JPS58223421A - Filter made of ceramic fiber - Google Patents

Abstract

PURPOSE:To control collecting efficiency and the life of a filter element, by mixing powdered ceramic having larger particle size to a composite of heat-resistant ceramic fibers and powdered ceramic, and forming the mixture by calcination to lower the packing density of a formed body. CONSTITUTION:Ceramic fibers having an average diameter of about 3mu are cut into 0.1-10mm. length, and are dispersed into water together with powdered ceramic of silica-aluminas to make a slurry. Powdered ceramic such as petalite, having 2-500mu particle size is mixed to the slurry, and a flocculant such as an aqueous solution of starch is also added to the admixed slurry to flocculate the powdered ceramic. The flocculated ceramic is formed by a prescribed mold and is dried to calcine the formed ceramic for bonding it at 900-1,300 deg.C. At this time, the bonded ceramic is manufactured into a paper-shaped sheet, and both are wrapped up into a honeycomb body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to a fiber ceramic filter, which is placed in a gas stream containing particulate dust, and is suitable for removing particulate dust. It is an object of the present invention to provide a fiber ceramic fill element.

Conventionally, as a dust filter, there are containers filled with heat-resistant metal LA wire, glass fiber, asbestos fiber, etc. These tend to cause variations in the packing density inside the container, and also have high ventilation resistance. This has resulted in an increase in the exhaust load of internal combustion engines and combustion furnaces, resulting in a decrease in energy efficiency. In addition, the heat resistance is also 100%.
It cannot withstand high temperatures around 0°C (page 2).

On the other hand, there are those that use a honeycomb structure such as cordierite composition obtained by extrusion molding and firing of ceramic powder, and those that form a honeycomb structure by forming a sheet of ceramic powder and making corrugates from it. Filters can also be seen. Since these are made of ceramic, they have excellent heat resistance, but the porosity is only around 40% even if the porosity is large, and the average pore size is 1 μm.
It is extremely small, around m. Therefore, the dust that is passed from door to door and has a large ventilation resistance from the beginning also accumulates on the honeycomb wall surface, which is so-called surface filtration, which tends to cause clogging.

Furthermore, if an attempt is made to increase the porosity and the average pore diameter, the mechanical strength will be extremely reduced, and the wall surface may not be able to withstand the pressure, leading to destruction.

Furthermore, when ceramic fibers are bonded and fired with ceramic powder, sufficient strength can be obtained, but the packing density of the fiber ceramic becomes high, resulting in high ventilation resistance and high pressure loss. On the other hand, the collection efficiency is extremely good and almost all dust in the exhaust gas can be removed, but clogging has already occurred in the thin layer near the surface, shortening the life of the filter element. was. Therefore, the filter must be replaced and regenerated frequently, resulting in a decrease in the energy efficiency and operating efficiency of the internal combustion engine and combustion furnace.

The present invention solves the above-mentioned drawbacks by mixing heat-resistant ceramic fibers such as alumina fibers and silica-alumina fibers into a composite of silica-alumina ceramic powder, and ceramic powder having a larger particle size. The purpose is to lower the packing density of the fiber ceramic and control the collection efficiency and filter element life by molding and firing it.

Microscopic observation of the structure of the filter obtained by the present invention revealed that this is because ceramic powder with a large particle size is mixed in and fired, resulting in a packing density of fiber ceramic around the large ceramic powder. It has become clear that rough areas are more likely to be generated.

5 pages JP-A-58-223421 (2) Describes the manufacturing method of the filter of the present invention Ceramic fibers with an average fiber diameter of about 3 μm are cut into lengths of 0.1 to 10 M and prepared using Honbushi clay, Frogme clay, or sericite clay. Disperse it in water with silica/alumina ceramic powder such as silica/alumina ceramic powder to create a slurry↓. An appropriate amount of ceramic powder such as C petalite, Subosiemen, or fused silica having a particle size of approximately 600 μm is mixed into this slurry and stirred. A flocculant such as a starch solution is added to this to agglomerate the ceramic powder around the ceramic fibers, which is then shaped into a predetermined mold and dried. At this time, if the particle size is 600 μff+ or more, it becomes difficult to uniformly suspend the particles in the slurry. Furthermore, after molding into a suitable structure as a filter element, a fiber ceramic filter element is obtained by performing bonding firing at a temperature within the range of 900 to 1300'C. If a Fourdrinier paper machine is used when forming the slurry with a mold, a long ceramic fiber paper with a predetermined thickness can be produced. This is made into a corrugated shape using a corrugate molding machine, and then laminated with a flat Heher sheet and rolled up to create a no-nickel structure.By firing, it is also possible to obtain a fiber ceramic honeycomb filter element. be.

