Note: Descriptions are shown in the official language in which they were submitted.
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A DRYER FOR DRYING A MINERAL SAMPLE
Field of the Invention
The present invention relates to dryer for drying a
mineral sample.
Throughout this specification the term "mineral sample" is
used for samples of any type of geological material also
including mined materials, such as ores, and fragments
thereof.
Background of the Invention
Samples of a mineral material, such as iron ore or another
material, often need to be analysed in order to determine
properties of the samples, such as an ore grade and other
chemical and structural properties. The samples of the
mineral material may be provided in a relatively small
quantity and should have material properties that are
representative of larger quantities of the mineral
material. As the moisture content has also an influence
on analyses results, the samples are usually dried before
being analysed.
Often large numbers of samples need to be analysed and the
time required for drying of the samples has a significant
influence on sample throughput. For example, a typical
Australian iron ore sample may have a moisture content of
approximately 10% and a required drying time using a
conventional dryer at a temperature of approximately 105 C
(which usually is sufficiently low to avoid mineralogical
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damage) may be as long as 11 hours. There is need for an
improved dryer that allows a reduction of the drying time.
Summary of the Invention
The present invention provides in a first aspect a dryer
for drying a mineral sample, the dryer comprising:
a loading region for receiving the mineral sample,
the loading region comprising a heater for heating the
mineral sample from a position below the mineral sample;
a component for vibrating a portion of the dryer in a
manner such that the mineral sample is agitated; and
a source of radiation, the radiation being suitable
for heating the mineral sample and the source being
arranged to direct the radiation to the mineral sample
from a position above the mineral sample;
wherein the dryer is arranged for simultaneous
heating of the mineral sample from a position below the
mineral sample and from a position above the mineral
sample during vibrating.
The source of radiation may be a source of any radiation
that is suitable for heating the mineral sample, such a
microwave radiation, and in one specific example is a
source of thermal infrared radiation.
The exposure of the mineral sample to heat form a position
below the mineral sample and radiation from a position
above the mineral sample during vibrating (and
consequently during agitating) using the dryer in
accordance with an embodiment of the present invention
results in a reduction of drying time.
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The heater of the loading region may be provided in any
suitable form, and may be a resistive, induction or oil-
based heater.
The dryer may further comprise a control circuitry that is
arranged to control at least a component of the dryer. The
control circuitry may be arranged to control the heater of
the loading region and/or the source of radiation and/or
the component for vibrating the portion of the dryer. The
control circuitry typically is arranged to control the
heater of the loading region and/or the source of
radiation in a manner such that significant structural
changes in the mineral sample are avoided. Further, the
control circuitry may be arranged to control the dryer
such that drying is interrupted when a moisture content of
the mineral sample is below a threshold value.
The dryer may comprise a temperature sensor that is
arranged to measure a temperature at a surface of the
mineral sample typically without direct contact with that
surface. For example, the temperature sensor may be an
infrared temperature sensor or a camera that is arranged
to determine the temperature of the surface of the mineral
sample as a function of infrared radiation emitted from
that surface. In this embodiment, the infrared sensor, the
source of radiation and the control circuitry may form a
feedback loop.
The apparatus may also comprise a further temperature
sensor that may be an electrical sensor, such as a
thermocouple, and that in use may be in contact with the
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mineral sample. The further temperature sensor, the heater
of the loading region and the control circuitry may form a
further feedback loop.
The dryer may further comprise a component for determining
a weight of the mineral sample during drying. The
component for determining the weight of the mineral
sample may be arranged to generate an output signal that
is indicative of the weight or a weight loss of the
mineral sample or a rate thereof.
The control circuitry may be arranged to receive the
output signal from the component for determining the
weight of the mineral sample. Further, the control
circuitry may be arranged to control components of the
dryer, such as the source of radiation and/or the heater
of the loading region and/or the component for vibrating
the base, as a function of the received output signal and
as a function of the determined weight, weight loss or
rate of weight loss during or after drying, which
typically is indicative of a remaining moisture content.
The control circuitry may also be arranged to stop the
drying (for example by interrupting a supply of electrical
power to components of the dryer) when the rate of weight
loss is below a predetermined threshold value.
The component for vibrating the portion of the dryer may
further be operable such that at least a portion of the
mineral sample is directed outside the loading region
after completion of drying. The dryer may comprise a
collection portion into which the at least a portion of
the mineral sample can be directed. In one embodiment the
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control circuitry is arranged to control the component for
vibrating such that, after reduction of a moisture content
to or below a threshold value, the component for vibrating
the mineral sample directs the mineral sample to a
collection portion of the dryer.
The present invention provides in a second aspect a method
of drying a mineral sample, the method comprising the
steps of:
loading the mineral sample into a loading region of a
dryer;
vibrating a portion of the dryer and thereby
agitating the mineral sample;
exposing the mineral sample to heat that is directed
to the mineral sample from a position below the mineral
sample during agitating;
and
exposing the mineral sample to radiation during
agitating, the radiation being directed to the mineral
sample and from a position above the mineral sample and
being suitable to heat the mineral sample.
The radiation may be any radiation that is suitable for
heating the mineral sample, such a microwave radiation,
and in one specific example is a source of thermal
infrared radiation.
The method typically comprises determining a rate of
weight loss of the mineral sample and using the control
circuitry to control the drying as a function of the rate
of reduction in weight.
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The method may further comprise a step of vibrating the
portion of the dryer in a manner such that at least a
portion of the mineral sample is directed outside the
loading region after a reduction of a moisture content to
or below a threshold value. For example, a direction of
the vibration may be modified.
The invention will be more fully understood from the
following description of specific embodiments of the
invention. The description is provided with reference to
the accompanying drawings.
