Patent ID: 9447131
Filing Date: 2016-09-20
CPC Classification: B01D,C07G,D21C,D21H

Claim Text:
1. Process for refining lignosulfonate at least partly derived from a spent sulfite cooking liquor in at least two steps, comprising: one step in which a lignosulfonate-containing fraction at least partly derived from the spent sulfite cooking liquor is subjected to filtration at a pressure, flow rate and temperature using a membrane having a cut-off of 40-150 kD (high cut-off) at the pressure, flow rate and temperature of the step and the permeate is recovered; another step in which a lignosulfonate-containing fraction at least partly derived from the spent sulfite cooking liquor is subjected to filtration at a pressure, flow rate and temperature using a membrane having a cut-off of 1-20 kD (low cut-off) at the pressure, flow rate and temperature of the another step and the retentate is recovered; wherein the spent sulfite cooking liquor is preheated to about 85-140° C. and the temperature is maintained throughout the filtration steps; and the spent sulfite cooking liquor that has been subjected to the two steps is concentrated by removal of water.