Furnaces – Including means to feed solid fuel – Movable grate
Patent
1997-11-07
1999-10-19
Yeung, James C.
Furnaces
Including means to feed solid fuel
Movable grate
110192, 110248, 110268, 110298, 110300, 110311, 126152R, 126152B, 126163R, 126181, F23H 902, F23H 102, F23N 520
Patent
active
059670649
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The point of departure of the roller grate of the present invention is the state of the art known from SU 1 756 741 A1. That document describes a roller grate wherein every intermediate component comprises a system of stationary bars with gaps between them. Accommodated below the intermediate components are air boxes. Air is supplied to the boxes by a fan that is independent of the primary-air system. The particular object is to improve burn-up.
A roller grate wherein air is blown into a nip or space between through bar-like intermediate components is also known from German Patent 600 546. The bar-like components are in two parts. The two are moved relative to one another and to the rollers by a cam. The motion is intended to poke the bed of fuel resting thereon. The intermediate components obtain their air from the adjacent rollers. The streams of air blown in by way of the intermediate components are accordingly component streams of the primary air.
As far as is known, the approaches suggested in these two documents have never been applied to garbage incinerators. The space between the adjacent rollers in the roller-grate combustion systems currently known and being built are bridged over by intermediate components in the form of slender strips, usually called strippers. Specific examples of such strips are described in German 3 420 020 C1 and German 4 300 636 C1 for instance. Supplemental air is not supplied to the nips or spaces between the rollers. All of the primary air supplied to the fuel bed arrives through the surfaces of the rollers.
The layer of fuel in the vicinity of the nip or spaces is considerably thicker than in the areas where it rests against the rollers. The fuel also has a tendency to become denser in the vicinity of the gaps, where there the material is finer. A lot of air is accordingly needed in these areas. The increased impedance offered by the garbage resting there on the other hand forces the primary air out of the nips and into the regions when the layer is thin and loose, at the edges of the grate for example.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the roller grate in order to allow the fire to be poked and fanned in the vicinity of the nips.
This object is attained whereby jets of air blown into the vicinity of the nip increase the supply of oxygen and loosen the fuel bed, for improving the contact between the particles of fuel and the oxygen. The fire, fanned in this manner within the nip, is more intense and even acts as ignition for the garbage above it. It accelerates combustion and accordingly contributes to increasing the furnace's combustion output.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the present invention will now be specified by way of example with reference to the accompanying simplified drawing, wherein
FIG. 1 is a schematic side view of a roller grate,
FIG. 2 is a top view of the same grate,
FIG. 3 is an enlarged detail of FIG. 1, and
FIG. 4 is a section through part of a blast pipe.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A furnace 1 in a garbage-incinerating plant illustrated in FIG. 1 is provided with a fueling hopper 2, an ash-removal shaft 3, and a flue-gas extractor 4. The floor of furnace 1 is in the form of a grate comprising six rollers 5 approximately 1.5 m in diameter. The axes of rollers 5 extend horizontal and parallel in a plane inclined approximately 20 to 30.degree. down toward ash-removal shaft 3. The surface of rollers 5 consists, as will be evident from the figure, of bars 6, each extending along a curve of 36.degree., ten bars 6 accordingly constituting a closed ring. Each bar 6 is about 5 cm wide. Between each pair of adjacent bars 6 is a gap of approximately 2 to 3 mm. Each roller is rotated by a drive mechanism at a continuously variable speed of 0.6 to 12 rotations an hour. Below the grate is a system essentially consisting of air boxes 7 that supply primary air to rollers 5. The flow of primary air to each roller 5 can be separately controlled. The
REFERENCES:
patent: 2367590 (1945-01-01), Lewers et al.
patent: 5042401 (1991-08-01), Ettehadieh
patent: 5405537 (1995-04-01), Goff et al.
patent: 5448957 (1995-09-01), Goldammer et al.
Frielingsdorf Othmar
Grell Peter
Keldenich Kai
Robson Colin Peter
Scheffler Jurgen
Ciric Ljiljana V.
Deutsche Babcock Anlagen GmbH
Fogiel Max
Yeung James C.
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