Experimental investigation of the power draw of tumbling mills in wet grinding

2016 ◽  
Vol 230 (15) ◽  
pp. 2709-2719 ◽  
Author(s):  
Moslem M Soleymani ◽  
Majid Fooladi ◽  
Masood Rezaeizadeh
Keyword(s):  
Critical Speed ◽  
Empirical Equation ◽  
Design Criterion ◽  
Copper Ore ◽  
Slurry Concentration ◽  
Critical Design ◽  
Power Increase ◽  
Power Draw ◽  
Tumbling Mills ◽  
Mill Speed

In comminution, mill power plays a major role from the economics standpoint and is a critical design criterion. It is influenced by a range of parameters such as media charge level (ball filling), slurry filling, slurry concentration and mill speed. In this work, the effects of these operating parameters were investigated using a pilot mill (1000 × 500 mm). To this end, a copper ore (−1000 µm) was used to prepare the slurry. The tests covered a range of slurry filling (U) from 0 to 1.7 with media charge between 12% and 36% of the mill volume and six different speeds between 60% and 85% of critical speed. A power analyser was utilized to measure mill power. Increase in mill speed and ball filling leads to a remarkable increase in the amount of the power. Preliminary results show that there is a definite trend between the power and the slurry filling U. Mill power draw is maximum at slurry concentration 60–70% and slurry filling 0.84. An empirical equation was given that fits the data reasonably well.

Experimental study the impact forces of tumbling mills

2016 ◽  
Vol 231 (2) ◽  
pp. 283-293 ◽  
Author(s):  
MM Soleymani ◽  
M Fooladi Mahani ◽  
M Rezaeizadeh
Keyword(s):  
Experimental Study ◽  
Critical Speed ◽  
Operating Parameters ◽  
Solid Concentration ◽  
Copper Ore ◽  
Slurry Concentration ◽  
Impact Forces ◽  
Tumbling Mills ◽  
Mill Speed ◽  
The Impact

Impact forces are one of the mechanisms for grinding in mill. This takes place when the particles elevated by the lifters get into cascade motion and their fall on the load causes the breakage of other particles. The present paper aimed to study the impact forces in terms of variables like: mill speed, solid charge filling (ball filling), slurry concentration, and slurry filling. In this work, the influence of these operating parameters was investigated using a pilot mill. To this end, a copper ore was used to prepare slurry at different solid concentration. The tests covered a range of slurry filling from 0 to 2 with five different balls filling between 12% and 36% of mill volume and six different speeds between 60% and 85% of critical speed. The results delineate that the increase in the mill speed leads to a remarkable increase in the amount and frequency of the impact forces. Increasing the charge volume leads to decrease the maximum impact forces. The results show that with the increase in slurry filling and the resulting formation of a pool, the impact forces will decrease. Moreover, it is found that with the increase in slurry concentration, the slurry will act as a damper decreasing the impact forces.

scholarly journals Experimental Study of Operational Parameters on Product Size Distribution of Tumbling Mill

2020 ◽  
Author(s):  
moslem mohammadi soleymani
Keyword(s):  
Size Distribution ◽  
Critical Speed ◽  
Operational Parameters ◽  
Copper Ore ◽  
Mill Product ◽  
Slurry Concentration ◽  
Pilot Model ◽  
Grinding Media ◽  
Grinding Mechanism ◽  
Mill Speed

Abstract To assess the effects of the mill operating parameters such as mill speed, ball filling, slurry concentration and slurry filling on grinding process and size distribution of mill product, it was endeavored to build a pilot model with smaller size than the mill. For this aim, a pilot mill with 1m × 0.5m was implemented. There are 15 lifters with 50mm height and face angle of 30˚. In the present work, the combination of the balls (40% of the balls with 60mm diameter, 40% of the balls with 40mm diameter and 20% of the balls with 25mm diameter) was used as grinding media with 10%, 15%, 20% and 25% of the total volume of the mill. The experiments were carried out at 60%, 70%, 80% and 90% of the critical speed. The feed of the mill is copper ore with the size smaller than 25.4 mm, which d80 and d50 of them are 12.7 and 8 mm, respectively and slurries with 40%, 50%, 60%, 70% and 80% of solid and the slurry filling between 0.5 and 2.5. The results showed that the best grinding and grading occurs at 70-80% of the critical speed and ball filling of 20-25%. Optimized grinding was observed when the slurry volume is 1-1.5 times of the ball bed voidage volume and the slurry concentration is between 60% and 70%. The mill grinding mechanism in this work is a combination of both impact and abrasion mechanisms.

scholarly journals Experimental Study of Operational Parameters on Product Size Distribution of Tumbling Mill

2021 ◽  
pp. 095440892110627
Author(s):  
Moslem Mohammadi Soleymani
Keyword(s):  
Size Distribution ◽  
Critical Speed ◽  
Operational Parameters ◽  
Copper Ore ◽  
Mill Product ◽  
Slurry Concentration ◽  
Pilot Model ◽  
Grinding Media ◽  
Grinding Mechanism ◽  
Mill Speed

