US3532078A - Furnace and afterburner - Google Patents

Description

Elite States utcnt 2,752,870 7/1956 Short ct 2,845,882

[72] Inventor Samuel Foresto 243 Willis Ave., Mineola, New York 11501 8/1 58 Brattonuu...

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Primary Examiner-Edward G. Favors Auorney-1erome Bauer ll0/8(A): 122/4, 7(C&D) 521x); 23/277 [51] [50] 1 Field g the residue found in e gaseous phase of burned fuel comprising a high temperature body heated by an electrical] ABSTRACT: Apparatus for consumin y resistant coil wrapped ource of power.

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D E W N U M U 122/52 about the body and connected to a s Patented Oct. 6, 1970 1 INVENTOR. SAMUEL FORESTO M ATTORNEY m FURNACE AND AIFTERBURNER BACKGROUND OF THE INVENTION The present invention relates to improvements in heating systems and, in particular, to an improved after burner for furnaces, ovens or other devices employing coal, oil, gas or the like, as the heating medium.

As is well known, the combustion of such fuels as listed above is rarely complete and there is nearly always considerable residue of particulate matter, fly ash and unburned fuel expelled to the atmosphere. This unburned fuel, fly ash, etc. is often noxious and harmful to health, as well as being of considerable nuisance as dirt.

Additionally, the accumulation of unburned fuel within the furnace in the form of soot severely affects, over a period of time, the efficiency of subsequent combustion and the heat exchange effects of the furnace or oven.

SUMMARY OF THE INVENTION It is the purpose of this invention to provide a novel afterburner for completing the combustion of fuels and, consequently, reducing to a most negligible amount the deleterious emission of toxic, noxious and harmful materials.

It is further an object of this invention to provide afterburner means for increasing the combustion efficiency of fuels as well as the heat exchange characteristics of furnaces and ovens.

It has been particularly found that the gaseous phase of combustion contains minute particles of fuel, ash, minerals or other impurities which do not burn at the normal temperature levels of the fuels, but are, in fact, consumed only at tempera tures far higher than initial combustion. Accordingly, it is also an object of this invention to provide afterburner means for increasing the temperature of the gaseous phase of combustion.

Briefly, the present invention provides an independently controlled electrically heated afterburner system adapted to be inserted within that part of an oven or furnace wherein the gaseous omissions of combustion are passed. This independent heating system increases the temperature of the gaseous phase to such a degree as to completely consume any residue contained therein.

The present device further enables modification to be made to the furnace or oven to produce greater heat exchange efficiency. With this mechanism the normal conduction of smoke or heated air, i.e., the gaseous phase need not be passed almost directly out of the furnace into the chimney, but because of its cleaner nature and hotter temperature it can be circulated more fully in the furnace so as to extract the heat therefrom in increased exchange effect.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages, as well as others, will be apparent from the following description wherein reference is made to the accompanying description in which:

FIG. I is a cross-sectional perspective view of a furnace employing one embodiment of a device made in accordance with the present invention, and

FIG. 2 is a cross-sectional view of a chimney flue showing another form of the present invention.

In FIG. 1, the general details of an oil or gas furnace is shown. It will be appreciated that such type of furnace is shown for its exemplary value and should not be taken to limit the application of the present invention. The furnace, of course, can be an incinerator, oven or an internal combustion engine.

The furnace IOcomprises an outer shell or cast iron casing 12 having a generally hollow interior in which is located a boiler heat exchange section 14 containing the media to be heated. Through the boiler 14 runs a plurality of open, generally parallel tubes 16 communicating at one end with a large open combustion chamber or fire box 18. The other end of tubes 16 communicate with a tortuous passage or second chamber 20 substantially surrounding the boiler 14 to which a chimney flue 22 is connected. It will be observed that the tubes 16 are not in direct communication with the chimney flue 22 which is also below the level of tubes 16 and that the passage 20 virtually surrounds the boiler 14. This is different from the standard prior construction of furnaces which generally have their chimney flues directly above the end of the tubes 16 so as to exhaust the gas and smoke almost immediately after its passage through the boiler. The advantages of the present novel construction will be enlarged upon in detail later.

Returning to FIG. 1, the construction of the furnace is generally completed by the insertion of a burner 24 into the fire box 18. Fuel line control systems, as well as access doors, are not here shown as they are well known and their addition serving little purpose to the exposition of the present invention is omitted for the sake of brevity.

Thus, except for the construction of the enveloping passage 20, there has been described a standard conventional furnace which when operated produces within the burner 24 a fire. The fire extends into the combustion chamber 18 as indicated by the heavy arrows F emitting intertwined heat radiation and convection and conduction currents exhausting its fumes, smoke, etc. through the furnace as indicated by the lighter arrows S. The heat rises together with the smoke through the combustion chamber into the tubes 16, heating the media in boiler 14 and, subsequently, passing out of chimney flue 22.

