U.S. patent application number 10/480820 was filed with the patent office on 2004-06-10 for exhaust purification apparatus and utilization thereof.
Invention is credited to Hirano, Mikio, Iwata, Misao, Kato, Shinji, Kurobe, Hisanori, Watanabe, Hirokazu.
Application Number | 20040110458 10/480820 |
Document ID | / |
Family ID | 27342075 |
Filed Date | 2004-06-10 |
United States Patent
Application |
20040110458 |
Kind Code |
A1 |
Kato, Shinji ; et
al. |
June 10, 2004 |
Exhaust purification apparatus and utilization thereof
Abstract
The present invention relates to an exhaust purification
apparatus for removing contaminants and odorous components from
exhaust from cooking or the like, to an exhaust purification
cabinet and cooking device equipped with the exhaust purification
apparatus, and to a cooking system equipped with such a cooking
device. The exhaust purification apparatus in accordance with the
present invention comprises a pretreatment unit (117) for trapping
contaminants present in the exhaust and an optical treatment unit
(119) comprising a photocatalytic filter (62) and disposed
downstream of the pretreatment unit. The exhaust purification
apparatus is disposed, for example, in an exhaust duct extending
from a kitchen. The pretreatment unit (117) preferably comprises a
dust collector (50) for trapping smoke particles present in the
exhaust and/or a de-oiling filter (20) for trapping oil and fat
components present in the exhaust. The exhaust purification cabinet
comprises the exhaust purification apparatus contained in a cabinet
having an exhaust path formed therein. The cooking device comprises
the exhaust purification apparatus in a cooking device body
comprising the cooking unit and having an exhaust path formed
inside thereof. The cooking system comprises a plurality of cooking
devices and a main duct connected to exhaust release openings of
the cooking units.
Inventors: |
Kato, Shinji; (Aichi,
JP) ; Iwata, Misao; (Aichi, JP) ; Watanabe,
Hirokazu; (Aichi, JP) ; Kurobe, Hisanori;
(Aichi, JP) ; Hirano, Mikio; (Aichi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Family ID: |
27342075 |
Appl. No.: |
10/480820 |
Filed: |
January 28, 2004 |
PCT Filed: |
July 13, 2001 |
PCT NO: |
PCT/JP01/06112 |
Current U.S.
Class: |
454/1 |
Current CPC
Class: |
F23J 15/003 20130101;
B01D 2255/802 20130101; F23J 2900/15024 20130101; B01D 53/86
20130101; F23J 15/025 20130101; F23J 2900/15003 20130101; F24C
15/2035 20130101 |
Class at
Publication: |
454/001 |
International
Class: |
F23J 011/00 |
Claims
What is claimed is:
1. An exhaust purification apparatus disposed in an exhaust
channel, comprising a pretreatment unit for trapping contaminants
present in exhaust, and an optical treatment unit having a
photocatalytic filter, wherein said optical treatment unit is
disposed downstream of said pretreatment unit.
2. The exhaust purification apparatus as described in claim 1,
wherein said photocatalytic filter comprises a ceramic substrate
and a photocatalyst supported on said ceramic substrate, said
ceramic substrate comprises a ceramic porous body having a
three-dimensional net-like structure and ceramic particles held in
said ceramic porous body, and the mean particle size of said
ceramic particles is from no less than 1 .mu.m to no more than 100
.mu.m.
3. The exhaust purification apparatus as described in claim 2,
wherein the mean diameter of skeletal sections of said ceramic
porous body is from no less than 100 .mu.m to no more than 1000
.mu.m.
4. The exhaust purification apparatus as described in claim 3,
wherein said photocatalytic filter satisfies at least one of the
following three conditions: (1) a porosity of from no less than 65%
to no more than 95%; (2) a bulk density of from no less than 0.15
g/cm.sup.3 to no more than 0.60 g/cm.sup.3; and (3) a number of
cells of from no less than 10 cells per 25 mm to no more than 30
cells per 25 mm.
5. The exhaust purification apparatus as described in claim 1,
wherein said pretreatment unit comprises a particulate filter for
trapping particles present in the exhaust.
6. The exhaust purification apparatus as described in claim 1,
wherein said pretreatment unit comprises a dust collector for
trapping smoke particles present in the exhaust.
7. The exhaust purification apparatus as described in claim 1,
wherein said pretreatment unit comprises a de-oiling filter for
trapping oil and fat components present in the exhaust.
8. The exhaust purification apparatus as described in claim 7,
wherein said de-oiling filter has a capacity of removing no less
than 70 wt. % of oil and fat components present in the exhaust.
9. The exhaust purification apparatus as described in claim 7,
wherein said de-oiling filter is a multi-layer plate-like
filter.
10. The exhaust purification apparatus as described in claim 1,
wherein said pretreatment unit comprises a de-oiling filter for
trapping oil and fat components present in the exhaust and a dust
collector for trapping smoke particles present in the exhaust, and
said dust collector is disposed downstream of said de-oiling
filter.
11. The exhaust purification apparatus as described in claim 10,
wherein the sectional area of the opening of said exhaust channel
at each flow inlet side of the zone where said de-oiling filter,
dust collector, and photocatalytic filter are located increases in
the order of description.
12. The exhaust purification apparatus as described in any one
claim from claims 1 through 11, which is further provided with a
cabinet comprising an intake opening, an exhaust release opening,
and an exhaust path from said intake opening to said exhaust
release opening.
13. The exhaust purification apparatus as described in any one
claim from claims 1 through 11, which is further provided with a
cooking device body comprising a cooking unit for heating and
cooking the product which is to be cooked, an intake opening for
sucking in the exhaust from said cooking unit, an exhaust release
opening for releasing exhaust that has been purified, and an
exhaust path passing from said intake opening to said exhaust
release opening.
14. The exhaust purification apparatus as described in any one
claim from claims 1 through 11, wherein said optical treatment unit
further comprises a light source for illuminating said
photocatalytic filter with light.
15. The exhaust purification apparatus as described in any one
claim from claims 1 through 11, which further comprises a means for
supplying ozone that supplies ozone into said exhaust channel.
16. An exhaust purification cabinet containing the exhaust
purification apparatus described in any one claim from claims 1
through 11 in a cabinet comprising an intake opening, an exhaust
release opening, and an exhaust path from said intake opening to
said exhaust release opening.
17. A cooking device containing the exhaust purification apparatus
described in any one claim from claims 1 through 11 in a cooking
device body comprising a cooking unit for heating and cooking the
product which is to be cooked, an intake opening for sucking in the
exhaust generated from said cooking unit, an exhaust release
opening for releasing exhaust that has been purified, and an
exhaust path passing from said intake opening to said exhaust
release opening.
18. A cooking system comprising a plurality of the cooking devices
described in claim 17 and a main duct connected to the exhaust
release opening of each cooking device.
Description
FIELD OF TECHNOLOGY
[0001] The present invention relates to an exhaust purification
apparatus for the purification of exhaust. In particular, the
present invention relates to an exhaust purification apparatus for
the purification of exhaust containing contaminants and odorous
components such as oil and fat components. Furthermore, the present
invention also relates to an exhaust purification cabinet and a
cooking device comprising the exhaust purification apparatus.
Moreover, the present invention relates to a cooking system
comprising the cooking device.
BACKGROUND TECHNOLOGY
[0002] When food is prepared, exhaust containing a large amount of
contaminants and odorous components such as oil and fat components
is generated. Japanese Utility Model Application Laid-open No.
H1-97136 disclosed an apparatus for conducting purification
treatment for removing the contaminants and odorous components from
such an exhaust. In this apparatus, a fan and a filter are
installed in the exhaust duct and contaminants are trapped with the
filter from the exhaust sucked in by the fan. Furthermore, Japanese
Patent Applications Laid-open Nos. H6-190223, H9-141024, and
H1-224025 disclosed filters to be used for trapping contaminants
present in the exhaust. Japanese Utility Model Application
Laid-open No. H7-24423 disclosed an exhaust purification apparatus
for trapping contaminants by passing the exhaust through a filter
that is held in a tube and rotated. However, none of the
above-mentioned exhaust purification apparatuses could effectively
remove odorous components contained in the exhaust.
[0003] On the other hand, Japanese Patent Application Laid-open No.
H11-207136 disclosed an exhaust purification apparatus in which a
filter (photocatalytic filter) supporting a photocatalyst was
irradiated with UV radiation and the oil and fat components or
odorous components contained in the exhaust were decomposed by the
photocatalytic action. A filter supporting a photocatalyst was also
disclosed in Japanese Patent Application Laid open. No. 2001-38218.
However, when exhaust containing a comparatively large amount of
contaminants is passed through such a photocatalytic filter, the
surface of the photocatalytic filter is covered with the
contaminants (oil and fat components, dust, tar-like substances,
and the like) trapped by the filter. As a result, in certain cases,
the photocatalyst is shielded from UV radiation and the
photocatalytic effect is not demonstrated.
DISCLOSURE OF THE INVENTION
[0004] It is an object of the present invention to provide an
exhaust purification apparatus capable of purifying the exhaust
containing contaminants (oil and fat components and the like) and
odorous components generated by cooking. Another object of the
present invention is to provide an exhaust purification cabinet
equipped with the exhaust purification apparatus. Yet another
object of the present invention is to provide a cooking device
equipped with the exhaust purification apparatus. Still another
object of the present invention is to provide a cooking system
equipped with the cooking device.
[0005] The exhaust purification apparatus in accordance with the
present invention is disposed in an exhaust channel and comprises a
pretreatment unit for trapping contaminants present in the exhaust
and an optical treatment unit having a photocatalytic filter. The
optical treatment unit is disposed downstream of the pretreatment
unit, with respect to the flow direction of the exhaust that passes
through the exhaust channel.
