At the end of the year, S&F GmbH delivered three new wood chip screens to England. The customer, a producer of high-quality woodchips, preferred a reliable and customisable solution for its three sites.

Stringent quality requirements for wood chips

The quality requirements for wood chips are manifold and regulated by standards. This is the prerequisite on which many supply contracts between fuel suppliers and plant operators are based. Smaller woodchip combustion plants - in contrast to larger combined heat and power plants - require screened woodchips of the highest quality.

Parameters for the various wood chip grades and thresholds include, for instance, water content, bulk density, and ash content. The standards for biogenic fuels demand first-rate quality.

The following requirements are achieved by sifting the wood-based biomass:

• High level of homogeneity (uniformity of the pieces)
• Low fine material fraction
• Minimum green content and contamination (foreign objects).

 The uniform homogeneity facilitates faster drying of the wood chips since the air can circulate better in the spaces in between the chips. They dry much faster than unscreened wood chips with a high proportion of needles. Furthermore, mould tends to form on wood chip piles having a high fraction of fine material.

Horizontal orbital oscillation makes the difference

It was clear from the outset that an ASM-type wood chip screening plant would be the right answer for this task - the reason being the orbital screen movement of the plant. The chips distribute themselves horizontally over the surface, thus preventing long thin pieces and splinters from standing upright on the screen or dropping through it. Chip screens of this type are often used for screening biomass. 

The ASM series screening plants offer many advantages, such as:

• high screening capacity with a low space requirement
• low noise level and extremely economical
• rapid and easy screen change
• material feed and discharge openings can be individually designed
• can be integrated into existing plants