Low emission direct fired process air heating

Abstract

A system and method for heating process air is disclosed. Low NOx burners are provided with low temperature combustion air, e.g., less than about 0° C., and fuel at varying amounts to maintain a desired balance between low NO 2 and low CO emissions. The amount of combustion air and the amount of fuel may be adjusted to achieve desired low NO 2 and low CO via a feedback control system.

1 . A method for controlling emissions for a direct fired ventilation heater comprising:
 measuring a temperature of process air;   determining, at a processor, to heat a flow of the process air in response to the temperature meeting a criteria;   discharging a flow of combustion products from a burner into the flow of the process air to produce a heated flow;   measuring an emissions level of the heated flow; and   adjusting an amount of excess air provided to the burner in response to the emissions level.   
     
     
         2 . The method of  claim 1 , wherein the burner is a low NOx burner. 
     
     
         3 . The method of  claim 2 , wherein the criteria is at or below 0 degrees Centigrade. 
     
     
         4 . The method of  claim 2 , wherein the amount of excess air is an amount of air supplied to the burner above a stoichiometric amount for complete combustion. 
     
     
         5 . The method of  claim 4 , wherein the amount of excess air is about equal to or greater than 15 percent of a volume of air comprising the stoichiometric amount for complete combustion. 
     
     
         6 . The method of  claim 4 , further comprising controlling an amount of fuel provided to the burner based on the temperature of the process air. 
     
     
         7 . The method of  claim 1 , wherein the amount of excess air provided to the burner is adjusted by controlling a speed of a combustion air blower. 
     
     
         8 . The method of  claim 7 , wherein the speed of the combustion air blower is controlled, by the processor, based on the emissions level of the heated flow. 
     
     
         9 . The method of  claim 1 , further comprising guiding the heated flow into a ventilation system, wherein the ventilation system is disposed in an underground mine. 
     
     
         10 . The method of  claim 1 , further comprising maintaining the emissions level of the heated flow to about 0.2 to 0.027 parts per million (ppm) of nitrogen dioxide, 1 to 5 ppm of carbon monoxide, and/or below 0.25 ppm of sulfur dioxide. 
     
     
         11 . The method of  claim 1 , further comprising cooling a flow of combustion air provided to the burner via a chiller. 
     
     
         12 . A system for controlling emissions for a direct fired ventilation heater comprising:
 a low NOx burner;   a combustion air blower fluidly coupled to the low NOx burner; and   a controller having one or more processors configured to:
 determine a temperature of a flow of process air; 
 initiate the low NOx burner in response to the temperature of the flow of process air meeting a criteria to generate a heated flow; 
 measure an emissions level of the heated flow; 
 adjust a speed of the combustion air blower in response to the emissions level. 
   
     
     
         13 . The system of  claim 12 , wherein the criteria is at or below 0 degrees Centigrade. 
     
     
         14 . The system of  claim 12 , wherein adjusting the speed of the combustion air blower adjusts an amount of excess air provided to the low NOx burner. 
     
     
         15 . The system of  claim 14 , wherein the amount of excess air is an amount of air supplied to the low NOx burner above a stoichiometric amount for complete combustion. 
     
     
         16 . The system of  claim 15 , wherein the one or more processors are further configured to maintain the amount of excess air at a level that is about equal to or greater than 15 percent of a volume of air comprising the stoichiometric amount for complete combustion. 
     
     
         17 . The system of  claim 12 , wherein the one or more processors are further configured to control an amount of fuel provided to the low NOx burner based on the temperature of the flow of process air. 
     
     
         18 . The system of  claim 12 , further comprising a ventilation fan fluidly coupled to the low NOx burner; and
 a ventilation system fluidly coupled to the ventilation fan.   
     
     
         19 . The system of  claim 12 , further comprising a chiller configured to cool a flow of combustion air provided to the low NOx burner. 
     
     
         20 . The system of  claim 12 , wherein the one or more processors are further configured to maintain the emissions level of the heated flow to about 0.2 to 0.027 parts per million (ppm) of nitrogen dioxide, 1 to 5 ppm of carbon dioxide, and/or below 0.25 ppm of sulfur dioxide.