CA2203573A1 - Method of combusting solid cellulose based fuel pellets - Google Patents

Description

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CA 02203~73 1997-04-24 ~ ~ 3 BACKGROUND OF THE INVENTION
a) Field of the Invention Method of cumbusting solid cellulose based fuel pellets by the use of an upright, cylindrical, top feed, two stage, close coupled, up draft gasifier reactor apparatus (burn pot). The burn pot can be incorporated into a negative/induced-draft or positive pressure/forced-draft heating apparatus or appliance stove normally used to burn solid fuel pellets in residential, commercial and industrial applications, who's fuel is delivered mechanically to the combustion area. The fuel feed system may also feed the pellet fuel to the burn pot the by the side or bottom of the gasifier. A grate in the bottom of the gasifier supports the the solid fuel pellets during gasification.
Unlike the prior art the design technology does not use excessive air to fuel ratios during combustion, resulting in greater overall efficiencies. As well. upon combustion, the ash from the combusted solid fuel is substantially exempt of slag (clinker, fused inorganic elements) and solid formations.
Gasification of solid fuels using this method and physical design, results in reduced temperatures of the solid fuel being gasified in the bottom of the verticaly designed cylindrical burn pot.
This lower temperature, is sufficiently below the melt point temperature of the silicate and associated fouling components usually found in the solid fuels.
The method of gasification of cellulose pellets, substantially inhibits initial deformation of the ash within the solid fuel, which permits for the combustion of a wide range of biomass feed stock materials having high or low ash content of say between 0.15 % ash to over 10 % ash. The densified, agglomerated, pelletized, extruded fuels of substantially increased bulk density are gasified without leaving undesirable fused ash residues, which could otherwise inhibit air to fuel ratios and further compromise overall stove performance.
More specifically, the present invention relates to a gasification combustion process to be used in a solid fuel pellet burning apparatus, whose design, not only substantially prevents CA 02203~73 1997-04-24 3 ~3 slag formation during combustion, but which raises the overall efficiency of the combustion process over existing designs by as much as 40~o or more.
The temperature of the combustion environment is below the initial melting point temperature of the solid fuel minerals and or silicate sand contained within the solid fuel being combusted.
Subsequent ash is substantially prevented from fusing together in the lower portion of the chamber and grate surface area, due to the reduced operating temperature and the resultant fine, granular ash falls through the grate to an ash containment area.
Close coupled two stage gasification of the cellulosic solid fuel pellet, effectively and substantially gasifies the solid fuel.
The resulting gases are drawn up in a vertically swirling and turbulent attitude, caused by the introduction of super heated combustion air, drawn through a conduit from the outside of the stove to the inner portion of the combustion pot, by the negative pressure blower fan.
The combustion air enters through the intake air conduit, delivering combustion air to the bottom offset burn pot opening. The air is drawn between the outside and inside walls of the cylindrical burn pot by a negative pressure blower fan and is super heated before entering into the combustion chamber.
The negative pressure combustion air is drawn through strategically spaced and sized openings from the inner cavity wall, to the inner chamber air inlet sights. The air inlet sights are located above the grate surface area and in a spiral mirror image on opposite sides, rise vertically to the top of the cylindrical burn pot. The air inlet holes are fashioned, so as to direct the air vertically upwards away from the grate surface gasification area.
The invention also relates to substantially increasing the efficiency of the combustion of pellet fuels by promoting better mixing and burnout of the fuel by the placement of combustion air within the combustion process, whereby during said combustion, excess air in the form of flue gases is restricted from leaving the combustion chamber and exhaust stack at substantially reduced levels compared to conventional pellet stove appliances.

Claims