Gold Processing With Method Carbon In Pulp

        Gold processing methods with the Carbon in pulp are often used in large-scale gold mining processing, where the active carbon in pulp method used for recovery of gold ore minerals in the washing tank. Tanks that are used are usually equipped with an agitator and air bubbles equipment and tools are designed to maintain solids in suspension in the slurry, and the achievement of leaching. In the process adsorption ore minerals in the soil material condition of the tank should be good enough to form a slurry that can flow under gravity or when pumped. To form a slurry, mineral ore in the mix with water and the reagent was added to the tank to get the gold leaching reaction

How to work the gold extraction process with carbon adsorption in the pulp can be explained by the following system

Operating A Mine And Ore Processing Newmont Mine

       The first part of the mining process involves finding the minerals and collected core samples from various depths. The core samples were assayed (tested) to determine the mineral content. Material mined from the open pit or from underground is either ore (containing gold and silver) or waste rock (little or no gold and silver). To find out which is which, samples of rock are collected. The samples are sent to an assay laboratory where the rock is tested for its gold content. Geologists use the results to mark out the sampled areas into zones of ore and waste rock so they can be mined separately. Research of a different sort followed; investigation and monitoring was carried out to assess potential environmental and social effects of a mining operation Newmont has both operational and closed tailings impoundments in a variety of climatic and topographic settings. 

      Newmont Mining Corporation, based in Greenwood Village, Colorado, USA, is one of the world's largest producers of gold, with active mines in Nevada, Indonesia, Australia, New Zealand, Ghana and Peru. Holdings include Santa Fe Gold, Battle Mountain Gold, Normandy Mining, Franco-Nevada Corp and Fronteer Gold. Newmont conducts extensive siting, engineering, environmental and social studies to support the specific selection and design of each facility. In 2013, Newmont managed the safe handling and disposal of 173 million tonnes of tailings that consisted of 142.1 million tonnes placed within surface facilities or used for backfilling of pits. An additional 31.9 million tonnes of tailings were deposited offshore in a deep sea canyon

There are two types of mineral mining designs for operating a mine from newmont mine :

•  Surface (open pit) and 
• Underground. Surface

1. Surface (open pit)  

       

    Surface mines are generally preferred if the ore body is relatively shallow and uniform, and are made by digging into the Earth’s surface one layer at a time. The final mine is cone-shaped.First, drilling holes in the ground and fill them with explosive. After the rock has been broken up by blasting, it is loaded into giant haul trucks using large shovels and front-end loaders. Each truck used in the open pit can carry about 90 - 100 tonnes of rock. The rock is hauled to the primary crushers. Rock containing gold, copper and other valuable minerals is hauled away for processing and waste rock is taken to a separate area for storage. Areas of waste rock are later rehabilitated.

      As dig farther down, it is necessary to dewater the mine to ensure that the water level remains below the pit floor. Each day, pump thousands of gallons of water from the pit. Some of this water is used on site to wash vehicles and to spray the haul roads to dampen dust. Excess water is piped over to the water treatment plant near the processing plant to be treated before it is discharged to nearby rivers or lakes.

 2. Underground 

      

       Underground mines are used to extract minerals or metals from deep in the Earth. When building an underground mine, dig a tunnel to get to the minerals, this can be a straight vertical tunnel called a shaft or a tunnel that spirals gradually downwards, called a decline. To access the ore from the shaft or decline, dig other tunnels. also mine out tunnels to provide proper ventilation and emergency exits. mine the tunnels and the ore bodies by drilling and blasting. The broken-up ore is then transported to the surface for processing. Waste rock may be transported to the surface or left in the mine and used to fill empty space.The type of ground support needed depends on how stable the ground is and how long the tunnel is going to be used for. These factors are identified in advance so that engineers can design the mine for maximum safety and value.

