For several years low NOx operation of oil field steam generators has been accomplished through the use of flue gas recirculation (FGR). FGR technologies can be easily retrofitted to existing steamers burning natural gas to achieve NOx emission levels between 25–30 ppmvd @ 3% 02. While fairly cost effective to install, FGR systems further incur an increase in operating costs due to the additional fan horsepower required for the flue gas supply. As permissible stack emission levels continue to decrease, alternative technologies must emerge which address the non-FGR NOx formation rate without risking loss of burner stability or unreasonably increasing combustion system operating costs.

North American Mfg. has combined its own patented ultra low NOx burner and control technology with Shell Oil's patented combustion process and installed the system on an oil field steam generator. The resulting combustion system produces 13–17 ppmvd @ 3% 02 of NOX while firing natural gas without the use of FGR. Further development of the technology may provide NOX emission performance approaching selective catalytic reduction (SCR) levels at a greatly reduced cost.

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