Documents disponibles écrits par cet auteur

An empirical mathematical model for the predictive analysis of the chemical absorption of hydroxide in eucalyptus wood / M. M. Costa in Industrial & engineering chemistry research, Vol. 47 n°11 (Juin 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3856–3860 Titre : An empirical mathematical model for the predictive analysis of the chemical absorption of hydroxide in eucalyptus wood Type de document : texte imprimé Auteurs : M. M. Costa, Auteur ; J. L. Gomide, Auteur ; J. L. Colodette, Auteur Année de publication : 2008 Article en page(s) : p. 3856–3860 Note générale : Bibliogr. p. 3859-3860 Langues : Anglais (eng) Mots-clés : Basic  density;  Chip  impregnation;  Empirical  mathematical  modeling;  Eucalyptus;  Kraft  pulping;  Kraft  pulping  operational  conditions Résumé : Chip steaming, heating, impregnation, and sugar acid neutralization of wood chips by an alkaline kraft liquor during the pretreatment and initial phase of pulping are critical physical−chemical phenomena for executing successful industrial kraft pulping operations. Specifically, these physical and chemical phenomena significantly affect the kraft pulping process performance in terms of chemical mass transfer that influences both delignification rate and the homogeneity of the pulp produced. Detailed fundamental knowledge about the aforementioned phenomena during the initial phase is necessary to obtain selective wood delignification and as a consequence better pulp homogeneities and yield. The present work evaluates the effect of selected critical variables on impregnation and neutralization of Eucalyptus spp wood chips. The independent variables used for this study were as follows: wood basic density (BD), 430, 490, and 550 kg/m3; effective alkali charge (EA), 5%, 9%, and 13% at 25% sulfidity; time (t), 30, 60, and 90 min; and temperature (T), 90, 110, and 130 °C. The wood chips were impregnated with the kraft liquor of specific EA and sliced into five layers, each having a thickness of 1 mm. The sodium and hydroxide ion contents in the layers were measured first by emission photometry and then by volumetric titration. These combined methods demonstrated a hydroxide ion consumption of 67%−69% from wood neutralization reactions. A nonlinear model that has a high correlation coefficient (R2 = 96.2%) was developed that described the effects of the operational variables on the sodium hydroxide content (Y) in the chip core (Y = −1.83 + 1.04 × t0.11 × 0.96 × T0.42 × 0.59 × EA0.69 × 0.82 × BD−0.33 + ε, where ε is the random error). A correlation matrix demonstrated that the sodium hydroxide content in the chip core is strongly influenced by the initial EA value. On the other hand, the wood density had a smaller influence. Reaction temperature and time were determined to have an intermediate influence. Neutralization reactions conducted with 40 mesh sawdust (i.e., material that has low physical limitations to impregnation, under the test conditions (60 min at 100 °C and 2% consistency) at different initial alkali concentrations) showed a consumption of 3.8% ± 0.4% of sodium hydroxide by wood weight at the point the alkali concentration tended toward zero. Therefore, it is anticipated that the amount of sodium hydroxide in the wood chip core should be ~3.8% by wood weight to obtain neutralization. From an operational control point of view, this proposed empirical mathematical model may be used to predict different Eucalyptus wood chip impregnation conditions to achieve uniform and selective kraft pulping operations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071119k [article] An empirical mathematical model for the predictive analysis of the chemical absorption of hydroxide in eucalyptus wood [texte imprimé] / M. M. Costa, Auteur ; J. L. Gomide, Auteur ; J. L. Colodette, Auteur . - 2008 . - p. 3856–3860. Bibliogr. p. 3859-3860 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3856–3860 Mots-clés : Basic  density;  Chip  impregnation;  Empirical  mathematical  modeling;  Eucalyptus;  Kraft  pulping;  Kraft  pulping  operational  conditions Résumé : Chip steaming, heating, impregnation, and sugar acid neutralization of wood chips by an alkaline kraft liquor during the pretreatment and initial phase of pulping are critical physical−chemical phenomena for executing successful industrial kraft pulping operations. Specifically, these physical and chemical phenomena significantly affect the kraft pulping process performance in terms of chemical mass transfer that influences both delignification rate and the homogeneity of the pulp produced. Detailed fundamental knowledge about the aforementioned phenomena during the initial phase is necessary to obtain selective wood delignification and as a consequence better pulp homogeneities and yield. The present work evaluates the effect of selected critical variables on impregnation and neutralization of Eucalyptus spp wood chips. The independent variables used for this study were as follows: wood basic density (BD), 430, 490, and 550 kg/m3; effective alkali charge (EA), 5%, 9%, and 13% at 25% sulfidity; time (t), 30, 60, and 90 min; and temperature (T), 90, 110, and 130 °C. The wood chips were impregnated with the kraft liquor of specific EA and sliced into five layers, each having a thickness of 1 mm. The sodium and hydroxide ion contents in the layers were measured first by emission photometry and then by volumetric titration. These combined methods demonstrated a hydroxide ion consumption of 67%−69% from wood neutralization reactions. A nonlinear model that has a high correlation coefficient (R2 = 96.2%) was developed that described the effects of the operational variables on the sodium hydroxide content (Y) in the chip core (Y = −1.83 + 1.04 × t0.11 × 0.96 × T0.42 × 0.59 × EA0.69 × 0.82 × BD−0.33 + ε, where ε is the random error). A correlation matrix demonstrated that the sodium hydroxide content in the chip core is strongly influenced by the initial EA value. On the other hand, the wood density had a smaller influence. Reaction temperature and time were determined to have an intermediate influence. Neutralization reactions conducted with 40 mesh sawdust (i.e., material that has low physical limitations to impregnation, under the test conditions (60 min at 100 °C and 2% consistency) at different initial alkali concentrations) showed a consumption of 3.8% ± 0.4% of sodium hydroxide by wood weight at the point the alkali concentration tended toward zero. Therefore, it is anticipated that the amount of sodium hydroxide in the wood chip core should be ~3.8% by wood weight to obtain neutralization. From an operational control point of view, this proposed empirical mathematical model may be used to predict different Eucalyptus wood chip impregnation conditions to achieve uniform and selective kraft pulping operations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071119k