OCR Text |
Show Introduction Almost all practical methods of reducing NOx emissions from burners involve reducing the product gas temperatures [1]. The basis of this approach is that the rates of formation of NO, the precursor to NOx, is exponentially dependent on temperature [2]. Currently many different burner designs are being developed with this strategy in mind. One method of reducing product gas temperatures that has not been exploited is to use lean premixed combustion. This paper is a preliminary work that explores this approach for practical burners. Premixed combustion is characterized by the fuel and air being mixed at the molecular level prior to burning. The combustion of liquid fuel droplets or solid fuel particles by definition is not premixed, and hence premixed combustion is only relevant to gas phase combustion. For practical burners this primarily means methane:air or propane:air burners. Based on the National Energy Board [3] and Environment Canada [4] estimates of fuel usage and pollution formation the impact of altering NOx emissions from these burners can be assessed. Figure 1 shows the breakdown of NOx emissions in Canada by industrial section. The two sectors that use substantial portions of natural gas for combustion are stationary facilities (refineries, gas plants, commercial boilers, residential furnaces, and power plants) and industry. The total of these two sectors accounts for 350/0 of the NOx produced in Canada, but not all energy used in these areas is natural gas. TheNational Energy Board's primary energy demands allow the portion of NOx produced as a result of natural gas combusti~n to be estimated. In total about 18% of all the NOx produced in Canada results from the combustion of natural gas either for heating, as part of an industrial process, or for electricity generation. It is this fraction of NOx emission that could be affected by using the lean premixed techniques described here. The advantage of using lean premixed combustion, is that the temperature of the product |