      

Ground support may be provided by rock bolts or split sets, which are forced into drilled holes to exert pressure on the surrounding rock, which keeps it intact. Chemicals or grouts are sometimes added with rock bolts to give them greater strength and install wire mesh to keep smaller rocks from falling down.High-pressure spraying of Shotcrete (a mortar/concrete mix) onto the tunnels’ walls and backs provides more support. As complete mining in each stope, backfill it with a cement mixture as well.Underground mines pose a greater safety risk and limit the size of equipment that can be used; however, they cause less environmental disturbance.

Ore Processing Newmont Mine

Basic Ore Processing 

Haul trucks transport the ore from open pits or underground operations to processing operations. Some ores may be stockpiled for later processing. Rock that is not economical to mine is stored in waste rock storage areas. The grade and type of ore determine the processing method used. Additionally, the geochemical makeup of the ore, including its hardness, sulfur content, carbon content and other minerals found within, impact the cost and methods used to extract gold.

Processing methods 
In mineral processing, newmont depending on the mineral ore, they process it using the following methods:

Removing the gold-bearing rock from the ground is just the first step. To isolate pure gold, mining companies use a complex extraction process. The first step in this process is breaking down large chunks of rock into smaller pieces. At a mill, large machines known as crushers reduce the ore to pieces no larger than road gravel.

The gravel-like material then enters rotating drums filled with steel balls. In these drums, feed ore into a series of crushers and grinding mills to reduce the size of the ore particles and expose the mineral.

Next, mill operators thicken the slurry with water to form pulp and run the pulp through a series of leaching tanks. Leaching dissolves the gold out of the ore using a chemical solvent. The most common solvent is cyanide, which must be combined with oxygen in a process known as carbon-in-pulp. As the cyanide and oxygen react chemically, gold in the pulp dissolves. When workers introduce small carbon grains to the tank, the gold adheres to the carbon. Filtering the pulp through screens separates the gold-bearing carbon.

The carbon moves to a stripping vessel where a hot caustic solution separates the gold from the carbon. Another set of screens filters out the carbon grains, which can be recycled for future processing. Finally, the gold-bearing solution is ready for electrowinning, which recovers the gold from the leaching chemicals. In electrowinning, operators pour the gold-bearing solution into a special container known as a cell. Positive and negative terminals in the cell deliver a strong electric current to the solution. This causes gold to collect on the negative terminals.

Alternative Ore Processing

Newmont mine use alternative gold recovery methods in some processing plants to accommodate different ore characteristics or other requirements. For example, ore that has a high level of sulfide minerals or carbon (or both) is called refractory ore. Refractory ore resists normal processing methods as the high sulfide minerals trap gold particles, making it difficult for the cyanide to reach the gold and leach it.

Heating

To leach gold from refractory ore, it must be subjected to high temperature, high pressure and/or oxygen. Newmont treats refractory ore in two ways: by using an autoclave or a roaster.

An autoclave is used before leaching occurs. First, the slurry is heated and fed into an autoclave, where high-pressure steam, water and oxygen are applied to oxidize the sulfide material by a chemical reaction. The slurry is then cooled and sent back into the process to be leached.

An alternative to an autoclave is a roaster, a very high temperature oven that is often used instead of an autoclave if the ore to process contains a large amount of organic carbon. Roasting uses heat and air to burn the organic carbon into fuel and to burn the sulfur off ore, which heat to 932 to 1,202 degrees F. 

Heap leaching

In heap leaching, newmont mine dump crushed ore into piles called heaps, to which apply a weak cyanide solution, using drip feeders. The gold dissolves into the cyanide solution. The entire heap leach area is lined with heavy duty liners to ensure no solution leaks into the environment. Next, collect the gold-cyanide solution in ditches and ponds, and then transport it to a recovery plant.

