US2108997A - Incineration of waste materials - Google Patents

Description

Feb. 22, 1938. F. B. SCHILLING INCINERATION OF WASTE MATERIALS Filed Sept. 14, 1936 2 Sheets-Sheet l lNV ENTOR Iredeniek l5. Shilling cum/ imijija BY C ATTORN EYS w Amy/l 2 Sheets-Sheet 2 INVENTOR Wedrxbk 1?. Schilluzg BY M M ATTORNEYS Feb. 22, 1938, F. B. SCHlLLlNG INCINERATION OF WASTE MATERIALS Fified Sept. 14, 1956 Patented Feb. 22, 1938 UNITED STATES PATENT OFFICE INCINERATION OF WASTE MATERIALS Application September 14, 1936, Serial No. 100,610

8 Claims.

This invention relates to the incineration of waste materials and is particularly adapted for use in connection with the process and apparatus as disclosed in the patent to Dudley Baird and Robert W. Rowen, No. 2,015,050, granted September 17, 1935.

The objects of this invention include the provision of a process and apparatus for drying and incinerating waste products such as sewage materials with a high degree of efficiency so that little or no extraneous fuel need be used and at the same time eliminating obnoxious odors from the evolved gases and vapor.

Various further and more specific objects, features and advantages will clearly appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by way of example preferred forms of the apparatus of the invention.

The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the apparatus herein disclosed, and also such novel methods and combinations of method steps as are disclosed and described herein.

In the drawings, Fig. 1 is a sectional view of a furnace structure, together with certain auxiliary apparatus somewhat schematically indicated, arranged for carrying out the invention in its preferred form; and

Fig. 2 is a view similar to Fig. 1, but illustrating an alternative embodiment of apparatus for carrying out the invention in certain of its phases.

In Fig. l a multiple hearth furnace structure is shown at 5. This furnace if desired may be similar in construction to that shown in greater detail in the above mentioned patent. It may be provided at its top portion with an intake hopper 6 equipped with a suitable feeding device as at l which seals the inlet against escape of gases or vapor at that point. A discharge outlet for the ash resulting from the incineration process, may be provided at the bottom of the furnace as indicated at 8. Fuel burners as at 9 may be mounted to project a flame into the furnace at various points, but with the equipment and process hereinafter described, these burners will ordinarily not be necessary except in bringing the furnace structure up to temperature when starting the incineration operation or when burning material of unusually high water content. The several hearths within the furnace are indicated at l I to ll inclusive, alternate hearths respectively being provided as shown with peripheral and central discharge openings, permitting the material being dried and incinerated to be rabbled over each hearth and from hearth to hearth down through the furnace while it is first dried on the upper hearths and later incinerated on intermediate or lower hearths, the resulting ash being allowed to become somewhat cooled on the lower hearth before it is discharged through outlet 8. The hearths are supported within a furnace wall [8.

The rabbling structure may comprise a central rotatable shaft l9 carrying a plurality of rabble arms as at 20, cooperating with each of the sev-' eral hearths. The shaft may be rotated in the manner disclosed in the above mentioned patent and the shaft and rabble arms may also prefer- 15 ably be provided with interconnected cooling air conduits as disclosed in said patent, whereby a supply of air from blower 21 is passed through such conduits, thereby maintaining the rabbling structure at a temperature low enough to prevent injury thereof in the presence of the relatively high temperatures within the furnace. This cooling air in flowing through the rabbling structure, becomes preheated and may be drawnofl as through a conduit 22 and forced as by a fan 23 through conduit 24 into a recuperator 25. As hereinafter explained, this air may become further preheated in the recuperator and may then be introduced at one or more of the 1 lower hearths of the furnace, as through a conduit 26. Thus a supply of preheated air is made available for efficient combustion at the incinerationhearths of the furnace. The amount of this'air may be adjusted by adjusting the speed of the fans 2i and 23.

