JP2001038117A - Dust removing and hazardous gas cracking apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously achieve a dust removal action and harmless action with a single apparatus by removing the dust in gaseous dust and simultaneously cracking the NOx and organic chlorine compounds in the gaseous dust to make the dust harmless by using filter cylinders consisting of ceramic fiber nonwoven fabrics on which catalysts are uniformly dispersed and deposited. SOLUTION: Waste combustion gases are supplied from a gas duct 10 and after gaseous ammonia is filled from a filling device 11 during the course of this supply, the gaseous ammonia is introduced from an inlet 6 into a vessel body 1. The dust is removed by the one-side wall surfaces 12 of the filter cylinders 2 consisting of the ceramic fiber nonwoven fabric on which the catalysts are dispersed and deposited and thereafter, the gas is introduced into the filter cylinders 2 where the NOx and organic chlorine compounds are cracked and made harmless by the effect of the catalysts. The cleaned gas is thereafter made to flow out of the other wall surfaces of the filter cylinders 2 and are discharged through a gathering section 13 to an apparatus outlet 8. On the other hand, compressed air is injected from a back washing device 9 to the gathering section 13 to peel and dislodge the dust 14 deposited in the filter cylinders 2s. This dust is dropped into a lower hopper 7 and is discharged from a dust outlet 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a waste incinerator,
Removal of dust in dust-containing gas emitted from combustion equipment using fossil fuels such as coal, various industrial furnaces for iron and metallurgy, cement firing furnaces, refractory firing furnaces, petroleum refining facilities, chemical plants, etc. , Nitrogen oxides and organochlorine compounds,
The present invention relates to a dust removal and harmful gas decomposition device that decomposes and detoxifies using a catalyst.

[0002]

2. Description of the Related Art Exhaust gas from a combustion furnace is removed, and nitrogen oxides and PCDD (polychlorinated dibenzodioxin, PCD) are removed.
FIG. 3 shows a typical example of a conventional system in which an organic chlorine compound such as DF (polychlorinated dibenzofuran) is decomposed and made harmless. The case where a bag filter (candle filter) using an externally-collected type bag filter using a woven cloth made of polycarbonate, which is very popular, will be described below.

[0003] Exhaust gas from the combustion furnace passes through a duct 101, is cooled to a temperature of 200 ° C. or less by a temperature reducer 102 using a water spray or a heat exchanger, and enters a bag filter inlet 103. The combustion exhaust gas flowing into the hopper of the can 104 is collected on the outer surface of the filter tube 105, becomes a gas containing no dust, and flows out of the gas outlet 107 via the gas collecting unit 106.

[0004] The dust accumulated on the outer surface of the filter tube 105 is periodically blown into the inside of the filter tube 105 by compressed air by the backwashing device 108 to increase the internal pressure of the filter tube 105 to peel off and remove the dust. The dust that has come off from the hopper 109
It falls in the direction of 0 and is discharged out of the system by a cut-off valve or a screw conveyor (not shown).

[0005] Combustion exhaust gas containing no dust from the gas outlet 107 has a temperature at which the heating device 111 can decompose nitrogen oxides and organic chlorine compounds most efficiently.
The temperature is raised from 0 ° C. to 350 ° C., and the mixed gas of the ammonia and the combustion exhaust gas injected by the ammonia injector 113 enters the inlet 115 of the can 114 of the decomposer. Thereafter, the mixed gas of ammonia and the combustion exhaust gas flows through the honeycomb groups 116, 117, and 118 supporting the catalyst through arrows 11
9, 120, 121 sequentially,
4 is discharged in the direction of arrow 123 from outlet 122.

[0006]

As described above,
In the conventional technology, two types of equipment, a dust removing device with a single function and a nitrogen oxide and organic chlorine compound decomposing device, are connected to the series to perform dust removal and decomposition of nitrogen oxide and organic chlorine compound respectively. I was going alone. In addition, in front of the dust remover, the gas cooler cools down to 200 ° C or less, and after leaving the dust remover, the heating device increases the temperature from 300 ° C to 350 ° C. This has led to an increase in cost and complexity of operation and control.

