80 GHZ LEVEL RADAR HELPS
RECYCLE APC RESIDUE INTO
CONCRETE BLOCKS
Figure 1 Useful construction blocks produced using recycled APCr, rather than sending to landfill
astle Environmental is
a leading supplier of
specialist waste treatment,
recycling and disposal
services, handling in excess
of 250,000 tonnes of waste each year.
They operate three fully permitted sites
in the UK and are proud to be ISO 14001
and ISO 9002 accredited. One type of
waste processed at their Cardiff site is
APCr (Air Pollution Control residue), the
fine powder that remains following the
cleaning of gases from Energy from Waste
facilities. It contains lime which is alkaline,
and consequently APCr is classified as
hazardous waste.
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For the past 18 months Castle have
used recycled APCr as an aggregate
replacement in the production of precast
concrete products. Following a detailed
end of waste review in full consultation
with Natural Resources Wales (NRW), APCr
is gainfully employed in the manufacture
of a range of concrete blocks. The
pre-processed APCr is combined with
additional aggregates and cement to
produce heavy duty interlocking concrete
blocks and 4” dense blocks, which are
used in construction, civil engineering
projects, barriers and bay walls. (See fig 1)
Part of this recycling process involves
mixing the APCr powder with recycled
water in a 4m high agitated vessel to form
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PECM Issue 32
a slurry which is then dewatered prior to
combining with other aggregates to form
the blocks. During this mixing process,
the level in the vessel requires careful
monitoring and control to ensure the
process is carried out under the correct
conditions. Inside the vessel there is a
very agitated surface, solids can build up
on the walls as well as the agitator itself
and surface foam can also be produced
under certain conditions. (See fig 2)
The uneven surface, foam and solids
build up - are accommodated by the
VEGAPULS 64’s 80 GHz radar technology
to deliver accurate and reliable level
readings. It employs focusing to avoid
unwanted interfering signals combined
with high sensitivity to read through
condensation, sensor build up and to
overcome the foaming surface. As well
as handling difficult conditions such as
these, they are also capable of measuring
very low reflectivity hydrocarbons, even
liquid gases, highly pure solvents, past
complicated vessel internals, down long
nozzles and even operating through
process isolation valves.
www.vega.com/uk
Figure 2 Challenging conditions - the mixing process produces a very turbulent surface, splashing,
surface foam, build up on the walls and vessel internals