A high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element

Abstract

The present invention discloses a high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element, which includes a filter tube and a mounting end disposed on the filter tube, wherein the mounting end is integrally formed with the open end of the filter tube and an axial through hole communicating with the inner cavity of the filter tube is disposed inside the mounting end, the blind end of the filter tube is integrally formed with the tube wall of the filter tube, the filter tube is composed of a cylindrical support layer sintered once and a cylindrical transition layer and a cylindrical filter layer sintered sequentially on the cylindrical support layer, the mounting end is provided with a filter element positioning plate for realizing the installation and positioning of adjacent filter elements and an externally threaded connecting pipe for realizing the connection and installation of the filter element and the filter element tube plate. The present invention also specifically discloses the preparation method and application of the metal sintered filter element. The gradient aperture filter element of the present invention is easier to backwash and regenerate than the uniform aperture filter element, and the required backwashing pressure and system energy consumption are smaller, which is conducive to long-term operation.

Description

Technical Field

[0001] The invention belongs to the technical field of asymmetric metal sintered filter elements, and in particular relates to a high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element. Background Art

[0002] The catalytic slurry filter is a filtering device for removing catalyst particles from the residual oil after catalytic cracking in the ACO light oil processing unit. ACO catalyst slurry is used as a blending component of fuel oil, so it is necessary to further remove the impurity solid content in the catalyst slurry. The filtering device used requires the outlet solid content to be less than 50ppmw. The catalyst content in the catalyst slurry is as high as 12000~18000ppmw, the working temperature is 200℃, and the slurry contains 10000ppmw of colloid and asphalt, and the online backwashing pressure is as high as 1.15MPa. Therefore, in order to achieve the required goals of the device, the required filtration accuracy and efficiency are at least 1μm@95%, and it must withstand a long period of 1.15MPa pressure backwashing at high temperature. This requires the filter element to have not only high precision, but also a high flow rate, high strength at high temperature, and the filter element filter material structure design is conducive to backwashing regeneration.

[0003] The DMTO process of methanol to ethylene and propylene is an important chemical technology at present. This technology uses methanol synthesized from coal or natural gas as raw material to produce low-carbon olefins, and is the core technology for developing non-petroleum resources to produce ethylene, propylene and other products. At present, domestic production enterprises that have adopted the above technology and put into production have encountered major problems in the operation of the system due to the excessive content of solid catalysts in the quenching (washing) water and the complex composition of by-products. Quenching (washing) water with too high solid content can cause extremely serious consequences in production, seriously affecting the safety, stability, long cycle, and full-load operation of the device, and even requiring shutdown for repairs. After investigation and analysis, it was found that the particle size distribution of solid catalyst particles in the quenching (washing) water is: <5μm=68.03%, 5~10μm=19.76%, 10~40μm=12.21%, and small particle size occupies the vast majority, which requires the filter element to have a small pore size, a large flow rate, and excellent backwashing regeneration ability.

[0004] At present, there are three main production processes for asymmetric metal sintered filter elements with the filter layer on the outside:

[0005] 1. Isostatic pressing substrate + spraying technology, see published patent CN102489079A, such as Figure 1-2As shown, a powder tube substrate with a large isostatic pressing aperture is first sintered, and then a fine powder layer with a powder particle size of 200-800 mesh is sprayed on the outer surface. Then, an asymmetric metal sintered filter element is produced after multiple sintering. Since wet spraying is used and both the substrate and the powder layer are metal materials, it is difficult for the two to be combined together without the presence of adhesive. After adding the adhesive, the problem of combining the filter layer with the substrate is solved, but a problem arises. After the sprayed filter tube is sintered, the adhesive will remain, which will seriously affect the opening rate and flow rate of the filter material. The spraying of the filter layer is based on the substrate (cylindrical pipe fitting) rotating with an axis. It requires the investment of automated equipment and the utilization rate of the spray material is low and cannot be recycled. The filter tube coating takes a long time to make and the overall production efficiency is low, because it contains adhesives and uses high-pressure spraying, which poses a great threat to the environment. In addition, the metal powder particle size is very small, and the addition of adhesives is also a great challenge to the spraying equipment. The nozzle is often blocked and production has to be stopped for maintenance after a period of time. In addition, high-precision nozzles are currently all imported in China, which is expensive and has no initiative and is easily controlled by others. The filter layer is to control the precision and the powder particle size will be as small as possible, but in order to ensure the flow rate, it is impossible to spray too thick. Therefore, if you want to have high strength, you can only improve the strength of the substrate. If the substrate uses a larger particle size powder, the strength is guaranteed, but the fine powder will block most of the pores on the substrate during spraying of the coarse powder substrate, so it is difficult to ensure the flow rate. To ensure strength, you have to sacrifice high filtration accuracy. Similarly, if a finer powder is used as the substrate material for spraying the filter layer, the accuracy and strength can be taken into account at the same time, but the flow rate and filter element resistance are greatly increased, the backwashing regeneration ability is seriously weakened, and the life of the filter element is reduced, which increases the operating cost of the customer. Even if the most optimized design is made, it is difficult to select a suitable substrate material to combine high precision, high strength, large flow, easy backwashing and other properties due to the restriction of the isostatic pressing process itself. And the isostatic pressing known in the industry relies on high-pressure fluid to form the same pressure on the inner and outer walls of the powder filter tube at the same time, so as to achieve the strength of the powder particles biting each other. Under the condition of a certain powder particle size, the isostatic pressing pressure is proportional to the substrate strength and inversely proportional to the substrate flow rate. Normally, the starting pressure of isostatic pressing equipment is above tens of MPa. Even if the minimum forming pressure is selected, the strong pressure will weaken the "arch bridge effect" between the powder particles, so that the pores of the porous materials produced are all below 30%. Because the substrate is a powder sintered tubular component, the roundness, straightness, coaxiality and diameter deviation of the products made by the industrial-grade high-temperature vacuum sintering process are all around 2mm. In order to ensure the flow rate, the filter layer cannot be sprayed too thick. In actual production, the thickness of the filter layer generally does not exceed 0.5mm. Even if the precision error of the spraying equipment is discarded, it is almost difficult to achieve uniform spraying of the filter layer on a substrate with a geometric size deviation of 2mm. The above actual production problems bring a lot of uncertainty to the performance of the filter layer.

