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IsaMill
The IsaMill is a type of efficient stirred grinding mill for fine and coarse griding used in mineral industry. It was jointly developed in the 1990s by Mount Isa Mines Limited ("MIM", a subsidiary of MIM Holdings Limited and now part of the Glencore Xstrata group of companies, Australia) and Netzsch Feinmahltechnik ("Netzsch"), a German manufacturer of bead mills. The IsaMill is primarily known for its ultrafine grinding applications in the mining industry, but is also being used as a more efficient means of coarse grinding. By the end of 2008, over 70% of the IsaMill's installed capacity was for conventional regrinding or mainstream grinding applications (as opposed to ultrafine grinding), with target product sizes ranging from 25 to 60 μm.
While most grinding in the mineral industry is achieved using devices containing a steel grinding medium, the IsaMill uses inert grinding media such as silica sand, waste smelter slag or ceramic balls. The use of steel grinding media can cause problems in the subsequent flotation processes that are used to separate the various minerals in an ore, because the iron from the grinding medium can affect the surface properties of the minerals and reduce the effectiveness of the separation. The IsaMill avoids these contamination-related performance issues through the use of an inert grinding medium.
First used in the Mount Isa lead–zinc concentrator in 1994, by May 2013 there were 121 IsaMill installations listed in 20 countries, where they were used by 40 different companies.
The IsaMill is a stirred-medium grinding mill, in which the grinding medium and the ore being ground are stirred rather than being subjected to the tumbling action of older high-throughput mills (such as ball mills and rod mills). Stirred mills often consist of stirrers mounted on a rotating shaft located along the central axis of the mill. The mixing chamber is filled with the grinding medium (normally sand, smelter slag, or ceramic or steel beads) and a suspension of water and ore particles, referred to in the minerals industry as a slurry. In contrast, ball mills, rod mills and other tumbling mills are only partially filled by the grinding medium and the ore.
In stirred-medium mills, the stirrers set the contents of the mixing chamber in motion, causing intensive collisions between the grinding medium and the ore particles and between the ore particles themselves. The grinding action is by attrition and abrasion, in which very fine particles are chipped from the surfaces of larger particles, rather than impact breakage. This results in the generation of fine particles at greater energy efficiency than tumbling mills. For example, grinding a pyrite concentrate so that 80% of the particles are less than 12 μm (0.012 mm) consumes over 120 kilowatt-hours per tonne (kWh/t) of ore in a ball mill using 9 mm balls, but only 40 kWh/t in an IsaMill using a 2 mm grinding medium.
The IsaMill usually consists of a series of eight disks mounted on a rotating shaft inside a cylindrical shell (see Figure 2). The mill is 70–80% filled with the grinding medium, and is operated under a pressure of 100 to 200 kilopascals. The disks contain slots to allow the ore slurry to pass from the feed end to the discharge end (see Figure 3). The area between each disk is effectively an individual grinding chamber, and the grinding medium is set in motion by the rotation of the disks, which accelerate the medium toward the shell. This action is most pronounced close to the disks. The medium flows back toward the shaft in the zone near the midpoint between the disks, creating a circulation of the grinding medium between each pair of disks, as shown in Figure 4.
The average residence time of the ore in the mill is 30–60 seconds. There is negligible short-circuiting of the grinding zone by the feed, as a result of having multiple grinding chambers in series.
The ground product is separated from the grinding medium at the discharge end of the mill. This is achieved without using screens by using a patented product separator that consists of a rotor and a displacement body (see Figure 2 and Figure 4). The relatively short distance between the last disk results in a centrifugal action that forces coarse particles towards the mill shell, from where they flow back towards the feed end. This action retains the grinding medium within the mill.
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IsaMill AI simulator
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IsaMill
The IsaMill is a type of efficient stirred grinding mill for fine and coarse griding used in mineral industry. It was jointly developed in the 1990s by Mount Isa Mines Limited ("MIM", a subsidiary of MIM Holdings Limited and now part of the Glencore Xstrata group of companies, Australia) and Netzsch Feinmahltechnik ("Netzsch"), a German manufacturer of bead mills. The IsaMill is primarily known for its ultrafine grinding applications in the mining industry, but is also being used as a more efficient means of coarse grinding. By the end of 2008, over 70% of the IsaMill's installed capacity was for conventional regrinding or mainstream grinding applications (as opposed to ultrafine grinding), with target product sizes ranging from 25 to 60 μm.
While most grinding in the mineral industry is achieved using devices containing a steel grinding medium, the IsaMill uses inert grinding media such as silica sand, waste smelter slag or ceramic balls. The use of steel grinding media can cause problems in the subsequent flotation processes that are used to separate the various minerals in an ore, because the iron from the grinding medium can affect the surface properties of the minerals and reduce the effectiveness of the separation. The IsaMill avoids these contamination-related performance issues through the use of an inert grinding medium.
First used in the Mount Isa lead–zinc concentrator in 1994, by May 2013 there were 121 IsaMill installations listed in 20 countries, where they were used by 40 different companies.
The IsaMill is a stirred-medium grinding mill, in which the grinding medium and the ore being ground are stirred rather than being subjected to the tumbling action of older high-throughput mills (such as ball mills and rod mills). Stirred mills often consist of stirrers mounted on a rotating shaft located along the central axis of the mill. The mixing chamber is filled with the grinding medium (normally sand, smelter slag, or ceramic or steel beads) and a suspension of water and ore particles, referred to in the minerals industry as a slurry. In contrast, ball mills, rod mills and other tumbling mills are only partially filled by the grinding medium and the ore.
In stirred-medium mills, the stirrers set the contents of the mixing chamber in motion, causing intensive collisions between the grinding medium and the ore particles and between the ore particles themselves. The grinding action is by attrition and abrasion, in which very fine particles are chipped from the surfaces of larger particles, rather than impact breakage. This results in the generation of fine particles at greater energy efficiency than tumbling mills. For example, grinding a pyrite concentrate so that 80% of the particles are less than 12 μm (0.012 mm) consumes over 120 kilowatt-hours per tonne (kWh/t) of ore in a ball mill using 9 mm balls, but only 40 kWh/t in an IsaMill using a 2 mm grinding medium.
The IsaMill usually consists of a series of eight disks mounted on a rotating shaft inside a cylindrical shell (see Figure 2). The mill is 70–80% filled with the grinding medium, and is operated under a pressure of 100 to 200 kilopascals. The disks contain slots to allow the ore slurry to pass from the feed end to the discharge end (see Figure 3). The area between each disk is effectively an individual grinding chamber, and the grinding medium is set in motion by the rotation of the disks, which accelerate the medium toward the shell. This action is most pronounced close to the disks. The medium flows back toward the shaft in the zone near the midpoint between the disks, creating a circulation of the grinding medium between each pair of disks, as shown in Figure 4.
The average residence time of the ore in the mill is 30–60 seconds. There is negligible short-circuiting of the grinding zone by the feed, as a result of having multiple grinding chambers in series.
The ground product is separated from the grinding medium at the discharge end of the mill. This is achieved without using screens by using a patented product separator that consists of a rotor and a displacement body (see Figure 2 and Figure 4). The relatively short distance between the last disk results in a centrifugal action that forces coarse particles towards the mill shell, from where they flow back towards the feed end. This action retains the grinding medium within the mill.