very low pressure drop this allows the recycling of the gas stream with a blower or an eductor it is to be noted that to preclude clogging of the packing by particulates the packing type and crimp angle are important in this regard structured packing 74 can have a packing density of between about 500 m 2 m 3 and is preferably koch type 1 x or 1 y which can be obtained from koch engineering company inc of wichita kansas random packing and trays could also be used with less effectiveness column 64 should be operated at a pressure of no less than 9 2 atmospheres absolute the oxygen should have a purity as high as is economical with 90 and above being preferred the reaction should proceed at a total pressure of no less than about 9 2 atmospheres absolute and more preferably at least about 11 2 atmospheres absolute additionally the reaction between the oxygen and the sodium sulfide should occur at a minimum temperature of about 110 u00b0 c a minimum reaction temperature of about 120 u00b0 c is more preferred and reaction temperatures at or above 150 u00b0 c are particularly preferred a particularly preferred temperature and pressure is about 200 u00b0 c and about 18 atmospheres absolute the reaction of oxygen and sodium sulfide is an exothermic reaction however to start the reaction heat must be added to the white liquor to raise it to the requisite reaction temperature to this end a heat exchanger 78 can be provided before inlet 66 in which the incoming white liquor is heated by indirect heat exchange with steam after the reaction progresses heat exchanger 78 can be shut down the oxidized white liquor collects as a column bottom 80 within bottom region 72 of.