稻草和麦草绿液蒸煮过程中各组分变化规律比较

对比了相同蒸煮温度下稻草和麦草绿液蒸煮过程中各组分变化规律。结果表明,稻、麦草原料绿液蒸煮脱木素过程呈明显的两个阶段：主要脱木素阶段木素脱出率约为64%~70%,残余脱木素阶段木素脱出率约为5%~10%。主要脱木素阶段二者脱木素速率相近,残余脱木素阶段稻草脱木素速率略高于麦草;两种原料在主要脱木素阶段和残余脱木素阶段均有聚糖溶出,其中主要脱木素阶段聚糖的溶出率分别为稻草60%、麦草34%,二者脱木素选择性分别为2.1和1.1;残余脱木素阶段聚糖溶出率分别为稻草6%、麦草14%,脱木素选择性分别为0.4和1.7。稻、麦草原料绿液蒸煮过程中硅的变化规律呈现三个阶段,每一阶段稻草浆中硅的保留率都高于麦草原料。150℃保温2 h后,原料中硅的溶出率分别为稻草9.3%和麦草45%。相应地,稻草绿液蒸煮黑液中硅的浓度远低于麦草原料,黑液的临界浓度可达45%,约为麦草的3倍。

Study on the Various Component Changes of Rice Straw and Wheat Straw during Green Liquor Cooking

The changes of lignin, glucan, pentosan and silica content in wheat straw and rice straw during green liquor cooking were contrasted. The results indicated that there were two delignification phases for both wheat straw and rice straw： a main phase where 64%~70% lignin were removed （to 150℃） and residual phase where 5%~10% lignin were removed. The delignification rates of wheat straw and rice straw were similar in main phase and rice straw was slightly higher than wheat straw in residual phase. Part of polysaccharides of wheat straw and rice straw were removed during delignification process. In main phase, the removing ratio of polysaccharides of rice was 60% and that of wheat straw was 34%. Corresponding the delignification selective ratio was 1.1 and 2.1 respectively. In residual delignification phase, the removing ratio of polysaccharides of rice was 6% and that of wheat straw was 14%. The delignification selective ratio was 1.7 and 0.4 respectively. The changes of silica revealed three phases, and the silica of 9.3% of rice straw and 45% of wheat straw were removed after remaining 2 hours at 150℃, correspondingly, the consistency of silica in the spent liquor of rice straw was much lower than that of wheat straw, and the critical concentration achieved about 45%, it was 3 times more than that of wheat straw.