MXPA99008261A - Recycling cooking oven with catalytic converter - Google Patents

Abstract

A recycling cooking oven (10) providing a substantially closed environment, includes a thermal plenum (20), for supplying a stream of hot air into a cooking chamber (22) and for receiving a stream of hot air from the cooking chamber, the thermal plenum (20) maintaining a reservoir of hot air therein. The cooking chamber (22) of the oven supplies a stream of hot air into the thermal plenum (20) and receives a stream of hot air from the thermal plenum, the cooking chamber (22) cooking foods therein at least partially with a stream of hot air and such foods adding oxidizable components to the hot air of the stream. A blower (24) and ducting (26) cause thestream of hot air to circulate in substantially a continuous travel path including the thermal plenum (20) and the cooking chamber (22). A catalytic converter (50) is disposed in the travel path of the stream of hot air, downstream of the cooking chamber (22) and upstream of the thermal plenum (20), for flamelessly oxidizing oxidizable components in the hot air of the stream leaving the cooking chamber (22), thereby both to remove them from the hot air of the stream and to release at least some additional heat energy into the hot air of the stream.

Description

"RECYCLING COOKING OVEN WITH CATALYTIC CONVERTER" BACKGROUND OF THE INVENTION The present invention relates to a recycling cooking oven and, more particularly, to a recycling cooking oven having a catalytic converter. U.S. Patent Nos. 5,254,823; 5,434,390; and 5,558,793 describe a recycling cooking oven that provides an essentially closed environment. Recycling cooking ovens typically use hot air to supply the heat energy to the hot air incidence cooking. In a recycling (hybrid) cooking oven both hot air and microwaves (magnetrons) provide the energy for cooking. These recycling cooking ovens are highly economical since the essentially closed environment means that the heat produced for the cooking objects is not necessarily discharged into the atmosphere outside the oven, but is used almost exclusively for its cooking purpose. it is destined However, a combination of the inevitable heat losses from the furnace into the ambient atmosphere (either through the furnace walls or through the - opening and closing of the cooking chamber door) plus the heat energy that is removed as part of the cooked elements that are removed from the cooking chamber, must be compensated in a certain way, traditionally at a considerable cost. Through the proper insulation of the oven and the careful design of the door through which the food is introduced and removed from the oven's cooking chamber, these unavoidable thermal losses can be minimized. However, recycling ovens are subject to unique problems that are not found or only minimally found in non-recycled ovens. In a recycling oven, hot air moving above and around the food in the cooking chamber tends to carry with it the same small food particles that have separated from the food as well as the grease carried in the air and other materials in particles that have been created or released by the cooking process. The maintenance of clean cooking air (and, of course, a clean oven) is important both for sanitation and high quality food as well as to maximize the operating efficiency of the cooking operation in the oven. For example, the operating efficiency of the magnetrons used in microwave cooking is particularly sensitive to the cleaning of the cooking air.