[0006] With the exhaust purification apparatus of such a
configuration, at least part of the contaminants (oil particles,
smoke particles, dust and other nonvolatile components) present in
the exhaust are trapped in the pretreatment unit. As a result, the
amount of the contaminants contained in the exhaust (exhaust
treated in the pretreatment unit) supplied to the photocatalytic
filter is decreased. Therefore, the problem associated with the
performance degradation of the photocatalytic filter caused by
adhesion of the contaminants is resolved or alleviated.
[0007] In a preferred configuration of the exhaust purification
apparatus in accordance with the present invention, the
photocatalytic filter comprises a ceramic substrate and a
photocatalyst supported on the ceramic substrate. The ceramic
substrate comprises a ceramic porous body having a
three-dimensional net-like structure and ceramic particles held in
the ceramic porous body. The mean particle size of the ceramic
particles is from no less than 1 .mu.m to no more than 100
.mu.m.
[0008] In a preferred photocatalytic filter, the mean diameter of
the skeletal sections of the ceramic porous body is from no less
than 100 .mu.m to no more than 1000 .mu.m. Furthermore, the
photocatalytic filter more preferably satisfies at least one of the
following three conditions: (1) a porosity is from no less than 65%
to no more than 95%; (2) a bulk density is from no less than 0.15
g/cm.sup.3 to no more than 0.60 g/cm.sup.3; and (3) the number of
cells is from no less than 10 cells per 25 mm to no more than 30
cells per 25 mm.
[0009] In yet another preferred configuration of the exhaust
purification apparatus in accordance with the present invention,
the pretreatment unit comprises a particulate filter for trapping
particles (oil particles, smoke particles, dust and the like)
present in the exhaust. A dust collector for trapping smoke
particles present in the exhaust and a de-oiling filter for
trapping oil and fat components (oil particles and the like)
present in the exhaust can be used as such a particulate filter.
The de-oiling filter preferably has a capacity of removing no less
than 70 wt. % (more preferably no less than 90 wt. %, and yet more
preferably no less than 95 wt. %) of oil and fat components present
in the exhaust. The percentage of oil and fat components that can
be removed from the exhaust when it passes through the de-oiling
filter is called the "oil removal rate" of the de-oiling filter.
When a plurality of de-oiling filters (for example, multi-layer
plate-like filters) are provided in the pretreatment unit, the
total percentage of the oil and fat components removed by those
de-oiling filters is considered as the oil removal rate.
[0010] In yet another preferred modification of the exhaust
purification apparatus in accordance with the present invention,
the pretreatment unit comprises a de-oiling filter for trapping oil
and fat components present in the exhaust and a dust collector for
trapping smoke particles present in the exhaust. Here, the dust
collector is disposed downstream of the de-oiling filter. It is
also preferred that the sectional area of the exhaust path at each
flow inlet side of the zone where the de-oiling filter, dust
collector, and photocatalytic filter are located increases in the
order of description.
[0011] In yet another exhaust purification apparatus provided in
accordance with the present invention, any of the above-described
exhaust purification apparatuses in accordance with the present
invention further comprises a cabinet comprising an intake opening,
an exhaust release opening.
[0012] In yet another exhaust purification apparatus provided in
accordance with the present invention, any of the above-described
exhaust purification apparatuses in accordance with the present
further comprises a cooking device body comprising a cooking unit
for heating and cooking the product which is to be cooked, an
intake opening for sucking in the exhaust from the cooking unit, an
exhaust release opening for releasing the exhaust that was
purified, and an exhaust path passing from the intake opening to
the exhaust release opening.
[0013] In any of the exhaust purification apparatuses in accordance
with the present, invention, the optical treatment unit preferably
further comprises a light source for illuminating the
photocatalytic filter with light. Further, it is preferred that an
ozone supply means for supplying ozone into the exhaust channel be
further provided.
[0014] The exhaust purification cabinet provided in accordance with
the present invention contains the exhaust purification apparatus
in accordance with the present invention in a cabinet comprising an
intake opening, an exhaust release opening, and an exhaust path
from the intake opening to the exhaust release opening.
[0015] The cooking device provided in accordance with the present
invention comprises the exhaust purification apparatus in
accordance with the present invention in a cooking device body
comprising a cooking unit for heating and cooking the product which
is to be cooked, an intake opening for sucking in the exhaust from
the cooking unit, an exhaust release opening for releasing the
exhaust that was purified, and an exhaust path passing from the
intake opening to the exhaust release opening.
[0016] Further, the cooking system provided in accordance with the
present invention comprises a plurality of the cooking devices in
accordance with the present invention and a main duct connected to
exhaust release openings of cooking devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an explanatory drawing illustrating schematically
the exhaust purification apparatus of the first embodiment.
[0018] FIG. 2 is an explanatory drawing illustrating schematically
a kitchen.
[0019] FIG. 3 is a cross-sectional view illustrating schematically
the optical treatment unit in the exhaust purification apparatus of
the first embodiment.
[0020] FIG. 4 is a plan view illustrating the photocatalytic
unit.
[0021] FIG. 5 is a view along the arrow in the V direction shown in
FIG. 4.
[0022] FIG. 6 is a perspective view illustrating schematically a
photocatalytic filter.
[0023] FIG. 7 is an explanatory drawing illustrating the structure
of the ceramic substrate.
[0024] FIG. 8 is a cross-sectional view along the VIII-VIII line
shown in FIG. 7.
[0025] FIG. 9 is a cross-sectional view showing schematically
another configuration of the optical treatment unit in the exhaust
purification apparatus of the first embodiment.
[0026] FIG. 10 is a characteristic diagram illustrating the
relationship between the mean diameter of skeletal sections and
pressure loss.
[0027] FIG. 11 is a characteristic diagram illustrating the
acetaldehyde decomposition capacity of the photocatalytic
filter.
[0028] FIG. 12 is a cross-sectional view showing schematically the
exhaust purification cabinet of the third embodiment.
[0029] FIG. 13 is a view along the arrow in the XIII direction
shown in FIG. 12.
[0030] FIG. 14 is a view along the arrow in the XIV direction shown
in FIG. 12.
[0031] FIG. 15 is a cross-sectional view showing schematically the
cooking device of the fourth embodiment.
[0032] FIG. 16 is a cross-sectional view showing schematically the
cooking device constituting the cooking system of the fifth
embodiment.
[0033] FIG. 17 is a cross-sectional view showing schematically the
cooking device constituting the cooking system of the sixth
embodiment.
BEST MODE FOR CARRYING OUT THE PRESENT INVENTION
[0034] The best mode for carrying out the present invention will be
described below. It is preferred that the photocatalytic filter
used in the exhaust purification apparatus in accordance with the
present invention comprises a ceramic substrate wherein ceramic
particles are supported on the surface of a ceramic porous body.
Owing to the presence of ceramic particles, peaks and valleys are
formed on the surface of the ceramic porous body. Because of the
anchor effect produced by those peaks and valleys, the
photocatalyst can be held with high stability on the ceramic
substrate. Furthermore, because the presence of such peaks and
valleys increases the surface area of the ceramic porous body a
large amount of the catalyst can be supported per unit surface
area. Moreover, those peaks and valleys can increase the surface
area of the photocatalytic filter per unit volume thereof. Due to
the above-described effects, the contact between the exhaust and
the photocatalyst is improved and the exhaust can be purified with
good efficiency.
[0035] Here, ceramic particles with a mean particle size of from no
less than 1 .mu.m to no more than 100 .mu.m are preferred as the
above-mentioned ceramic particles, and particles with a mean
particle size of from no less than 20 .mu.m to no more than 50
.mu.m are even more preferred. If the mean particle size of the
ceramic particles is less than 1 .mu.m, the efficiency of forming
peaks and valleys on the surface of the ceramic porous body is
decreased. On the other hand, if the mean particle size of the
ceramic particles exceeds 100 .mu.m, such ceramic particles are
difficult to hold with good stability on the surface of the ceramic
porous body.
[0036] It is also preferred that the ceramic porous body be
composed of skeletal sections with a diameter of from no less than
100 .mu.m to no more than 1000 .mu.m. The ceramic porous body with
a mean diameter of skeletal sections of no less than 100 .mu.m
(more preferably, no less than 300 .mu.m) has an appropriate
mechanical strength. Therefore, it can be easily manufactured and
handled. If the mean diameter of the skeletal sections is more than
1000 .mu.m, the light transmissivity of the photocatalytic filter
comprising the ceramic porous body is degraded and the
photocatalyst held inside the photocatalytic filter sometimes
cannot be adequately used. Furthermore, pressure loss occurring
when the exhaust passes through the photocatalytic filter sometimes
becomes too high.
[0037] Furthermore, the photocatalytic filter preferably satisfies
at least one of the following three conditions: (1) a porosity is
from no less than 65% to no more than 95%; (2) a bulk density is
from no less than 0.15 g/cm.sup.3 to no more than 0.60 g/cm.sup.3;
and (3) the number of cells is from no less than 10 cells per 25 mm
to no more than 30 cells per 25 mm.
[0038] A photocatalytic filter with a porosity of no more than 95%,
a bulk density of no less than 0.15 g/cm.sup.3, and a number of
cells of no more than 30 cells per 25 mm has an appropriate
mechanical strength. Therefore, it can be easily manufactured and
handled. If the porosity of the photocatalytic filter is less than
65%, or the bulk density is more than 0.60 g/cm.sup.3, or the
number of cells is less than 10 cells per 25 mm, the pressure loss
in the exhaust passing therethrough sometimes becomes too high.