As a material for the filter tube of the bag filter, in addition to the above-mentioned woven fabric made of polycarbonate resin, for example, there is an example in which a nonwoven fabric of ceramic fibers made of an alumina-silica compound is used. Since no catalyst is supported, a facility for decomposing nitrogen oxides and organochlorine compounds consisting of a honeycomb or the like carrying a catalyst in the downstream is required as in the case of the bag filter using the polycarbonate woven fabric.

Accordingly, an object of the present invention is to provide a dust removal and harmful gas decomposition apparatus capable of simultaneously achieving dust removal and decomposition of nitrogen oxides and organic chlorine compounds in combustion exhaust gas with one apparatus.

[0009]

In order to achieve the above object, a dust removing and harmful gas decomposing apparatus according to the first aspect of the present invention uses a filter tube made of a ceramic fiber non-woven fabric in which a catalyst is dispersed and supported substantially uniformly. To remove the dust in the dust-containing gas and to decompose and detoxify nitrogen oxides and organic chlorine compounds such as PCDD (polychlorinated dibenzodioxin, PCDF (polychlorinated dibenzofuran)) contained in the dust-containing gas. Features.

The shape of the filter tube may be a cylindrical shape with both ends open or a cylindrical shape (candle type) with one end open and the other end closed. However, in the case of using a cylindrical filter cylinder having both open ends, as shown in Fig. 1, the upper and lower ends of the cylinder are supported by tube sheets, dust-containing gas is passed inside the cylinder, and the inner wall surface of the cylinder is used. A so-called internal dust collection system is employed, in which flue gas that is dust-free and does not contain dust flows from the inner surface of the filter tube to the outside surface of the filter tube through the inside of the filter tube wall.

In the case of using a so-called candle-type filter tube having one end opened and the other end closed, as shown in FIG. 2, the upper end of the opened cylinder is supported by a tube sheet, The dust-containing gas is guided to the outside of the cylinder, dust is removed from the outer wall of the cylinder, and the flue gas containing no dust flows from the outer surface of the filter through the inside of the filter wall to the inner surface of the filter. Do
A so-called external dust collection system is used.

In any of the above methods, when the combustion gas passes through the inside of the filter tube wall, nitrogen oxides and organic chlorine compounds contained in the combustion gas are dispersed and supported inside the filter tube wall. Decomposed by the catalyst and detoxified.

For the purpose of decomposing nitrogen oxides, a facility for injecting ammonia, which is a reducing agent for nitrogen oxides, into an upstream pipe of a dust-containing gas inlet pipe of the dust removing and harmful gas decomposing apparatus according to the present invention. In addition, a mixing zone for uniformly dispersing the injected ammonia in the combustion exhaust gas is required. However, for the purpose of decomposing only the organic chlorine compound, injection of ammonia is unnecessary.

Any ceramic fiber can be used as long as it has heat resistance of at least 500 ° C. or more, has corrosion resistance to combustion exhaust gas, and can form a nonwoven fabric. Fiber consisting of a single component of alumina, silica, titania, magnesia, glass, silicon carbide, silicon nitride, or a fiber consisting of these compounds, or a ceramic fiber consisting of a composite composition of these fibers has heat resistance, corrosion resistance and Particularly preferred in terms of marketability.

The filter tube made of a ceramic fiber non-woven fabric carrying a catalyst has a ceramic fiber having a fiber diameter in the range of 1 to 10 μm and a fiber length of at least 10 mm or more, at least 50% of which is a ceramic fiber. In a nonwoven fabric having a thickness of at least 10 mm or more, a powdery catalyst having an average particle diameter of 20 μm or more and 80 μm or less made of vanadium pentoxide or tungsten trioxide or a mixture of both is substantially uniformly dispersed and supported. To form a filter tube.

When the diameter of the ceramic fiber constituting the filter tube is less than 1 micron, there is a difficulty in fiber production technology. When the diameter of the fiber exceeds 10 microns, the toughness of the fiber is reduced and the fiber is easily broken. This makes it difficult to construct a filter tube, which is not preferable.

