A new enzymatic product can improve freeness of multiple grades of secondary fiber with minimal yield loss and no negative impact on fiber properties. A cost effective solution from Novozymes has in full-scale mill trials shown to enhance dewaterability, increase machine speed, and reduce steam consumption while maintaining the quality of the end-product.
Finding the right cellulase to do the job
Enzymes are capable of selectively hydrolyzing colloidal substances containing cellulose which increases the freeness of mill furnishes. “At Novozymes, we have developed FiberCare D, a customized blend of cellulases that contains high levels of select endoglucanases. The endoglucanases selectively hydrolyzes the amorphic cellulose within the colloidal fraction of the pulp and provide enhanced dewaterability, as well as additional benefits such as improved formation and retention. The product works well on the full range of recycled waste; old corrugated container (OCC), mixed waste (MW), and old newsprint (ONP),” explains Greg DeLozier, Research Scientist at Novozymes.
Paving the way for significant savings for mills
Four full-scale mill trials in North America, Western Europe, and Asia demonstrated the benefits of FiberCare D. A North American mill, producing liner and medium from old corrugated container and mixed waste, was able to increase machine speed as a function of enzyme dose during production of 200g/m2 liner. “The mill tested the final product and found that all qualitative specifications were maintained and that it was even possible to increase the ring crush by two points,” says Greg DeLozier. “FiberCare D improves dewaterability of the board which allowed this mill to reduce steam consumption by 6-7%. In addition, the mill increased machine speed and approached maximum capacity of the machine when producing heavier basis weight grades. What is more, the mill saw improvements in formation and product appearance, and experienced significantly fewer web breaks.”
In Western Europe, a mill producing tissue and towel from recovered mixed waste investigated the impact of both refinability and runnability of stock treated with FiberCare D. “At a dosage of 100g per dry ton fiber, this European mill was able to increase machine speed and gradually reduce refining energy by 12.5%, without losing performance in the end product,” says Greg DeLozier. Another European mill that produces multiple basis weights of liner from mixed waste, saw similar benefits with Fiber Care D using the same amounts of enzymatic solution added directly to the pulper. “The mill observed improved drainage, marked by an increase in the solids content of the web leaving the press section, which translated into average steam savings of 5.5%. FiberCare D improved the effectiveness of wet-end chemicals that, in turn, improved retention thereby enabling the mill to cut the starch addition at the size press from 6.0% to 5.5% w/w.”
“All the mills in the trials have reported some kind of savings. Take the trials in Asia for example, where the mill, producing medium or various basis weights from 100% old corrugated container, could reduce the amount of steam on 112 and 140g/m2 medium by 2.6% and 4% respectively,” says Kumar N.K., Industry Sales Manager, Novozymes India.
Rolling out easy-to-use and cost-effective cellulases
Despite the trials showing a clear case of cost-savings and ease of implementation, Novozymes still meets hesitation among pulp and paper mills. “Although our mill trials show clear benefits there is a lot of reluctance among mills to incorporate this technology. The skepticism stems from past scenarios where overly aggressive multi component cellulases have reduced yield, burdened the water treatment operations, and damaged the already inferior fiber. Moreover, products based on mono-component cellulase technology have been costly in terms of development and optimization, so it is fully understandable that mills are cautious,” says Kumar N.K. “The cellulases used in FiberCareDwere, however, initially screened because they are readily and economically scalable to commercial production volumes. It means that we now have a commercial product that can improve in the runnability of a wide range of recycled waste, without negative impact on fiber properties. In the full-scale mill trials, we found that FiberCareD enhanced de-waterability – which meant mills could increase machine speed and reduce steam consumption and still produce an end-product of exceptional quality.”
