WO2012146392A1

WO2012146392A1 - Method and device for characterising physical properties of granular materials

Info

Publication number: WO2012146392A1
Application number: PCT/EP2012/001853
Authority: WO
Inventors: Michael Paul CIPOLD; Helge Benjamin WURST; Jan Felix BACHMANN
Original assignee: Sishen Iron Ore Company (Pty) Ltd.
Priority date: 2011-04-29
Filing date: 2012-04-30
Publication date: 2012-11-01
Also published as: AU2016200096A1; DE112012001932A5; AU2012247760A1

Abstract

The invention relates to a method and a device for characterising physical properties of granular materials. In order to obtain sufficient information about the shape and content of the individual particles of the granular material, the device for carrying out the method comprises an optical measurement section that, in order to carry out a laser triangulation, comprises at least one laser (16) and two cameras (12), an x-ray or gamma beam measuring device (18, 20) comprising an x-ray or gamma-ray source (18) and an x-ray or gamma-ray detector (20) arranged opposite said source, and a conveyor device (14) that moves the granular material along the measurement sections of the laser triangulation (12, 16) and the x-ray or gamma-ray measuring device (18, 20) in a mechanically supported manner.

Description

Method and apparatus for characterizing physical properties of granular materials

The present invention relates to a method and apparatus for measuring physical properties of granular products or materials.

In various industries, especially in mining, a characterization of the particles is of the utmost importance for the rational further processing of granular materials. The task is to specify as many criteria as possible for the execution of reprocessing processes for a given product or a given material flow. Two typical parameters of interest are, for example, the density and dimensions of the particles.

Well-established are various methods for the determination of particle sizes. In the range of particle sizes over 1 mm, sieving methods are normally used. However, sieve analysis has the disadvantage that the particle is only characterized by a single value corresponding to the mesh size of the particular sieve. This characterization is useful if the particles have a cubic or spherical shape. However, real particles in industrial operations often have other shapes, e.g. B. oblong or flat.

The determination of the density of the particles is carried out in the laboratory normally according to the Archimedian principle using heavy liquids to perform a swimming sink analysis. However, the fluids used are often toxic and banned for safety reasons. Time-,

CONFIRMATION COPY The cost and safety aspects of the sink-sink method have prompted a new approach to providing treatment criteria, in particular because the performance level of treatment plants can be maximized if readily accessible reliable information is available, based on an analysis of the treatment Density in connection with the particle size distribution and the content of valuable materials.

The invention seeks to do this by providing an improved system for the measurement of physical properties of granular products or materials.

The invention firstly provides a method for characterizing physical properties of granular materials, which is characterized

- That the individual particles of the granular material are optically measured individually non-contact and irradiated with X-rays or gamma rays, wherein the optical measurement provides data on the outer dimensions and the topography of the surfaces of the particles, while the X-ray or gamma-ray measurement data on the density distribution within the particles and / or the ingredients of the particles,

- And that the data of optical measurement with the data of the X-ray or gamma-ray measurement are linked online and in the result provide data for further processing of the granular material.

A particularly preferred embodiment of the invention provides that the X-ray or gamma-ray measurement is carried out in each case in at least two different energy levels, which provide different measurement results due to their different intensity, and that from the different measurement results of these measurements in combination with the measurement results of optical measurement additional Information about the density distribution within the particles and / or the ingredients of the particles be won. By this measure, it is possible to make much more accurate information in particular on the content and the density distribution in the particles.

The invention further relates to an apparatus for carrying out the above-described method, which is characterized by

an optical measuring section which has at least one laser and two cameras for performing a laser triangulation,

- An X-ray or gamma ray measuring device having an X-ray or gamma ray source and opposite an X-ray or gamma ray detector.

- And conveyors that mechanically support the granular material and / or move in free fall along the measuring sections.

The two measuring sections for the optical measurement and the X-ray or gamma-ray measurement can coincide locally.

In addition, the measuring sections can be assigned a measuring device for an X-ray fluorescence measurement.

Further features and advantages of the invention will become apparent from the following description and the claims.

