JPH06226023A - Chemical supply method for precoating type bag filter device - Google Patents

Abstract

PURPOSE:To provide the chemical supply method for a precoating type bag filter device which prevents a clogging accident in a chemical transportation route, continues high filtration performance in a stable state, efficiently utilizes the chemicals to be used and can decrease the amts. of the unreacted chemicals. CONSTITUTION:This chemical supply method is for the precoating type bag filter device which is constituted of unit dust collection mechanisms each consisting of plural filter chambers 51, a hopper chamber 52 and a clean gas chamber 4 and forms precoating layers on the surfaces of plural filter cloths 2 installed in the filter chambers 51 before the conduction of a filtration operation. The precoating layers are rapidly formed by supplying the necessary and sufficient amts. of the chemicals 9 to each of the unit dust collection mechanisms from a chemical supply device only in the block where a dislodging operation is completed. The precoating layers are uniformalized by decreasing the amts. of the chemicals to be supplied by the chemical supply device in the stage before the end of such formation and thereafter, chemical pipings 95 and chemical supply branch pipes 97, etc., are cleaned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bag filter device for separating dusts and suspended solids from a gas stream and removing or recovering the dusts. Type bag filter device.

[0002]

2. Description of the Related Art Among the types of bag filter devices currently in practical use, the most widely used one is to make the chemicals contained in the exhaust gas adhere to the filter cloth and to keep it on the filter cloth as the operation continues. The dust layer deposited on the surface is removed by the pulse jet method.

Although there are both a single-chamber structure and a multi-chamber structure from the viewpoint of dividing the filtration chamber, the multi-chamber structure type exhaust gas entrainment system will be described as a representative example of the prior art in the present application.

5 to 7 show a schematic structure of a conventional pulse jet type multi-chamber structure type exhaust gas entrainment type bag filter device.

In FIGS. 5 to 7, reference numeral a is a casing for accommodating a unit dust collecting mechanism constituting a bag filter device and for partitioning the unit dust collecting mechanism from each other. Each unit dust collecting mechanism suspends a plurality of filter cloths b. The partition plate c divides the filter chamber d in the lower part and the clean gas chamber e in the upper part into two parts.

In the clean gas chamber e, a plurality of nozzles f1 for injecting compressed air in a jet pulse shape into each filter cloth b through an opening / closing valve connected to an air compression source (not shown).
An air blow-in pipe f provided with is provided.

A hopper chamber h for collecting dust is formed below the filtration chamber d, and a discharge mechanism j for discharging dust is connected to the bottom of the hopper chamber h.

On the outer side surface of the hopper chamber h, there is provided a main flue k for introducing combustion gas containing soot and dust, acid harmful gas, etc. generated in an incinerator or a combustion furnace (not shown).
In the middle of, the chemical m for neutralization transported from a harmful gas removing device (not shown) is continuously supplied, and the chemical m is mixed with the combustion gas to form the exhaust gas g.

Exhaust gas g flows into each hopper chamber h from a main flue k through a branch introduction duct p branched for each unit dust collecting mechanism, and acidic harmful gas and chemical m contained therein are separated. While reaching the neutralization reaction, it reaches the surfaces of the plurality of filter cloths b suspended in the filtration chamber d.

The unit dust-collecting mechanism after the completion of the scrubbing work, which will be described later, has a low ventilation resistance, so that a larger amount of the exhaust gas g flows into the unit than the other sections in continuous operation, and when it passes through the filter cloth b, it is filtered. Due to the ability, the reacted and unreacted drug m is filtered and adheres to the surface, and the drug layer b1 (see FIG. 6) is formed by the partially reacted drug m, which is the main component of the filtration / neutralization operation.

Then, in the subsequent passing of the gas, the acidic harmful gas remaining in the exhaust gas g causes a neutralization reaction with the unreacted drug m in the drug layer b1, and also the soot and dust and the reacted particles flying with the exhaust gas g. And unreacted drug m is drug layer b
One surface is sequentially deposited to form a dust layer b2 (see FIG. 6).