- - Preferably, the recycling oven is capable of cooking a wide variety of foods and is capable of duplicating cooking methods ranging from roasting, baking, poaching and frying to roasting, roasting, steaming and brining, etc. Especially when the oven is cooking partially cooked or raw meats, a lot of fats carried in the air are introduced into the cooking chamber and therefore into the cooking air. As a result, there may be a flavor transfer between the different foods being cooked in the same cooking chamber either simultaneously (whether or not the oven is a recycling oven) or successively (i.e., in successive cooking operations). a recycling oven). A conventional commercial oven (either recycled or not) uses several methods to clear the air for re-use and reduce the amount of airborne particles that would otherwise be deposited on the internal cooking surfaces of the cooking chamber and / or "in the food items that are being cooked during that time or in subsequent cooking operations." The first method is a hook basket at the bottom of the cooking chamber that retains any of the large food particles that are released during cooking. the cooking operation The particles are retained in the basket by gravity for removal - - Easy during the daily cleaning operation. The second method is a metal filter screen through which all the air that has been used in the cooking operation passes before it can be returned to the cooking chamber in a recycling oven or discharged in a non-recyclable oven. recycling. The metal filter screen mechanically removes particles carried in the air, including larger particles of grease, and deposits these impurities in a latching tray placed under the filter screen. Both the filter screen and the hook tray can be easily removed from the cleaning oven during the daily cleaning operation. The third method is the daily cleaning operation itself whereby all the elements of the cooking chamber that come into contact with the air used in the cooking operation are cleaned in a prescribed manual operation. However, even the combination of these air clearing techniques has not proved to be entirely satisfactory. Accordingly, today's commercial kilns - even those for recycling - are frequently used in conjunction with an upper hood ventilation system to retain and ventilate any of the quantities of grease carried in the air that are discharged through the kiln in large-scale operations. amount of fat. Many municipalities and their regulatory agencies require these types of upper ventilation systems to ensure the safety of the cooking operation (since these accumulated deposits of grease can constitute a fire hazard) and the cavity of the cooked food. Most of these types of upper ventilation systems are permanent installations that are both costly and annoying. Currently, the fastest growing segment of the "fast food" industry is the so-called "non-traditional" site. Many of the large national chains have exhausted the availability of high traffic real estate sites for either buildings that rise up freely or locations in front of the store lined up. Also, since real estate has become more expensive on a square-foot basis, the pressure to shrink the size of the restaurant's kitchens has been intense. Nothing is more true than the "non-traditional" location where the total operating space is reduced from an average of 18,580 to 37,160 square centimeters to 3,716 to 7,432 square centimeters. These nontraditional locations often fall within larger buildings, such as airports, mass merchants, and convenience stores, where access to outside ventilation is even more expensive than at a restaurant site. traditional. Clearly, the need is great for an advanced air blasting system that avoids the need for a roof top ventilation system. Accordingly, an object of the present invention is to provide a recycling oven that requires the addition of only a minimum of heat energy for continuous cooking operation. Another object is to provide this oven where there is a minimum of flavor and odor transfer between the different foods in simultaneous or consecutive cooking. A further object is to provide this furnace that does not require a top hood ventilation system. It is also an object to provide this furnace which requires a minimum of manual labor during the daily cleaning operation.

COMPENDIUM OF THE INVENTION It has now been found that the aforementioned and related objects of the present invention are obtained in a recycling cooking oven that provides an essentially closed environment. The oven includes both a full thermal chamber for supplying a stream of hot air to the cooking chamber and for receiving a stream of hot air from the cooking chamber, and a cooking chamber for supplying a stream of hot air to the full chamber thermal and to receive a stream of hot air from the full thermal chamber. The full thermal chamber maintains a hot air tank in it, and the cooking chamber cooks the food in it, at least partially with a stream of hot air, adding these food oxidizable components to the hot air. The furnace further includes means for causing the hot air stream to circulate essentially in a continuous path including the full thermal chamber and the cooking chamber, and a catalytic converter placed in the path of travel of the hot air stream, in the downstream of the cooking chamber and upstream of the thermal plenum, to oxidize in a flame-free manner the oxidisable components in hot air of the current leaving the cooking chamber, so as to thereby remove the same of the hot air of the stream as to release at least some additional thermal energy towards the warm air of the stream. In a preferred embodiment, the full thermal chamber maintains the hot air reservoir at a temperature of at least 298 ° C, and the catalytic converter has an inlet temperature of at least 246 ° C. The temperature of the quenched light is preferably from 246 ° C to 287 ° C. The oxidizable components include fat, shortening, oils and similar hydrocarbons produced by cooking the food in the cooking chamber, and the oxidizable components are those oxidizable essentially in carbon dioxide and water.

BRIEF DESCRIPTION OF THE DRAWING The aforementioned and related objects and features and advantages of the present invention will be more fully understood by reference to the following detailed description of currently preferred embodiments, ie, illustrative of the present invention, when taken together with the drawing that is attached in which: Figure 1 is an isometric view of an oven according to the present invention; Figure 2 is an isometric view similar to Figure 1, but without the furnace housing; Figure 3 is a detailed schematic view of the furnace without the furnace housing; and Figure 4 is a sectional view of the furnace taken on line 4-4 of Figure 1.

- - DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Referring now to the drawings, and in particular to Figure 1 thereof, there is illustrated a recycling oven according to the present invention, generally designated by the reference number 10. The operating parts of the oven 10 are placed in a housing 12 supported by the legs 14. The operating parts are illustrated in Figure 2 if the housing and are illustrated schematically in the detailed view of Figure 3, where the arrows represent the path of travel of the hot air stream . In its conventional aspects, the oven 10 comprises a generally designated thermal plenum 20, a cooking chamber designated generally 22 and means 24, 26 to cause the hot air stream to circulate in an essentially continuous path (illustrated by the arrows of Figure 3) including the full thermal chamber 20 and the cooking chamber 22. More particularly, the circulation means 24, 26 include a motor driven blower 24 (the motor ho being shown) and ducts 26. More specifically, the full thermal chamber 20 is configured and sized to maintain a hot air reservoir in the same of an adequate volume of such - - so that, once the oven has been heated, the full chamber 20 has sufficient hot air in it to immediately begin the cooking process whatever the food placed in the cooking chamber 22. For this purpose, the full thermal chamber 20 contains heating means (not shown) such as electric heating elements (either with or without a heat phase change tank). A temperature sensor (not shown) is preferably placed within the full thermal chamber 20 to regulate the heating means and ensure that the hot air reservoir is maintained at an appropriate temperature. The full thermal chamber 20 preferably maintains the hot air reservoir at at least a temperature of 298 ° C due to the reasons that will become apparent below. The plenum 20 supplies a stream of hot air to the cooking chamber 22 through a series of perforations, manifolds or the like, as necessary to provide hot air incineration of the food within the cooking chamber 22 , and receives a stream of hot air from the cooking chamber 22 through the ducts 26, the blower 24, etc. The cooking chamber 22, as mentioned above, supplies a hot air stream - - towards the full thermal chamber 20 through the ducts 26, the blower 24 and the like and receives a stream of hot air from the full thermal chamber 20 through a series of perforations, collectors 30 or the like. The cooking chamber cooks the food therein (not shown) at least partially with the hot air stream and, in turn, the foodstuffs undergoing the cooking process add oxidizable components to the hot air of the stream. Depending on the specific foods that are cooking in the cooking chamber, the oxidizable components released or formed by the foods include fat, shortenings, oils, similar hydrocarbons produced by or resulting from the cooking of the food in the cooking chamber 22. The cooking chamber 22 includes a door 32 of the oven housing that can be opened for the "placement of food inside the cooking chamber 22 and the removal of the cooked items therefrom." A motor-driven blower 24, preferably of variable speed, causes the hot air stream to essentially circulate in a continuous path including the full thermal chamber 20, the cooking chamber 22 and the various elements of the duct 26.

