D. Lunt, T. Weeks, in Gold Ore Processing Second Edition, 2016.
Ultrafine grinding UFG has continued to evolve in terms of equipment development. A number of specialist machines are commercially available including Xstratax27s IsaMill, Metsox27s Vertimill, Outotecx27s High Intensity Grinding HIG mill, and the Metprotech mill. UFG equipment has been developed with installed powers of up to 5MW.
Compared with conventional ball or pebble milling, the specialist machines are significantly more energy efficient and can economically grind to 10m or lower, whereas the economical limit on conventional regrind mills was generally considered to be around 30m. Coupled with improvements in downstream flotation and oxidation processes, the rise of UFG has enabled treatment of more finely grained refractory ores due to a higher degree of liberation in the case of flotation or enhanced oxidation due to the generation of higher surface areas.
Ultrafine grinding is used to liberate gold finely disseminated in metallic sulfides. KCGM is the first gold mine using ultrafine grinding followed by cyanidation Ellis and Gao, 2002. The gold sulfide concentrate is grind with an IsaMill to a P80 of 1012m. In the first 3years of operation, high consumption of cyanide and high gold content in leach residues were experienced with difficulty overcoming these issues Deschnes etal., 2005.
Figure26.15. Effect of duration of pretreatment on gold extraction from the Eleonore flotation concentrates. Pretreatment 0.25Lminkg oxygen, pH 11.0 cyanidation 2000ppm NaCN, pH 11.0, DO 35ppm, 20C, 35 pulp density Deschnes and Fulton, 2013.
For the addition of oxygen in the pretreatment, it was found that increasing the flow rate of oxygen addition from 0.13Lminkg to 0.25Lminkg reduced the cyanide consumption from 6.4kgt to 6.0kgt Figure26.16, as well as the gold content of the leach residue from 2.52 to 1.92gt Au. When the oxygen addition was increased to 0.53Lmin, the gold content of the leach residue increased to 2.46, while the cyanide consumption went to 5.5kgt NaCN Figure26.16.
Figure26.16. Effect of oxygen flow in the pretreatment on gold extraction from the Eleonore flotation concentrate. Pretreatment 2.00kgt lead nitrate, pH11.0, 16h cyanidation 2000ppm NaCN, pH 11.0, DO 35ppm, 20C, 35 pulp density Deschnes and Fulton, 2013.
Figure26.17. Effect of lead nitrate in the pretreatment on gold extraction from the Eleonore flotation concentrate. Pretreatment 0.25Lminkg oxygen, pH 11.0, 16h cyanidation 2000ppm NaCN, pH 11.0, DO 35ppm, 20C, 35 pulp density Deschnes and Fulton, 2013.
Figure26.18. Effect of cyanide concentration on gold extraction from the Eleonore flotation concentrate. Pretreatment 0.25Lminkg oxygen, pH 11.0, 16h, 5.5kgt lead nitrate cyanidation 0.5kgt lead nitrate, pH 11.0, DO 35ppm, 20C, 35 pulp density Deschnes and Fulton, 2013.
Drive for gold ore grinding. Ball mill with ring motor drive. Brake of a ring motor drive. 8 Flotation Wet grinding Grinding is one of the most energy-inten-sive production stages and therefore has a substantial energy-saving potential. The single-compartment mill is ideal for the grinding of fine.
Metso Jar Mill point load sabc pilot sag Mill comminution sMc sagdesign starkey ultra fine grinding isaMilltM, Metso verti-mill, stirred Media detritor sMd, deswik, Metprotech unconfined compressive strength Flotation base Metal flotation batch amp bench scale flotation column flotation controlled potential sulphidisation cps.
Grinding circuits are fed at a controlled rate from the stockpile or bins holding the crusher plant product.
Ultra Fine Grinding A Practical Alternative To. operated an ultra fine grinding UFG circuit to supplement its roaster capacity for the treatment of the refractory gold flotation concentrate A second UFG mill was installed in 2002 taking the total UFG capacity to over 20tph while grinding to 1112 microns and achieving over 90 gold recovery A development program in 20023 involving plant.
