In a rotary drier, the average retention time of solid is (where Z = length of the drier, metres ρ = apparent solid density, kg/m3 L = flow rate of dry solids, kg/see. m2 drier crosssection H = hold up of solid.) ?
Correct answer: A
Explanation
Retention time is calculated by dividing the total mass of solid held (Z.H.ρ) by the rate at which solids flow through (L).