US2719497A - Metallic trash burner - Google Patents

Description

5 Sheets-Sheet l Filed Jan. 24. 1951 OOOOOOOOO OOOOOOO FREDERICK R. HOOK ATTORNEYS Oct. 4, 1955 F. R. HocK ETALLIC TRASH BURNER 5 Sheets-*Sheet 2 Filed Jan. 24, 1951 O O O O O OOO O OOOOO O OOO INVENTOR FREDERICK R. HOOK E N R O T.. T. A

Oct. 4, 1955 F, R HOCK 2,719,497

METALLIC TRASH BURNER Filed Jan. 24, 1951 5 Sheets-Sheet 3 FIG-3.

INVENTOR FREDERICK R. HOOK ATTORNEYS Oct. 4, 1955 F R, HOCK 2,719,497

METALLIC TRASH BURNER Filed Jan. 24, 1951 5 Sheets-Sheet 4 FIG. 6.

FIG. 5.

IN VENTOR FREDERICK R. HOCK ATTORN E Y-S Oct. 4, 1955 F, R HOCK A 2,719,497

METALLIC TRASH BURNER Filed Jan. 24, 1951 5 Sheets-Sheet 5 FIG.7.

INVENTOR FREDERIQK R. HOCK United rates Patent C METALLIC TRASH BURNER Frederick R. Hock, Bethesda, Md.

Application January 24, 1951, Serial No. 207,641

Claims. (Cl. 11G- 18) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The invention relates generally to a metallic device for burning trash such as paper, rags, boxes and similar refuse, and more particularly to a metallic trash burner having a metal casing comprising a double-walled shell through which air is passed for keeping the outer casing-wall comparatively cool, and having means for cooling and cleaning the combustion gases before they leave the trash burner.

The invention in its broader aspects is of general use for burning trash, but in its preferred form herein de* scribed, it is primarily for burning trash on board ships. For such use, it is desirable that a trash burner be small in size, light in weight, safe to operate, and effective for completely burning the trash fed to it. In many instances it is also desirable to have the combustion gases discharged clean and cool, substantially free from smoke and sparks, It is a primary object of this invention to provide an improved trash burner having the foregoing characteristics; the novel trash burner being relatively very small and compact for the lar e rate at which it can satisfactorily burn trash.

In accordance with the invention, the walls of the trash burner are of sheet metal, insofar as practical. A double-walled shell defines the combustion chamber and has passages about the combustion chamber through which cooling air can pass at a high velocity so as to keep the inner wall of the shell at a temperature low enough to discourage oxidation of the wall without overheating the outer wall. Convection tins between the walls of the shell increase the cooling action. The shell construction is such that a part of the cooling air, after it has heated up some, is diverted into the combustion chamber as a supply of pre-heated air for combustion. The pre-heated air passes into the combustion chamber in the form of jets that cause a turbulence in the combustion zone for improved burning of the trash.y

Further in accordance with the invention, the novel trash burner has a discharge duct-passage for combustion gases. This duct-passage includes a controllable gascooler means and a gas-cleaner means compactly arranged at the back of the trash burner. The gas-cooler means is of a type that mixes external air with the hot combustion gases.

Another important feature of the invention resides in the arrangement of a forced draft fan and induced draft fan in the duct system of the trash burner in order to obtain high ow of cooling air and of combustion gases through the trash burner. As a consequence, a rate of trash burning can be obtained in the small trash burner provided, that is comparable to that obtained in much larger and heavier trash burners.

Objects, features and innovations of my invention, in addition to the foregoing, will be discernible from the following description of the embodiment thereof at present 2,719,497 Patented Oct. 4, 1955 ICC preferred. The description is to be taken in conjunction with the accompanying drawings in which minor details have been omitted in the interests of clarity of illustration. In the drawings:

Fig. l is a vertical sectional view through the forward section of a trash burner embodying the invention;

Fig. 2 is a vertical sectional view at right angles to that of Fig. l, and taken substantially on the line II-II of Fig. 3;

Fig. 3 is a horizontal sectional view substantially on l the line III-III of Fig. 2;

Fig. 4 is a rear View, partly in section, substantially on the line IV--IV of Fig. 3;

Figs. 5 and 6 are sectional views partly in elevation, substantially on the lines V-V and VI-VI of Fig. 4, respectively; and

Fig. 7 is a vertical sectional view substantially on the line VII-VII of Fig. 3; and

Fig. 8 is a vertical sectional View substantially on the line VIII- VIII of Fig. 2.

