connected in parallel. Although the filters are good at separating solids from the water, the application does not mention whether they perform the function of removing oil from the wash water.

Chinese utility patent CN 205031975 U discloses a device for purifying and treating cooling water and wash water used in a methanol-to-olefin conversion process. The filtration device uses microporous filter elements of various shapes. Operational cleaning and regeneration of filter elements is carried out by introducing an effective gas and using a chemical cleaning method. However, the process of backflushing this system is complex and time-consuming. In addition, the equipment costs are high, and the operating costs are also high.

Chinese utility model patent CN 204275622 U discloses a device for filtering wash water used in the methanol to olefins conversion process. Filtration is carried out using a filter element containing a porous internal structure and a surface layer covered with a metal film. The blockage in the inner part of the filter element can be effectively eliminated, and the filtration accuracy is high. However, the cost of the device is high, and the operating costs for maintaining the device are also high. In addition, the filter element requires chemical regeneration, which can lead to secondary contamination.

Chinese Invention Patent Application CN 108328761 A discloses a method and apparatus for extending the continuous operating cycle of a methanol-to-olefins conversion process wash water treatment process, which uses fluidized separation technology to treat the methanol-to-olefins conversion process wash water. layer. This method has long operating cycle, low cost and low energy consumption, and also has a good effect of separating the catalyst particles from the wash water. However, the separating effect for paraffin-oil organic substances in the wash water is mediocre. In addition, the oil components of the wash water are complex and have different morphologies. Free oil and dispersed oil can be separated in the fluidized bed, but deep processing is necessary to separate the emulsified oil. Therefore, it is difficult for a single device or technology to meet the deep cleaning requirement.

Therefore, the treatment requirements of highly concentrated waste water obtained from the conversion of methanol to olefins and containing oil and solids cannot be met by traditional physical methods due to high cost and poor treatment effect, or by traditional chemical methods due to secondary pollution, caused by the consumption of chemicals and the difficulty of reusing water after purification, either by traditional physicochemical methods due to the consumption of chemicals and high operating costs, or by traditional biochemical methods due to the slow purification speed and poor processability of active suspension. Thus, there is an urgent need for a simple and effective treatment method to overcome the poor separation effect of existing methods.

SUMMARY OF THE INVENTION

The present invention provides a new device and method for deep purification of wash water used in the process of converting methanol to olefins, thereby solving the problems existing in the prior art.

One object of the present invention is to provide a device for deep purification of wash water used in the methanol to olefins conversion process, which has a long continuous operating cycle and provides an excellent separation effect of catalyst particles and paraffin-oil substances in the wash water.

Another object of the present invention is to provide a cleaning method using the above apparatus.

In the first aspect of the present invention there is provided a device for deep purification of wash water used in the process of converting methanol to olefins, containing:

cooling column,

a water washing column connected to an outlet at the top of the cooling column,

a fluidized bed separator, the upper part of which is connected to the lower part of the water washing column,

a fibrous coalescer connected to the bottom of the fluidized bed separator, and

a buffer settling tank connected to the side wall of the fluidized bed separator at a location near the top.

In a preferred embodiment, the fluidized bed separator comprises a plurality of fluidized bed separators that are arranged in parallel and each of which has an inlet at the top, an outlet at the bottom, and a drain and discharge hole at the side wall near the top; wherein the bottom of the water washing column is connected to each inlet through a centrifugal pump, and all drainage holes are connected to a common pipeline G1, which is then connected to a buffer settling tank; in this case, all discharge openings are connected to a common pipeline G2, which is then connected to a cyclone dewatering tank; wherein the lower part of the cyclone dewatering tank is connected to pipeline G1; wherein the outlet of each fluidized bed separator at the bottom is connected to pipeline G3; in this case, pipelines G3 are connected to a common pipeline G4; wherein the other end of pipeline G4 is connected to a fiber coalescer; wherein a nitrogen/steam pipeline and a wash water pipeline are connected to each of the G3 pipelines.

In another preferred embodiment, each inlet port has an inlet valve, each outlet port has a vent valve, each drain port has a drain valve, and each vent port has a vent valve, wherein an access valve is provided at the connection between the nitrogen/steam line and each G3 line. nitrogen/steam, and a G3 backwash valve is installed at the connection between the wash water pipe and each pipe.

In another preferred embodiment, the fluidized bed separator comprises a housing in which said inlet hole is located at the top, said outlet hole is located at the bottom, said drain hole is located on its side wall at a position near the top, and said hole is located at the top. reset; wherein in the body of the fluidized bed separator, a three-phase cyclone separator, a feed distributor, a granular bed and a separating plate are arranged sequentially from top to bottom, and a flow stabilizer is installed inside the outlet hole, and the inlet of the three-phase cyclone separator is connected to the inlet hole, the drainage hole is connected to the side surface three-phase cyclone separator, and a liquid distributor is installed on the upper surface of the separating plate.

In another preferred embodiment, the fiber coalescer comprises a plurality of fiber coalescers which are arranged in parallel and each of which has an inlet at its left end and an oil phase outlet and an aqueous phase outlet respectively at the top and at the bottom. a fiber coalescer on its right side, with the other end of the G4 conduit connected to the inlet through the G5 conduit, and each oil phase outlet connected to the G1 conduit through the G6 conduit.

In another preferred embodiment, the fiber coalescer includes a housing in which an inlet hole is located at the left end, and an outlet hole for the oil phase and an outlet hole for the aqueous phase are located in the upper and lower parts on the right side, respectively; in this case, the coagulator body has, in sequence, from left to right: an input distillation distributor, a coagulating module for enlarging oil droplets, a modified corrugated reinforced settling tank module and a nanomodified deep separation module.

In another preferred embodiment, the device further comprises an industrial control computer, wherein the inlet valve, the exhaust valve, the drain valve, the dump valve, the nitrogen/steam access valve and the backwash valve are solenoid valves, and all of them are electrically connected to the industrial control computer via current-carrying lines. wires, while a differential pressure sensor is additionally installed on the granular layer, which is electrically connected to the industrial control computer through a conductive wire.

In another aspect, the present invention provides a method for deep purification of wash water used in the methanol to olefins conversion process using the above apparatus, the method comprising the following steps:

Step 1: Turn on the power supply and set the filter pressure drop value and fluidized bed separator regeneration time using the industrial control computer;

Step 2: Opening the inlet and outlet valves to ensure normal operation of the device, the wash water is withdrawn from the bottom of the wash water column through a centrifugal pump and supplied to the fluidized bed separator through the inlet at the top of the separator, in which the wash water is directed into the granular bed through the feed distributor, where after the wash water is separated into a granular bed, it passes through the liquid distributor on the separating plate and through the flow stabilizer and is directed into the fiber coalescer from the outlet at the bottom of the fluidized bed separator, whereby the wash water enters the fiber coalescer through its inlet hole, wherein in the fiber coagulator, the wash water passes sequentially through the inlet distillation distributor and enters the oil droplet coagulation coagulation module, the modified corrugated reinforced sedimentation module and the nanomodified deep separation module, so that the emulsified oil droplets remaining in the wash water in the outlet hole of the fluidized bed , undergo adhesion to the hydrophilic-hydrophobic fiber, collision, growth and separation to ensure the gradual movement of oil droplets to the top layer of oil and the rapid descent of water droplets, while the clear wash water solution is withdrawn from the aqueous phase outlet and sent to the reboiler under the distillation column propylene of the olefin separation device as a heat source for partial recovery of the residual heat of the wash water, whereby after heat exchange, the light solution is subjected to further heat exchange through an air cooler and heat exchanger and returned to the water wash column, in which the waste oil is discharged from the oil phase outlet into a buffer settling tank a tank for achieving separation of oil and water, wherein the values of the fluidized bed separator differential pressure sensor are monitored in real time during normal operation of the device;