- - The duct 26 includes a filter mechanism 26a, a vertical duct 26b that opens from the filter mechanism 26a to the blower 24, and a horizontal duct 26c that receives the hot air from the blower 24 and inserts it into the full chamber 20. thermal Precisely, above the mechanism 26a of the filter, the lower surface of the cooking chamber 22 has a large circular hollow. A donut-shaped or donut-shaped basket 23 is placed in the recess in the lower part of the cooking chamber 22 and retains any of the large particles of the food that come off during the cooking operation with gravity retaining the large particles of the food in the hook basket for easy removal during the daily cleaning operation. The cooking disk (not shown) that holds the food product during cooking is mounted on the door 32 of the oven housing to move with it and sits above this hook basket 23 during cooking. The filter mechanism 26a includes an inclined metal filter screen 40 which is placed in a filter housing 42. All the hot air that has been used in the baking operation passes through the screen 40. This screen 40 mechanically removes the particles carried in the air, including the larger grease particles and deposits these in a hooking tray 23 placed by below. The latching tray 43 is preferably placed just below the interface of the filter housing 42 and a filter door 44 allowing access to the filter housing 42, in order to latch or retain any infiltration from the interface, especially when it is open the door 44. When the door 44 of the housing is opened, it allows the passage of the filter housing 42 (including the screen 40) through the door. Both the filter screen 40 and the hook tray 43 are easily removed from the oven 10 during the daily cleaning operation. The surface of the inner furnace (below the filter housing 42) is preferably inclined towards the center and is provided with a residual pipe 46 that transfers any liquid residue that accumulates in the center to a removable tray 48 placed outside the housing 12. (eg, slidably attached to the exterior bottom surface of the oven). The three aforementioned North American Patents are hereby incorporated by reference in their entirety. Since recycling ovens of the type described are well known to those skilled in the art - e.g., of the three North American Patents - it is not considered necessary to provide details - - additional ones. It will be appreciated, however, that the aforementioned conventional components of the present invention are similar to those described in conjunction with the aforementioned US Patents except that the sequence and relative locations of the various components have been modified to some degree. It will be appreciated that, while the illustrated embodiment relies exclusively on hot air incidence cooking, a hybrid oven in accordance with the present invention may depend on the cooking of icroonda. When appropriate, the center of the donut-shaped catch basket 23 can be capped in a manner that permits microwave transmission therethrough. Turning now to the novel aspects of the present invention, the furnace 10 of the present invention includes a catalytic conversion unit or converter 50 and a receptacle 52 therefor, both being disposed removably or adjacent to the rear part of the housing 42 of The catalytic converter 50 is placed in the path of travel of the hot air stream downstream of the mechanical filter 40. The receptacle 52 fits within the back of the filter housing 42 and holds the - converter 50 preferably at least partially in the vertical duct 26b which opens into the blower 24. To periodically clean the converter 50, the mechanical filter screen 40 is removed from its housing 42, the converter 50 is pushed upwards completely towards the vertical duct 26b, the filter housing 42 and the converter housing 52 are removed through a passage and then the converter 50 is pulled down and removed from the same passage. The oxidation catalyst 50 acts as a fuel mixture in much the same way as the spark or flame ignition, but at a lower temperature and without a flame. In this way, to complete the combustion both on and off and a sufficient amount of oxygen must be present. However, an important difference between catalytic oxidation and ignition is that the first can cause total combustion of very low concentrations of combustible material, which would not sustain combustion in the absence of the catalyst or very high temperatures. The reason is that the combustion reaction actually takes place on the surface of the catalyst. When combustible substances made of carbon, hydrogen and oxygen react with oxygen in the air, they produce carbon dioxide and water along with a predictable amount of heat. The heat released (ie, the exothermic heat of the reaction) causes the temperature of the gas to rise within the converter. The higher the air / fuel ratio the greater the amount of heat released. For most applications it is recommended that the air / fuel ratio be adjusted to provide a temperature rise between the output and the input of the converter no higher than 93 ° C to 150 ° C. For typical volatile hydrocarbons and a converter having an on and off temperature of 246 ° C to 287 ° C, the converter inlet should be at 246 ° C, resulting in an active catalytic surface. It has an operating temperature of 482-1, 38 ° C for most normal designs. The converter output is typically from 343 ° C to 454 ° C. The catalytic converter causes the combustion of grease carried in the cooking air to occur between 246 ° C and 287 ° C, which includes the scale of normal operation of the oven (with the temperature sensor in the chamber 20 full thermal graduated at 298 ° C and the cooking temperature being 271 ° C). In the absence of a catalyst, the grease carried in the air will burn at temperatures of 371 ° C to 427 ° C, which is significantly higher than the temperature at which a kiln operates - - typically, that is, from 246 ° C to 287 ° C. The catalyst materials typically work very effectively for this application within a temperature range of 246 ° C to 287 ° C. The normal fat and odor-laden air streams emanating from the cooking operations are oxidized efficiently at a temperature of about 260 ° C. The conversion of the grease carried in the air to the heat energy is about 20 percent for each pass of the hot air stream flowing through the converter 50. Since the volume of air used by the furnace is -circulate quickly and frequently, the successive and cumulative conversion allows a continuous and complete cleaning of the air stream. Taking now into account the catalyst and the substrate structure of the catalyst which is useful in the practice of the invention, it will be understood that catalysts and substrate structures other than those specifically described and illustrated herein can be used without deviating from the scope of the invention. Several catalysts capable of flame-free oxidation of fats, oils, etc. and the vapors and odors characteristic thereof may be used, the catalysts having different operating temperature scales different and being very effective for hydrocarbons different to different sub-scales than the operating temperature scales thereof. A preferred catalyst system comprises a honeycomb substrate of refractory material that is coated with a catalyst containing platinum. The alveolar substrate offers a large surface area to be coated by the catalyst and, therefore, a large effective surface area for contact between the catalyst and the organic materials to be oxidized. Suitable catalysts for coating the alveolar substrate include platinum-based catalysts, such as platinum nitrate tetramine (NH3) ^ Pt (NO3) 2 - mixtures of chloroplatinic acid, alumina and dextrose or a tetramine platinum nitrate solution of the Pt formula (NÜ3) 2- Mixtures of a platinum compound with a compound of another additive metal such as rhodium, palladium, ruthenium, iridium, etc. in various relationships, usually with the platinum compound predominating, are also useful in the practice of this invention. The catalyst material is deposited on the surfaces of the substrate, usually by immersing the substrate in a dispersion or solution thereof and then drying or heat treating the coated substrate to fix the catalyst material in the - - substrate The alveolar substrate can be formed from Torvex, a ceramic made by • Dupont Corporation, or similar materials manufactured by Dow Corning, Inc. or Minnesota Mining and Manufacturing Inc., etc. Granules coated with catalyst from a silica / alumina substrate material are also useful as other well-known refractory metal oxides. Other catalytic methods include granules, etc. An especially preferred catalytic converter formed from an alumina substrate calcined with a platinum on a stainless steel support can be obtained under the trade name CAMET OXIDATION CONVERTER (from WR Grace and Company, of Hiram, Ohio 44234, now Engelhard Corporation of Iselin , New Jersey). Typical densities for oxidation are 100-350, preferably 140 cells by 2.83 square centimeters and a preferred catalyst density is 30 grams / 2.83 cubic centimeters. Another preferred catalytic converter is especially made of a sheet of corrugated ferritic stainless steel placed in a design that promotes contact with the hot air stream. The thin sheet is coated with an aluminum oxide wash layer containing several metal oxide promoters and small amounts of an active catalyst of the platinum group - ie, platinum, palladium, or rhodium.

