how to improve coal mill grinding in ball mill

how to improve the grinding efficiency of the ball mill!_cement production process_lvssn

how to improve the grinding efficiency of the ball mill!_cement production process_lvssn

The grinding efficiency of ball mill is low, the treatment capacity is low, the production energy consumption is high, the product fineness is unstable and so on, which are the problems that most concentrators will encounter. How to effectively improve the grinding efficiency of ball mill is an important problem. This article summarizes 10 ways to improve efficiency, if you are worried about it, you might as well try! 1. Change the grindability of the original ore The hardness, toughness, dissociation and structural defects of the raw ore determine the difficulty of grinding. If the grinding degree is small, the ore is easy to grind, and the smaller the wear of mill liner and steel ball is, the smaller the energy consumption is; on the contrary, the opposite is true. The raw ore properties directly affect the productivity of the mill. In production, if the ore that is difficult to grind or the ore requires fine grinding, we can consider adopting a new treatment process to change the grindability of the ore if the economic and site conditions permit: One method is to add certain chemicals in the grinding process to improve the grinding effect and increase the grinding efficiency. Another method is to change the grindability of the ore, such as heating the minerals in the ore, changing the mechanical properties of the whole ore, reducing the hardness and so on. 2, more crushing and less grinding, reduce the granularity of grinding If the grinding particle size is large, the more work the mill needs to do to the ore, the more the workload of the ball mill is bound to increase, and the energy consumption and power consumption will also be increased in order to reach the prescribed grinding fineness. In order to reduce the grain size of grinding material, it is necessary to have a small particle size of broken ore, that is to say, "more crushing and less grinding". Moreover, the efficiency of crushing is obviously higher than that of grinding, and the energy consumption of crushing is low, which is about 12% of grinding energy consumption. 3. Reasonable filling rate When the speed of the ball mill is certain, the filling rate is large, the steel ball hits the material more times, the grinding area is large, the grinding effect is strong, but the power consumption is also large, and the filling rate is too high, it is easy to change the movement state of the steel ball and reduce the strike effect on the large particle material. On the contrary, the filling rate is too small and the grinding effect is weak. At present, many mines set the filling rate at 45% 50%, which is not necessarily reasonable, because the actual conditions of each separation plant are not the same, copying the data of others to load the ball can not achieve the ideal grinding effect, depending on the situation. 4. Reasonable size and ratio of steel ball Because the steel ball in the ball mill is in contact with the ore, and the ball diameter is too large, the crushing force is also large, which leads to the fracture of the ore along the direction of penetration force, rather than along the interface of different mineral crystals with weak bonding force, and the breakage is not selective, which is not in line with the purpose of grinding. In addition, when the filling rate of steel ball is the same, too large ball diameter leads to too little steel ball, low crushing probability, aggravation of overcrushing phenomenon and uneven particle size of the product. The steel ball is too small, the crushing force on the ore is small, and the grinding efficiency is low, so the influence of accurate steel ball size and its ratio on the grinding efficiency is very important. 5. precise addition of the ball In production, the grinding effect of steel ball and ore will cause the wear of steel ball, which will lead to the change of the ratio of steel ball of each size, which will affect the grinding process and cause the fineness change of grinding product. Therefore, a reasonable steel ball supplement system is needed to make the production stable. 6. Reasonable and appropriate grinding concentration The size of the grinding concentration influences the specific gravity of the ore pulp, the degree of adhesion of the ore grains around the steel ball, and the fluidity of the ore pulp. Because of the low grinding concentration, fast slurry flow and low adhesion of the material around the steel ball, the impact and grinding effect of the steel ball on the material is weak, the ore discharge particle size is not up to standard, and the grinding efficiency can not be brought into play. The grinding concentration is high, the adhesion degree of the material around the steel ball is good, and the impact and grinding effect of the steel ball on the material are good, but the slurry flow is slow, which is easy to cause the material to be overcomminuted, which is not conducive to improving the treatment capacity of the mill. In production practice, the grinding concentration is often controlled by controlling the feed quantity of the mill, the recharge water quantity of the mill, or adjusting the classification effect, controlling the particle size composition and moisture in the graded sand return. 7. Optimizing the grinding process In practical production, the grinding process can be optimized according to the ore properties of the original ore, such as the embedded particle size of useful minerals, the degree of monomer dissociation, the embedded grain size of gangue minerals and so on. Such as pre-tail throwing, pre-enrichment, stage grinding, pre-classification and other operations to optimize the grinding system, on the one hand, reduce the amount of grinding, on the other hand, early recovery of useful minerals. 8. Improve grading efficiency The influence of classification efficiency on grinding efficiency is self-evident. The high classification efficiency means that the qualified grain size can be discharged in time and efficiently, while the classification efficiency is low, which means that most of the qualified grain size products are not discharged and returned to the mill for re-grinding, which is easy to cause overgrinding, thus affecting the later selection effect. The efficiency of classification can be improved by using two-stage classification or improving classification equipment. 9. properly improve the ratio of graded sand return The ratio of sand return to raw ore feeding directly affects the productivity of the mill. One way to increase the sand return ratio is to increase the original ore feed, and the other is to reduce the shaft height of the spiral grader. However, there are also certain limits to the increase of sand return ratio. When it increases to a certain value, the productivity of the mill increases very little, and the total feed quantity of the mill is close to the maximum treatment capacity of the mill, which is easy to cause the belly increase, so the sand return ratio should not be too large. 10. Automatic control of grinding system There are many variable parameters in grinding operation, and a change will inevitably lead to the change of many factors one after another. if the artificial operation control is adopted, it will inevitably lead to the instability of production, and the automatic control of grinding operation can keep the grinding classification in a stable and suitable state, and the grinding efficiency can also be improved. According to foreign reports, the automatic control of grinding classification circuit can increase the production capacity by 2.5% and 10%, and the power consumption of one ton of ore can be saved by 0.4 1.4 kWht. In the grinding process, there are many factors that affect the grinding efficiency, many factors can only be qualitatively analyzed and judged, it is difficult to make quantitative analysis, which needs to be comprehensively analyzed according to the actual production situation and the results of qualitative analysis, so as to obtain reasonable parameters to guide the field production in order to reduce the production cost and achieve the purpose of energy saving and consumption reduction.

