EA005787B1 - Ceramic filtering element and method for production thereof - Google Patents

Abstract

The invention relates to filtering devices, in particular to the structural design of the filtering elements of disc ceramic filters and to methods for the production thereof. In order to increase the performance and the strength of a device, the inventive ceramic filtering element comprises a hollow block made of porous ceramic material whose inside elements are arranged in rows and offset along the arcs of a concentric circle and form with walls (4) a hollow volume (3). The ratio of the radius of the transition line between walls inside the hollow block (1) in the bottom part (6) of a sector element with respect to the radius of said interface line in the top part thereof rages from 0.5 to 0.75. An outlet fitting (7) is connected to the hollow block (1) with the aid of a screw joint provided with a seal (8). The inventive method for producing a ceramic filtering element consists in producing the replication thereof of a mixture of paraffin hydrocarbons, forming a porous blank by compaction and using vibration load, and, in order to protect environment, in removing the material of said replication at a temperature below the inflammability point of paraffin hydrocarbons.

Description

Technical field

The invention relates to the field of filtering devices, in particular, to the design of filter elements of disk ceramic filters and methods for their manufacture, and can be used in the design and manufacture of disk ceramic filters for filtering pulps of enrichment products in mining plants and wastewater from galvanic plants.

State of the art

In a number of technological processes of the ferrous, non-ferrous metallurgy and mining industry, it is necessary to use filtering ceramic elements of a complex and especially complex configuration with internal through or blind cavities. In the manufacture of such products, a set of technological parameters arises that determine the integrity and operational characteristics of manufactured products.

The prior art ceramic filter element containing a filter frame with a filter and inner surfaces, made in the form of a circular sector of porous ceramic with open pores, the dimensions of which are increasing in the direction of the filtrate outlet, the internal elements forming a hollow volume, and the neck with a discharge pipe (Patent of Ukraine No. 41623 A, MKI B 01 Ό 29/00, C 04 B 38/00, dated November 14, 2000).

A disadvantage of the known device is that the intersecting channels form internal elements forming a hollow volume, which practically do not participate in the filtering process, creating “dead” zones, which lead to a decrease in the permeability of the ceramic body along the filter surface and, as a result, throughput on the cake.

By technical nature, the closest to the proposed device is a ceramic filter element containing a hollow block of porous ceramics with the radii of the mating lines of the walls in the upper and lower parts, including internal elements and the neck with the outlet pipe (see patent No. 3641057, class C 04 In 38/00, published on June 16, 88).

However, the known device obtained by casting using a plaster mold does not provide the necessary performance, and its design does not differ in sufficient strength.

A known method of producing hollow ceramic products by the method of reverse replicas, consisting in the fact that the metal billet in the form of a future cavity is placed in the filler layer and heated in an oxidizing medium to the melting temperature of the metal and below the melting temperature of the product of its oxidation. Along with melting and oxidation, molten metal is absorbed and a cavity is formed.

The starting material is aluminum, as well as δί, Τι, Ζγ, NT. Filler in the form of powder, fibers, whiskers and containing aluminum oxide, cerium, hafnium, scandium. Oxidizing agents are gases - air, mixtures of Н ₂ / Н ₂ О, СО / СО _2, and others. Oxidation is carried out at a temperature of 850-1450 ° С (see patent I8 No. 4821875, CL 04B 33/32, NKI 264-59, publ. 05/09/1989).

The known method allows to obtain hollow ceramic products with an inner compacted layer and uneven distribution of components due to unregulated capillary impregnation forces, which leads to wedging stresses inside the shell and degradation of the mechanical properties of the products during operation.

Closest to the proposed invention is a method of manufacturing a ceramic filter element, including manufacturing a replica of a hollow space, preparing a mixture containing a fractionated ceramic filler and a binder, molding a porous preform, drying, removing replica material and firing (see application TP No. 1249677, class C04B 38/06, published on January 4, 1989).

The disadvantage of this method is the cracking of products during firing due to various thermal expansion of the liner and the product, as well as the formation of gaseous combustion products that create internal pressure, which leads to deformation of the walls of the product, the formation of microcracks, which is unacceptable in the conditions of filtration of fine pulps. In addition, in the process of removing replica material, the destruction of thermoplastic resins and the release of toxic substances polluting the environment occur.

Disclosure of invention

The basis of the invention is the task of developing the design of a filtering ceramic element of increased productivity and strength, as well as a method for its manufacture, providing improved product quality and environmental safety of the process.

To solve the technical problem, a ceramic filter element containing a hollow block of porous ceramic with radii of the mating lines of the walls in the upper and lower parts, including internal elements and a neck with an outlet pipe, according to the invention, the internal elements are arranged in rows with an offset along the arcs of concentric circles and form the walls are the hollow volume, and the ratio of the radius of the interface line between the walls inside the hollow block at the bottom of the sector element to the radius of the line friction in its upper part

- 1 005787 is 0.5-0.75, while the relationship between the outlet pipe and the hollow block is made by a threaded connection with a tight seal.

