CA1197730A - Incinerator having cooled hearth - Google Patents

Abstract

Abstract of the Disclosure A burning waste incinerator having an elongated hearth through which combustion air passes, the hearth having pipes adjacent the surface thereof for circulation of a cooling media to reduce the tendence of burning waste material to adhere to the hearth.

Description

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INCINERATOR HAVING COOLED HEARTH

Background of the Invention The invention rela-tes to incinerators for burn-ing waste materials including garbage and the like. Such i.ncinerators typically include a chamber or compartmen-t in which the gar~age is placed for burning. Wi-thin -this com-par-tment, suitable means are provided to ignite the garbage by means: of a gas burner and once the garbage has been ignited a sufficient amount of air is supplied to continue burning the garbage without any external fuel being lQ supplied.
To m~ximj ze the output of such incineratoxs, it is conventional to provide means for introducing batches of garb~age~ into the incinerator and moving the partially combusted garbage or ash. through the incinerator. Typical~
ly, the gar~age is inserted into one end of an elongated chamber by means of a loading ram. After -the charge has begun b.urning, successi.ve charges are inserted through the load end by the ram ~orcing the earlier load to proceed down the length of the incinerator chamber. Frequently, 2Q additional rams are provided to assure the continued move-ment of -the burning garbage or ash -through the incinera-tor.
The rate of insertion of the garbage and -the rate of combustion is such that the garbage is completely incin-erated by the time i-t reaches the remo-te end of the chamber~
be.ing reduced to ashes which are disch.arged by gravi-ty throuyh a chute leading to a conveyor or other means oE
dis.posal. During -the combus-tion of the garbage, -the hurn-ing conven-tionally takes place adjacen-t -the hearth wi-th ....~

the air supplied through -the hearth. As the hot gases from the combustlon rise -through the garbage, the ho-t gases thermally decompose the rest of the garbage. As a result o~ the decomposition taking place with a limited amount of air being present, the resulting gases are combustible and are typically burned before being discharged to the atmo-sphere.
One of the problems associated with prior art incinerators involves the clogging and obstruction caused by melted glass and metals which tend to fall to t~e hearth of the incinerator and adhere thereon preventing the remain-ing mass of garbage and ashes from moving through the incin~
erator. ~here seem to be no prior art incinerators of the type having an elongated hearth across which the burning garbage is processed which have dealt with the problem as descri~ed above. There are a number of pieces of prior art which disclose the use of water cooled grates, the water coollng being to prevent deterioration of the grates.
These prior art patents comprise Cragin, IJ. S. Pat. No.
2Q 773/248; Simeral et al, U. S. Pat. No. 1,977~651 and Simpson, U.~ ~, Pa~. No. 2,557,013. Examples of other types of furnaces or melting devices in w~ich water cooling has been used for various purposes are Bracken et al, U. S.
Pat~ NoO 3,~59,413; ~irtz et al, U. S. Pat. No. 3,705,713;
25 Astro~, U. S. Pat. No. 3,838,665; Herr, U. S. Pat. No.
3,80~4~584 and Drew, Jr., U. S. PatA No~ 4,1~9,84~. None of these prior art patents suggest the concept of cooling an incinerator hearth in the manner disclosed and claimed belo~.
Sum`mary of the Invention The instant invention represents an improvement ovex the prior art by providing an improved hearth structure which facilitates moving thç w~ste ma-terial through the inclneration zone to the ash disposal area. The garbage typically handled b~ an incinerator involves substantial ~uantities of glass and metallic material. The aluminum cans and so forth in the ~arbage melt and the iron or steel oxidizes and then melts becoming a solvent which tends to dissolve the refractory material of the furnace. In addi-tion, the glass bottles mel-t and fall to the surface of the hearth where it tends to stick. In the incinerator of the present invention, the hearth is cooled ~y means of pipes which are flush with the surface oE the hearth so that th.e melted glass and other materials neither s-tick to the hearth nor tend to dissolve the refractory portions thereof.
The heat generated by the combustion of the gar~age is very substantial and, therefore, considerable cooling is required to prevent any overheating of the h.ea,rth to achieve the objectives o-f the i.nvention. By ha~ing the cooling pipes flush with the surface of the hearth and in good heat transfer relation with the adjacent refra,ctory portions, it is possible to maintain the temper-ature of the hearth below l,QOO~F. ~t such a temperature, the glass and other materials which might collect on and s;tick to the hearth tend to ball up and not wet the surface Qf the hearth permitti.ng all such materials to be pushed through the incinerator with the ash and other material.
I:t is, therefore, an object of the present inven tion to provide an improved incinerator having a hearth provided wi.th cooling pipes imbedded in the refrac-tory surface of the hearth.
It is a further object of the presen-t invention to provide an improved incinerator suitable for burning 3Q ~arbage and having a hearth ~hich may be cooled to a tem~
perature of on the order of 1~000F~ so that waste products:of the garbage burni.ng will not stick to or de.posit on the hearth..
Another object o~ the present invention ls to proYide an i~proved incinerator having a cooled hearth ~L~L9t~ 73~3 including lengthwise extending, spaced cooling pipes dis-posed at the surface of the hearth wi-th wear plates secured to the surface of such cooling pipes and refractory material between such pipes flush with the surface of said wear plates, such cooling pipes being provided with a circulating heat transfer media such as water.
It is still another object of the present inven-tion to provide an improved incinerator having a hearth formed of transversely extending air supply pipes and lQ lengthwise extending water cooling pipes with refractory material between said cooling pipes Elush with the upper surface thereof forming the hearth and air discharge nozzles extending from said air supply pipes through said refractory material to the upper surEace of the hearth.
Brief Description of the Drawings Fig. 1 is a perspective view of an incinerator embodying my invention;
Fig. 2 is a vertical sectional view taken length-wise through the center of the primary and secondary chambers of the incinerator;
Fig. 3 is a vertical sectional view taken sub-stantially along line 3-3 of Fig. 2;
Fig. 4 is a plan view showing the layout of the cooling water pipes and the air pipes imbedded in the hearth of the subject incinerator;
E~ig. 5 is a sectional view taken substantially along line 5-5 of Fig. 2;
Fig. 6 is a sectional view oE the secondary chamber taken on line 6-6 of Fign 2;
Fig. 7 is an enlarged fragmentary sectional view taken on line 7-7 of Fig. 4;
Fig. 8 is a plan view of the coupling between the air conduit and the water cooling pipes with the assembly nut and washer removed;

