Mining

In its simplest form, washing in a thickener can consist of mixing solids and associated solution with water, settling the solids, decanting the clarified solution, and then repeating the process as required until the dissolved material is removed. The logical extension of this procedure is to use the more dilute, decanted solutions as wash liquid in earlier stages, a procedure which lends itself to continuous operation, and, hence, continuous countercurrent decantation.

The controlling factors in such a procedure are:

1. The number of mixing-settling stages;
2. The relative amounts of liquid in the feed and underflow; this can be expressed as the ratio of overflow volume to volume of liquid in the underflow, which is often termed “wash ratio”;
3. The “efficiency” of each stage, referring to the completeness of mixing of the underflow and overflow solutions which enter a thickener (defined quantitatively in later text).

CCD flowsheets can take many forms; the most common is the straight forward procedure in which a leach pulp enters the primary thickener, after being diluted with second stage thickener overflow, with the solids proceeding through the series of thickeners in a direction countercurrent to the wash solution.

ClearStream offers a complete line of equipment and services for your CCD plant that will improve your plants performance.

What are Tailings?

Tailings are a by-product of mining. After ore containing an economically-recoverable commodity is mined from the earth, that commodity is extracted in a processing plant or mill. After the commodity of value is extracted from the ore material, the resultant waste stream is termed “tailings”. Typically, mill tailings range from sand to silt-clay in particle size.

Mineral commodities commonly recovered are copper, gold, silver, iron, lead, zinc, uranium and coal.

Due to a number of factors, not all of the commodity is recovered during the extraction process and some residual commodity usually remains. Thus, the tailings may become valuable in the future depending on technological improvements and market conditions allowing them to be reprocessed.

How are Tailings Stored?

After processing, tailings are impounded so that their effect on the environment is minimized. There are several methods currently used in the mining industry for constructing tailings facilities, including:

• Conventional tailings facility, including in-pit disposal methods;
• Paste tailings including underground backfill; and
• Filtered tailings.

Each of these tailings impoundments utilizes a dam and engineered containment to minimize seepage of solutions into the environment. Generally, a pump system is used to collect any errant seepage and return it to the process or impoundment.

Conventional Tailings Facility

Tailings slurry is pumped or otherwise conveyed directly to a tailings facility, which consists of a dam and an engineered containment system. Solution decants from the solids and is usually recycled back to the processing plant.

A variation of this type of tailings facility would be the placement of tailings into all or a portion of a mined out pit. As with other methods, care is taken to account for any migration of contaminants that may occur. On some occasions, backfilling a pit with tailings can reduce or eliminate the production of acid rock drainage from the pit walls.

Paste Facility

In the final process before storage, water is separated from tailings slurry in special tanks called thickeners to make a “paste”. Depending on the amount of water in the tailings,  the resultant material may have the texture of toothpaste. The paste is pumped to a storage facility. There usually is a small amount of decant solution that is pumped back to the process.

Sometimes paste and cement are mixed and pumped back into an underground mine for storage, which actually helps the miners by filling voids and providing ground support. It also reduces the amount of area on the surface that would be used for the paste tailings facility.

Filtered Tailings

Tailings are pumped into high pressure filters that produce a rinsed filter cake product.  The filter cake can be transported by conveyors or trucks and stacked in a tailings facility. Usually, the size of the starter dam required to ensure slope stability is much smaller than conventional tailings facilities, but is highly project-specific. Ideally, there is usually very little solution left in the tailings, which may be moved and shaped in a pile by mechanical equipment.

ClearStream offers a complete line of equipment and services for your Tailings Management. Contact our Process Engineering team to discuss your project.

Mining is on the front line of water security risk. The mining industry uses water for a variety of purposes, including mineral processing, dust suppression, slurry transport and storage, extraction processes and site usage. In most mining operations, operators extract water from groundwater, streams, rivers, lakes or through commercial water service suppliers. Some mining sites are in areas where water is already scarce.

Sustainable water management within the mining industry is critical.

One of the most common ways to maximize the reuse of water is to install a water treatment system.  Choosing the system will depend on each project’s treatment requirements.

Wastewater treatment units treat effluent and recover water for reuse purposes. They also help minimize the environmental compliance challenges and risks associated with effluent discharges.

Let ClearStream work with you mine site to design a system the fits your needs.

Many industry operations are highly water-intensive, e.g., in the mining industry, they demand large quantities of water to operate efficiently. At the same time, many industrial companies generate pollutant wastewater streams. With a correct and effective wastewater treatment process, you can filtrate your wastewater to such an extent that it can be recycled.

The processes for heavy metal removal in industrial wastewater include many different processes.

The most common process used for heavy metal removal is chemical precipitation. The primary parameter that improves heavy metal removal in wastewater in this technology is the adjustment of pH. Lime is commonly employed as a precipitant agent due to its availability and low cost in most countries. Lime precipitation can be utilized to offer efficient treatment of the inorganic effluent with an appropriate metal concentration.

Once sites manage their water efficiently, they can significantly reduce their costs due to lowered water consumption by reusing the wastewater after treatment. They can lower their water processing costs by reusing the wastewater instead of discharging it and paying discharge fees. Simultaneously, they reduce their dependency on freshwater supplies due to their self-sufficient water supply.

Contact ClearStream to work with you mine site to design a system the fits your needs.

Abandoned mine drainage is water that is polluted from contact with mining activity, and normally associated with coal mining. It is a common form of water pollution in areas where mining took place in the past. There are several issues with abandoned mines that impact water quality:

• acid mine drainage (the most prevalent)
• alkaline mine drainage (this typically occurs when calcite or dolomite is present)
• metal mine drainage (high levels of lead or other metals drain from these abandoned mines)

Acid mine drainage is the formation and movement of highly acidic water rich in heavy metals. This acidic water forms through the chemical reaction of surface water (rainwater, snowmelt, pond water) and shallow subsurface water with rocks that contain sulfur-bearing minerals, resulting in sulfuric acid. Heavy metals can be leached from rocks that come in contact with the acid, a process that may be substantially enhanced by bacterial action. The resulting fluids may be highly toxic and, when mixed with groundwater, surface water and soil, may have harmful effects on humans, animals and plants.

ClearStream has the process knowledge and equipment solutions to solve your acid mine drainage needs. Contact us to discuss your project.