Where is leach mining used

Neither the year window nor the reliance on computer modeling should supersede monitoring. In-situ Leach Uranium Mining. Permitting and regulation In situ recovery process.

Regulation of ISL operations has proven problematic. These new proposals require: Testing: Baseline characterization of aquifer geochemistry before ISL recovery begins. This baseline study is essential so we can know whether ISL polluted the aquifer or something else.

The solution then percolates through the heap and leaches both the target and other minerals. This process called the 'leach cycle', generally takes from one or two months for simple oxide ores eg most gold ores to two years for nickel laterite ores.

The leach solution containing the dissolved minerals is then collected, treated in a process plant to recover the target mineral and in some cases precipitate other minerals, and recycled to the heap after reagent levels are adjusted. A simple flowchart for a gold heap leaching process.

Source: modified from Donald, I. Geological Survey Open-File Report — The significant advantage of the heap leaching method over conventional leaching and recovery techniques is that heap leaching consumes less than 0. Heap leaching is an industrial mining process used to extract precious metals, copper, uranium and other compounds from ore using a series of chemical reactions that absorb specific minerals and re-separate them after their division from other earth materials. Similar to in situ mining, heap leach mining differs in that it places ore on a liner, then adds the chemicals via drip systems to the ore, whereas in situ mining lacks these liners and pulls pregnant solution up to obtain the minerals.

Heap leaching is widely used in modern large-scale mining operations as it produces the desired concentrates at a lower cost compared to conventional processing methods such as flotation, agitation and vat leaching. Additionally, dump leaching is an essential part of most copper mining operations and determines the quality grade of the produced material along with other factors.

Due to the profitability that the dump leaching has on the mining process, ie it can contribute substantially to the economic viability of the mining process, it is advantageous to include the results of the leaching operation in the economic overall project evaluation. This, in effect, requires that the key controllable variables, which have an impact on the recovery of the metal and the quality of solution coming from a dump leaching process.

The process has ancient origins; one of the classical methods for the manufacture of copper as iron sulphate was to heap up iron pyrite and collect the leachate from the heap, which was then boiled with iron to produce iron II sulphate. Several major projects around the world are using this method of extraction.

As mentioned, the major proponents of this process are miners of gold and copper porphyry deposits and these are in the USA, Chile, Peru and Indonesia. These deposits are mainly lower grade and have a large tonnage. Interestingly, the other gold mining countries such as Australia, South Africa and Canada do not seem to practice this form of processing as much.

In terms of weather, the dry arid nature of Australia would be ideal, especially the low rainfall parts of the drier parts of Australia. Approximately 3MT on the pad as working inventory. According to the company website, the Tujuh Bukit Project consists of two distinct mining development opportunities:.

The heap leach pad working inventory is 3mt at 0. In addition to this planned leach cycle, there is potential for additional recovery of metal as the leach solution percolates through the underlying lifts. The Escondida deposit is one of a cluster of porphyry coppers in an elongated area about 18km north-south and 3km east-west. It is associated with the km-long West Fissure Falla Oeste system, which is in turn associated with most of the major Chilean porphyry deposits.

A barren, leached cap, in places up to metres thick, overlies a thick zone of high-grade secondary supergene mineralisation of the main ore body, largely chalcocite and covellite, which in turn overlies the unaltered primary mineralisation of chalcopyrite, bornite and pyrite. At mid, Escondida had total proven and probable reserves of Total resources, including reserves, were Exploration continues. It is piped down to the port of Coloso, where it is dewatered before shipping.

It is also crushed and dumped on large heaps, but here the leaching occurs through oxidation induced by microorganisms. In addition, N-Mining will have the right to economic participation equivalent to a 1.

Chulbatkan is in the industrialised district of Khabarovsk Krai, Far East Russia, about 15km southwest of Udinsk, a settlement on the Amgun River and has year-round transportation access. The mine is expected to be low-cost and the processing is focused on a heap leach process. The examples I have given above are very big, but on a smaller scale, there are also participants looking at a cheap alternative to mining.

