OCR Text |
Show as the motive force. Also, a significant quantity of the furnace gas is mixed with the combustion air in the primary combustion zone before mixing with the fuel. Callidus' design positioned primary fuel tips outside the burner block such that the fuel was injected through an opening in the burner block. The high pressure fuel jet draws the gases from the furnace and causes these furnace gases to mix with the combustion air and fuel in the primary combustion zone. This basic concept is now the standard of the industry. / COMBUSTION AIR INLET Figure VI Once again, the discussion of fuel N O x , prompt N 0 X and thermal N O x that is a part of all papers on N 0 X formation and reduction has been presented, along with the often repeated discussion of h o w staged air and staged fuel burners operate. Hopefully, at least the discussion of the different types of furnace gas recirculation burners have at least some descriptive content that has not been presented many times before. The intent of the discussion is to highlight the following important issues: 1. For gas fired process heater burners, the primary concern is thermal N 0 X that is formed at high temperatures and most, if not all, low N 0 X burner designs use the principle of flame "cooling" to lower the thermal N 0 X levels. 2. There is a significant difference in the way N 0 X reduction is accomplished in the internal flue gas recirculation burner, compared to other low N O x burners. The internal flue gas recirculation burner introduces additional mass into the primary combustion zone. As discussed, the burner shown in Figure VI introduces the flue gases in a different way than previous burner designs. This difference significantly impacts the effect in changes of various operating parameters on the N O x level produced by the burner, when compared to more conventional burners. NOx Correlations During the initial development of the first two types of internal flue gas recirculation burners discussed, the designs were changing rapidly and as a result no large data base was generated for any one type of burner. Callidus Technologies began the development of the L E burner (internal flue gas recirculation) in the summer of 1990. 6 rv-2i |