LU83055A1 - FILTER MEDIUM FOR FLUIDS - Google Patents

Description

/ 8451 2.4409 ow "Y f \ f · p

-Q, elj tr h GRAND-DUCHY OF LUXEMBOURG

jju 9 January 19 81 (¾¾¾¾ Minister gvpl>} of the Economy and the Middle Classes

Title issued: ........................................ Intellectual Property Service

--LUXEMBOURG

Request from Breyet of Inention I. Request

The company known as: AIKOH CO., LTD, 1-39, Ikenohata 2-chome, m fafto-ku ”Tokyo, Japan, represented by Mr. Charles München, patent attorney in Luxembourg, acting in the capacity of (2) agent

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to ........ 15. Where women at the Ministry of the Economy and the Middle Classes, in Luxembourg: 1. this request for obtaining a patent for invention concerning: ................ .................................................. .................: ................................ .................................................. .................................................. .................................................. .. (4) "Filter medium for fluids", ............................... ....... .............................................. Tofcÿ ö .. .................................................. ...... T 5 "'December T98 3. description in language _________________ rançai _______________________________ of the invention in two copies; 4 ........ LL ............... drawing plates, in two copies; 5. the receipt of the fees paid to the Luxembourg Registration Office on January 9, 1981 declares (s) assuming responsibility for this declaration, that the inventor (s) is (are) :

Mr. Masaru TAKASHIMA, 1047, Inokata, Komae-shi, Tokyo, ^ "Japon ............” .................... .................'................................ .................................................. .................................................. .................................................. .......

claims (s) for the above patent application the priority of one (s) request (s) of (6) ............. LL .......... .y ................................................ ............. filed in (7) ........................ LJ .... .................................................. ............................................

„The ................................ It ............... .................................................. .................................................. .................................................. .................................................. ............. (8)% ................................. ......................... /. / ...................... .................................................. .................................................. .................................................. ..................................................

on behalf of ........... ................................. fl .. .................................................. .................................................. .................................................. ....................................... (9) elect (elect) for him / her ) and, if appointed, for its representative, in Luxembourg ....................................

lia, b yes evar'd (10) requests (s) the grant of a patent for the invention for the subject described and represented in the abovementioned appendices, with postponement of this grant to .. ....... ..LL ............................... .............. month. (11) / The Π. Deposit Minutes

The above application for a patent for invention has been filed with the Ministry of the Economy and the Middle Classes, Intellectual Property Service in Luxembourg, on: January 9, 1981 / Itß '· Pr. The ^ Minister to P.? . hours / 3 \ t ^ Vle Economy and ^^ Middle Classes,

B Ql D a 68007 ......... / \ X

2.4409 Brief Description filed in support of a request for

PATENT

at

Luxembourg formed by: AIKOH CO., LTD.

for: Filter media for fluids.

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The present invention relates to a filtering medium intended to filter a fluid in the liquid or gaseous state.

Among the filter media for fluids, those made of ceramic material have a higher yield with regard to their resistance to heat and chemicals compared to organic and metallic filter media. Therefore, the filter media made of ceramic material are used. in a wide range of applications

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For example, for filtration, diffusion, recovery, transfer, mixing and foaming of fluids. However, a known and generally used filtering medium made of ceramic material is one whose aggregate consists of ground particles in the form of needles or a mass, this aggregate being obtained by grinding and classifying a mass formed after melting or sintering. natural or artificial ores, or a medium whose aggregate consists of molten glass beads $ therefore, a filtering medium has the following drawbacks: (1) an aggregate of ground particles, which is obtained at from a large molten or sintered mass, contains * internally fine cracks resulting from the shocks exerted during grinding, while the pointed, angular and sharp heads exposed on the surface of the filter medium are easily detached under the stresses of shocks or friction so that they come to mix with the fluid undergoing filtration, This disadvantage can be critical for the elements of a filter which undergo vibrations or shock, or also for the medium filtering a fluid of high viscosity and under high pressure, /? / »(2) The aggregate consisting of crushed particles has a low apparent specific gravity and a poor filling property. Consequently, if the molding pressure is raised to increase the density of the filtering medium, the structure of the latter may be distributed unevenly or the aggregate may be destroyed · (3) Because they are in the form of needles or a mass, the aggregates made up of crushed particles form a larger angle at their mutual points of contact

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and, in addition, they have a smaller contact surface and a smaller number of contact points · In a structure of this type, it may happen that the binder is not effectively concentrated at the contact points because it undergoes a fluidization which softens it, so that it is difficult to improve the mechanical resistance of the filtering medium * (4) The pores formed between the aggregates made up of crushed particles have a curved, helical or looped shape, thus offering an important resistance to filtration of fluids, (5) A filter medium consisting of glass beads as aggregates does not have these drawbacks but, since these glass beads are amorphous, they have both a low impact resistance and low heat resistance.