An embodiment of the invention provides a system for measuring physical properties of granular products or materials comprising:

an optical sensor which can be attached in the region of a conveyor belt,

a light source attachable in the area of the conveyor belt, - An X-ray source and an X-ray detector, which are attachable in the region of the conveyor and

a data processing system that uses data from the optical sensor, the light source, the x-ray source, and the x-ray detector to calculate physical properties of granular products or materials that are traveling past the conveyor belt.

The at least one light source may be a laser or a photodiode.

The optical sensor may be a camera.

The two figures show:

Fig. 1: A schematic exemplary

Representation of a system for implementing the method described below;

2 shows a schematic exemplary representation of the function of the light source and of the optical sensor;

Fig. 3: a schematic exemplary

Representation for the function of the laser and the cameras.

As shown in FIG. 1, the system 10 includes at least one optical sensor in the form of a camera 12 mounted over a conveyor belt 14. The granular product or material is usually supplied to the conveyor 14 via a vibrating conveyor or a slowly moving conveyor and then moves on the conveyor 14 in the direction of the arrow A.

The conveyor 14 is suitably a conveyor with variable conveyor speeds. In the illustrated embodiment, two cameras 12 are used, the function of which will be described in detail below.

As an alternative to the cameras, position-sensitive diodes (PSD) can be used, which can be used for a scanning laser triangulation. For this function, the spatially resolving sensors (PSD) are arranged on the same plane with the scanning laser beam, which preferably runs perpendicular to the conveying direction A of the granular material.

Another way to obtain triangulation data is to use an array of spatially resolved sensors (PSD) that record the same surfaces in a light-layer geometry.

The sensor arrays require a large number of one-dimensional sensors (photodiodes), which are arranged in parallel rows next to each other. The number of photodiodes in a row should correspond to the horizontal pixel count of a standard camera sensor.

The optical design using a PSD array is comparable to the geometrical arrangement discussed above in the context of the standard design.

However, the PSD array is rasterized only in one dimension, with each readout channel or each photodiode array corresponding to a series of pixels. The centroid calculation of pixel values is replaced by a general representation of difference and sum signal values for each PSD (photodiode array).

This measure significantly reduces data throughput and enables unprecedented high refresh rates.

The electronic PSD module contains integrated circuits for the control and processing of mixed signals, for amplification, for multiplexing, for image-oriented sampling and for A / D walling. Sensor arrays with 128 rows are already available. Sensor arrays with even more rows are under development.

Refresh rates of 1,000 to 10,000 frames per second are achievable. They allow complete topographic scanning of the particles within the time that these particles require to pass the optical scanner in free fall.

Furthermore, a light emitting device is mounted above the conveyor belt 14. In the illustrated embodiment, this light emitting device is a laser 16. However, another suitable light source may equally well be used, e.g. with one or more photodiodes, which can be arranged side by side or even two-dimensionally.

For example, more than one laser 16 may be used, with the at least one laser generating 16 laser spots or a laser line that may be evaluated.

In any case, the laser 16 projects a geometric pattern onto the granular particles or materials to be evaluated. This pattern is a line in the illustrated embodiment, which is projected across the conveyor belt 14.

Advantageously, several lasers with different wavelengths can be used.

In the illustrated embodiment, the lasers 16 project light, which is reflected by the material to be measured and recorded by the two cameras 12. The laser 16 and the cameras 12 together form a first measuring section.

In the exemplary embodiment, one or more cameras 12 are arranged in the conveying direction A in front of the laser 16 and one or more cameras 12 in the conveying direction behind the laser 16. The cameras 12 and the laser 16 will be used. to accomplish a non-contact optical examination by triangulation, which is described below. According to FIG. 2, the laser 16 projects a precisely focused light spot onto a surface. An image of this laser light spot is then projected by means of a lens 24 onto a detector 26, which may be a CCD line sensor or other location-resolving measuring device, to measure the distance by means of the lens 24. The lens 24, which "sees" the laser spot, is positioned at an angle to the surface onto which the laser spot is projected, and the location of the projected laser spot on the detector depends on the distance between the object to be measured and the detector and the distance between the laser and the sensor.

An optical distance measurement in the range of 10 to 100 cm is well possible with such a laser arrangement.