[0012] Therefore, when the exhaust gas g passes through the dust layer b2 and the drug layer b1, the retained dust is captured, and the residual acidic harmful gas comes into contact with the unreacted drug m, so that the medium is efficiently treated. The clean reaction is performed as a clean gas n and is discharged into the clean gas chamber e.

The clean gas n passes through a clean gas on-off valve r inserted in a branch discharge duct q arranged on the outer surface of the clean gas chamber e, passes through a discharge main duct s, and is sucked into an unillustrated draft fan. Then, it is released into the atmosphere from a chimney (not shown).

When the operation is continued in this state, the dust layer b2 gradually grows due to the dust and the reacted and unreacted chemicals m in the combustion gas that continues to fly, and the ventilation resistance increases. Therefore, by closing the clean gas on-off valve r of the corresponding unit dust collecting mechanism to stop the inflow of the exhaust gas g, and then jetting the compressed air from the air blowing pipe f,
The drug layer b1 attached to the surface of the filter cloth b and the accumulated dust layer b2 are peeled off and dropped. After that, the clean gas on-off valve r is opened again to restart the inflow of the exhaust gas g.

By sequentially performing this cleaning operation for each of the unit dust collecting mechanisms, the collected ash consisting of the soot and dust adhering to and depositing on each filter cloth b of the unit dust collecting mechanism and the reacted and unreacted chemicals m and the like. Can be removed. Note that the collected ash that has fallen into the hopper chamber h is discharged to the outside by the discharging mechanism j.

[0016]

In the case of the conventional multi-chamber structure type exhaust gas entrainment type bag filter device, the drug m forming the drug layer b1 is supplied all at once to the main flue k or a pre-reaction tower (not shown). Has been done.

Therefore, if the unit dust collecting mechanism with increased ventilation resistance is removed, the ventilation resistance of the section is reduced all at once, so that the exhaust gas g intensively flows into the section.
A large amount of the drug m is entrained, but as the drug layer b1 grows, the flow rate of exhaust gas to that section gradually decreases, and the drug supply amount also automatically decreases.

However, since a large amount of exhaust gas g flows into the section having the lowest filtration / neutralization capacity immediately after being blown off, soot and unreacted acidic harmful gas are kept until the drug layer b1 and the dust layer b2 grow. As a result, the dust trapping rate and the harmful gas removal rate of the entire apparatus including the unit dust collecting mechanism during other operation are temporarily reduced.

On the other hand, since the medicine m is continuously supplied, a part of the medicine m is immediately discharged to the other section.
Since all is supplied to each section during steady operation, the unreacted drug m that is continuously supplied after the drug layer b1 is formed is an excess amount, which promotes the increase of the dust layer b2.

[0020] Therefore, since the ventilation resistance rises quickly, the interval for removing the particles is shortened, and a large amount of unreacted drug is discharged. As a result, not only the drug cost is increased, but also harmful substances such as heavy metals and dioxins are contained. This will increase the amount of collected ash (exhaust ash) designated as “specially controlled waste”, which will increase post-treatment costs.

That is, the conventional multi-chamber structure is merely a section for preventing the release dusts from diffusing into other chambers at the time of brushing off, and has not been effective in supplying an appropriate amount of the drug m and stabilizing the filtration performance. .

On the other hand, in order to solve these problems, there has been proposed a precoat type bag filter device which is provided with a drug supply means for each unit dust collection mechanism. There is concern that the transport route may be blocked, or the chemical agent supply port tip may be blocked due to dew condensation due to temperature differences, and the pre-coat layer thickness unevenness that tends to occur during high-speed and short-time formation of the pre-coat layer may result in poor filtration performance. It is possible that it will decline.