The Applicant has observed that these drawbacks of a filtering medium made of ceramic material are due to the shape and the properties of the materials specific to the ground particles of the aggregate, as well as to the binding mechanism of these particles and also to the resistance of the aggregate in the case of glass beads 5 therefore, the Applicant has succeeded JC / improve the filter media. (// 7

The present invention relates to a filter medium for fluids, this medium consisting of a sintered body comprising 100 parts by weight of a refractory material based on alumina, more than 95% by weight of this refractory material consisting of spheroids in pellets with a granularity of less than 1 mm, as well as 15 to 30 parts by weight of an inorganic binder in particles with a granularity of less than 40 microns and / or 0.1 to 1 part by weight of lithium oxide, the average pore diameter of this filter medium being in the range of 500 to 1 microns, while its porosity is in the range of 15 to 40 # · The filter medium thus produced can withstand use at high temperatures .

The alumina-based refractory material can be obtained in spherical particles, for example, by a method of injecting a molten substance in which high purity mullite is melted, the molten mass being injected by a nozzle into a reducing atmosphere at a fixed temperature, while compressed gases such as air and argon are blown onto this stream of melt so as to disperse the latter and transform it into pellets. In addition, the refractory material based on alumina in spherical particles can be obtained by a pelletizing and sintering process in which a mixture in the form of a slurry is extruded under pressure by a nozzle, this mixture being obtained by adding a binding agent to the fine high purity mullite powder, for kneading them then, while the mixture thus injected is cut to predetermined lengths; the pieces thus cut are then rolled, in a pelletizing machine, to be transformed into spheroids of the desired granularity, the pas- / mullite thus obtained have a tenacious oristalline structure in which fine mullite crystals are mixed one in 1 * other, while the spherical shape of these crystals is excellent, thus constituting an ideal aggregate. When manufacturing a filter medium using, as an aggregate, an alumina-based refractory material in spherical particles, the average pore diameter of the spheroids can be determined based on the average particle diameter and the filling method. of 1 * aggregate. As a general rule, a filter medium is obtained by mixing the aggregates with an organic binder impregnated with water, while this mixture is then loaded into a mold and, after demolding, the filter medium is subjected to drying and cooking. However, in particular, when a uniform mixture is required, the addition of an organic binder makes it possible to obtain a denser filtering medium.

In other words, in order to exploit the excellent behavior of the refractory material based on alumina in spherical particles during filling, so that the filling ratio approaches the theoretical value and that the binder is strongly concentrated at the contact points of the aggregates j paraffin can be used, for example, as an organic additive and, to carry out these operations effectively, a combination of a hot kneading process and a process is used hot pressing.

The mullite spheroids are loaded into a hot kneading machine to bring them to a temperature in the range of 100 to 150 ° C, then solid paraffin is loaded in a weight ratio of 5 to 7% vis with respect to the aggregates and the mixture is stirred when the surface of the% spheroids is covered with a uniform thickness of molten paraffin.

Second, gradually add an inorganic binder (for example, fine glass powder) previously heated to the same temperature, then stir and within 10 to 15 minutes, you can form a uniform coating layer of the binder . Thirdly, the kneaded material is cooled by passing it through a sieve, then it is gradually dispersed by means of an air stream in order to prevent it from coagulating into a mass due to the viscosity of the paraffin, so that one can obtain a mixture of good fluidity. In the mixture thus obtained, under the effect of the paraffin, the binder adheres firmly hot to the spherical refractory aggregates based on alumina but, when the ambient temperature is reached after cooling, the paraffin has reached a viscosity at this point high that it is almost solid, so that there is no longer any mutual adhesion in the mixture and that the latter has a good fluidity, however it can be dispersed uniformly in each part of the metal mold . This condition is essential if we want to obtain a filtering medium in which the pores are uniformly distributed. If the mixture loaded into the metal mold is then pressurized while being heated to a temperature in the range of 100 to 150 ° C, the paraffin, the viscosity of which is thus reduced, softens by fluidization on the surface of the spheroids together with the binder thus coming to concentrate at the contact points of the aggregates. However, since the binder could come to concentrate at the points of contact of the aggregates in a molding process, inorganic binders can be used in an amount lying in a wider range than in the usual case and this only in function fluidity resulting from viscosity at high temperature. .

