WO1998046940A1 - Gas catalytic heaters with improved temperature distribution - Google Patents
Gas catalytic heaters with improved temperature distribution Download PDFInfo
- Publication number
- WO1998046940A1 WO1998046940A1 PCT/US1998/007345 US9807345W WO9846940A1 WO 1998046940 A1 WO1998046940 A1 WO 1998046940A1 US 9807345 W US9807345 W US 9807345W WO 9846940 A1 WO9846940 A1 WO 9846940A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- gas
- catalytic heater
- plenum chamber
- heater according
- gas catalytic
- Prior art date
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/12—Radiant burners
- F23D14/18—Radiant burners using catalysis for flameless combustion
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/12—Radiant burners
- F23D14/14—Radiant burners using screens or perforated plates
- F23D14/145—Radiant burners using screens or perforated plates combustion being stabilised at a screen or a perforated plate
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D2900/00—Special features of, or arrangements for burners using fluid fuels or solid fuels suspended in a carrier gas
- F23D2900/00003—Fuel or fuel-air mixtures flow distribution devices upstream of the outlet
Definitions
- the present invention relates to gas catalytic heaters in general and more particularly to a novel and improved system for uniformly dispersing a combustible gas or fuel within a catalytic heater.
- any catalytic heater heat is produced when a gaseous fuel is brought into contact with a catalyst in the presence of air containing a normal level of oxygen.
- the fuels are natural gas, propane and butane, for example.
- the combustible gas or fuel is fed through the bottom of the catalytic heater and is dispersed at atmospheric pressure into contact with a porous active layer.
- This layer contains a catalyst which may be platinum, for example.
- Oxygen from the atmosphere enters the porous catalytic layer and reacts with the gaseous fuel, promoted by the catalyst. This reaction releases the BTU content in the fuel in the form of radiant energy.
- Catalytic heaters are therefore used as a source for infrared heat.
- the chemical reaction that occurs during the oxidation reduction process produces temperatures within the catalyst of from about 500 to 1000 degrees Fahrenheit (F) .
- the by-products of the reaction include carbon dioxide and water vapor.
- the temperature at the surface of the catalytic heater is dependent upon the rate at which the fuel gas is introduced to the catalyst.
- the surface of the heater is typically rectangular or circular and ranges from about one square foot to about 10 square feet.
- the volume of gas delivered to the catalytic surface may range from about 2 to 6 cubic feet of gas per hour per square foot.
- the catalytic heaters that are commercially available today display a reasonably even or uniform distribution of temperature at the maximum rated input of 6 cubic feet of gas per hour per square foot. This will produce a reaction temperature on the heater surface of from about 750 to about 800 degrees Fahrenheit (F) .
- F degrees Fahrenheit
- the temperature distribution across the heater surface will vary from about 200 to about 800 degrees Fahrenheit (F) .
- the catalytic heaters develop hot and cold spots across the heating surface and produce an uneven heating profile to the object being heated. As a consequence, process control is very poor and efficiency is reduced.
- Another more specific object of the invention is to provide a gas catalytic heater in which the combustible gas or fuel is distributed more evenly or uniformly to the porous catalytically active layer of the heater.
- Still another object of the invention is to provide a gas catalytic heater in which the slippage of fuel gas passed the porous catalytically active layer is significantly reduced.
- the present invention is directed to a gas catalytic heater characterized by a significantly improved temperature distribution over the surface of the working element of the heater. This improvement is made possible by the provision within the catalytic heater of a sealed plenum chamber into which the combustible gas or fuel is introduced.
- the gas catalytic heater of the invention includes a body having an open end in which the working element is disposed.
- the working element may be a gas permeable catalytically active layer, that is, a porous layer containing a catalyst such as platinum metal.
- the sealed plenum chamber is disposed below the catalytically active layer and has a gas- permeable wall portion facing toward the active layer.
- the plenum chamber also has an inlet orifice for introducing the combustible gas or fuel under pressure into the plenum chamber.
- the gas-permeable wall portion of the plenum chamber is so constructed as to have a permeability such that at a given flow rate of the combustible gas or fuel through the gas inlet, the gas flows continuously through the wall portion under substantially the same pressure as the internal pressure within the chamber. After passing through the gas-permeable wall portion, the gas flows into contact with the catalytically active porous layer and is uniformly distributed over its entire surface. Upon reacting with oxygen from the atmosphere at the catalyst site, the working element radiates infrared heat at substantially the same temperature over its entire working surface. There are essentially no "cold spots" at the surface of the working element even at very low gas flow rates through the heater.
