By name: process-design-expert version: 1.0.0 description: Expert-level chemical process design covering process flow diagrams, mass and energy balances, equipment sizing, economic evaluation, and sustainable process design. author: luo-kai tags: [process design, PFD, mass balance, energy balance, equipment sizing, economics]
Process Design Expert
Before Starting
- Greenfield design or retrofit of existing plant?
- Which process chemistry?
- Preliminary or detailed design stage?
Core Expertise Areas
Process Flow Diagrams
BFD: block flow diagram, overall process blocks and streams. PFD: process flow diagram, major equipment, streams with conditions and flows. P and ID: piping and instrumentation diagram, all equipment, valves, instruments. Stream tables: document temperature, pressure, composition, flow for each stream.
Mass and Energy Balances
Overall balance: total mass in equals total mass out for steady state. Component balance: each species balanced separately. Recycle streams: iterative solution required, tear stream method. Energy balance: enthalpy difference between inlet and outlet streams. Reference state: choose consistent reference for enthalpy calculations.
Equipment Sizing
Heat exchangers: LMTD and U value determine area, tube and shell sizing. Pumps: head and flow from system curve, pump curve intersection. Compressors: isentropic work, polytropic efficiency, staging for high ratios. Vessels: residence time determines volume, L/D ratio for liquid-vapor separation.
Economic Evaluation
Capital cost: purchased equipment cost, installation factor, total fixed capital. Operating cost: raw materials, utilities, labor, maintenance, overhead. NPV: net present value, discounted cash flows over project life. Payback period: time to recover capital investment from operating profit.
Best Practices
- Converge mass and energy balances before equipment sizing
- Use simulation software for complex recycle systems
- Include contingency and accuracy range in all cost estimates
- Optimize energy use through heat integration from process start
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Wrong basis for calculations | Define basis clearly, usually per hour or per year |
| Ignoring recycle convergence | Check that recycle streams are converged before proceeding |
| Underestimating installation costs | Use appropriate Lang or Hand factor for total capital |
| Missing utility costs | Include steam, cooling water, electricity in operating cost |
Related Skills
- reaction-engineering-expert
- separation-processes-expert
- process-control-expert