The thickness of the ceramic fiber non-woven fabric supporting the catalyst constituting the filter tube is such that the catalyst dispersed and supported inside the filter tube and the gas passing through the filter tube are sufficiently in contact with each other, and nitrogen oxides and organic chlorine In order to reduce the compound below the environmental emission standard value, it is necessary to secure a thickness of 10 mm or more and secure a residence time of the gas in the filter tube of at least 0.5 seconds or more. In addition, a thickness of 10 mm or more is necessary for giving the filter tube strength as a structure.

The powdery catalyst supported in the filter tube made of the nonwoven fabric made of ceramic fibers has an average particle size of 20 μm to 80 μm, and 5% to 25% by weight of the total weight of the filter tube. Is desirably within the range.

The reason is that if the average particle size of the catalyst is 20 microns or less, the activity as a catalyst is reduced, and
In particular, in the case of manufacturing a filter tube by filtering a mixed solution of catalyst powder and ceramic fibers, the catalyst passes without being caught by the filter body, and as a result, the amount of catalyst to be discarded increases and the catalyst yield decreases. It depends. The average particle size of the catalyst is 80.
In the case of a micron or more, the specific surface area per unit weight of the catalyst is reduced, and the efficiency per weight of the catalyst is reduced. In addition, particularly when a mixed solution of the catalyst powder and the ceramic fiber is filtered to manufacture a filter tube. This is because the catalyst does not sufficiently disperse and float in the mixed solution and settles and accumulates at the bottom of the container. As a result, the amount of discarded catalyst increases and the catalyst yield decreases.

When the ratio of the powdery catalyst to the weight of the filter tube is 5% by weight or less, the powdery catalyst carried in the filter tube made of the ceramic fiber non-woven fabric penetrates through the ceramic fiber filter tube wall. Since the nitrogen oxides and the organochlorine compounds in the flowing combustion exhaust gas do not sufficiently come into contact with the catalyst and pass through, the ratio of the exhausted gas without being decomposed increases, which is not preferable. The ratio of the powdery catalyst in the filter tube 2 is 2
If the content is 5% by weight or more, the proportion of the powdery substance in the nonwoven fabric made of ceramic fibers increases, and the mechanical strength of the filter tube 2 decreases, which is not preferable.

As the catalyst dispersed and supported in the filter tube, a catalyst which has been previously formed into a powdery catalyst using titanium oxide having a high affinity for vanadium pentoxide and tungsten trioxide as a carrier may be used. it can.

Further, it is desirable that the porosity of the filter tube made of ceramic fiber non-woven fabric supporting the catalyst is 80% or more and 95% or less. The reason is that at a porosity of 80% or less, the packing density of the ceramic fibers per unit volume becomes excessive, and the pressure loss of the gas passing through the filter tube wall increases,
This causes an increase in the power of the suction blower or the forced blower to the combustor in the flue gas system. On the other hand, when the porosity is 95% or more, the packing density of the ceramic fibers per unit volume becomes too low, and the mechanical strength of the filter tube is reduced. Is insufficient, and it becomes impossible to configure as a dust removing device.

As a method for manufacturing a filter tube made of ceramic fiber in which a catalyst is dispersed and supported, for example, a single component or a composite component of a metal sol such as alumina sol, silica sol and titanium sol, and a surfactant such as starch are used. While adding and stirring the catalyst powder in the aqueous solution consisting of the agent, the ceramic fibers are sequentially charged to form a slurry-like mixed solution of the catalyst and the ceramic fibers, and then only the solid content is captured and the liquid component is permeated. Pour into a mold that can
After the drying treatment, the molded body can be removed from the mold and subjected to a baking treatment to obtain a molded body.

Alternatively, more ceramic fibers are put into the mixed solution comprising the metal sol, the surfactant and the catalyst, and a plastic gel material comprising the catalyst and the ceramic fibers is formed. A compact may be obtained by performing a drying treatment and a baking treatment.