In addition, paraffin, the viscosity of which has been reduced pav / 77 / heating, acts as a lubricant between the aggregates, thus making it possible to bring the filling ratio closer to the theoretical value, while the molding pressure is lowered, so that a filter medium can be molded, the density of which is uniformly distributed. These operations carried out during heating and pressurization can be carried out effectively if the aggregates are spherical, but not in the case of aggregates consisting of crushed particles due to the curved surface of the spherical particles.

In the case of a filtering medium made of ceramic material, the binder must be concentrated at the points of contact existing between the aggregates, because the binder adhering to parts other than these points of contact not only does not contribute to bind the aggregates, but in addition, it is detached by mixing with the fluid to be filtered.

When, after cooling, these molded parts are subjected to baking at a sintering temperature (1,320 ° C. in the case of a fine glass powder) of the binder by means of a known oven, the aggregates *

In the filter medium thus obtained for fluids, the filling ratio of the aggregates is high. Consequently, this filter medium has great mechanical resistance, it can withstand pressures greater than 500 kg / cm2 at room temperature, the pores are distributed therein uniformly and, in addition, it has excellent resistance chemicals,

The refractory material based on alumina in spherical particles which will constitute the material of the filtering medium for fluids according to the invention, is chosen from the group comprising industrial alumina containing more than 50 $ by weight of A ^ Og, corundum , mullite, bauxite, diaspore and sillimanite. this refractory material being transformed "into spherical particles by carrying out the steps described above, while it is then used as an aggregate ·

With regard to the granularity of the particles of the refractory material based on alumina, there must be more than 95% by weight of particles of less than 1 mm so that the diameter of the pores of the filtering medium is located in the interval of 500 to 1 microns and the porosity is between 15 and 40% during the manufacture of this filter medium · If the quantity of large particles of more than 1 mm exceeds $%> f the pores of the filter medium will not be not evenly distributed.

As inorganic binder, fine powder of kaolinite, bentonite, agalmatolite, baked and sintered alumina, siliceous rocks, feldspar, porcelain stone and glass having, as much as possible, is used. sintering does not lead to a reduction in the heat resistance of the aggregates, as does a fine mineral powder having specifically sintering properties and chosen from ores such as chromite, apatite and cole-manite. The finer the granularity of the particles, the better the results obtained · However, if the granularity of the particles is less than 40 microns, these ores can be used in practice, The proportion in which the binder is used; can be reduced when it is large aggregates, while it can be increased when the surface area increases as the aggregates become finer. However, even if the amount of binder exceeds 30 parts by weight per 100 parts by weight of aggregates, the binding effect will not be modified in any way * In addition, in this case, there will be an opposite effect giving rise to the coating pores of the filter medium · On the other hand, if less than 15 parts by weight of binder are used, the resistance to pressure of the filter medium decreases even with aggregates whose particles have a granularity of about 1 mm and sometimes there is even a risk of not reaching a pressure resistance of 500 kg / cm2 which is considered to be a value which can be adopted in practice. In addition, as an auxiliary sintering product for the binder, it is possible to use, in a mixture with the latter, lithium fluoride and / or lithium oxide in particles of the same granularity as the binder. However, if the amount of this auxiliary sintering product exceeds 1 part by weight per 100 parts by weight of the aggregates, the melting point of the binder can be lowered, thereby reducing the heat resistance of the filter medium which cannot then be used under a high temperature atmosphere such as that prevailing in a gas blowing nozzle. On the other hand, if the auxiliary sintering product is used in an amount of less than 0.1 part by weight per 100 parts by weight of the aggregates, the effect on adjusting the melting point of the binder is reduced, so much so that it is not practically useful to use this auxiliary sintering product in a smaller amount.

