In article results of a grinding such differing on the ability for grinding materials as a chalk, kaolin,  amorphous silicon oxide, in a spherical mill with a mixer are presented. In quality milling bodies of  2.8–3.0 mm were used pig-iron a ball in diameter. Speed of working body made 10 m/s. The initial  fraction of 0.5–3.0 mm as a result of a grinding is finished till the final size 0.2–50.0 ?m. Approximately  80% of particles had the size less than 10 ?m. Dependences of efficiency dispersion from duration of influence for the different defining sizes of particles are received. Possibility of analytical representation of  the total characteristic in the form of the equation of Rozina – Rammlera is shown

Kozlovski, V. I.

Vaytekhovich, P. E.

In article results of a grinding such differing on the ability for grinding materials as a chalk, kaolin, amorphous silicon oxide, in a spherical mill with a mixer are presented. In quality milling bodies of 2.8–3.0 mm were used pig-iron a ball in diameter. Speed of working body made 10 m/s. The initial fraction of 0.5–3.0 mm as a result of a grinding is finished till the final size 0.2–50.0 ?m. Approximately 80% of particles had the size less than 10 ?m. Dependences of efficiency dispersion from duration of influence for the different defining sizes of particles are received. Possibility of analytical representation of the total characteristic in the form of the equation of Rozina – Rammlera is shown

