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Show AFRC Fall 1990 INTRODUCTION As reported previously, l low NOx burners employing fuel staging combined with flue gas recirculation (FGR) have been developed to meet the strict emissions regulations mandated by the South Coast · Air Quality Management District (SCAQ11D) which oversees the Los Angeles area air basin. Specifically addressed have been Rille 1109 which effects existing process heaters over 40 million Btu/hr heat input in refineries and chemical plants and Rule 1146 which effects process heaters 40 million Btu/hr and less. Rille 1109 limitS emissions from the larger heaters to 0.03 lb of NOx per million Btu (approximately 25-28 PPM depending on fuel composition) and Rule 1146 limits emissions of the smaller heaters to 40 PPM (0.05 Ib/11NfBtu). Field test data have recently been reported2 showing that staged fuel burners without FGR can meet SCAQ11D Rille 1146. This paper presents full-scale development test data collected in the John Zink Research Center and field test data collected at the ARCO Los Angeles Refinery in Carson, CA showing that the more stringent Rille 1109 can be met with a recently developed natural draft staged fuel burner that self-recirculates products of combustion (John Zink NDR series burner). LOW NOx BURNER REQUIRENfENTS Burner requirements for refinery applications are difficult because the fuel composition is not well defined and it varies significantly during operation. The fuels are typically variable mixtures of hydrogen, methane, ethane, propane, butane, ethylene, propylene and butylene with some nitrogen (N£), carbon dioxide and higher hydrocarbons. Another complication with burners for process heaters is the requirement for natural draft operation. Rather than utilize blowers to provide forced draft air flow, process heaters are typically designed to utilize the negative pressure that naturally occurs in the firebox and stack to induce combustion air into the burner. The- available draft is generally 0.2 to 0.6 inches w.c. negative rather than the 6 inches w.c. or more positive pressure commonly seen for forced draft burners. This low air pressure reduces the "options" available to a burner . designer w~e~ addressing low NOx design tech;niques. : DEVELOPNfENT TESTS As reported in reference 1, considerable low NOx burner development work was done utilizing forced flue gas recirculation with a variety of fuel compositions. In the present effort a natural draft staged fuel burner, designated as the NDR burner, was developed which uses momentum and flame burst buoyancy to recirculate combustion products from .. 1 |
