U.S. patent application number 09/781766 was filed with the patent office on 2001-10-25 for unvented heating appliance having system for reducing undesirable combustion products.
This patent application is currently assigned to The Majestic Products Company. Invention is credited to Barkhouse, Sydney R., Campbell, Larry E., Rieger, Heinz H..
Application Number | 20010032641 09/781766 |
Document ID | / |
Family ID | 26685481 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010032641 |
Kind Code |
A1 |
Campbell, Larry E. ; et
al. |
October 25, 2001 |
Unvented heating appliance having system for reducing undesirable
combustion products
Abstract
A gas-fueled heating appliance having a system for reducing the
amount of undesirable combustion products released to the site in
which the appliance is installed. The appliance includes a firebox
partially surrounded by a heat exchanger. Ambient air is drawn into
the heat exchanger below the firebox and a portion of the ambient
air enters the firebox to assist in combustion, and the remaining
portion travels through the heat exchanger to be heated by
convection before being combined with combustion gases exiting
through the top of the firebox. The heat exchanger creates a low
pressure area relative to the firebox which induces a draft from
the firebox into the heat exchanger and ultimately to the ambient
environment through an exit provided above the firebox. A carbon
monoxide catalyst element is provided in the exit passageway from
the firebox to the heat exchanger to oxidize carbon monoxide into
carbon dioxide and filter away airborne particulates which would
otherwise be released to the ambient air.
Inventors: |
Campbell, Larry E.;
(Knoxville, TN) ; Barkhouse, Sydney R.;
(Mississauga, CA) ; Rieger, Heinz H.; (Toronto,
CA) |
Correspondence
Address: |
JOHN F. HOFFMAN
BAKER & DANIELS
Suite 800
111 East Wayne Street
Fort Wayne
IN
46802
US
|
Assignee: |
The Majestic Products
Company
|
Family ID: |
26685481 |
Appl. No.: |
09/781766 |
Filed: |
February 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09781766 |
Feb 12, 2001 |
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08821851 |
Mar 21, 1997 |
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6216687 |
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60013967 |
Mar 22, 1996 |
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Current U.S.
Class: |
126/512 ;
126/92B; 126/92R; 431/125 |
Current CPC
Class: |
F24B 7/025 20130101;
F24B 1/1808 20130101; F24C 3/006 20130101; F23G 7/07 20130101; F24B
1/006 20130101 |
Class at
Publication: |
126/512 ;
126/92.00R; 126/92.00B; 431/125 |
International
Class: |
F24C 003/04; F23Q
002/32; F23C 001/00; F24C 003/00; F24C 005/00 |
Claims
What is claimed is:
1. A heating appliance, comprising: a firebox having an outlet in
communication with ambient air adjacent said appliance; a gas
burner disposed within said firebox, said gas burner providing a
primary flame and heat source, and producing products of
combustion, said products of combustion exiting said firebox
through said outlet; and a carbon monoxide catalyst element
disposed in said firebox outlet, and carbon monoxide catalyst
element oxidizing carbon monoxide contained within said products of
combustion into carbon dioxide.
2. The heating appliance of claim 1, wherein said appliance is a
fireplace having a transparent front face.
3. The heating appliance of claim 1, wherein said appliance is a
stove.
4. The heating appliance of claim 1, wherein said appliance is a
fireplace insert.
5. The heating appliance of claim 1, wherein said carbon monoxide
catalyst includes a plurality of planar foils, a plurality of
corrugated foils alternatingly interposed between said planar
foils, and a ceramic oxide and precious metal coating disposed on
said planar foils and said corrugated foils.
6. The heating appliance of claim 5, wherein said planar foils and
said corrugated foils are manufactured from stainless steel chosen
from the group of ferritic stainless steels consisting of Alpha IV,
FeCrAlloy, 109, 304, and 316, said ceramic oxide is closer from the
group consisting of aluminum oxide, zirconium oxide, and titanium
oxide, and said precious metal is chosen from the group consisting
of platinum and palladium.
7. The heating appliance of claim 1, wherein said carbon monoxide
catalyst is disposed within a frame secured to said firebox outlet,
said frame adapted to allow removal of said carbon monoxide
catalyst for cleaning and replacement.
8. An unvented heating appliance located at least in part in a room
and comprising: a firebox having an inlet receiving room air and an
outlet in communication with the room for exhausting combustion
gases into the room; a gas burner disposed within said firebox,
said gas burner providing a primary flame and heat source, heating
room air drawn into said firebox, and producing products of
combustion; a heat exchanger having an inlet, an outlet, and a
plenum defining a heat exchanger airstream circuit between said
heat exchanger inlet and outlet, said heat exchanger inlet located
below and spaced from said heat exchanger outlet and receiving room
air into said plenum, said heat exchanger outlet exhausting heated
air from said heat exchanger plenum into the room, said heat
exchanger partially surrounding said firebox, said firebox outlet
in communication with said heat exchanger outlet, a draft resulting
from said firebox being under higher pressure than said heat
exchanger, said draft aspirating said products of combustion from
said firebox to said heat exchanger, whereby room air is drawn
through said heat exchanger airstream circuit and exhaust gases
from said firebox outlet are drawn into the room air stream; and a
carbon monoxide catalyst element disposed in said firebox outlet,
said carbon monoxide catalyst element oxidizing carbon monoxide
contained within said products of combustion into carbon dioxide,
and preventing airborne particulates from exiting said firebox.
9. The heating appliance of claim 8, wherein said appliance is a
fireplace.
10. The heating appliance of claim 9, wherein said fireplace has a
substantially sealed transparent front face.
11. The heating appliance of claim 8, wherein said appliance is a
stove.