Furthermore, in such a photocatalytic filter, the quantity of light
reaching the inside of the filter tends to decrease. Furthermore,
the contact ratio of the photocatalyst and the odorous components
(mainly gaseous organic compounds) present in the exhaust
decreases, and the photocatalytic efficiency sometimes drops.
[0039] The photocatalytic filter has a light transmissivity,
preferably, of from no less than 10% to no more than 50%
(preferably from no less than 20% to no more than 50%) at a
thickness of 5 mm. In the photocatalytic filter with a light
transmissivity of no less than 10%, light can penetrate to the
inner portions of the filter. Therefore, the photocatalyst
supported by the photocatalytic filter can be used effectively. The
light transmissivity within the above-described range can be
realized if at least one (preferably two, even more preferably all)
of the above-described three conditions is satisfied.
[0040] The photocatalytic filter can be advantageously obtained by
a manufacturing process comprising the steps of: (a) impregnating
an organic porous body having a three-dimensional net-like
structure with a slurry containing a ceramic fine powder and a
binding material; (b) causing ceramic particles to adhere to the
above-mentioned undried slurry; (c) heating to burn out the organic
porous body and to produce a ceramic substrate having ceramic
particles supported on a ceramic porous body; and (d) coating a
photocatalytic layer containing a photocatalyst on the surface of a
ceramic substrate.
[0041] A more specific example of the manufacturing method will be
described herein below.
[0042] First, a fine ceramic powder (one or two or more of the fine
powders selected from alumina, silica, and mullite can be used for
this purpose) and a binder as a binding material (any of organic
binders such as dextrin, methyl cellulose, and polyvinyl alcohol,
or inorganic binders such as clay and sodium silicate can be used)
are added to an appropriate amount of water and stirred to prepare
a slurry for the formation of a ceramic porous body. Then, an
organic porous body (foamed urethane resin or the like) having a
three-dimensional net-like structure is impregnated with the
slurry.
[0043] Ceramic particles (one or two or more of the fine powders
selected from alumina, silica, and mullite can be used for this
purpose) are then sprinkled over the organic porous body, which is
wetted with the slurry. As a result, the ceramic particles adhere
to the undried slurry.
[0044] The slurry is then dried and fired to burn out the organic
porous body and also to integrate it by sintering the ceramic
particles and fine ceramic powder constituting the slurry. As a
result, as shown in FIG. 7 and FIG. 8, a ceramic substrate 73 is
formed which comprises a ceramic porous body 71 formed by the
sintered particles of the fine ceramic powder and ceramic particles
72 integrally held by (sintered to) the surface of the ceramic
porous body. Furthermore, as shown in FIG. 8, burn-out marks 78 are
formed.
[0045] A photocatalytic slurry is then prepared, this slurry
containing a photocatalyst as the main component and also
comprising an organic or inorganic binder. The ceramic substrate 73
is impregnated with the photocatalytic slurry, followed by drying
and firing. As a result, a photocatalytic layer 76 covering the
surface of the ceramic substrate 73 (see FIG. 8) is formed. A
photocatalytic filter 62 is thus obtained.
[0046] One or two or more compounds selected from titanium oxide,
tungsten oxide, zinc oxide, vanadium oxide, and zirconium oxide can
be used as the photocatalyst. Titanium oxide is typically used for
this purpose.
[0047] In an optical treatment unit, the photocatalytic filters are
preferably arranged on both sides, opposite each other so as to
sandwich the light source. With such a configuration, light
illuminated from the light source to all sides can be used
effectively. A light source emitting a large amount of light with a
wavelength at which the photocatalyst can function effectively is
preferably used according to the type of the photocatalyst
supported on the photocatalytic filter. Typically, a UV lamp such
as a low-pressure mercury lamp, an ultrahigh-pressure mercury lamp,
or fluorescent lamp such as a so-called black light is used. When
the photocatalyst is titanium oxide, it is especially preferred
that a UV lamp emitting UV radiation (for example, UV radiation
with a peak of from no less than 360 nm and no more than 380 nm)
with a wavelength of from no less than 300 nm to no more than 420
nm be employed.
[0048] The exhaust purification apparatus in accordance with the
present invention can have a structure additionally comprising an
ozone supply means for supplying ozone into the exhaust channel.
Producing a strong oxidizing effect by ozone in addition to the
photocatalytic effect makes it possible to treat the odorous
components and/or contaminants present in the exhaust with even
higher efficiency. A UV lamp (for example, a low-pressure mercury
lamp) emitting light with a wavelength of about 185 nm can be used
as the ozone supply means. Ozone is generated by illuminating
oxygen present inside the exhaust path with light with a wavelength
of about 185 nm.
[0049] This UV lamp may be also employed as a light source for
illuminating the photocatalytic filter with light.
[0050] Examples of the dust collector used in the exhaust
purification apparatus in accordance with the present invention
include an electric dust collector, a filtration dust collector, an
acoustic dust collector, or a centrifugal dust collector.
Typically, an electric dust collector is used. The dust collector
is preferably disposed downstream of the de-oiling filter.
[0051] A typical de-oiling filter called a grease filter, grease
separator, grease extractor, or the like can be used as the
de-oiling filter employed in the exhaust purification apparatus in
accordance with the present invention. The preferred filter among
those de-oiling filters is a filter that has an oil removal rate of
no less than 70 wt. %, preferably no less than 90 wt. %, and even
more preferably no less than 95 wt. %. The de-oiling filter is
preferably composed of a nonflammable material such as metallic
fibers (for example, aluminum fibers) or a material with low
flammability, such as glass fibers. A de-oiling filter composed of
metallic wire such as steel wool (for example, stainless steel
wool) or metallic fibers such as metallic ribbons can be used.
[0052] Such a de-oiling filter can be arranged so that the exhaust
passes a plurality of times through the materials constituting the
filter, as it passes through the pretreatment unit (that is, so
that the exhaust flow is intercepted in a plurality of places by
the materials constituting the filter). For example, a
configuration can be employed in which the de-oiling filters are
supported as plates and a plurality of such plate-like filters are
arranged so as to intercept each exhaust flow.
[0053] From the standpoint of purification efficiency, it is
preferred that the exhaust be passed at a comparatively low
velocity to the dust collector (in particular, electric dust
collector) or photocatalytic filter of all the components
constituting the exhaust purification apparatus in accordance with
the present invention. The flow velocity of the exhaust can be
adjusted, for example, by varying the sectional area of the opening
in the exhaust channel (cross sectional area of the exhaust path).
More specifically, upstream (inflow side) of the de-oiling filter,
the cross sectional area of the exhaust path can be decreased to
increase the flow velocity, and upstream of the dust collector, the
cross sectional area can be increased to increase the flow
velocity. Furthermore, it is preferred that the cross sectional
area be further increased and dispersion (diffusion) of the exhaust
be caused upstream of the photocatalytic filter. With such a
configuration, exhaust streams with respectively appropriate flow
velocities are supplied to the de-oiling filter, dust collector,
and photocatalytic filter, and contaminants of various types can be
effectively removed.
[0054] Further, in addition to the above-described method of
changing the cross sectional area of the exhaust path, decreasing
the flow velocity by changing the flow of exhaust with a baffle
provided inside the exhaust path can be used as a means for
adjusting the flow velocity of the exhaust. Alternatively a fan may
be installed upstream of the de-oiling filter to increase the flow
velocity of the exhaust supplied to the de-oiling filter.
[0055] The exhaust purification apparatus in accordance with the
present invention can further comprise a cabinet comprising an
intake opening, an exhaust release opening, and an exhaust path
passing from the intake opening to the exhaust release opening. The
exhaust purification apparatus comprising such a cabinet (exhaust
purification cabinet) can be moved easily to any installation site.
Therefore, the utility of the exhaust purification apparatus is
increased. Furthermore, such an exhaust purification apparatus can
be used not only for the purification of exhaust, but also as an
air purifier for homes and vehicles.
[0056] In this case, it is preferred that the intake opening be
provided in the lower part of the cabinet, the exhaust release
opening be provided in the upper part of the cabinet, and the
exhaust path be formed so that the exhaust flows from the bottom to
the top inside the cabinet. With such a configuration, the
contaminants (oil particles and the like) present in the exhaust
are removed in the pretreatment unit provided in the lower part.
Therefore, even in the case of leakage of the oil and fat
components trapped in the pretreatment unit, those components do
not reach the optical treatment unit provided in the upper part.
Therefore, adhesion of oil and fat components to the photocatalytic
filter can be effectively prevented. Furthermore, another method
for preventing the penetration of oil and fat components into the
optical treatment unit preferably comprises the steps of
partitioning the inside of the cabinet into a plurality of
treatment chambers and disposing each structural component (for
example, the de-oiling filter, dust collector, and photocatalytic
filter) in those treatment chambers.
[0057] Furthermore, the intake opening may be formed in the upper
part and the exhaust release opening may be formed in the lower
part of the cabinet if the penetration of oil and fat components
trapped in the pretreatment unit into the optical treatment unit is
completely prevented, for example, by appropriately separating the
pretreatment unit and the optical treatment unit. Furthermore, a
configuration may be used in which the pretreatment unit and the
optical treatment unit aligned horizontally in the lengthwise
direction of the cabinet.
[0058] In such an exhaust purification cabinet, the exhaust release
opening thereof can be connected to a main duct of a kitchen or
other area to thereby connect the exhaust channel formed inside the
cabinet to the exhaust channel inside the main duct. An exhaust
purification system can be thus composed of one or a plurality of
exhaust purification cabinets connected to the main duct. An
exhaust purification system can be configured in this way with one
or a plurality of exhaust cabinets connected to the main exhaust
duct.
