US2992637A - Stoker system for burning bituminous coals or the like - Google Patents

Description

July 18, 1961 J. w. TIEMAN ETAL 2,992,637

STOKER SYSTEM FOR BURNING BITUMINOUS GOALS OR THE LIKE Filed May 21, 1957 5 Sheets-Shet 1 FIG INVENTORS JOHN W. TIEMAN 8:

JAMES R. GARVEY July 1 1961 J. w. TIEMAN ETAL STOKER SYSTEM FOR BURNING BITUMINOUS COALS OR THE LIKE Filed May 21, 1957 3 Sheets-Sheet 2 M 1 m 3mg 6 9 W 7 n w w W 3/ I n 4 I r m w@@@ m a M @QQ v w QQQ m WwQQQ 2 m a3 a? a m QQQ m @QQ m a Q in INVENTORS JOHN W. TIEMAN 8 JAMES R. GARVEY keyw w July 18, 1961 J. w. TIEMAN ETAL 2,992,637

STOKER SYSTEM FOR BURNING BITUMINOUS COALS OR THE LIKE Filed May 21, 195'? 3 Sheets-Sheet 3 @N unpfleoo 0 eodooooooo\e oooooo@0o ooooooa oowo V n do e I eeoooaoooooaoeoooceoeeoooeoooooeooooeooooooooooo v9" Q55 :1 9E2): a

I ooooeeooeooeoeooeoooeeooooeeoeeeooooooooaaooooeo N ueooeoooeooooesoeooeooooeeeoooeoeoooooeoooooaoeon C l C C C @000OOOOGOQOQOOOQGOOGOGOGOQQOQGQOOOOGGOGGOOOG000m OO009000000000000000000009GGQQQQQGGOOQQGOQOOGOOO 099G000GGQGQGGGOGOOGGOGOBOOODQ mu m INVENTORS JOHN W.

2,992,637 STOKER SYSTEM FOR BURNING BITUMINOUS GOALS OR THE LIKE John W. Tiernan and James R. Garvey, Columbus, 01110,

assignors to Bituminous Coal Research, Inc., Pittsburgh, Pa., a corporation of Delaware Filed May 21, 1957, Ser. No. 660,662 2 Claims. (Cl. 122-376) This invention relates to a new stoker for burning bituminous coal or the like in a boiler, furnace, or other equipment. More particularly, this invention pertains to means enabling caking and coking bituminous coals to be burned for relatively lower pressure steam and for hot water production and for heating purposes for use, for example, in smaller industrial and institutional buildings and enterprises.

Owing to the wide range of bituminous coals and the varying characteristics thereof among those ranging from ones which are relatively free burning and ones which are strongly caking, coking or which form clinker masses, the burning of such coals especially when from more than one mine area has given rise to a great deal of difiiculty in terms of troublefree performance particularly in smaller installations. The problem is complicated in many places by the need to reduce the heat released by a live fuel bed of such fuel as during a holdfire without either a cessation of combustion or a loss of ignition either or any undue building up of agglomerated masses of caked material, or coke, or ash on the stoker grate.

In the new stoker system of this invention, such difiiculties have been overcome and this invention enables bituminous coals of widely varyingcharacteristics to be used successfully. Other objects and advantages of this invention will be apparent from the following description and from the accompanying drawings, which are illustrative of one embodiment only, in which FIGURE 1 is an end view of the front of a fire tube boiler to which a new stoker of this invention has been applied in the illustrative form of a cross-feed stoker, with a portion of the boiler foundation removed to show the stoker in position in the firebox of the boiler;

FIGURE 2 is a side view of the embodiment shown in FIGURE 1 with a portion of the side of the boiler re moved to illustrate the gas flow therethrough;

FIGURE 3 is a section taken along line III-III of FIGURE 2;

FIGURE 4 is a plan view of the stoke-r grate and chute guide shown in FIGURE 3 while omitting adjacent mechanism for purposes of clarity;

. FIGURE 5 is a view taken along line V-V of FIGURE 3;

FIGURE 6 is a detail side view of the cam utilized in the illustrated embodiment to provide forward movement with quick terminal release for the grate;

FIGURE 7 is a detail view of a spring assembly for the quick return movement of such grate; and

FIGURE 8 is an enlarged view taken along line VIII- VIII of FIGURE 5.