[0023]

SUMMARY OF THE INVENTION A chemical supply method in a precoat type bag filter device of the present invention is a bag filter device filter chamber constituted by a plurality of unit dust collecting mechanisms consisting of a clean gas chamber, a filter chamber and a hopper chamber. A method for supplying a drug in a precoat type bag filter device, wherein a precoat layer is formed in a stage before performing a filtering operation on the surface of a filter cloth installed in the device, wherein each unit dust collecting mechanism supplies the drug from the drug supply device. Are individually supplied by the air-delivery means via a drug delivery route provided with a regulating valve, and after the precoat layer is formed, the supply of the drug by the drug delivery device is stopped and the air-delivery means remains in the drug delivery route. Remove the drug.

Further, the chemical supply method in the precoat type bag filter device of the present invention is installed in the filter chamber of the bag filter device composed of a plurality of unit dust collecting mechanisms consisting of the clean gas chamber, the filter chamber and the hopper chamber. A method for supplying a drug in a precoat type bag filter device, wherein a precoat layer is formed on a surface of a filter cloth before performing a filtering operation, wherein a drug supplied from the drug supply device is fed by means for each unit dust collecting mechanism. In addition to individually supplying via the drug delivery path provided with a regulating valve, the amount of drug supplied by the drug supply device is reduced so that the layer thickness of the precoat layer is averaged before the completion of formation of the precoat layer.

[0025]

[Function] The necessary and sufficient amount of the medicine is individually supplied from the medicine supplying device to the unit dust collecting mechanism which has completed the cleaning operation by the emptying means through the medicine transportation route provided with the adjusting valve, and is filtered. After the precoat layer that controls the neutralizing action is formed in a short time, the supply of the drug by the drug supply device is stopped, and the drug remaining in the drug transport route is removed by the emptying means to block the drug transport route. Prevent accidents.

Further, similarly to the above, by reducing the supply amount of the drug by the drug supply device before the end of forming the precoat layer in a short time, the layer thickness of the precoat layer is averaged and the filtration performance is improved. Improve.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show a schematic structure of a precoat type bag filter device for carrying out the chemical supply method in the precoat type bag filter device according to the present invention, and FIG. 3 shows an adhered state of the filter cloth surface in this device. FIG. 4 shows a schematic flow of this device.

In FIG. 1 and FIG. 2, reference numeral 1 is a casing for accommodating a plurality of unit dust collecting mechanisms constituting a precoat type bag filter device, and each unit dust collecting mechanism suspends a plurality of filter cloths 2. The partition plate 3 divides the upper clean gas chamber 4 and the lower gas inflow chamber 5.

The clean gas chamber 4 is a space communicated with the gas inflow chamber 5 via a plurality of filter cloths 2, and each clean gas chamber 4 has a common clean gas duct 42 via a clean gas opening / closing valve 41. And is connected to an induction fan (not shown).

In the clean gas chamber 4, one air blowing pipe 6 is provided for each horizontal row of a plurality of filter cloths 2, and the air blowing pipe 6 is connected to an air header 62 through an air opening / closing valve 61. And is connected to a compressed air source (not shown).

Further, at the lower part of the air blowing pipe 6, a nozzle 6 for blowing blown compressed air into the plurality of filter cloths 2 is provided.
The filter cloth 3 is disposed so as to face the opening of the filter cloth 2. The air blowing pipe 6, the air opening / closing valve 61, the air header 62, the nozzle 63, and the compressed air source constitute a dust removing mechanism.

The gas inflow chamber 5 is divided into a plurality of filtration chambers 51 partitioned by a plurality of partition walls 11 and a hopper chamber 52 which is continuous below the filtration chambers 51 and is similarly partitioned. A dust discharging mechanism 53, which is common to each unit dust collecting mechanism for discharging dust and the like separated and dropped from the filter cloth 2, is connected to the lower portion.

