PRESSURIZED GRINDING OF SAPWOOD AND HEARTWOOD OF SPRUCE

The purpose of this study was to investigate how the two wood componen ts, sapwood and heartwood, behave during atmospheric and pressurized g rinding. The influence of the wood components and pressurization on th e amount of dissolved substance was also investigated. The experiments were performed on a laboratory grinder. The results show that atmosph eric grinding of dry heartwood produced a low-quality pulp, while sapw ood pulps have a superior quality. Pressurization and hence an increas e in grinding temperature results in a better pulp quality for dry hea rtwood. The difference in quality between sapwood and heartwood pulps produced under pressurized conditions was diminishing. The amount of d issolved substances was somewhat higher for heartwood; pressurization also increase the amount of dissolved substances for both sapwood and heartwood.