[0059] Furthermore, the exhaust purification apparatus in
accordance with the present invention can further comprise a
cooking device body comprising a cooking unit, an intake opening,
an exhaust release opening, and an exhaust path passing from the
intake opening to the exhaust release opening. When the
pretreatment unit of such an exhaust purification apparatus
(cooking device) comprises a de-oiling filter, it is preferred that
the de-oiling filter and the photocatalytic filter be disposed with
a displacement in the horizontal direction such that the
photocatalytic filter be located not directly below the de-oiling
filter. Furthermore, the cooking device body may be also a movable
cooking table. Providing such a cooking table makes it possible to
construct the exhaust purification apparatus in accordance with the
present invention as a smokeless cooking device.
[0060] Connecting the exhaust release opening of such a cooking
device (cooking device equipped with an exhaust purification
apparatus) to the main duct of a kitchen or the like, makes it
possible to obtain a cooking system comprising one or a plurality
of cooking devices, similarly to the above-described exhaust
purification cabinets.
[0061] The present invention will be described herein below in
greater detail based on embodiments thereof.
[0062] <First Embodiment: Exhaust Purification Apparatus
(1)>
[0063] The First Embodiment relates to the installation of the
exhaust purification apparatus in accordance with the present
invention in an exhaust duct leading from a kitchen to the
outside.
[0064] As shown in FIG. 1 and FIG. 2, a kitchen 105 is partitioned
by a structural wall 104 of a building 101. A door way 103 is
formed in the structural wall 104. A plurality (for example, five)
cooking stands 106 are disposed in the kitchen 105. A range hood
111 is mounted above each cooking stand 106. One end of an exhaust
duct 108 extending to the rooftop exhaust release opening 112 along
the outer wall surface of the building 101 is opened in the range
hood 111.
[0065] The exhaust purification apparatus 107 can be said to be
generally composed of a pretreatment section 117 provided in
connection to one end of the exhaust duct 108, and an optical
treatment section 119 provided in the vicinity of the other end
inside the exhaust duct 108. A fan 114 is provided between the
pretreatment section 117 and the optical treatment section 119. If
the fan 114 is operated, the exhaust released from inside of the
kitchen 105 flows via the pretreatment section 117, exhaust duct
108, and optical treatment section 119 and is released to the
outside from the exhaust release opening 112, as shown by the
arrows in FIG. 1.
[0066] A de-oiling filter 20 is arranged in the pretreatment unit
117. The de-oiling filter 20 is a general grease filter and has a
capacity of removing no less than 70 wt. % of oil and fat
components present in the exhaust.
[0067] The optical treatment unit 119, as shown in FIG. 3,
comprises a plurality (two in this case) of photocatalytic units 61
disposed inside the exhaust duct 108. As shown in FIG. 4 and FIG.
5, each photocatalytic unit 61 comprises a plurality of (for
example, twelve) photocatalytic filters 62 and light sources 63 for
illuminating those photocatalytic filters 62 with light. The
photocatalytic filters 62 are arranged opposite each other so as to
sandwich the light sources 63, and all those components are held
integrally in a frame 64.
[0068] The photocatalytic filter 62, as shown in FIG. 6, is formed
to have a planar shape. The photocatalytic filter 62 comprises a
ceramic substrate 73 shown in FIG. 7 and a photocatalytic layer 76
(see FIG. 8) covering the surface of the ceramic substrate 73. The
photocatalytic layer 76 contains titanium oxide serving as a
photocatalyst as the main component. The ceramic substrate 73, as
shown in FIG. 7, comprises a ceramic porous body 71 composed of
skeletal sections 77 with three-dimensional net-like structure and
a plurality of ceramic particles 72 held on the surface of the
porous ceramic body 71. The ceramic particles 72 held on the
surface of the porous ceramic body 71 form peaks and valleys on the
surface of the ceramic substrate 73. Furthermore, for convenience
of explanation, in part of FIG. 7, ceramic particles 72 are removed
to expose the skeletal sections 77 of the porous ceramic body 71.
FIG. 8 is a cross-sectional view along the VIII-VIII line of the
configuration in which the photocatalytic layer 76 was formed on
the ceramic substrate 73 shown in FIG. 7.
[0069] In the photocatalytic filter 62 used in the present
embodiment, alumina particles with a mean diameter of 22 .mu.m are
used as the ceramic particles 72. Furthermore, the mean diameter of
the skeletal section 77 of the porous ceramic body 71 is within a
range of from no less than 100 .mu.m to no more than 1000 .mu.m.
The photocatalytic filter 62 has a porosity within a range of from
no less than 65% to no more than 95%, a bulk density within a range
of from no less than 0.15 g/cm.sup.3 to no more than 0.60
g/cm.sup.3, and a number of cells within a range of from no less
than 10 cells per 25 mm to no more than 30 cells per 25 mm.
Furthermore, the light transmissivity of the photocatalytic filter
62 is within a range of from no less than 10% to no more than 50%,
when the thickness is 5 mm.
[0070] As shown in FIG. 4 and FIG. 5, the frame 64 is formed to
have a box-like shape and is composed from a corrosion-resistant
metal such as stainless steel, and a pair of opposing side surfaces
thereof are open. Furthermore, a plurality (for example, six)
photocatalytic filters 62 are arranged in a row on the same
surface, and those filters are held on a lattice-like frame 68,
thereby forming a planar photocatalytic module 69. Two
photocatalytic modules 69 are mounted in the openings provided in
the two side surfaces of the frame 64. A plurality of light sources
63 held in the frame 64 are arranged parallel to each other between
those photocatalytic modules 169. In the photocatalytic unit 61 of
such a configuration, the photocatalytic filters 62 are exposed to
the outside from the openings in two sides of the frame 64. The
exhaust passes through the photocatalytic unit 61 via the two-layer
photocatalytic filter 62. In the present embodiment, four UV lamps
were used as the light sources 63.
[0071] Instead of arranging the photocatalytic unit 61 in which the
photocatalytic filters 62 were integrated with the light sources
63, the photocatalytic filters 62 and light sources 63 may be
arranged as separate components in the exhaust duct 108, for
example, as shown in FIG. 9. The light sources 63 can be arranged
between the two photocatalytic filters 62. Furthermore, the light
source 63 may be disposed further downstream of the photocatalytic
filter 62 which is located in the most downstream location with
respect to the flow direction of the exhaust. Furthermore, the
light source 63 may be disposed further upstream of the
photocatalytic filter 62 which is located in the most upstream
location with respect to the flow direction of the exhaust. Those
light sources 63 disposed upstream or downstream are preferably
provided with reflective plates 79, on the sides that do not face
the photocatalytic filter 62.
[0072] The operation of the exhaust purification apparatus 107 will
be described below.
[0073] As shown in FIG. 1, cooking conducted inside the kitchen 105
produces contaminants and odorous components. The exhaust
containing those contaminants and odorous components is sucked into
the range hood 111 by the operation of fan 114 and passed through
the de-oiling filter 20 provided in the pretreatment unit 117. As a
result, no less than 70 wt. % (preferably no less than 90 wt. %,
even more preferably no less than 95 wt. %) of the oil and fat
components contained in the exhaust are removed.
[0074] The exhaust that passes through the pretreatment unit 117
further flows inside the exhaust duct 108 to the optical treatment
unit 119 and passes through the photocatalytic filters 62 installed
in the photocatalytic unit 61. In this process, the exhaust
traverses a non-linear path so as to weave through the
three-dimensional net-like structure of the photocatalytic filter
62. As a result, a small amount of contaminants remaining in the
exhaust is trapped in the photocatalytic filters 62. Furthermore,
odorous components remaining in the exhaust are brought into
contact with the photocatalytic layer 76 formed on the surface of
the photocatalytic filter 62 by a turbulent flow generated by the
passage of the exhaust. Those contaminants and odorous components
are photo-decomposed by the photocatalytic action of titanium oxide
serving as the main component of the photocatalytic layer 76.
[0075] Thus, if titanium oxide is illuminated with UV radiation
emitted from the light sources 63, moisture (H.sub.2O) that adheres
to the surface of the photocatalytic layer 76 or moisture present
in the exhaust is oxidized, producing hydroxyl radicals (.OH). At
the same time, oxygen is reduced and superoxide ions
(.O.sub.2.sup.-) are produced. Because those hydroxyl radicals and
superoxide ions demonstrate a strong oxidizing effect, the
contaminants (in particular, organic compounds) trapped on or
brought into contact with the surface of the photocatalytic filter
62 can be decomposed. Therefore, odorous components and fine
contaminants present in the exhaust can be decomposed and removed
from the exhaust by photocatalytic action. Moreover, the exhaust is
converted into pure air and can be released to the outside through
the exhaust opening 112.
[0076] <Second Embodiment: Exhaust Purification Test>
[0077] Exhaust, generated from a daily dish-cooking site, was
purified by using the exhaust purification apparatus 107, having a
structure described in the First Embodiment.
[0078] A total of five friers, three small kitchen ranges, and one
steamer were disposed in the kitchen 105 shown in FIG. 1 and FIG.
2. Cooking of fried food, dumplings, boiled food, Japanese pickles
and preparation of marine products were carried out in the kitchen
105 for 10 h per day. The exhaust from the daily dish-cooking site
was purified with the exhaust purification apparatus 107 at a flow
rate of the exhaust of 2000 m.sup.3/h and a flow velocity of 0.76
m.sup.2/s.
