Higher alkalies

Hi

In our kiln, when we started using an alternate raw material(shale silica instead of silica) with higher alkalies content ( K2O), we need to run the PH fan at higher speed even for the same kiln feed, as of earlier. I hope that this is due to the additional oxygen demand by the alkalies. Please confirm

I know it is very difficult to explain in the forum,. So, Can anyone send some related artciles/materials/calculations  regarding the effect on alklies with respect to oxygen demand and kiln ouput to vinayak_cehnnai@yahoo.com

Thanks

Vinyak

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Re: Higher alkalies

You need to provide more information to get a precise answer. With these additional information you could perfom a full kiln analysis before and after your modifications.

It is essential that you look at the heat consumption, fuel package, chemical data, gas analysis, solids analysis (meal, hot meal, clinker, ...) , temperatures, ... .

For example, if the heat consumption has increased then you may have the answer probably. This might be due to a change in "burnability" and the cycles in the kiln.

Also, I don't see any direct O2 consumption related to alkalies. However shale silica might contain some C that can contribute effectively to the O2 demand without decrease the actual fuel consumption.

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Re: Higher alkalies

hi

thank u for ur efforts in answering. To answer ur querries

1. there was no appriciable change in burnabilty in terms of lab test as well as actual burning zone temp

2. The heat consumptio has increased by around 25 kcals/ kg of clinker as the prehaert exit volume ( Nm3/kg of clinker) as well as exit gas temperature has increased.

3. there was no carbon in the silica shale as confirmed by the loss on ignition

4.The hot meal alkalies has increased from 1.0 to 1.8%

I had a view as below

The alkalies might consuming some additional oxygen to form sulfates . To compensate this, the preheater fan speed  needs to be increasd by aout 3% and hence additional exit gas volume and thereby the heat loss.

Regards

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Re: Higher alkalies

K2O is an inhibitor of combination into the clinker minerals therefore that explains the higher thermal energy consumption. Higher thermal energy consumption means more combustion product gases therefore the need to run the preheater fan at higher speed. It is right to say that a full mass and energy ballance of the kiln is required. Also that the alkali to sulphate ballance is critical.

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