ball mill machine particle size

what's the difference between sag mill and ball mill - jxsc machine

A mill is a grinder used to grind and blend solid or hard materials into smaller pieces by means of shear, impact and compression methods. Grinding mill machine is an essential part of many industrial processes, there are mainly five types of mills to cover more than 90% materials size-reduction applications.

Do you the difference between the ball mill, rod mills, SAG mill, tube mill, pebble mill? In the previous article, I made a comparison of ball mill and rod mill. Today, we will learn about the difference between SAG mill vs ball mill.

AG/SAG is short for autogenous mill and semi-autogenous mill, it combines with two functions of crushing and grinding, uses the ground material itself as the grinding media, through the mutual impact and grinding action to gradually reduce the material size. SAG mill is usually used to grind large pieces into small pieces, especially for the pre-processing of grinding circuits, thus also known as primary stage grinding machine. Based on the high throughput and coarse grind, AG mills produce coarse grinds often classify mill discharge with screens and trommel. SAG mills grinding media includes some large and hard rocks, filled rate of 9% 20%. SAG mill grind ores through impact, attrition, abrasion forces. In practice, for a given ore and equal processing conditions, the AG milling has a finer grind than SAG mills.

The working principle of the self-grinding machine is basically the same as the ball mill, the biggest difference is that the sag grinding machine uses the crushed material inside the cylinder as the grinding medium, the material constantly impacts and grinding to gradually pulverize. Sometimes, in order to improve the processing capacity of the mill, a small amount of steel balls be added appropriately, usually occupying 2-3% of the volume of the mill (that is semi-autogenous grinding).

High capacity Ability to grind multiple types of ore in various circuit configurations, reduces the complexity of maintenance and coordination. Compared with the traditional tumbling mill, the autogenous mill reduces the consumption of lining plates and grinding media, thus have a lower operation cost. The self-grinding machine can grind the material to 0.074mm in one time, and its content accounts for 20% ~ 50% of the total amount of the product. Grinding ratio can reach 4000 ~ 5000, more than ten times higher than ball, rod mill.

Ball mills are fine grinders, have horizontal ball mill and vertical ball mill, their cylinders are partially filled with steel balls, manganese balls, or ceramic balls. The material is ground to the required fineness by rotating the cylinder causing friction and impact. The internal machinery of the ball mill grinds the material into powder and continues to rotate if extremely high precision and precision is required.

The ball mill can be applied in the cement production plants, mineral processing plants and where the fine grinding of raw material is required. From the volume, the ball mill divide into industrial ball mill and laboratory use the small ball mill, sample grinding test. In addition, these mills also play an important role in cold welding, alloy production, and thermal power plant power production.

The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mills crushing ratio is smaller. The feed size is usually between 20-30mm and the product size is 0-3mm.

Both the autogenous grinding mill and the ball mill feed parts are welded with groove and embedded inner wear-resistant lining plate. As the sag mill does not contain grinding medium, the abrasion and impact on the equipment are relatively small.

The feed of the ball mill contains grinding balls. In order to effectively reduce the direct impact of materials on the ball mill feed bushing and improve the service life of the ball mill feed bushing, the feeding point of the groove in the feeding part of the ball mill must be as close to the side of the mill barrel as possible. And because the ball mill feed grain size is larger, ball mill feeding groove must have a larger slope and height, so that feed smooth.

Since the power of the autogenous tumbling mill is relatively small, it is appropriate to choose dynamic and static pressure bearing. The ball bearing liner is made of lead-based bearing alloy, and the back of the bearing is formed with a waist drum to form a contact centering structure, with the advantages of flexible movement. The bearing housing is lubricated by high pressure during start-up and stop-up, and the oil film is formed by static pressure. The journal is lifted up to prevent dry friction on the sliding surface, and the starting energy moment is reduced. The bearing lining is provided with a snake-shaped cooling water pipe, which can supply cooling water when necessary to reduce the temperature of the bearing bush. The cooling water pipe is made of red copper which has certain corrosion resistance.

Ball mill power is relatively large, the appropriate choice of hydrostatic sliding bearing. The main bearing bush is lined with babbitt alloy bush, each bush has two high-pressure oil chambers, high-pressure oil has been supplied to the oil chamber before and during the operation of the mill, the high-pressure oil enters the oil chamber through the shunting motor, and the static pressure oil film is compensated automatically to ensure the same oil film thickness To provide a continuous static pressure oil film for mill operation, to ensure that the journal and the bearing Bush are completely out of contact, thus greatly reducing the mill start-up load, and can reduce the impact on the mill transmission part, but also can avoid the abrasion of the bearing Bush, the service life of the bearing Bush is prolonged. The pressure indication of the high pressure oil circuit can be used to reflect the load of the mill indirectly. When the mill stops running, the high pressure oil will float the Journal, and the Journal will stop gradually in the bush, so that the Bush will not be abraded. Each main bearing is equipped with two temperature probe, dynamic monitoring of the bearing Bush temperature, when the temperature is greater than the specified temperature value, it can automatically alarm and stop grinding. In order to compensate for the change of the mill length due to temperature, there is a gap between the hollow journal at the feeding end and the bearing Bush width, which allows the journal to move axially on the bearing Bush. The two ends of the main bearing are sealed in an annular way and filled with grease through the lubricating oil pipe to prevent the leakage of the lubricating oil and the entry of dust.

The end cover of the autogenous mill is made of steel plate and welded into one body; the structure is simple, but the rigidity and strength are low; the liner of the autogenous mill is made of high manganese steel.

The end cover and the hollow shaft can be made into an integral or split type according to the actual situation of the project. No matter the integral or split type structure, the end cover and the hollow shaft are all made of Casting After rough machining, the key parts are detected by ultrasonic, and after finishing, the surface is detected by magnetic particle. The surface of the hollow shaft journal is Polished after machining. The end cover and the cylinder body are all connected by high-strength bolts. Strict process measures to control the machining accuracy of the joint surface stop, to ensure reliable connection and the concentricity of the two end journal after final assembly. According to the actual situation of the project, the cylinder can be made as a whole or divided, with a flanged connection and stop positioning. All welds are penetration welds, and all welds are inspected by ultrasonic nondestructive testing After welding, the whole Shell is returned to the furnace for tempering stress relief treatment, and after heat treatment, the shell surface is shot-peened. The lining plate of the ball mill is usually made of alloy material.

