JPH10180039A - Bag filter for waste gas treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove an organic chlorine compound in a waste gas in a bag filter. SOLUTION: This bag filter for waste gas treatment is formed by carrying a removable material in a nonwoven or woven fabric made filter 31 to remove the organic chlorine compound in the waste gas. The removable material is formed from a fine particulate material carried inside and on the surface of the filter 31 and the fine particulate material is at least one of an organic chlorine compound decomposing catalyst (decomposition catalyst) 10 and an organic chlorine compound adsorbing agent (adsorbent) 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of flue gas exhausted from various combustion devices such as municipal solid waste incinerators, and more particularly to an exhaust gas treatment bag filter for removing organochlorine compounds in exhaust gas.

[0002]

2. Description of the Related Art Exhaust gas discharged from municipal solid waste incinerators and the like contains trace amounts of very toxic organic chlorine compounds such as polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). In order to suppress the generation of the organic chlorine compounds, the dust filter has adopted a bag filter system in place of the conventional electric dust collector which is operated near the generation temperature of the organic chlorine compounds. However, there is a limit to the control of the emission concentration of organic chlorine compounds by the bag filter. To meet the emission standards (0.1 ng TEQ / Nm ³ ) of Europe, etc., some removal operation of the organic chlorine compounds is performed by reducing the emission concentration. Need to reduce.

[0003] The method of reducing the amount of the organic chlorine compound is a method in which the organic chlorine compound is formed into fine particles by lowering the temperature, and the filter is removed by a bag filter due to the characteristics of the vapor pressure. An adsorption method in which organic chlorine compounds are adsorbed and removed by an adsorbent in an adsorption tower. There is a catalytic method for decomposing and removing an organic chlorine compound by a decomposition catalyst in a catalyst tower.

FIGS. 7 to 10 show a conventional technique. As shown in FIG. 7, the removal method by lowering the temperature of the above item sets the temperature of the bag filter 8 in the baghouse 7 to around 160 ° C., converts the gaseous organic chlorine compound contained in the exhaust gas 2 into mist, and The dust is removed on the surface of the bag filter 8 together with the dust, and the purified exhaust gas is discharged from the chimney 12 to the atmosphere. In the adsorption method, as shown in FIG. 8, an adsorbent powder such as activated carbon is put into a flue, an organic chlorine compound is adsorbed on activated carbon, and this activated carbon is removed together with soot and dust on the surface of the bag filter 8 (see FIG. 8). See JP-A-4-15692). As shown in FIG. 9, there is a method in which an adsorption tower 21 is provided downstream of the bag filter 8, and an adsorbent is built in the adsorption tower 21 stepwise to remove an organic chlorine compound (Japanese Patent Application Laid-Open No.
-31847 gazette). In the catalytic method shown in FIG. 10, a heater 23 and a catalyst tower 22 are provided downstream of the bag filter 8, and an organic chlorine compound is decomposed and removed by, for example, a honeycomb catalyst built in the catalyst tower 22 (Japanese Patent Application Laid-Open No. -7
No. 5720).

On the other hand, for removing nitrogen oxides (NOx) in exhaust gas from municipal solid waste incinerators and the like, a method of carrying a denitration catalyst on a bag filter and decomposing and removing the catalyst with this bag filter (Japanese Patent Publication No. 4-36729). And a method of providing a catalyst layer in a void portion inside a bag filter to remove NOx (see JP-A-4-363116 and JP-A-4-334512). The removal is not disclosed in any known examples.

[0006]

In the conventional bag filter for exhaust gas treatment, the organochlorine compound is removed together with the soot and dust by a low-temperature or adsorbent flue charging method. Will remain. Rather, since the organic chlorine compound is diffused in the incineration ash, it is necessary to treat the organochlorine compound in the incineration ash generated in a large amount. In addition, in the method of performing treatment by providing an adsorption tower or a catalyst tower downstream of the bag filter, a new treatment device must be added, and the installation area of the exhaust gas treatment device increases. This configuration goes against the space saving of the municipal solid waste incinerator, and also increases the equipment cost and the maintenance cost. Furthermore, the method of installing an adsorbent or a catalyst in the void portion of the bag filter has a remarkable effect of the backflow that shakes off the dust on the bag filter, considering the increase in the ventilation resistance of the conventionally used air pulse jet, etc. There is a problem of decline.

An object of the present invention is to provide a bag filter for treating exhaust gas, which can remove an organic chlorine compound in exhaust gas in the filter.

