It can be used to determine the grinding power required for a given throughput of material under ball mill. Bond ball mill index test brmwi a bond ball mill index test bbmwi is a standard test for determining the ball mill work index of a sample of ore. Results table i shows the bond ball mill work index obtained for the ore samples as well as the iron and silica content in concentrate and tail after lims. The load parameter inside a ball mill directly impacts the stability of production process, the grinding. Often, the ball used in ball mills is oversize just in case.
Ball mills are steel or ceramic jars in lab size mills or cylinders. A method to determine the ball filling, in miduk copper. The material grinding occurs during impact falling grinding balls and abrasion the particles between the balls. Ball mill designpower calculation 911 metallurgist. Dm mill with only singlesized balls and not a mixture without consideration for ball wear.
A material grinding process in ball drum mills is executed by grinding. How to calculate ball mill grinding media filling degree. By the 1970s, the application of conventional tended to be limited to relatively low capacities. The operating principle of the ball mill primo pizza. The ball size factor, f b, is added to the mall shaft power for mill sizes greater than 3. These parameters are thoroughly studied in 4, 5 and an empirical relation is suggested expressing the mill capacity as a ratio of the mill shaft power and the energy consumed in the grinding process. Rod mill power is dependent on mill capacity and work index. Additional power is required to keep the mill rotating.
The diameter of the gibbsite powder was measured using a master sizer 2000 sysmex corporation. Optimization of mill performance by using online ball and pulp measurements soon after a stop, a mill is a dangerous place to enter for the personnel tasked with taking measurements or samples. The operating principle of the ball mill consists of following steps. A multicompartment ball mill consists of two or more grate discharge ball mills in series.
A method of c alculating autogenous semiautogenous grinding. In this case the mill is operated with the feed turned off until all of the ore has exited the mill. To accelerate the math or calculation you can use the shortened formula. Rowland and kjos 1980 provided an expression to quantify power draw at the pinion shaft per unit mass of rods. Comparison of the ball mill power draw from the denver slide rule and the proposed model. Calculation of energy required for grinding in a ball mill. Calculation of the power draw of dry multicompartment ball mills. The basic parameters used in ball mill design power calculations, rod mill or any tumbling mill sizing are. None of the characteristics of the material being ground have any influence on k 1. The phantom cyclone is used to classify the agsag mill product into two products. The production capacity of the ball mill is determined by the amount of material required to be ground, and it must have a certain margin when designing and selecting.
So direct measurement must be taken for calculation of mill load. Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. Design method of ball mill by sumitomo chemical co. Effects of fins on ball motion in the mill to predict ball mill grinding behavior using the dis. Using plant data, the value of e is the specific energy input to the solid material as it passes through the plant mill the mill power draw divided by the mill solids throughput rate, and assumes plug. The following shows how the size or select the matching mill required to draw this power is. Calculation of the power draw of dry multicompartment ball mills 225 the mill load that is the volume of charge in the mill is the principal determinant of power draw. Accurate measurements of the ball filling can only be made after the mill is ground out. Calculate and select ball mill ball size for optimum grinding here is your ball mill designsizing procedure calculation of top size grinding media fred c bond calculation of top size grinding media azzaronis formula i attach fred bonds first empirical equ. A method of c alculating autogenous semiautogenous.
Figure 7 shows an example of the balls in a mill after a. A ball mill is a type of grinder used to grind, blend and sometimes for mixing of materials for use in mineral dressing processes, paints, pyrotechnics, ceramics and selective laser sintering. The ball impact energy on grain is proportional to the ball diameter to the third power. They are usually lined with a nonmetallic liner such as ceramics to avoid metallic contamination of the millbase.
Morrell 1996 proposed a mathematical model for autogenous, semiautogenous and ball mills which is based on the motion of grinding charge inside the mill. Measurements of the ball level within the mill can then be made. In cement plant and power plant, ball mills remain in current and widespread use. Pdf a comparison of wear rates of ball mill grinding media.
This is the rotational speed where balls will not fall away from the mill s shell. Run the ball mill for 40 minutes at the speed 1 rpm. Calculator for rod mill s as first stage of the circuit and ball mill s as second stage of the. Mills are mounted horizontally and are partially filled with natural pebbles, steel or ceramic balls, or cylinders. Axis of the shell horizontal or at small angle to the horizontal it is partially filled with balls made up of steel,stainless steel or rubber inner surface of the shell is lined with abrasion resistant materials such as manganese,steel or rubber length of the mill is. The calculation of ball mill energy efficiency mode. The power consumption calculation of a ball drum mill idosi. Also, the plotted rod mill p80 value, as shown in figure 1, is 2900. There are many factors affecting the production capacity of the ball mill, in addition to the nature of the material grain size, hardness, density, temperature and humidity, the degree of. Apr 24, 2015 ball mill consist of a hollow cylindrical shell rotating about its axis. Application of operating work indices in autogenous.
