بررسی قابلیت استفاده از کلش برنج در صنایع کاغذ

Wood supply from natural forests is diminishing and our environment is degrading, and the pressurefrom environmentalist is raising the public attention on our future environment. Thereforepaper industry is faced with tight situation is supply of wood raw material. On the other hand, hudge volumes of agricultural residues are available wordwide. Its utilization in pulp production not only doesn't damage our environment, but also helps us preserving it. Eventhough so of these residues are being used as cattlefeed, but rice straw is unique which contains a high percentage of silica and it usage for cattlefeed has not been very successful and therefore it is available for industrial utilization. Agricultural c\.tatistic~',indicates that almost 320.000 tons of rice straw i~'available annually in Iran. Based on thefact that Iran is located in an arid zone and itsforest cover is limited to a narrow strip in southern coast of caspian sea with limited production potential and also woodproduction from plantation is very coastly, Iran oughtto searchfor alternativesourcesof ligno cellulosicraw materialand amongthem rice strawpossess excellentpotential. Therefore this study wa~'undertaken to investigate the pulping characteristics of Iranian rice straws. As indicated from table 3, the stregth properties of rice straw pulp is excellent. Breaking length varies between 5270 to 7370 m with most of the values about 6500 m. Tear strenght and burst strength varies between 42.51 & 65.18 mN and 37.8 tb 41.3 kg/cm2 respectively Folding resistance is also comparatively high and varies between 21 to 70. The investigation has showed that soda pulping of rice straw is possible and good bleachable pulp can be obtained at 16% effective alkali, 150 c. cooking temperature and 25 minutes cooking time. The results of delignification studies indicates that to produce bleachable grade pulps from rice straw, the unsreened yield will be limited to about 45% and in some special condition it will be as high as 49.15% at kappa number of 12.88. Since delignification studies showed promising results, soda pupling process at 16% effeective alkali (Na20 basis), 150 c, 25 miniutes pulping time and liquor straw ratio of 8:1 was selected for further study to determined the pulp strength. Each sample was individually cooked and upon completion of cooking period, cooked straw was defibered and pulp was washed. All pulps were refined in PFI mill and freeness was measured. From each refined pulp, 60 glm2 hand sheets were produced and strenght were determined. The results of these measurements are sammarized in table 3.