EP0089294B1 - Method and installation for in situ lixiviation of ore - Google Patents

Method and installation for in situ lixiviation of ore Download PDF

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Publication number
EP0089294B1
EP0089294B1 EP83400540A EP83400540A EP0089294B1 EP 0089294 B1 EP0089294 B1 EP 0089294B1 EP 83400540 A EP83400540 A EP 83400540A EP 83400540 A EP83400540 A EP 83400540A EP 0089294 B1 EP0089294 B1 EP 0089294B1
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Prior art keywords
solution
pressure
conduit
lixiviation
injection
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German (de)
French (fr)
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EP0089294A1 (en
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Jacques Roussel
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LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/34—Arrangements for separating materials produced by the well
    • E21B43/40—Separation associated with re-injection of separated materials
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/28—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent

Definitions

  • the present invention relates to a method and an installation for in situ leaching of ores, such as nickel, cobalt, copper, uranium, etc., using a leaching solution composed of a basic solution in which oxygen is added which is circulated in a pipe placed in an injection well, said pipe emerging at its downstream end in a bottom zone called leaching, with recovery in one or more recovery wells a composite solution incorporating metal compounds extracted from the ore, which is treated to separate said compounds, then is regenerated with the optional addition of basic products, reoxygenation and recycling in said injection well pipe.
  • a network of a plurality of injection wells distributed on the surface is used with a plurality of recovery wells also distributed on the surface and at a distance from the injection wells.
  • oxidant the oxygen which is dissolved in the basic solution, because it is less expensive than hydrogen peroxide but its low solubility in aqueous solutions makes its use delicate.
  • the first drawback of the use of oxygen in a leaching solution lies in the formation, when incorporating sufficient quantities of oxygen, of oxygen bubbles with a diameter greater than a few tens of microns, thus forming a two-phase mixture which flows with difficulty through the micro-fractures of the rock so that one is forced to artificially fracture the ore between an injection well and a recovery well, for example with explosives, which allows the passage of the two-phase leaching solution, but such a fracturing operation is delicate and costly.
  • the average pressure in the vertical injection pipe is close to half of the fracturing pressure at the top of the leaching zone and therefore, the concentration of dissolved oxygen is at most equal to half of what 'one might hope for operational pressure in the leaching area. For all these reasons, the oxygen utilization yield is low, of the order of 40%.
  • the subject of the present invention is a process for in situ leaching of ore which avoids all the drawbacks mentioned above by certainly eliminating any formation of oxygen bubbles while approaching, throughout the leaching zone of the limit saturation for a pressure slightly lower than the fracturing pressure of the rock. Thanks to this measure, the leaching solution has very effective properties with regard to the dissolution of the ore, so that one can obtain an oxygen utilization yield very close to 100%.
  • the internal diameter of the injection pipe is chosen so that the pressure of the leaching solution increases, preferably, slightly, during its transfer into said pipe, the value of the pressure of said solution at the downstream end of said pipe being reduced to a value just equal to that of the pressure of said solution at the upstream end of said pipe, by expansion of said solution through throttling means placed in the lower part of said pipe.
  • the internal diameter of the injection pipe is chosen so that the pressure of the leaching solution increases, preferably, slightly, during its transfer into said pipe, the value of the pressure of said solution at the downstream end of said pipe being brought to a value barely higher than that of the pressure of said solution at the upstream end of said pipe, by expansion of said solution through throttling means placed in the lower part of said pipe.
  • the difference between the pressure at the downstream end and the pressure at the upstream end is preferably less than or equal to 1 bar.
  • the throttling means placed at the bottom of the injection pipe can be, for example, constituted by a thin-walled orifice or by a valve which may adjust the opening by suitable means placed on the surface.
  • the calculation of the diameter of the throttle orifice as a function of the desired effect is carried out by conventional methods such as those described in the "Unit Operations of Chemical Engineering" manual cited above.
  • the invention also relates to an installation for implementing the method according to the invention.
  • throttling means are placed at the bottom of the injection pipe.
  • FIG. 1 shows an installation which comprises, in the ground, a plurality of injection wells, only one of which is represented in (1), which are uniformly distributed on the surface and recovery wells, of which only one is shown in (2), also distributed between said injection wells.
  • Each injection well is equipped with an injection pipe (3) opening at its downstream end into a leaching zone (4).
  • the pipe (3) passes through a seal (5) with the well (1), the seal (5) being placed a little above the downstream end of said condite (3).
  • Each injection pipe (3) is supplied with leaching solution by a pipe (6) ending at one at the surface end of the injection pipe (3), on the other hand at the surface end d '' a recovery conduit (7) formed in each recovery well (2), each conduit (7) having a downstream end at a level lower than that of an injection conduit (3), but nevertheless at a level intermediate of the leaching zone (4).
  • Each recovery duct (7) incorporates a pump (11) located near its downstream end, which is set in motion for example by a vertical shaft (12) from a driving eccentric (13). In this way, the leaching solution loaded with dissolved metal compounds extracted from the ore and which flows in the direction of the arrow F is taken up by the pump (11) and is recycled through the conduit (6) to an injection well.
  • this conduit (6) successively incorporates from the recovery conduit (7), a separation device (20), from which the metals are extracted in (21) from the leaching solution, a pressure pump (22) carrying the leaching solution at an elevated pressure little lower than the fracturing pressure of the rock then, at this pressure, a supersaturation oxygenator (23), a phase separator (24), the liquid phase only being directed towards the injection conduits (3 ) by a flow measurement member (25), while the gas phase (26) is recycled by a booster (27) to the oxygenator (23), preferably on an oxygen supply duct (28) terminating to this oxygenator (23).
  • the oxygenator (23) is preferably a pipe-type reactor as described, for example, in the article by A.I. Ch. E. Journal of September 1964 "Gas Phase Controlled Mass Transfer in Two Phases Annular Horizontal Flow" by J. D. Anderson, R. E. Bellinger and D. E. Lamb.
  • the internal diameter d of the injection line (3) (for example, depending on the relationship so that the pressure of the leaching solution, which had the value P 3a at the upstream end 3a of the pipe (3) remains constant during its transfer into this pipe. More precisely, from the upstream end 3a to the downstream end 3b, at each elementary level of the pipe (3), the pressure decrease due to pressure losses is just equal to the pressure increase due hydrostatic effect; so that the pressure of the solution remains constant throughout its path in the pipe (3) and that its value P 3b at the downstream end 3b is equal to the value P 3a at the upstream end 3a.
  • FIG 2 there is shown an in situ ore leaching facility, much of which is similar to the facility shown in Figure 1 (the same references have been assigned to the same elements).
  • This installation comprises a plurality of injection wells (1) and recovery wells (2).
  • Each recovery well (2) is analogous to the recovery well shown in la_figure 1; the recovery duct (7) is connected, at its surface end, to a duct (6) which successively comprises a separation device (20), a pressure pump (22), a supersaturation oxygenator (23) , a phase separator (24), a flow measurement member (25), and which terminates at the surface end of the injection pipe (33) of the injection well (1).
  • This injection pipe (33) has a diameter greater than that of the injection pipe (3) of the installation of FIG. 1.
  • the pipe (33) passes through a seal (35) which is placed, for example, at the top of the injection well (1).
  • the pipe (33) has, at its downstream end, a thin-walled orifice (36) which reduces its diameter there.
  • the internal diameter d of the injection pipe (33) is chosen (for example according to the relation so that the pressure of the leaching solution which had the value P 33a at the upstream end (33a) of the pipe (33) increases, slightly preferably, during its transfer in said pipe until a value P 33c ⁇ More precisely, from the upstream end (33a) to the level (33c just upstream of the thin-walled orifice (36), at each elementary level of the pipe (33), the reduction in pressure due to the pressure losses is less than the increase in pressure due to the hydrostatic effect; so that the pressure of the leaching solution reaches at level (33c) a value P 33c higher, and preferably slightly higher, than the value P 33a.
  • the difference between the pressure P 33c of the leaching solution upstream of the orifice (36) and the pressure P 33b of said solution downstream of said orifice (36) is less than 5 bars.
  • the method is implemented in the installation shown in FIG. 1.
  • the injection pipe (3) of the well (1) has a length of 110m and an internal diameter of 18.58mm.
  • the leaching solution is sent into line (3) at a flow rate of 1.25 1 / sec.
  • This solution contains 0.5 g / liter of H 2 SO 4 , 6.25 g / liter of CaC1 2 and 1.75 g / liter of CaS0 4 . Its dissolved oxygen concentration is 200 ppm.
  • the temperature on the ground is 35 ° C and the temperature at the bottom of the well is 40 c , i.e. a average temperature in the pipe (3) of 37.5 ° C.
  • the pressure of the leaching solution P 3a , at the upstream end of the pipe (3), is 6.5 bars. As this pressure remains constant throughout the path of the solution in the pipe (3), the pressure P3b at the downstream end of the pipe (3), the pressure P 3b at the downstream end of the pipe is also 6, 5 bars.
  • the method is implemented in the installation shown in FIG. 2.
  • the injection pipe (33) of the well (1) has a length of 110m and an internal diameter of 20.96mm.
  • the diameter of the orifice (36) is 9.23mm.
  • the leaching solution has the same composition as that of Example 1. Its concentration of dissolved oxygen is 200 ppm. It is sent into the pipe (33) at a rate of 1.25 1 / sec.
  • the average temperature in the pipe (33) is 37.5 ° C (floor temperature 35 ° C and bottom temperature 40 ° C).
  • the pressure of the leaching solution P 33a , at the upstream end of the pipe (33) is 6.3 bars. It increases slightly during the transfer in the pipe (33) and reaches at level (33c), just upstream of the orifice (36), a value P 33c of 11 bars. After the solution has passed through the orifice (36), the pressure is brought back to a P 33b value of 6.5 bars.
  • the maximum dissolved oxygen concentration at the bottom of the well is 200 ppm.
  • the method is implemented in the installation shown in FIG. 2.
  • the injection pipe (33) of the well (1) has a length of 110m and the seal is placed 55m from the surface end of the well (1).
  • the leaching solution contains 0.5 g / liter of H 2 SO, 6.25 g / liter of CaC1 2 and 1.75 g / liter of CaSO 4 . Its dissolved oxygen concentration is 180 ppm. It is sent into the injection line (33) at a rate of 1.25 / sec.
  • the temperature on the ground is 35 ° C and at the bottom of the well 40 ° C, an average temperature in the pipe (33) of 37.5 ° C.
  • the diameter of the orifice (36) is a function of the diameter of the pipe (33), the flow rate of the leaching solution, the upstream pressures P 33a and downstream P 33b chosen, as well as the characteristics of the leaching solution.

