Patent ID: 6238517
Filing Date: 2001-05-29
Classification: D21C

Abstract:
A method of controlling an oxygen delignification process for a pulp having an initial kappa number in order to produce a delignified pulp having a desired kappa number reduction and a final pH of from about 10.5 to 11.5, said method comprising providing chemicals for a U.S. application Ser. No. 09/308,820 first oxygen delignification step with said pulp at a temperature of below about 90.degree. C., conducting said first oxygen delignification step with said chemicals without manipulation of temperature, conducting a second oxygen delignification step at a predetermined temperature to produce said delignified pulp, measuring the final kappa number of said delignified pulp subsequent to said second oxygen delignification step, adjusting said chemicals provided for said first oxygen delignification step and adjusting said temperature only in said second oxygen delignification step based upon said chemicals provided to said first oxygen delignification step and the difference between the measured actual kappa number reduction from said initial kappa number to said final kappa number and said desired kappa number reduction and the measured final pH.