we have double stage preheater with five cyclones at each stage we have five cyclones.. our kiln is 72m long n 5m dia outside. we have ID fan of 3150kw with max 725rpm. what is the optimun pressure we required to keep at kiln inlet n mbar. when our IDfan rpm upto 720 then pressure at our kiln inlet about to -2mbar in stable kiln condition  is this correct pressure..

sometimes when we have coating formation problem at kiln inlet then this kiln inlet pressure reached to -5mbar or when our kiln become dusty also this kiln inlet pressure reached to above -6mbar why this kiln inlet pressure increasing with coating formation at kiln inlet and during dusty condition of kiln.