JPH1066814A - Bag filter for treating exhaust gas and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove a plurality of gaseous harmful substances contained in exhaust gas of a waste refuse incinerator and to obtain filter cloth uniformly holding fine particles efficiently removing a plurality of gaseous harmful substances. SOLUTION: Water is added to a mixed powder of titanium oixide and vanadium pentoxide with a particle size of 0.6-5μm being a denitration catalyst to prepare a slurry and bag-shaped filter cloth with a diameter of 10cm, a thickness of 3mm and a length of 1m is immersed in this slurry. The impregnated filter cloth is dried while rotated around its horizontal long axis so as to equally distribute titanium oxide and vanadium pentoxide. The support amt. of the denitration catalyst per a unit area of the filter cloth is 480g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment bag filter for removing harmful components contained in exhaust gas from a refuse incinerator and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Waste incinerators, in particular, devices for removing dust in exhaust gas from municipal waste incinerators have been shifted from electric dust collectors to bag filters in order to suppress the generation of dioxins. As the amount of waste incineration increases, a large amount of exhaust gas is generated, and a filter having a large capacity is required, and the installation area and the installation volume are extremely large. Therefore, a bag filter for simultaneously removing not only the dust of the municipal solid waste incinerator but also the gaseous harmful substances has been required, and some of them have been put to practical use. Nitrogen oxide (N) is one of the harmful substances in the exhaust gas from municipal solid waste incinerators.
As a technique for removing Ox), there is an example in which a catalyst tower is provided downstream of a bag filter for denitration, and as described in Japanese Patent Publication No. 4-36729, there is an example in which a denitration catalyst is supported on a filter cloth to denitrate. A production technique for supporting a denitration catalyst on a filter cloth for removing nitrogen oxides with high efficiency has not been disclosed.

[0003]

In the denitration of exhaust gas from a municipal waste incinerator using a bag filter, the contact time between the exhaust gas and the supported denitration catalyst is longer than that of the filter cloth because the linear velocity of the exhaust gas passing through the filter cloth is relatively high. The parts also need to be equal. Therefore, it is important to uniformly support the denitration catalyst on the filter cloth, but the prior art does not take this point into consideration and has a problem in the denitration performance of the bag filter. In particular, the distribution when the particulate catalyst is supported on a nonwoven fabric or woven filter cloth is not uniform, and the filter cloth supporting the denitration catalyst for obtaining high denitration efficiency has not been optimized. An object of the present invention is to efficiently remove a plurality of gaseous harmful substances contained in waste gas from incinerators. Another object of the present invention is to produce a filter cloth which uniformly holds fine particles for efficiently removing a plurality of types of gaseous harmful substances.

[0004]

An object of the present invention is to provide a bag filter for exhaust gas treatment provided with a filter cloth for removing harmful substances contained in exhaust gas, wherein the filter cloth is a denitration catalyst, a mercury adsorbent,
This is achieved by holding a plurality of types of fine particles of the dioxin removal catalyst. The filter cloth desirably carries 300 g or more of each fine particle per 1 m ² of the area. The above object is to provide a method of manufacturing a bag filter for exhaust gas treatment in which fine particles for removing harmful substances contained in exhaust gas are supported on the filter cloth. This is achieved by drying while rotating. According to the above configuration, when the fine particles are carried on the filter cloth, by drying while rotating the axis of the filter cloth impregnated with the slurry of the fine particles horizontally, the fine particles are not concentrated at a specific position, and the thickness of the filter cloth is reduced. Fine particles can be uniformly dispersed and supported in all directions, circumferential directions and axial directions. According to the above configuration, the fine particles are uniformly supported on the filter cloth, so that the exhaust gas does not pass through the thin portion of the low-resistance fine particle supporting layer at a high speed and the contact time is short, so that blow-through does not occur. High removal efficiency of gaseous harmful substances can be obtained. According to the above configuration, the fine particles are added to the filter cloth in an amount of 30 / m < ² >.
A high removal efficiency is obtained by supporting 0 g or more.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. The filter cloth and the fine particles, which are basic members of the bag filter of the present embodiment, will be described. The filter cloth is a commercially available nonwoven fabric of plastic, and its material is polyimide, polyamide, polyphenylene sulfide, or polytetrafluoroethylene, and a woven glass fiber cloth is also used.
The area 1 m ² per 500g as physical properties of the filter cloth
The above weight and thickness of 2 mm or more are desirable. The fine particles include, in addition to the denitration catalyst described above, an adsorbent such as activated carbon for removing heavy metals, particularly mercury, a de-dioxin catalyst or an adsorbent.The shape of the fine particles may be not only crushed particles but also spherical particles. The diameter is desirably equal to or less than the pore size of the filter cloth.

