I see copper just as precious as gold and silver?

Hello All

Why you ask that I see copper just as precious as gold and silver?

Copper is a little treasure in the ground which is not as flashy as gold or silver it has always been a poor cousin to the nobler of metals. Once you know its story of the processes behind it you will see copper in a different light.

Here is the story of copper from its discovery, mining, processing as a tribute to all the men and women in hundreds of mines and smelters, refineries giving us such a useful metal we all take for granted.

The discovery.

Its journey begins many years ago when prospector on the ground discovered a lode of copper and sent specimens into assay office. The copper content and other precious metals such as silver lead and gold was deemed profitable enough for the ore body to be considered to be mined.

The finder can some times be rewarded for the discovery as it is in the interest of mining companies to essay samples. The fist thing will happen a legal team will negotiate the purchase of a mineral exploration lease of the site in question.

A mining exploration team under the companies head geologist will engage the services of a drilling contractor under the control of a junior geologist under instructions of the senior Geologist. The main object of this is to fully map the lease and to determine the size and depth of the ore body and to further sample the quality of the ore body by drilling core samples.

With this work done the head Geologist will refer this report to the companies planning team this will consist of senior mining engineers, geologists, financial planners and company management team which in turn will be referred to the directors who with the CEO of company will decide the viability of the project.

The company through a carefully managed Pr team will make the discovery of the ore body public as they will announce their discovery only after obtaining the relevant mining permits, environment impact studies, leases, labor agreements, transport facilities, water access and processing and smelting and refining agreements.

Depending on country location of the ore body size and financial position of the company they may look to a risk share an agreement with other partner companies to mitigate the risk. They may even keep to their own core activity of mining and on sell their ore for the processing by a Smelting and refining company if available nearby or internally or internationally export the ore to that site.

The company will start working on the mining lease when all agreements have been finalized and the financial plan put in place will go ahead and develop the ore body. The team on the ground will contract an earth moving contractor to remove overburden from the site. Depending on the location of the site the company may have direct underground mining or an open cut. Open cut if possible is much favored as the cost extracting rate of ore is much cheaper then the more costly shaft and tunnel mining.

The open cut.

The beginning of the open cut mine is started with the active the recruiting of mine workers for an open cut consisting of truck drivers, Dump truck drivers, loader operators, Drilling rig operators for drilling the blast holes to be used he explosives team. Fitters, boilermaker?s welders are included etc With Occupation health and safety supervisors, site and shift supervisors, site management mining planning team.

In time progressively after the overburden is removed and the proper mining can commence. The drilling team will drill a series of holes at a pre determined depth complex blasting pattern devised by the detonation crew under the supervision of the senior site geologist and mining engineer. The site will be evacuated and after series of safety checks the site is detonated. This process will be repeated day and night until the open cut becomes a gigantic hole with a series of roads descending down into the center.

The ore recovery team will recover the shattered rock either with excavator, large bucket wheel or front end loaders depending on the size of the mine. From there the blasted rock with the ore will be tipped into gigantic dump trucks transported to a rock crusher site to crush the rock even further.

The ore will be smashed up through a series of crushers and fall through a series of screens in a plant commonly known as an ore concentrator. Some smaller mines will process the ore off site however this is costly process as you have too much transportation cost carrying unprocessed ore. Most modern large mines will have a processing plant on site. After the crushing screening process the ore can be washed to directly export to a pelletiser plant depending once again on the size and location of the mine.

The under ground Mine.

Once the open cut has finished its useful life and depending on the size of the ore body and quality of the ore. A decision by the management team to mine underground. Underground mining is a complex and dangerous operation. Serious planning goes into the under ground mining with ventilation ore extraction in complex network of roads, workshops lunch rooms.

One such ore body at Mt Isa R62 had 29 levels over 500km of roads. Traveling down the two story elevator in a jumbo truck is like traveling downwards on a subway at night. There are huge underground workshops with overhead cranes working on maintenance of plant equipment.

