Particle breakage kinetics in horizontal stirred mills

Yue, J.; Klein, Bern

doi:10.1016/j.mineng.2004.06.009

Cited by 23 publications

(14 citation statements)

References 7 publications

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“…As it is known, the product obtained by cutting and abrasion forces can be reduced to finer sizes (Wills, 1985). Therefore, in studies where stirred mills were used, stirring speed, ball size, ball charge, pulp solid rate or pulp density (in wet grinding), feed size, flow rate or capacity of pulp in continuous systems (wet grinding), grinding period, stirring system design (type, shape), effect of gravity types, and amount of additives have been investigated (Yue and Klein, 2005;Yang et al, 2006;Jankovic and Sinclair, 2006;Ding et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

Samanli¹,

Cuhadaroglu²,

Hwang³

2011

Energy Sources, Part A: Recovery, Utilization, and Environmenta

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The structure and particle size of solid fossil fuels have effects on linear or nonlinear movements encountered in breakage rate, besides petrography types, inorganic materials, extensive network of pores, macro chemical forms, etc. Nonlinear breakage behavior in mono size groups of 3,350 C 2,360 m, 2,360 C 1,700 m, and 1,180 C 850 m was a result of heterogeneous structure of the material along with being coarser for grinding medium. The part having low-ash content (coallike) in the heterogeneous structure was exposed to faster breakage than the part having high-ash content (shale-like). As a result, over-sieve material was composed of shale, which is more difficult to grind, breakage behavior slowed down, and there occurred a deviation in linear breakage behavior with increasing grinding period. Linear breakage behavior in mono size groups of 425 C 300 m and 212 C 150 m was considered as a result of homogeneity of the material along with its adequate fineness for grinding medium. Variation of particle size in grinding is an important parameter in terms of breakage behavior. Maximum breakage rate was reached for 425 C 300 m size group in the stirred mill. The ratio of "grinding medium size/size of the material ground" (6.0/0.425) was calculated as approximately 14. A decrease in this ratio, i.e., an increase in particle size of material, caused engagement difficulties of particles by balls. An increase in the ratio, however, resulted in a pillowing effect of fine materials in the medium and, thus, a decrease in breakage rate.

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Section: Introductionmentioning

confidence: 99%

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

Samanli¹,

Cuhadaroglu²,

Hwang³

2011

Energy Sources, Part A: Recovery, Utilization, and Environmenta

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“…Therefore, the final size distribution may be the same in the different mills. In this study, the stirred mill, especially with stainless steel media, produced slightly more fine particles (-10 µm) than the rod mill, which may be due to a greater degree of attrition breakage in the stirred mill (Hogg 1999, Yue andKlein 2005). However, it is unlikely that the slight difference in size distribution produced by the two types of mills is the major contributing factor to the significant difference in chalcocite flotation displayed in Figure 7.2.…”

Section: Particle Sizementioning

confidence: 61%

“…Therefore, it has been assumed that the movement of the stirrer through the bed of grinding media, and the sliding/rolling motion that this imparts to the charge itself, provides a solely attrition breakage environment. However, recent studies suggest that impact breakage mechanisms may also exist in stirred mills, and the proportion of impact and attrition varies from case to case (Kwade and Schwedes 2002, Yue and Klein 2005, Roufail and Klein 2010.…”

Section: Particle Breakage Mechanisms During Regrindingmentioning

confidence: 99%

The effect of regrinding chemistry and particle breakage mechanisms on subsequent cleaner flotation

