Efeito dos sólidos dissolvidos da madeira na branqueabilidade e nas propriedades físico-mecânicas e ópticas de polpa kraft branqueada de eucalipto

Muitos estudos demonstram que o rendimento da polpação kraft pode ser melhorado pela readsorção de xilanas à polpa durante o cozimento, e o licor negro kraft contém fração significativa das xilanas da madeira, sendo uma importante fonte dessas macromoléculas. Porém, o efeito dessa técnica nas propriedades físico-mecânicas e ópticas de polpa branqueada de eucalipto, ainda não está bem esclarecido. Neste estudo foram produzidas polpas de eucalipto provenientes de cozimento kraft convencional, com diferentes adições de licor negro (0, 25, 50, 75 e 100 % v/v). Os cozimentos foram conduzidos até número kappa 17-18 e as polpas resultantes foram deslignificadas com oxigênio em condições fixas. O branqueamento foi realizado utilizando uma sequência DHT(EP)DP até alvura final 92 % ISO. Em seguida as polpas foram refinadas num moinho PFI a diferentes níveis de revoluções (0, 500, 1.500, 3.000 e 6.000) e realizados testes de resistência ao rasgo, ao arrebentamento e à passagem de ar, alongamento, opacidade, densidade, volume específico aparente, capilaridade Klemm e índice de retenção de água (WRV). A eficiência e o ganho de alvura da pré-deslignificação com oxigênio foram ligeiramente prejudicados pela adição de licor negro ao cozimento kraft. A adição de 50 % de licor negro aos cozimentos resultou em polpas de pior branqueabilidade, sendo a demanda de cloro ativo aumentada em 5,3 kg/t celulose seca para obtenção de alvura 92 % ISO. As propriedades físico-mecânicas e ópticas das polpas kraft branqueadas não foram influenciadas, significativamente, pelo uso de licor negro no cozimento.Many studies have shown that the yield of kraft pulping can be improved by xylan reabsorption to the pulp during the cooking, and kraft black liquor contains significant fraction of xylan from wood, an important source of these macromolecules. However, the effect of this technique in the physical-mechanical and optical properties of bleached eucalyptus pulp is not very clear. This study produced pulp from eucalyptus kraft conventional cooking with different additions of black liquor (0, 25, 50, 75 and 100% v/v). The cooking was conducted to kappa number 17-18 and the resulting pulps were delignified with oxygen in fixed conditions. Bleaching was performed using a sequence DHT (EP) DP to end whiteness 92% ISO. Next pulps were refined in a PFI mill at different levels of revolutions (0, 500, 1,500, 3,000 and 6,000) and tests of tear resistance, bursting and the air flow, elongation, opacity, density, apparent specific volume, Klemm capillary and water retention value (WRV). The efficiency and brightness gain of the pre-delignification were slightly affected by the addition of black liquor in kraft pulping. The addition of 50% of black liquor to cooking resulted in a worse pulp ability for bleaching, and the chlorine demand increased by 5.3 kg/t pulp oven dry to obtain 92% ISO brightness. The physical-mechanical and optical properties bleached kraft pulps were not influenced significantly by the use of black liquor in cooking

Reaction Rates of Lignin and Hexenuronic Acids with Chlorine Dioxide, Ozone, and Sulfuric Acid

The reaction rates of lignin and hexenuronic acids (HexA) with chlorine dioxide, ozone, and sulfuric acid were investigated. In unbleached and oxygen-delignified eucalyptus kraft pulps containing both lignin and HexA, only HexA, or only lignin reacted with chlorine dioxide, ozone, and sulfuric acid under typical bleaching conditions. The maximum reaction rates of chlorine dioxide with lignin and HexA were 57.2 and 26 mmol/kg/min, respectively, for unbleached pulp, and 26.7 and 13 mmol/kg/min, respectively, for oxygen-delignified pulp. The maximum reaction rates of ozone with lignin and HexA were 58.6 and 132 mmol/kg/min, respectively, for unbleached pulp, and 56.8 and 134 mmol/kg/min, respectively, for oxygen-delignified pulp. The maximum reaction rates of sulfuric acid with lignin, and HexA were 1.11 and 0.93 mmol/kg/min, respectively, for unbleached pulp, and 1.95 and 0.80 mmol/kg/min, respectively, for oxygen-delignified pulp. Chlorine dioxide reacts faster with HexA in the presence of the residual lignin. The kinetic results suggest that pulp treatment with ozone, when justifiable, should follow but not precede chlorine dioxide oxidation. Unbleached pulp residual lignin and HexA react twice as fast with chlorine dioxide than the lignin and HexA present in oxygen-delignified pulp, while the pulp type has no significant effect on lignin and HexA reactivity toward ozone. HexA reactions with sulfuric acid and ozone can be described by two-phase pseudo first-order reaction rates