Description

La présente invention concerne un procédé et une installation de lixiviation in situ de minerais, tels que nickel, cobalt, cuivre, uranium, etc..., à l'aide d'une solution de lixiviation composée d'une solution de base dans laquelle on adjoint de l'oxygène que l'on fait circuler dans une conduite placée dans un puits d'injection, ladite conduite débouchant à son extrémité aval dans une zone de fond dite de lixiviation, avec reprise dans un ou plusieurs puits de récupération d'une solution composite incorporant des composée métalliques extraits du minerai, qui est traitée pour séparar lesdits composés, puis est régénérée avec adjonction éventuelle de produits de base, réoxygénation et recyclage dans ledit conduit de puits d'injection. En pratique, on utilise un réseau d'une pluralité de puits d'injection répartis en surface avec une pluralité de puits de récupération également répartis en surface et à distance des puits d'injection. D'une façon générale, on préfère, à titre d'oxydant, l'oxygène que l'on dissout dans la solution de base, car il est moins onéreux que l'eau oxygénée mais sa faible solubilité dans les solutions aqueuses rend son emploi délicat.The present invention relates to a method and an installation for in situ leaching of ores, such as nickel, cobalt, copper, uranium, etc., using a leaching solution composed of a basic solution in which oxygen is added which is circulated in a pipe placed in an injection well, said pipe emerging at its downstream end in a bottom zone called leaching, with recovery in one or more recovery wells a composite solution incorporating metal compounds extracted from the ore, which is treated to separate said compounds, then is regenerated with the optional addition of basic products, reoxygenation and recycling in said injection well pipe. In practice, a network of a plurality of injection wells distributed on the surface is used with a plurality of recovery wells also distributed on the surface and at a distance from the injection wells. In general, it is preferred, as oxidant, the oxygen which is dissolved in the basic solution, because it is less expensive than hydrogen peroxide but its low solubility in aqueous solutions makes its use delicate.

Le premier inconvénient de l'utilisation de l'oxygène dans une solution de lixiviation réside dans la formation, au moment de l'incorporation de quantités suffisantes d'oxygène, de bulles d'oxygène d'un diamètre supérieur à quelques dizaines de microns, formant ainsi un mélange diphasique qui s'écoule difficilement au travers des micro-fractures de la roche en sorte que l'on est obligé de fracturer artificiellement le minerai entre un puits d'injection et un puits de récupération, par exemple avec des explosifs, ce qui permet le passage de la solution lixiviante diphasique, mais une telle opération de fracturation est délicate et coûteuse.The first drawback of the use of oxygen in a leaching solution lies in the formation, when incorporating sufficient quantities of oxygen, of oxygen bubbles with a diameter greater than a few tens of microns, thus forming a two-phase mixture which flows with difficulty through the micro-fractures of the rock so that one is forced to artificially fracture the ore between an injection well and a recovery well, for example with explosives, which allows the passage of the two-phase leaching solution, but such a fracturing operation is delicate and costly.

C'est la raison pour laquelle, dans une proposition récente rapportée dans le brevet américain No. 4.116.488, on a réalisé une solution lixiviante qui, bien qu'à l'état diphasique, se présente sous forme liquide avec des micro- bulles réparties et l'on s'est efforcé de faire en sorte déviter, lors de l'injection, la coalescence des bulles. D'une façon plus précise, la solution lixiviante diphasique injectée dans la zone de lixiviation est recyclée par un aspirateur du type "Venturi" de façon à empêcher la formation d'une poche gazeuse et, pour améliorer encore la stabilité du mélange diphasique en luttant contre la coalescence des bulles, on prévoit d'ajouter un produit tensio-Eclif dans la solution lixiviante.This is the reason why, in a recent proposal reported in American patent No. 4,116,488, a leaching solution was produced which, although in the two-phase state, is present in liquid form with microbubbles distributed and an effort was made to avoid, during the injection, the coalescence of the bubbles. More precisely, the two-phase leaching solution injected into the leaching zone is recycled by a vacuum cleaner of the "Venturi" type so as to prevent the formation of a gas pocket and, to further improve the stability of the two-phase mixture by fighting against coalescence of bubbles, it is planned to add a tensio-Eclif product to the leaching solution.