In addition, to solve the technical problem in a method of manufacturing a ceramic filter element, including manufacturing a replica of a hollow space, preparing a charge containing a fractionated ceramic filler and a binder, molding a porous preform, drying, removing the replica material and firing, according to the invention, the replica is made from a mixture hydrocarbons of the paraffin series, the porous preform is molded by pressing, and half of the calculated amount of shear is placed in a releasable mold you insert a centering template in the form of a replica into the mold, imprint it to a depth of half the thickness of the replica, extract the template and insert the replica into the obtained recess, load the second half of the calculated amount of the charge, compress the porous block of a given configuration and size by pressure on the upper mold punch and its movement by the calculated value, vibroload is carried out on the upper and lower mold punches, the workpiece is removed, it is transferred to drying, the replica material is removed at a temperature below the ignition temperature of the hydrocarbons of the paraffin series and move it to the stage of reuse, and firing is carried out at a temperature of 1250 ± 50 ° C.

A feature of the invention is that the vibroload is produced within 10-15 s, and the mixture of hydrocarbons of the paraffin series contains wax, paraffin and ozokerite.

The essence of the invention according to the proposed device lies in the fact that the implementation of the ceramic filter element in the above manner gives the filtering surface a wave shape, which intensifies the process of picking the cake and its uniform distribution, which ultimately allows him to provide the necessary strength and performance.

The essence of the invention according to the proposed method lies in the fact that when removing the replica, breaking tensile stresses do not occur, and the process of its liquid-phase removal and secondary use eliminates environmental pollution.

Brief Description of the Drawings

In FIG. 1 shows a ceramic filter element obtained by the claimed method, and in FIG. 2 - section along aa.

The best embodiment of the invention

A method of manufacturing a ceramic filter element includes manufacturing a replica of a hollow space, preparing a charge containing a fractionated ceramic filler and a binder, forming a porous preform, drying, removing the replica material and firing.

A feature of the technical solution according to the method is that the replica is made from a mixture of paraffin hydrocarbons, the porous preform is molded by pressing, and half the calculated amount of the charge is placed in a releasable mold, a centering template having the shape of a replica is inserted into the mold, an impression is made on the depth of half the thickness of the replica, the template is removed and a replica is inserted into the resulting recess.

Next, load the second half of the estimated amount of the charge, compress the porous block of a given configuration and size by pressure on the upper mold punch and moving it to the calculated value.

After that, vibroloading is carried out for 10-15 s on the upper and lower mold punches, the workpiece is removed and it is transferred to drying.

The replica material is removed at a temperature lower than the ignition temperature of the hydrocarbons of the paraffin series and transferred to the reuse stage, and firing is carried out at a temperature of 1250 ± 50 ° C.

A mixture of paraffin hydrocarbons may contain wax, paraffin and ozokerite.

An example of the method

1. The following materials are used for the manufacture of sector-type hollow ceramic elements with an outlet pipe: electrocorundum of grades M1, M3, M5, M20, M40, bentonite, a binder - sulphite-alcohol mash (SSB), beeswax, technical paraffin, ozokerite.

2. The replica hydrocarbon material was made from a mixture consisting of 10 wt.% Wax, 70 wt.% Paraffin and 20 wt.% Ozokerite.

The components were melted in a water bath to a temperature of 80-85 ° C and mixed thoroughly for 40 minutes. A flat matrix was made by pouring a gypsum mold, the inner cavity of which was wetted with water. Filling was carried out through the gate until the entire volume was completely filled. Similarly cast a cylindrical matrix of the outlet pipe with a screw thread. After cooling, the billets were removed, tides and gates were removed. A molded flat matrix having the shape of a circular sector was placed on a polished metal plate, a stencil was applied and a special tool was used to create perforation figures in geometry and dimensions according to the drawing.

3. For the manufacture of the mixture used fractionated ceramic filler in the form of electrocorundum powders of size M1, MZ, M5, M20, M40 with an equal weight ratio. Of

- 2 005787 a mixture of corundum powders, bentonite and CSP with a weight ratio of 70: 23: 7, respectively, the mixture was prepared by mixing in a Ζ-shaped mixer for 30 minutes.

4. Half of the calculated amount of the charge was placed in the mold, aligned on the surface and a centering pattern was used to print the contour of the perforated replica and the outlet pipe, after which the template was removed. The depth of the impression corresponded to half the height of the perforated replica and half the diameter of the replica of the outlet pipe.

