MATHEMATICAL-MODEL FOR KRAFT AND SODA PULPING OF SCANDINAVIAN SPRUCE

A mathematical model for kraft and soda pulping of Scandinavian spruce has been developed. In deriving this model exprimental results raported by Hagglund and Hedlund were used (see ref. 24). The model is presented by a linear logarithmic dependence of the main characteristics of pulping (yield and lignin content) on time and temperature parameters, both expressed by the H-factor. It is more convenient to express the logarithmic dependence yield vs. lignin content as the ratio yield/lignin vs. lignin content. This log-log plot is linear for a lignin content in pulp lower than 15%. The logarithmic dependence yield/H-factor vs. H-factor is linear over the whole range of the H-factor. The logarithmic dependence lignin/H-factor vs. The H-factor is for kraft and soda delignification linear, for an H-factor higher than 500 and 1000, resp. The derived model is caracterized by high values of the correlation coefficients (R2 = 0.999 - 1.000). The main characteristics of pulping can be efficiently calculated by the power form of the logarithmic straight line equation. As to the time temperature parameters, delignification is characterized by two phases: initial and bulk. Maximum temperatures of 150-degrees, 160-degrees and 170-degrees for kraft pulping and 160-degrees and 170-degrees for soda delignification, and a small difference in the input of EA (at equal input of AA) have no impact on the pulping of Scandinavian spruce wood.