FURNACE CONSTRUCTION

Abstract: Furnace construction which exhibits a furnace grate (3, 203) formed by a number of closely interspaced movably supported grate elements (25), in which furnace the removal of ashes and slag formed during the combustion on the grate (3, 203) takes place without the necessity to shut off the plant. The grate elements (25) are supported at their respective ends, and an actuating element (33), which preferably also constitutes a removing means for ashes and slag, is arranged and controlled in such a manner that at predetermined intervals it tilts said grate elements (25).

Description: Furnace construction The present invention relates to a furnace construction exhibiting a fire grate made of a number o.f travelling grate elements .placed close to -each other. It is a principal object of the invention to provide a furnace construction of the kind mentioned above, in which the quite substantial quantities of slag and ashes, which usually do not fall down between the grates, when by way of example bark, wood waste and peat are used as fuel material, are effectively removed without it being necessary to shut off the furnace with the accom¬ panying losses of heat and efficiency. Said object is ob¬ tained by means of a furnace construction according to the present invention, which is substantially characterized by the grate elements being supported at their respective ends and by an actuating means, which preferably also serves the purpose of a removing means of ashes and slag, being arrang¬ ed and controlled in such a manner that it causes said grate elements to tilt at predetermined intervals. ' A number of examples of embodiment of the invention are described in the following, reference being made to the accompanying drawings, in which Fig. 1 is a schematic view of a furnace con¬ struction equipped with straight fire bars and designed in accordance with the present invention, Fig. 2 is a sectional view of a furnace con¬ struction exhibiting a ring-shaped grate arrangement. Fig. 3 is a partly sectional vertical view of the furnace construction shown in Fig. 2, Fig. 4 is a view of a furnace construction of other design exhibiting a ring-shaped grate arrangement and provided with an actuating means forming part of the equipment, and Fig. 5 is a view of a portion of the ring- shaped grate arrangement as seen from above and at the OMPI /,, IPO ^Λ bottom in side elevation, from which views the co-opera¬ tion between the actuating means and the grate is evident. The furnace construction illustrated in Fig. 1 comprises a furnace 1 with a grate 2 placed in its center, said grate in the .present example of embodiment being of long extension and formed by a plane grate 3 and a multi-stage grate 4. A feeder worm 5 for the fuel i located in the space between two identically designed gra tes 2. The conveyor worm 5 is provided with a counter thr which from the bottom of a trough-shaped bin 6, in which said worm is rotatably mounted, presses the fuel charged in upwards direction, such fuel by way of example compris ing bark, wood waste and peat, so that it falls down on the multi-stage grate 4 and the plane grate 3 on which the combustion takes place. Two fans 7 and 8 respectively for primary air provide the air supply for the fuel, one 7 of said fans supplying hot air from for example a heating pla furnace or a boiler, so that- the air mixture can reach a temperature of up to 350-400 C. Draught valves 9 are pro- vided in the air supply ducts 10, 11, 12 to the fan 7 and to said trough-shaped bin 6, which latter one forms a re¬ tort, and to a space 13, which is for one thing surrounded by the multi-stage grate 4 and the retort 6 (belonging to the fuel charging equipment) and for another thing by a delimiting wall ' 16 by means of a column 15 supported on the bottom 14 of the furnace. The air, which is supplied to the retort 6 via the duct 11, heats and dries the fuel charged, whereas the air flowing via the duct 12 is supp¬ lied to the multi-stage grate 4. The fan 8 supplies air to the plane grate 3 via the duct 17, which debouches in a space 18 below 'the plane grate 3. An additional worm conveyor 19 is provided on the bottom 14 of the furnace and serves the purpose to feed out of the furnace ashes and slag falling down from the grates 2. A scraper 20, which is in a reciprocating movement displaceable along the bottom 14 of the furnace, OMPI ° is actuated by a preferably hydraulic power unit 21, with the piston of which it is connected via a draw bar 22, pene¬ trating the wall 23 of the furnace, and feeds the cinders to said feeding out worm conveyor 19, so that they fall down in a space 24 surrounding the same, from where they - are by means of said conveyor worm 19 fed out of the fur¬ nace 1. The multi-stage grate 4 occupies a fixed position, whereas the plane grate 3 is movable. This plane grate 3 is formed by a number of grate plates 25 arranged in pivotable mounting close to each other, as is evident from the bottom portion of Fig. 5. Each terminal edge 26 of these grate plates 25 exhibits supporting means 27, which can comprise interspaced pins 27 projecting in out- wards direction from said terminal edge. A centering device is provided between said pins 27 and comprises an upwards pointing cam 28 with oblique surfaces 28A, said cam in the embodiment shown exhibiting triangular shape. The pins 27 are supported by supporting surfaces 29 extending on both sides of the grate plates 25 as counted in the longitudinal direction of the same, which supporting surfaces can comprise beams 29. Each one of the grate plates 25 is preferably ri¬ gidly connected with a downwards hanging arm 30, which at its lower end is provided with a counterweight 31. In the space 32 below said plates 25 there are movable