OCR Text |
Show There are numerous practical factors in real industrial applications which will influence flame envelope conditions and, therefore, NO formation appreciably. - The excess combustion air factor during operation of burners which will alter flame temperatures and availability of oxygen. - The dimensions of and conditions inside the firebox which will determine rates of heat transfer and, therefore, mean flame temperatures. - The load factor or state of process turndown which will reduce flame temperatures and gas temperatures inside the firebox. - The use of combustion air preheat may be necessary for process efficiency reasons but it will increase flame temperatures detrimentally. - The amount of internal and external burner recirculation of reacted and partially reacted products of combustion, which will affect flame temperatures and atmosphere composition. - The use of multistaged combustion air to allow initial operation at reducing and/or low temperature conditions, followed by later addition of the balance of required air. - The size of the flame envelope because small flames will tend to lose temperature more readily than large ones in most furnaces. - The type and shape of flame which will also affect rates of transfer and flame temperatures. - The use of combustion air vitiated with flue gases which will reduce flame temperatures. - The obvious limitations imposed by smoke and hydrocarbon emissions which will prevent operating with overall reducing conditions, and may make it difficult at very low overall excess air. 13/5 |