The process includes the following steps. Salt solution mining wells inject clean water to dissolve the salt. The resulting salt water brine is pumped to the surface where the salt is extracted. Two extraction methods are used.
Copper is mined using injection wells only in a few states. A sulfuric acid solution is used to dissolve the copper ore. Sulfur may be mined via the Frasch process. Super-heated steam is injected into the mineral-bearing formation to generate a sulfur solution that can be recovered.
Injection wells are not being used to extract sulfur at this time. Solution mining through injection wells is an option that can minimize the environmental footprint and potential impact to surface water compared to more traditional mining processes.
To prevent contamination of ground water which in many cases is a USDW by Class III wells, more fluid is extracted than is injected in solution mining processes.
This prevents fluids from moving out of the mining areas. All Class III wells are operated under individual or area permits. Contamination from mining wells is prevented by implementing requirements for mining well operators. Before injection begins operators must obtain an aquifer exemption when:. Class III wells inject fluids for in-situ mining. Environmental engineers have become concerned with leaching more recently because of the multitude of dumps and landfills that contain hazardous and toxic wastes.
Sometimes the natural breakdown of a toxic chemical results in another chemical that is even more toxic. Rain that passes through these materials enters ground water, lakes, streams, wells, ponds, and the like. Furthermore, many toxic compounds are accumulated by living cells and can be more concentrated inside than outside a cell. This is why long-term exposure is a serious problem; encountering a low concentration of a toxic material a few times may not be dangerous, but having it in your drinking water day after day and year after year can be deadly.
Although adsorption and ion exchange can bind materials tightly to solids, we will simplify the analysis and consider only dissolving a soluble constituent away from an insoluble solid. An example is removing salt from sand by extraction with water. The solvent phase becomes concentrated as it contacts in a stage wise fashion the increasing solute-rich solid.
The raffinate becomes less concentrated in soluble material as it moves toward the fresh solvent stage. Harraz Presentation Solution mining Feb 6. Harraz Presentation Solution mining Feb 7. Harraz Presentation Solution mining Feb 8. However, due to a limited number of such sulfur deposits and the high cost of working them, this process for mining sulfur has not been employed in a major way anywhere in the world since It is an inexpensive bulk mineral also known as halite which can be found in concave rocks of coastal areas or in lagoons where sea water gets trapped and deposits salt as it evaporates in the sun.
Harraz Presentation Solution mining Feb Brines form by strong evaporation. These ponds on the shores of Great Salt Lake are sources of magnesium as well as salt. Thus, limestone calcite and dolomite are more common than gypsum, which is more common than halite, which is more common than potassium and magnesium salts.
Major groups of evaporite minerals More than eighty naturally occurring evaporite minerals have been identified. The intricate equilibrium relationships among these minerals have been the subject of many studies over the years. This is a chart that shows minerals that form the marine evaporite rocks, they are usually the most common minerals that appear in this kind of deposit. Technology of Solution Mining 2 The dissolution of the salt begins with the solution of a cavern sump.
The sump shall be accommodate the insolubles of the deposit: near the casings in the well. The cement must shut tight against the pressure of the blanket. The salt can be dissolved. The injected water is going trough the outer casing and the brine leave the cavern trough the inner casing.
This current direction is named indirectly. Important for the forming of the cavern is the precise controlling of the blanket level. Harraz Presentation Solution mining Feb 5 The last step is reached, if the cavern arrives the top of the deposit.
Because in the cavern the density of the brine increases from the top to the bottom, the brine current goes from the end of the outer casing under the blanket level to the side and then it flows to the inner casing and to the surface. In this case the salt was dissolved after the undercut in only one step. The entry of the solvent into the cavern is trough the inner tube.
From there the solvent rises up, dissolves the salt and goes to the outer casing. The sides of this cavern are more straightly as the caverns which is leached with the step-by- step technology. A disadvantage of this procedure is that the brine is in the most cases not saturated. For the production of brine is needed: i a building for a control room and an office, ii a workshop and a storage, iii a building for pumps, iv a blanket station, v-vii tanks for water and brine Technology of Solution Mining Cavern Sump Salt layer deposits Blanket Injection Inner Casing Roof Rock Water Injection Brine Recovery Blanket Level ii iii iv v vi vii Prof.
