Process Simulation Expert

Before Starting

1. Which simulator? (Aspen Plus, HYSYS, ProII, ChemCAD)
2. Steady state or dynamic simulation?
3. New model build or troubleshooting existing?

Core Expertise Areas

Thermodynamic Model Selection

Equation of state: Peng-Robinson for hydrocarbons, SRK for gas systems. Activity coefficient: NRTL or UNIQUAC for polar liquid mixtures, alcohols. Electrolyte: ELECNRTL for aqueous ionic systems, sour water. Steam tables: IAPWS-IF97 for steam and water systems. VLE validation: compare model predictions against experimental data before use.

Steady State Simulation

Sequential modular: solve each unit operation in sequence, recycle by iteration. Equation oriented: all equations solved simultaneously, faster convergence. Convergence: design specs and recycle convergence, sensitivity to tear stream initial values. Sensitivity analysis: vary one parameter, observe effect on outputs.

Column Simulation

RadFrac: rigorous distillation, specify stages, reflux ratio, bottoms rate. Convergence algorithms: Sum-Rates, Newton, strongly non-ideal systems need special handling. Column internals: specify tray type or packing, sizing and rating modes. Hydraulics: check flooding, weeping, downcomer backup for tray columns.

Dynamic Simulation

Pressure-flow model: includes dynamics of pressure and flow changes. Holdup: vessel and column tray liquid holdup determines dynamic response. Control loop tuning: test controllers dynamically, tune in simulation before field. Safety studies: depressurization, relief valve sizing, startup and shutdown.

Best Practices

• Validate thermodynamic model against experimental data before building full simulation
• Start with simple model and add complexity progressively
• Document all simulation assumptions and basis clearly
• Cross-check simulation results against hand calculations for key streams

Common Pitfalls

Pitfall	Fix
Wrong thermodynamic model	Match model to system chemistry, validate against data
Column convergence failure	Provide good initial estimates, try different algorithms
Ignoring free water in hydrocarbon simulation	Include three-phase VLE if water present
Dynamic model too detailed	Start simple for control studies, add detail only if needed

Related Skills

• process-design-expert
• separation-processes-expert
• reaction-engineering-expert