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Fig. 9 is a fragmentary sectional view of the hearth taken along line 9-9 of Fig. 5; and Fig. 10 is a fragmentary sectional ~iew through the hearth showing air delivery nozzles.
Description o~ the Preferred Embodiment ~ eferring to Fig. 1 of the drawings, there is shown a complete incinerator system which is designated generally by reference numeral 12. The system 12 includes the inclnerat:or 14 having a primary chamber 16 and a secondary chamber 18. The primary chamber 16 is provided with an automatic inline loader 20 which includes a ram 20a which is adapted to propel a ~uantity of waste material or garbage into the incinerator 14 as will be explained in greater detail below~
1~ The secondary chamber 18 is provided with an outlet conduit 22 which connects to a stack 24 the purpose of which is to deliver hot gases to the heat recovery boiler 26~ The above-described elements of the incinera-tion system 12 are conventional and in themselves form no part of the invention herein disclosed.
In the conventional mode of operation of an incinerator of this type, the waste material or garbage is inserted by means of the loader into one end of the primary chamber where it is ignited initially by some sort of avail~
able hydrocarbon fuel~ Once the initial charge has been ignitedt air is supplied to the primary chamber to maintain combustion of the garbage~ ~s additional garbage is in-serted in tHe inlet by the loader, the ~urning and consumed garbage is propelled down the length of the primary chamber from left to right as viewed in Fig. 1 with the waste products being dellvered to an automatic ash removal means 28 while the partially combusted waste gases pass from -the primary chamber 16 into the secondary chamber 18 in which further combustion of -the gases takes place. The waste gases are then vented through the outlet 22, the stack 24 ~L.~ '7~

