Kiln Speed

Dear Saprina,

 The kiln speed for optimum feed depends on the filling level on which we operate.  Now a days we are operating the   kiln filling level around 14% to 16% filling level.  For calculating the kiln speed we require following details.  The formula is

% of Filling Level = (3.2*production in tpd)/(Effective dia of kiln^3*kiln slope*kiln rpm)

Based on this universal formula in which all the cement plants use you can back calculate the kiln rpm based on what filling level your are maintaining.

 Regards,

Maddy

From ICR's Plant Operations Handbook:

Retention time:

t=11.2 L / (r D s)

Where L= kiln length (meters), r=kiln speed (rpm), D=effective diameter (meters), s=kiln slope (degrees)

Retention time should be 20-30 min for most calciner and preheater kilns. Calciner kilns can accomodate shorter times.

Volume loading:

% loading = 1.67  FR  W  t / ( L A )

Where FR=feed ratio (kg of material entering the rotary kiln per kg clinker), W= clinker production in ton/h, A= effective kiln cross area (m^2)

Volume loading should be typically 7-8% for precalciner kilns and is higher for preheater kiln. 

Higher rotation speed increase heat transfer to the charge because the surface of clinker charge exposed to the radiation of the flame and the surface in contact with (hot) refractory is higher compared to the clinker volume. Higher speed is generally better, until your retention time becomes too short and this point depends on kiln technology. I have seen kilns with modern calciner and high calcination degrees running with retention times shorter than 15 mins!

Best regards,

O. Van Cantfort

Hey;

How can we change the kiln slope from Percentage (%) to Degree?

If our kiln slope is 4%, kiln length is 56m, and kiln Diameter (effective) is 3.40 m what i our kiln slope in Degree???

Thanks