Grindability of Quartz under Compressive and Impact Forces

Mining, Metallurgy & Exploration, 2018

The main forces acting on minerals in conventional size reduction units are compression, impact, attrition, and/or abrasion. Usually a combination of these forces shares the breakage action of the minerals with one or more of these forces dominating the breaking action, depending on the machine used. The present work concentrates on the behavior of quartz when stressed with compression force in a confined piston die. Several size fractions within the size range minus 10 mm to plus 0.85 mm were compressed in the piston die. The measured parameters are compression load, bed thickness, displacement as a result of compression, rate of displacement, and the size distribution of the products. It was found that the size distributions are, to some extent, different from those produced by the ball mill or the high-pressure roll mill. This is mainly because of the differences in the type of the acting forces in each case. It was also found that the cumulative weight of the distributions is reasonably normalizable with respect to the median particle size of the product. The specific energy expended is inversely proportional to the median size of the products, and the reduction ratios, x f /x p , are directly proportional to the applied compression force, and hence, to the specific energy expended. A simple model is suggested for predicting the particle size distribution as a function of the expended energy. The calculated values of the size distributions match fairly well with the experimental values, except at the very low energy levels, where most of the energy expended is consumed in the rearrangement and packing of the particles in the confined space with little or no breakage.

Quartz crystals are used in the electronic industry, frequency control oscillator and frequency filters. Milk quartz and quartz glass by grinding and preparation procedures through the glass, detergent, paint, ceramic, sand, fill, and metallurgical industries, fine sizes (micronized) are used. Micronized feldspar group minerals, ceramics and glass industries within the limits of a certain quality have an important market due to the grinding of raw materials are widely used. In the size reduction, energy-intensive process is consumed about 3% of the energy produced in the industrialized countries in the world (Schonert, 1979; Narayanan, 1987). The size reduction operations are spent on approximately 55-70 % of the total energy consumed in the mineral processing plants (Cohen, 1983; Lynch et al., 1986). In this study, the behavior of quartz and feldspar broken into the same grinding conditions was presented Bond Grinding test and then analyzed using the kinetic model. The results obta...

Journal of Petroleum and Mining Engineering

Comminution tests are a vital element in the proper design of mineral processing plants. Several grindability tests have been developed over the years for different applications and each test has its strengths and weaknesses. Among test methodologies considered, is the universally accepted high-pressure grinding roller (HPGR) test procedures based on small-scale tests. The present work has been carried out to compare the grinding characteristics of different ore minerals. It was observed that all tested minerals, (quartz, chromite, marble, hematite, magnesite, dolomite) showed a general similar trend while being compressed. Moreover, because those minerals have wide differences in their mineralogical, physical, and mechanical properties they have different comminution behaviour under compression. The consumed energy as well as the reduction ratios are affected by the mineral hardness. The percentage product at a certain cut-size was found to be proportional to the expended energy for each mineral. A convenient grindability index under compression has been suggested as the specific productivity, in ton/kWh. This index is quite sensitive to the material hardness.

Applied Sciences

The present study investigates four materials, namely quartz, marble, quartzite and metasandstone and aims to establish correlations, with the use of simple and multiple regression analysis, between their properties and breakage rate parameters. The material properties considered in this study derived from the application of destructive and non-destructive tests and include P-wave velocity (V p), Schmidt rebound value (R L), uniaxial compressive strength (UCS) and tangent modulus of elasticity (E t), while the breakage rate parameters determined from batch grinding tests, include breakage rate S i , maximum breakage rate S m , α T and α, and optimum particle size x m. The results indicate that the properties of all materials examined show very good correlation and can be used to predict S i or α T. Furthermore, parameter α is well correlated with V p , R L and E t using inverse exponential functions, while S m is strongly correlated with R L and UCS. Overall, it is deduced that multiple regression analysis involving two independent variables is a reliable approach and can be used to identify correlations between properties and breakage rate parameters for quartz, quartzite and metasandstone, which are silica rich materials. The only exception shown is the determination of x m for marble.

Powder Technology, 1999

. The behaviour of a powder impacted on a target depends on its size, its particle size distribution PSD , the material mechanical properties and the industrial rig. A methodology for the study of impact in an air jet mill allows one to evaluate the relation between the impact energy and the grindability of the impacted solids. Moreover, the behaviour of an impacted powder is determined by its process conditions. An example is given with the study of different hydrargillites and aluminas produced in different ways and having different morphologies. The impact test allows one to classify these solids with grindability and attrition criteria. Morphological analysis relates them to external structural descriptors. q 1999 Elsevier Science S.A. All rights reserved.

Particle & Particle Systems Characterization, 2007

In the present study, the effect of grinding media shape on breakage parameters was investigated. Balls and cylpebs were used as the grinding media. It was observed that the grinding of quartz obeyed first-order breakage kinetics in the case of balls and cylpebs. Higher breakage rates were noted with cylpebs than with balls. Furthermore, it was found that the primary breakage distribution function is dependent on the feed size (i.e., non-normalizable), but independent of the grinding media shape. The effect of grinding time on the product size distribution has also been investigated. Following four and ten minute grindings, cylpebs produced a relatively finer product compared to balls.

