IDE-PULPING OF COMMON REED

摘要

The IDE-process is a new pulping process suitable for pulp production of softwood, hardwood and nonwood. The name of the process, IDE, originates from the division of the process into three subprocesses, e.g. the Impregnation stage, the Depolymerisation stage and the Extraction stage. The IDE-process was first presented in 1994 and it appeared quite soon that high-yield softwood pulp at low Kappa number could be produced, that the strength properties were excellent and the bleachability reasonable. It is a sulphur-free alkaline pulping process where ethanol and anthraquinone (AQ) are used to speed up the delignification significantly. The application of AQ also increases the carbohydrate yield at higher charges. The main advantage of the IDE-process is better pulp yield compared to the kraft process. The IDE-process also produces pulp with lower extractives content and lower alkali consumption than those of kraft pulp. Most nonwood raw materials can be pulped without the use of sodium hydroxide which simplifies the recovery of the inorganic components. Previous studies concentrated on the optimisation of the impregnation stage and the depolymerisation stage and also on the role of AQ in the process. The studies were mainly focusing on hardwood, softwood and some nonwoods. This paper is dealing only with IDE-pulping of common reed. Time and temperature of the impregnation and delignification stages are discussed. The study was considering that the fiber source may significantly improve if fractionated in some way, and further it was also considering that a nonwood fiber material in general is very different from common wood materials, and therefore the pulping conditions should accordingly be adapted, it was clearly seen that straw only (without leaves) provided a much better yield > 53 %, as it was ranging from 47 to 50 for the materials including leaves in various proportions. The corresponding residual lignin content was 3-4 expressed as the Chlorine number. The average fiber length of the pulps were 0.7 - 0.8 mm and may thus compare to many hardwood pulps. In this study certain pulps were analysed for monosaccharides, and the results show that common reed contained large amounts of xylan, which is common for many hardwoods. Initial peroxide bleaching experiments, made in one step improved the pulp brightness from 25 to > 45 ISO, and it might thus be used for certain purposes without further bleaching.