MANAGEMENT OF SEGREGATING INDUSTRIAL TAILINGS BY USING THICKENERS PRODUCING SEGREGATED THICKENED TAILINGS

GESTION DE LA SEPARATION DES PRODUITS DE QUEUE INDUSTRIELS AU MOYEN D'EPAISSISSANTS PRODUISANT DES PRODUITS DE QUEUE SEPARES EPAISSIS

English Abstract

The present invention claims that for the management of segregating industrial
tailings,
such as tailings produced by oil sands, mining and coal industry, the tailings
is thickened
by using a suitable thickener producing segregated thickened tailings as
thickener
underflow and release water as thickener overflow. The production of
segregated
thickened tailings in the thickener is the key factor for fast recovery of the
released water
from the tailings stream. Thickener overflow is the release water, which is
preferably
reconditioned and recycled. The thickener underflow is the segregated
thickened tailings,
which can be converted to engineered tailings product and discharged for land
reclamation, further consolidation of which would produce more release water.
As an
example, the thickener underflow (segregated thickened tailings) can be
blended with the
coarser and finer fractions of the main tailings stream, at certain
proportions, preferably
with the help of chemical additives, to produce blended composite tailings.
Blended
composite tailings can be disposed for land reclamation, further consolidation
of which
would produce more release water.

Claims

Claims

The present invention claims:

1. The segregating industrial tailings is physically processed using some kind
of size
clarification equipment, such as a cyclone. Using cyclone as size
clarification
equipment, as an example, the main tailings is divided into two streams: (i)
cyclone
underflow and (ii) cyclone overflow effluents. Cyclone underflow has larger
solid
content and larger coarse per cent (or smaller fines per cent) than that of
those of
cyclone overflow.

2. The particles described in Claim 1 as "coarse" are the particles greater
than 44 micron
size, which are generally sand particles. The particles described in Claim 1
as
"fines" are the particles smaller than 44 micron size, which are generally
silt and clay
particles.

3. Cyclone overflow preferably treated with a chemical to improve the
formation of
flocculent, which improves the sedimentation of the solid particles in the
suspension
during the thickening process in the thickener.

4. The cyclone overflow, preferably after treating it with a chemical, is
thickened in a
thickener operating under the conditions of segregating consolidation. The
thickening process takes place under segregating conditions in the thickened
phase,
producing segregated thickened tailings as thickener underflow and release
water as
thickener overflow.



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5. The term "segregating" in Claim 4 is used to describe the phenomena of
consolidation where fraction of the solid particles (for example coarse sand
particles)
in the suspension segregate and settle faster than the rest of the solids (for
example
fine particles such as silt and clay). In segregating thickening process
solids
concentration in the thickened phase decreases as a function of the distance
from the
bottom of the thickener. In non segregating thickening process segregation of
solids
does not take place and solid concentration in the thickened phase becomes
independent to the height, for example independent to the distance from the
bottom of
the thickener.

6. The per cent water release during the thickening process is defined as the
fraction of
the water in the tailings recovered as release water. The measure of percent
water
release as a function of time is a measure to compare thickening processes.

7. During the formation of segregated thickened tailings in the thickener
relatively high
water release rate is achieved. The segregated solids probably opened channels
by
theirs downwards motion in the thickened phase, resulting in increase in the
permeability and consequently decrease in pore pressure and fast water release
rate.

8. The thickening process explained in Claim 7 can not take place during the
non segregating thickening process. As a result, segregation of solids in the
thickened
phase is desired for fast water release in the thickener. The production of
segregated
thickened tailings in the thickener is the key factor for fast recovery of the
released
water from the tailings stream.

9. Per cent water release rate for a given tailings is a function of the feed
tailings per
cent solid content, as well as per cent fines of the solids. For fast water
recovery in
the thickener by segregating thickening process, it may be required that the
feed
tailings per cent solid content be lower than a limit concentration. This
limit solid
concentration of the tailings is a function of the per cent fines of the
solids. If the
feed tailings concentration is high, dilution of the tailings with recovered
or make-up
water may be required for fast water release during the segregating thickening
process
in the thickener.

10. Thickener overflow is the release water, which is preferably reconditioned
and
recycled.

11. The thickened phase, which is segregated thickener underflow effluent, can
be
blended with the coarse and fine fractions of the main tailings, probably with
the help
of some chemical additives, to produce blended composite tailings.

12. The thickener underflow is the segregated thickened tailings, which can be
converted
to engineered tailings product and discharged for land reclamation, further
consolidation of which would produce more release water.


