High-consistency Electrochemical Delignification of Poplar Kraft Pulp

The electrochemically mediated delignification of pulp fibers is one of the promising bleaching methods, which can give the delignified pulp with good subsequent bleachability and high pulp viscosity. Our previous work has shown that the poplar kraft pulp can be delignified to 45% delignification ratio with less than 10% pulp viscosity loss at the condition of 1% pulp consistency which limits the application of this method in pulp industry. The high-consistency electrochemical delignification of poplar kraft pulp was investigated in this paper. The delignification ratio, pulp viscosity loss and brightness were measured as well as the delignification conditions, such as pulp consistency, voltage of electrolysis cell, temperature, circulation of electrolysis liquor and time, were discussed. The results showed that at the 10% pulp consistency, the circulation of electrolysis liquor between pulp cell and electrolysis cell can efficiently improve the delignification ratio, and the pulp viscosity loss is less than 10%. The subsequent bleachability for H2O2 is similar as that of 1% consistency delignified pulp. The pulp also can be bleached to higher than 80% ISO with following EP stage at 2.5% H2O2 dosage.