In order to verify that the decomposition of the nitrogen oxide and the organochlorine compound described above can be simultaneously realized,
Monochlorobenzene (MCB), a pseudo-dioxin for which the correlation of decomposition characteristics with actual dioxins has been obtained.
, A test for confirming the decomposition characteristics of nitrogen oxides and organic chlorine compounds was carried out.

Tables 1 and 2 show the ceramic fiber non-woven fabric and the catalyst which were subjected to the test, and the test conditions and test results carried out using these materials. From the above test results, it has been clarified that dust removal and decomposition of nitrogen oxides and organochlorine compounds according to the present invention can be realized by a filter tube made of a ceramic fiber non-woven fabric supporting a catalyst.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of a dust removing device and a harmful gas decomposing device according to the present invention, which is a so-called internal dust collecting type dust removing device and a harmful gas decomposing device using a cylindrical filter tube having both open ends. , A can body 1 and a non-woven filter tube made of a ceramic fiber having a cylindrical shape open at both ends.
A plurality of filter tubes 2 each comprising a powdery catalyst made of vanadium pentoxide or tungsten trioxide or a mixture of both dispersed and supported substantially uniformly in the thickness direction of the filter tubes; A filter unit 5 comprising a pair of tubesheets 3 and 4; a dust-containing gas inlet pipe 6 connected to the can body communicating with the filter unit; and a unit for collecting and discharging dust removed by the filter unit. A dust hopper 7 provided in a lower space of the can body, a clean gas outlet pipe 8 for taking out a clean gas obtained through a filter tube wall of the filter unit to the outside of the can body, and a surface of the filter tube. It is characterized by comprising a backwashing device 9 for removing dust adhering to the air, and an ammonia injection device 11 provided in the middle of a pipe 10 connected to the dust-containing gas inlet pipe 6.

FIG. 2 shows another embodiment of the dust removing device and the harmful gas decomposing device according to the present invention, which is a so-called external dust collecting type dust removing device using a cylindrical filter tube having one end opened and the other end closed. A powdery catalyst made of vanadium pentoxide or tungsten trioxide or a mixture of both in a can body 1 and a filter tube of a non-woven fabric made of a cylindrical ceramic fiber having an open upper end and a closed lower end in a can body 1. A plurality of filter tubes 2 which are substantially uniformly dispersed and supported in the thickness direction of the filter tubes, a filter unit 5 comprising a tube sheet 3 for supporting the upper end of the filter tubes and hanging the filter tubes, A dust-containing gas inlet pipe 6 connected to the can body communicating with the filter unit; and a dust hopper 7 provided in a lower space of the can body for collecting and discharging dust removed by the filter unit. And the filter unit A clean gas outlet pipe 8 for taking out the clean gas obtained through the filter tube wall to the outside of the can body, a backwashing device 9 for removing dust adhering to the surface of the filter tube, and a dust-containing gas inlet tube 6 It is characterized by comprising an ammonia injection device 11 provided in the middle of a pipe 10 to be connected. Note that among the symbols in the drawing, those having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

In any of the dust removers and harmful gas decomposers shown in FIGS. 1 and 2, the combustion exhaust gas containing nitrogen oxides and organic chlorine compounds passes through a gas duct 10.
It is mixed with the ammonia injected from the ammonia injection device 11, guided into the device through the harmful gas decomposition device inlet 6, and is dust-removed on the gas inflow side wall surface 12 of the filter tube 2 made of a ceramic fiber non-woven fabric carrying a catalyst. It flows into the inside of the cylinder wall. The gas that has flowed into the inside of the filter tube wall is decomposed and detoxified by the action of the catalyst dispersed and supported inside the filter tube wall, and flows out from the gas outflow side wall surface 13 of the filter tube. I do. The detoxified gas flowing out of the filter tube 2 is discharged from the device outlet 8 in the direction of the arrow 15 through the collecting portion 14.

