Ball Mill Grinding Research Articles

Effect of sample preparation method on quantification of polymorphs using PXRD

The purpose of this study was to improve the sensitivity and accuracy of quantitative analysis of polymorphic mixtures. Various techniques such as hand grinding and mixing (in mortar and pestle), air jet milling and ball milling for micronization of particle and mixing were used to prepare binary mixtures. Using these techniques, mixtures of form I and form II of clopidogrel bisulphate were prepared in various proportions from 0–5% w/w of form I in form II and subjected to x-ray powder diffraction analysis. In order to obtain good resolution in minimum time, step time and step size were varied to optimize scan rate. Among the six combinations, step size of 0.05° with step time of 5 s demonstrated identification of maximum characteristic peaks of form I in form II. Data obtained from samples prepared using both grinding and mixing in ball mill showed good analytical sensitivity and accuracy compared to other methods. Powder x-ray diffraction method was reproducible, precise with LOD of 0.29% and LOQ of 0.91%. Validation results showed excellent correlation between actual and predicted concentration with R2 > 0.9999.

Horizontal roller mill (Horomill ®) application versus hybrid HPGR/ball milling in finish grinding of cement

Industrial scale Horomill ® and hybrid HPGR/two-compartment ball mill applications at puzzolanic portland cement production were presented with emphasis on the general operational characteristics of the circuit configurations, size reduction and energy efficiencies of the Horomill ® and two-compartment ball mill grinding conditions. Horomill ® circuit configuration indicated to have advantages in terms of production of high strength cement as compared to Hybrid HPGR/two-compartment ball milling, depending on the classification performance of the separators influencing the circuit performance.

Flexural and Morphological Properties of Poly(Methyl Methacrylate)/ Hydroxyapatite Composites: Effects of Planetary Ball Mill Grinding Time

Poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) composites have potential applications in bone cement, prosthesis, and dental implant. In this study, PMMA containing 5 wt% of HA is prepared using polymerization followed by compression molding. PMMA and HA powder are ground using planetary ball milling. The grinding time takes from 30 to 120 min. The effects of the grinding time and particle size of the PMMA/HA powder on the flexural properties and morphology of the composites are investigated. The structure patterns of PMMA/5HA are characterized using X-Ray diffraction (XRD). No new phase is observed in the XRD pattern with the different sizes of PMMA/HA powder. This indicates that planetary milling solely reduces the size of PMMA/ HA powder. However, it does not modify the structure of PMMA and HA. A reduction of ~40% in the particle diameter is observed in both PMMA and PMMA/5HA powder after subjected to planetary milling for 60 min. For the planetary ball mill-ground PMMA/HA powder, the flexural modulus of the respective PMMA composites is slightly increased. Planetary milling can increase the volume of fine particles in the composites specimens, which results in a more homogeneous distribution of HA and a reduction of void contents in PMMA matrix. The reduction in void content is observed on the fractured surface of PMMA composites through field emission scanning electron microscopy.

Development of efficient system for ethanol production from paper sludge pretreated by ball milling and phosphoric acid

High-solid paper sludge was investigated for its potential to produce renewable biofuel. As a pretreatment method without consuming a large amount of energy, mechanical grinding for a comparatively short time followed by chemical swelling was used for optimal enzyme saccharification and ethanol production from paper sludge. Chemical swelling by phosphoric acid was more favorable than ball mill grinding. However, sequential pretreatment system using ball milling for 2 min and then phosphoric acid swelling for 1 h enhanced the enzyme saccharification rate and the reducing sugar productivity, 84.1% and 28.1 mg/g/h, respectively. The simultaneous saccharification and fermentation (SSF) from the sequential pretreatment system resulted to 81.5% ethanol conversion rate, the productivity being 1.27 g/L/h compared to untreated raw paper sludge which gave 54.3% ethanol conversion rate and 0.424 g/L/h productivity. Our work shows that consecutive mechanical grinding and chemical swelling are effective pretreatment methods for the enhancement of enzyme saccharification and efficient ethanol production from paper sludge.

