Boiler apparatus for combusting processed agriculture residues (PAR) and method

An apparatus that extracts energy from processed agriculture residue (PAR) fuel, comprising:

• a vertically elongated combustion chamber having a top end, a flame containment portion, and a lower end portion;
• a supply of a processed agriculture residue (PAR) fuel for combusting in the combustion chamber, the PAR fuel having a moisture content of about 12% by weight or less;
• at least one suspension burner mounted at the top end of the combustion chamber and receiving a mixture of combustion air and PAR 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 hopper 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 PAR fuel combusted within the combustion chamber yields a mixture containing hot flue gas of a first temperature and entrained molten ash above the exhaust opening, the first temperature at about a combustion 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 of a second temperature and non-molten ash, the 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 receives cooling gas from a supply of the cooling air at a third temperature, which modulator meters the cooling air into the combustion chamber proximate to the exhaust opening, to cool the warm flue gas and yield a mixture containing cool flue gas at a fourth temperature and non-molten ash, the fourth temperature less than the ash fusion temperature, the fourth temperature lower than the second temperature, which cool flue gas exits from the combustion chamber through the exhaust opening