To remain both competitive and profitable, mills must harness their supply chains to optimize their products, processes, organizational set-ups and business models. For many paper producers, these big themes can be addressed by looking more closely at some of the smallest components – the fibers their products are made of.

But, with generally low margins and limited capital budgets, the priority for spending in paper mills is typically on required maintenance, followed by projects that remove bottlenecks to increase productivity and ensure a good return. For innovative projects to attract investment, it is necessary to find opportunities that offer low risk and high potential returns.

It has long been time for the pulp and paper sector to get beyond its traditional mindset by recognizing the huge potential that small, but significant, optimization projects can make. One such example is the adoption of advanced fiber measurements, which, when combined with artificial intelligence (AI) techniques, can provide far greater control of end-product quality, generating high value with minimal, if any, risk. It is often the low-hanging fruit—the everyday tools such as fiber measurement—we take for granted that can yield the greatest returns. The sooner the industry starts recognizing the potential value that can be mined from their processes with easily accessible tools, the better!

Employing new advancements in fiber measurements can benefit operations – from new product development to better quality products – and help in the drive for better efficiency and higher profitability.

A recent trend in cellulosic pulps is the development and use of micro-cellulose and nano-cellulose formats to produce new, improved and more sustainable paper products. These include; micro-fibrillated cellulose (MFC) produced by manufacturers such as Borregaard, Norske Skog and FiberLean, cellulose nanofiber (CNF) produced by Nippon Paper and others, and cellulose fibrils (CF) produced by Kruger.

All of these nanofiber products are very small with a high specific surface area, and are often used as strengthening agents because they increase the amount of hydrogen bonding in a sheet to improve its tensile strength. Because the nanofibers are cellulose-based, they can be used to replace other bonding agents such as polymers derived from petroleum products, and thus offer a more sustainable alternative.

One challenge with nanofibers, however,  is that conventional fiber analyzers are not designed for detecting and characterizing such small fibers, although an analytical method that can detect and characterize small particles in a pulp suspension was developed and patented in the 1980s. Since 2016, a commercial lab instrument using this concept has been available as an add-on module for ABB’s L&W Fiber Tester, the L&W Crill.

Crill particles are typically 100 times smaller than a pulp fiber, but are important indicators of fiber bonding and strength properties. Unlike the detection of conventional pulp fibers, which depends on image analysis with visible light, this technique compares the intensity of two wavelengths of light transmitted through a pulp suspension: ultraviolet light (365 nm) and infrared light (850 nm). The crill content is presented as the crill quota, or the ratio of the UV/IR transmission losses.

The crill measurement technique was originally developed to monitor the process of refining, where crill particles are removed from the fiber wall. A linear relationship was discovered between the crill quota and the refining energy, both in high-consistency mechanical pulp refining and in low-consistency chemical pulp refining. As more facilities for the manufacture of nano-cellulose products are built in the future, crill measurement will become an invaluable tool for quality control and for controlling the refining energy, given that the manufacture of these products can be energy intensive

Shape factor is an important pulp quality measurement used to determine the straightness of fibers. While a high shape factor correlates well with tensile strength and stiffness, a lower shape factor indicates there are deformations present that enable the fibers to stretch.

The kink index is used to identify local deformations or “knees” in the fibers. To calculate the kink index, changes in the direction of the main axis of the fibers within a limited distance of the fiber are counted when the angle is 20° or greater. Kink measurement correlates well with shape factor in most cases, since local deformations are included in the shape factor.

By using one or both of these measurements and correlating them with the measured stretch of handsheets or the final product, manufacturers can optimize their chemical or mechanical curl-setting treatments to achieve the desired stretchability. This will undoubtedly lead to new extensible paper products that will become important as sustainable replacements for plastic packaging.