BOUILLIES MINERALES

MINERAL SLURRIES

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
Mineral Slurries
A pumpable slurry of mineral particles, e.g., coal, in water
contains 50 to 85% by weight of mineral particles based on the combined
weight of mineral particles and water. The mineral component contains at
least 30% by weight of coarse particles having a particle size in the range
5 to 50 mm, 10 to 40% by weight of fine particles having a particle size
less than 200 micron and the balance to 100% of intermediate sized
particles.
The slurry is stable without the use of additives and can be
pumped through a pipeline.

Revendications

The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A pumpable slurry of mineral particles in water comprising
coarse mineral particles having a particle size in the range 5 to 50
mm and fine mineral particles having a particle size less than 200
micron wherein the slurry contains 50 to 85% by weight of mineral
particles based on the combined weight of mineral particles and
water, at least 30% by weight of the mineral particles being in the
form of coarse particles, 10% to 40% by weight being in the form of
fine particles and the balance to 100% by weight being intermediate
sized particles.
2. A pumpable slurry according to claim 1 wherein the slurry
contains 65% to 80% by weight of mineral particles.
3. A pumpable slurry according to claim 1 wherein at least 50% by
weight of the fine particles are less than 100 micron in size.
4. A pumpable slurry according to claim 1 wherein the fine
particles contain less than 10% by weight of particles having a
particle size below 10 micron.
5. A pumpable slurry according to claim 1 wherein the mineral
particles have a continuous particle size distribution.
6. A pumpable slurry according to claim 1 wherein the slurry
consists essentially of mineral particles and water and does not
contain any added stabiliser.
7. A pumpable slurry according to claim 1 wherein the mineral
particles are coal particles.

8. A method for transporting mineral particles in water through a
pipeline which method comprises pumping through the pipeline a
pumpable slurry of mineral particles in water comprising coarse
mineral particles having a particle size in the range 5 to 50 mm and
fine mineral particles having a particle size less than 200 micron
wherein the slurry contains 50 to 85% by weight of mineral particles
based on the combined weight of mineral particles and water, at
least 30% by weight of the mineral particles being in the form of
coarse particles, 10 to 40% by weight being in the form of fine
particles and the balance to 100% by weight being intermediate sized
particles.
9. A method for transporting a pumpable slurry of mineral particles
in water through a pipeline according to claim 8 wherein the fine
particles are separated from the slurry at the distant end of the
pipeline and are returned for re-use.
10. A mineral in the form of particles suitable for dispersion in
water to form a pumpable slurry wherein the mineral comprises at
least 30% by weight of coarse particles having a particle size in
the range 5 to 50 mm, based on the total weight of mineral
particles, 10 to 40% by weight of fine particles having a particle
size less than 200 micron, and the balance to 100% by weight of
intermediate sized particles.

Description

I 5367 (2)
MINERAL SLURRIES
This invention relates to a pump able slurry of particles of a
mineral such as coal in water and to a method for transporting such
a slurry.
There have been previous proposals to transport coal by
preparing slurries of particles of coal in water and pumping the
slurries through pipelines. These slurries tend to be Instable and
the coal tends to sediment.
GO 2068056-A discloses a method of transporting coal as a coal
water slurry through a pipeline wherein the coal in the slurry
comprises at least 95% by weight of coal particles having a particle
size smaller than 700 micron and at most 10% by weight of coal
particles having a particle size smaller than 44 micron.
There have also been proposals to provide slurries of coal
particles in water for use as fuels. However, such slurries are
based on even finer particles.
It is an object of the present invention to provide a pump able
slurry of improved stability containing relatively large size
mineral particles in water.
According to the present invention there is provided a pump able
slurry of mineral particles in water comprising coarse mineral
particles having a particle size in the range 5 to 50 mm and fine
mineral particles having a size less than 200 micron wherein the
slurry contains 50 to 85% by weight of mineral particles based on
the combined weight of mineral particles and water, at least 30% by
weight of the mineral particles being in the form of coarse

