GRATE FOR A FURNACE, PARTICULARLY AN INFEED GRATE FOR A REFUSE INCINERATOR

Abstract: The infeed grate consists of grate blocks (1) arranged in rows placed side-by-side and extending in the direction of movement of the fuel, said grate blocks being secured mutually overlapping on grate beams (2, 3) inclined downwardly and parallel in said direction, every other of the grate beams (2) belonging to a first set and the remaining grate beams (3) belonging to a second set of grate beams. The two sets of grate beams (2 and 3) and the grate blocks (1) secured thereto are reciprocated in their longitudinal direction in opposite phase by means of drivers (14) fastened to a first restrictedly rotatable shaft (13) engaging with recesses (15) in the lower side of each grate beam (2) of the first set, and other drivers (17) fastened to another restrictedly rotatable shaft (16) engaging with recesses (18) in the lower side of each grate beam (3) of the second set, said shafts (13 and 16) rotating back and forth in opposite phase.

Description: GRATE FOR A FURNACE. PARTICULARLY AN INFEED GRATE FOR A REFUSE INCINERATOR TECHNICAL FIELD The present invention relates to a grate for a furnace, particularly an infeed grate for a refuse incinerator, said grate being of the kind referred to in the pre-char- acterizing part of claim 1. BACKGROUND ART In a grate of this kind disclosed in US-A-4,471,704, wherein both sets of grate beams are reciprocatingly movable in opposite phase in their longitudinal direc¬ tion, the motive mechanism consists of a single shaft disposed beneath the grate beams and transversely to their longitudinal direction, said shaft being restric¬ tedly rotatable back and forth by means of a rack-and- pinion mechanism, the rack of which is reciprocated by a fluid-operated piston-cylinder mechanism and the pinion of which is secured to the shaft. On the shaft below each of the first set of grate beams, pinions are provided engaging with superjacent racks secured to the lower side of each of these grate beams, and below each of the second set of grate beams the shaft has pinions engaging with subjacent racks disposed in a box-like structure secured to the lower side of each of these grate beams. Rack-and-pinion mechanisms are expensive to manufacture and moreover, in the use herein referred to, extremely subject to malfunctions. As there must, necessarily, be a clearance between the sides of the grate surfaces in mutual opposite reciprocation on the adjacent grate beams, ash and slag or unburned particles, e.g. refuse parts, will unavoidably fall down through such clearances and may be deposited on the motive mechanism beneath the grate, especially on the subjacent racks, and thereby impede its functioning and cause wear on it or perhaps even destroy it, this being the more disadvantageous, since this motive mechanism of the known grate is not easily accessible for cleaning, replacement of worn parts or more extensive repairs. Applicants' US-A-4,494,469 discloses another grate of the kind referred to for an incinerator, in which only one set of grate beams are reciprocated in their longitudinal direction, whereas the second set of grate beams are stationary. In this known grate, the motive mechanism consists of a single shaft disposed below the grate beams transversely to their longitudinal direction, said shaft via a crank arm being restrictedly rotatable back and forth by a hydraulic piston-cylinder unit. Below each of the reciprocating grate beams, the shaft has radially protruding drivers engaging with recesses in the lower side of these grate beams and on rotation back and forth of the shaft, said drivers implying a reciprocating move¬ ment to the beams. This motive mechanism is simple and insensitive to solid combustion products or fuel particles falling down through the clearances between the grate blocks on the stationary and movable grate beams, since the region of engagement between the latter and the dri¬ vers lies well protected against such falling through of residues in the lower sides of the grate beams. Particularly in the case of infeed grates for incinera- tors it is in itself desirable that both sets of grate beams are reciprocating in opposite phase, thus achieving a better disintegration and a more uniform distribution over the surface of the grate of the often strongly co¬ herent refuse. DISCLOSURE OF THE INVENTION Therefore, it is an object of the invention to provide a grate of the kind stated in the pre-characterizing part of claim 1 satisfying this desire without having the drawbacks of the known grate referred to previously. This object is achieved according to the invention by the features stated in the characterizing part of claim 1. Preferably the motive mechanism of the grate is also constructed as stated in claim 2, making it possible to control the guantity conveyed on an infeed grate as well as the disintegration of refuse on such grate. It is preferred, particularly