Minimizing TMP Energy Consumption Using a Combination of Chip Pretreatment, RTS and Multiple Stage Low Consistency Refining, 2007 International Mechanical Pulping Conference

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High intensity thermomechanical pulps were produced from white spruce on the pilot scale using a combination of pressurized chip destructuring and fibration, chemical treatment, RTS ◙ primary refining and multiple stage low consistency refining. Competitive news grade TMP pulp quality was achieved with approximately 1500 kWh/ODMT using the new process configuration. The physical pulp properties using the multiple stage LCR configuration were equivalent to the HCR control pulps at a given freeness and superior at a given application of specific energy. An interesting finding was that the conditioned spruce fibers following primary refining were equally developed in a Low Consistency Refiner as compared to High Consistency Refiner; eliminating the need for a secondary high consistency refining stage. Results from this investigation shed light on the importance of pulp fiber conditioning for maximizing the displacement of HCR with less energy intensive LCR.

In a separate study using a similar process configuration, it was found that increasing the consistency of the LCR component to 5%-6% is a feasible alternative. The energy consumption and pulp quality development were similar to that obtained with multi-stage LCR at 4% consistency. The displacement of more HCR with LCR in thermomechanical pulping will continue to increase as pulp and paper producers strive to reduce operating, capital and installation costs.