FR2621927A1 - Process for accelerated static leaching of clayey ore - Google Patents

Abstract

Process for accelerated acidic leaching of clayey uranium ore, characterised in that it comprises the following stages: - the clayey ore which has a moisture content higher than approximately 20 % is dried so that it reaches a moisture content of approximately 0 % to approximately 10 %; - the ore obtained in the preceding stage is crushed to particles with a particle size of approximately 10 mu to approximately 20 mm; - the particles are converted into the form of pellets (pelletising stage) from approximately 5 to approximately 60 mm in diameter, with the aid of a liquid and/or an acid in such quantity that the moisture content of the pellets is from approximately 13 % to approximately 21 %; - the uranium ore thus pelletised is leached (leaching stage) with the aid of a solution containing water or an acid or a mixture of water and of an acid, an acid being employed during at least one of the pelletising and leaching stages, the liquid and the acid which are employed during the pelletising and the solution employed during the leaching having to be compatible with each other, the yield of uranium dissolved in the production liquors obtained being at least approximately 85 % and especially at least approximately 90 %.

Description

PROCESS FOR ACCELERATED STATIC LIXATION OF ORE
CLAY
The invention relates to a process for accelerated static leaching of clay ore, in particular uranium or copper.

 The invention is more particularly directed to an accelerated acid leaching process for uranium clay ore.

 The accelerated acid leaching has been described, in particular in the patent application FR No. 86 00718, in a heap of uranium ore by crushing the uranium ore into granulometry particles allowing dissolution of the uranium from minus 75%, then forming pellets from the particles obtained after crushing, using a liquid, and then leaching the ore and pelletized with an acid solution, the liquid used to form the pellets and the acid used during leaching to be compatible with each other.

 This process gives good yields on rock-core ores, especially those whose mineralization is composed of pitchblende and its oxidation products, and possibly coffinite, but is inapplicable to clay ores, in particular because of the impossibility of to form pellets, which leads to percolation only at the surface and a poor efficiency of dissolution of the uranium, making heap leaching industrially inapplicable.

 However, the Applicant Company has developed a static leaching process, that is to say for ores stored, for example in piles, suitable for clay ores and which largely overcomes the disadvantages mentioned above and in particular allows to percolate industrially clay ores and obtain a very good yield of solution of uranium.

 One of the aspects of the invention is to propose an accelerated acidic acidic lixiviation process for stored clayey ores, particularly in heap, which makes possible the leaching of such ores which, without this technique, can be leached only superficially.

 Another aspect of the invention is to provide an accelerated acid leaching process for uranium ore, which makes it possible to obtain excellent uranium solution dissolution efficiencies.

 Another aspect of the invention is to propose a process for accelerated acid leaching of uranium ore, which makes it possible to exploit uranium on an industrial scale from the clay ores containing it.

 Clay ores have the distinction of being generally relatively wet.

 However, the Applicant Company has unexpectedly found that by decreasing the initial humidity of the uranium clay ore by drying, in order to regulate the moisture of the ore pelletizing on a particular interval, it is possible on the one hand to pellet the ore and secondly after leaching of the ore and pelletized to obtain very good yields of dissolution of uranium.

The accelerated acid leaching process according to the invention of uranium clay ore is characterized in that it comprises the following steps
the uranium clay ore is dried until the moisture content is at most equal to about 10.

the ore is crushed into particles of particle size less than about 20 mm,
pellets (pelletizing step) are formed from the above-mentioned particles with the aid of a liquid and / or acid added in such a quantity that the moisture during pelletizing is from about 13 g to about 21 g. %, preferably from about 15% to about 18%,
the uranium ore (leaching step) thus leached is leached with a solution containing water, or an acid, or a mixture of water and an acid, an acid being used in the during at least one of the pelletizing and leaching steps, the liquid and acid used during pelletizing and the acid used during leaching to be compatible with each other.

More specifically, the process for leaching the uranium clay ore according to the invention comprises the following steps
the clay ore having a moisture content greater than about 20%, in particular about 25%, is dried so that it reaches a moisture content of about 0% to about 10%, in particular from about 10% to about 10%. %, and preferably from about 3% to about 8% and preferably about 5%,
the ore obtained in the preceding step is crushed into particles having a particle size of from approximately 10 μm to approximately 20 mm, and preferably from approximately 500 to approximately 10 mm, and advantageously from approximately 4 to 10 mm,
the particles are pelleted (pelletizing step) with a diameter of about 5 to about 60 mm, preferably about 5 to about 20 mm, using a liquid and / or a acid, in an amount of about 120 l / t to about 200 l / t, especially from about 120 to about 160 l / t,
the uranium ore (leaching step) thus leached is pelleted with the aid of a solution consisting of an acid or water or a mixture of water and acid, an acid being used in the during one or less of the pelletizing and leaching stages, the liquid and acid used during the pelletizing process and the solution used during the lixiviation to be compatible with each other, the yield of the uranium put in solution in the production liquors obtained being at least about 85%, and preferably at least about 90%.

 In the foregoing and what follows, the term moisture in%, the ratio between the weight of water on the one hand and the sum of the weight of water and the weight of the dry ore and on the other hand by moisture in l / t, the ratio between the weight of water on the one hand and the weight of dry ore on the other.

 The clay ore treated according to the process of the invention is such that the particle size of a clay elemental particle of this ore is less than 2.

 Also defined by clay ore is an ore of which about 50%. ore particles are less than about 50.

 For the sake of clarity, the ore treated by the process according to the invention has a natural moisture of about 20% to about 25%.

 Drying is generally carried out under the following conditions: the clay ore used is in block form, about 20 to about 80 mm in size.

 Drying takes place at a temperature of about 100 to about 300 ° C, especially about 200 ° C, for a period of about 30 mm to about 4 hours.

 Drying results from a compromise between the need to use the least possible number of calories to reduce humidity, since the amount of reagents used for pelletizing leads to the desired moisture range for pelletizing. and on the other hand the fact that when the moisture of the clay ore reaches a certain value, it sticks in the apparatuses, which makes the ripple difficult, and in these conditions, the pelletization is difficult to begin, if not impossible.

 Drying should lower the moisture of the ore to such a range that it is possible to add the liquid and / or acid subsequently used in the pelletizing process and the drying moisture should be approximately 6 to about 10 '6, and preferably from about 3 to about 8, and preferably about 5 to 6.

 In the rest of the text, for reasons of convenience, particle size (or grinding or crushing) is defined by a single number, as it is frequently agreed to define first the fineness of an ore (see minerals from "Testut", document Society of Mineral Industry).

Thus, when the expression "x mm particle size" (or "x mm grinding" or "x mm crushing") is used in the rest of the text, this means that the particle size is such that that 5% of said particles are rejected by a sieve of x mm.

 In other words, a particle size of x mm means that 95% of the particles have sizes such that they pass through the sieve of x mm, it being understood that the distribution of the size of these particles is distributed according to a curve of Gauss.

 In view of this, the meaning of particle size from about 10 p to about 20 mm corresponds to the fact that the figure which determines the particle size is a number belonging to this range.

 With regard to the upper value of the figure which determines the particle size, it is in principle limited by the value beyond which the particles can no longer be formed into pellets.

 In an advantageous embodiment, the uranium ore particles have a particle size of from about 10 microns to about 20 millimeters, preferably from about 500 microns to about 10 millimeters, and preferably from about 4 millimeters to about 10 millimeters. mm.

 The ore, after drying, is put into particles of the size indicated above, by crushing or shredding, and which can be carried out in a crusher.

 With regard to the pellet shaping step, hereinafter referred to as "pelletizing", it is carried out under conditions which make it possible to obtain pellets with a moisture content of about 13 seconds to about 21%, especially from about 15% to about 18% so that the pellets can form and have a size giving them good mechanical strength.

 Indeed, beyond about 21, the pellets formed are soft and difficult to handle and for values less than about 13 '6, only the finest particles are moistened and there is no formation of pellets.

 When the pellets have been dried and left to rest for a time (before crushing) sufficient for the moisture to be homogeneous from the core to the periphery of the pellets, the pelletizing is advantageously carried out under conditions which make it possible to obtain a moisture corresponding to the lower values in the range 13-21 s.

 When the pellets are crushed immediately after drying or in a period of time which does not make it possible to obtain a homogeneous humidity of the core at the periphery of the pellets, the pelletizing is advantageously carried out under conditions such that the humidity corresponds to the higher values in the range 13-21%.

 The pellets obtained by pelletizing have an average diameter of about 5 mm to about 60 mm, especially about 5 mm to about 20 mm in diameter.

 The mean diameter of a pellet is defined below as the limit diameter towards which the arithmetic average of n diameters tends when n increases indefinitely.

 The size of the pellets depends in particular on the size of the particles of the ore, and the operating conditions of the pelletizing.

 In general, the lower value of the average diameter of the pellets is about 5 mm, given the minimum particle size of the ore particles.

 As for the upper value of the average diameter, it is about 60 mm, a diameter greater than this value not being desired because the pellets may no longer have sufficient strength in the pile, resulting in a settlement of the pellets which may be detrimental to the uranium dissolution performance during the leaching process.

 Depending on the operating conditions, the pellets advantageously have an average diameter of about 5 to about 20 mm.

 One of the advantages presented by the process of the invention is to obtain pellets having sufficient mechanical strength so that it is not necessary to subject them to an additional hardening operation, for example by heating.

 The formation of the pellets or their non-formation depends on pellet moisture, which should range from about 13% to about 21%, especially from about 15% to about 18%.

 To reach the moisture range indicated above, and taking into account the moisture of the ore particles (after drying), the total amount of liquid and / or acid used for pelletizing is from about 120 to about 200 1 per tonne of ore to be processed.

 The term "total amount of liquid and / or acid" is hereinafter referred to as the total amount of liquid used if only a liquid is used, or the total amount of acid used if only liquid is used. acid, or the sum of the amount of acid and the amount of liquid used, if both an acid and a liquid are used.

 The lower value is a critical value, because below the value of 120 1 per ton of ore to be treated, and pellets are no longer formed.

 Above 200 1 per ton of ore to be treated, the pellets become wet and soft enough to settle the pellets, which can be detrimental to the yield of solution of uranium.

 Advantageously, a total amount of liquid and / or acid of from about 120 to about 160 l per ton of ore to be treated is used.

 The size of the pellets depends on several operating parameters including the amount of liquid used during pelletizing, as well as the moisture of the ore after drying.

 Thus, for an ore whose moisture after drying is about 3 t, and in the case where the total amount of liquid and / or acid used is about 120 to about 140 l / t of ore at to treat, the pellets obtained have an average diameter of about 5 mm to about 20 mm.

 Another parameter used in the preparation of the pellets is constituted by the speed of rotation of the apparatus used to make the pellets.

 The pellets are usually formed by rotating the ore under conditions such that the particles roll on themselves.