The grinding efficiency of ball mill is low, the treatment capacity is low, the production energy consumption is high, the product fineness is unstable and so on, which are the problems that most concentrators will encounter. How to effectively improve the grinding efficiency of ball mill is an important problem. This article summarizes 10 ways to improve efficiency, if you are worried about it, you might as well try!

The hardness, toughness, dissociation and structural defects of the raw ore determine the difficulty of grinding. If the grinding degree is small, the ore is easy to grind, and the smaller the wear of mill liner and steel ball is, the smaller the energy consumption is; on the contrary, the opposite is true. The raw ore properties directly affect the productivity of the mill. In production, if the ore that is difficult to grind or the ore requires fine grinding, we can consider adopting a new treatment process to change the grindability of the ore if the economic and site conditions permit: One method is to add certain chemicals in the grinding process to improve the grinding effect and increase the grinding efficiency. Another method is to change the grindability of the ore, such as heating the minerals in the ore, changing the mechanical properties of the whole ore, reducing the hardness and so on.

If the grinding particle size is large, the more work the mill needs to do to the ore, the more the workload of the ball mill is bound to increase, and the energy consumption and power consumption will also be increased in order to reach the prescribed grinding fineness. In order to reduce the grain size of grinding material, it is necessary to have a small particle size of broken ore, that is to say, "more crushing and less grinding". Moreover, the efficiency of crushing is obviously higher than that of grinding, and the energy consumption of crushing is low, which is about 12% of grinding energy consumption.

When the speed of the ball mill is certain, the filling rate is large, the steel ball hits the material more times, the grinding area is large, the grinding effect is strong, but the power consumption is also large, and the filling rate is too high, it is easy to change the movement state of the steel ball and reduce the strike effect on the large particle material. On the contrary, the filling rate is too small and the grinding effect is weak. At present, many mines set the filling rate at 45% 50%, which is not necessarily reasonable, because the actual conditions of each separation plant are not the same, copying the data of others to load the ball can not achieve the ideal grinding effect, depending on the situation.

Because the steel ball in the ball mill is in contact with the ore, and the ball diameter is too large, the crushing force is also large, which leads to the fracture of the ore along the direction of penetration force, rather than along the interface of different mineral crystals with weak bonding force, and the breakage is not selective, which is not in line with the purpose of grinding. In addition, when the filling rate of steel ball is the same, too large ball diameter leads to too little steel ball, low crushing probability, aggravation of overcrushing phenomenon and uneven particle size of the product. The steel ball is too small, the crushing force on the ore is small, and the grinding efficiency is low, so the influence of accurate steel ball size and its ratio on the grinding efficiency is very important.

In production, the grinding effect of steel ball and ore will cause the wear of steel ball, which will lead to the change of the ratio of steel ball of each size, which will affect the grinding process and cause the fineness change of grinding product. Therefore, a reasonable steel ball supplement system is needed to make the production stable.

