Heating – Work chamber having heating means – Combustion products heat work by contact
Reexamination Certificate
1999-11-12
2001-03-20
Ferensic, Denise L. (Department: 3749)
Heating
Work chamber having heating means
Combustion products heat work by contact
C432S002000, C422S178000, C165S005000
Reexamination Certificate
active
06203316
ABSTRACT:
BACKGROUND OF THE INVENTION
The subject invention relates to an improved method for cleaning the elements of a rotary valve regenerative oxidizer. More specifically, the subject invention relates to a method for continuously cleaning the elements of rotary valve regenerative oxidizer while on-line.
Regenerative oxidizes are used to remove contaminated gas, such as volatile or condensable and particulate organic compounds from an air stream. The contaminated gas is typically generated from an industrial process such as, for example a paint application or bake process in an automotive paint shop, and the wood industry, grain industry, etc. Two types of regenerative oxidizers are commonly used, a thermal oxidizer, and a catalytic oxidizer. The regenerative thermal oxidizer removes contaminated gas by a combustion reaction. To remove the contaminated gas, the combustion reaction must reach a temperature that breaks down the volatile organic compounds to corresponding CO
2
and H
2
O. The catalytic oxidizer removes the contaminated gas by a catalyzed reaction that is typically an exothermic reaction. This is achieved by accelerating the oxidation process of volatile organic compounds with precious metals on a ceramic substrate.
Referring to a thermal oxidizer, which is more widely used than a catalytic oxidizer, the contaminated gas is passed through a first heat exchange chamber having a media disposed therein. The media is preheated to a combustion temperature to facilitate the combustion reaction as the gas contacts the media. The heated and purified gas passes through a single or a plurality of first heat exchange chambers into a combustion chamber. The combustion chamber includes a flame source that only operates when heat is required to be added to the process, which is typically only during a start-up period. The heated and purified gas passes through the combustion chamber and into a second heat exchange chamber having media disposed therein and subsequently out of the oxidizer through an outlet stack. As the process continues the first heat exchange chamber will become fouled with organic solids that can build up to a level of becoming a potential source for fire.
As disclosed in U.S. Pat. No. 5,538,420 to Klobucar et al, to operate the oxidizer continuously, a third heat exchange chamber is added to the process. The third heat exchange chamber receives purge gas drawn from ambient air that has been passed through a heater element for heating the gas to a temperature that will clean volatilized organic solids from the media and walls of heat exchange chamber. The purge gas pass into the combustion chamber, and subsequently out through the second heat exchanger. The purge gas originates as ambient air and is heated from ambient air temperature to the cleaning temperature. The Klobucar et al patent discloses three independent chambers each having an inlet valve, an outlet valve, and a purge valve. The valves cycle during operation so that one chamber is operating as in inlet chamber for heating and purifying the gasses, one chamber is operating as an outlet chamber, and one chamber is being cleaned.
The Klobucar et al patent provides the ability to operate the regenerative oxidizer continuously. However, the valves required for continuous operation are complex and costly. In addition, heating ambient air to a temperature high enough to clean organic solids from the heat exchange chambers is not energy efficient and adds to the operating costs. The valve design also prevents rapid rotation of heat exchange chambers to the cleaning stage of the process.
An alternative embodiment is disclosed in English Patent no. 791,222. The invention, as disclosed in this patent, replaces the three valves disclosed in the Klobucar et al patent with a rotary valve. The rotary valve includes an inlet section, an outlet section, and a purge section, each aligned with pie shaped heat exchange chambers that are arranged in a circular fashion. The rotary valve pivots about a tubular member
40
for alternating the chambers that align with the various valve sections. Cleaning vapors are directed into the tubular member and through the purge section for cleaning volatilized solids from the heat exchange chambers.
The English '222 patent discloses a more simplified structure by replacing the valves, as disclosed in the Klobucar et al patent, with a rotary valve. It does not, however, disclose a method for reducing the energy requirements associated with cleaning the various heat exchange chambers.
Therefore, a need exists for a method of continuously cleaning the heat exchangers in a regenerative oxidizer at a rapid rate, and in an energy and cost efficient manner.
SUMMARY OF THE INVENTION AND ADVANTAGES
A regenerative oxidizer includes a combustion chamber and a plurality of pie shaped heat exchange chambers having media disposed therein. As used herein, pie-shaped refers to radial sections of a cylinder and the sections are generally equal. The heat exchange chambers are arranged in a symmetrical or circular fashion. Each of the heat exchange chambers communicates with the combustion chamber at a first end and communicates with a rotary valve at a second end. The oxidizer includes at least a first, second, and third group of heat exchange chambers.
A method for continuously operating the oxidizer includes directing a contaminated gas through an inlet of the rotary valve, through the media disposed within the first group of heat exchange chambers and into the combustion chamber thereby heating and purifying the gas. The heated and purified gas is directed from the combustion chamber through the media disposed within the second group of heat exchange chambers and through an outlet of the rotary valve.
A portion of the heated and purified gas received from the outlet of the rotary valve is continuously directed through a heating element. The gas is directed into a urge section of the rotary valve and through the media disposed within the third group of heat exchange chambers for cleaning the media. The gas passes through the combustion chamber and out of the oxidizer through the second group of heat exchange chambers.
The heated and purified gas is heated by the heating element for creating a purge gas at a cleaning temperature selected to be sufficient to oxidize organic solids which are expected to be coated on the plurality of the heat exchange chambers and the media disposed therein.
The rotary valve is sequenced for aligning the purge section of the rotary valve with a heat exchange chamber originally from the first group of heat exchange chambers and with a heat exchange chamber originally from the second group of heat exchange chambers. This allows for rapid and continuous cleaning of the heat exchange chambers while the oxidizer is operating.
By heating the heated and purified gas to a temperature selected to be sufficient to oxidize organic solids rather than heating ambient air, as disclosed in the prior art, energy requirements are reduced, thereby producing a more efficient process. In addition, continuously sequencing the rotary valve to prevent the buildup of volatilized organic solids in the heat exchange chambers reduces the potential for fires inside the chambers caused from the solids build up.
REFERENCES:
patent: 4280416 (1981-07-01), Edgerton
patent: 5016547 (1991-05-01), Thomason
patent: 5352115 (1994-10-01), Klobucar
patent: 5503551 (1996-04-01), Houston
patent: 5538420 (1996-07-01), Klobucar et al.
patent: 5562442 (1996-10-01), Wilhelm
patent: 5692892 (1997-12-01), Houston
patent: 5707229 (1998-01-01), Klobucar
patent: 5730945 (1998-03-01), Klobucar
patent: 5871349 (1999-02-01), Johnson et al.
patent: 791222 (1958-02-01), None
Ferensic Denise L.
Howard & Howard
Regenerative Environmental Equipment Co., Inc. (REECO, Inc.)
Wilson Gregory A.
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