JPS61268332A - Dust removal purifying apparatus - Google Patents

Abstract

PURPOSE:To obtain the titled apparatus capable of stably performing dust removal even if the temp. of dust-containing gas changes, by supporting a catalyst for making the harmful component in dust-containing gas innoxious in a ceramic filter cylinder and setting the thickness of the filter cylinder to 3mm or more. CONSTITUTION:A filter cylinder 1 made of porous ceramics having air permeability supports a catalyst for making the harmful component in dust-containing gas innoxious so as to arrange the same through a water cooling tube plates 2. The wall thickness of the filter cylinder 1 is set to 3mm or more in order not only to hold the heat accumulation action of the dust-containing gas but also the temp. of the dust-containing gas passing through the wall of the filter cylinder 1 to a degree preventing the lowering in the activity of the calalyst. Further, the filter cylinder 1 is opened at the upper and lower ends thereof so as to largely fall collected dust. Therefore, not only the dust removal of the dust-containing gas is performed but also the harmful component is made innoxious and stable purification can be performed even if the temp. of the dust-containing gas changes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a dust removal and purification device having a filter cylinder made of porous ceramics.

[Prior art and its problems] In recent years, various dust removal and purification devices using porous ceramics having air permeability as a filter material have been proposed for application to dust removal and purification, particularly of high-temperature exhaust gas. For example, those using ceramic foam or filter tubes made of porous ceramics (Japanese Patent Laid-Open No. 58-20E
i028, JP-A No. 58-225721), etc. are known.

However, in addition to dust, high-temperature exhaust gas contains harmful components such as hydrocarbons (HC), carbon oxides (CO), and nitrogen oxides (NOx), which cause pollution such as bad odors. It has become. It has been difficult to remove such harmful components simply by passing through the porous ceramic wall as described above.

On the other hand, it is used to remove carbon particles and unburned hydrocarbons contained in exhaust gas from diesel engines, etc.
A device using a ceramic honeycomb body is known (see JP-A-57-1361122). This dust removal and purification device closes the cells of a ceramic honeycomb body alternately (in a checkered pattern), supports a catalyst on the wall of the ceramic honeycomb body, and allows exhaust gas to flow in from one end face and purify gas from the other end face. It is designed to flow out.

That is, when the exhaust gas passes through the walls of the cells of the ceramic honeycomb body, carbon particles are collected, reburned, and gasified. Further, unburned hydrocarbons are oxidized by the catalyst and deodorized.

However, in the above-mentioned dust removal and purification device, since the walls of the cells of the ceramic honeycomb body are formed extremely thin, there is a risk that the thin walls will melt when the carbon particles are reburned. Also, the activity of the supported catalyst could be reduced as carbon particles were deposited in the thin walls of the cells. Furthermore, the work of alternately closing the cells of the ceramic honeycomb body was extremely difficult.

In addition, exhaust gas after preheating scrap in an electric furnace in a steel factory contains a large amount of dust and odor generated from organic matter contained in the scrap, and is a source of pollution. In this case, since the scrap preheating device in the electric furnace is a batch process, the temperature of the exhaust gas varies from 50 to 800°C. Therefore, when attempting to treat this exhaust gas with an oxidation catalyst as in the above-mentioned dust removal and purification device, the activation temperature of the oxidation catalyst is usually 240°C or higher, so when the temperature of the exhaust gas drops, the catalytic action is not performed. The deodorizing effect becomes insufficient.

"Objective of the Invention" The object of the present invention is to solve the problems of the prior art described above, to remove dust from a dust-containing gas, to render harmful components harmless, and to prevent the temperature of the dust-containing gas from fluctuating roughly. Another object of the present invention is to provide a dust removal and purification device that can perform stable cleaning.

"Structure of the Invention" The dust removal and purification device according to the present invention introduces dust-containing gas from one side of a filter cylinder made of porous ceramics having air permeability, and
A device for extracting clean gas from the other side by passing through the wall of the filter cylinder, wherein the filter cylinder supports a catalyst that renders harmful components in the dust-containing gas harmless, and the wall of the filter cylinder It is characterized by having a thickness of 3III1 or more.