Cette solution connue nécessite un dispositif "Venturi" aménagé au fond du puits, ce qui est délicat et risque d'ailleurs de provoquer des bouchages. En fait, il est illusoire d'espérer maintenir, sans aucune coalescence des bulles, un écoulement d'un fluide diphasique dans un conduit vertical de plusieures centaines de mètres malgré les aménagements rappelés ci-dessus. En outre, dans un conduit vertical d'une telle longueur, la pression est loin d'être constante et en fait croit linéairement depuis le niveau du sol jusqu'au sommet de la zone de lixiviation, où elle atteint une valeur légèrement inférieure à une limite qui correspond à la pression de fracturation de la roche en ce point. En réalité donc, la pression moyenne dans le conduit d'injection vertical est voisine de la moitié de la pression de fracturation au sommet de la zone de lixiviation et par conséquent, le concentration en oxygène dissous est au plus égale à la moitié de ce qu'on pourrait espérer pour la pression opérationnelle dans la zone de lixiviation. Pour toutes ces raisons, le rendement d'utilisation en oxygène est faible, de l'ordre de 40%.This known solution requires a "Venturi" device fitted at the bottom of the well, which is delicate and may also cause blockages. In fact, it is illusory to hope to maintain, without any coalescence of the bubbles, a flow of a two-phase fluid in a vertical conduit of several hundreds of meters despite the arrangements recalled above. Furthermore, in a vertical duct of such length, the pressure is far from constant and in fact increases linearly from ground level to the top of the leaching zone, where it reaches a value slightly less than a limit which corresponds to the fracturing pressure of the rock at this point. In reality therefore, the average pressure in the vertical injection pipe is close to half of the fracturing pressure at the top of the leaching zone and therefore, the concentration of dissolved oxygen is at most equal to half of what 'one might hope for operational pressure in the leaching area. For all these reasons, the oxygen utilization yield is low, of the order of 40%.

La présente invention a pour objet un procédé de lixiviation in situ de minerai qui évite tous les inconvénients mentionnés ci-dessus en supprimant à coup sûr toute formation de bulles d'oxygène tout en s'approchant, dans toute la zone de lixiviation de la limite de saturation pour une pression peu inférieure à la pression de fracturation de la roche. Grâce à cette mesure, la solution lixiviante a des propriétés très performantes en ce qui concerne la dissolution du minerai, si bien que l'on peut obtenir un rendement d'utilisation en oxygène très voisin de 100%.The subject of the present invention is a process for in situ leaching of ore which avoids all the drawbacks mentioned above by certainly eliminating any formation of oxygen bubbles while approaching, throughout the leaching zone of the limit saturation for a pressure slightly lower than the fracturing pressure of the rock. Thanks to this measure, the leaching solution has very effective properties with regard to the dissolution of the ore, so that one can obtain an oxygen utilization yield very close to 100%.

Le procédé selon l'invention est caractérisé par la combinaison des mesures suivantes:

  • a) le diamètre interne de la conduite d'injection est choisi, compte tenu du débit volumétrique de la solution lixiviante, de l'accroissement hydrostatique de la pression et de la diminution de pression par pertes de charge lors du transfert de ladite solution lixiviante de l'extrémité amont à l'extrémité aval de ladite conduite, de façon à ce que la pression de ladite solution lixiviante à l'extrémité aval soit sensiblement égale à la pression de ladite solution lixiviante à l'extrémité amont, la pression de ladite solution dans ladite conduite ne devenant jamais, au cours de son transfert dans ladite conduite, notablement inférieure à la valeur de sa pression à l'extrémité amont de ladite conduite, ledit diamètre interne d de la conduite d'injection étant substantiellement déterminé par la relation suivante:
    Figure imgb0001
    dans laquelle:
    • Qest le débit volumétrique de la solution en m 3 .s-1
    • f=0,0014+0,125 Re-o.32 avec Re=
      Figure imgb0002
    • g=9,81 m.s-2
    • p est la masse spécifique de la solution en kg.m-3
    • !lest la viscosité dynamique de la solution en poiseuille,
  • b) la pression de la solution lixiviante, à l'extrémité amont de ladite conduite, a une valeur inférieure à la pression de fracturation de la roche au sommet de la zone de lixiviation, de préférence peu inférieure à ladite pression de fracturation;
  • c) la concentration d'oxygène dissous dans la solution lixiviante, assurée en amont, est inférieure à la limite de saturation pour la pression amont de ladite solution, et de pré- "érence, peu inférieure à ladite limite de saturation.
The method according to the invention is characterized by the combination of the following measures:
  • a) the internal diameter of the injection pipe is chosen, taking into account the volumetric flow rate of the leaching solution, the hydrostatic increase in pressure and the reduction in pressure due to pressure drops during the transfer of said leaching solution from the upstream end to the downstream end of said pipe, so that the pressure of said leaching solution at the downstream end is substantially equal to the pressure of said leaching solution at the upstream end, the pressure of said solution in said pipe never becoming, during its transfer in said pipe, significantly less than the value of its pressure at the upstream end of said pipe, said internal diameter d of the injection pipe being substantially determined by the following relation :
    Figure imgb0001
     in which:
    • Q is the volumetric flow rate of the solution in m 3 .s - 1
    • f = 0.0014 + 0.125 Re-o.32 with Re =
      Figure imgb0002
    • g = 9.81 ms- 2
    • p is the specific mass of the solution in kg. m - 3
    • ! is the dynamic viscosity of the poiseuille solution,
  • b) the pressure of the leaching solution, at the upstream end of said pipe, has a value less than the fracturing pressure of the rock at the top of the leaching zone, preferably slightly less than said fracturing pressure;
  • c) the concentration of dissolved oxygen in the leaching solution, provided upstream, is less than the saturation limit for the pressure upstream of said solution, and preferably, little less than said saturation limit.

Compte tenu du problème posé, à savoir: d'une part avoir une solution concentrée le plus possible en oxygène (donc avoir une pression d'oxygène la plus forte possible), et d'autre part, ne pas avoir risque de dégazage provoquant la formation de bulles d'oxygène gênantes pour l'efficacité du procédé (c'est-à-dire éviter une chute de pression) au cours du transfert de la solution lixiviante dans la conduite d'injection, les études du demandeur l'ont amené à observer que:

  • -d'une part, dans le cas où la conduite d'injection présente un gros diamètre, la diminution de la pression due aux pertes de charge est inférieure à l'augmentation de pression due à l'effet hydrostatique; la pression de la solution lixiviante à l'extrémité aval de la conduite est donc supérieur à la pression à l'extrémité amont, ce qui implique que l'on n'a pas risque de dégazage, mais que, par contre, on n'a pas dissous autant d'oxygène dans la solution lixiviante que l'on aurait pu;
  • -d'autre part, dans le cas où la conduite d'injection présente une faible diamètre, la diminution de pression due aux pertes de charges est supérieure à l'augmentation de pression due à l'effet hydrostatique; la pression de la solution lixiviante à l'extrémité aval de la conduite est donc inférieure à la pression à l'extrémité amont, ce qui implique que l'on a pu dissoudre le plus possible d'oxygène dans la solution lixiviante, mais que, par contre, il y a risque de dégazage puisque l'on a une chute de pression le long de la conduite et donc désaturation de la solution.
In view of the problem posed, namely: on the one hand having a solution that is as concentrated as possible in oxygen (therefore having the highest possible oxygen pressure), and on the other hand, not having the risk of degassing causing the formation of troublesome oxygen bubbles for the efficiency of the process (i.e. avoiding a pressure drop) during the transfer of the leaching solution into the injection line, the applicant's studies have led it note that:
  • on the one hand, in the case where the injection pipe has a large diameter, the reduction in pressure due to pressure drops is less than the pressure increase due to the hydrostatic effect; the pressure of the leaching solution at the downstream end of the pipe is therefore higher than the pressure at the upstream end, which implies that there is no risk of degassing, but that, on the other hand, there is no did not dissolve as much oxygen in the leach solution as one could have;
  • on the other hand, in the case where the injection pipe has a small diameter, the pressure decrease due to the pressure drops is greater than the pressure increase due to the hydrostatic effect; the pressure of the leaching solution at the downstream end of the pipe is therefore lower than the pressure at the upstream end, which implies that as much oxygen as possible was dissolved in the leaching solution, but that, on the other hand, there is a risk of degassing since there is a pressure drop along the pipe and therefore desaturation of the solution.

