Calculator Inputs
Example Data Table
| Case | Mode | Feed Flow | xF | Solvent Flow | K | Stages | Expected Use |
|---|---|---|---|---|---|---|---|
| A | Single contact | 1000 | 0.050 | 650 | 2.8 | 1 | Fast screening test |
| B | Crosscurrent | 1000 | 0.050 | 650 | 2.8 | 4 | Batch extraction estimate |
| C | Countercurrent | 1000 | 0.050 | 650 | 2.8 | 4 | Column design estimate |
Formula Used
The calculator uses a dilute, immiscible phase model. The distribution coefficient is:
K = y / x
Here, y is the solute concentration in the extract phase. x is the solute concentration in the raffinate phase.
For one equilibrium contact, the raffinate outlet concentration is:
xout = (F × xF + S × yin) / (F + S × Keff)
Stage efficiency adjusts the distribution ratio:
Keff = K × stage efficiency
For countercurrent operation, the extraction factor is:
A = Keff × S / F
The remaining raffinate fraction is estimated with:
xN / x0 = (A - 1) / (A^(N + 1) - 1)
When A is close to 1, the calculator uses 1 / (N + 1). Recovery is calculated as:
Recovery = ((xF - xout) / xF) × 100
This model is best for screening, teaching, early design, and sensitivity checks. Real systems may need ternary phase data, tie lines, activity coefficients, density changes, and entrainment corrections.
How to Use This Calculator
- Select single contact, crosscurrent stages, or countercurrent stages.
- Enter the feed flow and feed solute concentration.
- Enter the solvent flow and distribution coefficient.
- Add the number of stages and the expected stage efficiency.
- Use zero solvent inlet concentration for fresh solvent.
- Add a target recovery if solvent demand is needed.
- Press the calculate button.
- Review recovery, raffinate quality, extract concentration, and mass balance.
- Download the CSV or PDF report for records.
Liquid Liquid Extraction Calculation Guide
What This Tool Estimates
Liquid liquid extraction separates a solute between two liquid phases. One phase is usually the feed or raffinate phase. The other phase is the solvent or extract phase. The method is useful when distillation is difficult. It also helps when heat may damage the product.
Why Distribution Ratio Matters
The distribution coefficient controls the driving force. A larger value means the solute prefers the solvent. This usually improves recovery. It can also reduce solvent demand. Low values need more solvent, more stages, or both. The calculator adjusts this value with stage efficiency.
Stage Selection
A single contact is simple. It is useful for quick checks. Crosscurrent extraction contacts fresh solvent in each stage. It can give strong removal in batch work. Countercurrent extraction is common in columns. It often gives better recovery for the same solvent flow.
Reading the Results
Raffinate concentration shows the solute left in the feed phase. Extract concentration shows the combined solvent outlet strength. Recovery shows the percentage removed from the feed. The extraction factor compares solvent strength with feed flow. Values above one are often favorable. Mass balance error should stay near zero.
Practical Limits
Real extraction systems can be more complex. Solvents may partly dissolve in each other. Emulsions can slow settling. Temperature can change equilibrium. A design may also need selectivity, density, viscosity, and safety checks. Use this calculator for planning and comparison. Confirm final designs with laboratory or plant data.
FAQs
1. What is liquid liquid extraction?
It is a separation method where a solute moves from one liquid phase into another. The two phases should be mostly immiscible, so they can separate after mixing.
2. What does the distribution coefficient mean?
It is the ratio of solute concentration in the extract phase to solute concentration in the raffinate phase at equilibrium. Higher values usually mean easier extraction.
3. Which operation mode should I choose?
Use single contact for quick screening. Use crosscurrent for batch style solvent contacts. Use countercurrent for staged columns or mixer-settler trains.
4. Why is stage efficiency included?
Actual stages rarely reach perfect equilibrium. Stage efficiency reduces the effective distribution ratio, giving a more realistic estimate for plant or pilot systems.
5. Can I use grams per liter?
Yes, if all concentrations use the same basis. The model needs consistent concentration units for feed, solvent inlet, raffinate, and extract values.
6. What does extraction factor show?
The extraction factor compares solvent capacity with feed flow. It equals the effective distribution ratio multiplied by the solvent-to-feed flow ratio.
7. Why can recovery become negative?
Negative recovery can occur when the entering solvent already contains too much solute. In that case, solute may transfer into the feed phase instead.
8. Is this enough for final plant design?
No. This is a screening calculator. Final design should use measured equilibrium data, phase diagrams, settling tests, safety review, and equipment vendor input.