Patent ID: 8117974

Claim:
An apparatus that extracts energy from biomass fuel or fiber, comprising: a vertically elongated combustion chamber having a top end, a flame containment portion, and a lower end portion; a supply of a biomass fuel for combusting in the combustion chamber; at least one suspension burner mounted at the top end of the combustion chamber and communicating with the supply of the biomass fuel, the burner configured for projecting a flame down a longitudinal axis of the flame containment portion of the combustion chamber; a wall of the combustion chamber defining a heat transfer apparatus having at least a portion of a heat collection surface located radially from the flame; and an exhaust opening in a side wall of the combustion chamber vertically spaced from a distal end of the flame containment portion and vertically spaced lower of a substantial majority of the heat collection surface, whereby the biomass fuel combusted within the combustion chamber yields a mixture containing hot flue gas and entrained molten ash above the exhaust opening, the hot flue gas at about a combustion temperature that is about the temperature of the flame, with heat from the hot flue gas transferring to the heat collection surface substantially by radiation to yield a mixture of warm flue gas and non-molten ash, the warm flue gas at a second temperature in a range from about an ash fusion temperature to about an ash molten temperature, the range lower than the combustion temperature; a temperature modulator that communicates with a supply of a cold air or gas and meters the cold air or gas into the combustion chamber proximate to the exhaust opening, to cool the warm flue gas and yield a mixture containing cool flue gas and non-molten ash, the cool flue gas at third temperature in a range from ambient temperature to about the ash fusion temperature, the third temperature lower than the second temperature, which cool flue gas communicates from the combustion chamber through the exhaust opening.