Compte tenu de ces observations, le demandeur a imaginé de choisir une conduite d'injection de diamètre tel que, d'une part, les valeurs de la pression de la solution lixiviante soient sensiblement égales à l'extrémité aval et à l'extrémité amont de ladite conduite, d'autre part, la pression de la solution lixiviante au cours de son transfert dans la conduite ne devienne jamais notablement inférieure à la valeur de sa pression à l'extrémité amont de ladite conduite. Ainsi, grâce au procédé de l'invention tel que défini précédemment, on peut établir en surface une teneur en oxygène dissous dans la solution lixiviante voisine de la limite de saturation, sans pour autant provoquer de dégazage intempestif ultérieur puisqu'il n'y a pas de chute de pression importante lors du transfert de la solution lixiviante dans la conduite.In view of these observations, the applicant has imagined choosing an injection pipe with a diameter such that, on the one hand, the values of the pressure of the leaching solution are substantially equal at the downstream end and at the upstream end of said pipe, on the other hand, the pressure of the leaching solution during its transfer into the pipe never becomes significantly lower than the value of its pressure at the upstream end of said pipe. Thus, by virtue of the process of the invention as defined above, it is possible to establish on the surface a content of oxygen dissolved in the leaching solution close to the saturation limit, without however causing untimely degassing subsequently since there is no no significant pressure drop when transferring the leaching solution into the line.

Selon une première variante du procédé, le diamètre interne de la conduite d'injection est choisi de façon à ce que la pression de la solution lixiviante soit substantiellement constante au cours de son transfert dans ladite conduite. De façon plus précise, on calcule le diamètre interne d de la conduite par des méthodes classiques telles que celles décrites dans le manuel "Unit Operations of Chemical Engineering" de Warren L. Mc Cabe et Julian C. Smith. Par exemple, le diamètre d peut être déterminé par la relation:

Figure imgb0003
dans laquelle:

  • Q est le débit volumétrique de la solution en m3.s-1
  • f=0,0014+0,125 Re-O.32 avec Re=
    Figure imgb0004
  • g=9,81 m.s-2
  • p est la masse spécifique de la solution en kg.m-3
  • p est la viscosité dynamique de la solution en poiseuille.
According to a first variant of the method, the internal diameter of the injection pipe is chosen so that the pressure of the leaching solution is substantially constant during its transfer into said pipe. More precisely, the internal diameter d of the pipe is calculated by conventional methods such as those described in the manual "Unit Operations of Chemical Engineering" by Warren L. Mc Cabe and Julian C. Smith. For example, the diameter d can be determined by the relation:
Figure imgb0003
 in which:
  • Q is the volumetric flow rate of the solution in m 3. s -1
  • f = 0.0014 + 0.125 Re- O.32 with Re =
    Figure imgb0004
  • g = 9.81 ms- 2
  • p is the specific mass of the solution in kg.m-3
  • p is the dynamic viscosity of the poiseuille solution.

Selon une deuxième variante de réalisation du procédé, le diamètre interne de la conduite d'injection est choisi de façon à ce que la pression de la solution lixiviante augmente, de préférence, légèrement, au cours de son.transfert dans ladite conduite, la valeur de la pression de ladite solution à l'extrémité aval de ladite conduite étant ramenée à une valeur juste égale à celle de la pression de ladite solution à l'extrémité amont de ladite conduite, par détente de ladite solution à travers des moyens d'étranglement placés dans la partie inférieure de ladite conduite.According to a second variant embodiment of the method, the internal diameter of the injection pipe is chosen so that the pressure of the leaching solution increases, preferably, slightly, during its transfer into said pipe, the value of the pressure of said solution at the downstream end of said pipe being reduced to a value just equal to that of the pressure of said solution at the upstream end of said pipe, by expansion of said solution through throttling means placed in the lower part of said pipe.

Selon une troisième variante de réalisation du procédé, le diamètre interne de la conduite d'injection est choisi de façon à ce que la pression de la solution lixiviante augmente, de préférence, légèrement, au cours de son transfert dans ladite conduite, la valeur de la pression de ladite solution à l'extrémité aval de ladite conduite étant ramenée à une valeur à peine supérieure à celle de la pression de ladite solution à l'extrémité amont de ladite conduite, par détente de ladite solution à travers des moyens d'étranglement placés dans la partie inférieure de ladite conduite. L'écart entre la pression à l'extrémité aval et la pression à l'extrémité amont est de préférence inférieur ou égal à 1 bar.According to a third alternative embodiment of the method, the internal diameter of the injection pipe is chosen so that the pressure of the leaching solution increases, preferably, slightly, during its transfer into said pipe, the value of the pressure of said solution at the downstream end of said pipe being brought to a value barely higher than that of the pressure of said solution at the upstream end of said pipe, by expansion of said solution through throttling means placed in the lower part of said pipe. The difference between the pressure at the downstream end and the pressure at the upstream end is preferably less than or equal to 1 bar.

Dans le cas des deuxième et troisième variantes du procédé de l'invention, les moyens d'étranglement placés à la partie inférieure de la conduite d'injection peuvent être, par exemple, constitués par un orifice en mince paroi ou par une vanne dont on peut régler l'ouverture par des moyens appropriés placés en surface. Le calcul du diamètre de l'orifice d'étranglement en fonction de l'effet recherché s'effectue par des méthodes classiques telles que celles décrites dans le manuel "Unit Operations of Chemical Engineering" cité précédemment.In the case of the second and third variants of the process of the invention, the throttling means placed at the bottom of the injection pipe can be, for example, constituted by a thin-walled orifice or by a valve which may adjust the opening by suitable means placed on the surface. The calculation of the diameter of the throttle orifice as a function of the desired effect is carried out by conventional methods such as those described in the "Unit Operations of Chemical Engineering" manual cited above.

Selon ces deuxième et troisième variantes du procédé le diamètre interne d de la conduite d'injection peut être, par exemple, déterminé par la relation suivante:

Figure imgb0005
dans laquelle:

  • Qest le débit volumétrique de la solution en m2.s-1
  • f=0,0014+0,125 Re-0.32 avec Re=
    Figure imgb0006
  • g=9,81 m.s-2
  • p est la masse spécifique de la solution en kg.m-3
  • p est la viscosité dynamique de la solution en poiseuille
According to these second and third variants of the method, the internal diameter d of the injection pipe can be, for example, determined by the following relationship:
Figure imgb0005
 in which:
  • Q is the volumetric flow rate of the solution in m 2 .s -1
  • f = 0.0014 + 0.125 Re -0.32 with Re =
    Figure imgb0006
  • g = 9.81 m . s - 2
  • p is the specific mass of the solution in kg. m - 3
  • p is the dynamic viscosity of the poiseuille solution

L'invention a également pour objet une installation de mise en oeuvre du procédé conforme à l'invention.The invention also relates to an installation for implementing the method according to the invention.

