Gas separation: apparatus – Electric field separation apparatus – Including gas flow distribution means
Reexamination Certificate
2001-10-31
2003-10-21
Chiesa, Richard L. (Department: 1724)
Gas separation: apparatus
Electric field separation apparatus
Including gas flow distribution means
C096S069000, C096S079000, C096S097000
Reexamination Certificate
active
06635106
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dust collector which is designed to collect a dust in the outside air, a dust in a room or the like in an air-conditioning field and an industrial field, and which is provided with a charging section for electrostatically charging a dust without utilization of a corona discharge, wherein ozone is hardly generated, and to an air-conditioning system including such a dust collector.
BACKGROUND ART
There is such a conventionally known dust collector, for example, described in Japanese Patent Laid-open No. H6-31200. The conventionally known dust collector will be described below with reference to FIG.
8
. As shown in
FIG. 8
, a charging section
101
comprises a linear electrode
102
and an earthed electrode plate A
103
. A dust-collecting section comprising a voltage applied electrode plate
105
and an earthed electrode plate B
106
is mounted at a location downstream of the charging section
101
in an air-flowing direction. In usual, a voltage is applied to each of the linear electrode
102
and the voltage-applied electrode plate
105
by a high-voltage regulated power supply
107
, so that there is a difference in potential in a range of 5 to 15 kV between the linear electrode
102
and the earthed electrode plate
103
in the charging section
101
, and there is a difference in potential in a range of 2 to 6 kV between the voltage-applied electrode plate
105
and an earthed electrode plate B
106
in the dust-collecting section
104
.
In such arrangement, a high voltage is applied to the linear electrode
102
in the charging section
101
, whereby a very intensive electric field is produced in the vicinity of the linear electrode
102
. Therefore, a substance contained in air and having an electric charge collides with molecules of air, whereby electrons are separated from the molecules of air, and separated electrons are deposited to the air molecules to become ionized air. This is called the ionization of air herein. Air present as an insulating material between the earthed electrode and the linear electrode produces a dielectric breakdown and as a result, the ionization of the air occurs, while being accompanied by a large uniform discharged current. Such a discharging phenomenon is called a corona discharge. Ionized air produced by the corona discharge is deposited to a dust contained in the air supplied to the dust collector to electrostatically charge the dust. The electrostatically charged dust is introduced along a flow of fed air into the dust-collecting section
104
and deposited to either of the electrode plates under a force of an electric field between the voltage-applied electrode plate
105
and the earthed electrode plate B
106
. In this manner, the dust is removed, and the cleaned air is blown out from the rear of the dust-collecting section
104
. In the above conventional example, the linear electrode is illustrated as a discharging electrode, but even if another electrode having a shape forming an uneven electric field, e.g., a needle-shape is used, a corona discharge occurs likewise in a state in which a uniform current flows between a tip end of the needle-shaped electrode and the earthed electrode plate A
103
, whereby a dust is electrostatically charged and removed in a similar mechanism.
There is also a conventionally known dust collector of a type in which the dust-collecting section
104
is replaced by a filter
108
. Such conventionally known dust collector will be described below with reference to FIG.
9
. As shown in
FIG. 9
, a charging section
101
comprising a linear electrode
102
and an earthed electrode plate A
103
and a filter
108
are mounted in the named order in an air-flowing direction. A conductive lattice plate
109
is placed at a location downstream of the filter
108
and connected to earth. Usually, a voltage is applied to the linear electrode
102
by a high-voltage regulated power supply
107
, so that there is a difference in potential in a range of 5 to 15 kV between the linear electrode
102
and the earthed electrode plate A
103
in the charging section
101
.
In the above arrangement, a corona discharge is produced in the vicinity of the linear electrode
102
in the charging section
101
to electrostatically charge a dust and at the same time, an electric field is generated between the linear electrode
102
and the lattice plate
109
by applying a voltage to the linear electrode
102
, whereby a filter medium of the filter
108
is polarized by the electric field. The electrostatically charged dust introduced into the filter receives a force for causing the dust to flow along a polarized electric field within the filter medium toward a surface of a filter medium fiber. As a result, the dust is easy to become collected to the filter medium, and the dust collection performance is enhanced.
Such conventional dust collector is accompanied by a problem that a discharged current in the charging section for electrostatically charging the dust is large. If the discharged current is increased, the amount of power consumed and the amount of ozone (harmful to a human body) generated are increased and for this reason, it is required to electrostatically charge the dust in such a manner that the discharged current does not flow much.
In the charging section of the conventional electric dust collector, a plus voltage is applied to the discharging electrode in order to inhibit the amount of generated ozone. Therefore, the conventional dust collector suffers from a problem that minus ions commonly alleged to provide a good effect of relaxing a human's frame of mind cannot be released simultaneously with the electrical charging of the dust. Therefore, it is required that minus ions can be released simultaneously with the electrical charging of the dust without flowing of discharged current.
The conventional charging section is generally of an arrangement in which a linear electrode made of tungsten is used as a discharging electrode, and the earthed electrode plate is mounted in an opposed relation to the linear electrode. However, there is a problem that the delivery and reception of an electric charge occurs in all portions of a surface of the linear electrode simultaneously with the ionization of air in the vicinity of the linear electrode and for this reason, useless discharged current flows. Another problem is that the air cannot be ionized efficiently for the reason that it is difficult to intensify the electric field to more than before, because the surface of the linear electrode is smooth. A further problem is that charged particles such as electrons, ions and charged dust particles collide against the discharging electrode, whereby the discharging electrode is liable to be worn, because a high voltage is applied to the discharging electrode and a very intensive electric field is formed in the vicinity of the discharging electrode. Therefore, it is required that the air is ionized efficiently with useless discharged current eliminated, and the collision of the charged particles against the discharging electrode is reduced.
The conventional charging section is designed so that discharged current on the order of 10 to 20 &mgr;A per 0.1 m of the linear electrode and on the order of 100 to 200 &mgr;A per air flow rate of 1 m
3
/min is permitted to flow, thereby providing a dust collection efficiency of 80% or more. Even when the needle-shaped electrode is used, discharged current on the order of 100 to 200 &mgr;A per air flow rate of 1 m
3
/min flows, and likewise, a corona discharge is produced to electrostatically charge a dust. If the discharged current of such level flows, the following problem is encountered: the amount of power consumed is large, and ozone is also generated in an amount on the order of 20 ppb to 100 ppb, which is a level not good for the health of a human and which is more than a threshold value of odor, resulting in an uncomfortable ozone odor. Therefore, it is required that the discharged current is reduced remarkably, while en
Katou Ryou
Tashiro Yoshikazu
Armstrong Westerman & Hattori, LLP
Chiesa Richard L.
Matsushita Seiko Co., Ltd.
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