Catalytic combustor

Details Catalytic combustor Catalytic combustor

1998-02-17

1999-11-02

Dority, Carroll

Combustion

Porous, capillary, particulate or sievelike flame holder,...

Means supplying fuel for passage through the flame holding...

126 92AC, 126 92B, F23D 1412

Patent

active

059758902

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a catalytic combustor which effectively utilizes radioactive heat rays produced due to burning reaction heat, and more specifically effective utilization of the reaction heat and stabilization of combustion.


BACKGROUND ART

There have conventionally been proposed a large number of catalytic combustors which use catalysts having oxidative activities to fuels composed mainly of hydrocarbons and there is known a combustor which utilizes radioactive heat rays emitted from a surface of a catalyst directly or as radioactive heat supplied by way of a heat ray transmissive window.
In the conventional appliances described above, heat rays are radiated from a downstream surface of an exposed catalytic body to use the rays for heating, etc. in a type which supplies only a fuel through communicating slots of a catalyst body and allows catalytic oxidization to take place in the vicinity of the downstream surface of the catalytic body by diffusing and supplying oxygen in atmosphere, whereas heat rays are radiated from an upstream surface by way of a heat ray transmission window disposed in opposition to an upstream surface of a catalytic body to use the rays for heating, etc. in a type which allows a catalytic oxidative reaction to take place mainly in the vicinity of an upstream surface of the catalytic body by supplying a premixed gas of a fuel and air, and discharges an exhaust gas through communicating slots of the catalytic body.
The conventional catalytic combustors described above are useful for heating, but when they are used for illumination, they have defects as explained below.
That is, the catalytic combustors do not always provide high efficiencies when they are used for illumination in particular due to a fact that the heat rays which are obtained as radiation have a broad wavelength distribution ranging from the visible region (wavelengths not longer than 1 .mu.m) to the far infrared region (wavelengths not shorter than 3 to 5 .mu.m) which is variable dependently on surface temperatures of catalytic materials though they provide radiation efficiencies (ratios of obtained radioactive heat relative to reaction heat of fuels) higher than those of combustors which heat radiative materials with exhaust gases obtained by flame combustion due to a fact that the oxidative reaction of the fuels proceeds on surfaces of the catalyst bodies, the reaction heat is transferred directly to the catalyst bodies and radiated from the catalyst bodies with high efficiencies. Speaking concretely of a range within which the catalytic combustion is practically usable, an upper limit of a combustion rate of a catalyst body having a unit volume is restricted by a heat-resisting limit temperature of an active component (for example, a metal of a platinum group) carried on a catalyst layer and a lower limit of the combustion rate is restricted by a lower limit temperature at termination of a reaction due to a characteristic of the catalytic combustion that a temperature of the catalyst body is enhanced or lowered correspondingly to an amount of a fuel which reacts on a surface of the catalyst body. Though catalyst body is usable within a range from approximately 100.degree. C. to approximately 900.degree. C. in cases of fuel components such as hydrogen and carbon monoxide which are apt to be oxidized at low temperatures, lower limit temperatures of the catalyst body are 400.degree. C. to 500.degree. C. for propane, butane, kerosine which are ordinary domestic hydrocarbon fuels, and 650.degree. C. to 700.degree. C. for methane which is a main component of natural gases, whereas upper limit temperatures are on the order of 900.degree. C. for all the fuels mentioned above, whereby radioactive heats (rays) emitted from the catalyst body have broad wavelength distributions each of which has a peak at 1 to 3 .mu.m and includes components exceeding 10 .mu.m. Accordingly, radiated-ray components are usable for illumination only at several percents or low efficiencies and almost all heats a

REFERENCES:
patent: 3203413 (1965-08-01), Hartzell et al.
patent: 4413612 (1983-11-01), Nakamura et al.
patent: 5158448 (1992-10-01), Kawasaki et al.
patent: 5352114 (1994-10-01), Numoto et al.

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