Within the furnace and for example at hearths I4, l5 and IS, the incineration of the waste material will be effected in the presence of a countercurrent stream of preheated air and evolved gases rising up through the furnace. This countercurrent stream may finally be largely withdrawn through an exit opening 21, located for example above hearth I3. The temperature conditions within the furnace are preferably so arranged that the exit gases passing through outlet 21 will be at a temperature of 1100 F. or higher, which will ordinarily be sufficient to insure substantial elimination of noxious odors in such gases.

From the outlet 21 the exit gases may be forced as by a fan 28, through conduits 29 within the recuperator 25, whereby such gases are brought into heat interchanging relationship with the intake air for the furnacev for. pre-- heating the latter. Sufficient heat may be efliciently absorbed from the exit gases within the-1 conduits 29 so as to bring their temperature down to in the neighborhood of from 750 to 850 F., whereupon such gases may be conducted out through conduit 30 connected as shown to the 12, it will be noted that the apparatus as thus.

far described, is similar to that of the above mentioned Patent No. 2,015,050. However, in order to more efficiently utilize the fuel valueof the burning waste material and. to avoidloss of-the useful heat in the exit gases passing through, conduit 30, I have provided means for passing a part or all of such gases over one. or; more preliminary drying or prewarming hearths at the,

top of the furnace. In this way the exit gases available. inconduit;v 30sat a. temperature in the neighhorhood-ofr800? for. example, may be.

brought: into .heatizexchanging relationship with the cold wet waste materialqentering thefurnace, and thusenoughotthe heat of the exit gases maybe. absorbedby. the wet materialto bring the. temperature of the gases-down. to -.in themeighborhoodof 3.5.0 to,-400 F. for xample, before. they. are discharged :to the stack, In this manner most, of Y the; useful-v heat, which it is economicalJto recover.;from,the exit gases, may be reabsorbedwithin the furnace so that the waste material even: though it may have from 65 to 70% moisture for example, may; besafely incineratedzwithin the; furnace withouttthe use of the fueLburners or other extraneous fuel and without: discharge; of noxious-gases from theapparatus- The. particular apparatus shown in. Fig. 1; for

accomplishing;- these objects, maycomprise a.

branch -.conduit; 3 l communicating with; conduit- 3fl'eforeconductingsthe. -.exitngases; to one. or more furnace inlets, asat; 34 841141135,- communicating withithe spaces. over. hearths I l and 12 for example. The hot-waste gas may as ver the relatively cold wetv material, on, these hearths and; thence throughqexitg openings. at t 3 6 and 3], conduit-.38, fan- 3.9 =1and;condu it; 40, back to thestack; connection.

. Theproportion of; the exit gaseswhich it is.

desiredtoby-passoyer, thetop hearths (if it is not desired to;pass all of such gases over; these.

hearths) may be regulatedby; adjusting dampers aszate3lf and 3,3,: Under;somel circumstancesthe tion;of;odori-ferous gases .at this part of .the fur-v nace. To-avoidthis result, some air at room temperatureimayebeintroduced into the conduit 31 'through a conduit 32: anddamper 32], to lower the..-.temperature.withinconduit 3| tojthe desired degree. The relativeproportions of the hot exit gases. which are. reintroduced into the furnace over hearths Hand l-Z- respectively, may be. ad-v justed by means-of dampers-34., 35 3.6; and 31. A relatively large. portion of the exit gases may be passed over hearth. ll: without danger of scorching" the material. thereon. since. at this hearth the material is'relatively cold and wet. If it islfoundv that the material on hearth l2; is being raised'toa temperaturesuch as to tend to-cause scorching and odors, the-amount of the hot gases introduced overthis hearth may be readily reduced by partially closing dampers 35' and 31'. However, the hot exit gases being largely inert, will tend to retard combustion of the waste material on the upper drying hearths even though the material may be of low moisture content.