The size of the grinding concentration influences the specific gravity of the ore pulp, the degree of adhesion of the ore grains around the steel ball, and the fluidity of the ore pulp. Because of the low grinding concentration, fast slurry flow and low adhesion of the material around the steel ball, the impact and grinding effect of the steel ball on the material is weak, the ore discharge particle size is not up to standard, and the grinding efficiency can not be brought into play. The grinding concentration is high, the adhesion degree of the material around the steel ball is good, and the impact and grinding effect of the steel ball on the material are good, but the slurry flow is slow, which is easy to cause the material to be overcomminuted, which is not conducive to improving the treatment capacity of the mill. In production practice, the grinding concentration is often controlled by controlling the feed quantity of the mill, the recharge water quantity of the mill, or adjusting the classification effect, controlling the particle size composition and moisture in the graded sand return.

In practical production, the grinding process can be optimized according to the ore properties of the original ore, such as the embedded particle size of useful minerals, the degree of monomer dissociation, the embedded grain size of gangue minerals and so on. Such as pre-tail throwing, pre-enrichment, stage grinding, pre-classification and other operations to optimize the grinding system, on the one hand, reduce the amount of grinding, on the other hand, early recovery of useful minerals.

The influence of classification efficiency on grinding efficiency is self-evident. The high classification efficiency means that the qualified grain size can be discharged in time and efficiently, while the classification efficiency is low, which means that most of the qualified grain size products are not discharged and returned to the mill for re-grinding, which is easy to cause overgrinding, thus affecting the later selection effect. The efficiency of classification can be improved by using two-stage classification or improving classification equipment.

The ratio of sand return to raw ore feeding directly affects the productivity of the mill. One way to increase the sand return ratio is to increase the original ore feed, and the other is to reduce the shaft height of the spiral grader. However, there are also certain limits to the increase of sand return ratio. When it increases to a certain value, the productivity of the mill increases very little, and the total feed quantity of the mill is close to the maximum treatment capacity of the mill, which is easy to cause the belly increase, so the sand return ratio should not be too large.

There are many variable parameters in grinding operation, and a change will inevitably lead to the change of many factors one after another. if the artificial operation control is adopted, it will inevitably lead to the instability of production, and the automatic control of grinding operation can keep the grinding classification in a stable and suitable state, and the grinding efficiency can also be improved. According to foreign reports, the automatic control of grinding classification circuit can increase the production capacity by 2.5% and 10%, and the power consumption of one ton of ore can be saved by 0.4 1.4 kWht. In the grinding process, there are many factors that affect the grinding efficiency, many factors can only be qualitatively analyzed and judged, it is difficult to make quantitative analysis, which needs to be comprehensively analyzed according to the actual production situation and the results of qualitative analysis, so as to obtain reasonable parameters to guide the field production in order to reduce the production cost and achieve the purpose of energy saving and consumption reduction.

Active lime is produced from limestone dolomite chalk and other minerals with high calcium carbonate content by the calcination process under the temperature of 1000-1100 C. There are various processes for the active lime production mainly

how to improve ball mill grinding

how to improve ball mill grinding

Functional performance analysis of ball milling has been described previously by Mclvor. Coarse versus fine or product particle cut-off size is first selected, usually equal to some benchmark passing size of the circuit product (e.g., 80%). The function of the grinding circuit is to generate new product size material (or fines) from coarse particles in the circuit feed as efficiently as possible. Because all breakage takes place inside the mill, it can be stated that the production rate of fines of the circuit (PR circ) is equal to the energy being (effectively) applied to the coarse particles (E effec) multiplied by the energy specific grinding rate of coarse particles in the mill (GR co). This process is represented by Equation 1.

The effective energy, i.e., that portion being applied to the coarse particles, is the total rate that energy is consumed by the mill (E tot) multiplied by the fraction (or percent) of the mill inventory of coarse versus fine material. Since the mill coarse solids inventory quantifies the circuits ability to sort and present the desired (i.e., coarse) particles for breakage (McIvor, 1988b), it may also be termed the circuit classification system efficiency (CS eff).

We can also multiply and divide the last term of the above equation by the grindability (G lab) of the coarse material as measured in a standard laboratory procedure and reported, for example, in grams per revolution.

The reason for doing this is that the third term in the above equation now is the ratio of the grinding rates of the plant mill versus a standard laboratory mill on the same coarse material which, therefore, is also a measure of the relative efficiency of the two grinding environments. Since the laboratory equipment and procedure is standardized (i.e., constant) for all circuit surveys, this term represents the grinding efficiency of the environment of the plant mill (GM eff).

This simple equation elegantly demonstrates that circuit production rate of fines is directly related to two inputs, energy and material grindability, and two distinct operational efficiencies, one due to the classification system and the other due to the mill grinding environment.

It also presents an excellent means of strategizing circuit improvements to increase production rate, for example, by increasing energy input (the mill power draw); by adjusting the classification system performance through pump and cyclone modifications; or, by improving the efficiency of the grinding mill environment through the media sizing, percent solids, liner design, etc.

