Effect of harvesting age of Eucalyptus camaldulensis on bleached kraft pulp manufacture | |
| Author | Sawitree Pisuttipiched |
| Call Number | AIT Diss. no.PP-02-1 |
| Subject(s) | Eucalyptus camaldulensis Pulpwood--Havesting time |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science |
| Publisher | Asian Institute of Technology |
| Abstract | The main objectives of this work were to study the effect of harvesting age on 1) the fiber morphology, specifec gravity and chemical composition, 2) unbleached pulp properties, 3) oxygen delignified ard ECF bleached pulp properties, 4) the relationship between wood properties and bleached pulp properties and 5) bleached pulp qulity and manufacturing costs. The materials used in this study were 4, 6 and 8 years old Eucalyptus camaldulensis plantation trees that come from the same clone. The plantations were located at Eastern part of Thailand and not far from each other. All experiments were performed in laboratory scale. Three debarked wood disks from each tree age were cut at 1.3 m above ground for analyzing wood density, chemical composition, fiber length and coarseness, cell distribution and fiber wall thickness. Logs were chipped; chips then dried and screened. Kraft pulps were prepared at a liquor to wood ration of 4 and with 35% sulfidity white liquor. The charge of effective alkali (EA, as NaOH on o.d. wood) was varied from 16% to 22%. H-factors used were 1000 and 1200. Unbleached pulp at the kappa number of 15 of each tree age was selected to oxygen delignification. The oxygen delignified pulp at the dappa number ca 10 was bleached to brightness 88% ISO by a D0EopD1 sequence. Bleached, pulps were beaten in a PF1 mill with 500 to 8000 revolution. Drainability, grammage, thickness, apparent density, smoothness, tensile strength, tearing resistance, folding endurance, bending resistance, brightness, opacity, light-absorption and light-scattering coefficient were measured. Wood densities at green volume of 4-,6- and 8-year-oldtrees were 530, 600 and 640 kg/m3, respectively, Older trees have higher basic densities although it does not sharply vary from pith to bark side, The density of the 1- to 4-growth rings of 8-year-old trees is very high, It possibly comes from the tylose deposited in the vessel. The densities of the 8-year-old trees were higher than the recommended level of 600 kg/m3 for pulping. Pentosan content (13.8%-15.3%) slightly decreased while extractive content (7.5%-8.8%) increased with increasing tree age, Tree age did not affect holoecllulose (71.9%-72.5%), ligmin (26.9%-27.1%) and ash contents (0.7%-1.1%). The extractive content of 1-4-growth the vessels. The finer and shorter fibers of 4-year-old wood (45 ug/m and 0.69mm) give slightly higher munbers of fiber per pram (28 million/g) than the coarser and longer fibers of 45-47 ug/m and 0.76-0.79 mm for 6 and 8 years (26 million/g). Wood cross section was composed of 15.4%-21.0% vessel area, 27.0%-27.1% parenchyma cell area and 57.6%-51.2% fiber brea. Vessel and fiber increase from pith to bark, especially at 6- to 8-growth rings of 8 years old trees. Diameter, lumen and wall thickness of 4- to 8-year E. camaldulensis fibers were 13.2-13.9, 5.4-7.5 and 3.2-3.9 micron, respectively, Tree age did not affect fiber diameter but wall thickness slightly increased while lumen decreased with increasing tree age. However, the changes were small. The 6-year old trees gave the highest cooking yield and the 4- and 6-year-old trees consumed less alkali than 8 years old trees The 8 years old trees gave the lowerpulping yield and consumed more alkali. The 8-year old trees seem to be more difficult to cook. Hight density and tylose formationmay explain the more difficult cooking. At incoming kappa number of 15, brightness over 88% can be reached with the bleaching sequence of ODoEopD1. The pulps from 4- and 6-year-old woods were easier to bleach than 8-year pulp. After final bleaching, the 4- and 6-year pulp displayed higher brightness than the 8-year pulp. the 6-year-old trees gave the highest viscosity and pulp yield, the 8-year-old trees the lowest. Pulp from younger wood with finer fibers was beaten faster but the differences in teartensile relationships were small. The same concerns bulk and smoothess. Because of smaller fibers (higher amount of fiber per weitht unit), the pulp from 4-ear-old wood gave higher light-scattering coefficient so this advantage of the pulp from 4-year-old wood was not marked. The economic consequences of harvesting age were estimated roughly. In these specific plantations, the grwth of wood increased stell rapidly up to the studied age of 8 years, probaly a few more years. The growth was clearly higher than reported earlies, the mean annual increment (MAI) up to 22.3 m3/ha/a at the age of 8 years; compared to 4-year rotation, the rowth was double. Tho maximize wood production the rotation should be higher than 8 years in Thailand. The influences of age on pulp mill operations were evaluated based on model calculations utilizing yields and chemical charges found in this study as a basis. Because of the highest yield and the lowest cooking chemical requirements, the 6-year-old wood is clearly best in terms of recovery loading. This is generally true but should be reconfimed with more extensive trails. In optimizing the harvesting age the wood production, the pulp mill operations and the pulp quality shall be considered. Pulp quality aspects slightly favor short rotation of 4 years but the defferences anr not significant. Wood production strongly favors a rotation time above 7 years. Based on this study, aging E. camaldulensis was becoming too dense for pulping and the tylose formation proven made cooking more difficult. The optimum harvesting age was therefore the age with the acceptable basic density of about 600 kg/m3 and with no tylose, This study gave the best result with 6-year-old wood, which shall be ascertained with more extensive trails including harvesting ages up to 10-12 years. |
| Year | 2002 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Pulp and Paper Technology (PP) |
| Chairperson(s) | Malinen, Raimo;Retulainen, Elias; |
| Examination Committee(s) | Kolehmanine, Heikki;Ruhanen, Mauno;Preeda Parkpian; |
| Scholarship Donor(s) | Government of Finland; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2002 |