DWSIM — The Complete Guide: A Free Chemical Process Simulator

DWSIM is an open-source chemical process simulator that runs on Windows, macOS and Linux. In principle it does what Aspen HYSYS and Aspen Plus do: you build a flowsheet of a plant or process unit, choose a thermodynamic model, and get mass and energy balances, compositions and conditions in every stream.

DWSIM

DWSIM Project

Steady-state and dynamic process simulation for chemical plants.

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What is in DWSIM

Flowsheet — drag-and-drop units: pumps, compressors, heat exchangers, separators, distillation and absorption columns, reactors (conversion, equilibrium, Gibbs, CSTR, PFR).
Thermodynamics — Peng-Robinson, SRK, NRTL, UNIQUAC, UNIFAC, steam models and more, with a component database.
Analysis — sensitivity analysis, optimisation, phase envelopes and distillation curves.
Extension — CAPE-OPEN support, Python scripting and export of results to a spreadsheet.

How to build a first process

1. Choose components and a suitable thermodynamic model (for example Peng-Robinson for hydrocarbons, NRTL for polar mixtures). 2. Define a feed stream with flow, composition, temperature and pressure. 3. Drag units and connect streams. 4. Set up each unit and run. 5. Check the balances — and if there is a recycle, give it a reasonable initial guess.

What's missing

The component database and ready equipment models are smaller than Aspen's, and on large processes with many recycles convergence is less robust. There is no commercial support, and the documentation is less comprehensive. Detailed equipment design (rigorous heat exchangers, columns by real trays) usually needs additional tools.

Who it suits

Chemical engineering students, lecturers, process engineers in small offices and start-ups, and anyone who needs a feasibility check or a quick balance without an Aspen licence.