7/29/2019 kiln formulas.doc

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to calculate the retention time use the commonly accepted formula published by the USBureau of Mines and used by most rotary equipment manufacturers. T = (1.77x L x (A)^0.5)/

(P x D x N) Where A = the natural angle of repose of the material in degrees P = slope of the

kiln in degrees D = the inside diameter of the kiln in feet L = length of the kiln shell in feet N

= rotation speed in revolutions per minute T = retention time in minutes Calculate twice; once

with the feed material characteristics and again with product characteristics and average the

two. When internal lifters are present, as is typical with dryers, the time is usually increased

50%

may multiply the fuel feed by CV For ex

Kiln fuel feed rate = 6000 kgs/hr

C.V = 6500 Kcals*4.184 = 27196 Kj/Kg of coal

Thermal Input = 6000 X 27196 KJs/Hr

= 163.176 GJs/Hr

Kiln dia (inside Lining) = 3.6 m

C.S Area = (3.14/4)*3.6*3.6

=10.17 m2

Thermal load on kiln = 163.176/10.18

=16.04 Gj/hr.m2

Regards

Vinayak