A biomass co-firing facility
enables Drax Power Station
in North Yorkshire to receive,
handle, store and process a
variety of biomass materials
that are directly injected into
coal-fired boilers where they
are burnt alongside coal.

Biomass feedstock
products vary from forestry
residues, or cultivated
products such as Miscanthus
and Willow, to agricultural
by-products like straw. Stock
rotation/retention time needs
careful management as the
products need regular
rotation to avoid degradation.

Even with large silo sizes,
the biomass typically only
has a retention time of 24-
48h, before being sent to
electricity production.

A key area of this fuel
stock management is level
measurement. A non-contact
technology is preferred on
site to mitigate the potential
for fouling and wear.

Silos are frequently fed
into and discharged from,
giving an uneven product
surface and the need for long
range measurement. VEGA
installed non-contact
Vegapuls 68 level radars for
solids, working over a range
of about 27m. Two units are
installed on each of the large
silos, to give an average
reading, as well as for dual
redundancy level
measurement of the biomass
material. They are mounted
towards the centre of the silo,
aimed down and slightly
outwards, measuring at a
point about half the radius, to
deliver a good average level
reading over the surface
profile. Units work reliably,
regardless of the filling
stream. There are no crosstalk
issues, even with multiple
units in the same silo.