TRADUCTION NON-DISPONIBLE

URANIUM EXTRACTION

Abrégé anglais

ABSTRACT OF DISCLOSURE
A process for extracting uranium values from a pyrite
concentrate containing at least 20% by weight sulphur
and at least 50 grams per ton of uranium, calculated at
U308, including the steps of roasting the concentrate at
a temperature in the range 650 to 750°C to convert the
uranium to uranium sulphate, and solubilising the uranium
sulphate in the roasted concentrate by means of a sulphuric
acid leach of pH not exceeding 3.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS
1.
A process for extracting uranium values from a pyrite con-
centrate containing at least 20% by weight sulphur and at
least 50 grams per ton of uranium, calculated as U3O8,
including the steps of roasting the concentrate to convert
the uranium to uranium sulphate, and solubilising the
uranium sulphate in the roasted concentrate by means of an
acid leach solution of pH not exceeding 3.
2.
A process according to claim 1 wherein the roast is carried
out at a temperature in the range 650 to 750°C.
3.
A process according to claim 1 wherein the roast is carried
out at a temperature in the range 650 to 700°C.
4.
A process according to claim 1 wherein the pyrite concentrate
contains 20 to 50% by weight sulphur.
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5.
A process according to claim 1 wherein the pyrite con-
centrate contains 30 to 40% by weight sulphur.
6.
A process according to claim 1 wherein the pyrite con-
centrate contains uranium calculated at U3O8, in the range
of 50 grams to 2000 grams per ton.
7.
A process according to claim 1 wherein the pH of the leach
solution is in the range 1 to 3.
8.
A process according to claim 7 wherein the leach solution is a
sulphuric acid leach.
9.
A process for extracting uranium values from a pyrite con-
centrate containing at least 20% by weight sulphur and at
least 50 grams per ton of uranium, calculated at U308, in-
cluding the steps of roasting the concentrate at a temperature
in the range 650 to 750°C to convert the uranium to uranium
sulphate, and solubilising the uranium sulphate in the roasted
concentrate by means of a sulphuric acid leach of pH not
exceeding 3.
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10.
A process according to claim 9 wherein the pH of the
leach solution is in the range 1 to 3.
A process according to claim 9 wherein the roast is
carried out at a temperature in the range 650°C to 700°C.
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Description

:l~93~3~ ;
T~IIS -invention re'lat'es to the extraction of uraniLIm values
from pyrite (FeS2) concentrates.
Pyr-ite concentrates are obtained, for example, by flotation
of pyrite ores. Such concentrates con-tain at least 20% by
weight sulphur and often gold, uranium and base meta'ls'in
addition to iron. Some pyrite concentrates contain
. a relat;vely high uranium content, i.e. a uranium content
. of at least 50 grams per ton~.calculated as U308. Thls-
invention is concerned ~lith the extraction of uranium values
from pyrite concentrates which contain at least 50 (Jrams per
ton of uran;um~ calculatecl as U308, and more particu'larly
with such concentrates which have a uranium content in the
rarige 50 grams to 2000 grams per ton, again calculated as
U308 .. ::
1~ According to the present invention, a pro'c'ess for extracting
uranium values from a pyrite concentrate as deFined a~ove
includes the steps of roasting the concentrate to convert
the uranium to uranium sulphate, and solubilising uranium
sulphate in the roasted concentrate by means of an acid
leach oF pH not exceeding 3;
The first step in the process is the roasting of the pyrite
concentrate. This roast converts the uranium values in the
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concentrate to uranium sulphate. The roast is preferably
carried out at a temperature in the range of 650 to 750C
and more preferably in the range 650 to 700C. Roasting
temperatures in excess of 750C are undesirable because
refractories tend to forlll at these temperatures and this
is disadvantageous.
The roast is preferably carried out in a standard fluidised
bed roaster such as those illustrated in the article oF
R.B. Thompson and R. Roesner ''Fluid ~ed Roasting - Principles
and Practice" in "Extractive Metallurgy of Copper, Nickel and
Cobalt" by Paul Queneau, Interscience 1961.
The extraction of uranium values from the pyrite concentrate
is improved by carrying out the roast in the presence of a
suitable alkali metal salt such as sulphate or carbonate or
alkali metal hydroxide. The preferred alkali metal is
sodium and the preferred salt is the sulphate. Only small
quantities of the salt or hydroxide are required to improve
the extraction. The salt or hydroxide is typically used in
an amol1nt of 1 to 10%, preferably 1 to 5%, by weight of the
concentrate.
The residence time in the roaster ~ill Yary according to the
nature of the concentrate and the degree of conversion of
uranium to uranium sulphate required. In general, the
longer the residence time~ ~he better the final extraction.
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~ 3~3
The uranium sulphate is ex-tracted frolll the roas~ed con~
centrate by means of an acid leach of pH no~ exceecling
3. The p~l oF the acid leach i5 typically in the range
1 to 3. The preferred acid leach is sulphuric acid. The
leach time can vary~ but is typically 20 - 120 minutes.
The pyrite concentrate is generally fed to the roasting
step either as a dry mass or as a slurry. When the con
centrate is in the fornl of a slurry, the water content
will generally be less than 50% by weight of the slurry.
10 - The pyrite concentrate will typically have a sulphur
content of 20 to 50%5 generally 30 to ~0%, by weight.
Any base metals such as copper, cobolt and nickel present
in the pyrite concen~rate are simultaneously extracted
with the uraniunl values. The uraniuln values from the
uranium rich leach solution may be recovered by methods
known in the art such as solvent extraction or iron ex-
change .
The process of the invention provides a very efFective
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~3~3~3~33~L
extrac~ion of uran-ium values from pyrite concentrates and
a far better extract-ion than has been achieved in the past
using a stron~ acidic''leach on its own.
The invention is illustrated by means of the fo'llowing
examples.
'EXAMPLE i
A pyrite concentrate, obta;ned from -the flotation of a
~,' pryite ore was found on analysis to contain 600 grams per
ton of uranium, calculated as U308, and a sulphur content
of 35% by weight.
The pyrlte concentrate was roasted -in a standarcl f1uidisecl bed
roaster at 6~0C for an average period of 3 hours in the presence
of sodium sulphate. The sodium su'lphate was present in an
amount of 2% by weight of the concentrate. The roasted ~-~
concentrate was then subiected to a sulphuric acid leach of pH3
~ ' for 60 minutes.
( ,i
Analysis of the 'leach solution showed a uranium extraction
in excess o-F 90%.
''E MPLE 2
A pyrite concentrate was found on analysis to contain 4'l%
by ~eight su'lphur and 600 grams per ton of uranium~ calculated
as U308
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~, . .. . . .
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3~3~33'~
This concentrate was subjected to the same procedure as
Example 19 save ~hat in a first experiment a roast temperature
of 680C ;n the absence of sodium sulphate was used and in a
secolld experiment a ~emperature of 690C in the presence of
4% by weight sodiunl sulphate was used. The leach tilne in each
case was 20 minutes. The results obtained were as follows:
.
' Roast Temperature Na2$04 .~ % U Extraction
680 o 25
690 4 91
: :
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' EXAMPLE 3
_ . :
A pyrite concentrate was found on analysis to contain 24%
by weigh~ sulphur and 300 grarns per ton of uranium, calculated
as U88
~:.. ~) `' .
This concentrate was subjected to the same procedure as in
Example 1~ save that the t~mperatures and sodium sulphate
contents as set out below and a sulphuric acid leach solution of
pH 1,1 were used:
Roast Temperature . Na2S04 % .. % U Extraction
665 0 41
'. ~0 680 2 48
680 4 73
660 6 8~