Re: Raw meal to clinker ratio

armankhan:

please sir explain the kiln feed dust losses. as in our system we take hot gases frm kiln for rawmix grinding and aslo for coal grinding. so now how we can calculate kiln feed dust losses. 

Hello Armankhan,

The amount of recirculating dust is related to the separation efficiency of the uppermost cyclone(s). This separation efficiency is normally around 90-95%

Michel (lalbatros) has provided a comprehensive engineering description of how this separator efficiency is calculated in the following thread;-

http://www.cemnet.com/cs/forums/thread/3824.aspx

If your kiln system configuration physically allows it, it is possible to determine the amount of recirculating dust by diverting the recycled dust (s) to a suitably-sized enclosed truck, over say an hour or so, and weighing the collected dust. The t/h recirculated dust is obviously the weight of dust collected, divided by the time taken for collection. You may need to do this several times to get a decent average value.

Also, if the chemistry of the dust is sufficiently different from the rawmeal and kiln feed (fed to the top cyclones), you may be able to estimate the amount of recirculation dust that is being added to fresh raw meal to make kiln-feed by using a chemical mass balance, with respect to the LSF and/or LOI of each stream. ie

if D = % dust in kiln-feed (fed to the top cyclones) then  % fresh raw meal in kiln feed = (100-D)

and if  DL = LSF of dust, RL = LSF of fresh raw meal and KL = LSF of Kiln feed

Then;-

D*DL  + (100-D)*RL = 100*KL

D*DL+ 100*RL - D*RL  = 100*KL

100*RL + D*(DL-RL) = 100*KL

D*(DL-RL) = (100*KL - 100*RL)

D = (100*KL - 100*RL) / (DL-RL)

D = 100 * (KL-RL) / (DL-RL)

So if the LSF of the Kiln feed, fresh raw meal and dust are known, by this last formula you can calculate the % of dust incorporated in the kiln feed which is lost at the top cyclones.

Subtracting this value from 100 will also give you an estimation of the efficiency of the top cyclones (or cyclone, in the case of a single string kiln). It should be noted however, that this is an estimate only and is only as accurate as the analyses of the material streams which are used to calculate it.

Hope this helps,

Ted.

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