GRATE WITH MEANS FOR DISCHARGING OF ASH

Abstract: Grate (1) comprises essentially concentrically set stationary and rotating unified grate rings (6a-d, 7a-c), which alternate from the centre outwards to the peripheral ring. Each grate ring is lower than the next ring further in and has a larger diameter than it, when the fuel fed from beneath to the centre of the grate flows over the grate rings while it burns to the peripheral ring, in which the ash drops through openings (30) arranged in it to an ashbox (5). The peripheral ring has stationary and circumferentially oriented moving units (15, 16), which are arranged in one extreme position to cover the entire peripheral ring and in the opposite extreme position to interlap in pairs on top of each other and form the aforesaid openings (30) between the interlapped pairs.

Description: Grate with means for discharging of ash. The present invention relates to a grate, which comprises essentially concentrically arranged stationary and rotating grate rings, which alternate from the centre outwards to the peripheral ring and in which each grate ring is lower than the next one inwards and has a greater diameter than it, so that fuel fed from underneath in the centre flows while it burns towards the peripheral ring, where the ash drops through openings arranged in it into an ashbox. A grate of the type referred to above is described in Finnish patent No. 95964. The rotating grate rings are set slightly eccentrically, when they also move the downwards flowing mass radially. In addition, the grate rings rotate in opposite directions, which improves the transport of the ash over the grate rings. An opening has been left between the peripheral ring of a grate of this kind and the wall, from which the ash drops into an ashbox beneath it. The opening must be quite wide, because the ash contains some large clinkers. As the fuel feed is increased, the proportion of unburnt material in the ash increases. This limits the available output of the grate, though the grate could otherwise burn a much larger amount of fuel . The purpose of the invention is to create an improvement over the case referred to above. The characteristic features of the invention are described in the accompanying Claims. With the aid of units according to the invention, the intermediate space that was previously a free opening is covered with a grid construction, in which openings can be formed if necessary. The grate can then be loaded much more than previously, particularly for short periods, with no fear of considerable quantities of unburned material flowing with the ash. Even large lumps of clinker can be removed through the openings formed at regular intervals between the units, though otherwise the elements form a grid structure, on top of which combustion continues, with the fine ash nevertheless dropping through. Other advantageous embodiments of the invention and advantages are described later concerning the example of application. In the following, the invention is described with the aid of the accompanying drawings, which show one grate according to the invention. Figure 1 shows a vertical cross-section of a combustion chamber, to which a grate according to the invention has been adapted. Figure 2 shows a partial enlargement of the cross-section in Figure 1 in the area of the peripheral ring, in which there is the new arrangement for removing ash. Figure 3 shows an adaption arranged on the peripheral ring, comprising stationary and moving units with the ash openings closed; the Figure includes a partial en- largement . Figure 4 shows the arrangement in Figure 3 with the units overlapped and forming ash openings; the Figure includes a partial enlargement. Figure 5 shows the vertical bracket in figure 2, seen from in front. In Figure 1, a grate 1 according to the invention is adapted to a combustion chamber with a circular horizontal cross-section, which in this adaptation acts as the front chamber of a boiler. Grate 1 conforms to the patent publication referred to above, except for the arrangement of the periphery. The lower part of combustion chamber 2 is cylindrical, while the upper part is conical. The conical upper part is connected to flue 3, which is connected to the after combustion chamber and to a boiler (not shown) for recovering heat from the flue gases. The jacket arranged in the lower part of combustion chamber 2. An annular ashbox surrounds grate 1. Grate 1 according to the invention includes stationary and rotating grate sections. The stationary grate componens are grate rings 6a, 6b, 6c, and 6d, while the rotating grate sections are correspondingly grate rings 7a, 7b, and 7c. These are mutually arranged so that every other grate ring is stationary, while the others rotate. The inner and outermost grate rings 6a and 6d are stationary grate rings. The fuel feed channel 8 is arranged to run horizontally beneath grate 1 from the outside of the combustion chamber 2 to its centre. Fuel, e.g. woodchips, conveyed by feed screw 9 travels along the feed channel 8 to the centre of the grate and rises through the feed cone to the top of grate 1. There the fuel ignites and while burning flows over the grate rings 6a-d, 7a- c. Ash and possible burning residue move to the peripheral ring, in which there is an arrangement according to this invention. The enlargement in Figure 2 shows the new arrangement according to the invention in detail. In this arrangement too, the ash openings 30 are formed between stationary grate ring 6d and the wall of the combustion chamber, but the openings can be closed by stationary and moving units 15 and 16. The moving units are installed on arm 19, which is in turn attached to support ring 14. This is supported vertically on five bearings 13 from the support structure of the grate. Figure 2 shows one bearing 13 in cross-section, while Figure 5 shows it seen from the front. Units 15 and 16 comprise circumferentially oriented bars 15.1 and 16.1. According to Figure 2, bars 15.1 and 16.1 interlap, so that the bars 16.1 of moving unit 16 push between the stationary bars 15.1. Figure 3 shows the general arrangement of the units 15 and 16 that cover the entire ring, with the ash openings closed. However, fine ash can flow down, due to the grid construction of units 15 and 16. The partial enlargement shows the construction of the units in greater detail. They each comprise three bars 15.1 and correspondingly 16.1 set at a distance to one another. Bars 15.1 are attached to arm 18 and correspondingly bars 16.1 are attached to arm 19. In general, each unit 15, 16 comprises 2 - 4 bars 15.1, 16.1, at a radial distance of 2 - 4 cm. Support ring 14 is not only supported vertically, but also horizontally on five rollers 20, which roll along the cylindrical support structure. The support ring is driven by operating device 21, for example, a pneumatic cylinder, which is installed in air intake duct 22. In this way the operating device remains cool. In this example 16 pairs of units are used, but advantageously these are 10 - 20. The ash openings 30 are formed according to Figure 4 by using operating device 21, by means of which support ring 14 is turned slightly, so that the attached units 16 interlap with the stationary units. Even large lumps of clinker will fit through the ash openings 30 that are formed. According to Figure 5, the rolling surface of the support ring incorporates a step 17, which raises the units 16 when they are moved. This improves the cleaning of the units and reduces the risk of them j amming .

