Getting the most from used wood
There’s no getting around it - for over a year the German waste wood market has been suffering from a drastic oversupply of material, more than processors can quite cope with. Mild winters, longer power station down times, and greatly increased quantities of material from collection and construction waste are some of the factors that have brought about this situation.
For these reasons effective, targeted processing is more important than ever in order to deal with the volumes while achieving the necessary product quality at acceptable cost, for recycling or fuel use. For some time now Komptech has devoted attention and resources to the development of waste wood processing machinery.
Whether for recycling or fuel use, quality comes first.
There are some things that need to be considered when processing used wood, because the material can vary widely. This starts with the amount of hazardous material contamination, which is classified in waste wood categories AI to AIV and the special PCB category.
The origin of the wood is just as important for the various processing steps. Whether from bulk waste, packaging or demolition, the wood is typically delivered unsorted and more or less heavily contaminated with foreign objects and contraries. These include metallic contraries, as well as plastic and many other materials.
Material reclamation, i.e. recycling, takes pride of place over thermal reclamation, i.e. use as fuel. Particle board manufacture is a typical application where reclaimed waste wood is increasingly replacing new wood. But regardless of the intended use, the quality of the reclaimed material is always the first priority. It must have minimal contaminants and fines, and be as homogeneous as possible with a defined composition.
Komptech has examined different processing methods very thoroughly with regard to product yield and operating costs. Testing of high and low-speed shredders measured throughput, energy consumption and granular size composition, the latter by screening. To evaluate operating costs, tests compared single-stage processing with high and low-speed shredders, and two-stage processing with low-speed shredder and screener to return overlengths for reshredding.
Testing was performed on three different system scales. For systems running up to 15,000 tonnes annually, single or two-stage processing had the same operating costs, while at up to 30,000 or 50,000 tonnes annual throughput the two-stage configuration with screener for overlength return was the more economical solution.
Naturally, in this context the insensitivity of low-speed machines like the Crambo and Terminator to metallic contraries is very important, especially in contrast to high-speed chippers like the Axtor, which despite its free-swinging blades is still liable to more wear or damage over long term.
The most economical variant: Crambo and Multistar One
Waste wood processing is most effective with the new Multistar One star screen downstream of a Crambo or Terminator shredder. The Multistar One separates out a defined useful fraction while returning overlengths to the shredder. With a feed hopper for precise material transfer to the generously dimensioned screen deck, a discharge conveyor with four meter discharge height and a return conveyor that can pivot through 220°, the One provides a throughput of up to 200 cubic meters per hour.
The current for the electric motors can come either directly from the grid or from a combination of additional hydraulic pump on the shredder and hydraulic generator on the Multistar One. With its compact crane lift frame and variable conveyors for flexible setup plus electric drive, this new Komptech star screen is a very economical machine.