GREEN LIQUOR AS A NOVEL PRETREATMENT AGENT TO DERIVE HIGHER VALUE WOOD PRODUCTS

摘要

Kraft mill green liquor is a by-product of the recovery operations whose main purpose is to undergo slaking and causticization reactions to provide mill white liquor (“cooking liquor”). The conversion of green liquor to white liquor is necessary because green liquor does not have a sufficiently high alkalinity to delignify wood for the ultimate production of pulp. Remarkably, a relatively nonconventional burden has been placed upon green liquor within the last 10 years: directly treat wood chips within not only the concept of the kraft pulp mill, but within the construct of the wood-based biorefinery. Green liquor possesses balanced chemical functionality which allows it to efficiently soften wood chips for use in a number of potential operations, namely, (1) a higher value wood pulp operation, (2) value prior to pulping, (3) pretreatment of wood for enzymatic digestion and bioethanol conversion, and (4) value prior to combustion. This presentation will survey in a general sense critical aspects of each of these conversion processes with a general overview of the chemistry, engineering, and economics.