The LDX 2101® hydrogen peroxide reactor
under construction at Smurfit Kappa
Kraftliner Piteå at the end of August 2006.

With its annual output of 700,000 tons, Smurfit Kappa Kraftliner Piteå is Europe’s largest producer of kraftliner – base paper or paperboard made mostly from new fiber pulp and used to manufacture high-quality corrugated containerboard. As an industry leader, the company has followed closely market trends and pioneered innovations.

The Piteå plant is putting final touches on a new hydrogen peroxide reactor for the bleaching of pulp used to produce the company’s white Royal Kraftliner products. The reactor’s pressure vessel is the first in the world built out of Outokumpu’s proprietary duplex stainless steel grade LDX2101^® (EN 1.4162).

LDX2101^® replaces traditional hydrogen peroxide reactor materials – the high-performance, high-alloyed austenitic stainless steel grade 904L (EN 1.4539) or the more commonly used Duplex 2205 (EN 1.4462). LDX2101^®, which has a very low nickel content, is well adequate to handle the hydrogen peroxide reactor process, an environment with a low corrosion rate under alkaline conditions but high pressures up to 10 bars and temperatures around 110 degrees Celsius.

“Using either 904L or 2205 today is an overkill in this application,” says Lena Wegrelius, Outokumpu’s Pulp & Paper Segment Leader, heralding the end of an era in reactor pressure vessels for pulp bleaching processes.

The breakthrough comes in the wake of recent trends in paperboard packaging: demand for white paperboard has been on the increase as the packaging industry moves to new, more demanding printing methods. At the same time, pulp and paper producers seek to achieve higher environmental standards and better environmental profiles for their products, so they have sought to meet the growing demand for pulp bleaching with non-chlorine bleaching processes. Hydrogen peroxide is a strong oxidizer that has increasingly been replacing chlorine-containing bleaching chemicals. The process, known as TCF bleaching (“totally chlorine free”), is more environmentally friendly than the conventional chlorine and chlorine dioxide bleaching.

The main reason for the selection of LDX2101^® for the new reactor was its high strength, which allowed the designers to use thinner gauges compared to traditional grades. That and the low nickel content of LDX2101^® brought considerable cost savings. Additional benefits to the tank fabricators came from the good machinability of LDX2101^®. The contractor at the site expressed surprise at the easiness of the fabrication process.

The investment is part of an ongoing capacity expansion at Smurfit Kappa Kraftliner Piteå. The new, second reactor allows the company to extend the dwell time in the hydrogen peroxide process stages.

The site of Smurfit Kappa Krafliner in Piteå, Sweden. Photo courtesy: Smurfit Kappa Kraftliner Piteå.