Components, mixtures and property methods
Pure components
Open Tasks ▸ Pure components… or the ⚛ Components toolbar button. The Pure Components window lists every component registered in the process with its physical and economic properties.
- + Add from library searches the built-in component library of about 70 substances: water and WFI, gases (oxygen, nitrogen, CO₂, air, hydrogen, methane, ammonia), sugars and polyols, organic acids, salts, acids and bases, buffers, nutrients (yeast extract, corn steep liquor, peptone), biomass and cells (E. coli, CHO cells, yeast), proteins (mAb, insulin, host cell protein), common solvents and more. About 25 of them carry critical constants and UNIQUAC parameters for the equation-of-state and activity models.
- + New custom adds a blank component (named “Component N”) that you fill in yourself.
A new process starts with Water, Oxygen, Nitrogen and Carbon Dioxide. Water, Oxygen and Nitrogen cannot be removed, because utilities and aeration rely on them.
Component properties
| Group | Columns |
|---|---|
| Identity | Name, Formula, Phase (liquid, solid or gas) |
| Physical | MW, density ρ (kg/m³), Cp (kJ/kg·K), normal boiling point Tb (°C), heat of vaporisation ΔHv (kJ/kg) |
| Vapour pressure | Antoine A, B, C; vapour Cp; Henry constant (bar) |
| Equation of state | Tc (K), Pc (bar), acentric factor ω, molar volume, dρ/dT |
| Activity models | UNIQUAC r and q |
| Economic | Price $/kg (purchase), Sell $/kg (revenue), Waste $/kg (disposal) |
| Environmental | ThOD, BOD/COD ratio, VOC flag, Biomass flag |
| Solids | Solubility (for crystallisation) |
Further per-component data for wastewater and energy (TKN, TP, TOC, lower heating value, acid/base behaviour) is edited under Tasks ▸ Energy, heat integration & wastewater… on the Component data tab.
Stock mixtures
Media, buffers and cleaning solutions are defined as stock mixtures: named mass-fraction compositions with a price. Open Tasks ▸ Stock mixtures… or ⚗ Mixtures.
- Click + New mixture (it starts as 100 % Water).
- Rename it, set its Price $/kg, and use + Add component… to add ingredients with their mass fractions.
If the fractions do not add up to 100 %, FlowState warns you and normalises them when the mixture is used. Mixtures belong to the process; for example, the Recombinant Enzyme example defines an Elution Buffer (97 % water, 3 % NaCl) and a CIP Caustic (0.5 % NaOH).
To use a mixture, select a feed stream and pick it under Composition (per batch) ▸ Stock mixture; then enter the Total mass instead of individual component masses.
Resources: heat-transfer agents, power and labour
Tasks ▸ Resources (utilities, labor)… (toolbar 🔥 Resources) defines:
- Heat-transfer agents: name, heating or cooling duty, supply and return temperatures, Cp, latent heat and cost per tonne. Add more with + Add agent.
- Electricity: price per kWh.
- Operating labor: basic rate, benefits and overhead, giving the effective rate.
Property methods
Open Tasks ▸ Property methods & convergence…. The Property Methods window sets the thermodynamic model for the whole process.
Phase-equilibrium model
| Model | Use it for |
|---|---|
| Ideal (Raoult) (default) | Raoult’s law with Antoine vapour pressures; similar, non-polar mixtures |
| NRTL | Strongly non-ideal liquids, azeotropes and partially miscible liquids |
| Wilson | Strongly non-ideal but fully miscible liquids |
| UNIQUAC | VLE and LLE (needs r and q for each component) |
| Peng–Robinson | Cubic equation of state (needs Tc, Pc, ω): gases, hydrocarbons, high pressure |
| Soave–Redlich–Kwong | As Peng–Robinson |
Options
| Option | Effect |
|---|---|
| Second liquid phase (VLLE): Allow liquid–liquid split | Three-phase flash; NRTL and UNIQUAC only |
| Liquid density: Temperature dependent | Liquid density varies with temperature (off by default) |
| Vapor phase (γ–φ): Ideal gas, Peng–Robinson or SRK | Vapour fugacities for activity models |
| Liquid corrections: Poynting factor, Excess enthalpy | Corrections for activity models |
| Carboxylic acids: Vapor dimerization | Chemical-theory association of acetic and formic acid in the vapour |
| EOS enthalpy: Residual (departure) enthalpy | Departure enthalpy for PR and SRK |
Binary interaction parameters
The Binary interaction parameters table lists each pair (component i, component j) with aij, aji, bij, bji (K), the NRTL non-randomness α, the equation-of-state kij, and the source. Load built-in parameters fills the table from FlowState’s library; + Add pair adds your own. A few built-in pairs are FlowState’s own fits and are marked as such in the Source column.
Excess enthalpy derived from VLE-fitted parameters is only qualitative. Carboxylic acids dimerise only with themselves.
Recycle convergence
The same window controls the recycle solver. FlowState chooses tear streams automatically; you can mark a stream as Preferred tear stream in its Inspector.
- Tolerance (default 10⁻⁶) and Max iterations (default 500).
- Acceleration: Wegstein (default) or Direct substitution.
- Initial tear guess: current state, zero flows, or custom tear guesses.
- Convergence test: component flows or total flow only, optionally with temperature.
- A residual plot shows how the last solve converged.
Design specs
Tasks ▸ Design specs (controllers)… adjusts one variable until a result reaches a target, for example a feed rate that gives a required product purity. Choose the variable to Vary, its Bounds, the result to watch (Until … Equals) and the method (Secant or Brent (bracket = bounds)).