In the prior art devices, the heated gases, smoke, etc. would normally contain huge amounts of unburned particles, soot, etc. which would first deposit in the combustion chamber and, subsequently, the tubes and then exhaust into the atmosphere. The efficiency of the furnace is thereby constantly diminished and the air polluted with noxious and toxic material.

According to the present invention, the unburned gases, etc. are consumed and treated by the insertion within the exit portion of the combustion chamber 18 of an independent heating unit or afterburner apparatus generally indicated by the arrow 26. This heating unit comprises a high heat resistant ceramic body 28 about which is wrapped a heating coil 30 connected to a suitable source of electricity such as a battery or house current (not shown in FIG. 1). Suitable switch means for activating the coil 30 and for variably controlling its temperature may also be employed although not shown in FIG. 1. Such switches and controls are shown in connection with the form described later in connection with FIG. 2.

The ceramic body 28 is shaped or contoured in flaring or enlarging fashion and is located in the passage directly connecting the fire box 18 with the heat exchange section 14. This results in providing a larger surface of the body 28, in that exit portion of the fire box 18 that is remote from or upstream of the heat exchanger section 14. It is noted that the exit portion of the passage is thus restricted by the unit 26 that substantially fills the passage. The coil 30 may be made of any high resistance wire. Nichrome, an alloy of nickel and chromium, has been found suitable. The coil 30 may also be wrapped in any suitable manner about the ceramic body 28 to effect the degree of heat and temperature desired. The body 28 may, if desired, be provided with holes or openings 32 to facilitate passage of gas or smoke through the heating unit 26 and the heating unit 26 is itself spaced from the walls of the combustion chamber or furnace so as to permit passage of air therearound.

In operation, the afterburner 26 is activated so that its coil 30 assumes a temperature which by its own nature is far in excess than the combustion temperature of the fuel in the burner 24. The heat of the coil 30 is transmitted directly to the ceramic body 28 raising its temperature far in excess of the temperature of fuel combustion. It will be observed that no matter how the coil 30 is wrapped, the upper edges of the heat resistant ceramic body 28 become hotter than the lower edges. This occurs because heat tends to rise. Therefore, upon the movement of the exhaust smoke and heated gas from the fire box 18 on its way into the tubes 16, the particles of dirt, fly ash, vapor and unburned fuel contained in the moving gas coming into contact with the hotter body 28, are heated to such a degree that virtually all such residue is immediately ignited and consumed. Consequently, the heated gas leaving the unit 26 is not only cleaned and freed of pollutants but it is cleansed prior to its entry into the heat exchanger tubes 16.

As a result of the use of the present device 26, within the furnace, greater heat exchange efficiency in the boiler is immediately possible. Thus, more efficient heat exchange is obtained over substantially longer periods of time because the tubes remain free and clean of insulating particles that normally accumulate and deposit on them. The life of the furnace, i.e., before it requires cleaning, is significantly longer. Because of the total consumption of pollutants by the device 26, the deposition of soot or caked dirt within the furnace and in particular within the tubes is markedly reduced. Moreover, the smoke exhausted from the furnace is free of pollutants and its harmful constituents, contributing to a cleaner atmosphere.

The beneficial results obtained with the present device 26 now enables even the furnace itself to be modified to obtain even greater efficiencies. The exhausted gas, of course, is hotter than the air produced in the combustion chamber therefore it may be utilized over a longer period in heat exchange relationship with the boiler. Thus, the exit passage from boiler to flue 22 may be enlarged so that the heated air circulates about the boiler 18 in contact with its outer surface. Consequently, the medium contained in the boiler is heated not only from the inside, through tubes 16, but from the outside. This construction has been found not to decrease or adversely effect the draft" within the furnace and, in fact, the draft is most often assisted to provide a more efficient flow so that the chimney flue exit may be located anywhere.

In prior art furnaces the flue was located above and to the rear of the boiler (indicated by the dotted lines). This is no longer necessary in the present invention. The exhaust flue 22 now may be located in any convenient position even at the front of the furnace as shown. This is possible because the exhaust gas is cleaned of all pollutants during its movement through the furnace and, therefore, the prior art need for a strong draft to remove and lift the pollutants out of the furnace into the atmosphere by locating the flue at the hottest point of the furnace is obviated. By locating the flue 22 at a lower point, as shown, the hot clean gas applies its heat longer to the heat exchanger 14 thereby resulting in a more efficient use of the exhaust gas over a longer period.