12. The heating appliance of claim 8, wherein said appliance is a
fireplace insert.
13. The heating appliance of claim 8, wherein said carbon monoxide
catalyst element includes a plurality of planar foils, a plurality
of corrugated foils alternatingly interposed between said planar
foils, and a ceramic oxide and precious metal coating disposed on
said planar foils and said corrugated foils.
14. The heating appliance of claim 13, wherein said planar foils
and said corrugated foils are manufactured from stainless steel
chosen from the group of ferritic stainless steels consisting of
Alpha IV, FeCr Alloy, 109, 304, and 316, said ceramic oxide is
chosen from the group consisting of aluminum oxide, zirconium
oxide, and titanium oxide, and said precious metal is chosen from
the group consisting of platinum and palladium.
15. The heating appliance of claim 8, wherein said heat exchanger
includes a blower to assist in inducing said draft.
16. The heating appliance of claim 8, wherein said carbon monoxide
catalyst element is disposed within a frame secured to said firebox
outlet, said frame adapted to allow removal of said carbon monoxide
catalyst element for cleaning and replacement.
17. A carbon monoxide catalyst element for oxidizing carbon
monoxide into carbon dioxide and for use in heating appliances,
said catalyst element comprising: a plurality of planar foils
manufactured from stainless steel; a plurality of corrugated foils
manufactured from stainless steel, said corrugated foils
alternatingly interposed between said planar foils; a ceramic oxide
coating disposed on said plurality of planar foils and said
plurality of corrugated foils; and a precious metal coating
disposed on said plurality of planar foils and said plurality of
corrugated foils.
18. The carbon monoxide catalyst element of claim 17 wherein said
planar foils and said corrugated foils are manufactured from
stainless steel chosen from the group of ferritic stainless steels
consisting of Alpha IV, FeCrAlloy, 109, 304, and 316, said ceramic
oxide is chosen from the group consisting of aluminum oxide,
zirconium oxide, and titanium oxide, and said precious metal is
chosen from the group consisting of platinum and palladium.
19. A gas-fueled stove, comprising: a firebox having an outlet in
communication with ambient air adjacent said stove; a gas burner
disposed within said firebox, said gas burner providing a primary
flame and heat source, and producing products of combustion, said
products of combustion exiting said firebox through said outlet; a
heat exchanger partially surrounding said firebox, said heat
exchanger drawing ambient air in through an entrance provided below
said firebox, and exhausting convection heated air through an exit
provided above said firebox; a combustion gas circuit including an
inlet communicating air to said firebox and an outlet communicating
products of combustion out of said firebox; and a carbon monoxide
catalyst element disposed within said combustion gas outlet, said
carbon monoxide catalyst element oxidizing carbon monoxide
contained within said products of combustion into carbon dioxide,
and preventing airborne particulates from exiting said stove.
20. The stove of claim 19, wherein said carbon monoxide catalyst
element includes a plurality of planar foils, a plurality of
corrugated foils alternatingly interposed between said planar
foils, and a ceramic oxide and pressure metal coating disposed on
said planar foils and said corrugated foils.
21. The stove of claim 20, wherein said planar foils and said
corrugated foils are manufactured from stainless steel chosen from
the group of stainless steels consisting of Alpha IV, FeCr alloy,
109, 304, and 316, said ceramic oxide is chosen from the group
consisting of aluminum oxide, zirconium oxide and titanium oxide,
and said precious metals chosen from the group consisting of
platinum and palladium.
22. The stove of claim 19, wherein said heat exchanger entrance is
provided on the back of said stove, said heat exchanger exit is
provided on the front of said stove, said combustion gas inlet is
provided on the back of said stove and said combustion gas outlet
is provided on the top of said stove.
23. The stove of claim 22, wherein said heat exchanger entrance and
exit and said combustion gas inlet and outlet further include a
louvered grill.
24. The stove of claim 19, wherein said heat exchanger includes a
blower to assist in inducing air through said heat exchanger.
25. The stove of claim 19, wherein said carbon monoxide catalyst
element is disposed within a frame, said frame adapted to allow
removal of said carbon monoxide catalyst element for cleaning and
replacement.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under Title 35, U.S.C.
.sctn. 119(e) of U.S. Provisional Patent Application Serial No.
60/013,967, entitled UNVENTED GAS FIREPLACE HAVING SYSTEM FOR
REDUCING UNDESIRABLE COMBUSTION PRODUCTS, filed on Mar. 22,
1996.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention generally relates to heating appliances and,
more particularly, relates to gas-fueled heating appliances, both
ventless, which vent combustion gases directly into the room in
which the appliance is installed and vented, which vent combustion
gases to atmosphere.
[0004] 2. Description of the Related Art
[0005] Gas-fueled heating appliances, such as fireplaces, stoves,
and fireplace inserts, have the cleanest exhaust of any combustion
process and typically include a combustion chamber, or firebox,
which is provided with a source of flammable gas. The flammable gas
is then combusted to provide heat and aesthetic value to the room
in which the appliance is installed. The combustion typically
produces carbon monoxide, carbon dioxide, water, oxygen, nitrogen,
nitrogen oxide, and carbon soot, which are vented away from the
fireplace and to the outside environment through a flue network or
chimney. The major constituents are oxygen, nitrogen, carbon
dioxide, and water with significantly lower levels of carbon
monoxide, nitrogen oxides, and carbon soot. The mercaptan odorant
found in gas fuel oxidizes and forms sulfuric oxides. Although such
gases are vented to atmosphere, causing no serious problems in the
space adjoining the appliance, increasing concerns about the
environment may bring this process under heavy scrutiny and
eventual regulation.
[0006] In certain locations, it is desirable to have an appliance
capable of operating without venting to the outside environment.