An example is Tartana Resources, a company at the time of research was quoted as looking to list on the ASX. To ensure uniform distribution of the lixiviant to the ore heap and to minimize evaporation, drip irrigation systems are the preferred distribution method. As with the leach pad liner system, the drip irrigation system also has to withstand the harsh chemical stresses and environmental conditions it is subjected to. Moreover, the drip irrigation system should provide excellent anti-clogging resistance, and offer exceptional leaching solution distribution throughout every solution drop point.

Following the crushing and or agglomeration stage, the ore is then transferred onto a heap leach pad, where the long process of metal leaching from the ore to the lixiviant takes place. To contain the leaching solution and prevent seepage to the environment leach pad liner systems are used. Liner systems can vary from operation to operation and are typically engineered based on surface conditions and leach pad specifications, but primarily involve the use of compacted clays, geo-textiles and geomembranes with additional use of geo-nets for lateral support.

Most importantly is that the liner system must meet and fulfill strict specifications, be completely impermeable, withstand prolonged exposure to acidic and alkaline solutions, resistant to abrasions and puncture, and offer overall chemical and thermal resistance. The pregnant solution produced by the stripping cycle is then precipitated by the addition of ammonia, hydrogen peroxide, caustic soda or caustic magnesia.

The uranium is then stripped from the loaded organic liquid using ammonia followed by an ammonia precipitation. The resultant slurry is then dried at high temperature as per the IX process. After recovery of the uranium, the barren solution is re-fortified with oxidant and complexing agent before being returned to the wellfield via the injection wells. However, a small flow about 0.

This waste water contains various dissolved ions such as chloride, sulphate, sodium, radium, arsenic and iron from the orebody and is reinjected into approved disposal wells in a depleted portion of the orebody.

This bleed of process solution ensures that there is a steady flow into the wellfield from the surrounding aquifer, and serves to restrict the flow of mining solutions away from the mining area. Acid consumption in acid leach environments is variable depending on operating philosophy and geological conditions. In general, the acid consumption in Australian ISL mines is only a fraction of that used in a Kazakh mine per kilogram of uranium produced. A general figure for Kazakh ISL production is about 40 kg acid per kgU, though other figures of up to twice that are quoted and some mines are a bit lower.

Beverley in Australia in was 7. For very small orebodies which are amenable to ISL mining, a central process plant may be distant from the mine, so a satellite plant will be set up.

Hence very small deposits can become viable, since apart from the wellfield, little capital expenditure is required at the mine site. It is used for Four Mile in South Australia, where for historical reasons the main treatment plant at Beverley is several kilometres distant.

Initial tests using ISL commenced in and were successful. All except one of the operating and planned ISL mine groups are in the Chu-Sarysu province in the central south of the country and controlled by the state corporation Kazatomprom. Mines in the Western No. All have substantial resources. Mining is at depths of metres, though some orebodies extend to metres.

Tortkuduk, Budenovskoye, Inkai, South Inkai and Moinkum are the largest ISL mines, and Cameco's description of Inkai's operation is: Uranium occurs in sandstone aquifers as coatings on the sand grains at a depth of up to metres. Uranium is largely insoluble in the native groundwater which is not potable due to naturally high concentrations of radionuclides and dissolved solids.

Using a grid of injection and production wells, a mining solution containing an oxidant sulfuric acid is circulated through the orebody to dissolve the uranium. The uranium-bearing solution generally containing less than 0.

The water is re-oxidized and re-injected into the orebody. This process is repeated to remove as much uranium as is economically feasible. When mining at the site is complete, the groundwater will be restored to its original quality. This is a closed loop recirculation system since the water from the production well is reintroduced in the injection wells. Slightly less water is injected than is pumped to the surface to ensure that fluids are confined to the ore zones intended for extraction.

Monitor wells are installed above, below and around the target zones to check that mining fluids do not move outside a permitted mining area. ISL uranium production in Kazakhstan requires large quantities of sulfuric acid , due to relatively high levels of carbonate in the orebodies. This was a serious constraint on production over In Kazatomprom with other mining companies and two acid producers, KazZinc JSC and Kazakhmys, set up a coordinating council to regulate acid supplies and infrastructure.

Since then acid supply has been adequate, and new acid plant capacity has been built. See also paper Uranium and Nuclear Power in Kazakhstan. At established operations overseas, after ISL mining is completed, the quality of the remaining groundwater must be restored to a baseline standard determined before the start of the operation, so that any prior use can be resumed.