[0008]

In order to solve the above-mentioned problems, an exhaust gas treatment bag filter according to the present invention has a structure in which a substance capable of removing an organic chlorine compound in exhaust gas is carried on the filter. .

[0009] The removable substance may be a particulate substance carried inside and on the surface of the filter.

The substance that can be removed is particulate matter carried inside and on the surface of the filter, and the particulate matter is at least one of an organic chlorine compound decomposition catalyst and an organic chlorine compound adsorbent. Some configuration may be used.

Further, the exhaust gas treatment device is provided with a bag house which incorporates any one of the above exhaust gas treatment bag filters.

According to the present invention, at least one of an organochlorine compound decomposition catalyst and an organochlorine compound adsorbent is supported on a filter as fine particulate matter capable of removing an organochlorine compound, so that the exhaust gas contains Organochlorine compounds are catalytically decomposed or adsorbed and removed in the filter.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, the filter 31 of a nonwoven fabric or a woven fabric carries a removable substance so as to remove an organic chlorine compound in the exhaust gas 2. The substance that can be removed is the filter 3
1 is formed of fine particulate matter carried on the inside and on the surface, and the fine particulate matter is at least one of an organic chlorine compound decomposition catalyst (decomposition catalyst) 10 and an organic chlorine compound adsorbent (adsorbent) 9 It is assumed that the substance is

The operation of the embodiment will be described. Incinerator 1
Exhaust gas 2 discharged from the flue
A reaction aid for improving the releasability of dust from the alkaline powder 4 for neutralizing chloride (HCl) and sulfur oxide (SOx) and the bag filter (bag filter for exhaust gas treatment) 8 5 are supplied. In addition, an ammonia compound such as ammonia gas or urea is blown into the flue as a reducing agent 6 from a supply device (not shown) and exhaust gas 2
Mixed with. The exhaust gas 2 a in which the neutralizing agent 4, the reaction assistant 5 and the reducing agent 6 are mixed passes through a bag filter 8 housed in a bag house 7. As shown in FIG. 2, a decomposition catalyst 9 and / or an adsorbent 10 or both are carried on the inside and the surface of a filter (filter fiber) 31 of the bag filter 8.

One of the decomposition catalysts is a metal oxide catalyst using titanium oxide as a carrier. This metal oxide catalyst also functions as a denitration catalyst without being affected by SOx or the like, and is used in a temperature range of 200 to 300 ° C. to 60 to 95%.
Is obtained. One of the adsorbents supported on the bag filter is coconut shell activated carbon powder having a pore size of about 20 angstroms and a particle size of about 300 mesh. The amount of particulate matter carried on these bag filters depends on their activity and adsorption capacity, but 300 g or more is required per 1 m ^{2 of} bag filter area.

The filter material is conventionally commercially available, and can support fine particulate matter. Examples of the material include polyimide, polyamide, polyphenyl sulfide, polylatrafluoroethylene, and heat-resistant poly. A non-woven fabric filter such as paraphenylene benzobisoxazole or a woven filter such as glass fiber is used. The filter media, filter area 1 m ² per 500
It is preferable that the filter can support fine particles of at least g and have a filter thickness of at least 2 mm.

The most suitable method for loading the particulate matter on the filter is a method in which the filter material is immersed in an aqueous slurry of the particulate material, the filter material is uniformly impregnated with the particulate material, and then dried. However, the present invention is not limited to this. Using the bag filter prepared by this means and performing backwashing with an air pulse jet or the like, the fine particulate matter of the bag filter surface layer 200 to 300 μm in the initial stage is slightly smaller than that carried on the central portion in the bag filter. Although there is less, there is no problem in removing gaseous harmful substances.

According to the present embodiment, the exhaust gas 2b that has passed through the bag filter 8 is one from which harmful substances such as organic chlorine compounds have been removed, and in particular, since organic chlorine compounds are decomposed and removed in the bag filter, they are incinerated. The residual amount in the ash can be suppressed. In addition, this bag filter can be applied to an existing waste incineration plant, and can be used in a new waste incineration plant in the same manner as in the past, so that the exhaust gas treatment device can be simplified.