Therefore, the dust contained in the dust-containing gas is collected and removed when passing through the wall of the filter tube, and harmful components are rendered harmless by the catalyst. In addition, even if the temperature of the dust-containing gas fluctuates, the thickness of the wall of the filter cylinder is 3 mm or more, so it has a heat storage effect, and the temperature of the dust-containing gas passing through the wall of the filter cylinder is kept to a level that does not reduce the activity of the catalyst. can be kept. In addition, the thickness of the wall of the filter tube is more preferably 5 mm or more in order to further enhance the heat storage effect. On the other hand, if the wall thickness of the filter tube is too large, it will not be easy to manufacture and will be susceptible to thermal shock, so it is preferably 20 mm or less.

According to a preferred embodiment of the present invention, the catalyst is supported on the side of the filter cylinder from which the dust-containing gas is cleaned and flows out. In other words, the dust in the dust-containing gas is mainly collected on the gas inflow side of the filter cylinder, but if the catalyst is buried in the dust, its effect is weakened, so the catalyst is supported on the gas outflow side. This is because it is possible to prevent a decrease in the activity of the catalyst.

However, in the present invention, the catalyst may be supported on the dust-containing gas inflow side surface of the filter cylinder or inside the wall of the filter cylinder. The method of supporting the catalyst is to coat the catalyst liquid on the wall of the filter cylinder.
Various methods can be employed, including a method of immersing a filter tube in a catalyst liquid, and a method of forming a filter tube by mixing a catalyst in a ceramic material.

According to another preferred embodiment of the invention, the catalyst is an oxidation catalyst. By using an oxidation catalyst, combustible components such as hydrocarbons and carbon oxides in the dust-containing gas can be oxidized to be deodorized and rendered harmless. As the oxidation catalyst, for example, a platinum-based catalyst or a palladium-based catalyst can be used. however,
In the present invention, a reduction catalyst can also be used particularly for dust-containing gas containing Now and the like.

According to a further preferred embodiment of the invention, the dust-containing gas is introduced into the inside of the filter cylinder. By feeding the dust-containing gas into the inside of the filter cylinder, the pressure for feeding the dust-containing gas can be increased, and the collected dust can be easily removed.

According to a further preferred embodiment of the present invention, the filter tube is made of porous ceramics with an average pore diameter of 50 ILI11 or less. This is because if the average pore diameter exceeds 501L+1, a sufficient dust removal effect cannot be obtained, and dust easily flows into the inside of the wall and causes clogging.

Note that various materials such as cordierite, β-subodumene, alumina, mullite, and aluminum titanate can be used as the material for the filter cylinder.

The shape of the filter tubes is not particularly limited, such as cylindrical or square tubes, but it is preferable to provide a large number of cylindrical tubes from the viewpoint of ease of manufacture and increasing the filtration area.

"Embodiment of the Invention" FIGS. 1 and 2 show an embodiment of the dust removal and purification apparatus according to the present invention. A large number of filter tubes 1 made of air-permeable porous ceramics are arranged in parallel with each other, both ends of which are supported by a water-cooled tube plate 2 and sealed by an appropriate method. The water-cooled tube plate 2 has a water inlet 3 and a water outlet 4. In this embodiment, a group of filter cylinders 1 supported by a water-cooled tube plate 2 are arranged in five stages in the vertical direction with the water-cooled tube plate 2 interposed therebetween. The filter cylinders 1 corresponding to the vertical direction are vertically communicated at the position of the water-cooled tube plate 2, and constitute a tube extending long in the vertical direction. In addition, clean gas outlets 6 are provided in the can wall 5 surrounding the outer periphery, corresponding to each stage divided by the water-cooled tube plate 2. Further, a header 8 having a dust-containing gas lower part is attached to the uppermost water-cooled tube plate 2. Further, a dust hopper 8 is attached to the lowermost water-cooled tube plate 2.

