3
altered to utilize as coarser feed size in hopes of producing
a viable paste without reducing the metallurgical results.
After numerous “tweaks” to the process Veragold was finally
able to achieve a product sufficient for paste thickening and
surface stacking to eliminate the need for a conventional
tailings’ facility. Thus, we were now able to meet the com-
munity needs while not impacting the process parameters,
a decision that was well received by the community.
Once feasibility was confirmed by testing of drill core
and existing heap leach material, the ore processing flow-
sheet was revised to (a) use flotation that would eliminate
any outdoor use of cyanide and (b) produce paste tailings
instead of conventional liquefied tailings. These and other
design changes have created new opportunities to generate
longer-term benefits from all extracted materials, inclusive
of waste rock, paste tailings, and future agricultural output
produced sustainably from the regenerated landscape.
Veragold has continued building the bond between
them and the neighboring communities with a farmstead
supporting a “Comador” kitchen, a regional computer cen-
ter, Sewing Academy for vocational training, contributed
land and other resources for a regional hospital, to name
a few. This community focus has played a critical part in
the success of the whole area. Through testing and research,
Veragold selected safe mineral beneficiation process and
low-risk surface stacking of the plant tailings. A key factor
in the surface staking success was the selection of a trusted
thickener supplier. ClearStream paste thickener design has
been optimized over the past 20 years and the operational
training and support contribute greatly to the success of the
tailings system.
TAILING STORAGE—SURFACE STACKED
In the 1960’s the British National Coal Board (BNC) devel-
oped what we recognize today as the first paste thickeners.
These units were used to make coal refuse thick enough
to be placed on and transported by a conveyor belt. This
“new” technology had mixed success but did introduce
paste thickening to the world. By the 1970’s, Alcan applied
and improved upon the BNC paste thickening technology
to increase the efficiency of alumina red mud washing in
counter current decantation (CCD) circuits.
Building on those early applications, today the use
of paste thickening has expanded to many other mining
sectors. These include Gold, Nickel, Lead, Zinc, Copper,
Iron, Phosphates, Kimberlites, Mineral Sands and others.
The use and service of paste thickening has also broad-
ened to include Tailings disposal/stacking, CCD washing,
Underground backfill, Leach feed, Kiln feed, Sub-aqueous
deposition and Tailing re-work.
By the late 1990’s and early 2000’s the installation base
and experience of paste thickening had grown. There was
wide consensus within the minerals industry that “paste”
was simply part of a continuum of concentration and rhe-
ological properties. Descriptives terms of this continuum
were “slurry,” “thickened tailings,” “paste,” and “cake.” Each
of these generally described a range of the rheological prop-
erty of yield stress, or more precisely the ability of a suspen-
sion to resist a stress to a point of yielding. One end of the
spectrum is a slurry with little or no appreciable resistance
to a shear stress, to a “cake” that has significant resistance to
a shear stress and even exhibits the beginning of compres-
sive strength. The range of practical yield stress rheology for
“thickened tailings” to “paste” is roughly 50 Pa to 300 Pa.
Low rheology values are indicative of suspensions that can
segregation (particle size classification by sedimentation)
and flow with relative ease, while increasing yield stress pro-
duces very little segregation and significant flow resistance
making these materials more suitable for direct deposition
and surface stacking.
The maturity of paste technology and its benefits is
demonstrated quite clearly by an important paste thick-
ening project in Brazil. Paragominas bauxite mine (1) is
located in the state of Pará, in Northern Brazil. The mine
started production in 2006 with a production capac-
ity of approximately 16 Mtpy of run-of-mine, producing
about 11.5 Mtpy of bauxite and generating approximately
4.5 Mtpy of tailings. A tailing system was designed that
incorporated a paste thickener to improve the rheological
properties and concentration of the tailings and enable con-
sistent surface disposal stability. Mill tailings were delivered
at 4%wt to 6%wt solids and the paste thickener increased
concentration from 33% to 35% solids while developing
yield stress rheology. Tailings were deposited in 50cm lifts
to facilitate desiccation and improve consolidation.
The site practice included the use of a paste- type
thickener that was fed with the concentrator tailings at 4
to 6 wt% solids. The paste-thickener underflow, dewater-
ing to 35 wt% which had Non-Newtonian properties. The
underflow was pumped to the storage facility in the next
valley where the drying cycle between depositions was 4 to
8 weeks. The dried stack contained 60 wt% solids when the
next layer was applied. The 60 wt% stack had dried to be
very stable with a moisture content where large cracks had
developed.
The Paragominas study included drill core in a rela-
tively uniform pattern with some hole extending to more
than 30 meters. The cores revealed that the full depth con-
sistently was 65.4 wt% (±2.4 wt%). The result was a tack
with well consolidated material. Paragominas is an excellent
altered to utilize as coarser feed size in hopes of producing
a viable paste without reducing the metallurgical results.