The transmission part comprises a gear and a gear, a gear housing, a gear housing and an accessory thereof. The big gear of the transmission part of the self-grinding machine fits on the hollow shaft of the discharge material, which is smaller in size, but the seal of the gear cover is not good, and the ore slurry easily enters the hollow shaft of the discharge material, causing the hollow shaft to wear.

The big gear of the ball mill fits on the mill shell, the size is bigger, the big gear is divided into half structure, the radial and axial run-out of the big gear are controlled within the national standard, the aging treatment is up to the standard, and the stress and deformation after processing are prevented. The big gear seal adopts the radial seal and the reinforced big gear shield. It is welded and manufactured in the workshop. The geometric size is controlled, the deformation is prevented and the sealing effect is ensured. The small gear transmission device adopts the cast iron base, the bearing base and the bearing cap are processed at the same time to reduce the vibration in operation. Large and small gear lubrication: The use of spray lubrication device timing quantitative forced spray lubrication, automatic control, no manual operation. The gear cover is welded by profile steel and high-quality steel plate. In order to enhance the stiffness of the gear cover, the finite element analysis is carried out, and the supporting structure is added in the weak part according to the analysis results.

The self-mill adopts the self-return device to realize the discharge of the mill. The self-returning device is located in the revolving part of the mill, and the material forms a self-circulation in the revolving part of the mill through the self-returning device, discharging the qualified material from the mill, leading the unqualified material back into the revolving part to participate in the grinding operation.

The ball mill adopts a discharge screen similar to the ball mill, and the function of blocking the internal medium of the overflow ball mill is accomplished inside the rotary part of the ball mill. The discharge screen is only responsible for forcing out a small amount of the medium that overflows into the discharge screen through the internal welding reverse spiral, to achieve forced discharge mill.

The slow drive consists of a brake motor, a coupling, a planetary reducer and a claw-type clutch. The device is connected to a pinion shaft and is used for mill maintenance and replacement of liners. In addition, after the mill is shut down for a long time, the slow-speed transmission device before starting the main motor can eliminate the eccentric load of the steel ball, loosen the consolidation of the steel ball and materials, ensure safe start, avoid overloading of the air clutch, and play a protective role. The slow-speed transmission device can realize the point-to-point reverse in the electronic control design. When connecting the main motor drive, the claw-type Clutch automatically disengages, the maintenance personnel should pay attention to the safety.

The slow drive device of the ball mill is provided with a rack and pinion structure, and the operating handle is moved to the side away from the cylinder body The utility model not only reduces the labor intensity but also ensures the safety of the operators.

ball mill: operating principles, components, uses, advantages and

A ball mill also known as pebble mill or tumbling mill is a milling machine that consists of a hallow cylinder containing balls; mounted on a metallic frame such that it can be rotated along its longitudinal axis. The balls which could be of different diameter occupy 30 50 % of the mill volume and its size depends on the feed and mill size. The large balls tend to break down the coarse feed materials and the smaller balls help to form fine product by reducing void spaces between the balls. Ball mills grind material by impact and attrition.

Several types of ball mills exist. They differ to an extent in their operating principle. They also differ in their maximum capacity of the milling vessel, ranging from 0.010 liters for planetary ball mills, mixer mills, or vibration ball mills to several 100 liters for horizontal rolling ball mills.

Im grateful for the information about using a ball mill for pharmaceutical products as it produces very fine powder. My friend is working for a pharmaceutical company and this is a good article to share with her. Its good to know that ball mills are suitable for milling toxic materials since they can be used in a completely enclosed for. Thanks for the tips!

what particle size range does ball mill grinding produce?

Ball Mill The ball mill has been around for eons. There are many shapes and sizes and types. There is a single enclosed drum-type where material is placed in the drum along with a charge of grinding media. These can be in various shapes, and typically they are balls. There is a whole science in the size of the starting material versus the ball size, shape material of construction and charge percentage of grinding media. All of these variables affect particle size, shape, and grinding efficiency. This type of grinding is very good for abrasive materials to prevent contamination. The grinding media as well as the interior surfaces of the mill can be lined with abrasion resistant materials suited to the material being ground. In some cases, it can even be the material being ground. However, the batch type system is not a very efficient means of grinding. There is a variety of ball mill that is a continuous process versus a batch process. It has an external classifier which returns the oversized material to the ball mill for further milling. This system is much more efficient in the grinding ability, but it is much more difficult to line the entire system with wear parts to grind an abrasive material.

Ball mill grinding is one method of crushing ore to an appropriate size fraction.Specifically, ore is put into a large receptacle (a drum) and then it rotates slowly around.Inside the receptacle, there are balls, usually made of metal, that as the ore is rotated around the revolving drum the ore is crushed as the balls rise and fall.The drum has a slight tilt to it, from one end to the other so that the ore slowly works its way to discharging end.The trick or art to all of this is to rotate the drum at a distinct rpm and the balls are harder than the ore so as to efficiently crush the continuous stream of ore to the desired size at the discharge end.

The ball mill is a key piece of equipment for grinding crushed materials, and it is widely used in production lines for powders such as cement, silicates, refractory material, fertilizer, glass ceramics, etc. as well as for ore dressing of both ferrous and non-ferrous metals. The ball mill can grind various ores and other materials either wet or dry. There are two kinds of ball mill, grate type and overfall type due to different ways of discharging material. There are many types of grinding media suitable for use in a ball mill, each material having its own specific properties and advantages. Key properties of grinding media are size, density, hardness, and composition.

The grinding chamber can also be filled with an inertshield gasthat does not react with the material being ground, to prevent oxidation or explosive reactions that could occur with ambient air inside the mill.

how to size a ball mill -design calculator & formula

A) Total Apparent Volumetric Charge Filling including balls and excess slurry on top of the ball charge, plus the interstitial voids in between the balls expressed as a percentage of the net internal mill volume (inside liners).

B) Overflow Discharge Mills operating at low ball fillings slurry may accumulate on top of the ball charge; causing, the Total Charge Filling Level to be higher than the Ball Filling Level. Grate Discharge mills will not face this issue.

