Process variables effect on the reject fraction in an industrial Kraft pulping operation.

INALBON, M.C.; MUSSATI, M.C.; MONTAGNA, P.; ZANUTTINI, M.A; FRANCISCO FUENTES, J.L.

Sao Paulo

Congreso; 45th ABTCP International Pulp and Paper Congress and VII IberoAmerican Congress on Pulp and Paper Research CIADICYP; 2012

ABTCP Associacao Brasileira Tecnica de Celulose e Papel / RIADICYP-Red Ibero-Americana de Docencia e Investigación en Celulosa y Papel

Wood chip impregnation has a strong effect on the efficiency of an industrial process and also influences the pulp properties. In this work, a mathematical model of the phenomenon was used to predict the impregnation level achieved in the impregnator and the relation between this and the reject fraction obtained at the end of the pulping process. Industrial data corresponding to seventy working days (representative of one year data) of a continuous process were used. To analyze the chip thickness distribution influence, five characteristic thicknesses, of a normal distribution, were used with their respective weights. Wood chips flow, steaming time, impregnation time, and effective alkali incoming for impregnation were used as data to obtain an impregnation level (distance from the interphase reached by alkali) by the use of this model. This level is difficult to know in the process because the sampling is no possible in the impregnation stage. Different chips thickness impregnation was considered simultaneously as well as the reagents consumption in a co-current impregnation. A correlation between the impregnation level and the production, EA concentration and other variables were found with R2 of 82.5%. Then, the reject dependence on the pulping variables: impregnation level (parameter obtained using the model), production, chips initial moisture, over thickness proportion, and total EA on pulp, was analyzed. A correlation between these variables was obtained with R2 of 80%. This allows knowing the effect of the most important process variables on the level of impregnation and the effect of this on the reject fraction in the pulp production.