- the gas- permeable wall portion of the sealed plenum chamber comprises a perforated metal plate having a plurality of tiny holes or apertures therein which are substantially equally spaced apart from one another.
- the total open area provided by the tiny holes or aperture is significantly less than that provided by the perforated plates used in prior catalytic heaters.
- the perforated plate used in the catalytic heater of the invention is preferably placed within the bottom of the heater body in spaced apart relation from its bottom wall and is sealed around its outer peripheral edges to form a sealed plenum chamber according to the invention.
- At least one layer of a porous heat insulating material is interposed between the gas-permeable wall portion of the sealed plenum chamber and the porous catalytically active layer.
- the porous insulating layer serves to prevent heat loss from occurring beneath the working element and also aids in distributing the gas or fuel evenly prior to reaching the catalyst.
- An important feature of the invention that is used in this preferred embodiment is the provision of a porous baffle member interposed between the gas-permeable wall portion of the sealed plenum chamber and the heat insulating layer.
- the insulating layer is typically made from a fibrous material the individual fibers of which upon contacting the perforated plate can easily block, plug and seal off the tiny holes or apertures, thereby reducing the effectiveness of the sealed plenum chamber.
- the porous baffle member according to the invention is positioned on top of the perforated plate and keeps the fibers from entering and blocking the tiny holes or apertures.
- the baffle member also aids in a uniformly distributing the gas through the heat insulating layer after leaving the plenum chamber.
- Figure 1 is a perspective view, partly in section, of a gas catalytic heater according to the invention
- Figure 2 is an enlarged sectional view of a portion of the gas catalytic heater shown in Figure 1;
- FIG 3 is a perspective view of the perforated plate and porous baffle number used in the gas catalytic heater shown in Figures 1 and 2;
- Figure 4 is a view similar to Figure 2 showing a different embodiment of the invention.
- Figure 5 is a similar view of a gas catalytic heater showing still another embodiment of the invention.
- the catalytic heater includes a body 10 in the form of a shallow, rectangular shaped metal pan 11 having a flat bottom wall 12, upstanding side walls 13 and an upper open end 14.
- the open end 14 of the pan 11 is formed with a peripheral flange portion 15 which supports a thin, porous, catalytically active layer 16.
- This catalytically active layer 16 is made from a fibrous, ceramic material, such as silica or alumina, for example, and is impregnated with an oxidation catalyst such as platinum, palladium or the oxides of chromium, cobalt or copper, for example.
- An open wire mesh or screen 17 rests on top of the porous catalytic layer 16 and allows for easy access of air and oxygen to the surface of the catalytic layer 16 from the surrounding atmosphere.
- a plenum chamber as shown at 18.
- the plenum chamber 18 is formed by mounting a perforated metal plate 19 in spaced apart relation above the bottom wall 12 of the metal pan 11.
- the perforated plate 19 rests on a resilient or adhesive bead 20 which is interposed between its outer peripheral edges and the bottom wall 12.
- the bead 20 serves to separate the plate 19 from the bottom wall 12 and to seal off the plenum chamber 18.
- the perforated metal plate 19 contains a plurality of tiny holes or apertures 21 which communicate directly with the interior of the sealed plenum chamber 18.
- the holes or apertures 21 are substantially evenly spaced apart from one another within the plate 19 as best shown in Figures 2 and 3.
- the size and more particularly the open area provided by the tiny holes or apertures 21 is an important factor to be considered in the practice of the invention as shall be described in greater detail hereinafter.
- the plenum chamber 18 is relatively shallow in height but extends across the entire bottom of the catalytic heater providing a relatively large space or volume for containing the combustible gas or fuel prior to distribution to the catalytically active layer 16.
- the gas or fuel is fed to the sealed plenum chamber 18 via a small gas orifice 22 mounted within the bottom wall 12.
- porous fibrous layers 23, 24 Disposed between the porous catalytic active layer 16 and the sealed plenum chamber 18 are two porous fibrous layers 23, 24 of heat insulating material, such as silica fibers, for example.
