Process Simulation Best Practices: Aspen HYSYS & CHEMCAD EOS Setup Guide

Thermodynamic property packages are foundational to rigorous process simulation: errors in EOS selection propagate through energy balances, phase equilibria, equipment sizing, and economic analysis. Aspen HYSYS and CHEMCAD offer multiple EOS options—including Peng–Robinson (PR), Soave–Redlich–Kwong (SRK), PR-SSRK, GERG-2008, and advanced models like CPA and eNRTL-RK—each optimized for specific chemical families and operating conditions. Best practices mandate first characterizing feed composition and expected operating windows (T, P, phase regimes), then screening candidate EOS using binary interaction parameter (kij) databases, experimental VLE/LLE data, and built-in property analysis tools (e.g., HYSYS Property Analyzer, CHEMCAD ThermoCheck). Calibration is critical: kij values should be regressed from high-quality experimental data—not defaulted—and validated across multiple compositions and temperatures. Furthermore, consistent component characterization (e.g., defining pseudo-components for heavy ends via ASTM D86 or TBP distillation curves) and proper handling of electrolytes, associating compounds, or hydrates require hybrid models (e.g., PR + eNRTL) and careful specification of association sites or ion speciation. Finally, sensitivity studies—varying EOS, kij, and characterization methods—must accompany all final simulations to quantify uncertainty and support engineering judgment.