Characterization of spruce wood chips after mild steam explosion

The effect of steam explosion under very mild conditions; 160 degrees C and 10 minutes, has been studied. Even during this mild treatment a small decrease in hemicellulose content, due to acidic hydrolysis, was found. The content of lignin and cellulose stay in the same range as in the raw material. The decrease in hemicellulose content was found to persist during Kraft pulping. A slightly lower kappa number after a Kraft cook was found for the steam exploded samples than for the water impregnated samples. This suggests that the steam treatment had a small influence on the wood structure, making it slightly more open. No negative effect of the steam explosion, as pertains to ISO-brightness, fiber length or fines was found after Kraft pulping.