5. The replicas were laid in the recesses and the second half of the charge was poured. The mixture was leveled on the surface, a load was applied to the upper punch and it was moved until it came into contact with the backfill and stepwise vibrocompression was performed so that at the initial moment the pressing force was 20-30% of the final one (about 10-15 kg / cm ² ), applied vibration loading on the upper and lower punches for 10-15 s, and after the complete attenuation of the residual vibrational vibrations, the specific pressing pressure was brought to 50 kg / cm ² . As a result of moving the punch by a fixed value, a monolithic block of a semi-finished product of a sector shape was obtained, and the workpiece was removed from the mold.

6. The resulting blocks were kept at room temperature for one day and dried. At the same time, low-temperature heat treatment was carried out in two stages.

In the first stage, in the range lower than the hydrocarbon ignition temperature of 55-70 ° C, the matrix material was removed at a temperature rise rate of 5 ° C / h with isothermal holdings of 1520 min at 55, 63 ° C and 3 h at 70 ° C. In the second stage, the temperature was raised to 85 ° C and isothermal exposure was performed for 12 hours to remove moisture.

During low-temperature heat treatment, billets were installed in a pallet at an angle of 70-80 ° to the vertical. Smelted components were collected in a baking sheet for further use in production.

7. Dried preforms with a residual moisture content of 0.1-0.2% were placed on carborundum plates and fired at a temperature of 1250 ± 50 ° С with isothermal exposure for two hours.

8. The obtained hollow porous ceramic filter elements of the sector type were subjected to visual inspection and testing according to standard and developed methods.

The characteristics of sector-type ceramic filter elements are presented in the table.

Table 1

Index unit of measurement Filter element Prototype Received by the proposed method Filter wall thickness μm 5000 5000 Average hydraulic pore diameter: On the filter surface On the surface filtrate outlet μm 1.0-1.5 1.0-1.5 1.5-2.0 30-35 Structural Strength <^ sr SGRAST. MPa 30.0-35.0 0.2-0.25 65-70 0.6-0.65 Average filter performance l / m ^{2 -} hour 280-320 530-560

These tables show the advantage of the proposed technical solution over the known.

This is achieved by a set of operations and the sequence of their implementation:

making a replica from a mixture of hydrocarbons of the paraffin series allows to obtain a material consisting of components having different melting points, and thereby reduce the effect of increasing the volume of the replica during drying on the deformation of the porous preform;

the initial loading of half the calculated amount of the charge is necessary for applying a replica of the replica contour to a depth equal to half the height of the replica, which allows you to set the replica exactly in the center of the volume of the buried charge and to exclude uneven deformation loads when pressing the porous block;

- 3 005787 moving the upper punch of the mold by the calculated value allows you to fix the shape of the workpiece with a certain porosity and the possibility of moving particles of ceramic filler under the action of vibration loads;

the effect of vibration loading on the upper and lower punches provides a redistribution of particles of the ceramic filler in such a way that porous walls with an increasing pore size in the filtrate exit direction and with a minimum pore size on the filter surface are formed during firing, and the optimal exposure time of the vibration load of 10-15 s is determined experimentally;

the drying process ensures at the first stages the removal of replica material by smelting hydrocarbon components at different temperatures, practically in the range of 30-80 ° C, which leads to a gradual relaxation of stresses caused by the elastic aftereffect;

at the second stage, moisture is removed from the binder component of the charge, and under the influence of the pressure of the forming vapor in the pores, the remaining matrix components are removed (~ 2-3 wt.%);

the melted components of the matrix material are heated, mixed, and fed to the replica secondary manufacturing, which leads to the saving of starting materials and the absence of environmental pollution;

the firing process provides a hollow porous ceramic product with the necessary performance characteristics, and the optimal heat treatment temperatures are determined by the dispersion and chemical ingredients of the ceramic filler.

The device comprises a hollow block 1, including internal elements 2, which are arranged in rows with offset along arcs of concentric circles, a hollow volume 3 formed by internal elements 2 and side walls 4.

The hollow block 1 is made of porous ceramic with radii K. and g of the pairing lines in the upper and lower parts 5 and 6 of the sector element, respectively.

In addition, the device contains an outlet pipe 7, the connection of which with the hollow block 1 is made by a threaded connection with a tight seal 8.

A design feature is that the ratio of the radius r of the interface line between the walls inside the hollow block 1 in the lower part 6 of the sector element to the radius K of the interface line in its upper part 5 is 0.5-0.75.

The arrangement of the internal elements 2 by displaced rows along arcs of concentric circles gives the filtering surface a wave shape, which intensifies the process of picking the cake and its uniform distribution.

The ratio of the radii r and K of the conjugation lines inside the block below 0.5 increases the tensile stress in the upper part of the sector element at the interface of the walls 4, which leads to destructive loads below the strength of the material of the filtering surface when blowing cake, especially when filtering fine-grained products. As a result, the structural strength and the service life of the filter surface are reduced.

