クラフト蒸解に関する速度論的研究 有効アルカリの消費速度

Abstract

A rate of effective alkali consumption by wood components has been studied in the bulk delignification phase and the final phase of kraft cooking. Experimentally, kraft cooking was carried out on matchstick-like wood chips. Black liquor was titrated potentiometrically with HCl.It was found that the rate of effective alkali consumption was expressed as-d [OH-] e/dt=1/α·t-1where [OH-] e was effective alkali concentration at cooking time t, 1/α was a constant. The apparent activation energy of effective alkali consumption for kraft cooking carried out on wood with 14.0 and 15.8% effective alkali was 41.3 and 35.8 kcal·mol-1 respectively. However, effective alkali was consumed by degradative products from both lignin and carbohydrates in the bulk delignification phase and the final phase, the concentration of residual effective alkali was closely correlated to the extent of delignification. A known kinetic equation for delignification is not applicable to conditions of time-varying liquor concentration. Consequently, the above rate equation for effective alkali consumption is useful to describe the kraft pulping process quantita-tively together with a kinetic equation of delignification.