Thus on the top hearth II the waste material maybe warmedto a considerable extent and the drying process initiated through utilization of heat which would otherwise be wasted. This warming and drying action may continue to a further degree on hearth I 2 and if desired, one or more additional drying hearths might alsobe provided with heat in the same manner as hearthsH andIZ; With the particular example shown, the. drying action may be largely completed on hearths l3 and 14 so that combustionmay. begin onthese hearths and proceed to completion with the substantial elimination of all organic matter of the waste material at the lower. hearths.

.In cases; wherethe incoming waste material may be particularly dry, so, that, the burning might be initiated on .oneof the tophearths, the.

exit gases maybe passeddirectly; to thestack without being reintroduced into the furnace at the drying hearths. Then in such cases, the possibility of passing obnoxiousa es resulting from scorchingthe material,- out through conduit 38 vmay be avoided bye-closing; dampers 3 4' to 31'.

Thereafter, any, obnoxious gases and vapor evolved from the to-p two hearths, may pass down and out in admixture with the hot gases hr u hc it 1. os hatfih o s a e lim nated,

S n n. he urnac s. ab e scribed wh n e a e inits ierredwa he e rth L n are; s d: s rew rmins. r ns h rt uc h ar hs ma e nstruc ed. f :m a agindicated, instead of using the. refractory material ractica nec s r er ei ew eh sll em era r earth hqwni n as h -i c nr t on; ll nitia ed forx m le n r h th 2; his h r h ax SQ e er mad ir f c cr materiat, l-re d metal top hearths permitsmore ready access of heat by conduction to the under surfacesof the layers of wastema r on hes hear thereby n rea ing thespeed of: drying.

n h embodim nt f hei -ii n lus in Fig. 2, many of the parts maybe similar to: thoseabove described and-are. accordingly identified bylike-referencenumerals. As shown in this embodiment, an additionaldrying hearth I 3 is used. The waste materialpasses over the various hearthsand down through the furnace in a manner similar to that above described in connection with Fig, 1, and the preheated intake air,- for supporting combustion is similarly intro.- duced through conduit 26 The countercurrent stream of. air and gases in Fig. 2, however, is

preferably-withdrawn through anoutlet conduit 50 from substantially the; hottest area, within the furnace, the rate of withdrawalbeingregulated by adjustment of; the damper 50'. The vapor evolved from the drying material on the upper hearths may bepassed downwardly in the drying portion of the furnace along the direction of movement of the. waste material and out through a discharge conduit asat 51 having a regulating damper 5|. The hot outlet gases. from conduit 50, meet the relatively cooler vapor from conduit 5| and maybe mixed. therewith forexample in a chamber 52. Usually after the processv has gotten under way, the exit gases from. conduit 50,;will

be at a temperature sufficiently high above 1100 F. so that the resulting mixture within chamber 52 will be at a temperature sufficient to destroy odors of the vapor coming through conduit 5|. If under special circumstances there is danger of this temperature not being suificient to destroy odors in the gas and vapor mixture, the chamber 52 may be provided with a fuel burner as at 53. Ordinarily, however, it will be unnecessary to use this burner except when starting the process. The gas and vapor mixture passes from chamber 52 through conduit 54 into conduits 55 within the recuperator 25, and thence through conduit 56 to a stack connection. A part of this gas if desired may be by-passed through a conduit 5'! and conduits 58 and 59 into the space above the top hearth of the furnace. The portion of the gases thus by-passed may be regulated by adjustment of dampers 56' and 51'.

Thus a sup-ply of hot waste gases mixed with some vapor is reintroduced over the top drying hearths of the furnace and since this mixture will contain only a relatively small quantity of air, there will be little or no tendency for the waste material to start to burn on the upper hearths. Yet the temperature of the gas and vapor mixture will be such as to insure efficient drying on these upper hearths, thereby placing the material in such condition that it will be rapidly, efficiently and tho-roughly incinerated in the lower portions of the furnace. And the serious odors of the gaseous products of combustion evolved from the incineration hearths will be substantially eliminated because of the withdrawal of such gases through the hottest area of the furnace. The less serious odors of the vapor evolved from the drying hearths will be eliminated as a result of mixture of such vapor with said hot exit gases, yet without bringing the vapor into the incineration areas of the furnace which would tend to blanket the fire. It will be noted that the arrangement provides for recirculation through the drying portion of the furnace of a considerable part of the hot inert exit gases. This makes possible an efficient drying action without introducing an excess of preheated air into the furnace beyond what is necessary for combustion purposes, plus a factor of safety. This in turn avoids the necessity of preheating as large a supply of intake air as might otherwise be required to insure an adequate stream of gases and air to quickly dry and burn the material treated.