- Contamination of catalytic sites due to chemical reactions with the catalyst and masking of the sites (by materials that cover, but do not chemically combine with the sites) can be treated in a normal manner, typically using various cleaning or replenishment techniques. Even though the basic operation of the recycling furnace is efficient in its use of electrical energy, the addition of a relatively free energy source for available heat (ie, the catalytic converter) makes it even more efficient. The free secondary energy source reduces the demand for heating in the heat reservoir and allows temperatures of the pre-graduated full thermal chamber to be maintained at a lower operating cost. The efficiency of the catalytic conversion process vastly reduces the amount of grease carried in the air - and the accompanying odor - which is re-circulated through cooked food products simultaneously or in sequence. This allows the operator to cook a wider variety of food products, each maintaining its distinct taste with a much higher production yield than conventional cooking methods, which require similar foods that must be segregated and cooked separately.

For example, in accordance with the present invention, an inflated delicate pasta can be baked in the same cooking sequence or a sequence as a raw fish fillet. As another example, a cooked peperoni pizza has a distinct aroma associated with the peperoni that can subsist in an oven due to the presence of grease in the circulating air. This remaining aroma can be transferred to the subsequently cooked food products such as a cheese pizza, which is particularly sensitive to odor absorption. However, the efficiency of the catalytic conversion process allows these foods (ie, pepperoni pizza and cheese pizza to be cooked in sequence). The present invention not only minimizes heat energy costs and provides superior cooking and a variety of different food products (either simultaneously or in sequence), but also reduces the amount of manual labor required in the operation of daily cleaning. The catalytic combustion process removes a large amount of grease carried in the air (and converts it into heat energy) so that it does not deposit on the surface of the cooking chamber and the mechanical filters. Since fat is the most incidious foreign element produced in the cooking process, its removal considerably reduces the time (and cost) required to clean the oven by hand in daily maintenance procedures. Finally, because the present invention greatly reduces the amount of grease carried in the air that is discharged into the air in a restaurant kitchen, it eliminates the need for a top hood ventilation system and minimizes the odor of the noticeable unpleasant airborne grease that can reach customers, especially in "open kitchen" configurations where customer traffic comes into direct contact with the cooking area. To summarize, the present invention provides a recycling oven that requires the addition of only a minimum amount of heat energy for continuous cooking operation, allows different foods to be cooked in simultaneous or consecutive cooking with only a minimum of flavor transfer and smell between different foods. In addition, the furnace does not require a top hood ventilation system and minimizes the amount of manual labor required for the daily cleaning operation. Now, that the preferred embodiments of the present invention have been shown and described in detail, various modifications and improvements thereof will be - easily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention should be broadly construed and limited only by the appended claims and not by the foregoing specification.

