Field of the Invention The present invention relates to dryer for drying a sample of a mineral material.

Throughout this specification the term "mineral material" is used for any type of geological material including any type of mined materials, such as ores, and fragments thereof .

Further, throughout this specification the term "tray" is used for any suitable material portion, plate container or the like on which or in which a sample, such as a sample of the mineral material, can be positioned.

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 damagechanges ) may be as long as 11 hours. Further it is often required to determine the moisture content of the mineral material, such as iron ore. The moisture content influences a value of the iron ore cargo and also influences safety aspects for shipment of the ore .

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; a heater for heating the mineral sample in the loading region from a position below the mineral sample; 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;

a weighing component for determining a quantity that relates to a weight of the mineral sample and is arranged to provide an output; and

a control circuitry for controlling drying of the mineral sample as a function of the output of the

weighting component; wherein the dryer is arranged to control drying of the mineral sample as a function of a rate of weight loss of the mineral sample. 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 heater may be provided in any suitable form, such as a resistive or oil-based heater (such as a hotplate) or an induction heater.

The control circuitry may be arranged to control the source of radiation and/or the heater as a function of the output of the weighing component.

The weighing component may be arranged to determine the weight, weight loss or rate of weight loss of the mineral sample during drying in a continuous or periodic manner, such as in predetermined intervals. Further, the weighing component may be arranged to determine the weight before and after drying. The dryer may be arranged such that the weighing component determines the weight of the mineral sample together with that of the heater. The dryer may also comprise a tray for the mineral sample and may be arranged such that the weighing component determines the weight of the mineral sample together with that of the heater and the tray. Alternatively, the dryer may be arranged such that the weighing component determines the weight of the mineral sample independent from that of the heater. Further, the dryer may comprise a tray for the mineral sample and may be arranged such that the weighing component determines the weight of the mineral sample and the tray independent from that of the heater.

In a first embodiment the heater, which may for example be an electrical or oil-based heating plate, is positioned below, and in direct or indirect contact with, a tray for receiving the mineral sample and the weighing component is arranged to lift the tray with the mineral sample above the heater for weighing the tray with the mineral sample without the heater. The weighing component may comprise suitable projections that may protrude through a portion of the heater and that enable lifting the tray above the heater . In an alternative second embodiment at least a portion of the heater is positioned at a location that is spaced apart from a tray for receiving mineral sample. For example, the heater may be an induction heater and an inductor of the induction heater may be positioned below and spaced apart from a tray for the mineral sample. The inductor and the weighing component may be positioned relative to each other such that the weighing component is able to weigh the mineral sample with the tray and without the inductor.

The control circuitry may be arranged for controlling the weighing component. For example, the control circuitry may be arranged to control the weighing component such that the weight is determined periodically or continuously.

The control circuitry may be arranged to determine a moisture content from a determined a rate of weight loss during drying of the mineral sample. Further, the control circuitry may be arranged to stop the drying (for example by interrupting a supply of electrical power) when the rate of weight loss is below a predetermined threshold value or substantially zero. The control circuitry may alternatively or additionally also be arranged to generate an alarm signal when the rate of weight loss is below the predetermined threshold value. The control circuitry may be arranged to control the heater and/or the source of radiation such that a drying time of the mineral sample is reduced or minimised

compared with an unregulated dryer. Further, the control circuitry may be arranged to control the heater and/or the source of radiation in a manner such that significant structural changes in the mineral sample are avoided.

The dryer may comprise a temperature sensor that is arranged to measure a temperature at a surface of the mineral sample without direct contact with that surface. For example, the temperature sensor may be an infrared temperature sensor 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 . In one embodiment, the dryer also comprises a further temperature sensor that may be an electrical sensor, such as a thermocouple, and that in use is in contact with the mineral sample. The further temperature sensor, the heater and the control circuitry may form a further feedback loop.

The dryer may further be arranged to provide information indicative of a loss of weight of the mineral sample during drying such that a moisture content of the mineral sample before the drying can be determined

retrospectively . 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;

exposing the mineral sample to heat that is directed to the mineral sample from a position below the mineral sample ;

exposing the mineral sample to radiation that is directed to the mineral sample from a position above the mineral sample, the radiation being suitable to heat the mineral sample;

determining a rate of weight loss of the mineral sample; and

controlling drying of the mineral sample as a

function of the rate of weight loss. The radiation may be any type of radiation that is suitable for heating the mineral sample, such a microwave radiation, and in one specific example is thermal infrared radiation .

The method may further comprise determining a moisture content of the mineral sample by comparing weights of the mineral sample before and after the drying. 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 an 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 sample 12 such as a mineral sample. An example for a mineral sample is iron ore which is typically pre-processed into a powder form prior to drying. An iron ore sample typically has a moisture content of approximately 10 percent. By heating the sample 12 to a suitable temperature, the moisture content will eventually be reduced to a minimum amount. For an iron ore sample, a suitable temperature typically is above 100 ^° C and below 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 is in the form of an oven. The oven 10 comprises a loading region 14 for loading the sample 12. The oven 10 further comprises a heater 18 for heating the sample 12 from a position below the sample 12 when the sample 12 is positioned in the tray 16 within the oven 10.

The heater 18 is in the form of a resistive hotplate. In this example, the hotplate 18 is located such that the tray 16 can be positioned directly on the hotplate 18. 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 oil-based heater. The oven further comprises a source of radiation 20 which in this particular example is in the form of an infrared lamp. The infrared lamp 20 is positioned such that the sample 12 can be exposed with infrared radiation from a position above the sample 12.

