Non-catalytic biomass fuel burner and method

Abstract

The present invention relates to a non-catalytic biomass burner that may be used to burn a variety of fuel types at high efficiencies. The burner may include a cylindrical combustion chamber with an auxiliary igniter to heat the fuel in the combustion chamber until desirable combustion temperatures are reached. Fuel may be added to the chamber via a fuel feed assembly, and the rate of fuel addition to the chamber by the fuel feed assembly may be controlled by a computer. A fan located on the distal side of a flue pipe from the chamber may also be provided that pulls air into the chamber through one or more air inlets that are designed to encourage cyclonic air and exhaust flow in the chamber. Methods are further provided for controlling the manner of operation of the burner by a computer that may be instructed by a computer program code.

What is claimed is: 
     
         1 . A non-catalytic biomass burner comprising:
 a combustion chamber for burning a fuel to produce an exhaust gas, wherein the combustion chamber has a cylindrical interior shape with the sides of the combustion chamber enclosed by a side wall;   one or more air inlets spanning the side wall of the combustion chamber to allow air to enter the combustion chamber from the outside of the combustion chamber through the one or more air inlets;   a flue pipe connected at its proximal end to the top of the combustion chamber, the flue pipe being configured to receive the exhaust gas from the combustion chamber through a flue opening,   a heat exchanger for transferring heat from the exhaust gas to a circulating fluid of the heat exchanger, wherein the heat exchanger is positioned in the path of the exhaust gas between the flue pipe and an exit opening of the burner, and wherein the flue pipe delivers the exhaust gas to the heat exchanger;   a fuel inlet tube having an upper portion and a lower portion, wherein a fuel opening in the side wall of the combustion chamber allows fuel to enter the combustion chamber from the lower portion of the fuel inlet tube; and   an auxiliary igniter pointed toward the combustion chamber through an igniter opening in the side wall of the combustion chamber, the auxiliary igniter configured to direct heat into a lower portion the combustion chamber.   
     
     
         2 . The biomass burner of  claim 1 , further comprising:
 a first temperature sensor positioned near the top of the combustion chamber to measure a combustion temperature of the exhaust gas exiting the combustion chamber.   
     
     
         3 . The biomass burner of  claim 2 , wherein the first temperature sensor is positioned in a proximal portion of the flue pipe. 
     
     
         4 . The biomass burner of  claim 2 , further comprising:
 a computer; and   a fuel feed assembly,   wherein the computer is in communication with the fuel feed assembly and the first temperature sensor, and   wherein the computer controls the rate at which the fuel is added to the combustion chamber through the fuel inlet tube based on the combustion temperature from the first temperature sensor by controlling the speed of operation of the fuel feed assembly.   
     
     
         5 . The biomass burner of  claim 4 , wherein the fuel feed assembly comprises one or more auger screws and one or more motors, the auger screws being rotated by the one or more motors to deliver fuel to the upper portion of the fuel inlet tube, and
 wherein the computer controls the rate at which fuel is added to the fuel inlet tube by controlling the speed of rotation of at least one of the auger screws.   
     
     
         6 . The biomass burner of  claim 4 , wherein the fuel feed assembly further comprises a hopper for holding the fuel,
 wherein the auger screws comprise a feed auger and an elevator screw,   wherein the feed auger directs the fuel from the hopper through an opening in the side of the hopper and into the elevator screw, and   wherein the elevator screw transports the fuel into the upper portion of the fuel inlet tube of the burner.   
     
     
         7 . The biomass burner of  claim 1 , wherein the longitudinal axis of the fuel inlet tube is angled greater than 45° and less than 90° relative to the ground. 
     
     
         8 . The biomass burner of  claim 1 , further comprising:
 a computer, and   a first temperature sensor positioned near the top of the combustion chamber to measure a combustion temperature of the exhaust gas exiting the combustion chamber,   wherein the computer controls when the auxiliary igniter is turned on or off based on the combustion temperature from the first temperature sensor.   
     
