Efficient Pulp Washing on KP Brown Stock Washing Process

Abstract

The purpose of brown stock washing is to separate spent cooking chemicals and dissolved organic wood solids from unbleached fibers. Recently, some pulp mills are trying to improve pulp yield, but this operation usually tends to make pulp with high blow line kappa number. Also, we need more bleaching agents or oxygen delignification efficiency than conventional operation to meet required fiber brightness. If we use water alone for this process, we cannot remove hydrophobic materials, like dissolved lignins and extractives, from unbleached fibers completely. Our pulp wash aid has dual effect; one is to improve drainage and the other is to remove wash hydrophobic materials efficiently. Using our pulp wash aid, we can reduce the amount used of wash liquor and bleaching agents, and also achieve improvement of oxygen delignification, etc. This article describes the theory of our pulp wash aid, and introduces some case studies from actual mills in overseas.