Phantom cyclone - Revision history

Alex Doll: /* Other models */

2023-08-29T18:07:33Z

Other models

Alex Doll: /* SAG mills and HPGRs */

2015-04-16T17:51:47Z

SAG mills and HPGRs

Alex Doll: /* SAG mills and HPGRs */

2015-04-14T21:01:04Z

SAG mills and HPGRs

Alex Doll at 16:36, 14 April 2015

2015-04-14T16:36:28Z

Alex Doll: Created page with "category:Bond/Barratt Model category:Models ==Phantom cyclone effect== SAG and AG mills produce more fines, as a proportion of the whole particle size distribution, th..."

2015-04-13T19:34:01Z

Created page with "category:Bond/Barratt Model category:Models ==Phantom cyclone effect== SAG and AG mills produce more fines, as a proportion of the whole particle size distribution, th..."

New page

[[category:Bond/Barratt Model]]
[[category:Models]]
==Phantom cyclone effect==
SAG and AG mills produce more fines, as a proportion of the whole particle size distribution, than more classical comminution machines such as rod mills. This causes a problem for power-based models because only a single point (the 80% passing point) is used as a proxy to represent the whole particle size distribution, and the whole distribution is assumed to be "normal".

===Bond models===
Fred Bond

@@ Line 29: / Line 29: @@
 A plant survey will not return this 80% passing size; it contains the extra fines.  One way to model this plant survey data is to mathematically pass the stream through a hydrocyclone and strip off the extra fines.  The cyclone underflow stream should have a Bond-compatible size distribution which matches the Bond power-model transfer size.  The ''phantom cyclone'' is named for this method of treating SAG product for modelling.
-==Other models==
+==Amelunxen SGI model==
 The [[Model:Amelunxen SGI|Amelunxen SG]]I model is calibrated for actual transfer size measurements from operating plants and do include the extra fines.  The CFball calibration factor is used to "soak up" the extra fines when using an SGI model.

@@ Line 21: / Line 21: @@
 Autogenous and semi-autogenous grinding mills were not unknown during Bond's day, but they were relatively minor equipment that was used in a few boutique applications.  The widespread adoption of SAG milling happened in the 1970's and 1980's, well after Bond's Third Theory was already established.  High pressure grinding rolls (HPGR's) did not exist in a modern sense during Bond's day, and they were only adopted into the minerals industry from the very early part of the 21<sup>st</sup> century (although they existed earlier in the cement industry).
-[[ File:LB-SABC TransferPSD.png | frame | right | alt=Particle size distribution chart]]
+[[ File:LB-SABC TransferPSD.png | frame | right | alt=SAG discharge particle size distribution chart|Example SAG discharge particle size distribution]]
 The problem with SAG mills and HPGRs, from a modelling sense, is that their particle size distributions do not follow Bond's specification; both have more fines in their product stream than Bond's specification of an "average" size distribution.  There are a variety of ways to describe this phenomenon; arguably the most common terms are the ''phantom cyclone effect'' in SAG milling and ''microcracking'' in HPGRs (which are treated as the same effect for power-modelling purposes).

@@ Line 20: / Line 20: @@
 ===SAG mills and HPGRs===
 Autogenous and semi-autogenous grinding mills were not unknown during Bond's day, but they were relatively minor equipment that was used in a few boutique applications.  The widespread adoption of SAG milling happened in the 1970's and 1980's, well after Bond's Third Theory was already established.  High pressure grinding rolls (HPGR's) did not exist in a modern sense during Bond's day, and they were only adopted into the minerals industry from the very early part of the 21<sup>st</sup> century (although they existed earlier in the cement industry).
 The problem with SAG mills and HPGRs, from a modelling sense, is that their particle size distributions do not follow Bond's specification; both have more fines in their product stream than Bond's specification of an "average" size distribution.  There are a variety of ways to describe this phenomenon; arguably the most common terms are the ''phantom cyclone effect'' in SAG milling and ''microcracking'' in HPGRs (which are treated as the same effect for power-modelling purposes).

← Older revision		Revision as of 16:36, 14 April 2015
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	===Bond models===		===Bond models===
		+	Fred Bond spends a lot of effort describing the shapes of particle size distribution curves in his Third Theory (Bond, 1952) and several earlier works. He sums up the intended shape of a size distribution for which is model is calibrated as:
−	Fred Bond
		+
		+	''Experience has shown that the average slope [...] of the size distribution percent passing [...] on a log-log plot of the percent passing against the sieve opening, is very close to <math>1 \over {\sqrt{2}}</math>'' <sup>[[Bibliography: Specific energy consumption models\|Bond, 1952]]</sup>
		+
		+	Bond also proposed this model of a particle size distribution:
		+
		+	<math>Y = 80 \left( {{X}\over {P} } \right) ^ {1 \over {\sqrt{2}}}</math>
		+
		+	where:
		+	''Y'' is the percent passing a size ''X'' and ''P'' is the 80% passing size (all sizes in µm).
		+
		+	Bond claims this model to be suitable for most of the crushing, rod milling and ball milling machines and applications that were surveyed by Bond and his colleagues in the 1940's and 1950's.
		+
		+	===SAG mills and HPGRs===
		+	Autogenous and semi-autogenous grinding mills were not unknown during Bond's day, but they were relatively minor equipment that was used in a few boutique applications. The widespread adoption of SAG milling happened in the 1970's and 1980's, well after Bond's Third Theory was already established. High pressure grinding rolls (HPGR's) did not exist in a modern sense during Bond's day, and they were only adopted into the minerals industry from the very early part of the 21<sup>st</sup> century (although they existed earlier in the cement industry).
		+
		+	The problem with SAG mills and HPGRs, from a modelling sense, is that their particle size distributions do not follow Bond's specification; both have more fines in their product stream than Bond's specification of an "average" size distribution. There are a variety of ways to describe this phenomenon; arguably the most common terms are the ''phantom cyclone effect'' in SAG milling and ''microcracking'' in HPGRs (which are treated as the same effect for power-modelling purposes).