JPH0483505A - Dust collecting method by bag filter - Google Patents

Abstract

PURPOSE:To peel solid substances which are water-absorptive and have high adhesion strength efficiently with even a small amount of a peeling agent by leading a peeling assisting agent beforehand to a dust collecting chamber and forming a peeling assisting agent layer on a filter cloth while leading a waste gas to the dust collecting chamber before dust collecting process starts. CONSTITUTION:Dust collecting process to collect water-absorptive solid substances in a waste gas A by a filter cloth 11 of a bag filter 1 after the waste gas A is led to dust collecting chamber 2a-2c and dust dropping off process to drop off the collected solid substances are repeated. Before the dust collecting process is carried out after the waste gas A is led to the dust collecting chamber 2a-2c, a peeling assisting agent B(e.g. diatomaceous earth) is led beforehand to the dust collecting chambers to form a peeling assisting agent layer 12 on the filter cloth 11. As a result, even solid substance 13 layers which are water-absorptive and have high adhesion strength can be peeled off with a small amount of the peeling assisting agent.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dust collection method using a bag filter, and in particular improves the peelability of solid matter attached to a filter cloth and reduces the amount of peeling aid used. This paper relates to a dust collection method using a bag filter.

[Conventional technology]

As a dust collector for removing solid matter from gas, particularly dust from combustion exhaust gas, for example, an electric precipitator, an Ikron, a bag filter, etc. are used.

Recently, the characteristics of bag filters have been recognized, and they can reduce SOx and HC contained in the exhaust gas emitted from garbage incinerators.
1! It is also used for the removal of harmful acidic components such as , so-called desulfurization and desalination.

When desalinating exhaust gas discharged from a garbage incinerator using a bag filter device, first an alkaline reactant such as slaked lime is supplied into the exhaust gas on the upstream side of the bag filter, and the alkaline reactant is applied to the filter cloth surface of the bag filter. A layer is formed and the exhaust gas is desalted as it passes through the alkaline reactant layer. That is, harmful acidic components in the exhaust gas react with the alkaline reactant when passing through the alkaline reactant layer, and are collected on the filter cloth as a neutralization reaction product.

However, the neutralization reaction products, such as calcium chloride (CaCj!2), are highly hygroscopic and easily solidify, resulting in extremely poor removability during filter cloth cleaning, which increases the pressure loss in the dust collection chamber. The problem has arisen that normal operation cannot be continued. In order to improve the peelability of the collected solids, a stripping aid is usually supplied together with the exhaust gas, but the required amount of this stripping aid is about 20 to 50% by weight of the alkaline reactant. As a result, running costs become high, which is a problem.

[Problem to be solved by the invention]

An object of the present invention is to solve the problems of the prior art described above and to provide a dust collection method using a bag filter that can efficiently remove even highly hygroscopic and highly adhesive solids with a small amount of removal aid. It is in.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a dust collection process in which exhaust gas is introduced into a dust collection chamber and hygroscopic solids in the exhaust gas are collected using a filter cloth, and a dust collection process in which the collected solids are brushed off. In a dust collection method using a bag filter that repeats the dropping process, when introducing exhaust gas into the dust collection chamber and entering the dust collection process, a peeling aid is introduced into the dust collecting chamber in advance and the peeling aid is applied to the filter cloth surface. It is characterized by forming a layer.

[Effect]

When entering the dust collection process, that is, when starting to introduce the waste gas to be treated into the dust collection chamber, a predetermined amount of stripping aid is introduced into the dust collection chamber to remove the filter cloth or solid matter immediately after replacement. By forming a stripping aid layer on the filter cloth close to the initial layer, the solids collected on the stripping aid layer are hygroscopic and adhesive, such as neutralization reaction products in the desalting process. Even if it is high, it will be almost completely removed in the next removal process.

Examples of the stripping aid used in the present invention include diatomaceous earth and perlite, which are commonly used as filter aids. The stripping aid is temporarily supplied to form a stripping aid layer of a predetermined thickness on the filter cloth surface of the bag filter when replacing the filter cloth or when starting the dust collection operation after the dusting process. ,
The amount used may be as small as, for example, about 1/4 of that in the case of conventional continuous supply. The thickness of the peeling aid layer is monomolecular layer or more, 1
It is preferably 1 or less.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is an explanatory diagram of a multi-chamber bag filter device used in one embodiment of the present invention. This bag filter device is
Dust collection chambers 2a, 2b in which a plurality of bag filters 1 are housed,
2C... and a gas introduction valve 3a to the dust collection chamber, respectively.
, 3b, 3C .
A stripping aid supply pipe 6 that supplies stripping aid B via b, 5C, and so on, and a gas outlet valve 7a, which supplies the treated exhaust gas C,
7b, 7c, . 9a, 9b, 9c... are
This is a back pressure valve installed in each dust collection chamber that blows out high pressure air for pulse cleaning.

In such a configuration, when removing dust and desalting the combustion exhaust gas A discharged from a garbage incinerator or the like, first, the gas is introduced into the dust collection chamber 2a through the gas introduction pipe 4, for example, via the gas introduction valve 3a.
At the same time, exhaust gas A is introduced into the stripping aid supply pipe 6.
A predetermined amount of diatomaceous earth B is introduced into the dust collection chamber 2a by pneumatic transport via the stripping aid supply valve 5a.