Having thus described one form of the invention, its mode of operation and its advantages, it will be appreciated that various changes and adaption can be made. For example, the flaring contour of the afterburner 26 may be made to take any shape and it may be located at any position in the furnace l4 and associated structure. The device 26 may be employed in any type furnace not only that having a supplied fuel such as gas or oil but one having an indigenous fuel as an incinerator or waste burner. Internal combustion units may also be fitted with the present device. The device is not expensive to operate since electricity is cheap and plentiful and the amount used need not be too great.

The present device may be used also to dispose of the pollutant in the gas exhausted into the atmosphere. This application is shown in FIG. 2 wherein the device 26a comprises a conical high heat resistant ceramic body 34 about which is wrapped a heating coil 36. The conical body 34 is supported within a cylindrical flue 36 of a chimney 38 by brackets 40. The direction of air flow is indicated by arrows T. The body 34 may be provided with holes or openings 42 to facilitate passage of air through the chimney and to also increase its effective heated surface.

It will be clearly observed in FIG. 2 that the total volume of air is forced almost completely into contact with the surface of the body 34, which will, of course, be hotter at its upper end. Since the device 260 is located in the chimney flue 38, ignition and consumption of the pollutants carried in the flue gas results prior to the discharge of the flue gas into the at mosphere. As the flue gas rises in the chimney 38, it strikes and impinges upon the far hotter surface of the body 34. Because heat rises, the upper wider portion of the conical body 34 is hotter in comparison to the lower narrower apex portion of the same body that is directed toward the upstream of the gas. In consequence, those pollutants that strike the surface of the body 34 and which ignite at low temperatures will combust completely immediately upon contact with the narrower portion of the body 34. However, those pollutants carried by the gas that ignite under higher temperatures will travel upward along the surface of the body 34 and during their movement they will come into contact with the hotter portions of the surface of the body and, thus, will ignite also. Hence, the pollutants in the gas rising in the chimney 38 will be ignited and consumed thereby removing them from the gas that exits into the atmosphere.

The openings 42 provided in the body 34 serve to increase the effective surface area of the body and, thus, cause the gas to follow a tortuous path during which the gas is so heated that pollutants moving with the gas must come into contact with some surface portion of the device to thereby assure the ignition and combustion of the pollutants to remove them from the flowing gas. The holes 42 further increase the effective opening between the device 26a and the surrounding surface of the chimney 38 so that the movement of the gas through the chimney is not slowed. Rather, the construction of the body 34 assures that the gas is attracted and its pollutants carried thereby strike and impinge upon the body 34 to complete their combustion prior to their exhaust into the atmosphere.

In FIG. 2, the source of current 44 and the variable temperature controls 46 and switch 48 are shown conventionally connected to operate in the conventional manner.

In the aforedescribed embodiments and uses of the afterburner devices 26 and 26a, the means to initially heat and retain such devices at temperatures in excess of the unburned matter or pollutants contained in the gaseous phase of the burned fuel were described as electrically operated. Such description was to enable an understanding of the simplicity of the purpose of the invention. Those skilled in the art will readily recognize that the devices 26 and 260 may be raised to the desired operating temperatures in excess of the combustion temperatures of the pollutants by heating the same with gas or oil fired elements. This is especially true in the embodiment of FIG. 1 where some of the oil fired heat of the burner 24 may be diverted to heat the device 26 to its desired temperature to fully consume what unburned matter or other pollutants remain in the gaseous phase of the burned fuel.

It will be observed that the term afterburner when used in this specification refers to an independent heating device employed both within the furnace and in the exhaust portion or chimney of an oven or engine. It is intended to broadly define a device located in flow relationship with the gas phase so as to consume the residue left after the initial burning of fuel.

It will thus be appreciated that the objectives and advantages of the present invention are simply obtained and while described herein as taking some definite form is adaptable to various modifications and changes. It is thus intended that the invention be limited only by the appended claims.

I claim:

1. A furnace comprising:

a casing;

heat exchange means located within said casing and defining therewith a first chamber for the combustion of fuel and a second chamber at least in part surrounding the outer surface of said heat exchange means;

said heat exchange means having an inner surface in connection with each of said first and second chambers thereby permitting heat to pass in contact with said heat exchanger from one surface to said other;

said second chamber being in communication with exhaust means to exhaust gas from said furnace; and

an afterburner located in gas flow relationship between said firstchamber and said heat exchanger to increase the temperature of the gaseous phase of the burned fuel to consume residue matter therein prior to contact with said inner surface of said heat exchange means whereby heated gas free of residue passes in contact with each of the surfaces of said heat exchanger prior to passage through the exhaust means.

2. The furnace according to claim 1 wherein said heat exchange means comprises a boiler having a plurality of hollow tubes located therein, each communicating with both the first and second chambers of said furnace.

3. The furnace according to claim 1 wherein said exhaust means is located at the farthest extreme in gas flow relationnected with said coil for controlling the temperature of said coil.

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