to a boiler 26 in which the heat of the waste gas is re-covered.
Turning now to Fig. 2, there is shown a vertical section taken through the primary chamber 16 and the secondary chamber 18 lengthwise of the incinerator 1~.
Fig. 3, which is a sectional view taken on line 3-3 of Fig~ 2, discloses the shape of the primary chamber 16 and the secondary chamber 18 as being generall~ cylindrical.
The primary chamber 16 is formed with an outer cylindrical steel wall 16a which is lined with refractory material 16b.
The primary chamber 16 is formed with an entrance opening 16c which in one constructed embodiment was approximately 3 feet high and 5 feet wide. A vertically movable sliding door 16d serves as a closure for the opening 16c and is movable between the closed position shown in Fig. 2 to an elevated in which free access is provlded to the opening 16c. In the load position, the ram 20a of the automatic inline loader 20 is retractable to permlt a charye of garbage to be placed between the ram 20a and the door 16d.
When the ram 20a is advanced, it moves the load to a posltion well within the primary chamber 16 before it is withdrawn and the door 16d is moved to the closed position.
The bottom of the primary chamber 16 is defined hy a horizontal hearth 30 which ls formed in three steps to provide an entrance hearth 32, an lntermediate hearth 34 and an exit hearth 36~ In one constructed embodiment, the various portiOns of the hearth 32, 34 and 36 were 110 in. t 75 in. and 80 in., respectively, in length and differed in helght between each by 16 in~ Each of the 3Q sections of the hearth 30 are supported by a series of transversely extending I-beams. The transversely e~tending I-beams in turn support the network o~ air distrlbuting and water cooling pipes, In order to better understand the constructlon of the hearth and the manner of coollng~ reference should be made to Fig. 4 whe.rein the piplng for the hearth 30 is shown in detall~ The water cooling pipes are designated generally by reference numeral 38 and include longitudl-nally extending and parallel spaced pipes 38a in the entrance hearth 32, 38b in the intermediate hearth 34 and 38c in the exlt hearth 36.
The layout of the water coollng pipes 38 is essentially identical in all three hearth por-tlons except for the length of the plpes 38a, 38b and 38c slnce the entrance zone is longe.r than elther of the other two zones and the exit zone is slightly longer than the inter-mediate zone, as explalned above. The plpes 38a in the entrance hearth are supplled wlth cooling water through a supply pipe 38d and each of the adjacent lengths of pipe 38a are lnterconnected by 180 conduits 38e~ The entrance or supply pipe 38d extends entirely across the front edge of the step between the entrance hearth and the inter~
mediate hearth. as is best shown in Flgs. 2 and 4~ The purpose of th.ls transverse length of the supply pipe 38d 20. is to cool the nose o.r step bet~een the two hearths. The pipe 38d actually runs beneath the looped ends 38e which interconnect the inner ends of the pipes 38a~
For -the purpose of illustration/ the pipes in the thre.e hearth portions 32, 34 and 36 are shown in Fig. 4 as not overlapping. Actually, as is evident from Flg. 2, the pipes on each of the upper hear-ths 32 and 34 overlie the ends of th.e pipes in the adjacent lower hearths for reasons which will ~ecome more apparent as the description proceeds.
The intermediate hearth 34 is also formed with a total of 14 lengthwise extending sections of water cooling pipe. 38~, each of which is connected at both end.s to i-ts adjacent sections ~y 18Q~ connectors 38f to form a con-tinuous length of pipe to cool the entire intermediate hearth portion 34. The pipe in the in-termediate hearth portion 34 is connected at its inlet ~y conduit 38g from 3~

the lowermost conduit 38a of the hearth 32 as shown in Fig.
4 with the conduit 38g across the width of the hearth beneath the ends of the connected pipes 38b to supply water to the uppermost pipe 38b as shown in Fig. 4. The position of conduit 38g below the level of the other pipes in the in-termediate llearth 34 is best shown in Fig.

