| 摘要 |
<p>Delignification of cellulose pulp. obtd. by chemical digestion of lignocellulosic prods. is effected by contacting the pulp, in an activation phase, with a gaseous phase contg. NO2, and O2-contg. gas (I) being fed to that activation phase so that the intermediate NO is used to activate the pulp, the activation phase being effected under energetic conditions, i.e. at high temps. so as to cause degradation of the cellulosic molecules. Improvement is that the pulp is then subjected to a (I) + alkali treatment in a mixt. of pulp and water, the partial pressure of (I) being 0.005-0.18 MPa and not falling below the lowest pressure limit at any time during the treatment. Compared to known processes, the above is more favourable to the environment and more selective, i.e. more lignin is removed from the pulp, while maintaining a higher viscosity. The residual liquors can be recovered and evaporated, as well as burnt together with the residual digesting liquors (cf. bleaching with chlorine).</p> |
