Rotary oxidizer systems for control of restaurant emissions

Details Rotary oxidizer systems for control of restaurant emissions Rotary oxidizer systems for control of restaurant emissions

1997-11-05

2001-05-22

Tran, Hien (Department: 1764)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Waste gas purifier

C422S175000, C422S177000, C422S178000, C422S180000

Reexamination Certificate

active

06235249

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a system for abating the smoke containing particulate matter (PM) (i.e., liquid droplets of grease or fat) and volatile organic compounds (VOCs) generated from the burning of fats, greases, proteins, and/or carbohydrates, during food preparation. More particularly, this invention is concerned with restaurant emissions smoke abatement using a rotary regenerative thermal or catalytic oxidizer.
2. Related Art
In the treatment of restaurant emissions except for chain-driven charbroilers, restaurant catalysts are normally installed inside the exhaust duct of a cooking ventilation system at a position close to the exhaust hood outlet. Due to the mixing with cool room air, the hot exhaust generated from the cooking process is significantly cooled before it reaches the exhaust hood. To initiate thermal or catalytic oxidation, the exhaust gas stream is needed to be reheated back to higher temperatures more conducive to either thermal or catalytic oxidation of the cooking exhaust contaminants. The additional heat is applied either directly on the catalyst support or to the exhaust gas stream. In addition to the preheating, the exotherm generated by the catalytic oxidation reaction also elevates the temperature of the exhaust gas. This often makes the temperature of the gas coming out of the catalytic reactor exceed the temperature operation limitation of the exhaust fan located at the end of the ductwork. To resolve this problem, outside makeup air is typically introduced into the duct before the fan to lower the exhaust temperature. Therefore, the capacity of the exhaust fan is undesirably increased to handle the extra load of air flow. The high costs of additional heating and oversized exhaust fans often hinder the use of catalytic systems for restaurant emission control.
U.S. Pat. No. 4,138,220 describes an apparatus for catalytic oxidation of grease and fats in low temperature fumes. The apparatus recovers at least some of the heat energy of the treated, exiting stream as heat from this stream is transferred to the entering stream prior to passage over the catalyst. The heat exchange device describes is a countercurrent heat exchanger, separate and apart from the catalyst. However, this patent is silent with regard to a heat exchange device for recovering heat exiting the apparatus which rotates and is an integral part of the catalyst system, i.e., the catalyst in the '220 patent is not deposited in or on the heat exchange device.
Applicants provide an advance over the prior art in the treatment of restaurant emissions by providing a rotary heat exchange device for thermally or catalytically destroying restaurant emissions. The advantages of which are herein below described.
SUMMARY OF THE INVENTION
The present invention provides a smoke abatement system for removal of particulate matter (PM) and volatile organic compounds (VOCs) from a cooking emissions stream comprising:
an inlet duct for receiving the cooking emissions stream and directing the stream to a rotary, heat regenerative device;
the rotary device comprising means to recover heat from the emissions stream after thermal or catalytic oxidation and before the oxidized emission stream is returned to the atmosphere; and
an outlet duct for directing the oxidized emission stream from the rotary device to the atmosphere.
As used herein, the term atmosphere is intended to include both the ambient “outside” atmosphere and the ambient “inside” atmosphere of enclosed structures such as buildings. Therefore, the present invention contemplates treating emissions from an indoor kiosk-type cooking device, wherein the treated cooking emissions exiting from the rotary device of the present invention is exhausted or vented to the atmosphere (“indoor”) of the building.
The method of the present invention provides directing the cooking emissions stream from an inlet duct to the rotary regenerative oxidizer, for heating and oxidation therein. The emissions stream then flows through a transfer chamber, which, if desired, thermally oxidizes any remaining particulates or VOCs, in the stream, and thereafter flows through an output portion of the rotary oxidizer for venting to the atmosphere or other use.
A second embodiment also operates in steady state and comprises a stationary catalyzed or uncatalyzed heat regenerative bed, and, a one-piece rotary element that continuously rotates the air flow entering and exiting the bed, thereby alternating the various gas flows through the system.
If desired, the present invention may accommodate a purge stream which redirects cleansed exhaust air or other air back through the regenerative bed, thereby removing trapped contaminants. Furthermore, the aspects of the present invention also correspond to embodiments containing an uncatalyzed thermal oxidizer of the same rotary heat regenerative design.
A further advantage of the invention provides simplified, in-situ cleaning of the rotary oxidizer as the speed of rotation of the oxidizer may be conveniently lowered or stopped to allow for flow of a hot, cleaning stream to oxidize any greases or fats that may accumulate on the “cold” spots of the rotary oxidizer. This advantage circumscribes the inconvenience associated with current restaurant catalysts which typically have to be removed from the apparatus to be cleaned.
Yet another advantage of the present invention, as would be understood by one skilled in the art, is the inherent removal of odors while oxidizing with the smoke generated by cooking emissions. That is to say, oxidation of cooking emission contaminants will desirably destroy the organic compounds responsible for the odors emitted during cooking. Thus, an added benefit of this invention is removal of undesirable odors emanating from cooking emissions.


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Girocat Sales Brochure, G E C Alsthom, Air Industrie Systemes, No Date.
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Synopsis on Set Public Hearing Nov. 14, 1997 to Adopt Proposed Rule 1138—“Control of Emissions from Restaurant Operations”, South Coast Air Quality Management District, Agenda No. 5.

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