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Aspen Plus Radfrac Convegence Issue

aspen radfrac aspen plus absorption convergence tolerance simulation

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#1 AspenJack

AspenJack

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Posted 02 September 2022 - 03:05 AM

I am trying to converge an absorption column for a range of conditions using the RadFrac model, but for some conditions, there are convergence issues. What's confusing is that the error tolerance reaches very low values, but just plateaus there:

 

   Block: ABSORBER Model: RADFRAC
  *** SEVERE ERROR
      FLASH CALCULATIONS FAILED TO CONVERGE IN  300  ITERATIONS.


       Convergence iterations:
         OL   ML   IL     Err/Tol
          1    1   10      16901.
          2    1   10      12542.
          3    1   10      75805.
          4    1    1      37903.
          5    1    1      18951.
          6    1    1      9475.7
          7    1    1      4737.8
          8    1    1      2368.9
          9    1    1      1184.5
         10    1    1      592.23
         11    1    1      296.11
         12    1    1      148.06
         13    1    1      74.029
         14    1    1      37.014
         15    1    1      18.507
         16    1    1      9.2536
         17    1    1      4.6268
         18    1    1      2.3134
         19    1    1      1.1567
         20    1    1     0.57835
         21    1    1     0.28917
         22    1    1     0.14459
         23    1    1     0.72294E-01
         24    1    1     0.36147E-01
         25    1    1     0.18073E-01
         26    1    1     0.90367E-02
         27    1    1     0.45184E-02
         28    1    1     0.22592E-02
         29    1    1     0.11296E-02
         30    1    1     0.56479E-03
         31    1    1     0.28240E-03
         32    1    1     0.14120E-03
         33    1    1     0.70599E-04
         34    1    1     0.35300E-04
         35    1    1     0.17650E-04
         36    1    1     0.88249E-05
         37    1    1     0.44125E-05
         38    1    1     0.22062E-05
         39    1    1     0.11031E-05
         40    1    1     0.55156E-06
         41    1    1     0.27578E-06
         42    1    1     0.13791E-06
         43    1    1     0.68952E-07
         44    1    1     0.34474E-07
         45    1    1     0.17222E-07
         46    1    1     0.86162E-08
         47    1    1     0.42977E-08
         48    1    1     0.21440E-08
         49    1    1     0.10893E-08
         50    1    1     0.55589E-09
         51    1    1     0.30308E-09
         52    1    1     0.17206E-09
         53    1    1     0.14079E-09
         54    1    1     0.13308E-09
         55    1    1     0.13248E-09
         56    1    1     0.13226E-09
         57    1    1     0.13225E-09
         58    1    1     0.13224E-09
         59    1    1     0.13224E-09
         60    1    1     0.13224E-09

         ...

 

This goes on for 200 iterations. Also, how do I check/change the tolerance of the convergence of the column? Perhaps if I increased it, it would work? I tried playing around with convergence options, column estimates as well as different tear stream conditions (there is a pumparound recycle stream), but that didn't help for all conditions.

 

Any help would be appreciated!

 

Best,

AspenJack

Attached Files


Edited by AspenJack, 02 September 2022 - 03:10 AM.


#2 breizh

breizh

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Posted 02 September 2022 - 08:37 PM

Hi ,

Did you try without recirculation loop ? 

my 2 cents

Breizh 






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