| 摘要 |
Cellulose pulp, particularly medium consistency (i.e. 5-25%) sulphate chemical pulp digested to a low Kappa number (25 or less if an oxygen delignification stage is used, or 12 or less if not), is subjected to various TCF bleaching sequences. The pulp is treated in an acid stage at a pH between 2-7 (preferably about 2-5) for a time period (10 seconds to hours) sufficient to insure that the pulp fibers themselves are at the desired pH. Then the pulp is washed (e.g. a fractionating wash) or pressed. The pulp is subjected to a multistage bleaching sequence including at least one peroxide stage after the washing or pressing (e.g. an Op, Po, or Pa, (such as a Pa Q/A) stage). The temperature during each stage of the bleach sequence is between about 80120.degree.C so that energy is conserved and equipment minimized. |