Next, as another embodiment of the present invention, as shown in FIG. 1, an exhaust gas treatment apparatus includes a bag house 7 having any one of the above-described exhaust gas treatment bag filters 8.
Powder supply for supplying an alkaline powder 4 for neutralizing chlorides (HCl) and sulfur oxides (SOx) and a reaction aid 5 for improving the removability of soot and dust from a bag filter 8 into a flue. A device 3, a supply device (not shown) for supplying an ammonia compound such as ammonia gas or urea as a reducing agent 6 into the flue, and a chimney 1 for sucking the treated exhaust gas
2 and a blower 11 for releasing the air to the atmosphere. According to the other embodiments, the same operation and effect as described above can be obtained.

Next, examples and comparative examples implemented to confirm the effects of the present invention will be described.

[0021]

Example 1 A predetermined amount of a titanium oxide vanadium pentoxide catalyst for removing an organic chlorine compound was added to water to form a slurry,
A filter made of polyimide felt having an inner diameter of 15 cm and a length of 1.2 m was immersed in the slurry to impregnate the slurry. The bag filter impregnated with the slurry was dried so that the slurry did not drip. The bag filter adjusted by this means carried 480 g of catalyst per m ^{2 of} filter area. Using this bag filter, the moisture concentration in the exhaust gas is 18 to 20%, the NOx concentration is 150 to 220 ppm,
O concentration 250-300 ppm and HCl concentration 400-5
Exhaust gas of 00 ppm, filter permeation speed 1m / mi
n, neutralizing agent addition amount Ca (OH) ₂ / HCl molar ratio 2.7
The filter temperature was set to a temperature range of 160 to 240 ° C. under the conditions of the addition amount of the reducing agent and the NH ₃ / NO molar ratio of 1, and the concentration of the organic chlorine compound at the baghouse outlet was determined.

FIG. 3 shows the concentration of the organic chlorine compound at the bag house outlet with respect to the filter temperature. Organochlorine compound concentration of the bag filter inlet was 30~50ng / Nm ^3. In the temperature range where the filter temperature is 220 to 240 ° C., the concentration of the organochlorine compound is 0.1 ng / Nm ³ ,
The removal rate was 99% or more. 200 ° C filter temperature
At the following temperatures, the effect of agglomeration by lowering the temperature and removal of the filter by atomization became more dominant than decomposition and removal by the organochlorine compound decomposition catalyst. When the filter temperature is 2
The denitration rate in the temperature range of 20 to 240 ° C is 60 to 85.
%Met.

(Comparative Example) Using a filter made of polyimide felt having an inner diameter of 15 cm and a length of 1.2 m, the water concentration in the exhaust gas was 18 to 20%, and the NOx concentration was 150 to 200 pp.
m, CO concentration 250-300 ppm and HCl concentration 40
Exhaust gas of 0 to 500 ppm is passed through a filter at a speed of 1 m /
min, the neutralizer addition amount Ca (OH) ₂ / HCl molar ratio 2.7 and the reducing agent addition amount NH ₃ / NO molar ratio 1, the filter temperature was set to a temperature range of 160 to 240 ° C. at the bag house outlet. The organic chlorine compound concentration was determined.

FIG. 4 shows the concentration of the organic chlorine compound at the bag house outlet with respect to the filter temperature by a broken line. The concentration of organic chlorine compounds at the bag filter inlet is 30 to 50 ng / Nm
^{Was 3} . The lower the filter temperature, the lower the concentration of the organochlorine compound at the baghouse outlet was 0.2 ng / Nm ³ at a filter temperature of 160 ° C. In this case, it is considered that the organochlorine compound was atomized by the low temperature and was removed by the filter.

[0025]

Embodiment 2 Pore diameter: about 20 angstroms, particle size: 3
A filter made of polyimide felt having an inner diameter of 15 cm and a length of 1.2 m was immersed in an aqueous slurry of coconut shell activated carbon powder of about 00 mesh to impregnate the slurry. The bag filter impregnated with the slurry was dried so that the slurry did not drip. The bag filter prepared by this means carried 350 g of activated carbon powder per m ² of filter area. Using this bag filter, the moisture concentration in the exhaust gas is 18 to 20%, the NOx concentration is 150 to 220 ppm,
CO concentration 250-300 ppm and HCl concentration 400-
Exhaust gas of 500ppm, filter permeation speed 1m / mi
n and the amount of neutralizing agent added Ca (OH) ₂ / HCl molar ratio 2.7
Under the conditions described above, the concentration of the organic chlorine compound at the baghouse outlet was determined at a filter temperature of 160 to 240 ° C.

