US 3357379 A
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Description (OCR text may contain errors)
Dec. 12, 1967 s. K. WILEY, JR
DOMESTIC INCINERATOR APPLIANCE Filed Oct. 22. 1965 EXHAUST j COMPRESSED AIR m ll IO 3 2 J. RU E P W P mw .IIIJ
CONTACTS INVENTOR Sumner K. Wiley, Jr.
ATTORNEY United States Patent 3,357,379 DOMESTIC INCINERATOR APPLIANCE Sumner K. Wiley, Jr., Hampton, N.H., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 22, 1965, Ser. No. 501,546 6 Claims. (Cl. 110-8) ABSTRACT OF THE DISCLOSURE An improved incinerator device of a type in which loose household waste material is compacted into a plug that is presented to a combustion chamber for burning at a controlled rate, which improvement includes temperature regulating means for maintaining temperature in the combustion chamber above the allotropic transformation temperature of tin can material present in such waste, whereby tin cans are made more brittle and their crumbling is facilitated during burning of the waste.
The object of the invention is to extend the utility of the small sized household incinerator by making it capable of disposing of tin cans, plastic containers, foil wrappings, and the usual household discarded trash which is not by ordinary means quickly oxidizable. The disposal of this sort of trash is no problem in the large municipal incinerators where unburned trash is simply raked up and dumped, but in the small sized device where a tin can may blanket a substantial portion of the burning face of the trash it becomes of importance because it should not be allowed to interfere with the operation thereof. It is an object of the invention that the refuse be reduced to ash and not merely flattened out metal. Accordingly, the mechanical structure of the tin cans must be transformed by a chemical process into a structure which may be reduced to an ash-like residue by conventional mechanical means in an acceptably short time.
The present invention resides fundamentally in a chemical process by which the household tin can may be trans formed structurally to a brittle and easily crumbled mass of ash. The material from which a tin can is fabricated may be oxidized, but by ordinary processes this requires such a long time that none of these ordinary processes may be used for. domestic waste disposers. Household incinerators have been devised with crushing means incorporated therein whereby the discarded tin cans may be compacted for disposal in the ordinary. manner, but no means for reducing such material to ash or ash-like residue within the time of operation of a domestic appliance has been provided.
According to the present invention, tin cans and similar objects are stuffed into the trash bin of a domestic incinerator where, in time, each will be subjected to a temperature above that at which allotropic transformation takes place whereupon these discarded bits of trash become brittle and easily comminuted so that the remains thereof pass into the ash receiver. By this means then, the household incinerator is rendered capable of disposing of all household waste.
Heretofore domestic incinerators have been constructed and arranged to operate at a temperature of substantially 1500 F. which was found suflicient to reduce oxidizable material to a clear and odorless gas. However, throughout development of the disposers ability to destroy all types of waste, it was found that at these temperatures the common household tin can would merely form a protective tight-oxide coating on its outer surface, allowing a high percentage of metal to remain intact. Even after continuous exposure to an oxygen-rich atmosphere at 1500 F., cans would not reach the fully oxidized, brittle state which "ice might render them susceptible to complete destruction by comminution. The problem was further aggravated by the fact that at these temperatures tin cans which had not completely oxidized and broken up would merely flatten out in a softened, still metallic, condition and clog the combustion chamber thereby choking off further combustion.
It has been discovered that by exposing tin cans to disposer combustion chamber atmosphere (corrosive), at temperatures above the transformation temperature for hypoeutectoid steel, somewhere in the range of l600 to 1800 F., the oxidation process is drastically accelerated to the point where destruction of tin cans by incineration becomes practical. It has been determined that the common household tin can, when subjected to a 1900 F. combustion chamber atmosphere, will, in less than a half hour, reduce to a completely oxidized, brittle, flaking, fragile, distorted shape, which is totally susceptible to crumbling, crushing, or comminution by others means.
Applicant believes that the reasons for the drastic change in oxidation rate which he has discovered are due to at least two facts. Firstly, there is greatly increased susceptibility to corrosion attack as a result of complete allotropic transformation of low carbon iron crystalline structure from body centered cubic to face centered cubic, i.e. alphairon to gammairon. When the transformation temperature is exceeded, a net shrinkage of metal results which, when simultaneously being coated with ferric oxide of higher specific volume, results in rapid destruction of the protective oxide coating by cracking and flaking. Allotropic transformation also tends to produce a sensitized metal surface due to grain boundary precipitation. Secondly, there is increased chemical reaction since chemical action in this temperature range approximately doubles for every 10 increase in temperature. These reasons for accelerated oxidation are based on commonly known information concerning iron-carbon hypoeutectoid compositions and studies concerning the inhibiting of corrosion and oxidation.
Unique to this disclosure, however, is a practical method for accelerating the destruction of tin cans and other similar household metallic waste by intentionally permitting or causing active oxidation of this material to take place in a disposer operating at or above 1700 F. This is the lowest temperature where allotropic transformation of common tin can metal can be expected to be complete and oxidation becomes rapid enough to make destruction of this type waste in a disposer practical from a time consideration.
