Explosion pulping of eucalyptus: a comparison with CTMP and CMP

Abstract

Explosion pulping results in strong pulp with breaking length at 100 ml CSF (Canadian standard freeness) higher than 6.5 kg and burst index approaching 4 KPa m2/g. The real advantage of eucalyptus explosion pulp over conventional CMP (chemical-mechanical pulp) and CTMP (chemical-thermo-mechanical pulp) is observed when the impregnation solution contains less than 2% NaOH along with 8% Na2SO3, and when the liquor/chips ratio equals 3. The strength of eucalyptus explosion pulp obtained by using a pretreatment solution consisting of 8% Na2SO3 and 1% NaOH is comparable with that of eucalyptus kraft pulp. The concentration of NaOH present in the pretreatment solution has a very important effect on the specific refining energy of eucalyptus explosion pulp as well as of CMP and CTMP. The explosion pulp obtained from eucalyptus pretreated with a solution containing an appropriate quantity of caustic along with Na2SO3 not only requires a minimum specific refining energy but also provides the highest strength values in comparison to that of CMP and CTMP.