In this example, each filter tube l is made of cordierite ceramics with an average pore diameter of 30 pLm, and an outer diameter of 17
0mm, inner diameter 140am, wall thickness 15+am, and length 2m. Further, a platinum thread oxidation catalyst is coated and supported on the outer periphery of the wall of the filter cylinder l. In each stage divided by the water-cooled tube plate 2, 23 filter cylinders are arranged parallel to each other. Furthermore, by connecting the filter cylinders 1 in five stages vertically, the length of the connected filter cylinders 1 in the vertical direction is 10 m in total.

In this dust removal and purification device, dust-containing gas G is introduced from a dust-containing gas-containing lower part, passes through a header 8, and flows into each filter cylinder 1. Then, when passing through the wall of the filter tube l, the filter tube l
Dust is collected on the inner surface of the wall. In this case, large pieces of dust fall downward due to inertia and gravity and are collected in the dust hopper 8. Also, most of the small dust aggregates and falls downward, but some of the small dust falls into the filter tube.
deposits on the inner surface of the gas, increasing the pressure drop of the gas passing through it.

However, this can be removed by backwashing regularly. Backwashing is performed by force-feeding air or nitrogen gas backflow through the clean gas supply 6 to brush off dust accumulated on the inner surface of the filter cylinder 1.

In this dust removal and purification device, the water-cooled tube plate 2 is used to
Since it is divided into chambers, backwashing can be performed in each chamber sequentially during operation of the device. Furthermore, the dust-containing gas G is
When passing through the wall from the inside to the outside, it comes into contact with a platinum-based oxidation catalyst supported on the outer periphery of the filter cylinder 1, and the hydrocarbons, carbon monoxide, etc. contained therein are oxidized and deodorized. In this dust removal and purification device, since the platinum-based oxidation catalyst is supported on the outer periphery of the filter cylinder 1, the catalytic action will not be weakened by being buried in dust. In this way, the obtained clean gas G° is
The clean gas flows out from the outlet 6.

When this dust removal and purification device is applied to exhaust gas after preheating of electric furnace scrap in a steel factory, the temperature of the exhaust gas changes from 50 to 800°C because of batch processing as described above. However, in this dust removal and purification device, the wall of the filter cylinder 1 has a thickness of 15 layers, so it has a heat storage effect, so even if the exhaust gas temperature drops to 100°C or lower for a short time,
The temperature of the gas passing through the wall of the filter cylinder 1 can be maintained above 240° C. without reducing the activity of the catalyst.

In the above embodiment, the gas throughput is about 3200 Nrn"/h, and the actual flow rate of gas passing through the wall of the filter cylinder 1 is about 3 cm/s.
However, it is preferable to change the length, number, and number of vertical stages of the filter cylinder 1 as appropriate depending on the gas amount and gas temperature. Furthermore, it is also possible to reduce the cost by changing the gas temperature and the sealing structure without water-cooling the water-cooled tube plate 2.

FIG. 3 shows another embodiment of the dust removal and purification apparatus according to the present invention. In this embodiment, a large number of filter tubes 1 made of air-permeable porous ceramics are arranged parallel to each other, and both ends of the filter tubes 1 are supported by a tube plate 2' which is not water-cooled, and are sealed by an appropriate method. There is. A header 8 having a dust-containing gas lower and a burner 10 is attached to the upper tube sheet 2''.A dust hopper 8 is attached to the lower tube sheet 2''. A clean gas outlet 6 is formed in the can wall 5 surrounding the outer periphery.

Further, a platinum-based oxidation catalyst is supported on the outer periphery of each filter cylinder 1. In this example, the filter tube 1 has an average pore diameter of 2
Made of cordierite ceramics with a diameter of 0.8 mm, the outer diameter is 83 mm, the inner diameter is 43 mm, the wall thickness is 10 mm, and the length is 24 mm.
00mm, and 14 pieces are arranged in parallel in the horizontal direction.

