2 replies to this topic

[donchris34]

Hello Friends,

First I would like to thanks the administrators for giving us this wonderful opportunity.I am new to Aspen Tech and have been trying to simulate a co2 absorbing and stripping stripping plant with MEA using AspenPlus V7.1. I have been having problems with mass balance after running the program.I have always use try and error approach to converge the program after changing the inputs(flows,temperature or pressure) of the system.But sometimes it just can't converge.I could say,my pre-knowledge of the MEA co2 system do help me in choosing my inputs.My question is;

1; is there a standard of calculating the mass-balance when working with AspenPlus or should one just use try and error approach if you are having a mass balance problem?

2; What are the special property that are included in AspenPlus when one is working with MEA co2 system




thanks you all for your replys

[saeed.s]

Hi,
If aspen show "Simulation calculations completed" massage with a blue chek result , u can be sure all the mass and energy balanceses are true, but thence it works in SM (sequential-modular), some inappropriate inlets make problem , for example , in a tower aspen can't converge because specified reflux & bottom product flow are grater than inlet stream or in a heat exchanger the inlet cooling flow rate is n't enogh to reach specified target , in these circumstances u can use try and error to find suitable inlet or u can use "Design Spec" in "Data" --> "Flowsheeting options" ---> "Design Spec".
another point for stripping or absorption in aspen plus columns is that u shoud do this procedure :
open column block . select "convergence" ----->"advanced" and change "NO" to "YES" in front of "absorber" option.
To start a new simulation it's better to reinitialize previous calculations because aspen (and all the simulation softwares ) use previous results to start new calculations.
To select Property Method u can use "Aspen plus Help" ---> "Physical Property Methods" .u can find good guidances & charts there to select an appropriate property method.
good job

Edited by behnam, 23 March 2010 - 02:25 AM.

[donchris34]

Hi,
If aspen show "Simulation calculations completed" massage with a blue chek result , u can be sure all the mass and energy balanceses are true, but thence it works in SM (sequential-modular), some inappropriate inlets make problem , for example , in a tower aspen can't converge because specified reflux & bottom product flow are grater than inlet stream or in a heat exchanger the inlet cooling flow rate is n't enogh to reach specified target , in these circumstances u can use try and error to find suitable inlet or u can use "Design Spec" in "Data" --> "Flowsheeting options" ---> "Design Spec".
another point for stripping or absorption in aspen plus columns is that u shoud do this procedure :
open column block . select "convergence" ----->"advanced" and change "NO" to "YES" in front of "absorber" option.
To start a new simulation it's better to reinitialize previous calculations because aspen (and all the simulation softwares ) use previous results to start new calculations.
To select Property Method u can use "Aspen plus Help" ---> "Physical Property Methods" .u can find good guidances & charts there to select an appropriate property method.
good job

thankthanks for your solution.