Page 11 - GlobalEyes Edition 6 Dec 2011

Basic HTML Version

Coal particle trajectory for the V2 design, coloured by velocity (m/s)
CFD modelling is a branch
of fluid mechanics that uses
numerical methods to analyse
problems that involve fluid
flow. High speed computers
are used to perform the
calculations required to
simulate the interaction of
particles, liquids and gases
with surfaces defined by
boundary conditions. The
main styles of throat currently
in use, both static and
rotating were replicated and
individually put into a CAD
model of a common mill type.
In addition to the common
throat geometry (which was
used as a control to ensure
the CFD results were realistic)
the Bradken design team
devised several alternative
geometries using different
permutation of aperture and
vane angle, rotating and static.
The common static throat is
a simple design made of a
series of slotted plates through
which the air flows. The results
from the first simulation had
good correlation with actual
data from the mill, giving
confidence in the setup for
the new Bradken designs.
It was found that higher
air velocity through the
throat resulted in a slightly
greater mass of oversized
coal particles exiting the
classifier to the boiler while
lower velocities resulted
in fall back through the
throat and loss of material
into the sweeper zone. The
effect of rotation of the
throat on the air velocity
was determined and
criteria for fine tuning of the
classifier were established.
This study was used to
optimise the rotating throat
geometry and demonstrated
the potential benefits by
means of simulation.
Bradken’s UK sales team
have since supplied trial
throats into two Polish
coal fired power stations.
Rotating throat to V2 design, ready for despatch to Poland
TECHNOLOGY
"CFD modelling is a branch
of fluid mechanics that uses
numerical methods to analyse
problems that involve fluid flow"
Air velocity through the OEM throat
11
globaleyes / edition 6