Therefore, gas appliances have been designed which are clean
burning but "unvented" in that the gas combusts and the products of
the combustion are allowed to enter the room in which the appliance
is installed. With such designs, a chimney or flue network is not
necessary and consequently such designs can be placed in many
locations which would otherwise not be able to accommodate a vented
appliance.
[0007] Because such designs allow combustion gases to enter the
room in which the fireplace is installed, any combustion products,
such as carbon monoxide, and airborne particulates, are also
exhausted from the appliance directly into the room in which the
appliance is located.
[0008] In addition, with conventional unvented appliances, the
combustion gases rise within the firebox and heat the top wall of
the firebox before exiting into the room in which the fireplace is
installed. If the heat is not controlled, this can potentially
damage the top wall of the firebox or a mantle associated
therewith.
[0009] U.S. Pat. No. 5,054,468, issued to Moon, discloses an
unvented gas-fueled fireplace heater which vents all combustion
gases and airborne particulates directly into the room in which the
heater is installed, but does not include any means for reducing
undesirable emissions.
[0010] U.S. Pat. No. 5,139,011, also issued to Moon, discloses an
unvented gas-fueled fireplace heater which vents combustion gases
and particulates directly to the ambient room air, and further
includes a sensor which detects a low oxygen level and a gas supply
switch which is activated by the oxygen sensor.
[0011] Early attempts at ventless appliances suffer from drawbacks
such as: 1) water build-up in the space, 2) acid gases, such as
nitrogen oxide and sulfuric oxide, are discharged into the space
potentially causing respiratory distress and corrosion in the home,
3) excessive oxygen consumption, and 4) excessive build-up of
carbon monoxide levels in the space.
SUMMARY OF THE INVENTION
[0012] The present invention is for use in either vented or
unvented, gas-fueled, heating appliances and includes a system for
reducing the amounts of undesirable combustion products which are
released into the atmosphere or space in which the appliance is
installed. However, the catalyst of the present invention is
particularly useful in unvented applications, where the discharge
and treatment of products of combustion is even more critical. The
present invention also includes a system for inducing a draft to
aspirate the combustion gases from the firebox, and thereby avoid
thermal damage to the firebox or mantle.
[0013] In particular, the present invention provides a carbon
monoxide catalyst element to oxidize the carbon monoxide released
by the appliance into carbon dioxide before the combustion gases
are vented into the atmosphere or ambient room air. The catalyst
element also serves as a filter to screen airborne particulates,
such as ceramic fibers dislodged from the synthetic logs disposed
within the firebox of a fireplace.
[0014] The carbon monoxide catalyst element is disposed within a
heating appliance which includes a firebox and a heat exchanger
surrounding the firebox. In one embodiment, ambient air enters the
heat exchanger through an opening on the bottom front of a
fireplace, below the firebox, and is divided such that a portion of
the ambient air enters the firebox through openings below gas
burners disposed within the firebox, and the remaining portion
proceeds through the heat exchanger along a plenum below the
firebox, along an adjoining plenum behind the firebox, and then
along an adjoining plenum above the firebox. The air within the
heat exchanger then merges with combustion air being vented from
the firebox, and the recombinant air then exits the fireplace
through an opening at the top front of the fireplace.
[0015] The front face of the fireplace is enclosed with a glass
window to assure complete venting of the combustion gases through
the top of the firebox and heat exchanger plenum. The carbon
monoxide catalyst element is disposed in the combustion gas exit
located at the top of the firebox and the openings at the top and
bottom front of the fireplace are covered by a grill, louvers,
mesh, or other similar device.
[0016] The present invention induces a draft which assists in the
aspiration of the combustion gases by drawing the combustion gases
from the hot air, high pressure firebox to the cooler air,
low-pressure heat exchanger and ambient environment of the room in
which the appliance is installed. In addition to the natural draft
created by the present design, the appliance can optionally include
a blower within the heat exchanger to further assist the aspiration
of the combustion gases and increase the thermal output of the
appliance.
[0017] Moreover, the draft is of a sufficient velocity to aspirate
the combustion gases from the firebox at a flowrate sufficiently
high to avoid structural damage to the firebox top wall, or an
associated mantle.
[0018] One advantage of the present invention is that it
substantially reduces the amount of carbon monoxide and other gases
released by the appliance into the atmosphere or room in which the
appliance is installed.
[0019] Another advantage of the present invention is that is
reduces the number of airborne particulates, such as ceramic
fibers, released by the appliance into the room in which the
appliance is installed.
[0020] Another advantage of the present invention is that the
combustion gases are aspirated from the firebox at a rate
sufficiently fast to avoid thermal damage to the firebox or an
associated mantle.
[0021] Another advantage of the present invention is that
pollutants from sources present in the space in which the heating
appliance is located are destroyed when heated in the combustion
chamber and passed through the catalyst.
[0022] A still further advantage of the present invention is that
it provides an appliance which can be installed into any site
regardless of the availability of a chimney or other venting
medium.
[0023] The present invention, in one form thereof, provides a
heating appliance comprising a firebox, a gas burner, a heat
exchanger, and a carbon monoxide catalyst element. The firebox
includes an outlet and the gas burner which produces products of
combustion. The heat exchanger partially surrounds the firebox and
a draft results from the firebox being under higher pressure than
the heat exchanger. The draft aspirates the products of combustion
away from the firebox. The carbon monoxide catalyst element is
disposed within the firebox outlet, and oxidizes carbon monoxide
contained within the products of combustion into carbon dioxide and
prevents airborne particulates from exiting the firebox.
