Paper360 - March/April 2016 - (Page 44)

techlink | BLEACHING Standard Bleaching Sequences Including an Ozone Stage - Part I EMIL GERMER AND ALEXIS METAIS Ozone bleaching began on an industrial scale in 1992 and today is implemented by leading pulp and paper companies on six continents (excluding Antarctica, of course). It is used in ECF bleaching (then called Light-ECF or Z-ECF) and TCF bleaching on kraft and sulfite pulps, hardwood and softwood pulps, and for all sorts of end products in 23 mills worldwide operating 25 bleach plants. Over the last three years of economic crisis, three new ozone bleaching sequences were started; we expect that pace to accelerate in coming years due to continuous improvement of both ozone production and ozone mixing technologies. Today, ozone bleaching fulfills every parameter of the "Best Available Technology" (BAT) standards and is as mature and reliable as ECF bleaching process (which is 10 years older) or chlorine dioxide bleaching technology (which is 50 years older). Moreover, it brings significant economic and environmental benefits to conventional ECF bleaching for a similar pulp quality (Germer et al. 2011). Benefits include: * lower bleaching chemical costs, because ozone has a specific cost similar to that of chlorine dioxide, for a 1.7 higher oxidation power; * lower costs for anti-pitch chemicals, since ozone effectively removes extractives; * lower brightness reversion, thanks to ozone action on hexenuronic acids; * possibility of short bleaching sequences with lower CAPEX; * 10% lower energy requirements for refining; * COD and BOD reduction by 30-40% in the bleach plant effluent; * AOX reduction by 50-75% in the bleach plant effluent; * Color load reduction by 60% in the bleach plant effluent. Ozone bleaching efficiency has also improved as scientists gain better understanding of its impact on the overall bleaching 44 Paper360º MARCH/APRIL 2016 A containerized ozone system. An ozone generator inside the ozone plant module.

Table of Contents for the Digital Edition of Paper360 - March/April 2016

Over the Wire
Engineering: A Continuing Evolution
RISI’s European CEO of the Year
Sappi Europe: Serious About the Future of Paper
Reliability and Maintenance Beliefs – Part IV
Discovering Hidden Causes of Converting Problems
Barrier Technologies: The New Revolution in Food Packaging
Standard Bleaching Sequences Including an Ozone Stage – Part I
TAPPI Journal Summaries
Consolidation Watch
SWM Gets Faster ERP Financial Data
Battling Rejection Burnout
Association News
Index of Advertisers

Paper360 - March/April 2016