[0006] In summary, the asymmetric metal sintered filter element produced by isostatic pressing substrate + spraying technology can only achieve high precision, large flow, and easy backwashing in the above two typical working conditions, which cannot solve the contradictions in actual production. To ensure performance, life must be sacrificed, and if life is guaranteed, performance will not meet the standard. The asymmetric sintered filter element produced by this process generally has high investment cost, complex process, and low production efficiency.

[0007] 2. Rolling substrate + spraying technology, see published patent CN107983016A and announced patent CN204767841U, such as Figure 3-4 As shown, a roll-formed substrate is first sintered (the principle of roll-forming is to use the gap between two tangential rollers to form pressure on the material to continuously press the required sheet material), and then a layer of fine powder with a powder particle size of 200-800 mesh is sprayed on the outer surface of the rolled substrate, and then an asymmetric sheet filter material is produced through vacuum sintering. Because of the sheet filter material, the final filter element has at least one more filter material roll and longitudinal seam welding process than other forming methods.

[0008] The rolled substrate is generally one of the following materials: metal powder sintered plate, multi-layer metal sintered mesh, metal fiber sintered felt, or a combination of two materials. Like the first method, the substrate is still responsible for the strength of the filter material. The spray layer is used as the filter layer. Because it is a sheet material and is a flat spray construction, the pore size selection of the substrate is particularly important. If the pore size is large, the flow rate will be increased, but the fine powder of the filter layer will fall into the support layer and block some pores. If the pore size is too small, the problem of the fine powder of the filter layer combining with the support layer is solved, but it is bound to cause a decrease in strength (the pore size of the woven mesh and sintered felt is proportional to the strength). It seems that metal powder sintered plate can be selected as the substrate. Material, because the pore size of the powder material is inversely proportional to the strength. Although the powder rolling plate selected with the fine powder of the filter layer will not cause the fine powder to block the substrate, the selection of a substrate with too small an aperture has already reduced the flow rate. This combination still only sacrifices the flow rate to ensure strength and production feasibility. Even if the appropriate substrate is selected to make an asymmetric sintered sheet that basically meets the requirements, the subsequent filter element production is a difficult challenge. The process of rolling the filter material into a cylinder will cause tensile damage to the original pore structure, and the heat generated by the longitudinal seam welding often causes the filter layer to crack, which poses a fatal hidden danger to the filtration accuracy of the filter element. When the filter element diameter is the same, the filter element with a weld is usually smaller than the filter element without a weld. Although the impact on a single filter element is not significant, it is a world of difference for a device with hundreds of filter elements installed. Because of the existence of the weld, there is a blind spot in the backwashing process, and the high pressure generated by the backwashing is also generated. The weld cannot be unloaded in time, and the strength of the weld will be damaged over time.

[0009] In summary, the asymmetric metal sintered filter element produced by rolling substrate + spraying technology cannot achieve high-precision filtration and excellent backwashing effect in the above two typical working conditions. It is only suitable for some niche working conditions that do not require high precision but have strength requirements, and the economic benefits are very limited. In addition, the asymmetric metal sintered filter element produced by this process has extremely stringent requirements on substrate rolling, filter material winding, and welding processes. Any mistake in any link is fatal, so the product scrap rate is also relatively high.

[0010] 3. Vacuum deposition technology, see published patent CN103446806A, such as Figure 5 As shown, a porous substrate is first sintered, and the porous substrate is fixed in a closed deposition chamber by a clamp, and the side of the porous support to be deposited is connected to the powder feeder at one end of the deposition chamber, and the other side of the porous support is connected to the vacuum pump at the other end of the deposition chamber. The powder raw material to be deposited is added to the powder feeder, and the vacuum pump is turned on to generate a pressure difference on both sides of the porous substrate. Then, the powder feeder is turned on, and the powder raw material in the powder feeder is transported to the side of the porous substrate to be deposited by gas, and the pressure difference on both sides of the substrate is used to deposit the powder raw material on the surface of the substrate. Although this method has a simple process and can produce asymmetric metal sintered filter materials with gradient pore size, it is only suitable for producing sheet materials because the design principle only relies on negative pressure deposition. For the production of tubular products, it is difficult to produce a gradient pore size with consistent surface due to the difference in air flow fields in multi-dimensional space.

[0011] Because this technology can only produce sheet materials, as far as the asymmetric coating production of sheet materials is concerned, although the technical solution to the pore size gradient distribution of the filter layer has been solved and the production efficiency has been greatly improved, there are still problems such as difficulty in substrate selection, deformation of the pore size of the filter roll, welding cracks, and poor backwashing effect that appear in the second method.

