Modelagem e analise de digestores Kraft descontinuo




Global1y, the Kraft pulping process is beginning to get use of the benefits of the recent developments in the modeling area and process control. Advanced techniques of simulation and control offer tools that allow the analysis and efficient design of multivariable non-linear process, involving the optimization and the advanced control of the process. The pulp industry uses some equipment named digesters, which are pressure vessels where the chip of wood are treated with cooking liquor (sodium hydroxide and sodium sulfide) with defined composition, established pressure and temperature, aiming to the cellulosic pulp production. In this context, the digesters can be c1assified as continuous (Kamyr) and discontinuous digester (Batch). The aim of this work is to study the production process of the cellulosic pulp from the analysis of the Physical-Chemical Phenomena that occur in a discontinuous kraft digester. The predictions from the considered model (Mirams e Nguyen, 1994) allow the evaluation of the dynamic behavior and the analysis of the parametric sensitivity of the process, observing which is the operational parameter and variable of process that influence the most reactor behavior. The model for a descontinuous digester considers the diffusion into the wood pores initiated during the impregnation of the chips. Another characteristic of the model is its adaptation in order to consider the delignification reactions as simultaneously reactions with three different types of lignin, with the most reactive lignin reacting more quickly. This approach present a new point of view for the theory of three phases of the reaction, interpreting its results as if the reaction qf each lignin was responsible for a specific phase of the reaction (initial delignification, bulk and residual). Regarding the solution of the model it was based on "Line Method", which consist on usaged of Orthogonal Collocation for discretization of the partial differential equations. The temporal integration of the ordinary differential equations was solved by integrator LSODE (Vasco de Toledo, 1999). The obtained results from the model reproduced the main dynamic characteristics of the system, making possible the knowledge of the main stages in the production of the cellulose under determined operational conditions of the digester. These results can them be used in control, optimization and design studies in a safe and efficient way


hemicellulose lignina polpação alcalina por sulfato sulpate pulping process hemicelulose autoclaves lignin cellulose autoclaves celulose

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