in an infeed grate, that the grate is constructed as stated in claim 3, thereby a- chieving a more reliable removal of fuel and a stronger disintegration and spreading of the refuse, respectively, when the grate blocks on adjacent grate beams in the uppermost area of the grate at the same time rise during their movement towards and away from each other, respec¬ tively. Used as infeed grate in a refuse incinerator, the grate according to the invention is placed as stated in claim 4. BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention is explained in more detail with reference to the drawing, in which Figure 1 is a side view, partly in section, of a grate beam of the first set of grate beams with a number of grate blocks supported on the beams, Figure 2 in perspective shows a grate block disposed at the end of a grate beam, Figure 3 in broken sections A and B shows the mechanism for reciprocating movement of a grate beam of the first set and of the second set, respectively, in the longitu¬ dinal direction, Figure 4 is an elevation of the mechanism for restricted rotation back and forth of the first and the second shaft, respectively, and Figure 5 is a vertical sectional view substantially along the line V-V in Figure 3 through the infeed grate accord¬ ing to the invention between the first and second shaft and showing the drivers secured to the latter engaging in recesses in the lower side of the second set of grate beams. DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows five grate blocks 1 secured to cross mem- bers 12 of a grate beam 2 of the first set of grate beams. At its upper end, the grate beam 2 comprises in its lower side a recess 15 adapted to engage with a driver, as will be explained later. As shown, the grate blocks 1 overlap each other, the front part of an upper grate block 1 protruding over the rear part of the succeeding grate block 1 in the row. Each of the grate blocks 1 comprises two substantially horizontal surfaces 4 disposed at a distance from each other and two downwardly inclined surfaces 5, so that the upper side of the row of grate blocks 1 extends like a regular flight of stairs. The surfaces 5 could extend at right angles to the surfaces 4, i.e. substantially vertically. The uppermost grate block 1 comprises a hook-like projection 6 protruding upwardly from the rear part of the upper surface 4, and serving as air seal (cf. Figure 3) . The grate beams 3 of the second set of grate beams are constructed in the same manner as the grate beam 2 shown, and the grate blocks 1 are located thereon in the same manner, but the grate beams 3 differ from the grate beam 2 shown in that the engagement recess 18 (Figure 3) in their lower sides are located a distance from the upper end of the grate beams 3, as will be explained later. Figure 2 is a perspective view of a grate block 1 placed at the lower end of a grate beam 2 or 3. The grate block 1 consists of two mutually spaced, parallel side members 7 interconnected by means of tie rods 8 on which a number of grate bars 9 are supported, the latter mutually de- fining passages 10 for air. Instead of supporting grate bars 9 with air passages 10 on the tie rods 8, as shown, continuous grate surfaces may be supported on the tie rods, this being particu- larly preferred as regards grate blocks in infeed grates in refuse incinerators that are located close to the upper ends of the grate beams 2 and 3, whereas the lower grate blocks 1 on the grate beams are constructed as shown in Figure 2 with a view to supplying primary co - bustion air to the ignited refuse on these grate blocks. The grate beams 2 and 3 likewise consist of two parallel, vertical and mutually spaced side stringers 11 rigidly interconnected by means of e.g. welded-on cross members 12 also serving to secure the grate blocks 1. In Figure 3, the broken section A shows the motive mecha¬ nism making a grate beam 2 of the first set of grate beams reciprocate in its longitudinal direction, whereas the broken section B shows the motive mechanism causing a corresponding reciprocation of a grate beam 3 of the second set of grate beams. In the broken sections A and B, the grate beams 2 and 3, respectively, are shown in the same phase of their movements, viz. in their uppermost positions, but it will be understood that when the grate beam 2 is in the uppermost position shown, the grate beam 3 will be in its opposite, lowermost position. In the broken section A, the motive mechanism comprises a shaft 13 capable of limited back-and-forth rotation, on which an outwardly protruding driver 14 is fastened, said driver engaging the recess 15 in the lower side of the grate beam 2 and, when the shaft 13 rotates back and forth, makes the grate beam 2 reciprocate in its longi¬ tudinal direction. In a similar manner, the motive mechanism shown in the broken section B comprises a shaft 16 capable of limited back-and-forth rotation, on which an outwardly protruding driver 