luokai0 Process Simulation Expert
Before Starting
- Which simulator? (Aspen Plus, HYSYS, ProII, ChemCAD)
- Steady state or dynamic simulation?
- 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