Engineering & Mining Journal

AUG 2018

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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Page 32 of 107

MINERAL PROCESSING AUGUST 2018 • E&MJ 31 centrates with metal recoveries in the low to mid 80% range were consistently achieved. Breaking the size distribution range up into two or three smaller particle size ranges, will bring recoveries up to the low 90% range. The Sahara gold pilot plant operation demonstrated this is feasible. Development Trial Results This submission follows development work first reported in the June/July 2014 issue of the Canadian Mining Journal in an article entitled "Waterless Wonder." That article described the initial trials to produce a dry gravity separator. This article describes the results for the binary tungsten-carbide/cobalt standard, two gold standards, and for two placer samples. Gold standard rougher concen- trate metal recoveries in the low to mid 80% range were consistently achieved into 1% to 5% rougher concentrate weights. The placer samples were from the Kal- goorlie area of Western Australia. A total of five, minus 50 mesh, placer runs, were completed with head grades that varied be- tween 0.97 g/mt to 2.32 g/mt. The rougher concentrate weights varied between 2.8% and 4.6% and gold metal rougher recover- ies between 82% and 85.5%. Of the two binary gold standards, the first was made up of silica sand and por- tions of a 1.1-g gold nugget. That nug- High-intensity dry vibrating magnet filters (DVMFs) have been designed to remove very fine iron-bearing contaminants from hard-to-flow fine powders such as lithium. The standard design consists of a solenoid electromagnet, which generates a mag- netic field into the bore of the separation zone. A filter element of expanded metal placed in the separation zone concentrates the magnetic flux of the magnetic field. This produces scores of high-gradient collection zones which capture magnetic contami- nants as feed material filters through the element. The DVMF is perfect for both lithium producers and users. Producers pulverize lithium before it goes to the user as a very fine powder. DVMF units are placed prior to and after mill pro- cessing. As an additional check, many users apply the DVMF when they receive lithium purchased from the producer. DVMFs reduce contamination in lithium dramatically by us- ing a high-intensity electromagnet and revolutionary flux con- verging matrix. The DVMF is fed vertically via gravity flow. As the feed material filters through the matrix and exits out the bottom, the matrix captures and holds the magnetic material as the nonmagnetic material passes through. The magnetic collection of fine particles requires a high-in- tensity, high-gradient magnetic field. This type of separator uti- lizes a high-intensity electromagnet and flux converging matrix. The matrix amplifies the magnetic field and provides high-gra- dient collection sites for the magnetic material as the feed ma- terials filter through. The canister is attached to dual high-fre- quency, low-amplitude vibratory drives. These drives deliver a strong vibratory action to the canister assembly, which enhances the fluidity of very fine powders, resulting in a smooth and even flow of product through the matrix grid. This has proven to be the most effective separation process. The magnetic filters consist of a solenoid electromagnetic coil enclosed in a steel housing. The coil generates a uniform magnetic field throughout the bore of the coil, which represent background magnetic field. A stack of expanded metal discs are packed in the bore and induced by the magnetic field. These expanded met- al discs, termed the matrix, provide the vehicle for separation. The matrix amplifies the background mag- netic field, produces local regions of extremely high gradient, and provides the collection sites for magnetic particle capture. The dry filters are rated by the magnetic field strength gen - erated in the bore of the solenoid coil with the matrix removed. The background magnetic field, often termed the open bore field, represents the driving force that produces the amplified high magnetic gradient throughout the matrix. Depending on the matrix configuration, it is typically the case that a 5,000-gauss background field will result in an excess of 10,000 gauss in localized regions of the matrix. The electromagnet is a solenoid coil completely sealed in a steel housing. Standard model filters generate background mag- netic field strengths of either 2,000 or 5,000 gauss. The solenoid coils are wound from copper to dissipate heat and operate at rel- atively cool temperatures. The 2,000-gauss models operate with static oil cooling. The 5,000-gauss models are oiled-cooled and use a heat exchanger where it is cooled with a 10-gpm water flow. Eriez state-of-the-art DVMFs are fully automated and feature a simplified cooling system. Other highlights include program- mable controllers and the ability to handle four to 12-in. di- ameter sizes. The standard filters' background magnetic field capacities are based on fine powder flow range up to 100 lb/in. 2 of cross sectional area of matrix. A 6-in. diameter is capable of treating up to 2,800 lb/h of material weighing 400 lb/ft 3 . Jose Marin, Eriez director, minerals and materials processing For more information, call (814-835-6000), visit or email High-intensity DVMFs Remove Fine Iron-bearing Contaminants From Lithium By Jose Marin Dry-vibrating magnetic fi lters are designed speci fi cally for dry applications — the treatment of powders. Its purpose is to remove fi ne ferrous contaminants from dry powder. There are two available strengths — 2,000 and 5,000 gauss. The DVMF consists of a thick steel box with a canister in the bore. Aluminum or copper coils are positioned around the canister. Direct current power energizes the coil and allows the matrix to collect magnetic particles.

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