The pulp and paper industry is increasingly seeking a sustainable and conscientious development, minimizing the environmental impacts caused by it. Therefore, reducing efficiently the number of stages used in the bleaching process can mean less consumption of water and chemical reagents, contributing to the reduction of harmful waste to the environment. Thus, this study sought to evaluate the pulp quality and some physical-mechanical properties (smoothness, tear and tensile indexes) of two new bleaching sequences A*DP and A*E*DP and compare them with the reference D0(E+P)D1P. To do so, industrial eucalyptus Kraft pulp pre-delignified with oxygen was used. The bleached pulp was refined to 1200, 1800 and 2400, in PFI mill and tested according to TAPPI standards to determine smoothness, tear and tensile indexes. Based on the results obtained, it was verified that the sequences studied are viable for using in bleaching plants, which allowed a reduction in the chlorine dioxide consumption and presented satisfactory smoothness, tear and tensile indexes for paper.
One way to obtain high quality pulp production is to improve selectivity delignification of step, maximize yield. Brown pulp yield and chemical composition were studied, with variation of temperature and effective alkali in Kraft cooking. Considering that these variables directly affect lignin removal rate and final product quality. Industrial wood chips from Eucalyptus grandis x Eucalyptus urophylla hybrids were used in this study. The cooking was performed to obtain pulps with kappa number 13, 15 and 17 for temperatures 155 °C, 160 °C and 165 °C, using the same Factor H (695). Yields were analyzed according to: total yield, rejects content and screened pulp yield. Klason lignin content, wood and pulp sugars, levels of hexenuronic acids in pulp were also determined. Results indicate that lower cooking temperatures are beneficial in relation to cooking performance, selectivity and preservation of xylans. With a screened pulp yield of 57.1 % for KN 17 at the lowest temperature 155 ºC and 55.3 % at the same KN at 165 ºC. The lowest screened pulp yield obtained, 51 %, was for KN 13 at 165 ºC, with 54.1 % with the same KN at 155 ºC. Evidencing a decreasing linear trend of screened pulp yield with temperature increase and kappa number reduction.
O estágio de hidrólise ácida (AHT), usado em sequências de branqueamento de polpa, tem como objetivo principal a degradação dos ácidos hexenurônicos, que estando presentes na polpa podem afetar sua alvura, reversão de alvura, entre outros. Apesar do benefício da utilização do estágio de hidrólise ácida, o pH desta etapa não é o mais adequado para a degradação da lignina, pois esta é mais reativa em meio alcalino. Portanto, o presente trabalho buscou estudar uma melhoria no processo de branqueamento pela adição de um estágio de extração alcalina após o estágio AHT, obtendo o melhor aproveitamento possível do estágio de dióxido cloro. Para este estudo foi utilizada polpa Kraft de eucalipto pré-deslignificada com oxigênio. Diferentes sequências de branqueamento ECF (Elemental Chlorine Free) foram realizadas na polpa, sendo elas: D0(E+P)D1, AHTD0(E+P)D1, AHT/ED0(E+P)D1 e AHTED0(E+P)D1. Os resultados encontrados com a inclusão do estágio de extração alcalina simples após a hidrólise ácida apontam um efeito positivo na sequência de branqueamento, havendo uma significativa redução do consumo de dióxido de cloro. A inclusão da extração alcalina simples também possibilitou a redução do número Kappa e aumento na alvura, com uma redução de 0,3 pontos na média do número Kappa e aumento de 1,3% ISO na alvura, analisados após a extração alcalina com peróxido de hidrogênio da sequência OAHT/ED0(E+P)D1, se comparada à sequência sem extração alcalina simples.
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