C) This value represents the Volumetric Fractional Filling of the Voids in between the balls by the retained slurry in the mill charge. As defined, this value should never exceed 100%, but in some cases particularly in Grate Discharge Mills it could be lower than 100%. Note that this interstitial slurry does not include the overfilling slurry derived from the difference between the Charge and Ball Filling.

D) Represents the so-called Dynamic Angle of Repose (or Lift Angle) adopted during steady operation by the top surface of the mill charge (the kidney) with respect to the horizontal. A reasonable default value for this angle is 32, but may be easily tuned to specific applications against any available actual power data.

The first step in mill design is to determine the power needed to produce the desired grind in the chosen ore. The most used equation, for this purpose, is the empirical Bond equation (Bond, 1960, 1961; Rowland and Kjos, 1978).

In this equation, E is the specific energy required for the grind, and F80 and P80 are the sizes in micrometers that 80% of the weight passes of the mill feed and product respectively. The parameter Wi, known as the work index of the ore, is obtained from batch bench tests first devised by Bond (1961). The power calculated on using equation 1, (Bond, 1961; Rowland and Kjos, 1978), relates to:

1) Rod milling a rod mill with a diameter of 2.44 meters, inside new liners, grinding wet in open circuit. 2) Ball milling a ball mill with a diameter of 2.44 meters, inside new liners, grinding wet in open circuit.

When the grinding conditions differ from these specified conditions, efficiency factors (Rowland and Kjos, 1978) have to be used in conjunction with equation 1. In general, therefore, the required mill power is calculated using the following equation

where n is the number of efficiency factors, EFi, used and fo is the feed rate of new ore to the mill. The power calculated from equation 2 can be looked up in published tables (Rowland and Kjos, 1978) and the correct mill size and type can be selected.

The philosophy in the development of the MRRC grinding simulation package was to build interactive software that could be used as an inexpensive means of providing a semi-quantitative check on a grinding mill design. In addition the software is designed to slot in to a general mineral processing package now undergoing development at the MRRC.

particle size distribution of grinding mill products

Size analyses of mineral products are usually made by screening with a set of sieves having mean apertures arranged in the Tyler scale, which is a geometric progression with a constant ratio equal to the square root of two. For this reason it is convenient to represent particle size as a logarithmic function of the particle diameter

The variable, x, may be defined as the logarithm to the base s of the ratio of the particle diameter to the reference diameter, d. The inverse of the transformation given in equation 1 is given by equation 2:

where yi is the weight fraction in the size interval between xi-l and xi; N is the total number of size intervals. If the reference diameter is equal to the maximum sieve aperture represented in the screen analysis and this is taken as the axis for the first moment, xo is zero and the first moment is the value of x corresponding to the mean particle size:

These higher moments contain the essential information concerning the form of the distribution function; that is, they are parameters that measure various aspects of the way in which the weight fraction is distributed about the mean. The second moment, or variance, measures the width of the distribution; the third moment measures the skewness or asymmetry; the fourth moment measures the kurtosis or peakedness; etc. Obviously, higher moments are increasingly dependent on values of the weight fraction remote from the mean which represent only a small fraction of the sample. For this reason, moments beyond the fourth are usually not considered. The third and fourth moments are usually represented as dimensionless ratios with respect to the second moment:

Moment analysis is a well-established method for analyzing and characterizing statistical distribution. Quoting from one of the standard treatises in mathematical statistics: For all ordinary purposes, therefore, a knowledge of the moments, when they exist, is equivalent to a knowledge of the distribution function: equivalent, that is, in the sense that it should be possible theoretically to exhibit all the properties of the distribution in terms of the moments.The procedures that have been developed for computation of moments and deriving distribution functions that best fit the data are fully discussed in a book by Elderton which has recently been published in a new edition. The application of moment analyses to particle size distribution data is discussed in a previous paper by the author.

When uniform sized samples of cryptocrystalline quartz were crushed by impact in a drop-weight machine, the reduction in size, as measured by the change in the mean value of x, was found to follow the relationship in equations 8 and 9

Equation 8 is an empirical relationship derived by multiple regression analyses of various combinations of independent variables from the data on the impact crushing experiments. The logarithms of E, the impact energy per unit weight of mineral, and d0, the initial mean particle diameter, gave the greatest decrease in variance between the observed and expected values. The threshold energy, Eo, which is the energy corresponding to zero size reduction, varies approximately inversely as the diameter of the particle being crushed.

Analyses of other data obtained by Hukki, using a double pendulum apparatus for impact crushing, gave slightly larger values for the coefficients in equations 8 and 9 and the exponent of do was slightly larger than one. If the exponent of do is assumed to be unity, the equation derived for the combined data from the Hukki and Bureau of Mines experiments gives the equations 10 and 11

These equations represent a best fit of data from 39 experiments on impact crushing of quartz particles ranging in size from .156 to 5.75 cm in diameter. The standard error for x is .387 as compared with 1.192 for the observed data.

The form of the distribution curve was found to be primarily a function of the size reduction. The distribution function of the initial uniform sample is a delta function. As soon as any size reduction occurs, there is a transfer of material to a wide range of sizes thereby increasing the dispersion. The change in distribution is asymetric since crushing transfers material only to the finer sizes, and so the skewness, as measured by 1, initially has a very large value. In other words, as a uniform sample is progressively decreased in size, there is a progressive increase in dispersion as measured by 2 and a decrease in skewness as measured by 1.

These changes are shown in Figure 1 which depicts the changes in distribution that occur in size distribution when quartz samples are subjected to increasing impact energy. As size reduction proceeds, the effect of the initial uniform distribution is gradually obliterated and both ant! tend to approach steady values. The variance tends to approach a steady value of 18 which corresponds to a standard deviation of 4.25 or a little more than four intervals in the Tyler sieve scale. The skewness levels off at a value between 1.6 and 1.8.

The manner in which energy is employed in a ball mill to effect size reduction is much more complex than in simple impact crushing. The application of energy in a drop-weight machine is similar to that occurring in a stamp mill, in which a considerable size reduction is produced by a single impact of relatively high energy input. In a tumbling mill, such as a ball mill, the size reduction occurs by repeated application of kinetic energy of less intensity by impact and rolling action of a large number of crushing media, in certain circumstances an appreciable amount of size reduction may occur by abrasion.

