US2147152A - Incineration method and apparatus - Google Patents

Description

Feb. 14, 1939. G. EICONNOLLY INCINERATION METHOD AND APPARATUS Filed Oct. 22, 1956 2 Sheets-Sheet l Feb. 14, 1939. e. E. CONNOLLY INCINERATION METHOD AND APPARATUS Filed Oct. 22, 1936 2 Sheets-Sheet 2 INVENTOR ATTORNEYS Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE 2,147,152 INCINERATION METHOD AND APPARATUS George E. Connolly, Oakland, Calif., assignor to Nichols Engineering '& Research Corporation, New York, N. Y., a corporation of Delaware Application October 22, 1936, Serial No. 106,945

10 Claims.

"' embodies various improvements and modifications of the method and apparatus of the patent to Dudley Baird and-Robert W. Rowen, No.

2,015,050, granted September 17, 1935.

Important features of this invention involve methods and apparatus whereby waste material may be thoroughly incinerated and the evolved gases and vapor efficiently and thoroughly treated to eliminate noxious odor. The invention also if desired may embody arrangementswherebydesired quantities of the waste material may be efficiently dried without burning the same, such quantities of the material then being withdrawn from the apparatus for use as fertilizer, while any remaining or excess portions of the material may be incinerated and the heat resulting from such' incineration may be utilized to effect the drying operation, or to aid in effecting the same.

Various further and more specific objects, features and advantages will clearly appear from F55 detail, "the furnace may 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 illustrates somewhat diagrammatically a preferred embodiment of the invention; 'Fig. 1a. illustrates a modification of a portion of Fig. 1;

Fig. 2 similarly illustrates another desirable embodiment of the invention; and

Fig. 3 schematically illustrates a third embodiment. 7 a

Referring to Fig. 1, the apparatus there shown may comprise a furnace I having a-plurality of superposed hearths as at l I, mounted within the upper portion of the furnace wherein the operation of burning or incinerating the material is preferably conducted, and also a plurality of superposed hearths. as at l2 mounted within the lower portion of the furnace, wherein the operation of drying the material is carried out. Except for the features hereinafter described in further be of the same general type of construction as that disclosed in the above mentioned Patent No. 2,015,050, a plurality of rabble arms as at l3 being provided at each hearth, these'rabble arms each being in turn provided with teeth as at l3 whereby the material will be distributed over each hearth as a relatively thin layer and will be periodically rabbled and gradually advanced over each hearth and through drop holes to the'hearth below.

However, one of the hearths, for example hearth 10 M, at the midportion of the furnace, may be formed without the usual drop holes'whereby the furnace will be substantially divided into an upper incinerating portion and a lower drying portion for purposes hereinafter explained.

The rabble arms may be mounted upon a rotatable central shaft as at l5 and the rabble arms and shaft may be provided with internal cooling conduits as in the above mentioned Patent No. 2,015,050. In the particular construction shown, cooling air may be supplied by a blower [6 at the base of the shaft structure. This air after passing through the rabbling structure and being heated therein, may pass out from the top of the central shaft through a conduit l1. If desired, additional quantities of air may be also conducted into the conduit I! as through a butterfly valve 18 or the like, located at the top of the shaft. 1

' The material to be treated may comprise for example, sewage sludge filter cake or sewage sludge of other form, which has preferably been so treated as to eliminate a considerable portion of the water content, as for example by any well-known mechanical dehydrating process. Or the material may comprise for example, groundgarbage or garbage mixed with sewage sludge filter cake or other waste material, and should preferably have a water content in the neighborhood of 75% or less, although material having a substantially higher water content may also be treated in the apparatus.

