The kinetics of lignin extraction in oxygen delignification.

Purpose and goal:

The purpose of this project is therefore to study the oxygen delignification with a focus on mass transport, with the objective to improve the process, and also increase understanding, so that problem solving in practical production is facilitated. The approach is relatively broad with both experimental and theoretical elements. A special reactor, CSTR, (continuous stirred tank reactor) will be used to study mass transport from masses, and parameters that will be varied are primarily time, temperature, pressure and pH.

Expected results and effects:

A problem with the sulphate process, however, is its lack of specificity; in addition to removing lignin, the process also damages the cellulose and hemicelluloses, which you want to keep in the fiber, and if you run the process far, in the end the damage to the fiber becomes unacceptable, and the cooking must be stopped. The solution has been to introduce the oxygen delignification which removes lignin with significantly higher specificity than that which applies at the end of the sulphate boiling, and in addition in an environmentally and economically favorable manner.

Approach and implementation:

However, oxygen delignification is not an uncomplicated process - oxygen has low solubility in water, and the treatment takes place in a three-phase mixture of oxygen, solid mass and alkaline water. Although technical solutions such as efficient gas blending, double oxygen steps, etc. are used, it is likely that oxygen delignification is not yet used to its full potential., fractionated masses and different types of raw materials.