Belarusian State Technological University

ISSN 1683-0377. Proceedings of BSTU. 2012. Issue 3. Chemistry and Technology of Inorganic Substances 118UDC 621.926 V. I. Kozlovski, PhD student (BSTU); P. E. Vaytekhovich, PhD (Engineering), assistant professor, head of department (BSTU) CRUSHING OF MATERIALS IN THE SPHERICAL MILL WITH THE MIXER In article results of a grinding such differing on the ability for grinding materials as a chalk, kaolin, amorphous silicon oxide, in a spherical mill with a mixer are presented. In quality milling bodies of 2.8–3.0 mm were used pig-iron a ball in diameter. Speed of working body made 10 m/s. The initial fraction of 0.5–3.0 mm as a result of a grinding is finished till the final size 0.2–50.0 μm. Approximately 80% of particles had the size less than 10 μm. Dependences of efficiency dispersion from duration of in-fluence for the different defining sizes of particles are received. Possibility of analytical representation of the total characteristic in the form of the equation of Rozina – Rammlera is shown. Introduction. Recently in foreign and Russian literature there have appeared a lot of information on the research of spherical mills with mixers [1–6], which are applied in various industries to crush par-ticles till micron sizes and even less than 1 μm. As crushing bodies in them glass and corundum balls in diameter of 1–3 mm are used. Data on creation of large-sized spherical mills with mixers [7] with productivity to 20 t/h are given. The analysis of process of spherical crushing showed [8] that such units can have big prospects for superthin crushing when the main way of impact on a material is at-trition. The prospects of the specified crushing unit as a mechanical system have predetermined the urgency of scope of scientific researches on studying of its technological and design data and their optimization. Main part. The spherical mill with a mixer of a horizontal type (Fig. 1) is chosen as the object of the research. The diameter of the installation case makes 196 mm, total amount – 9 l. The role of the mixing device is carried out by disks with the openings, estab-lished on a driving shaft. The obligatory elements of the studied mill, as well as all modern mills with mix-ers, are the trellised dynamic separator and the mesh filter. As the crushing bodies pig-iron balls in the di-ameter of 2.8–3.0 mm, and the crushed material – chalk with the size of particles of 1–3 mm, kaolin – 0.5–2.0 mm, amorphous oxide of silicon (“white soot”) – 0.2–0.5 mm were used. The choice of the materials is caused by a wide use of their finely dis-persed fractions in the production of various products: rubber, dyes, paper and pottery. Besides these materi-als considerably differ on their grindability. At the initial stage of studying of any crushing unit the kinetics of grinding of a material in it is important. Therefore the researches were carried out on a mill working in a periodic mode. The grinding was carried out only in a wet condition at the volume ratio of crushing bodies, the material and the water, equal to 1 : 0.75 : 0.5. At the initial stage of studying of any crush-ing unit the kinetics of grinding of a material in it is important. Therefore the researches were car-ried out on a mill working in a periodic mode. The grinding was carried out only in a wet condi-tion at the volume ratio of crushing bodies, the material and the water, equal to 1 : 0.75 : 0.5. Thus the frequency of rotation of a shaft with mixers remained constant – 1,420 rev/min that corresponds to linear speed on mixers edges – 10.03 m/s. Through certain periods in the range of 5–30 min the tests of the crushed product from the grinding zone were selected. The analysis of the tests was carried out on the laser microana-lyzer of Fritsch firm, by means of the measuring Analysette 22 complex.   Fig. 1. Scheme of laboratory installation: 1 – cylindrical case; 2 – rotating disks (mixers);  3 – separator; 4 – mesh filter; 5 – circulating branch pipe; 6 – crushing balls  On Fig. 2 the fineness characteristics for three studied materials after 15-minute processing in a mill with a mixer are presented. In all cases the maximum size of particles doesn't exceed 50 μm. The minimum size made 0.2 μm and increased from “white soot” to kaolin and chalk that testifies to the best grindability of these materials. Thus the disperse structure of the crushed product for “white soot” is more uniform. On the private characteristic of “white soot” one maximum of about five-percent maintenance of particles in diameter of 10 μm is noted. There are few such peaks for chalk, and especially kaolin on the characteristic that points to higher polydisper-sity of the product. The reason for that can be the heterogeneity of the structure of these materials, in particular the presence of a considerable share of Initial productFine product5621 4 3ωChemical Engineering, Heat Engineering and Energy-Saving 119such hard crushed component, as quartz sand in which crystal oxide of silicon prevails. In this re-gard the kinetics of crushing is best of all traced on the dispersion change of “white soot” (Fig. 3). Here the fineness characteristics of the specified product are presented at a 5- and 30-minute processing in a mill with a mixer. In the aggregate with a 15-mi-nute processing (Fig. 2, c) they reflect the real pic-ture of the change of the crushing product disper-sion in time. The fact of its increase with time is evident, but at the same time the fact of decrease in speed of this increase is obvious as well. So, the comparison of the private characteristics at a 15-and 30-minute grinding indicates its shift towards smaller product, yet its maximum characterized in the size of 10 μm decreases slightly. Studying fine-ness total characteristics received by means of the laser microanalyzer, gives the chance to establish the interrelation between the size of a certain class and its share in the product total mass. In Table 1 the data for “white soot” at different time of grind-ing are presented. Besides some share of a class (fraction) from 5 to 99% is taken for defining pa-rameter and its maximum size is established.     