RU2504648C1 - Method borehole cil from deep lying placers and man-made mineral formations - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: proposed CIL method comprises injection of activated leaching solution in producing bed via system of injection wells with subsequent extraction of gold. Said leaching solutions are injected via said system of injection wells in separate jets. First, hydrocarbonate-peroxide solution subjected to photo electrochemical processing is injected. Then after a pause, hydrochloric acid plus hydrogen peroxide subjected beforehand to UV radiation are injected. After detention of solution in producing bed till transition of the main portion of gold from mineral bulk into producing solution, perforated capsules with sorbent fitted with electrodes are placed into wells. Voltage is fed to said electrodes for direction diffusion of dissolved gold ions to sorbent and its sorption and extra leaching of gold remained in ore bed. Then sorbent saturated with gold is extracted to be recovered.

EFFECT: higher CIL efficiency.

Description

The invention relates to the technology of underground leaching of precious metals, for example, gold from sands of deep-lying placers or from man-made mineral formations (tailings of ore dressing and galefel dumps), and can be used in the development of placer deposits, mainly deep-lying, by pumping solutions of leaching reagents into the reservoir sand through a system of injection wells and sorption extraction of gold from productive solutions.

Known hydrometallurgical method of leaching gold and silver in an alkaline medium (pH = 8-13) with a solution containing 12% chloride and 1% sodium hypochlorite. After the cementation of gold and silver with zinc, hypochlorite is regenerated by electrolysis and the solution is returned to leach (see US patent N 4342592, 1982).

The leach solution composition recommended in the patent cannot be used for underground leaching for environmental reasons due to the high chloride content.

Closest to the claimed method is a method of leaching metals, in particular gold and silver, carried out in two stages. At the first stage of leaching, a chlorine solution is used, and the chlorine supply is controlled so that the pumped solution has a pH of at least 3. Excess active chlorine in the productive solution is restored before it is processed, and the solution is processed using one of the known methods - sorption, cementation or electrolysis. In the second stage, the development of the formation is continued with a sodium thiosulfate solution. At the same time, the unreacted active chlorine is restored and the water is neutralized, which ensures environmental requirements for the formation waters of the ore-containing horizon (see RF patent No. 2074958, IPC ЕВВ 43/28, publ. 10.03.97).

The disadvantage of this method is the low metal recovery due to its loss with working solutions and reprecipitation on particles of clay minerals with sorption active properties.

The technical result of the proposed method is to increase the leaching efficiency by reducing the loss of gold with working solutions and its reprecipitation on clay minerals.

The result is achieved in that the method of downhole leaching of gold from deep-lying placers and man-made mineral formations, which includes feeding activated leaching solutions to the reservoir through an injection well system followed by gold recovery, differs in that the leaching solutions are fed through an injection well system by separate injection of the solution jets, while initially supplying a hydrocarbonate-peroxide solution subjected to photoelectrochem thermal processing, then, after a pause, a solution of hydrochloric acid is added with the addition of hydrogen peroxide, subjected to ultraviolet irradiation before feeding, after the solution has matured in the reservoir until the main part of the gold passes from the mineral mass into the reservoir, perforated capsules with sorbent are placed in the wells equipped with electrodes supply voltage to the electrodes to provide directional diffusion of dissolved gold ions to the sorbent and its sorption, as well as add-on Ivanov remaining ore in the formation of gold, gold followed by saturated sorbent is recovered and subjected to regeneration.

The method is as follows.

Drilling and casing of injection wells are carried out. In this case, the casing of the injection wells is performed by two coaxial perforated pipes, the external of which are casing. The places of perforation of the external and internal pipes are connected by short nozzles. Through the internal pipes, leaching solutions, initially of a hydrocarbonate-peroxide composition, obtained in a photoelectrochemical reactor, are fed, then, after a pause, a solution of hydrochloric acid with the addition of hydrogen peroxide, irradiated before being fed into the formation by UV rays. Hydrocarbonate-peroxide composition solutions, during pulse jet injection into the reservoir, due to subsequent diffusion processes, ensure the propagation of hydrocarbonate ions and active oxygen into the film waters surrounding mineral particles, including sulfide minerals and magnetite with dispersed gold. This ensures the initial oxidation of minerals in the near-surface region and in the space adjacent to the surface of microcracks and pores, respectively, and a significant decrease in oxidizing agents in the composition of the main leach solution. The main leach solution containing a complexing agent and an oxidizing agent for gold is also supplied through wells several tens of hours after the supply of the primary hydrocarbonate-peroxide solution. In this case, the components of the main solution also from diffusion zones of an initially high concentration diffuse into the bulk of the formation. Moreover, due to the developed contact surface formed after treatment with a high concentration of a hydrocarbonate-peroxide composition with an active solution, the components of the chloride-peroxide solution oxidize and leach the gold relatively quickly.