A one-dimensional view gives little information about each particle on the conveyor. In the best case, a length and height profile can be obtained along a single line of the particle. In the worst case, a particle is not seen or wrong because it is not exactly centered. If the particle is detected a second time and its orientation does not exactly match the previous orientation, the measurement will show a completely different result.

In the exemplary embodiment, a two-dimensional measurement is used which uses a line laser 16, wherein the optical measuring path comprises the two cameras 12. The same effect could be achieved with a fast proximity sensor using a rotating mirror. However, the mechanical complexity of a rotating mirror would be much higher than using a standard industrial camera. Therefore, an imaging device is used. This device can be connected to a computer, which is a fast and easily configurable evaluation device. Theoretically best result can be achieved if the camera is aligned with the conveyor, which means that the camera position is aligned parallel to the conveying direction. As a result, the distance between the projection of the laser image point in the absence of a particle on the one hand and in the presence of a particle of a given height on the other hand, is maximized on the camera monitors. In this configuration, however, the back of the particle remains completely invisible from the camera's line of sight. The larger the angle α (see Figure 2), the worse the possible measurement result with a given camera. The angle α is at the same time the largest (negative) inclination of the rear surface, at which the measurement still works.

Even with α equal to 45 degrees between front and camera, there are still many particles where some parts of the surface can not be seen because they are too steep. To avoid this, the back of the particle is observed at the same time with a second camera.

To project a laser line onto particles with very steep flanks, two or more lasers can be installed to the right and left of the conveyor belt.

In addition, the perception of the particles can be improved by the use of another camera in a very shallow angle α.

The calculations described above are performed with a computer 22 that calculates, using data provided by the components discussed above, the physical properties of granular products or materials transported on the conveyor belt 14.

In the embodiment, those determined by laser triangulation

physical properties of granular products or materials the length, width and height of the particles in a three-dimensional Cartesian coordinate system. In addition, the parameters determined can be used to determine the volume of the measured particles of the granular products or materials.

In addition, at least one X-ray source 18 and an X-ray detector 20 are arranged in the region of the belt conveyor 14. These form a second measuring section.

The energy level of the x-ray source may be fixed or adjustable. Instead of the X-ray source, a gamma ray source can also be used.

In the embodiment, the detector 18 is a X-ray or gamma ray detecting line detector or flatbed area detector.

Alternatively or additionally, the detector 18 is a broad band energy detector operating in many energy levels.

Of course, the X-ray measurement and the optical measurement need not be carried out spatially separated, but can be carried out together in a common measurement section. In addition, the measurement periods are preferably coincident. This reduces the space required for the instrument and the requirements in the evaluation in the computer. In addition, the consistency of the data acquired from the various subsystems improves.

The X-radiation is examined for its energy and assigned to determine the density of each particle of the granular product or material. The intensity of the damping is determined by the atomic number of the material (materials with higher atomic numbers attenuate the X-ray radiation more strongly than materials with a low atomic number) and the thickness of the material. For this reason, the measurement of unrestrained (penetrating) radiation gives an idea of the mass distribution in each particle. In conjunction with the optical measurement, the density distribution inside each particle can be deduced therefrom.

The density of each particle of granular products or materials is preferably determined at two levels of energy by dual-energy x-ray absorptiometry (DXA). In addition to a measurement with a low energy level, in a second measurement with a higher energy level with higher permeability is used to increase the dynamic density measurement range towards larger masses per unit area. In addition, the measurement method can be extended by a subsystem with X-ray fluorescence analysis, which provides information about the elemental composition for each particle (see U.S. Patent No. 7,200,200).

Finally, X-ray measurement and triangulation measurements are combined to determine the basis weight of the individual particles of the granular products or materials and to determine the density distribution within the individual particles. Once the above parameters are known, the measured particles or materials are classified or sorted according to the material properties found. This allows for further classification with regard to certain density classes or specific size classes. For example, particles of a particular density class can be collected, ground, and chemically analyzed in the laboratory.

The sorting can be done with an automatic mechanical system that includes a sorting robot. This automatic mechanical system spatially separates the individual particles and places them in temporary or final collection containers.

Provided that the present and future positions of all detected particles are accessible and additionally the assigned ones

Physical properties are known, each particle can be sorted into a specific container, and accordingly one comprehensive set of selected criteria. For example, so-called pick-and-place robots are fast enough to detect and sort all particles once the quality parameters have been evaluated.