Referring to the drawings which are substantially to scale a compact and light-weight trash burner in accordance with a preferred form of the invention is made mostly of metal sheet suitably shaped and joined to form the required walls of the trash burner. To this end, the trash burner is made in sections and sub-sections. A first of these sections can be identified as the forward section and includes a combustion chamber 11. A second of these sections can be identified as the rear section and includes the major air inlets, the combustion-gas outlet and equipment for forcibly moving the air and combustion gases. A vertical sheet metal central wall 12 of the trash burner divides the forward section from the rear section.

The forward Section of the trash burner The forward section comprises an outer casing 13 and an inner casing 14. The central wall 12 forms the outer back wall of the outer casing 13. In addition to its back Wall 12, the outer casing comprises a vertical sheet metal front wall 15 provided with openings for a firing-door assembly 16 and an ash-door assembly 17, and a sheet metal, outer casingwall 18 which is oval-shaped in vertical cross-section and extends to and between the walls 12 and 15, being carried thereby.

The inner casing 14 is carried inside the outer casing 13 in spaced relation thereto so as to provide a doublewalled arrangement, identified for convenience as a shell. The double-walled shell contains the combustion chamber 11 and an ash pit 22 therebelow. The walls of the inner casing 14 are of sheet metal, and comprise an oval-shaped inner shell-wall or inner casing-wall 23 parallel to but shorter than the outer casing-wall 18, an inner front wall 24 paralleling the front wall 15 and having a firing-door tube 25 and an ash-door tube 26, and a back wall 27 paralleling the central wall 12. If desired, the lower part of the inner casing 14, at the ash pit 22, may be made shorter than the upper part, as shown in Fig. 2. Such an arrangement provides an enlarged outlet chamber 28 at the lower rear of the forward section of the trash burner.

Opposite sides of the lower part of the inner casing 14 have welded thereto a plurality of stepped metal plates 31 that carry metal shelves 32 and 33. The lower shelves 32 carry a cast iron grate 34 that divides the combustion chamber 11 from the ash pit 22. The upper shelves 33 carry refractory tire-brick walls 35 for a fuel-zone that extends upwards slightly above the bottom of the tiringdoor assembly 16. The fire-brick walls 35 terminate below a plurality of rows of small staggered air-holes 36 in the lower portion of the inner casing-Wall 23.

The space between the outer casing-wall 18 and the inner casing-wall 23 contains a plurality of spaced metal tins 39 that are substantially co-extensive with the wall 23. Each tin has an angular contact-portion or leg 4t) that is secured, as by welding, with good thermal contact, to the outside of the inner casing-wall 23. It is to be observed that the other angular iin-portions or legs 41 of the ns 39 slant with respect to the outer casing-wall 18. The edges of the fin-portions 4.1 are not secured to the casing-wall 18 but press thereon with a spring action so as to permit expansion and contraction of the walls. In a sense the inner wall 23 is floatingly positioned by the ins 39.

Except at the front walls 15 and 24, the space between the inner casing 14 and the outer casing 13 is horizontally divided to form two separate gas duct-passages between the front and rear of the forward section of the trash burner. This separation is effected by an open frame 42 of metal plates which also cooperate to form joints 43 with the metal sheets that form the casings, as more clearly illustrated in Fig. l. As better illustrated in Figs. 2 and 3, the construction described provides a plenum header 44 at the upper rear of the forward section of the trash burner, this header 44 being separated from the lower outlet chamber 28 by the frame 42, and provides a turning chamber 45 at the front of the trash burner, the chamber 45 extending substantially for the full height of the casings. The spaced iins 39 provide a series of narrow longitudinal passages 46 about the inner shell-wall 23. The passages 46 in the upper half of the trash burner communicate or extend between the plenum header 44 and the front turning chamber 45; and the passages 46 in the lower half of the trash burner communicate or extend between the chamber 45 and the outlet chamber 28. Cooling air passes into the plenum chamber 44 through an upper opening 47 in the back wall 12 (Fig. 7), and leaves the outlet chamber 2S through a lower opening 48 in the back wall 12. It should be borne in mind that the back wall 12 of the forward section is the central wall of the trash burner.