After numerous “tweaks” to the process Veragold was finally
able to achieve a product sufficient for paste thickening and
surface stacking to eliminate the need for a conventional
tailings’ facility. Thus, we were now able to meet the com-
munity needs while not impacting the process parameters,
a decision that was well received by the community.
Once feasibility was confirmed by testing of drill core
and existing heap leach material, the ore processing flow-
sheet was revised to (a) use flotation that would eliminate
any outdoor use of cyanide and (b) produce paste tailings
instead of conventional liquefied tailings. These and other
design changes have created new opportunities to generate
longer-term benefits from all extracted materials, inclusive
of waste rock, paste tailings, and future agricultural output
produced sustainably from the regenerated landscape.
Veragold has continued building the bond between
them and the neighboring communities with a farmstead
supporting a “Comador” kitchen, a regional computer cen-
ter, Sewing Academy for vocational training, contributed
land and other resources for a regional hospital, to name
a few. This community focus has played a critical part in
the success of the whole area. Through testing and research,
Veragold selected safe mineral beneficiation process and
low-risk surface stacking of the plant tailings. A key factor
in the surface staking success was the selection of a trusted
thickener supplier. ClearStream paste thickener design has
been optimized over the past 20 years and the operational
training and support contribute greatly to the success of the
tailings system.
TAILING STORAGE—SURFACE STACKED
In the 1960’s the British National Coal Board (BNC) devel-
oped what we recognize today as the first paste thickeners.
These units were used to make coal refuse thick enough
to be placed on and transported by a conveyor belt. This
“new” technology had mixed success but did introduce
paste thickening to the world. By the 1970’s, Alcan applied
and improved upon the BNC paste thickening technology
to increase the efficiency of alumina red mud washing in
counter current decantation (CCD) circuits.
Building on those early applications, today the use
of paste thickening has expanded to many other mining
sectors. These include Gold, Nickel, Lead, Zinc, Copper,
Iron, Phosphates, Kimberlites, Mineral Sands and others.
The use and service of paste thickening has also broad-
ened to include Tailings disposal/stacking, CCD washing,
Underground backfill, Leach feed, Kiln feed, Sub-aqueous
deposition and Tailing re-work.
By the late 1990’s and early 2000’s the installation base
and experience of paste thickening had grown. There was
wide consensus within the minerals industry that “paste”
was simply part of a continuum of concentration and rhe-
ological properties. Descriptives terms of this continuum
were “slurry,” “thickened tailings,” “paste,” and “cake.” Each
of these generally described a range of the rheological prop-
erty of yield stress, or more precisely the ability of a suspen-
sion to resist a stress to a point of yielding. One end of the
spectrum is a slurry with little or no appreciable resistance
to a shear stress, to a “cake” that has significant resistance to
a shear stress and even exhibits the beginning of compres-
sive strength. The range of practical yield stress rheology for
“thickened tailings” to “paste” is roughly 50 Pa to 300 Pa.
Low rheology values are indicative of suspensions that can
segregation (particle size classification by sedimentation)
and flow with relative ease, while increasing yield stress pro-
duces very little segregation and significant flow resistance
making these materials more suitable for direct deposition
and surface stacking.
The maturity of paste technology and its benefits is
demonstrated quite clearly by an important paste thick-
ening project in Brazil. Paragominas bauxite mine (1) is
located in the state of Pará, in Northern Brazil. The mine
started production in 2006 with a production capac-
ity of approximately 16 Mtpy of run-of-mine, producing
about 11.5 Mtpy of bauxite and generating approximately
4.5 Mtpy of tailings. A tailing system was designed that
incorporated a paste thickener to improve the rheological
properties and concentration of the tailings and enable con-
sistent surface disposal stability. Mill tailings were delivered
at 4%wt to 6%wt solids and the paste thickener increased
concentration from 33% to 35% solids while developing
yield stress rheology. Tailings were deposited in 50cm lifts
to facilitate desiccation and improve consolidation.
The site practice included the use of a paste- type
thickener that was fed with the concentrator tailings at 4
to 6 wt% solids. The paste-thickener underflow, dewater-
ing to 35 wt% which had Non-Newtonian properties. The
underflow was pumped to the storage facility in the next
valley where the drying cycle between depositions was 4 to
8 weeks. The dried stack contained 60 wt% solids when the
next layer was applied. The 60 wt% stack had dried to be
very stable with a moisture content where large cracks had
developed.
The Paragominas study included drill core in a rela-
tively uniform pattern with some hole extending to more
than 30 meters. The cores revealed that the full depth con-
sistently was 65.4 wt% (±2.4 wt%). The result was a tack
with well consolidated material. Paragominas is an excellent