US3417716A - Method for the combustion of waste materials, particularly refuse - Google Patents

Description

Dec. 24, 1968 'r. IACOBOVICI METHOD FOR THE COMBUSTION OF WASTE MATERIALS, PARTICULARLY REFUSE Filed July 2, 1965 Tkaolaa wdnvaci INVENTQR Un Z-m M I United States Patent 0 3,417,716 METHOD FOR THE COMBUSTKUN OF WASTE MATERIALS, PARTHCULARLY REFUSE Theodore laeobovici, Zurich, Switzerland, assignor to Von Roll AG, Gerlafingen, Switzerland, a corporation of Switzerland Filed July 2, 1965, Ser. No. 469,104 Claims priority, application Switzerland, July 8, 1964, 8,954/64 4 Claims. (Cl. l1tl-7) ABSTRACT OF THE DISCLOSURE The present invention relates to an improved method for the combustion of waste materials of all types containing combustible and normally non-combustible com- U ponents, particularly refuse.

It is generally known to those versed in the art that the combustion of wastes of all types containing combustible and normally non-combustible components brings with it considerable difliculties. Thus, research has for many years been extremely active in this field of endeavor, particularly since it is desired to bring about destruction of the waste materials under the best possible hygienic and economical conditions.

Now, it is already known to the art that combustion at temperatures above the slag melting limit in so-called high-temperature furnaces brings with it quite considerable advantages over combustion techniques performed at lower combustion temperatures. Thus, with such high temperature furnaces there is first of all obtained a simpler, practically constant firing schedule. Furthermore, the permissible thermal load in the combustion compartment is higher and, therefore, a larger specific throughput is also possible. Moreover, the over-all combustion process is improved and it is thus possible to make removal and after-treating of the products or residues of combustion simpler. Additionally, these residues from combustion with appropriate after-treatment, for instance by granulation of the liquid slag, can possibly be commercially utilized as construction materials. Finally, dust formation is considerably smaller so that regulations or ordinances concerning cleanliness of the flue gases conducted into the open atmosphere, and which regulations are becoming nowadays more and more exacting, can be more easily complied with.

However, it has not up to the present been possible to utilize such high temperature furnaces in a simple and operationally satisfactory manner for the destruction of wastes, for instance refuse. Previously known methods and furnaces for the combustion of such wastes, apart from the disadvantage of a difiicult, and during operation, quite considerable unstable firing, possessed a relatively low thermal load for the combustion compartment, generally incomplete combustion, and thus hygienic unsatisfactory and economically unusable residues of combustion, as well as also considerable dust formation.

Accordingly, it is a primary object of the present invention to provide an improved method for the combustion of waste materials of all types containing combustible and normally non-combustible components, particularly refuse, in which the previously mentioned disadvantages of the prior known methods can be overcome in a very simple and reliable manner.

A further considerable object of this invention is directed to an improved method of the elfective combustion of waste materials of all types containin combustible and normally non-combustible components, in which the flue gases resulting from combustion are relatively dust-free, and the waste materials undergoing combustion are considerably completely burned, so that the resulting residues from combustion have economic value and can be employed as a useful product.

Another object of this invention relates to an improved method of the very effective and reliable combustion of waste materials of all types containing combustible and normally non-combustible components, wherein the furnace possesses increased thermal efliciency, the throughput of materials through the furnace is considerably improved, the combustion process results in a more complete combustion of the materials, and a cleaner flue gas is ejected into the atmosphere.

As already stated, one important aspect of the present invention is directed to an improved method for the combustion of waste materials of all types containing combustible and normally non-combustible components, particularly refuse. Characteristic of the inventive method is that the combustion air is enriched with oxygen and thus a combustion compartment temperature is reached and maintained which is above the melting point of the residues of combustion.

Other features, objects and advantages of the present invention will become apparent by referring to the following detailed description and drawing in which the single figure schematically illustrates a preferred embodiment of inventive furnace for carrying out the inventive method, such furnace being generally depicted in longitudinal section and illustrating certain accessory equipment.