 The peripheral rotational speed is from about 0.7 to about 1.3 m / s, preferably from about 0.85 to about 1 m / sec and preferably 0.95 m / sec.

 Below this value, the ore slides into the pelletizer, without rolling on itself, which prevents the formation of pellets.

 For a speed greater than about 1 m / s, the energy expenditure is higher and the pellets can break.

 The pellets are generally formed either in a rotating cylindrical tube, called "trommel bouletteur", or in a plate to be pelletized, the plate to be pelletized is preferred to the extent that the pellets formed are more homogeneous vis-à-vis the size .

 The duration of the pelletization advantageously has a duration of about 3 minutes to about 15 minutes. It is preferable to use a duration of about 6 minutes to about 10 minutes, for a speed of about 8 m / s.

 An extension of the residence time and / or an increase in the peripheral speed, all other things being equal, do not lead to a significant change in the size of the pellets.

 On the other hand, a prolongation of the residence time and / or an increase in the peripheral speed as well as a complementary addition of liquid very quickly lead to an increase in the size of the pellets and to a new state of equilibrium.

 The liquid and acid used during the pelletization step and the acid used during the leaching step must be compatible with each other.

 This compatibility means, in particular, that the liquid and the acid used during pelletizing must not prevent the leaching action of the acid used, that is to say in particular not diminish the dissolution efficiency of the acid. 'uranium.

 As a liquid used during pelletizing, water is advantageously used.

According to a preferred embodiment of the process of the invention
the uranium ore is crumbled into particle size of approximately 30 to 70 mm,
the clay ore having a moisture of from about 20% to about 25% is dried so that it reaches a moisture of about 5%;
the ore obtained above is crushed to obtain particles having a size of about 10 mm;
pellets are formed from the particles with the aid of water at a rate of approximately 120 to 160 liters per ton of ore to be treated;
the uranium ore thus pelleted is leached with a sulfuric acid solution at a rate of approximately 30 kg of sulfuric acid per ton of ore to be treated, expressed relative to the sulfuric acid of density about 1.8.

 During pelletizing, water and acid can be used advantageously. The acid used during pelletizing is preferably the same as that used during leaching.

 During pelletizing, water and sulfuric acid, water and nitric acid, water and hydrochloric acid can be used.

 It is advantageous to use water and sulfuric acid.

 The amount of acid used during pelletizing can vary from 0 up to about the total amount of acid required for solution of the uranium.

 The amount of acid used during pelletizing is advantageously about all of the amount necessary for the dissolution of the uranium.

 According to one embodiment of the process of the invention, all the acid used for pelletizing and leaching is about 5 kg / t to about 80 kg / t, in particular about 30 kg acid per ton of ore to be treated.

 The amount of acid used during pelletizing ranges from about 0 to about 80, especially from about 15 to about 30 kg per ton of ore to be treated, based on concentrated acid, as is generally available in the art. trade.

 The initial concentration of the acid used during pelletization ranges from about 30 to about 1800 g / l (the case of the "pure" acid at 97 6 industrial, and in particular about 300 g / l.

 The amount of sulfuric acid used in pelletizing generally depends on the ore to be treated.

 For some ores, the uranium dissolution performance is independent of the addition of some or all of the acid during pelletizing.

 For certain other ores, the uranium yield may be increased by adding, during the pelletizing step, a portion of the acid or all of the acid that would normally be used for leaching, if had no prior acid addition during pelletizing.

 In the case where the whole of the acid which would be in principle used during the leaching for the dissolution of the uranium is used during pelletizing, it may be advantageous to add acid during the leaching process. , for the dissolution of uranium, because a portion of the acid used in the pelletization may have been consumed by some constituents of the ore and no longer be available for the dissolution of uranium.

 In the case where a part of the acid is added after pelletizing, this acid is advantageously used in concentrated form during pelletizing and in diluted form during leaching.

 For example, during pelletizing, sulfuric acid can be used in about 75 to about 145 liters of water per tonne of ore, including about 120 liters of water per ton of ore (the initial concentration of the acid used being from about 500 g / l to about 1800 g / l) and during the leaching sulfuric acid can be used in about 100 to about 200, especially in about 150 liters of water per ton of ore (The initial concentration of the acid used is from about 15 g / l to about 550 g / l).

 According to an advantageous embodiment of the process of the invention, the entire quantity of acid necessary for the dissolution of the uranium is pelletized, and during the leaching, only water is used. This has the advantage of handling the acid only once during the implementation of the process.

 In the case where all acid is used during pelletizing, it is used in about 65 to about 135 liters of water per ton of ore, including about 110 liters of water per tonne of ore. (the initial concentration of acid used being from about 500 to about 1800 g / l).

 For the leaching step, the amount of acid possibly used during the pelletization step should be taken into account.

 As regards leaching, use is made of sulfuric acid, nitric acid and hydrochloric acid, sulfuric acid being generally preferred.

The leaching step comprises two steps:
1g) a first phase, hereinafter referred to as the etching phase, during which the acid is added;
2 *) a second phase, hereinafter called washing phase, during which water, preferably acid, is added.

 During the attack phase, the acid added to put the uranium in solution circulates in a closed environment. As the acid circulates, it is therefore gradually loaded with uranium and is what will be designated in the following by leach liquors.

 The acid required for leaching is introduced at a rate of about 5 kg to about 80 kg; in particular from about 20 kg to about 50 kg, and preferably about 30 kg per ton of ore to be treated; these figures are referred to as concentrated acid as commercially available.

 Sulfuric acid is advantageously employed in concentrated form at about 97% (density of about 1.8).

 Generally, acid is used whose initial concentration is from about 50 to about 800 g / l, especially from about 200 to about 500 g / l, and preferably about 300 g / l.

 The amount of liquid added in the first leaching stage depends on the amount of acid required to put the uranium in solution and the initial concentration of the acid used.

 The amount of liquid added in the first leaching phase generally ranges from about 150 l to about 350 l per ton of ore to be treated (for an acid with an initial concentration of about 15 to about 550 g / l).

 The flow rate during the first leaching stage is from about 4 to about 60, preferably from about 10 to about 25 l / m2.h.

 The duration of the first leaching stage is from about 0 to about 15 days, and generally from about 5 to about 10 days.

 The first leaching stage continues until the amount of free acid contained in the leach liquors reaches a value of less than about 15 g / l.

 With regard to the second phase (washing phase) it therefore starts when the amount of acid in the leach liquors is less than about 15 g / l.

 During the second phase, water is added and the liquor (wash liquor) formed from the water circulates in an open circuit. It is preferable to use water having a pH of less than 1.8, and preferably about 1.5, in order to avoid, if necessary, the precipitation of uranyl phosphate, which may take place at from a pH of about 1.8.

 The wash water is added at a rate of about 4 to about 60 l / m 2 h, preferably about 10 l / m 2 h to about 25 1 / m 2 h.

 The wash phase ends when the wash liquors contain less than about 20 mg / l of uranium.

 The washing phase lasts from about 15 to about 30 days.

 The leaching step can take place directly after the pelletizing step.

 In practice, the time elapsing between the end of pelletizing and leaching is approximately 24 hours.

According to a preferred embodiment, the method of the invention comprises the following steps:
the clay ore having a moisture of from about 20% to about 255 is dried so that it reaches a moisture of about 5%.
the ore obtained above is crushed to obtain particles having a size of about 10 mm;
pellets (pelletizing step) are formed from the particles using a binder and a liquid, or a binder and an acid, or a binder and a mixture of liquid and acid, at a rate of about 120 to about 160 1 per ton of ore to be treated;
leaching the uranium ore (leaching step) and pelletizing with a solution containing water or an acid or a mixture of water and acid, an acid being used during at least one of the pelletizing and leaching steps, the binder used during the pelletization being compatible on the one hand with the liquid and the acid used during the pelletizing step and on the other hand part with the solution used during the leaching stage.

 It has been found that by using a binder compatible with the elements indicated above, the phenomenon of packing of the pellets is reduced, and the mechanical strength of the pellets and the ore dissolution efficiency are improved.

 For uranium ore, it is preferably crushed to a particle size of from about 500 microns to about 10 millimeters.

 As regards the pellets, their average diameter is in particular from about 5 to about 20 mm.

 With respect to the liquid added during the pelletizing step, water is advantageously used.

 As regards the amount of liquid used, it is advantageously such that, after being added to the ore to be treated, it contains from about 150 to about 270 l per ton, preferably from about 175 to about 220 l. per tonne of ore to be processed.

 In these values, it is necessary to take into account the quantity of water initially contained in the ore to be treated and which can vary from 0 to 110 1 / ton, in particular from about 30 to about 90 1 / t of ore.

 It is defined by the term "binder used during the pelletization to be compatible on the one hand with the liquid and the acid used during the pelletizing step and secondly with the solution used during the step a binder which, on the one hand, has the quality of being resistant in an acid medium and of not being destroyed during pelletizing or leaching, which allows the pellets to retain their mechanical strength and, on the other hand, who has the quality of not being responsible, in the presence of liquid used during the pelletizing and acid used during the pelletizing and / or the leaching, of reactions harmful to the solution of the uranium or susceptible of reduce the yield of dissolution of uranium.

 One of the advantages presented by the method of the invention is its ease of implementation, requiring only small amounts of binder, when it is possibly used.

 It is advantageous to use a binder capable of being polymerized with the acid used during leaching, which improves the mechanical strength of the pellets.

 When the acid used is sulfuric acid, the binder which is advantageously used is sodium silicate, potassium silicate or a mixture of these elements, calcium sulphate (CaSO4), 1/2 H2O), gypsum (CaSO 4, 2H 2 O) or a mixture of these elements.

 It is also possible to use sodium silicate marketed by the company RHONE POULENC, whose SiO2 / Na2O ratio is from about 2 to about 4.

 Sodium silicate marketed by Rhone Poulenc under the name 16N34 whose SiO 2 / Na 2 O ratio is 3.4 is also used.

As potassium silicate, one of the products marketed by the company RHONE can be used
POULENC, whose ratio Sio2 / K20 varies from about 2.3 to about 1.4.

 The binder chosen from sodium silicate, potassium silicate or their mixture is used in a proportion of about 0.5 to about 40 kg per ton of ore to be treated, expressed with respect to these elements as they are generally available. in the trade. Advantageously, the binder is used in a proportion of about 3 to 8, in particular about 5 kg / t of ore to be treated.

The density of sodium silicate varies from 1.26 to 1.56 and the density of potassium silicate varies from 1.26 to 1.62, which corresponds in volume:
- at least 0.309 l / t (0.5 kg / t for a density of 1.62)
- maximum 31.74 1 / t (40 kg / t for a density of 1.26).

 5 kg of sodium silicate are advantageously used per ton of ore to be treated (expressed relative to sodium silicate whose density is 1.33).