The drawings illustratively show but one embodiment of a stoker system of this invention portrayed as a cross feed type for use in a fire tube boiler. However, the new stoker system may be embodied in other types of stokers and many be utilized with other kinds of boilers and, in addition, in furnaces and other equipment. In the illustrated embodiment, a fire tube boiler 10 may be set on foundations 11 andhave appliedthereto a new stoker device 12 of this invention with a reciprocable unitary shaker grate 13 extending into the firebox of boiler 10. Boiler 1-0 in the illustrated form is provided with vertical water legs 14 at the sides and ends and a water and steam space 15 between an inner shell 16 and an outer atet shell 17. A firebox is provided in boiler 10 in the space therein and in foundation 11 below a crown sheet 18. A bank of fire tubes 19 communicates with the firebox to afford passage for hot gases therethrough which hot gases are returned by a return dome 20, the upper portion of which communicates with a second bank of fire tubes 21 leading to a stack connection 22. As will be understood, suitable apertures and openings are provided in the boiler for the functioning and maintenance thereof with connections and closures therefor as required. Thus, such connections would include suitable means for supplying water to the water space in boiler 10 and for the removal of either hot water therefrom or steam, or both, dependent upon the kind of service in which boiler 10 is being used.

Our new stoker system 12 is constructed with grate 13 inclined slightly downwardly between the entry or coal feed end 23 and its ash discharge end 24. As shown, grate 13 is double-walled on the bottom 27 and sides 28 thereof to provide for water circulation cooling thereof through pipes 25 and 26 respectively flexibly connected to lower and upper portions of the water-cooling space in boiler 10 and by pipes 25a and 26a to lower and upper portions of the water-cooling space in grate 13 between such double walls respectively. Grate 13 is provided with horizontal trunnions 29 at the upper and lower portions thereof for respectivepivotal suspension of grate .13 by hangers 39, the length of which hangers can be adjusted. The upper ends of the hangers 30 at the upper end of grate 13 are supported by and depend from a mounting plate 31 to each side of grate 13, said mounting plates being affixed to the boiler foundation 11. The hangers 30 connected to the lower end of grate 13 movably depend from rigid brackets 32 extending away from the respective mounting plates 31 to which they are fastened respectively. Thereby, grate 13 is free for limited reciprocation in a longitudinal direction for the feeding of the fuel bed thereon toward the ash discharge end 24 and the feeding of a supply of fresh coal to the upper end of grate 13 through a relatively narrow slot or chute 33 extending substantially across the width of grate 13 between the sides 28. Chute 33 is located at. the lower end of a sloping side hopper connected to the side of boiler 19. Coal to be fed to stoker 12 may be maintained at desired level in hopper 34 either manually or by any of a number of known automatic, semi-automatic or manually controlled conveyor means (not illustrated). In like manner, the ash continuously falling from the discharge end 24 of grate 13 can be removed either manually or by suitable automatic screw conveyor or other known means which are not illustrated herein.

In our new stoker construction 12, the inner side of chute opening 33 is defined by a transversely extending relatively J-shaped guide 35 while the rear or outer side of chute 33 is defined by the lower n'ser portion of a plate 36 attached to the sloping side of hopper 34. Guide 35 is hollow and extends entirely across the distance between sides 28, a coolant like water being circulated through the interior of guide 35 by circulation pipes 37 having suitable valves and flexible portions thereof inasmuch as guide 35 is adjustable in height. As shown, guide 35 is provided holes and engage a threadedopening 41 in the upper end of each of the straps 38: Hence, guide 35 may be fixed horizontally level at a selected heightdependent upon the respective selected holes in the brackets 39 engaging the respective bolts 40*. By such means, the bottom face 42 of guide 35 helps to regulate the fuel flowing out on to the upper coal feed end of grate 13 and thereby generally predetermines the thickness of the fuel bed on grate 13. Normally, a stronger caking bituminous coal has a higher heating value and requires a thinner fuel bed for a given heat demand than the more moderately caking and weaker caking coals which tend to have a lower heating value and normally would require a somewhat thicker fuel bed under such given heat demand condition. In addition, guide 35 keeps the fresh coal adjacent thereto relatively cooler, thereby inhibiting both the occurrence of ignition and burning back into the coal in hopper 34 and the occurrence of higher temperatures in the coal freshly fed to grate 13 which would tend to promote caking or coking, or both, if it should have such characteristics.

As shown, the inner or front end of guide 35 has a sealing toeplate 43 which is watertight and defines the back end of a transverse tubular pipe section 44 through which a supply of overfire air is passed. The front 45 of the overfire air pipe 44 is provided with an inwardly and longitudinally directed, horizontally spaced, series of orifices 46 providing overfire air jets at that location. Instead of such jetting of overfire air, such overfire air may be issued from a slotted opening adjacent the top of a fuel bed passing therebeneath as grate 13 is reciprocated. Such overfire air promotes the rapid ignition of the freshly fed coal and correspondingly minimizes any tendency for the bed to generate smoke and to cake or coke where the coal has such a characteristic. Preferably, the overfire air tube 44 and outlets 46 are located beneath a water leg of boiler 10 as shown in FIGURE 3.

