GB143874A - Method of treating waste sulfite liquors and products obtained therefrom - Google Patents

Abstract

In the preparation of a dry non-hygroscopic product substantially free from sulphur dioxide, calcium, and magnesium, containing a reduced glucose content, and suitable for a binding or adhesive, from waste sulphite liquors, bases such as calcium and magnesium are precipitated and the liquor rapidly concentrated or evaporated by spraying under pressure of 100 to 1000 lbs. per square inch into a chamber through which hot flue or other gases pass. The evaporation may be effected in one or two stages. Where two stages are used, the gases leaving the chamber after the final stage may be passed at approximately 200 DEG F. into a second chamber where the preliminary concentration is effected, in which chamber a liquor containing 30 to 60 per cent of solids is obtained. The final evaporation is effected at from 300 DEG to 500 DEG F. and the dry product comprises minute glazed solid spheres or hollow spheres each having a blow hole. Chromium sulphate, aluminium sulphate, sodium sulphate or "bisulphate," ammonium sulphate, sulphuric acid, or oxalic acid may be used to precipitate the bases and the presence of magnesium free from combination with an organic complex is unobjectionable. The fine powder may be used as a binding material to form briquettes which may be used to supply heat for the evaporation. Any fine powder carried away by the hot gases may be separated therefrom by electrostatic precipitation or by filtering, or the pressure of the gases may be reduced and the dust brought down in a settling chamber by the fog produced. In the latter case the damp product would be re-dissolved and the solution sprayed again into the drying chamber. The liquors may be first concentrated in a multiple effect evaporator.