A main flue 7 is constructed outside the plurality of hopper chambers 52. From the main flue 7, each hopper chamber 5 is constructed.
A branch flue 71 leading to 2 is piped.

A dust-containing gas introduction duct is constituted by the main flue 7 and the branch flue 71 described above, and each hopper chamber 52 is generated in the incinerator or combustion furnace (not shown) via this gas introduction duct. Exhaust gas 81 containing dust and soot and acidic harmful gas flows in.

A harmful gas removing means is continuously provided in each of the hopper chambers 52. As shown in FIG. 4, the harmful gas removing unit is composed of a drug supply device A, an air feeding unit B, and a drug transporting route C.

The chemical supply device A is installed below the chemical storage tank 91 for storing the neutralization chemical 9 such as slaked lime, and the neutralization chemical 9 is supplied to the unit dust collecting mechanism in a predetermined amount. It is composed of a screw conveyor 92 for supplying and a fixed quantity supply feeder 93.

The emptying means B supplies the neutralizing chemical 9 supplied from the chemical supply device A to each hopper 52 via the chemical transport path C, and is composed of a supply blower 94.

The medicine transporting route C has one end connected to the supply blower 94, and one end side which receives the supply of the neutralizing medicine 9 from the constant quantity supply feeder 93 of the medicine supply apparatus A, and a medicine pipe 95. It is composed of a medicine supply branch pipe 97 branched from the medicine pipe 95 and communicated with each hopper chamber 52 of each unit dust collecting mechanism, and a medicine control valve 96 provided in each medicine supply branch pipe 97. .

It should be noted that in FIG. 4, each unit dust collecting mechanism is arranged from the left side, and each unit dust collecting mechanism, if necessary, is followed by each reference numeral of each constituent member. By assigning the number of the dust mechanism, the reference numerals of the above-mentioned respective constituent members are differentiated into three digits.

Next, when the drug supply method of the present invention is carried out by the precoat type bag filter device configured as described above, the precoat layer is formed, the drug supply route cleaning work and the filtration work are carried out, and then the filtration work is restarted. The operation up to is described.

For example, suppose that the unit dust collecting mechanism in FIG. 4 has finished the scrubbing work described later, and only the chemical regulating valve 961 of the unit dust collecting mechanism is opened to remove the neutralizing chemical 9 from the harmful gas removing device. When supplied to the hopper chamber 521 via the chemical regulating valve 961 and the chemical supply branch pipe 971, the neutralizing chemical 9 is blown up by the exhaust gas 811 and rises, reaches the surfaces of the plurality of filter cloths 201, and is short-timed. Then, the precoat layer 21 is formed only by the neutralizing agent 9 shown in FIG.

When the precoat layer 21 is formed in this manner, the screw conveyor 92 and the fixed amount supply feeder 93 shown in FIG. 4 are stopped to stop the supply of the neutralizing chemical 9 from the chemical storage tank 91. The blower 94 is kept in an operating state, and the feed pipe 94 pushes air to pump the chemical pipe 95, the chemical regulating valve 961, and the neutralizing chemical 9 remaining in the chemical supply branch pipe 971 into the hopper chamber 52.
Discharge into 1 to remove. Therefore, it is possible to prevent the clogging accident due to the cleaning of the drug supply path C, the clogging due to the solidification of the residual drug in the drug supply path C, and the clogging of the drug supply branch pipe 971 due to the desorption of the drug due to the dew condensation on the periphery of the outlet.

After forming the precoat layer,
The exhaust gas 811 that has entered the branch flue 711 from the main flue 7 flows into the hopper chamber 521, rises, and passes through the precoat layer 21 formed on the surfaces of the plurality of filter cloths 201. that time,
Pre-coat layer 21 with soot and dust retained in exhaust gas 811
While being adsorbed and filtered by, the acidic harmful gas contained therein is removed by the neutralizing action with the neutralizing agent 9 to become the clean gas 82, which is discharged to the clean gas chamber 401.