In the internal dust collecting type dust removing device and harmful gas decomposing device shown in FIG. 1, compressed air is periodically injected by the backwashing device 9 to increase the internal pressure of the clean gas collecting portion 13, and the filter cylinder inner surface 12 The dust that has accumulated on the surface is peeled off and dropped, and dropped into the lower hopper. The dust 14 that has fallen into the lower hopper is discharged in the direction of arrow 15 by a dust extraction valve or a screw conveyor (not shown).

In the external dust collecting type dust removing device and harmful gas decomposing device shown in FIG. 2, compressed air is periodically injected by the backwashing device 9 to increase the internal pressure of the clean gas collecting portion 13.
The dust accumulated on the outer surface 16 of the filter tube is peeled off and dropped, and is dropped on the lower hopper. Dust dropped into lower hopper 1
4 is discharged in the direction of arrow 15 by a dust extraction valve or a screw conveyor (not shown).

When the present apparatus is used only for decomposing organic chlorine compounds, it is not necessary to inject ammonia.

In any of the dust removing device and harmful gas decomposing device shown in FIGS. 1 and 2, it is desirable to control the temperature of the combustion exhaust gas flowing into the device within the range of 200 ° C. or more and 400 ° C. or less. The reason is that at a temperature of 200 ° C. or less, the possibility that the sulfur oxides contained in the flue gas and the ammonia injected into the flue gas react with each other to form ammonium sulfate and increase the possibility of poisoning the catalyst is increased. is there.

Further, when the gas temperature is 200 ° C. or lower, chlorine gas and hydrocarbons mainly contained in the exhaust gas from a waste incinerator are catalyzed by metal oxides such as copper contained in fly ash. Then, the organic chlorine compound is resynthesized (de novo synthesis), and the concentration of the organic chlorine compound in the ash removed increases. Therefore, even when the organochlorine compounds are re-synthesized, they remain in a gaseous state at a temperature of 200 ° C. or more, preferably around 350 ° C., without being adsorbed by the dust-free ash. It is desirable to control the temperature of the combustion exhaust gas to be in the range of 200 ° C. or more and 400 ° C. or less in order to allow the catalyst to pass through the ash deposit layer and be effectively decomposed by the catalyst dispersed and supported inside the filter tube material.

On the other hand, when the temperature of the combustion exhaust gas flowing into the apparatus is 4
When the temperature exceeds 00 ° C., the resolution of nitrogen oxides and organic chlorine compounds in the exhaust gas by the catalyst decreases,
An increase in the volume flow rate of the exhaust gas leads to an increase in the required filtration area of the filter tube, which is not preferable because the apparatus becomes large.

[0036]

As described above, the use of the dust removing and harmful gas decomposing apparatus according to the present invention makes it possible, in particular, to use a waste incinerator,
Combustion equipment using fossil fuels such as coal, various industrial furnaces for iron and metallurgy, cement sintering furnace, refractory sintering furnace, petroleum refining equipment, dust from gas containing dust discharged from chemical plants, etc. on the filter tube surface Removal and at the same time, nitrogen oxides and organochlorine compounds can be decomposed and made harmless by using a catalyst dispersed and supported inside the filter tube.Conventionally, devices having different functions have been connected to the series, respectively. Compared to the method of controlling at different inlet gas temperatures, the system of the equipment is simplified, not only can the equipment and maintenance costs be greatly reduced, but also the operation and control are simplified, and both reliability and operability are improved. Can also be expected to improve significantly.

[Brief description of the drawings]

FIG. 1 is an assembly sectional view and a system diagram showing a first example according to an embodiment of the present invention.

FIG. 2 is an assembly sectional view and system diagram showing a second example according to the embodiment of the present invention.

