Flameless Oxidation as a Means to Reduce NOx Emissions in Glass Melting Furnaces

Abstract

In the glass industry, very high process temperatures are required in order to melt the raw materials. These temperature levels are usually achieved by burning natural gas with strongly pre-heated air. However, this creates ideal conditions for a strong formation of nitrous oxides (NOX), a pollutant whose emissions are strictly regulated. The industry is therefore very much interested in technologies to suppress the production of NOX within the furnace itself. One possible approach is the so-called flameless oxidation, a novel combustion regime which is characterized by very homogeneous temperature distributions and low NOX production. While this form of combustion is firmly established in the steel industry, the glass industry has been reluctant to change its production methods as the glass melt is very sensitive to changes in the furnace conditions. Gas- und Warme-Institut Essen e.V. (GWI), in cooperation with its partners, investigated how to best introduce flameless oxidation into glass melting furnaces. Using both simulation and experimental techniques, a GlasFLOX burner was developed and then examined with regards to its NOX reduction performance. In a second step, the retrofitting of an operating furnace was carried out, based on a strategy determined by extensive CFD simulations. After five years of operation, the operators of the retrofitted plant report unchanged product quality, while NOX emissions have been reduced by about 50 %.