According to a preferred embodiment, the method according to the invention comprises:
the pelletization step, which takes place using 5 kg of sodium silicate per ton of ore to be treated (expressed relative to sodium silicate with a density of 1.33);
- and the leaching step, using a sulfuric acid solution used at a rate of about 30 kg per tonne of ore to be treated (expressed relative to 1,8 density sulfuric acid) .

 According to another preferred embodiment of the process according to the invention, the pelletizing step takes place using a binder and an acid is advantageously the same as that used during leaching.

During the pelletization step, you can:
- add the binder at the same time as the acid;
- add the binder before the acid;
- add the acid before the binder.

 The binder and the acid should not be premixed before being added to the pelletizing.

 According to an advantageous embodiment of the process according to the invention, the acid is added before the binder.

 What has been said about the use of acid during the pelletizing step of the embodiments of the method of the invention, previously described, also applies to the case where the pelletisation takes place by resorting to a binding and to acid.

 Thus, when a binder and acid are used during pelletizing, the amount of acid used with the binder during pelletizing corresponds to a portion of the total amount of acid required for pelletizing. uranium solution or may correspond to all the acid that would be used during leaching, if there was no prior acid addition during pelletizing.

 The amount of acid used during pelletizing can vary from 0 to about all of the acid required for the use of uranium.

 The amount of acid used during pelletizing varies depending on the ore to be treated.

 The amount of acid used during the pelletizing is advantageously the totality of the quantity necessary for the dissolution of the uranium.

 The amount of acid used during pelletization ranges from about 5 to about 80, especially about 20 kg per ton of ore to be treated, based on concentrated acid, as is generally available commercially.

 The initial concentration of the acid used during pelletizing ranges from about 500 g / l to about 1500 g / l and is especially about 1800 g / l.

 Therefore, during the leaching step, it is necessary to take into account the amount of acid already possibly used during pelletizing.

 Advantageously, during the pelletization step, addition of sodium silicate and sulfuric acid is used.

 In this embodiment, sodium bicarbonate, at a density of about 1.33, during leaching, and / or sulfuric acid in concentrated form at about 97 k, can be used as a binder.

 According to another preferred embodiment, the quantity of water required is distributed substantially equally between the binder and the sulfuric acid added to the pelletizing.

 According to a preferred embodiment for pelletizing, sodium silicate is used at a rate of 5 kg to 10 kg per ton of ore to be treated with a density of 1.33 (ie 3.75 to 7.5 1 per tonne of ore to be treated ) diluted in approximately 60-80 liters of water per ton of ore to be treated and sulfuric acid at a rate of 10 kg to 30 kg per ton of ore to be treated, of density 1,8 (ie 5.5 to 16 , 5 1 per ton of ore to be treated) diluted in about 60-80 liters of water per ton of ore to be treated.

According to a preferred embodiment of the process of the invention
the uranium ore is crumbled into particle size of about 30 mm to about 70 mm;
the clay ore having a moisture of from about 20% to about 25% is dried so that it reaches a moisture of about 3% to about 8%; ;
the ore obtained above is crushed to obtain particles approximately 10 mm in size
- pellets are formed from the particles using
approximately 60-80 liters of water
per ton of ore to be treated,
sulfuric acid at a rate of about
15 kg per ton of ore to be treated,
expressed in relation to acid
sulfuric whose density is
about 1.8,
and a binder consisting of
sodium silicate, about
5 kg per ton of ore to be treated,
expressed with respect to silicate of
sodium density about 1.33 diluted
in about 60-80 liters of water per ton
ore to be processed
- The uranium ore thus pelleted is leached with a sulfuric acid solution at a rate of approximately 15 kg of sulfuric acid per ton of ore to be treated, expressed relative to sulfuric acid. 1.8 density
According to another preferred embodiment of the process of the invention, it is possible to use an oxidizer of uranium, according to the degree of oxidation of uranium, to transform UIV into UVI.

In this case, the method of the invention then comprises the following steps
the clay ore having a moisture of from about 20% to about 25% is dried so that it reaches a moisture of from about 0% to about 10%, especially from about 3% to about 8%, and preferably about 5%;
the ore obtained in the preceding step is crushed to particles of particle size of about 10 mm
pellets are formed from the above particles using a liquid and / or an acid
the uranium ore thus pelleted is leached with the aid of a solution consisting of acid, water, or a mixture of water and an acid, an acid being used in the course of at least one of the pelletization and leaching phases
an oxidizer of the uranium capable of transforming UIV into UVI is added.

According to a preferred embodiment of the invention, the method comprises the following steps
- the ore is dried so that its moisture goes from about 25 '6 to about 5' 6
the uranium ore is crushed into particles of particle size of about 10 μm to about 20 minutes
pellets with an average diameter of about 5 mm to about 60 mm are formed using a quantity of liquid ranging from about 120 to about 200 liters per ton of ore to be treated
the uranium ore thus pelleted is leached with an acid solution, the liquid used during the pelletizing and the acid used during the oxidation must be compatible with each other;
- an oxidizing agent is preferably added during the leaching process and is capable of transforming UIV into
UVI.

 The oxidant can be used at any stage of the process.

 The oxidant is preferably used during the leaching phase and advantageously during the etching phase.

 As the oxidant of uranium, it is possible to use sodium chlorate, manganese oxide derived from pyrolusite, or monopersulphuric acid, also known under the name Caro acid of formula H 2 SO 5.

 The amount of oxidant used is about 0.5 to about 20 kg per ton of ore to be treated, expressed relative to the oxidants as marketed.

 When the oxidant used is sodium chlorate, it is advantageously used, when the concentration of sulfuric acid has reached a value equal to or less than about 100 g / l, so that the sodium chlorate is not destroyed by the acid sulfuric.

 Preferably, the oxidant is added when the concentration of sulfuric acid has reached a value greater than about 50 g / l.

 According to a preferred embodiment of the process according to the invention, it is advantageous to use approximately 10 kg of Caro acid per tonne of ore to be treated, expressed relative to Caro acid of approximately 100 to approximately 450 g / l. l, especially about 100 g / l.

 The Caro acid can for example be obtained from H2O2 oxygenated water and 588 sulfuric acid, in a weight ratio H2SO4 / H2O2 of about 4.3 / 1.

 According to another preferred embodiment of the process according to the invention, approximately 2 kg of sodium chlorate are advantageously used per ton of ore to be treated, expressed relative to 100% dry sodium chlorate and used in the form of a solution. which has a concentration of about 200 to about 400 g / l.

 According to another preferred embodiment of the process of the invention, it is possible to use acid during pelletizing. What has been said previously about the use of acid during pelletizing also applies to the process of the invention in the case of using a uranium oxidant.

 According to another preferred embodiment of the process of the invention, a binder can be used during pelletizing. What has been said previously about the use of acid during pelletizing also applies to the process of the invention in the case of using a uranium oxidant.

 According to another preferred embodiment of the process of the invention, a binder and acid can be used during pelletizing. What has been said above about the use of acid and a binder during pelletizing also applies to the process of the invention in the case of using a uranium oxidant.

According to a preferred embodiment, the method of the invention comprises the following steps
the clay ore with a moisture of about 25% is dried until it reaches a moisture of about 0 s. at 10 s.

the uranium ore is crushed into particles with a particle size of from about 10 μm to about 200 mm, and advantageously from about 500 μm to about 10 mm.
pellets having an average diameter of from about 5 to about 60 mm are formed, especially from about 5 to about 20 mm, using from about 120 to about 200, especially from about 120 to about 160 1 per ton. of ore to be treated, a liquid, in particular water or an acid or a mixture of water and an acid, in particular sulfuric acid, and with the aid of a binder, in particular silicate of sodium
- leaching with water or an acid or a mixture of water and an acid, including sulfuric acid, an acid to be used during at least one of two stages of pelletizing and leaching; ;
an oxidizing agent, in particular sodium chlorate, capable of converting UIV to UVI, is preferably added during the leaching process.

According to a preferred embodiment of the process of the invention
the clay ore having a moisture of from about 20% to about 25% is dried at a humidity of about 5%.
the uranium ore obtained above is crushed to particles of particle size of about 10 mm;
- pellets are formed from particles using water at a rate of about 120 to 160 l / t of ore to be treated and sulfuric acid at a rate of about 15 kg / t of ore to be treated, expressed with respect to sulfuric acid with a density of about 1.8;
the uranium ore thus pelleted is leached with acid from a solution of sulfuric acid at a rate of approximately 15 kg / t of sulfuric acid per ton of ore to be treated, expressed relative to sulfuric acid with a density of about 1.8
during the leaching, preferably during the etching phase, sodium chlorate is added at a rate of approximately 2 kg / t of ore to be treated, in the form of a pure dry product at 100%, advantageously works as a 300 g / l water solution.

According to a preferred embodiment of the process of the invention
the clay ore having a moisture of from about 20% to about 25% is dried so that it reaches a moisture of about 2.5%;
the ore obtained above is crushed to give particles having a size of approximately 10 mm;
- pellets are formed from the particles using
. approximately 60-80 liters of water
per ton of ore to be processed
. sulfuric acid at a rate of about
15 kg per ton of ore to be treated,
expressed in relation to acid
sulfuric whose density is
about 1.8
. a binder consisting of silicate
about 5 kg per
tonne of ore to be processed, expressed
compared to sodium silicate
density of about 1.33 diluted in in
60 to 80 liters of water per tonne of
ore to be processed;
- The uranium ore thus pelleted is leached with a sulfuric acid solution at a rate of approximately 15 kg of sulfuric acid per ton of ore to be treated, expressed relative to sulfuric acid. 1.8 density
~ during the leaching stage, sodium chlorate is added during the leaching stage at a rate of approximately 2 kg per ton of ore to be treated, expressed relative to 100% pure sodium chlorate, advantageously implemented as a solution of about 300 g / l.

 In the process of the invention, the yield of uranium is preferably from about 90% to about 95%.

The process of the invention is advantageously applied to uranium ores whose composition is as follows
U: from about 200 ppm to about 50,000 ppm, especially from about 500 ppm to 2000 ppm
Total: from about 0.1% to about 1%, especially from about 0.5% to about 0.7%
SiO2. from about 40% to about 80%, especially from about 60% to about 70%
Al 2 O 3: from about 5% to about 20%, especially from about 10% to about 15%
CO 3: from about 0.05% to about 0.5%, especially from about 0.1% to about 0.3%.

The process of the invention is advantageously applied to uranium ores also containing
P2O5: from about 0.05% to about 0.5%, especially about 0.1%;
Fie203: from about 2% to about 6%, especially from about 4% to about 4.5%.

 The invention will be better understood thanks to the examples given below.