- the heat insulating layers 23, 24 thermally isolate the catalytic layer 16 from the bottom of the heater and also aid in distributing the gas evenly as it emerges from the perforated plate 19 prior to reaching the catalyst.
- a baffle member 25 is disposed between the plate and the adjacent fibrous insulating layer 24.
- the baffle member 25 may be composed of metal, fiberglass, ceramic or an engineered plastic and can be cast or woven from these materials.
- the baffle can also be a non-woven material composed of randomly dispersed fibers or other similar structure.
- the baffle number 25 is a woven metal mesh or screen.
- the main purpose of the baffle number 25 is to prevent the combustible gas or fuel from being obstructed as it leaves the plenum chamber 18 and enters the insulating layers 23, 24.
- the baffle member also serves to more evenly distributed the gas or fuel as it emerges from the tiny holes or apertures 21.
- the perforated metal plate 19 may also be formed with an upstanding rim portion 26 which fits snugly against the side walls 13 of the metal pan 11. This rim portion 26 aids in sealing off the plenum chamber 18 and also serves to secure the baffle member 25 within the bottom of the catalytic heater.
- Figure 4 shows a different embodiment wherein the rim portion 26 is eliminated and the plenum chamber 18 is sealed off by a rectangular strip 27 of an adhesive type sealant.
- the sealing bead 20 shown in Figures 1 and 2 may also be composed of a resilient material, such as rubber, for example.
- a resilient sealing bead 28 is provided and is compressed into sealing relation between the perforated plate 19 and bottom wall 12 by a bold and nut 29.
- the plate 19 in this embodiment also includes the peripheral rim 26 as described above .
- a perforated plate is used that covers a gas dispersion tube within the bottom of the heater. This plate is loosely placed, but not sealed, into the heater and supports the insulation layers, electric resistance heaters used to start the catalytic heater and finally the catalyst layer. The entire depth of the heater (approximately two inches) is employed for distributing the gas. The volume changes of gas within this apace are in the range of about 18 per hour for low fire rates and 36 per hour for high fire rates .
- the sealed plenum chamber used in the catalytic heater of the invention is capable of between about 200 volume changes per hour at 3 cubic feet of gas flow per square foot per hour (low fire) and 800 volume changes at 6 cubic feet of gas flow per square foot per hour (high rate) .
- the catalytic heater of the invention is far more responsive to volume changes, providing rapid stabilization when changing from one flow rate to another. This is highly desirable, if not necessary when adjusting the heaters to obtain the correct level of heat output for a given heating process.
- the perforated plate used in prior art catalytic heaters typically has an "open area" of about 50 percent (%) . In essence, this means that for every square foot of plate, there are 72 square inches of open area, and 72 square inches of closed area .
- the large open area perforated plate of the prior art has been replaced with a perforated plate, which not only serves to form a sealed plenum chamber as described, but in addition provides an open area of between about 0.009 and 0.06 percent (%) of the total area of the plate, with an average open area of about 0.03 percent (%), for example.
- the perforated plate in the present heater is sealed to the bottom of the heater pan, and replaces the gas distribution tubes presently used in commercial heaters.
- the 0.03% average open area provided by the present perforated plate is equal to about 0.0432 square inches of open area per square foot as compared to the 72 square inches on conventional heaters.
- the average open area of 0.0432 square inches per square foot is the sum of the area of between 20 to 40 holes or apertures per square foot in the perforated plate 19 of the invention.
- Such a configuration is represented in Figure 3 wherein there is shown a total of 36 holes or apertures 21 (6 by 6 rows) in one square foot of plate area. It is important to note that the size of the holes or apertures 21 are shown in the drawings ( Figures 1-3) on a much larger scale than might actually be employed in practice merely for the purposes of illustration.
- the gas enters the sealed plenum chamber 18 through a pre-sized gas orifice 22.
- the purpose of the orifice is to limit the volume of gas entering the plenum chamber 18 for a given pressure of gas from a suitable supply (not shown) .
- the pressure drop across orifice 22 is equal to the pressure prior to the orifice minus the pressure in plenum chamber which is typically less than about 0.5 of a Water Column inch.
- a pressure of around 0.5 Water Column inches will register on the pressure gage.
