China
Africa
Explore chapters and articles related to this topic
Green and sustainable mining
Published in A.J.S. (Sam) Spearing, Liqiang Ma, Cong-An Ma, Mine Design, Planning and Sustainable Exploitation in the Digital Age, 2023
A.J.S. (Sam) Spearing, Liqiang Ma, Cong-An Ma
Although openpit mining contributes about 85% of all mineral mining, it is one of the most environmentally taxing. About 73% of extracted rock goes to waste. Meanwhile, underground mining wastes is only 7% of the global extracted rock and is more expensive to produce (Hartmann & Mutmansky, 2002). In-situ mining can be more environmentally friendly than underground mining and is cheaper than many mining methods (Ulmer-Scholle, 2022). However, in-situ mining cannot be implemented in all cases as the ore needs to be beneath the water table (the level at which the ground is saturated with water) and it needs to be porous enough to let the leaching solution dissolve (Topf, 2011). Unfortunately, in-situ leaching can also be very harmful if the solution leaks into the water supply. There are plenty of examples of past leaks at in-situ leaching mines (“Coloradoans Against Resource Destruction”, 2008).
The Anatomy of a Mine
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
Leaching is the process of extracting a soluble metallic compound from an ore by selectively dissolving it in a solvent such as water, sulfuric or hydrochloric acid, caustic soda or cyanide solution. The desired metal is then removed from the ‘pregnant’ leach solution by chemical precipitation or another chemical or electrochemical process. Leaching may be carried out in situ, in heaps, or in vats (tanks). In situ leaching is widely used for uranium extraction; heap leaching is widely used in the gold industry, and dump leaching in the copper industry.
Hydrometallurgy — An Introductory Appraisal
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2019
In situ leaching is neither new nor unusual and is recorded to have been used on a small scale in Hungary during the 15th century. The in situ leaching method is known by other names such as leaching in place and solution mining. In this case, the ore is not mined at all, but is leached where it occurs. The ore is first fractured by explosives, and leaching is effected by alternate and intermittent circulation, first of air, followed by water and spent solution from the precipitation process. Natural drainage is relied on for accumulating the leach solution, either through the construction of drainage tunnels under the ore body or, in the case of exhausted or mined-out ore bodies, lower workings in the mine. The solution is pumped to the surface and processed for metal recovery. The efficiency of the process is difficult to evaluate in view of the variables of unknown tonnages and content either before or after leaching operations. In situ leaching has been applied successfully in a number of cases, both on mined-out ore bodies or on ore bodies too low in grade to be otherwise considered for economic treatment. The main difficulties in the process arise from channeling, which interferes with the even distribution of leach solution over the ore, and a later possibility of slimes and accumulated salts, in time filling the openings and thus interfering with solution-ore contact. The advantages of solution mining are (1) less surface disturbance and environmental impact than conventional mining, beneficiation, and smelting; (2) lower capital and operating costs; (3) potential economic advantage for recovery of metals from materials that could not be treated by conventional methods; and (4) increased ore resources. The disadvantages are (1) complex technology relative to chemical and physical features, (2) testing short of field operation is difficult, (3) groundwater contaminants may result, and (4) a detailed data base has not been established commercially. In situ leaching of copper ores has received renewed interest, and the ore deposits amenable for treatment by this process have been classified into three general groups: (1) surface dumps or heaps located above the natural water table; (2) deposits located below the natural water table but accessible by conventional mining techniques; and (3) deposits located below the natural water table and too deep for economic mining by conventional methods. The first and second type of ore deposits have been practiced in commercial in situ leaching for the extraction of copper. For the third type of ore deposits, the technology is not available yet for in situ operations.
Development and evaluation of a mathematical model in an in situ uranium leaching technique
Published in Applied Earth Science, 2019
An in situ leaching method develops uranium deposits in which the ore body is usually within a well-permeable geological environment in an underground aquifer, as shown in Figure 1. The extraction of uranium from the ore body occurs with the help of technological well systems that are combined in technological cells and blocks. A working solution containing reagents that are capable of dissolving uranium minerals is injected through injection wells to form a productive horizon (Pastukhov and Skripchenko 2017). As a result of the physicochemical interaction of uranium minerals and host rocks with leaching reagents in the underground aquifer, a productive solution is formed, which is discharged to the surface through the system of pumped wells. Uranium is extracted from the uranium-enriched solution while the latter is processed. The remaining mother liquors are strengthened with leaching reagents and again fed to the injection wells as a working solution (Panfilov et al. 2016). At present, weak aqueous solutions of sulphuric acid are used as working agents (working solutions) in the above-ground leaching of uranium. To ensure the required flow rate of pumping wells and the transport of uranium-enriched solutions to a collection site, a method to lift solutions using deep-well pumps was adopted. The supply (injection) of injected solutions into wells is carried out by injection wells. A borehole pump control is operated at the receiving node of uranium-enriched solutions (Becherkin et al. 1968).