A series of studies has been made at the University of California in Berkeley on the grinding of dolomite in a ball mill. These tests were made in a specially designed mill in which the input energy can be measured.

A series of impact crushing experiments was made on a sample of the same dolomite used by Berlioz. The results of those experiments are summarized in Table 1. The results of these experiments permit comparison of the size reduction by impact and by ball mill grinding for the same energy input. Differences in the behavior of the particle size distribution may also be observed.

A comparison of the size reduction by impact and ball mill grinding is shown in figure 2. The ball mill experiments show the size reduction versus energy input for 7 series of experiments in which the weight of dolomite was 660, 1320, 1980, 2640, 3300, 3960, and 5420, respectively. The charge was composed of equal portions of -7 +8 and -8 +10 size fractions. The ball load was 455 stainless steel balls one inch in diameter, having a total weight of 30 kg. The particle size distribution was observed after 20, 40, 60, 80, 100, 150, 200 and 300 ball mill revolutions. The energy input was calculated from the net torque (corrected for the torque for the empty mill) and the number of revolutions.

For light ball loads the ball mill is less efficient as might be expected. As the load exceeds 1980 gm it has no influence on size reduction. The relationship between size reduction and input for optimum grinding in the ball mill is represented by the solid curve. The corresponding relationship for crushing by impact is represented by broken lines.

It is evident, as might be expected, that for moderate size reduction (x<5) the input energy is utilized much more effectively in the drop-weight machine than in the ball mill. For example, reduction to one-half of the original particle size requires about 4-3 kg cm per gm by impact as compared to 18.5 kg-cm by ball mill; that is, the energy requirements are less than 25 percent as much for impact crushing as for ball milling. For great size reduction the application of energy by a single impact becomes less effective so that there would be no advantage in applying more impact energy than would be required for about a four-fold reduction of particle diameter; this is equivalent to x = k. The energy required would be about percent that required for an equivalent size reduction in the ball mill.

The change in particle size distribution during ball milling is shown by the graphs of the variance and skewness in Figure 3. Here again, the points representing variance for those experiments with light ball mill loads show a noticeable divergence from those for optimum loading. The skewness is not affected by the load.

The differences in distribution between the products from the ball mill and those from impact crushing can be observed by comparing the solid lines, which represent the ball mill products, with the broken lines, which represent the products from the drop-weight experiments. The greatest difference is in the variance. The products from the ball mill show considerably greater dispersion over the size range and this dispersion develops sooner as the mean size is decreased. On the other hand, the skewness decreases earliest for impact crushing. The differences in size distribution are essentially difference in degree of dispersion and asymmetry. Actually there is a surprising similarity in the evolution of the distribution from uniform particle size to a typical skewed bell-shaped curve as the size is reduced whether by the ball mill or impact crushing.

The comminution process may be represented mathematically in terms of a set of state variables that define the mean size and size distribution of the feed to and product from a grinding machine. Three variables are required to specify the particulate state of the mineral undergoing size reduction; these variables define quantitatively the mean particle size, degree of dispersion and asymmetry of the distribution. Such a set of variables may be calculated by moment analysis of the screen analysis of the aggregate being studied. Conversely, if the mean, variance, and skewness of a size distribution are known, a gamma distribution function may be derived that will approximate the weight fraction in any given size range.

When a sized fraction of particles is subjected to comminution, the size distribution undergoes progressive change characterized by a steady increase in the variance or second moment and an abrupt decrease in skewness or third moment. As size reduction proceeds further, both the variance and skewness approach steady values and the form of the distribution becomes more and more stable.

effect of ball and feed particle size distribution on the milling efficiency of a ball mill: an attainable region approach - sciencedirect

In this article, alternative forms of optimizing the milling efficiency of a laboratory scale ball mill by varying the grinding media size distribution and the feed material particle size distribution were investigated. Silica ore was used as the test material. The experimental parameters that were kept constant in this investigation was the grinding media filling, powder filling and the mill rotational speed. The data obtained from these batch tests was then analyzed using a model free technique called the Attainable Region method. This analysis technique showed that the required product fineness is a function of grinding media and feed material size distributions. It was also observed from the experimental results that in order to increase the milling efficiency of a ball mill, towards optimum production of material in the desired size class, there is a need to correlate the ball size and the feed size distributions.

ball mill - an overview | sciencedirect topics

The ball mill accepts the SAG or AG mill product. Ball mills give a controlled final grind and produce flotation feed of a uniform size. Ball mills tumble iron or steel balls with the ore. The balls are initially 510 cm diameter but gradually wear away as grinding of the ore proceeds. The feed to ball mills (dry basis) is typically 75 vol.-% ore and 25% steel.

The ball mill is operated in closed circuit with a particle-size measurement device and size-control cyclones. The cyclones send correct-size material on to flotation and direct oversize material back to the ball mill for further grinding.

Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles, as well as collision energy. These forces are derived from the rotational motion of the balls and movement of particles within the mill and contact zones of colliding balls.

By rotation of the mill body, due to friction between mill wall and balls, the latter rise in the direction of rotation till a helix angle does not exceed the angle of repose, whereupon, the balls roll down. Increasing of rotation rate leads to growth of the centrifugal force and the helix angle increases, correspondingly, till the component of weight strength of balls become larger than the centrifugal force. From this moment the balls are beginning to fall down, describing during falling certain parabolic curves (Figure 2.7). With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls are attached to the wall due to centrifugation:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 6580% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

The degree of filling the mill with balls also influences productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 3035% of its volume.

The mill productivity also depends on many other factors: physical-chemical properties of feed material, filling of the mill by balls and their sizes, armor surface shape, speed of rotation, milling fineness and timely moving off of ground product.

where b.ap is the apparent density of the balls; l is the degree of filling of the mill by balls; n is revolutions per minute; 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.

A feature of ball mills is their high specific energy consumption; a mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, i.e. during grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

The ball mill is a tumbling mill that uses steel balls as the grinding media. The length of the cylindrical shell is usually 11.5 times the shell diameter (Figure 8.11). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, AG mills, or SAG mills.

Ball mills are filled up to 40% with steel balls (with 3080mm diameter), which effectively grind the ore. The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture.

When hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. As mentioned earlier, pebble mills are widely used in the North American taconite iron ore operations. Since the weight of pebbles per unit volume is 3555% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus, in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly a higher capital cost. However, the increase in capital cost is justified economically by a reduction in operating cost attributed to the elimination of steel grinding media.

In general, ball mills can be operated either wet or dry and are capable of producing products in the order of 100m. This represents reduction ratios of as great as 100. Very large tonnages can be ground with these ball mills because they are very effective material handling devices. Ball mills are rated by power rather than capacity. Today, the largest ball mill in operation is 8.53m diameter and 13.41m long with a corresponding motor power of 22MW (Toromocho, private communications).

Planetary ball mills. A planetary ball mill consists of at least one grinding jar, which is arranged eccentrically on a so-called sun wheel. The direction of movement of the sun wheel is opposite to that of the grinding jars according to a fixed ratio. The grinding balls in the grinding jars are subjected to superimposed rotational movements. The jars are moved around their own axis and, in the opposite direction, around the axis of the sun wheel at uniform speed and uniform rotation ratios. The result is that the superimposition of the centrifugal forces changes constantly (Coriolis motion). The grinding balls describe a semicircular movement, separate from the inside wall, and collide with the opposite surface at high impact energy. The difference in speeds produces an interaction between frictional and impact forces, which releases high dynamic energies. The interplay between these forces produces the high and very effective degree of size reduction of the planetary ball mill. Planetary ball mills are smaller than common ball mills, and are mainly used in laboratories for grinding sample material down to very small sizes.

Vibration mill. Twin- and three-tube vibrating mills are driven by an unbalanced drive. The entire filling of the grinding cylinders, which comprises the grinding media and the feed material, constantly receives impulses from the circular vibrations in the body of the mill. The grinding action itself is produced by the rotation of the grinding media in the opposite direction to the driving rotation and by continuous head-on collisions of the grinding media. The residence time of the material contained in the grinding cylinders is determined by the quantity of the flowing material. The residence time can also be influenced by using damming devices. The sample passes through the grinding cylinders in a helical curve and slides down from the inflow to the outflow. The high degree of fineness achieved is the result of this long grinding procedure. Continuous feeding is carried out by vibrating feeders, rotary valves, or conveyor screws. The product is subsequently conveyed either pneumatically or mechanically. They are basically used to homogenize food and feed.

CryoGrinder. As small samples (100 mg or <20 ml) are difficult to recover from a standard mortar and pestle, the CryoGrinder serves as an alternative. The CryoGrinder is a miniature mortar shaped as a small well and a tightly fitting pestle. The CryoGrinder is prechilled, then samples are added to the well and ground by a handheld cordless screwdriver. The homogenization and collection of the sample is highly efficient. In environmental analysis, this system is used when very small samples are available, such as small organisms or organs (brains, hepatopancreas, etc.).

The vibratory ball mill is another kind of high-energy ball mill that is used mainly for preparing amorphous alloys. The vials capacities in the vibratory mills are smaller (about 10 ml in volume) compared to the previous types of mills. In this mill, the charge of the powder and milling tools are agitated in three perpendicular directions (Fig. 1.6) at very high speed, as high as 1200 rpm.

Another type of the vibratory ball mill, which is used at the van der Waals-Zeeman Laboratory, consists of a stainless steel vial with a hardened steel bottom, and a single hardened steel ball of 6 cm in diameter (Fig. 1.7).

The mill is evacuated during milling to a pressure of 106 Torr, in order to avoid reactions with a gas atmosphere.[44] Subsequently, this mill is suitable for mechanical alloying of some special systems that are highly reactive with the surrounding atmosphere, such as rare earth elements.

A ball mill is a relatively simple apparatus in which the motion of the reactor, or of a part of it, induces a series of collisions of balls with each other and with the reactor walls (Suryanarayana, 2001). At each collision, a fraction of the powder inside the reactor is trapped between the colliding surfaces of the milling tools and submitted to a mechanical load at relatively high strain rates (Suryanarayana, 2001). This load generates a local nonhydrostatic mechanical stress at every point of contact between any pair of powder particles. The specific features of the deformation processes induced by these stresses depend on the intensity of the mechanical stresses themselves, on the details of the powder particle arrangement, that is on the topology of the contact network, and on the physical and chemical properties of powders (Martin et al., 2003; Delogu, 2008a). At the end of any given collision event, the powder that has been trapped is remixed with the powder that has not undergone this process. Correspondingly, at any instant in the mechanical processing, the whole powder charge includes fractions of powder that have undergone a different number of collisions.

The individual reactive processes at the perturbed interface between metallic elements are expected to occur on timescales that are, at most, comparable with the collision duration (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b). Therefore, unless the ball mill is characterized by unusually high rates of powder mixing and frequency of collisions, reactive events initiated by local deformation processes at a given collision are not affected by a successive collision. Indeed, the time interval between successive collisions is significantly longer than the time period required by local structural perturbations for full relaxation (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b).

These few considerations suffice to point out the two fundamental features of powder processing by ball milling, which in turn govern the MA processes in ball mills. First, mechanical processing by ball milling is a discrete processing method. Second, it has statistical character. All of this has important consequences for the study of the kinetics of MA processes. The fact that local deformation events are connected to individual collisions suggests that absolute time is not an appropriate reference quantity to describe mechanically induced phase transformations. Such a description should rather be made as a function of the number of collisions (Delogu et al., 2004). A satisfactory description of the MA kinetics must also account for the intrinsic statistical character of powder processing by ball milling. The amount of powder trapped in any given collision, at the end of collision is indeed substantially remixed with the other powder in the reactor. It follows that the same amount, or a fraction of it, could at least in principle be trapped again in the successive collision.

This is undoubtedly a difficult aspect to take into account in a mathematical description of MA kinetics. There are at least two extreme cases to consider. On the one hand, it could be assumed that the powder trapped in a given collision cannot be trapped in the successive one. On the other, it could be assumed that powder mixing is ideal and that the amount of powder trapped at a given collision has the same probability of being processed in the successive collision. Both these cases allow the development of a mathematical model able to describe the relationship between apparent kinetics and individual collision events. However, the latter assumption seems to be more reliable than the former one, at least for commercial mills characterized by relatively complex displacement in the reactor (Manai et al., 2001, 2004).

