Gas dispersion and de-inking in a flotation column

The role of four gas dispersion parameters in ink particle collection was investigated in 4″ and 20″ flotation columns. Gas holdup (εg) and superficial gas velocity (Jg) were measured on-line and bubble size (db) was estimated using drift flux analysis that enabled bubble surface area flux (Sb) to be calculated. Operating with approximately zero froth depth ink recovery as a function of retention time (controlled by underflow rate) was determined. Using a mixing model, the collection zone flotation rate constant (kc) was estimated from the recovery––time data. The rate constant was not related to Jg or db but was linearly dependent on εg and Sb, similar to findings in mineral flotation studies.