The material to be treated may be conducted as by a conveyor Hi. to a hopper 20, thence through a suitable furnace inlet feeding device as at 2|, which will preferably substantially continuously permit the material to be fed into the furnace but without any substantial escape of gases or vapor at this point. From the device 2| the material may be fed through a conduit 22 on to the upper drying hearth l2. The material is then periodically rabbled and gradually advanced over each of the drying hearths and from hearth to hearth down through the drying portion of. the furnace ,to an outlet as at 23. This r and finally conducted to .a stack drying may proceed in the presence of heated air and/or vapor introduced through a conduit 24, as hereinafter explained. If necessary, the temperatures within this portion of the furnace may be increased as by the use of one or more gas or oil burners as indicated at 25. However, the temperatures in this portion of the furnace are preferably kept within a range such that there will be no burning or scorching of the material on the lower hearths, although the temperatures are made sufiicient to rapidly and thoroughly dry the material being treated, while due to the rabbling action, the material may become gradually broken into finer and finer pieces as it becomes more and more dry and less adhering.

From the outlet 23 the driedmaterial may be conducted through a chute 23a to the base of a conveyor 26, thence to the top-of the conveyor and down through a chute 26a to a furnace inlet feeding device 21, which may be similar to the device 2| above referred to, From the feeding device 21 the'dried material may fall on to the top incinerating hearth ll. Here the rabbling means serves to periodically agitate and gradually advance the material over each of the burning hearths and from hearth to hearth down through the upper or incinerating portion of the furnace, and to an ash chute as at 28 having its intake end at hearth I4 and its outlet connected to an ash bin as at 29. Suitable temperatures may be secured Within the incineration portion of the furnace as by the use of one or more oil or gas burners as indicated at 30, provided if desired with a supply of preheated air for supporting combustion, this air supply being furnished through conduit 3! in a manner hereinafter explained. Vapor evolved from the drying material in the drying portion of the furnace, together with some warm air, may be conducted through gas'ports as at 33, from the space above the upper drying hearth into the space above the lower burning hearth. The incineration action within the upper portion of the furnace may therefore take place in the presence of 'countercurrent streams of preheated air, together with gaseous products of combustion and vapor evolved from the drying and burning material. These countercurrent streams may finally be drawn off as through an exit opening 34 to conduit 35 connectedv to the upper portion of the'furnace.

Thus it will benoted that all of the gaseousprodnets of combustion and vapor evolved from the drying and burning material, may be drawn off through substantially the hottest part of the furnace and hence may be readily subjected before their exit to temperatures in the neighborhood of 1100 to 1500 E, which are ordinarily sufficient to safely destroy the noxious odors of the gases and vapor.

From the conduit 3.5 the gases and vapor may be drawn down in succession through a pair of recuperators 36 and 31, asbya suction fan 38,

39 or other means of'disposal thereof.

The air within conduit I! which has been somewhat preheated bypassage through the rabbling structure, together with any additional air introduced through the butterfly valve l8,:may be forced as by'a fan 40 into the recuperator 36 in heat exchanging relationship with the hot exit gases and vapor, so that such air thus be- :comes further preheated and is then conducted from the recuperator throughponduit 24 into the space above" the :upper' drying hearth I2.

'This supplyofhot air may'then pass'over'the material being dried on each of the hearths I2 in succession and along the path of travel of such material and downwardly through the drying section of the furnace. Such air, together with vapor evolved from the drying material, may then be drawn out through a conduit 4| by fan 40 and become mixed with fresh quantities of preheated air from conduit I1, and the resulting mixture is then heated in the recuperator 36 and again circulated over the drying hearths. As soon as air and vapor accumulate in the drying section of the furnace in quantities greater than maybe readily recirculated by the blower 40, the excess will pass up through the gas ports or cavities 33 into the incinerating section of circulation assures that all of the constantlychanging exposed surfaces of the drying material will be brought into contact with streams of the reheated air and vapor.