A further obvious condition for the successful development of a mathematical description of MA processes is the one related to the uniformity of collision regimes. More specifically, it is highly desirable that the powders trapped at impact always experience the same conditions. This requires the control of the ball dynamics inside the reactor, which can be approximately obtained by using a single milling ball and an amount of powder large enough to assure inelastic impact conditions (Manai et al., 2001, 2004; Delogu et al., 2004). In fact, the use of a single milling ball avoids impacts between balls, which have a remarkable disordering effect on the ball dynamics, whereas inelastic impact conditions permit the establishment of regular and periodic ball dynamics (Manai et al., 2001, 2004; Delogu et al., 2004).

All of the above assumptions and observations represent the basis and guidelines for the development of the mathematical model briefly outlined in the following. It has been successfully applied to the case of a Spex Mixer/ Mill mod. 8000, but the same approach can, in principle, be used for other ball mills.

The Planetary ball mills are the most popular mills used in MM, MA, and MD scientific researches for synthesizing almost all of the materials presented in Figure 1.1. In this type of mill, the milling media have considerably high energy, because milling stock and balls come off the inner wall of the vial (milling bowl or vial) and the effective centrifugal force reaches up to 20 times gravitational acceleration.

The centrifugal forces caused by the rotation of the supporting disc and autonomous turning of the vial act on the milling charge (balls and powders). Since the turning directions of the supporting disc and the vial are opposite, the centrifugal forces alternately are synchronized and opposite. Therefore, the milling media and the charged powders alternatively roll on the inner wall of the vial, and are lifted and thrown off across the bowl at high speed, as schematically presented in Figure 2.17.

However, there are some companies in the world who manufacture and sell number of planetary-type ball mills; Fritsch GmbH (www.fritsch-milling.com) and Retsch (http://www.retsch.com) are considered to be the oldest and principal companies in this area.

Fritsch produces different types of planetary ball mills with different capacities and rotation speeds. Perhaps, Fritsch Pulverisette P5 (Figure 2.18(a)) and Fritsch Pulverisette P6 (Figure 2.18(b)) are the most popular models of Fritsch planetary ball mills. A variety of vials and balls made of different materials with different capacities, starting from 80ml up to 500ml, are available for the Fritsch Pulverisette planetary ball mills; these include tempered steel, stainless steel, tungsten carbide, agate, sintered corundum, silicon nitride, and zirconium oxide. Figure 2.19 presents 80ml-tempered steel vial (a) and 500ml-agate vials (b) together with their milling media that are made of the same materials.

Figure 2.18. Photographs of Fritsch planetary-type high-energy ball mill of (a) Pulverisette P5 and (b) Pulverisette P6. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).

Figure 2.19. Photographs of the vials used for Fritsch planetary ball mills with capacity of (a) 80ml and (b) 500ml. The vials and the balls shown in (a) and (b) are made of tempered steel agate materials, respectively (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).

More recently and in year 2011, Fritsch GmbH (http://www.fritsch-milling.com) introduced a new high-speed and versatile planetary ball mill called Planetary Micro Mill PULVERISETTE 7 (Figure 2.20). The company claims this new ball mill will be helpful to enable extreme high-energy ball milling at rotational speed reaching to 1,100rpm. This allows the new mill to achieve sensational centrifugal accelerations up to 95 times Earth gravity. They also mentioned that the energy application resulted from this new machine is about 150% greater than the classic planetary mills. Accordingly, it is expected that this new milling machine will enable the researchers to get their milled powders in short ball-milling time with fine powder particle sizes that can reach to be less than 1m in diameter. The vials available for this new type of mill have sizes of 20, 45, and 80ml. Both the vials and balls can be made of the same materials, which are used in the manufacture of large vials used for the classic Fritsch planetary ball mills, as shown in the previous text.

Retsch has also produced a number of capable high-energy planetary ball mills with different capacities (http://www.retsch.com/products/milling/planetary-ball-mills/); namely Planetary Ball Mill PM 100 (Figure 2.21(a)), Planetary Ball Mill PM 100 CM, Planetary Ball Mill PM 200, and Planetary Ball Mill PM 400 (Figure 2.21(b)). Like Fritsch, Retsch offers high-quality ball-milling vials with different capacities (12, 25, 50, 50, 125, 250, and 500ml) and balls of different diameters (540mm), as exemplified in Figure 2.22. These milling tools can be made of hardened steel as well as other different materials such as carbides, nitrides, and oxides.

Figure 2.21. Photographs of Retsch planetary-type high-energy ball mill of (a) PM 100 and (b) PM 400. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).

Figure 2.22. Photographs of the vials used for Retsch planetary ball mills with capacity of (a) 80ml, (b) 250ml, and (c) 500ml. The vials and the balls shown are made of tempered steel (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).

Both Fritsch and Retsch companies have offered special types of vials that allow monitoring and measure the gas pressure and temperature inside the vial during the high-energy planetary ball-milling process. Moreover, these vials allow milling the powders under inert (e.g., argon or helium) or reactive gas (e.g., hydrogen or nitrogen) with a maximum gas pressure of 500kPa (5bar). It is worth mentioning here that such a development made on the vials design allows the users and researchers to monitor the progress tackled during the MA and MD processes by following up the phase transformations and heat realizing upon RBM, where the interaction of the gas used with the freshly created surfaces of the powders during milling (adsorption, absorption, desorption, and decomposition) can be monitored. Furthermore, the data of the temperature and pressure driven upon using this system is very helpful when the ball mills are used for the formation of stable (e.g., intermetallic compounds) and metastable (e.g., amorphous and nanocrystalline materials) phases. In addition, measuring the vial temperature during blank (without samples) high-energy ball mill can be used as an indication to realize the effects of friction, impact, and conversion processes.

More recently, Evico-magnetics (www.evico-magnetics.de) has manufactured an extraordinary high-pressure milling vial with gas-temperature-monitoring (GTM) system. Likewise both system produced by Fritsch and Retsch, the developed system produced by Evico-magnetics, allowing RBM but at very high gas pressure that can reach to 15,000kPa (150bar). In addition, it allows in situ monitoring of temperature and of pressure by incorporating GTM. The vials, which can be used with any planetary mills, are made of hardened steel with capacity up to 220ml. The manufacturer offers also two-channel system for simultaneous use of two milling vials.

