| abstract |
A method for producing crude tall oil from black liquor soap while removing calcium carbonate and lignates is disclosed. Black liquor soap is first combined with an alkaline wash medium having a lower concentration of lignates and inorganic solids than the black liquor soap. The resulting mixture comprises washed tall oil soap, fortified brine, lignates, and calcium carbonate. The washed tall oil soap is then separated from the fortified brine, lignates, and calcium carbonate, preferably by centrifugation, decantation, filtration, settling, or a combination of these techniques. Acidification of the washed tall oil soap gives crude tall oil, and a spent acid mixture. The crude tall oil is separated from the spent acid. The spent acid is made alkaline, and at least a portion of it is returned for use as alkaline wash medium. The method enables soap washing in a crude tall oil production process while avoiding process upsets caused by accumulation of calcium sulfate in or downstream from acidulation units. |