[0079] An AirWonder.TM. filter manufactured by TotekJapan Co., Ltd.
was used as the de-oiling filter 20 employed in the pretreatment
unit 117.
[0080] In the photocatalytic unit 61 of the optical treatment unit
119, as shown in FIG. 4 and FIG. 5, a total of six photocatalytic
filters 62 were held in the frame 68 so as to form a configuration
with a length of 500 mm, a height of 400 mm, and a thickness of 13
mm. The units were assembled in the frame 64 so as to form two
layers with a spacing of 38 mm therebetween in the thickness
direction thereof (exhaust flow direction). The photocatalytic unit
61 had the following external dimensions: length 506 mm, height 444
mm, thickness 64 mm. Each photocatalytic unit 61 comprised four UV
lamps as power sources 63. A 6 W black light (manufactured by
Noritake Co., Limited, trade name "HL Lamp," wavelength 300-420 nm,
peak wavelength 360-380 nm) was used as the UV lamp. A total of
three of photocatalytic units 61 were connected in the lateral
direction, and two such sets were fabricated and arranged inside
the exhaust duct 108 so as to obtain two layers against the flow
direction of exhaust.
[0081] Exhaust was purified for 1 month and 4 months under the
above-described conditions. Then, the concentration of odor in the
exhaust discharged from the exhaust release opening of the exhaust
duct, was measured with a three-point odorous cloth method by an
odor measurement officer. The UV lamps were operated continuously
during exhaust purification. The concentration of odor in the
exhaust discharged from the exhaust release opening of the exhaust
duct before the installation of the exhaust purification apparatus
and the concentration of odor in the kitchen refuse collection site
where the kitchen refuse discharged from the kitchen was collected
were measured in a similar manner for the sake of comparison. The
results are shown in Table 7. The relation between the odor index Z
and odor concentration Y is represented by the formula
Z=10logY.
1TABLE 1 Odor Odor concentration concentration Sample No. Y Z Under
the range hood 550 27 (original odor) Exhaust release opening 730
29 (before the installation of the exhaust purification apparatus)
Exhaust release opening 98 20 (one month after the installation of
the exhaust purification apparatus) Exhaust release opening 41 16
(four months after the installation of the exhaust purification
apparatus) Kitchen refuse collection site 730 29
[0082] As shown in Table 1, the exhaust discharged from the exhaust
release opening before the installation of the exhaust purification
apparatus had a high odor concentration similarly to the kitchen
refuse collection site. The odor concentration in the exhaust is
higher than the exhaust odor (original odor) under the range hood
apparently because of the effect of contaminants and odorous
components that had already adhered inside the exhaust duct. On the
other hand, the odor concentration one month after the installation
of the exhaust purification apparatus decreased substantially and
the exhaust odor could not be sensed at all. This is apparently
because the contaminants and odorous components contained in the
newly discharged exhaust and the odorous components that have
already adhered inside the exhaust duct were almost completely
removed by the installed exhaust purification apparatus.
Furthermore, four months after the installation of the exhaust
purification apparatus, the results obtained were equivalent to or
better than those obtained one month after the installation.
TEST EXAMPLE 1
[0083] A filter comprising a ceramic substrate in which ceramic
particles were held in a porous ceramic body with a
three-dimensional net-like structure and a photocatalyst supported
on the ceramic substrate was used as the photocatalytic filter
constituting the exhaust purification apparatus of the First
Embodiment. Several tests were devised, and the effect produced by
the photocatalytic filter composed by using the ceramic substrate
of such a shape was studied together with the optimum size of
ceramic particles.
[0084] The samples for the tests were fabricated as follows: A
total of 446.5 g of fine ceramic powder (fine alumina powder), 16.0
g of talc, 36.5 g of kibushi clay, 155 g of water, and 12.5 g of a
dispersant were placed into a pot mill made of polyethylene and
having a capacity of 2 L. Furthermore, alumina balls with a
diameter of 10 mm were also placed into the pot mill to about 1/3
thereof and the components were stirred and mixed for 5 h. Then,
127.1 g of an organic binder (manufactured by Daiichi
Pharmaceuticals Co., Ltd., trade name "Seramo TB-01") was added to
the pot mill, and the components were further stirred for 20 h. A
slurry for the formation of a porous ceramic body was thus
prepared.
[0085] An organic porous body (in this case, planar urethane foam)
having a three-dimensional net-like structure was placed into the
slurry and impregnated therewith. The urethane foam was then
removed from the slurry and the excess slurry was pressed out and
removed with a roller.
[0086] Ceramic particles (alumina particles) were then sprinkled
over the urethane foam and caused to adhere to the undried slurry.
At this time, the alumina particles were sprinkled while the
urethane foam was subjected to vibrations. As a result, nonuniform
adhesion of the alumina particles was prevented and the excess
alumina particles were caused to fall to the rear surface side of
the urethane foam.
[0087] The slurry and the urethane foam with the alumina particles
adhered thereto were dried for 24 h at a temperature of 70.degree.
C. and fired for 1 h at a temperature of 160.degree. C. As a result
of firing, the urethane foam was burned out and ceramic substrate
was obtained in which the alumina particles were supported on
(sintered to) the porous ceramic body with a three-dimensional
net-like structure.
[0088] A variety of ceramic substrates were fabricated in the same
manner as described hereinabove, except that the mean diameter of
alumina particles that were caused to adhere to the undried slurry
was changed.
[0089] Those ceramic substrates were impregnated with a
photocatalytic slurry and fired at a temperature of 500.degree. C.
As a result, a photocatalytic layer covering the front surface of
the ceramic substrate was baked to the ceramic substrates. A
photocatalytic slurry (manufactured by Ishihara Sangyo K. K., trade
name ST-K01) containing silica (20 wt. % based on the slurry) as an
inorganic binder and having fine particles of anatase-type titanium
oxide (photocatalyst) monodispersed in an aqueous solvent was used
as the above-mentioned photocatalytic slurry. A variety of samples
(photocatalytic filters) were prepared with alumina particles
(ceramic particles) of different mean particle sizes constituting
the ceramic substrates.
[0090] Samples were then prepared in which a photocatalytic layer
was formed on the surface of a porous ceramic body (no alumina
particles were supported thereon) in the same manner as described
hereinabove, except that no alumina particles were used.
[0091] The weight of the photocatalytic layer supported on the
samples was found from the difference between the weight of the
ceramic substrate (porous ceramic body in the sample using no
alumina particles) and the weight of the sample and the supported
amount of the photocatalyst was found by multiplying the result by
the content of the photocatalyst. Furthermore, external dimensions
(volume) of the samples were measured and the mass of the
photocatalyst supported per unit volume of each sample was
calculated from the supported amount of the photocatalyst and the
volume of the samples.
[0092] Furthermore, the bulk density of the samples was calculated
from the volume and mass of each sample. A specific surface area of
each sample was measured using the single-point BET
(Brunauer-Emmett-Teller) method. Based on those values, the surface
area of each sample per unit volume thereof was calculated by the
following calculation formula:
(Surface area per 1 cm.sup.3 of sample)=(specific surface area
[m.sup.2/g]).times.(bulk density [g/cm.sup.3]).
[0093] Surface area and the supported amount of the photocatalyst
per unit volume are shown in Table 2 for each sample. Each value is
the mean of measurements of six samples.
2TABLE 2 Supported Mean particle amount of size of alumina
photocatalyst Surface area particles (.mu.m) (g/cm.sup.3)
(m.sup.2/cm.sup.3) 0.8 0.006 0.62 22 0.013 3.73 47 0.013 4.50 102
0.012 4.43 (No alumina particles) 0.006 0.61
[0094] As shown in Table 2, in samples provided with a
photocatalytic layer on a ceramic substrate having alumina
particles with a mean particle size of no less than 1 .mu.m and no
more than 100 .mu.m, the surface area and the supported amount of
photocatalyst per unit volume were greatly increased in comparison
with those of the sample in which a photocatalytic layer was
provided on a ceramic porous body that supported no alumina
particles. Furthermore, when the surface of the samples was
observed with a scanning electron microscope after the samples were
subjected to vibration, it was found that alumina particles fell
off in the samples with the mean particle size of alumina particles
of more than 100 .mu.m. Furthermore, in samples with a mean
particle size of alumina particles supported on a ceramic porous
body of less than 1 .mu.m, no increase in the surface area and
supported amount of photocatalyst was observed.
TEST EXAMPLE 2
[0095] A photocatalytic slurry (manufactured by Ishihara Sangyo
K.K., trade name STS-01) containing no inorganic binder was used
instead of the photocatalytic slurry used in Test 1. The
concentration of titanium oxide in this photocatalytic slurry was
about 30%. Alumina particles with the mean particle size shown in
Table 3 were used as the ceramic particles. With respect to other
aspects, a variety of samples were formed in the same manner as in
Test Example 1. Furthermore, similarly to Test Example 1, a sample
was prepared in which a photocatalytic layer was formed on the
surface of a ceramic porous body in which no alumina particles were
held.
[0096] With respect to those samples, the supported amount of
photocatalyst and the surface area were measured in the same manner
as in Test Example 1. Furthermore, the surface of the samples was
observed in scanning electron microscope after subjecting the
samples to vibrations. The results are shown in Table 3. All the
values in the table are mean values of the results obtained in
measurements conducted for six samples.
