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 using plastics in the calciners of cement kiln plants. In order to obtain information about their combustion behaviour various plastics were compared with gas-flame coal as fuels in preliminary trials. During the investigations it became apparent that the thermal utilization of plastics can, definitely be appropriate from the technical point of view. Plastics have a favourable effect on the emission values of NOx and CO. An increase in emissions due to the raw meat feed, which became particularly noticeable during stepped air supply with simultaneous stepped raw meal feed teas observed during the experimental investigations. The result was that the NOx emissions did not drop as expected, but rose because of the limited sire of the reactor. In contrast to this the theoretical examinations showed that the NOx emissions 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 and kiln feed and by the use of plastics. The reference calculations using gas-flame coal have also confirmed that the emission values of nitrogen oxides can be favourably affected by the use of plastics.