L'installation de lixiviation in situ de minerai considérée pour la mise en oeuvre du procédé ci-dessus est du genre comprenant un puits d'injection dans lequel est placée une conduite d'injection raccordée, à son extrémité amont, à un oxygénateur lui-même alimenté en solution lixiviante régénérée par une pompe de pression ainsi qu'un organe de mesure de débit. Elle se caractérise en ce que le diamètre interne d de la conduite d'injection est choise de façon à ce que la pression de la solution lixiviante à l'extrémité aval de ladite conduite soit sensiblement égale à la pression de ladite solution lixiviante à l'extrémité amont de ladite conduite, le diamètre interne d de la conduite d'unjection étant déterminé par la relation suivante:

Figure imgb0007
dans laquelle:

  • Q est le débit volumétrique de la solution en m3.s-1
  • f=0,0014+0,125 Re-0.32 avec Re=
    Figure imgb0008
  • g=9,81 m.s-2
  • p est la masse spécifique de la solution en kg.m-3
  • p est la viscosité dynamique de la solution en pioseuille.
The in situ ore leaching installation considered for implementing the above process is of the type comprising an injection well in which is placed an injection pipe connected, at its upstream end, to an oxygenator itself. even supplied with leaching solution regenerated by a pressure pump and a flow measurement device. It is characterized in that the internal diameter d of the injection pipe is chosen so that the pressure of the leaching solution at the downstream end of said pipe is substantially equal to the pressure of said leaching solution at upstream end of said pipe, the internal diameter d of the injection pipe being determined by the following relationship:
Figure imgb0007
 in which:
  • Q is the volumetric flow rate of the solution in m 3 .s -1
  • f = 0.0014 + 0.125 Re -0.32 with Re =
    Figure imgb0008
  • g = 9.81 ms- 2
  • p is the specific mass of the solution in kg. m - 3
  • p is the dynamic viscosity of the pipette solution.

Selon une variant de réalisation, des moyens d'étranglement sont placés à la partie inférieure de la conduite d'injection.According to an alternative embodiment, throttling means are placed at the bottom of the injection pipe.

Les caractéristiques et avantages de l'invention ressortiront de la description qui suit, à titre d'exemple, en référence aux dessins annexés sur lesquels:

  • -la figure 1 représente une vue schématique en coupe d'un premier mode de réalisation d'une installation selon l'invention;
  • -la figure 2 représente une vue schématique en coupe d'un deuxième mode de réalisation d'une installation selon l'invention.
The characteristics and advantages of the invention will emerge from the description which follows, by way of example, with reference to the appended drawings in which:
  • FIG. 1 represents a schematic sectional view of a first embodiment of an installation according to the invention;
  • FIG. 2 represents a schematic sectional view of a second embodiment of an installation according to the invention.

Sur la figure 1, on a représenté une installation qui comporte, dans le sol, une pluralité de puits d'injection, dont un seulement est représenté en (1), qui sont répartis de façon uniforme en surface et de puits de récupération, dont un seulement est représenté en (2), également répartis entre les dits puits d'injection. Chaque puits d'injection est équipé d'une conduite d'injection (3) débouchant à son extrémité aval dans une zone de lixiviation (4). La conduite (3) traverse un joint d'étanchéité (5) avec le puits (1), le joint (5) étant placé un peu au-dessus de l'extrémité aval de ladite condite (3). Chaque conduite d'injection (3) est alimentée en solution lixiviante par un conduit (6) aboutissant d'une à l'extrémité de surface de la conduite d'injection (3), d'autre part à l'extrémité de surface d'un conduit de récupération (7) ménagé dans chaque puits de récupération (2), chaque conduit (7) présentant une extrémité aval à un niveau plus bas que celui d'une conduite d'injection (3), mais cependant en un niveau intermédiaire de la zone de lixiviation (4). Chaque conduit de récupération (7) incorpore une pompe (11) située près de son extrémité aval, qui est mise en mouvement par exemple par un arbre vertical (12) à partir d'un excentrique menant (13). De la sorte, la solution lixiviante chargée en composés métalliques dissous extraits du minerai et qui s'écoule selon le sens de la flèche F est reprise par la pompe (11) et est recyclée par le conduit (6) vers un puits d'injection (3); ce conduit (6) incorpore successivement à partir du conduit de récupération (7), un dispositif de séparation (20), dont on extrait en (21) les métaux de la solution lixiviante, une pompe de pression (22) portant la solution lixiviante à une pression élevée peu inférieure à la pression de fracturation de la roche puis, à cette pression, un oxygénateur à sursaturation (23), un séparateur de phase (24), la phase liquide étant seule dirigée vers le conduits d'injection (3) par un organe de mesure de débit (25), tandis que la phase gazeuse (26) est recyclé par un surpresseur (27) vers l'oxygénateur (23), de préférence sur un conduit d'alimentation en oxygène (28) aboutissant à cet oxygénateur (23). L'oxygénateur (23) est, de préférence, un réacteur du type tuyau tel que décrit, par exemple, dans l'article de l'A.I. Ch. E. Journal de septembre 1964 "Gas Phase Controlled Mass Transfer in Two Phases Annular Horizontal Flow" par J. D. Anderson, R. E. Bellinger et D. E. Lamb.FIG. 1 shows an installation which comprises, in the ground, a plurality of injection wells, only one of which is represented in (1), which are uniformly distributed on the surface and recovery wells, of which only one is shown in (2), also distributed between said injection wells. Each injection well is equipped with an injection pipe (3) opening at its downstream end into a leaching zone (4). The pipe (3) passes through a seal (5) with the well (1), the seal (5) being placed a little above the downstream end of said condite (3). Each injection pipe (3) is supplied with leaching solution by a pipe (6) ending at one at the surface end of the injection pipe (3), on the other hand at the surface end d '' a recovery conduit (7) formed in each recovery well (2), each conduit (7) having a downstream end at a level lower than that of an injection conduit (3), but nevertheless at a level intermediate of the leaching zone (4). Each recovery duct (7) incorporates a pump (11) located near its downstream end, which is set in motion for example by a vertical shaft (12) from a driving eccentric (13). In this way, the leaching solution loaded with dissolved metal compounds extracted from the ore and which flows in the direction of the arrow F is taken up by the pump (11) and is recycled through the conduit (6) to an injection well. (3); this conduit (6) successively incorporates from the recovery conduit (7), a separation device (20), from which the metals are extracted in (21) from the leaching solution, a pressure pump (22) carrying the leaching solution at an elevated pressure little lower than the fracturing pressure of the rock then, at this pressure, a supersaturation oxygenator (23), a phase separator (24), the liquid phase only being directed towards the injection conduits (3 ) by a flow measurement member (25), while the gas phase (26) is recycled by a booster (27) to the oxygenator (23), preferably on an oxygen supply duct (28) terminating to this oxygenator (23). The oxygenator (23) is preferably a pipe-type reactor as described, for example, in the article by A.I. Ch. E. Journal of September 1964 "Gas Phase Controlled Mass Transfer in Two Phases Annular Horizontal Flow" by J. D. Anderson, R. E. Bellinger and D. E. Lamb.

Selon un mode de réalisation représenté à la figure 1, on choisit le diamètre interne d de la conduite d'injection (3) (par exemple, selon la relation

Figure imgb0009
de façon telle que la pression de la solution lixiviante, qui avait la valeur P3aà l'extrémité amont 3a de la conduite (3) reste constante au cours de son transfert dans adite conduite. De façon plus précise, de l'extrémité amont 3a jusqu'à l'extrémité aval 3b, à chaque niveau élémentaire de la conduite (3), la diminution de pression due aux pertes de charges est juste égale à l'augmentation de pression due à l'effet hydrostatique; ce qui fait que la pression de la solution reste constante tout au long de son trajet dans la conduite (3) et que sa valeur P3bà l'extrémité aval 3b est égale à la valeur P3a à l'extrémité amont 3a. Ainsi, on peut choisir une valeur de P3a maximale (mais toutefois légèrement inférieure à la pression de fracturation de la roche), donc une teneur en oxygène dissous la plus élevée possible, sans risque de dégazage de l'oxygène puisque la pression de la solution lixiviante reste constante et que P3b=P3a.According to an embodiment represented in FIG. 1, the internal diameter d of the injection line (3) (for example, depending on the relationship
Figure imgb0009
 so that the pressure of the leaching solution, which had the value P 3a at the upstream end 3a of the pipe (3) remains constant during its transfer into this pipe. More precisely, from the upstream end 3a to the downstream end 3b, at each elementary level of the pipe (3), the pressure decrease due to pressure losses is just equal to the pressure increase due hydrostatic effect; so that the pressure of the solution remains constant throughout its path in the pipe (3) and that its value P 3b at the downstream end 3b is equal to the value P 3a at the upstream end 3a. Thus, it is possible to choose a maximum value of P 3a (but however slightly lower than the fracturing pressure of the rock), therefore a content of dissolved oxygen as high as possible, without risk of degassing of the oxygen since the pressure of the leaching solution remains constant and that P 3b = P 3a .