FIG. 3 shows a prior art process for purifying flue gas.
It is a system diagram showing an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Can body 2 Filter tube supporting catalyst 3 Upper tube sheet 4 Lower tube sheet 5 Filter unit 6 Dust-containing gas inlet tube 7 Dust hopper 8 Clean gas outlet tube 9 Backwashing device 10 Dust-containing gas inlet duct piping 11 Ammonia injection device 12 Inner wall surface of filter tube carrying catalyst 13 Clean gas collecting part 14 Dust 15 Dust discharge direction 16 Outer wall surface of filter tube carrying catalyst

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01J 23/30 B01D 53/36 102A F-term (Reference) 4D019 AA01 AA10 BA05 BB03 BC07 BD01 CA03 CB04 CB06 CB09 DA02 DA03 4D048 AA06 AA17 AB03 AC04 BA01Y BA03Y BA06Y BA07Y BA10X BA23X BA27X BA41X BA45Y BA46Y BB05 BB08 BB14 BB17 CC08 CC23 CC38 CC39 CD05 DA03 DA06 4D058 JA02 JA04 JB06 JB25 KA01 KA11 KB04 MA03 A04 BA04 BB06B BB11A BB15A BC54A BC54B BC60A BC60B BD05A CA02 CA04 CA10 CA13 CA19 EA06 EA10 EA27 EB14X EB18X EC27 EE07 FA01 FB30 FB71 FC08

Claims (8)

[Claims] 1. A vanadium pentoxide or a tungsten trioxide or a mixture of both, inside a can body and a cylindrical non-woven fabric made of ceramic fibers having both ends opened and a cylindrical shape or one end closed and the other end opened. A plurality of filter tubes each having a powdery catalyst dispersed and supported substantially uniformly, and a set of tube sheets provided in a can body for supporting the upper and lower ends of the filter tubes having both open ends, or one end closed and others. A filter unit comprising a single tube sheet supporting the upper end of the filter tube having an open end and suspending the filter tube; a dust-containing gas inlet tube connected to the can body communicating with the filter unit; A dust hopper provided in a lower space of the can body for collecting and discharging dust removed by the filter unit, and a clean gas obtained by passing through a filter tube of the filter unit is taken out of the can body. Clean gas outlet When, characterized in that said comprising a backwash device which was shake off dust adhering to 濾筒 surface, dust and harmful gas decomposition apparatus having a 濾筒 made of ceramic fiber nonwoven fabric carrying a catalyst. 2. The catalyst having an average particle size of not less than 20 μm and not more than 80 μm in the filter tube is 5 wt.
The dust removing and harmful gas decomposition apparatus according to claim 1, wherein the content is in the range of not less than 25% by weight and not more than 25% by weight. 3. The powdery catalyst, comprising titanium oxide as a carrier,
2. The dust removing and harmful gas cracking apparatus according to claim 1, wherein the catalyst is a powdery catalyst having an average particle diameter of 20 to 80 microns made of vanadium pentoxide or tungsten trioxide or a mixture of both. 4. The fiber according to claim 1, wherein the ceramic fiber is a fiber composed of any one of alumina, silica, titania, magnesia, glass, silicon carbide, and silicon nitride, a fiber composed of a compound thereof, or a composite composition of these fibers. 2. The ceramic fiber according to claim 1, wherein the ceramic fiber has an average fiber diameter in a range of 1 to 10 microns and a fiber length of at least 10 mm or more and accounts for 50% or more of the whole. Dust removal and harmful gas decomposition equipment. 5. The dust removing and harmful gas decomposition apparatus according to claim 1, wherein the filter tube is a nonwoven fabric having a porosity in a range of 80% or more and 95% or less. 6. The filter tube according to claim 1, wherein the alumina sol, the silica sol,
Using any one or more components of a metal sol such as titanium sol, the ceramic fibers and the ceramic fibers and the catalyst are adhered to each other, and then dried and fired, and the ceramic fibers and the ceramic fibers and the catalyst are bonded together. 2. The device according to claim 1, wherein
The dust removal and harmful gas decomposition device described in the above. 7. The dust removing device and the harmful gas decomposing device,
2. The dust removing and harmful gas decomposition apparatus according to claim 1, wherein a combustion exhaust gas containing dust having a temperature of from 00 to 400 [deg.] C. is passed. 8. An ammonia injection device and a mixing zone for uniformly mixing the injected ammonia and the combustion exhaust gas are provided in an upstream gas pipe connected to a combustion exhaust gas inlet of the dust removal device and the harmful gas decomposition device. The dust removing and harmful gas decomposition apparatus according to claim 1, wherein: