Trying to understand why my HYSYS file first converges and then says it can't converge after like 5 min. Is it just rerunning the simulation and doesn't work the second time?
Distillation columns in Hysys, like in any other process simulation software, can sometimes converge and then diverge during the simulation. This can happen for several reasons, including:
1. Poor initial estimates: The initial estimates used for the column simulation may not be accurate enough, causing the simulation to converge to a false solution. In this case, modifying the initial estimates or using different initialization methods may help.
2. Unstable process conditions: If the process conditions are unstable, such as a fluctuating feed flow rate or composition, the column may converge initially but then diverge as the conditions change. In this case, stabilizing the process conditions may help.
3. Incorrect specifications: The specifications for the column may be incorrect or too tight, causing the simulation to converge initially but then diverge as the specifications cannot be met. In this case, adjusting the specifications or using different specification methods may help.
4. Inaccurate physical properties: The physical properties used in the simulation may not be accurate enough, causing the simulation to converge initially but then diverge as the properties are not able to accurately represent the behavior of the system. In this case, using more accurate physical properties or adjusting the model assumptions may help.
5. Numerical issues: The numerical methods used to solve the simulation may encounter issues, such as convergence criteria that are too tight or numerical instability. In this case, adjusting the numerical methods or settings may help.
Overall, it's important to carefully analyze the specific reasons why the column is converging and then diverging in Hysys and to make appropriate adjustments to the simulation inputs and settings to ensure accurate results.
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