Residence Time
also known as contact time · retention time
Residence time is the reactor or contactor volume divided by the volumetric flow through it, expressed as a mean value for a continuous unit or as a batch duration. For leaching it must be long enough for dissolution to reach the target recovery; for solvent extraction it is the time the phases spend mixed in the mixer, which is normally seconds to a couple of minutes.
Why it matters in practice
Residence time is the parameter most often traded away to raise throughput, and it is usually the wrong thing to trade. In extraction, mixing time above the optimum buys no extra mass transfer but does produce finer droplets, longer disengagement and more entrainment.
Where this appears on this site
Calculators that use this
Equipment referenced in this entry
Lab-Scale PP Reactor
9 Specifications · pp reactor
80mm Rotary Drum Centrifugal Extractor
9 Specifications · centrifugal extractor
Related terms
Reference entry GL-RESIDENCE-TIME. Definitions on this page describe engineering practice in hydrometallurgical process design; they are not a substitute for test work on your own material.