The main section of the working ore body is drilled will automated drilling machine which are run on air which drill blast holes in the rock. As with the open cut all operating personnel leave the mine when there is blasting operations.

The deeper the mine the hotter it gets. Air conditioning is pumped into the mine because the rock is warm to touch. Gigantic shafts are designed by ventilation engineers to extract dangerous fumes from machinery and some trucks are automated eclectic trolley trucks driven by remote control to reduce fume emissions.

The ore will be retrieved by truck to the surface using a road that winds around the underground to the surface like a gigantic corkscrew. Or depending of the mine the rock carried around a series of conveyor belts to the surface. Some mines will process the ore on site through a Copper concentrator to the point where it becomes slurry and piped sometimes hundreds of km to a port to pelletiser plant where it will be process into pellets at a nearby port on the coast to be shipped to copper smelters all over the world.

The Smelter.

Some mining complexes are so big they will have a smelter on site. The ore process either as a dust or pellets depending on the requirements of the smelter. Those requirements are dictated by the feed prep system.

The ore can be feed blended and pre processed with lime and other materials in a sinter plant that prepare to send the processed ore in a blast furnace or an old reverbertory furnace or Noranda reactor. Different types of furnace to melt ore but the principles are nearly the same. The ore which is fed through the top of the furnace allowing it to melt before it hits the bottom of the furnace.

It is very crucial to control the flow rate of the ore into the furnace. Too much can cool the furnace down so the ore or the pellets do not melt before hitting the molten bath of the furnace. If ore or the pellets hit the bath it will case the molten metal to foam. This is very dangerous as it builds up gas pressures in side the furnace which the temperature will change from rapid cooling furnace to a rapid rise in temperature and pressure. A by product of this is slag which floats on top of the furnace. If there is a high slag level in the furnace at the time gas will build up under the slag to the point of catastrophic explosion resulting in smelting terms a ?foam over?. In short the furnace erupts like a volcano or Roman candle. Believe me not a nice place to be when it?s raining molten metal!

If the flow rate of the ore is controlled the slag will naturally build up on the surface of the Molten bath. The furnace is designed to have pressure point these are what we call tap holes on 2 levels. The Bottom Level is designed to tap molten copper at this stage of the process referred as matt to receive further processing in a furnace called converters.

Tap hole are holes blocked up with clay and are essentially a plug to drain molten metal out of the furnace. Around the tap to stop the tap hole from burning out there is what we call a water jacket to stop the tap hole from melting.

The upper tap hole is for the slag is drained from the furnace and which run down a launder into another furnace called an electric arc furnace. Inside the Electric arc furnace is 3 gigantic electrodes. To stop the electric arc furnace from exploding water is constantly flushing over the outer skin of the furnace to cool the outer casing.

The electric arc furnace is so hot it melts another 3-4% copper still in the slag which is tapped and fed into the converters. The waste slag is granulated with water. In effect a slow controlled explosion. The waste slag is reused in the building industry to make cement.

The converters are small barrel like furnaces designed to pump air into the molten bath of matt copper to push out all the remaining slag and other impurities such as bismuth and large amount of sulfur dioxide dust that is collected from all furnaces through a vacuum system that extracts the sulfur to a plant call the bag house.

The bag house which is basically a chamber filled with bags collecting the white sulfur dioxide dust. This dust is reprocessed with water in an acid plant to make sulfuric acid. Some of this acid will be on sold to another acid plant to be processed into battery acid and a cleaning acid for oil refineries. Another part of this acid will be spun in gigantic centrifuge mixed and baked will be processed into sodium M?tis bisulfate which will end up as food preservative. Some things to think about the next time you brush your teeth!

However once the converter have finished purging the sulfur out of the molten metal the Copper is transferred to the Anode furnaces.