- the pressure will be higher as the flow of gas is increased into plenum chamber 18 and will decrease when the flow of gas is decreased into plenum chamber.
- the pressure remains the same at any of the 20 - 40 apertures per square foot, thereby ensuring an equal flow of gas through each of the apertures per square foot across the entire surface of plate 19 regardless of its total or overall surface area.
- the gas As the gas flows through the holes or apertures 21, it has a velocity perpendicular to the perforated plate 19.
- the velocity is greater at higher gas inputs into the catalytic heater and lower with less gas entering the heater.
- it is essential to keep the apertures open and free from contact with other materials within the heater, particularly the fibers within the insulating layers 23, 24.
- the gas velocity is reduced and redirected partially parallel to plate 19.
- a woven or non-woven baffle member 25 is provided according to the invention. The baffle separates the insulation material from the plate 19 and prevents the apertures from becoming blocked by the insulation.
- Table I below shows typical ranges of percent open area, hole diameters and pressure drops across the perforated plate in a catalytic heater according to the invention.
- the table shows data from 7 cubic feet/square foot gas flow into the heater.
- the gas exits the perforated plate directly to a baffle and then to the catalyst.
- the tubular arrangement of the prior art employs 1-4 holes per square foot on average. The holes are about an 1/8 inch (.125 inch) in diameter. As seen in Table I, the catalytic heater of the invention can have up to 40 holes per square foot of heater area.
- the plenum depth and hole diameters in the present catalytic heaters are designed to create just the right velocity of the gas as it exits the plenum chamber. Too much velocity and the gas "squirts" through the catalyst not allowing enough resonance time for the gas to be chemically oxidized by the platinum in the catalyst bed.
- a sealed plenum exerts equal pressure in all directions within the plenum. Therefore, if the holes in perforated plate are all of equal diameter, then the same flow or velocity of gas will take place at every hole.
- Catalytic heaters of the invention consistently demonstrate improved methane slip rates as compared to catalytic heaters of the prior art.
- Prior catalytic heaters have shown methane slip rates up to as high as 25 percent (%) at typical operating levels of about 15 percent (%) .
- the catalyst receives the gas in an even, consistent flow across the entire surface of the heater. As a result, there is a consistent chemical reaction that takes place at the catalyst layer. This in turn produces an even temperature across the entire heater surface.
- gas is unevenly distributed causing varying quantities of the gas to react with the catalyst. As a result, non-uniform temperature distributions and " cold spots" occur on the working element.
- methane slippage it is in the areas where larger quantities of fuel gas contact the catalyst and cannot be chemically reacted, that is, at high gas flow rates, that methane slippage most frequently occurs.
- Laboratory testing of catalytic heaters made according to the invention have shown methane slippage to be less than about 5 percent (%) of the input levels.
- the gas dispersion system of the invention thus allows the catalytic reaction to be more efficient in converting the BTUs of the gas into heating energy. Because of this increased efficiency, greater heat outputs are possible with the catalytic heaters of the invention.
- methane slippage may even be even further reduced as the output is increased.
