Analysis of fibre comminution rates during high intensity thermo-mechanical pulping of spruce and pine

摘要

A three-fraction comminution analysis was conducted on thermo-mechanical pulps produced from two predominant North American softwoods, black spruce (P. mariana) and loblolly pine (P. taeda). High intensity pulps were produced from both wood species at elevated temperature and refiner disk speeds, using a pilot scale two-stage pressurized refining configuration. The rates of Bauer McNett R14 and R28 comminution and P28 formation increased with refiner disk speed. Conversion of R14 into R28 was the most favoured breakdown process, requiring less energy than the breakdown of R14 to P28 or R28 to P28. The pine comminuted at a faster rate than the spruce, at all levels of refining intensity. With the pine furnish a critical level of wood breakdown was observed, beyond which pulp strength properties deteriorated rapidly. The morphological properties of a given wood species have a defining influence on the refining behaviour, and the study suggests that further increases in refining intensity might further reduce energy consumption during manufacture of high temperature thermo-mechanical pulps, particularly when using softwoods with more resilient fibres.