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13. As an example to Claim 11, the thickener underflow (segregated thickened
tailings)
can be blended with the coarser and finer fractions of the main tailings
stream, at
certain proportions, preferably with the help of chemicals additives, to
produce
blended composite tailings. Blended composite tailings can be disposed for
land
reclamation, further consolidation of which would produce more release water.
The
release water can be reconditioned and recycled.

Description

CA 02363932 2001-11-23
Descriution
The present invention relates to a method of thickening, which would find
applications
for the management of segregating industrial tailings. In this thickening
method, the
tailings is thickened by using a thickener operating at the segregating
thickening
conditions. Main benefit of the segregating thickening process is the fast
recovery of the
release water.
One of the major applications of the present invention would be in the
management of oil
sands tailings in Northern Alberta, Canada. In this particular application,
the main
tailings stream will be processed for the separation of particles based on the
particle
diameter. Coarse particles in the oil sands tailings, which are the sand
particles, are
precipitated during the processing of the tailings. A cyclone may also be used
for this
separation process. Using cyclone, the main tailings of about 57 per cent
solids, about 20
per cent fines can be converted into: (i) cyclone overflow of about 39 per
cent solids,
about 50 percent fines, and (ii) cyclone underflow of about 68 per cent
solids, about 8
percent fines. The cyclone overflow can be treated with Ca(OH)2 lime and C02
as
described in Canadian Patent No. 2,188,064 or any other chemical process to
alter its
sedimentation and consolidation characteristics and could be diluted with
water before
feeding into a suitable thickener such as the thickener described by the
Canadian Patent
Application No 2,355,575. The present invention suggests that the thickener
would be
operated under the segregating thickening condition, which is the condition
achieves the
fastest release water recovery rate. The segregated thickened tailings
(thickener
underflow) can be blended with the cyclone underflow for the production of
blended
composite tailings BCT), which can be discharged for land reclamation. If
needed,
mature fine tailings (MFT, about 33 per cent solids, about 99 % fines) and
some chemical
additives can also be used for the production of BCT. As an another option,
MFT and
cyclone underflow can be blended to produce composite tailings (CT), and CT
can be
blended with thickener underflow (segregated thickened tailings) to produce
BCT. The
release water recovered as thickener overflow can be reconditioned as
described in
Canadian Patent No. 2,188,064 and recycled. The release water recovered during
the
consolidation of the BCT can also be blended to the release water recovered as
thickener
overflow. As an example, the schematic of the tailings management option
described in
this section is depicted in Figure 1.
It is accustomed to believe in oil sands tailings management practice that
formation of
nonsegregating tailings is needed by the chemical treatment of the oil sands
tailings. The
present invention challenges this accustomed believe and proves the fact that
formation
of segregating tailings as result of the chemical treatment is beneficial for
the

CA 02363932 2001-11-23
Management of Segregating Industrial Tailings by Dsing Thickeners ... Page S
management of oil sands tailings. This invention proves that the segregating
behavior of
the tailings helps to attain fast water recovery during the thickening of the
tailings in the
thickener.
This invention suggests that the composition and the characteristics of the
thickener
underflow would not be altered if the thickening process in the thickener is
taking place
in segregating or nonsegregating fashion. This fact is the advantage of the
use of
thickeners in the management of oil sands tailings, provided that a suitable
thickener,
such as the thickener described in Patent Application No. 2,355,575, would be
available
for the thickening of chemically treated oil sands tailings under segregated
thickening
process conditions.
Brief Description of the Drawing
Figure 1 is a schematic of an application of the present invention for the
management of
oil sands tailings. WT Whole Tailings; CO Cyclone Overflow; CU Cyclone
Underflow;
CT Composite Tailings; BCT Blended Composite Tailings; RW Released Water; TU
Thickener Underflow; % S per cent solids; % F per cent fines.
Summary of the Invention
A primary objective of the present invention is to provide an improved
sedimentation
method for the management of segregating industrial tailings. The present
invention
shows that segregating behavior of the chemically treated tailings would
improve the
water release rate during the thickening process, provided that a suitable
thickener
operating segregating thickening condition is used. The solid content of the
feed tailings
and its fine content are significant parameters for the performance of the
segregating
thickening process in the thickener, which have to be determined
experimentally. If the
solid content of the thickener feed is high, it can be adjusted by dilution
with water. The
segregated thickened tailings (thickener underflow) can be utilized to produce
engineered
products (by blending it with coarser and finer fractions of the main tailings
stream, at
certain proportions), such as BCT, for its disposal for land reclamation.
Baki Ozum, Ph.D., P. Eng. C~ ~.~~ Dated: ~ /~
Director
Apex Engineering Inc.