The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight. The mill and all feed streams should be stopped simultaneously but, often, they are stopped around about the same time. Common equations for optimal performance too high of a speed or too light of a feed leads to reduction in tool life. In the tables below, the relationship of peripheral speed to the diameter of the tool, and the rotational speed of the.
Speed is measured in feet per minute and is referred to as cutting speed, surface speed, or peripheral speed. A significant shortcoming of these mills is high specific energy consumption on grinding. The power supplied to the mill is used primarily to lift the load medium and charge. Well, this safety factor can cost you much in recovery andor mill liner wear and. If above calculation were done again for b 2%, total ball abrasion will get 60. Determining energy cost for milling solid matter in a ball mill core. A ball mill consists of a hollow cylindrical shell rotati.
Relationships between comminution j energy and product size. A comparison of wear rates of ball mill grinding media. The ball mill motor power requirement calculated above as 1400 hp is the power that must be applied at the mill drive in order to grind the tonnage of feed from one size distribution. In grinding, selecting calculate the correct or optimum ball size that allows for the best and optimumideal or target grind size to be achieved by your ball mill is an important thing for a mineral processing engineer aka metallurgist to do. The same equation is used to calculate the power that. Therefore, in practice we can expect some difficulties and errors when the energy consumption is determined according to this formula in the case when, for a. The ball loads within the mills were measured by different methods proposed in the literature and power draw of each mill were calculated. Please find below two calculators for sizing mills using the bond and rowland methods. Bond ball mill is a small universal laboratory mill used in calculating the. Details of the experimental conditions are given in table 2. Design method of ball mill by discrete element method collected.
Ball mill power draw predicted from the denver slide rule, kw 0 200 400 600 calculated ball mill power draw from the m odel derived, kw data compared line yx fig. These parameters are thoroughly studied in 4, 5 and an empirical relation is suggested expressing the mill capacity as a ratio of the mill shaft power and. Calculator for ball mill s in a single stage circuit. The grindingproduct size, p, in a bond ball mill, which is given by the aperture size which passes 80% of the grinding product as a function of the aperture size of the test screen p k, can be expressed by the formula p p k k 2. Ball mill calculation formulas infinity for cement equipment. A ball mill, a type of grinder, is a cylindrical device used in grinding or mixing materials like ores, chemicals, ceramic raw materials and paints. Calculator for rod mills as first stage of the circuit and ball mills as second stage of the circuit. Relationships between comminution j energy and product. Dec 12, 2016 ball mill power calculation example a wet grinding ball mill in closed circuit is to be fed 100 tph of a material with a work index of 15 and a size distribution of 80% passing. For all model based methods, a reliable method to calculate mill power draw for a given mill is required for the calculation of power draw. Ball mill power calculation example a wet grinding ball mill in closed circuit is to be fed 100 tph of a material with a work index of 15 and a size distribution of 80% passing. Fill the lime stone powder to new set of sieves of small sizes. In a continuously operating ball mill, feed material fed through the central hole one of the caps into the drum and moves therealong, being exposed by grinding media.
Central drive ball mill torque and power calculation pdf. Calculation of ball mill grinding efficiency page 1 of 1. The critical speed for a grinding mill is defined as the rotational speed where centrifugal forces equal gravitational forces at the mill shells inside surface. Calculator for ball mills in a single stage circuit. After 40 minutes take out lime stone powder from the ball mill. None of the characteristics of the material being ground have any. Load lime stone to the ball mill along with metal balls. This is the rotational speed where balls will not fall away from the mills shell. The following shows how the size or select the matching mill required to draw this power is calculated from known tables the old fashion way. To calculate grinding media charge for continuous type ball mill, m 0. Technical notes 8 grinding rp king mineral technologies. Ball mill torque and power rating calculations pdf home ball mill torque and power rating calculations pdf calculation of power at ball mill drive rating ofr1 ball read more measurements of the losses are mill runs with a torquefree dummyload accurately centered in the com calculate horse power of a ball mill. Calculate and select ball mill ball size for optimum grinding.
Estimation of the ball load that is mixed with the cement charge is difficult and can be highly erroneous. Jun 27, 2017 deals with two most important topics of food engineering namely ball mill and sphericity. Calculation of circulating load of a grinding mill pdf. Throughout the batch grinding tests, the power draw of the mill was measured using a purpose built power meter to facilitate the calculation of specific grinding energy. The bbmwi is a measure of the resistance of the material to crushing and grinding.
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