APPLICATIONS
Our dewatering screens can be applied in the processing of a wide range of materials including:
• Sand
• Aggregates (construction)
• Construction and Demolition Waste
• Iron Ore
• Coal
• Other Mineral Ores
WHY MEKA DEWATERING SCREEN?
• Maximum dewatering of your sand product
High frequency vibrating motors ensure a high power to area ratio ensuring the most efficient dewatering of your sand product.
• Maximum wear resistance
Replaceable polyurethane side wall protection on the MDS screen minimises material on steel contact, reducing wear and increasing the working life of the machine. Fully rubber lined discharge chutes for maximum wear resistance
• Efficient grading of your sand product
Deeper bed depth allows screens to remove more moisture and retain highest percentage of saleable product
• Ease of maintenance
Modular Polyurethane non-bolted panels as standard for ease of maintenance.
HIGHLIGHTS
• Adjustable high g-forces, drier Product
• Adjustable incline (0° to 5°) (standard is 5° incline unless otherwise specified at the time of order)
• Stress relieved, fabricated motor bridge
• Steel coil springs
• Can be used as a trash screen
What is a dewatering screen?
Any material that comes into contact with water
will get wet. Material needs to be washed or transported as concentrate and
waste pulp in the enrichment of the ore for the production of the aggregate and
sand necessary for ready-mixed concrete production in ore preparation
facilities and in the construction sector.
Finely ground sand or concentrates that are to
be transported by ship should have 5% water content. Otherwise, the material in
the ship's hold will liquefy due to the movement of the ship over waves, making
it behave like water, and may cause the ship to sink. Furthermore,
transportation costs are increased by the water content of the ore. For this
reason, moist materials must be dehumidified.
It is possible to reduce the humidity of wet
material to below 1% in a furnace at a temperature of 105 degrees. This is a
costly operation, and it is more economical to dry the remaining surface
moisture when the free water in wet or washed materials is removed through
special treatments.
After a certain stage, washed sand must be
purged of free water prior to use in aqueous concentrate, for transportation or
for the following process. Dewatering processes remove the free water from
liquid-solid mixtures through the use of screens or centrifugal force.
For which processes/applications are
dewatering screens used?
The simplest and least costly dewatering
process involves leaving the material in a pile and waiting for the water in
the material to filter out. This is a time consuming process and requires a large
storage area, and is applied in businesses have no time or space constraints.
Dewatering screens quickly remove free water
from the material and reduce its moisture to a level that can be transported,
used, or dried on belt conveyors.
After washing the salt, clay, lime and waste
from concentrate, waste, coal, sea or river sand, dewatering screens are used
to remove the free water from the material.
Dewatering screens are also used for the dry
storage of waste produced by ore preparation and enrichment facilities, or
before dehydration.
What are the main criteria to follow when
selecting a dewatering screen?
Dewatering screens are usually horizontal or
very close to horizontal. The screen opening and the direction, amplitude and
frequency of the vibration are selected based on the size of the solid to be
separated from the water and the expected outcome of the process.
If the flow rate of the liquid+solid to be
dehydrated is too high, water will flow over the screen alongside the material
without passing through sieve during dewatering process, defeating the object
of the exercise. Using multiple dewatering screens side by side can overcome
this problem, but in such cases, the dewatering process will be uneconomical
and so the density of the pulp should be increased first by subjecting the
solid+liquid mixture to a cyclone treatment before treating with a dewatering
screen.
What are the main criteria to be followed
when selecting a dewatering screen?
·
The
inclination of dewatering screen is between 0 and 5 degrees, and these screens
operate at a frequency of 1000–1500 rpm. If necessary, the screen sieve can be
moved in the opposite direction to its inclination.
·
The
screen opening should be selected based on the size of the material to be
dewatered. As the material size increases, so should the screen opening, and
can be as small as 45 microns for small-sized materials, and up to up to 500
microns for larger materials.
·
For
example, screens with a 250–500 micron screen opening are used for dewatering
coal in sizes larger than 6.3 mm. If the part under the screen contains coal,
it is evaluated separately – the screen opening for 2 mm waste iron ore is
around 100 microns.
·
Motion
is provided by two linear motion vibrators operating in tandem. These vibrators
can be connected to the screen sieve in the same direction or vertically. By
changing the direction and weight angles of the vibrators, the screen vibration
can be optimized to suit the operating environment.
·
Unbalanced
weighted vibration motors are used in dewatering screens. Each of the
unbalanced weights attached to either side of the shaft have two parts that can
slide over the other. The vibration characteristics can be changed by changing
the position of the unbalanced weights placed on top of each other on either
side of the shaft in symmetry.
·
The
weights on the vibration motors of the screen should be located symmetrically.
The imbalance created by the asymmetrical weights on the screen body prevent
the screen from running.
·
Dewatering
screens generally feature a single-layer moving screen system with an
adjustable slope, and contain linear channels that collect the water as it
filters through to below.
·
If
the screen vibration is insufficient, the material will not accumulate on the
screen and the water-solid separation will be inefficient. If screen vibration
is too high, on the other hand, the water will flow over the screen with the
material and will not pass through the sieve.
·
Dewatering
screens are made of modular polyurethane materials. The modules have a very
long useful life and are easy to replace when necessary. Polyurethane screen
sieves, and pumps and cyclones covered with polyurethane material are protected
from abrasion.
·
In
solid+water mixtures, the material density is high and there is a tendency to
collapse. During dewatering processes, solid-water separation occurs in the
layer formed on the screen sieve, and the material close to the screen opening
forms a layer on the sieve due to the vibration. This layer naturally prevents
water from passing through the screen. Water flowing over this layer formed by
material creates also a water layer on the top that prevents the material from
passing through. In order to prevent these layers from forming, “V” shaped or
“--------“ lath-shaped sets are placed on the screen at certain intervals. When
it is necessary to obtain very clean material from the dewatering screen, the
washing water supplied to the screen sieve through the crowbar jets for washing
also prevents stratification.
·
In
properly operated dewatering screens, the layer formed by the material at the
bottom acts as a filter.
·
A
dewatering screen with holes should never be used.
·
In
ore preparation plants, very fine material may enter the concentrate or waste,
which is undesirable for the following process, and these can be removed using
dewatering screens.
·
In
dewatering screen processes, unwanted fine particles are removed as slime by
dewatering cyclones.
·
Single
cyclones are used in ore preparation and sand facilities, while 1st or 2nd
grade construction sand is produced using double cyclone dewatering screens,
especially in sand washing facilities.
·
In
double cyclone dewatering screens, sieves with two different opening sizes can
be used with a separating plate on the screen surface. This dewatering system
can be used to produce washed sand measuring 0–5 mm.
·
Dewatering
screens are used for ore preparation, and for sand and gravel production, as
well as for cleaning stagnant water, and sludge from the beds of rivers and
ports.
·
Through
the use of polyurethane screens attached to high-frequency motion system, the
moisture of the treated material can be reduced to 10–15%, bringing it to a
state in which it can be transported by belt conveyors.
MDS 1224 |
MDS 1824 |
MDS 1840 |
|
WidthxLength (mm) | 1200x2400 | 1800x2400 | 1800x4000 |
Capacity (mtph) | 90 | 150 | 210 |
Power (kW) | 2x2,88 | 2x7,35 | 2x6,1 |
Weight (kg) | 1900 | 2750 | 4300 |
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