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.