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Aspen Stoichiometries In Reactors

stoichiometries aspenplus reactions normalization mass coefficients

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#1 SteFanIstas

SteFanIstas

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Posted 26 April 2022 - 05:04 PM

Hi
 
I am a new Aspen user and I would appreciate if someone would help me to resolve some confusions:
  1. In a RStoich reactor. All the materials/components we are about to use in the reactions should be defined as input streams. Right? Aspen does not have the ability to fetch components from the list. Only those that are assigned in its streams as inputs. Right?
     
  2. In the stoichiometries, the coefficients stand for mass coefficients? Do they count for 0-1 or 0-100? Can I insert values over than 1 up to 100 or 0-1 in the coefficients section? Same question applies for the mass-fraction values in the input streams. Is it 0-1 or 0-100? Or it doesn't matter. Aspen normalizes it automatically.
     
  3. The total mass coefficients in both the reactants and products should be closely equal and again should it be written 0-1 or 0-100? Do I need to normalize, convert or calculate the mass coefficients at all?
     
  4. The mass coefficient assigned to each component in the stoichiometries should be equal or less to the amount/mass fraction that was assigned in the input stream. Right? For example, it is impossible to assign 0.3 of H3PO4 in the input stream and put 0.5 of H3PO4 in the stoichiometry. Right?
Thanks and apologize if all of those are so standard and basic for some people here.
I hope for your understanding

 



#2 Pilesar

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Posted 26 April 2022 - 09:51 PM

Try a web search for "rstoic aspen" to get tutorial videos which might provide the help you need. These should at least get you farther along and allow you to reduce the question list.



#3 SteFanIstas

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Posted 27 April 2022 - 06:16 AM

I continuously get this error

 

" ERROR WHILE CHECKING INPUT SPECIFICATIONS
BLOCK NAME: B1 MODEL NAME: RSTOIC HIERARCHY: WWAT
REACTION NUMBER "1" DOES NOT SATISFY MASS BALANCE.
THE ABSOLUTE ERROR IS -1412.0
CHECK STOICHIOMETRY/MOLECULAR WEIGHTS."

 

For various absolute errors. What could be the prob?



#4 Pilesar

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Posted 27 April 2022 - 07:07 AM

Try these suggestions from Raquel de Souza:
You may also check the molecular weights of the species involved (in the database), as Aspen databank components data are sometimes slightly different from the data you have from literature. Then manually check the balance using the values you retrieved from the database.
Do you have recycle streams in your process? Sometimes when you have recycle you need to ask to reconcile the streams.
Another thing to do is to increase the acceptable range of error. (Simulation – Setup- Calculation Options- Check results). 

 

de Souza, Raquel. (2017). Re: How do I rectify mass balance error in RCSTR in ASPEN PLUS ?. Retrieved from: 

https://www.research...R-in-ASPEN-PLUS


Edited by Pilesar, 27 April 2022 - 07:15 AM.





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