Process reasoning
Set the system boundary first. A centrifuge may receive feed, wash liquid, polymer solution or rinse liquid and may temporarily retain material inside the bowl, cake or collection vessels. During a batch, compare total collected masses for the whole cycle. During stable continuous operation, compare simultaneous mass flow rates. Dry-solids balances and component balances answer different questions: a dissolved impurity can follow the liquid even when suspended solids are almost fully captured.
ILLUSTRATIVE EXAMPLE
Apply the reasoning
For an illustrative stable test, 10,000 kg/h of feed and 200 kg/h of added solution enter the boundary. Measured cake is 900 kg/h and collected liquid is 9,050 kg/h. The missing 250 kg/h is 2.45% of the total input. That does not automatically invalidate the trial, but it requires an explanation such as unmeasured drainage, accumulation or meter uncertainty. Choose the acceptable closure tolerance before testing.
What to record
| Item | Basis to document |
|---|---|
| Overall balance | All mass in − all mass out = accumulation |
| Solids balance | Feed dry solids + added solids = outlet dry solids + retained solids |
| Recovery | Target component in desired product / target component in feed |
| Closure error | (Measured input − measured output) / measured input × 100% |
Review checklist
- Include polymer dilution water and cake-wash streams.
- Use mass units or document the density used for volume conversion.
- Synchronize collection periods.
- Check accumulation before assuming steady state.
Your next decision
Request both raw measurements and the calculated balances. A supplier should be able to explain why closure is reasonable for the instruments and sampling method used. If the feed changes during collection, repeat the test or account for the change explicitly. High capture, low cake moisture and low chemical use should be demonstrated on the same stated balance basis.