Reducing NOx and CO emissions by burning plastics in the calciner of a rotary cement kiln plant

These investigations dealt with the reduction of NOx and CO emissions by us ing plastics in the calciners of cement kiln plants. In order to obtain inf ormation about their combustion behaviour various plastics were compared wi th gas-flame coal as fuels in preliminary trials. During the investigations it became apparent that the thermal utilization of plastics can, definitel y be appropriate from the technical point of view. Plastics have a favourab le effect on the emission values of NOx and CO. An increase in emissions du e to the raw meat feed, which became particularly noticeable during stepped air supply with simultaneous stepped raw meal feed teas observed during th e experimental investigations. The result was that the NOx emissions did no t drop as expected, but rose because of the limited sire of the reactor. In contrast to this the theoretical examinations showed that the NOx emission s can be lowered from about 800 mg NO2/m(3) (stp) to 300 to 350 mg NO2/m(3) (stp) at 10 vol.% oxygen by accurately controlled stepped supply of air an d kiln feed and by the use of plastics. The reference calculations using ga s-flame coal have also confirmed that the emission values of nitrogen oxide s can be favourably affected by the use of plastics.