Decreasing specific energy of thermomechanical pulps from reduction of raw materials variability

Abstract

Wood chip characteristics including species, basic and bulk densities, moisture content, freshness, bark content, and size distribution strongly influence the specific energy consumption (SEC) of thermomechanical pulping. Changes in these characteristics lead to variations in the mass flow rate of the chips fed into the refiner, causing SEC variations. In a typical mill with normal operating conditions, up to 30% of the disturbances in the pulp-ing process can be explained by chip variations. For this paper, researchers used an online measurement system, CMSE (chip management system, extended version), to monitor chip characteristics to study the effect of chip variability on SEC. Models and simulations were built from pilot experiments and results were validated by mill trials.