Mass transfer in oxygen delignification systems: mill survey results, analysis and interpretation - Some mills report a delignification increase of 20%

A survey of North American oxygen delignification systems was used to link delignification efficiency with operating practice, in particular, the meth ods used for contracting pulp with gases. Responses from 19 systems, mostly Canadian mills, were interpreted in terms of chemical variables, the strat egies used for steam and oxygen contacting/mixing, and tower configuration. Chemical and mass transfer parameters were found to describe most of the t heoretical delignification achieved by the mills, and provided guidance for system optimization. In the course of this work, the efficiency of several systems was markedly improved - in some cases delignification was increase d 20%.