Step 3: Start the regeneration operation, when the differential pressure sensor detects the set value of the filter differential pressure, and the inlet valve and outlet valve are closed; the drain valve, dump valve, backwash valve and nitrogen/steam access valve are opened, the flow direction of the wash water is changed to enter the fluidized bed separator from the outlet, and simultaneously nitrogen is mixed with the wash water, which then passes through the granular bed from below upward to bring the granular bed to a boiling state, so that the fine catalyst powder and organic wax-oil substance adhering to the separation medium are released, thereby cleaning and regenerating the medium, while the separation medium and contaminants are introduced into the three-phase cyclone separator at the top of the separator with a fluidized bed to ensure purification of medium particles in a cyclone field, enhanced regeneration of the medium and simultaneous extraction of medium particles, while contaminants are removed from the drainage hole on the side surface of the device along with the liquid phase, and nitrogen is removed from the outlet hole in the upper part; And

Step 4: Closing the drain valve, dump valve, backwash valve and nitrogen/steam access valve, and opening the inlet valve and outlet valve when the set regeneration time is reached, so that the device continues to operate normally.

In the preferred embodiment, in step 1, the pressure drop across the filter is set to 0.1-0.4 MPa, the regeneration operation time is set to 20-60 minutes and the catalyst separation accuracy in the wash water is set to D85 = 0.1 μm.

In another preferred embodiment, the catalyst particle content of the wash water used in the methanol to olefin conversion process is 100-500 mg/L, the average diameter of the catalyst solids is 0.5-5 microns, and the oil content is 200-1000 mg/L .

Beneficial Effects:

1) The present invention combines granular bed filtration and fiber coagulation, which solves the problem of insufficient efficiency of the original fluidized bed separator in separating oil in the wash water, and at the same time effectively eliminates the problem of fouling caused by the catalyst particles in the wash water sticking to the internal parts of the fiber coalescer. Meanwhile, the comprehensive treatment of waste liquid and waste gas generated by the regeneration of the purification device, and the recovery of residual heat of purified washing water is achieved, so as to realize almost zero pollutant discharge, almost zero waste and efficient use of heat.

2) The present invention utilizes the functions of the separating medium in the form of a granular bed in a fluidized bed separator to screen, trap and adsorb particles and wax-oil substances in water to gradually reduce the solid content and oil content of water with the depth of the filter bed. Subsequently, the hydrophilic-hydrophobic fiber in the fiber coalescer is used to physically break the emulsion to achieve the purpose of deep separation of oil and water. Compared with membrane filtration and precision filtration, this method requires simple equipment, low capital investment, low energy consumption, easy regeneration of the separation medium, long continuous operating cycle and low maintenance costs. The method has an excellent separation effect of catalyst particles and paraffin-oil substances in the wash water due to a simple separation process. It overcomes the shortcomings of the existing process, including easy clogging of separation equipment, the need for frequent cleaning, short equipment cycle times and incomplete removal of waxes and solids from water.

3) The present invention uses a fluidized bed process to regenerate the separating medium, and at the same time enhances the effect of regenerating the medium by cyclonic shifting of the upper three-phase separator. The hydrophilic-hydrophobic fiber in the coagulator is used to separate water and oil, which are then removed. The method is suitable for purifying wash water used in the methanol to olefins conversion process, which has a high oil content.

DESCRIPTION OF DRAWINGS

The accompanying drawings are provided for further understanding of the invention. They form part of the description only to further explain the invention without limiting it.

Fig. 1 is a schematic view showing the structure of a device for deep purification of wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the invention.

Fig. 2 is a schematic view showing the structure of a fluidized bed separation system and a fiber coalescer in an apparatus for deep purification of wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the invention.

Fig. 3 is a schematic view showing a flowchart of a treatment process of a wash water treatment apparatus discharging waste water into a waste water treatment plant in accordance with a preferred embodiment of the invention.

Fig. 4 is a schematic view showing the structure of a fluidized bed separator in an apparatus for deep purifying wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the invention.

Fig. 5 is a schematic view showing the structure of a coalescer in a device for deep purification of wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the invention.

Fig. 6 is a diagram showing an electrical connection between a fluidized bed separator in a methanol-to-olefins conversion plant and an industrial control computer, in accordance with a preferred embodiment of the invention.

Item numbers in the drawings are described as follows:

1-1. Cooling column; 1-2. Water washing column; 1-3. Fluid bed separator; 1-4. Fiber coagulator; 1-5. Buffer settling tank; 1-6. Cyclonic dehydration tank; 1-7. Nitrogen/steam pipeline; 1-8. Wash water pipeline; 1-9. Industrial control computer; 1-10. Differential pressure sensor; 1-11. Pressure filter; 1. Inlet; 2. Outlet; 3. Drainage hole; 4. Relief hole; 2-1. Inlet valve; 2-2. Exhaust valve; 2-3. Drain valve; 2-4. Relief valve; 2-5. Nitrogen/steam access valve; 2-6. Backwash valve; 3-1. Oil catcher; 3-2. Air flotation pool; 3-3. Biochemical installation; 3-4. Biological aerated filter; 3-5. Sand filtration installation; 4-1. Fluid bed separator housing; 4-2. Granular layer; 4-3. Partition; 4-4. Liquid distributor; 4-5. Power distributor; 4-6. Flow stabilizer; 4-7. Three-phase cyclone separator; 5-1. Fiber coagulator body; 5-2. Entrance; 5-3. Input distillation distributor; 5-4. Coagulating module for enlarging oil droplets; 5-5. Modified corrugated reinforced settling tank module; 5-6. Nanomodified deep separation module; 5-7. Output of the aqueous phase; 5-8. Oil phase output.

DETAILED DESCRIPTION

Based on the study of the microscopic movement of small particles, control of structural alignment, regularity of particle aggregation and control of the mechanism of particle capture of microdispersed phase, the authors of this application have developed a fluidized bed separation technology in which the functions of collision and adsorption of the separating medium, as well as the function of high-precision interception by microchannels formed by the separating medium media are used to effectively remove fine particles and some oily organic matter present in the wash water. Microchannel separation is different from membrane separation. Since microchannels are not fixed, contain long passages, and have a large capacity for contaminants, the problem of contaminant clogging can be effectively avoided. In addition, based on the study of coagulation kinetics at the liquid-liquid-solid interface, regulation of the flow structure of fiber channels and mechanisms of emulsion breaking and oil removal from the reinforced structure of hydrophilic/hydrophobic fiber combination, the inventors developed a fiber-mediated coagulation technology in which the function of deep Emulsion Breaker The highly efficient emulsion breaker coagulation module is used to effectively remove nano-micron oily organic matter remaining in the wash water. In addition, the fiber coalescer can allow traces of suspended solids to penetrate. The combined process of two separation technologies, fluidized bed separation and fiber coagulation, is expected to effectively solve the problem of deep oil and solids removal from methanol-to-olefins wastewater faced by existing technology.

