Dust collector

Details Dust collector Dust collector

2002-08-27

2003-08-05

Chiesa, Richard L. (Department: 1724)

Gas separation: apparatus

Electric field separation apparatus

With means to add charged solid or liquid particles to...

C055S360000, C095S071000, C096S053000, C239S690000, C239S705000

Reexamination Certificate

active

06602329

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a dust collector and method for collecting dust, which is used to remove dust, mist, and the like contained in a gas.
In order to efficiently collect fine dust (submicron particles), mist, and the like, the applicant has before proposed a dust collector in Japanese Patent Provisional Publication No. 10-174899 (No. 174899/1998).
This dust collector includes charging means for charging a substance to be collected such as dust and mist contained in a gas, spray means for spraying a dielectric on the substance to be collected charged by the charging means, electric field forming means for forming an electric field for dielectrically polarizing the dielectric sprayed from the spray means, and dielectric collecting means for collecting the dielectric which has arrested the substance to be collected.
The above-described dust collector has a high voltage applied electrode
100
and a ground electrode
200
, shown in
FIG. 24
, as the electric field forming means, and allows an exhaust gas containing the substance to be collected such as dust and mist (in this example, SO
3
mist indicated by the black dots in the figure)
300
and a dielectric (in this example, water mist)
400
sprayed from the spray means to flow between the electrodes
100
and
200
.
The substance to be collected
300
has been charged, for example, negatively in advance by the charging means. On the other hand, the dielectric
400
is dielectrically polarized by a direct current electric field formed between the electrodes
100
and
200
. Therefore, the substance to be collected
300
is collected by the dielectric
400
by means of the Coulomb's force acting between the particles of dielectric
400
.
When an alternating voltage is applied between the electrodes
100
and
200
as shown in
FIG. 25
, the polarization polarity of the dielectric
400
changes with time, and the charged substance to be collected moves in a zigzag form. Thus, the substance to be collected
300
is collected by the dielectric
400
by means of the Coulomb's force acting between the particles of dielectric
400
.
According to this dust collector of the earlier application, submicron particles can be collected efficiently despite the compact configuration.
OBJECT AND SUMMARY OF THE INVENTION
In order to further increase the efficiency in collecting the substance to be collected
300
, it is necessary for the dielectric
400
to exist enough up to the upper part (rear part) of the electrodes
100
and
200
. In the conventional collector, however, the dielectric shows a tendency to rarefy at the upper part (rear part) of the electrodes
100
and
200
.
The inventors found that the aforementioned tendency is ascribed to the charging of the dielectric sprayed from the spray means.
Specifically, the particles of dielectric sprayed from the spray means are charged positively or negatively because the particles of dielectric exchange charges at the boundary of a pipe through which the dielectric itself flows. Therefore, the dielectric
400
having been charged positively or negatively is sprayed from the spray means, which is a cause of bringing about the aforementioned tendency as described below.
In
FIG. 26
corresponding to
FIG. 24
, the circle mark applied to the side of the particle of dielectric
400
indicates the charging state of the particle of dielectric
400
. If the charged dielectric
400
is supplied between the electrodes
100
and
200
, the positively charged dielectric
400
is attracted to the electrode
100
, and the negatively charged dielectric
400
is attracted to the electrode
200
by means of the Coulomb's force. Therefore, most of the dielectric
400
is collected by the electrodes
100
and
200
before it arrives at the upper part (rear part) of the electrodes
100
and
200
.
FIG. 27
shows a case where an alternating electric field is applied to between the electrodes
100
and
200
. In this case, the charged dielectric
400
goes while being swayed to right and left with the change cycles of alternating electric field. At this time, the particles of dielectric
400
having a positive and negative charge are attracted to one another and aggregate, so that the distribution concentration of the dielectric
400
decreases toward the upper part of the electrodes
100
and
200
. That is, even if an alternating electric field is applied to between the electrodes
100
and
200
, the dielectric
400
rarefies at the upper part of the electrodes
100
and
200
.
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a dust collector and method for collecting dust in which the rarefaction of dielectric at the rear part of electric field forming means is prevented, whereby the collecting efficiency can be increased.
To achieve the above object, the present invention provides a dust collector, comprising charging means for charging a substance to be collected, such as dust and mist, contained in a gas; spray means for spraying a dielectric on the substance to be collected charged by the charging means; electric field forming means, having first and second electrodes for forming a direct current electric field, for dielectrically polarizing the dielectric sprayed by the spray means by means of the direct current electric field; dielectric collecting means for collecting the dielectric which has arrested the substance to be collected; and grounding means, provided in the spray means, for electrically grounding the dielectric before being sprayed, wherein a charge of the dielectric is caused to escape by the grounding means so that the dielectric is made electrically neutral.
According to the present invention, since the electrically neutral dielectric is sprayed from the spray means, the arrest of the sprayed dielectric by the electrode of the electric field forming means is restrained. Therefore, a shortage of dielectric in the rear zone of an electric field forming section is prevented, so that the efficiency in collecting the substance to be collected is increased.
A metallic net is used as the grounding means, and the net can be disposed in a flow path of the dielectric in the spray means so as to traverse the flow path. With the use of the metallic net as de-electrifying means, a satisfactory de-electrifying effect can be achieved without obstructing the flow of the dielectric.
Also, the present invention provides a dust collector, comprising charging means for charging a substance to be collected, such as dust and mist, contained in a gas; spray means for spraying a dielectric on the substance to be collected charged by the charging means; electric field forming means, having first and second electrodes for forming a direct current electric field, for dielectrically polarizing the dielectric sprayed by the spray means by means of the direct current electric field; and dielectric collecting means for collecting the dielectric which has arrested the substance to be collected, wherein a plurality of corona discharge sections arranged in the flow direction of the gas at given intervals are formed on the opposed surfaces of the first and second electrodes to generate band-shaped uniform corona discharge perpendicular to the gas flow, and the dielectric is provided with a charge of reverse polarity alternately by the corona discharge.
According to the present invention, the dielectric goes in a zigzag form to the rear zone of the electric field forming means under the action of the charge developed by discharge of the corona discharge section, so that the substance to be collected can be collected very efficiently.
The arrangement interval between the corona discharge sections on the first electrode and the arrangement interval between the corona discharge sections on the second electrode are preferably set so as to be equal to each other. Also, both of the corona discharge sections are preferably provided so as to have an arrangement phase difference of ½

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