17 is fastened, said driver engaging the recess 18 in the lower side of the grate beam 3 and, when the shaft 16 rotates back and forth, reciprocates the grate beam 3 in its longitudinal direction. The shafts 13 and 16 rotate back and forth in opposite phase. This does not appear from Figure 3, in which the grate beams 2 and 3, as mentioned, are shown in the same phase of their movement. Another important feature to be mentioned is the fact that, when the shaft 13 rotates clockwise from its extreme position shown in the broken section A into its opposite extreme position, the part of the driver 14 engaging the recess 15 will pass through a circular arc, and so will the recess 15 and with it the uppermost end of the grate beam 2. Thus, for each reciprocation of the grate beam 2, its uppermost end will in the same manner carry out an up-and-down movement transversely to the longitudinal extent of the grate beam 2, whereas its lowermost end, i.e. the right-hand end in Figure 1, undergoes a purely translatory motion. Thus, during each of its reciprocating movements, the grate beam 2 will carry out a rocking movement about its lowermost end. With reference to the broken section B, exactly the same applies to the grate beam 3, i.e. for each reciprocating movement it will carry out a rocking movement about its lowermost end. These rocking movements of the grate beams 2 and 3 taking place simultaneously for the grate beams 2 and 3 being reciprocated in counter-phase partly facilitate the dis¬ charge of refuse from a chute placed above the uppermost part of the infeed grate, partly contribute to the dis¬ integration and spreading of the refuse having been dis¬ charged. Figure 4 shows the motive mechanism for limited back- and-forth rotation of the shafts 13 and 16. This motive mechanism comprises a fluid-driven, preferably hydrauli- cally driven, piston-cylinder unit 19, the cylinder of which as shown at 20 is pivotably secured to a bracket 21 mounted on the lower structure of the infeed grate, and the piston rod of which, as shown at 22, is linked at its end to one arm of a two-armed lever 23 being secured to a protruding end of the shaft 13. The other arm of the two-armed lever 23 is as shown at 24 linked to one end of a link rod 25. The other end of the link rod 25 is, as shown at 26, linked to a one-armed lever 27 secured to a protruding end of the shaft 16. Reciprocation of the piston rod in the piston-cylinder unit 19 will cause a back-and-forth rotation of the two- armed lever 23 and hence also the shaft 13, as the back- and-forth rotation of the lever 23 via the link rod 25 at the same time causes an opposing back-and-forth rotation of the one-armed lever 27 and consequently of the shaft 16. These rotating movements are naturally restricted by the length of stroke of the piston-cylinder unit 19, said length of stroke as well as the extent of the stroke and its frequency preferably being adjustable in a manner well-known to the skilled person. Finally, Figure 5 is a vertical sectional view, mainly along the line V-V in Figure 3, through the infeed grate according to the invention and showing grate blocks 1 secured to the grate beams 2 and 3 and the shaft 16 being rotated back and forth by the one-armed lever 27 and being equipped with the upwardly protruding drivers 17 engaging the recesses in the lower sides of the grate beams 3. Reference numeral 28 designates walls in the combustion furnace (not shown) of the incinerator, while 29 indicates the lower structure (not shown) of the infeed grate according to the invention. It will be understood that above the infeed grate accord¬ ing to the invention and approximately above a section of it corresponding to the horizontal extent of the broken section A in Figure 3 there is, as previously mentioned, a chute or receiving hopper for refuse to be incinerated, and from where the refuse is removed by means of the uppermost grate blocks 1 on the grate beams 2 and 3. In the above description, the infeed grate according to the invention is solely mentioned in connection with infeed of refuse in an incinerator, but as will be evi¬ dent, it can equally well be used for infeeding other fuels, such as e.g. solid fossil fuels or a mixture of refuse and solid fossil fuel in the incinerator, if the latter's operating conditions make this desirable or necessary. Also other types of fuel, e.g. wood chippings, can be feed into the incinerator, either alone or together with refuse by means of the infeed grate according to the invention. Likewise, it will be evident that even though the grate according to the invention has been described in the preceding detailed description as being an infeed grate for introducing fuel into an incinerator, grates according to the invention, possibly modified in an appropriate manner, can be used as downstream grate sections in an incinerator of the type, in which only advancing and rear¬ ranging of the fuel on the grates take place.