Two major quotoffencesquot in grinding - 1. under grind and 2. over grind. You have not maximized the targeted recovery. You have wasted energy. Grind priorities can be assisted with best practice ball use, blended sizes of compatible grades can give better results. By adjusting the percentages of ball sizes in the blend fine tuning can be tweaked.
The high unit capacity SAG millball mill circuit is dominant today and has contributed toward substantial savings in capital and operating costs, which has in turn made many low-grade, high-tonnage operations such as copper and gold ores feasible. Future circuits may see increasing use of high pressure grinding rolls Rosas et al., 2012.
Autogenous grinding or semi-autogenous grinding mills can be operated in open or closed circuit. However, even in open circuit, a coarse classifier such as a trommel attached to the mill, or a vibrating screen can be used. The oversize material is recycled either externally or internally. In internal recycling, the coarse material is conveyed by a reverse spiral or water jet back down the center of the trommel into the mill. External recycling can be continuous, achieved by conveyor belt, or is batch where the material is stockpiled and periodically fed back into the mill by front-end loader.
SAG mill product feeds two parallel ball mills of 6.6m11.1m internal diameterlength, each with a 9.7MW twin pinion drive. The ball mills are operated at a ball charge volume of 3032 and 78.5 critical speed. The SAG mill trommel undersize is combined with the ball mills discharge and pumped to two parallel packs clusters of twelve 660mm diameter cyclones. The cyclone underflow from each line reports to a ball mill, while the cyclone overflow is directed to the flotation circuit. The designed ball milling circuit product is 80 passing 150m.
Several large tonnage copper porphyry plants in Chile use an open-circuit SAG configuration where the pebble crusher product is directed to the ball mills SABC-B circuit. The original grinding circuit at Los Bronces is an example the pebbles generated in the two SAG mills are crushed in a satellite pebble crushing plant, and then are conveyed to the three ball mills Mogla and Grunwald, 2008.
Figure 9.8. Partition curves for cyclones and screens in the grinding circuit at El Brocal concentrator.
Changeover is not one way, however a recent example is a switch from screen to cyclone, to take advantage of the additional size reduction of the denser payminerals Sasseville, 2015.
Batch flotation tests were conducted on a haematitebearing Sishen iron ore slimes sample from South Africa using reverse cationic flotation The effect of grinding on flotation performance the flotation response of various key impurities in the sample and the feasibility of increasing metal recovery by refloating tailings in a scavenger flotation step were investigated.
May 20, 2020nbsp018332Limonite is crushed into the size of 3 mm and sent to the ball mill for grinding into 200 mesh, setting the pulp density of 50 to 60. After screening by the high-frequency screen of 200 mesh, the pulp density is adjusted into 20 to 25, and the larger iron particles are sent back to the ball mill for further grinding. Gravity separation.
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Ball mill is the key equipment for grinding materials. those grinding mills are widely used in the mining process, and it has a wide range of usage in grinding mineral or material into fine powder, such as gold, ironzinc ore, copper, etc.
JXSC Mining produce reliable effective ball mill for long life and minimum maintenance, incorporate many of the qualities which have made us being professional in the mineral processing industry since 1985. Various types of ball mill designs are available to suit different applications. These could include but not be restricted to coal mining grate discharge, dry type grinding, wet mineral grinding, high-temperature milling operations, stone amp pebble milling.
1. High beneficiation efficiency, high fineness of ore powder.2. Large discharge port, large handling capacity.3. High production capacity, smooth operation.4. Easy to install and maintain.
A ball mill grinds ores to an end product size of thirty-five mesh or finer.The feeding material to a ball mill is treated by Single or multistage crushing and screening Crushing, screening, andor rod milling Primary crushing and autogenoussemi-autogenous grinding.
Normal feed sizes eighty percent of six millimeters or finer for hard rocker eighty percent of twenty-five millimeters or finer for fragile rocks Larger feed sizes can be tolerated depending on the requirements.
The ratio of machine length to the cylinder diameter of cylindrical type ball mills range from one to three through three to one. When the length to diameter ratio is two to one or even bigger, we should better choose the mill of a Tube Mill.
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