The reduced natural durability and low energy density of eucalyptus wood hampers its use to generate energy. Torrefaction or pre-carbonization, treatment in low oxygenation with temperatures between 200 ℃ and 300℃, ...The reduced natural durability and low energy density of eucalyptus wood hampers its use to generate energy. Torrefaction or pre-carbonization, treatment in low oxygenation with temperatures between 200 ℃ and 300℃, accumulates carbon and lignin, decreases hygroscopicity, increases energy efficiency and reduces the wood attractiveness to xylophagous organisms, such as termites. Therefore, this work had as its main aim to study the influence of the roasting temperature on the endurance of the Eucalyptus urophylla wood in natura as well as roasted, both exposed to the attack of dry-wood termites. To the execution of this study, in natura wood chips and torrefied chips (torrefied for 20 min at the following temperatures: 180, 220 and 260 ℃) were submitted to the dry-wood termite resistance test. In this experiment, termites of the Cryptotermes brevis species were used. After 45 d of exposure, it was possible to observe that the torrefied treatment presented a greater resistance that consequently increased the endurance when exposed to the termite’s attack, observing that the control sample, loss five times more than mass than the chips torrefied at 260℃. Besides, in the treatment with in natura chips, was observed less mortality of the termites and greater visual damage, confirming the lower durability of such material compared to torrefied chips.展开更多
Acid hydrogen peroxide catalyzed with molybdenum (PMo stage) is effective to decrease pulp kappa number and potentially minimize chlorine dioxide demand in subsequent ECF bleaching. This study aimed at developing cost...Acid hydrogen peroxide catalyzed with molybdenum (PMo stage) is effective to decrease pulp kappa number and potentially minimize chlorine dioxide demand in subsequent ECF bleaching. This study aimed at developing cost-effective methods for applying PMo as the first stage bleaching for eucalyptus kraft pulp and evaluating their impact on pulp properties and effluent quality in relation to current ECF bleaching techniques. The PMo(EP)DP and A/PMo(EP)DP sequences proved to be most cost-effective for PMo stage application. The pulp properties and effluent quality derived from bleaching with these two sequences were compared with those of the conventional bleaching with the DHT(EP)DP sequence. The PMo(EP)DP sequence produced pulp of refinability and physical properties similar to that of the reference but the A/PMo(EP)DP one resulted in pulp of 20% lower refinability and 10% lower tearing strength. Untreated effluents of the PMo(EP)DP and A/PMo(EP)DP sequences presented similar COD, but lower AOX and color than the DHT(EP)DP effluents. None of the effluents exhibited acute toxicity. The effluents from the PMo(EP)DP sequence showed much lower BOD and BOD/COD ratio than that of the A/PMo(EP)DP one. All effluents were readily treated in bench-scale reactors, and achieved COD removal efficiencies of greater than 70%.展开更多
文摘The reduced natural durability and low energy density of eucalyptus wood hampers its use to generate energy. Torrefaction or pre-carbonization, treatment in low oxygenation with temperatures between 200 ℃ and 300℃, accumulates carbon and lignin, decreases hygroscopicity, increases energy efficiency and reduces the wood attractiveness to xylophagous organisms, such as termites. Therefore, this work had as its main aim to study the influence of the roasting temperature on the endurance of the Eucalyptus urophylla wood in natura as well as roasted, both exposed to the attack of dry-wood termites. To the execution of this study, in natura wood chips and torrefied chips (torrefied for 20 min at the following temperatures: 180, 220 and 260 ℃) were submitted to the dry-wood termite resistance test. In this experiment, termites of the Cryptotermes brevis species were used. After 45 d of exposure, it was possible to observe that the torrefied treatment presented a greater resistance that consequently increased the endurance when exposed to the termite’s attack, observing that the control sample, loss five times more than mass than the chips torrefied at 260℃. Besides, in the treatment with in natura chips, was observed less mortality of the termites and greater visual damage, confirming the lower durability of such material compared to torrefied chips.
文摘Acid hydrogen peroxide catalyzed with molybdenum (PMo stage) is effective to decrease pulp kappa number and potentially minimize chlorine dioxide demand in subsequent ECF bleaching. This study aimed at developing cost-effective methods for applying PMo as the first stage bleaching for eucalyptus kraft pulp and evaluating their impact on pulp properties and effluent quality in relation to current ECF bleaching techniques. The PMo(EP)DP and A/PMo(EP)DP sequences proved to be most cost-effective for PMo stage application. The pulp properties and effluent quality derived from bleaching with these two sequences were compared with those of the conventional bleaching with the DHT(EP)DP sequence. The PMo(EP)DP sequence produced pulp of refinability and physical properties similar to that of the reference but the A/PMo(EP)DP one resulted in pulp of 20% lower refinability and 10% lower tearing strength. Untreated effluents of the PMo(EP)DP and A/PMo(EP)DP sequences presented similar COD, but lower AOX and color than the DHT(EP)DP effluents. None of the effluents exhibited acute toxicity. The effluents from the PMo(EP)DP sequence showed much lower BOD and BOD/COD ratio than that of the A/PMo(EP)DP one. All effluents were readily treated in bench-scale reactors, and achieved COD removal efficiencies of greater than 70%.
