REDUCING NOX AT THE BREVIK-CEMENT-WORKS IN NORWAY - TRIALS WITH STEPPED FUEL SUPPLY TO THE CALCINER

A kiln with a Low-NO(x) calciner for precalcination has been in operation at Norcem AS's Brevik works since 1987. The combustion is carried out in stages in the calciner. About 50 % of the fuel is divided between a Low-NO(x) burner and a calciner burner. The calciner is fueled with pulverized coal. Only for testing the Low-NO(x) part of the calciner uses both pulverized coal through the burner and shredded used tyres through a chute (up to a maximum of 15% of the kiln plant's total energy consumption). The concentrations of NO(x), SO2 and CO in the clean gas are measured by continuous emission measuring equipment. Initial investigations showed that when using coal as the reducing fuel the NO(x) emission did drop, but there was a significant increase in the concentration of CO and SO2. On the other hand the increases in CO and SO2 concentrations were less with the addition of shredded tyres. Further investigations should provide explanations about the causes, and in particular should also explain the effect on the kiln operating characteristics during continuous operation. So far the NO(x) concentration level in the clean gas without stepped combustion has been between about 0.8 and 1.1 g NO2/m3 (dry, standard state) at 10 vol. % 02.