Metal-Fach GHT, Operation And Maintenance Documentation

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Definition of size classes of wood chips according to EN ISO 17225-4
(a) The number in the size class refers to the maximum particle size in the main fraction. The particles must fit into a round mesh
sieve (ISO 17827-1) of the size determined for that class in mm. The lowest possible property class must be given.
(b) The length and area of the section should be determined only for particles in the coarse fraction. In a sample of about 10 l, a
maximum of 2 pieces may exceed the maximum length if the cross-sectional area is < 0,5 cm2.
(c) For measuring the cross-sectional area, it is recommended to use a transparent ekier with a protractor, position the particles
vertically behind and estimate the maximum cross-sectional area of these particles using the cm2 graduation.
Requirements for wood chips
For combustion in the
GHT
boiler, use wood chips with a maximum thickness of ≤ 6% (> 45
mm), 4 cm2 section and a maximum length of 15 cm (P31S). The water content of wood chips
can be max. 30% (M30).
Bulk density of wood chips depending on water content according to EN ISO 17225-4
Quality characteristics of wood chips
Good quality wood chips:
■ low, homogeneous water content, without
moisture or mould clusters
■ small proportion of needles, leaves, small
twigs and bark
■ small proportion of the wood fineness (very
few particles < 3 mm)
■ no contamination with earth or other
substances or bodies
strangers
■ uniformly shaped particles (no particles too
long)
■ Smoothly cut, unframed edges
Poor quality wood chips:
■ Frayed surface or edges
■ high proportion of needles, leaves, small twigs
and bark
■ contamination with soil or other foreign
substances and bodies
■ different particle sizes
■ high proportion of fine fraction and water
content
Basic information on burning wood pellets to
produce heat
1.4.3 Basic information on the combustion of wood pellets to produce heat.
What is a wood pellet?
The raw material for the production of wood pellets comes 100 percent from natural wood
waste. This material occurs in large quantities as waste from the woodworking industry in the
form of shavings and sawdust. This waste is compacted under high pressure and granulated,