[0024] The present invention, in another form thereof, provides a
carbon monoxide catalyst element for oxidizing carbon monoxide into
carbon dioxide, and comprises a plurality of planar foils, a
plurality of corrugated foils, a ceramic oxide coating, and a
precious metal coating. The plurality of planar foils and the
plurality of corrugated foils are manufactured from stainless steel
with the corrugated foils being alternatingly interposed between
the planar foils. The ceramic oxide and precious metal coatings are
disposed on the plurality of planar foils and the plurality of
corrugated foils.
[0025] The present invention, in yet another form thereof, provides
an unvented, gas-fueled fireplace comprising a firebox, a gas
burner, a heat exchanger, and a carbon monoxide catalyst element.
The firebox includes an outlet with the gas burners being disposed
within the firebox and producing products of combustion. The heat
exchanger partially surrounds the firebox and draws ambient air in
through an entrance provided below the firebox and exhausts
convection heated air through an exit provided above the firebox. A
draft results from the firebox being under higher pressure than the
heat exchanger, with the draft aspirating the products of
combustion away from the firebox and to the ambient environment
through the heat exchanger exit. The carbon monoxide catalyst
element is disposed within the draft and oxidizes carbon monoxide
contained within the products of combustion into carbon dioxide and
prevents airborne particulates from exiting the fireplace.
[0026] The present invention, in still another form thereof,
provides an unvented gas-fueled stove comprising a firebox, a gas
burner, a heat exchanger, a combustion gas circuit, and a carbon
monoxide catalyst element. The firebox includes an outlet with the
gas burner being disposed within the firebox and producing products
of combustion. The heat exchanger partially surrounds the firebox
and draws ambient air in through an entrance provided below the
firebox and exhausts convection heated air through an exit provided
above the firebox. The combustion gas circuit includes an inlet
communicating ambient air to the firebox and an outlet
communicating products of combustion out of the firebox. The carbon
monoxide catalyst element is disposed within the combustion gas
outlet and oxidizes carbon monoxide contained within the products
of combustion into carbon dioxide and prevents airborne
particulates from exiting the stove.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0028] FIG. 1 is a side sectional view of a fireplace incorporating
one embodiment of the present invention including the carbon
monoxide catalyst element;
[0029] FIG. 2 is top view of the fireplace shown in FIG. 1 showing
the placement of the carbon monoxide catalyst element;
[0030] FIG. 3 is right side perspective view of the fireplace shown
in FIG. 1;
[0031] FIG. 4A is top view of the carbon monoxide catalyst element
shown in FIG. 3;
[0032] FIG. 4B is a cutaway enlarged top view of the catalyst
element of FIG. 4A taken along line 4B;
[0033] FIG. 5 is an enlarged fragmentary, sectional view of the
carbon monoxide catalyst element shown in FIG. 4B which shows
alternating individual planar and corrugated, sinusoidal-shaped
foils with a catalyst coating disposed thereon;
[0034] FIG. 6 is a side sectional view of an alternative embodiment
of the present invention;
[0035] FIG. 7A is a perspective view of the carbon monoxide
catalyst element being assembled;
[0036] FIG. 7B is a perspective view of the carbon monoxide
catalyst element of FIG. 7A in a final assembled state;
[0037] FIG. 7C is a top view of the carbon monoxide catalyst
element of FIG. 7B;
[0038] FIG. 7D is an enlarged, top view of the carbon monoxide
catalyst element of FIG. 7C taken along lines 7D;
[0039] FIG. 7E is a perspective view of the corrugated foil member
of FIG. 7A taken along lines 7E;
[0040] FIG. 8A is a left front perspective view of the fireplace of
FIG. 1 with an alternative carbon monoxide catalyst element
arrangement showing a method of assembly;
[0041] FIG. 8B illustrates the fireplace of FIG. 8A with the carbon
monoxide catalyst element fully assembled;
[0042] FIG. 8C is a side sectional view of the carbon monoxide
catalyst element of FIG. 8B taken along lines 8C;
[0043] FIG. 9 is a partial side sectional view of a horizontally
vented fireplace incorporating the present invention including the
carbon monoxide catalyst element; and
[0044] FIG. 10 is a partial side sectional view of a vertically
vented fireplace incorporating the present invention including the
carbon monoxide catalyst element.
[0045] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrates possible embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Referring now to the drawings and particularly to FIG. 1,
the exemplary embodiment is shown as unvented fireplace 20 having
firebox 22 partially surrounded by heat exchanger 24.
[0047] Fireplace 20 includes bottom wall 26, back wall 28, opposing
side walls 30 and 32 (FIG. 2), and top wall 34. Firebox 22 includes
bottom wall 36, back wall 38, opposing side walls 40, and top wall
44. Heat exchanger 24 includes bottom plenum 46 disposed between
fireplace bottom wall 26 and firebox bottom wall 36, back plenum 48
disposed between fireplace backwall 28 and firebox backwall 38, and
top plenum 50 disposed between fireplace top wall 34 and firebox
top wall 44.
[0048] Back plenum 48 and top plenum 50 are divided into inner
passageway 52 and outer passageway 54 by room air deflector 56.
Similarly, top plenum 50 is further divided by combustion gas
deflector 58, as best shown in FIG. 1, to assist in the aspiration
of combustion gases 59 from fireplace 20. Heat shield deflector 60
is disposed above combustion product deflector 58 and room air
deflector 56 to prevent the top of fireplace 20, or an associated
mantle (not shown), from becoming overheated and potentially
damaged.
