Low NOx Retrofit Technologies for Regenerative Glass Melters

The Southern California Gas Co. (SoCaIGas), Gas Research Institute (GRI), Institute of Gas Technology (IGT), and their industrial partners, Combustion Tec, Inc. (CTI), Air Products and Chemicals, Inc. (APCI), and Anchor Glass Container (Anchor) have undertaken a program to develop a retrofit second generation NOx control technology for natural gas-fired endport regenerative glass melters. The technology would also be applicable to many other types of high-temperature furnaces, as well as to other advanced high-performance burners. This second generation technology utilizes a unique method of air staging to reduce the oxygen availability and somewhat increase the luminosity in the flame's high temperature zone while improving flame temperature uniformity. The technique involves removing a portion of the hot combustion air that is normally supplied to the burners to create an oxygen-deficient flame condition that inhibits NOx formation. The hot air is withdrawn using an oxygen-driven ejector and injected into the furnace, at strategic locations downstream of the flame, to effectively complete the combustion without forming additional NOx. The technique has been retrofitted to Anchor's 165-ton/day endport furnace in Huntington Park, California, where it has been in operation since July 1993. Data collected during this operation show 35% to 50% NOx reduction to below 2.S lb/ton of glass produced, using oxygen representing less than S% of stoichiometric requirements. The changes made to the furnace were basically transparent to the operators and the glass pull rate and quality remained unaffected. Computational fluid dynamics (CFD) modeling was used to confirm the selected secondary oxidant injection location. Use of compressed air instead of oxygen for hot air ejection was also effective in reducing NOx, however, this resulted in an increase in CO levels in the top of the regenerators. This paper discusses the results from the field evaluation of air staging on the 165-ton/day endport furnace in Huntington Park, California.