A more sustainable approach to assessing comminution efficiency

The Bond operating work index is in common use for assessment of comminution efficiency. This method was developed for rod and grinding ball mill circuits and is not well suited to AG/SAG mills or the wide range of comminution devices now in common use. Traditional measures of efficiency only consider the net motor power of the drive unit. However, ancillary processes such as materials handling and classification can consume a substantial fraction of motor power. Wear resistant liners and grinding media are also consumed by the comminution process. These consumables themselves require substantial energy to mine, refine and to manufacture. This embedded (or indirect) energy can be of similar order to motor power. This paper outlines several ways to estimate of comminution efficiency. These methods can be applied to a wide range of equipment. The paper also describes how to estimate indirect energy consumption.

Functionalization of glassy carbon spheres by ball milling of aryl diazonium salts

Solvent free derivatization has been achieved by a simple ball mill grinding procedure to functionalize glassy carbon spheres with anthraquinonyl and nitrophenyl groups using aryl diazonium salts. Grinding facilitates the mechanical activation of the carbon substrate material with the creation of active centres and may induce the decomposition of the diazonium salt. The functionalized glassy carbon spheres were characterized electrochemically by studying their cyclic voltammetry. These modified carbon spheres were also characterized by X-ray powder diffraction and Transmission electron microscopy to ascertain particle size reduction or change in surface morphology of the carbon spheres. The covalent attachment of these functional moieties to the surface of glassy carbon spheres were studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.

A Comparative Study on PSD Models for Chromite Ores Comminuted by Different Devices

AbstractThe objective of this study was to characterize the particle size distributions (PSDs) of chromite ores comminuted by different devices, i.e., subjected to different breakage modes and to compare the performances of the PSD functions selected. Different PSDs were obtained for five different mineralogical samples of chromite ores by jaw, cone and hammer crushing and ball mill grinding. The PSDs of the products were characterized to find the most suitable model by Gates–Gaudin–Schuhmann (GGS) and Rosin–Rammler (RR) functions. It was found that the PSDs of all chromite types in single‐pass devices, i.e., jaw and cone crushing were better described by the GGS model than RR model. The RR model gave the best results for all ore sample PSDs generated by retention type systems, i.e., hammer crushing and ball mill grinding. Both distribution functions gave higher R2 values as the size distribution became uniform. The results of piecewise regression were found very useful to improve the performance of GGS distribution in terms of correlation coefficients for samples from a hammer crusher and ball mill.

Disturbance observer based multi-variable control of ball mill grinding circuits

Ball mill grinding circuits are essentially multi-variable systems characterized with couplings, time-varying parameters and time delays. The control schemes in previous literatures, including detuned multi-loop PID control, model predictive control (MPC), robust control, adaptive control, and so on, demonstrate limited abilities in control ball mill grinding process in the presence of strong disturbances. The reason is that they do not handle the disturbances directly by controller design. To this end, a disturbance observer based multi-variable control (DOMC) scheme is developed to control a two-input-two-output ball mill grinding circuit. The systems considered here are with lumped disturbances which include external disturbances, such as the variations of ore hardness and feed particle size, and internal disturbances, such as model mismatches and coupling effects. The proposed control scheme consists of two compound controllers, one for the loop of product particle size and the other for the loop of circulating load. Each controller includes a PI feedback part and a feed-forward compensation part for the disturbances by using a disturbance observer (DOB). A rigorous analysis is also given to show the reason why the DOB can effectively suppress the disturbances. Performance of the proposed scheme is compared with those of the MPC and multi-loop PI schemes in the cases of model mismatches and strong external disturbances, respectively. The simulation results demonstrate that the proposed method has a better disturbance rejection property than those of the MPC and PI methods in controlling ball mill grinding circuits.