[0049] Bottom plenum 46 is provided with inlet 62, and top plenum
50 is provided with outlet 64 to create a heat exchanger circuit,
shown by flowpath arrows 66, which commences with ambient air being
drawn in through inlet 62, continuing through back plenum 46 and
top plenum 50, and exhausting through outlet 64. In this manner, a
cold air draft is induced by introducing relatively cool space
temperature air into vent inlet 62 and directing the air flow
around the outside of firebox 22. The cold air draft flow 66 exits
through vent outlet 64 just above combustion gas flowpath 104,
thereby inducing draft which helps aspirate the firebox exhaust
along path 104.
[0050] Louvered grills 68 and 70 are provided over inlet 62 and
outlet 64, respectively, to prevent the passage of relatively large
particles and objects. Any combustible products and particles which
do pass through louvers 68, such as lint or dust, are combusted
within firebox 22. To assist in the creation of a draft through
heat exchanger 24, fan assembly 72 is provided within bottom plenum
46. In other embodiments, fireplace 20 can be provided without fan
assembly 72. Fan 72 does not run continuously, but rather a thermal
disk or thermostat is placed in the unit. When the unit reaches a
certain temperature, the thermostat makes a switch and fan 72 is
energized. When the unit falls below a certain temperature, the
thermostat breaks the switch and deenergizes the fan. This
operation may be carried out by any one of many known acceptable
means to achieve the desired result.
[0051] Firebox bottom wall 36 includes a plurality of air inlets 74
which feed air from bottom plenum 46 into firebox 22. In the
exemplary embodiment firebox 22 is provided with main burner 76 and
front burner 78, although other burner configurations are possible.
Burners 76 and 78 are supplied combustible gas via a gas inlet (not
shown), and with air through air inlets 74 positioned proximate gas
burners 76 and 78 as shown in FIG. 1.
[0052] Ceramic logs 80 are also disposed within firebox 22 atop
bottom wall 36 to provide an aesthetically pleasing flame and
fireplace appearance. Raised grate 82 is provided to give fireplace
20 the appearance of having a larger number of logs than are
actually present, and thus reduce manufacturing costs. Glass front
84 substantially seals, in conjunction with sealing elements 86,
the front of firebox 22 such that all combustion gases 59 must exit
firebox 22 through firebox outlet 88 provided in firebox top wall
44. The average temperature of glass front 84 will be approximately
380.degree. F. with a maximum temperature at the glass of
approximately 450.degree. F.
[0053] The combustion of gas at gas burners 76 and 78 produces
combustion gases 59 which include, but are not limited to, carbon
monoxide. To reduce the amount of carbon monoxide released to the
ambient air, fireplace 20 includes carbon monoxide catalyst element
90 which is disposed in, and substantially bridges, firebox outlet
88 as shown in FIGS. 1 and 2. In vented applications, catalyst
element 90 may be disposed in the flue or stack or virtually
anywhere in the flow path of the products of combustion. Carbon
monoxide catalyst element 90 oxidizes the carbon monoxide within
combustion gases 59 into carbon dioxide before the gases are
released into the ambient environment.
[0054] During operation, the firebox operates at a temperature
approximately between 300-600.degree. F. Because there is little or
no heat generation within catalyst element 90, the catalyst element
also operates at approximately the same temperature as the firebox
or more accurately the temperature of the firebox at outlet 88.
This is in sharp contrast to prior art ceramic converters used in
wood burning applications in which large amounts of heat is
generated by the combuster or converter. This primarily results
from burning off creosote formed during the wood burning process.
In the present gas burning application, no creosote is created and
therefore no creosote is burned off by the catalyst element.
[0055] In prior art wood burning appliances, ceramic honeycomb-type
combusters were used because metal was not an acceptable material.
Prior art known metals were not acceptable because the metal could
not operate under the high temperature conditions associated with
burning off creosote. Unlike previously known metals, which had
poor oxidation resistance characteristics, the new alloy high
temperature stainless steel utilized in the foils of the present
invention provides effective oxidation at higher temperatures. The
ceramic oxide coating on the stainless steel interacts with the
platinum catalyst to convert the carbon monoxide to carbon dioxide.
This is in contrast to porcelinized ceramic honeycomb structures
used in the wood burning applications. The porcelinized ceramic
combusters virtually always crack and are typically held together
by an outer skin or by framing with perforations to permit the
communication of gas from the firebox through the combuster. A face
plate is typically used to prevent the collapse of the porcelinized
combuster and to help maintain it in its desired form. It is
virtually impossible to remove and clean such a combuster because
the ceramic structure is so likely to fall apart. Such problems are
absent from the catalyst coated, stainless steel foils of the
present invention.
[0056] As best shown in FIGS. 4 and 5, carbon monoxide catalyst
element 90, in the exemplary embodiment, is manufactured from a
plurality of alternating corrugated stainless steel foils 92 and
planar stainless steel foils 94. The stainless steel is a ferritic
stainless steel such as Alpha IV, FeCr Alloy, SR-18, or other
stainless steels such as 409, 304, or 316. The new stainless steel
alloys are acceptable in applications with operating temperatures
as high as 1600.degree. F. In the exemplary embodiment, foils 92
and 94 have a thickness of between 0.001 inch and 0.01 inch,
preferably 0.002 inch. Foils 92 are corrugated and interposed
between planar foils 94 to increase the overall surface area of
catalyst element 90 exposed to the combustion gases to thereby
increase the oxidizing capabilities of catalyst element 90. The
cell density associated with the configuration of the foils is
preferably about 20-30 cells per square inch resulting in a
porosity of approximately 90% or greater. Combustion in gas burning
appliances is especially sensitive to flow obstruction. Very slight
pressure drop increases, such as caused by placement of the
catalyst element in the exhaust, greatly affects the amount of
oxygen present and therefore the amount of carbon monoxide
produced.