[0012] The current installation methods of asymmetric metal sintered filter elements are: Figure 6-7 The installation method used has been used for many years. Although it is simple to manufacture, it is labor-intensive to install later. It takes at least two people to assemble the filter element to the tube sheet. Since the filter element is not positioned, the reaction force can only be generated by holding the lower filter tube by hand when tightening the nut. This operation method has the risk of damaging the high-precision filter layer. Generally, in order to save costs as much as possible, the filter element on the tube sheet is arranged relatively compactly. As the number of filter element assemblies increases, tightening the filter element in a limited space becomes more and more difficult. Because the working conditions using asymmetric filter elements have backwashing or backblowing designs, the nuts of such unpositioned filter elements will often fall off under the vibration of long-term high-pressure backwashing / blowing media. Figure 8-9It is improved on the basis of the traditional installation structure. There are two main improvements. First, a locating pin is added on the top of the filter element end cover, and the locating pin and the filter element are fixed by interference fit; secondly, a countersunk hole matching the locating pin is processed on the filter element tube plate, and it is necessary to pay attention to the tolerance matching of the countersunk hole specifications and the locating pin. Although this design solves the problem of insufficient manual preload force for filter element installation and reduces the damage to the filter layer that may be caused by manual intervention, it increases the difficulty in production and processing. The tube plate is usually large in size. In order to process a countersunk hole suitable for tolerance matching, large equipment such as a machining center must be used, which increases production costs. In addition, although this single-point support positioning method can play a certain role in fixing the filter element, under long-term high-pressure backwashing / blowing medium vibration, the local force of the filter element will cause stress concentration over time, resulting in gaps on the sealing surface and ultimately seal failure. Summary of the invention

[0013] The present invention provides a metal powder sintered filter element with a gradient pore size and a preparation method thereof, which is intended to solve the problem encountered in the above-mentioned methods for producing asymmetric metal filter elements that the selection of fine powder in the filter layer and the matching of the pore size of the substrate cannot take into account both the backwashing effect and the strength of the filter element;

[0014] The present invention provides a fast and convenient method for preparing a multi-layer metal clad material, which is intended to simplify the existing asymmetric metal sintered filter element preparation method, which requires powder screening, mold making of blanks, isostatic pressing or rolling forming of substrates, sintering, filter layer pulping, powder spraying, filter layer shaping sintering, finished product sintering, mechanical turning or filter tube winding and longitudinal seam welding, component welding and other complex processes;

[0015] The present invention provides an asymmetric metal sintered filter element with high precision, large flow and easy backwashing and a preparation method thereof, which effectively solves the problem that the filtration precision, filtration flow and backwashing effect of the existing asymmetric metal sintered filter element cannot be taken into account in practical applications;

[0016] The present invention provides a method for preparing an integrally formed multi-layer metal cladding material, which effectively avoids damage to the filter layer caused by welding between components and secondary processing;

[0017] The present invention provides a faster and fatigue-resistant installation structure and installation method, so as to reduce the cost of parts processing and the processing procedures as much as possible, make the filter element installation process simple and reliable, and ensure efficient and stable on-site operation;

[0018] The present invention provides an asymmetric metal sintered filter element with simple process operation, green environmental protection, safety and reliability, high processing efficiency, recyclable powder raw materials, and integrated filter element. The production process of the metal sintered filter element of the present invention does not require redundant secondary processing, has low production cost, low requirements on production equipment, and is suitable for large-scale industrial production.

[0019] The installation structure design of the metal sintered filter element designed by the present invention is also different from the traditional metal sintered filter element, with the purpose of easy installation, reduced labor intensity, and high reliability, which is very suitable for large-scale promotion in industrial applications. The filtration efficiency of the asymmetric metal sintered filter element prepared by this method is much higher than that of the traditional asymmetric metal sintered filter element. The asymmetric metal sintered filter element produced by the present invention can be widely used in gas-solid and liquid-solid separation in industries such as petrochemicals, coal, water treatment, and biopharmaceuticals, and is particularly suitable for working conditions with high temperature, high impurity content, high viscosity, high precision, and online regeneration requirements for the filter element. Typical applications include ACO light oil processing catalyst slurry filtration, coal gasification fly ash filtration, nylon plant caprolactam hydroxylamine oxime process catalyst recovery, methanol to olefin process water slurry filtration, and chemical plant alkaline wastewater filtration and other industrial fields.

[0020] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element, characterized in that it includes a filter tube and a mounting end head arranged on the filter tube, wherein the mounting end head is integrally formed with the open end of the filter tube and an axial through hole communicating with the inner cavity of the filter tube is provided inside the mounting end head, and the blind end of the filter tube is integrally formed with the tube wall of the filter tube, the filter tube is composed of a cylindrical support layer sintered once and a cylindrical transition layer and a cylindrical filter layer sequentially arranged on the cylindrical support layer, the mounting end head is provided with a filter element positioning plate for realizing the installation and positioning of adjacent filter elements and an externally threaded connecting pipe for realizing the connection and installation of the filter element and the filter element tube plate.

[0021] It is further defined that the filter element positioning plate is a hexagonal prism structure, which is used to achieve the installation positioning of adjacent filter elements through the mutual support of the hexagonal prism sides of adjacent filter elements and thereby achieve the installation of the filter elements and the filter element tube plate. The filter element positioning plates support each other and form a whole to avoid loosening of threads caused by backwashing vibration.

[0022] It is further defined that an annular groove is provided on the outer side of the filter element positioning plate, and a sealing ring is provided in the annular groove for pressing and sealing with the filter element tube plate.

[0023] It is further defined that a stepped serrated interface is provided at the bottom end of the mounting end and a plurality of radial through holes are distributed along the circumferential direction on the side wall of the stepped serrated interface. After the filter tube is sintered, a plug-in tenon that engages with the radial through hole is formed on the inner side of the open end of the filter tube, which is used to effectively improve the bonding strength between the filter tube and the mounting end after sintering. The radial through hole is designed to strengthen the sintering bonding strength between dense metal materials and loose powder materials. After the powder raw materials are added, the through hole on the rear end will be filled with powder, and the through hole will no longer exist after the blank is made. Dense metal and loose materials are very difficult to combine due to their different thermal expansion coefficients. The stepped serrated interface and radial through hole design in the present invention also contribute to the perfect combination of dense metal and loose powder materials during sintering.

