Patent Grant
9335094
This invention generally relates to heating devices used in drying equipment. More particularly, the invention relates to heating devices used in drying equipment that make use of an exhaust gas stream from a gasoline, propane, natural gas, or combustible fueled internal combustion engine as a means of generating heat for dissipating and evaporating moisture from a surface.
Any variety of commercial tasks, endeavors or public events can be delayed for indefinite periods of time while waiting for natural evaporation to occur after a moisture-generating event (e.g., dew, mist, rain, frost, snow, plumbing failures).
Prior art drying equipment either extracts moisture from the surface-to-be-dried (see e.g., U.S. Pat. No. 8,281,499 B2) or generates a stream of heated air to dry the surface. The heated air stream is usually achieved by the use of a heating device having an open flame or electric-resistance heater, infrared combustion of an air/fuel mixture, or infrared radiation from electric lighting such as a halogen or other high intensity lamp. Air is passed over, around or through the heating device using one of these techniques and then the heated air is directed as needed.
The disadvantages of drying equipment that makes use of prior art heating devices include (1) lack of mobility or portability and a limited ability to access all surface areas with the heated air stream; (2) safety hazards posed by the device to users and bystanders; (3) complex design with an associated higher operating and maintenance cost; (4) a limited lifespan of the heating source and an inability of the heat source to withstand rough handling and service; (5) a need to be connected to a main source of high amperage electrical power; and (6) limitations on the amount of heated air that can be generated due to the engineering constraints of the materials from which the heating device is constructed.
An engine exhaust-driven heating device made according to this invention generates a high volume, steady stream of hot gas by passing an exhaust stream from a gasoline, propane, natural gas, or combustible fueled internal combustion engine through a catalyst that reduces the atmospheric emissions of the stream and liberates the energy of the pollutants in the stream, and then combining that catalytic-treated air stream with a fresh air stream to further react with remaining pollutants and generate additional heat. The hot gas may be used to dry a variety of surfaces and, when integrated without other components typically found in surface drying equipment, provides an ideal system for use in a variety of moderate- to large-sized portable surface drying equipment. The heating device provides a reliable and continuous heat source and, when integrated into a controlled delivery system, dries the moisture from a surface faster and more effectively than prior art heating devices.
In a preferred embodiment of the portable heating system, a catalytic chamber which houses at least one catalyst for treating engine emission pollutants is arranged to receive an exhaust gas stream from an engine, preferably being run in a fuel-rich condition. The exhaust gas stream passes through the catalyst, which can be arranged in one or more stages, into a baffled mixing chamber arranged to receive the catalytic-treated exhaust gas stream. The baffled mixing chamber mixes the catalytic-treated exhaust gas stream with an ambient air stream to produce a cleaner and higher temperature mixed gas stream. A distribution chamber is arranged to receive the mixed gas stream and direct it toward a surface to be dried or stripped of an unwanted layer of material.
The system can include a pressurized air source arranged in communication with the catalytic chamber for injecting pressurized air into the chamber. The pressurized air—which could be pure oxygen and preferably has a greater percentage of oxygen than the ambient air stream (which is typically about 21% oxygen at sea level but varies according to altitude)—can be arranged to inject the pressurized air ahead of the catalyst.
In a preferred embodiment of the portable heating apparatus a baffled mixing chamber is located downstream of a catalytic chamber that at least one catalyst suitable for reducing a level of undesired pollutants present in an engine exhaust gas stream. A source of pressurized air, which could be pure oxygen, can be included to inject pressurized air into the chamber, ahead of the catalyst in the chamber. The baffled mixing chamber receives the catalytic-treated exhaust gas stream and mixes it with an ambient air stream. The ambient air stream can be provided by a blower. A distribution chamber then takes this cleaner, higher temperature mixed gas stream and directs its flow, preferably downward through a perforated plate.
In a preferred embodiment of a method for removing an undesired layer of material residing immediately above a desired base layer of material (e.g., water on a road, ice on a sidewalk) includes the steps of:
Objects of this invention include providing a heating device that (1) contains and controls a catalytic reaction of combustible exhaust gases; (2) uses the catalytic-reacted gas as a heat source; (3) uses fewer components and is less complex than prior art devices; (3) is portable and able to integrate into a range of equipment sizes best suited for a user application; (5) is easy to operate and maintain; (6) has minimal environmental impact; (7) is safer than prior art devices; and (8) creates a very cost effective choice relative to prior art surface drying technology.
Referring to
The two streams—ambient air stream 13 and either catalytic treated exhaust stream 4 or catalytic treated exhaust stream 4 with pressurized air stream 12—meet in baffled mixing chamber 5 as combined stream 11 where additional reaction occurs, breaking down remaining constituents in the exhaust stream 4 and releasing additional heat in the process. Stream 11 is then passed into distribution chamber 6 where the hot air or gas flow 7 exits the perforated bottom plate 14 of the chamber 6. The hot gas flow 7 then comes into contact with a moist surface 8, dissipating moisture and drying the surface 8.