Bulk air for combustion may be supplied to the new stoker system 12 in a variety of ways. In the illustrated embodiment, a fan 47 is mounted on a panel 48 enclosing the lower portion of the front of stoker 12 below hopper 34. An electric motor 49 turns the rotor in fan 47 forcing air into an air tube 50. An adjustable damper valve 51 may be positioned in air tube 50 to adjust the quantity of air admitted to an enclosed plenum chamber or windboX -2 rigidly fastened to the underside of grate 13 and extending generally along the length and across the breadth thereof. Such air windbox 52 supplies undergrate air as the bulk air for combustion which passes upwardly through the hollow tubes or tuyeres 53 into the underside of a fuel bed on grate 13. Such tuyeres 53 are sealed around the outside so that Water between the double walls of grate 13 cannot enter the interior of tubes 53. In addition, the air tube 50 is provided with a pair of branches 54 and 55 which through flexible hose connections denominated 54a and 55a respectively direct air into the ends of the overfire air pipe 44 and into the end of a further overfire air supply pipe 56. The branches 54 and 55 are provided with adjustable damper valves in rigid portions thereof to regulate the quantity of overfire air and further overfire air so supplied, respectively.

The head end 57 of grate 13 is also provided with a double wall so that the coolant may circulate therein, the front of said head end 57 being behind but closely adjacent the back 36 of chute 33. Head end 57 is provided with a plurality of horizontally spaced openings 58 extending longitudinally therethrough so that reciprocable slice bars 59 may be operated through such openings. Each such slice bar is connected at its rear end to a reciprocable rod 60 which extends through a guide 61 fastened to panel 48 at a proper angle. The slice bars 59 on one side of the vertical median plane of stoker 12 are connected to a crossbar 62 which in turn is pivotally connected by a link 63 to a crank arm 64 driven by a shaft 65. The other end of shaft 65 is connected to a like crank arm '64 angularly displaced 180 degrees from the other crank arm so that the slice bars 59 on the respective sides of such median plane alternate in their inward and outward movement during rotation of shaft 65. Shaft 65 is keyed to a spiral gear 66 driven by a pinion train in a gear casing 67 and having a driven shaft 68 which is rotated by a drive pulley 69 connected to a drive shaft in a gear mechanism 70 which is in the assembly with fan 47 and motor 49 in the illustrated embodiment. Such slice bars 59 act as pokers, as the fuel bed is fed downwardly along grate 13, to break up any residual tendency for fuel like bituminous coals to coke or cake in the upper portion of the grate 13, which in turn means that as the fuel bed moves downwardly, such coals act as relatively free burning coals despite any caking, coking or clinkering characteristics that they might have had.

Drive pulley 69 is rotated by the rotation of motor 49, the shaft of fan 47 extending into gear mechanism 70 for that purpose. Fan 47 is provided with an outlet 72 and connected to the outer end of air tube 50 by a flexible hose connection section 73. Provision is made in gear mechanism 70 for any desired adjustment of the speed of rotation of shaft 65, or the pulley ratio can be changed between mechanism 70 and the gears in gear box 67 to accomplish the same result.

The reciprocation of grate 13 in stoker 12 may be accompilshed by a number of means. As shown, grate 13 is normally held in its rearmost position by rods 74 which are properly bushed as they pass through panel 48. The outer ends of rods 74 are affixed to spring retainers 75 for springs 76 which extend between the panel 48 and the respective retainers 75. In addition, a rod 77 is also aflixed centrally to head 57 of grate '13 with the outer end of rod 77 also extending through panel 48. A lever 78 is pivotally connected to a post 79 secured to panel 48 and resiliently connected to rod 77. The lower end 80 of lever 78 is acted upon by a cam 81 or other means periodically in such timing cycle as may be suitable, through gear mechanism or otherwise as will be understood by those skilled in the art. Hence, upon the counterclockwise rotation of cam 81 as viewed in FIGURE 6, end 80 of lever 78 will be moved toward panel 48 compressing the springs 76 and moving grate 13 forwardly a predetermined distance because of the connection of lever 78 to rod 77 When end 80 drops into the fall portion 82 of cam 81, the springs 76 will quickly reciprocate grate 13 back to its rearmost position. The extent of movement of grate 13 may be varied by adjustment of the resilient connection between lever 78 and the rod 77. In the course of such reciprocation of grate 13, a fuel bed is moved downwardly toward ash discharge end 24 and fresh fuel like bituminous coal in hopper 34 passes through the chute slot 33 on to the entry end of the grate 13, such reciprocation of grate 13 not being interfered with in any manner by the operation of the slice bars 59.

