FIELD OF THE INVENTION
The present invention relates to an arrangement to measure settling profile
of slimes and dewatering of reagents optimization used for dewatering of
slimes/tailings of mineral.
BACKGROUND OF THE INVENTION
In the process of beneficiation of Iron ore, the ore undergoes multiple
processes steps, such as crushing, screening, gravity separation and jigging.
In this process, a huge quantity of slimes gets generated which is very finer
in size below 150 micron to 10 micron.
These slimes in the form of slurry finally reports to a slime dam where it is
dumped and stored. In this process, the slimes sediments in a very slow
process and subsequently water is recovered from the other end which is
recycled back to beneficiation plant for washing of ore. To enhance the
process of dewatering of these slimes different reagents are applied to the
slurry coming to the slime dam. These reagents acts as a flocculating reagent
by binding the fine particles which causes rapid dewatering of water
entrapped in the slurry.
The efficiency of this dewatering reagent and subsequent rapid removal of
water along with binding of solids is the most critical factor in the process of
slime dewatering. The life of the slime dam can be enhanced if the extent of
dewatering and compaction of the slime in the slime day can be monitored,
measured and accordingly suitable measures to maintain the dam are taken.
Measurement of slime compaction and efficiency of dewatering of the slurries
is a very daunting task and nearly un-measurable at plant scale.
In the slime pond, the slurry mixed with flocculating reagent is discharged at
the one end and in its course of flow it settles across the entire length of the

pond. There is no way to measure quantitatively the settling profile of the
slurry developed or the compaction achieved by these slimes in the pond. The
compaction achieved and settling profile are the major criteria which
determines the life of the pond. Also optimization of the reagent dosage also
becomes challenging as there is no arrangement in the slime pond to
differentiate the effectiveness of dewatering process at different dosages. All
these constraints leads to poor slime management and hence the space of
the slime pond generally gets filled very quickly which calls for creation of
new slimes storing facility.
At present there are several methods of measuring effectiveness of
dewatering or flocculation property of different reagents using cylinder and
jar test.
Cylinder/Jar Test:
The batch cylinder and jar test is carried out using four/six identical jars
containing same volume and concentration of feed (slurry). These are
charged simultaneously with different reagent and doses. The jars are stirred
simultaneously at predetermined speeds. The treated feed samples are mixed
rapidly and then slowly after which they are allowed to settle. These three
stages correspond respectively to the fundamental process of dispersing the
flocculant onto the particle surface, gently sweeping the colloidal particles
together to form large flocs, allowing them to settle. At the end of the settling
period, test samples are drawn from the jars and turbidity of supernatant
liquid is measured. A plot of turbidity against the flocculants dose gives an
indication of optimum dose (i.e.; the minimum dose required to attain the
desired clarity).

Settling Test:
Settling test is conventionally conducted according to the standard procedure,
in 1000 ml of standard measuring cylinders. A suspension of high solids
content is taken in the cylinder and mixed well by shaking. Require dosage of
flocculants solution is added. The cylinder is inverted up and down for ten
times and is allowed to keep undisturbed situation to form interface between
flocs and supernatant. Settling curves showing fall in the interface heights vs
settling time is plotted.
With the above mentioned standard practices many works has been done to
evaluate the suitable reagent for dewatering from arrays of reagents.
Equipment like capillary suction time apparatus has been also used to
measure both the dewatering efficiency of reagents.
According to the work done by G W Chen, W W Lin and D J Lee the
dewaterability of sludge can be determined by two ways: the residue
moisture amount in the sludge cake after dewatering process (the bound
water), and the easiness of filtration of the sludge (the filterability). Also
various techniques had been proposed for measuring the bound water in the
sludge (Lee and Lee 1995).The Buchner filtration/dewaterability test is a
common test.
The whole purpose of capillary suction time apparatus is to characterize
sludge dewatering ease and rapidity. The time the filtrate requires to travel a
fixed distance in the filter paper is referred to as the capillary suction time. A
large capillary suction time implies poor filterability and vice-versa.
In the work done by B P Singh and L Besra in ‘The effect of flocculants and
surfactants on the filtration and dewatering of Iron ore fines’, the filtration
and separation characteristic of iron ore fines has been investigated. This

work included characterization, evaluation of suitable reagent to enhance
settling and dewatering rate, determination of optimum dosage of flocculants.
A common setup used to measure the effect of dewaterability of slurry on
addition of reagent and in general is shown in figure 1.
Also there are many other techniques to measure the dewaterability,
filterability and selection of suitable reagent for the mentioned purpose for
any sludge.
But in case of selection of suitable reagent and amount for sludge dewatering
in the slime pond selection of reagent only on the basis on settling rate
cannot serve the entire purpose. As the pattern in which the settling profile
gets generated during the settling of slime, amount of water recovered and
compaction achieved are the other important parameters which needs to be
measured in order to select a suitable reagent and also to efficiently utilize
the pond space.
Mechanism for measuring this parameter hence becomes a challenging task.
OBJECT OF THE INVENTION
In view of foregoing limitations inherent in prior art, it is therefore an object
of the invention is to propose an arrangement to measure settling profile of
slimes and dewatering efficiency of reagents used for dewatering of
slimes/tailings of mineral.