Claims: Patent Claims 1. A grate (1), which comprises essentially concentrically set stationary and rotating unified grate rings (6a - d, 7a - c) , which alternate from the centre outwards to the peripheral ring and in which each grate ring is lower than the next ring further in and has a larger diameter than it, when the fuel fed from beneath to the centre of the grate flows over the grate rings while it burns to the peripheral ring, in which the ash drops through openings (30) arranged in it to an ashbox (5) , characterized in that the peripheral ring has stationary and circumferentially oriented moving units (15, 16), which are arranged in one extreme position to cover the entire peripheral ring and in the opposite extreme position to interlap in pairs on top of each other and form the aforesaid openings (30) between the interlapped pairs . 2. A grate (1) according to Claim 1, characterized in that units (15, 16) are components comprising circumferentially oriented rods, in which the rods are radially at a distance to each other, forming a grid structure and that the rods (16.1) of the moving units are set between the rods (15.1) of the stationary units (15), so that they take a position between them, when the units (15, 16) are in the interlapped position. 3. A grate according to Claim 2, characterized in that each unit (15, 16) comprising 2 - 4 bars (15.1, 16.1), the radial intervals of which are 2 - 4 cm. 4. A grate according to one of Claims 1 - 3, characterized in that there are 10 - 20 of both stationary and moving units (15, 16) covering together the entire ring. 5. A grate according to Claim 1 or 2, characterized in that the moving units (16) are supported from a unified support ring (14) that is arranged to rotate, and which is supported in the axial and radial directions from the support structure of the grate (1) and to which an operating device (21) is connected to drive it, so that the moving units (16) can be moved to the open/closed position. 6. A grate according to Claim 5, characterized in that the unified support ring (14) is carried both axially and radially at several support points on bearings (13), over which the support ring rolls, and that the rolling surface includes a step (17) over part of its length, which creates a change in the level of the moving element (16) during the movement. 7. A grate according to Claim 5 or 6, characterized in that the operating device (21) is located in the air intake duct (22), so that the intake air effectively cools it.

Inventors: BLOMBERG TEUVO, HUTTUNEN PEKKA, RANTONEN MARKKU, BLOMBERG, TEUVO, HUTTUNEN, PEKKA, RANTONEN, MARKKU
Applicants: BLOMBERG TEUVO, HUTTUNEN PEKKA, RANTONEN MARKKU, SERMET OY, BLOMBERG, TEUVO, HUTTUNEN, PEKKA, RANTONEN, MARKKU
Application year: 1998
Main classification: F23J1
IPC codes: F23H9, F23H13, F23J1, F23K3