Chemitermomechanical pulp made from birch at high temperature

The inherent stiffness of birch wood-fibres makes birch an excellent raw material in the manufacture of high bulk pulp. By a combination of chemical impregnation of birch chips and pre-heating of the chips to high temperature prior to refining, it is possible to manufacture CTMP with very high bulk using a low energy input. Trials revealed that the high pre-heating temperature lowers the energy consumption considerably. At 500 ml CSF an increase in the pre-heating temperature from 110C to 160C reduced the energy consumption by more than 40 %. Despite the low energy input, the shive content remained low or was even reduced and the internal bond strength, in terms of Scott-Bond, compared favourably with Spruce CTMP. In summary, a high pre-heating temperature can be used to manufacture birch CTMP with very high bulk, at a low energy consumption.