Harraz Presentation Solution mining Feb Today, there are three methods used to produce dry salt based on the method of recovery Abu- Khader, Mining is carried out at depths between m to more than m below the surface. Solar and wind energy is used in the evaporation process.
The method is used in regions where the evaporation rate exceeds the precipitation rate. The saline brine is pumped to the surface where water is evaporated using mechanical means such as steam- powered und mining: Also known as rock salt mining, this process involves conventional mining of the multiple effect or electric powered vapour compression evaporators. In the process, a thick slurry of brine and salt crystals is formed.
More than one third of the salt production worldwide is produced by solar evaporation of sea water or inland brines Sedivy, In the salt crystallization plants, saturated brine or rock salt and solar salt can be used as a raw material for the process. A summary of the possible process routes for the production of crystallized salt based on rock salt deposits is shown in Fig.
Processes that are used in the production of vacuum salt from sea water or lake brine as a raw material are shown in Fig. Harraz Presentation Solution mining Feb Fig. Processes for production of crystallized salt based on rock salt deposits Westphal et al. Processes for salt production from brine Westphal et al. Carnallite can be crystallised by evaporation of a few amount of water and cooling the brine. Therefore halite and also kieserite remain in the cavern as residue.
In only one well would exchange the heat between the concentric inner and outher tube or casing. An example is a dump or landfill. Liquid and solids move counter currently to the adjacent stages. To prevent this, only ore bodies that are beneath an impermeable layer of clay or shale are targeted. Monitoring wells are placed above the impermeable layer to watch for any changes in the ground water content or leaks from the layer below.
Chemicals introduced for the solution mining processes are leaching solutions, which dissolve the desired minerals, and reducing agents that precipitate the dissolved minerals. These chemicals can have adverse effects on the local water table, bringing with them dissolved metals or minerals. The United States and Canada have clean water and environmental protection acts that limit the extents of solution mining. They ensure that the ground water returns to its pre-solution mining state and limits the chemicals and dissolved solids in the ground water to be less than ppm.
That water must be returned to its pre-mining condition In uranium solution mining, special considerations must be made to ensure no radioactive material escapes into the local environment in any stage of the process. Although there is less contact with radioactive material via ore dust or radon release seen in conventional uranium mining, workers must still be monitored for alpha and gamma radiation to comply with OSHA guidelines The water requirements in solution mining are extremely high and can have adverse effects on the local environment if a large source of water is not readily available for use.
The water can be rehabilitated after processing, however the costs and processing methods may leave water that is too contaminated to be reintroduced into the local water ways or tables. Tailing dams are used to store the contaminated water. The waste water can also be pumped back underground where the minerals were extracted however, this will require additional monitoring of the site to ensure no movement of the contaminated water to the local water table through the impermeable layer.
In salt or potash solution mining the creation of large salt caverns is common. Due to the soft nature of the rock, subsidence of the rock is common. Measures must be taken to ensure that the deposit is deep or small enough that there is no notable ground subsidence or that subsidence is permitted and allowed in that location These salt caverns can be used to store materials that do not dissolve the salt barriers. This has been used for the storage of hydrocarbon liquids and gasses, industrial waste, nuclear waste and tailings.
Salt falls in the cavern can cause leakage or blockage in the system. These problems have had mixed results of fixing the problem with remotely controlled submersibles. Graham Taylor Maxim Seredkin Ore Geology Reviews. In-Situ Recovery.
SX-EW copper and the technology cycle. In Situ Leach Mining of Uranium. Uranium One Inc. Code of Practice for the management of particulate matter PM2. Environment and Climate Change Canada. Solution Mining. Gensource Potash Corp. Solution Mining — Introduction. K-Utec Salt Technologies. Available: www. Uranium Mines and Mills. Thoms and R. Gehle Jump to: navigation , search.
0コメント