Aspects in Mining & Mineral Science

These studies have been carried out to compare the grinding characteristics of different morphological mineral matters. Coal, dolomite, manganese and iron ores samples were ground using a ball mill in different grinding conditions (dry and wet) and at different critical speed (R 45% , R 70% and R 90%) during wet grinding. Results are compared considering the relative impact on particle size and shape. Materials were ground in a lab scale ball mill for 2hours with steel balls and size analysis of products were carried out using different size sieves (1, 0.5, 0.25, 0.15, 0.106 and 0.053mm). Microscopic studies were carried out to know the effect of different grinding conditions on particle properties. Light, fine grain and soft dolomite shows only 8% reduction in D 80 whereas heavy, friable and hard manganese ore shows a 29% reduction in D 80 for similar dry and wet grinding conditions. It was found that light materials are less sensitive towards mill speed (R) during wet grinding. Energy calculations indicated that wet grinding is less efficient for low density and soft materials than high density and hard materials. The relative increase in the fineness (D 80) for coal, dolomite, manganese ores and iron ores were 8.9, 6.5, 25, and 15.8%, respectively for wet and dry grinding. Variation in D/L indicates that abrasion is a prominent phenomenon in dry grinding and chipping is more prominent in wet grinding especially for material with bedded structures.

Powder Technology, 1999

The grinding of quartz sand to produce high purity silica flour was studied using ceramic balls, ceramic cylinders or flint pebbles in a laboratory mill and three full-scale closed circuit mills of 2.2, 2.3 and 2.8 m internal diameter. The primary breakage distribution Ž. determined in laboratory tests was the same for the three media types but the characteristic slope g was changed from 1.05 to 0.95 to fit the full-scale results. An approximate correction was used for non-first order breakage kinetics. Simulation models were developed for the air separator and the mills. Simulations indicated that a mill lining of smooth ceramic gave media slip and was less efficient than flint linings. Higher circulating loads reduced specific grinding energy even though the recycle of fine mill product to mill feed increased. Ceramic balls gave the lowest grinding energy, wear rate and cost per ton of product. Resumé Le broyage du sable de quartz afin d'obtenir de la poudre de silice de haute purete a ete etudie par l'usage de billes de ceramique, dé´´´´ć ylindres de ceramique ou de pierres de silex dans un broyeurs grandeur nature de 2.2, 2.3 et 2.8 m de diametre interne montes en circuit`f erme. La distribution de la casse primaire determinee par les tests en laboratoire a ete la meme pour les trois materiaux utilises mais lá´´´ˆ´ṕ ente caracteristique a ete changee de 1.05 a 0.95 pour s'adapter aux resultats des broyeurs de grandeur nature. Une correctioń´´´á pproximate a ete utilisee afin de prendre en consideration des cinetiques de casse superieures au premier ordre. Des modeles dé´´´´´s imulation ont ete developpes pour le separateur d'air et pour les broyeurs. Des simulations ont indique qu'un broyeur a paroi eń´´´´´c eramique lisse resultait en des glissements des materiaux et etait moins efficace que les parois en silex. L'accroissement des taux´´d 'ecoulement a reduit l'energie specifique de broyage meme quand le recyclage du produit fini vers l'entree du broyeur a augmente. Leś´´ˆ´b illes de ceramique ont demontre la meilleure efficacite, taux d'usure le plus bas et au cout de production a la tonne minimal. q 1999´´ˆÈ lsevier Science S.A. All rights reserved.

Mineral Processing and Extractive Metallurgy, 2005

The kinetics of batch dry grinding of ceramic raw materials, which are quartz, kaolin and K-feldspar, from the feeds of sieve sizes -3·350+2·360, -2·360+1·400, -1·400+0·850, -0·850+0·600, -0·500+0·425 and -0·300+0·212 mm have been determined using a Bond mill with a mixture of five ball sizes. The mill used was a size of 30·5 cm diameter, 30·5 cm length, providing a total mill volume of 22 272 cm 3 with a total mass of 22 648 g steel ball mixtures of 38·10, 31·75, 25·40, 19·05 and 12·70 mm diameters, occupying 22% of mill volume and with a speed of rotation of 70 rpm. The specific rates of breakage (S i ) and primary breakage distribution (B i,j ) values, called grinding breakage parameters, were determined for those feed size fractions to predict the product size distributions by simulation for comparison to the experimentally obtained data. As the feed sizes increase, the S i values also increase, that is, faster breakage values from higher to lower values were in the order of quartz, Kfeldspar and kaolin by comparison with their α values. The B i,j values obtained for these minerals were different in terms of characteristic fineness factor, γ. Thus, kaolin produced more fines, while K-feldspar and quartz produced less fines in the mill. In other words, the simulations of product size distributions for these minerals were in good agreement with the experimental data using a ball mill simulation program, called PSUSIM. However, the slowing down effect in the mill started earlier than expected for the minerals studied, unlike the laboratory size ball mill used extensively in our studies. Nevertheless, there exist linear relationships between the simulated time (θ) and experimental time (t) for these minerals.

Wear, 2009

The results of the milling experiments of different mineral ores and laboratory wear testing with different abrasives have shown that the abrasivity of treated materials does not depend only on their hardness, but, to a great extent, on the particle shape of the materials. The grindability of materials milled by collision depends on the properties of materials as well on the treatment parameters (specific treatment energy). The aims of this investigation were (1) to study the abrasivity and the grindability of different minerals (granite, quartzite, etc.) and to predict the relative wear resistance of the materials prospective for the grinding media of milling equipment, using a centrifugal type impact wear tester. Experiments conducted with abrasives of different hardness and with particles of different shape have shown that the wear rate of materials used as wear resistant materials in grinding devices depend more on the angularity of abrasive particles than on their hardness. It was shown that the grindability depends more on the composition and properties (fracture toughness, homogeneity of the structure) than on the hardness of the mineral ores. The main size reduction occurs at first collision, later in the multiple milling of mineral materials particle rounding takes place. The angularity parameter has good correlation with the wear rate in the case of the studied commercial steels as well as with metal matrix composites. Experiments with cermets showed that erosion does not practically depend on abrasive particle shape.