Análise da cinética da secagem da celulose branqueada extraída quimicamente da madeira do eucalipto
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Tipo de produção
Dissertação
Data
2017
Autores
Schmidt, Alex Karl Oscar
Orientador
Condotta, R.
Periódico
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Citação
SCHMIDT, Alex Karl Oscar. Análise da cinética da secagem da celulose branqueada extraída quimicamente da madeira do eucalipto. 2017. 88 f. Dissertação (Mestrado em Engenharia Química) - Centro Universitário FEI, São Bernardo do Campo, 2017. Disponível em: . Acesso em: 17 set. 2018.
Texto completo (DOI)
Palavras-chave
Secagem,Celulose,Polímeros
Resumo
A celulose extraída da madeira é utilizada como a matéria-prima para a produção de diversos produtos. Geralmente, são dois os tipos de árvores utilizados para a extração, as de fibra longa e curta, que propiciam características físicas diferentes ao produto final. O Brasil é o maior produtor de celulose de fibra curta do mundo, sendo assim um setor fundamental para a economia do país. Parte fundamental do processo e da viabilidade econômica da produção de papel e celulose é a operação da secagem onde, depois de extraída, depurada e branqueada, a celulose é concentrada, através da remoção do solvente, até que se atinja uma consistência de aproximadamente 90%. Sendo assim, o objetivo deste trabalho consistiu na investigação da cinética do fenômeno de secagem quando aplicado à celulose de fibra curta extraída da madeira do eucalipto. Para tanto, foram conduzidos ensaios de secagem em estufa à diferentes temperaturas, com o objetivo de verificar a influência destas no tempo e na taxa de secagem, e outros em túnel de vento com o agente secante em condições variadas – velocidade e temperatura, coerente com o realizado no experimento da estufa, com o objetivo de escrutinar a sensibilidade do processo à convecção forçada. Avaliou-se também a influência da espessura da amostra e sua umidade inicial no tempo e taxa do processo. Posteriormente, os dados colhidos foram ajustados aos modelos semi-teóricos e empíricos para a secagem das amostras de celulose, obtendo-se as constantes de cada equação para cada situação. Uma das constantes obtidas, a partir dos modelos semi-teóricos, é a constante de secagem k (s-1), a qual contempla fatores externos ao sólido que influenciam na transferência da úmida do meio sólido para o meio secante. Os coeficientes de difusividade efetiva de umidade foram obtidos a partir da equação teórica, derivada a partir da segunda lei de Fick. Observou-se a variação do coeficiente difusivo em função do tempo de processo de secagem, sendo o seu comportamento também avaliado em função da temperatura e velocidade relativa do ar secante.
Pulp extracted from wood is used as the raw material for the production of various products. Generally, there are two types of trees used for the extraction, those of long and short fiber, that provide different physical characteristics to the final product. Brazil is the largest producer of short fiber pulp in the world, thus being a key sector for the country's economy. A fundamental part of the process and economic viability of pulp and paper production is the drying operation where, after extraction, purification and bleaching, the cellulose is concentrated by removing the solvent until a consistency of approximately 90% . The objective of this work was to investigate the kinetics of the drying phenomenon when applied to short fiber pulp extracted from eucalyptus wood. In order to verify the influence of these in the time and in the drying rate, and others in wind tunnel with drying agent under different conditions - speed and temperature, coherent with which was performed in the greenhouse experiment, with the aim of scrutinizing the process sensitivity to forced convection. The influence of sample thickness and its initial moisture on time and process rate were also evaluated. Subsequently, the data collected were adjusted to the semi-theoretical and empirical models for the drying of the cellulose samples, obtaining the constants of each equation for each situation. One of the constants obtained from the semi-theoretical models is the drying constant k (s-1), which considers all the external factors that influence the transfer of the wet from the solid medium to the drying medium. The coefficients of effective moisture diffusivity were obtained from the theoretical equation, derived from the second Fick law. It was observed the variation of the diffusive coefficient as a function of the drying process time, and its behavior was also evaluated as a function of the temperature and relative velocity of the drying air.
Pulp extracted from wood is used as the raw material for the production of various products. Generally, there are two types of trees used for the extraction, those of long and short fiber, that provide different physical characteristics to the final product. Brazil is the largest producer of short fiber pulp in the world, thus being a key sector for the country's economy. A fundamental part of the process and economic viability of pulp and paper production is the drying operation where, after extraction, purification and bleaching, the cellulose is concentrated by removing the solvent until a consistency of approximately 90% . The objective of this work was to investigate the kinetics of the drying phenomenon when applied to short fiber pulp extracted from eucalyptus wood. In order to verify the influence of these in the time and in the drying rate, and others in wind tunnel with drying agent under different conditions - speed and temperature, coherent with which was performed in the greenhouse experiment, with the aim of scrutinizing the process sensitivity to forced convection. The influence of sample thickness and its initial moisture on time and process rate were also evaluated. Subsequently, the data collected were adjusted to the semi-theoretical and empirical models for the drying of the cellulose samples, obtaining the constants of each equation for each situation. One of the constants obtained from the semi-theoretical models is the drying constant k (s-1), which considers all the external factors that influence the transfer of the wet from the solid medium to the drying medium. The coefficients of effective moisture diffusivity were obtained from the theoretical equation, derived from the second Fick law. It was observed the variation of the diffusive coefficient as a function of the drying process time, and its behavior was also evaluated as a function of the temperature and relative velocity of the drying air.