In a first aspect of the present invention, there is provided an apparatus for deep purification of wash water used in a methanol to olefins conversion process, comprising a cooling column in which an outlet at the top of the cooling column is connected to a water washing column; wherein the lower part of the water washing column is connected to the upper part of the fluidized bed separation system through a centrifugal pump; wherein a lower portion of the fluidized bed separation system is connected to the fibrous coalescer system, and wherein the buffer settling tank is further connected to a side wall of the fluidized bed separation system at its upper portion.

In the present invention, the fluidized bed separation system includes a plurality of fluidized bed separators arranged in parallel, with an inlet port located at the top of the fluidized bed separator; the outlet is located at the bottom of the fluidized bed separator; and a drain hole and a discharge hole are located on the side wall of the fluidized bed separator near the top; wherein the lower part of the water washing column is connected to each inlet through a centrifugal pump; in this case, all drainage holes are connected to a common pipeline G1, which is then connected to a buffer settling tank; in this case, all discharge openings are connected to a common pipeline G2, which is then connected to the cyclone dewatering tank; wherein the bottom of the cyclonic dewatering tank is connected to pipeline G1; wherein the outlet of each fluidized bed separator at the bottom is connected to pipeline G3; in this case, pipelines G3 are connected to a common pipeline G4; wherein the other end of the pipeline G4 is connected to the fiber coalescer system; wherein a nitrogen/steam pipeline and a wash water pipeline are connected to each of the G3 pipelines.

In the present invention, each inlet port has an inlet valve; each outlet has an outlet valve; each drain hole has a drain valve; and each relief port has a relief valve; a nitrogen/steam access valve located at the junction between the nitrogen/steam line and each G3 line; and a backwash valve located at the connection between the wash water line and each G3 line.

In the present invention, the fluidized bed separator includes a housing, wherein an inlet port is located at an upper part of the fluidized bed separator housing; the outlet is located at the bottom of the fluidized bed separator body; a drainage hole is located on the side wall of the fluidized bed separator housing in its upper part; and a discharge hole is located at the top of the fluidized bed separator body; wherein in the body of the fluidized bed separator, a three-phase cyclone separator, a power distributor, a granular bed and a separating plate are arranged sequentially from top to bottom; a flow stabilizer is located inside the outlet hole; wherein the inlet of the three-phase cyclone separator is connected to the inlet; wherein the drainage hole is connected to the side surface of the three-phase cyclone separator; and wherein a liquid distributor is located on the upper surface of the separating plate. The fiber coalescer system contains multiple fiber coalescers arranged in parallel, with an inlet located at the left end of the fiber coalescer; and the oil phase outlet and the water phase outlet are located, respectively, at the top and bottom of the fiber coalescer on the right side; wherein the other end of conduit G4 is connected to the inlet through conduit G5; and wherein each oil phase outlet is connected to line G1 through line G6.

In the present invention, the fiber coalescer includes a body in which an inlet is located at the left end; and the oil phase outlet and the water phase outlet are located at the top and bottom of the fiber coalescer body, respectively, on the right side; in this case, they are installed in series in the coagulator body. from left to right, inlet distillation distributor, coagulating oil droplet coagulation module, modified corrugated reinforced settling tank module and nano-modified deep separation module.

In the present invention, the apparatus further comprises an industrial control computer, in which the inlet valve, the outlet valve, the drain valve, the dump valve, the nitrogen/steam access valve and the backwash valve are solenoid valves, wherein the inlet valve, the outlet valve, the drain valve, the dump valve , the nitrogen/steam access valve and the backwash valve are electrically connected to the industrial control computer through live wires; in this case, a differential pressure sensor is additionally installed on the granular layer; wherein the differential pressure sensor is electrically connected to the industrial control computer via a conductive wire.

In a second aspect, the present invention provides a method for deep purification of wash water used in a methanol to olefins conversion process, wherein the above apparatus for deep purification of wash water used in a methanol to olefins conversion process is used in the method, wherein the method includes the following steps:

Step 1: Turn on the power supply and set the filter pressure drop and fluidized bed separator regeneration time using the industrial control computer;

Step 2: Opening the inlet and outlet valves to ensure the normal operation of the device, the wash water is drawn from the bottom of the wash water column through the centrifugal pump and enters the fluidized bed separator through the inlet at the top of the fluidized bed separator, in which the wash water is directed into the granular bed through the feed distributor, and after the wash water is separated by the granular bed, it passes through the liquid distributor on the separating plate, passes through the flow stabilizer, and is sent to the fiber coalescer from the outlet at the bottom of the fluidized bed separator, and the wash water enters fiber coagulator through the inlet of the fiber coagulator, in which the wash water sequentially passes through the inlet distillation distributor and the oil droplet coagulation coagulation module, the modified corrugated reinforced sedimentation module and the nanomodified deep separation module, so that the emulsified oil droplets remaining in the wash water exit The fluidized bed undergoes hydrophilic-hydrophobic fiber adhesion, collision, growth and separation to ensure that oil droplets gradually move to the top oil layer and water droplets quickly descend, while a clear wash water solution is discharged from the aqueous phase outlet and sent to the reboiler below the column propylene rectification of the olefin separation device as a heat source to partially recover the residual heat of the wash water, and after heat exchange, the clear solution is further heat exchanged through the air cooler and the wash water heat exchanger, and returned to the wash water column, and the waste oil is discharged from the oil outlet phases into the buffer settling tank to achieve the purpose of oil and water separation, while the values of the fluidized bed separator differential pressure sensor are monitored in real time during normal operation of the device;

Step 3: Start the regeneration operation when the set differential pressure value is detected by the filter differential pressure sensor, and the inlet valve and outlet valve are closed; The drain valve, dump valve, backwash valve and nitrogen/steam access valve are opened, the direction of wash water to enter the fluidized bed separator from the outlet is changed, and at the same time nitrogen is mixed with the wash water, which is then directed through the granular bed from bottom to top to bring the granular bed to a boiling state, so that the fine catalyst powder and paraffino-oil organic substances adhered to the separating medium are released, thereby cleaning and regenerating the medium, while the separating medium and contaminants are introduced into the three-phase cyclone separator at the top of the separator with a fluidized bed to ensure the purification of medium particles in the cyclone field, enhance the regeneration of the medium and at the same time extract the medium particles, while contaminants are discharged from the drainage hole on the side surface of the device along with the liquid phase, and nitrogen is discharged from the outlet at the top; And

Step 4: Closing the drain valve, dump valve, backwash valve and nitrogen/steam access valve, and opening the inlet valve and outlet valve when the set regeneration time is reached, so that the device continues to operate normally; and the above steps are repeated in cycles.

In the present invention, in step 1, the pressure drop value across the filter is set to 0.1 to 0.4 MPa, preferably 0.3 MPa; the regeneration operation time is set to 20-60 minutes, preferably 40 minutes; and the accuracy of catalyst separation in the wash water is set to D85 = 0.1 µm.

