RDH PULPING OF SOUTHERN HARDWOODS

Southern hardwoods were kraft pulped using laboratory rapid-displaceme nt heating (RDH) and conventional processed. RDH pulping achieved acce ptable hardwood kappa numbers at lower H-factors than required by conv entional batch pulping. The RDH pulps had lower yields at given kappa number than a conventional batch pulp. However, RDH and conventional c ooks produced the same amount of screen rejects at a given kappa numbe r. Reduction of alkali concentration in the black liquor diminished th e rate of delignification, but id did not change the pulp yield. Resul ts for RDH pulping of five hardwood species showed significant intersp ecies variability with respect to pulping rate and selectivity. This s uggests that mills using RDH to pulp hardwoods could experience signif icant swings in kappa number and yield with a change in the mix of woo d species.