While the invention has been described in detail with respect to particular preferred examples, it will be understood by those skilled in the art after understanding the invention, that various changes and further modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1. Process of drying and incinerating waste material to form an ash substantially free of organic matter and evolved gases free of noxious odor, which comprises passing such material successively through a plurality of zones, temporarily retaining said material in substantially horizontal layers at each of said zones while periodically agitating it and causing it to be broken into fine pieces and maintaining it in finely divided condition while advancing it through each zone and gradually from zone to zone, preliminarily warming the material in the first zone or zones, then drying the material in a succeeding zone or zones, then burning the material in a subsequent zone or zones, such drying and burning being conducted in the presence of a stream of preheated air passedcountercurrent to the passage of the material and including gaseous products of combustion and vapor evolved from the drying and burning material, withdrawing said stream from a drying zone, then bringing such stream before any substantial cooling thereof, into heat exchanging relationship with a supply of air to provide said preheated air, thereafter absorbing further heat from said with drawn stream by passing at least a substantial part thereof into contact with the material at said preliminary warming zone or zones, and then discharging such part from said warming zone or zones independently of said withdrawal of gases from the drying zone.

2. Process of incinerating waste material, which comprises preliminarily warming, drying, and burning the material by passing the same through a plurality of zones in succession, effecting said drying and burning operations in the presence of a stream of air together with gaseous products of combustion and vapor evolved from the drying and burning material, withdrawing said stream from said zones and bringing the same into heat exchanging relationship with a supply of said air for preheating the latter before introduction into said burning and drying zones, thereafter absorbing further heat from said withdrawn stream by passing at least a substantial part thereof intocontact with the material at the preliminary warming zone, and then 1 discharging such part from the warming zone independently of said withdrawal of the gaseous stream from succeeding zones.

3. Process of incinerating waste material, which comprises preliminarily Warming, drying, and burning the material by passing the same through a plurality of zones in succession, effecting said burning operation in the presence of a countercurrent stream of preheated air together with gaseous products of combustion evolved from the burning material, withdrawing said stream from said zones at a point prior to its passage into the preliminary warming zone or zones,

.bringing said withdrawn stream into heat exchanging relationship with a supply of air to provide said preheated air, thereafter passing at least a part of said withdrawn stream through the warming zone or zones in contact with the material therein to heat the latter, and then discharging such part from said warming zone or zones independently of the above mentioned Withdrawal of said stream from succeeding zones.

4. Apparatus for incinerating waste material, com-prising a furnace having a plurality of superposed hearths including an upper hearth or hearths for preliminarily warming and drying the material and a lower hearth or hearths for burning the material, means for feeding the material on to the top hearth, rabbling means cooperating with each of the hearths for periodically agitating and advancing the material over each hearth and gradually from hearth to hearth down through the furnace, a recuperator, means for conducting a supply of air through said recuperator and into the lower part of the furnace to provide preheated air for supporting combustion therein, means for withdrawing from the furnace hot gaseous products of combustion evolved at the burning hearth or hearths and passing such products through said recuperator in heat exchanging relationship with said .air, means for thereafter passing said products over the material onsaid upper hearth r hearths for providing heat to warm and dry the material thereon, while further reducing the temperature of said products, and means for then discharging said products from said upper hearth or hearths independently of the above mentioned withdrawal of the hot gaseous products from the furnace. 5. Apparatus for incinerating waste material, comprising a furnace having a plurality of superposed hearths including an upper hearth or hearths for preliminarily warming and drying the material and a lower hearth or hearths for burning the material, means for feeding the material onto the top hearth, means for advancing the material over each hearth and from hearth to hearth down through the furnace, a recuperator, means for withdrawing hot gaseous products of combustion from the furnace at a point adjacent or above the upper zone of burning, and passing such products through said recuperator, means for conductingva supply of air through said recuperator in heat exchanging relationship with said products and thence into the burning zones of the furnace, conduits provided with adjustable means for conducting predetermined portions of said gaseous products, after passage through said recuperator, over the material being dried and warmed on said upper hearths, and means for then discharging said products from said upper hearths independently of the above mentioned withdrawal of the hot gaseous products from the furnace.