means 33, by way of example comprising a stud element 33 serving the purpose of an actuating means and being displaceable along the grate 3. This stud 33 can in a straight grate 3 be mount¬ ed on for example an endless chain, a drawbar or on any other suitable means. The fuel, that by means of the conveyor worm 5 is fed into the construction described, is heated up and dried by the hot air supplied to and surrounding the fuel. According to fresh fuel being charged, it falls down over the upper edge of the bin 6 and further on to the multi¬ stage grate 4, where it is burned, the air being supplied via the duct 12. The fuel also falls down on the plane grate 3, where its combustion is continued, air being,, supplied via the duct 17. Slag and ashes, which form on the top surfaces of the grate plates 25 and which do not fall down through the openings 34 between the grates ex- . tending in the longitudinal direction of the plates 25, fall down under the grate 3, when the grate plates 25 are tilted round the supporting means 27, as is shown in Fig. 5, this taking place in co-operation with the stud 33, which during its movement pivots the downwards hanging arm 30 in order to cause said tilting movement of the grate plates 25. The intervals between said tilting move¬ ments can be adjusted by a regulation of the travelling speed of the stud 33, and each grate plate 25 can by way of example be brought to tilt every twelfth hour. All of the grate plates 25 are then tilting at substantially the same time, so that all cinders are emptied simultaneously, the plates 25 not being permitted to remain in an upwards pivoted position for any extended period of time. The stu 33 can be pivotable in one direction, viz. the direction of the return stroke, if the tilting always is carried ou in one and the same direction. The cinders falling down on the floor 14 of the furnace are by means of the recipro¬ cating movement of the scraper 20 moved down into the shaf 24 by the same and is conveyed out of the plant by means o the conveyor worm 19. The construction illustrated in Figs. 2 and 3 differs from the one described above substantially by th positioning and connection of the duct 109 for the supply of hot air or the. mixture of hot air and a gas.- In this embodiment the duct establishes a direct communication bet ween a fan 107 and the bin 6 for the fuel charge, an addi¬ tional fan 108 feeding air to the multi-stage grate 204 and the plane grate 203, both of which in this case exhibi ing a ring-shaped design. The furnace illustrated in Figs. 4 and 5 li wise exhibits a ring-shaped plane grate 203, whereas a m_j_l OMP stage grate 204 of substantially conical design occupies an inclining position towards the plane grate 203 in ■ direction from the central axle 35 of the latter one. The grate plates 25 of the plane grate 203 are shown in the upper portion of Fig. 5, from which it is .evident that the individual plates 25 exhibit a sector shape. The front end sides of these plates 25 facing in direction towards the centre of the ring are provided with a project¬ ing shaft 36, which constitutes one of the supports for the plate 25. As was the case with the previously described plane grate 3, two pins 27 project from the opposite front- end side, said pins, thus, constituting the other supports for the plate 25. Arms hanging downwards and provided with counterweights 31 are also a feature of the ring-shaped plane grate 203 now described. An arm 37, which can rotate round the central axle 35 of the ring-shaped grate 203, serves the purpose of an actuating means 37 and is in the illustrated example of embodiment formed by a wing 37, which suitably also serves the purpose of a slag scraper. During the rotation of the wing 37 its edge 37A scrapes the bottom of the furnace and at the same time, as the wing 37 actuates the downwards hang¬ ing arms 30 causing each respective plate 25 to pivot round its axle 36 and one of the other two axles 27 depending upon the pivoting direction of the arm 30, the wing scrapes down slag, ashes and other combustion residues into a shaft 38 located at the bottom of the furnace in the space for said central axle 35 and extending along substantially the whole length of the bottom of the furnace. In this shaft 38 there is a conveyor worm 39, which feeds the downscraped material out of the furnace. Also this arm 37 can be provided with studs 33 for co-operation with the downwards hanging arms 30, and the number of revolutions of the arm 37 can be ad¬ justed in such a manner that the plates 25 tilt with suit- able intervals. The weight 31 on the arm 30 causes the plate 25 to occupy its normal position after a tilting action has taken place. Each one of the long sides 40 of the respect ive plates 25 preferably exhibits surfaces 40, which . occupy a downwards inclining position towards its res¬ pectively corresponding downwards hanging arm 30, and said surfaces can suitably be curved in order to facili- . tate said tilting movement relative to adjacent plates 25. The conveyor worms or other conveyor means used in connection with anyone of the plants described above are preferably provided with automatically function- ing devices, which automatically drive the coveyor worm backwards and forwards for a number of times, when the conveyor worm tends to be jammed by such objects of vary¬ ing hardness as split portions of roots, chunks, stones, pieces of board and bark or congestions of combustion chip If the jamming situation is not automatically relieved, th trouble is indicated, so that the service hands will be alarmed. The invention is not limited to the embodi¬ ments described above and illustrated in the drawings by way of example only, but can be varied as to its details within the scope of the following claims.