EFEITO DOS S 3LIDOS DISSOLVIDOS DA MADEIRA NA BRANQUEABILIDADE E NAS PROPRIEDADES F\ucdSICO-MEC\uc2NICAS E 3PTICAS DE POLPA kraft BRANQUEADA DE EUCALIPTO

Muitos estudos demonstram que o rendimento da polpa\ue7\ue3o kraft pode ser melhorado pela readsor\ue7\ue3o de xilanas \ue0 polpa durante o cozimento, e o licor negro kraft cont\ue9m fra\ue7\ue3o significativa das xilanas da madeira, sendo uma importante fonte dessas macromol\ue9culas. Por\ue9m, o efeito dessa t\ue9cnica nas propriedades f\uedsicomec\ue2nicas e \uf3pticas de polpa branqueada de eucalipto, ainda n\ue3o est\ue1 bem esclarecido. Neste estudo foram produzidas polpas de eucalipto provenientes de cozimento kraft convencional, com diferentes adi\ue7\uf5es de licor negro (0, 25, 50, 75 e 100 % v/v). Os cozimentos foram conduzidos at\ue9 n\ufamero kappa 17-18 e as polpas resultantes foram deslignificadas com oxig\ueanio em condi\ue7\uf5es fixas. O branqueamento foi realizado utilizando uma sequ\ueancia DHT(EP)DP at\ue9 alvura final 92 % ISO. Em seguida as polpas foram refinadas num moinho PFI a diferentes n\uedveis de revolu\ue7\uf5es (0, 500, 1.500, 3.000 e 6.000) e realizados testes de resist\ueancia ao rasgo, ao arrebentamento e \ue0 passagem de ar, alongamento, opacidade, densidade, volume espec\uedfico aparente, capilaridade Klemm e \uedndice de reten\ue7\ue3o de \ue1gua (WRV). A efici\ueancia e o ganho de alvura da pr\ue9-deslignifica\ue7\ue3o com oxig\ueanio foram ligeiramente prejudicados pela adi\ue7\ue3o de licor negro ao cozimento kraft. A adi\ue7\ue3o de 50 % de licor negro aos cozimentos resultou em polpas de pior branqueabilidade, sendo a demanda de cloro ativo aumentada em 5,3 kg/t celulose seca para obten\ue7\ue3o de alvura 92 % ISO. As propriedades f\uedsico-mec\ue2nicas e \uf3pticas das polpas kraft branqueadas n\ue3o foram influenciadas, significativamente, pelo uso de licor negro no cozimento.Many studies have shown that the yield of kraft pulping can be improved by xylan reabsorption to the pulp during the cooking, and kraft black liquor contains significant fraction of xylan from wood, an important source of these macromolecules. However, the effect of this technique in the physical-mechanical and optical properties of bleached eucalyptus pulp is not very clear. This study produced pulp from eucalyptus kraft conventional cooking with different additions of black liquor (0, 25, 50, 75 and 100% v/v). The cooking was conducted to kappa number 17-18 and the resulting pulps were delignified with oxygen in fixed conditions. Bleaching was performed using a sequence DHT (EP) DP to end whiteness 92% ISO. Next pulps were refined in a PFI mill at different levels of revolutions (0, 500, 1,500, 3,000 and 6,000) and tests of tear resistance, bursting and the air flow, elongation, opacity, density, apparent specific volume, Klemm capillary and water retention value (WRV). The efficiency and brightness gain of the pre-delignification were slightly affected by the addition of black liquor in kraft pulping. The addition of 50% of black liquor to cooking resulted in a worse pulp ability for bleaching, and the chlorine demand increased by 5.3 kg/t pulp oven dry to obtain 92% ISO brightness. The physical-mechanical and optical properties bleached kraft pulps were not influenced significantly by the use of black liquor in cooking

Reaction Rates of Lignin and Hexenuronic Acids with Chlorine Dioxide, Ozone, and Sulfuric Acid