In all the examples, except when it will be explicitly specified:
- the quantities expressed in kg of sulfuric acid per ton of ore to be treated (kg / t) refer to sulfuric acid with a density of approximately 1.8
- the quantities expressed in kg of sodium silicate per tonne of ore to be processed (kg / t) refer to sodium silicate with a density of approximately 1.33
- the quantities expressed in kg of sodium chlorate per ton of ore to be treated (kg / t) refer to dry sodium chlorate, 100% pure.

 The process for treating uranium clay ores according to the invention makes it possible to achieve yields of greater than about 90%, and advantageously at least about 95% of the dissolution of uranium.

 The invention will be better understood on reading the examples which follow given by way of illustration and which should not be considered as limiting.

EXAMPLE 1
The ore comes from Nord-Aquitaine, its composition is shown in Table V, below, in the part entitled "sample average elimination" and its initial humidity is about 25
These tests were designed to determine
- the influence of the silicate dose on the behavior of the pellets and possibly the uranium yield
the influence of the amount of acid added to the pelletization on the uranium yield, the consumption of acid, and possibly the holding of the pellets
- the influence of the size of the pellets on their behavior and the yield of uranium.

 This ore is totally dried to reach a humidity of 2.6%.

 This ore is then crushed into particle size of about 10 mm.

 The trommel pelletization is carried out with a diameter of 600 mm, a length of 535 mm, an outlet opening with a diameter of 450 mm, or a threshold of 7.5 cm, for a residence time of approximately 8 minutes.

 Pelleting is done with water, sulfuric acid and sodium silicate.

 Sulfuric acid is diluted in about 100 l / t and added to 10 cm of the ore feed.

 The sodium silicate is diluted in about 30 1 / t and added by spraying 28 cm from the feed.

 The trommel used for pelletizing is equipped with a scraper to avoid encreasing of the walls.

 Each pelletized batch of approximately 80 kg is placed in a 240 mm diameter column at a height of approximately 1.80 m.

After 24 hours of ripening, the ore to be treated undergoes the following treatment cycles
- the first leaching phase is carried out using approximately 330 1 / t of acid solution with a recycling of 6 days at a flow rate of 50 l / m2h
- The second leaching phase is carried out with open water in open circuit for 2.5 days at 25 1 / m2h, followed by a spin for 24 hours.

 The washing volume is adjusted to obtain a constant production of about 1 m3 / t.

Results and comments
The influence of the sodium silicate dose on the uranium yield, settlement and silica content of the pellets is shown below.

The sodium silicate used is a Rhône Poulenc liquid product, reference 16 N 34, of composition
SiO2: 27.7% SiO2 / Na2O molecular ratio
Na2O: 8.3% = 3.4 to 3.5
H2O: 63.7%
Influence of sodium silicate on uranium yield
The results obtained with the tests 1 to 15 are summarized in Table I. It should be pointed out that the test n-13 is identical to the test No. 10, but is carried out with a different dilution of the reagents. indeed, in test No. 10, H2SO4 is used in 100 l / t and sodium silicate in 30 l / t, while in test n-13, H2SO4 is used in 30 l / t and the silicate of sodium in 100 1 / t. TABLE I

BOULETTAGE <SEP> PROOUCTION
<tb> Test <SEP> Leaching <SEP> Total
<tb> Add <SEP> Consumption <SEP> Content <SEP> Content <SEP> Yield
<tb> H2SO4 <SEP> Silicate <SEP> H2SO4 <SEP> H2SO4 <SEP> Volume
<tb> liquid <SEP> H2SO4 <SEP> residue <SEP> feed <SEP> U
<tb> restored
<tb> n <SEP> kg / t <SEP> kg / t <SEP> l / t <SEP> kg / t <SEP> kg / t <SEP> m3 / t <SEP> kg / t <SEP> ppm <SEP>%
<tb> ppm
<tb> 1 <SEP> 15 <SEP> 0 <SEP> 140 <SEP> 22.0 <SEP> 37.0 <SEP> 1.09 <SEP> 17.8 <SEP> 95 <SEP> 1 <SEP > 454 <SEP> 93.0
<tb> 2 <SEP> 15 <SEP> 1.0 <SEP> 130 <SEP> 23.0 <SEP> 38.0 <SEP> 1.14 <SEP> 16.5 <SEP> 76 <SEP> 1 <SEP> 263 <SEP> 94.0
<tb> 3 <SEP> 15 <SEP> 2.5 <SEP> 130 <SEP> 17.7 <SEP> 32.7 <SEP> 0.96 <SEP> 13.3 <SEP> 84 <SEP> 1 <SEP> 468 <SEP> 94.3
<tb> 6 <SEP> 15 <SEP> 4.0 <SEP> 130 <SEP> 17.2 <SEP> 32.2 <SEP> 1.02 <SEP> 9.5 <SEP> 84 <SEP> 1 <SEP> 665 <SEP> 95.0
<tb> 4 <SEP> 15 <SEP> 5.0 <SEP> 130 <SEP> 18.0 <SEP> 33.0 <SEP> 1.07 <SEP> 12.8 <SEP> 75 <SEP> 1 <SEP> 454 <SEP> 94.8
<tb> 10 <SEP> 15 <SEP> 6.0 <SEP> 130 <SEP> 16.7 <SEP> 31.7 <SEP> 1.10 <SEP> 14.0 <SEP> 88 <SEP> 1 <SEP> 552 <SEP> 94.3
<tb> 7 <SEP> 15 <SEP> 7.5 <SEP> 130 <SEP> 17.2 <SEP> 32.2 <SEP> 0.93 <SEP> 18.9 <SEP> 82 <SEP> 1 <SEP> 577 <SEP> 94.3
<tb> 14 <SEP> 15 <SEP> 8.5 <SEP> 130 <SEP> 19.9 <SEP> 34.9 <SEP> 1.47 <SEP> 7.6 <SEP> ND <SEP> ND <SEP> ND
<tb> 5 <SEP> 15 <SEP> 10.0 <SEP> 130 <SEP> 16.3 <SEP> 31.3 <SEP> 1.37 <SEP> 9.7 <SEP> 81 <SEP> 1 <SEP> 368 <SEP> 94.0
<tb> 15 <SEP> 15 <SEP> 15.0 <SEP> 130 <SEP> 19.6 <SEP> 34.6 <SEP> 1.25 <SEP> 4.9 <SEP> ND <SEP> ND <SEP> ND
<tb> 8 <SEP> 0 <SEP> 5.0 <SEP> 130 <SEP> 37.6 <SEP> 37.6 <SEP> 1.20 <SEP> 19.6 <SEP> 143 <SEP> 1 <SEP> 678 <SEP> 91.5
<tb> 9 <SEP> 30 <SEP> 5.0 <SEP> 130 <SEP> 0 <SEP> 30.0 <SEP> 1.11 <SEP> 9.2 <SEP> 77 <SEP> 1 <SEP > 578 <SEP> 95.1
<tb> 11 <SEP> 15 <SEP> 6.0 <SEP> 123 <SEP> 16.7 <SEP> 31.7 <SEP> 1.23 <SEP> 12.2 <SEP> 81 <SEP> 1 <SEP> 558 <SEP> 94.8
<tb> 12 <SEP> 15 <SEP> 6.0 <SEP> 140 <SEP> 18.2 <SEP> 33.2 <SEP> 1.15 <SEP> 10.7 <SEP> 90 <SEP> 1 <SEP> 495 <SEP> 94.0
<tb> 13 <SEP> * <SEP> 15 <SEP> 6.0 <SEP> 130 <SEP> 17.5 <SEP> 32.5 <SEP> 1.10 <SEP> 8.1 <SEP> 94 <SEP> 1 <SEP> 811 <SEP> 94.8
<tb> ND: not determined
Conclusions on Table I
Except for test No. 1 (in which no silicate is used), the uranium yield does not appear to be influenced by the silicate dose (1 to 15 kg / t). The observed yields range from 94 to 95% (residue levels: 75 to 85 ppm).

- Influence of sodium silicate on settlement
The results are collated in Table II below and Figure 1.

 More precisely, Figure 1 has 2 curves, an upper curve and a lower curve.

 The upper curve represents the dry density variation (ordinate) as a function of the pelletized silicate dose (on the abscissa).

The lower curve represents the variation of the percentage of settlement (on the ordinate) as a function of the pelletized silicate dose (on the abscissa). TABLE II

BOULETTAGE <SEP> RESIDUAL
<tb> Essay
<tb> H2SO4 <SEP> Silicate <SEP> Liquid <SEP> Settlement <SEP> Final <SEP> Moisture
<tb> Density <SEP> dry <SEP> Density <SEP> dry <SEP> Density <SEP> dry <SEP> Difference <SEP> from <SEP> density
<tb> n <SEP> kg / t <SEP> kg / t <SEP> l / t <SEP>% <SEP>%
<tb> 1 <SEP> 15 <SEP> 0 <SEP> 140 <SEP> 0.82 <SEP> 23.6 <SEP> 1.08 <SEP> + <SEP> 0.26 <SEP> 28.0
<tb> 2 <SEP> 15 <SEP> 1.0 <SEP> 130 <SEP> 0.85 <SEP> 18.8 <SEP> 1.05 <SEP> 0.20 <SEP> 30.0
<tb> 3 <SEP> 15 <SEP> 2.5 <SEP> 130 <SEP> 0.84 <SEP> 16.1 <SEP> 1.00 <SEP> 0.16 <SEP> 30.5
<tb> 6 <SEP> 15 <SEP> 4.0 <SEP> 130 <SEP> 0.81 <SEP> 9.6 <SEP> 0.89 <SEP> 0.08 <SEP> 30.6
<tb> 4 <SEP> 15 <SEP> 5.0 <SEP> 130 <SEP> 0.83 <SEP> 11.5 <SEP> 0.94 <SEP> 0.11 <SEP> 30.4
<tb> 10 <SEP> 15 <SEP> 6.0 <SEP> 130 <SEP> 0.86 <SEP> 9.9 <SEP> 0.96 <SEP> 0.10 <SEP> 31.0
<tb> 7 <SEP> 15 <SEP> 7.5 <SEP> 130 <SEP> 0.81 <SEP> 9.6 <SEP> 0.89 <SEP> 0.08 <SEP> 29.9
<tb> 14 <SEP> 15 <SEP> 8.5 <SEP> 130 <SEP> 0.85 <SEP> 9.5 <SEP> 0.93 <SE> 0.08 <SEP> ND
<tb> 5 <SEP> 15 <SEP> 10.0 <SEP> 130 <SEP> 0.83 <SEP> 11.5 <SEP> 0.94 <SEP> 0.11 <SEP> 29.2
<tb> 15 <SEP> 15 <SEP> 15.0 <SEP> 130 <SEP> 0.87 <SEP> 4.8 <SEP> 0.91 <SEP> 0.04 <SEP> ND
<tb> 8 <SEP> 0 <SEP> 5.0 <SEP> 130 <SEP> 0.79 <SEP> 16.8 <SEP> 0.95 <SEP> 0.16 <SEP> 32.7
<tb> 9 <SEP> 30 <SEP> 5.0 <SEP> 130 <SEP> 0.83 <SEP> 14.4 <SEP> 0.97 <SEP> 0.14 <SEP> 31.3
<tb> 11 <SEP> 15 <SEP> 6.0 <SEP> 123 <SEP> 0.91 <SEP> 6.7 <SEP> 0.970.06 <SEP> 27.6
<tb> 12 <SEP> 15 <SEP> 6.0 <SEP> 140 <SEP> 0.86 <SEP> 10.2 <SEP> 0.96 <SEP> 0.10 <SEP> 28.0
<tb> 13 <SEP> 15 <SEP> 6.0 <SEP> 130 <SEP> 0.87 <SEP> 8.0 <SEP> 0.95 <SEP> 0.08 <SEP> 30.3
<tb> ND: not determined
Conclusions on Table II and Figure 1
The mechanical strength of the pelletized ore may be characterized by the percentage of settlement observed; the residual porosity, by the apparent dry density after leaching.

 It is noted that the addition of silicate makes it possible to limit the settlement of the ore and thus to maintain a high porosity during leaching.

The influence of silicate is very marked between
O and 5 kg / t, then the differences are reduced for higher doses.

 The influence of the amount of acid, the influence of the size of the pellets, and direct influences on the process of the invention are indicated below.

 Tests 8, 4 and 9 were carried out with the same dose of silicate (5 kg / t), but with increasing amounts of pelletized acid: 0.15 and 30 kg / t.

We aknowledge
no significant difference is visible on the settlement
that the addition of a portion of the acid to the pelletization clearly improves the yield of uranium from 91.5 to 95%. On the other hand, no significant difference appears between 15 and 30 kg / t H2504.

 FIG. 2 shows the influence of the addition of acid to pelletizing. On the x-axis, the production volume expressed in m3 / t and on the y-axis the uranium yield in m3 / t.

 Figure 2 has two curves, a curve on the right and a curve on the left.

 The curve on the right corresponds to test n 8 (in which pelletized sulfuric acid was not used).

 The curve on the left corresponds - for the points represented - to the test n 4 (15 kg / t of sulfuric acid added to the pelletisation) and - for the crosses represented - to the test n 9 (30 kg / t of sulfuric acid pelletizing).

 It should be noted from Figure 2 that the effect of the addition of acid to the pelletizing is mostly clear on the kinetics of uranium production during washing.

- Influence of the size of the pellets
These tests confirmed that pelletizing was only possible within a very precise range of humidity.
. the minimum addition of liquid is 120 l / t,
. the maximum addition of liquid is 150 l / t.

 Within this range, the particle size of the product obtained increases with the addition of liquid.

Three tests were carried out with 15 kg / t of H2SO4 and 6 kg / t of silicate
. test 11: 123 l / t - pellets: 5 to 10 mm
, test 10: 130 l / t - pellets: 10 to 15 mm
, test 12 140 l / t - pellets: 20 to 30 mm.

 From Table IX, which shows the settlement, it is found that it increases with the particle size of the pellets, however the apparent dry densities after leaching are not different (0.96 to 0.97): although the holding mechanical small pellets is better, the final porosity seems the same.

- Various influences
Test n-13 was carried out with the same reagent doses as test No. 10, only the dilutions are different
* Test 10: H2504 (15 kg / t in 100 l / t
Silicate (6 kg / t) in 30 l / t
* test 13: H2SO4 (15 kg / t in 30 l / t)
Silicate (6 kg / t) in 100 l / t.

 No difference appears, either on the physical behavior of the pellets, or on the uranium yield.

The final moisture content of leach residues is relatively constant: 30% on average (Table n-
II), and does not seem to depend on the doses of reagents used.

EXAMPLE 2
The process of the invention was carried out on the same ore as that of Example 1, the initial moisture of which was about 25%.

 The embodiment of the process of the invention consists in leaching the uranium ore stored in stalls.

This ore is dried in successive fractions in a stream of hot air created by a fuel nozzle until it reaches an average humidity of about 2.6
This ore is crushed into particles whose particle size is less than about 10 mm in a gyratory crusher.

 With regard to pelletization, the main parameters are shown in Table III below.

TABLE II @

<tb> Geometry <SEP> of the <SEP> trommel
<tb> Diameter <SEP> 117.5 <SEP> cm
<tb> Length <SEP> 210 <SEP> cm
<tb> Opening <SEP> of <SEP> output <SEP>: <SEP> diameter <SEP> 97.5 <SEP> cm
<tb> either <SEP> a <SEP> threshold <SEP> of <SEP> 10 <SEP> cm
<tb> Speed <SEP> of <SEP> rotation <SEP> 14 <SEP> to <SEP> 15 <SEP> rpm
<tb> Speed <SEP> device <SEP> 0.85 <SEP> e <SEP> 0.93 <SEP> m / s
<tb> Position <SEP> of <SEP> additions <SEP> of <SEP> reagents <SEP>: <SEP> t <SEP>
<tb> (by <SEP> rappost <SEP> to <SEP> the <SEP> entry of the <SEP> trommel)
<tb> Water <SEP> 30 <SEP> cm
<tb> Acid <SEP> 50 <SEP> cm
<tb> | <SEP> Silicate <SEP> pulverized <SEP> 110 <SEP> cm <SEP> l <SEP>
<tb> The <SEP> trommel <SEP> is <SEP> equipped <SEP> with a <SEP> scraper <SEP> destined <SEP> to <SEP> avoided <SEP> a <SEP> enroûtement
<tb> too <SEP> important <SEP> on <SEP> the <SEP> walls
<tb> Food
<tb>. <SEP> Ore <SEP> (moisture <SEP> to <SEP> 2.6 <SEP>%) <SEP> 738 <SEP> kg / hr
<tb> Time <SEP> of <SEP> stay <SEP> - <SEP> 8 <SEP> minutes
<tb> I <SEP> Total <SEP> total <SEP> of <SEP> pelletization <SEP> - <SEP> 20 <SEP> hours <SEP> | <September>
<tb> Granulometry <SEP>: <SEP> see <SEP> table <SEP> n <SEP> 19
<tb> | <SEP>. <SEP><SEP> Reagents (<SEP>SEP> Variable <SEP><SEP>Functions><SEP><SEP><SEP> Behavior
<tb> in <SEP> the <SEP> trommel)
<tb> I <SEP> Water <SEP> 40 <SEP> a <SEP> 50 <SEP> l / h <SEP> I
<tb> Acid <SEP> (H2S04 <SEP> to <SEP> 98 <SEP> X) <SEP> - <SEP> 6 <SEP> l / h <SEP> g <SEP>
<tb> Silicate <SEP> 7N34 <SEP>: <SEP> - <SEP> diluted <SEP> a <SEP> 100 <SEP> g / l <SEP> 49 <SEP> l / h <SEP> | <September>
<tb> I <SEP> - <SEP> then <SEP> to <SEP> 150 <SEP> g / l <SEP> 33 <SEP> l / h <SEP> I
<tb> g <SEP> Product <SEP> average <SEP> obtained
<tb> | <SEP> Total <SEP> Humidity <SEP> 12.76 <SEP> X <SEP> l <SEP>
<tb> (or <SEP> 146 <SEP> l / t)
<tb> either <SEP> a <SEP> add <SEP> average <SEP> of <SEP> liquid <SEP> from <SEP> 119 <SEP> l / t
<tb> H2SO4 <SEP> (100 <SEP>%) <SEP> 16.1 <SEP> kg / t
<tb> Silicate <SEP> 7N34 <SEP> (25.8 <SEP>% <SEP> SiO2) <SEP> 5.5 <SEP> kg / t
<tb> either <SEP> in <SEP> SiO2 <SEP> 1.4 <SEP> kg / t
<tb> Granulometry <SEP>: <SEP> see <SEP> table <SEP> IV <SEP> below
<Tb>
The pelletized product has the following characteristics moisture: 12.8 '6 (146 l / t)
H2SO4: 16.1 kg / t sodium silicate: 5.5 kg / t (1.42 kg / t SiO2)
Sodium silicate is a product marketed by Rhône Poulenc Product under the reference 7 N 34 and composition following 25.8 t. SiO2 SiO2 / Na2O
7.7% Na 2 O = 3.4 to 3.5 66.3% H 2 O
As regards the particle size distribution, reference is made to Table IV below.

TAUBLEAU IV

<tb> ORE <SE> SEC <SEP> ORE <SEP> SEP <SEP> *
<tb> Power <SEP> trommel <SEP> Output <SEP> trommel
<tb> Slice <SEP>% <SEP>% <SEP> Weight <SEP> Slice <SEP>% <SEP>% <SEP> Weight
<tb> granulometric <SEP> Weight <SEP> cumulative <SEP> granulometric <SEP> Weight <SEP> cumulative
<tb> + <SEP> 20 <SEP> mm <SEP> 0.24 <SEP> 0.24 <SEP> + <SEP> 50 <SEP> mm <SEP> 1.56 <SEP> 1.56
<tb> + <SEP> 10 <SEP> mm <SEP> 4.06 <SEP> 4.30 <SEP> + <SEP> 30 <SE> mm <SEP> 3.17 <SEP> 4.73
<tb> + <SEP> 8 <SEP> mm <SEP> 5.63 <SE> 9.93 <SEP> + <SEP> 20 <SE> mm <SE> 1.76 <SEP> 6.49
<tb><SEP> + <SEP> 4 <SEP> mm <SEP> 23.78 <SEP> 33.71 <SEP> + <SEP> 15 <SEP> mm <SEP> 2.21 <SEP> 8, 70
<tb> + <SEP> 2 <SEP> mm <SEP> 21.44 <SEP> 55.15 <SEP> + <SEP> 10 <SE> mm <SEP> 21.14 <SEP> 29.84
<tb> + <SEP> 1 <SEP> mm <SEP> 14.87 <SEP> 70.02 <SEP> + <SEP> 8 <SEP> mm <SEW> 15.40 <SEQ> 45.24
<tb> + <SEP> 0.5 <SEP> mm <SEP> 10.55 <SEP> 80.57 <SEP> + <SEP> 4 <SEP> mm <SEP> 38.35 <SE> 83.59
<tb> - <SEP> 0.5 <SEP> mm <SEP> 19.43 <SE> 100.00 <SEP> + <SEP> 2 <SE> mm <SE> 13.54 <SE> 97.13
<tb> - <SEP> 2 <SEP> mm <SEP> 2.87 <SE> 100.00
<tb> *: weight distribution after drying
Table V shows the analytical results of the samples taken from the mean samples at the feed (U = 1406 ppm), hourly samples at the pellet outlet (U = 1362 ppm) and samples to determine the sample. humidity, when putting in stall.

TABLE V - SAMPLE MEDIUM POWER SUPPLY
Humidity: 2.63%.