This is the state of the unit dust collecting mechanism on the right side of FIG. 2, for example.

As the filtration work continues, dust particles are deposited on the surface of the precoat layer 21 to form the dust layer 22 shown in FIG. 3, and the growth of the dust layer 22 increases the ventilation resistance of the exhaust gas 81. Then, first, the clean gas on-off valve 412 of the corresponding unit dust collecting mechanism, for example, the unit dust collecting mechanism of FIG. 4, is closed to block the inflow of the exhaust gas 812 into the filtration chamber 512.

Subsequently, the air opening / closing valve 612 corresponding to the filtration chamber 512 is opened, and compressed air from an air source (not shown) is discharged from the nozzle 63 through the filter cloth 202 in the filtration chamber 512.
If the jet gas is jetted into the inside for a short time, the clean gas 82 in the clean gas chamber 402 becomes a secondary air flow induced by the jet jet, and flows back into the filter cloth 202 together with the jet air, and the collision wave of the jet jet and the 2 Due to the backflow effect of the secondary air, the filter cloth 20
2 Precoat layer 21 and dust layer 22 attached to the surface
The collected ash consisting of can be peeled off.

This spray is used as a unit dust collecting mechanism filter cloth 202.
If you have done this for all the columns of the group, the work of clearing this section is completed.

In order to show the process of this removal work, in the unit dust collecting mechanism in the center of FIG. 2, the filter cloth 2 at the left end is stopped by the exhaust gas 81 from flowing into the precoat layer 21.
In the state in which the collected ash composed of the dust layer 22 and the dust layer 22 is attached, the filter cloth 2 in the center opens the air opening / closing valve 61 to open the nozzle 6
3 shows a state in which compressed air is jetted from the nozzle 3 to separate the collected ash, dust is falling, and the filter cloth 2 at the right end is in a state in which the above-mentioned wiping operation is completed.

Then, the separated collected ash is collected in the hopper chamber 52.
After being deposited on the bottom of the, the dust is discharged to the outside by the dust discharging mechanism 53.

After the above-mentioned cleaning operation is completed, the clean gas on-off valve 412 and the medicine control valve 962 shown in FIG. 4 are opened,
If the neutralizing chemical 9 is supplied from the chemical supply branch pipe 972,
The exhaust gas 812 rises due to the suction force of an unillustrated draft fan, and the precoat layer 21 can be formed again on the surfaces of the plurality of filter cloths 2.

When the work of forming the precoat layer 21 is completed,
After the above-mentioned cleaning operation of the medicine regulating valve 962 and the medicine supply branch pipe 972, the normal filtration operation is restarted.

Here, compared with the conventional method, the time required for forming the precoat layer 21 is much shorter, but since it is formed at a high speed, the precoat layer thickness is likely to be nonuniform. Therefore, at the stage before the formation of the precoat layer 21 is completed, the rotation speed of the fixed amount supply feeder 93 is reduced to supply the neutralizing agent 9 little by little. As a result, the neutralizing agent 9 is sucked and adhered to a thin portion where the ventilation resistance is low and the flow velocity of the exhaust gas 81 is high, so that the layer thickness can be averaged.

Such an operation is sequentially performed for each filtration chamber 51.

In this example, the condition for starting the cleaning work was explained by increasing the ventilation resistance. However, an exhaust gas concentration meter is installed in the clean gas chamber 4 or the clean gas duct 42, and the reaction of the neutralizing agent 9 is completed by the neutralizing action. May be detected, or may be performed in combination with an increase in ventilation resistance.

If the precoat layer thickness is systematically set by performing the cleaning work in this way by increasing the ventilation resistance due to the accumulation of dust and the completion of the neutralization reaction of the chemicals, only the reacted chemicals will be discharged. In addition to the efficient use of the chemicals, the amount of the collected ash discharged can be reduced, so that the post-treatment cost of the collected ash that causes secondary pollution can be reduced.

