EFFECT OF SODIUM SULFIDE PRETREATMENT ON KRAFT PULPING, 2002 Kraft Pulp Yield Symposium

Please Note: This document will be available in PDF format in the "My Electronic Documents" link on the home page once your order has been completed. Please make sure you have the latest version of Acrobat Reader. Click on the Acrobat Reader icon to check for the latest version, it’s FREE. To print a hardcopy of a PDF file correctly you must have a postscript printer. If you are not sure if your printer is a postscript printer please refer to your owner’s manual.

A high sulfide concentration is very important during the transition form initial to bulk delignification. This transition occurs at approximately 150^oC. It is well known that the shortage of hydrogen sulfide ions at this point of the kraft cook leads to the formation of stable enol ether structures in the residual fiber lignin, since this type of compounds are formed from -aryl ether linkages under alkaline conditions. This is an undesirable reaction since the formation of such structures effects bleachability and the ability to pulp to a low kappa number. The objective of this research was to study the impact of pretreatment with a range of hydrosulfide and hydroxide ions on pulping selectivity. In this study, the wood chips were treated with sodium sulfide followed by a standard kraft stage. The impact of the various treatment conditions on the amount of sulfur adsorbed on to the chips was also quantified using a sulfur mass balance. Pretreating chips with Na₂S solution results in a higher pulp yield and viscosity as compared to a reference kraft cook.