Process for the treatment of black liquor of cellulosic pulp wherein oxidation is performed both before and after black liquor concentration

摘要

A process for the treatment of black liquor in which in a first oxidation stage there is blown into dilute black liquor a quantity of oxygen ranging from 0.5 to 1 times that theoretically necessary for oxidizing the sodium sulphide to sodium thiosulphate and, in a second oxidation stage, there is blown into black liquor after it has been concentrated a quantity of oxygen greater than that necessary for converting the residual sodium sulphide to sodium thiosulphate. The process is applicable to the recovery of chemical elements, notably from Kraft pulps.