In this example, the chemical supply port 97 is arranged in the hopper chamber 52, but it may be arranged in the middle of the branch flue 71.

Further, although the clean gas on-off valve 41 is provided for controlling the exhaust gas inflow, an exhaust gas on-off damper may be inserted in the branch flue 71.

[0059]

As described above, according to the method of the present invention, the necessary and sufficient amount of the medicine is adjusted from the medicine supply device by the air-feeding means only to the unit dust collecting mechanism which has finished the cleaning operation. Since it is a system that forms a precoat layer that controls filtration / neutralization in a short time by supplying it individually via a drug delivery route equipped with a valve and then passing gas, the removal rate decreases as in the conventional system. High efficiency dust and suspended matter trapping rate and acidic harmful gas removal rate can be obtained from the beginning without any problem, and the performance of the entire device can be stably continued, and the excessive supply of neutralizing agent is eliminated. As a result, the amount of ash discharged will be reduced, and it will be possible to reduce drug costs and post-treatment costs.

Further, the supply of the drug by the drug supply device is stopped after the precoat layer is formed, and the drug remaining in the drug transport route is removed by the air-feeding means, so that the drug is blocked by the neutralizing drug remaining in the transport route. In addition to preventing the above, it is possible to prevent a blocking accident due to dew condensation on the tip of the drug supply port.

Further, before the completion of forming the precoat layer in a short time, the amount of the drug supplied by the drug supply device is reduced to average the layer thickness of the precoat layer, thereby improving the filtration performance. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional side view showing a schematic configuration of a precoat type bag filter device for carrying out a drug supply method in a precoat type bag filter device according to the present invention.

FIG. 2 is a diagram in which a front view showing a schematic configuration of a precoat type bag filter device according to the present invention and a cross section taken along line XX of FIG. 1 are combined.

FIG. 3 is an enlarged view showing a state of adhesion and deposition on the surface of the filter cloth.

FIG. 4 is a diagram showing a schematic flow of a precoat type bag filter device according to the present invention.

FIG. 5 is a side sectional view showing an outline of a conventional precoat type bag filter device.

6 is a sectional view taken along line YY in FIG.

FIG. 7 is a cross-sectional front view showing the outline of a conventional precoat type bag filter device.

[Explanation of symbols]

 2 Filter cloth 21 Precoat layer 51 Filtration chamber 52 Hopper chamber 9 Neutralizing chemical agent 96 Chemical regulating valve A Chemical feeding device B Pneumatic feeding means C Chemical transportation route

Claims (2)

[Claims] 1. A precoat layer at a stage before performing a filtering operation on a surface of a filter cloth installed in a filter chamber of a bag filter device composed of a plurality of unit dust collecting mechanisms including a clean gas chamber, a filter chamber and a hopper chamber. A method for supplying a drug in a precoat type bag filter device, wherein each of the unit dust collecting mechanisms individually supplies the drug supplied from the drug supply device through a drug transport path provided with an adjusting valve by an air feeding means. In addition, after the precoat layer is formed, the supply of the drug by the drug supply device is stopped, and the drug remaining in the drug transport route is removed by the emptying means, and the drug supply method in the precoat bag filter device is characterized. . 2. A precoat layer at a stage before performing a filtering operation on a surface of a filter cloth installed in a filter chamber of a bag filter device composed of a plurality of unit dust collecting mechanisms including a clean gas chamber, a filter chamber and a hopper chamber. A method for supplying a drug in a precoat type bag filter device, wherein each of the unit dust collecting mechanisms individually supplies the drug supplied from the drug supply device through a drug transport path provided with an adjusting valve by an air feeding means. In addition, the drug supply method in the precoat type bag filter device is characterized in that the amount of the drug supplied by the drug supply device is reduced so that the layer thickness of the precoat layer is averaged before the completion of the precoat layer formation.