luokai0 Reaction Engineering Expert
Before Starting
- Homogeneous or heterogeneous reaction?
- Which reactor type? (batch, CSTR, PFR, packed bed)
- Isothermal or non-isothermal operation?
Core Expertise Areas
Reaction Kinetics
Rate law: r = k times CA to power alpha times CB to power beta. Arrhenius equation: k = A times exp of negative Ea over RT. Elementary vs non-elementary: rate law derived from mechanism not stoichiometry. Conversion: X = moles reacted over moles fed. Selectivity: desired product formed over total product formed.
Ideal Reactor Design
Batch: dX over dt = negative rA over CA0, closed system, time-dependent. CSTR: V = FA0 times X over negative rA at exit, well-mixed, steady state. PFR: dFA over dV = rA, plug flow, axial concentration gradient. Levenspiel plot: 1 over negative rA vs X, area gives reactor volume. CSTR in series: approaches PFR performance as number of CSTRs increases.
Non-Isothermal Reactors
Energy balance: heat generated equals heat removed at steady state. Adiabatic temperature rise: delta T = negative delta H times CA0 times X over rho Cp. Multiple steady states: CSTR energy and mole balance can intersect multiple times. Runaway: temperature sensitivity, Damkohler number determines stability.
Heterogeneous Catalysis
Langmuir-Hinshelwood: adsorption, surface reaction, desorption steps. Effectiveness factor: ratio of actual rate to rate without diffusion limitation. Thiele modulus: phi = L times sqrt k over De, large means diffusion limited. Packed bed reactor: pressure drop from Ergun equation, catalyst deactivation.
Best Practices
- Collect kinetic data at multiple temperatures to determine Ea
- Check for mass and heat transfer limitations before fitting intrinsic kinetics
- Design for worst case temperature for safety analysis
- Validate lab kinetics at pilot scale before full scale design
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Ignoring heat effects for exothermic reactions | Always include energy balance for non-isothermal design |
| External diffusion limitation in kinetic studies | Use differential reactor or high flow rate |
| Wrong residence time distribution | Characterize RTD with tracer experiment before design |
| Catalyst deactivation not accounted for | Include deactivation kinetics in design equations |
Related Skills
- process-design-expert
- separation-processes-expert
- safety-engineering-expert