Friday, July 2, 2010

Mine slimes and tailings stabilized using geopolymers

A serious problem in the mining industry is the production of mine slimes from various refining processes. These slimes can be encapsulated permanently using the geopolymer process. At the present most of these slimes are stored in ponds or lagoons that can break releasing the slimes into the environment. Once treated with geopolymers the encapsulated slimes can be used as building materials replacing concrete, or stored in worked out portions of the mine.

Mine slimes are produced as part of the ore beneficiation process when the raw ore is placed in a large ball mill with large steel or ceramic balls that reduce the ore to a powder as fine as flour. The ground up ore is transferred to a flotation tank full of water and a flotation agent that is similar to dish washing liquid. Compressed air is forced up through the ore causing foam in the flotation tank. Most metals are in the form of sulfides that stick to the resulting bubbles. The barren ore remains in the bottom of the tank the foam is periodically scraped from the top of the tank with the sulfide minerals going to the smelter. The barren ore remains behind in the bottom of the flotation cell.

After each cycle of the flotation cell the barren ore is removed as mine slime consisting of silt sized particles that are transferred to a holding pond for storage. There are times when the pond holding the slime overflows especially during floods releasing the slime to cause extensive property and environmental damage.

It’s cousin coal fly ash resulting from burning coal in generating plants. This waste is stored in a similar way in a pond or other holding area. Recently a storage pond holding coal fly ash broke loose in Kingston, Tennessee causing tremendous damage to both the environment and the surrounding property.

Using the geopolymer process it is possible to encapsulate mine slimes and tailings into useable building materials in a cost effective way. The encapsulating process makes use of practically all waste products like mine wastes and coal fly ash, or wood ash in a way that in isolated mining sites the resulting material can be used locally for building purposes.

Geopolymers can be cast into any number of shapes to address the construction needs of a mine like bricks or building blocks. It also can make Jersey barriers or large concrete blocks that are used in many mining camps for mineral storage bins.


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