Laboratory Bleaching System for Oxygen and Ozone Bleaching

Abstract

A multi-functional bleaching equipment for laboratory use was developed. The setup allowed the bleaching of four pulp samples at the same time. The bleaching setup works for traditional oxygen and ozone bleaching, using caustic soda and calcium hydroxides as bleaching additive. This newly developed setup allows creating the tests as flexible as possible, for multiple wood fiber-based pulps. The installation work to change from chemical to gas bleaching can be done in a couple of minutes. The new trial setup showed improvements for the second and third bleaching stage using oxygen and ozone gas. For Kraft pulp using caustic soda as bleaching agent the Kappa number could be reduced by over 97.8%. Calcium hydroxide as bleaching agent resulted in a reduction of 90.0%. Both bleaching agents allowed an increase in L* brightness and tensile index of up to 74.1% and 80.1%% respectively for caustic soda and 17.6% and 80.1% respectively for calcium hydroxide as bleaching agent. For straw and coffee filter pulp an increase in L* brightness of up to 58.6% and an increase of the tensile index of up to 67.0% could be achieved without using bleaching agents. Recycled pulp showed an increase in tensile index of up to 71.5% but a decrease of 1% for the L* brightness.