The sole purpose of the anode furnaces is to pump natural gas or depending on the type furnace liquid napalm into the bath of copper to remove the oxygen that was pumped in by the converter to remove the sulfur and remaining slag and bismuth. Some times the converter process was not always complete. To improve quality of copper being processed scrap copper from the refinery or from recycle yards can be fed into this furnace. Even copper coins out of circulation.

If there is too much slag in the furnace? This would result in one unhappy furnace man. Because he may have to rabble slag off the anode furnace which is a very dangerous and hot job. On the side of drum like anode furnace there are two entry points where tywers are inserted. This is a special pipe with a special insert when the furnace rotates natural gas will be pumped through the tywers expelling the Oxygen used to expel the sulfur in the converting process. This process is called the reduction process. Copper purity at this point is about 97-98% copper.

When the Anode furnace has reduced the oxygen out of the copper the furnace is ready to rotate into casting position over the cast house floor. After confirmation from samples the copper is poured out down a series of brick refractory and steel launders to the intermediate casting ladle. Depending on the set up there could be two casting ladles in which the intermediate casting ladle will alternately tilt from one side to the other filling each respective casting ladle up in the process with molten copper.

The casting ladle pours a set weight of molten copper into bone ash coated mold with two lugs on the end of the mound. The cast house floor has a gigantic rotating wheel of, depending on size 24 to 36 molds. The molds when filled up with copper move as the wheel turns until they go under a spray hood where they are cooled. Every 3 anodes make up 1 ton of copper. There is an old saying in the cast house floor hot copper is good copper. Cold copper is bad copper.

After leaving the spray hood the cooled copper anode in the mold moves to a position where a hydraulic ram comes from underneath the wheel and pushed two steel pins in the center of the mold pushing up the Anode. The anode is picked up by a pair of robotic arms with cups that clamps onto the anode and flips the anode over into another cooling tank called a Bosh tank. The lugs sit of a chain which slowly as each anode. When a certain amount of anodes are on the chain the chain will move all the anodes in the bosh tank to the end, where another hydraulic ram from the inside of the tank will push the anodes up for a forklift to pick up or an overhead crane.

The molds continue the turn of the wheel and are sprayed with bone ash again under the spray hood to be re poured into by the casting ladle. So an end the first smelting process of the copper as the cast copper anodes are all stacked up in bunches is transported to the refinery for further processing.

see pictures of the anode casting process.

The Refinery.

The copper Anodes are processed through a straitening machine that grinds and lugs on the anodes or over wash of the cast so the anodes are uniform. They are then transport to a large building called the tank house.

The Tank house is a massive build with hundreds of concrete or fiberglass tanks designed to let the anode sit on a specially formed rack. In between each copper anode is a more pure sheet of copper called a cathode, the tank is filed with weak sulfuric acid and an electrical current is transmitted through the tank. This is called electrolysis.

Over a period of time the cast anode dissolve and the copper from the anodes leaches onto the pure sheets of copper the cathode. The impurities such as gold, silver, lead, palladium and platinum falls to the bottom of the tank which is then later pumped over to the precious metals plant and reprocessed. The remaining pieces of dissolved copper anode are reprocessed but tipping back into the anode furnace to make anodes again.

The copper remaining is now 99.8 or 99.99% copper on the sheets. These copper sheets are re melted into a vertical pipe Furnace called a billet caster. A 10 story building where the copper is melted and cast into billets 2 m bar with 30cm circumference. The molten copper is poured down a pipe slowly cooled as gravity feeds the copper down the pipe. At a predetermined length about 2m a mechanical saw cuts through the copper creating the copper bar called a billet.

The billet bars are either sold to independent copper pipe extrusion plants or copper wire extrusion plants. The bars are heated up in a horizontal furnace and stretched into a required pipe length and size. The bars can be processed into wire with special copper wire extrusion furnaces. Other items will be processed by various other plants buying the processed copper bars.

And so when I see a piece of copper today I see a long processing story with more functions for manufacturing purposes than gold or silver, the show ponies of the precious metals.

And that my friends, is why I see copper just as precious as gold.

Hardluck Wink