ABSTRACT
An environmental concern in the kraft pulping is the odor caused by the reduced sulphur compounds.There are many simple equipments to detect on-line the total reduced sulphur (TRS), like the coulometric titrator. This study had as aim to measure the components of the total reduced sulphur compounds generated in kraft and pre-hydrolysis kraft laboratory cooking. Two types of hardwood chips were used in the cookings: one with 25% of lignin (on dry wood), the other with 20% lignin. The wood containing less lignin generated less total reduced sulphur compounds. Considering the gases formed in the two types of cooking processes, no significant differences could be detected in terms of generated amounts of reduced sulphur compounds. However, the lignin content of the woods under evaluation had important role in generating TRS. The pre-hydrolysis kraft process was proved to be more sensitive to the higher lignin content in the wood. It is recomended to work with low lignin content wood when cooking by this process. Dimethyl sulphide and methyl mercaptan were the dominant TRS compounds in the relief gases from the digester.
Key words:
kraft process; pre-hydrolysis kraft; TRS; gases; lignin.