In the present invention, the content of catalyst particles in the wash water used in the process of converting methanol to olefins is 100-500 mg/L; the average diameter of solid catalyst particles is 0.5-5 microns; oil content 200-1000 mg/l.

Reference will now be made to the accompanying drawings.

Fig. 1 is a schematic view showing the structure of an apparatus for deep purification of wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the present invention. As shown in FIG. 1, the device includes a cooling column 1-1, wherein an outlet at the top of the cooling column 1-1 is connected to a water washing column 1-2; wherein the lower part of the water washing column 1-2 is connected to the upper part of the fluidized bed separator 1-3 through a centrifugal pump; wherein the lower part of the fluidized bed separator 1-3 is connected to the fibrous coalescer 1-4, and the buffer settling tank 1-5 is further connected to the side wall of the fluidized bed separator 1-3 at a location near the upper part. The bottom of the buffer settling tank 1-5 is connected to the pressure filter 1-11 through a centrifugal pump. The reaction product gas enters the cooling column 1-1 through its inlet. Cooling water is discharged from the outlet of the cooling column 1-1 by a centrifugal pump. The residual heat generated by the fiber coalescer 1-4 is recovered and returned to the cooling column 1-2. The upper product from the water-washing column 1-2 is sent to the separation of olefins. The upper products from the buffer settling tank 1-5 and the fibrous coagulator 1-4 are sent for oil processing through fine cleaning. The catalyst produced by the pressure filter 1-11 is removed.

Fig. 2 is a schematic view showing a fluidized bed separation and fiber coagulation system in a wash water deep purification apparatus used in a methanol to olefins conversion process in accordance with a preferred embodiment of the present invention. As shown in FIG. 2, the fluidized bed separation system includes a plurality of (m in total, where m is greater than or equal to 2) fluidized bed separators 1-3 arranged in parallel, with an inlet located at the top of the fluidized bed separator 1-3; the outlet is located at the bottom of the fluidized bed separator 1-3; and a drain hole and a discharge hole are located on the side wall of the fluidized bed separator 1-3 near the top; wherein the lower part of the water washing column is connected to each inlet through a centrifugal pump; in this case, all drainage holes are connected to a common pipeline G1, which is then connected to a buffer settling tank 1-5; wherein all the outlets are connected to a common pipeline G2, which is then connected to the cyclone dewatering tank 1-6; wherein the lower part of the cyclonic dehydration tank 1-6 is additionally connected to the pipeline G1; wherein the outlet of each fluidized bed separator 1-3 at the bottom is connected to pipeline G3; in this case, pipelines G3 are connected to a common pipeline G4; wherein the other end of the pipeline G4 is connected to the fiber coalescer system; wherein the nitrogen/steam line 1-7 and the wash water line 1-8 are connected to each of the pipelines G3; wherein each inlet port has an inlet valve 2-1; each outlet has a 2-2 outlet valve; each drainage hole has a 2-3 drainage valve; and each relief hole has a relief valve 2-4; a nitrogen/steam access valve 2-5 located at the junction between the nitrogen/steam line 1-7 and each line G3; and a backwash valve 2-6 located at the junction between the wash water line 1-8 and each line G3.

The fiber coalescer system contains several (total n, where n is greater than or equal to 2) fiber coalescers 1-4 arranged in parallel, with the inlet located at the left end of the fiber coalescer 1-4; and the oil phase outlet and the water phase outlet are located at the top and bottom of the fiber coalescer, respectively, on the right side; wherein the other end of conduit G4 is connected to the inlet through conduit G5; and wherein each oil phase outlet is connected to line G1 through line G6.

Untreated wash water is introduced through inlet valve 2-1; nitrogen/steam is introduced through nitrogen/steam access valve 2-5; and the wash water is introduced through the backwash valve 2-6. The mixed exhaust gas from the top of the cyclone dehydration tank 1-6 enters the burner; a clear solution of wash water from the bottom of fibrous coagulators 1-4 is returned to the column; the catalyst suspension from the bottom of the buffer settling tank 1-5 is sent for pressure filtration; and oily organic substances from the side wall are sent for processing through fine cleaning.

Fig. 3 is a schematic view showing a processing flowchart of a wash water treatment apparatus discharging waste water into a waste water treatment plant in accordance with a preferred embodiment of the present invention. As shown in FIG. 3, the average flow rate of waste water discharged from the wash water treatment device to the waste water treatment plant is 3 t/h. Waste water from the washing water purification device is first sent to an oil trap 3-1, in which suspended solids and oil are preliminarily separated from the waste water due to the difference in the specific gravities of suspended solids, oil and water. The waste water, purified by the oil trap 3-1, is sent to the air flotation pool 3-2, in which the suspended flocs and oil droplets in the wastewater are further deposited in the form of flakes and grow, and together with the bubbles released by the aerated water, they form large flocs, which rise to the surface of the water under the influence of buoyancy and rising water, thereby further separating the oil and solids in the waste water. After treatment by air flotation, the waste water is sent to the biochemical unit 3-3, in which the substances COD (chemical oxygen demand), ammonia nitrogen, oil/fat, etc. removed from waste water by microbial decomposition. Then the waste water is sent to a biological aerated filter 3-4, in which the substances COD, ammonia nitrogen, oils/fats, suspended solids, etc. further removed from waste water through the function of oxidative decomposition of biofilm on the surface of the filter material and the function of intercepting the filter material in the filter tank. Finally, the waste water is sent to a 3-5 sand filtration unit for deep removal of suspended solids from the waste water, after which the water is drained or reused. Sludge is removed from the bottoms of oil traps 3-1, air flotation pool 3-2, biochemical unit 3-3, biological aerated filter 3-4 and sand filtration unit 3-5.

Fig. 4 is a schematic view showing the structure of a fluidized bed separator in an apparatus for deep purifying wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the present invention. As shown in FIG. 4, the fluidized bed separator includes a housing 4-1, the fluidized bed separator housing 1-4 having an inlet 1 at the top, an outlet 2 at the bottom, a drain hole 3 on the side wall at a location at the top, and a discharge hole 4 at top part. A three-phase cyclone separator 4-7, a feed distributor 4-5, a granular bed 4-2 and a separating plate 4-3 are arranged sequentially from top to bottom in the fluidized bed separator body. Inside the outlet 2 there is a flow stabilizer 4-6. The inlet of the three-phase cyclone separator 4-7 is connected to the inlet 1. The drain hole 3 is connected to the side surface of the three-phase cyclone separator 4-7. The liquid distributor 4-4 is located on the upper surface of the separation plate 4-3.

Fig. 5 is a schematic view showing the structure of a coalescer in a device for deep purification of wash water used in a methanol to olefins conversion process in accordance with a preferred embodiment of the present invention. As shown in FIG. 5, the fiber coalescer includes a body 5-1, with an inlet 5-2 located at the left end of the fiber coalescer body 5-1; an outlet 5-8 for the oil phase and an outlet 5-7 for the aqueous phase, respectively located at the top and bottom on the right side. The coagulator housing 5-1 has, sequentially from left to right, an input distillation distributor 5-3, a coagulating module 5-4 for enlarging oil droplets, a modified corrugated reinforced settling tank module 5-5 and a nano-modified deep separation module 5-6.