Embodiment 1 First, a method for supporting fine particles on a filter cloth will be described.
As a denitration catalyst, water is added to a mixed powder of titanium oxide and vanadium pentoxide having a particle size of 0.6 to 5 μm to form a slurry.
A filter cloth of bag-shaped polyimide nonwoven fabric (Toyobo P84) having a length of m, a length of 1 m and a density of 600 g / m ² was dipped. The filter cloth impregnated with the slurry was dried such that the long axis of the filter cloth was horizontal so that titanium oxide and vanadium pentoxide were evenly distributed, and the filter cloth was rotated around the long axis. The carrying amount of the denitration catalyst per unit area of the filter cloth was 480 g / m ² . Next, the distribution evaluation of the fine particles carried on the filter cloth will be described.

[0007] A part of the filter cloth supporting the denitration catalyst is cut and embedded in a thermosetting resin, and the X-ray microanalyzer (X
MA) was used to measure the thickness, circumference and axial distribution of the vanadium filter cloth. FIG. 1 is a table showing the distribution of vanadium supported on the filter cloth according to the embodiment of the present invention in the thickness direction. The abscissa in this figure indicates the thickness of the filter cloth, and the ordinate indicates the relative concentration of vanadium. As shown in this figure, vanadium is carried at substantially the same concentration in the thickness direction of the filter cloth.

FIG. 2 is a chart showing a circumferential distribution of vanadium carried on a bag-shaped filter cloth according to the embodiment of the present invention. The abscissa in this figure indicates the circumferential position of the filter cloth, and the ordinate indicates the relative concentration of vanadium. The filter cloth was sliced, and the relative concentration of vanadium at each position on the circumference was measured. As shown in FIG. A, vanadium is carried at substantially the same concentration in the circumferential direction of the filter cloth.

FIG. 3 is a table showing the distribution in the length direction of vanadium supported on the filter cloth according to the embodiment of the present invention. The abscissa in this figure indicates the relative concentration of vanadium, and the ordinate indicates the axial length of the filter cloth. A part of the filter cloth was cut in the axial direction, and the relative concentration of vanadium at each position was measured. As shown in this figure, vanadium is carried at substantially the same concentration in the axial direction of the filter cloth. It was clarified that the thickness, circumferential direction and axial direction of these filter cloths were all the same, and the fine particles were uniformly supported.

Next, the evaluation of the peel resistance of the fine particles carried on the filter cloth will be described. The filter cloth supporting the denitration catalyst is pressed at a pressure of 3k.
Backwashing was performed with an air pulse jet of g / cm ² , and the relationship between the number of backwashing and the relative weight of the denitration catalyst was determined. FIG. 4 is a table showing the relationship between the number of backwashing of the filter cloth and the relative weight of the denitration catalyst according to the embodiment of the present invention. The abscissa in this figure indicates the number of backwashing, and the ordinate indicates the relative weight of the denitration catalyst. The denitration catalyst was slightly peeled off by 50 times in the initial stage of backwashing, but no peeling was observed thereafter. After 1,700 times of backwashing, the vanadium concentration in the thickness direction of the filter cloth was measured.

FIG. 5 is a table showing the distribution in the thickness direction of vanadium supported on the filter cloth after backwashing the filter cloth according to the embodiment of the present invention. The abscissa in this figure indicates the thickness of the filter cloth, and the ordinate indicates the relative concentration of vanadium. As shown in this figure, the relative concentration of vanadium is slightly reduced in the surface layers 200 to 300 μm on both sides of the filter cloth, but the inside is in a substantially uniform state. In this state, there is no hindrance to the removal of the gaseous harmful substance, and it may be considered that the carrier is uniformly loaded.

Next, the denitration performance of the fine particles supported on the filter cloth will be described. Exhaust gas temperature 220 ° C, moisture 1 in exhaust gas
8 ~ 20vol%, NOx inlet concentration 130 ~ 150pp
m, the performance of the denitration catalyst supported on the filter cloth under the condition of NH ₃ / NOx ratio: 1.2 was determined. FIG. 6 is a chart showing the denitration performance of the embodiment of the present invention. The horizontal axis of this figure indicates the exhaust gas flow rate, and the vertical axis indicates the denitration rate. As shown in FIG. C, the denitration rate became 60% at an exhaust gas flow rate of 1 m / min. Also,
The denitration rate after backwashing 2000 times with an air pulse jet was 57 to 60%.

Comparative Embodiment 1 As in Embodiment 1, water was added to the denitration catalyst to form a slurry, and a filter cloth was immersed in the slurry. The filter cloth impregnated with the slurry was allowed to stand without rotating and dried. The relative concentration of vanadium at each location on the circumference of the dried filter cloth was measured. As shown in FIG. 2B, vanadium is not carried at substantially the same concentration in the circumferential direction of the filter cloth, and the concentration is high at the center of the figure. This is because the slurry gathered at the bottom position when the filter cloth was dried and the amount of vanadium increased. Further, the denitration performance was measured as in the first embodiment. As shown in FIG.
At a rate of m / min, the denitration rate was 43%, and the rate at which the denitration rate decreased as the exhaust gas flow rate increased was significant.