For the further regulation and inhibition of coking, caking or clinkering conditions, as the case may be in connection with the particular bituminous coal or the like fed to our new stoker system 12, we provide a baflle member 83 which, as shown, is hollow and supported by pipes 84 and 85 in position adjacent and above grate 13. A further overfire air supply pipe 56 is connected to the back or out-ward part thereof toward the rear or upper portion of gate 13. Further overfire air supply pipe 56 is preferably provided along its length with outlet jets 87 directed so as to supply such further air for combustion to the fuel bed on grate 13. The respective pipes 84 and 85 may be connected in sealed relation to the water space in boiler 10 for circulation of water therethrough, thereby obtaining additional liquid capacity in the boiler as well as maintaining baflle member 83 in a suitable condition to protect it from the heat of burning gases from the fuel bed on grate 13. An adjustable length 86 of relatively universal flexible pipe with a sealed telescoping section is provided in pipe 84 intermediate the ends thereof so that the position of baffle 83 may be adjusted. Baflie 83 may be made of refractory instead of being a hollow watercooled shell.

Bafiie member 83, together with the overfire air supply from pipes 56 and 44, has a tendency to divert hot gases generated in the burning of fuel on grate 13 so that while combustion is maintained even under holdfire conditions,

fuel bed conditions, in the case of coals having detrimental caking and coking characteristics, are kept so as to avoid detrimental caking, coking and outfires. Moreover, the temperature in the intermediate portion of the fuel bed is kept from reaching the ash fusion clinkering stage without impairing the heat output from the fuel bed. The result is that even diificult fuels like certain bituminous coals fed to our new stoker system 12 will act in a relatively free burning manner.

Hot gases generated in the course of an operation of mechanism 12 as heretofore described will pass beneath the crown sheet 18 and into the open ends of the first bank 19 of fire tubes, from whence the gases will make a return bend and exit through the second bank of fire tubes 21 before going into the stack through connection 22, in the illustrated form of the invention. Moreover, the new system of this invention enables a wide range of coal such as bituminous coals and the like from caking, coking and ash fusion characteristics to be burned in a relatively free burning manner in other kinds of boilers such as water-tube boilers; furnaces and heating devices by virute of various features hereinabove described to inhibit the normally troublesome burning qualities of such fuels.

Various embodiments of this invention may be made including changes to the illustrative example without departing from the spirit of our invention or the scope of the appended claims.

We claim:

1. In a stoker furnace for burning bituminous coals or the like, apparatus comprising, in combination, a reciprocable grate having a fuel entry end and an ash discharge end, said .grate being inclined somewhat downwardly toward said ash discharge end, a fuel chute extending across substantially the width of said grate at said entry end, laterally spaced slice bars extending longitudinally along the top ofsaid grate adjacent said entry end, means for reciprocating said slice bars in a1ternating arrangement, resilient means normally urging said grate toward one extreme position, means for moving said grate toward its other extreme position and quickly releasing the same, means for supplying bulk combustion air to a fuel bed on said grate through said grate, a water-cooled guide extending substantially across the width of said grate, said guide'defining the front edge of said chute, a back plate extending substantially across the width of said grate to define the rear edge of said chute, said guide being generally J-shaped, means to adjust said guide vertically to regulate the thickness of a bed of fuel fed through said chute, an overfire air supply pipe mounted on the front of said guide, said pipe [having laterally spaced discharge orifices to discharge overfire air over the top of a fuel bed on said grate, a water-cooled baffle positioned above an intermediate portion of said grate and forwardly of and above said guide, a further overfire air supply pipe mounted on said baffle adjacent the back thereof, said baffle being adjustable relative to said grate, means having flexible connections for respectively supplying combustion air in regulatable quantities to the underside of said grate and to said overfire air supply pipes respectively, and means having flexible connections for supply ing cooling water to said grate, guide and bafile respectively.

2. In a stoker furnace for burning bituminous coals or the like, apparatus comprising, in combination, a unitary grate reciprocable as a whole having a fuel entry end and an ash discharge end, said grate being inclined somewhat downwardly toward said ash discharge end, a fuel chute extending across substantially the width of said grate at said entry end, laterally spaced slice bars extending longitudinally along the top of said lgrate adjace'nt said entry end, means for reciprocating said slice bars in alternating arrangement, resilient means normally urging said grate toward one extreme position, means for moving said grate toward its other extreme position and quickly releasing the same, means for supplying bulk combustion air to a fuel bed on said grate through said :grate, a heat resistant guide extending substantially across the width of said grate, said guide defining the front edge of said chute, a back plate extending substantially across the width of said grate to define the rear edge of said chute, means to adjust said guide vertically to regulate the thickness of a bed of fuel fed through said chute, an overfire air supply pipe positioned adjacent said guide to discharge overfire air across the top of a fuel bed on said grate, a heat resistant baflie positioned above an intermediate portion of said grate and forwardly of and above said guide, said baflle being adjustable relative to said grate, and means for respectively supplying combustion air in regulatable quantities to the. underside of said grate and to said overfire air supply pipe respectively.

References Cited in the file of this patent UNITED STATES PATENTS Switzerland Nov. 16, 1939

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