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Ball mill is the vital equipment for recrushing after being crushed.

Processing ability:0.5-500t/h

Feeding size:≤25mm

Applied material:cement, silicate, new-type building material, refractory material, fertilizer, ore dressing of ferrous metal and non-ferrous metal, glass ceramics, etc.

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p80 of bond ball mill work index tests

This chart is adapted from the large number of ball mill tests done by Yardin Josefin, which were presented at Procemin in 2018. The work index of this copper ore drops as you grind finer until about 55 µm where we interpret that a grain size is encountered that causes the work index to rise due to the extra effort to break these grains. This is a pretty normal-looking chart; the slope of the main body of the results might be positive (as this one is) or negative, and there might be sizes where inflection points break the trend

This pattern seems at odds with the way a lot of mineral processing is taught -- "Bond's Law" says that work index should be relatively constant and the "one over the square root" operation soaks up the variation in product size. You may also hear that "work index is the specific energy consumption to grind from infinite size to 100 µm" which makes no sense if the work index changes as a function of size

The reality is that the response of an ore to progressively finer grinding is different for different ores. Just as you can measure a work index for an ore, you can also measure its "exponent" and you'll find it isn't precisely –½, which is another way to express "one over the square root"

p80 of bond ball mill work index tests

The bigger picture is "Bond's Law" isn't a law at all, it is just a regression line drawn through a bunch of data collected in the 1930's and 1940's that "kinda-sorta" had a slope of –½ when plotted on log-log graph paper. Fred Bond's regression equation was a remarkable achievement in the days before the first primitive electronic desktop calculators, but we now have the means to look much closer at the testing and perform analysis such as the one by Josefin.

The method outlined here roughly mimics the conjecture by Hukki, 1963 (among others: Charles, 1957 can also be credited). Grinding specific energy consumption, E can be expressed as a function of size x over sufficiently narrow size ranges:

correction of bond ball mill work index test for closing

The laboratory procedure for running a Bond ball mill work index test requires that the operator choose a closing screen sieve size. The instruction is to choose a sieve size that results in the test product 80% passing size (P80) similar to the P80 of the industrial operating mill. Usually this means you choose, for example, a 212 µm closing mesh size if you desire a 180 µm target, or a 150 µm closing mesh size if you desire a 100 µm target size. The reason for this is that work index can change as a function of size

This chart is adapted from the large number of ball mill tests done by Yardin Josefin, which were presented at Procemin in 2018. The work index of this copper ore drops as you grind finer until about 55 µm where we interpret that a grain size is encountered that causes the work index to rise due to the extra effort to break these grains. This is a pretty normal-looking chart; the slope of the main body of the results might be positive (as this one is) or negative, and there might be sizes where inflection points break the trend

This pattern seems at odds with the way a lot of mineral processing is taught -- "Bond's Law" says that work index should be relatively constant and the "one over the square root" operation soaks up the variation in product size. You may also hear that "work index is the specific energy consumption to grind from infinite size to 100 µm" which makes no sense if the work index changes as a function of size

The reality is that the response of an ore to progressively finer grinding is different for different ores. Just as you can measure a work index for an ore, you can also measure its "exponent" and you'll find it isn't precisely –½, which is another way to express "one over the square root"

correction of bond ball mill work index test for closing

The bigger picture is "Bond's Law" isn't a law at all, it is just a regression line drawn through a bunch of data collected in the 1930's and 1940's that "kinda-sorta" had a slope of –½ when plotted on log-log graph paper. Fred Bond's regression equation was a remarkable achievement in the days before the first primitive electronic desktop calculators, but we now have the means to look much closer at the testing and perform analysis such as the one by Josefin.

The method outlined here roughly mimics the conjecture by Hukki, 1963 (among others: Charles, 1957 can also be credited). Grinding specific energy consumption, E can be expressed as a function of size x over sufficiently narrow size ranges:

bond tests | sgs

The grinding circuit is among your largest capital investments and greatest operating costs. SGS can reduce your risk by combining different test procedures and design methodologies to ensure that you optimize this critical part of your plant

Our philosophy is to first determine the variability of your ore using rigorous comminution testing, including Bond tests for ball and rod mills. We conduct a small number of expensive tests that require a larger sample size, such as the Bond Ball Mill Grindability Test. The results are used to calibrate a large number of less expensive tests that require only a small sample, such as the Modbond Grindability Test.

Similar to a Comparative Work Index, this test is an open circuit dry batch grindability test run in the standard Bond Ball Mill for a set time. It can be used at mesh sizes from 65 to 200 mesh (normally 100 mesh). The test requires calibration against the standard Bond Ball Mill Work Index test to estimate the Work Index. It is used to show the orebody hardness profile and to predict throughput in a ball mill circuit

SGS created the Modbond grindability test and has a large proprietary database. The small sample size enables many tests to be conducted, resulting in extensive variability information that our experts use to efficiently design your grinding circuit

bond tests | sgs

Where  W = Net power consumption in kWh/t             Wi = Bond work index (either Imperial or Metric units)            P = The 80% passing size of the ground product in µm            F = The 80% passing size of the feed in µm

The test determines the Bond Impact Work Index which is used with Bond’s Third Theory of Comminution to calculate net power requirements when sizing crushers*. It is also used to determine the required open-side settings (jaw crushers and gyratory crushers) or closed-side settings (cone crushers) for a given product size

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