Análise da dissolução de um incrustante de uma indústria de celulose

Abstract

In the pulp and paper industry is common the presence of incrustation, due to the inefficient combustion of black liquor. The sticky is usually found on top of the kraft recovery boiler superheater. These deposits are responsible for the heat exchange efficiency reduction and unscheduled shutdowns to clean the boiler. The sticky is a compound rich in chloride and potassium, the main cause of the incrustation. The objective of this work was to propose a strategy for the dissolution of sticky, in order to facilitate the cleaning process of the boilers and, consequently, increase the efficiency of the equipment. Therefore, it was determined the concentration of chloride and potassium in the sticky, evaluating in its dissolution, the behavior in basic and acidic medium. For this, a multivariate analysis was carried out, providing a complete factorial design of order 2³, for three variables: temperature (20 – 40 °C), pH (2.0 – 12.0) and the volume of solution (10 – 50 mL). Thus, it was possible to determine the best fouling dissolution condition. It was verified that, for the first proposed planning, the temperature had no level of significance. Thus, a second factorial design was performed, disregarding the temperature and modifying the ranges of volume variations to 30 – 90 mL, since its ncrease leads to better dissolution conditions for both elements. It was then defined that for a pH value of 2.0 and a volume of 60 mL, the solution had a higher efficiency in the dissolution, that is, if a higher chloride and potassium content was obtained. After the choice of the best sticky dissolution solution, it was proposed to study the dissolution kinetics applied to two models, Page and Hixson-Crowell. The Page model was the one that resulted in a better fit presenting a coefficient of determination of 0.989 and 0.997 for the dissolution curves of potassium and chloride respectively, obtained through Matlab software.