     
         9 . The biomass burner of  claim 1 , wherein the combustion chamber comprises an upper portion and a lower portion separated by a boundary, and
 wherein an inner part of the side wall facing the upper portion of the combustion chamber comprises a material that is different than the material of an inner part of the side wall facing the lower portion of the combustion chamber.   
     
     
         10 . The biomass burner of  claim 9 , wherein the inner part of the side wall facing the upper portion of the combustion chamber comprises a ceramic fiber composite, and the inner part of the side wall facing the lower portion of the combustion chamber comprises a refractory brick or castable. 
     
     
         11 . The biomass burner of  claim 9 , wherein the fuel opening in the side wall where the lower portion of the fuel inlet tube meets the combustion chamber intersects the boundary between the upper and lower portions of the combustion chamber. 
     
     
         12 . The biomass burner of  claim 9 , wherein the igniter opening in the side wall of the combustion chamber intersects the boundary between the upper and lower portions of the combustion chamber. 
     
     
         13 . The biomass burner of  claim 1 , further comprising:
 a variable speed fan positioned on the distal side of the heat exchanger that is configured to pull air into the combustion chamber.   
     
     
         14 . The biomass burner of  claim 13 , further comprising:
 a computer; and   a first temperature sensor positioned near the top of the combustion chamber to measure a combustion temperature of the exhaust gas exiting the combustion chamber,   wherein the computer is in communication with the variable speed fan and the first temperature sensor, and wherein the computer controls the fan speed of the variable speed fan based on the combustion temperature from the first temperature sensor.   
     
     
         15 . The biomass burner of  claim 1 , wherein each air inlet is angled downward toward the combustion chamber and has a longitudinal axis that is tangential to the inner surface of the side wall of the combustion chamber. 
     
     
         16 . The biomass burner of  claim 15 , wherein the one or more air inlets are configured to produce cyclonic air flow within the combustion chamber. 
     
     
         17 . The biomass burner of  claim 15 , further comprising:
 a plurality of vertical side panels positioned above a floor of the burner, the plurality of vertical side panels surrounding the side wall of the combustion chamber to define a plenum space between the side wall and the plurality of vertical side panels; and   one or more air intake holes in the floor of the burner between the outside of the combustion chamber and the plurality of vertical side panels.   
     
     
         18 . The biomass burner of  claim 17 , further comprising:
 one or more channels within the plenum space adjacent to the outside of the side wall of the combustion chamber,   wherein the one or more channels span from near the floor of the burner to a location near the top of the plenum space, and wherein a gap is present between the top of the one or more channels and the top of the plenum space to allow air to enter the top of the one or more channels from the plenum space, and   wherein the air inlets span from a lower portion of the one or more channels to the interior of the combustion chamber.   
     
     
         19 . The biomass burner of  claim 18 , wherein the top of the plenum space is enclosed by a top panel and the bottom of the plenum space is enclosed by the floor of the burner, and
 wherein the gap is present between the top of the one or more channels and the top panel of the plenum.   
     
     
         20 . The biomass burner of  claim 1 , further comprising:
 a computer; and   a second temperature sensor that measures a distal exhaust gas temperature on the distal side of the heat exchanger,   wherein the computer controls the operation of a fuel feed assembly of the burner based on the distal exhaust gas temperature from the second temperature sensor.   
     
     
         21 . The biomass burner of  claim 1 , wherein the burner burns a biomass fuel at an efficiency of 80% or greater. 
     
     
         22 . The biomass burner of  claim 1 , wherein the burner has a predetermined output in a range of about 100,000 to about 500,000 BTU/hr. 
     
     
         23 . The biomass burner of  claim 1 , further comprising:
 a fuel stirrer located at the bottom of the combustion chamber for stirring the fuel.   
     
