Early-stage companies ask this question in cost terms, which is understandable and slightly beside the point. The simulator matters far less than the property package and the data behind it. A well-regressed DWSIM model beats a carelessly built Aspen model every time.
That said, the choice does have consequences.
Where Aspen Plus earns its licence
Solids handling, electrolytes and rate-based column modelling. If your process involves crystallisation, precipitation, an electrolyte system, or reactive absorption, Aspen Plus has capability that the alternatives do not match. The electrolyte NRTL implementation and the built-in databank are the real product, not the interface.
Where HYSYS fits
Hydrocarbon and gas processing, dynamic simulation, and anything where you will eventually hand the model to an operating company that uses HYSYS. Its pressure-driven dynamics are genuinely good for start-up and relief studies.
Where DWSIM is the right answer
It is open source, which means three practical things for a startup. You can hand the model to an investor's technical diligence consultant without a licence negotiation. Your own team can open and run it after the engagement ends. And you are not renewing a five-figure subscription for a model you touch twice a year.
For a straightforward flowsheet with well-characterised components — distillation, flash separations, heat exchange, simple reactors — DWSIM's results are perfectly defensible. Its thermodynamic engine implements the same equations of state.
Its limits are real: weaker solids handling, no serious electrolyte capability, a smaller component databank, and less mature dynamic simulation.
The decision in practice
| If your process involves | Use |
|---|---|
| Crystallisation, solids, slurries | Aspen Plus |
| Electrolytes, acid gas, aqueous ionic systems | Aspen Plus |
| Hydrocarbon processing, dynamics, relief studies | HYSYS |
| Distillation, extraction, standard unit operations | DWSIM is sufficient |
| A model your own team must maintain | DWSIM |
The thing that actually matters
Whichever tool you use, the property package selection deserves more thought than the tool selection. Choose it deliberately, state the choice in the design basis, and where the system is unusual, regress the binary parameters against your own laboratory VLE or solubility data. A model built on a default parameter set for a novel solvent system is a confident-looking guess.
Working on something like this? Sherle designs pilot plants and basic engineering packages for companies scaling a chemical process. Book a technical call.