Cristiane Pedrazzi

Xylan deposition onto eucalypt pulp fibers during oxygen delignification

Abstract A novel alternative was investigated for elevating the xylan content of eucalyptus pulp through xylan deposition in the course of the oxygen delignification stage. The pH in the range of 10–13 was the only variable evaluated, while the other variables were kept constant in a range similar to industrial practice. Xylans were obtained from unbleached and bleached eucalyptus pulps by cold caustic extraction (CCE), giving rise to brown xylan liquor (BXL) and white xylan liquor (WXL), respectively. The liquors were added to a commercial brown pulp during oxygen delignification. The xylan-enriched pulps were subsequently bleached to 90% ISO with the D(EP)D sequence, beaten in a PFI mill and evaluated for their physical and mechanical properties. Xylan deposition occurred at variable degrees depending upon the pH. Pulp bleachability was not impaired by WXL xylan deposition but was slightly negatively affected by BXL xylan. Pulp beatability was improved by both WXL and BXL xylan deposition. The deposited xylan was more stable across bleaching and beating with the WXL xylan than the BXL xylan deposits. At low energy consumption, the deposited xylan improved pulp physical and mechanical properties. Xylan extraction by CCE with subsequent deposition in the oxygen delignification is an interesting technique to manufacture eucalypt pulps of high xylan content. The potential for industrial application is high as no significant modification of current pulp mill installations is needed.

Qualidade de chapas de partículas de madeira aglomerada fabricadas com resíduos de uma indústria de celulose.

The objective of this work was to investigate the quality of particleboards made with Eucalyptus saligna wood residues, resulting from the chiping of logs for pulp production. The boards were producted with two types of residues, sticks and sawdust, used pure. The adhesive used was urea-formaldehyde resin in proportions of 4, 8 and 12% (based on ovendry weight of wood particles) and the nominal densities were 0.55, 0.65 and 0.75 g/cm 3 . Bending properties, internal bond, screw withdrawal, water absorption and thickness swelling ware evaluated. The results indicated that the bending properties, internal bond and screw withdrawal were slightly higher with the sawdust type residue than boards made with sticktype residue. For water absorption, the values increased with the reduction of the density, for both type of particles. Thickness swelling increased with the reduction of resin proportion, independent of the type of residue used. Results showed that using both particles type with larger resin proportion and larger densities, boards with acceptable quality can be made.

Adição de aparas de papel reciclável na fabricação de chapas de madeira aglomerada.

In this work, there were analyzed the properties of particleboards produced with two types of recycled paper (newspaper and offset) and slash pine wood particles ( Pinus elliottii Engelm.). The paper was introduced into the mattress in two forms: strands and after hammer milling, in different proportions: 0, 20, 40, 60 and 100% of ovendry weight of the particles. The adhesive used was 10% tannin-formaldehyde (100:10 parts by weight). The experiment was set according to a factorial model, with three replications. The tests were conducted following ASTM D1037 (1995). Boards produced both with offset and newspaper strand inclusions showed tendency to blow at press opening. The inclusion of paper caused decrease in the properties, in such degree that boards did not meet commerce standards DIN 68761 (1)-1961, (3)-1971 and ANSI A 208.1 (1987). Water absorption after 24 hours, internal bond and screw whitdraw were the properties most affected. In general, the use of newspaper was more encouraging than offset paper.

AVALIAÇÃO DOS RESÍDUOS DE UMA SERRARIA PARA A PRODUÇÃO DE CELULOSE KRAFT

The forest-based industries have low yield and generate large amounts of waste, especially the primary processing industries, such as sawmills. In Brazil, initiatives are being created to combine the use of sawmill residues to pulp production. With this in mind, this study aimed to evaluate the performance of a medium-sized sawmill in the city of Rio Grande, in Rio Grande do Sul state, and to promote physical and chemical analysis of waste wood generated in the sawing process. It was used 20 logs of Pinus elliottii, divided into two diameter classes. The residues, except the sawdust, collected for analysis were disposed in the courtyard of the company in the form of chips. The following physical and chemical properties of the chips were examined: density, extractives content soluble in acetone, acetyl groups, soluble and insoluble lignin on acid (Klason lignin), uronic groups and carbohydrates. Comparing the results of the wood properties to the ones found in literature, it was evaluated the quantity and quality of waste that can be used as feedstock for the production of kraft pulp. As the main results there was a slight increase of sawing yields in the larger diameters logs compared to the smaller diameters. From the physical and chemical analyses, it was obtained the following results: density of 0.402 g / cm ³, cellulose content of 43.67% and 24.37% for hemicellulose, klason lignin of 26.75% and 3,80% for extractives content. As conclusion, the low sawing yield can be associated to the lack of a classification diametric and appropriate diagrams sections, resulting in a greater loss in the form of waste. Regarding the chemical and physical composition of the sawmill residues, the results were within the standards of quality wood used for kraft pulp of softwood material, presenting some advantages over younger woods commonly used in industry.

