Abstract: This invention relates to a process for the cryogenic separation of oxygen-containing mixtures to produce an enriched product whereby oxygen concentrations greater than 21% by volume are achieved in the process via passing streams of liquid and vapor countercurrently through a mass transfer zone which contains packing elements fabricated from a material having a thickness of less than about 1 millimeter, having a copper concentration of at least about 30% by weight and a heat of combustion of less than 1.0 Kcal/g, thereby avoiding the risk of flammability.

Abstract: High recovery of useful energy from the heat of reaction in the oxidation of black liquor is obtained by integrating the oxidation into the multiple effect evaporation system of the pulp mill recovery sequence. The heat of reaction is thereby recovered as flash steam, which when combined with the vapors from an appropriate evaporator body enables recovery of its energy through further evaporation. The oxidation reaction may be carried out on the liquor leaving the second effect of the evaporation sequence for maximum energy recovery, or in accordance with an alternative embodiment, the reaction is carried out between the first effect and the flash tank with preferable addition of a second flash tank in series with the first.