Note: Descriptions are shown in the official language in which they were submitted.
Procedure for analysis ore blocks
The present invention concerns a procedure for radlometrically
analyslng ore blocks in said procedure the ore blocks briny India
viduall~ irradiated with gamma radiation to the purpose of exciting
x-ray fluorescence radiation and Compton-scattered radiation and
the intensities of said radiations being mutually compared in order
to determine the contents of precious minerals in the surface ox the
blocks, for sorting the blocks.
In the art is known through the Finnish Patent No. 61 ~61~ the
analyzing of ore for sorting by irradiating the blocks individually
lo with two different energy gamma radiation sources and to study the
scattering caused by the blocks with the aid of an energy-disper-
size detector. With the aid of the detector eke intensity of
scattered radiation is measured for each swallowers and from the ratio
of these intensity values is formed the result value of analysis
after first deducting the effect of background radiation from the
values that have been measured. The result value reflects the
proportion of heavy elements present in the block under examine-
lion, and the block is sorted to go into the ore category if the
result value surpasses a certain, desired threshold value.
In the course of diminishing mineral deposits in the world how-
ever! increasingly lower trade minerals have to be processed, and
this also involves the need to improve the accuracy of analysis
achieved with apparatus and procedures known in the art taking
into account in addition to the analysis contents of the irradiated
part of the whole block also the potential concentration peaks
present in the block eye. in the surface of the lump. In this case
the result value obtained from the irradiated part of the whole
block e.g. by the method of the Finnish Patent No. 61 ~61 may yield
an end result which fat 15 short of the desired result value that is
demanded of the ore.
~2~6~
The present invention seeks to provide a procedure in
which the blocks to be analyzed are irradiated in-
dividually with radiation, more especially gamma ray
diction, for the purpose of sorting in such manner that
interaction is achieved in the blocks for exciting
x-ray fluorescence radiation and Compton-scattered ray
diction and for determining with -their aid the content
of precious minerals in the surface of the blocks.
In accordance with the invention there is provided,
a procedure for analyzing ore blocks, wherein the ore
blocks are irradiated individually with gamma radiation
for accomplishing sorting on the basis of precious
mineral contents in the ore block surface, comprising:
irradiating the ore blocks to excite the X-ray flyer-
sconce radiation and Compton-scattered radiation;
measuring the intensities of the excited radiators with
at least one detector; and comparing the measured in-
densities with each other for eliciting the precious
metal contents in the block surfaces.
In an especially preferred embodiment the blocks are
irradiated with at least two gamma radiation sources
to excite the X-ray fluorescence and Compton-scattered
radiation, and at least one of the excited radiations
is caused by a source of its own.
The procedure of the invention may be applied with ad-
vantage either alone or in conjunction with a block-
analysing'method known in itself, such as the so-
called gamma scattering method known from Finnish Patent
No. 61,361. When using the procedure of the invention
in conjunction with the analyzing and sorting pro-
seedier of Finnish Patent No. 61,361, one first per-
forms by the procedure of the prior art a sorting
of the block to ore or dead rock. In conjunction
with or immediately after the analysis by the method
-pa- ~2~9~8
of prior art, the blocks are irradiated as taught
by the invention with gamma radiation for exciting
x-ray fluorescence radiation. It is possible to
use for the intensity value of the Compton-sca-ttered
radiation according to the invention, the intensity
value measured according to the method of the prior
art if the energy of the source exciting the x-ray
fluorescence radiation has been properly selected.
In that case one obtains from the intensity ratio
of the x-ray fluorescence and Compton-scattered ray
dilations measured by means of an energy-dispersive
detector, a characteristic value which reflects the
content of valuable metals in the surface of the
block. When the characteristic value exceeds the
desired threshold value, a block that was first
classified as dead rock will be sorted in the ore
category.
When using the procedure of the invention in con-
junction with the analysis procedure of the prior
art, it is possible to excite the x-ray fluorescence
either with the aid of a gamma radiation source of
its own or in the way that at least one of the ox-
citatory energy sources in the block analyzing method
is replaced with a target arrangement wherein in
front of the primary source, or sources, is
..
I
placed a plate made of an appropriate element, e.g. an clement of
the lantanide group.
The procedure of the invention may be used alone by itself when the
x-ray fluorescence and the Compton scattering both are excited by
their own primary source. In this easel too one obtains from the
ratio of intensities measured with an energy-dispersive detector a
characteristic value reflecting the content of precious minerals in
the surface of the stone. This advantageous embodiment of the
invention, too, can be used in conjunction with a bluck-analysing
lo procedure of prior art, eye. the procedure of the Finnish Patent
No. 61 3~1~ in which case the procedure of the present invention is
advantageously applied only on those blocks which have been classic
fled as dead neck in the analyzing procedure of prior art.
When applying the procedure of the invention the sorting of blocks
is carried out by a procedure of prior art in that an air blast is
directed with a compressed air nozzle against the brook meant to be
deflected from the analysis line. With the aid of an electronic
control circuit controlling the compressed air nozzle and serving
as receiver for the signals supplied by the detector and in which
in a way known in itself in the art has been predetermined a
threshold value according to the present invention for separating
between ore and dead neck.