Avaliação das propriedades físico-mecânicas de polpas produzidas por novas sequências de branqueamento.

The efficiency of oxygen delignification is very low for pulps of low number kappa and with high concentrations of hexenuronic acids, therefore the oxygen does not react with these acids, so being minimum the elimination of these during the oxygen delignification (pre-O 2 ) in simple or double stage. In this study, the physical-mechanical properties of pulp of kappa number 17 and 14, produced with modified cooks and with the application of AD(EO)D techniques for pulp of kappa 17 and D HT (EPO)DP for pulp of kappa 14 for the bleaching up to 90% ISO, had been investigated. The main objective of this study was to evaluate the physical-mechanical properties in pulps submitted to the bleaching sequences without oxygen in the beginning of the sequence. As references, cooks had been carried until numbers kappa 17 and 14, oxygen delignification and conventional bleaching for sequences A/D(EO)D for pulp of kappa 17 and D HT (EPO)DP for pulp of kappa 14. The alternative bleaching, without pre-O 2 , resulted in bleached pulps with bigger integrity that of the reference, what it was confirmed by the values significantly higher of bulk, tear index, opacity and air resistance of the pulp weakly refined (for tissue papers). However, the high integrity of the fibers from pulps bleached with alternative processes lowered their conformabilities and collapsibility, with consequent reduction of tensile index of the pulp weakly refined. Therefore, with more intensive beating (for printing and writing papers), the tensile index was recovered. The high integrity of the bleaching pulps without pre-O 2 makes beating difficulty. To reach the draining degree of 35°SR with the pulps proceeding from alternative processes of bleaching, it was necessary to apply 30% more energy than the reference.

Technical and Economic Viability for the Briquettes Manufacture

This work aimed to evaluate the production briquettes cost, using two samples of forest residues from paper and pulp companies. The samples approached in this study were chips of Eucalyptus spp. and bark of Pinustaeda. The conditions to produce the briquettes were: pressure of 100 bar, temperature of 393 K (± 5 K), pressing time of 3 minutes and cooling time of 5 minutes. While the conditions previously used for this work were: 150 bar pressure, 393 K (± 5 K) temperature, 5 minute pressing time and 6 minute cooling time. The compaction levels remained the same and no cracking was observed. Quality parameters of the briquettes were also evaluated and were analyzed the costs of briquetting process in different stages. The most energy consuming stage was the briquetting process for both samples, this stage dominates the briquettes producing cost. The briquettes production cost was 415.70 and 508.96 R

COMPOSIÇÃO QUÍMICA DA MADEIRA DE Cordia trichotoma (Vell.) Arráb. ex Steud.

/ton, Eucalyptus spp. and Pinustaeda, respectively, while using the previously technique would cost 603.22 and 817.06 R

Anatomia do lenho de Maclura Tinctoria D. Don ex Steud.

/ton. The total briquetting costs obtained in this study are higher than the literature, because the manufacturing process was not performed in an industrial scale.

O PROCESSO AD(EO)D - UM NOVO CONCEITO

The pressure on rainforests due to fragmentation of natural landscapes has caused changes in the substitution pattern of the species present in the plant community. In the case of abandoned pastures, there is an increased environmental vulnerability to colonization by invasive exotic grasses, which represent a barrier to the establishment of native plants, since the dispersion and seed germination until the later stages of their development. We proposed to discuss some of the processes of natural regeneration in pastures, addressing issues that hinder the recruitment of desirable woody species and, in this context, the exposure of some methodologies based on the concept of nucleation that can help this process. Through understanding of the mechanisms involved in the maintenance of plant communities, we observed that the seed germination and seedling recruitments are crucial steps in the process of vegetation restoration. Because only a narrow range of conditions is suitable ( safe sites ) for the recruitment, successful regeneration depends on the environment ability to provide an appropriate bed for germination ( seedbed ). The use of methodologies that aimed the natural regeneration, to be effective in pasture areas, should be technically well established and adequate to the local reality, because although they have promising initial results, may no longer be effective over time.

Pulpability and Bleachability of Xylan-Depleted Eucalyptus Wood Chips

O lenho de Maclura tinctoria e anatomicamente descrito e ilustrado com fotomicrografias, com base em material procedente de Porto Maua, RS, Brasil. Na estrutura da madeira destacam-se: poros solitarios, em sua maioria; placas de perfuracao simples; elementos vasculares de comprimento medio; pontoacoes intervasculares alternas e ornamentadas; parenquima axial predominantemente vasicentrico; raios homogeneos; fibras libriformes; tubos laticiferos; e cristais prismaticos.