In the illustrated embodiment, the material is additionally transversely irradiated with X-rays or gamma rays. In addition, the surfaces of the material are measured without contact.

It should also be emphasized that the physical properties of the particles are not changed.

In another, not shown embodiment, the optical measurement is carried out without mechanical support of the particles. In particular, the measurement is proposed in free fall. In this way, the optical measurement of the entire surfaces can be performed while the particle falls onto the conveyor or falls off the conveyor.

The unsupported state is realized when all sides of the particles can be detected between two changes of the frame of reference. The state is also reached when at least one side can be reached, which is inaccessible in other transport steps due to the mechanical means of transport.

In this context, advantages arise for the mechanically unaided measurement, preferably when the topographical measurements are to be combined by scanning or frame-related images with other imaging methods in order to additionally evaluate and correct them by means of rotational movements. Multiple imaging steps can also be used to record the kinematic behavior of the particles.

Such a subsystem for the optical detection of topographical and kinematic data is preferably combined with a mechanically unsupported X-ray measurements. The measurement periods are coordinated so that the imaging on the basis of X-ray throughput Radiation operates with a sequence of high frequency and that the space-monitoring X-ray detector works one or two-dimensional, allows rapid data acquisition and is largely integrated into the particle transport system.

It should be noted that a combination of kinematic information and frame-related X-ray measurements will allow the computation of volumetric information if the particle has a spin that is not zero, thereby allowing classification of the three-dimensional spatial resolution particles.

The invention thus describes an optical method in which the particles can be characterized by the determination of all three dimensions: length, width, height - as well as the volume of the particles. In addition, from these measurements, further characterizing dimensional ratios such as the ratio of width to length can be derived.

Another important advantage of the invention is the application of the method in an online arrangement. By using an automatic sampling device, the system according to the invention can provide a continuous analysis of the density and size distribution without the intervention of laboratory personnel.

Moreover, the invention describes an optical measuring method by which the particles can be accurately characterized by determining the particles both in terms of the total or partial topography of their surfaces and in terms of their volume, combined with complementary X-ray analysis techniques, the information on provide the internal nature of the particles.

Finally, additional characteristics can be derived from the measurements, e.g. For example, the aspect ratio and density distribution within each particle.

- Claims -

Claims

claims

1. A method of characterizing physical properties of granular materials,

characterized,

- That the individual particles of granular material are optically measured individually and non-contact and are irradiated with X-rays or gamma rays, wherein the optical measurement provides data on the outer dimensions and the topography of the surfaces of the particles, while the X-ray or gamma-ray measurement of the data Density distribution within the particles and / or the ingredients of the particles provides,

2. The method according to claim 1, characterized in that the X-ray or gamma-ray measurements are carried out in each case with at least two different energy levels, which provide different measurement results due to their different intensity, and that from the different measurement results of these measurements in combination with the measurement results of the optical measurement additional information about the density distribution within the particles and / or the ingredients of the particles can be obtained.

3. The method according to claim 1 or 2, characterized in that the optical measurement is carried out with laser triangulation.

4. The method according to claim 1, characterized in that the granular material lying on a conveyor is moved past the one or more measuring sections.

5. The method according to claim 1, characterized in that the granular material is moved in free fall on the one or more measuring sections.

6. The method according to any one of claims 1 to 5, characterized in that the determination of the ingredients of the particles is supplemented by an X-ray fluorescence measurement.

7. The method according to any one of claims 1 to 6, characterized in that the particles of the granular material are finally classified based on the measurement results by size and / or shape or sorted by ingredients.

8. Apparatus for carrying out the method according to claim 1, characterized by

an optical measuring section which has at least one laser and two cameras for performing the laser triangulation,

an X-ray or gamma ray measuring device which has an X-ray or gamma ray source and, opposite, an X-ray or gamma ray detector,

9. Apparatus according to claim 8, characterized in that the measuring path for the optical measurement and the X-ray gamma ray measuring path coincide locally.

10. Device according to claims 8 or 9, characterized in that the measuring sections are additionally assigned a measuring device for an X-ray fluorescence measurement.

- Summary -