Gold has been a very precious metal for thousands of years. It is not only a special currency for reserves and investment, but also an important material for the jewellery, electronics, modern communications, aerospace and other sectors.
The gold mineral are in different grades, the average content of gold in the earth’s crust is about 1.1 parts per billion (0.0011 ppm), and in seawater is about 1 part per 100 billion (0.00001 ppm). Because of the crustal movement and geology of hundreds of millions to several billion years, this makes gold elements rich in gold deposits. The general gold grade is 2-3 g/ton, the rich ore is 5-50 g/ton, the special rich mine is 50-500 g/ton, and there is lump gold. There is smallest piece of lump gold like dozen grams, also large in dozen kilograms, and the rare huge piece of lump gold could be hundred kilograms. The lean ore is only 0.1-1 g/ton, and it worthy of exploit when gold content is 0.5 g/ton or more.
For the general and lean gold ore which contains less gold and higher mud. How to extract the valuable gold? The carbon in pulp (CIP) process has become the first choice in over 50% of the goldplant.
There are 7 steps of the CIP process for glod plant:
- Crushing and grinding, crushing the massive ore (up to 650mm) by the crusher and vibrating screen, make the bulk ore broken into small grains, about 10mm or even smaller. Then grinding the mineral grains into powder, for the leach pulp preparation. After grinding and classification, the ore mineral would be finer than 200 mesh, which could meet the leaching requirements. If the ore contains some particle gold, the gravity separation process would be set in the first stage of grading.
- Pulp and cyaniding leaching, add the sodium cyanide solution into the tank accurately to get cyanidum pulp, the gold comes to free gold ion, then add flocculants into the slurry, make solid contants from 18% to over 50% to improve the efficiency.
- Screening, removing the impurities like wood chips, sands etc. by the linear screen. The linear screen is a revolutionary screening system that has solved a major problem in the CIP process in gold plants. It use the polyester linear screen cloth which is chemical resistance, and capable of screening between 150 and 2,000 microns. It avoid wood fiber and tramp adsorb the gold ion and block the activated carbon.
- Absorption.
Activated carbon is the ideal medium to accumulate and recover the gold in the pulp, dut to its own micro-porous structure. Put the activated carbon into adsorption tank, absorption the gold particles and get the gold-loaded carbon. Separate the slurry and collect the carbon at the absorption chamber exit. After screening and washing, the gold-loaded activated carbon will be sent to the desorption operation. ³.
- Desorption, Lift the gold-loaded carbon to the carbon storage tank and the slurry and water flow into the first absorption tank.
Separate the gold mud from the carbon by high temperature and high pressure, then smelting, pickling and impurity removal, to get the gold bullion.
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