[0024] The method for preparing the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element of the present invention is characterized by the following specific steps:

[0025] Step S1: Preparation of support layer

[0026] Step S11: connecting port A of the substrate manufacturing tool to a vacuum pump, connecting port A to a motor in a circumferential direction through a transmission wheel, and connecting port B to a pneumatic powder feeder;

[0027] Step S12: Install the mounting end and the inner airbag seal onto the rotating suction cup at the bottom of port A, and then install the outer airbag and the tooling shell seal onto the bottom of the substrate manufacturing tooling to form a vacuum chamber;

[0028] Step S13: injecting dispersant ethanol into the space between the inner airbag and the outer airbag inside the tooling shell through the B port;

[0029] Step S14: Start the vacuum pump and pneumatic powder feeder, and add D 50 =50 mesh irregular metal powder, turn on the motor to let the rotating suction pipe, i.e., port A, rotate counterclockwise at a speed of 300r / min. At this time, adjust the vacuum degree of the vacuum pump to -0.1MPa. Use the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump to suck the powder slurry in the tooling shell into the outer wall of the inner air bag in the form of a filter cake. Control the thickness of the inner layer blank of the substrate according to the powder feeding amount set by the powder feeder. Calculate the amount of support layer material in advance. After the required raw materials are used up, turn off the pneumatic powder feeder, and keep the vacuum pump and motor running for 2 minutes, so that the slurry in the tooling shell can be fully utilized to make the support layer blank;

[0030] Step S15: turn off the motor, wait for the rotating suction pipe to stop, turn off the vacuum pump, connect compressed air to port A, disconnect the powder feeder at port B to make port B empty, and then connect compressed air to port C;

[0031] Step S16: adjust the compressed air pressure at port A to 100 KPa, then slowly increase the compressed air pressure at port C to 100 KPa, maintain the pressure for 2 minutes, then release the pressure at port C, and after the pressure is released, release the pressure at port A until the pressure at ports A and C is completely released to obtain the inner support layer of the filter element;

[0032] Step S2: Preparation of transition layer

[0033] Step S21: Repeat the process of steps S11-S14, but this time add D into the powder feeder. 50= 80 mesh irregular metal powder, turn on the motor to let the rotating suction pipe rotate counterclockwise at a speed of 120r / min, at this time adjust the vacuum degree of the vacuum pump to -0.08MPa, use the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump to suck the powder slurry in the shell into the form of filter cakes onto the outer wall of the support layer, and control the thickness of the transition layer I blank according to the powder feeding amount set by the powder feeder. The material amount of the support layer is calculated in advance, and the pneumatic powder feeder is turned off after the required raw materials are used up, and the vacuum pump and the motor are kept running for 2min, so that the slurry in the tooling shell is fully utilized to make the transition layer I blank;

[0034] Step S22: Repeat the process of steps S11-S14, but this time add D into the powder feeder. 50 =150 mesh irregular metal powder, turn on the motor to let the rotating suction pipe rotate counterclockwise at a speed of 80r / min, at this time adjust the vacuum degree of the vacuum pump to -0.06MPa, use the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump to suck the powder slurry in the shell into the form of filter cakes onto the outer wall of the transition layer I, and control the thickness of the transition layer II blank according to the powder feeding amount set by the powder feeder. The material amount of the support layer is calculated in advance, and the pneumatic powder feeder is turned off after the required raw materials are used up, and the vacuum pump and the motor are kept running for 2min, so that the slurry in the tooling shell is fully utilized to make the transition layer II blank;

[0035] According to the design requirements, the transition layer can be one layer or multiple layers, and the production process is the same as above;

[0036] Step S3: Preparation of filter layer

[0037] Repeat the process of steps S11-S14, but this time add D 50 =2500 mesh spherical powder and 40μm stainless steel staple fiber, the spherical powder and stainless steel staple fiber are mixed in a mass ratio of 2:1, the motor is turned on to let the rotary suction pipe rotate counterclockwise at a speed of 60r / min, at this time, the vacuum degree of the vacuum pump is adjusted to -0.05MPa, and the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump are used to suck the powder slurry in the shell into the outer wall of the transition layer in the form of filter cake. Due to the bridging effect of the fiber, the powder particles are attached to the intersection of the fibers and are naturally evenly distributed. The thickness of the inner layer of the substrate blank is controlled according to the powder feeding amount set by the powder feeder. The amount of support layer material is calculated in advance. After the required raw materials are used up, the pneumatic powder feeder is turned off, and the vacuum degree of the vacuum pump is increased to -0.08MPa. The motor is kept running for 2min, and the slurry in the tooling shell is fully utilized to make a multi-layer laminated filter layer material asymmetric filter element blank;

[0038] Step S4: Filter element molding

[0039] Step S41: Connect the port A of the tooling for making the filter layer to compressed air, but do not ventilate at this time, cut off the circumferential transmission motor, connect the compressed air to the port B and slowly open it, open the port C to discharge the residual slurry, close the valve of the port C when no liquid flows out, open the compressed air valve of the port A, and simultaneously increase the pressure of the ports A and B to 2000Pa at a rate of 100Pa / S and maintain the pressure for 1min;

[0040] Step S42: Reduce the pressure of the compressed air at ports A and B at a rate of 50 Pa / S at the same time. When the pressures on both sides reach 1000 Pa respectively, open port C to release the pressure until the pressures of the compressed air at ports A and B drop to 0 Pa, open the tooling housing, and remove all the tools connected to the filter element to obtain the asymmetric filter element blank after molding;

[0041] Step S5: Filter element vacuum sintering process

[0042] The molded asymmetric filter element blank is placed in a vacuum sintering furnace for sintering. In the first stage, the temperature is increased to 250°C at a heating rate of 2°C / min and kept at this temperature for 1 hour. In the second stage, the temperature is increased to 600°C at a heating rate of 2°C / min and kept at this temperature for 1 hour. In the third stage, the temperature is increased to 900°C at a heating rate of 20°C / min and kept at this temperature for 1 hour. In the fourth stage, the temperature is increased to 1050°C at a heating rate of 2°C / min and kept at this temperature for 1.5 hours.

