Experimental Determination and Empirical Modeling of Oxalate Formation During Oxygen Delignification of Wheat Straw Kraft Pulp

The formation of oxalate during oxygen delignification causes a number of operational problems in pulp and paper mills. In this work, the oxygen delignification of wheat straw pulp was carried out under various conditions and the concentration of resulting oxalate in the effluent was determined. The experimental results show that the amount of oxalate in the effluent was closely related to the reaction conditions, specifically reaction temperature, oxygen pressure, and alkali charge. Raising reaction temperature and/or oxygen pressure could promoted oxalate formation. The oxalate concentration increased linearly with the consumption of alkali but logarithmically with reduction of kappa number. An empirical model for describing the oxalate formation in the oxygen delignification of wheat straw pulp was generated with a reasonably high correlation coefficient (R 2 =0.909), which can provide useful guidance for control of oxalate formation during oxygen delignification through adjustment of process parameters.