WATER PRE-EXTRACTION BERORE RICE STRAW ALKALI PULPING

In this study, the effect of water pre-extraction on rice straw alkali pulping properties was investigated. Some parameters which may affect the pre-extraction were optimized, such as liquid-to-solid ratio, pre-extraction temperature and time. It was shown that the content of dissolved hemicelluloses and lignin kept rising with the increase of pre-extraction temperature and time. However, when the pre-extraction temperature was higher than 80 degrees C, the content of dissolved hemicellulose and lignin had no significant change, and the cellulose would be dissolved if the pre-extraction temperature was too high or the time was too long. The optimized condition for water pre-extraction before rice straw alkali pulping was obtained as follows: pre-extraction temperature was 80 C, liquid-to-solid ratio was 1 : 20, and pre-extraction time was 150min. Under the above mentioned condition, polyose content in rice straw decreased from 20.46% to 16.18%, lignin content in rice straw from 15.66% to 13.59%, and ash content in rice straw from 13.67% to 7.15%, correspondingly.