Brief Description of the Drawings
Figure 1 is a schematic illustration of a dryer in
accordance with a embodiment of the present invention; and
Figure 2 is a flow chart of a method in accordance with an
embodiment of the present invention.
Detailed Description of Specific Embodiments
Referring initially to Figure 1, there is shown a
schematic illustration of a dryer 10 that is arranged to
dry a mineral sample, such as a mineral sample.
An example for a mineral sample is iron ore which is
typically pre-processed into a granular form prior to
drying. An iron ore sample typically has a moisture
content up to 10 percent. By heating the sample to a
suitable temperature, the moisture content will eventually
be reduced to a minimum amount. For an iron ore sample, a
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suitable temperature ranges from 100 to 110 C, such as
105 C in order to avoid structural change of the sample.
A person skilled in the art will appreciate that other
suitable temperature ranges are envisaged depending on the
sample.
In this particular embodiment, the dryer 10 comprises a
loading region 12 for loading the sample. Specifically,
the loading region 12 may be a space or a chamber 13
within the dryer 10 which can receive the sample or a tray
with the sample which could be placed into the drying
chamber. Samples can typically be loaded from the top.
The dryer 10 further comprises a component 14 for
vibrating a portion of the dryer 10 in a manner such that
the sample is agitated during drying. In this particular
embodiment as shown in Figure 1, the component 14 for
vibrating a portion of the dryer 10 is arranged to vibrate
the chamber 13 to agitate the sample.
The dryer 10 further comprises a heater 16 for heating the
sample from a position below the sample when the sample is
positioned in the chamber 13. Specifically, the heater 16
is arranged such that a base 17 of the chamber 13 can be
heated during vibrating. The sample may be positioned in
direct contact with the base 17. In this example, the
heater 16 is an oil-based heater. However, a person
skilled in the art will appreciate that other suitable
heaters that may or may not be in direct contact with the
sample are envisaged. For example, the heater may be an
induction heater.
The dryer 10 further comprises a source of radiation 18
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which in this particular example is in the form of an
infrared lamp. The infrared lamp 18 is positioned such
that the sample can be exposed with infrared radiation
from a position above the sample during vibrating.
The dryer 10 further comprises a sensor for measuring a
temperature of the sample, for example, on a surface of
the sample. The sensor may be a contact sensor or a non-
contact sensor, such as a suitable camera. In this
particular embodiment as shown in Figure 1, the dryer 10
comprises a non-contact sensor 20 in the form of an
infrared sensor which determines the temperature of a top
surface of the sample by measuring infrared radiation
emitted from that top surface of the sample. By
determining the temperature of the surface of the sample,
it can be ensured that the sample is not overheated. The
person skilled in the art will appreciate that other
temperature sensors are envisaged.
The dryer 10 also comprises a further temperature sensor
(not shown) in the form of a thermocouple which is placed
below the base 17 of the chamber 13 and measures the
temperature in the proximity of the base 17.
The component for vibrating the chamber 13 is also
arranged such that the sample is directed outside the
chamber 13 and into a collector 22 after drying. The
collector 22 may be in the form of a sample container.
The component 14 for vibrating the chamber 13 is arranged
such that a direction of vibration is selectable and is
posited such that for one selectable vibration direction
the dried mineral sample is directed into the collector
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22.
The dryer 10 comprises a weighing component 23 for
determining a weight of the sample. The weighing
component 23 is positioned below the base 17 of the
chamber 13 and measures the mass of the sample within the
chamber 13 when the chamber 13 is not vibrated. The
weighing component 23 determines the weight of the sample
in the chamber 13 continuously, periodically or before and
after the drying process and in one embodiment determines
a rate of weight loss. The rate of weight loss is an
indication of remaining moisture content. Generally, the
weight as a function of time during the drying process can
be described by an exponential curve that reaches
saturation after a certain time.
The dryer 10 also comprises a control circuitry (not
shown) for controlling the heater 16, the source of
radiation 18 and the component 14 for vibrating the sample
as directed by a user or as a function of the determined
weight, weight loss or rate of weight loss of the of the
sample. Further, the control circuitry is arranged to
control the weighing component 23.
In one embodiment the control circuitry is arranged to
interrupt the vibrating when the weighing component is in
use. Further, the control circuitry is arranged such that
below a threshold rate of weight loss (sample is dry or
nearly dry) the control circuitry stops the drying process
by controlling the radiation source 18 and/or the heater
16 and then effects a change in vibration direction such
that the mineral sample is directed into the collector 22.
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The control circuitry may also provide information to a
user that the drying process has been completed. For
example, an audio or visual alarm signal may be generated
to be communicated to the user.
Referring now to Figure 2, there is shown a flowchart
illustrating a method 30 of drying a sample. In a first
step 32, a mineral sample is loaded into a loading region
of a dryer. When the mineral sample is positioned within
the dryer, the sample is exposed to heat that is directed
to the mineral sample from a position below the sample
(step 34) and is exposed to radiation that is directed to
the sample from a position above the mineral sample (step
36). The radiation is suitable for heating the mineral
sample, such as infrared radiation or microwave radiation.
In a next step 38, a portion of the dryer is vibrated such
that the sample is agitated.
As shown in the flowchart, the method 30 comprises a
further step 40 of controlling the vibration such that at
least a portion of the sample is directed outside the
loading region and into a collection portion of the dryer.
In one specific embodiment the method also comprises using
a control circuitry to control the heater and/or the
source of radiation such that the drying process is
automated. This also comprises determining a rate of
weight loss of the mineral sample, which is indicative of
a moisture content of the sample and interrupting the
drying process once the rate of weight loss is below a
threshold value after which the sample is directed to a
collection portion.
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Although the invention has been described with reference
to particular examples, it will be appreciated by those
skilled in the art that the invention may be embodied in
many other forms.
