What will happen if you put a micro-chip drum on Bruks 806ST?

Microchips has many uses, today and in the future. It is used as raw material in pelletizing, for co-firing with other fuels in large power and combined heat and powerplants, and is an interesting raw material for chemical processing of woody biomass. However, earlier studies has shown that a reduction of the target chip size reduces chipper productivity and increases fuel consumption.
– In this study we wanted to determine the effects on productivity, fuel consumption and chip size distribution when using a micro-chip drum on a Bruks 806ST, says Lars Eliasson, researcher att Skogforsk.
As expected the micro-chip drum produced more chips in the 8-16 mm class, than the standard drum. However, the amount of chips in the 16-31.5 mm class was higher than expected. Most of these chips were rather thin but wide pieces. And will probably crack during further handling, thus reducing their size to the 8-16 mm class.
The study also indicates that chipper productivity was reduced by 10.5 percent, when the standard drum was substituted with the micro-chip drum. At the same time fuel consumption increased by 12.5 percent per hour and by 23.9 percent per produced odt of chips.
– As the chipper was studied in a test setting in a controlled environment and using small quantities of wood per replication, the productivity reduction can be expected to be a bit higher when used under commercial conditions, says Lars Eliasson, researcher att Skogforsk.

The study is presented in the article "Bruks 806ST equipped with a micro-chip drum".

About the study

The chipper was studied when chipping aspen dominated fuel wood logs. The standard drum has two opposing knifes and an expected chip length of 45 mm. The microchip drum has 4 knifes evenly spread around the drum and an expected chip length of 11 mm.

On average each pile of wood had a weight of 5.3 metric tonnes and a moisture content of 33 per cent. Time studies as well as measurement of fuel consumption were made during chipping of three wood piles for each drum type. Fuel consumption has only been measured for the chipper, not the loader feeding it with logs.