Influence of raw material particle size on quality of pellets

Pellet plant (4·2 MPta capacity) of JSW Steel Ltd imports iron ore fines from different mines to produce pellets for its Corex and Blast Furnace plants. The pelletisation process involves drying the ore fines to reduce the moisture content to less than 1%, grinding in open circuit ball mills to get required fineness. To produce good quality of pellets certain additives are important and limestone is employed for modifying the pellet basicity. Iron ore fines of −10 mm size and limestone are ground together in a ball mill to get sufficient fineness for the balling process. However, as limestone is harder than iron ore fines the + 100 mesh size limestone particles is higher than required and not all the limestone is fully consumed in the reaction for melt formation. Microstructural studies were conducted under a Leica DMRX polarized microscope at different level fineness (−325# − 56, 58 and 60%) to investigate its effect on the pellet quality. The cold crushing strength of the pellet improved from 203 to 220 kg p−1 with increase in fineness. With increase in percentage of −325# particle size in the ground product RDI of the pellet decreased from 13·8 to 11·9% with increased melt formation from 5 to 9%. With increase in fineness −325# from 56 to 60% the 150 to 500 μm size pores decreased from 51·8 to 13·6%.

Preparation and Characterization of Micro-nanoscale MSWI Ash and Their Metal Release on MSW Anaerobic Digestion

This paper investigates the preparation of the micro-nanoscale municipal solid waste incinerator (MSWI) ashes by using ball mills (PM 100). The physiochemical properties of MSWI ashes such as particle size, mineral compounds and metal content were further characterized by X-ray powder diffractometer (XRPD), X-ray energy dispersive spectrometer (EDS), field-emission scanning electron microscope (FE-SEM) and induced coupled plasma optical emission spectrometer (ICP-OES). In addition, titrations were carried out to obtain the potential metal release of MSWI ashes in MSW and distilled water at different pHs. Batch anaerobic digesters were also conducted to test the MSWI ash as catalyst in the co-digestion process of MSW and MSWI ashes. Results showed that micro-nanoscale size of MSWI ashes could be obtained by ball mill grinding and was verified by EDS analysis and laser particle size analyzer although some agglomeration phenomenon were found. Metals releases were found higher with pHs lower than 3. Gas accumulation in the batch anaerobic digesters also showed that suitable ratios of MSWI ash addition was found to show beneficial effects, however, higher than a critical amount of MSWI ash was found to exert a detrimental effects on anaerobic digestion.

粉砕方式を変えた転動ミル粉砕によるＳｒフェライト微粒子の生成

The processes for obtaining fine Sr-ferrite particles have direct efects upon the crystallite size and distribution of sintered Sr-ferrite specimens. The influence of grinding conditions on the production of fine Sr-ferrite particles during ball mill grinding was investigated. The grinding experiments were carried out under dry and wet conditions, and dry condition with methanol as a grinding aid. Particle size distributions of the ground products were measured by the microscopic method, and could be expressed accurately as described by a modified Gaudin-Schuhmann equation. The fine grindability of Sr-ferrite particles was evaluated by the median particle size in undersize distribution, and the ratio of 10% and 90% cumulative weight passing sizes that showed the broadness of the size distribution. Sr-ferrite particles with a median particle size of 0.8-1.0μm were produced. The broadness of the size distribution increased with decreasing median particle size of the ground products. The broadness of the size distribution by wet grinding and dry grinding with a grinding aid was lowered using larger grinding media.

媒体径分布をもつ転動ミルの乾式・湿式粉砕における媒体摩耗

The wear generated in grinding balls having a ball size distribution in a tumbling mill was investigated using a laboratory-scale mill for both dry and wet grinding. The balls were divided into five diameters with the same mass fractions. The weight loss of grinding balls with a diameter Db, Mb appeared to have a non-linear relationship with the time of milling t in the ball mill. The kinetics of wear could be expressed as a power law of the type Mb=Atb, where the coefficient A is a function of the ball diameter Db, and the exponent b is a constant. The coefficient A obtained for each ball diameter, with the exception of the maximum diameter, followed the power law A ∝Dbn-3, based on the formulation of the weight loss of a grinding ball mb as mb∝Dbn. The exponent n indicates the ball wear mechanism in ball mill grinding. A value of n = 2 fits the surface theory which indicates that the intensity of the abrasive interactions in ball milling can be improved, while a value of n = 3 is in accord with the volume theory which shows that the intensity of the impactive interactions can be increased. In this study, the ball wear mechanism for dry milling changed from the volume theory to the surface theory with an increase of the milling time, while the mechanism of wet milling was consistent with the volume theory irrespective of the milling time.