Fig. 6 is a diagram showing an electrical connection between a fluidized bed separator in a methanol to olefins conversion process and an industrial control computer in accordance with a preferred embodiment of the present invention. As shown in FIG. 6, 2-1 inlet valve, 2-2 outlet valve, 2-3 drain valve, 2-4 dump valve, 2-5 nitrogen/steam access valve and 2-6 backwash valve are solenoid valves, and they are all electrically connected to the industrial control computer by 1-9 wires. A differential pressure sensor 1-10 is additionally installed on the granular layer. The differential pressure sensor 1-10 is electrically connected to the industrial control computer 1-9 via a conductive wire.

The operating principle of the device for deep purification of wash water used in the process of converting methanol into olefins, in accordance with the present invention, is as follows:

During normal operation of the device, the inlet valve 2-1 and the outlet valve 2-2 are opened, and the drain valve 2-3, the discharge valve 2-4, the backwash valve 2-6 and the nitrogen/steam access valve 2-5 are closed. The rinsing water is withdrawn from the bottom of the water wash column 1-2 through a centrifugal pump, fed into the fluidized bed separator 1-3 through the inlet 1 at the top of the separator 1-3, passed through the granular bed from top to bottom, thereby filtering the wash water used in the conversion process methanol to olefins, to remove solids, free oil and dispersed oil in water. Primary purified wash water is discharged from outlet 2 in the lower part and sent to several fiber coagulators 1-4 connected in parallel for secondary deep cleaning. The aqueous phase, purified in a fluidized bed, is subjected to physical destruction of the emulsion by a hydrophilic-hydrophobic fiber in a fiber coagulator 1-4 to achieve separation of oil and water. The clear wash water solution is removed from the aqueous phase outlet 5-7 at the bottom of the fiber coalescer and is sent as a heat source to the reboiler under the propylene distillation column of the olefin separation device to partially recover the residual heat of the wash water. After heat exchange, it is subjected to further heat exchange through the air cooler and the wash water heat exchanger, and then returned to the wash water column. The waste oil is discharged from the oil phase outlet 5-8 at the top of the fiber coalescer 1-4. When the fluidized bed separators 1 to 3 are operated continuously until the pressure difference increases to 0.3 MPa, the multiple fluidized bed separators are switched to the backwash mode in turn. During backwashing, the inlet valve 2-1 and outlet valve 2-2 of the corresponding fluidized bed separator 1-3 are closed, and the drain valve 2-3, discharge valve 2-4, nitrogen/steam access valve 2-5 and valve 2- 6 backwash is opened. Raw wash water and nitrogen are supplied to bring the granular bed in the separator to a boiling state, so that the contaminants intercepted and adsorbed in the granular bed are released, thereby achieving regeneration of the separation medium. The suspension of pollutants formed during regeneration is discharged from the drainage hole 3 and sent to a buffer settling tank 1-5 for separation of oil and water by settling. The upper product in the form of an oil phase in the buffer settling tank 1-5 is sent to the waste oil purification system for reuse, and the lower product in the form of a catalyst slurry is sent to a pressure filtration unit for pressure filtration treatment to recover the catalyst, thereby achieving near-zero disposal rates waste. Waste water containing trace amounts of oil and solids produced by the pressure filtration unit is discharged to a wastewater treatment plant. After removing organic matter and suspended substances from waste water, the water brought to the standard is discharged into the environment or reused. The mixed exhaust gas is discharged through the outlet 4 and sent to the burner after removing water from it by the cyclone dehydration tank 1-6. Gaseous organics carried by the mixed exhaust gases from the fluidized bed regeneration process are burned to achieve near-zero pollutant discharge. Since the fiber coalescer operates continuously, the waste oil is also sent to the buffer settling tank 1-5 through the upper oil phase outlet 5-8 for settling, and then sent together with the waste oil generated by fluidized bed regeneration to the waste oil purification system.

The operating principle of the fluidized bed separator according to the present invention is as follows:

During normal operation, wash water is drawn from the bottom of the wash column 1-2 by a centrifugal pump, supplied to the fluidized bed separator 1-3 through the inlet 1 at the top of the fluidized bed separator 1-3, and directed to the granular bed through the distributor 4- 5 food. After separation by the granular layer 4-2, the wash water is passed through the liquid distributor 4-4 on the separation plate 4-3 and directed into the fiber coalescer 1-4 from the outlet at the bottom after passing through the flow stabilizer 4-6. After the device switches to the backwash mode, the inlet valve 2-1 and the outlet valve 2-2 are closed, and the drain valve 2-3, the discharge valve 2-4, the nitrogen/steam access valve 2-5 and the backwash valve 2-6 are opened. Then, the wash water is supplied to the fluidized bed separator 1-3 from the outlet 2, and at the same time nitrogen is mixed into the wash water. Wash water is passed through the granular bed from bottom to top, bringing the bed to a boil. The fine catalyst powder and organic wax-oil substance adhering to the separation medium are released, thereby cleaning and regenerating the medium. The separation medium and contaminants are supplied to the three-phase cyclone separator 4-7 at the top of the fluidized bed separator, so that the medium particles are washed in the cyclone field, the regeneration of the medium is enhanced, and the medium particles are extracted at the same time. Contaminants are removed from the drainage hole 3 on the side surface of the device along with the liquid phase, and nitrogen is removed from the hole 4 in the upper part.

The fluidized bed separator constructed in accordance with the present invention is equipped with an industrial control computer, and a pressure drop value (filtration pressure drop) is set on the industrial control computer. When the filtration pressure drop reaches a set value, the fluidized bed separator can automatically switch to regeneration mode to clean and regenerate the separating medium. The industrial control computer enables the fluidized bed separator to filter the wash water and effectively regenerate the separating medium without manual operation. An example of an industrial control computer is the Siemens S7-300 industrial control computer. Its control interface is shown in Fig. 6. The main function of the industrial control computer is to control the opening and closing of 2-1 inlet valve, 2-2 exhaust valve, 2-3 drain valve, 2-4 discharge valve, 2-5 nitrogen/steam access valve, 2-6 valve backwashing of each fluidized bed separator to perform switching between different states to achieve the purpose of automatic control. Specifically, it monitors the open/closed state of each valve and real-time data on the filtration pressure drop across the fluidized bed separator. Based on the feedback between the real-time differential pressure data and the set upper limit of the differential pressure, the six main valves perform the opening/closing operation according to the system preset logic to achieve the purpose of online switching between the filtration state and the fluidized bed backwash state. During normal operation of the fluidized bed separator for filtration, the inlet valve 2-1 and the outlet valve 2-2 are in the open state. When the filtration pressure drop reaches the set value, the device switches to backwash mode. Specifically, the inlet valve 2-1 and the outlet valve 2-2 are closed sequentially. Then the drain valve 2-3 and the discharge valve 2-4 are opened simultaneously, and the backwash valve 2-6 and the nitrogen/steam access valve 2-5 are opened simultaneously. Unlike what was described previously, the wash water enters the fluidized bed separator from outlet 2. Nitrogen is mixed with the wash water at the same time. The washing water passes through the granular layer from bottom to top, activating the operation of the separating medium regeneration device. When the duration of the regeneration operation reaches the set value, the backwash valve 2-6 and the nitrogen/steam access valve 2-5 are closed simultaneously, and the drain valve 2-3 and the discharge valve 2-4 are also closed simultaneously. Then the exhaust valve 2-2 and the inlet valve 2-1 open sequentially. Thus, the fluidized bed separator returns to normal filtration mode. According to the present invention, when the filtration pressure drop reaches a set value of 0.3 MPa, the device switches to backwash operation.