Claims: C L A I M S ; 1. Grate for a furnace, particularly infeed grate for a refuse incinerator, and comprising a plurality of grate beams (2,3) disposed side by side and extending in the feeding direction of the fuel, said grate beams being inclined downwardly in said feeding direction and each carrying a number of grate blocks (1) placed in a row extending in said direction, the upper faces of said blocks together forming a regular stepped configuration and consisting of the substantially horizontal upper surfaces of grate elements or grate bars (9) , preferably with air passages (10) between them, and wherein said grate beams (2,3) alternately belong to a first set of grate beams (2) and a second set of grate beams (3) which are relatively reciprocatable in the longitudinal direc¬ tion of the grate beams (2,3) by means of an actuating mechanism below the grate comprising at least one shaft (13,16) capable of limited back-and-forth rotation extend- ing transversely to the longitudinal direction of the grate beams (2,3) and having engagement means engaging complementary engagement means at the lower sides of the reciprocatable grate beams, c h a r a c t e r i z e d in a) that a first (13) and a second (16) shaft capable of limited back-and-forth rotation are placed with their axes spaced from each other, b) that radially protruding drivers (14) on the first shaft (13) in a per se known manner engage with at least one recess (15) in the lower side of each grate beam (2) of the first set, c) that radially protruding drivers (17) on the second shaft (16) similarly engage with at least one recess (18) in the lower side of each grate beam (3) of the second set, and d) that the first (13) and the second (16) shafts are adapted to be rotated back and forth in opposite phase by a mechanism, in which one arm of a two-armed lever (23) fixed to the first shaft (13) is rotatably connected to the piston rod in a pivotably supported fluid-operated piston-cylinder unit (19) , the other arm of said two-armed lever (23) being linked to a one-armed lever (27) secured to the second shaft (16) , whereby the first set of grate beams (2) and the second set of grate beams (3) can be reciprocated in opposite phase in the longitudinal direc¬ tion of the grate beams (2,3). 2. Grate according to claim 1, c h a r a c t e r- i z e d in that the length of stroke, the region of stroke and the frequency of stroke of the fluid-operated piston-cylinder unit (19) are individually adjustable. 3. Grate according to claim 1 or 2, c h a r a c- t e r i z e d in that the recesses (15) in the lower side of each of the first set of grate beams (2) are placed in the immediate proximity of the uppermost end of said grate beams, and that the recesses (18) in the lower side of each of the second set of grate beams (3) are placed at a greater distance from the uppermost ends of said grate beams corresponding to the distance between the axes of the first and the second shaft (13,16), so that the uppermost ends of the grate beams (2,3) for each reciprocating movement of said beams make an upward and downward movement transversely to the longitudinal direc¬ tion of the grate beams (2,3). 4. Grate according to any one or any of the preceding claims used as infeed grate in a refuse incinerator, c h a r a c t e r i z e d in that the uppermost part of the grate is placed below a chute adapted to contain refuse to be incinerated.

Inventors: BINNER SIEGFRIED, JENSEN RARMUS STIG, BINNER, SIEGFRIED, JENSEN, RARMUS, STIG
Applicants: BINNER SIEGFRIED, JENSEN RARMUS STIG, VOELUND ECOLOGY SYSTEMS AS, BINNER, SIEGFRIED, JENSEN, RARMUS, STIG, VOELUND ECOLOGY SYSTEMS A/S
Application year: 1995
Main classification: F23H7
IPC codes: F23H7