Using different ball mills as examples, it has been shown that, on the basis of the theory of glancing collision of rigid bodies, the theoretical calculation of tPT conditions and the kinetics of mechanochemical processes are possible for the reactors that are intended to perform different physicochemical processes during mechanical treatment of solids. According to the calculations, the physicochemical effect of mechanochemical reactors is due to short-time impulses of pressure (P = ~ 10101011 dyn cm2) with shift, and temperature T(x, t). The highest temperature impulse T ~ 103 K are caused by the dry friction phenomenon.

Typical spatial and time parameters of the impactfriction interaction of the particles with a size R ~ 104 cm are as follows: localization region, x ~ 106 cm; time, t ~ 108 s. On the basis of the obtained theoretical results, the effect of short-time contact fusion of particles treated in various comminuting devices can play a key role in the mechanism of activation and chemical reactions for wide range of mechanochemical processes. This role involves several aspects, that is, the very fact of contact fusion transforms the solid phase process onto another qualitative level, judging from the mass transfer coefficients. The spatial and time characteristics of the fused zone are such that quenching of non-equilibrium defects and intermediate products of chemical reactions occurs; solidification of the fused zone near the contact point results in the formation of a nanocrystal or nanoamor- phous state. The calculation models considered above and the kinetic equations obtained using them allow quantitative ab initio estimates of rate constants to be performed for any specific processes of mechanical activation and chemical transformation of the substances in ball mills.

There are two classes of ball mills: planetary and mixer (also called swing) mill. The terms high-speed vibration milling (HSVM), high-speed ball milling (HSBM), and planetary ball mill (PBM) are often used. The commercial apparatus are PBMs Fritsch P-5 and Fritsch Pulverisettes 6 and 7 classic line, the Retsch shaker (or mixer) mills ZM1, MM200, MM400, AS200, the Spex 8000, 6750 freezer/mill SPEX CertiPrep, and the SWH-0.4 vibrational ball mill. In some instances temperature controlled apparatus were used (58MI1); freezer/mills were used in some rare cases (13MOP1824).

The balls are made of stainless steel, agate (SiO2), zirconium oxide (ZrO2), or silicon nitride (Si3N). The use of stainless steel will contaminate the samples with steel particles and this is a problem both for solid-state NMR and for drug purity.

However, there are many types of ball mills (see Chapter 2 for more details), such as drum ball mills, jet ball mills, bead-mills, roller ball mills, vibration ball mills, and planetary ball mills, they can be grouped or classified into two types according to their rotation speed, as follows: (i) high-energy ball mills and (ii) low-energy ball mills. Table 3.1 presents characteristics and comparison between three types of ball mills (attritors, vibratory mills, planetary ball mills and roller mills) that are intensively used on MA, MD, and MM techniques.

In fact, choosing the right ball mill depends on the objectives of the process and the sort of materials (hard, brittle, ductile, etc.) that will be subjecting to the ball-milling process. For example, the characteristics and properties of those ball mills used for reduction in the particle size of the starting materials via top-down approach, or so-called mechanical milling (MM process), or for mechanically induced solid-state mixing for fabrications of composite and nanocomposite powders may differ widely from those mills used for achieving mechanically induced solid-state reaction (MISSR) between the starting reactant materials of elemental powders (MA process), or for tackling dramatic phase transformation changes on the structure of the starting materials (MD). Most of the ball mills in the market can be employed for different purposes and for preparing of wide range of new materials.

Martinez-Sanchez et al. [4] have pointed out that employing of high-energy ball mills not only contaminates the milled amorphous powders with significant volume fractions of impurities that come from milling media that move at high velocity, but it also affects the stability and crystallization properties of the formed amorphous phase. They have proved that the properties of the formed amorphous phase (Mo53Ni47) powder depends on the type of the ball-mill equipment (SPEX 8000D Mixer/Mill and Zoz Simoloter mill) used in their important investigations. This was indicated by the high contamination content of oxygen on the amorphous powders prepared by SPEX 8000D Mixer/Mill, when compared with the corresponding amorphous powders prepared by Zoz Simoloter mill. Accordingly, they have attributed the poor stabilities, indexed by the crystallization temperature of the amorphous phase formed by SPEX 8000D Mixer/Mill to the presence of foreign matter (impurities).

ball mill refiners vs roller refiners - community | thechocolatelife

There are differences in flavor and texture with every different combination of equipment used in the production chain. Most people never have the luxury to experiment with different production methods until they outgrow one and have to step up to a new one.

It's not always true that roll refiners and ball mills are mutually exclusive: I know of one Italian equipment manufacturer that offers a "turnkey" system that includes a roaster, cracker/winnower, roll refiner (used a liquor grinder), AND a ball mill. One of their customers has purchased an old-style melangeur and goes from the ball mill (particle size reduction) to the melangeur (using it like a conche for flavor development).

There are some well-known and respected companies that use ball mills: Domori is one; of course, Netzsch's ChocoEasy machines incorporate their ball mils - ball mills are ideally suited to continuous production lines. One of the knocks against most conventional ball mills is uneven particle size distribution. The peak tends to be wider than other methods and their is often a bump in the tail where there are large sizes.

I would have to disagree that most startups use ball mills, though. Apart from the Netzsch machines, which are very expensive - a 50kg machine costs over $90,000 - the only other small ball mill unit I know of is from BLT. At close to $100k their "turnkey" systems are still too expensive for most startups.

My experience is that most startups start out with a small (5kg) kitchen appliance wet grinder and then graduate to one or more of the larger ones as it is comparatively economical to grow the business this way and, because the technique is essentially the same the finished product is not too different. The challenge is the support equipment. Finding comparably scaled (and priced) roasters, crackers, and winnowers is not so easy. I just solved the winnower problem (~50 lbs/hr for about $5k) and am working on an alternative to the most-used small cracker that uses an entirely different principle and should create much smaller quantities of "fines" (which increases yield). I will have a prototype sometime this summer. If it works, we plan to open-source the plans as well as offer it in kit form for those who don't want to build one themselves.

We've corresponded privately about your soon-to-open school in Irvine and I think it's something that's absolutely necessary for the industry. I applaud Qzina for taking the initiative on this. I think that starting small (with respect to batch sizes) and offering the widest possible variety of equipment to work with is a sound approach. Making good chocolate is as much (or more) ART as Science. No one way is better than another; they're all different and can all produce good chocolate. Which way (if any) is better depends on what the desired outcome is.