, Semi-quantitative analysis by X-ray fluorescence

<tb> Fe2O3 <SEP> K2O <SEP> SiO2 <SEP> CaO <SEP> Al2O3 <SEP> TiO2
<tb>% <SEP>% <SEP>% <SEP>% <SEP>% <SEP>%
<tb> 4.51 <SEP> 2.34 <SEP> 68.87 <SEP> 0.52 <SEP> 16.30 <SEP> 6.21
<tb> Chemical analyzes

<tb> U <SEP> As <SEP> Se <SEP> Na <SEP> SO4 <SEP> SiO2 <SEP> Al2O3
<tb> ppm <SEP> ppm <SEP> ppm <SEP>% <SEP>% <SEP>% <SEP>%
<tb> 1 <SEP> 406 <SEP> 125 <SEP> 34 <SEP> 0.41 <SEP> 3.68 <SEP> 63.16 <SEP> 14.3
<tb> - TIME SAMPLES EXIT BOULETTEUR
. Average humidity: 12.76 X
Chemical analyzes

<tb> U <SEP> Na <SEP> SO4 <SEP> SiO2
<tb> ppm <SEP>% <SEP>% <SEP>%
<tb> 1 <SEP> 362 <SEP> 0.42 <SEP> 4.94 <SEP> 62.00
<tb> - SAMPLE FOR HUMIDITY (when loading the stall)
Humidity: 11.45%
The pelleted ore was loaded into the stall at a height of 2 m 50, which corresponds to 13.5 dry tons.

 The leaching is carried out under the following conditions: the first leaching stage consists of an attack by recycling the liquors for 11 days, and the second phase comprises washing with water for 20 days.

 The main parameters and results of the test are shown in Table VI below.

TABLE VI

<tb> ORE <SEP> Weight <SEP> wet <SEP> 15 <SEP> 244 <SEP> kg
<tb><SEP> Weight <SEP> sec <SEP> calculated <SEP> 13 <SEP> 500 <SEP> kg
<tb><SEP> Initial <SEP> Humidity <SEP> 11.45 <SEP>%
<tb><SEP> Humidity <SEP> final <SEP> 28.1 <SEP>%
<tb> ATTACK <SEP> Initial <SEP> Volume <SEP> 311 <SEP> l / t
<tb><SEP> Acid <SEP> 11.6 <SEP> (+ <SEP> 16.1 <SEP> *) <SEP> kg / t
<tb><SEP> Time <SEP> 11 <SEP> days
<tb><SEP> Flow rate <SEP> 14 <SEP> to <SEP> 17 <SEP> 1 / m2.h
<tb> WASHING
<tb><SEP> Volume <SEP> total <SEP> passed <SEP> 1 <SEP> 3.9 <SEP> m3 / t <SEP> I
<tb><SEP> Time <SEP> I <SEP> 20 <SEP> Days <SEP>
<tb><SEP> Flow rate <SEP> average <SEP> 21 <SEP> 1 / m2.h
<tb><SEP> PRODUCTION <SEP> Volume <SEP> 2.13 <SEP> m3 / t
<tb> I <SEP> BALANCE SHEET <SEP> URANIUM
<tb><SEP> Content <SEP> analyzed <SEP> residue <SEP> 105 <SEP> ppm
<tb><SEP> Content <SEP> reconstituted <SEP> feed <SEP> 1 <SEP> 363 <SEP> ppm
<tb><SEP> Extraction <SEP> yield <SEP> U <SEP> 92.3 <SEP>%
<tb> BALANCE SHEET <SEP> H2SO4
<tb> Acid <SEP> mis <SEP> in <SEP> work <SEP> 27.7 <SEP> kg / t
<tb><SEP> Acid <SEP> consumed <SEP> 18.2 <SEP> kg / t
<tb> OBSERVATIONS <SEP> Retention <SEP> Liquid <SEP> in <SEP> Recycling <SEP> 390 <SEP> l / t
<tb><SEP> (y <SEP> inclusive <SEP> humidity <SEP> initial) <SEP> | <September>
<tb><SEP> Settlement <SEP> 1 <SEP> 14 <SEP>% <SEP>
<tb><SEP> Acidity <SEP> in <SEP> end <SEP> of attack <SEP> t <SEP> 20 <SEP> g / l <SEP> I
<tb> acid added to the pelletizing
Conclusion on Table VI
It can be noted that the volume of production (2.1 m3 / t almost doubled compared to a conventional ore): the washing was continued until the uranium content of the production contents were in the order of 20 mg / l.

 The content of the residue is 105 ppm, the reconstituted content of the feed of 1,363 ppm: the extraction efficiency of uranium is therefore 92.3 8.

 The acid consumption is 18.2 kg / t for 27.7 kg / t used.

- Percolation flow
The watering rate was gradually increased from 15 to 22 l / m2h during the test.

 A percolation test was then carried out at the end of the washing over 3 days: the percolation remains correct up to 35-40 l / m2h. When the flow becomes higher, we notice the creation and the extension of puddles on the surface of the ore.

 The pelletized ore can therefore accept a maximum flow rate of the order of twice the values currently practiced on a conventional industrial pile (20 l / m2h).

- Behavior of the pellets
It was noted during the unloading of the stall, that the pellets had retained their individuality, and this over the entire height of the ore (except the two superficial centimeters).

Dry apparent densities are significantly higher than those found on the columns
. initial apparent density: 1.03
. apparent density after leaching: 1.20
. as well as the settlement: 14 5.

 In spite of this, the interstitial voids remaining between the pellets allow a good percolation of the liquors.

 In addition, although the ore seems relatively coherent (packed) during the opening of the stall, the pellets are individualized and collapse during the recovery.

 The unloading of the stall did not pose any particular problem of gluing.

- Sampling of the residue
Sampling of the residue (free of uranium) was done in two ways
on the residue in place, by grab samples (26) at different heights in the stall.

 by taking samples from each of the buckets (16) of destocked ore.

The results are shown on the chart
VII.

TABLE VII

<tb><SEP> I <SEP> * <SEP> I <SEP> I
<tb><SEP> Sample <SEP> Content <SEP> U <SEP> Content <SEP> U <SEP> Medium
<tb><SEP> one-time <SEP> Situation <SEP> average <SEP> general
<tb><SEP> n <SEP> ppm <SEP> ppm <SEP> ppm
<tb><SEP> I <SEP> - <SEP> I <SEP> ~~~~~~~ <SEP> I <SEP> - <SEP> I <SEP> ~~~~~~ <SEP> I <SEP> I <SEP>
<tb><SEP> I <SEP> I <SEP> - <SEP> I <SEP> I
<tb><SEP> 1 <SEP> 100
<tb><SEP> 2 <SEP> 100
<tb><SEP> 3 <SEP> 112
<tb><SEP> I <SEP> I <SEP> I <SEP> I <SEP> I <SEP> I
<tb><SEP> 9 <SEP> 1 <SEP> 104
<tb><SEP> 10 <SEP> Top <SEP> 109 <SEP> - <SEP> 102
<tb><SEP> I <SEP> 11 <SEP> I <SEP> 1 <SEP> 83 <SEP> | <September>
<tb><SEP> I <SEP> I <SEP> | <SEP> I <SEP> I <SEP> I
<tb><SEP> 18 <SEP> 92
<tb><SEP> 19 <SEP> 115
<tb><SEP> 20 <SEP> 112
<tb><SEP> 4 <SEP> 95
<tb><SEP> 5 <SEP> 117
<tb><SEP> I <SEP> I <SEP> I <SEP> I <SEP> I <SEP> I
<tb><SEP> 12 <SEP> 118
<tb><SEP> 13 <SEP> 13 <SEP> Medium <SEP> 1 <SEP> 99 <SEP> l <SEP> - <SEP> 109 <SEP> 1 <SEP> - <SEP> 106 <SEP> | <September>
<tb><SEP> 14 <SEP> 99
<tb><SEP> 21 <SEP> 118
<tb><SEP> 22 <SEP> 124
<tb><SEP> 23 <SEP> 100
<tb><SEP> 6 <SEP> 1 <SEP> I <SEP> 89 <SEP> I <SEP> I
<tb><SEP> 7 <SEP> 129
<tb><SEP> 8 <SEP> 84
<tb><SEP> I <SEP> 15 <SEP> I <SEP> I <SEP> | <SEP> 135 <SEP> 1 <SEP> I <SEP> I
<tb><SEP> 16 <SEP> 1 <SEP> Low <SEP> I <SEP> 88 <SEP> l <SEP> - <SEP> 106 <SEP> 1 <SEP> | <September>
<tb><SEP> 17 <SEP> 90
<tb><SEP> 24 <SEP> 118
<tb><SEP> 25 <SEP> 100
<tb><SEP> 26 <SEP> 123
<tb><SEP> | <SEP> I <SEP> I <SEP> I <SEP> I <SEP> I
<tb><SEP> Sample <SEP> Medium <SEP> **
<tb> taken <SEP> at <SEP> destocking <SEP> 105
<tb> *: samples n 1 A 26: dry weight 1 1.5 kg / sample (total: 37kg) **: average sample destocking: 8 to 10 kg / bucket, ie 150 kg in total
Conclusion on Table VII
The two samplings lead to the same result: the residue contains 105 - 106 ppm of uranium.

 In addition, the content of the residue is homogeneous, and in particular there is no difference in the content between the top and bottom of the residue.

 The excellent results of this pilot test confirm those obtained in columns, while allowing an industrial extrapolation.

 The uranium yield reaches 92.3%, with a residue at 105 ppm U.

 The acid consumption is 18 kg / t for 28 kg / t H2SO4 used.

 The volume of production is 2.1 m3 / t, obtained on a leaching cycle of the order of 5 weeks (11 days of attack, 20 days of washing).

 It is of particular interest to note that these results are totally equivalent to those obtained on the pilot drive pulp / resins in sieved sieves.

 The settlement and the apparent densities are higher in stall (no wall effect as on the columns).

 Correlatively, the maximum percolation rate is also reduced (40 l / m2h at best), which remains largely sufficient since industrially current flow rates are of the order of 20 l / m2h.

COMPARATIVE EXAMPLE 3
This example relates to the implementation of a leaching process in which the ore was neither dried nor pelletized.

 A static leaching test was carried out on 1000 tonnes of the ore referred to in Example 1.

 2/3 of the ore received was shredded at 70 mm during the sampling operation, and the remaining 1/3 was sent as is to the treatment area.

 The ore was received on the treatment area as it arrived and then homogenized before stockpiling.

 The average grade obtained by the geologists, as a result of this sampling operation, is 1,520 ppm (PGT).

 The ore was stockpiled on a height of 1.50 m, the ground surface being 570 m2 (19 mx 30 m), an average surface area of the heap halfway up the order of 500 m2 (volume 737 m2, apparent density 1,25).