In this case, due to the reaction catalyzed by UV irradiation between hydrogen chloride and hydrogen peroxide in the main leach solution, active metastable hypochlorous acid is formed, periodically clustering in hydrochloric acid and decomposing into atomic oxygen, chlorine and water 4 OHCl - 4Cl * + 2O * + 2H ₂ O. Hypochlorous acid and products formed from it by the above reaction react with gold to yield complex anions of the type Au (OHCl) ^- and Au (Cl) ₄ ^- . The complex gold ions formed in the electric field periodically dissociate into cations and anions, and cations, before recombination with chlorine and hydroxyl anions, have time to shift to the cathode and, therefore, to the sorbent placed in the wells.

An example of a specific use of the method.

A deep-lying (more than 12 m downstream) gold placer, with a sand layer thickness of 3-3.5 m, represented mainly by fine (up to 0.5 mm) and dispersed (sorbed by clay minerals included in the lattice of magnetite and other schlich minerals) metal precipitates.

The filtration coefficient in the sand is 1.5 m / day.

Initially, wells with a diameter of 150 mm are drilled through a 5 * 5 m network. The injection wells are cased with plastic pipes with a diameter of 150 mm and 100 mm, which are perforated and the perforation sites of these pipes are connected with 50 mm diameter pipes. Drainage wells are drilled along the block’s contour through a 10 * 10 network and equipped with airlifts for periodic pumping of produced water, which can reduce the concentration of leaching reagents.

The leaching solutions are prepared in special photoelectrochemical (hydrocarbonate-peroxide composition) and photochemical (hydrochloric acid solutions with the addition of hydrogen peroxide) reactors. A hydrocarbonate-peroxide solution is prepared from a 5% solution of sodium carbonate by electrolysis, subsequent input of 10 g / l of 30% hydrogen peroxide and irradiation of the resulting suspension with a DRT-230 ultraviolet lamp.

Solutions of the hydrocarbonate-peroxide composition are fed into the formation through pipes placed in the wells in a jet pulse mode until the calculated T: W = 50: 1 is reached. After a pause of 48 hours, during which the solution diffuses into the main volume of the formation, a solution of the chloride-peroxide composition is pumped into it in the same manner, and before the solution is fed into the formation, the solution is irradiated with a DT-230 UV lamp for 10 minutes. After a pause of 72 hours, during which gold is leached in diffusion mode from the minerals oxidized at the first stage, the injection pipes are removed from the wells and capsules with electrodes are lowered into them, with the anodes and cathodes placed in separate wells and the cathodes placed in an ion-exchange resin A-100. After applying voltage of 5-8 V to the electrodes, electrodiffusion of gold leached with a chloride solution is carried out and its sorption by resin. In addition, due to the release of chlorine on the anode and the formation of new chlorine-oxygen complexes that are mobile in the electric field, the leaching of gold remaining in the solid phase is intensified. Due to the combination of electrosorption processes of gold leached at the first stage (when the primary chloride-peroxide solution is aged) of gold and its leaching, the total time of its transfer to the solution and accumulation in the cathode zones on the resin is 10 days when 75-85% is recovered from the solid. At the end of the sorption process, the resin capsules are removed from the wells and transferred to regeneration.

Claims (1)

The method of downhole leaching of gold from deep-lying placers and man-made mineral formations, comprising supplying activated leaching solutions to the reservoir through injection system with subsequent extraction of gold, characterized in that the leaching solution is supplied through the injection well system by injection of the solution in separate jets, while initially supplying a hydrocarbonate-peroxide solution subjected to photoelectrochemical treatment, then after a pause, a solution of hydrochloric acid is added with the addition of hydrogen peroxide, subjected to ultraviolet irradiation before feeding, after the solution has matured in the reservoir until the main part of the gold passes from the mineral mass into the reservoir, perforated capsules with sorbent equipped with electrodes are placed in the wells and fed to the electrodes voltage to ensure directed diffusion of dissolved gold ions to the sorbent and its sorption, as well as additionally leaching remaining in the ore aste gold, gold followed by saturated sorbent is recovered and subjected to regeneration.