Oil palm, because its form looks like a coconut, also known as “oil coconut.” The origin is the western and central parts of Africa, and there are a large number of plants in Malaysia, Indonesia and Thailand. Since 1926, Hainan, Guangdong Leizhou Peninsula, Guangxi Beihai, and Yunnan Estuary have been introduced successfully, and are widely cultivated in the south of the Yangtze River Basin. Oil palm fiber mainly comes from its compound leaves, empty husks, and trunks. Oil palm is similar in structure to sugar cane and contains a large number of parenchyma cells. The parenchyma cell is most easily penetrated by chemicals during chemical pulping, but too high content of parenchyma cells will lead to an increase in chemicals consumption and a decrease in pulp yield. Therefore, the selection of oil-palm shells with relatively low content of parenchyma cells as a pulping material has advantages far greater than that of palm trunks and compound leaves.
In order to make full use of resources, the empty fruit shell as a by-product of palm oil extraction has attracted the interest of many paper-making enterprises. CNBM is a paper pulper machines manufacturer from China, we can provide paper pulp solution and paper pulp making machine, including pulp digester, blow tank, single screw press, twin roll press, vacuum drum washer, disc filter, and etc.
To this end, this paper analyzes the chemical composition of palm silk in the empty shell of palm trees and uses the caustic soda pulping and the kraft pulping test to determine the feasibility of palm silk pulping and papermaking.
Fiber morphology of palm silk
Palm silk has a weighted length of 0 · 74 mm, a weighted width of 14.96 m, and an aspect ratio of 49.96. The width is smaller than that of wheat straw and bagasse, and the length is smaller than the two, so the aspect ratio is also less than wheat straw and bagasse. However, the majority distribution of palm fiber length is not much different from the distribution range of wheat straw and bagasse. The aspect ratio is small due to the excessive content of fine fibers (fiber length less than 0 · 2mm) of palm silk, reaching 20 · 9%. According to the experience, the raw material with a fiber aspect ratio of less than 45 has a low value of pulping and papermaking, and the aspect ratio of palm silk is greater than 45, which is considered to have better pulping performance. Therefore, the processing of fine fibers is the key to palm silk pulping.
Chemical composition of palm silk
The chemical composition of palm silk was analyzed and compared with the chemical constituents of wheat straw and bagasse raw materials which have been used in papermaking. The results show that the cold water extract of palm silk is similar to the hot water extract, and the hot water extract and ash of palm silk are both lower than that of grass pulping materials such as wheat straw and bagasse, indicating that the content of inorganic salts, tannins, and pigments of palm silk is lower than that of wheat straw and bagasse. The 1% NaOH extract is also between the wheat straw and the bagasse. The amount of alkali for cooking and the cooking yield should also be comparable to those of the grass. The content of phenyl alcohol extract is high. Since palm silk as a by-product of oil extraction contains certain compounds such as fats and waxes, the pulping process should also pay sufficient attention to resin acids and fatty acids to prevent “pitch trouble”. The content of cellulose and hemicellulose is equivalent to the content of grass raw materials and is higher than grass raw materials such as straw, and the lignin content is lower than that of grass raw materials. Therefore, through the above analysis, palm silk has a certain pulping performance, but also need more attention to the effects caused by special components.
Chemical pulping and bleaching of palm silk
Palm silk pulp is obtained by the conventional cooking process, and all the indexes can meet the requirements of grass fiber pulping. Add anthraquinone into the cooking liquid, and the cooking yield is also improved, indicating that anthraquinone has a certain effect on the cooking of palm silk. In the process of washing, there are a lot of fibers in the outer layer of the washing bag. The content of the microfibers is large, and the selection of the net mesh number is paid attention to during the washing process. In addition, the upper of black liquor will form an oil layer, it shows that the content of resin saponification in palm silk is high, and papermaking aid can be added during the washing process to prevent pitch trouble and affect papermaking.
From the perspective of environmental protection, the two pulps obtained by pulping are subjected to single-stage bleaching with oxygen to remove lignin. The bleaching process conditions are: 3% NaOH, 10% pulp, 0.5% MgS04 · 7H20 (as Mg2), 4% H202, bleaching temperature 100 °C, oxygen pressure 0 · 8 MPa, bleaching time 1h, After the bleaching, the pulp was subjected to PFI grinding, and the paper strength was measured. The beating concentration is 10%, the number of grinding disc grinding is 8500 rpm, and in a short period of time, the beating reaches about 42 degrees, indicating that palm silk is easy to beat as other grass materials.
The pulp obtained by caustic soda cooking has a relatively low Kappa number, and the whiteness after bleaching is relatively high, but the other physical indexes of the caustic soda cooking pulp are lower than the sulfate pulping. After the papermaking, the folding resistance, the fracture resistance index and the cracking index are relatively high, which can be used to produce high-grade paper, but the tear index is low, and the palm pulp can be used together with some high-grade pulp to make paper. It’s a good way to make full use of palm silk by-products.
The average length of palm fiber is 0.74mm and the width is 14.96, which is close to the fiber shape of common grass raw materials. However, due to the high content of fine fiber, the average length of fiber is low. Pay attention to the protection and recovery of fine fibers during pulping.
The cellulose and lignin content of palm silk was 40.05% and 14.69%, respectively, which are lower than that of softwood and hardwood. The yield of pulp is lower than that of softwood and hardwood, but it is easy to make pulp compared to softwood and hardwood. The content of hot water extract, 1% NaOH extract and benzene alcohol extract are higher, especially the content of 1% Na0H extract is 30 · 02%, which is higher than that of softwood and hardwood, which affects the chemical consumption and the pulp quality in pulping. The black liquor obtained after the pulping contains the saponified product, and it is necessary to pay attention to the removal of the resin in the pulp, so as not to affect the pulp making.
The palm silk can be made by the caustic soda pulping or the Kraft pulping. Under the same alkali amount, the pulp obtained from caustic soda pulping is lower in the kappa number, and the Kraft pulp is easily bleached to a higher whiteness. The physical index of the Kraft pulp is better than that of the caustic soda pulp. Taken together, palm sulfate pulp is slightly better than palm caustic soda pulp.