3TABLE 3 Mean particle Supported size of amount of alumina
photocatalyst Surface area particles (.mu.m) (g/cm.sup.3)
(m.sup.2/cm.sup.3) 8 0.061 25.00 22 0.068 23.08 47 0.065 25.23 No
alumina particles 0.011 2.26
[0097] Comparison of Table 2 and Table 3 demonstrates that the
samples (Table 3) prepared by using a photocatalytic slurry
containing no inorganic binder had more titanium oxide held per
unit surface area than the samples (Table 2) prepared by using a
photocatalytic slurry containing an inorganic binder. Furthermore,
when the mean particle size of alumina particles is within a range
of from 8 to 47 .mu.m, the application of vibration was found to
cause no separation of alumina particles and peeling of the
photocatalytic layer.
TEST EXAMPLE 3
[0098] The relationship between the mean diameter of the skeletal
section constituting the ceramic porous body and the compressive
strength of the photocatalytic filter was studied.
[0099] A urethane foam with a mesh size of #13 was used as the
organic porous body, alumina particles with a mean particle size of
22 .mu.m were used as the ceramic particles, and a slurry
manufactured by Ishihara Sangyo K. K. (trade name STS-01) was used
as the photocatalytic slurry. A variety of samples with skeletal
sections of different mean diameters were prepared by a method
similar to that used in Test Example 1. The thickness of the
samples was 15 mm. The mean diameter of the skeletal sections was
varied by changing the concentration of solids and/or viscosity of
photocatalytic slurry used for the preparation of the samples. The
diameter of the skeletal sections was measured in 30 locations by
observing the samples with an electron microscope, and the mean
value calculated from the measurement results was used as the mean
diameter of skeletal sections.
[0100] The compressive strength of each sample was measured with a
universal testing machine (manufactured by Shimadzu Seisakusho K.
K.). The results obtained are shown in Table 4.
4 TABLE 4 Mean diameter of Compressive skeletal sections (.mu.m)
strength (MPa) 76 0.01 101 0.2 560 0.4 981 0.8 1490 1.5
[0101] Table 4 shows that the compressive strength decreased as the
skeletal section became thinner. The samples with a mean skeletal
section diameter of less than 100 .mu.m were damaged and broken
when held the hand. By contrast, the samples with a mean diameter
of skeletal section of no less than 100 .mu.m had a sufficient
handling strength.
TEST EXAMPLE 4
[0102] The relationship between the mean diameter of the skeletal
sections and pressure loss was studied.
[0103] A pressure loss at the usual flow rate of exhaust inside an
exhaust duct in a restaurant or the like was measured for all the
samples prepared in Test Example 3. The results are presented in
Table 5 and FIG. 10.
5 TABLE 5 Mean diameter of Pressure loss (mm Aq) skeletal sections
Flow rate Flow rate Flow rate (.mu.m) 1.5 m/sec 3.0 m/sec 4.5 m/sec
76 1.4 2.6 5.9 101 1.6 2.7 6.1 560 2.5 4.2 7.5 981 3.4 5.9 10.1
1490 8.2 13.7 18.5
[0104] As shown in Table 5 and FIG. 10, if the mean diameter of the
skeletal sections exceeds 1000 .mu.m, the pressure loss rapidly
increases. The results obtained in Test Examples 3 and 4
demonstrate that the mean diameter of skeletal section constituting
the ceramic porous body is preferably from no less than 100 .mu.m
to no more than 1000 .mu.m.
TEST EXAMPLE 5
[0105] The light transmissivity of the photocatalytic filter was
examined.
[0106] A total of eight samples were prepared in the same manner as
in Test Example 3. The samples were of two groups with a mean
diameter of skeletal section of 891 .mu.m and 1490 .mu.m, each
group consisting of four samples with a thickness of 5 mm, 10 mm,
15 mm, and 20 mm.
[0107] The light transmissivity of the samples was measured in the
manner as follows. In greater detail, a black light (manufactured
by Toshiba Linek Co., Ltd., trade name FL10BLB, wavelength 300-420
nm, peak wavelength 360 nm) was disposed in a position at a
distance of 7 cm from the sample surface. A UV intensity meter
(manufactured by Minolta Co., Ltd., trade name UM-10) was disposed
in contact with the rear surface of the sample, and the intensity
of UV light transmitted through the sample was measured. Light
transmissivity was calculated according to the equation given below
based on the ratio of the results obtained when the sample was
arranged between the black light and UV intensity meter to when the
sample was not arranged therebetween.
Light transmissivity (%)=[(Measured intensity obtained when the
sample was arranged)/(Measured intensity obtained when the sample
was not arranged)].times.100.
6 TABLE 6 Light transmissivity (%) Thickness of Mean diameter of
Mean diameter of photocatalytic filter skeletal sections skeletal
sections (mm) 891 .mu.m 1490 .mu.m 20 0.5 0.0 15 2.0 0.0 10 8.4 0.6
5 27.0 8.0
[0108] As shown in Table 6, in the samples with a mean skeletal
section diameter exceeding 1000 .mu.m, the light transmissivity was
almost 0% when the sample thickness was greater than 10 mm. On the
other hand, in the samples with a mean skeletal section diameter of
no more than 1000 .mu.m, the light transmissivity at a thickness of
10 mm was 8.4%, and that at a thickness of 5 mm was no less than
25%, indicating satisfactory light transmissivity. These test
results relating to light transmissivity also demonstrate that the
mean diameter of skeletal section constituting the ceramic porous
body is preferably no more than 1000 .mu.m.
[0109] Furthermore, the porosity, bulk density, and the number of
cells per length of 25 mm were also measured for those samples. The
porosity was measured by a mercury impregnation method, the bulk
density was measured in the same manner as in Test Example 1, and
the number of cells was measured with an optical microscope.
[0110] As a result, all the samples for which satisfactory test
results were obtained satisfied at least one of the following three
conditions: (1) porosity is no less than 65% and no more than 95%
(more preferably, no less than 75% and no more than 85%), (2) bulk
density is no less than 0.159/cm.sup.3 and no more than
0.609/cm.sup.3 (more preferably, no less than 0.189/cm.sup.3 and no
more than 0.409/cm.sup.3), and (3) the number of cells is no less
than 10 cells per 25 mm and no more than 30 cells per 25 mm (more
preferably, no less than 12 cells per 25 mm and no more than 20
cells per 25 mm). Even better results were demonstrated by the
samples satisfying two of those conditions, and still better
results were demonstrated by the samples for which all the
above-described conditions were satisfied.
TEST EXAMPLE 6
[0111] The ability of the filter to decompose acetaldehyde
decomposition was examined.
[0112] A sample with a height of 50 mm, a length of 50 mm, and a
thickness of 10 mm was hung so that the plan-view surface (50
mm.times.50 mm surface) of the sample was vertical inside a
container (manufactured by PYLEX Co.) having a capacity of 0.0013
m.sup.3 (1.3 L) and equipped with a stirring element. This
container was equipped with a stirring element creating a flow of
gas inside the container. A black light was installed below the
container, and the plan-view surface of the sample was illuminated
with UV light at 1 mW/cm.sup.2 and a wavelength of 360 nm.
[0113] A sample (sample 1) prepared by forming a photocatalytic
layer on a ceramic substrate supporting alumina particles with a
mean diameter of 22 .mu.m and a sample (sample 2) prepared by
forming a photocatalytic layer on a ceramic substrate which
supported no alumina particles were used as the samples. A
photocatalytic slurry identical to that used in Test Example 2 was
employed for forming the photocatalytic layer.
[0114] Acetaldehyde (purity 90%, saturated state at 23.degree.) was
injected into the container in an amount of 0.2 mL 0 min (when the
black light was turned on), 20 min, 40 min, 60 min, and 80 min
after the black light was turned on, while the stirring element was
rotated to create gas flow inside the container. The black light
was turned off 58 min after it was turned on. After the prescribed
intervals from the time the black light was turned on had passed,
gas present inside the container was sampled and quantitatively
analyzed by gas chromatography. The results are shown in Table 7
and FIG. 11.
7 TABLE 7 Acetaldehyde concentration (ppm) Time (min) Sample 1
Sample 2 No sample 0 107 107 107 1 26 62 102 10 0 12 99 20 0 0 96
Injection 107 107 203 21 22 61 198 30 0 10 195 40 0 0 193 Injection
107 107 300 41 25 60 296 50 0 11 293 60 0 0 291 Injection 107 107
398 61 21 62 395 70 1 16 392 80 1 5 388 Injection 108 107 495 81 23
68 490 90 2 19 485 100 1 10 482
[0115] As shown in Table 7 and FIG. 11, in a blank test in which
illumination with black light was conducted without placing a
sample into the container, the concentration of acetaldehyde inside
the container showed practically no decrease, accumulating upon
each injection. This result indicates that UV irradiation alone
practically fails to decompose acetaldehyde. By contrast, in the
test utilizing sample 2 (photocatalytic filter which was not
equipped with alumina particles) the concentration of acetaldehyde
decreased to about 3/5 of the initial concentration within 1 min
after the introduction of acetaldehyde into the container, and
after 20 min from the introduction, practically no acetaldehyde was
detected. Furthermore, in the test utilizing sample 1
(photocatalytic filter comprising alumina particles), the
concentration of acetaldehyde decreased to about 1/4 of the initial
concentration within 1 min after the acetaldehyde was introduced
and practically no acetaldehyde was detected (i.e., it had
completely decomposed) after 10 min. Those results indicate that
under the above-described test conditions, both sample 1 and sample
2 almost completely decompose 0.2 mL acetaldehyde by photocatalytic
action within 20 min. Furthermore, sample 1 comprising a
photocatalytic layer on a ceramic substrate holding alumina
particles exhibited decomposition ability even better than that of
sample 2.
[0116] <Third Embodiment: Exhaust Purification Cabinet>
[0117] An embodiment (exhaust purification cabinet) in which the
exhaust purification apparatus in accordance with the present
invention comprises a cabinet will be described herein below with
reference to FIGS. 12 through 14. Parts operating similarly to
parts described in the First Embodiment are assigned the same
reference symbols, and explanation thereof will be omitted.
