Engineering - Metallurgy
Metallurgy is taken to mean the extraction of metals from their various ores, the heat treatment of metals and the production of alloys.
Metallic minerals are usually found in nature in the form of ores. An ore is a solid, naturally occurring mineral compound from which at least one metal can be obtained. These ores are mined and then the extraction of the metal occurs.
There are four main mining methods :
1. Open Cast Mining
Used to gather ores that are in fairly horizontal layers near to the surface. Overburden may need to be removed first in order to get at the ore. If the mineral is in rock explosives may be used.
2. Underground Mining
Underground Mining is the most expensive type of mining, and so there must be enough ore to make the process worthwhile. The ore is to be found deep beneath the surface and deep shafts are sunk. A series of tunnels are dug from the main shaft. The ore is blasted and drilled, then usually crushed, transferred to Transport Cars, which carry the ore to a Hoist Bucket, which in turn carries the ore to the surface. There the ore is treated and the metal mineral extracted.
3. Open Pit Mining
Used when the ore is in deep wide layers. This is a relatively cheep form of mining as a lot of mechanisation can be used. The ore is blasted, then moved to truck which take it to the refining plant. This process is similar to quarrying.
Dredging occurs in shallow waters in rivers or in the sea. The overburden is stripped first and then the Dredge Barge removes the ore, which is separated on the ship. The waste product is then returned to the water in an area that has already been dredged. The Dredge Barge then gives its cargo to a larger Carrier Ship for transportation to shore.
Mining Methods Compared
Concentration Of Ores
As it is bad business to transport waste material the ore that is removed from the earth is concentrated as much as possible before transportation. The ore is first mined, then crushed, then ground into fine particles and then concentrated.
Methods of Concentration :
Now the metal has to be extracted from the ore. There are three main methods :