Full Chemical Pulping With Mixtures of Methonal and Acid Sulfate Liquors, 1998 Breaking the Pulp Yield Barrier Symposium Proceedings

In earlier publications, the concept of producing full chemical sulfite pulps using methanol as a pulping adjunct has been presented. The three common bases, sodium, ammonium, and magnesium have been investigated, and similar benefits from the use of methanol have been observed with each base. Using small chips, completely defibered full chemical pulps can be produced in one hour or less under isothermal conditions with no burning of the chip centers, using the proper amount of methanol; total pulp yields in the 60-65% range are common, and occasional yields over 70% have been observed. pulp brightnesses are normal, and the integrity of the unbeaten pulp handsheets is remarkable. Pulp strengths are generally superior to those of other high yield sulfite pulps in the same range of total yield. Laboratory experiments suggest that only 8 kg of methanol are consumed per ton of pulp, so that more than 99% of the added solvent is potentially recoverable. In view of the steady decrease in the wood supplies of the world an improved method of producing high yield chemical pulps for a variety of unbleached pulp uses should be a valuable addition to the repertory of the pulping industry.