 
Flotation 

Flotation is a method of separating minerals depending on their ability to attach to air bubbles. Flotation can be used for a number of materials by adjusting the chemicals. At Newmont, it is used for copper recovery and, in a very limited number of cases, for gold processing. 

introduce air bubbles to the slurry while it is in small tanks, called flotation cells. With add some chemicals to the slurry to assist the process. The desired minerals stick to the bubbles and rise to the top, resulting in froth. The froth overflows from the tank, and is removed and sent to the next step in processing.

Gravity circuit

A gravity circuit recovers coarse gold before it is leached. Gravity circuits use the same principles as gold panning: coarse gold is heavier than other material and will settle to the bottom so that it can be removed (gold is 19.3 times heavier than an equal volume of water).

How Newmont mine exploration team discovered a new mineral

         So how do exploration newmont mine teams locate future large-scale projects for a discovered a new mineral ?

       Finding new mineral reserves is critical to the success of company. Locating, extracting and processing these natural resources is a multiyear process that involves complex scientific, environmental and social planning. Searching for gold is a complex, scientific and time-intensive process. With odds of only one in 3,000 discoveries leading to mine development, and only 10 percent of the world’s gold deposits containing enough gold to mine, exploration can be wearisome and expensive. While gold is found throughout the world at concentrations of between two and four parts per billion, need to discover areas that contain 2,000 to 3,000 parts per billion to be profitable. 

       The first step is finding mineral prospecting. With search gold veins typically spanning just a few feet in width, and curving along the Earth’s geography, it is extremely difficult to pinpoint an area of exploration among thousands of square miles of land. Obviously, it makes sense to start in areas known to contain gold, but there are nearly 900 such locations in the world to choose from. Ideally, it is best to start looking in areas less explored first.

Newmont uses several methods to reduce the size of land to explore:

• Evaluate the land geology 
• Analyze the geochemistry of soil sediment and water 
• Commission airborne geophysics surveys to record the level of electrical and magnetic current in the crust below.

       Once a target area has been identified, and geological, geophysical and geochemical data indicate a high probability of a deposit, drilling is conducted. Drilling helps evaluate the type and grade of minerals in the ore. But how many samples are needed? In what direction? How far apart? How deep? Because per-foot drilling costs are expensive, these decisions must be made carefully. Another way newmont mining sample is through trenching, which hugs the surface and is carried out by backhoes or bulldozers. As crews drill, they mark the exact location and depth of each sample taken. Samples are then sent to an accredited lab, which identifies the type of minerals and grade of gold within them. Once information is back from the lab, supplement those findings with geologic, geochemical and geophysical data. Understanding the local geology is a very important part of the process, both economically and environmentally. The geology affects mining, processing and the ways in which manage waste rock, tailings and water. It is also an important aspect of rehabilitation plans.

    Production geologists use information they obtain from sampling, testing, mapping and observation to determine the most efficient and effective mining techniques, as well as to identify the grade (amount of mineral) in the ore. In gold and silver mining, grade is reported as grams per ton. Copper grade is reported as a percentage. It is important to know the grade to determine which rock is sent to the plant for processing and which rock is sent to the waste rock storage area. By using this data and complex computer programs to more accurately define the orebody, mine engineers can determine mining methods, design blast patterns, design dig patterns, and maximize the safety and efficiency of production – as well as determine how the ore should be processed. Geologists also use drilling and sampling data to identify wet areas. Water can cause major problems in both open pit and underground mines. If areas of high water content can be avoided or planned for in advance, can reduce safety risks, costs and production interruptions.

HOW TO WORK THE HEAP LEACHING MINING

Heap leach is a method developed by Henin and Lindstrom to process low-grade ore on a large scale with small production cost so that the levels below the cut-of grade can still be economical. Heap leach is the process of leaching of low grade gold rocks thrown, then the solution containing the metal particles are screened and separated by electrolysis. Heap leach done repeatedly and on a large scale.

