OPTIMIZING REFINER OPERATION WITH STATISTICAL MODELING

A series of pilot scale refining trials has been conducted to study th e impact of refining conditions on the energy efficiency of the proces s and on the handsheet quality of a chemimechanical pulp. Black spruce (Picea mariana) chips, cooked to a yield of 90% and a sulphonate cont ent of 1.4%, were refined in two atmospheric stages. Plate gap and con sistency in each stage was controlled according to a central composite design; Statistical models of refiner performance were constructed fr om these experimental results and a non-linear optimization of process conditions was conducted. Optimization results were verified with pla nt trials which indicate that increasing the ratio of specific energy applied in the first stage leads to a reduction of approximately 15% i n the total energy required. Inversely, this strategy can be used to o btain significant increases in pulp quality for a given energy input. The results also indicate that the largest proportion of energy must b e applied to the fibres at high consistency.