3447
Developments in High Tonnage Paste Thickening
Fred Schoenbrunn, Craig Gilbert, Antonio Accioly
FL Smidth
ABSTRACT: Deep Cone Thickeners have been quite successful at achieving much higher underflow densities
compared with conventional high-rate designs. Hundreds of these machines have been designed and installed,
but with the great bulk being less than 25 m in diameter. For many applications and operations that size range
is suitable, including most alumina refineries and underground mines. However, some markets operate at much
larger capacities as some commodities like Copper and Iron are often processed at much higher tonnages. In one
instance for a Copper operation the solution was to use a dozen 24 m DCTs. However, the same tonnage can
be handled in three 45 m thickeners. Above 25 m, paste thickener designs have tended to use lower floor slopes
to save on height and cost for both in-ground concrete and elevated steel tanks.
One Copper mine requested a design to handle over 80,000 tpd, thickening the underflow to 68 wt%, which
is a higher solids content than any current high tonnage operation. Based on testing, the desire for redundant
capacity and keeping to proven sizes, (3) × 45 m DCTs were selected to handle the tonnage, with capacity for
any two to handle the total flows in case of mechanical or maintenance issues.
In order to manage the high throughput of high density mud, avoid ratholing, and hit the density target, an
innovative large spiral inner blade design was used. This innovation effectively shifts the second rake blade to
connect the first and third blades, each one spanning both long and short rake arms. This greatly improves rak-
ing capacity and mud movement in the inner area, facilitating a more even mud bed residence time distribution.
CFD modeling was used to confirm the design and the narrower residence time distribution. A narrower resi-
dence time distribution implies minimizing ratholing and short circuiting as well as dead zones and regions
where some material stays in the thickener for a long time and thickens to high densities.
Performance data and operational results will be presented.
INTRODUCTION
Deep Cone Thickeners (DCTs) are designed and generally
able to produce significantly higher underflow densities
compared with traditional high-rate thickeners. Features to
enable this include a much deeper mud bed in the thickener
with much longer mud retention time and significantly
more torque to drive the rake through the thicker mud.
The feed system including feed dilution, flocculation and
the feedwell are generally the same. The higher densities
that can be achieved with DCTs offer a variety of benefits
for applications including counter-current decantation, fil-
ter feed, paste backfill, reactor feed, and tailings disposal
(Schoenbrunn).
Developments in High Tonnage Paste Thickening
Fred Schoenbrunn, Craig Gilbert, Antonio Accioly
FL Smidth
ABSTRACT: Deep Cone Thickeners have been quite successful at achieving much higher underflow densities
compared with conventional high-rate designs. Hundreds of these machines have been designed and installed,
but with the great bulk being less than 25 m in diameter. For many applications and operations that size range
is suitable, including most alumina refineries and underground mines. However, some markets operate at much
larger capacities as some commodities like Copper and Iron are often processed at much higher tonnages. In one
instance for a Copper operation the solution was to use a dozen 24 m DCTs. However, the same tonnage can
be handled in three 45 m thickeners. Above 25 m, paste thickener designs have tended to use lower floor slopes
to save on height and cost for both in-ground concrete and elevated steel tanks.
One Copper mine requested a design to handle over 80,000 tpd, thickening the underflow to 68 wt%, which
is a higher solids content than any current high tonnage operation. Based on testing, the desire for redundant
capacity and keeping to proven sizes, (3) × 45 m DCTs were selected to handle the tonnage, with capacity for
any two to handle the total flows in case of mechanical or maintenance issues.
In order to manage the high throughput of high density mud, avoid ratholing, and hit the density target, an
innovative large spiral inner blade design was used. This innovation effectively shifts the second rake blade to
connect the first and third blades, each one spanning both long and short rake arms. This greatly improves rak-
ing capacity and mud movement in the inner area, facilitating a more even mud bed residence time distribution.
CFD modeling was used to confirm the design and the narrower residence time distribution. A narrower resi-
dence time distribution implies minimizing ratholing and short circuiting as well as dead zones and regions
where some material stays in the thickener for a long time and thickens to high densities.
Performance data and operational results will be presented.
INTRODUCTION
Deep Cone Thickeners (DCTs) are designed and generally
able to produce significantly higher underflow densities
compared with traditional high-rate thickeners. Features to
enable this include a much deeper mud bed in the thickener
with much longer mud retention time and significantly
more torque to drive the rake through the thicker mud.
The feed system including feed dilution, flocculation and
the feedwell are generally the same. The higher densities
that can be achieved with DCTs offer a variety of benefits
for applications including counter-current decantation, fil-
ter feed, paste backfill, reactor feed, and tailings disposal
(Schoenbrunn).