     
         24 . A non-catalytic biomass burner comprising:
 a combustion chamber for burning a fuel to produce a hot exhaust gas, wherein the combustion chamber has a cylindrical interior shape with the sides of the combustion chamber enclosed by a side wall;   one or more air inlets spanning the side wall of the combustion chamber to allow air to enter the combustion chamber from the outside of the combustion chamber through the one or more air inlets;   a plurality of vertical side panels positioned above a floor of the burner, the plurality of vertical side panels surrounding the side wall of the combustion chamber to define a plenum space between the side wall and the plurality of vertical side panels;   one or more air intake holes near the bottom of the plenum space to allow air to enter the plenum space;   a flue pipe connected at its proximal end to the top of the combustion chamber, the flue pipe being configured to receive the exhaust gas from the combustion chamber through a flue opening and deliver the exhaust gas to a heat exchanger,   a fuel inlet tube having an upper portion and a lower portion, wherein a fuel opening in the side wall of the combustion chamber allows fuel to enter the combustion chamber from the lower portion of the fuel inlet tube; and   an auxiliary igniter pointed toward the combustion chamber through an igniter opening in the side wall of the combustion chamber, the auxiliary igniter configured to direct heat into a lower portion the combustion chamber.   
     
     
         25 . The biomass burner of  claim 24 , further comprising:
 one or more channels within the plenum space adjacent to the outside of the side wall of the combustion chamber,   wherein the one or more channels span from near the floor of the burner to a location near the top of the plenum space, and wherein a gap is present between the top of the one or more channels and the top of the plenum space to allow air to enter the top of the one or more channels from the plenum space, and   wherein the air inlets span from a lower portion of the one or more channels to the interior of the combustion chamber.   
     
     
         26 . The biomass burner of  claim 24 , wherein the one or more air intake holes are in the floor of the burner between the outside of the combustion chamber and the plurality of vertical side panels. 
     
     
         27 . The biomass burner of  claim 24 , wherein the air inlet is angled downward toward the combustion chamber and has a longitudinal axis that is tangential to the inner surface of the side wall of the combustion chamber. 
     
     
         28 . A non-catalytic biomass burner comprising:
 a combustion chamber for burning a fuel to produce an exhaust gas, wherein the sides of the combustion chamber are enclosed by a side wall;   one or more air inlets spanning the side wall of the combustion chamber to allow air to enter the combustion chamber from the outside of the combustion chamber through the one or more air inlets;   a flue pipe connected at its proximal end to the top of the combustion chamber, the flue pipe being configured to receive the exhaust gas from the combustion chamber through a flue opening,   a fuel inlet tube having an upper portion and a lower portion, wherein a fuel opening in the side wall of the combustion chamber allows fuel to enter the combustion chamber from the lower portion of the fuel inlet tube; and   an auxiliary igniter pointed toward the combustion chamber through an igniter opening in the side wall of the combustion chamber, the auxiliary igniter configured to direct heat into a lower portion the combustion chamber;   a first temperature sensor positioned near the top of the combustion chamber to measure a combustion temperature of the exhaust gas exiting the combustion chamber; and   a computer in communication with the first temperature sensor, the computer receiving the combustion temperature from the first temperature sensor.   
     
     
         29 . The non-catalytic biomass burner of  claim 28 , wherein the computer controls when the auxiliary igniter is turned on or off based on the combustion temperature from the first temperature sensor. 
     
     
         30 . The non-catalytic biomass burner of  claim 28 , further comprising:
 a fuel feed assembly,   wherein the computer is in further communication with the fuel feed assembly, and   wherein the computer controls the rate at which the fuel is added to the combustion chamber through the fuel inlet tube based on the combustion temperature from the first temperature sensor by controlling the speed of operation of the fuel feed assembly.   
     
     
         31 . The non-catalytic biomass burner of  claim 28 , further comprising:
 a variable speed fan positioned on the distal side of the flue pipe that is configured to pull air into the combustion chamber.   wherein the computer is in further communication with the variable speed fan, and wherein the computer controls the fan speed of the variable speed fan based on the combustion temperature from the first temperature sensor.