The oven 10 further comprises a weighing component 22 for determining a weight of the sample 12. The weighting component 22 is positioned below the hotplate 18. In this embodiment the component 22 has projections (such as pins, not shown) that project through apertures of the hotplate 18. The component 22 is arranged such that the tray 16 with the sample can be lifted above the hotplate 18 using the projections. The lifting is achieved using any

suitable means and in this embodiment the component 22 includes pneumatic cylinders 17 that enable lifting of the component 22 and consequently the tray 16 with the sample above the hotplate 18 such that the weight of the sample with the tray 16 can be determined independent form that of the hotplate 18. Lifting of the tray 16 with the sample in this manner has the advantage that weight measurements of the sample can be conducted more accurately. For example, the electrical cables may extend from the

hotplate, and a change in a position of the electrical cables could result in a change in a measured weight if the weight cannot be determined independent from that of the hotplate 18, which is avoided by the described

embodiment of the present invention.

In an alternative embodiment the hotplate 18 may be replaced with an induction heater. The induction heater has an inductor that is arranged to heat the sample by induction either directly or indirectly via another component, such as a tray in or on which the sample is positioned. The inductor has electrical contact leads, but is positioned spaced apart from the tray 16 with the sample 12. The inductor and the weighing component 22 are positioned such that the weighing component 22 can weigh the sample 12 with the tray 16 without the inductor. The component 22 may determine the weight of the sample 12 in the tray 16 continuously. However, in one specific embodiment the component 22 is arranged to determine the weight periodically (for example every 5 minutes or in any other suitable intervals) until a change in weight is no longer detectable and the sample consequently is dry.

Alternatively or additionally the component 22 may also be arranged to determine the weight of the sample and the tray 16 before and after the drying process.

The oven 10 has a sensor for measuring a temperature of the sample, for example, on a surface of the sample 12. The sensor may be a non-contact sensor or a contact sensor. In this particular embodiment as shown in Figure 1, the oven 10 comprises a non-contact sensor 24 in the form of an infrared sensor or a camera which determines the temperature of a top surface of the sample 12 by measuring infrared radiation emitted from that top surface of the sample 12. By determining the temperature of the surface of the sample 12, it can be ensured that the sample 12 is not overheated.

In this particular example, the oven 10 comprises a further temperature sensor in the form of a thermocouple which is placed below the hotplate 18 and measures the temperature in the proximity of the hotplate 18.

The oven 10 has a control circuitry 27 for controlling the heater and/or the source of radiation as a function of the determined weight of the sample 12. For example, the temperature and/or the intensity of radiation that is measured by the temperature sensor may be controlled. In the embodiment shown in Figure 1, the infrared lamp 20, the infrared temperature sensor 24 and the control circuitry form a feedback loop. Similarly, the hotplate 18, the thermocouple 26 and the control circuitry form a feedback loop.

The oven 10 further comprises a processor (not shown) which determines the weight as a function of time. As such, a rate of weight loss per time during drying of the sample 12 can be determined. Generally, the weight as a function of time during the drying process can typically be described by an exponential curve that reaches

saturation after a certain time. In this particular example, when the rate of weight loss per time has reached a threshold value which may for example be substantially zero, the control circuitry 27 stops the drying process by switching off the hotplate 18 and the infrared lamp 20 and provides 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.

Furthermore, by determining the weight loss as a function of time during the drying process, a moisture content of the sample 12 prior to drying may be determined. For example, the weights of the sample 12 before and after drying may be measured to determine the moisture content of the sample 12 before drying.

The moisture content of the sample 12 may be of

significant interest. In particular, if the moisture content of the load exceeds a particular limit, water eventually settles at the top of the ore in the ship where it follows a movement of the ship when at sea. Such movement of the water poses a safety hazard. By

determining the total amount of moisture content, it can be ensured that an average moisture content of the

material is below a threshold value for safe shipment. Also, it is advantageous to determine the moisture content for commercial reasons since the value of iron ore per weight is influenced by the moisture content.

Referring now to Figure 2, there is shown a flow chart illustrating a method 30 of drying a sample 12. In a first step 32, a sample is loaded into a loading region of a dryer. When the sample is positioned within the dryer, the sample is exposed to heat that is directed to the 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 sample (step 36) . The radiation is suitable for heating the sample, such as infrared

radiation or microwave radiation. In a next step 38, a weight of the sample is determined. Subsequently, the drying of the sample is controlled as a function of a rate of reduction in weight during drying of the sample (step 40) .

As shown in the flowchart, the method 30 comprises a further step 40 of determining moisture content of the sample by comparing a weight before and after the drying.

Using the method 30 as described above and shown in Figure 2, the drying time of an iron ore sample in comparison with conventional drying times using a conventional dryer may significantly be reduced to less than an hour, advantageously to approximately 20 minutes. In contrast, using a conventional dryer, the iron ore sample is placed within the dryer and heated for

approximately 4 hours. Subsequently, the sample is removed from the dryer in order to determine the weight of the sample. After placing the sample back into the dryer and heating the sample for an additional time period in a range of 30 minutes to 1 hour, the weight of the sample is measured in order to determine the weight loss. The above described steps are repeated until the weight loss reaches approximately zero. The time for completing such a drying process is typically in the range of 11 hours.

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 .