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 raport ed by Hagglund and Hedlund were used (see ref. 24). The model is prese nted 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/li gnin vs. lignin content. This log-log plot is linear for a lignin cont ent 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 logar ithmic dependence lignin/H-factor vs. The H-factor is for kraft and so da delignification linear, for an H-factor higher than 500 and 1000, r esp. The derived model is caracterized by high values of the correlati on coefficients (R2 = 0.999 - 1.000). The main characteristics of pulp ing can be efficiently calculated by the power form of the logarithmic straight line equation. As to the time temperature parameters, delign ification is characterized by two phases: initial and bulk. Maximum te mperatures of 150-degrees, 160-degrees and 170-degrees for kraft pulpi ng and 160-degrees and 170-degrees for soda delignification, and a sma ll difference in the input of EA (at equal input of AA) have no impact on the pulping of Scandinavian spruce wood.