February 17, 2009 | General

Wood Processing Innovations

Grinder equipment modifications and product introductions reflect the growing demand for biomass fuel, and the need for processing more contaminated wood waste streams.
Rhodes Yepsen

IN LAST month’s article, “Historical Perspective: Grinders, Chippers, Shredders,” BioCycle conducted interviews with manufacturers to learn the history of their companies, and the development of that equipment sector. During those interviews, it became apparent that many innovations were in response to market trends, whether it be demand for a specific finished product, like biomass fuel, or changes in feedstock, such as more C&D and other contaminated wood.
Manufacturers discussed these trends, and the equipment modifications enabling them to service these markets. For example, Bandit Industries is working with the Idaho National Laboratory, testing different grinds and cuts for biofuels. “It’s essentially a prototype plant for ideal biofuel production,” explains Jerry Morey, President of Bandit. “The model is using two tools, one with knives, as in a chipper, then another carbide cutter, with a cutting tooth. A cut is preferred for biofuels – compared to grinding and shredding – because the end product is neither long and stringy, which can jam grates, nor so fine that it blows up the stack.”
West Salem Machinery Co. has found a strong demand for customized solutions, combining equipment from its diverse line-up of wood waste chippers, grinders, screens and vibrating conveyors. “We’re definitely seeing a resurgence in biomass power, and West Salem, with grinders ranging from 50 HP up to 1500 HP, and several styles of screens, can build a turnkey system that manufactures a very specific product from start to finish,” says Mark Lyman, President of West Salem. “This has been particularly valuable to customers like pellet manufacturers, and will be useful as renewable energy markets expand. Although cellulosic ethanol companies are still in pilot stages, and don’t necessarily require large front-end systems for processing feedstocks yet, that market is about to boom, and we’re positioned to provide the systems they will require.”
Within the existing biomass fuel market, fuel specifications have changed over the years, leading to adaptations in grinding equipment, notes Dave Benton, Marketing Manager for Peterson. “Customers purchasing ground wood are getting more specific about what material they want, for instance with tighter specifications for biomass fuel, instead of just ‘hog fuel.’ This may mean tighter specs for maximum sized pieces, or the amount of allowable fines, and consequently our equipment has become more customizable. Our sizing grates are made up of multiple sections, offered in different sizes and shapes to make any finished product the market demands.”
One of the most rapidly growing sources for biomass fuel is slash from forestry operations. However, processing this material can be complicated, leading Komptech to develop the Crambo Forest. “Forestry operations typically have to bring in two or more machines if they want to grind slash into a finished boiler fuel on site,” says Todd Dunderdale, Komptech USA’s Director of Sales. “The Crambo Forest is an all-in-one machine, grinding slash wood efficiently, with a star screen deck instead of a conventional discharge conveyor. In a single pass, the wood is ground and screened, leaving dirt and pine needles behind, with clean biomass entering the chip truck. The Crambo Forest can be mounted onto a truck chassis with a grapple loader. Although this is an expensive option, the overall cost is far less than purchasing a screen and transporting it into the job site.”

In response to customers expressing interest in an intermediate-sized industrial drum chipper for biomass production, Morbark introduced the Model 40/36 biomass chipper in May 2008. “These customers wanted more production capacity and a larger infeed than the popular Model 30/36, but still wanted a ‘street-legal’ package, and at a more economical cost to own and operate than the Model 50/48,” says Tom Mitchell, Northeast Regional Sales Manager for Morbark. “An oversized infeed is especially desirable in northeast biomass chipping operations because the feed material primarily consists of tops and brush left over from logging jobs, and a large chipper opening is critical to achieving high production rates with materials of low density.” Morbark also made improvements to its staggered drum design on the chipper, including upgrades to the knife holders and hardware for greater durability.
With the decline in the housing industry, by-products such as sawdust have become increasingly scarce, leading companies like pellet manufacturers to look for alternatives. “Pellet manufacturers came to CBI, and we helped them make a feedstock that in the past was a brokered by-product,” says Aaron Benway, Northeast Regional Sales Manager for CBI. “We developed a four-pocket drum chipper head, which can produce a short microchip, about a quarter-inch in size. The development of the short microchip seems to be the best replacement for the loss of sawdust feedstock right now.”
While conventional wood waste supplies are dwindling, demand for woody biomass has increased, notes Shane Donnelly, Sales Manager for DoppstadtUS. Different applications are therefore emerging for grinding equipment. “The growing interest in cogeneration, and all around higher demand for wood, have led customers to find other sources, such as contaminated wood,” says Donnelly. “Our AK series high-speed grinder, with an up-swing hammermill, is very resistant to tramp metal in contaminated wood, and does a better job of shredding grass and leaves than a rigid hammermill. It is therefore quite useful for processing these previously undesirable materials.”

Interest in processing “previously undesirable materials” isn’t solely driven by wood shortages. Landfill bans on materials like C&D also influenced the development of equipment that is more durable, capable of handling contamination. “Chipboard manufacturers in the United Kingdom, for instance, are using a lot of C&D for manufactured lumber, instead of cutting new growth,” notes Jerry Roorda, Environmental Product Specialist for Vermeer. “Before, when landfills were unrestricted, this material was buried. Now, with new restrictions, processing C&D is quite popular, so we’ve developed high-wear items, such as more robust anvils and screens, to handle contamination.” The Duplex Drum, for instance, has modular components, allowing operators to change out an individual hammer within minutes, without removing other hammers.
Interest in processing a wider range of materials for biofuels led Rotochopper to offer an add-on component for its wood grinders. The Bale Pre-Feeder can be integrated into Rotochopper horizontal grinders to better process materials like hay, straw, grasses and corn stover, instead of just wood. “Rather than simply tearing chunks unevenly from the bale, the Bale Pre-Feeder automatically adjusts to feedstock consistency, allowing the grinder to better process the bale material,” says Kevin Rogers, Rotochopper’s Sales and Operations Manager. “It separates tightly bound fibers into a smooth flow, optimizing rotor efficiency and providing a better end product.”

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