[0118] The present exhaust purification apparatus comprises
de-oiling filters 80, 81 for removing oil and fat components, a
dust collector 50 for removing smoke particles, a photocatalytic
unit 61 for deodorization, and a fan 207 for sucking the exhaust
into the cabinet 203 and releasing it after purification, all those
components being installed inside the cabinet 203 having an intake
opening 201 and an exhaust release opening 202 formed therein. The
structure of the photocatalytic unit 61 is similar to that
described in the First Embodiment.
[0119] The cabinet 203 is formed to have an elongated box-like
shape and has a caster 208 for transportation attached to the
bottom surface thereof. The intake openings 201 are formed at the
central portions in the lower parts on the two opposing side
surfaces of the cabinet 203. The intake openings 201 are in the
form of round holes. The exhaust release openings 202 are formed in
the upper portions of the same side surfaces where the intake
openings 201 were formed. The exhaust release openings 202 are in
the form of a plurality of slits. The exhaust release openings 202
may be provided not only on the two side surfaces of the cabinet
203, but also on three or four side surfaces. Furthermore, they may
be also formed at the upper surface of the cabinet 203.
Alternatively, an exhaust release opening may be formed only on one
side surface and upper surface.
[0120] The internal space of the cabinet 203 is divided into 4
chambers stacked in layered configuration. The intake openings 201
are provided in the lowermost-layer chamber 210, which is the
lowermost chamber. A first treatment chamber 211 with the de-oiling
filters 80, 81 disposed therein, a second treatment chamber 212
with the dust collector 50 disposed therein, and a third treatment
chamber 213 with the photocatalytic unit 61 and the fan 207
disposed therein are arranged in the order of description above the
lowermost-layer chamber 210. As shown in FIG. 12, an orifice 214
leading to the first treatment chamber 211 is formed in an edge of
the upper surface of the lowermost chamber 210. An orifice 215
leading to the second treatment chamber 212 is formed at an edge
(on the right side as shown in FIG. 12) of the upper surface of the
first treatment chamber 211. An orifice 216 leading to the third
treatment chamber 213 is formed at another edge (on the side
opposite that of the orifices 214, 215; on the left side as shown
in FIG. 12) of the upper surface of the second treatment chamber
212. The exhaust release openings 202 are provided in the third
treatment chamber 213. As a result, an exhaust path passing from
the intake opening 201 to the exhaust release opening 202 via the
lowermost-layer chamber 210, the first treatment chamber 211, the
second treatment chamber 212, and the third treatment chamber 213
is formed inside the cabinet 203. The exhaust sucked in through the
intake opening 201 flows as shown by arrows in FIG. 12 and FIG. 13
along the exhaust path.
[0121] The first treatment chamber 211 is divided into two layers
(upper layer and lower layer) by a partition board 218 having an
orifice 217 in the other edge (side opposite to that of the
orifices 214, 215). The exhaust that flows from the orifice 214
into the first treatment chamber 211 flows from one side to the
other end side along the lower layer of the first treatment
chamber, through the orifice 218, and then from the other side to
the first side in the upper layer to the orifice 215. Planar
de-oiling filters 80, 81 are arranged with a certain spacing
therebetween in the portion where the exhaust is curved. Thus, one
de-oiling filter 80 is mounted in a state inclined with respect to
the flow direction so as to cross the exhaust path, wherein the
other de-oiling filter 81 is mounted above it in a state inclined
in the direction opposite to that of the de-oiling filter 80. When
the de-oiling filters 80, 81 are thus inclined, the contact surface
area of the de-oiling filters 80, 81 with the exhaust can be
increased and a larger amount of contaminating substances can be
trapped. The de-oiling filters 80, 81 are typical grease filters
and the oil removal efficiency of those de-oiling filters 80, 81 is
no less than 70 wt. %. Furthermore, three or more de-oiling filters
may be arranged in this zone.
[0122] The dust collector 50 is an electric dust collector with a
structure in which discharge electrodes 51 and dust collection
electrodes 52 are arranged and installed alternately and parallel
to the exhaust flow direction in a dust collection case 53. When a
high voltage is applied to the discharge electrodes 51, a corona
discharge is generated, and negative ions and electrons are
generated from the discharge electrodes. When particles such as
smoke or mist collide with those ions and electrons, the particles
are charged. The charged particles are electrostatically attracted
to the dust collection electrodes 52. As a result, particles (smoke
particles and the like) present in the exhaust are separated and
removed.
[0123] Two dust collectors 50 are detachably mounted in series in
the exhaust path inside the second treatment chamber 212. Here, the
cross-sectional area in the second treatment chamber 212 is larger
than the cross-sectional area of the exhaust path in the first
treatment chamber 211. Therefore, the flow rate of exhaust is
slower in the second treatment chamber 212 than in the first
treatment chamber 211. The dust collectors 50 trap particles by
electrostatically attracting the charged particles. Therefore, if
the movement speed of the charged particles is higher than the
attraction speed, the particles pass through without being
attracted to the dust collection electrodes 52. Increasing the
cross-sectional area of the second treatment chamber 212 over that
of the first treatment chamber 211, as in the present embodiment,
makes it possible to pass the exhaust at a relatively low speed
through the dust collector 50, thereby increasing the particle
removal efficiency.
[0124] As shown in FIG. 13, the photocatalytic unit 61 is disposed
so as to cover the exhaust release opening 202 formed in the side
wall of the third treatment chamber 213. The third treatment
chamber 213 has a volume larger than that of other treatment
chambers. Furthermore, the fan 207 is disposed in the third
treatment chamber 213. As shown in FIG. 12, the fan 207 is disposed
so as to cover the orifice 216 connecting the second treatment
chamber 212 and the third treatment chamber 213. Exhaust sucked in
through the second treatment chamber 212 is released, so as to be
dispersed inside the third treatment chamber 213 by the fan 207
(see FIG. 13). Because the exhaust is thus caused to diffuse inside
the third treatment chamber 213, the exhaust passes through the
exhaust path with a larger cross-sectional area. As a result, the
flow rate of exhaust is decreased. Therefore, the time of contact
between the exhaust and the photocatalytic filter 61 is extended
and a better deodorization effect can be obtained. Because the
photocatalytic unit 61 is disposed in the uppermost layer of
cabinet 203, the oil and fat components present in the exhaust do
not reach the unit. Therefore, the adhesion of oil and fat
components to the photocatalytic filter 62 and a drop in the
function thereof can be prevented.
[0125] The operation of the exhaust purification cabinet will be
described below. First, the cabinet 203 comprising the exhaust
purification apparatus is moved into the kitchen. Exhaust generated
by cooking (including contaminating substances such as oil
particles and smoke particles and also odorous components) is
sucked through the inlet opening 201 into the cabinet 203 by the
suction force generated by the fan 207. The exhaust that was sucked
in passes from the lowermost-layer chamber 210 into the first
treatment chamber 211, as shown in FIG. 12, and then passes through
the de-oiling filters 80, 81. As a result, no less than 70 wt. % of
oil and fat components present in the exhaust are removed.
[0126] The de-oiling filters 80, 81 are suitable for removing
components (oil and fat components and the like) with a
comparatively large mass among the contaminating substances. On the
other hand, part of fine contaminating substances such as smoke
particles and most of the gaseous odorous components pass through
the de-oiling filters 80, 81. Exhaust containing those components
flows from the first treatment chamber 211 into the second
treatment chamber 212. When the exhaust enters the second treatment
chamber 212, because the cross-sectional area of the exhaust path
increases, the exhaust reaches the dust collector 50 in a state in
which the flow velocity thereof is reduced. When the exhaust passes
through the dust collector 50, particles, such as smoke, present
therein are charged electrically and attracted to the dust
collection electrodes 52. As a result, smoke and mist particles
present in the exhaust are removed.
[0127] The exhaust treated in the second treatment chamber 212 is
sucked into the third treatment chamber 213 and, as shown in FIG.
13, diffused and dispersed inside this chamber with the fan 207.
The exhaust filling the third treatment chamber 213 is brought into
uniform contact with the photocatalytic unit 61, passes
therethrough and is released from the exhaust release opening 202
to the outside of the cabinet 203. At this time, the contaminating
substances that could not be removed by the dust collector 50 and
the odorous components present in the exhaust are brought into
contact with or trapped by the surface of the photocatalytic filter
62. Those odorous components and fine particles are decomposed by
photocatalytic action.
[0128] As the cabinet is used, oil and fats trapped by the filters
80, 81 can start dripping or flowing along the de-oiling filters
80, 81 in the exhaust purification cabinet of the above-described
configuration. For this reason, it is preferred that an oil
receptacle be provided below the de-oiling filter 80. Furthermore,
even when oil and fats fall drop-wise from the de-oiling filters
80, 81, because the exhaust path is formed so that the upper part
of the cabinet 203 is located downstream, the downstream exhaust
path cannot be contaminated by the dripping oils and fats.
[0129] Furthermore, a cleaning means for cleaning the de-oiling
filters 80, 81 may be also provided. For example, a nozzle for
ejecting a cleaning solution can be provided above the de-oiling
filters 80, 81 and a solution receptacle can be installed below the
filters. With such a configuration, spraying the cleaning solution
from the nozzle onto the de-oiling filters 80, 81 makes it possible
to wash out the oil and fat components trapped in the de-oiling
filters 80, 81. Furthermore, the performance of the de-oiling
filters 80, 81 can be maintained for a long time and maintenance
frequency can be reduced.