The reaction rates of lignin and hexenuronic acids (HexA) with chlorine dioxide, ozone, and sulfuric acid were investigated. In unbleached and oxygen-delignified eucalyptus kraft pulps containing both lignin and HexA, only HexA, or only lignin reacted with chlorine dioxide, ozone, and sulfuric acid under typical bleaching conditions. The maximum reaction rates of chlorine dioxide with lignin and HexA were 57.2 and 26 mmol/kg/min, respectively, for unbleached pulp, and 26.7 and 13 mmol/kg/min, respectively, for oxygen-delignified pulp. The maximum reaction rates of ozone with lignin and HexA were 58.6 and 132 mmol/kg/min, respectively, for unbleached pulp, and 56.8 and 134 mmol/kg/min, respectively, for oxygen-delignified pulp. The maximum reaction rates of sulfuric acid with lignin, and HexA were 1.11 and 0.93 mmol/kg/min, respectively, for unbleached pulp, and 1.95 and 0.80 mmol/kg/min, respectively, for oxygen-delignified pulp. Chlorine dioxide reacts faster with HexA in the presence of the residual lignin. The kinetic results suggest that pulp treatment with ozone, when justifiable, should follow but not precede chlorine dioxide oxidation. Unbleached pulp residual lignin and HexA react twice as fast with chlorine dioxide than the lignin and HexA present in oxygen-delignified pulp, while the pulp type has no significant effect on lignin and HexA reactivity toward ozone. HexA reactions with sulfuric acid and ozone can be described by two-phase pseudo first-order reaction rates

The role of bound chlorine in the brightness reversion of bleached hardwood kraft pulp

Our previous paper showed fragmentary evidence that pulp brightness reversion may be negatively affected by its organically bound chlorine (OX) content. A thorough investigation on eucalyptus kraft pulp led to the conclusion that OX increases reversion of certain pulps but this trend is not universal. Alkaline bleaching stages decrease reversion regardless of pulp OX content. Pulps bleached with high temperature chlorine dioxide revert less than those bleached with conventional chlorine dioxide in sequences ending with a chlorine dioxide stage but similarly in sequences ending with a final peroxide stage. The use of secondary condensate for pulp washing decreases reversion

COMPARISON BETWEEN ANALYTICAL PYROLYSIS AND NITROBENZENE OXIDATION FOR DETERMINATION OF SYRINGYL/GUAIACYL RATIO IN Eucalyptus spp. LIGNIN

Pyrolysis-gas chromatography/mass spectrometry (Py-GC-MS) was applied to measure the lignin syringyl/guaiacyl (S/G) ratio in E. dunni, E. grandis, E. nitens, E. urograndis, and E. urophylla woods. A total of 41 compounds were identified, of which 11 were derived from carbo-hydrates and 30 from lignins. The S/G ratio was calculated on the basis of the areas of peaks recorded in the pyrograms and compared with the results obtained by alkaline nitrobenzene oxidation. The values of S/G found by pyrolysis were similar for all the species using the compounds guaiacol, 4-methylguaiacol, 4-vinylguaiacol, vanillin, 4-ethylsyringol, 4-vinylsyringol, homosyringaldehyde, acetosyringone, and syringylacetone, as lignin markers. The selected markers were efficient for the deter-mination of S/G ratio in eucalyptus wood by Py-GC-MS. The Py-GC-MS technique produced results that are comparable to the nitrobenzene oxidation method, with the advantage of requiring small wood samples and a short analysis time

