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Conveying
the lid that matches the profile of the top half of the screw. This
construction totally encloses the screw during its operation yet
allows the screw to be completely cleaned in situ.
When a material's flow properties are affected by changes due
to process or environmental conditions, problems often occur at
the interface between process equipment, for example, a
powder and granule mixture stored in a large mixer has to be
transferred to a milling machine. The pressure of the powder in
the mixer may cause transfer problems if the conveyor screw
geometry is wrong. To overcome these potential problems a
screw conveyor with a ribbon auger featuring a variable pitch
Lynflow ribbon screw and good flow diverging inlet can be used;
with the flights designed such that it is difficult to 'choke' the
conveyor. LynFlow ribbon flights are an enhanced form of ribbon
screws which acts positively to sweep material away from the
shaft and at the same time provide robust attachment.
Increased production The Clariant conveyor
Clariant Chemicals has used an innovative twin screw conveyor
to significantly boost Leather Process Chemical productivity at production of the dried product by up to two tonnes per day,
its Selby plant by replacing a reversible screw conveyor with a while still maintaining production of the wet intermediate.
twin screw conveyor. The conveyor takes wet slurry cake from a The technique has been exploited in other installations to
belt filter and discharges it into either a dryer for subsequent provide mass flow from a hopper by running the screws
packaging or a storage keg where it is used as an intermediate independently at appropriate speed ratios to provide fully live
in another process. However with increasing demand for the flow across the length of the hopper outlet slot as well as
intermediate, the existing reversible conveyor was causing a offering the possibility to serve two outlets simultaneously. With
bottleneck as the flow of wet cake had to be disrupted to divert a standard reversible screw it would not be possible to get mass
cake to the keg. flow form the hopper.
Working within the same space occupied by reversible screw
conveyor, a twin screw conveyor has been installed with one Innovative cleaning process
casing but featuring two independent screws each driven by British Nuclear Fuels plc (BNFL) has used conveyors to wash
their own motor mounted at both ends of the conveyor. With a residue materials. It uses three screw conveyors positioned in a
single inlet chute allowing wet cake to be fed into both screws, tiered arrangement such that they convey and process the
the two screws can either operate in the same direction allowing materials as they are transferred to a dissolving vessel. The
all the cake to be exclusively fed to either the dryer or a new seven metre length screw conveyors are made of stainless steel
packaging machine replacing the earlier storage keg. (grade 304) with a warm water jacket and feature a 6" inch
Alternatively, with both screws operating simultaneously in quadrant paddle screw. In order to process the residues material
opposite directions, Clariant is able to maintain continuous effectively, an acidic solution is pumped in a contra flow to the
transfer of the product to the dryer while being able to convey direction of the screw. The level of the solution is controlled by a
cake to the packaging machine for subsequent processing when weir gate. The conveyors are tiered such that as the material
needed. The twin conveyor also gives Clariant an energy saving. reaches the end of one conveyor it is lifted into a chute, using a
Until now the company often had to use some of the dried novel box scoop, and transferred to the next conveyor. All the
product instead of the wet cake intermediate to ensure sufficient conveyors are fully enclosed.
quantity to satisfy internal production demand. As a result of For more information contact Ajax Equipment on
using the twin screw conveyor Clariant is able to increase tel: +44 (0) 1204 386723 or visit
www.ajax.co.uk
DESIGN
MANUFACTURE
INSTALL
SUPPORT
Complete turnkey projects
for the Quarrying &
Waste Recycling Industries
DUO MANUFACTURING
Mendip Works, Leigh Road, Chantry, Nr. Frome, Somerset. BA11 3LR
T +44 (0)1373 836451 F +44 (0)1373 836879 E
sales@ljhgroup.co.uk
www.duomanufacturing.com
36 Solids & Bulk Handling • August 2007
www.solidsandbulk.co.uk
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