Enhancing kraft pulping through unconventional, higher sulfide-containing pretreatment liquors--a review.

Application: Mills may be able to retrofit this technology for gains in pulp strength and yield.

This review analyzes the advances of pretreatment with sulfide-containing liquors to modify kraft pulping. In the past several decades, modified kraft pulping has advanced rapidly, based on the principle that high sulfide content at the first stage of cooking would improve both pulp quality and the selectivity of delignification. Pretreatment of wood chips with sulfide-containing liquors (i.e., black liquor impregnation) is now an industrial reality. Many research investigations for improving kraft pulping by means of pretreatment are underway, such as green liquor pretreatment, split-sulfidity cooking, and related technologies. High-sulfidity pretreatment of wood chips is one of the most promising means available to achieve significant pulping improvements. This is especially true for green liquor, an easily accessible and rich hydrosulfide source in kraft pulp mills, as part of a pretreatment stage program.

Ban and Lucia are with the Institute of Paper Science and Technology, 500 10th St., N.VK, Atlanta, GA 30318-5794, USA. Email Lucia at [e-mail]