The melting tank for TV funnel glass at Schott Glas was converted in 1996 from regenerative to oxy-fuel firing. The conversion was necessary to allow the required increase in tank size and pull. In connection with the conversion, NOx emissions were to be reduced to less than 1000mg/3. Due to the special conditions regarding oxy-fuel firing, the local authorities accepted an equivalent, mass-related NOx emission limit. Furthermore, the authorities demanded the implementation of the SNCR denitrification process for further improvements. During the test period, problems with stability of the temperature in the reaction zone and homogenization between flue gas and ammonia appeared. The process was optimized. Additional purging air was used in the reaction zone in order to control the temperature in the flue gas in order to improve the mixing of the ammonia with the flue gas.