The filter medium for fluids according to the invention, "which is obtained by mixing, molding and baking each of the aforementioned constituent materials in accordance with the above processes, is best suited for the inert gas blowing nozzles or for the plugs intended for the casting of metals, due to its characteristics of resistance to heat. However, it goes without saying that it is also useful for filtration, diffusion, recovery, transfer, mixing and foaming of fluids for which a filtering medium made of ceramic material is used,

The present invention will be described below by way of example with reference to a porous plug intended for an operation "1-10-

Particle size of spherical particles of 1 ”mullite aggregate More than 1 mm $ 0 by weight 1 mm - 500 microns. $ 43 by weight 500 - 350 microns 375g by weight 350 - 177 microns $ 17 by weight I77 - 74 microns $ 3 by weight.

Composition of mixtures:

Spherical mullite aggregates $ 100.0 by weight

Sintered alumina $ 5.0 by weight

Cooked alumina $ 7.5 by weight

Agalmatolite $ 2.0 in weight

Porcelain stone $ 2.0 by weight

Bentonite $ 1.0 by weight

Chromium oxide $ 2.0 by weight

Lithium fluoride $ 0.5 by weight

Apparent specific weight of the molded item: 2.10 g / cm3

Cooking temperature s 1,550 ° C

(l) Ownership of the material of which the product is made:%

Apparent specific weight 2.47 g / em3 * Compressive strength 550 kg / cm2

Porosity $ 26.7

Gas permeation ratio 2.5 cm3 / cm2 »cm * sec.

cm of air column

Average pore diameter 80 microns.

(2) Comparative article:

Ground particles of mullite of the same standardized granularity as that of the invention are mixed with the binder consisting of the same components and in the same ratio and then the mixture is subjected to baking at the same temperature. The material of the article thus trained has the pro ^ nnn q4 · a «0111 · / // / - 11 -

Apparent specific weight: 2.35 g / cm3 Compressive strength î 510 kg / cm2

Porosity; $ 25.5

Gas permeation ratio s 1.5 Cm3 / cm2.cm- sec, · cm of water column.

Both the product of the present invention and the comparative article are installed at the bottom of a 20-tonne ladle as a gas blowing plug having a diameter of 100 mm at its top, a diameter of 150 mm at its base and a height of 200 mm. In this ladle, molten steel is poured brought to a temperature in the range of 1,600 to 1,700 ° C and, via this plug, argon gas is introduced under a pressure of 0.5 at 2 kg / cm2 in order to carry out a degassing treatment for 50 to 90 minutes. At the end of this period, the frequencies of use of the product of the invention and of the comparative article are compared} the following results are obtained s

Product of the invention 3-5 times

Comparative article: * - 1-2 times.

Therefore, there will be an important difference between the product of the invention and the comparative article, the life of the first can be extended from 1.5 · to 5 times co 1 compared to that of the second, / jV

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Claims (3)

1 · Filtering medium for fluids, this medium being a sintered body comprising 100 parts by weight of a material *, * * ♦ * refractory based on alumina of which more than 95% by weight consist of spheroids pelletized with a granularity less than 1 mm, 15 to 30 parts by weight of an inorganic binder in particles of a granularity less than 40 microns and 0.1 to, 1 part by weight of fluoride and / or lithium oxide, the average diameter pores of this filtering medium lying in the range of 500-1 microns, while the porosity is between 15 and 40 $, 2, Filtering medium for fluids, according to claim 1, characterized in that the alumina-based refractory material is chosen from one or more of the following refractory materials with a high alumina content: industrial alumina, corundum, mullite , bauxite, diaspore and sillimanite, 3 # Filter medium for fluids, according to any one of claims 1 and 2, characterized in that% the inorganic binder is chosen from one or more of the following sintered materials: kaolinite, bentonite, agalmatolite, alumina baked or sintered, siliceous stone, feldspar, porcelain stone, glass and other ores, Drawings: —planks ...... Â.1 ..... pages of which —— cover page ..... pages here; description _......... J ... rr: ··? s r’o revenoicatiG ''. __Z _____ c.L.egé descriptif Luxembourg,! E - * · * ·! «^ / ¾