2. At its outlet, the water cooling pipes in the inter-mediate hearth 34 are connected by a conduit 38h to -the longitudinal pipes 38c in the exit hearth 36. The number of pipes 38c correspond to those in the intermediate hearth 34 and entrance hearth 32 and are connected by 180 con-duits 38j. As in the case of the other hearths, the supply conduit 38h for the exit hearth 36, traverses the hearth at a lower level than -the other pipes 38c provided therein as is best shown iII Fig. 2.
Referring to Figs. 7 and 8, there is a showing of the-manner in which the wate:r cooling pipes 38 are secured to and suppoxted by a network of air supply pipes 4~ The layout of the air supply pipes 4Q is shown in a some~hat fragmentary fashion in Fig. 4 in order to indicate -the number and arrangemen-t of the pipes. In contrast to the ~ater cooling pipes 38 which extend lengthwise of the furnace, the network of air supply pipes 40 is formed of transyersely extending parallel spaced pipes ~Oa which 25 are interconnected by 180 connectors 40b to form a con-tinuous air canduit for each of the hearths 32, 34 and 36.
~s~ shown in Fig. 7 ~ the air supply pipes 4Oa are provided with threaded studs 42 which are welded to the upper surface of the pipes 40a and are positioned to extend 3Q between the water cooling pipes such as 38b shown in Fig.
7r The adjacent water cooling pipes 38b are formed with welded connecting webs 44 having elonyated apertures 44a through which the studs 42 may extend for connection with an assem~ly nut 46~ The elongated opening is positioned to ~ccom~oda-te expansion which takes place between the '7~73~

various sections of air and water pipes imbedded in the hearth 30.
For a better understanding of the manner in which the network of air supply pipes 40 is disposed with respect to the water cooling pipes 38, reference may be had to Fig. 2 where the transversely extending pipes 4Oa are shown in section supporting the dotted line showings of the water cooling pipes 38a, 38b and 38c. While con~
sidering the details of the water cooling pipes 38, it should be noted that the pipes 33a, 38b and 38c are pro~
vided with rails 48 which serve the dual purpose of pro-viding a wear plate and transmitting or conducting heat between the pipes 38 and the surface of the hear-th. The rails 48 are welded to the pipes as shown best in Fig. 7.
The fragmentary section view of Fig. 9 also shows the manner in which the water cooling pipes and air supply pipes are arranged i.n the hearth. ~efractory material 50 is filled in between both the air pipes and the water pipes to provide a smooth, solid hearth with the network of air supply pipes 40 and water cooling pipes 38 imbedded therein~ The surface of the refractory material 50 is made flush with the top surface of the rails 48 secured to the water cooling pipes 38~
It should be understood that the cooliny pipes 38 may he oriented transversely of the hearth rather than longitudinally thereof and in such cases it may be prefer-able to use rectangular -tubing rather than the circular cross section pipes shown.
The only interruption in the surface of the 3Q hearth is that provided by the openings through which the air supplied by the pipes 40 is discharged through the hearth~. As best shown i.n Fig~ 10, the air supply pipes 48 are formed with nipples 40c which are threadedly received in the top of the pipes 4Qa and provided with elbows 40d at their upper ends~ The refractory material SO of the hearth is essentially flush with the upper edge of the elbows 40d. Smaller pockets 50a are formed in the refrac-tory to permit discharge of the air from the pipes 4Oa through the nipples 40c and the elbows 4~d. These elbows 4Od are arranged to be directed downstream of the :Elow of garbage through the primary chamber 16 to minimize the tendency of material to obstruct the Elow of air from -the pipes 4Oa.
Referring again to Fig. 2 and the general organ-ization of the incinerator 14, the primary chamber 16 is formed with an exit opening 52 at the riyht end thereof as viewed in Fig. 2. The exit opening 52 connects with a funnel-like portion 54 which discharges to the automatic as-h removal 23 referred to above. Adjacent the exit open-ing 52 there is an access opening 56 closed by a door 58 wh.ich may be removed so that the interior of the incinera-tor 14 may be serviced or large clinkers may be removed.
Immediately above the exit opening 52 there is provided a gas discharge opening 60 which permits gases to flow from the primary chamber 16 to the secondary chamber 18.
: Refore considering the details of the secondary cham~er 18, it shoul.d be noted that the primary chamber 16 is provided with a burner 62 which is supplied with natural gas or other suitable fuel in order to initially ignite the garbage placed in the incinerator l~. As ind.~Gated above, once th.e garbage has been thoroughly ignited by the burner 62, the air supply through the hearth 30 maintains combustion of the garbage without the use of any external fuel, The garbage is partially pro-3Q pelled through the primary chamber 16 from left to rightby the loading ram 20a as it pushes additional loads of garbage onto the entrance hearth 32. As the partially consumed garbage falls over the step between the entrance hearth.32 and the intermediate hearth 34, it is further propelled through the incinerator 14 by means of an upper