Combustion gases, that is, the products of combustion, leave the combustion chamber 11 through an outflow pipe 49 that passes rearwardly through the upper part of the header 44.

The rear section of the trash burner The rear section comprises a compact arrangement of equipment for cooling, cleaning and discharging the combustion gases, and of equipment for feeding and exhausting cooling air to and from the forward section. To this end, the rear section comprises a vertical sheet metal side wall 52 extending backwardly from the central wall 12 of the trash burner, and an intermediate sheet metal wall 53 that parallels the side wall S2, as better shown in Figs. 3 and 4. A sheet metal back wall 54 and a bottom wall 55 are secured to the walis 52 and 53 to provide an opentopped duct compartment 56 at the rear of the central wall12.

The upper part of the duct compartment 56 carries a profusely perforated, five sided, sheet metal liner 57 or mixing box that is open on its bottom side. A short tube S extends from an upper part of a side of the liner 57 and is, in eect, an extension of the outflow pipe 49, so that the combustion gases flow into the liner 57. The gases are drawn downwardly through the liner 57 by an induced draft fan in a manner that will shortly be apparent. This fan also draws external air through the open top of the compartment 56 and into the liner 57 for diluting and cooling the combustion gases. An adjustable or controllable multivane damper 59 across the open top of the compartment 56 controls the amount of dilution air that mixes with the combustion gases in the perforated liner. The dilution air feeds into the liner 57 along all of its perforated sides which are spaced from the facing portions of the walls of the compartment 56 so that these wall-portions are cooled by the air before it mixes with the combustion gases. The upper part of the compartment 56,

the liner 57 and the damper 59 comprise a controllable gas-cooler means.

The lower part of the compartment 56 contains a gascleaner means of any suitable form. That shown comprises a tangential swirler 62 having deflector-slots 63 around its periphery that turn the downwardly flowing combustion gases into a horizontal path and at the same time impart a rotating component of motion to the gasflow. The circular, ared discharge end 64 of the swirler 62 is tightly secured to small sheet metal walls 65 that cooperate with the walls 53 and 55 to define a small closed clean-out chamber 66 in the lower part of the compartment 56. The clean-out chamber 66 can be provided with any suitable door to provide access thereto for removing accumulated dirt. A short circular tail pipe or tube 67 of smaller diameter than that of the discharge end 64 is arranged co-axially therewith. The tube 67 is spaced from the end 64 and extends through the Wall 53 into the inlet 68 of the induced draft fan 69 which is of a centrifugal type and is arranged alongside the wall 53 and is driven by any suitable means including a coupling shaft 70. The exhaust of the fan 69 connects to a short curved outlet pipe 71 that terminates in an opening in a at vertical frame 72 that is in the upper middle portion of the rear section of the trash burner. A chimney or stack pipe can be connected to the pipe 71.

The main equipment of the rear section is completed by a complete motor-driven axial-flow fan 73 and a sloping air-outlet duct 74. The motor-driven fan 73 comprises a tubular housing or air-supply duct having an open feed end, and has a discharge end that is secured to the central wall 12 about the opening 47 to the plenum chamber 44. The outlet duct 74 has an end secured to the wall 12 about the opening 48 of the exhaust chamber 28. The duct 74 extends upwardly and rearwardly to a second opening in the frame 72, so that the exhaust openings from the duct 74 and the outlet pipe 71 are adjacent. Suitable channels or angles can be carried by the walls ofthe rear section for further supporting the fans and ducts.

Operation Assume that the fans 69 and 73 are operating and that trash on the grate 34 is burning, thereby heating the shell-wall 23.

The fan 73 forces air from its inlet at the upper part of the rear section of the trash burner into the plenum header 44 of the forward section. The air ows under pressure from the header 44 horizontally through the passages 46 in the upper half of the double-walled shell formed by the oval-shaped walls 18 and 23, and into the turning chamber 45. The air then passes down- Wardly into the lower half of the chamber 45, moving around the firing and ash door-assemblies 16 and 17 and associated tubes 25 and 26. The air then passes horizontally through the passages 46 in the lower half of the double-walled shell and into the exhaust chamber 28, from where it leaves the forward section via the outlet duct 74 leading to the upper part of the rear section. In its travel, the air cools the walls of the forward section of the trash burner, and becomes heated, the effectiveness of this action being considerably increased by the fins 39. A large quantity of air is moved so that the walls of the outer casing are kept comparatively cool.