STUDY OF THE BLEACHABILITY OF EUCALIPTUS KRAFT PULP

O objetivo do estudo foi avaliar de que modo a branqueabilidade da polpa se correlaciona com as caracter\uedsticas qu\uedmicas da madeira, as condi\ue7\uf5es de polpa\ue7\ue3o, o grau de deslignifica\ue7\ue3o da polpa marrom (n\ufamero kappa) e as sequ\ueancias de branqueamento, baseando-se na alvura da polpa branqueada, viscosidade, consumo de qu\uedmicos de branqueamento e branqueabilidade da polpa. As madeiras de eucalipto (A, B e C), devidamente caracterizadas quanto aos constituintes qu\uedmicos (holocelulose, teor de ligninas insol\ufavel e sol\ufavel, teor de extrativos totais, cinzas e cinzas insol\ufaveis em \ue1cido clor\ueddrico) foram utilizadas para a produ\ue7\ue3o de polpa celul\uf3sica atrav\ue9s de duas condi\ue7\uf5es de polpa\ue7\ue3o kraft modificada: Condi\ue7\ue3o I (PI) - \ue1lcali efetivo de 16,5%, sulfidez de 30% e temperatura de cozimento de 155\ub0C; e Condi\ue7\ue3o II (PII) - \ue1lcali efetivo de 17,5%, sulfidez de 32% e temperatura de cozimento de 147\ub0C. Ambos os cozimentos foram realizados buscando-se n\ufamero kappa de 15,5 \ub1 0,5 e de 18,0 \ub1 0,5. Os par\ue2metros de polpa\ue7\ue3o e as propriedades das polpas marrons avaliados foram: rendimento depurado, viscosidade, alvura, teor de \ue1cidos hexenur\uf4nicos e o \uedndice k/kappa corrigido (raz\ue3o entre o \uedndice de absor\ue7\ue3o de luz, um dos termos da f\uf3rmula da alvura, e o valor do n\ufamero kappa corrigido, descontando a contribui\ue7\ue3o dos \ue1cidos hexenur\uf4nicos). Cada uma das polpas foi branqueada, at\ue9 90% ISO de alvura, seguindo tr\ueas sequ\ueancias de branqueamento pr\ue9-definidas: Sequ\ueancia 1 - OA(ZE)DP; Sequ\ueancia 2 - OA/D(EOP)DP; e Sequ\ueancia 3 \u2013 OD(EOP)DP. As polpas branqueadas foram avaliadas quanto \ue0 alvura, viscosidade, consumo de qu\uedmicos de branqueamento e branqueabilidade. A branqueabilidade das polpas foi afetada pela madeira. Al\ue9m disso, as branqueabilidades sofreram influ\ueancia da condi\ue7\ue3o de polpa\ue7\ue3o e do n\ufamero kappa da polpa marrom. As Sequ\ueancias de branqueamento 1 e 2 mostraram-se satisfat\uf3rias para a produ\ue7\ue3o de polpa na alvura de interesse (90 \ub1 1% ISO), diferentemente do verificado para as polpas produzidas pela Sequ\ueancia 3. As melhores branqueabilidades foram obtidas para as polpas com n\ufamero kappa da polpa marrom de 18,0 \ub1 0,5. Verificou-se estreita correla\ue7\ue3o entre branqueabilidade e \uedndice k/kappa corrigido o que indicou a possibilidade de se utilizar esta propriedade da polpa marrom para a predi\ue7\ue3o de branqueabilidades de polpas.The aim of this study was to evaluate how the pulp bleachability ability is correlated with the wood chemical characteristics, the cooking conditions, the kappa number of the brown pulp and the bleaching sequences, based on the pulp bleached brightness, viscosity, bleaching chemical consumption and bleachability. The eucalyptus wood (A, B, and C), appropriately characterized as the chemical constituents (holocellulose content, insoluble and soluble lignin content, total extractive content, ash and insoluble ash in hydrochloric acid) were used for pulp production by modified kraft cooking, using two different pulping conditions: Condition I (PI) - 16.5% effective alkali, 30% sulfide, and 155\ub0C cooking temperature; and Condition II (PII) - 17.5% effective alkali, 32% sulfide, and 147\ub0C cooking temperature. Both conditions were performed to kappa number 15.5 \ub1 0.5 and 18.0 \ub1 0.5. The pulping parameters and pulp properties evaluated were: screened yield, viscosity, brightness, hexenuronic acid content, and index k/corrected kappa (ratio between the light absorption rate, a brightness formula term, and the corrected kappa number, disregarding the hexenuronic acid contribution). Each one of the pulps was bleached, to achieve 90 \ub1 1% ISO brightness, following three pre-defined bleaching sequences: 1 Sequence - OA(ZE)DP; 2 Sequence - OA/D(EOP)DP; and 3 Sequence - OD(EOP)DP. The pulps were investigated for brightness, viscosity, bleaching chemical consumption and bleachability. The bleachability was affected by the wood. Furthermore, the bleaching abilities were affected by the cooking condition and the brown pulp kappa number. The 1 and 2 sequences were satisfactory to achieve the required brightness (90 \ub1 1% ISO) unlike to the verified to the 3 sequence. The best bleachabilities were obtained from the brown pulps with higher kappa number 18.0 \ub1 0.5. It was verified close correlation between bleaching ability and index k/corrected kappa, which indicated the possibility of using this property of unbleached pulp for predicting pulp bleachability