' Although a substantial part of the heat value of the exit gases will be removed and recovered therefrom within the recuperator 36, these gases will still have considerable recoverable heat value and the recuperator 31 offers a desirable means for recovering such remaining heat. That is, a supply of air may be forced by a fan 42 through conduit 43, thence through recuperator 31 in heat exchanging relationship with the exit gases, and then through conduit 3| to such of the burners 25 and 30 as may be in use, whereby each of the burners will be supplied with preheated air for supporting efficient combustion of the fuel. The proportion of this air supplied to eration hearths. The conveyor 26 and the various chutes and conduits for conducting the material into and out of the furnace are preferably suitably enclosed so as to prevent the escape of any 'odoriferous gases, vapor or dust.

In cases where it may be desired to use some of the dried material as fertilizer, fuel, or for other purposes, then a portion or at times all of the dried material at the outlet 23 may be allowed to fall through a chute as at 45 on to a conveyor as at 46. The proportion of the dried material thuswithdrawn from the apparatus may be adjusted by adjustment of a gate member as at 41. The material which is not withdrawn at this point may be conveyed to the incinerating portion of the furnace and burned in the manner above explained. I

In-case the supplies of waste material at times embody: an abnormal percentage of moisture, it

may be desirable to treat a substantial part of the material more than once inthe drying portion of the furnace. Or in some cases it may be possible to reduce the number or area of ,the drying hearths considerably by recirculating part'of the partially dried material through the drying hearth spaces. This may be done by conducting a part of the dried material from chute 26a through a chute 48 into hopper 20. The proportion of the partially driedmaterial thus recirculated may be varied or regulated by adjusting a gate member as at 49 atthe entrance to chute 48. Since the drying and burning operations are effectively isolated against merging with each other, this recirculation of the dried material may be efficiently carried out without danger of introducing ignited material into the wet sludge with consequent lumping and irregular drying and the discharge of obnoxious gases and steam, as would occur if such recirculation were attempted with the prior multiple hearth apparatus.

With the above described form of the apparatus, it will be noted that the gaseous products of combustion evolved from the burning material, are substantially free to follow their natural upward direction of flow through the burning section of the furnace, and yet the arrangement is such as to permit all of the evolved vapor and gases to be drawn off through substantially the hottest portion of the furnace at the incineration hearths whereby noxious odors from the'evolved gases may be efficiently and thoroughly eliminated. I

Also since the drying portion of the furnace is substantially sealed against the admittance thereto of material from the burning portion ofthe furnace, the arrangement is such as to permit the withdrawal of substantial amounts of the dried material from the furnace for use as fertilizer, etc., without danger that this withdrawn material will embody any odoriferous scorched or burned material or ash.

Since the exit gases'and vapor are withdrawn from the high temperature portion of the furnace, they will be of av sufficient temperature to efficiently transfer heat to the recirculated .air and vapor for maintaining the efficient drying action within the lower section of the furnace.

While with the apparatus operating as above described, the recirculated air and vapor within the drying section of the furnace is passed downwardly throughthis section, it may under some circumstances be preferable to recirculatethis air and vapor in an upward direction through the drying section. In that event, as shown in Fig. 1a the operation of the blower may be reversed as at 40' and the conduit l1 may be connected into conduit 24 instead of into the blower.

The hearth l4 having no material drop holes, will prevent glowing clinkers and ash fromfalling into the drying material, so that danger of igniting the drying material will be eliminated, at the same time keeping the drying material free of ash in case it is desired to use'the same for fertilizer without such-ash. However, if the material being' treated is ofsuch a nature that the presence of a relatively small amount of ash in the dried fertilizer product is not objectionable, then the ash from the burning hearths may be conducted from chute 28 onto one .of the drying hearths. 1

-' While I have illustrated the apparatus with fuel burners for maintaining the desired temperatures both in the drying and burning poretions of the furnace, in some cases especially where the material being treated does not have an unusually large moisture content, the process may be carried on without the use of extraneous fuel in view of the recovery of heat by the use of the recuperator 36.

