AU779236B2

AU779236B2 - Apparatus and method of determining composition of mineral sands

Info

Publication number: AU779236B2
Application number: AU35312/00A
Authority: AU
Inventors: Nicholas George Cutmore; Thressa Grace Rowlands
Original assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Current assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Priority date: 1999-05-27
Filing date: 2000-05-15
Publication date: 2005-01-13
Anticipated expiration: 2020-05-15
Also published as: AU3531200A

Description

I b

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH

ORGANISATION

Invention Title: APPARATUS AND METHOD OF DETERMINING COMPOSITION OF MINERAL SANDS The following statement is a full description of this invention, including the best method of performing it known to me/us: a 2 APPARATUS AND METHOD OF DETERMINING COMPOSITION OF MINERAL SANDS The present invention relates to a method and apparatus for determining the composition of mineral sands.

One of the main products derived from mineral sands is titanium dioxide. Titanium dioxide is used primarily as an opaque white pigment for paint, plastics and paper.

Consequently, impurities such as iron which can discolour 10 titanium dioxide destroy its utility as a white pigment.

Titanium dioxide can be separated from many contaminants by :'.".chlorinating a source of crude titanium dioxide in a fluidised bed of a reductant such as coke. Titanium tetrachloride and the chlorides of most of the contaminant metals have different boiling points and can be separated by this means. The titanium tetrachloride is then oxidised to produce pure titanium dioxide.

Naturally occurring rutile was initially used as feed to the chlorinator. However, as demand for titanium dioxide grew and the price of natural rutile increased, the incentive to discover a means of using ilmenite grew. Ilmenite is essentially an ore comprising titanium dioxide and ferric oxide and is a far more prevalent titaniferous ore than natural rutile.

The Becher process and variants of it provided a means of producing synthetic rutile from ilmenite.

However, the process parameters and post-treatment steps are determined by the composition of the ilmenite which is the major constituent of most mineral sands. The Becher process essentially involves heating ilmenite to an elevated temperature in a reducing atmosphere to reduce iron oxides contained in the ilmenite to metallic iron.

The metallic iron is subsequently removed by effectively rusting the iron away from the titania or by acid leaching.

Conventional analysis procedures to determine the constituents of mineral sands are based on wet chemical analyses, sometimes involving concentrated acids such as 3 concentrated hydofluoric acid. Wet chemical analysis is time consuming and involves the use of hazardous chemicals.

Consequently, alternative techniques that permit the direct and rapid determination of the chemical composition of mineral sands that do not involve use of hazardous chemicals offers considerable advantages.

The present invention is based on the discovery that there is a correlation between changes in the characteristics of a microwave resonant cavity induced by a 10 sample of mineral sands and the chemical composition of the sample.

:.-Accordingly the present invention provides a :.:'-method of analysing a sample of mineral sands to determine its composition which method includes the steps of launching a microwave signal into a measurement chamber comprising a microwave resonant cavity containing a mineral sands sample, receiving a signal from the resonant cavity, determining changes in a characteristic of the resonant cavity induced by the mineral sands sample and producing a S 20 measure of a component of the mineral sands sample from the determined changes in the resonant characteristic.

The invention also provides apparatus for analysing a sample of mineral sands to determine its chemical composition, the apparatus including containing means for containing a sample of mineral sands in a microwave resonant cavity, launching means for launching a microwave signal into the microwave resonant cavity, receiving means for receiving a signal from the resonant cavity and processing means for determining changes in a characteristic of the resonant cavity induced by the mineral sands sample and for producing a measure of a component of the mineral sands sample from determined changes in the resonant characteristic.

Characteristics of the resonant cavity that may be used in determining the chemical composition of a sample of mineral sands include resonant frequency and resonant power. Preferably, both changes in resonant frequency and

O

4 resonant power induced by the sample of mineral sands, as shown in Fig. 2 are used to determine the chemical composition of the sample.

Typically, mineral constituents such as wt% iron titanate (FeT) and FeO are determined using equations of the form: Predicted wt.% FeT a. al. f(AP) a 2 f(AF) (1) Predicted wt.% FeO bo bl. f(AP) b 2 f(AF) (2) where AP is the change in resonant power at the resonant frequency induced by the sample of minerals sands, AF is the change in resonant frequency induced by the sample of 15 mineral sands, ao bo are fitting constants and al, a 2 bl and b 2 are correlation coefficients.

The correlation coefficients in equations and are derived by correlating chemical composition determined by conventional wet chemical analysis with determined changes in resonant frequency and resonant power for the same sample of mineral sands. Other components such as the wt% Fe 2

O

3 and wt% TiO 2 may also be measured by similar means.

•Preferably only one resonant cavity is used and the change in resonant characteristic induced by the sample is determined by measuring the characteristic with and without the sample.