: The invention is described in the following with reference to the
attached drawings wherein:-
.
Fig. 1 illustrates schematically an advantageous embodiment of the
invention;
Fig. 2 illustrates schematically the embodiment of Fig. l in con-
junction with the block analyzing method known through the Finnish
Patent No. 61 361;
Fig. 3 illustrates schematically another embodiment of the invent
lion when only x-ray fluorescence radiation is excited with a
I it
specific primary source;
Fig. 4 illustrates schematically an advantageous embodiment of the
invention when the Roy fluorescence radiation primary source has
been replaced with a target arrangement;
Fig. illustrates a photocell arrangement common to the embody-
mints of Figs l to 4, or determining the time for analyzing the
blocks.
As shown in Fig. 1, when the procedure is applied alone by itself
by action of the radiation source 1 is excited x-ray fluorescence
0 radiation in the block 5 constituting the object and by action of
the radiation source 2J Compton-scattered radiation. For measuring
the intensities of the radiations thus excited, there has been
placed within the radiation shield 3 a detector I, for instance an
energy-dispersively Dperatin~ scintillation detector. The signals
lo or pulses from the detector are received by the electronic
control circuit 1~3 which from the measured intensity values forms
the sorting characteristic value according to the invention and
which has been further connected to control the compressed air
Noah 15. The characteristic value that has been wormed it come
pared with a preset threshold value, in accordance with which the
block 5 is sorted to go either to the valuable ore category or to
the valueless dead rock category.
In the advantageous embodiment of Fig. I the analyzing procedure
known through the Finnish Patent Jo. 61 361 has been combined with
the procedure design illustrated by Fly. l. In this case, the block
S to be analyzed is irradiated with two mamma radiation sources
6;7J the energy of one ox them being 50 selected that the Compton
interaction is dominant while in the other photoelectric inter-
action and Compton interaction compete with each other. The intent
sties emitted by the block 5 are measured by means Do the detector
in the radiation shield I. The signals from the detector are
conducted to an electronic control circuit 16, where of the intent
sties is formed a characteristic value as taught by the Finnish
~23L96~3~
s
Patent No. 61 361J and in which the characteristic value and a
preset threshold value are compared for sorting the block S. When
the characteristic value falls short of the threshold value, the
block S is defined to be dead rock pa, which it moved by the aid
of the air jet from the compressed air nozzle to go to the left of
the radiation partition 13 in Fig. 2. The blocks Spa designated by
the analysis to be dead rock are further analyzed by the procedure
of the present invention. This is effected with an apparatus like
that of Fig. 1 and shown in the lower part of Fig. I the ratio of
the intensities of the x-ray fluorescence radiation and Compton-
scattered radiation measured with the detector 4 being processed to
give a characteristic value as taught by the invention, this char-
acteristic value owing compared with a threshold value preset in
the electronic control circuit 14. When now the characteristic
value surpasses the threshold value, the block pa is designated to
be ore, on which by the compressed air nozzle 15 is directed an air
jet to move the block over among the ore blocks 5.
In the embodiment of the invention depicted in Fig. I there has
been added within the radiation shield 8 of the apparatus arrange-
mint according to the Finnish Patent No. 61 361 fig. 2, top purity
a radiation source 1 exciting x-ray fluorescence. For source exalt-
in the Compton scattering radiation required for implementation
of the procedure of the present invention is then used the source
71 which thus is common to the analyzing modes according to the
I Finnish Patent No. 61 361 and to the present invention. If the
characteristic value in the sorting according to the Finnish Patent
No. 61 361 falls below the level required of ore, the caricaturist-
to value found in the analysis according to the present invention
will also be taken into account. When the last-mentioned kirk-
touristic value surpasses the level which Dye is required to meet
the analyzed block 5 will be classified as ore.
In the apparatus set-up of Fig. 4, the x-ray fluorescence radian
tion-excitin~ source 2 has been replaced with a target arrangement
by disposing in front of one or the other radiation source of the
Finnish Patent Jo. 61 361 a ovate 101 advantageously made e.g. of
go
an element of the lantanide group.
In the advantageous embodiments of Figs 3 and I the sorting of
blocks is effected as shown in Fig. 1, employing an electronic
control circuit I and a compressed air nozzle 15.
To the purpose of determining the starting point of the analysis
measurement, there has been disposed, slightly above the primary
sourcetdetector assembly a photocell 11l substantially similar for
each embodiment presented, which observes the arriving block 5 as
it interrupts the light beam between the light source 12 and the
photocell 11.
In the procedure of the invention, when it is being used in con-
junction with a method of analysis known in the anti such as the
gamma scattering method known through the Finnish Patent No.
61 361l it is possible to use for x-ray fluorescence radiation
source a source with about 30-lS0 key energy such as Am-241, and
for Compton radiation source a source with energy level about
300-1500 key, such as Shea. When the procedure of the invention
it applied as shown in Fig. 1 alone by itself, the energy level of
the x-ray fluorescence radiation source will be lower, about
cove.