The cyclonic shear action provided by the three-phase cyclone separator 4-7 at the top of the fluidized bed separator during regeneration of the fluidized bed separator enhances the regeneration effect of the separation medium and simultaneously helps to achieve the recovery of medium particles. The fluidized bed separator uses anthracite, carbon balls and other filter media that can remove oil and solids as the separation media. They exhibit good effect in adsorption and trapping of catalyst particles, free oil and dispersed oil in the wash water.

The operating principle of the fiber coagulator, in accordance with the present invention, is as follows:

During normal operation, the wash water is fed into the fiber coagulator through the fiber coagulator inlet 5-2, passed through the inlet distillation distributor 5-3, and then sequentially fed into the oil drop coagulation coagulation module 5-4, the modified corrugated reinforced settling tank module 5-5 and nano-modified deep separation module 5-6, so that the emulsified oil droplets remaining in the wash water at the outlet of the fluidized bed undergo adhesion to the hydrophilic-hydrophobic fiber, collision, growth and separation, ensuring the oil droplets gradually move to the upper oil layer and quickly sink drops of water. A clear wash water solution is discharged from the aqueous phase outlet 5-7 and returned to the wash water circulation heat exchange system. The waste oil is discharged from the oil phase outlet 5-8 into a buffer settling tank to separate oil and water.

The body 5-1 of the fiber coalescer made in accordance with the present invention is a horizontal circular tank or a horizontal rectangular tank. At the water phase outlet 5-7 there is a continuous discharge, and at the oil phase outlet 5-8 there is an intermittent discharge or a continuous discharge of a small flow. The oil droplet coagulating module consists of a compacted layer formed by a solid material with a lipophilic surface. Oil droplets in water can stick to the surface of a dense layer and gradually accumulate into large oil droplets, which speeds up their separation. A corrugated reflective plate with a lipophilic surface is used as a modified corrugated reinforced settling tank module. Drops of oil collect on the top of the corrugation of the reflective plate and rise to the oil layer. Drops of water collect on the concave part of the reflective plate, merge, grow upward and then quickly sink. The nanomodified deep separation module 5-6, which is the main unit of the fiber coagulator, uses a coagulation module made of organic polymer material, mainly nylon, glass, Teflon or steel wool. The material is woven in the shape of the letter Ω. The emulsified oil in the wash water can be separated quickly and efficiently.

When implementing the method according to the present invention, after fluidized bed separation, the suspended solids content in the wash water is reduced to 20 mg/L or less, and the oil content is reduced to 150 mg/L or less. After deep cleaning with fiber coalescer, the oil content in the wash water drops to 30 mg/L or less.

EXAMPLES

The present invention will be further illustrated with reference to the following specific examples. However, it should be understood that these examples are intended only to illustrate the present invention without limiting the scope of the present invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally carried out under normal conditions or under conditions suggested by the manufacturers. Unless otherwise noted, all parts are parts by weight and all percentages are percentages by weight.

Example 1:

In the methanol to olefins conversion process with a capacity of 1.8 million tons per year for deep purification of wash water containing solid catalyst and paraffino-oil substances, a device made in accordance with the present invention is used to achieve the goal of effectively separating solid particles and paraffino-oil substances from the wash water . The experimental parameters and effects are as follows:

1. Material properties and processing methods

The wash water used in the methanol to olefins conversion process was a two-phase liquid-solid mixture. The water contained solid catalyst particles and oil. The main components of the oil were highly concentrated aromatic hydrocarbons that were resistant to degradation. The operating temperature was 90°C. The content of spent catalyst is 100-500 mg/l, the average particle size is 2 microns. Oil content 200-1000 mg/l.

For the 1.8 ppm methanol to olefins process being studied, the main measures currently taken in the prior art include continuous flush water discharge at 160 t/h, fresh water replenishment to balance solids and oil in the wash water, and the continuous addition of xylene to facilitate the precipitation of catalyst and oil-based organic matter and eliminate the blockage they cause. Although such measures can reduce clogging of the water system used to convert methanol to olefins, water consumption is high and the economics of the process are poor. In addition, the load on the wastewater stripping plant and downstream treatment plants increases, and the heat of the discharged waste water is difficult to utilize. For example, if wash water is discharged at a temperature of 90°C, then when it is cooled to an ambient temperature of 25°C, the heat loss of 1 ton of waste water is about 270 MJ. With a wash water flow rate of 160 t/h, the daily heat loss is 1,036,800 MJ, which is equivalent to 35.4 tons of equivalent coal/day. Therefore, the measures currently taken are unprofitable from the point of view of safety, environmental protection and economy.

2. Wash water purification device

The wash water purification device was a device containing a fluidized bed separator and a fiber coalescer connected in series. The fluidized bed separator had a diameter of 300 mm and a height of 1500 mm. A three-phase cyclone separator was installed on top. The separating medium was a filter material made of anthracite particles 0.5-1 mm in size. The layer height was 1300 mm. The productivity of one filter was 1 m ³ /h. The fibrous coagulator was a horizontal vessel. The water inlet, water outlet and oil outlet were equipped with sight glasses. The oil was discharged periodically or continuously at a small flow rate from the oil phase outlet. Water was continuously discharged from the aqueous phase outlet. A drainage hole was made in the bottom of the coagulator

3. Implementation process

As shown in FIG. 2, the wash water used in the methanol to olefins conversion process, containing catalyst and paraffinic oil substances, was sent to the fluidized bed separator by a centrifugal pump to remove catalyst particles, free oil and dispersed oil, and then entered the fiber coalescer to deeply remove the emulsified oils in rinsing water. After operating the fluidized bed separator continuously until the pressure drop reached 0.3 MPa, it was switched to backwash mode. The regeneration liquid from the fluidized bed was sent to a buffer settling tank to separate the oil from the water. The upper oil phase, together with the waste oil from the coagulator, was sent to the waste oil purification system. The bottom layer of catalyst slurry was sent to a pressure filtration unit for pressure filtration treatment to recover the catalyst. Waste water generated in the pressure filtration unit was sent to treatment facilities.

4. Analysis of results

By using a treatment process combining fluid bed separation and fiber coagulation, the solids content of the wash water was reduced from 100-500 mg/L to 20 mg/L or less, and the oil content was reduced from 200-1000 mg/L to 30 mg/L or less. In tests, after 1000 hours of continuous operation of the fluidized bed separator, which was washed 50 times to regenerate, the original separation effect was still maintained and the separation efficiency exceeded 90%.

