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 method of operating a non-catalytic biomass burner comprising:
 (a) turning on an auxiliary igniter, the igniter pointed toward a combustion chamber of the burner through an igniter opening in a side wall of the combustion chamber, the auxiliary igniter configured to direct heat into a lower portion the combustion chamber;   (b) monitoring by a computer a combustion temperature of an exhaust gas exiting the combustion chamber, the combustion temperature of the exhaust gas measured by a first temperature sensor positioned near the top of the combustion chamber, the exhaust gas being produced by the burning of a fuel in the combustion chamber, and the computer receiving the combustion temperature from the first temperature sensor;   (c) adding fuel to the combustion chamber at a first predetermined fuel rate when the combustion temperature reaches a first fuel temperature, wherein the rate of fuel addition to the combustion chamber is controlled by the computer controlling a fuel feed assembly that delivers fuel to a fuel inlet tube of the burner;   (d) adding fuel to the combustion chamber at a second predetermined fuel rate by controlling the fuel feed assembly when the combustion temperature reaches a second fuel temperature, the second fuel temperature being higher than the first fuel temperature; and   (e) turning off the auxiliary igniter when the combustion chamber temperature reaches an igniter off temperature.   
     
     
         2 . The method of  claim 1 , wherein the first fuel temperature is a temperature between about 400° F. and about 700° F. 
     
     
         3 . The method of  claim 1 , wherein the second fuel temperature is a temperature between about 900° F. and about 1100° F. 
     
     
         4 . The method of  claim 1 , wherein the igniter off temperature is a temperature between about 1400° F. and about 1600° F. 
     
     
         5 . The method of  claim 1 , wherein the second predetermined fuel rate is a user selected fuel rate, and wherein the first predetermined fuel rate is less than the second predetermined fuel rate. 
     
     
         6 . The method of  claim 5 , wherein the first predetermined fuel rate is about half of the second predetermined fuel rate. 
     
     
         7 . The method of  claim 1 , further comprising:
 (f) heating a circulating fluid of a heat exchanger by transferring heat from the exhaust gas to the circulating fluid.   
     
     
         8 . The method of  claim 1 , further comprising:
 (g) pulling air into the combustion chamber through one or more air inlets by operation of a fan positioned near an exit opening of the burner on the distal side of the heat exchanger, wherein each of the air inlet spans the side wall of the combustion chamber such that air flows into the combustion chamber from the outside of the combustion chamber through the one or more air inlets.   
     
     
         9 . The method of  claim 8 , further comprising:
 (h) controlling the speed of the fan by the computer based on the combustion temperature from the first temperature sensor.   
     
     
         10 . The method of  claim 8 , further comprising:
 (i) controlling the rate of fuel addition to the combustion chamber by the computer controlling a fuel feed assembly based on a distal exhaust gas temperature from a second temperature sensor in the path of exhaust flow near an exit opening of the burner.   
     
     
         11 . A method of operating a non-catalytic biomass burner comprising:
 (a) measuring by a first temperature sensor a combustion temperature of an exhaust gas exiting a combustion chamber of the burner, the exhaust gas being produced by the burning of a fuel in the combustion chamber;   (b) monitoring by a computer the combustion temperature of the exhaust gas exiting the combustion chamber, the computer receiving the combustion temperature from the first temperature sensor;   (c) determining a fuel rate for adding fuel to the combustion chamber, wherein the fuel rate is determined by the computer based on the combustion temperature; and   (d) adding fuel to the combustion chamber at the fuel rate determined in step (c), wherein the rate at which the fuel is added to the combustion chamber is controlled by the computer controlling a fuel feed assembly that delivers fuel to a fuel inlet tube of the burner.   
     
     
         12 . The method of  claim 11 , wherein the fuel rate is determined in step (c) to be a first predetermined fuel rate if the combustion temperature is equal to or greater than a first fuel temperature, and wherein the fuel rate is determined in step (c) to be a second predetermined fuel rate if the combustion temperature is equal to or greater than both the first fuel temperature and a second fuel temperature, and
 wherein the second fuel temperature is greater than the first fuel temperature, and wherein the second predetermined fuel rate is greater than the first predetermined fuel rate.   
     
     
         13 . The method of  claim 12 , wherein the first fuel temperature is a temperature between about 400° F. and about 700° F. 
     
     
         14 . The method of  claim 12 , wherein the second fuel temperature is a temperature between about 900° F. and about 1100° F. 
     
     
         15 . The method of  claim 12 , further comprising:
 (e) selecting by a user the second predetermined fuel rate.   
     
     
         16 . The method of  claim 12 , wherein the first predetermined fuel rate is about half of the second predetermined fuel rate. 
     
     
         17 . The method of  claim 11 , further comprising:
 (f) turning off the addition of fuel to the burner such that the fuel rate is zero if the combustion temperature is greater than a user combustion temperature.   
     
     
         18 . The method of  claim 17 , wherein the user combustion temperature is selected by a user and is a temperature between about 1500° F. and 1700° F. 
     
     
         19 . The method of  claim 17 , further comprising:
 (g) turning on the addition of fuel to the burner at the fuel rate determined in step (c) if the combustion temperature is less than the user combustion temperature.   
     
     
         20 . The method of  claim 11 , wherein step (c) of determining the fuel rate comprises:
 (h) calculating the fuel rate automatically using a proportional-integral-derivative (PID) function based on monitored combustion temperatures.   
     
     
         21 . The method of  claim 20 , wherein step (c) further comprises:
 (i) determining by the computer if the fuel rate calculated in step (h) is greater than a maximum fuel rate equal to a user selected fuel rate plus a maximum fuel offset; and   (j) setting the fuel rate to the maximum fuel rate if the fuel rate calculated in step (h) is greater than the maximum fuel rate.   
     