Any chance you'd give us more info about the bean cracker you're working on? After all, the biggest strength of open source is in the development process--"given enough eyeballs, all bugs are shallow" and all that.

I'm particularly interested as this is something I've been thinking about lately, too. I've read of bean crackers that fling the beans against a metal plate and been thinking of a way to build something like this myself. I'd probably start with metal plates attached to a drill and dropping beans through them. Hopefully, they'd get hit a couple times on the way down.

I would be more than happy to share what we're doing. At the moment, if this were a software project, I would characterize it as "we're still in the early design phase, have a direction, and want to do one proof of concept before we open things up to the community." Very definitely when we get to the point that we have our first physical prototype - we'll open it up for community review.

I can tell you that we are working on the impact principle. There is a long way to go from your description of a drill with plates to something that works ("hoping" the beans crack is not an option unless you have an automatic return for uncracked beans on your winnower - otherwise huge amounts of extra manual labor are involved). We actually took a look at four different approaches that I had come up with after talking to a lot of people with a lot of experience cracking cocoa and building machines, and narrowed it down to one approach that we can easily prototype.

There are a bunch of fun challenges to solve, including finding an inexpensive way to control the rate at which the beans enter the cracker. The brute force method the Crankandstein relies on won't work for this method.

Another thing we're set on doing is incorporating a small digital controller - based on an Arduino - so that users can program the speed of the central cracking mechanism as well as the feed mechanism. We'll open source that, too.

IMO, there aren't a lot of people looking to set up production facilities in par with the scale of TCHO. Their Universal is a 3MT machine and is fronted by a ball mill. Theoretically, they could be producing 15-20MT/week in their plant - from liquor as they have no roaster and, on the pier, they are not likely to.

The real growth in the market (as I see it) is how to help companies that are in their real startup phase (i.e., producing in 5Kg batches) or in small production (e.g., producing 40-50kg batches) move up to the next level of production and to do so cost effectively. Going the Mast Brothers route (without the Selmi) a used convection oven, Crankandstein, CPS (or similar) winnower, and a 65L CocoaTown costs about $10k.

What's the next step? Spending over $70K for the basic (15Kg) BLT setup is too big a jump for most startups. It's not enough increase in production to justify the price differential. The cost structure goes up but the throughput to pay for the increased costs does not go up at the same rate.

If I was looking to spend roughly 110K Euros on new equipment there are solutions which offer up to 400Kg/day throughput (not including tempering/molding) for that amount of money. The throughput increase is great enough to justify the cost difference.

It's also really, really, really important to note that once you get above a certain production size, what really matters is materials handling. Everything can be moved around by hand when you're doing up to a couple of hundred kilos a day, but above that you really do need to consider where you're going to be storing beans (receiving/cleaning, storage, staging before and after roasting), where you're going to be storing chaff and nib, how you're moving/pumping (and storing) liquor and finished chocolate. The issues associated with materials handling are critical when considering growth above a certain size.

Where's the tipping point? I don't know - it depends on how much experience you have. I visited Pralus's factory in 2009 and they still move everything around by hand. They have 3, 250Kg Universals (two dark, one dedicated to milk). There's a 35kg ball roaster and a cracker/winnower. I did not see where they store/age their chocolate after it comes out of the Universal and before it gets molded or what they store it in. But Pralus did not start out at this production level, he's grown into it over many years. If he started from scratch today, with little experience is that how he'd set it up? Probably not.

With respect to your question about conching. It's really about three things: final particle size reduction, breaking up agglomerates and covering all the powder particles with fat, and flavor development. The "beauty" of the Netzsch approach is that it decouples the physical processes from the flavor development processes. You run it through the ball mill until you get the particle size you want and then stop pumping the chocolate through the ball mill and only beat it and aerate it to evaporate out aromatics you don't want.

You could do the physical processes another way (e.g., a grinder into a roll refiner then into a universal for a short while) and then use a device like the Duyvis-Wiener taste changer for final flavor development. (You could also blow a lot of air through the universal using both push and pull fans.)

What's important to know - and this is where having a variety of equipment on hand helps - is that the optimum time required for the the physical processes is not the same as the optimum time required to develop flavor. If it takes 48 hours of continuous grinding to get the texture where you want it you run the risk of driving off a lot of interesting flavors.

I think, in the realm of information that is likely to be publicly shared with you or freely available, what you find is going to be heavily influenced by the type of mfr you speak to (ie the refiner guys will tell you that their product is the best, ball milling guys the same). It will be heavily influenced by tradition and unproven beliefs (you will find folks in every camp that believe their way is the best simply because that's what they've always done, or that's what their predecessor or admired teacher told them - chefs are notorious for this). You yourself are already predisposed towards roll refiners; however in the above text you're only comparing it to one other production method (i can think of at least 8 particle size reduction technologies that are used commonly), and chances are very high that at least some of the chocolates you've consumed, you have no idea what process was used to convert it. Additionally, you will find that those who have spent the time and resources to do a scientific study to determine and quantify the differences in the various production methods will guard their results closely, as there are distinct competitive advantages that can be leveraged if one understands the options at a detailed level.

I will tell you that it is quite possible to make very similar (read: indistinguishable via the consumer) chocolate via multiple production methods (for example, i can make a dark chocolate on a refiner as well as another type (or types) of production kit that you will not be able to distinguish from one another. There are also chocolates that require a very specific type of kit to make, and that you simply can not make via another method. It is very dependent upon the type of chocolate you are making, and the specifics of that chocolate's physical and sensory components become very important. There is no single answer to the question you seek.

Generally speaking, each approach will have thematic pros and cons associated with it. Some are more heavily weighted towards product (ie how it handles raw materials and converts to finished product) while others are more heavily weighted towards throughput and energy utilization. Chocolate processing has far more science behind it than most admit to, as quite frankly most don't understand it, and the industry abounds with myth and misperception. Many companies continue to do things 'because that's the way it's always worked' and have, over time, created hypothesis as to why something does or doesn't work - but by and large, those theories haven't really been tested or challenged in a valid fashion. There are exceptions, of course, and those exceptions will, for the most part, be treated as trade secrets due to the advantage the understanding offers.