Turning attention to the drawing, it will be recognized that a suitable apparatus 1 for comminution of the waste material e.g. refuse is provided with an infeed or filling funnel 1a. This comminuting apparatus 1 communicates via a delivery device 2 with a waste materialsupport means or receptacle, here shown as a pan 3 stationarily arranged in the forward portion 12a of a combustion furnace 12. In the exemplary embodiment illustrated this delivery device 2 is constructed as an infeed chute 2a. The supporting pan or vat 3 is provided with a trough 3a formed by a lining of refractory material, and serving as gas impervious support means for the material to be burned. Additionally, the trough 3a incorporates an overflow edge 3b for the removal of the liquid slag collecting in trough 3n.

In a rear flue 13 of the furnace 12 there is arranged an air pre-heater 5. The air heated in this air pre-heater 5, and serving as combustion air for combustion of the refuse in the furnace 12, is delivered via a conduit 14 to the forward region 12a of the furnace 12. Before this heated air is delivered to the forward furnace region 12a it is enriched with oxygen obtained in a suitable oxygen generating installation 4 and delivered via a short conduit 15 into the hot-air conduit 14. The hot combustion air enriched with oxygen is blown into the combustion chamber or compartment 30 of the furnace 12 through the agency of injection nozzles 6 mounted to a nozzle box or housing 16. Specifically, the injected air is introduced at sufficiently high pressure so that the air jets emanating from these nozzles 6 reach the pan 3 and the material to be burned located in the trough 3a thereof and, thus, impinge such material. In order to generate the necessary air pressure, for this purpose there is provided a high-pressure blower 11. The latter is conveniently connected to the conduit 14 for the combustion air in front of the nozzle housing 16 in the flow direction of such air and behind the point of connection of the oxygen conduit 15 with the hot-air conduit 14. It will also be observed that a discharge shaft 7 communicates with the pan or vat 3 and delivers the liquid slag, overflowing the molten bath in the trough 3a and overrunning the overflow edge 31;, into a granulation vessel 8 filled with water. An immersion tube or stud 17 is arranged at the lower end of the discharge shaft 7 and immerses somewhat into the water bath of the granulation vessel 8, thus ensuring that no cold air can infiltrate in undesired manner from beneath via the discharge shaft 7 into the interior of the furnace 12. The path of the flue gases resulting from combustion of the refuse or otherwise through the furnace 12 is indicated in the drawing by arrows A.

The combustion or flue gases generated in the combustion compartment or chamber 3c flow through the furnace 12 along the path represented by the arrows A, and initially flow through an uptake flue 18 and thereafter through the already mentioned rear flue 13, constructed as downtake flue. The downtake flue 13 is separated from the uptake flue 18 by a vertical, intermediate wall 19 which near its top 19a forms together with the housing of the furnace 12 a throughfiow opening 20. Heating surfaces 9 and 9 of a waste-heat boiler are arranged in the uptake flue 18 and downtake flue 13, respectively. After passing the air pre-heater the flue gases arrive via a waste-gas stud 21 into a combined de-dusting and suction device 10, then escape into the open or surrounding atmosphere via a pipe a which, as the case may be, can be constructed as a sheet metal chimney possessing appropriate height. At the lower end of the downtake flue 13 there is provided a funnel-shaped ash discharge 13a by means of which larger ash particles can be removed. Finer ash and dust particles are first separated from the flue gases in the de-dusting installation 10 and leave this de-duster 10 via an outlet stud 10b.