Catalyst 3 converts constituents of the exhaust stream 4 (such as carbon monoxide, unburned or partially burned hydrocarbons from the fuel) and liberates heat as a result. Additional reaction occurs after the catalytic treated exhaust stream 4 meets the ambient air stream 13 in baffled mixing chamber 5, burning any remaining carbon monoxide and hydrocarbons and liberating heat. A suitable catalyst is an engine emission control catalyst provided by Catalytic Combustion Corporation (Bloomer, Wis.).
An air cooled engine is preferred because, to best manage the heat liberated by the combustion of fuel in the cylinders, an air-cooled engine runs in a fuel-rich condition and prevents perfect stoichiometric combustion. The fuel-rich condition limits the amount of heat released by the combustion reaction without sacrificing too much of the power generated when the fuel/air mixture ignites. Fuel-rich conditions also produce less nitrogen oxides by limiting the amount of oxygen in the cylinder which, in turn, keeps the combustion temperature lower. Lower temperature inhibits the temperature-dependent chemical reactions that produce nitrogen oxides. However, running an engine in a fuel-rich condition results in the exhaust containing more carbon dioxide and unburned hydrocarbons compared to engines which run closer to the stoichiometric point or optimum lean fuel mixture.
Catalyst 3 is operated to optimize the generation of heat available through the chemical conversion of unburned or partially burned fuel, carbon monoxide, and nitrogen oxides that are present in the exhaust stream 4. Because the engine is preferably run in a fuel-rich condition, the introduction of more oxygen is needed so that the catalyst 3 can initiate the chemical reactions. This can be done by injecting a pressurized air stream 12 prior to the catalyst 3. Pressurized air stream 12 can be a pure oxygen stream.
Introducing additional oxygen prior to a catalyst is not typically done in engine applications because of the need to control nitrogen oxide. The additional oxygen leads to higher temperatures which enable the production of nitrogen oxide.
In applications where the heating device, using an air cooled engine, is running in a confined space and build-up of carbon monoxide gas is to be avoided, the engine may be run less fuel rich (i.e., leaner) or pressurized air stream 12 may be injected ahead of the catalyst to provide more oxygen for additional stoichiometric combustion (further reducing harmful toxic emissions). Catalyst 3 may be applied in series a minimum of two to three times within the exhaust system to provide an operator-safe atmosphere.
Pressurized air stream 12 should be such that it draws in just enough air to permit the catalyst 3 to convert sufficient carbon monoxide to satisfy applicable government regulations. The engine should be adjusted to optimize its heat generating performance and excess air 13 is introduced in the baffled mixing chamber 5 (or injected ahead of the catalyst at 12) to combine surplus oxygen with the exhaust stream 4. This permits catalyst 3 to convert a substantial amount of the exhaust constituents in the exhaust stream 4 and significantly boost the temperature of the catalytic treated exhaust steam 4 when it flows into the baffled mixing chamber 5. In chamber 5, a self-initiating thermal reaction completes the combustion of any remaining residual combustible constituents.
Catalyst 3 could be sized so overall conversion of the carbon monoxide and hydrocarbons takes place in the catalyst 3, thereby liberating all of the heat in a single step or stage. However, this approach would raise the temperature of the catalyst 3 to a level beyond the point of thermal stability, resulting in degradation of the amount of heat generated over time and a significant shorting of the catalyst lifespan. Therefore two to three catalytic treatment stages of the exhaust constituents are preferred.
By way of example, a prototype system was built using a 25 hp Subaru v-twin engine model EH72.2. The following temperature profiles were recorded:
This engine exhaust and catalytic hot air stream supply, when integrated with the other necessary system components, can be used to dissipate and dry moisture from most hard surfaces; such as but not limited to concrete, asphalt, terrazzo, and other like surfaces, as well as compacted gravel and dirt.
Small apparatus—such as push- or self-propelled walk-behind devices designed to provide a drying area in a range of about 5 to 9 sq. ft. (0.46 to 0.84 m2) and powered by a single internal combustion engine—could incorporate a dual catalytic heater plenum as shown in
Any combination of internal combustion engines, including those in which multiple engines are incorporated, can be powered to accommodate a range of temperature requirements. Regardless of device size, the invention has the ability to divert the heated air flow through a single, manually operated drier wand for isolated or discrete application needs. A single catalytic heater plenum and distribution chamber via a flexible conduit can be utilized for this purpose.
The invention is also not limited to surface drying applications. The heat generated from the free byproduct of combustion as a significant heat source lends itself to many other applications where a portable and flexible source of heat is required indoors or out including, but not limited to ice, snow, and stripping finishes.
This application claims the benefit of U.S. Prov. Appl. Ser. No. 61/971,675 filed Mar. 28, 2014, the content of which is hereby incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 8281499 | Friesen et al. | Oct 2012 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20160010918 A1 | Jan 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61971675 | Mar 2014 | US |
