oxygen level for 4 stage-SP kiln

We have installed the kiln inlet gas analyzer, here the measurements of the ID fan and kiln inlet gas analyzers

             Kiln Inlet    ID fan                                                                                       CO  (%)          2        0,2

O2   (%)        0,3       3,6

NOx (ppm)    420     210

Kiln inlet temperature is 1130 C, Sintering zone is 1460 C, Secondary air is 996 C. 94 tph clinker production rate.

The kiln is firing 100% petcoke. 2250 tpd capacity. 840 kcal/kg is specific heat consumption.

If the O2 level is true for both then there should be an opened man-hole for that much of air inleakage. But i couldn't such a hole. What 's your comment on this?

Best regards,

Firat