2 ~;~2~3~
particles, 10~ to 40~ by weight being in the form of fine particles,
and the balance to 100% by weight being intermediate sized
particles.
Above 85% by weight, the slurry becomes too viscous to be
pumped and below 50% the slurry is unstable and suspended particles
settle out.
Preferably the slurry contains owe to 80% by weight of mineral
particles.
Preferably the fine particles contain a significant proportion,
erg at least 50~ by weight, of particles less than 100 micron in
size.
Desirably the fine particles have a low content, ego less than
10% by weight of particles less than 10 microns in size as these
tend to increase the viscosity of the slurry, although some at least
should be present.
Conveniently the mineral particles have a continuous particle
size distribution. This may be chosen to obtain the closest packing
of particles.
The preferred mineral for use in a slurry according to the
present invention is coal, but coal waste and ores of copper, nickel
and gold sure also suitable.
A slurry according to the present invention has a high
viscosity when static and a low viscosity after shearing and in
motion. It is stable without requiring the addition of a
25 stabilizer. The flow of slurry can be stopped, started and the
velocity altered at will without causing sedimentation of coarse
particles or pipeline blockage.
According to another aspect of the present invention, there is
provided a method for transporting a pump able slurry of mineral
particles in water through a pipeline which method comprises pumping
a slurry as herein before described through the pipeline.
It is believed that in motion the fine particles concentrate at
the wall of the pipeline and the coarse particles at the core. The
fines at the pipeline wall act as a lubricant for the coarse
particles at the core.

I
The pipelines may be primed with a slurry of the fines to
prevent difficulties in starting up.
Conveniently the fines may be separated at the distant end of
the pipeline and returned to the near end for reuse.
Separation may be effected by diluting the slurry with further
quantities of water to reduce its stability followed by filtration
and/or centrifuging.
The fines can be returned as a slurry in water through another
pipeline. Conveniently the loading of fines in the returned slurry
is about 50-65~ by weight.
According to a further aspect of the invention there it
provided a mineral in the form of a pump able slurry as herein before
described, wherein the mineral comprises at least 30% by weight of
coarse particles having a particle size in the range 5 to 50 mm,
based on the total weight of mineral particles, 10 to 40~ by weight
of fine particles having a particle size less than 200 micron, and
the balance to 100% by weight of intermediate sized particles.
The invention is illustrated with reference to the following
example.
Example
A 1:1 by weight mixture of pulverized Grime Thorpe coal fines
(particle size less than 100 micron) and water was slurries in a
cement mixer. Two parts by weight unwashed Coventry coal (particle
size in the range 5 to 50 mm) were then mixed in.
The resulting slurry was then pumped under non-turbulent flow
conditions through R 100 m long 8 inch diameter (20.32 cm) pipeline
using a Putzmeister BRA 211 concrete pump.
Samples of the slurry were taken from the pipeline at the times
indicated in Table 1 and 2 and the particle size distribution of the
sample was determined and recorded in Table 2.
The example shows that a slurry according to the present
invention can be pumped under conditions of non-turbulent flow and
the slurry is stable and pump able without the use of additives such
as surfactants which have previously been proposed to prevent
aggregation of coal particles.

~L22~3~
TABLE 1
Flow Delivery Wall Tire
5 Velocity Pressure Shear
Stress
(m/s) (Barnum)
0.62 I 387 10-45
0.47 8.25 400 11-05
0.74 9.2 447 11-10
0.70 4.6 217 11-30
1.01 6.1 292 11-35
0.51 7.1 342 12-17
1.05 9.7 472 12-25
0.68 5.4 257 12-32
0.68 5.0 237 12-33
0.68 4.0 187 12-35
0.~l8 3.0 1~7 12-38
0.68 2.5 112 12-41
0.68 2.0 87 12-43
0.68 1.5 62 12-46
0.68 1.5 62 13-20
0.68 1.0 37 13-23
0.68 0.5 15 13-29
0,51 4.6 217 14-56
0.51 4.75 224 15-05
0.51 4.95 235 15-30
0.51 5.10 242 15-48
0.51 5.6 267 15-55
0.51 5.6 267 15-55

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