Hydroclone separation efficiency measurement

ChemIndustrial’s hydroclones are highly modular, so they are quickly and easily assembled into many different configurations whose performance can be accurately measured and compared in the customer’s actual process, using our HydrocLOAN™ rental program.

The most common hydroclone application is to concentrate solids in a flowing liquid/solid mixture. In this application, the purpose of the hydroclone is to separate inlet flow into:

• an overflow stream which contains less solids than the inlet flow and…

• an underflow stream which contains more solids than the inlet flow.

Perfect information about hydroclone separation performance would require mass balance trials. In layman’s terms hydroclone mass balance means this: The mass of everything that goes in to the hydroclone must come out of it.

True mass balance trials are cumbersome, but in most cases mass balance accuracy isn’t needed for practical evaluations of process separation.

The widely used quick and easy alternative to a mass balance trial is the volumetric separation trial.

An Imhoff cone is used for manual volumetric separation trials. This is a clear 1000ml conical settling vessel with calibration markings.

To perform a volumetric separation trial, three Imhoff cones are needed, labeled Inlet, Overflow and Underflow: 

Actual trial run

Decide on the hydroclone configuration to be tested.

Measure all 3 flow rates:

• Inlet flow rate

• Overflow rate

• Underflow rate

Inlet flow rate = Overflow rate + Underflow rate

Flow measurements must be consistent with the above equation. For valid results, don’t go ahead without resolving any discrepancy.

Use the Imhoff cones to take one sample for each of the 3 flows.

Allow complete settling to occur. If the particles are small and/or light, settling may take some hours.

Record the 3 values:

• Inlet solids level (ml)

• Overflow solids level (ml)

• Underflow solids level (ml)

It is tempting to look at the 3 settled samples and draw an immediate conclusion about the hydroclone’s separation efficiency. But this measurement will not be accurate because inlet flow doesn’t usually split equally to overflow and underflow. Thus you must correct for the difference between the overflow rate and the underflow rate. Record the results of the following three calculations:

The Total separated solids value can be larger than the Inlet solids level value. One possible reason for this difference is the size of particles reporting to the hydroclone’s overflow (smaller particles) versus the particles reporting to the underflow (larger particles). Small particles can fit into the interstices among the larger particles in the undifferentiated inlet solids.

To evaluate hydroclone performance in a particular application, ChemIndustrial offers customers short-term use of a hydroclone system under the  HydrocLOAN™ rental program.