There are several steps that are used in processing gold ores using heap leaching system

• Preparation of the foundation of leaching with an angle of 1 degree to 6 degrees. : The foundation of this leaching can be made by permanently using a hardening of the concrete floor or foundation and geo-coated membrane (High Density Polyethylene)

• Then the rock minerals that have been taken from the mine area was destroyed. Destruction of rock done to get smaller sized rocks. Size obtained usually ± ½ or up to 1 inch. machines used in the process of destruction is the engine or Stone Mill Hammer Crusher and Crusher Jaws.

• After the material to be crushed and refined, then placed into the foundation of leaching that has been provided

• Then through the spray in the spray solution of sodium sianide. And in general the use of sodium sianide NaCN. This process aims to take the gold extraction is formed in the chlorination process and transformed into compounds Dicyano Aurrat (Au (CN) 2). Because the compound that would be too absorption within the pores of activated carbon

In the cyanidation process consists of two important stages, namely the process of dissolution and separation of gold from the solution process. Solvents commonly used in the process cyanidasi is NaCN, KCN, Ca (CN) 2, or a mixture of all three. The solvent most often used is NaCN, being able to dissolve gold better than any other solvent. 

From this it will spray cyanide in the extraction process produces a chemical reaction in the form:

 Au + NaCN + O2 + H2O = NaAu (CN) 2 + NaOH (from equation Elsener and Adamson)
 Au + NaCN + O2 + H2O = NaAu (CN) 2 + H2O2 + NaOH (from equation Adamson)

Gold extraction is generally effective at pH 9.5 to 11. Optimum near 10.5. The more acidic, hydrolysis to hydrogen cyanide had cyanide (HCN), the more alkaline reaction the more it will slow down. To speed up the process of gold dissolution in cyanide solution will be added to the catalyst. Namely lead Nitrate (PbNO3), because the catalyst can also increase the recovery of gold to be 95%. Generally cyanide complex solution containing between 1 ppm to 3 ppm.

• Once the cycle is completed the leaching process of leaching in the wash with water to remove residual cyanide is used peroxide. Decision-stop solution if the gold content down to 0.005 ounces of gold per ton of solution. Taking gold in the solution can be done by using activated carbon or by direct receipts using zinc cementation process (Merrill - Crowe Process). In addition to using the carbon and cementation, other techniques can be used is elektrorefining and ion exchange resins. Elektrorefining is the process of attachment of the metal contained in the solution on the cathode rod, in this process is stailess steel rod anode and cathode in the form of steel brush.

     In heap leaching using carbon adsorption techniques in coulumn Carbon (CIC) in which the solution containing the gold complex flows in tanks containing activated carbon in series and terraced. Activated carbon can absorb gold from 100 up to 400 ounces per ton of carbon, the efficiency will drop if content of the solution decreases. Precious metals in the capture of carbon by passing a hot solution of caustic soda and cyanide mixture (1% NaOH and 1% NaCN) Activated carbon can be reused by reactivation in advance using the rotary kiln at a temperature of 730 degrees Celsius for 20 minutes. In traditional mining usually carbon that has been filled with gold complexes directly in the fuel, the dust from the burning of carbon was then taken to be melted down. Contained metal can be purified directly. This is done because the aged and technological considerations.

Heap Leaching Mining

      Heap leaching mining was developed as a mineral processing low-grade metal that is more efficient and minimal cost. Compared with conventional cyanidation process of the mineral leaching process with stirred tank Heap leaching has several advantages in the form of designs that use a very simple, operating costs are also minimal, and in requiring less investment, because the heap leaching recovery is around 60% to 80 %.

 In large-scale process technology was first used and applied to the mining of gold ore at Carlin Nevada USA in 1970. This process has really made ​​a lot of mines that can easily take on geological resources that have a low grade and transforming them into the category of proven ore. Ore value as low as 0.01 oz Au can be processed by heap leaching system is economically.

       Besides gold and silver, cyanidation is also often used to recover copper content in the rock, due to the nature of this metal is very easily soluble in both the cyanide. And sometimes too much copper in the rocks encountered in the content of gold and silver cyanidation method on the rocks so that it is still economical given.