The previously described exemplary embodiment of inventive combustion furnace operates in the following manner:

The material to be burned introduced via the delivery device 2 into the furnace 12 arrives at the receptacle or support pan 3 and in the trough 3a where it ignites and burns. Due to the combustion air enriched with oxygen and injected by means of the nozzles 6 there is obtained and maintained a combustion chamber temperature which is above the melting point of the residues of combustion, so that the resulting residues of combustion, i.e. slag, are melted and liquefied and there forms in the trough 3a a molten bath 3d of higher temperature. This molten bath 3d replenishes itself continually, since the pan 3 at its forward region has delivered thereto new material to be burned whereas liquid slag is fimoved from this pan 3 at the rear via the overflow edge 31;. Due to these measures ignition and combustion of the subsequent delivered fuel is guaranteed. In order to start the combustion process when the furnace is cold there is provided for this purpose an oil burner 22. With refuse possessing a lower calorific value H =l800 kcal./kg. and a content of moisture, combustibles and ash in a ratio of 30%/44%/26%, it is possible to reach and maintain with an oxygen surplus of a combustion chamber temperature of approximately 1500' C. without supplementary fuel, with the aid of combustion air at 400 C. enriched to 35% 0 In fact, the combustion chamber temperature can be increased to approximately 1600 C. by enriching the combustion air to 40% oxygen content.

The flue gases resulting from combustion of the refuse possess a temperature of 1500 C. to 1600 C. and are guided through the heating surfaces 9, 9 of the wasteheat boiler and then through the air pre-heater 5, whereby they deliver with countercurrent flow their sensible heat while cooling down to about 350 C. The air pre-heater 5 must possess a suitable construction, i.e. possibly constructed as ceramic regenerative air pre-heater, in order to heat up the necessary combustion air from about 50 C to about 500 C., so that after its admixing with the delivered oxygen an average temperature of the enriched combustion air of approximately 400 C. results. So as to make possible heating of the air to about 500 C., of course the temperature of the flue gases entering the pre-heater 5 must lie considerably above 500 C. and the terminal portion of the air preheater can be arranged in the flue gas stream at a location where such flue gases possess sufliciently high temperature.

It will further be appreciated that instead of the pan 3 with its trough 3a stationarily mounted in the furnace 12 it would also be possible to pivotably mount such within the furnace, whereby there is achieved an intensive mixing and acceleration of the slag melting process.

While there is shown and described a present preferred embodiment of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.

What is claimed is:

1. A method for the incineration of waste material of all types containing combustible and normally noncombustible components, and concomitant smelting of its residues, comprising the steps of: preheating the combustion air, enriching said combustion air with oxygen, continually feeding raw waste material directly into a receptacle in a combustion chamber, burning said waste material in said combustion chamber in the presence of said preheated and oxygen-enriched combustion air in the absence of additional fuel, supplying said preheated and oxygen-enriched combustion air in an amount sufficient to attain and maintain a temperature in said combustion chamber which is above the smelting point of the residues of combustion resulting from said noncombustible components to thereby concomitantly smelt the residues of combustion within the combustion chamber, and collecting the smelted residues in said receptacle.

2. A method for the incineration of waste material of all types containing combustible and normally noncombustible components, and concomitant smelting of its residues, according to claim 1, further including the step of enriching said combustion air with oxygen to a total oxygen content of at least about 35% oxygen.

3. A method for the incineration of waste material of all types containing combustible and normally noncombustible components, and concomitant smelting of its residues, according to claim 1, further including the step of preheating said combustion air before enriching the same with oxygen such that said oxygen-enriched combustion air has an average temperature of about 400 C.,

thereby attaining and maintaining a temperature in the combustion chamber which is above the melting point of the residues of combustion.

4. Method for the combustion of Waste materials of all types containing combustible and normally noncombustible components, and concomitant smelting of its residues, according to claim 1, further including the steps of introducing the oxygen-enriched combustion air under pressure into said combustion chamber, selecting the pressure at which the oxygen-enriched combustion air is introduced sufficiently high that said combustion air 10 reaches and impinges against the Waste material located upon the receptacle, and continually Withdrawing from the receptacle the smelted residues of combustion.

References Cited UNITED STATES PATENTS 4/ 1926 De Coninck 110-24 11/1931 Waern.

2/1937 Hermanns 110-14 1/1951 Komline 110-8 9/1956 Grosse 110-1 12/ 1958 Firl.

7/1959 Brunes 110-1 US. Cl. X.R.

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