[0057] The primary design criteria in gas burning appliance designs
are: 1) maintain aesthetic appearance of flickering flame, 2)
provide highest temperature in firebox without compromising
tempered glass front, and 3) providing effective destruction of
products of combustion. Optimal flow rate has been found to be
approximately 40-60 ft.sup.3/minute. The pressure drop across the
catalyst element affects all three of the design criteria. The
greater the pressure drop the lower the flow rate resulting in: 1)
choking off flame and loss of flickering effect, 2) temperature in
firebox may be too great, thereby compromising the tempered glass
front, and 3) more effective destruction of products of combustion.
The lower the pressure drop and greater the flow rate results in:
1) enhanced flame quality, 2) good operating temperature for glass
front, and 3) less effective removal of products of combustion.
This would require more catalyst to achieve effective operation
resulting in increased unit cost. Must balance the advantages and
disadvantages to arrive at a pressure drop/flow rate relationship
that yields the most effective catalyst element configuration.
[0058] Ceramic oxide and precious metal coating 96 is disposed on
stainless steel foils 92 and 94 as shown in FIG. 5. In the
exemplary embodiment, coating 96 is comprised of either aluminum
oxide, zirconium oxide, titanium oxide, or a mixture thereof, with
the precious metal being platinum or palladium or the like or a
mixture thereof. The ceramic oxide coating is applied to the foils
in basically two steps. First, an alumina-cerium oxide substance is
colloidally dispersed and applied on the foil. Second, platinum,
palladium, or a combination of the two metals at submicron levels
are highly dispersed and impregnated on the foils at the surface of
the ceramic oxide.
[0059] Carbon monoxide catalyst element 90 is disposed within
catalyst element frame 98. Frame 98 is spot welded, or otherwise
attached to firebox top wall 44 in firebox outlet 88. Frame 98 is
provided with rim 100 which retains catalyst element 90 within
frame 98. The top of frame 98 is open to allow removal of catalyst
element 90 for cleaning or replacement. In other embodiments, frame
98 could be provided with a screen (not shown) in lieu of rim 100
to retain catalyst element 90 within frame 98 and enable gases to
pass through for oxidation. Carbon monoxide catalyst element 90
also filters out any ceramic fibers released by logs 80 as a result
of gas burners 76 and 78 impinging flames 102 upon, and heating,
logs 80.
[0060] In operation, burners 76 and 78 combust gas drawn in through
the gas inlet and create flames 102 within firebox 22. Flames 102
within firebox 22 are fed air through air inlets 74 which allow
communication between heat exchanger 24 and firebox 22. Combustion
gases 59 rise through firebox 22 and ultimately pass through
firebox outlet 88 and carbon monoxide catalyst element 90 along
flowpath 104. The carbon monoxide within combustion gases 59 is
converted from carbon monoxide to carbon dioxide and is exhausted
from fireplace 20 through top plenum 50 and ultimately plenum
outlet 64.
[0061] Combustion gases 59 are drawn from firebox 22 as a result of
the draft created within heat exchanger 24. Combustion gases 59,
being heated and under pressure, are naturally drawn toward the
relatively cool, low pressure heat exchanger 24 and outside ambient
air. The glass cover is fixed in place as by hooks in the top of
the frame and screws in the bottom, or by other suitable means. A
gasket is used to help seal the firebox. This is necessary to
maintain proper flow of the heated gas through the catalyst element
90. If front cover 84 is not fixed, then the path of least
resistance would be through the openings between the cover and the
frame. The fixed cover also reduces the possibility of lint or
other debris from entering the firebox. Because the front of
firebox 22 is substantially sealed by glass front 84 and sealing
elements 86, combustion gases 59 are forced to exit firebox 22
through firebox outlet 88. Therefore, all combustion gases 59
emanating from burners 76 and 78 pass through carbon monoxide
catalyst element 90 and substantially all carbon monoxide is
oxidized into carbon dioxide. In addition, any ceramic fibers
released by logs 80 are prevented from exiting fireplace 20 by
catalyst element 90. In contrast to the ceramic honeycomb-type
combusters associated with wood burning applications, which are
characterized by a wall thickness of approximately 0.03 inch and a
porosity of 50-60 percent, the catalyst element of the present
invention is characterized by a porosity of approximately 90
percent or greater. This is primarily due to the significantly
reduced wall thickness in the catalyst element of the present
invention.
[0062] An alternative embodiment of the present invention is shown
in FIG. 6 wherein the heating appliance is free standing stove 106.
Free standing stove 106 includes base 112, back panel 114, top
plate 116, glass front 118, and firebox 108 surrounded by heat
exchanger 110. Firebox 108 includes bottom wall 120, back wall 122,
opposing side walls 124, and top wall 126. Heat exchanger 110
includes bottom plenum 128 disposed between base 112 and firebox
bottom wall 120, back plenum 130 disposed between back panel 114
and firebox back wall 122, and top plenum 132 disposed between
firebox top wall 126 and stove top plate 116.
[0063] As shown in FIG. 6, back plenum 130 and top plenum 132 are
divided into inner passageway 134 and outer passageway 136 by
deflection baffle 138. Bottom plenum is optionally provided with
blower fan 140 to draw ambient air in through inlet 42, through
heat exchanger 110, and out through outlet 144 as indicated by
flowpath arrows 145. In the embodiment shown in FIG. 6, inlet 142
is provided on the bottom back side of stove 106, while outlet 144
is provided on the top front side of stove 106.
