Solid fuel burner for a heating apparatus

• US 6,336,449 B1
• Filed: 02/04/2000
• Issued: 01/08/2002
• Est. Priority Date: 04/24/1997
• Status: Expired due to Fees

• Current Assignee: Dell-Point Combustion Incorporated
• Original Assignee: Dell-Point Combustion Incorporated
• Inventors: Lapointe, Claude, Drisdelle, Mark
• Primary Examiner(s): Lazarus, Ira S.
• Assistant Examiner(s): Cocks, Josiah C.
• Application Number:
  US09/403,032
• Time in Patent Office: 704 Days
• Field of Search: 126/73, 126/68, 126/77, 126/58, 126/540, 126/542, 126/543, 126/554, 126/555, 126/107, 126/112, 126/146, 126/245, 126/242, 126/25.R, 126/152.R, 126/155, 110/165.R, 110/166, 110/294, 110/293, 110/233, 110/110, 110/185, 110/186, 110/188, 110/297, 110/300, 431/337, 431/351
• US Class Current: 126/73
• CPC Class Codes: F23B 1/36 shaft-type
• CPC Class Codes: F23B 50/12 the fuel being fed to the combustion zone by free fall or by sliding along inclined surfaces, e.g. from a conveyor terminating above the fuel bed
• CPC Class Codes: F23B 60/00 Combustion apparatus in which the fuel burns essentially without moving
• CPC Class Codes: F23B 90/06 the primary combustion being a gasification or pyrolysis in a reductive atmosphere
• CPC Class Codes: F23G 2203/107 with vibrating grate
• CPC Class Codes: F23G 2207/103 for oxygen
• CPC Class Codes: F23G 2207/30 Oxidant supply
• CPC Class Codes: F23G 2209/261 Woodwaste
• CPC Class Codes: F23L 15/00 Heating of air supplied for combustion
• CPC Class Codes: F23M 5/085 using air or other gas as the cooling medium
• CPC Class Codes: F23N 5/006 the detector being sensitive to oxygen
• CPC Class Codes: F24B 1/024 for pulverulent fuels
• CPC Class Codes: Y02A 40/928 Cooking stoves using biomass
• CPC Class Codes: Y02E 20/34 Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Abstract

A burner system is described for burning granular pellets and similarly sized solid biomass heating fuel, e.g. wood pellets. It includes an air tight fire chamber having an exhaust outlet in an upper region thereof and a burner (10) in the bottom thereof for converting the solid fuel to fuel gases and ash in the presence of a limited air supply and combusting the gases formed. The burner comprises upright co-axial inner (12) and outer (11) cylindrical walls providing a confined central gasification/combustion chamber surrounded by an annular combustion air manifold (15). The annular combustion air manifold (15) is closed at the top and bottom with an air inlet (16) in the outer wall and a plurality of spaced aperatures (17) arranged in upward rows in the inner cylindrical wall providing air inlets from the combustion air manifold to the combustion zone of the chamber. A grate at the bottom of the gasification/combustion chamber holds the solid fuel while allowing ash to pass through the grate.

Claims

1. A burner system for burning pellets or granules of solid biomass heating fuel, comprising an air tight combustion chamber having an exhaust outlet in an upper region thereof and a burner means in the bottom thereof for converting the solid fuel to fuel gases and ash in the presence of a limited air supply, said burner means comprising upright co-axial inner and outer cylindrical walls providing a central gasification/combustion chamber surrounded by an annular combustion air manifold, said annular manifold being closed at the top and bottom and having an air inlet in the outer wall and a plurality of spaced apertures in the inner cylindrical wall arranged in at least one spiral path extending up the wall providing air inlets from the annular combustion air manifold to the gasification/combustion chamber, a grate at the bottom of the gasification/combustion chamber for holding solid fuel while allowing ash to pass through, an air tight ash-receiving chamber below the gasification/combustion chamber and fan means adapted to provide a negative pressure in the gasification/combustion chamber to thereby draw combustion air into and upwardly through the chamber with a swirling motion, whereby solid fuel fed to the grate at the bottom of the gasification/combustion chamber is pyrolyzed in the presence of a limited air supply to form combustion gases which are drawn upwardly through the gasification/combustion chamber while contacting heated combustion air entering through said spaced air inlets.

2. A burner system according to claim 1 wherein the air inlet holes are arranged in at least two spiral paths extending up the wall.

3. A burner system according to claim 1, wherein air inlet holes in the region of the grate are adapted to provide sufficient air only to pyrolyze the solid fuel and form fuel gases.

4. A burner system according to claim 1 wherein the spiral arrays of air inlet holes are arranged as mirror images spiral paths on opposite sides of the chamber and are spaced a distance vertically above the grate sufficient to maintain the temperature of the solid fuel below melting temperatures.

5. A burner system according to claim 1 which includes feeder means for feeding solid fuel into the gasification/combustion chamber through the top thereof.

6. A burner system according to claim 1 which includes feeder means for feeding solid fuel in a horizontal path onto the grate at the bottom of the chamber.

7. A burner system according to claim 1 which includes an oxygen sensor in the exhaust outlet, said oxygen sensor being adapted to control the fan speed and thereby the amount of combustion air.

8. A burner system according to claim 1 wherein the grates are formed of parallel triangular shaped rods.

9. A burner system according to claim 1 which includes a pair of vertically spaced grates located below the gasification/combustion chamber.

10. A burner system according to claim 1 mounted in the bottom wall of a fire chamber of a pellet stove.

11. A burner system according to claim 10 wherein the fire chamber has an exhaust gas outlet.

12. A burner system according to claim 11 wherein a fan is mounted in the exhaust gas outlet for providing a negative pressure in the gasification/combustion chamber.

13. A burner system according to claim 12 wherein heat exchange passages surrounded said stove fire chamber and fan means are adapted to circulate room air through said heat exchange passages and back into the room.

14. A burner system according to claim 1 adapted to operate as an air tight system at an air:

fuel ratio of less than 8;

1.