Oxalic acid pretreatment for mechanical pulping greatly improves paper strength while maintaining scattering power and reducing shives and triglycerides

Abstract

In this paper we introduce a new technology based on a mild chemical pretreatment process prior to mechanical pulping. Chips are treated with a dilute solution of oxalic acid (OA) for only 10 minute at 130°C, in a typical example. The properties of the pulp produced by this OA process are quite different from those obtained via conventional chemical pretreatments, providing a much more valuable pulp, and at higher yields. Refining results obtained at the Andritz Pilot Plant in Springfield, Ohio show an outstanding combination of strength improvements, energy savings, and shive and triglycerides reduction, with only a modest loss in brightness. Under suitable conditions the light scattering coefficient of the oxalic-treated treated chips was fully recovered without losing the above benefits. Maintaining light scattering coefficient with this treatment is of great interest, particularly to those mills producing lightweight coated paper (LWC). Refining results are presented here, along with an evaluation of the process economics for a LWC example case. Based on strength improvements (kraft replacement in the final furnish) and energy savings, the production cost savings are substantial. For the LWC example, at least $9 million/year net savings before license fees can be realized in an operation producing 372 t/d of OA mechanical pulp for 600 t/d of blended LWC furnish. Based on this strong economic potential, several mechanical pulp mills have expressed interest in conducting in-mill evaluations. Planning for mill trials is currently underway.

Citation

Swaney, Ross; Akhtar, Masood; Horn, Eric; Lentz, Michael; Klungness, John; Sabourin, Marc. 2003. Oxalic acid pretreatment for mechanical pulping greatly improves paper strength while maintaining scattering power and reducing shives and triglycerides. 2003 TAPPI Fall Technical Conference: Engineering, Pulping & PCE&I. Atlanta, GA: TAPPI Press, 2003: [5] pages.