Embodiment 2 The same denitration catalyst as in Embodiment 1 is used to change the slurry concentration to change the carrying amount of the denitration catalyst on the filter cloth.
The denitration performance was measured under the same conditions as described above. FIG. 7 is a table showing the relationship between the denitration catalyst carrying amount and the denitration rate according to the embodiment of the present invention. As shown in this figure, when a denitration catalyst is supported on the filter cloth by 300 g or more per 1 m ² of the area of the filter cloth, the denitration rate exceeds 60% and a substantially constant value is obtained.

Embodiment 3 A filter cloth similar to that of Embodiment 1 was immersed in an aqueous slurry of coconut shell activated carbon, and the filter cloth impregnated with the slurry was rotated to dry so that the slurry did not drip. At this time, the supported amount was 320 g per 1 m ² of the area of the filter cloth. Using this filter cloth, the mercury removal performance was determined under the conditions of an exhaust gas temperature of 180 ° C., a moisture content of the exhaust gas of 20 vol%, a mercury inlet concentration of 0.2 mg / Nm ³ (in terms of HgCl ₂ ), and an exhaust gas flow rate of 1 m / min. The mercury exit concentration was not detected when the cumulative amount of treated exhaust gas reached 10 ⁵ Nm ³ .

Embodiment 4 A catalyst similar to that of Embodiment 1 was supported on a bag-like polyimide filter cloth having a diameter of 15 cm and a length of 1.2 m in the same manner as in Embodiment 1. Six of these filter cloths were loaded into a baghouse of a test device attached to a refuse incinerator, and the exhaust gas of the refuse incinerator was led to a temperature of 245 ° C., a water content of 22 vol% in the exhaust gas, a dioxin inlet concentration of 32 ng TEQ / Nm ³ , and an exhaust gas flow rate of 1 m. / Min, the dioxin removal performance was determined under the condition of no addition of NH ₃ . The dioxin had a baghouse exit concentration of 0.09 ng TEQ / Nm ³ and a removal rate of 99% or more.

As described above, the filter cloth of the present embodiment can be applied to an existing refuse incinerator without any problem, and can be used in a newly installed refuse incinerator in the same manner as the conventional one, thereby simplifying the exhaust gas treatment apparatus. .

[0018]

According to the present invention, the filter cloth impregnated with the slurry of fine particles is dried while rotating horizontally while rotating, thereby obtaining an effect of uniformly supporting the fine particles in both the circumferential direction and the axial direction of the filter cloth. Can be And, since the fine particles are uniformly supported on the filter cloth, a thin portion of the support layer that causes blow-through is not formed, and high removal efficiency of gaseous harmful substances can be obtained. In addition, when 300 g or more of fine particles are supported per 1 m ² of filter cloth area, high removal efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a table showing distribution of vanadium supported on a filter cloth in an embodiment of the present invention in the thickness direction of the filter cloth.

FIG. 2 is a chart showing distribution of vanadium carried on a bag-shaped filter cloth in the circumferential direction of the filter cloth according to the embodiment of the present invention.

FIG. 3 is a table showing distribution of vanadium supported on the filter cloth in the embodiment of the present invention in the filter cloth length direction.

FIG. 4 is a table showing the relationship between the number of backwashing of the filter cloth and the relative weight of the denitration catalyst supported on the filter cloth according to the embodiment of the present invention.

FIG. 5 is a table showing the distribution of vanadium in the thickness direction of the filter cloth after backwashing the filter cloth according to the embodiment of the present invention.

FIG. 6 is a table showing the denitration performance of the embodiment of the present invention.

FIG. 7 is a table showing a relationship between a denitration catalyst carrying amount and a denitration rate according to the embodiment of the present invention.

Claims (3)

[Claims] An exhaust gas treatment bag filter provided with a filter cloth for removing harmful substances contained in exhaust gas, wherein the filter cloth holds a plurality of fine particles of a denitration catalyst, a mercury adsorbent, and a dioxin catalyst. Characteristic bag filter for exhaust gas treatment. 2. The bag filter for exhaust gas treatment according to claim 1, wherein the filter cloth carries 300 g or more of each of the fine particles per 1 m ^{2 of} its area. 3. A method for manufacturing a bag filter for exhaust gas treatment, wherein fine particles for removing harmful substances contained in exhaust gas are supported on the filter cloth, wherein a long axis of the filter cloth impregnated with the slurry of the fine particles is horizontal and the long axis is long. A method for producing a bag filter for exhaust gas treatment, characterized in that drying is performed while rotating about a center.