The utility of functional performance analysis thus lies in its ability to relate circuit design and operating variables to classification, size reduction, and overall grinding circuit efficiencies using data readily obtained from plant experiments (McIvor, 1988a).

5 ways to improve grinding efficiency of ball mills - news step systems - a step to explore the world

5 ways to improve grinding efficiency of ball mills - news step systems - a step to explore the world

According to Bond (1954), the grinding efficiency of a mill depends on the ball mill diameter, size of the media and mill speed. Ball mills with different length to diameter ratios for a particular power rating will produce different material retention times. The longer units are used for high retention ratios while shorter units are used where overgrinding is a factor to be considered.

Closely related to media and material retention is the discharge arrangement. According to Mokken (1978), the faster the pulp is removed, the better. This is evidenced by the evolution trend from grates with pulp lifters, to peripheral and eventually to open discharge design.

With increasing popularity in the use of coarse ball milling, it is becoming increasingly critical to offer an appropriate feed material top-size to the mill. A considerable amount of inefficiencies are introduced due to the need for bigger (and thus fewer) grinding balls. Also, because ball mill performance is closely related to complete size distribution of the feed materials, all the previous stages of classification and grinding the materials into smaller sizes which would eventually influence feed size distribution will ultimately affect the grinding efficiency of the ball mill.

Another factor that affects ball mill cement grinding efficiency and effectiveness as it relates to a specific material size distribution is the circulating load. It has been observed with increased circulating load and classifier efficiency; there is an increase in the grinding efficiency. When the circulating load is increased, it results in a reduction in overgrinding, and it offers the media a more effective size distribution with which to work on. However, at a point, diminishing returns would set in, and limitations would set in due to material handling and the classifying requirements.

The feed of the ball mill, in most cases, is made up of several constituents, apart from the ore itself. The most common of these constituents is water which shows a wide spectrum of effects on the ball mill grinding process, based on the nature of the material itself and the number of solids in it.

In most cases, dry grinding may take up to 10-50% more power, compared to wet grinding. This is however offset by the severely reduced liner and media consumption. Addition of moisture without introducing heated gas can completely stop the grinding of fine materials. When more water is added, it carries it through this sticky phase to the standard wet grinding phase of 60-80% solids by weight.

At this point, optimum water content for efficient grinding would have been attained depending on the total effects of some prevailing conditions like pulp viscosity, physical design parameters of the mill, material transport characteristics, mill retention time and the internal friction and filling of the interstices of the charge.

It is common practice to match the material size distribution and the most effective media size distribution. This would involve the media top selection size and the graded ball recharging as well. The principle applied here is that larger balls are suitable for coarse grinding while smaller balls are suited for fine grinding. This same principle is applied in ball mill cement grinding either with the use of division head, classifying liners or ox.

Choosing grinding ball material is usually based on cost-effectiveness as regards material consumption. There are however reports that increase in the specific gravity and surface hardness had resulted in significant improvement in the use of grinding energy.

With just a few exceptions, a grinding circuit would contend with changes in the feed characteristics that would result in the prevalent operating conditions to consistently shift away from what is desired. As a result of the frequency of these digressions, the response time, as well as the reliability of the operator, automatic control systems, have been applied with reports indicating as much as 15% improvement in energy efficiency.

Broadly speaking, the mechanism of grinding in a ball mill can be classified into impact or attrition, with each type accounting for at least two forms of breakages. Impact breakage may be due to the particle being crushed between the balls or between a ball and the lining of the mill. It also includes slow compression fracturing or the crushing of the particle between grinding media.

Attrition grinding, on the other hand, includes surface removal of grains by a rubbing action, abrasion and chipping off of pieces by those forces which did not break the full particle. Attrition leads to the production of a smaller daughter particle as wells as the bigger parent particle.

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exploring ball size distribution in coal grinding mills - sciencedirect

exploring ball size distribution in coal grinding mills - sciencedirect

BSD affects milling efficiency.Ball top up policy in turn affects BSD.Wear rate models can predict BSD for a given top up policy.Fine BSD generally enhances milling rate for uncontaminated coal feed.

Tube mills use steel balls as grinding media. Due to wear in the abrasive environment it is necessary to charge new balls periodically to maintain a steady balanced ball charge in the mill. The amount and ball size distribution in this charge, as well as the frequency with which new balls are added to the mill, have significant effects on the mill capacity and the milling efficiency. Small balls are effective in grinding fine particles in the load, whereas large balls are required to deal with large particles of coal or stone contaminant. The steady state ball size distribution in the mill depends on the top-up policy.

The effect of the ball size distribution on the milling rate of coal has been measured as a function of ball size distribution. The change in ball size distribution as affected by wear and ball top-up policy has been modelled. From this a best ball top-up policy can be recommended that will ensure a close approximation to the desired steady-state ball size distribution that gives the required PF size distribution for the selected mill demand.

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