5. Technical effects

In recent years, microcyclone separation, metal membrane separation, ceramic membrane separation and bag filtration have gradually been used in the treatment of waste water used in the methanol-to-olefins conversion process. Based on domestic field research, the authors of this application have discovered that all of the above methods have certain disadvantages. Thus, treating waste water used in the methanol to olefins conversion process has always been a major challenge that is difficult to solve in the MTO industry. Microcyclones and metal membranes are used in more than 10 sets of MTO equipment. The two devices are typically operated in series, with the microcyclone used for primary separation and the metal membrane used for deep cleaning. The separation error of the microcyclone separator is low. It shows good separation effect only for particles larger than 3 microns and has difficulty separating particles smaller than 3 microns. Due to the problem of membrane fouling in microfiltration with metal membranes, the membrane flux will be reduced to 20% or less of the normal membrane flux within one month of operation, making normal operation difficult. At some MTO plants, ceramic membranes and bag filters are added during technical re-equipment. Ceramic membranes are effective for filtering fine particles in waste water used in the methanol-to-olefins conversion process, but the equipment costs are high and the membrane pressure is high. In addition, the problem of clogging of membrane channels will gradually arise after operation for more than a year. Currently, ceramic membranes are used in 3 sets of MTO equipment for waste water treatment. Due to the low separation accuracy and short service life of the bag filter, the cleaning efficiency will be significantly reduced after one year of operation, and this problem must be solved by replacing the bag filter. This method is used only at one MTO plant.

Compared with previous technologies, fluidized bed separation technology is second only to ceramic membrane separation technology in terms of separation efficiency. However, fluidized bed separation technology is based on the principle of deep filtration, and filtration channels are formed by the accumulation of loose particles of filter material. As a result, the channels are volatile. Contamination and clogging of metal or ceramic membranes can in principle be avoided. The granular layer of filter material has a high porosity, and the filtered particles can be located in the voids between the particles of the filter material. Consequently, the capacity of the granular bed retains contaminants, and the granular bed needs to be backwashed much less frequently than in surface filtration methods such as metal membrane filtration and ceramic membrane filtration. On the other hand, since the channels are variable, contaminants remaining in the channels can be easily released. In addition, a cyclone is used to enhance washing, so contaminants are easily removed from the surface of the filter material. Therefore, the filter material can be regenerated more efficiently than in a conventional deep filtration device. In addition, since the filter material can be selected from traditional anthracite, carbon spheres, etc., which are inexpensive, investment in equipment and maintenance fees are very low.

A comparison of several technologies for treating wastewater from the methanol to olefins conversion process in industrial applications (at a treatment capacity of 200 m ³ /h) is shown in Table 2 below. Fluidized bed separation technology is superior to other technologies in terms of equipment investment, processing costs, operating costs, wastewater discharge frequency and separation energy consumption. Its separation efficiency is second only to ceramic membrane technology and is sufficient to separate catalyst fines in an aqueous MTO system. However, it requires more space than other technologies. Comprehensive evaluation shows that the fluidized bed separation technology has excellent performance in treating waste water used in the methanol to olefins conversion process, so it is more suitable for the industrial treatment of this waste water.

Fiber coagulation technology has also been successfully applied to treat highly emulsified oily wastewater from a 100 billion tonne gas field platform in the South China Sea. The fiber coalescer has a compact structure and high impact resistance, and also eliminates the need for a demulsifier, which is used in the prior art oil removal method. Fiber coagulation technology has obvious technical and economic advantages. In particular, separation occurs quickly and efficiently; pressure drop is low (pressure drop less than 0.3 MPa); and energy consumption is low. The modular design allows you to flexibly control the space required according to the actual situation. The service life is long and operating and maintenance costs are low. A comparison of oil removal technology using fiber coagulation and prior art oil removal technology using an emulsion breaking agent is shown in Table 2 below.

In accordance with the present invention, the granular bed filtration method and the fiber coagulation method are creatively combined for highly efficient separation of fine catalyst powder and oil in the wash water used in the methanol to olefins conversion process. This combination compensates for the insufficient separation efficiency of oil in the wash water of the fluidized bed separator, and also effectively eliminates the problem of contamination of the internal parts of the fiber coalescer caused by catalyst particles in the wash water, so as to achieve the purpose of deep purification. Specifically, anthracite, carbon beads or other oil and solids removal filter materials are used as the separation medium in the fluidized bed separator to effectively trap and adsorb fine catalyst powder, free oil and dispersed oil in the wash water. Then, the emulsified oil in the wash water adheres to the hydrophilic-hydrophobic fiber woven into the Ω shape in the fiber coalescer, collides, grows and separates so that physical demulsification is achieved, and then the emulsified oil in the wash water is removed. The pilot industrial test and industrial application of the present invention can achieve not only the deep removal of nano-micron particles and wax-oil substances in the wash water and water reuse, but also waste oil purification, catalyst concentration and regeneration, harmless treatment of regenerated exhaust gas and partial recovery of residual heat of the wash water, thereby achieving comprehensive treatment of the wash water used in the process of converting methanol into olefins. The suspended solids concentration in waste water is reduced to 20 mg/L or less, and the oil content is reduced to 30 mg/L or less. The cleaning frequency of the heat exchanger and air cooler in the wash water treatment system can be reduced by more than 80%, and the clogging of the wash water column and cooling column is effectively reduced. In addition, the initial discharge of rinse water at a rate of 160 t/h can be eliminated. In the event that the wash water is used as a heat source for the reboiler under the propylene distillation column of the olefin separation device to recover part of the residual heat, provided that the wash water is discharged at a temperature of 90°C when it is cooled, to 65°C due to recovery residual heat, heat recovery is about 100 MJ per ton of wastewater. With a wash water consumption of 160 t/h, 384,000 MJ of heat per day can be saved, which is equivalent to 13.1 tons of standard fuel per day. In addition, the wash water containing oil and solids is a highly concentrated organic waste water that is resistant to decomposition. When discharged to a treatment plant with a flow rate of 160 t/h in accordance with the prior art, the cost of treating waste water will increase. Now, according to the present invention, the waste water discharged to the waste water treatment plant is mainly produced by the pressure filtration plant and contains a small amount of oil and solids, and the average discharge is 3 t/h. Assuming that the treatment cost is 10 yuan per ton of water, 12.56 million yuan per year can be saved in the treatment of wash water.

The examples listed above are only preferred examples in the invention, and they are not intended to limit the scope of the invention. All equivalent variations and modifications made in accordance with the invention within the scope of this application for invention fall within the technical scope of the invention.

All documents referred to in the specification are incorporated herein by reference as if each were individually incorporated by reference in the specification. Moreover, it is to be understood that various changes or modifications to the invention may be made by those skilled in the art upon examination of the above inventive teachings, and such equivalent changes also come within the scope of the appended claims.