The ratio of the radii r and K of the interface lines between the walls 4 inside the block above 0.75 reduces the total filtration area and increases the integral humidity of the cake, which leads to an increase in the drying time.

The threaded connection of the nozzle 7 with the hermetic seal 8 increases the connection between the metal nozzle 7 and the ceramic block 1, and the hermetic seal 8 prevents pressure loss during cake blow-off during the regeneration of the filter surface.

The device operates as follows.

Using the outlet pipe 7, the sector is attached to the hollow shaft of the filter unit. The ceramic disk filter is composed of twelve sectors - ceramic filter elements. During the rotation of the filter unit shaft, the sector of the disk ceramic filter is partially immersed in the reservoir for the substance that needs to be filtered. As a result of suction through the hollow shaft, the filtering process begins through the porous hollow block 1 and the internal elements 2. The filtrate is collected in the hollow volume 3 formed by the internal elements 2 and the side walls 4 of the porous hollow block 1. The incoming filtrate is removed through the outlet pipe 7, the cross section of which allows output per unit time the volume of liquid is not less than the volume of the incoming filtrate.

On the filtering surface of the hollow block 1, a solid precipitate forms, which is removed by a scraper installed at the position of entry of the sector into the tank. The ceramic filter element cleaned of sediment is operational during subsequent cycles of immersion in the reservoir for the substance that needs to be filtered.

As a result of repeated cyclic use of a disk ceramic filter, a thin layer of filtered sediment is formed on the filter surface of the hollow block 1 of the ceramic filter element, which is not removed by a scraper. This layer increases the hydraulic resistance and reduces the performance of the device.

In this case, periodic regeneration of the filtering surface of the hollow block 1 is carried out by back-flushing with regenerating components. Through the outlet pipe 7 serves the regenerating component under excess pressure in the hollow volume 3.

- 4 005787

The increased pore size at the inlet of the regenerating component has little effect on hydraulic flow resistance, and the main pressure is concentrated in areas located near the filtering surface of the hollow block 1, which leads to an intensification of the regeneration process. During regeneration, the internal elements 2 act as stiffeners, increasing the strength of the structure as a whole.

After regeneration, the ceramic filter element is used in subsequent multiple cyclic operating conditions as part of a ceramic disk filter.

Comparative tests have shown that the use of the proposed device in comparison with the known one allows to increase productivity by 2-2.5 times with identical cake moisture.

The table shows the test results of the prototype and the proposed technical solution with a different ratio of the radii of the mates between the walls inside the block.

table 2

Index unit of measurement Prototype The ratio of the radii of the pairing lines 0.5 0.6 0.75 Compressive strength MPa 35 fifty 55 65 Bending strength kN 2.00 6.8 7.0 7.2 Regeneration Pressure (destructive) MPa 0.15 0.45 0.5 0.6 Cake humidity % 11.3-12.4 And, 1 of 12.1

Industrial applicability

The proposed method and device can be widely used in the mining industry in the manufacture of ceramic disk filters designed for filtering pulps of enrichment products.

Claims (4)

CLAIM 1. Ceramic filter element containing a hollow block (1) made of porous ceramics with radii of the mating lines of the walls in the upper and lower parts (5 and 6), including internal elements (2) and a neck with an outlet pipe (7), characterized in that internal elements (2), formed using a removable replica from a mixture of hydrocarbons of the paraffin series, are arranged in rows with a displacement along the arcs of concentric circles and form a hollow volume (3) with the walls (4), and the ratio of the radius of the interface line between the walls is and a hollow block (1) of a given configuration and size, determined by a detachable mold and a replica, in the lower part (6) of the sector element to the radius of the interface line in its upper part (5) is 0.5-0.75, and the relationship the outlet pipe (7) with the hollow block (1) is threaded to the hermetic seal (8). 2. A method of manufacturing a ceramic filter element, including manufacturing a replica of a hollow space, preparing a charge containing a fractionated ceramic filler and a binder, molding a porous preform, drying, removing replica material and firing, characterized in that the replica is made from a mixture of paraffin hydrocarbons, a porous preform formed by pressing, and in a detachable mold put half the estimated amount of the charge, insert into the mold a centering template having the shape of the replica, an impression is made to a depth of half the thickness of the replica, the template is removed and the replica is inserted into the obtained recess, the second half of the calculated quantity of the charge is loaded, the porous block of the given configuration and size is pressed by pressing the upper mold punch and moving it to the calculated value, carry out vibration loading on the upper and lower punches of the mold, remove the workpiece, move it to drying, the replica material is removed at a temperature below the ignition temperature of the hydrocarbon steam Finns series and move it to step reuse, and firing is performed at a temperature of 1250 ± 50 ° C. 3. The method according to claim 2, characterized in that the vibration load is produced within 10-15 seconds. 4. The method according to claim 2, characterized in that the mixture of hydrocarbons of the paraffin series contains wax, paraffin and ozokerite.