1984-07-31
1986-06-10
Favors, Edward G.
Furnaces
Fronts
110110, F23J 102
Patent
active
045936293
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a solid fuel stoker as comprising a hearth, a fuel conveyor for feeding fuel to the hearth and blower means for supplying combustion air to the hearth through bottom and/or side openings therein.
Automatically stoked furnaces are used to an increasing extent, because they can handle a wide variety of solid fuels, including many types of waste material. Traditional stoker hearths are open combustion chambers, which are mountable almost as an oil burner in a furnace and receive the fuel in a continuous manner from a fuel silo, normally by means of a conveyor worm. The fuel, pushed through the chute shaped hearth, leaves the hearth as ashes, which may be collected in an ashtray underneath the inner, free end of the hearth. The bottom and/or sides of the hearth are made as a hollow double steel plate construction, the interior of which is connected with an air blower for supplying air to the combustion area through holes in the inner plate, whereby the air will also have a desired cooling effect on the hearth material.
It has been observed that, for several fuel materials, some combustible gases escape from the fuel so as to be incompletely combusted, and it has been suggested, therefore, to shape the hearth in a cylindric manner, whereby the gases are better maintained within the combustion chamber, and combustion air may even be introduced into this chamber through holes near top area of the interior cylindrical wall plate of the chamber. The combustion air will be well preheated inasfar as it moves through the annular cylindrical space of the tunnel hearth, even over a topside thereof, where the temperature is rather high. At the same time, of course, the air has the important function of cooling the top portion of the tunnel hearth, which could otherwise be exposed to overheating.
While the tunnel shape of the hearth is an improvement for holding the combustible gases inside the active burning area, it has been found that the hearth construction can nevertheless be essentially further improved, and it is the object of the invention to provide such a further improved stoker hearth.
According to the invention there is provided a hearth generally of the tunnel type, but wherein the top portion of the hearth is made of a suitable ceramic material, preferably shaped as a solid thick-walled roof member, i.e. without forming part of the combustion air supply system, while the lower part of the hearth is of a conventional hollow-wall design, in which combustion air inlet holes are provided in an inner wall portion thereof.
With this construction the ceramic and uncooled roof portion will, in operation, be heated to a relatively very high temperature, so as to normally be red- or white-glowing, and it will consequently be a powerful source of radiation heat, which will operate to ignite the fuel and all escaping combustible gases. Practical tests have demonstrated that the combustion efficiency of such a hearth is clearly better than the efficiency of the discussed known hearths.
In the following the invention is described in more detail with reference to the drawing, in which:
FIG. 1 is a general sectional side view of a stoker system according to the invention as mounted in connection with a furnace,
FIG. 2 is a perspective view of the hearth of the stoker system, and
FIGS. 3 and 4 are cross sectional views of modified shapes of the hearth.
As shown in FIG. 1, a furnace 2 includes a firing chamber 4 and a smoke outlet channel 6. A stoker hearth 8 is disposed forwardly of the firing chamber 4 and is connected with a fuel supply tube 10 projecting forwardly from a fuel silo 12 and housing a conveyor worm 14 driven by a motor 16. The shaft 18 of the motor 16 is operatively connected, through suitable transfer means 20, with reciprocable grate elements 22 arranged at a bottom of the silo for facilitating material supply to the worm 14, and the shaft 18 is connected with an underlying conveyor worm 24 so as to cause the latter to rotate with reduced speed, through a gear or driving paw
REFERENCES:
patent: 454037 (1891-06-01), Edgar
patent: 1315158 (1919-09-01), Risdon
patent: 4444127 (1984-04-01), Spronz
Pedersen Marianne G.
Vaughan Michael
Favors Edward G.
Maskinfabrikken Dan-Trim ApS
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