Claims (6)

- R E I V I N D I C A C I O N S

1. A recycle cooking oven for cooking at least partly by hot air incidence and providing an essentially closed environment, comprising: (A) a full thermal chamber for supplying a stream of hot air to the air incidence collectors hot from a cooking chamber and to receive a stream of hot air from the cooking chamber, the full thermal chamber maintains a hot air reservoir therein; (B) a cooking chamber with hot air collectors to supply a hot air stream to the thermal plenum to receive a stream of hot air from the full thermal chamber through the hot air collectors, the cooking chamber cooks the food therein, at least partially with a hot air current from the collectors of hot air incidence and these foods add oxidizable components to the hot air; (C) a means for causing the hot air stream to circulate essentially in a path of - continuous travel that includes the full thermal chamber and the cooking chamber; and (D) a catalytic converter placed in the path of travel of the hot air stream, downstream of the cooking chamber and upstream of the thermal plenum, to oxidize the oxidizable components in a flame-free manner. hot air from the stream coming out of the cooking chamber, in order to both remove the same from the hot air of the stream and to release at least some additional heat energy towards the warm air of the stream.

2. The furnace of claim 1, wherein the full thermal chamber maintains the hot air reservoir at a temperature of at least 198 ° C.

The furnace of claim 1, wherein the catalytic converter has an inlet temperature of at least 246 ° C and an off temperature of 246 ° C at 287 ° C.

4. The furnace of claim 1, wherein the oxidizable components include fat, shortenings, oils and the like hydrocarbons produced by cooling the food in the cooking chamber.

The furnace of claim 1, wherein the oxidizable components are essentially oxidizable in carbon dioxide and water. -

6. A recycle cooking oven for cooking at least partly by hot air incidence and providing an essentially closed environment, comprising: (A) a full thermal chamber for supplying a stream of hot air to the air incidence collectors hot from a cooking chamber and to receive a stream of hot air from the cooking chamber, the full thermal chamber maintains a hot air tank therein at a temperature of at least 298 ° C; (B) a cooking chamber with collectors of hot air incidence to supply a stream of hot air to the thermal plenum and to receive a stream of hot air from the full thermal chamber through collectors of hot air incidence, the cooking chamber cooks the food in it, at least partially with a hot air stream from the collectors of hot air incidence and these foods are added to the hot air of the oxidizable components of the stream, including hydrocarbons produced by cooking the food in the cooking chamber; (C) a means for causing the hot air stream to circulate essentially in a path of - continuous travel including the full thermal chamber and the cooking chamber; and (D) a catalytic converter having an input temperature of at least 246 ° C and a quenching temperature of 246 ° C to 287 ° C, the catalytic converter is placed in the path of travel of the air stream hot, downstream of the cooking chamber and upstream of the thermal plenum, to oxidize in a flame-free manner the oxidisable components in the hot air of the stream leaving the cooking chamber, essentially in dioxide carbon and water, in this way both to remove the hot air from the current from them and to release at least some additional thermal energy to the warm air of the stream. - - SUMMARY OF THE INVENTION A recycle cooking oven (10) that provides an essentially closed environment includes a full thermal chamber (20) for supplying a stream of hot air to a cooking chamber (22) and for receiving a stream of hot air from the cooking chamber, the full thermal chamber (20) keeps a hot air tank in it. The cooking chamber (22) of the oven supplies a stream of hot air to the full thermal chamber (20) and receives a stream of hot air from a full thermal chamber, the cooking chamber (22) bakes the food therein, at least partially with a stream of hot air and these foods are added to the oxidizable components to the hot air of the stream. A blower (24) and a duct (26) cause the hot air stream to circulate essentially in a continuous path including the full thermal chamber (20) and the cooking chamber (22). The catalytic converter (50) is placed in the path of travel of the hot air stream, downstream of the cooking chamber (22) and upstream of the thermal plenum (20), to oxidize in an exempt manner of flame the oxidisable components in the hot air of the current leaving the chamber of - cooking (22), in order to both remove the same from the hot air of the stream, and to release at least a certain amount of additional heat energy towards the warm air of the stream.