Preferably the resonant cavity is cylindrical but other resonant cavities of other shapes are equally suitable. In a preferred embodiment of the invention, a sample to be analysed is placed in a dielectric tube that is located along the axis of a cylindrical resonant cavity having a resonant frequency in the range from 1 to 4 Ghz, as shown in Fig. 1.

A preferred embodiment of apparatus according to the invention is illustrated with reference to the accompanying drawings in which Figure 1 represents a schematic illustration of a cylindrical microwave resonator 5 and sample container for analysis of mineral sands. Figure 2 is a graph illustrating the change in return signal power and resonant frequency when a microwave resonant cavity is empty and when it is loaded; and Figure 3 is a plot of typical data obtained using the method described in the example.

Figure 1 illustrates a cylindrical resonant cavity (TE010). A glass test tube 2 filled with a sample of mineral sands is located within the resonant cavity 1 10 aligned along one of the axes of the resonant cavity. A microwave signal is launched into the resonant cavity from a tunable microwave oscillator 3 via a circulator 4. A return microwave signal is directed by the circulator 4 to a detector 5. The detector 5 records the change in resonant power and resonant frequency induced by the sample. The change in resonant power and resonant frequency induced by the sample and recorded by the detector is schematically illustrated in Figure 2.

EXAMPLE

An empty glass test tube is placed in an opening of a cylindrical resonant cavity, having a resonant frequency of 3 Ghz, so that it is parallel and coincident with the cavity axis. The microwave resonant frequency and microwave resonant power of the cavity is then measured to provide Fempty and Pempty of the cavity. The glass test tube is then filled with a sample of mineral sands and the tube gently vibrated to compact the sample. The test tube packed with the sample is then placed in the microwave resonant cavity and the microwave resonant frequency and microwave resonant power of the cavity again determined to provide Fsampie and Psample.

The change in resonant power AP Psample Pempty is calculated and the change in resonant frequency AF 1 Fempty is also calculated. The wt% FeO and wt% iron titanate is then determined using equations and Typical data obtained is shown in Fig.3.

Claims

1. A method of analysing a sample of mineral sands to determine its composition, the method including the steps of launching a microwave signal into a measurement chamber which includes a microwave resonant cavity containing a sample of mineral sands, receiving a signal from the resonant cavity, determining changes in a characteristic of the resonant cavity induced by the sample of mineral sands, and producing a measure of a component of the sample of mineral sands from the determined changes in the resonant characteristic.

2. A method according to claim i, wherein the 15 characteristic of the resonant chamber is resonant frequency, resonant power or both.

3. A method according to claim 1 or claim 2, which includes the step of measuring changes in resonant power I. and resonant frequency induced by the sample of mineral 20 sands.

4. A method according to any one of claims 1 to 3, wherein the measurement chamber consists of a single resonant cavity and the change in a characteristic of the resonant cavity induced by the sample of mineral sands is determined by measuring the characteristic with and without the sample of mineral sands.

A method according to any one of the preceding claims, wherein the resonant cavity has a resonant frequency in a range from 1 to 4 Ghz.

6. Apparatus for analysing a sample of mineral sands to determine its chemical composition when used in the method of any one of claims 1 to 5, the apparatus including containing means for containing a sample of mineral sands in a microwave resonant cavity, launching means for launching a microwave signal into the microwave resonant cavity, receiving means for receiving a signal from the H:\narie&g\Keep\Speci\PQ 0634 Conlete.doc 16/1/04 7 microwave resonant cavity, and processing means for determining changes in a characteristic of the resonant cavity induced by the sample of mineral sands and for producing a measure of a component of the sample of mineral sands from changes in the resonant characteristic.

7. Apparatus according to claim 6, wherein the characteristic of the resonant cavity is resonant frequency, resonant power or both.

8. Apparatus according to either claim 6 or claim 7, wherein the characteristic of the resonant cavity is both resonant frequency and resonant power.

9. Apparatus according to any one of claims 6 to 8, wherein the containing means consists of a single chamber 15 and the change in resonant characteristic is determined by o ""measuring the characteristic with and without the sample in the chamber.

Apparatus according to any one of claims 6 to 9, wherein the resonant cavity has a resonant frequency in a 20 range from 1 to 4 Ghz.

11. Apparatus according to any one of claims 6 to wherein the resonant cavity is cylindrical.

12. Apparatus according to any one of claims 6 to 11, wherein the containing means is a dielectric tube that is located along an axis of a cylindrical resonant cavity.

13. A method substantially as hereinbefore described with reference to the Example. Dated this 16th day of November 2004 COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H: \wmrieag\Keep\Speci\PQ 0634 Conpete.doc 16/11/04