When this dust removal and purification device is applied to exhaust gas from a diesel engine, etc., the exhaust gas is introduced from the dust-containing gas lower.
It passes through the header 9 and flows into each filter cylinder 1. and,
When passing through the wall of each filter tube 1, unburned carbon particles are collected on the inner surface of the filter tube 1. Most of the carbon particles fall downward and are collected in the dust hopper 9, and the rest of the carbon particles are deposited on the inner surface of the filter tube l. Furthermore, when the exhaust gas passes through the wall of the filter tube 1, the unburned hydrocarbons and carbon monoxide contained therein are oxidized and deodorized by the platinum-based oxidation catalyst supported on the outer periphery of the filter tube 1. . The clean gas thus obtained flows out from the clean gas outlet 6. In the case of this embodiment, for example, when exhaust gas from a 100 horsepower diesel engine is introduced, almost 100% of carbon particles can be captured, and the odor of the exhaust gas can be deodorized to such an extent that the odor is no longer felt. When carbon particles accumulate on the inner surface of the filter cylinder 1 and the pressure loss of the exhaust gas exceeds a certain value, the burner 10 is combusted to send high-temperature gas.
The deposited carbon particles can be removed by self-combustion. In this case, since the deposited carbon particles are burned in a short time, the action of the platinum-based oxidation catalyst supported on the outer periphery of the filter cylinder 1 is not inhibited. Further, since the wall thickness of the filter tube 1 is 10 mm, there is no problem that the wall melts when the carbon particles self-combust.

Furthermore, by passing exhaust gas from a diesel engine or the like through this dust removal and purification device, an excellent noise reduction effect can be obtained.

"Effects of the Invention" As explained above, according to the present invention, a catalyst that detoxifies harmful components in dust-containing gas is supported on a filter cylinder made of porous ceramics having air permeability. Not only can dust be removed from the gas, but also harmful components contained in the gas can be rendered harmless by the catalyst. Further, since the wall thickness of the filter cylinder is set to be 3 mm or more, the activity of the catalyst can be maintained at a good level due to the heat storage effect of the filter cylinder even if the temperature of the dust-containing gas fluctuates. Furthermore, there is no risk that the wall of the filter tube will melt when the dust accumulated on the filter tube is caused to self-combust and disappear.

Furthermore, since the upper and lower ends of the filter cylinder are open, much of the collected dust falls. Therefore, in the case of filter cylinders in which one end of the filter cylinder is alternately closed, as in the prior art,
It is necessary to reburn all of the collected carbon particles, and severe heat resistance is required for the catalyst and filter tube, but the present invention reduces this burden. In addition, the exhaust gas from the electric furnace scrap preheating device contains a considerable amount of nonflammable dust, which accumulates in a filter cylinder with a closed end, but as in the present invention, the upper and lower ends are open. By doing so, this problem is also avoided.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the dust removal and purification device according to the present invention, FIG. 2 is a plan view of the same dust removal and purification device, and FIG. 3 is a view showing another actual flow side of the dust removal and purification device according to the present invention. FIG. In the figure, l is a filter tube, 2 is a water-cooled tube sheet, 2' is a tube sheet that is not water-cooled, 5 is a can wall, 8 is a clean gas outlet, 7 is a dust-containing gas inlet, 8 is a ladder, and 8 is a dust Hopper, G is dust-containing gas,
Go is a clean gas.

Claims (5)

[Claims] (1) In a dust removal and purification device, a dust-containing gas is introduced from one side of a filter tube made of porous ceramics having air permeability, and the clean gas is extracted from the other side after passing through the wall of the filter tube. A dust removal and purification device characterized in that the filter cylinder supports a catalyst that renders harmful components in the dust-containing gas harmless, and the wall thickness of the filter cylinder is 3 mm or more. (2) The dust removal and purification device according to claim 1, wherein the catalyst is supported on the surface of the filter cylinder on the side from which the dust-containing gas is cleaned and flows out. (3) The dust removal and purification device according to claim 1 or 2, wherein the catalyst is an oxidation catalyst. (4) The dust removal and purification device according to any one of claims 1 to 3, wherein the dust-containing gas is fed into the inside of the filter cylinder. (5) The dust removal and purification device according to any one of claims 1 to 4, wherein the filter tube is made of porous ceramics with an average pore diameter of 50 μm or less.