[0130] The de-oiling filters 80, 81, dust collector 50, and
photocatalytic unit 61 are mounted inside the cabinet 203, and each
of them can be easily attached and detached. Thus, when the
contaminating substances removed from the exhaust in the course of
the exhaust purification process have accumulated, those units can
be removed from the cabinet 203 and cleaned or replaced with new
products.
[0131] <Fourth Embodiment: Cooking Device Equipped with the
Exhaust Purification Apparatus>
[0132] An embodiment in which the exhaust purification apparatus in
accordance with the present invention comprises a cooking device
body (cooking device equipped with the exhaust purification
apparatus) is shown in FIG. 15. A so-called smokeless roaster of a
well-known structure can be used as the cooking device body. A
central orifice is provided in a ceiling plate 301a of a cooking
device body 301, and a cooking unit comprising a heater 302 and a
cooking plate 303 is fit into the orifice. A gas, heater, electric
heater, coal heater, or electromagnetic induction heater may be
used as the heater 302. A roaster, grill, iron plate, or
non-conductive plate can be used as the cooking plate 303.
[0133] An exhaust purification apparatus for conducting
purification (de-oiling, defuming, and deodorizing) of the exhaust
generated from the cooking unit is installed in the cooking device
body 301. The exhaust purification apparatus comprises a de-oiling
filter 20 for removing oils and fats contained in the exhaust that
was sucked in, a dust collector 50 for removing smoke particles, a
photocatalytic unit 61 for deodorizing, and a fan 307 for sucking
in the exhaust and releasing it after purification. The
configuration of the de-oiling filter 20 and the photocatalytic
unit 61 are similar to those of the first Embodiment, and the
configuration of the dust collector 50 is similar to that of the
Third Embodiment.
[0134] The heater 302 and cooking plate 303 are detachably mounted
in an inner box 308. The inner box 308 is installed inside an outer
box 309. The outer box 309 is fixed to the cooking unit body 301.
An intake plate 310 is attached on the outer periphery of the
central orifice in the ceiling plate 301a, and an intake opening
311 is formed between the intake place 310 and the upper outer
periphery of the inner box 308. A gap is formed between the inner
box 308 and the outer box 309 so as to surround the inner box 308,
and the intake opening 311 leads to this gap. An exhaust release
opening 312 is formed in the lower portion of at least one side
surface of four side surfaces of the cooking device body 301.
[0135] The de-oiling filter 20 is disposed at the side of the outer
box 309, the dust collector 50 and the fan 307 are disposed below
the outer box 309, and the photocatalytic unit 61 is disposed so as
to face the exhaust release opening 312 (to cover the exhaust
release opening 312). Furthermore, an exhaust path passing from the
intake opening 311 through the de-oiling filter 20, dust collector
50, and photocatalytic unit 61 to the exhaust release opening 312
is formed inside the cooking device body 301. Furthermore, the gap
formed between the inner box 308 and the outer box 309 also becomes
part of the exhaust path. Exhaust (containing oil and fat
components, smoke particles, odorous components and the like)
generated from the cooked food during heating and cooking in the
cooking unit is sucked into the exhaust path from the intake
opening 311 by the suction force generated by the fan 307 as shown
by the arrows in the drawing. This exhaust flows sidewise along the
outer surface of the inner box 308 and downward from the side of
the outer box 309 through the de-oiling filter 20. Then, it flows
through the dust collector 50 and photocatalytic filter 61 and is
released to the outside through the exhaust release opening
312.
[0136] The area where the de-oiling filter 20 was installed is a
portion where the exhaust path is a portion curved downwardly from
the side of the outer box 309. Furthermore, the exhaust path
leading to the de-oiling filter 20 is formed between the side
surface of the cooking device body 301 and the outer box 309.
Therefore, it has a small cross-sectional area. For this reason,
the flow velocity of the exhaust passing through this portion is
comparatively high.
[0137] On the other hand, the dust collector 50 is detachably
attached inside the exhaust path below the outer box 309. The
exhaust path from the filter unit 10 to the dust collector 50
expands in the horizontal direction below the cooking unit. The
cross-sectional area of the exhaust path in this portion can be
larger than that of the exhaust path in the portion leading to the
de-oiling filter 20. As a result, the flow velocity of the exhaust
can be reduced by comparison with that in the zone upstream of the
de-oiling filter. Appropriately decreasing the flow velocity of the
exhaust makes it possible to efficiently separate and remove smoke
particles present in the exhaust with the dust collector 50
disposed herein.
[0138] The photocatalytic unit 61 is disposed so as to cover the
exhaust release opening 312 formed in the side surface of the
cooking device body 301, and the photocatalytic filter 62 faces the
exhaust release opening 312. The exhaust path where the
photocatalytic unit 61 is disposed is in the lower portion inside
the cooking device body 301. Therefore, a large space can be easily
provided. The exhaust sucked in herein is released, so as to be
dispersed by the fan 307 to all four sides inside the cooking
device body 301. As a result, the flow velocity of the exhaust can
be further decreased and odorous components, present in the
exhaust, can be efficiently removed by the photocatalytic filter
62, similar to the Third Embodiment.
[0139] <Fifth Embodiment: Cooking System (1)>
[0140] The present embodiment relates to a cooking system having
connected therein a plurality of cooking devices equipped with the
exhaust purification apparatus in accordance with the present
invention. A cooking device used in this embodiment is shown in
FIG. 16. This cooking device has a configuration similar to that of
the cooking device of the Fourth Embodiment; the difference between
the two is described below.
[0141] The de-oiling filter 20 is disposed below the outer box 309.
The dust collector 50 and the photocatalytic unit 61 are disposed
one above the other at the side of the de-oiling filter. Exhaust
generated from the cooking unit flows from the side surface of the
inner box 308 along the lower surface toward the de-oiling filter
20 located below the inner box 308. The exhaust path in this
portion is formed so as to become narrower toward the de-oiling
filter 20, thereby increasing the flow velocity of the exhaust. In
the present embodiment, the photocatalytic units 61 are installed
in two layers with respect to the flow direction of the exhaust. As
a result, the contact surface area of the exhaust and the
photocatalyst is increased and purification efficiency is enhanced.
No fan is installed inside the cooking device.
[0142] A duct 370 is connected to the exhaust release opening 312
provided in the bottom surface of the cooking device body 301. The
exhaust release opening 312 of the cooking device body 310 is
connected to the main duct (not shown in the figure) via the duct
370. With such a configuration, the exhaust channel formed inside
the cooking device body 301 and the exhaust channel inside the main
duct are connected to each other. Furthermore, due to the operation
of a large fan (not shown in the figures) provided in the main
duct, exhaust is sucked in from the intake opening 311 of the
cooking devices, purified in the process of flowing toward the
exhaust release opening 312, and sucked into the main duct from the
duct 370.
[0143] A valve is provided in the duct 370 of each cooking device.
The valves of unused cooking devices are closed, and the suction
force generated by the large fan installed in the main duct can be
used effectively by opening only the valves of those cooking
devices, which are being used. As a result, the suction capacity of
exhaust is increased. Furthermore, the purification capacity of
exhaust can be also increased.
[0144] <Sixth Embodiment: Cooking System (2)>
[0145] The present embodiment relates to another example of a
cooking system having connected therein a plurality of cooking
devices equipped with the exhaust purification apparatus in
accordance with the present invention. A cooking device used in
this embodiment is shown in FIG. 17. In the present embodiment,
instead of installing the de-oiling filter 20 used in the Fifth
Embodiment, two planar filters 80, 81 are disposed in the exhaust
path with a certain spacing therebetween. Filters 81, 81 similar to
those of the Third Embodiment were used. Similarly to the Fourth
Embodiment, the filters 80, 81 are disposed at the side of the
outer box 309, and the dust collector 50 is disposed below the
outer box 309. Furthermore, the cross-sectional area of the exhaust
path from the dust collector 50 to the duct 370 is increased and a
plurality (two in this case) of photocatalytic units 61 are aligned
horizontally. The configuration of the other components is similar
to that of the Fifth Embodiment.
[0146] Similarly to the Third Embodiment, the filters 80, 81 are
disposed in the portion wherein the exhaust path is curved
downwardly from the side of the outer box 309. However, unlike the
Third Embodiment, in the present embodiment, exhaust flows from
above to below the filters 80, 81. Furthermore, a recess 84 is
formed on the lower surface of the exhaust path where the filter
81, which is located lower than the other filter, is disposed. This
recess 84 functions as an oil receptacle when oils and fats trapped
by the filters 80, 81 drip down or flow down along the filters 80,
81. As a result, contamination of the downstream side of exhaust
path with oil and fat components is prevented. Similarly to the
Third Embodiment, this cooking device can be further provided with
a cleaning means for cleaning the filters 80, 81.
[0147] Furthermore, a flow dividing plate may be provided upstream
(for example, in the central zone) of the photocatalytic unit 61.
As a result, the exhaust can be guided to both sides of the
photocatalytic unit 61, and the horizontally aligned photocatalytic
units 61 (over a large area) can be utilized effectively.
[0148] The present invention was described hereinabove based on
specific examples thereof, which however place no limitation on the
scope of the claims. The above-described specific examples can be
variously changed and modified within the framework of the
technology described in the claims.
[0149] Furthermore, technological features explained in the present
specification or appended drawings demonstrate the technological
utility thereof individually or in a variety of combinations and
are not limited to the combination in the description requested at
the time of filing of the application. Moreover, the technology
described as an example in the present specification or appended
drawings attains a plurality of objects at the same time, and
attaining one of those objects has by itself technological
utility.
* * * * *