The humidity of the ore, estimated from a few samples, was taken at a flat rate of 23
for all the ore: for a pile of 925 tons wet, a dry ore weight of 712 t.

Leaching:
- Acid:
A volume of 110 m3 has an average acidity of 184 g / 1
H2SO4 was used, ie 20.2 tonnes H2SO4, or 28.4 kg / t H2SO4.

- Watering flow
It was mounted very gradually, up to 12 l / m2h to avoid a possible blockage of percolation. The flow rate was then maintained at 12 l / m2h for the duration of the test.

 Despite these precautions, puddles and runoff soon appeared and it is clear that only a small proportion of the flow sent actually percolated through the pile.

- Follow-up of the attack
The recycling of the sulfuric liquors continued for about 55 days followed by the beginning of the washing and the sending in production.

 Table VIII shows the analytical results of the follow-up of the test.

TABLE VIII

<tb> Content <SEP> U <SEP> Acidity <SEP> free <SEP> Redox
<tb> Observations
<tb> mg / 1 <SEP> g / 1 <SEP> mV
<tb> 52 <SEP> 20.6
<tb> 63 <SEP> 6.4
<tb> 180 <SEP> 16.7 <SEP> 610
<tb> 1 <SEP> 470 <SEP> 1 <SEP> 46.2 <SEP> 1
<tb> 1 <SEP> 231 <SEP> t <SEP> 15.9 <SEP> | <September>
<tb> 1 <SEP> 538 <SEP> 1 <SEP> 67.1 <SEP> 1
<tb> 1 <SEP> 540 <SEP> 1 <SEP> 61.2 <SEP> 1 <SEP> 447 <SEP> 1 <SEP>
<tb> 1 <SEP> 572 <SEP> 1 <SEP> 59.3 <SEP> 1
<tb> 1 <SEP> 651 <SEP> 1 <SEP> 56.8 <SEP> 1
<tb> 1 <SEP> 850 <SEP> 1 <SEP> 54.9 <SEP> 1 <SEP>
<tb> 1 <SEP> 913 <SEP> 1 <SEP> 50.0 <SEP> 1 <SEP>
<tb> 926 <SEP> 440
<tb> 1 <SEP> 950 <SEP> 1
<tb> 1 <SEP> 990 <SEP> 1 <SEP> 45.6 <SEP> 1 <SEP>
<tb> | <SEP> 1 <SEP> 170 <SEP> 1 <SEP> 48.5 <SEP> 1
<tb> 1 <SEP> 150 <SEP> 47.3
<tb> 1 <SEP> 330 <SEP> 49.0 <SEP> 438
<tb> 1 <SEP> 390 <SEP> 50.5
<tb> 1 <SEP> 1 <SEP> 090 <SEP> 1 <SEP> 38.2 <SEP> 1 <SEP> 1 <SEP> Adding <SEP> 50 <SEP> m <SEP> Water <SEP >
<tb> | <SEP> 1 <SEP> 460 <SEP> 1 <SEP> 37.7 <SEP> 1 <SEP> 438 <SEP> 1
<tb> 400 <SEP> 11.8 <SEP> Thunderstorm <SEP> important <SEP>:
<tb> 460 <SEP> 11.3 <SEP> coming <SEP> of water
<tb> 490 <SEP> 9.8
<tb> 1 <SEP> 580 <SEP> 1 <SEP> 8.8 <SEP> 1 <SEP> 650 <SEP> 1
<tb> 1 <SEP> 580 <SEP> 1 <SEP> 9.3 <SEP> 1 <SEP> 526 <SEP> 1
<tb> 435 <SEP> 11.3 <SEP> 490
<tb> 725 <SEP> 1 <SEP> 13.7 <SEP> 1 <SEP> 480 <SEP> 1
<tb> 1 <SEP> 798 <SEP> 1 <SEP> 14.2 <SEP> 1 <SEP>
<tb> start <SEP> of <SEP> wash <SEP> to <SEP> water
<Tb>
The strong variations observed have several causes
concentration of evaporation solutions
brutal dilutions of the solutions resulting on the one hand from a supply of 50 m3 of water, and on the other hand a stormy rain of exceptional violence.

- Washing and sending in production
The washing was carried out with neutral water. Given the low penetration of the solutions, and therefore the low U contents, each volume of water was recycled three to four days on the job before it was sent to production (cycle washing).

 Despite the use of this method, which reduces the specific volume of production, production reaches 2.7 m3 / t (compared with 1 to 1.2 m3 / t for "conventional" leaching).

 Table IX shows the monitoring of the production phase.

TABLE IX
Ore: Wet weight: 925 t
Humidity - 23%
Dry weight calculated 712 t

<tb><SEP> Volume <SEP> Production <SEP> U
<tb> Content <SEP> Yield
<tb> calculated
<tb> Day <SEP> Cumulative <SEP> Specific <SEP> U <SEP> Day <SEP> Cumulative
<tb><SEP> m3 <SEP> m3 <SEP> m3 / t <SEP> mg / l <SEP> kg <SEP> kg <SEP>%
<tb><SEP> 82 <SEP> 82 <SEP> 0.12 <SEP> 445 <SEP> 36.5 <SEP> 36.5 <SEP> 3.6
<tb><SEP> 106 <SEP> 188 <SEP> 0.26 <SEP> 434 <SEP> 46.0 <SEP> 82.5 <SEP> 8.2
<tb><SEP> 238 <SEP> 426 <SEP> 0.60 <SEP> 689 <SEP> 164.0 <SEP> 246.5 <SEP> 24.4
<tb><SEP> 241 <SEP> 667 <SEP> 0.94 <SEP> 319 <SEP> 76.9 <SEP> 323.4 <SEP> 32.0
<tb><SEP> 100 <SEP> 767 <SEP> 1.08 <SEP> 154 <SEP> 15.4 <SEP> 338.8 <SEP> 33.5
<tb><SEP> 266 <SEP> 1 <SEP> 033 <SEP> 1.45 <SEP> 132 <SEP> 35.1 <SEP> 373.9 <SEP> 37.0
<tb><SEP> 125 <SEP> 1 <SEP> 158 <SEP> 1.63 <SEP> 110 <SEP> 13.7 <SEP> 387.6 <SE> 38.3
<tb><SEP> 160 <SEP> 1 <SEP> 318 <SEP> 1.85 <SEP> 108 <SEP> 17.3 <SEP> 404.9 <SEP> 40.0
<tb><SEP> 84 <SEP> 1 <SEP> 402 <SEP> 1.97 <SEP> 163 <SEP> 13.7 <SEP> 418.6 <SEP> 41.4
<tb><SEP> 262 <SEP> 1 <SEP> 664 <SEP> 2.34 <SEP> 42 <SEP> 11.0 <SEP> 429.6 <SEP> 42.5
<tb><SEP> 205 <SEP> 1 <SEP> 869 <SEP> 2.62 <SEP> 29 <SEP> 5.9 <SEP> 435.5 <SEP> 43.0
<tb><SEP> 61 <SEP> 1 <SEP> 930 <SEP> 2.71 <SEP> 29 <SEP> 1.8 <SEP> 437.3 <SEP> 43.2
<Tb>
Conclusions on Table IX
The yields obtained in uranium are very low, around 43%.

The residue was sampled at the time of destocking and point samples were collected and analyzed for uranium: the results are shown in Table X below.
PAINTINGS