' Where the drying hearths are within the top of the furnace, with the burning hearths below, in accordance with the practice heretofore, there is a marked'tendency at times for the high temperature flame to progress upwardly from the burning hearths along-the scattering stream of falling dried sludge, into the drying hearths. Thus it will be apparent that the line of division between the drying and burning hearths cannot be so sharply defined as to permit withdrawal of thoroughly dried sludgefor use as fertilizer, etc., with the arrangements heretofore available, without at times also withdrawing smoldering, charred or odoriferous sludge and gases. However, with the above described arrangement having the drying hearths at the bottom and the burning hearths at the top, a definite predetermined separation is possible between the drying and burning hearths, with no substantial possibility for the flames of the burning gas or for hot coals from the burning hearths to enter and start combustion in the drying hearths. This will be apparent when it is noted that the first drying hearth carrying the wettest and least combustible material, is the one which is located nearest the cooler burning hearth carrying little but ash. Thus the particular burning hearth which is substantially free of flames and carries few if any live coals of burning material, is closest to the drying hearth which is carrying the material in a condition where it is most difiicult to ignite. These facts, together with the above described arrangements of gas passages, make possible a substantial isolation of the burning hearths against passage of burning material or flames into the drying hearths. Although the arrangement permits the drying and burning operations to be thus substantially isolated against merging with each other, yet the structure is such as to permit all of the hearths to be enclosed within a single cylindrical furnace wall providing a compact structure conserving of heat and space. In fact, the required floor space is notincreased over the requirements of the previously known apparatus, which cannot fulfill several of the above described functions of the present invention.

- The arrangement of the drying hearths below the 'incinerating hearths also has further advantages. For example, the provision of a recirculating stream of vapor may be much more easily controlled if the drying hearths containing this stream are at the bottom of the furnace. This will insure that the vapor stream cannot tend to flow by reason of its weight down to any lower hearths and that it will not leave the drying hearths until it has accomplished its purpose and until sulficient excess vapor has been evolved to cause the excess to be forced upwardly into the burning section of the furnace for heat treatment before discharge. V

The embodiment of the invention illustrated in Fig. 2 is in many respects similar to the arrangement above described, corresponding parts being identified by the same reference numerals. However, in Fig. 2, the air'which is preheated by passage through the rabbling system, instead of being withdrawn at the top of the furnace shaft, may be admitted into the drying section of the furnace through a plurality of air Outlets as at 60 formed in the walls of the rabble arms at one or more drying hearths of the furnace. The openings 60 at some of the rabble arms, may be closed or partially closed as desired, as by the use of mechanism disclosed in the patent to Henry J. Hartley, No. 1,842,782, granted January 26, 1932. V

The fan 40 as shown in Fig. 2 may be operated in either direction so as to recirculate the hot air and vapor within the drying section of the furpace in either direction, i. e. upwardly from hearth to hearth, or downwardly from hearth to hearth, as indicated by the arrows shown within the recirculating conduits.

Fig. 2 also illustrates an alternative arrangement for withdrawing a part of the dried material from the apparatus and for conducting the same 7 to storage. That is, instead of using a chute 45 and gate 4! as indicated in Fig. 1, the dried material may all be conducted to the top of the conveyor .26 and then portions thereof which are to be conducted away to storage may be allowed to fall from chute 26a through a chute 6|, an entrance to whichmay be controlled as by a gate 62. Other portions of the dried material may be reintroduced into the drying section of the furnace through chute 48, as in Fig. 1.

Under some circumstances it may be desirable with the arrangement of Fig. 2, to maintain an atmosphere within the drying section of the furnace substantially wholly comprising vapor evolved from the drying material. In that event instead of introducing the preheated air through rabble arm openings 60, the air preheated within the rabbling structure may be introduced into the burning section of the furnace as through rabble opening 60, just above hearth M, and in this case burner 25 would not be used. The drying action within the lower or drying section of the furnace may be thus made quite intense through the use of recirculated hot vapor at temperatures in excess of the temperature of the drying material, and yet the presence of the vapor will preclude the possibility of unintended combustion of the material in this portion of the furnace even though the material may become quite dry by the time it reaches the bottom hearth.