As the air moves through the last portion of its travel` path, through the lower passages 46, some of the air is diverted through the holes 36 in the inner wall 23 and iiows into the combustion chamber 11 as overre air for combustion. The air flows through the holes 36 in the form of strong jets, producing a strong turbulence for the burning gases in the combustion chamber 11 and facilitating complete combustion. A small amount of underre air may be drawn into the combustion chamber through conventional adjustable openings in the ashpit door of the ashdoor assembly 17.

The fan 69 produces a suction that helps draw combustion air through the ash pit door and the holes 36. The main function of the fan 69, however, is to draw combustion gases from the combustion chamber 11 through the gas-cooling means and the gas-cleaning means. To this end the fan draws external air through the damper 59 and into the gas-mixing liner 57. The air mixes with the hot combustion gases, enough air being admitted to bring the resultant mixture to a temperature at which it can ow through the swirler 62 and the fan 69 without damage to the fan. In passing through the swirler 62, the gas-mixture is given a rotational movement. Solid particles and sparks contained in the gas are driven radially outward by centrifugal action, and fly out into the clean-out chamber 66 while cleaned gas ows through the tube 67, the fan 69, and the discharge pipe 71. Accordingly, the rear section of the trash burner comprises a discharge passage for the combustion gases, the passage comprising the gas-cooler means including the liner 57, and comprising a centrifugal-type gas-cleaner means including the swirler 62. The discharge passage is downward along one portion of the rear section, and upward along the lower part of the remaining or second portion of the rear section.

The damper 59 controls the proportion of air that mixes with the combustion gases. Preferably, the vanes of the damper are adjustable from the front of the trash burner through a linkage 75. If desired the linkage can be connected to the door of the firing-door assembly, so that the damper will close when the door is opened, so that blow out through the door is avoided when trash is inserted therethrough.

It is apparent that a trash burner in accordance with the invention is compact, light in weight, and of high capacity. The sheet metal construction has a long life, a large volume of air being passed through the cooling passages 46 for keeping the temperature of the inner casing 14 below the range in which the sheet metal might oxidize or scale rapidly. Only in the fuel zone irnmediately above the grate is it necessary to have weight-increasing fire-brick.

As an indication of the high capacity obtainable with a trash burner in accordance with the invention, a speciiic trash burner having a double-walled shell about 6 feet high and 41/2 feet wide maximum outside dimensions and having a combustion chamber about 31/2 feet long, 31/2 feet wide and 4 feet high from the grate, maximum inside dimensions, was capable of burning about 350 pounds of trash per hour.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

What is claimed is:

1. A trash burner of the type described comprising a double-walled shell including an outer casing, a metal sheet inner casing spaced from said outer casing for defining a controlled air cooling passage therebetween, a horizontal dividing means dividing said cooling passage into an upper cooling passage and a lower cooling passage, said shell providing further a front air turning chamber connecting said upper and lower cooling passages, a central wall forming a back wall for said shell, said back wall, said inner casing and said dividing means providing an upper plenum header and a lower outlet chamber each of which are respectively connected to said upper cooling passage and said lower cooling passage, means defining a combustion chamber and an ash pit within said shell, said inner casing having a plurality of overire holes formed therein adjoining the lower cooling passage communicating with said combustion chamber and said lower cooling passage, a forced air means for supplying air to said cooling passage and to said combustion chamber 6 through said overfire holes, said lower outlet chamber' having an outlet, said air from the forced air means agitating the combustion gases within the combustion chamber for fast and complete combustion, and a discharge means connected to said combustion chamber comprising passage means including a gas-mixing chamber and centrifugal gas-cleaning means and an induced draft fan for drawing gases from said combustion chamber and said gas cleaning means.