6. Apparatus for incinerating waste material, comprising a furnace having a plurality of superposed hearths including upper hearths for preliminarily warming and drying the material and a lower hearth or hearths for burning the ma terial, means for feedingv the material on to the top hearth, means for advancing the material over each hearth and from hearth to hearth down through the furnace, means for causing hot gaseous products of combustion to pass countercurrent to the material over said burning hearth or hearths and out of the furnace at a pointadjacent or above the upper zone of burning and for causing the vapor evolved from the material on the drying hearths to pass along the,

path of travel of the dryingmaterial and thence out of the furnace, a recuperator, means for conducting said gaseous products and vapor after leaving the furnace through said recuperator in heat exchanging relationship with a supply of air for preheating saidair, means for conducting saidpreheated air over the material on the burning hearths of the furnace, conduits for conducting a portion of said gaseous products and vapor after leaving the recuperator into the upper part of the furnace to provide heat for warming and drying the material therein, and means for then discharging said, portion of the gaseous products and vapor from the upper part of the furnace independently of the withdrawal of the hot gaseous products from the furnace.

7. Apparatus for incinerating sewage material, comprising a furnace having a plurality of supperposed hearths including upper hearths for preliminarily warming and drying the material and lower hearths for burning the material, means for feeding the material on to, the top hearth, rabbling means cooperating with each of the hearths for periodically agitating and advancing the material over each hearth and gradually from hearth to hearth down through the furnace, a recuperator, means for conducting a supply of air through said recuperator and into the lower part of the furnace to provide preheated air for supporting combustion therein, and whereby said air together with gaseous products of combustion evolved from the burning material then pass countercurrent to the passage of the material over the burning hearths, means for withdrawing saidproducts from the furnace at a point after their passage over an upper burning hearth and before such products pass into the presence of. the material on the uppermostwarming and drying hearths, means for passing said Withdrawn products through said recuperator in heat exchanging relationship with said air, and means for thereafter passing at least a substantial part of said products over the material on said upper warming and drying hearth or hearths to warm and dry the material thereon.

8. Apparatus for incinerating sewage material,

comprising a furnace having a plurality of superposed hearths including upper hearths for preliminarily Warming and drying the material and lower hearths for burning the material, means for feeding the material on to the top hearth, rabbling means cooperating with each of the hearths for periodically agitating and advancing the material over each hearth and gradually from hearth to hearth down through the furnace, a recuperator, means for conducting a supply of air through said recuperator and into the lower part of the furnace to provide preheated air for supporting combustion therein, and whereby said air together with gaseous products of combustion evolved from the burning material then pass countercurrent to the passage of the material over the burning hearths, means for withdrawing said products from the furnace at an upper burning hearth before such products pass into the presence of the material on the upper warming and drying hearths, means for passing said withdrawn products through said recuperator in heat exchanging relationship with said air, means for thereafter passing at least a substantial part of said products over the material on said upper warming and drying hearth or hearths to warm and dry the material thereon, and means for causing the gaseous products and vapor evolved at the warming and drying hearths to pass downwardly and along the path of travel of the drying material on the warming and drying hearths and thence out of the furnace at a point adjacent the upper burning hearth.

FREDERICK B. SCHILLING.

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