The arrangement schematically illustrated in Fig. 3 is also somewhat similar to that of Fig. 1, except that the streams of gases, vapor and air within the incinerating section of the furnace are passed along the path of travel of the burning material, 1. e. downwardly through the burning-section of the furnace and thence out through a gas exit conduit Hi through the recuperator 36. Air for supporting combustion within the burning se'ction'of the furnace may be introduced, for example at the burners 30 located at one or more of the upper burning hearths. This air together with the evolved gaseous products of combustion then passes downwardly. Vapor and air from the drying section of the furnace may be also introduced into the burning section through one or more of the gas ports as at 33. Thus this vapor will become mixed with the hot gaseous products of combustion and thereby heated to an extent sufficient to destroy noxious odors of the vapor and finally the vapor will pass out through conduit 70 with the hot gases.

A supply of air. preheated within the rabbling structure may be introduced into the'drying section of the furnace in a manner similar to the method as explained in connection with Fig. 2,

or if desired, air maybe drawn through the rabbling structure and thereby preheated, by the use of a. suction fan as at H mounted at the top of the furnace shaft, this preheated air then passing through a conduit 12, thence into the drying section of the furnace.

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 of the United States is:

1. A furnace for drying and burning moist material, comprising a plurality of superposed hearths including one or more lower hearths for drying the material and one or more upper hearths for burning the material, means for introducing the material on to said drying hearth or hearths and. for rabbling the material thereover, means for then conveying the material to said burning hearth or hearths and for rabbling the material thereover, means for recirculating over said drying hearth or hearths, a stream of vapor evolved from the drying material, and means for maintaining said stream at a temperature sufficiently high to efiect drying of the material on said drying hearth or hearths.

2. A furnace for drying and burning moist material, comprising a plurality of superposed hearths including one or more lower hearths for drying the material and one or more upper hearths for burning the material, means for introducing the material on to said drying hearth or hearths and for rabbling the material thereover, means for then conveying the material to said burning hearth or hearths and for rabbling the material thereover, means for withdrawing vapor from a point within the lower portion of the furnace, and for heating said withdrawn vapor and reintroducing the same at another point within the lower portion of the furnace whereby the drying action is promoted by a recirculating stream of hot vapor passing over the material on said drying hearth or hearths.

3. A furnace for drying and burning moist material, comprising a plurality of superposed hearths'including one or more lower hearths for drying the material and one or more upper hearths for burning the material, means for in- 'troducing the material onto said drying hearth or hearths and for rabbling the material thereover, means for then conveying the material to said burning hearth or hearths and for rabbling the material thereover, means for withdrawing vapor from a point within the lower portion of the furnace, and for heating said withdrawn vapor and reintroducing the same at another point within the lower portion of the furnace whereby the drying action is promoted by a recirculating stream of hot vapor passing over the material on said drying hearth or hearths, and means also permitting vapor to pass from the lower portion of the furnace, into and through the upper portion thereof.

4. Afurnace for drying and burning moist material, comprising a plurality of superposed hearths including one or more lower hearths for drying the material and one or more upper hearths for burning the'material, means for introducing the material onto said drying hearth or hearths and for rabbling the material thereover in the presence of a stream of heated vapor flowing along the path of travel of the material, means for causing at least substantial portions of said stream to be reheated and repeatedly circulated over said drying hearth or hearths, means for conveying the material after passage over said drying hearth or hearths to said burning hearth or hearths and for rabbling the material over the latter, means for conducting said stream together with vapor evolved from the drying material into contact with the material on said burning hearth or hearths and for then conducting said stream together with gaseous products of combustion evolved from the burning material countercurrent to the burning material over the burning hearth or hearths, and an exit opening above an upper burning hearth whereby said gases and vapor may be withdrawn from the furnace through a high temperature burning zone for the destruction of noxious odor of such gases and vapor.

