Modelagem e simulação da etapa de caustificação do processo kraft de extração de celulose.

Abstract

The proposed work aims the modeling, simulation and optimization of caustizing process in a pulp extraction and paper production industry in Latin America, using Aspen Plus commercial software. The caustizing system plays a major role in the chemical recovery kraft process in the pulp extraction industries. In it occurs the recovery of white liquor used in the cooking of chips in the digester. To this end, a first reaction between green liquor (solution rich in sodium sulfide and sodium carbonate) and lime (calcium oxide) forms calcium hydroxide (Ca(OH)2), which in turn reacts withsodium carbonate (NaCO3), yielding sodium hydroxide (NaOH) and calcium carbonate (CaCO3) with an efficiency greater than 70%. As a consequence, it is possible to recover a white liquor (NaOH + Na2S) that presents the ideal characteristics for operation in the digesters. To achieve this goal, an optimization routine was implemented that uses the BOBYQA method to determine the best value of the ratio between green liquor and calcium oxide, the main process efficiency measurement parameter. Adjusting this variable resulted in a 1.6% increase in the caustification efficiency.