SUMMARY OF THE INVENTION
For the above mentioned prior art problems, a prototype of a slime pit is
developed in which flocculated slime is allowed to settle in a space of known
dimension or trough to measure the compaction achieved by slimes. This
model also helped in calculating the percentage water recovered from the
slurry, reagent selection and optimization of dosages in an arrangement
provided for the purpose.
The prototype slime pond allows evaluating the amount of water recovered,
moisture content of the settled solid including the settling profile generated
by the slimes once it is mixed with the dewatering reagent and settle in the
slime pond. By measuring the mentioned parameters, a reagent for slime
dewatering can be selected from a wide range of available commercial
reagents. This also helps in determining the optimum dosage to establish the
best settling pattern for slime so that the slime pond space can be utilized to
the maximum extent.
The arrangement has unit for preparation of slurry of any desired pulp
density, reagent of any desired concentration and respective pumps to deliver
both of them to the attached tray which acts as a prototype of slime pond. In
course of movement of slurry and reagent towards the tray via pump , both
gets mixed with each other with the help of an arrangement known as in-line
mixture or static mixture which has inbuilt baffles inside it which provides
enough shear forces for creating suitable condition for mixing of slurry with
the reagent. The tray has scale attached in the middle of its breadth across
the entire length and are spaced at equal interval of distance. The system has
mechanism to alter the inclination of the tray so as to create similar
inclination as in live scale slime dam. The slurry is discharged at one end of
the tray, after which the slurry flow towards the other end in course of which
the slurry dewaters and gets settled across the length of the tray. The

rheology of the slurry gets modified after the addition of reagent with the
slurry and the extent in this rheology modification depends upon the amount
of reagent added and the inclination provided to the tray. The clear water is
collected from the overflow end and thus the amount of water recovered in a
particular time can be calculated.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 Shows a prior art arrangement to measure the effect of
dewaterability of slurry upon addition of reagents.
Fig. 2 Shows a schedule of the proposed arrangement of the
invention.
Fig. 3 Shows settling profile graph as an example.
DETAILED DESCRIPTION OF THE INVENTION
The present disclosure focuses on development of methodology and test
using prototype of plant scale slime dam to measure the dewatering
efficiency of reagent used for slime dewatering and the compaction level
achieved after application of reagent with it.
The disclosed arrangement enables measuring of all the parameters which
cannot be measured at plant scale. This lab scale setup helps in measuring
the compaction achieved, volume of water recovered, settling profile
developed, size and chemical composition wise distribution of the slimes in
the pond and the final moisture content of the solids settled in the pond. This
setup allows selection of the most suitable reagent including optimum dosage
required to obtain the most desired settling profile which further helps in
utilizing the slime pond space in the most effective manner. Proper
management of slime reciprocates in enhancement of slime pond life which
from the both environment and commercial point of view is always beneficial.

Figure 2 depicts an arrangement (200) comprises a slurry tank (204) and a
reagent tank (208). The arrangement (200) is for preparation of slurry,
reagent solution and respective pumps to deliver both of them to an
attached calibrated tray (216) which acts as a prototype of slime pond.
In course of movement of slurry and reagent towards the tray (216) via
pumps, both gets mixed with each other with the help of an inline mixing
means (212) with inbuilt baffles inside it which provides enough shear forces
for creating suitable condition for mixing of slurry with the reagent. The
mixing generates flocculated slime which is further conveyed to the tray.
The tray (216) comprises plurality of scales (220) attached in the middle of its
breadth across the entire length and are spaced at equal interval of distance.
For the sake of brevity only two scales has been shown whereas in operation
it can any number scales can be employed as per the convenience.
The arrangement (200) has mechanism to alter the inclination of the tray
(216) so as to create similar inclination as in live scale slime dam. The slurry
is discharged at one end of the tray (216), after which the slurry flow towards
the other end in course of which the slurry dewaters and gets settled across
the length of the tray (216). The rheology of the slurry gets modified after
the addition of reagent with the slurry and the extent in this rheology
modification depends upon the amount of reagent added and the inclination
provided to the tray. The clear water is collected from the overflow end and
thus the amount of water recovered in a particular time can be calculated.
A tap is positioned at the end of the calibrated tray (216) to collect clear
water. The height can also be adjusted of calibrated tray (216) as per the
requirement. Similarly the length of the calibrated tray (216) height can also
be adjusted.