<tb> Sample * <SEP> Content <SEP> U <SEP> (ppm)
<tb> n <SEP> Up <SEP> Middle <SEP> Down
<tb> I <SEP> I <SEP> I
<tb> I <SEP> FT <SEP> 1 <SEP> - <SEP> V <SEP> 1 <SEP> 1 <SEP> 117 <SEP> 1 <SEP> 80 <SEP> 1 <SEP> 208 <SEP ><SEP> 1
<tb> V <SEP> V <SEP> 2 <SEP> 1 <SEP> 929 <SEP> 1 <SEP> 745 <SEP> 1 <SEP> 171 <SEP> | <September>
<tb> I <SEP> -V <SEP> 3 <SEP> 1 <SEP> 183 <SEP> 1 <SEP> 489 <SEP> 1 <SEP> 1 <SEP> 584 <SEP> 1
<tb> V <SEP> 4 <SEP> 11 / <SEP> 346 <SEP> 321
<tb> FT <SEP> 2 <SEP> - <SEP> V <SEP> 1 <SEP> 411 <SEP> 1 <SEP> 980 <SEP> 784
<tb> I <SEP> V <SEP> 2 <SEP> 1 <SEP> 260 <SEP> 1 <SEP> 781 <SEP> 1 <SEP> 288 <SEP> i <SEP>
<tb> I <SEP> V <SEP> 3 <SEP> 1 <SEP> 963 <SEP> í <SEP> 1 <SEP> 053 <SEP> 1 <SEP> 2 <SEP> 084 <SEP> í <SEP >
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 193 <SEP> 1 <SEP> 342 <SEP> | <SEP> 447 <SEP> 1
<tb> I <SEP> FT <SEP> 3 <SEP> - <SEP> V <SEP> 1 <SEP> I <SEP> 1 <SEP> 170 <SEP> 1 <SEP> 1 <SEP> 269 <SEP > 1 <SEP> 698 <SEP> | <September>
<tb> I <SEP> V <SEP> 2 <SEP> | <SEP> 165 <SEP> 1 <SEP> 1 <SEP> 349 <SEP> 1 <SEP> 1 <SEP> 910 <SEP> | <September>
<tb> V <SEP> 3 <SEP> 124 <SEP> 835 <SEP> 1 <SEP> 280
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 178 <SEP> 1 <SEP> 1 <SEP> 900 <SEP> 1 <SEP> 266 <SEP> | <September>
<tb> FT <SEP> 4 <SEP> - <SEP> V <SEP> 1 <SEP> 1 <SEP> 259 <SEP> 1 <SEP> 1 <SEP> 319 <SEP> 1 <SEP> 1 <SEP > 590 <SEP> 1 <SEP>
<tb> I <SEP> V <SEP> 2 <SEP> 1 <SEP> 210 <SEP> 1 <SEP> 2 <SEP> 014 <SEP> 1 <SEP> 2 <SEP> 060 <SEP> | <September>
<tb> V <SEP> V <SEP> 3 <SEP> 1 <SEP> 203 <SEP> 1 <SEP> 267 <SEP> 1 <SEP> 1 <SEP> 429 <SEP> | <September>
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 135 <SEP> 1 <SEP> 267 <SEP> 1 <SEP> 377 <SEP> | <September>
<tb> FT <SEP> 5 <SEP> - <SEP> V <SEP> 1 <SEP> 115 <SEP> 437 <SEP> 1 <SEP> 747
<tb> V <SEP> 2 <SEP> 1 <SEP> 514 <SEP> 1 <SEP> 765 <SEP> 1 <SEP> 379
<tb> V <SEP> 3 <SEP> 231 <SEP> 1 <SEP> 216 <SEP> 1 <SEP> 234
<tb><SEP> V <SEP> 4 <SEP> 168 <SEP> 858 <SEP> 987
<tb> I <SEP> FT <SEP> 6 <SEP> - <SEP> V <SEP> 1 <SEP> 1 <SEP> 124 <SEP> 1 <SEP> 477 <SEP> 1 <SEP> 691 <SEP > 1
<tb> I <SEP> V <SEP> 2 <SEP> 1 <SEP> 904 <SEP> 1 <SEP> 1 <SEP> 412 <SEP> 1 <SEP> 1 <SEP> 549 | <September>
<tb> i <SEP> V <SEP> 3 <SEP> 1 <SEP> 216 <SEP> 1 <SEP> 1 <SEP> 229 <SEP> | <SEP> 1 <SEP> 912 <SEP> | <September>
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 178 <SEP> 1 <SEP> 1 <SEP> 707 <SEP> 1 <SEP> 1 <SEP> 673 <SEP> 1
<tb> FT <SEP> 7 <SEP> - <SEP> V <SEP> 1 <SEP> 1 <SEP> 134 <SEP> 1 <SEP> 735 <SEP> 1 <SEP> 1 <SEP> 382 <SEP > 1
<tb> I <SEP> V <SEP> 2 <SEP> 1 <SEP> 207 <SEP> 1 <SEP> 2 <SEP> 566 <SEP> 1 <SEP> 1 <SEP> 476 <SEP> | <September>
<tb> I <SEP> V <SEP> 3 <SEP> 1 <SEP> 182 <SEP> 1 <SEP> 613 <SEP> 1 <SEP> 1 <SEP> 236 <SEP> | <September>
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 413 <SEP> 1 <SEP> 1 <SEP> 015 <SEP> 1 <SEP> 490 <SEP> 1
<tb> | <SEP> FT <SEP> 8 <SEP> - <SEP> V <SEP> 1 <SEP> | <SEP> 99 <SEP> 1 <SEP> 642 <SEP> 1 <SEP> 1 <SEP> 350 <SEP> 1
<tb> I <SEP> V <SEP> 2 <SEP> 1 <SEP> 161 <SEP> 1 <SEP> 710 <SEP> 1 <SEP> 1 <SEP> 160 <SEP> | <September>
<tb> I <SEP> V <SEP> 3 <SEP> 1 <SEP> 206 <SEP> 1 <SEP> 1 <SEP> 170 <SEP> 1 <SEP> 1 <SEP> 213 <SEP> | <September>
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 133 <SEP> 1 <SEP> 300 <SEP> 1 <SEP> 364 <SEP> | <September>
<tb> I <SEP> FT <SEP> 9 <SEP> - <SEP> V <SEP> 1 <SEP> 1 <SEP> 159 <SEP> 1 <SEP> 716 <SEP> 1 <SEP> 949 <SEP > 1
<tb> I <SEP> V <SEP> 2 <SEP> 1 <SEP> 189 <SEP> 1 <SEP> 186 <SEP> 1 <SEP> 1 <SEP> 547 <SEP> | <September>
<tb> I <SEP> V <SEP> 3 <SEP> 1 <SEP> 363 <SEP> 1 <SEP> 1 <SEP> 156 <SEP> 1 <SEP> 1 <SEP> 904 <SEP> | <September>
<tb> I <SEP> V <SEP> 4 <SEP> 1 <SEP> 124 <SEP> 1 <SEP> 609 <SEP> 1 <SEP> 1 <SEP> 419 <SEP> | <September>
<tb> Content
<tb><SEP> 318 <SEP> 960 <SEP> 1 <SEP> 143
<tb><SEP> average
<tb> Average
<tb> 807 <SEP> ppm
<tb><SEP> General
<tb> *: dry weight: 2 to 3 kg per sample
The average grade of these 108 samples is 807 ppm, which replenishes a feed grade of 1,420 ppm and an average yield of 43.2 "t.

In spite of the high dispersion of the contents, we can see (Table XI) a very clear content gradient between the lower part and the upper part of the pile.
Medium content Yield U
ppm. Top slice (50 cm): 318 77.6 Average slice (50 cm): 960 32.4. Bottom slice (50 cm): 1,143 19,5
It is clear that only the superficial part of the pile has been leached, and this despite the small thickness of it.

 The main results of the test are shown in Table XI below.

TABLE XI

<tb> ORE
<tb> Weight <SEP> wet <SEP> 925 <SEP> t
<tb> Humidity <SEP> initial <SEP> 23 <SEP>%
<tb> Weight <SEP> sec <SEP> calculated <SEP> 712 <SEP> t
<tb> Humidity <SEP> final <SEP> No <SEP> determined
<tb> ATTACK <SEP> Initial <SEP> Volume <SEP> 155 <SEP> l / t
<tb> Acid <SEP> 28.4 <SEP> kg / t
<tb> Duration <SEP> 57 <SEP> days
<tb> Flow rate <SEP> 12 <SEP> 1 / m2.h
<tb> WASH <SEP> with <SEP> cycle <SEP> Water <SEP> Neutral
<tb> Volume <SEP> total <SEP> passed <SEP>#<SEP><SEP> 5 <SEP> m3 / t
<tb> Duration <SEP> 26 <SEP> days
<tb> Flow rate <SEP> 12 <SEP> 1 / m2.h
<tb> PRODUCTION <SEP> Volume <SEP> 2,71 <SEP> m3 / t
<tb> BALANCE SHEET <SEP> URANIUM
<tb> Content <SEP> analyzed <SEP> residue <SEP> 807 <SEP> ppm
<tb> Content <SEP> reconstituted <SEP> feed <SEP> 1 <SEP> 421 <SEP> ppm
<tb> Extraction <SEP> yield <SEP> U <SEP> 43.2 <SEP>%
<tb> BALANCE SHEET <SEP> H2SO4
<tb> Acid <SEP> mis <SEP> in <SEP> work <SEP> 28.4 <SEP> kg / t
<tb> Acid <SEP> consumed <SEP> ND <SEP> kg / t
<tb> OBSERVATIONS <SEP> Retention <SEP> liquid <SEP> in <SEP> recycling <SEP> No <SEP> determined
<tb> Tessement <SEP> No <SEP> visible
<tb> Acidity <SEP> in <SEP> end <SEP> of attack <SEP> 10 <SEP> to <SEP> 15 <SEP> g / 1
<tb><SEP> (dilution <SEP> by <SEP> thunderstorm)
<Tb>
In view of this test, it is clear that the bad percolation of the liquors inside the ore allows to attack only the superficial layer of the pile (at best the first 50 centimeters).

 This comparative test demonstrates the fact that the process of the invention has great advantages over known processes, insofar as it allows an efficient percolability of clay ores placed in piles which thus makes the treatment of such ores economically profitable. .

Claims (13)

 leaching the uranium ore (leaching step) thus pelletized with a solution containing water, or an acid or a mixture of water and an acid, an acid being used during of one or less of the pelletizing and leaching steps, the liquid and acid used during pelletizing and the solution used during leaching to be compatible with each other, the yield of uranium dissolved in the production liquors obtained being equal to at least about 85%, and in particular at least equal to about 90%.  the particles are pelleted (pelletizing step) with a diameter of about 5 to about 60 mm, preferably about 5 to about 20 mm, using a liquid and / or a acid in an amount such that the moisture of the pellets is from about 13% to about 21, especially from about 15% to about 18, the amounts of liquid used being from about 120 l / t to about 200 l / t, in particular from about 120 l / t to about 160 l / t  the ore obtained in the preceding step is crushed into particles having a particle size of from about 10 μm to about 20 mm, and preferably from about 500 μm to about 10 mm, and advantageously from about 4 to about 10 mm;  the clay ore having a moisture content greater than about 20%, in particular of about 25%, is dried so that it reaches a moisture content of about 0% to about 10%, in particular from about 3% to about 8%, and advantageously about 5 g  1. Process for accelerated acid lixiviation of uranium ore, characterized in that it comprises the following steps  2. A process for accelerated acid delivery of uranium clay ore according to claim 1, characterized in that the ore is dried by bringing it to a temperature of about 100 to about 300xi, especially about 200su.  3. Process for accelerated acid leaching of uranium ore according to claim 1 or 2, characterized in that when the pelletization is carried out using a liquid and / or using acid and when the leaching is carried out using a solution of water and acid or acid, the acid used during the pelletizing is identical to that used during the leaching and is chosen from hydrochloric acid, nitric acid and preferably sulfuric acid.  4. Process for accelerated acid leaching of uranium ore according to claims 1 to 3, characterized in that the liquid used during pelletizing is water.  5. Process for accelerated acid leaching of uranium ore according to claims 1 to 4, characterized in that the pelletization is carried out using water and acid, preferably identical to that possibly used in the leaching, the amount of acid used during pelletization ranging from about 1/10 to about 100% of the acid needed to solution the uranium.  6. Process for accelerated acid leaching of uranium ore according to claims 1 to 5, characterized in that the pelletization is carried out using water and an acid and that the solution used during leaching is some water.  7. Process for accelerated acid leaching of uranium ore according to claims 1 to 6, characterized in that in the pelletizing step, a binder is used, the latter having to be compatible on the one hand with the liquid and the used in pelletizing and secondly with the solution used during the leaching step.  8. Process for accelerated acid leaching of uranium ore according to claims 1 to 6, characterized in that the binder consists of a member selected from the group comprising sodium silicate, potassium silicate or a mixture of these elements , calcium sulphate (CaSO4), plaster (CaSO4, 1/2 H2O), gypsum (CaSO4, 2H2O) or a mixture of these elements.  9. Process for accelerated acid leaching of uranium ore according to any one of claims 1 to 8, characterized in that a uranium oxidant capable of oxidizing UIV in UVI, chosen from sodium chlorate, is used. , Caro H2505 acid or manganese oxide.  10. Process for accelerated acid leaching of uranium ore according to any one of claims 1 to 9, characterized in that all of the acid used for pelletizing and leaching is from about 5 to about 80, in particular at approximately 30 kg per ton of ore to be treated.  11. A process for accelerated acid leaching of uranium ore according to any one of claims 1 to 7, characterized in that the acid used during pelletizing is from about 0 to about 80, in particular from about 15 to 30 kg per ton of ore to be treated.  12. Process for accelerated acid leaching of uranium ore according to any one of claims 1 to 11, characterized in that the binder is used in a proportion of about 0.5 to about 40, preferably about 3 to about 8, and preferably about 5 kg per ton of ore to be treated.  13. Process for accelerated acid leaching of uranium ore according to claim 11, characterized in that the oxidizer of the uranium is used in a proportion of about 0.5 to about 20 kg per ton of ore, in particular of about 2 to about 10 kg per ton of ore.