| 摘要 |
The present invention relates to a method of preventing scale formation in a pulping process of chemical pulp. The method comprises at least the following steps: a) comminuted cellulosic fibrous material is treated with cooking liquor at a temperature below 120 DEG C, b) a first waste liquor flow containing metals, e.g. calcium, is separated from the material and a waste liquor flow is obtained, the temperature of which is below 120 DEG C, c) fresh cooking liquor is added to the fibrous material, d) fibrous material is degested at a temperature of 140 - 170 DEG C to produce chemical pulp, e) a second waste liquor flow is separated from the pulp and a waste liquor flow is obtained, the temperature of which is over 130 DEG C, f) the first waste liquor flow from step b) is heated to a temperature over 120 DEG C, g) the heated waste liquor flow from step f) is maintained at a temperature over 120 DEG C for at least 0.1 min, preferably 1 - 20 min in order to precipitate metals, especially calcium, present in waste liquor, h) the heat-treated waste liquor flow is passed to further treatment, and i) the pulp from step e) is washed.
|
