JPS6113845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ceramic filter for purifying high-temperature exhaust gas that removes soot and dust from high-temperature combustion exhaust gas and purifies the exhaust gas.

Combustion exhaust gas discharged from boilers, combustion furnaces, incinerators, etc. of thermal power plants and various factories contains combustible substances such as unburned carbon and tar, gases produced by thermal decomposition, and non-flammable substances such as fly ash. Contains a large amount of dust. All of these substances need to be removed to prevent air pollution, and the exhaust gas purification process generally includes a re-burning process for combustible substances and a dust removal process in the subsequent process.

In other words, in the past, the purification treatment of these combustion exhaust gases was carried out once the combustion exhaust gases were placed in a combustion furnace.
The combustion exhaust gas is guided to the next combustion chamber or to a re-combustion furnace installed separately from the combustion furnace, where unburned combustible substances contained in the combustion exhaust gas are re-burned, and then the combustion exhaust gas is guided to a dust removal device to remove dust. be. There are two known methods for removing dust from exhaust gas: a wet method and a dry method. However, the dry method requires a water treatment device and a mist separator in addition to a dry dust collector. They have drawbacks such as being large and complex, and also requiring troublesome operation and maintenance.
In addition, with the dry method, except for cyclone dust collectors, it is of course impossible to use combustion exhaust gas at a high temperature of about 500°C to 900°C with equipment that uses general electrostatic precipitators or bag filters. For example, when using an electrostatic precipitator, the temperature of high-temperature combustion exhaust gas that is emitted in large quantities is 300℃ to 350℃.
degree, and when using a negative filter
It is necessary to cool down to about 100°C, which requires a large cooling device, which has disadvantages such as making the dust removal equipment complex, large and expensive.

The high-temperature ceramic filter of the present invention has been developed to solve these conventional drawbacks, and can efficiently remove soot and dust contained in the combustion exhaust gas by directly using the high-temperature combustion exhaust gas without cooling it. It collects and removes combustible substances contained in exhaust gas and promotes the combustion of combustible substances contained in exhaust gas. The partition wall near the open end of the cylindrical body has an annular thick part that is thicker than the partition walls in other parts, and the refractory particles forming the bottomed cylindrical body are composed of particles with an average particle size of 60 to 250μ. The porosity of the bottomed cylindrical body is 25% to 45%.
This is a high-temperature ceramic filter that removes soot and dust from combustion exhaust gas.

A more detailed configuration of the present invention will be described based on FIG. 1 showing a specific example. Silica sand, crushed ceramics, metal oxides such as Al ₂ O ₃ , TiO ₂ , ZrO ₂ , silicon carbide, nitride, Refractory particles 2 made of boride or other refractory materials and sized to a predetermined particle size
is made of a fire-resistant binder such as water glass, frit, glaze, etc., into a porous bottomed cylindrical body 1 having air permeability, and has a large number of pores communicating with the inner and outer surfaces. The partition wall 4a near the open end 3 of the bottom cylindrical body 1 has a shape that forms an annular thick portion 5 that is thicker than the partition wall 4b in other parts, and the refractory forming the bottomed cylindrical body particle size 2 or average particle size 60
Ceramic filter made of sized particles of μ to 250 μ, more preferably 120 μ to 160 μ, and the porosity of the bottomed cylindrical body 1 is within the range of 25% to 45%, more preferably 30% to 40%. It is.

That is, in the present invention, the filter has a specific shape, and the particles forming the filter and the porosity of the filter are within a predetermined range. This study revealed a high-temperature filter with a pore structure.

In other words, it is most important that the porosity of the bottomed cylindrical body be within the range of 25% to 45%; if it is less than 25%, the mechanical strength will increase, but the ventilation resistance will increase significantly, making it difficult to use as an exhaust gas filter. It becomes difficult to use it in practice, and if it exceeds 45%, the collection efficiency decreases and mechanical strength decreases, making it difficult to use stably and continuously for a long period of time.

In addition, the average particle size of the refractory particles is 60μ to 250μ.
This is because, in addition to the above-mentioned porosity, pore size is a very important factor in ceramic filters, and if the average particle size of the refractory particles is extremely small, clogging will occur even if the porosity is large. On the other hand, if the particle size is too large, the blow-through phenomenon is likely to occur even if the porosity is small.

