Just received a copy of CHETAH 8.0.  This is a program for thermochemical and energy release evaluation and is distributed by ASTM. It will calculate enthalpy of combustion and thermochemical properties of compounds and reactions including- LFL, LOC, MIE, lower limit flame temperatures, maximum flame temperature, fundamental burning velocity, and quenching distance.

I have only had it installed for 2 days, so it’s way too early to give an appraisal. It came highly recommended by several colleagues in the process safety field.  The only snag so far is a balky SMILES input module. This feature was very appealing because it allows one to copy a ChemDraw structure in SMILES format and paste it into the CHETAH GUI. The rep at ASTM gave me a link which ended up offering very cryptic instructions. Naturally, the problem is some obscure setting in Windows.

Until I get this fixed, I’ll have to enter Benson groups by hand. As it happens, I began studying guitar in my spare time, so there are all kinds of new things for my addled brain to stumble over assimilate. So when I’m not picking at strings, I’m picking at Benson groups.

Update 3/5/09:  After a service pack download, the SMILES module is functioning. This is a very powerful tool.

We’ve recently caught up with the times and have been pressing Accelerating Rate Calorimetry (ARC) into service. Or more accurately, paying to have the data collected.  ARC is really quite informative in that it can offer a Time to Maximum Rate (TMR) equation from which a TMR can be determined for any desired temperature. You can calculate an adiabatic delta T as well. I do not know how reliable this number is, but it certainly reminds one of the importance of considering the effect of phi factor in process scale up.

The ARC data I get includes an Antoine curve which can indicate that the accelerated rate behavior is or is not characteristic of classical liquid/vapour equilibrium behavior. What this says to the wary is that other volatiles (besides the subject material) may be generated which are not condensable. This is helpful in considering what kind of controllability is available to the process engineers.

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