| 摘要 |
The continuous treatment of a cellulosic material in the form of chips to produce at least partial delignification of the material without true mechanical grinding is effected in apparatus comprising two parallel meshing screws which are rotated in the same direction in a sheath and have identical threads providing a plurality of zones of different pitch. The material is passed in succession through a first zone for feeding the material downstream, a first braking zone for causing a first compression of the material, a second zone for feeding the material downstream and in which the material is brought into contact with a reagent, e.g. steam or a chemical reagent, and a second braking zone for causing a second compression of the material. In each compression stage the material is subject to alternate increases and decreases in pressure, the first compression stage causing the expulsion of any water present in the material and the second compression stage causing the expulsion of any spent reagent and residual liquors in the material. |
