High Temperature Extraction: Understanding the Interaction of Variables through Modeling, 2004 Engineering, Pulping, and PCE&I Conference

Well-operated extraction stages decrease bleaching costs but the optimum configuration of the stage is unclear. Experimental design software was used to establish how pulp properties and effluent quality are affected by altering the active chlorine multiple (ACM) in the D0 stage, and the temperature, time at pressure, H2O2 charge, and NaOH charge in an oxidative extraction stage. The results show that the ACM in the D0 stage and temperature and peroxide in the Eop stage have the most influence on delignification and brightening.

The kappa number after D0Eo correlates very well with brightness provided no peroxide is added to the extraction stage. The high brightness imparted by peroxide in the Eop stage is not sustained after further chlorine dioxide bleaching when the pulps are delignified to the same extent as measured by the kappa number. The strength properties of the pulp are not affected by the temperature and peroxide charges applied in the Eop stage. The model also identified the conditions which achieved a specific kappa number target at lowest cost.