[0043] Step S6: Filter element cooling process

[0044] After the filter element is sintered, it is cooled to 850°C at a cooling rate of 2°C / min and kept at this temperature for 10 minutes. Then, argon is passed into the vacuum sintering furnace and the temperature is further cooled to room temperature at a cooling rate of 5°C / min. After being taken out of the furnace, a finished high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element is obtained.

[0045] The application of the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element described in the present invention is characterized by: the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element is used for gas-solid separation and liquid-solid separation in the petrochemical, coal, water treatment, and biopharmaceutical industries, and is particularly suitable for working conditions with high temperature, high impurity content, high viscosity, high precision, and online regeneration requirements for the filter element; it is specifically used in the industrial fields of ACO light oil processing catalyst slurry filtration, coal gasification fly ash filtration, nylon plant caprolactam hydroxylamine oxime process catalyst recovery, methanol to olefin process water slurry filtration, and chemical plant alkaline wastewater filtration.

[0046] The application of the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element described in the present invention is characterized in that the specific installation process is: first, a sealing ring is installed in the annular groove on the outside of the filter element positioning plate at the installation end, and then the externally threaded connecting tube at the installation end is inserted into the installation hole of the filter element tube plate. The installation of the first filter element requires the use of external force to fix the filter tube or filter element positioning plate of the filter element so that the end of the externally threaded connecting tube is connected and fixed to the filter element tube plate by a nut. The installation of other filter elements is achieved by the mutual support of the hexagonal prism structure filter element positioning plate and the hexagonal prism side of the filter element positioning plate of the adjacent filter element to achieve the self-installation and positioning of the filter element. Then, the end of the externally threaded connecting tube is connected and fixed to the filter element tube plate by a nut to achieve the installation of the filter element. The filter element positioning plates support each other and form a whole to avoid loosening of the threads caused by backwashing vibration.

[0047] The centrifugal suction method adopted by the present invention uses at least four specifications of powders with extremely coarse, relatively coarse, fine and extremely fine particle sizes and ultrafine stainless steel short fibers as raw materials to make slurry (the slurry does not contain molecular organic matter, and there will be no carbon deposits occupying the pores of the filter material after sintering), and uses special tooling to gradually adsorb and finally attach a layer of ultrafine metal membrane filter layer to the outer surface. In order to improve the porosity of the filter layer, the present invention has been tested many times and finally adopted a mixed pulping process of adding a stainless steel short fiber and ultrafine powder of the filter layer (the bridging effect of the stainless steel short fiber during the centrifugal suction process makes the powder particles adhere to the intersection of the fibers, and the powder relies on the three-dimensional structure generated by the fiber to greatly increase the porosity) to successfully solve the current situation of using only the porosity of the powder. This structure can well balance the filtering performance and the backwash (backwash) regeneration ability. The inner layer metal with a coarse pore size is used as a carrier, which can provide a channel similar to the Venturi effect for backwashing while ensuring the mechanical strength of the filter element, and the function of separating solid particles is undertaken by the metal membrane filter layer. The separation accuracy of the filter element made by this method can reach up to 0.1 microns. Traditional asymmetric sintered filter elements, including isostatically pressed tubular elements and rolled sheet elements, are currently mainly produced by the three methods mentioned above. Although each has its own characteristics, they all have shortcomings. The pore size formed by the powder in the direction of the tube cross section does not have an obvious gradient change in the direction of fluid penetration. The filtration mechanism of this asymmetric structure filter element is mainly deep filtration. During deep filtration, the filter medium is easily embedded in the middle pores of the filter element, thereby blocking the pores, and it is not easy to remove by backwashing. It is impossible to optimize and integrate high precision, high strength, large flow rate, and excellent backwashing effect. The difference between the filter element of the present invention and other asymmetric sintered filter elements is that the filter layer is thin in thickness and small in pore size, the support layer has at least two layers of transition, and the pore size from the filter material inlet surface to the outlet surface increases in a step-like manner. The pore size distribution of the filter layer is uniform and consistent, and the interval range is small. The tighter pore size distribution ensures that the particles are retained on the surface of the porous material (surface filtration mechanism). During the filtration process, even if small particles enter the filter layer, they will not be retained in the pores because the pore size increases from the outside to the inside. These particles are driven by the filter medium to the downstream of the filter element, and after entering the backwash / blowing cycle, the filter cake intercepted on the surface of the filter layer will not suffer too much loss when the backwash pressure is transmitted to the filter cake layer because the filter layer is thin, and backwashing becomes extremely easy with the "Venturi" structure where the pore size of the filter layer gradually decreases from the inside to the outside. In this way, the flowability of the filter element will not be attenuated after repeated operation, thus achieving high-precision, large-flow, and long-cycle operation to save costs and bring considerable economic benefits to customers.

[0048] The filter element of the present invention is different from other asymmetric sintered filter elements that require welding of longitudinal seams or welding of mounting parts at both ends. The filter element of the present invention is produced using special tooling, and can obtain an asymmetric filter element blank in one go. It only needs to be sintered once, and no secondary processing or welding of mounting parts is required, which greatly improves production efficiency. The installation structure of the filter element design of the present invention is simple and fast, and the structure is ingenious. It can be obtained at a relatively low cost and is suitable for mass production.