5. A furnace for drying and burning moist material, comprising a plurality of superposed hearths including one or more lower hearths for drying the material and one or more upper hearths for burning the material, means for introducing the material on to said drying hearth or hearths and for rabbling the material thereover, means for then conveying the material to said burning hearth or hearths and for rabbling the material thereover, means for causing a stream of vapor evolved from the material to pass countercurrent to the movement of the material over said drying hearth or hearths and then into the presence of the material on said burning hearth or hearths, means including an exit opening at a burning hearth for withdrawing said vapor from the furnace through a high temperature burning zone thereof, and a heat exchanging device and connections whereby heat of said withdrawn vapor may be transferred to the vapor over said drying hearths.

6. A furnace for drying and burning moist material, comprising a plurality of superposed burning hearths within the upper part of the furnace,

a plurality of superposed drying hearths within the lower part of the furnace isolated against the passage of solid material thereto from said burning hearths, means for rabbling the material over said drying and burning hearthsrespectively, means for conveying dried material from said drying hearths on to said burning hearths, said rabbling means being formed with cooling conduits, means causing air to pass through said conduits and to be discharged in heated condition on to the material on said drying hearths, and means causing hot vapor to repeatedly flow over the material on said drying hearths and then to said burning hearths.

'7. The process of drying sewage material without burning the same, and burning portions of the resultingdried material to supply heat for the drying operation, which comprises passing the material in succession through a plurality of superposed drying zones in the presence of a stream of heated vapor, the material being introduced into an upper drying zone and temporarily retained as a layer at each of said zones while periodically agitating it and gradually advancing it through each zone and downwardly from zone to zone, removing the dried material from a lower drying zone and then passing portions of the same in succession through a plurality of burning zones located above said drying zones, said burning zones being isolated against the passage of the solid material therefrom into said drying zones, agitating saidportions of the material in said burning zones in the presence of a stream of evolved gases and air at a temperature sufiicient to incinerate said portions, conducting the evolved gases from said burning zones, and utilizing heat thereof to heat said stream of vapor for said drying zones.

8. The process of drying sewage material, which comprises passing said material in succession through a plurality of superposed drying zones in the presence of a stream of heated vapor, the material being introduced into an upper drying zone and temporarily retained as a layer at each of said zones while periodically agitating it and gradually advancing it through each zone and downwardly from zone to zone, removing the dried material from a lower drying zone and then reintroducing portions thereof into an upper drying zone for further drying in conjunction with the material initially introduced, and passing at least a portion of the removed material into a burning zone, agitating said portion in said burning zone in the presence of a stream of evolved gases and air at a temperature sufficient to incinerate said portion, conducting the evolved gases from said burning zone, and utilizing heat thereof to heat said stream of vapor for said drying zones.

9. Furnace apparatus comprising aplurality of superposed hearths, means for rabbling and advancing material to be treated first over each lower hearth and from hearth tohearth and then over the upper hearths, means for burning fuel at a hearth within the upper portion of the furnace, the hearths being provided with or accompanied by ports permitting gases to flow from hearth to hearth, a conduit extending from a hearth intermediate the top and bottom of the furnace to a lower hearth, whereby a recirculating stream of gas may be maintained over the lower hearths, and means for causing gases within the upper portion of the furnace to flow downwardly and out from the intermediate portion of the furnace and in heat exchanging relationship with said recirculating stream,

10. Furnace apparatus comprising a plurality of superposed hearths, means for rabbling and advancing material to be treated first over each lower hearth and from hearth to hearth and then over the upper hearths, means for burning fuel at a hearth within the upper portion of the furnace, the hearths being providedwith or accompanied by ports permitting gases to flow from hearth to hearth, a conduit extending from a hearth intermediate the top and bottom of the furnace to a lower hearth, whereby a recirculating stream of gas may be maintained over the lower hearths, a source of air supply for said fuel burning means, and means for causing gases within the upper portion of the furnace to flow downwardly and out from the intermediate portion of the furnace, and in heat exchanging relationship with said recirculating stream and with said air supply.

GEORGE E. CONNOLLY.

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