3 replies to this topic

[shvet1]

Good day, forum

 

I have a problem with flue gas enthalpy predicted by process simulation software. I work with model of woxic wastes incinerator and stumbled on flue gas enthalpy mistake. AspenPlus shows flue gas enthalpy ~1.5 more than manual proved methods. I tried many thermodynamic methods and algorithms with no result. Manual contains a little worth information so I could not understand how to fix it.

 

Manual computations data transfer (e.g. Excel <=> Aspen) but it is convenient to work with process side and flue gas side in one simulation software.

 

Can anyone give an advice about flue gas simulation in Aspen+, HYSYS?

Edited by shvet1, 14 June 2018 - 08:36 AM.

[PaoloPemi]

(absolute) values of  enthalpy can differ (it depends from base condition) but given a initial (Tin, Pin) and final (Pfin, Tfin) conditions you should obtain a comparable value for dH ,

you do not mention if the problem is about absolute H or dH, also I presume you do not include reactions (combustion) but similar considerations are possible,

I use mainly Prode Properties with Excel,

Prode allows to define the base (reference) condition for Enthalpy and Entropy (which can be useful to replicate steam tables etc.) but it doesn't influence heat balance (see above)

Edited by PaoloPemi, 14 June 2018 - 10:16 AM.

[winchester427]

It's not a mistake - Different software or resources use different datum points for enthalpy. The important thing is that you use a consistent source for calculation of enthalpy change and never mix sources. 

[Technical Bard]

Enthalpy is a relative property, not a state property.  You need to know the datum point.  Even in one simulation, if you switch thermodynamic methods, you may see changes in the absolute values of enthalpies, while the delta H values between two states don't change.  Check your specific heats for the flue gas by both methods - are they similar?