Fig. 2. The fineness characteristic of distribution of the particle size in the test volume after 15 min of grinding: a – chalk; b – kaolin; c – “white soot”   Fig. 3. The fineness characteristic of distribution of the particle size in the test volume “white soot”: a – 15 min; b – 30 min Q3(x) 0.5   1 0.1 5   10 50 100 500 1,000 The size of particles, μm а The size of particles, μm b 0.5  1 0.1 5   10 50 100 500 1,000 0.5  1 0.1 5   10 50 100 500 1,000 The size of particles, μmc1009080706050403020100Sumarnyj exit of a glass, % 5  4  3  2  1  0Exit of a glass for the private characteristic, % 1009080706050403020100Sumarnyj exit of a glass, % 5  4  3  2  1  0Exit of a glass for the private characteristic, % 1009080706050403020100Sumarnyj exit of a glass, % 10 9 8 7 6 5 4 3 2 1 0Exit of a glass for the private characteristic, % 0.5  1 0.1 5   10 50 100 500 1,000 The size of particles, μm a1009080706050403020100Sumarnyj exit of a glass, % 5  4  3  2  1  0 Exit of a glass for the private characteristic, % dQ3(x) Q3(x) dQ3(x)Q3(x) dQ3(x) Q3(x) dQ3(x)Q3(x) dQ3(x)1009080706050403020100Sumarnyj exit of a glass, % 0.5  1 0.1 5   10 50 100 500 1,000 The size of particles, μm b 10 9 8 7 6 5 4 3 2 1 0Exit of a glass for the private characteristic, % ISSN 1683-0377. Proceedings of BSTU. 2012. Issue 3. Chemistry and Technology of Inorganic Substances 120According to Table 1 the reduction of the size of particles and the increase of a share of smaller fractions is accurately traced at grinding time in-crease. For 30 min of processing in a spherical mill with a mixer the size of particles of “white soot” doesn't exceed 30 μm, and 80% from them –  11 μm. Table 1 The maintenance of the sizes of particles  in a test at different duration of grinding Maximum size of particles  at different time of grinding, μm Fraction share, % 5 min 15 min 30 min 5 1.997 1.728 1.468 50 11.583 8.518 6.392 80 25.276 14.260 10.926 99 38.310 29.594 30.657  Using the total characteristics of fineness “on a minus” which are presented as results of the analy-sis of dispersion, it is possible to solve another task – having chosen a certain size, to define in the ground product a share of particles less than this size. Such data for different materials are provided in Table 2. These indicators once again confirm the decrease in a grindability of materials from chalk to “white soot”. By the received results for “white soot” the dependences of dispersion efficiency on impact time (Fig. 4) are constructed. The effi-ciency thus was determined from the formula 100 ,E R= −  (1)where R – the share of a product exceeding any certain size, %.  Table 2 Share of particles  of the ground product in the selected tests Share of fractions, %, for different materials at 5 min grinding duration The defining size, μm chalk kaolin “white soot” 1.0 9.7 8.7 2.5 10 71.1 62.9 42.5  We have taken 1 μm as the particle size in  Fig. 4, a, and 10 μm in Fig. 4, b. By the kinetic curves (Fig. 4) there accurately Ftraced the reduction of the size of particles (in-crease in dispersion) both for the fraction of 1 μm, and for the fraction of 10 μm. Notably in the stud-ied time span (5–30 min) the share of a small frac-tion (1 μm) decreases for only 1%, and a large  (10 μm) – for more than 30%. It testifies that at the reduction of the size of particles the process of their dispersion is made difficult. Processing of the experimental data gave the chance to receive the empirical dependences for the calculation of the dispersion efficiency. They are presented in the form of a polynom of the sec-ond degree: –  for fraction less than 1 μm: 21 0.0013 0.0067 1.5;E t t= − +  (2)–  for fraction less than 10 μm: 210 0.0263 2.253 32.08,E t t= − + +  (3)where Е1 and Е10 – efficiency of crushing for the size 1 and 10 μm respectively, %; t – time of cru-shing, min. The divergence of the experimental and calcu-lated data doesn't exceed 0.013–0.05%. The main, universally accepted in technology and engineering is the total characteristic by which it is possible to determine an output of any fineness class [9]. In logarithmic system of coordinates this charac-teristic will be more often transformed to a straight line. On this basis, the experimental data can be proc-essed in the form of Rozin – Rammler equation [9]: 100 ,nbdpR e−=  (4)where Rp – a total class output “on plus” (d is lar-ger); d – the defining size of particles (class size), μm; b and n – the parameters depending on the property of the material and the dimension of d.   0             10             20            30            40 Grinding duration t, min а   0                10              20             30             40 Grinding duration t, min b Fig. 4. The dependence  of the dispersion efficiency from the impact time  for the different defining sizes of particles: a – 1 μm; b – 10 μm 80706050403020100Efficiency of crushing Е, % 32.521.510.50Efficiency of crushing Е, % Chemical Engineering, Heat Engineering and Energy-Saving 121The processing of the experimental results pre-sented in the form of the total characteristic for ”hite soot” with the grinding time of 15 min (Fig. 2, c), allowed to receive the Rozin – Rammler equation with the corresponding factors: 0.21698.4136100 .dpR e−−=  (5)The error of calculation for the equation (5) doesn't exceed 0.004%. Such equations can be received for all total characteristics. Conclusion. As a result of the researches of crushing of materials with various grindability in a spherical mill with a mixer the disperse structure of the final product is established. Their total charac-teristics by which it is possible to determine an out-put of any fineness class are received. Possibility of analytical submission of the total characteristic in the form of Rozin – Rammler equation is shown. The kinetics of crushing of materials in a spherical mill with a mixer is analysed and the equations for calculation of the change of the dis-perse structure of the final product in time are received. It is established that the initial product in the size of 0.2–3.0 mm during 5–30 min can be fin-ished to particles in the size of 0.2–50.0 μm. In some cases the minimum size doesn't exceed 30 μm, and 80% of these particles is less than 10 μm.  It testifies to high efficiency of crushing in a spherical mill with a mixer. References 1. Hiem, A. The effekt of the number of contact points grinding elements on the rute of grinding in ball mills / A. Hiem, T. P. Olejnik, A. Powlak // Physico-chem. Probr. Miner. Process. – 2004. – Vol. 38. − P. 147−155.  2. Joost, B. Einfluβ vor Mahlköper Eigenschaf-ten auf die Zerkleinerung in Rührwerkskugelmühlen / B. Joost, J. 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Crushing of materials in the spherical mill with the mixer

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Crushing of materials in the spherical mill with the mixer

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