Claims (19)

1. A method for deep purification of wash water used in the process of converting methanol into olefins, which uses a device for deep purification of wash water used in the process of converting methanol into olefins, containing: cooling column (1-1), a water washing column (1-2) connected to an outlet at the top of the cooling column (1-1), a separator (1-3) with a fluidized bed, the upper part of which is connected to the lower part of the water-washing column (1-2), a fibrous coalescer (1-4) connected to the bottom of a fluidized bed separator (1-3), and a buffer settling tank (1-5) connected to the side wall of a fluidized bed separator (1-3) at a location near the top, wherein the method includes the following steps: step 1: turn on the power supply and set the filter pressure drop and regeneration operating time for the fluidized bed separator (1-3) using the industrial control computer (1-9); step 2: opening the inlet valve (2-1) and outlet valve (2-2) to ensure the normal operation of the device, while the wash water is taken from the bottom of the water wash column (1-2) through a centrifugal pump and supplied to the separator (1- 3) with a fluidized bed through the inlet (1) in the upper part of the specified separator (1-3), in which the wash water is directed into the granular bed (4-2) through the feed distributor (4-5), and after separating the wash water from the granular layer (4-2) it is passed through the liquid distributor (4-4) on the separating plate (4-3), passed through the flow stabilizer (4-6) and directed into the fiber coagulator (1-4) from the outlet (2) in the lower part, while the wash water is supplied to the fibrous coagulator (1-4) through the inlet (5-2) of the coagulator (1-4), in which the wash water passes through the inlet distillation distributor (5-3) and sequentially enters a coagulating module (5-4) for enlarging oil droplets, a modified corrugated reinforced module (5-5) for a settling tank and a nanomodified module (5-6) for deep separation, so that the emulsified oil droplets remaining in the washing water at the outlet of the fluidized bed are subject to adhesion to hydrophilic-hydrophobic fiber, collision, growth and separation, ensuring the gradual movement of oil droplets to the upper layer of oil and the rapid descent of water droplets, while a clear solution of wash water is removed from the outlet (5-7) for the aqueous phase and sent to the reboiler under the column propylene rectification of the olefin separation device as a heat source for partial recovery of the residual heat of the wash water, and after heat exchange, the clear solution is subjected to further heat exchange through the air cooler and the wash water heat exchanger and returned to the water wash column (1-2), while the waste oil is discharged from outlet (5-8) for the oil phase into a buffer settling tank (1-5) for separating oil and water, while the values of the differential pressure sensor (1-10) of the fluidized bed separator (1-3) are monitored in real time during normal operation of the device; step 3: start the regeneration operation when the set value of the filter differential pressure is detected by the differential pressure sensor (1-10), the inlet valve (2-1) and outlet valve (2-2) are closed, and the drain valve (2-3 ), the discharge valve (2-4), the backwash valve (2-6) and the nitrogen/steam access valve (2-5) are opened, and the flow of wash water into the fluidized bed separator (1-3) from the outlet is changed. (2), and at the same time nitrogen is mixed into the wash water, which is then passed through the granular bed (4-2) from bottom to top to bring the granular bed (4-2) to a boiling state, so that the fine catalyst powder and paraffino-oil organic matter adhering on the separating medium are released, thereby purifying and regenerating the medium, while the separating medium and contaminants are fed into the three-phase cyclone separator (4-7) at the top of the fluidized bed separator to ensure particle removal of the medium in the cyclone field, enhanced regeneration of the medium and simultaneous extraction of particles of the medium, while pollutants are discharged through the drainage hole (3) on the side surface of the device along with the liquid phase, and nitrogen is removed from the discharge hole (4) in the upper part; And step 4: closing the drain valve (2-3), vent valve (2-4), backwash valve (2-6) and nitrogen/steam access valve (2-5) and opening the inlet valve (2-1) and outlet valve (2-2) when the set regeneration operating time is reached, so that the device continues to operate normally. 2. The method according to claim 1, in which at stage 1 the pressure drop across the filter is set to 0.1-0.3 MPa, the time of the regeneration operation is set to 20-60 minutes and the accuracy of catalyst separation in the wash water is set to D ₈₅ = 0.1 µm. 3. The method according to claim 1, in which the content of catalyst particles in the wash water used in the process of converting methanol to olefins is 100-500 mg/l, the average diameter of the solid catalyst particles is 0.5-5 μm and the oil content is 200 -1000 mg/l. 4. The method according to claim 1, in which the fluidized bed separator (1-3) contains several fluidized bed separators, which are arranged in parallel and each of which has an inlet (1) at the top, an outlet (2) at the bottom parts, a drain hole (3) and a discharge hole (4) on the side wall near the top, with the bottom of the water washing column (1-2) connected to each inlet hole (1) through a centrifugal pump, all drain holes (3) are connected with the common pipeline G1, which is then connected to the buffer settling tank (1-5), and all the discharge holes (4) are connected to the common pipeline G2, which is then connected to the cyclone dewatering tank (1-6), the lower part of which is connected to the pipeline G1, wherein the outlet (2) of each fluidized bed separator at the bottom is connected to a pipeline G3, and the pipelines G3 are connected to a common pipeline G4, while the other end of the pipeline G4 is connected to a fiber coalescer (1-4), and to each pipeline G3 connects pipeline (1-7) nitrogen/steam and pipeline (1-8) wash water. 5. The method according to claim 4, in which each inlet (1) has an inlet valve (2-1), each outlet (2) has an outlet valve (2-2), each drain hole (3) has a drain valve ( 2-3), and each discharge hole (4) has a relief valve (2-4), and at the junction between the nitrogen/steam pipeline (1-7) and each G3 pipeline there is a nitrogen/steam access valve (2-5) , and at the junction between the flush water pipe (1-8) and each G3 pipe there is a backwash valve (2-6). 6. The method according to claim 5, in which the fluidized bed separator (1-3) contains a housing (4-1), in which the specified inlet hole (1) is located in the upper part, and the specified outlet hole (2) is located in the lower part. , in the side wall in a place near the upper part there is said drain hole (3) and in the upper part there is said discharge hole (4), while in said housing (4-1) a three-phase cyclone separator (4-7) is located sequentially from top to bottom. , a power distributor (4-5), a granular layer (4-2) and a separation plate (4-3), with a flow stabilizer (4-6) located inside the outlet (2), while the inlet of a three-phase cyclone separator (4- 7) is connected to the inlet hole (1), the drain hole (3) is connected to the side surface of the three-phase cyclone separator (4-7), and a liquid distributor (4-4) is located on the upper surface of the separating plate (4-3). 7. The method according to claim 4, in which the fiber coalescer (1-4) contains several fiber coalescers, which are arranged in parallel and each of which has an inlet (5-2) at its left end and an outlet (5-8) for oil phase and an outlet (5-7) for the aqueous phase, respectively, at the top and bottom of the fiber coalescer (1-4) on its right side, while the other end of pipeline G4 is connected to the inlet (5-2) through pipeline G5, and each oil phase outlet (5-8) is connected to line G1 through line G6. 8. The method according to claim 1, in which the fiber coalescer (1-4) contains a housing (5-1), in which an inlet hole (5-2) is located on the left end, and on the right side, respectively, at the top and bottom of the housing (5-1) there is an outlet (5-8) for the oil phase and an outlet for the aqueous phase (5-7), while the body (5-1) of the coagulator has, in sequence from left to right, an input distillation distributor (5-3), coagulating module (5-4) for enlarging oil droplets, a modified corrugated reinforced module (5-5) for a settling tank and a nanomodified module (5-6) for deep separation. 9. The method according to claim 6, wherein said device further comprises an industrial control computer (1-9), wherein an inlet valve (2-1), an outlet valve (2-2), a drain valve (2-3), a valve The vent (2-4), nitrogen/steam access valve (2-5) and backwash valve (2-6) are solenoid valves and are electrically connected to the industrial control computer (1-9) via conductive wires, while on the granular bed (4-2) a differential pressure sensor (1-10) is additionally installed, which is electrically connected to the industrial control computer (1-9) via a conductive wire.