[0064] Firebox 108 is provided with combustion air inlet 146 and
firebox outlet 148. In the embodiment shown in FIG. 6, combustion
air inlet 146 is provided on the bottom back side of stove 106,
while firebox outlet 148 is provided in top wall 126. Outlet 148
leads to stove outlet 161 such that combustion air follows flowpath
147. Firebox 108 also includes front burner 150 and main burner 152
which are supplied gas via a gas conduit (not shown) and with air
through combustion air inlet 146. Synthetic logs 154 are provided
on raised grate 156 similar to the exemplary embodiment shown in
FIG. 1. Glass front 118 substantially seals, in conjunction with
sealing elements 158, the front of firebox 108 such that all
combustion gases 160 must exit firebox 108 through firebox outlet
148.
[0065] Carbon monoxide catalyst element 162, having the same design
as the embodiment shown in FIG. 1 is disposed in firebox outlet
148, and is held within frame 164 as described in reference to FIG.
1. Although stove 106 is shown in FIG. 6 having air inlets placed
at the bottom back side of stove 106 with air outlets placed on the
front and top of stove 106, it is to be understood that the inlets
and outlets may be placed in other positions. It is also to be
understood that top plate 116 of stove 106 can be utilized as a
heating or cooking surface.
[0066] Catalyst 90 was tested in two fireplaces of differing
designs. The first fireplace included a flue having two concentric
ducts with ambient air entering through the outer duct, and hot
combustion gases exiting through the inner duct. The catalyst was
constructed of two 4".times.41".times.2" pieces each having 32
cubic inches of volume. The temperature in the firebox was not
measured directly, but the catalyst was glowing faintly red
indicating a temperature of 500.degree. to 600.degree. C.
[0067] The other test fireplace drew ambient air through two holes
located on the rear wall of the firebox above the burners. A single
catalyst with 42.4 cubic inches of volume was installed in the
exhaust flow path approximately 12 inches above the firebox in the
exhaust duct. The temperature was measured at approximately
400.degree. F.
[0068] Exhaust gases were pulled from the exhaust pipe at a rate of
approximately three liters per minute using a diaphragm pump and
the exhaust gases were then forced, under pressure, through a
refrigerator device designed to separate water from combustion
gases with minimum removal of carbon dioxide, nitrogen oxide, and
sulphur oxide. The dry gases were then analyzed for water, oxygen,
carbon dioxide, carbon monoxide, nitrogen oxide, and sulphur oxide.
The gas concentrations were calculated on a wet basis. Flow rates
were also monitored to assure placement of the catalyst in the
exhaust flowpath did not prevent creation of an adequate draft.
[0069] Tests were conducted with the fireplaces in three separate
modes of operation. The first test was conducted without the
catalyst placed in the fireplace. The second test was conducted
with the catalyst support frame inserted, and a final test was
conducted with the catalyst located within the catalyst support
frame. The results of the test of the first fireplace are shown in
the following Table #1, and the results of the tests of the second
fireplace, are shown in the following Table #2.
1 TABLE 1 Fireplace Empty Bare Support Catalyst CH.sub.4 0.57 0.57
0.57 Combustion Air 5.35 5.35 5.35 Supplement Air 7.18 4.78 5.15
Total Air 12.52 10.12 10.50 Total Flow Rate 13.09 10.69 11.07
CO.sub.2 4.31% 5.27% 5.09% H.sub.2O 9.57% 11.48% 11.13% O.sub.2
11.35% 9.24% 9.63% N.sub.2 74.79% 74.01% 74.15% CO, ppm 36 57 3
NO.sub.2, ppm 37 35 34 NO, ppm 22 12 25
[0070]
2 TABLE 2 Fireplace Blank Support Catalyst CH.sub.4 0.43 0.43 0.43
Combustion Air 4.09 4.09 4.09 Supplement Air 10.40 9.45 10.32 Total
Air 14.49 13.54 14.41 Total Flow Rate 14.92 13.97 14.84 CO.sub.2
2.89% 3.09% 2.91% H.sub.2O 6.76% 7.15% 6.79% O.sub.2 14.44% 14.02%
14.41% N.sub.2 75.90% 75.75% 75.89% CO, ppm 15 18 1 NO.sub.2, ppm
21 21 22 NO, ppm 13 13 19
[0071] As shown in Table #1, when the bare catalyst support frame
was inserted in the fireplace exhaust, the air draft was
effectively choked off with a corresponding increase in carbon
dioxide concentration from 4.31 percent to 5.27 percent. The carbon
monoxide concentration increased from 37 parts per million to 57
parts per million.
[0072] However, when the catalyst was placed into the support
frame, the air draft flow rate was relatively unchanged, but the
carbon monoxide levels were dramatically reduced from 57 parts per
million to 3 parts per million. This represents a 91.8 percent
reduction in carbon monoxide emission.
[0073] As shown in Table #2, without a catalyst the carbon monoxide
concentration was 15 to 18 parts per million. However, when the
catalyst was inserted, the flow rate was approximately the same as
for the empty fireplace, but the carbon monoxide levels were
dramatically reduced to approximately one part per million.
[0074] Referring now to FIGS. 7A-7E, corrugated foil members 200
and planar foil elements 202 are alternatingly placed in catalyst
element frame 204. The foil members are sized so as to friction fit
along sidewalls 206 and 208 of frame 204 during assembly. Inwardly
projecting flanges 210 and 212 are provided at the base of frame of
204 to engage the outermost bottom portions of foil members 200 and
202 so as to prevent excessive downward axial movement by the foil
members and to thereby hold them in place within frame 204. An
upper lip may be provided along the upper edge of frame 204 to
prevent upward axial movement of foil members 200 and 202 once
placed in frame 204. At the bottom of frame 204 and along the
lengths of front and back walls 214 and 216, respectively, flanges
218 and 220 extend outwardly and engage the inside surface of
ceiling 222 along the perimeter of catalyst element receiving
apertures 224 and 226. Catalyst 234 is attached to firebox 236 at
mounting apertures 228 by mounting screws 230 as shown in FIGS.
