Separation efficiency of coal cleaning equipment is typically assessed by Probable Error in Separation (Ep) and Organic Efficiency (Eorg). The first one is determined on the basis of precise cut point density of separation and implies that for ideal separation the error is zero. The second one is calculated on the basis of yield of clean coal/ middling at the target ash and implies that for ideal separation the efficiency is 100%. Plant operators worldwide being accountable for the tonnage of the clean coal and middling produced regularly monitor Eorg with some application in plant design in India. Ep is universally used as an equipment selection criterion from among the vendors, in commercial contracts and sometimes for performance analysis of coal cleaning equipment carried out at the plants. Since both are performance measures there should possibly be a relationship between the two for specific cleaning equipment or for a particular type of density separators. Such relationships are however rarely observed. Moreover there are many instances where high to very high Eorg does not translate into low to very low Ep.
Therefore, is there a dichotomy between the two performance measures?