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plow or ram 64. A reciprocating drive shaft 64a is pro-vided with means to remove the ram 6~ across the surface of the intermediate hearth 34 to progress the burning garbage and ash through the incinerator 14 The front edge of the entrance hearth 3~, adjacent the step ~e-tween the hearths, is provided with a high temperature castable refractory nose 66 within which the water cooling pipe 38d is positioned. As shown in Fig. 2, -the nose 66 directly overlies the refractory face of the ram 64 in its retracted position. The cooling water pipes in the intermediate hearth 32 extend beneath the nose 66 and the pipe 38d thus providing cooling above and below the ram 64 to minimize overheat conditions.
Similarly, the exit hearth 36 is provided with a lower ram 68 driven by a reciproca-ting shaft 68a which drives the ram 68 to traverse the entire exit hearth 36 and c~use the ashes positioned thereon to be discharged to the exit opening 52. The edge of the intermediate hearth 34 adjacent the step ~etween the exit hearth 36 is provided ~ith a castab'e refrac-tory nose 70 ~ithin which the water cooling pipe 38g is received. The water cooling pipes in the exit hearth 36 extend beneath the refractory face of the lower ram 68 to provide ade~uate cooling of the ram 68 and the step between the hearths. A similar construction is used in the edge of the exit hearth 36 adjacent the exit opening 52.
The use of the water cooling pipes 38 arranged as shown in Fig. 4 and disposed in intimate engagement wi:th the refractory material 50, permits cooling the surface of the hearth to a temperature below l,OOQF~
It has been discovered that at this temperature the melted glass and other materials which might stick to or attack eithe~ the refractory or rails imbedded thereln tend to ball up and not wet the surface of the hearth~ In so doing, the materials neither stick -to nor a-t-tack -the t~-7 ~V

surface of the hearth and may be moved through the furnace as they ~re consumed as much as possible and discharged as ash or clinkers through the exit opening 52.
It should be noted that the pipes 38 may be supplied with a cooling media other than water, as for exam-ple air, oil or other known gases or liquids which have been used for such heat e~change purposes.
The gas which is discharged from the primary chamber 16 is further oxidized in the secondary chamber 18. The secondary chamber 18 is made to provide sufficient volume for good mixing and complete combustion of the gasesO
The secondary chamber 18 is provided with burhers 7Z
immediately above the opening 60. These burners are to assure ignition and combusti.on of the gases flowing there-through. Air is introduced into the secondar~ chamber 18 thxough a first series of openings 74, a second series of tangential openings 75 and a third series of forwardly projecting openings 76~ The air openings 74 are supplied by air de.livered to a plenum 78 while an annular plenum 20 80 deli:vers air to the openings 75 and 76~ The conEigura-tion of the tanyentially disposed openings 75 is shown in Fig. 6.
The secondary chamber 18 is of similar construc-tion as the primary chamber 16 having a steel outer shell.
82 and a refractory lining 84, ~t the end of the secondary chamber remote from the inlet opening 60 there i.s provided an outlet ~pening 86 which interconnects with the previous-ly described conduit 22 which in turn connects to the stack 24 and the heat recovery boiler 26, 3Q The described incinerator 14 wi-th the cooling pipes 38 positioned in the hearth. 30 provides a novel and improved incinerator which eliminates many of the problems encountered in prior art incinerators in which deteriora tion of the hearth occurred as a consequence of sticking or adherence of mater.ials to the surface of -the hearth~

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A controlled air incinerator comprising an elongated housing having a load end provided with a door through which material to be incinerated may be introduced into the housing, said housing having a discharge opening at the end remote from said door, a hearth extending from said door to said discharge opening to support material being incinerated, burner means to ignite said material upon introduction into said housing, air supply means to deliver air through said hearth for oxidation of said material, said hearth including spaced cooling pipes extending lengthwise in said housing for cooling said hearth, means for circulating a cooling media through said pipes, said pipes being disposed in a horizontal plane with refractory filling the space between said pipes to form a continuous cooled horizontal hearth surface, said air supply means including conduit means extending through said refractory between said pipes to supply air at multiple positions across said hearth.