     
         22 . The method of  claim 20 , wherein step (c) further comprises:
 (k) determining by the computer if the fuel rate calculated in step (h) is less than a minimum fuel rate equal to a user selected fuel rate minus a minimum fuel offset; and   (l) setting the fuel rate to the minimum fuel rate if the fuel rate calculated in step (h) is less than the minimum fuel rate.   
     
     
         23 . The method of  claim 20 , wherein step (c) further comprises:
 (m) determining by the computer if the combustion temperature is greater than a user combustion temperature plus a temperature offset; and   (n) setting the fuel rate to a preset minimum fuel rate if the combustion temperature is greater than the user combustion temperature plus the temperature offset.   
     
     
         24 . The method of  claim 20 , wherein the temperature offset is a temperature difference in a range from about 20° F. to about 100° F. 
     
     
         25 . The method of  claim 20 , wherein step (h) is performed if an auto combustion state has a status of being enabled. 
     
     
         26 . The method of  claim 20 , wherein step (h) is performed if the combustion temperature is greater than a user stable temperature. 
     
     
         27 . The method of  claim 26 , wherein user stable temperature is a temperature in a range from about 1200° F. to about 1400° F. 
     
     
         28 . The method of  claim 20 , wherein step (h) is performed if a system status is set to stable, wherein the system status is set to stable if the combustion temperature is greater than a user combustion temperature or if the combustion temperature is greater than a user stable temperature for a period of time greater than a stable countdown timer. 
     
     
         29 . The method of  claim 28 , wherein the system status is reset and not set to stable if the combustion temperature is less than or equal to a user stable temperature or if an auxiliary igniter is turned on. 
     
     
         30 . The method of  claim 11 , further comprising:
 (o) turning off the addition of fuel to the burner such that the fuel rate is zero if the combustion temperature is greater than a combustion warning off temperature.   
     
     
         31 . The method of  claim 11 , further comprising:
 (p) determining by the computer if the combustion temperature is less than an igniter on temperature; and   (q) turning on an auxiliary igniter if the combustion temperature is less than the igniter on temperature,   wherein the igniter is pointed toward the combustion chamber of the burner through an igniter opening in a side wall of the combustion chamber, the auxiliary igniter configured to direct heat into a lower portion the combustion chamber.   
     
     
         32 . The method of  claim 31 , wherein the igniter on temperature is determined by a user selected smoke guard setting. 
     
     
         33 . The method of  claim 31 , wherein the igniter on temperature is a temperature within a range from about 800° F. to about 1300° F. 
     
     
         34 . The method of  claim 31 , further comprising:
 (r) determining by the computer if the combustion temperature is greater than an igniter off temperature; and   (s) turning off the auxiliary igniter if the combustion temperature is greater than the igniter off temperature,   wherein the igniter off temperature is greater than the igniter on temperature.   
     
     
         35 . The method of  claim 34 , wherein the igniter off temperature is determined by a user selected smoke guard setting. 
     
     
         36 . The method of  claim 34 , wherein the igniter off temperature is a temperature within a range from about 1100° F. to about 1700° F. 
     
     
         37 . The method of  claim 11 , further comprising:
 (t) operating a fan at a fan speed, wherein the fan operates to pull air into the combustion chamber of the burner, and wherein the fan speed of the fan is controlled by the computer based on the combustion temperature.   
     
     
         38 . The method of  claim 37 , further comprising:
 (u) determining by the computer if the combustion temperature is equal to or greater than a maximum fan temperature; and   (v) setting the fan speed of the fan to a maximum fan speed if the combustion temperature is equal to or greater than the maximum fan temperature.   
     
     
         39 . The method of  claim 38 , wherein the maximum fan temperature is a temperature between 1500° F. and 2100° F. 
     
     
         40 . The method of  claim 38 , wherein the maximum fan speed is between about 60% and about 100% of the capacity of the fan. 
     
     
         41 . The method of  claim 37 , further comprising:
 (w) determining by the computer if the combustion temperature is equal to or less than a minimum fan temperature; and   (x) setting the fan speed of the fan to a minimum fan speed if the combustion temperature is equal to or less than the minimum fan temperature.   
     
     
         42 . The method of  claim 41 , wherein the minimum fan temperature is a temperature between 800° F. and 1200° F. 
     
     
         43 . The method of  claim 41 , wherein the minimum fan speed is greater than 0% but less than about 50% of the capacity of the fan. 
     
     
         44 . The method of  claim 31 , further comprising:
 (y) determining by the computer if the combustion temperature is greater than a minimum fan temperature and less than a maximum fan temperature; and   (z) setting the fan speed of the fan to an intermediate fan speed if the combustion temperature is greater than the minimum fan temperature and less than the maximum fan temperature,   wherein the intermediate fan speed depends on a predetermined number of temperature intervals between the minimum fan temperature and the maximum fan temperature and on which temperature interval includes the combustion temperature.   
     
     
         45 . A computer program product for controlling the operation of a non-catalytic biomass burner comprising:
 a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising:
 computer readable program code configured to receive from a first temperature sensor a combustion temperature of an exhaust gas exiting a combustion chamber of the burner, the exhaust gas being produced by the burning of a fuel in the combustion chamber; 
 computer readable program code configured to monitor by a computer the combustion temperature of the exhaust gas exiting the combustion chamber; 
 computer readable program code configured to determine by the computer based on the combustion temperature a fuel rate for adding fuel to the combustion chamber; and 
 computer readable program code configured to control by the computer the addition of fuel to the combustion chamber a fuel feed assembly at the determined fuel rate, wherein the fuel rate is controlled by the computer controlling a fuel feed assembly that delivers fuel to a fuel inlet tube of the burner.