2. A trash burner as defined in claim l but further characterized by said discharge means including a duct compartment having an opening therein to the atmosphere, adjustable means controlling said opening, a perforated mixing box within said compartment adjacent said adjustable opening, said mixing box communicating with said discharge means whereby cooling air entering the adjustable opening passes through said perforated mixing box to combine with and cool the combustion gases passing therethrough, a deiiecting means associated with said discharge means including means for directing the path of movement of the combustion gases leaving the mixing chamber, and a clean out chamber interposed between said deliecting means and said induced draft fan.

3. A lightweight forced air cooled high capacity trash burner comprising, a metal sheet inner casing including means defining a combustion chamber and an ash pit, a metal sheet outer casing spaced from and completely surrounding said inner casing for forming an air passage therebetween, a cooling means for said inner casing comprising an air supply duct extending from the exterior of said outer casing to said air passage for supplying forced air thereto, separating means dividing said air passage into upper and lower communicating portions, iin means positioned longitudinally between said inner and outer casing for controlling the movement of forced air within said air passage, and an air outlet duct extending from said lower air passage portion to the atmosphere, said inner casing having overfre means formed therein, said overire means communicating with the lower air passage portion and said combustion chamber for supplying heated air to said combustion chamber and for agitating burning gases in said combustion chamber, and separate forced draft means extending between the exterior of said outer casing and said combustion chamber.

4. A lightweight forced air cooled high capacity trash burner as defined in claim 3 but further characterized by said iin means having a iirst longitudinal portion secured to one of said casings and having a second longitudinal portion abutting the other of said casings whereby the iin means are operative to oatingly support said inner casing and combustion chamber within said outer casing.

5. A trash burner of a type described comprising a forward section and a rear section having a metal separating wall therebetween, said forward section comprising a double-walled shell including a metal outer casing, a metal inner casing spaced from said outer casing for de iining a controlled air cooling passage therebetween, a plurality of fins in said passage secured to said inner casing, each of said fins having a spring action and engaging said outer casing for iioatingly positioning the inner casing within said outer casing, said metal separating wall forming a back wall for said shell, said shell including means defining a combustion chamber and an ash pit, said inner casing having a plurality of holes therein communicating with said cooling passage and said combustion chamber for a supply of heated overiire air from said cooling passage to said combustion chamber, said rear section comprising an air supply duct communicating with said cooling passage for supplying forced air to said cooling passage and said holes, said rear section further comprising an induced draft discharge passage communicating with said combustion chamber for combustion gases from said combustion chamber, said discharge passage having gas-cooling means and gas-cleaning means therein.

6. A trash burner of a type described comprising a forward section and a rear section having a central wall therebetween, said forward section comprising a doublewalled shell including a metal sheet outer casing, a metal sheet inner casing iioatingly positioned within said outer casing and spaced therefrom to provide controlled air cooling passages therebetween, a horizontal metal sheet dividing means interposed between said inner and outer casings for dividing said cooling passages into an upper portion and a lower portion, said shell having a front airturning chamber connecting said portions, said central wall forming a back wall for said shell, and forming with said casings and dividing means an inlet and an outlet chamber for said controlled air cooling passages, said shell including means defining a combustion chamber and an ash pit, said rear section comprising an air supply duct communicating with the atmosphere and said inlet chamber for supplying air under pressure to said inlet chamber and said upper portion of said cooling passages and comprising an air outlet duct connected between said outlet chamber and atmosphere for exhausting air from said outlet chamber and said lower portion of said passages, said ducts being at a first side of said rear section, said rear section further comprising a discharge passage communicating with said combustion chamber for combustion gases from said combustion chamber, said discharge passage comprising an open-topped compartment along a second side of said rear section, said discharge passage further comprising a gas-mixing chamber, centrifugal gas-cleaning means, and an induced draft fan serially connected together for drawing gases from said gas-cleaning means and said combustion chamber.

7. A trash burner as defined in claim 6 but further characterized by said inner casing having a plurality of small holes therein communicating with said combustion chamber and said cooling passages for a supply of overfire air from said cooling passages to said combustion chamber.

