World’s first True Environmental Friendly Mineral Processing Plant in Unju, Korea

Avimetal has won the contracts of 5 million USD for six environmental friendly mineral  processing plants on 30 April 2021. First plant will be completed by the end of June, Avimetal based in USA and has a branch office in Korea has been developed a solution to clean up heavy metal such as cadmium, cyanide and mercury contaminated tailings. Avimetal has started research and development for the treatment of mining tailings and slags past 10 years and final results are various environmental friendly processes of tailings and slags only clean but it recover precious metal and valuable base metal in the tailings and slags.

 

Unju Mine in Korea was developed during the Japanese colonial rule. In 1997, they decided to re-develop an abandoned mine and applied for a mining license in Jeonbuk Province in December of last year, and was disapproved for violating the Mountain Management Act in January of this year.

Accordingly, residents of Yangchon-myeon, Nonsan City, near the Unju Mine, are protesting, saying, “If the Unju Mine is re-developed, not only will Topjeong Lake and Nonsan Stream, which are the feeding lines of Nonsan, be contaminated, but eco-friendly agricultural products such as strawberries and lettuce will suffer great damage.

 

In a letter of command in the name of Mayor Hwang Myung-seon on the 18th of last month, Nonsan City requested, “If Unju Mine is developed, there is a concern that the agricultural base of Nonsan will be uprooted.”

 

Unju mine has currently approximately 1 million tons of tailings contaminated by cyanide and cadmium. Currently, soil contamination occurring in abandoned mine and tailing deposits and nearby areas can be contaminated by  acidic water containing heavy metals, contaminating rivers and adjacent agricultural land. In general, the phenomenon of mine damage occurs continuously for a long period of time once it occurs, and considerable effort and cost are required for healing and restoration. In addition, the phenomenon of mine damage is closely related to the natural environment and living environment, so it is subject to many civil complaints. As a national project, the government is carrying out a cover project on an annual basis to prevent soil contamination and groundwater contamination from acid leachate and cyanides from the existing tailings landfill.

 

Simon Korea will clean up 1 million tons of tailings by using Avimetal’ s technology and follow up with further developing under ground mine. Avimetal designed the plant from crushing, milling, drying, electrostatic concentration, leaching with salt water, cyclone electrowinning system and 100% recycling waste water system. Avimetal’ s environmental friendly mineral processing technologies will be revolution in the mining industry worldwide where all processes are dependent upon using tones of water and toxic chemicals.  Existing mining process involve gravity concentration by water and froth flotation which use lots of water and chemicals.

 

Avimetal system adapts micronization milling system in place of ball mill or Raymond mill. It saves electrical power, plant size and finer particle up to 400~600 mesh. Fine particle is important in mineral processing gold ore as most gold particles is very fine and invisible, called micron silica cluster as micron size of tiny gold is enclosed by silica. Finer particle, the more gold recovery. First process is crushing and milling in the initial stage of the mining industry. Ultra fine micronization milling is a patented, innovative, and commercialized method for particle size reduction to reduce, within seconds, solids that are capable of fracturing into a particle-sized powder. It replaces a conventional ball mill, impact mill, hammer mill, Raymond mill and tower mill, etc. The ultra fine micronization milling has created the potential to revolutionize the mineral processing industry due to the benefits attained through being able to economically mill finer and to enhance particle liberation for improved precious metals recovery. A ultra-fine Raptor by means of tornado/vortex airstream. The Raptor is done by mechanical impact of rotating impeller as well as intensive vortex airstreams and high frequency of air pressure oscillation generated at the backside of rotating rotor and the groove slopes.  Material is taken into the mill being carried by airstream. The airstream containing material is given spiral motion in the inlet spiral chamber and transmitted evenly into the milling chamber.

 

Avimetal’ s dry concentration is based on triboelectricity principle. Electrostatic concentration has been used by industry long time ago and it has very limit in the use f mining industry due to unit price and processing capacity and incapable of tiny particle. There are two main types of electrostatic separators. These work in similar ways, but the forces applied to the particles are different and these forces are gravity and electrostatic attraction. The two types are electrodynamic separators; high tension rollers or electrostatic separators. In high tension rollers, particles are charged by a corona discharge. This charges the particles that subsequently travel on a drum. The conducting particles lose their charge to the drum and are removed from the drum with centripetal acceleration. Electrostatic plate separators work by passing a stream of particles past a charged anode. The conductors lose electrons to the plate and are pulled away from the other particles due to the induced attraction to the anode. These separators are used for particles between 75 and 250 micron which is not applicable in mineral separation due to incapability of micron size of the ore and capacity less than hundred kilograms per hour. MIT developed belt type separator works on micron size tiny particles and large capacity of separation 5 tons per hour but unit cost is several million USD. Avimetal’ s electrostatic separator is plate types which have four stage of graphene oriented anode plates and cathode pair and able to treat 5 ton per hour capacity and able to separate micron size using benefit of graphite’s super conductivity of electrons with low costs. It also a Full Know Down(FKD) kit concept where miner can assemble the machine in few hours and saving logistic costs when transport 20 times volume ratio. The electrostatic separator is a device for separating particles by mass in a low energy charged beam. It works on the principle of corona discharge, where two plates are placed close together and high voltage is applied. This high voltage is used to separate the ionized particles. Electrostatic separation is a process that uses electrostatic charges to separate crushed particles of material. This process can help remove valuable material from ore. Generally, electrostatic charges are used to attract or repel differently charged material. Quadrant Roller Electrical Sorter is one of the major equipment in electricity mineral separation. The disadvantage of the roller type is a limit for separating micron size as most precious metal forms in tiny micron size and low capacity of separation. MIT has developed a  tribo-electrostatic belt separator has the demonstrated capability to process fine particles and large capacity. For this reason, we have developed a low costs electrostatic separators which are combination of roller type and belt type superiors. Our plate type is vertically positioned and 8 pairs of plates are in the system. Advantage of this system compared to competitors are compact size, low sales price,  ability of separating micron size, large production capacity and using low power.