When the obtained fiber ceramic filter element was observed using a scanning electron microscope, it was found that large ceramic particles were incorporated into the laminated ceramic fibers, and the filling state of the fiber ceramic was found to be at that location. A situation in which sparse voids are formed can be found. These voids were found to be particularly likely to occur around ceramic particles having a large particle size of 3 μm and 1:9, which is the same as the fiber diameter. Therefore, as a result of the existence of these voids around a large number of large particles, the ventilation resistance becomes low and the initial pressure loss becomes small. Furthermore, since dust as well as gas can easily pass through the gaps, the dust removal effect can be exerted even inside the wall of the filter element, and the internal permeation effect can be effectively utilized. Since the dust collection capacity increases due to this internal overloading, the service life becomes longer, and the load on the combustion engine and the internal combustion engine can be reduced, resulting in an increase in energy efficiency.

In addition, since the ceramic fiber is made into a ceramic along with the clay component, it exhibits excellent pressure resistance and heat resistance. For example, for bending strength, the bulk density is 0.3 to O-5'f
With An4, it is possible to obtain 60-10 Nozomi d, and 1000-1
It has the ability to sufficiently withstand high temperatures within the range of 300°C.

Next, an embodiment of the filter according to the present invention will be shown and described.

After cutting 29 parts by weight of silica-alumina ceramic fibers to a fiber length of 0.1 to 10 M using a cutter, the fibers were dispersed in 3000 parts by weight of water together with a small amount of surfactant. On the other hand, 12 parts by weight of Honbushi clay mixed with sericite clay as a ceramic powder was weighed out. As a large particle additive, 4 parts by weight of Betalite powder whose particle size was adjusted to about 100 μm was mixed with the above fractionated clay, and this was suspended in 600 parts by weight of water. These ceramic fiber dispersions and mixed clay suspensions were stirred and mixed to prepare a slurry.

Acrylic emulsion as a binder.

After adding the starch solution and adjusting the viscosity by adding an appropriate amount of polyvinyl alcohol, diluted with 30,000 parts by weight of water, and making paper from this diluted slurry using a Fourdrinier paper machine in a conventional manner to obtain paper with a thickness of 1 inch. A sheet was produced. It has been found that during paper making, the time required for dehydration and drying is shorter than when large particles are not included. The obtained paper sheet is divided into two parts, one of which is formed into a corrugated shape using a corrugated molding machine, and then the other paper sheet is laminated to a flat plate and a certain amount is rolled up. Next, the cell openings of the honeycomb are alternately closed with the same material as the paper sheet, forming a honeycomb in which a large number of cells with one end closed are assembled alternately.

When this nicum was heated at 600"C in an air atmosphere for 1 hour, and then heated and calcined at 1250°C for 1.6 hours,
A honeycomb-shaped fiber ceramic filter element was obtained.

An example of this honeycomb-shaped fiber ceramic filter element is shown in the figure. In the figure, reference numeral 1 denotes a honeycomb-shaped filter element made of fiber ceramic, which is an assembly of a large number of Q honeycomb cells with one end closed.
The closed part 2 and the opening part 3 of the honeycomb cell were placed at one end of the fiber ceramino silica obtained in this example in a constant flow of exhaust gas for a certain period of time, and the characteristics were measured. The results are shown in the table below in comparison with the characteristics of a similar Nirta element prepared without mixing large-sized particles of ':talite powder.

As is clear from the table below, the thickness of the collection layer, that is, the depth at which the dust enters the wall through SEM observation, is measured. , which was observed, confirms that the above-mentioned internal overflow effect is working effectively. Others, initial pressure loss,
Excellent pressure drop increase characteristics and almost the same collection efficiency 2 bending strength! rF property was obtained.

Table on page 9 with blank space Comparison of characteristics with and without petalite powder From the above results, the fiber ceramic filter element containing large-sized particles according to the present invention has particularly low initial pressure loss and pressure drop rise, and has an extremely long life as a filter. Because of its high heat resistance, it reduces the load on combustion furnaces and internal combustion engines, and produces excellent ripple effects such as improving energy efficiency and operational efficiency.

[Brief explanation of drawings]

The figure is a perspective view of one embodiment of a fiber ceramic filter according to the invention. 10, - Filter element, 2... Obstruction part, 3
-Curves/openings.

Claims (1)

[Claims] A fiber ceramic filter 0 characterized in that it is formed by molding and firing a mixture of ceramic fibers and ceramic powder having a particle size larger than the average fiber diameter of the ceramic fibers.