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Calcine kiln energy requirement

Calcine kiln energy requirement

Calcine kiln energy requirement

(OP)
Hello all

Im looking at getting some rough numbers for energy requirements for a calcination kiln

The kiln feed is a hydrated compound, the goal is to produce an anhydrous product

The way i see it there are 3 things to consider:
1) Enthalpy input required to break the bonds of the hydrated structure and free the water, producing steam and the anhydrous solid
2) Heat energy required to heat and then vaporize free water (moisture) in the feed (including both sensible and latent heat)
3) Heat energy to raise the feed solids to the required temperature at which the de-hydration reaction proceeds quickly enough to be viable

My approach is as follows:
1) Hesse equation (using summed heat of formation: products - reactants in the balanced chem. equation) to find the heat of reaction in kJ/mol_basis. Then convert this number into kJ/kg_feed
2) Q=m*C*deltaT+m*L
3) Q=m*C*deltaT... the problem here is that Perry's does not have the heat capacity (C) for my hydrated compound - only the anhydrous form. I imagine the hydrated compound has a much higher heat capacity than the anhydrous form. Ive found some papers that attempt to measure the hydrated compound Cp but their range of applicable temperature isnt where i need it to be

Once i have 1, 2 and 3 i can apply an efficiency and im off to the races. Ive got some rough numbers in now but the energy requirement values are far too high and im not sure where im going wrong... Can anyone advise if my approach is correct? Also any general advice on how i can obtain the needed Cp values?

Help is much appreciated

RE: Calcine kiln energy requirement

Mechagigatron.
Looks like you are on the correct path to me.
The only other thing I would add is that depending on the dryer type you probably have air or inert gas to heat up as well.
You can probably get a dryer quote from a good vender that will give you the heat required to compare to what you are calculating on your own.

Regards
StoneCold

RE: Calcine kiln energy requirement

You can use the heat capacity for the unhydrated form- just add in the energy required to heat the water that is part of the hydrated structure to the required temperature (i.e. treat it as free water). This won't work if you're calculating for a part of the reactor where the dehydration has not yet occurred - but it should be fine for your end state.

As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"

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