Claims: C l i m s 1. Furnace construction exhibiting a furnace grate (3, 203) formed by a number of movably supported and closely interspaced grate .elements (25), c h a r a c t e " - r i z e d b y the grate elements (25) being supported at 5 their respective ends and by an actuating element (33, 37) , which preferably also constitutes a removing device for ashes and slag, being arranged and controlled to the effect that at predetermined intervals it tilts said grate ele¬ ments (25) . -*- υ 2. Furnace construction according to claim 1, c h a r a c t e r i z e d b y the grate (3, 203) exhibit- ' ing a substantially ring-shaped combustion surface, the grate elements (25) comprising grate plates (25) of sector shape. *■ - •• > 3. Furnace construction according to claim 2, c h a r a c t e r i z e d b y the grate plates (25) at their respective short ends exhibiting supporting means (27, 36) , of which at least one (27) has a widespread exten¬ sion. 20 4. Furnace construction according to anyone of the preceding claims, c h a r a c t e r i z e d b y a rotatably mounted arm (37) pivoted on the central axle (35) of the grate (203) constituting said actuating element and by the arm (37) being arranged in such a manner that it co- 25 operates with the underside of the grate elements (25) in order to bring about said tilting movement. 5. Furnace construction according to anyone of - the preceding claims, c h a r a c t e r i z e d b y the grate elements (25) on the side of them facing away from 0 the combustion surface exhibiting a downwards hanging arm (30) , which is arranged to be actuated by said actuating element (33, 37) . 6. Furnace construction according to claim 5, c h a r a c t e r i z e d b y the downwards hanging arm (30) being rigidly connected with the grate element (25) and exhibiting a counterweight (31) preferably positioned at its low end. 7. Furnace construction according to anyone, o the claims 3-6, c h a r a ,c t e r i z e d - b y the grate plates (25) at the short end side of them facing away fro the centre (35) of the grate exhibiting two interspaced pivots (27) projecting in outwards direction from said ce re (35) , a guiding centering device (28) occupying a posi tion between sa±d pivots. 8. .,„..■.-- - " Furnace construction according to claim 7, c h a r a c t e r i z e d b y said centering device (28) comprising a cam (28) projecting in upwards direction fro the supporting surface (29) of the grate (203) and prefer ably exhibiting inclining surfaces (28A) . 9. Furnace construction according to anyone o the preceding claims, c h a r a c t e r i z e d b y the long sides of the grate plates, (25) facing each other ex¬ hibiting preferably curved and in the direction from the top side inclining surfaces (40) . 10. Furnace construction according to anyone o the claims 4-9, c h a r a c t e r i z e d b y the actua ing element (37) comprising a rotatably mounted wing (37) , which preferably forms a scraping surface (38) extending along the whole length of the wing, said wing (37) in the space of the grate surface (203) exhibiting an upwards ex¬ tending portion, which by way of example can comprise a stud (33) or a cam serving the purpose to pivot the arm (30) hanging from the grate (203) in downwards direction in order to bring about said tilting movement of the grate plate (25) . ___OMPΓ

Inventors: JOHANSSON S
Applicants: JOHANSSON S
Application year: 1981
Main classification: F23H15
IPC codes: F23H15