Chen¹

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Regrinding rougher flotation concentrates is typically used to liberate valuable minerals from gangue prior to the cleaner separation stage in processing of low grade ores. Compared to the rougher flotation after primary grinding, it is usually more challenging to achieve a satisfactory performance in post-regrind cleaner flotation especially when fine particles are generated. One main factor which results in this reduction in flotation is the unsuitable particle surfaces produced after regrinding. However, this factor is not usually considered when designing and optimizing the regrinding process.Extensive studies have demonstrated that grinding chemistry can influence mineral floatability.However, earlier studies focused on primary grinding and rougher flotation rather than regrinding and cleaner flotation. In addition, different types of regrind mills are used in industry, and these provide different particle breakage mechanisms which may also influence mineral floatability.Therefore, the overall objective of this thesis study is to investigate the effects of regrinding chemistry and particle breakage mechanisms on the cleaner flotation. The implementation of regrinding in the copper and pyrite flotation circuits at Telfer gold mine was taken as a case study and four research areas were addressed with the objective of developing fundamental understanding to provide practical guidance for the plant operation. The four areas investigated are:1. Effect of regrinding chemistry on copper activation of pyrite and its flotation; 2. Separation of different copper sulphide minerals from pyrite after regrinding; 3. Importance of pulp chemistry during regrinding rougher concentrates; 4. Effect of particle breakage mechanisms on subsequent flotation.In this study, it was found that copper activation of pyrite and its flotation in the cleaner stage were affected by regrinding. In general, a decrease in surface concentration of collectors due to the increased surface area after regrinding contributed to the low pyrite recovery in the cleaner. Surface analysis revealed that both the surfaces that were carried from the rougher flotation concentrate and those which were freshly created were modified by the strong electrochemical reactions occurring inside the regrind mill. Stainless steel media promoted pyrite oxidation, especially on the copper activated surfaces. Mild steel media produced a greater amount of iron oxidation species which could adsorb on the carried surfaces. It was also found that mild steel media generated a reducing condition which favoured the copper activation on the freshly created surfaces.ii The research has also shown that the separability of chalcopyrite and chalcocite from pyrite was significantly different after regrinding, which was related to their electrochemical properties.Chalcocite was more active and therefore presented a stronger galvanic interaction with pyrite.Consequently chalcocite was more oxidised, which not only depressed its flotation but also produced sufficient copper ions...

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“…These variables were chosen as their effect on the gravity induced stirred mill operation are significant. Yue and Klein (2005) by them. The variables were set at three levels following the typical operational regime in the production mill.…”

Section: Experimental Designmentioning

confidence: 98%

“…Many researchers modelling stirred mills have used a straight line to represent its selection function such as Menacho and Reyes (1989), Tuzun (1993), Yue and Klein (2005) and . The high ratio of the grinding media to feed particle size enables the mill to break the top particle size in most of the cases; however, this phenomenon depends on the types of materials being ground in the mill.…”

Section: Selection Function At Different Operating Conditionsmentioning

confidence: 99%

Process modelling of gravity induced stirred mills

Hasan¹

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Fine grinding is becoming an integral part of mineral processing plants to liberate valuable minerals from fine-grained low-grade ore bodies. Stirred mills are becoming recognized by the industry as a more efficient technology selection compared to the ball mill for fine grinding (< 100 µm). The increasing number of stirred mill installations in mineral processing concentrators has necessitated a process model development that enables full circuit modelling and simulation. Many researchers have developed mathematical models to assist in the design and optimization of the stirred mill operation including gravity induced stirred mills such as the Metso Vertimill and the Nippon Eirich Tower Mill.Most of the developed models lack sufficient responses to changes in process conditions. Furthermore, there is an internal classification effect that is previously mentioned in several publications but was not quantified through experiments. Therefore, a research program was designed and carried out to describe and model different sub-processes related to the operation of the gravity induced stirred mill. The sub-process models (i.e. grinding and internal classification) were combined into a single model structure to represent the operation in a gravity induced stirred mill.During this research, comprehensive test work was carried out in a batch gravity induced stirred mill using Cu-Au ore and limestone to evaluate the effect of operating conditions (i.e. specific energy consumption, slurry density, grinding media size and stirrer tip speed) on particle size and fines generation (-75μm). The test data showed a finer product size when the mill operates at higher specific energy, lower slurry density, smaller grinding media size and higher stirrer tip speed. The test work also identified that attrition breakage mechanism is predominant in the gravity induced mill. Sub-process models that relate the selection function to the process operating conditions were developed. The internal classification effect on mill operation was also measured through test work by using industrial grade silica to identify its effect on the mill operation. The result showed that particle classification takes place inside the gravity induced mill in certain favorable conditions. Models were developed to link the classification parameters and the mill operating conditions to be included in the combined model structure.ii A process model (using a time-based population balance technique) was developed, integrating individual sub-processes models such as breakage, selection and classification functions. The model was validated with industry survey data in different process conditions. The validation result showed that the developed model was capable to predict the mill product size distribution when mill power, feed rate, slurry solids concentration and grinding media size are varied.The thesis has successfully developed a process model of the gravity induced stirred mill with predictive capability. Moreover, it has developed an in-depth understa...

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Particle breakage kinetics in horizontal stirred mills

Cited by 23 publications

References 7 publications

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

The effect of regrinding chemistry and particle breakage mechanisms on subsequent cleaner flotation

Process modelling of gravity induced stirred mills

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