This diatomaceous earth B is dispersed along with the airflow of the exhaust gas A, and is uniformly deposited on the filter cloth surface of the bag filter 1 to form a stripping aid layer. The exhaust gas A contains, in addition to dust and harmful acidic components, an alkaline reactant added for desalination upstream of the bag filter, and neutralized salts produced by the reaction between the alkaline reactant and the harmful acidic components. is continuously introduced into the dust collection chamber 2a, and the solids in the exhaust gas are deposited on the stripping aid layer formed on the bag filter to form solids containing the alkaline reactant. Unreacted harmful acidic components in the exhaust gas A passing through this solid layer react with the alkaline reactant in the solid to become neutralized salts, which are collected here together with solids such as dust. The exhaust gas from which harmful acidic components, dust, etc. have been removed in this manner is discharged as clean exhaust gas C to the outside of the dust collection chamber 2a. After the peeling aid layer is similarly formed in the other dust collection chambers 2b, 2c, . . . , the exhaust gas is subjected to dust collection and desalination treatment.

When the above exhaust gas treatment is performed continuously in all dust collection chambers of a multi-chamber bag filter device, and clogging of the bag filter is detected due to an increase in pressure loss in the dust collection chamber or a decrease in filtration speed, etc. , pulse cleaning is performed sequentially for each dust collection chamber. That is, the gas introduction valve 3a of the dust collection chamber where the pressure loss has increased, for example 2a, is closed to stop the introduction of exhaust gas, and then the back pressure valve 9a is opened to introduce high pressure air for backwashing and clean the filter cloth. The solid matter adhering to the surface is brushed off.

FIG. 2 is a diagram schematically showing how solid matter is removed during pulse cleaning. In the figure, the filter cloth 1 of the bag filter
A peeling aid layer 12 and a solid layer 13 formed on 1 are shown, and the peeling aid layer 12 serves as a peeling boundary 14 to remove neutralized salt, dust, unreacted alkali reactant, etc. after desalting. A solid layer consisting of is removed.

After the dust removal is completed, the back pressure valve 9a is closed to stop the supply of high pressure air for backwashing, and then the exhaust gas A is introduced again to enter the desalination and dust collection process.

At this time, a predetermined amount of diatomaceous earth B is introduced together with the re-introduction of the exhaust gas A, and a stripping aid layer 12 is formed on the filter cloth surface near the initial layer from which the solids have been brushed off. Desalination processing continues.

Thereafter, the dust collection process and the dust removal process are repeated in each nitrogen collecting chamber in the same manner, and the exhaust gas discharged from the waste incinerator is subjected to dust collection and desalination treatment.

According to this embodiment, at the start of the dust collection process, a peeling aid layer of a predetermined amount of peeling aid is formed on the filter cloth just after replacement or on the filter cloth close to the initial layer from which solid matter has been brushed off. Since the peeling aid layer serves as a peeling boundary, adhering solid matter can be efficiently peeled off.

Further, since the stripping aid is temporarily introduced at the start of the dust collection process and does not need to be constantly introduced, the amount used can be reduced to, for example, about 1/4 of the conventional amount.

Furthermore, since the solid matter attached to the filter cloth can be easily removed, the number of pulse cleanings can be reduced, and operating costs can be reduced.

In this example, desalination treatment of exhaust gas containing harmful acidic components discharged from garbage incineration equipment has been described, but the present invention is not limited to this, and can be applied to various gaseous Applicable to solid separation.

〔Effect of the invention〕

According to the present invention, even highly adsorbent and hygroscopic solids such as neutralized salts generated by desalination of exhaust gas can be efficiently removed, and the amount of removal aid used can be reduced. can.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram of a multi-chamber bag filter device used in an embodiment of the present invention, and Fig. 2 is a schematic diagram of a solid matter removal situation in an embodiment of the present invention. FIG. 1... Bag filter, 2a, 2b, 2c... Dust collection chamber, 3a, 3b, 3C... Gas introduction valve, 4... Gas introduction pipe, 5a, 5b, 5c... Stripping aid Supply valve, 6... Peeling aid supply pipe, 7a, 7b, 7C... Gas outlet valve, 8... Gas outlet pipe, 9a, 9b, 9C
...Reverse pressure valve. Applicant Mitsui Zosen Co., Ltd. Agent Patent Attorney Takenaga Kawakita Figure 1: Bag filter A: Exhaust gas 53' to C a -C 9a to C: Gas inlet pipe stripping aid supply valve: Stripping aid supply Pipe: Gas outlet [1 valve ° Gas outlet pipe: Counter pressure valve

Claims (1)

[Claims] (1) Using a bag filter that repeats a dust collection process in which exhaust gas is introduced into a dust collection chamber and hygroscopic solids in the exhaust gas are collected using a filter cloth, and a dusting process in which the collected solids are brushed off. In the dust collection method, when introducing exhaust gas into the dust collection chamber and entering the dust collection step, a peeling aid is introduced into the dust collecting chamber in advance to form a peeling aid layer on the filter cloth surface. Dust collection method using a bag filter.