High yield bio-products could revive idled Canadian TMP mills

TMP-bioprocess pilot plant at FPI's Pointe Claire, QC laboratory

Mark Willliamson
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

A large-scale pilot plant at Resolute’s Thunder Bay mill will further develop FPInnovations’ patented process to produce “2G” sugars and hydrolysis lignin (H-lignin) using mechanical refining, mild chemical treatment and enzymatic hydrolysis.

Eventually, a production plant of 500 t/d or higher operating at 90% yield may be possible.

Until now, bio-refined forest products have been thought of as side streams of chemical pulp mills, not TMP mills. But that is changing according to recent news. FPInnovations and Resolute Forest Products jointly announced that a large-scale pilot plant will be built at Resolute's Thunder Bay, Ontario mill to further develop the technology and commercial potential of FPInnovations' patented TMP-bio process. This process uses existing TMP refining equipment, mild chemical treatment and enzymatic hydrolysis to produce so-called "2G" or second-generation sugars and H-lignin from non-food chain biomass. Thus, the door is opened for revenue streams at TMP-based publication paper mills which don't have a kraft pulping process. The expected startup will be in May, 2019. The biomass processing capacity will be 100 tonnes per year.

The objective of the pilot plant is to verify and adapt, if necessary, the process which has been demonstrated at a small-scale pilot plant at FPInnovations' Pointe Claire, QC laboratories, and thereby de-risk the scale-up to a production plant. That could be 500 t/d or higher according to expectations. Samples of sugars and lignin will be supplied to bio-product researchers and sizeable lots will be shipped to potential end users for production trials.

The development process started at FPInnovations in 2011 when the Canadian publication paper industry was in sharp decline, the TMP plants feeding it were idled or scaled back and other profitable revenue streams were direly needed. The decision to take this chemi-mechanical route involved several factors, according to Zhirun Yuan, Senior Manager, Industrial Technology Integration, at FPInnovations. "The goal was to produce consistent quality bio-products from renewable forest resources, not derived from the food chain or other agricultural uses. In parts of Canada where many TMP mills are located the cost of electricity is low, so this led us to a chemi-mechanical process using common TMP refining equipment, which was idled or used under capacity. A combination of mechanical refining and low chemical, low temperature treatment leads to the production of high-quality H-lignin and clean sugars that can be fermented directly without detoxification. We targeted hardwood biomass, which is available but under utilized, " he explains. Jean Hamel, Vice President, Industry at FPInnovations elaborates on this last point and about the business justification for this approach: "In Canada, there is a significant quantity of unutilized and low quality hardwood that could find a real economic value, opening new business opportunities for mills that have access to both hardwood and softwood biomass." he says.

High production with low energy

One of the most striking goals of the program is to achieve very high production rates of bio-products, fully utilizing the production capacity of a TMP mill. This means that a 500 t/d mill could produce almost the same tonnage of bio-products. This is made possible by using the biomass in the full chip with the very high 90% yield of sugars and H-lignin. This is in contrast to processes that extract lignin from a fraction of the kraft black liquor. Zhirun Yuan adds, "The lignin production from kraft black liquor is limited by how much liquor can be extracted without adversely affecting the operation of the recovery boiler. It is a bolt-on process, whereas the TMP-bio process is not bolt-on. In the chemi-mechanical process. the biomass of the whole chip is converted to-bio-products in the following hydrolysis process, including the cellulose, the hemicelluloses and the lignin." Thus, the bio-products are not side streams of a pulping process; they are the full production of the TMP-bio process. This has the potential to have a large impact on the business model of a forest company.

The process involves mild, low temperature treatment of the wood chips either before or after refining. This means it is adaptable to either CTMP processes with existing chemical impregnation equipment or to traditional TMP mills, where the chemicals can be added in or after refining. The refining energy is a fraction of that used in TMP furnishes for papermaking, where fiber development is required. Even though electricity costs are low in some parts of Canada, this even lower consumption is a bonus.

The chemi-mechanical process ensures the biomass is easily digestible in the following enzymatic hydrolysis process. After that, the biomass slurry is separated into sugars and H-lignin, as shown in Figure 1.

Figure 1. TMP bio process stages

Consistent sugar quality

The end users of the sugar products want consistent quality products for subsequent processing steps, and that is something that forest biomass can provide. Zhirun Yuan says, "Forest biomass, which has a much longer growing cycle than food crops, is not subject to their short-term term weather conditions and different growing locations. Forest biomass is a consistent source of supply." Figure 2 shows that, in 12 batches of pilot trials, the concentrations of glucose and xylose are very consistent from batch to batch.

The 2G sugars produced by the process will be converted by companies into intermediate building block chemicals such as lactic and succinic acids, which will then be transformed into a wide variety of products such as polyurethanes, paints, plastics, textiles, cosmetics and personal care products.

Figure 2. The concentrations of glucose and xylose are consistent from batch to batch in the pilot plant.

Wide spectrum of lignin types

H-lignin is physically and chemically different from lignin precipitated from kraft black liquor as is done in FPInnovations's LignoForce™ process. The most notable sensory difference is that the color of H-lignin is the same as the wood it comes from rather than dark grey. Although there are undisclosed potential applications, Zhirun Yuan hints that animal feed and adhesives for wood products are target markets. There may be some overlap between H-lignin and kraft lignin applications, but in time each will find its own niche markets, as they have different properties.

The first H-lignin products will be based on hardwood chips. Using softwood chips will require more severe chemical treatment and advanced enzyme development. That possibility is being looked into. Once the plant is started up next year and up to full production by mid-2019, FPInnovations will have access to a wide spectrum of lignin products, including H-lignin and hardwood and softwood kraft lignin from the existing LignoForce ™ demonstration plant at the Resolute Thunder Bay mill. That plant has been in operation since 2011. The new plant will share existing lab facilities and will have its own additional testing and monitoring equipment.

With two operating biorefinery plants producing a wide variety of lignin products and sugars at the host Resolute mill plus the research support and facilities of nearby Lakehead University, it seems that a vibrant biorefinery cluster is developing in Thunder Bay.

The existing kraft lignin extraction plant at Resolute's Thunder Bay mill has been in operation since 2011.
Photos and figures are courtesy of FPInnovations