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US 4,095,958 AGranted
Apparatus and method for producing combustible gases from biomass material
AssigneeForest Fuels, Inc.
InventorRobert A. Caughey
Life of this patent
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AssigneeForest Fuels, Inc.
InventorRobert A. Caughey
Estimating the term…
A reactor wherein a biomass is moved progressively downwardly along the upwardly facing side of an inclined grate supported with an enclosure comprising a retort, the rear and front walls of which provide, in conjunction with the grate, a plenum chamber at the downwardly facing side of the grate and a mixing chamber at the upwardly facing side of the grate, the said structure providing for converting the biomass by a process of destructive distillation to CO and ash characterized in that the grate is maintained at a temperature below the fusion temperature of the ash to prevent slagging of the ash by the expedient of supplying an excess of primary air to the plenum chamber at the lower end of the grate so that it flows upwardly along the downwardly facing side thereof, the surplus discharged at the top, providing the grate with a plurality of relatively small openings distributed throughout its length and breadth and providing fins at the downwardly facing side of the grate perpendicular to the plane of the underside of the grate which extend into the flowpath of the primary air. The rear wall of the retort is spaced rearwardly from and parallel to the downwardly facing side of the grate and forms therewith a manifold for containing the primary air as it flows upwardly therein, a force draft fan provides for delivering the primary air to the lower end of the manifold chamber and a damper at each end of the manifold chamber provides for controlling the flow of primary air.
A reactor for producing combustible gases suitable for delivery to the firebox of a furnace comprising means defining a confining retort, said means containing at the top a charging opening, a grate, means supporting the grate in the retort in a downwardly inclined position with its upper end adjacent the charging opening at the top, said grate dividing the retort into a plenum chamber at the downwardly facing side and a mixing chamber at the upwardly facing side, means for feeding a biomass material through the top opening to the upwardly facing side of said downwardly inclined grate in the form of a substantially uniformly thick bed for burning of the biomass material resting on the grate in the zone near the lower end of the grate and destructive distillation of the biomass material resting on the grate and the evolution of a gaseous medium in the zone above the zone of burning, said grate containing a plurality of relatively small openings through which primary air is supplied to the bed resting on the upwardly facing side of the grate in a sufficient quantity to sustain combustion and convert the burning mass to CO and ash, a pit at the bottom of the grate for receiving the ash means for supplying an excess of primary air to the downwardly facing side of the grate at the lower end, and a plurality of transversely spaced, longitudinally extending fins at the downwardly facing side of the grate so that the air flows along the downwardly facing side of the grate at a rate to maintain the grate and ash resting thereon at below the fusing temperature of the ash so that it remains particulate and, hence, loose and free to slide continuously downwardly on the upwardly facing side of the grate into said pit.
The method of generating combustible gases from a biomass material comprising forming a substantially uniformly thick bed of biomass material on the upwardly facing side of a downwardly inclined grate containing longitudinally and transversely distributed openings of 0.050 to 0.125 inch diameter and 1/2 inch spacing supported within a confining retort, establishing a zone of combustion within the retort on the upwardly facing side of the grate near the lower end thereof, supplying primary air to the bed through said openings in the grate to heat the descending biomass material to progressively convert the mass as it descends from the top of the grate to said zone of combustion to a gaseous medium and charcoal and, at the zone of combustion, converting the charcoal to CO and ash, conducting the heat away from the grate through fins at the downwardly facing side of the grate immersed in the flowpath of primary air to thus maintain the grid at a temperature lower than the fusion temperature of the ash such that the ash remains unfused and flows freely downwardly on the grate, providing means for receiving the ash from the zone of combustion at the lower end of the grate so that the distilled biomass material above the zone of combustion descends progressively into said zone of combustion and is converted into CO and ash, combining the evolved gases and CO within the mixing chamber at the upwardly facing side of the grate and supplying fresh biomass to the upper end of the grate at a rate such as to restrict the upwardly moving combustion to the lower end of the grate.
Dependencies are inferred from the claim text.