Electric heating – Microwave heating – Fluid heater
Reexamination Certificate
1999-09-29
2001-08-07
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
Fluid heater
C219S759000, C219S756000, C204S157300, C096S015000
Reexamination Certificate
active
06271509
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of Invention
This invention relates to a device and process for thermal treatment of waste gases and reactive gases. The invention is used for the destruction and reduction of pollutants from effluent waste streams, and to produce gaseous products from reactant gases.
BACKGROUND
Devices which operate on electricity to thermally treat gases from wastestreams to reduce pollution and thermally react gases for synthesis of products do not rely on natural gas for supplying energy. Devices that use natural gas to produce energy for such applications create carbon dioxide, carbon monoxide and nitrogen oxides from the energy source. Electricity is consider to have cleaner operation when used in such devices since the above chemical species are not produced during operation from the heat source. Electric devices for pollution control applications produce less pollution at the point source when compared to the counter technologies operating on natural gas. The reduced pollution is favorable to reduce greenhouse gases and to the meet the requirements of the Clean Air Act of 1990. There are many types of electric heating methods, this discussion will focus on designs used to produce heat and reaction with applied electromagnetic energy.
The scope of this current invention is a device for thermal treatment of gases and pollutants 1) that employs alternate cavity and susceptor geometries for providing more homogeneous interactions of applied electromagnetic energy in the volume of the susceptor regardless of the flow rate and diameter of the exhaust duct width, 2) heat transfer methods to improve the overall heat efficiency of the device, 3) a susceptor structure which has reflectivity as principle mode of interaction with applied electromagnetic energy which allows for energy to penetrate a susceptor, 4) composite susceptor materials, 5) a simple method of controlling the temperature versus energy concentration in the susceptor and 6) field concentrators to concentrate the energy density of the applied electromagnetic energy.
BACKGROUND
Cavity geometries in these devices effect the optical properties of the electromagnetic energy within the susceptor. Electromagnetic energy, whether the frequency is either ultraviolet, infra red, microwave or radio frequencies, exhibit the same optical properties as the visible spectrum when interacting with geometric shapes and surfaces which are similar to a lens. The electromagnetic energy in a susceptor can either converge or diverge due to the geometric shape of the susceptor following the same principles as optical lenses. Additionally the modes of propagation of the electromagnetic energy is dependent upon the cavities geometry. These modes effect the distribution of electromagnetic energy in the cavity. These modes are different for cylindrical and rectangular cavities (
Handbook of Microwave Engineering
).
Electromagnetic energy, which is incident perpendicular to the perimeter of circular cross-section of a cylindrical susceptor, will cause the energy to converge initially, concentrating the energy within the cross-section. This concentration will cause the material inside the susceptor to absorb more energy than the material near the surface, changing the dielectric properties of the material inside the cross-section. This concentration of energy can make the material which is located in the susceptor's interior, between the center and the perimeter, to absorb more energy, thereby reducing the depth of penetration of the material due to the susceptor's geometry. The optical properties of rectangular cavities and planar surfaces are different. Rectangular cavities with a susceptor having a rectangular geometry and planar surfaces will follow the optical properties of a flat surface. A flat surface does concentrate or disperse energy as curved surfaces, convex and concave. With a flat surface of incidence for applied electromagnetic energy, the absorption of electromagnetic energy in a susceptor is due only to the materials properties and is not influenced by energy which is concentrated by curved geometries. Incident energy on susceptors with flat surfaces will not concentrate energy within a structure with homogeneous material, and the depth of penetration will be influenced by the incident energy's power, the electric fields and magnetic fields inside the susceptor. Conversely, incident energy on susceptors with curved geometry can concentrate energy within a susceptor with homogeneous materials, and the depth of penetration of the energy will be influenced by the ability of the curved surface to concentrate energy inside the susceptor.
The overall energy efficiency of such devices for thermal treatment of gases can be improve with a better heat transfer process to capture that energy that is lost from cooling the tube which is the source for the applied electromagnetic energy. In industrial microwave drying operations, the heat produced from cooling the magnetrons with air is applied to the articles which are being dried with the microwaves. This synergistic drying which uses hot air and microwaves, increases the energy efficiency of the drying process.
Alternative composite materials and susceptor structures can be use to facilitate the thermal treatment of gases. These composite materials and susceptor structures are known as artificial dielectrics.
Artificial dielectric structures date back to the 1940's. Artificial dielectric were used as lenses to focus radio waves for communication (Koch). Artificial dielectric use conductive metal plates, rods, spheres and discs (second phase material) which are embedded in matrices of low dielectric constants and low dielectric losses to increase the index of refraction, thus reducing size of a lens to achieve the desired optical properties. The second phase material reflects the energy and uses diffusse reflection to transmit electromagnetic energy. These plates, rods, spheres and discs can be arranged in a lattice structure to produce an isotropic or anisotropic structure. When conductive elements are embedded in a low dielectric constant and low dielectric loss matrix, the effect of these on the matrix material's dielectric loss factor is negligible and the dielectric constant of the composite lens is increased. However, these above effects are limited and influenced by the size, shape, conductivity and volume fraction of the material embedded in a materials of low dielectric loss, low dielectric constant of the material as well as the wavelength of the incident radiation. The dielectric strength and complex dielectric constant of the matrix material plays important additional roles in the design of artificial dielectric lenses. On the other hand, selection of matrix materials with different dielectric properties and incorporation second phase materials such as semiconductors, ferroelectrics, ferromagnetics, antiferroelectrics, antifermagnetics, dielectrics with higher dielectric losses, dielectrics with conductive losses produce absorption of microwave energy, producing heat in an artificial dielectric.
Lossy artificial dielectrics have been demonstrated by the 1950's, and subsequently used at the microwave frequencies to sinter ceramic articles, in food packaging for heating food stuffs, browning apparatuses for foodstuffs, consumer products, and to render adhesives flowable for bonding applications.
The structure of the artificial dielectric determines the electromagnetic properties. When the volume fraction of the 2nd phase materials inside the artificial dielectric reaches a certain level, the artificial dielectric will reflect incident electromagnetic energy, shielding the artificial dielectric from absorbing electromagnetic energy. The volume fraction of the 2nd phase material at which the artificial dielectric shields electromagnetic energy is dependent on the 2nd phase material's reflectivity, the shape of the 2nd phase material and temperature. By controlling the amount of reflection, the susceptor's reflectivity ca
Leung Philip H.
Technoprop Colton LLC
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