- the slip rate is about 5 percent (%) at 6000 BTUs output
- the slippage may be reduced to as little as about 3 percent (%) at 8000 BTUs.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Catalysts (AREA)
- Gas Burners (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP98918134A EP1015816A4 (en) | 1997-04-14 | 1998-04-11 | Gas catalytic heaters with improved temperature distribution |
CA002286000A CA2286000C (en) | 1997-04-14 | 1998-04-11 | Gas catalytic heaters with improved temperature distribution |
GB9924190A GB2338659B (en) | 1997-04-14 | 1998-04-11 | Gas catalytic heaters with improved temperature distribution |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US4363697P | 1997-04-14 | 1997-04-14 | |
US60/043,636 | 1997-04-14 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998046940A1 true WO1998046940A1 (en) | 1998-10-22 |
Family
ID=21928135
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1998/007345 WO1998046940A1 (en) | 1997-04-14 | 1998-04-11 | Gas catalytic heaters with improved temperature distribution |
Country Status (5)
Country | Link |
---|---|
US (1) | US6045355A (en) |
EP (1) | EP1015816A4 (en) |
CA (1) | CA2286000C (en) |
GB (1) | GB2338659B (en) |
WO (1) | WO1998046940A1 (en) |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6561794B1 (en) | 2000-04-21 | 2003-05-13 | Honeywell Asca Inc. | Infrared heater |
DE10038716C2 (en) * | 2000-08-09 | 2002-09-12 | Bosch Gmbh Robert | Gas burner with a porous material burner with a homogeneous combustion process |
CA2469061C (en) * | 2001-12-03 | 2008-11-04 | New England Catalytic Technologies, Inc. | Method of preheating catalytic heaters |
US8784739B2 (en) | 2006-09-07 | 2014-07-22 | Environmental Purification, Llc | Method and apparatus for controlling fecal odors |
US20090053664A1 (en) * | 2007-08-23 | 2009-02-26 | Csps Metal Company Ltd. | Catalytic patio heater |
US20120282556A1 (en) * | 2010-11-18 | 2012-11-08 | Air Products And Chemicals, Inc. | Method and Fuel Composition for Catalytic Heater |
DE102011050368A1 (en) * | 2011-05-15 | 2012-11-15 | Webasto Ag | evaporator assembly |
US10532315B1 (en) | 2015-08-27 | 2020-01-14 | Advanced Catalyst Systems Llc | System for flameless catalytic destruction of fugitive organics and producing environmentally clean hot gas for other uses of thermal energy |
WO2017052398A1 (en) * | 2015-09-21 | 2017-03-30 | Общество с ограниченной ответственностью "Уникат" | Catalytic heating apparatus with a gas flow distributor |
GB201519449D0 (en) * | 2015-11-03 | 2015-12-16 | Eco Burner Products Ltd | Improvements in or relating to organic material |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3024836A (en) * | 1954-10-19 | 1962-03-13 | American Infra Red Radiant Co | Radiating thermic element with catalytic gas oxidation |
US3029802A (en) * | 1958-10-15 | 1962-04-17 | Otto Bernz Company Inc | Automobile heater |
US3073379A (en) * | 1959-05-11 | 1963-01-15 | Maywick Appliances Ltd | Gas operated heaters |
US3087041A (en) * | 1957-10-09 | 1963-04-23 | Era Heater Corp | Space heater |
US3245459A (en) * | 1963-03-01 | 1966-04-12 | Engelhard Ind Inc | Catalytic heater and catalyst therefor |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3057400A (en) * | 1954-11-12 | 1962-10-09 | Fireless Gas Heater Corp | Glow burner for fuel-air mixture |
US3784353A (en) * | 1972-01-28 | 1974-01-08 | G Chapurin | Flameless gas catalytic heater |
-
1998
- 1998-04-11 GB GB9924190A patent/GB2338659B/en not_active Expired - Fee Related
- 1998-04-11 WO PCT/US1998/007345 patent/WO1998046940A1/en not_active Application Discontinuation
- 1998-04-11 EP EP98918134A patent/EP1015816A4/en not_active Withdrawn
- 1998-04-11 US US09/059,055 patent/US6045355A/en not_active Expired - Fee Related
- 1998-04-11 CA CA002286000A patent/CA2286000C/en not_active Expired - Fee Related
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3024836A (en) * | 1954-10-19 | 1962-03-13 | American Infra Red Radiant Co | Radiating thermic element with catalytic gas oxidation |
US3087041A (en) * | 1957-10-09 | 1963-04-23 | Era Heater Corp | Space heater |
US3029802A (en) * | 1958-10-15 | 1962-04-17 | Otto Bernz Company Inc | Automobile heater |
US3073379A (en) * | 1959-05-11 | 1963-01-15 | Maywick Appliances Ltd | Gas operated heaters |
US3245459A (en) * | 1963-03-01 | 1966-04-12 | Engelhard Ind Inc | Catalytic heater and catalyst therefor |
Non-Patent Citations (1)
Title |
---|
See also references of EP1015816A4 * |
Also Published As
Publication number | Publication date |
---|---|
GB2338659A (en) | 1999-12-29 |
US6045355A (en) | 2000-04-04 |
CA2286000A1 (en) | 1998-10-22 |
EP1015816A1 (en) | 2000-07-05 |
CA2286000C (en) | 2004-06-22 |
EP1015816A4 (en) | 2001-02-07 |
GB9924190D0 (en) | 1999-12-15 |
GB2338659B (en) | 2001-12-19 |
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