Therefore, in order to obtain the optimum pore size for collecting soot and dust, the average particle size of the refractory particles should be set to 60 μm or more.
It is important to size the particles to 250μ; if the average particle size is less than 60μ, the collection efficiency will be high in the short term, but ventilation resistance will increase and clogging will occur after short time use. If it exceeds 250μ, the collection efficiency decreases significantly due to exhaust gas blow-through, and in either case, a practical filter cannot be obtained, which is not preferable. Incidentally, the more uniform the particle diameter of the refractory particles is, the better; however, it is preferable that 80% or more of the refractory particles be contained within a particle size range of ±50 μ of a predetermined average particle diameter.

Further, the wall thickness of the partition wall of the cylindrical part of the ceramic filter may be 5 mm or more, but preferably 10 mm or more.
Approximately 20 mm to 20 mm is best.

Furthermore, as refractory particles, particles made of the above-mentioned refractory material are sufficient, but the higher the exhaust gas temperature or the more harmful gas components in the exhaust gas, the more thermally and chemically stable the particles become. In such cases, particles of alumina, silicon carbide, nitrides, borides, etc. are particularly good, and of course the binder is also more thermally and chemically stable. It is better to use the one that has been prepared.

The high-temperature ceramic filter of the present invention has the above-described structure, and when in use, the thick annular portion 5 is held and suspended in exhaust gas.
Directs high-temperature combustion exhaust gas discharged from various combustion devices from the outside of the ceramic filter toward the inner cylinder.
When the combustion exhaust gas passes through the pores of the partition wall 4b, the soot and dust contained in the combustion exhaust gas are collected and removed on the outer surface of the ceramic filter, and fine dust is collected and removed during the process of passing through the pores. . When combustible substances such as unburned carbon and tar are included in the soot and dust, the combustible substances are burned on the surface of the ceramic filter in a high temperature state. This has the effect of having both a combustion bed and a combustion bed.

As described above, the high-temperature ceramic filter of the present invention is a porous bottomed cylindrical body made of an aggregate of refractory particles and has an air permeability, and the partition wall near the open end of the bottomed cylindrical body is A high-temperature ceramic filter for removing soot and dust from combustion exhaust gas, which has an annular wall thicker than the partition wall of the section, and the refractory particles forming the bottomed cylindrical body have an average particle diameter of 60 μm or more.
The diameter of the cylindrical body must be 250μ and the particles must contain 80% or more of fire-resistant particles within ±50μ of the average particle size, the porosity of the cylindrical body must be between 25% and 45%, and the thickness of the partition wall of the cylindrical part. When the diameter is 5 to 20 mm, it can be expected that the efficiency of collecting and removing soot and dust in the combustion exhaust gas will be significantly improved. Furthermore, since the ceramic filter of the present invention can be used directly for combustion exhaust gas at a high temperature of 500°C to 900°C, it has the effect of completely burning unburned components. Therefore, the dust removal device using the filter of the present invention does not require any cooling device unlike the conventional ones, so the dust removal equipment can be simple and compact, and furthermore, it does not require post-treatment. Moreover, it has a pore structure most suitable for collecting and removing soot and dust in combustion exhaust gas by having an average pore part and pore volume within a predetermined numerically limited range,
This filter has extremely high collection efficiency. In addition, when flammable substances such as carbon and tar are included in the soot and dust, it is expected that the dust removal effect will be improved by burning the flammable substances on the surface of the ceramic filter in a high temperature state. The ceramic filter of the present invention has many advantages such as being effective in both dust removal and a combustion bed, and is therefore an extremely useful filter that is useful for preventing air pollution.

[Brief explanation of the drawing]

FIG. 1 is an explanatory longitudinal cross-sectional view showing a specific example of the high temperature ceramic filter of the present invention. 1... Bottomed cylindrical body, 2... Fire-resistant particles, 3...
Opening end, 4a... partition wall near the opening end, 4b... partition wall, 5... annular thick part.

Claims (1)

[Claims] 1 Combustion in which a porous bottomed cylindrical body made of an aggregate of refractory particles has an air permeability, and the partition wall near the open end of the bottomed cylindrical body has an annular thick part that is thicker than the partition walls in other parts. In high-temperature ceramic filters that remove soot and dust from exhaust gas, the refractory particles forming the bottomed cylindrical body have an average particle diameter of 60μ to 250μ.
and within the range of ±50 μ of the particle size of the average particle size 80
% or more of refractory particles, the porosity of the cylindrical body is 25% to 45%, and the wall thickness of the partition wall of the cylindrical part is 5 to 20 mm. A high-temperature ceramic filter that removes soot and dust inside.