Le fait d'avoir installé en fond d'un conduit de récupération (7) une pompe volumétrique dont le débit est le débit Q transféré par la conduite d'injection (si le nombre de conduits de récupération est égal au nombre de conduites d'injection) permet d'assurer une autorégulation en cas de modification de la perméabilité du terrain intéressé par l'opération. En effet, le changement correspondant de la perte de charge est alors exactement compensé par une variation du niveau h de la solution dans les puits de récupération: le débit Q mesuré par le débimètre (25) et les,pressions aux points (3a) et (eb) sont conservés. Il est à noter qu'aucune vanne ou dispositif similaire n'est nécessaire pour assurer cette régulation.The fact of having installed at the bottom of a recovery duct (7) a positive displacement pump, the flow rate of which is the flow rate Q transferred by the injection pipe (if the number of recovery pipes is equal to the number of injection) ensures self-regulation in the event of a change in the permeability of the terrain concerned by the operation. Indeed, the corresponding change in pressure drop is then exactly compensated by a variation in the level h of the solution in the recovery wells: the flow rate Q measured by the flow meter (25) and the pressures at points (3a) and (eb) are kept. It should be noted that no valve or similar device is necessary to ensure this regulation.

D'autre part, si, pour une raison accidentelle, l'écoulement de la solution à travers le terrain venait brusquement à être interrompu (bouchage total), cet incident est facilement détecté en observant une croissance brusque de la pression au point (3a) et une décroissance brusque du débit extrait. On prévient alors une augmentation dangereuse de la pression au point (3b) simplement en arrêtant la pompe d'injection (22).On the other hand, if, for an accidental reason, the flow of the solution through the ground suddenly stopped (total blockage), this incident is easily detected by observing an abrupt increase in pressure at point (3a) and a sudden decrease in the extracted flow. A dangerous increase in pressure at point (3b) is then prevented by simply stopping the injection pump (22).

Sur la figure 2, on a représenté une installation de lixiviation in situ de minerai dont une grande partie est analogue à l'installation représentée à la figure 1 (les mêmes références ont été affectées aux mêmes éléments). Cette installation comporte une pluralité de puits d'injection (1) et de puits de récupération (2). Chaque puits de récupération (2) est analogue au puits de récupération représenté sur la_figure 1; le conduit de récupération (7) est relié, à son extrémité de surface, à un conduit (6) qui comporte, successivement, un dispositif de séparation (20), une pompe de pression (22), un oxygénateur à sursaturation (23), un séparateur de phases (24), un organe de mesure de débit (25), et qui aboutit à l'extrémité de surface de la conduite d'injection (33) du puits d'injection (1).In Figure 2, there is shown an in situ ore leaching facility, much of which is similar to the facility shown in Figure 1 (the same references have been assigned to the same elements). This installation comprises a plurality of injection wells (1) and recovery wells (2). Each recovery well (2) is analogous to the recovery well shown in la_figure 1; the recovery duct (7) is connected, at its surface end, to a duct (6) which successively comprises a separation device (20), a pressure pump (22), a supersaturation oxygenator (23) , a phase separator (24), a flow measurement member (25), and which terminates at the surface end of the injection pipe (33) of the injection well (1).

Cette conduite d'injection (33) présente un diamètre supérieur à celui de la conduite d'injection (3) de l'installation de la figure 1. La conduite (33) traverse un joint d'étanchéité (35) qui est placé, par exemple, à la partie supérieure du puits d'injection (1). La conduite (33) comporte à son extrémité aval un orifice en mince paroi (36) qui réduit son diamètre à cet endroit là.This injection pipe (33) has a diameter greater than that of the injection pipe (3) of the installation of FIG. 1. The pipe (33) passes through a seal (35) which is placed, for example, at the top of the injection well (1). The pipe (33) has, at its downstream end, a thin-walled orifice (36) which reduces its diameter there.

Selon le mode réalisation représenté à la figure 2, on choisit le diamètre interne d de la conduite d'injection (33) (par exemple selon la relation

Figure imgb0010
de façon telle que le pression de la solution lixiviante qui avait la valeur P33a à l'extrémité amont (33a) de la conduite (33) augmente, légèrement de préférence, au cours de son transfert dans ladite conduite jusqu'a une valeur P33c· De façon plus précise, de l'extrémité amont (33a) au niveau (33c juste en amont de l'orifice en mince paroi (36), à chaque niveau élémentaire de la conduite (33), la diminution de pression due aux pertes de charges est inférieure à l'augmentation de pression due à l'effet hydrostatique; ce qui fait que la pression de la solution lixiviante atteint au niveau (33c) une valeur P33c supérieure, et de préférence légèrement supérieure, à la valeur P33a. Cette augmentation de pression est compensée par détente de la solution au travers de l'orifice (36) et la pression de la solution lixiviante est ramenée à l'extrémité aval (33b) à une valeur P33b qui est, selon le diamètre choisi pour l'orifice (36), soit juste égale à la pression amont P33a, soit à peine supérieure à P33a (l'écart entre P33b et P33a, dans ce cas là, ne dépassant pas, de préférence, 1 bar).According to the embodiment shown in FIG. 2, the internal diameter d of the injection pipe (33) is chosen (for example according to the relation
Figure imgb0010
 so that the pressure of the leaching solution which had the value P 33a at the upstream end (33a) of the pipe (33) increases, slightly preferably, during its transfer in said pipe until a value P 33c · More precisely, from the upstream end (33a) to the level (33c just upstream of the thin-walled orifice (36), at each elementary level of the pipe (33), the reduction in pressure due to the pressure losses is less than the increase in pressure due to the hydrostatic effect; so that the pressure of the leaching solution reaches at level (33c) a value P 33c higher, and preferably slightly higher, than the value P 33a. This increase in pressure is compensated for by expansion of the solution through the orifice (36) and the pressure of the lixiviation solution is cooled to the downstream end (33b) to a value P 33b which is, as the diameter chosen for the orifice (36), either just equal to the upstream pressure P 33 a, or pe ine greater than P 33a (the difference between P 33b and P 33a , in this case, preferably not exceeding 1 bar).

De préférence, l'écart entre la pression P33c de la solution lixiviante en amont de l'orifice (36) et la pression P33b de ladite solution en aval dudit orifice (36) est inférieure à 5 bars.Preferably, the difference between the pressure P 33c of the leaching solution upstream of the orifice (36) and the pressure P 33b of said solution downstream of said orifice (36) is less than 5 bars.

On donne, ci-dessous, à titre non limitatif, trois exemples de réalisation du procédé conforme à l'invention.Three exemplary embodiments of the process according to the invention are given below, without implied limitation.

Exemple 1Example 1

On met en oeuvre le procédé dans l'installation représentée à la figure 1.The method is implemented in the installation shown in FIG. 1.

La conduite d'injection (3) du puits (1) a une longueur de 110m et un diamètre interne de 18,58mm.The injection pipe (3) of the well (1) has a length of 110m and an internal diameter of 18.58mm.

On envoit la solution lixiviante dans la conduite (3) à un débit de 1,25 1/sec. Cette solution contient 0,5 g/litre d'H2SO4, 6,25 g/litre de CaC12 et 1,75 g/litre de CaS04. Sa concentration en oxygène dissous est de 200 ppm.The leaching solution is sent into line (3) at a flow rate of 1.25 1 / sec. This solution contains 0.5 g / liter of H 2 SO 4 , 6.25 g / liter of CaC1 2 and 1.75 g / liter of CaS0 4 . Its dissolved oxygen concentration is 200 ppm.