 

Avimetal’ s dry concentration technology has been successfully first commercialized in Quilabamba, Peru by Picchu Rio Gold inc. Mining permit in Peru has been suspended since 2012 due to contamination water downstream of Amazon river by mercury and cyanide. Pichu Rio Gold has a processing permit first time in 2018 since suspension permit. Peru government legalized the EPA rule for permitting is allowed for use the Avimetal’ s dry concentration technology. Avimetal company is a leading technology frontier for providing dry concentration, milling and non cyanide leaching system without waste water.

 

Refinery

Valuable and precious metals from dry concentrated materials can be further refined by cold plasma, hot plasma gasification or cyclone electrowinning system followed by NaCl(salt water) hypochlorite leaching depending one characteristics of ore contents.

 

Cold Plasma System

Plasma is a new and potentially revolutionary system which uses an advanced state of matter called plasma, but it is also a very special type of plasma called “cold plasma.” Plasma, sometimes referred to as the fourth state of matter, behaves like a gas, but also conducts electricity like a wire, because it is ionized. Plasmas play important roles in several scientific and industrial applications. This unique system is invented by Richard Woodford and James Gim and will be commercialized for the metallurgical refining application. The molecules of hydrogen in the gas are ionized when applied a DC pulsed electric power. Thus the different radicals are produced. The refining ability of hydrogen is enhanced in such process. While the radicals reach the surface of the melt, they react with the impurities to form some volatile compounds, such as NH3, H2S and PH3. Because the compounds are insoluble into the melts, they will be carried off by fluent gas. Finally the impurity elements are removed from metal. An embodiment of a cold plasma device is described that has a reactor having a positive electrode, negative electrode, membrane and agitator. The electrode is configured to generate cold plasma, with the cold plasma having a temperature in the range of 65 to 120 degrees Fahrenheit. The membrane and electrodes are our proprietary, and also electrolyte is a Nacl with our proprietary chemicals. Metals will be recovered by adjusting PH level.

 

Hot Plasma System

Market needs more economical and efficient technology of head ore & slag concentration and refining technologies of precious metals in mining industry. Break Even Point (BEP) of Gold Ore, Slag and other material is at least 0.2 ounce per ton of Gold. Several million tons of material area available in the region of South Western area below 0.2 OPT and above 0.1 OPT. Plasma gasification technology has been proven to a recovery of value-added metals from slag or ore past decade. Plasma gasification is a process which converts organic matter into synthetic gas, electricity, and slag using plasma. A plasma torch powered by an electric arc, is used to ionize gas and catalyze organic matter into synthetic gas and solid waste. However, cost of plasma plant is very expensive and limited small capacity of production. Turn around time of the order to installation is a year to two years with large space required.

Avimetal has developed affordable low costs of compact sized RF Plasma Gasification System from 120 KW system to 960 KW system which will be available to install in parallel and increase capacity by implementing multiple feeders and torches in one system. It is modular concept of turnkey system is simply plug-in system.

 

Cyclone electrowinning

Cyclone electrowinning technology has a number of significant advantages over conventional electrowinning as a simple, single step method for treating these solutions and overcoming the requirement to return the contained metal to the process. The key benefits are the cyclone electro-winning technology is capable of application at significantly higher current densities than applied in conventional tanks. The result is as substantial increase in production rate per square meter of cathode and resultant lowering in capital costs. From an engineering point of view, the cyclone electro-winning circuit is extremely simple and has few moving parts. It is modular in construction and suits progressive installation/expansion and ease of relocation. The operating windows under which the technology maintains high current efficiency and product quality are extremely broad with one of the technology’s inherent features being its capability to electrowinning metals efficiently down to very low concentrations. The cell is totally enclosed and does not result in an acid mist problem–with consequent and potentially significant savings in capital cost in building and infrastructure.

No additives are used to maintain high product quality and electro winning is generally performed at ambient temperature. The Cyclone Electro-winning cell is more tolerant of contaminants in solution than a conventional cell. Its high mass transport capabilities maximize recovery of the target metal and thereby minimize co-plating of other metals. Its closed nature and the lack of a ‘water line’ in the cell result in significantly higher tolerance to entrained organic and chlorides. In its standard configuration the cell does not contain a lead based anode, therefore excluding a potential source of contamination of the product. Capital cost of the electro winning circuit is relatively low, particularly considering the size of operation. Single cyclone electro-winning cell has only one cathode (Ti starting sheet) and our proprietary one anode(Graphene Coated Ti composite). The qualified electrolyte is pumped into cyclone electro-winning cell from the bottom our proprietary water turbine and goes through the cell with high speed. The Cu2+ content in electrolyte will decrease while copper cathode deposit on Ti cathode. The oxygen will generate nearby the negative anode, and then discharges from the cell and is collected and treated in a large acid mist treatment system. The final copper cathode deposits around 70~75kg per 23 hours cycle.

 

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