The higher capacity tank is the slurry tank in which slurry of desired solid
concentration is prepared by taking particular amount of solid and then
adding calculated amount of water. The tank (204) has agitator attached with
it for uniform mixing of solids with water for slurry preparation. The reagent
(208) tank is used for preparation of reagent of desired strength and
concentration. The tank (208) has baffles attached to the inner walls of the
tank (208) to avoid cavity creation and to have proper mixing of reagent with
water. Two different pumps are employed for discharging slurry and the
reagents respectively to the tray (216) attached in the arrangement. Slurry
and reagent pumps deliver slurry and the prepared reagent to the attached
tray (216) which acts as a prototype of slime pond. In the course of
movement of slurry and reagent towards the tray via the pump , both gets
mixed with each other with the help of an arrangement known as in-line
mixing means (212) having inbuilt baffles inside it which provides enough
shear forces for creating suitable condition for mixing of slurry with the
reagent. The tray (216) has plurality of scales attached in the middle of its
breadth across the entire length and are spaced at equal interval of distance.
The system has mechanism to alter the inclination of the tray so as to create
similar inclination as in live scale slime dam. The calibrated tray (216) can be
inclined at an angle 1-7 deg. clockwise. The slurry is discharged at one end of
the tray, after which the slurry flow towards the other end in course of which
the slurry dewaters and gets settled across the length of the tray (216). The
rheology of the slurry gets modified after the addition of reagent with the
slurry and the extent in this rheology modification depends upon the amount
of reagent added and the inclination provided to the tray. The clear water is
collected from the overflow end and thus the amount of water recovered in a
particular time can be calculated.

During operation of this arrangement it is ensured that all the valves in the
slurry and reagent line are open. Once the experiment is over the solids are
allowed to settle as it is and some retention time is given. The Mud level
index or the level of solids settled in the tray is noted from the sale attached
in the tray. Also moisture of the sample is taken at different interval of time
from different locations (samples are taken from space near scale 1, 2 and
3).
The graph is plotted for settling profile (as shown in FIG. 3) obtained from
different reagents and also the variation of moisture contained in the solids.
The analysis of data obtained from the experiment helps us in finding out the
optimum dosage range in which the particles settles as desired and the
settling profile developed will help in properly utilizing the pond space. The
data also helps in finding the maximum dosing limit which is very critical as
above certain dosage range there is no improvement in the dewatering and it
also acts in reverse phenomena and makes the cake spongy which leads to
entrapment of moisture within the cake and may lead to quick filling of slime
pond.
Advantages:
Development of methodology and the lab scale arrangement to evaluate the
following:
• Efficient Tailings/Slime management process for all kind of coal and
minerals.
• We can measure the flow behavior as well the settling behavior of
flocculated/un-flocculated slurry in the slime pond. By arriving at the
appropriate settling profile we can accordingly have a similar
procedures for plant scale slime dam which will lead to the appropriate
settling profile at the slime dam.

• This can be used to evaluate the amount of water recovered from the
slime pond and the effectiveness/usefulness of reagent addition with
the slurries for rapid dewatering in the slime pond.
• Helps in selecting the most suitable reagent and the optimum dosage
for quick dewatering of slimes.
• Helps in finding the size wise and reagent composition wise
distribution of slimes/tailing in the pond.
• Can be used for developing and verification of mathematical model for
settling of solids in the slimes/tailing pond.
• The dimension of tray can be altered accordingly for studying the
settling behavior for slimes containing high quantity of ultrafines.
Higher ultrafine content slime have poor settling characteristic and
require more retention time to settle , which calls for longer and
deeper slime/tailings pond. The setup has provision to change the tray
of different length to study the settling process accordingly.

WE CLAIM:
1. An arrangement (200) for determining settling profile of mineral ore
slimes, in a slime dam, the arrangement (200) comprising:
- a slurry tank (204) and a reagent tank (208);
- an inline mixing means (212) coupled to the slurry tank (204) and the
reagent tank (208) for receiving and mixing slurry and reagent to
generate flocculated slime, the inline mixing means (212) configured
to convey the flocculated slime to a calibrated tray (216); wherein
the calibrated tray (216) is constructed to receive the flocculated
slime, and comprising a plurality of scales (220) separated at a
distance in line of flow of the flocculated slime, the plurality of scales
(220) configured to assess mud level index of the settled solid against
the dose level of the reagent and time to determine a settling profile
for the mineral ore slime as well as determine optimum value of the
reagent for settling of mineral ore.
2. The arrangement (200) as claimed in claim 1, wherein the calibrated
tray (216) is inclined at an angle 1-7 deg. clockwise.
3.The arrangement (200) as claimed in claim 1, wherein a tap is
positioned at the end of the calibrated tray (216) to collect clear water.
4.The arrangement (200) as claimed in claim 1, wherein the calibrated
tray (216) is height adjustable.
5.The arrangement (200) as claimed in claim 1, wherein the calibrated
tray (216) comprises a length adjustable means.

6.The arrangement (200) as claimed in claim 1, wherein the slurry tank
(204) and the reagent tank (208) comprises agitator for continuous
agitation of the slurry and reagent.