Le température au sol est de 35°C et la température en fond de puits de 40cC, soit une température moyenne dans la conduite (3) de 37,5°C.The temperature on the ground is 35 ° C and the temperature at the bottom of the well is 40 c , i.e. a average temperature in the pipe (3) of 37.5 ° C.

La pression de la solution lixiviante P3a, à l'extrémité amont de la conduite (3), est de 6,5 bars. Comme cette pression reste constante tout au long du trajet de la solution dans la conduite (3), la pression P3b à l'extrémité aval de la conduite (3), la pression P3b à lextrémité aval de la conduite est également de 6,5 bars.The pressure of the leaching solution P 3a , at the upstream end of the pipe (3), is 6.5 bars. As this pressure remains constant throughout the path of the solution in the pipe (3), the pressure P3b at the downstream end of the pipe (3), the pressure P 3b at the downstream end of the pipe is also 6, 5 bars.

Dans ces conditions, la concentration maximale en oxygène dissous en fonds de puits est de 200 ppm.

  • Il est à noter que l'on aurait pu dissoudre en surface dans la solution lixiviante un peu plus que 200 ppm d'oxygène (par exemple 210 ppm). Mais, pour éviter tout risque de dégazage, dû à l'augmentation de température, on dissout un peu moins d'oxygène que la concentration maximale possible.
Under these conditions, the maximum dissolved oxygen concentration at the bottom of the well is 200 ppm.
  • It should be noted that a little more than 200 ppm of oxygen (for example 210 ppm) could have been dissolved on the surface in the leaching solution. However, to avoid any risk of degassing, due to the increase in temperature, a little less oxygen is dissolved than the maximum possible concentration.

Exemple 2Example 2

On met en oeuvre le procédé dans l'installation représentée à la figure 2.The method is implemented in the installation shown in FIG. 2.

La conduite d'injection (33) du puits (1) a une longueur de 110m et un diamètre interne de 20,96mm. Le diamètre de l'orifice (36) est de 9,23mm.The injection pipe (33) of the well (1) has a length of 110m and an internal diameter of 20.96mm. The diameter of the orifice (36) is 9.23mm.

La solution lixiviante a la même composition que celle de l'exemple 1. Sa concentration en oxygène dissous est de 200 ppm. Elle est envoyée dans la conduite (33) à un débit de 1,25 1/sec.The leaching solution has the same composition as that of Example 1. Its concentration of dissolved oxygen is 200 ppm. It is sent into the pipe (33) at a rate of 1.25 1 / sec.

La température moyenne dans la conduite (33) est de 37,5°C (température au sol 35°C et température en fonds 40°C).The average temperature in the pipe (33) is 37.5 ° C (floor temperature 35 ° C and bottom temperature 40 ° C).

La pression de la solution lixiviante P33a, à l'extrémité amont de la conduite (33) est de 6,3 bars. Elle augmente légèrement au cours du transfert dans la conduite (33) et atteint au niveau (33c), juste en amont de l'orifice (36), une valeur P33c de 11 bars. Après passage de la solution dans l'orifice (36), la pression est ramenée à une valeur P33b de 6,5 bars.The pressure of the leaching solution P 33a , at the upstream end of the pipe (33) is 6.3 bars. It increases slightly during the transfer in the pipe (33) and reaches at level (33c), just upstream of the orifice (36), a value P 33c of 11 bars. After the solution has passed through the orifice (36), the pressure is brought back to a P 33b value of 6.5 bars.

Dans ces conditions, la concentration maximale en oxygène dissous en fonds de puits est de 200 ppm.Under these conditions, the maximum dissolved oxygen concentration at the bottom of the well is 200 ppm.

En ce qui concerne la concentration maximale en oxygène dissous qu'aurait pu avoir la solution lixiviante en surface, on peut faire la même remarque que dans l'exem;le 1 ci-dessus.With regard to the maximum dissolved oxygen concentration that the leaching solution could have had on the surface, the same remark can be made as in example 1 above.

Exemple 3Example 3

On met en oeuvre le procédé dans l'installation représentée à la figure 2.The method is implemented in the installation shown in FIG. 2.

La conduite d'injection (33) du puits (1) a une longueur de 110m et le joint d'étanchéité est placé à 55m de l'extrémité de surface du puits (1).The injection pipe (33) of the well (1) has a length of 110m and the seal is placed 55m from the surface end of the well (1).

La solution lixiviante contient 0,5 g/litre d'H2SO, 6,25 g/litre de CaC12 et 1,75 g/litre de CaSO4. Sa concentration en oxygène dissous est de 180 ppm. On l'envoie dans la conduite d'injection (33) à un débit de 1,25 /sec.The leaching solution contains 0.5 g / liter of H 2 SO, 6.25 g / liter of CaC1 2 and 1.75 g / liter of CaSO 4 . Its dissolved oxygen concentration is 180 ppm. It is sent into the injection line (33) at a rate of 1.25 / sec.

La température au sol est 35°C et en fonds de puits de 40°C, soit une température moyenne dans la conduite (33) de 37.5°C.The temperature on the ground is 35 ° C and at the bottom of the well 40 ° C, an average temperature in the pipe (33) of 37.5 ° C.

On souhaite que la pression de la solution lixiviante P33a, à l'extrémité amont de la conduite (33) soit de 5,5 bars et que la pression P33b à l'extrémité aval de ladite conduite soit de 6,5 bars.It is desired that the pressure of the leaching solution P 33a , at the upstream end of the pipe (33) is 5.5 bars and that the pressure P 33b at the downstream end of said pipe is 6.5 bars.

Dans ces conditions, la concentration maximale en oxygène dissous en fonds de puits est de 180 ppm. - Le diamètre de l'orifice (36) est fonction du diamètre de la conduite (33), du débit de la solution lixiviante, des pressions amont P33a et aval P33b choisies, ainsi que des caractéristiques de la solution lixiviante.Under these conditions, the maximum dissolved oxygen concentration at the bottom of the well is 180 ppm. - The diameter of the orifice (36) is a function of the diameter of the pipe (33), the flow rate of the leaching solution, the upstream pressures P 33a and downstream P 33b chosen, as well as the characteristics of the leaching solution.

On a représenté, sur la figure 3 jointe, les courbes donnant, compte-tenu des paramètres choisis rappelés ci-dessus, d'une part le diamètre do de l'orifice (36), d'autre part la pression P33c de la solution lixiviante juste en amont de l'orifice (36), en fonction du diamètre interne d de la conduite d'injection (33).Is shown in Figure 3 attached, the curves giving, taking into account the selected parameters recalled above, on the one hand the diameter d o of the orifice (36), on the other hand the pressure P 33c the leaching solution just upstream of the orifice (36), as a function of the internal diameter d of the injection pipe (33).

Ainsi, par exemple, si l'on dispose d'une conduite d'injection de diamètre interne d=21mm, en se reportant à la figure 3, on voit, d'après la courbe (l) que le diamètre do de 1 orifice (36) doit être de 9,65m; d'après la courbe (II), on voit que la pression P33c de la solution lixiviante, juste en amont de l'orifice, atteindra une valeur de 10,35 bars.Thus, for example, if there is an injection pipe with an internal diameter d = 21 mm, referring to FIG. 3, it can be seen from curve (l) that the diameter d o of 1 orifice (36) must be 9.65m; from curve (II), it can be seen that the pressure P 33c of the leaching solution, just upstream of the orifice, will reach a value of 10.35 bars.

