Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1999-10-05
2001-12-11
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S177000, C422S180000
Reexamination Certificate
active
06328936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a catalytic reactor for promoting a chemical reaction on a fluid passing therethrough. More specifically, the apparatus is a structure for step-wise heating of a fluid passing therethrough such that the fluid obtains or maintains a temperature wherein the desired chemical reaction, in the presence of a catalyst, can occur.
2. Brief Description of the Related Art
Catalytically supported reactions are used in numerous applications, with the automotive converter being one of the more well known. Catalyst characteristics dictate that these reactions occur within a given temperature range with the operational temperature range being chemistry dependent. When a catalyst reaches its operational temperature range it is said to light-off; prior to reaching light-off the catalyst is too cold to support the desired reaction. After light-off the catalyst temperature must be maintained to support the reaction.
Several methods have been employed to raise the temperature of the catalyst to achieve light-off and/or maintain operational temperature. One common method uses the heat energy in the fluid on which the chemical reaction is to occur. This approach, common in automotive converters, imparts the heat in the exhaust gas, resulting from the combustion in the engine, to the catalyst in the downstream catalytic converter.
A second method which is fluid independent employs an auxiliary heat source. The most common auxiliary source being powered by electricity. In this method, the substrate that supports the catalyst is an electrically conducting material that heats up by its electrical resistance when an electric potential is put across the substrate. Auxiliary heating sources are used primarily where the extraction of heat from the fluid is either too slow to effectuate a timely light-off of the catalyst, or the heat of the fluid is below the light-off temperature of the catalyst.
Auxiliary heating sources, as the name implies, are additional systems to the primary system. It is, therefore, critical that these auxiliary heating systems be highly efficient in bringing the catalyst to or maintaining the catalyst at the appropriate operational temperature. The art is well aware of the efficiency of extremely short-channel, metal-substrate catalysts. When these catalysts are bundled, however, the resulting elements have extremely low resistance thus making electrical heating impractical, due to large current requirements for a given electrical potential resulting in excessive power supplies and cables. Currently, spacing is used to solve this problem, but the resulting devices are extremely long. A method of efficient bundling that permits auxiliary electrical resistive heating is required.
SUMMARY OF THE INVENTION
The present invention is a catalytic reactor for promoting a chemical reaction on a fluid passing therethrough. The invention is comprised of a plurality of heater elements with each element having multiple flow channels. The channels of the heater elements are aligned such that a fluid passing through the reactor passes through each heater element in turn, thereby step-wise heating the fluid.
In the present embodiment of the invention, the heater element is made of a single piece of expanded metal. This, however, should not be limiting. For this invention a heater element can have any number of layers, for example two or three layers of expanded metal. A heater element is simply an element that heats up uniformly as a unit.
The heater elements are electrically isolated from one another by at least one insulator. Like the heater element, the insulator has multiple flow channels. The insulator flow channels are oriented to the flow channels of the heater elements, such that the fluid flows through both the heater element and the insulator.
The present invention can also incorporate a catalytic feature. The catalytic feature can be associated with the at least one heater element, at least one insulator element, a separate downstream catalyst or any combination of the above. The present embodiment incorporates a catalyst feature in the heater elements, the insulator elements and a downstream catalyst. In this embodiment, the insulator has the dual function of insulating and supporting the catalyst.
The heater elements of the present invention are made from material that is electrically conductive. The insulators are made from woven silica yarn, which is electrically non-conductive. The heater elements are connected electrically, in series being preferred, with the insulators assuring no electrical short circuits between the heater elements. For operation, each end of the electrical circuit is connected to an electrical power source. In the case of the present invention, the power source was direct current.
The catalyst chosen for use in the invention is application dependent. The specific application of the present invention is as a component of an air purification system, therefore the catalyst employed has as its active ingredients platinum and palladium. For the present application, the catalyst was deposited on both the heater elements and the insulator elements.
To provide a sealed flow path through the catalytic reactor, gaskets were incorporated. A gasket is only one method of sealing the reactor flow path. Gaskets are used as required.
In the present embodiment of the invention, three downstream catalysts were added. The downstream catalyst or catalysts can be of any design. In the present invention, the first downstream catalyst was merely additional catalytically coated insulator elements. Again, gaskets were employed to assure the integrity of the flow path. The second and third downstream catalyst were packets of Microlith elements, such as those found in U.S. Pat. No. 5,051,241, incorporated herein by reference.
REFERENCES:
patent: 5146743 (1992-09-01), Maus et al.
patent: 5229079 (1993-07-01), Harada et al.
patent: 5465573 (1995-11-01), Abe et al.
patent: 5538697 (1996-07-01), Abe et al.
Pfefferle William C.
Roychoudhury Subir
McCormick Paulding & Huber LLP
Precision Combustion Inc.
Tran Hien
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