In accordance with the present invention a combustion chamber is provided in which a thin face layer of a compacted imporous mass of household trash may be ignited and consumed at a temperature of substantially 1900 F. Oxygen rich air is heated in a firing chamber and played onto the face of the plug. A temperature probe reaches into the combustion chamber and acts to control flow of combustion air or burning rate of the plug, and hence temperature. Close regulation of the temperature at the burning face of the plug is important because this high temperature must be maintained in order to render the tin cans brittle and easily converted to ash, but must not be allowed to reach much above this point due to materials limitations.
A feature of the invention is an incinerator device where the trash is compacted into an imporous mass having a face comparable in size to a pie tin, the botom face of which constitutes a wall of a combustion chamber and which is fired and maintained under combustion at a closely regulated high temperature above the temperature of allotropic transformation of tin can metal.
Reference is made to patent application Ser. No. 329,- 044, filed Dec. 9, 1963, by Malick, now Patent No.
3 3,313,253, which discloses certain features mentioned herein, which application is incorporated herein and made a part hereof for the purpose of a full explanation of the present invention.
Reference is also made to patent application Ser. No. 501,362, filed on even date herewith in the name of Malick, which discloses a means for controlling the temperature of a combustion chamber in general at any predetermined value and that disclosure should be incorporated herein as a part hereof.
Other features will appear hereinafter.
The drawings consist of a single sheet havinga single figure in the form of a schematic illustration partly in cross section of the elements of an incinerator embodying the features of the present invention.
A combustion chamber 1 is constructed of a ceramic lining 2 in the lower part of an air tight container 3. Resting on the upper part of this ceramic lining 2 is a funnel shaped restriction ring 4. The upper part of the container 3 constitutes a trash bin into which trash 5, including tin cans 6, 7 and 8, may be stuffed. A bellows like inflatable bag 9 is clamped by a cover 10 to the top of the trash bin 3 and may be inflated from any convenient source of compressed air lL The pressure exerted by the bag 9 as it becomes inflated compacts the trash into an imporous plug which is held back from any further downward movement by the funnel shaped restriction ring 4. The bottom face 12 of this plug of compacted material thus forms one wall of the combustion chamber and it is this face which is maintained under combustion. As a thin layer of this face becomes eroded and shrunken, the prtssure exerted by the bag 9 causes the plug to move forwardly keeping the carbonized and incandescent burning face substantially at the same place as burned material falls or is eroded away by other means. Where a tin can 6 has been moved downwardly until part thereof protrudes from this bu-rning face, the metal thereof has, through the maintenance of a temperature in the combustion chamber at a point slightly above the allotropic transformation value for tin can metal, becomes so brittle that only simple agitation is required for complete comminution.
Combustion of fact 12 is inducedby high temperature air flowing through orifices 13, 14 and 15. The air comes from an air supply 16, which is then switched by air valve 17 either. to duct 18 or duct 19. Duct 18 leads to a firing chamber 20 which houses electrical resistance heater 21 and which heats the air for delivery to the face 12 of the plug through the orifices 13, 14 and 15. The duct 19 delivers fresh air to the combustion chamber but at a distance from the burning face 12.
A temperature probe 24 is inserted in the combustion chamber 1 and acts to switch the fresh air to duct 19 when the temperature rises beyond the predetermined point to which it has been set or, alternatively, to switch the fresh air to duct 18 when the temperature falls. The air valve 17 may be operated by a solenoid 22.
An exhaust vent 23 is provided to strip the combustion chamber of the gaseous product of combustion.
What is claimed is:
1. An improvement in an incinerator device for reducing oxidizable waste material to a clear odorless gas with a minimum of large solid remains which includes:
means (2) defining a combustion chamber (1);
wastecompacting means (3, 4, 9, '10, 11) to compact trash which includes tin cans (7, 8) into a plug (5) and to introduce such plug to said combustion chamt ber 1) for burning; and
air supply means (16) for said combustion chamber;
wherein the improvement comprises temperature regulating means (24, 22, 17, 18, 19, 20, 13) including a temperature sensor (24) for maintaining temperature in said combustion chamber (1) during burning of the plug (5) above the allotropic transformation temperature of the material of said tin cans, whereby oxidation and brittleness of such cans is enhanced to facilitate crumbling.
2. The incinerator device of claim 1, wherein said temperature regulating means maintains the combustion chamber temperature between substantially 1600 F. and 1900 F.
3. The incinerator device of claim 1, further comprising electric heating means (21) under control by said temperature regulating means for raising combustion chamber temperature independently of plug-burning when required.
4. The incinerator device of claim 1, wherein said temperature regulating means includes said air supply means (16).
5. The incinerator device of claim 3, wherein said temperature regulating means includes said air supply means (16).
6. The incinerator device of claim 1, further comprising a vertical trash bin (3) disposed above and opening downwardly into the top of said combustion chamber 1), and wherein said waste compacting means includes a movable abutment (9) disposed in said trashbin, and said plug of trash is imporous and exposed only at its bottom end to said combustion chamber.
References Cited UNITED STATES PATENTS JAMES W. WESTHAVER, Primary Examiner.