Heap leaching generally requires 60 to 90 days for processing of ore that can be leached in 24 hours in a conventional agitated leach process. Gold recovery is usually 70% compared with 90% in agitated leach plant. Even with this low performance, the heap leaching process has facilitated the processing of natural resources, because the processing cost is much reduced compared with agitated leaching.

        The process involves the leaching of rocks and placed as well as the destruction of rock minerals that contain metal ore in a heap on the building on a floor stand. The foundations of leaching (leaching pad) can be made permanently using a hardening of the concrete floor or foundation and geo-coated membrane (high density polyethylene) cyanide solution is distributed at the top of the stack and then the liquid seeps down through the pile of ore and dissolves the gold through a pile interrupted. Gold laden minerals flowing out from the bottom of the pile and is collected for gold recovery by carbon adsorption either with or zinc precipitation. Barren solution is then recycled to the next pile.

Some of the benefits or advantages from the use of heap leaching system are as follows:

1. Extraction from the heap leaching is usually carried out on the rocks -3 / 4 inches, whereas extraction in agitated leaching in stirred tank requires a reduction to -200 mesh size of 100 mesh or need. 
2. Solid liquid separation step is not necessary to heap leaching on the heap leaching system.
3. Tailings disposal costs are high enough for the modern agitated leach plant. Large dam expensive fluid retention is required. For comparison, heap leach pads can generally be left in place after reclamation.

Some Disadvantages heap leaching system, in addition to a lower recovery compared with agitated leaching heap leaching, including: 

1. Ore stacked must be porous enough to allow solution to drip or drain water solution through the slit pore. There are plenty of recovery failure due to inability to obtain the flow solution. It's a lot of experience when the ore has high clay content or in rocks containing clay very much. This problem is often solved by agglomeration prior to stacking piles. 
2. In areas of high rainfall, the solution of balance problems can arise, so it requires a lot of care and discharge processes. 
3. In areas where extremely cold, freezing the pile can result in low recovery period. Modification of operational procedures such as subsurface application solutions has been reduced, but not eliminated this concern.

System Flow Chart In a Simple Heap Leaching 
In general, processing system gold using heap leaching method can be described as the chart below

Transport of rock minerals on lands open pit using dump trucks

 

Rock mineral that is ready to be destroyed and soften

 

 

Destruction of rock done to get smaller sized rocks. Size obtained usually ± 20mm. And used machines are machines Hammer Mill, Stone Crusher or Jaws Crusher

 

 

Placement of material that has been crushed and refined into the foundation leaching 

Cyanide solution through water storage tank in the pump and the pipe through the hose and spray the spray solution of sodium cyanide on rock minerals on the leaching

 

Recharge cycles in which the metal minerals will drop to flow down through the rock broke into the flow of irrigation. The solution then percolates through the pile and dissolve both the target and other minerals. Leach solution containing dissolved minerals are then collected, processed in a factory process to recover the mineral targets. In heap leaching using carbon adsorption techniques in column Carbon (CIC) in which the solution containing the gold complex flows in tanks containing activated carbon in series and multilevel 

 

In heap leaching using carbon adsorption techniques in column Carbon (CIC) in which the solution containing the gold complex flows in tanks containing activated carbon in series and terraced. 

 

Activated carbon that has been filtered and removed from the vat of mineral-rich bath solution can absorb gold from 100 up to 400 ounces per ton of carbon, the efficiency will drop if content of the solution decreases. Precious metals in the capture of carbon by passing a hot solution of caustic soda and cyanide mixture (1% NaOH and 1% NaCN) Activated carbon can be reused by reactivation in advance using the rotary kiln at a temperature of 730 degrees Celsius for 20 minutes

 

Melting Process of activated carbon and Metal Refining Gold.

gold bullion metals