8A-8C, discussed in detail below.
[0075] As opposed to sinusoidal-shaped corrugated member 92, of
FIG. 5, corrugated foil member 200, as best shown in FIG. 7E, is
semi-hexagonal along oppositely faced turns 230 and 232. The
corrugated foil members may be shaped in a variety of
configurations, such as sinusoidal, hexagonal, triangular, square,
etc. When selecting a shape for the corrugated foil member, the
important consideration is that when coating the foil member with
ceramic oxide, coating tends to build up along sharp angles in the
foil. The triangular shape may be most efficient and economical
because less overlapping of metal occurs and less catalyst coating
is required. Planar foils 202 may be removed altogether when using
corrugating foil members that are shaped so as to engage one
another in a spaced apart relationship when disposed in frame 204.
An acceptable range of wall thickness for the foils, both
corrugated and planar, is preferably between 0.001 and 0.01 inch
with a preferred thickness of 0.002 inch. The final completed
assembly of carbon monoxide catalyst element 234 is shown in FIGS.
7B and 7C.
[0076] FIGS. 8A-8C illustrate an alternative embodiment of the
present invention in which a pair of catalyst elements 234 are
mounted to the firebox, as opposed to the single catalyst element
of FIG. 1. FIGS. 8A-8C illustrate the method of assembling
completed catalyst element 234 onto firebox 236 by inserting the
catalysts into receiving apertures 224 and 226 provided in ceiling
222 of firebox 236. From within the firebox, the catalyst elements
are disposed axially upward into and through the apertures until
support flanges 218 and 220 engage the inside surface of ceiling
222. Mounting apertures 228 are aligned with mounting holes 238
formed in ceiling 22 adjacent apertures 224 and 226. Mounting bolts
230, or any other suitable fastening device or means, are received
into and through apertures 228 and holes 238 and rotatably engage
bolts 240 to secure catalyst elements 234 to ceiling 222 of firebox
236.
[0077] The base of frame 204 is essentially hollow so that gases
may flow from within firebox 236 through apertures 224 and 226
through frame aperture 242 and over foils 200 and 202 through
catalyst element 234 as shown in FIG. 8C. Catalyst elements 234 may
be cleaned by detaching bolts 230 from bolts 240 and removing the
catalyst element from the firebox. Once removed, the catalyst
element may be cleaned by immersing the entire catalyst element,
frame, and foils, in a cleaning solution such as sodium bicarbonate
or vinegar. It is preferred not to remove the individual foils once
catalization has occurred. The cell density is approximately 20-30
cells per square inch in completed catalyst element 234. Catalyst
element 234 generally operates at a temperature approximately equal
to the temperature in firebox 236, typically between 300 and
600.degree. F., because there is little or no heat generation
within the converter. This is in sharp contrast to ceramic
converters used in wood burning applications in which substantial
heat is generated by the converter, thereby resulting in a much
elevated converter operating temperature. In wood burning
applications, creosote is produced and is burned off in the ceramic
converters resulting in a significant increase in the operating
temperature of the ceramic converter. By contrast, the gas burning
applications associated with the present invention does not result
in the creation of creosote. Catalyst element 234 does burn carbon
monoxide in converting it to carbon dioxide. The catalyst also
oxides some methane, formaldehyde, given off from insulation or
carpets or out gases, from sources such as paint, polish remover,
or other household objects. The catalyst burns CO to CO.sub.2 and
also some of the methane uncombusted by the burner. The catalyst
also burns formaldehyde and other volatile organic compounds that
may be present in the combustion air. Such volatile organic
compounds come from paint, polish remover, or other household
objects.
[0078] FIG. 9 illustrates the catalytic converter of the present
invention in a vented type appliance, an example of a prior art
vented appliance in which the present invention may be incorporated
is illustrated in U.S. Pat. No. 5,320,086 (Beal), which is hereby
incorporated into this document by reference and which is assigned
to the assignee of the present invention. As shown in FIGS. 9 and
10, a concentric flue pipe assembly 242 includes a fresh air pipe
244 and exhaust pipe 246.
[0079] During operation, air flow through direct vent gas fireplace
20' is as follows: combustion air flows through the annular space
defined between fresh air pipe 244 and exhaust pipe 246 from the
ambient environment outside the building in which direct vent gas
fireplace 20' is installed. The combustion air flows through an air
intake duct and combustion air duct 54 into the combustion chamber
formed within firebox 22'. The flow of combustion air into the
combustion chamber is represented by air flow directional arrows
104'. Combustion products produced in firebox 22' flow through the
opening defined between baffle plate 89 and firebox top wall 44,
pass over catalyst 90, through the lower portion of exhaust pipe
246, and are exhausted to the outside environment through the
outermost portion of exhaust pipe 246. The operation of the
catalyst unit is as describer hereinabove. In this manner, the
expulsion of products of combustion into the atmosphere is
essentially eliminated. As illustrated in FIGS. 9 and 10,
respectively, the vent flue arrangement may be vertical or
horizontal. The vented application does not have to be a concentric
intake/exhaust configuration and may take any conventional
form.
[0080] While the present invention has been described as having an
exemplary design, the present invention can be further modified
within the spirit and scope of this disclosure. Although the
present invention has been described as being particularly useful
in unvented applications, the present invention is nonetheless
useful in vented applications as well. This application is
therefore intended to encompass any variations, uses, or
adaptations of the invention using its general principles. Further,
this application is intended to encompass such departures from the
present disclosure as come within known or customary practice in
the art to which this invention pertains, and which fall within the
limits of the appended claims.
* * * * *