To assess the effects of the mill operating parameters such as mill speed, ball filling, slurry concentration and slurry filling on grinding process and size distribution of mill product, it was endeavored to build a pilot model with smaller size than the mill. For this aim, a pilot mill with 1 m × 0.5 m was implemented. There are 15 lifters with 50 mm height and face angle of 30˚. In the present work, the combination of the balls (40% of the balls with 60 mm diameter, 40% of the balls with 40 mm diameter and 20% of the balls with 25 mm diameter) was used as grinding media with 10%, 15%, 20% and 25% of the total volume of the mill. The experiments were carried out at 60%, 70%, 80% and 90% of the critical speed. The feed of the mill is copper ore with the size smaller than 25.4 mm, which d80 and d50 of them are 12.7 and 8 mm, respectively and slurries with 40%, 50%, 60%, 70% and 80% of solid and the slurry filling between 0.5 and 2.5. The results showed that the best grinding and grading occurs at 70–80% of the critical speed and ball filling of 20–25%. Optimized grinding was observed when the slurry volume is 1–1.5 times of the ball bed voidage volume and the slurry concentration is between 60% and 70%. The mill grinding mechanism in this work is a combination of both impact and abrasion mechanisms.

scholarly journals Development of a method to measure charges in tumbling mills

2014 ◽  
Vol 67 (3) ◽  
pp. 311-316
Author(s):  
Eduardo Nozawa Caetano de Araujo ◽  
Homero Delboni Jr.
Keyword(s):  
Low Cost ◽  
Total Charge ◽  
Main Aspect ◽  
Product Size ◽  
Confined Spaces ◽  
Power Draw ◽  
Grinding Media ◽  
Tumbling Mills ◽  
The Common ◽  
Tumbling Mill

Tumbling mills are often taken as the object of optimization studies because they are a type of equipment that consume large amounts of energy. Among the current available resources to conduct such studies, mathematic modelling presents great efficiency due to its low cost, speed and reliability. The total charge and grinding media charge are very important variables to conduct modelling exercises that aim at power draw and product size distribution forecasting. However, the common measurement methods require people entering the equipment, which carries a number of adversities related to confined spaces. In this regard, this paper presents the development of a method and the prototype of a device able to measure tumbling mill charges, quickly, precisely, with low cost and, above all, ensuring safety. The result of this work is a method that allows equivalent or superior precision in comparison to the existing methods, whose main aspect is to eliminate the requirement of people entering dangerous environments, such as tumbling mills.

Effects of slurry filling and mill speed on the net power draw of a tumbling ball mill

2014 ◽  
Vol 56 ◽  
pp. 45-56 ◽  
Author(s):  
François K. Mulenga ◽  
Michael H. Moys
Keyword(s):  
Ball Mill ◽  
Power Draw ◽  
Mill Speed

scholarly journals Comparative Analysis of Autogenous and Media Assisted Grindability of a Copper and Manganese Ores

2018 ◽  
pp. 1-12
Author(s):  
E. O. Ajaka ◽  
G. Dombo ◽  
O. Abiodun
Keyword(s):  
Comparative Analysis ◽  
Size Analysis ◽  
Copper Ore ◽  
Manganese Ores ◽  
Dry Grinding ◽  
Close Relationship ◽  
Speed Up ◽  
Mill Speed ◽  
The Relationship ◽  
Mill Charge

This paper presents a comparative analysis of autogenous and media assisted grinding of a manganese ore and copper ore both obtained from Otjihase in Namibia. The objective was to understand the relationship between ore properties and Grindability and thus effectively select comminution circuit and equipment based on this relationship. Laboratory studies were carried out to determine the ease of grinding the ore samples relative to one another. The sample of known weight was crushed and the particles thoroughly homogenized for sieve size analysis and Grindability tests. The Grindability test on each ore was both autogenous and media assisted for dry grinding at -250 microns with constant mill charge of 200 g per run, media charge of 40% by weight and mill operations of 100 to 500 revolutions corresponding to mill speeds of 5 to 25 rpm. The Grindability index of each ore was calculated and compared based on the tests results and used to calculate work indexes for the ores based on the Bond’s model. The autogenous tests produced average Grindability values of 0.55 kg/ton/rev and 0.65 kg/ton/rev for the copper and manganese ores respectively; and media assisted tests gave average values of 0.8 kg/ton/rev and 1.45 kg/ton/rev respectively for the copper and manganese ores. The results show that although media charge grinding produced higher Grindability values, both ores are economically amenable to autogenous grinding which suggests that with proper circuit design, the use of autogenous grinding for these ores (especially the manganese) can save significant cost. The results also show that Grindability increases with mill speed up to an optimum value beyond which grindability decreases with increasing speed and may even drop to zero while mill is running. It is also observed that grindability has close relationship with ore properties especially hardness and compressive strength. It should be noted that the inefficiency factors for the grinding are not considered in these results.

scholarly journals The Influence of Forearm and Wrist Orientation on Static Grip Strength as a Design Criterion for Hand Tools

1976 ◽  
Vol 20 (1) ◽  
pp. 28-32 ◽  
Author(s):  
Robert Terrell ◽  
Jerry L. Purswell
Keyword(s):  
Grip Strength ◽  
Design Criterion ◽  
Neutral Position ◽  
Wrist Flexion ◽  
Forearm Rotation ◽  
Hand Tools ◽  
Critical Design ◽  
Hand Tool

The amount of force required to use a hand tool and its relationship to the user's capacity to exert this force is a critical design criterion of hand tools, often affecting the immediate safety of the tool user and the propensity of the tool to cause injury to the user with long-term use. Because the wrist is often placed in deviated positions, the available data on grip strength with an undeviated wrist configuration may not be applicable to the design of many hand tools. This study demonstrates the decreases in grip strength due to wrist deviations and forearm rotation. The position of maximal static grip strength is the neutral wrist with a supinated forearm. Decrements from the neutral position for wrist flexion, hyperextension, radial flexion and ulnar flexion are 30%, 22%, 18% and 15%, respectively. The pronated forearm allows only 87% of the strength of the supinated forearm, and the differences between the supinated and the midposition forearm are not significant.

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