2. The incinerator of claim 1 including a waste gas combustion chamber which is coextensive with said housing and extends along the top thereof, said combustion chamber communicating with said housing through an entrance opening adjacent said discharge opening and having an exit opening at the end remote from said entrance opening, controlled air supply means in said chamber to introduce and mix air with the gas from said housing to complete oxidation thereof before discharge to the atmosphere through said exit opening.

3. The incinerator of claim 1 wherein said hearth is divided into a plurality of portions positioned at different levels, said hearth portions each being lower from an entrance hearth portion extending from said door to an exit hearth portion adjacent said discharge opening, a loading ram associated with said door for introducing material into said housing and additional rams associated with each other hearth portion to move combusting material toward said discharge opening, said cooling pipes in each of said other hearth portions extending toward said door beneath the additional rams and hearth portions.

4. The incinerator of claim 1 wherein said cooling pipes are provided with plates disposed on top of said pipes and secured in good heat transfer relation therewith, said plates being positioned flush with the surface of the refractory portion of said hearth.

5. The incinerator of claim 1 wherein said air supply means includes transversely extending air supply pipes positioned below and supporting said cooling pipes, means connecting cooling pipes to said air supply pipes, said connecting means accommodating the expansion of said cooling pipes.

6. The incinerator of claim 5 wherein said air supply pipes include vertical pipes extending from said transverse pipes through said refractory between said cooling pipes.

7. The incinerator of claim 6 wherein said vertical pipes include discharge nozzles which direct the air flow horizontally in the direction of garbage movement through said incinerator and into pockets formed in said refractory at the surface of said hearth.

8. A controlled air incinerator comprising an elongated housing having a load end provided with a door through which material to be incinerated may be introduced into the housing, said housing having a discharge opening at the end remote from said door, a hearth extending from said door to said discharge opening to support material being incinerated, burner means to ignite said material upon introduction into said housing, air supply means to deliver air through said hearth for oxidation of said material, said hearth including spaced cooling pipes for cooling said hearth, means for circulating cooling water through said pipes, said pipes being disposed in a hori-zontal plane with refractory filling the space between said pipes to form a continuous cooled horizontal hearth surface, said air supply means including conduit means extending through said refractory between said pipes to supply air at multiple positions across said hearth, said conduit means being formed with nozzles directing the flow of air in a direction away from the movement of garbage through said incinerator, a pocket formed in said refractory into which said air is discharged at each nozzle.

9. The incinerator of claim 8 wherein said hearth is divided into a plurality of portions positioned at different levels, said hearth portions each being lower from an entrance hearth portion extending from said door to an exit hearth portion adjacent said discharge opening, a loading ram associated with said door for introducing material into said housing and additional rams associated with each other hearth portion to move combusting material toward said discharge opening, said cooling pipes in each of said other hearth portions extending toward said door beneath the additional rams and hearth portions, each hearth portion ending in a nose of high temperature cast-able refractory at the step between hearth portions and at the exit opening, a transverse cooling water pipe in each said nose.

10. The incinerator of claim 8 wherein said cooling pipes are provided with elongated heat transfer plates secured to the top surface of said pipes and positioned flush with the surface of the refractory portion of said hearth, said plates being coextensive with said lengthwise extending pipes and having substan-tially the same width as said pipes.

11. The incinerator of claim 8 wherein said air supply means includes transversely extending air supply pipes positioned below and supporting said cooling pipes, said conduit means and nozzles being mounted in spaced relation along said pipes, means connecting cooling pipes to said air supply pipes, said connecting means accommodat-ing the expansion of said cooling pipes.