On rappelle que l'écart entre la pression P33c en amont de l'orifice (36) et la pression P33b en aval dudit orifice (36) doit être de préférence inférieur à 5 bars. Dans le cas présent, il ne faut donc pas que P33c dépasse 11,5 bars.It will be recalled that the difference between the pressure P 33c upstream of the orifice (36) and the pressure P 33b downstream of said orifice (36) must preferably be less than 5 bars. In the present case, therefore, P 33c must not exceed 11.5 bars.

Claims (11)

1. Method for in situ lixiviation of ore by means of a lixiviation solution formed by a basis solution, in which oxygen is added, which solution is rendered to circulate in a conduit (3) located in an injection shaft (1), the said conduit terminating at its downstream end in a fond lixiviation zone (4), with a resumption of a composed solution incorporating metallic compositions extracted from the ore which solution is treated in order to separate the said compositions, then regenerated by possibly adding base products, reoxidized and recycled in the said injection conduit, characterized by the combination of the following measures:
a) the internal diameter d of the injection conduit (3), considering the volumetric amount of the lixiviation solution, the hydrostatic increase of the pressure and the pressure diminution by loss of charge during the transfer of the said lixiviation solution from the upstream end to the down- steam end of the said conduit, is selected in such a way that the pressure of the said lixiviation solution at the downstream end is essentially equal to the pressure of the said lixiviation solution at the upstream end, the pressure of the said solution in the said conduit, in the course of its transfer in said conduit, never becomes considerably lower than a value of its pressure at the upstream end of the said conduit, the said internal diameter d of the injection conduit being substantially determined by the following relation:
Figure imgb0024
in which:
Q is the volumetrical amount of the solution in m3· s-1
f=0,0014+0,125 Re-0.32 with Re=
Figure imgb0025
g= 9,81 m · s-2
p is the specific mass of the solution in kg . m-3
µ is the dynamic viscosity of the solution in Poiseuille,
b) the pressure of the lixiviation solution at the upstream end of the said conduit (3) has a value lower than the fracture pressure of the rock at the top of the lixiviation zone, preferably a bit lower than the said fracture pressure;
c) the concentration of oxygen dissolved in the lixiviation solution, insured upstream, is lower than the saturation limit for the pressure upstream of the said solution, and preferably a bit lower than the said limits of saturation.
2. Method according to claim 1, characterized in that the internal diameter d of the injection conduit is selected in such a way that the pressure of the lixiviation solution is essentially constant in the course of its transfer in the said conduit.
3. Method according to claim 1, characterized in that the internal diameter of the injection conduit is selected in such a way, that the pressure of the lixiviation solution increases, preferably moderately, in the course of its transfer in the said conduit, the value of the pressure of the said solution at the downstream end of the said conduit being rendered to a value just equal to that of the pressure of the said solution at the upstream end of the said conduit by expansion of the said solution through throttling means located in the lower part of the said conduit.
4. Method according to claim 1, characterized in that the internal diameter of the injection conduit is selected in such a way that the pressure of the lixiviation solution increases, preferably moderately, in the course of its transfer in the said conduit, the value of the pressure of the said solution at the downstream end of the said conduit being rendered to a value hardly superior to that of the pressure of the said solution at the upstream end of the said conduit, the distance between the pressure at the downstrem end and .the pressure at the upstream end being preferably lower or equal to 1 bar, by expansion of the said solution through throttling means located in the lower part of the said conduit.
5. Method according to one of the claims 3 or 4, characterized in that the internal diameter d of the injection conduit is substantially determined by the following relation:
Figure imgb0026
in which:
Q is the volumetric amount of the solution in m3·S-1
f=0,0014+0,125 Re-0.32 with Re=
Figure imgb0027
g=9,81 m. s
p is the specific mass of the solution in kg - m-3
p is the dynamic viscosity of the solution.
6. Method according to one of the claims 3 to 5, characterized in that the distance between the pressure of the lixiviation solution downstream of the throttling means and the pressure of the lixiviation solution upstream of the said throttling means is lower than 5 bars.
7. Method according to one of the claims 1 to 6, according to which an injection shaft network associated to a recuperation shaft network is used, characterized in that each recuperation shaft is equipped with a recuperation conduit incorporating, in fond position at an intermediate level of the lixiviation zone, a volumetrical pump with constant amount corresponding to the nominal extraction amount of a recuperation shaft.
8. Installation for the performance of the method according to the claims 1 to 7 of the type comprising an injection shaft (1) in which an injection conduit (3) is located connected with an oxigenator (23) at the upstream end thereof, which oxigenator itself is fed with regenerated lixiviation solution by a pressure pump (22), as well as an amount measuring organ, characterized in that the internal diameter d of the injection conduit (3) is selected in such a way, that the pressure of the lixiviation solution at the downstream end of the said conduit (3) is essentially equal to the pressure of the said lixiviation solution at the upstream end of the said conduit, the internal diameter d of the injection conduit (3) being determined by the following relation:
Figure imgb0028
in which:
Q is the volumetrical amount of the solution in m3 · s-1
f=0,0014+0,125 Re -0'32 with Re=
Figure imgb0029
9=9,81 m · s
p is the specific mass of the solution in kg - m-3
u is the dynamic viscosity of the solution.
9. Installation for in situ lixiviation of ore according to claim 8, characterized in that the oxigenator (23) is followed by a phase separator (24) with recycling the gaseous phase in the oxigenator.
10. Installation for lixiviation according to one of the claims 8 or 9, characterized in that a recuperation conduit (7) is equipped in the fond position with a volumetrical pump (11) with constant amount of power.
11. Installation according to one of the claims 8 to 10, characterized in that the injection conduit (33) comprises throttling means (36) located in its lower part.
EP83400540A 1982-03-17 1983-03-16 Method and installation for in situ lixiviation of ore Expired EP0089294B1 (en)

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FR8204480A FR2523636A1 (en) 1982-03-17 1982-03-17 METHOD AND INSTALLATION OF IN SITU LIXIVIATION OF ORE
FR8204480 1982-03-17

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ES2036491B1 (en) * 1991-12-30 1994-04-01 Minera De Santa Marta S A PROCEDURE FOR THE EXPLOITATION OF GLAUBERITA DEPOSITS.
CN107605438A (en) * 2017-09-30 2018-01-19 中核通辽铀业有限责任公司 A kind of ground-dipping uranium extraction mining area central station of floating dock modular unit and method
CN107858536B (en) * 2017-12-04 2019-07-26 江西理工大学应用科学学院 Ion type rareearth full-covering type mine in_situ leaching Hole pattern parameters design method
CN107858537B (en) * 2017-12-04 2019-07-26 江西理工大学应用科学学院 Ion type rareearth naked foot formula mine in_situ leaching Hole pattern parameters design method
FR3088364B1 (en) * 2018-11-14 2022-12-16 Orano Mining Method and installation for operating a mine by in situ leaching
CN109577940B (en) * 2018-12-26 2021-04-13 核工业北京化工冶金研究院 In-situ leaching uranium mining gas control system and method
CN110714131B (en) * 2019-10-23 2021-06-29 核工业北京化工冶金研究院 Air pre-oxidation method for in-situ leaching uranium mining
CN112627262B (en) * 2020-12-17 2022-05-13 乌海市錦宇矿业有限公司 Portable unloading formula ore mining machine that is suitable for not co-altitude ore heap

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DE3364624D1 (en) 1986-08-28
ES8401564A1 (en) 1983-12-16
FR2523636B1 (en) 1984-05-25
BR8301329A (en) 1983-11-29
CA1226514A (en) 1987-09-08
AU550655B2 (en) 1986-03-27
AU1253683A (en) 1983-09-22
US4498705A (en) 1985-02-12
ZA831798B (en) 1984-02-29
FR2523636A1 (en) 1983-09-23
ES520645A0 (en) 1983-12-16

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