8. A trash burner of a type described comprising a forward section and a rear section having a central wall therebetween, said forward section comprising a doublewalled shell including an inner metal sheet casing, an outer metal sheet casing spaced from and completely surrounding said inner metal sheet casing for defining a controlled air cooling passage therebetween, spring action means in said passage secured on one of said casings for maintaining said casings in separated relation, said shell including means defining an interior combustion chamber, a horizontal dividing means dividing said cooling passage into an upper portion having a plenum header at said central wall and a lower portion having an outlet y chamber below said plenum chamber, said casings providing an air-turning chamber at the front end of said shell, said rear section comprising a forced air supply duct to said header and an air outlet duct from said outlet chamber.

9. A trash burner as defined in claim 8 but further characterized by said inner casing having a plurality of holes formed therein adjoining the lower portion of the cooling passage, said overfire holes communicating with said combustion chamber and said lower portion of the cooling passage for supplying heated overfire air from said cooling passage to said combustion chamber.

10. A trash burner as defined in claim 8 but further characterized by said spring action means comprising a plurality of longitudinal fins in the space between said metal sheet casings, each of said fins being secured to one of said casings and engaging the other of said casings for fioatingly supporting said inner casing within said outer casing.

11. A trash burner as defined in claim 8 but further characterized by said spring action means comprising a plurality of longitudinal fins positioned in the space between said casing-walls, each of said fins being transversely angular, having a leg secured to a first of said 8 walls and another leg edgewise substantially abutting the second of said casing-walls, said fins being operative to control the movement of forced air in a predetermined path, transfer heat energy to the forced air, and support said inner casing within said outer casing.

12. A trash burner as defined in claim 8 but further characterized by said spring action means comprising a plurality of longitudinal fins positioned in the space between said casing-walls, each of said fins being transversely angular, having a leg secured to a rst of said casing-walls and another leg edgewise substantially abutting the second of said casing-walls, the last said legs being at an angle to said second casing-wall.

13. A trash burner of a type described comprising a forward section and a rear section having a separating wall-means therebetween, said forward section comprising a generally oval-shaped, double-walled shell including a metal outer casing and a metal inner casing spaced from said outer casing for defining an air-passage therebetween, a metallic front wall for said shell, a plurality of spaced fins in said air-passage secured to one of said casings and engaging the other of said casings, said separating wall comprising a metal sheet back wall for said shell, means comprising a grate providing an upper combustion chamber and a lower chamber inside said inner casing, said inner casing having a plurality of holes therein above said grate and establishing air-communication between said air-passage and said combustion chamber for a supply of heated overfre air, means comprising an air supply duct communicating with said air-passage for supplying air to said air-passage, said holes being spaced from said air supply duct whereby supply air is preheated before fiowing through said holes, said rear section further comprising an induced draft discharge passage communicating with said combustion chamber for removing combustion gases from said combustion chamber, said discharge passage terminating at a discharge outlet and having gascooling means and gas-cleaning means.

14. A light-weight metallic trash burner operative to burn a large quantity of trash with a minimum use of tire brick comprising a generally oval-shaped double-walled metal shell comprising a longitudinal metal sheet inner casing-wall and a longitudinal metal sheet outer casingwall, a metal back wall and a metallic front wall7 said inner and outer casing-walls being spaced to define a passage for Aair therebetween, said passage having an inlet and an outlet for cooling air, means comprising a grate providing an upper combustion chamber and an ash pit inside said inner casing-wall, a plurality of spaced fins positioned between said casing-walls for guiding the movement of the air in said passage, said fins being secured to one of said casing-walls and engaging the other of said casing-walls, and a section of fire brick along a minor portion of said inner casing-wall immediately above said grate.

15. A trash burner as defined in claim 14 but further characterized by said inner casing-wall having a plurality of overre holes above said fire brick section for establishing air communication between said passage and said combustion chamber.

References Cited inthe file of this patent UNITED STATES PATENTS 955,199 Piper Apr. 10, 1910 1,194,385 Hoover Aug. 15, 1916 1,932,759 Vincent Oct. 31, 1933 1,937,095 Prat Nov. 28, 1933 2,212,222 Austin Aug. 20, 1940 2,254,383 Nelson Sept. 2, 1941 2,299,901 Johnston Oct. 27, 1942 2,327,197 Lincoln Aug. 17, 1943 2,515,869 Gregg July 18, 1950 2,527,934 Jeffries Oct. 31, 1950

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