| 摘要 |
<p>Preparation of polysulphide for treatment of wood chips so that the wood consumption is reduced in kraft digestion of paper pulp. In an impregnation stage the wood chips are caused to react with black liquor, or black liquor components containing digestion liquor prepared of white liquor, while introducing oxygen of appropriate concentration in an impregnation vessel. The content of monosulphide, and to a certain extent other sulphur compounds present in the liquors, thereby forms polysulphide in contact with the wood chips which instantaneously absorb the polysulphide. Generation of polysulphide is promoted by wood reactions. Black liquor having a reduced concentration of hydroxide is withdrawn from the wood chips before delignification thereof in digestion liquor prepared of white liquor and residual impregnation liquor from the wood chips. The withdrawn black liquor is conveyed to a plant for regeneration of hydroxide in white liquor and sulphide, which wholly or partly is recovered in the form of white liquor, and which sulphide is repeatedly polysulphide-oxidized. The yield increment of pulp from the digester, as well as after the bleaching stage, is greater in oxidative polysulphide processing in presence of wood chips than in separate processing thereof in liquor before the charging into wood chips. This is interpreted such that more polysulphide is formed in the presence of chips than without.</p> |