WOOD QUALITY EFFECT ON KRAFT PULPING PERFORMANCE

O objetivo do estudo foi avaliar o efeito da qualidade de madeiras de eucalipto no desempenho da polpa\ue7\ue3o kraft sob duas diferentes condi\ue7\uf5es de polpa\ue7\ue3o e em dois n\uedveis de deslignifica\ue7\ue3o, baseando-se no rendimento, alvura, viscosidade e \uedndice k/kappa corrigido das polpas produzidas. As madeiras de eucalipto (A, B e C), foram analisadas quanto \ue0s suas propriedades f\uedsico-qu\uedmicas (densidades b\ue1sica e aparente, teor de ligninas insol\ufavel e sol\ufavel, teor de extrativos, cinzas e cinzas insol\ufaveis em \ue1cido clor\ueddrico) e utilizadas para a produ\ue7\ue3o de polpa celul\uf3sica por meio do cozimento kraft modificado, utilizando duas condi\ue7\uf5es de polpa\ue7\ue3o, sendo elas: Condi\ue7\ue3o I (PI) - \ue1lcali efetivo de 16,5%, sulfidez de 30% e temperatura de cozimento de 155\ub0C; e Condi\ue7\ue3o II (PII) - \ue1lcali efetivo de 17,5%, sulfidez de 32% e temperatura de cozimento de 147\ub0C. Ambos os cozimentos foram realizados buscando-se no n\ufamero kappa de 15,5 \ub1 0,5 e de 18,0 \ub1 0,5. Foram avaliados os seguintes par\ue2metros de polpa\ue7\ue3o e propriedades das polpas produzidas: fator H, rendimento depurado, viscosidade, alvura, conte\ufado de \ue1cidos hexenur\uf4nicos e o \uedndice k/kappa corrigido. A madeira A, que apresentou menores teores de extrativos e lignina em sua constitui\ue7\ue3o, bem como menores densidades b\ue1sica e aparente quando comparada com as madeiras B e C, apresentou os melhores resultados para os par\ue2metros de cozimento avaliados, com destaque para a polpa produzida pela condi\ue7\ue3o de cozimento PII com o n\ufamero kappa de (18,0 \ub1 0,5), que apresentou maior rendimento, alvura e viscosidade dentre todas as polpas produzidas. Polpas produzidas com maior n\ufamero kappa apresentam menores \uedndices k/kappa corrigidos.The aim of this study was to evaluate the wood quality in the kraft pulping performance under two different pulping conditions at two delignification degrees based on results for the yield, brightness, viscosity, and k/ kappa corrected index. Eucalyptus wood (A, B, and C) was analyzed about their physicochemical properties (basic and apparent density, insoluble and soluble lignin content, extractive content, ash and insoluble ash in hydrochloric acid) and used for pulp production by modified kraft cooking, using two different pulping conditions: Condition I (PI) - 16.5% effective alkali, 30% sulfidity, and 155\ub0 of cooking temperature; and Condition II (PII) - 17.5% effective alkali, 32% sulfidity,and 147\ub0C cooking temperature. Both conditions were performed to kappa number 15.5 \ub1 0.5 and 18.0 \ub1 0.5. The following pulping parameters and pulp properties produced were evaluated: H factor, screened yield, viscosity, brightness, hexenuronic acid content, and the k/kappa corrected index. The A wood, which had lower extractives and lignin content in its constitution, as well as lower basic and apparent density when compared with B and C woods, showed good results for cooking parameters, especially the pulp produced at PII condition at kappa number 18.0 \ub1 0.5.Also, the A wood showed higher screened yield, brightness, and viscosity comparing to the other pulps produced. Those pulps produced with higher kappa number have lower k/kappa corrected index

Determinação da relação siringila/guaiacila da lignina em madeiras de eucalipto por pirólise acoplada à cromatografia gasosa e espectrometria de massas ( PI - CG/ EM)

The use of analytical pyrolysis combined with gas chromatography/mass spectrometry (Py-GC/MS) to determine the syringyl/guaiacyl ratio (S/G) in lignins from Eucalyptus spp woods was investigated. Sample of E. grandis and "E. urograndis" wood, with and without extractives, were subjected to pyrolysis from 300 ºC to 600 ºC. The products that results from pyrolysis were identified by mass spectrometry and the S/G ratio was determined based on the areas of the peaks corresponding to the guaiacyl and syringyl derivatives. The best S/G estimation is achieved when pyrolysis is carried out at 550 ºC. Extractives and carbohydrate present in the woods do not interfere with the results