FIG. 5 shows the concentration of the organic chlorine compound at the bag house outlet with respect to the bag filter temperature. The organochlorine compound concentration at the bag filter inlet is 30-50 ng / Nm ³
Met. The lower the filter temperature, the lower the organochlorine compound at the baghouse outlet, and 0.1 ng /
Nm ³ . It is considered that the reason why the outlet concentration is lower than that of the bag filter that does not carry anything is that there is an effect of the adsorbent carried on the filter in addition to the effect of lowering the temperature.

[0027]

EXAMPLE 3 A predetermined amount of the catalyst for removing organic chlorine compounds of Example 1 and the activated carbon powder of Example 2 were added to water to form a slurry. A filter made of polyimide felt having an inner diameter of 15 cm and a length of 1.2 m was added to the slurry. Was impregnated with the slurry. The bag filter impregnated with the slurry was dried so that the slurry did not drip. The bag filter prepared by this means carried 450 g of catalyst and adsorbent mixture per m ² of filter area. Using this bag filter, the water concentration in the exhaust gas is 18 to 20%, the NOx concentration is 150 to 200 ppm, and the CO concentration is 250 to 300 pp.
m, exhaust gas having an HCl concentration of 400 to 500 ppm, a filter permeation speed of 1 m / min, and a neutralizing agent addition amount Ca (OH)
_Under the conditions of a molar ratio of ₂ / HCl of 2.7 and a molar ratio of the additive amount of NH ₃ / NO of 1 and a filter temperature of 160 to 240 ° C., the concentration of the organic chlorine compound at the baghouse outlet was determined.

FIG. 6 shows the concentration of the organic chlorine compound at the bag house outlet with respect to the filter temperature. Organochlorine compound concentration of the bag filter inlet was 30~50ng / Nm ^3. When the filter temperature was in the temperature range of 220 to 240 ° C., it was 0.1 ng / Nm ³ and the removal rate was 99% or more.
Further, even at a filter temperature of 160 ° C., a removal rate of 99% was obtained. This is considered to be due to the effect of decomposition and removal by the decomposition catalyst using the organochlorine compound decomposition catalyst on the high temperature side, and the effect of the filter removal and the effect of the adsorbent on the low temperature side. The denitration ratio in the temperature range where the filter temperature was 220 to 240 ° C. was 60 to 85%.

[0029]

According to the present invention, the organic chlorine compound in the exhaust gas is efficiently decomposed and removed or adsorbed and removed by the particulate matter carried inside and on the surface of the filter, and the filter is used in an existing device. Since it is possible, there is an effect that the device can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus using an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing one embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the bag filter temperature and the concentration of an organic chlorine compound at the bag house outlet in Example 1.

FIG. 4 is a graph showing a relationship between a bag filter temperature and an organic chlorine compound concentration at a bag house outlet in a comparative example.

FIG. 5 is a graph showing a relationship between a bag filter temperature and an organic chlorine compound concentration at the bag house outlet in Example 2.

FIG. 6 is a graph showing the relationship between the bag filter temperature and the concentration of an organic chlorine compound at the bag house outlet in Example 3.

FIG. 7 is a diagram showing a conventional technique.

FIG. 8 is a diagram showing a conventional technique.

FIG. 9 is a diagram showing a conventional technique.

FIG. 10 is a diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incinerator 2 Exhaust gas 2a Exhaust gas in which a neutralizing agent, a reaction auxiliary agent, and a reducing agent were mixed 2b Exhaust gas after treatment 3 Powder supply device 4 Alkaline powder 5 Reaction auxiliary agent, 6 Reducing agent 7 Baghouse 8 Bag filter 9 Decomposition catalyst 10 Adsorbent 11 Blower 12 Chimney 31 Filter

Claims (4)

[Claims] 1. A bag filter for treating exhaust gas, wherein the filter carries a substance capable of removing an organic chlorine compound in exhaust gas. 2. The bag filter for exhaust gas treatment according to claim 1, wherein the removable substance is a particulate substance carried inside and on the surface of the filter. 3. The exhaust gas treatment bag filter according to claim 1, wherein the removable substance is a particulate substance carried inside and on the surface of the filter, and the particulate substance is an organochlorine compound decomposition catalyst. And an at least one of an organic chlorine compound adsorbent and an exhaust gas treatment bag filter. 4. An exhaust gas treatment apparatus comprising a bag house having the exhaust gas treatment bag filter according to claim 1, 2 or 3.