[0049] The filter element of the present invention is composed of ultrafine powder, ultrafine stainless steel short fiber, medium-sized powder and extremely coarse powder in the direction of medium entry according to the product precision requirements. Such a design can obtain a gradual aperture. During normal filtration, the medium enters from the small aperture side and is trapped and accumulated. As the differential pressure rises, clean high-pressure fluid is drawn from the inside of the filter element to clean and regenerate the filter cake formed on the outer surface of the filter element. This gradual aperture is easier to backwash and regenerate than a uniform aperture filter element, and the required backwash pressure and system energy consumption are smaller, which is conducive to long-term operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of manufacturing an asymmetric sintered filter element substrate by a medium static pressure process in the prior art;

[0051] Figure 2 This is the structural diagram of the asymmetric metal sintered filter element in the medium static pressure process of the prior art;

[0052] Figure 3 This is a structural diagram of asymmetric metal sintered filter material using rolling technology in the prior art;

[0053] Figure 4 This is a structural diagram of an asymmetric metal sintered filter element using a rolling process in the prior art;

[0054] Figure 5 It is a schematic diagram of manufacturing asymmetric metal sintering filter material by vacuum deposition process in the prior art;

[0055] Figure 6 This is the installation structure diagram of the traditional asymmetric metal sintered filter element;

[0056] Figure 7 This is the assembly diagram of the traditional asymmetric metal sintered filter element;

[0057] Figure 8 This is the installation structure diagram of the asymmetric metal sintered filter element after the existing technology is improved;

[0058] Fig. 9 It is an assembly diagram of an asymmetric metal sintered filter element after improvement of the prior art;

[0059] Fig.10 This is a flow rate comparison chart of the asymmetric metal sintered filter element of the present invention and the sintered filter element produced by other processes;

[0060] Fig.11 It is the pore size distribution and liquid-solid separation efficiency diagram of asymmetric metal sintered filter element in isostatic pressing process;

[0061] Fig.12 It is the pore size distribution and liquid-solid separation efficiency diagram of asymmetric metal sintered filter element by rolling process;

[0062] Fig.13 This is a diagram showing the pore size distribution and liquid-solid separation efficiency of the asymmetric metal sintered filter element of the present invention;

[0063] Fig.14 This is a schematic diagram of the manufacturing principle of the asymmetric metal sintered filter element substrate, namely the support layer and the transition layer of the present invention;

[0064] Fig.15 This is a schematic diagram of the manufacturing principle of the filter layer of the asymmetric metal sintered filter element of the present invention;

[0065] Fig.16 It is a schematic diagram of the molding principle of the asymmetric metal sintered filter element of the present invention;

[0066] Fig.17 It is a schematic diagram of the structure of the asymmetric metal sintered filter element in the present invention;

[0067] Fig.18 It is a schematic diagram of the structure of the filter tube in the asymmetric metal sintered filter element of the present invention;

[0068] Fig.19 yes Fig.18 Schematic diagram of the local structure;

[0069] Fig. 20 This is a diagram of the installation structure of the asymmetric metal sintered filter element of the present invention;

[0070] Fig.21 It is an assembly diagram of the asymmetric metal sintered filter element of the present invention.

[0071] In the figure: 1-filter tube, 2-installation end, 3-cylindrical support layer, 4-cylindrical transition layer, 5-cylindrical filter layer, 6-filter element positioning plate, 7-external threaded connecting pipe. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is described in detail in conjunction with the accompanying drawings. The theoretical prototype of the technical solution of the present invention is divided into two categories of filtration mechanisms: surface filtration, i.e., filter cake filtration, and deep filtration. As the name implies, surface filtration is to intercept particles on the surface of the filter element, and deep filtration is to retain particles in the pores inside the medium. Since the filter needs to operate stably for a long time, backwashing and regeneration are performed during the process. Therefore, in order to ensure the long-term stable operation of the filter, the working principle determines that only surface filtration can be performed. According to the surface filtration working mode, the working pressure difference during the operation of the filter satisfies the Darcy fluid theory: , V-flow, d-thickness of filter layer, η-viscosity of medium, S-filtration area, α-permeability coefficient of filter material. According to Darcy fluid theory, the flow rate through the filter element is inversely proportional to the filtration accuracy and thickness of the filter element. Therefore, if you want to obtain a high-throughput filter element, it is in line with the design principle to adopt an asymmetric structure with a gradual aperture change. Reducing the thickness of the filter layer (metal film) while ensuring the strength of the filter element is an inevitable choice to reduce resistance and increase flux.

[0073] The high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element described in the present invention comprises a filter tube 1 and a mounting end 2 arranged on the filter tube 1, wherein the mounting end 2 is integrally formed with the open end of the filter tube 1 and an axial through hole communicating with the inner cavity of the filter tube 1 is provided inside the mounting end 2, and the blind end of the filter tube 1 is integrally formed with the tube wall of the filter tube 1, the filter tube 1 is composed of a cylindrical support layer 3 sintered once and a cylindrical transition layer 4 and a cylindrical filter layer 5 sequentially arranged on the cylindrical support layer 3, a filter element positioning plate 6 for realizing the installation and positioning of adjacent filter elements and an externally threaded connecting pipe 7 for realizing the connection and installation of the filter element and the filter element tube plate are provided on the mounting end 2; the filter element positioning plate 6 is a hexagonal column structure, which is used to realize the installation and positioning of adjacent filter elements by mutual support of the hexagonal column sides of adjacent filter elements and thereby realize the installation of the filter element and the filter element tube plate, and the filter element positioning plates 6 support each other and form an integral body to avoid thread loosening caused by backwashing vibration.

[0074] The high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element of the present invention is used for gas-solid separation and liquid-solid separation in the petrochemical, coal, water treatment, and biopharmaceutical industries, and is particularly suitable for working conditions with high temperature, high impurity content, high viscosity, high precision, and online regeneration requirements for the filter element; it is specifically used in the fields of ACO light oil processing catalyst slurry filtration, coal gasification fly ash filtration, nylon plant caprolactam hydroxylamine oxime process catalyst recovery, methanol to olefin process water slurry filtration, and chemical plant alkaline wastewater filtration.

[0075] The specific installation process of the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element described in the present invention is: first, a sealing ring is installed in the annular groove on the outside of the filter element positioning plate at the installation end, and then the externally threaded connecting tube at the installation end is inserted into the installation hole of the filter element tube plate. The installation of the first filter element requires the use of external force to fix the filter tube or filter element positioning plate of the filter element so that the end of the externally threaded connecting tube is connected and fixed to the filter element tube plate by a nut. The installation of other filter elements is achieved by the mutual support of the hexagonal prism structure filter element positioning plate and the hexagonal prism side of the filter element positioning plate of the adjacent filter element to achieve the self-installation and positioning of the filter element. Then, the end of the externally threaded connecting tube is connected and fixed to the filter element tube plate by a nut to achieve the installation of the filter element. The filter element positioning plates support each other and form a whole to avoid loosening of the threads caused by backwashing vibration.

[0076] The filter element of the present invention is composed of ultrafine powder, ultrafine stainless steel short fiber, medium-sized powder and extremely coarse powder in the direction of medium entry according to the product precision requirements. Such a design can obtain a gradual aperture. During normal filtration, the medium enters from the small aperture side and is trapped and accumulated. As the differential pressure rises, clean high-pressure fluid is drawn from the inside of the filter element to clean and regenerate the filter cake formed on the outer surface of the filter element. This gradual aperture is easier to backwash and regenerate than a uniform aperture filter element, and the required backwash pressure and system energy consumption are smaller, which is conducive to long-term operation.

[0077] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element, characterized in that: The high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element comprises a filter tube and a mounting end head arranged on the filter tube, wherein the mounting end head is integrally formed with the open end of the filter tube and an axial through hole communicating with the inner cavity of the filter tube is arranged inside the mounting end head, and the blind end of the filter tube is integrally formed with the tube wall of the filter tube, and the filter tube is composed of a cylindrical support layer sintered once and a cylindrical transition layer and a cylindrical filter layer sequentially arranged on the cylindrical support layer, and a filter element positioning plate for realizing the installation and positioning of adjacent filter elements and an externally threaded connecting pipe for realizing the connection and installation of the filter element and the filter element tube plate are provided on the mounting end head; the filter element positioning plate is a hexagonal prism structure, which is used to pass through the corresponding The mutual support of the hexagonal prism sides of adjacent filter elements realizes the installation and positioning of adjacent filter elements and then realizes the installation of the filter element and the filter element tube plate. The filter element positioning plates support each other and form a whole to avoid the loosening of the threads caused by backwashing vibration; the outer side of the filter element positioning plate is provided with an annular groove, and the annular groove is provided with a sealing ring that is tightly sealed with the filter element tube plate; the bottom end of the installation end is provided with a stepped serrated interface and a plurality of radial through holes are distributed along the circumferential direction on the side wall of the stepped serrated interface. After the filter tube is sintered, a plug-in tenon that is snap-fitted with the radial through hole is formed on the inner side of the open end of the filter tube, which is used to effectively improve the bonding strength between the filter tube and the installation end after sintering; The specific preparation steps are: Step S1: Preparation of support layer Step S11: connecting port A of the substrate manufacturing tool to a vacuum pump, connecting port A to a motor in a circumferential direction through a transmission wheel, and connecting port B to a pneumatic powder feeder; Step S12: Install the mounting end and the inner airbag seal onto the rotating suction cup at the bottom of port A, and then install the outer airbag and the tooling shell seal onto the bottom of the substrate manufacturing tooling to form a vacuum chamber; Step S13: injecting dispersant ethanol into the space between the inner airbag and the outer airbag inside the tooling shell through the B port; Step S14: Start the vacuum pump and pneumatic powder feeder, and add D 50 =50 mesh irregular metal powder, turn on the motor to let the rotating suction pipe, i.e., port A, rotate counterclockwise at a speed of 300r / min. At this time, adjust the vacuum degree of the vacuum pump to -0.1MPa. Use the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump to suck the powder slurry in the tooling shell into the outer wall of the inner air bag in the form of a filter cake. Control the thickness of the inner layer blank of the substrate according to the powder feeding amount set by the powder feeder. Calculate the amount of support layer material in advance. After the required raw materials are used up, turn off the pneumatic powder feeder, and keep the vacuum pump and motor running for 2 minutes, so that the slurry in the tooling shell can be fully utilized to make the support layer blank; Step S15: turn off the motor, wait for the rotating suction pipe to stop, turn off the vacuum pump, connect compressed air to port A, disconnect the powder feeder at port B to make port B empty, and then connect compressed air to port C; Step S16: adjust the compressed air pressure at port A to 100 KPa, then slowly increase the compressed air pressure at port C to 100 KPa, maintain the pressure for 2 minutes, then release the pressure at port C, and after the pressure is released, release the pressure at port A until the pressure at ports A and C is completely released to obtain the inner support layer of the filter element; Step S2: Preparation of transition layer Step S21: Repeat the process of steps S11-S14, but this time add D into the powder feeder. 50 = 80 mesh irregular metal powder, turn on the motor to let the rotating suction pipe rotate counterclockwise at a speed of 120r / min, at this time adjust the vacuum degree of the vacuum pump to -0.08MPa, use the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump to suck the powder slurry in the shell into the form of filter cakes onto the outer wall of the support layer, and control the thickness of the transition layer I blank according to the powder feeding amount set by the powder feeder. The material amount of the support layer is calculated in advance, and the pneumatic powder feeder is turned off after the required raw materials are used up, and the vacuum pump and the motor are kept running for 2min, so that the slurry in the tooling shell is fully utilized to make the transition layer I blank; Step S22: Repeat the process of steps S11-S14, but this time add D into the powder feeder. 50 =150 mesh irregular metal powder, turn on the motor to let the rotating suction pipe rotate counterclockwise at a speed of 80r / min, at this time adjust the vacuum degree of the vacuum pump to -0.06MPa, use the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump to suck the powder slurry in the shell into the form of filter cakes onto the outer wall of the transition layer I, and control the thickness of the transition layer II blank according to the powder feeding amount set by the powder feeder. The material amount of the support layer is calculated in advance, and the pneumatic powder feeder is turned off after the required raw materials are used up, and the vacuum pump and the motor are kept running for 2min, so that the slurry in the tooling shell is fully utilized to make the transition layer II blank; The transition layer can be one or more layers according to the design requirements, and the production process is the same as above; Step S3: Preparation of filter layer Repeat the process of steps S11-S14, but this time add D 50 =2500 mesh spherical powder and 40μm stainless steel staple fiber, the spherical powder and stainless steel staple fiber are mixed in a mass ratio of 2:1, the motor is turned on to let the rotary suction pipe rotate counterclockwise at a speed of 60r / min, at this time, the vacuum degree of the vacuum pump is adjusted to -0.05MPa, and the centrifugal force generated by the rotating shaft and the negative pressure of the vacuum pump are used to suck the powder slurry in the shell into the outer wall of the transition layer in the form of filter cake. Due to the bridging effect of the fiber, the powder particles are attached to the intersection of the fibers and are naturally evenly distributed. The thickness of the inner layer of the substrate blank is controlled according to the powder feeding amount set by the powder feeder. The amount of support layer material is calculated in advance. After the required raw materials are used up, the pneumatic powder feeder is turned off, and the vacuum degree of the vacuum pump is increased to -0.08MPa. The motor is kept running for 2min, and the slurry in the tooling shell is fully utilized to make a multi-layer laminated filter layer material asymmetric filter element blank; Step S4: Filter element molding Step S41: Connect the port A of the tooling for making the filter layer to compressed air, but do not ventilate at this time, cut off the circumferential transmission motor, connect the compressed air to the port B and slowly open it, open the port C to discharge the residual slurry, close the valve of the port C when no liquid flows out, open the compressed air valve of the port A, and simultaneously increase the pressure of the ports A and B to 2000Pa at a rate of 100Pa / S and maintain the pressure for 1min; Step S42: Reduce the pressure of the compressed air at ports A and B at a rate of 50 Pa / S at the same time. When the pressures on both sides reach 1000 Pa respectively, open port C to release the pressure until the pressures of the compressed air at ports A and B drop to 0 Pa, open the tooling housing, and remove all the tools connected to the filter element to obtain the asymmetric filter element blank after molding; Step S5: Filter element vacuum sintering process The molded asymmetric filter element blank is placed in a vacuum sintering furnace for sintering. In the first stage, the temperature is increased to 250°C at a heating rate of 2°C / min and kept at this temperature for 1 hour. In the second stage, the temperature is increased to 600°C at a heating rate of 2°C / min and kept at this temperature for 1 hour. In the third stage, the temperature is increased to 900°C at a heating rate of 20°C / min and kept at this temperature for 1 hour. In the fourth stage, the temperature is increased to 1050°C at a heating rate of 2°C / min and kept at this temperature for 1.5 hours. Step S6: Filter element cooling process After the filter element is sintered, it is cooled to 850°C at a cooling rate of 2°C / min and kept at this temperature for 10 minutes. Then, argon is passed into the vacuum sintering furnace and the temperature is further cooled to room temperature at a cooling rate of 5°C / min. After being taken out of the furnace, a finished high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element is obtained.

2. Application of the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element prepared by the method according to claim 1, characterized in that: This high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element is used for gas-solid separation and liquid-solid separation in the petrochemical, coal, water treatment, and biopharmaceutical industries. It is suitable for working conditions with high temperature, high impurity content, high viscosity, high precision, and online regeneration requirements for the filter element.

3. The application of the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element according to claim 2 is characterized by: The high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element is specifically used in the fields of ACO light oil processing catalyst slurry filtration, coal gasification fly ash filtration, nylon plant caprolactam hydroxylamine oxime process catalyst recovery, methanol to olefins process water slurry filtration and chemical plant alkaline wastewater filtration.

4. The application of the high-precision, large-flow, easy-to-backwash asymmetric metal sintered filter element according to claim 2 is characterized in that The specific installation process is: first, install a sealing ring in the annular groove on the outside of the filter element positioning plate at the installation end, and then insert the external threaded connecting pipe at the installation end into the mounting hole of the filter element tube plate. The installation of the first filter element requires the use of external force to fix the filter tube or filter element positioning plate of the filter element so that the end of the external threaded connecting pipe is connected and fixed to the filter element tube plate through a nut. The installation of other filter elements is achieved by the mutual support of the hexagonal prism structure filter element positioning plate and the hexagonal prism side of the filter element positioning plate of the adjacent filter element to achieve the self-installation and positioning of the filter element. Then, the end of the external threaded connecting pipe is connected and fixed to the filter element tube plate through a nut to achieve the installation of the filter element. The filter element positioning plates support each other and form a whole to avoid loosening of the threads caused by backwashing vibration.

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