Constrained model predictive control in ball mill grinding process

Stable control of grinding process is of great importance for improvements of operation efficiency, the recovery of the valuable minerals, and significant reductions of production costs in concentration plants. Decoupled multi-loop PID controllers are usually carried out to manage to eliminate the effects of interactions among the control loops, but they generally become sluggish due to imperfect process models and a close control of the process is usually impossible in real practice. Based on its inherent decoupling scheme, model predictive control (MPC) is employed to handle such highly interacting system. For high quality requirements, a three-input three-output model of the grinding process is constructed. Constrained dynamic matrix control (DMC) is applied in an iron ore concentration plant, and operation of the process close to their optimum operating conditions is achieved. Some practical problems about the application of MPC in grinding process are presented and discussed in detail.

Expert system based adaptive dynamic matrix control for ball mill grinding circuit

Ball mill grinding circuit is a multiple-input multiple-output (MIMO) system characterized with couplings and nonlinearities. Stable control of grinding circuit is usually interrupted by great disturbances, such as ore hardness and feed particle size, etc. Conventional model predictive control usually cannot capture the nonlinearities caused by the disturbances in real practice. Multiple models based adaptive dynamic matrix control (ADMC) is proposed for the control of ball mill grinding circuit. The novelty of the strategy lies in that intelligent expert system is developed to identify the current ore hardness and then select a proper model for ADMC. Compared with the various nonlinear DMC strategies, the approach can synthesize and analyze as many variables and status as possible to adequately and reliably identify the process conditions, and it does not introduce additional computational complexity, which makes it readily available to the industrial practitioner. Simulation results and industrial applications demonstrate the effectiveness and practicality of this control strategy.

Effect of Processing Conditions of Dolomite on the Antiviral Activity

The effect of the processing conditions of dolomite powders on the antiviral activity was studied against H5N3 avian influenza virus. When dolomite was fired in the ambient atmosphere, it decomposed into MgO and CaO by two stages at different temperatures, namely into MgO+CaCO3 at ca.1010 K and MgO+CaO at ca. 1070 K. Strong antiviral activity was observed after the complete decomposition into CaO and MgO. However, when the firing temperature exceeded 1673 K, the antiviral activity was degraded. It was also found that the degraded antiviral activity was recovered by sever ball mill grinding.

Dry grinding of Ca and octadecyltrimethylammonium montmorillonite

Structural changes in Ca and octadecyltrimethylammonium (ODTMA) montmorillonite induced by dry grinding in a high-energy planetary ball mill were investigated by X-ray powder diffraction (XRD) analysis, infrared (IR) spectroscopy, and scanning electron microscopy (SEM). The organomontmorillonite is more resistant toward mechanical destruction than the Ca form. Both XRD and IR analyses indicate a complete breakdown of the mineral layers after 5 min of grinding of Ca-JP. The XRD pattern of the ODTMA clay shows disappearance of the layer ordering along the c axis after 40 min of grinding, while persistence of the layered structure for all tested samples is proven by the IR spectroscopy. The grinding process affects chemical bonds in the O H, Si O Al, and Si O Si groups of montmorillonite; however, no changes are observed for C H bonds of the organocations. In contrast to the Ca form, all absorption bands typical for montmorillonite appear in the IR spectrum of the ODTMA montmorillonite even after 40 min of grinding. The majority of the bands are undetectable in the spectrum of Ca montmorillonite ground for 5 min. Amorphization of the montmorillonite caused by an intense grinding process is markedly slower after replacing the inorganic cations with the long-chain alkylammonium cations.

The influence of grinding technique on the liberation of clinker minerals and cement properties

This paper describes a study of the relationship between the physical, chemical and mineralogical parameters of cement products obtained by different grinding mechanisms namely high pressure grinding rolls (HPGR) and ball milling, and their effects upon the properties of cements prepared from the ground clinker. Samples were prepared as narrow size fractions and also as distribution samples. Characterization parameters were ascertained by using XRF, laser sizing, Blaine and BET surface area and image analysis methods. HPGR grinding resulted in higher degrees of liberation of clinker phases arising from the intergranular breakage along the grain boundaries compared to ball mill grinding. As for service properties, water demand of HPGR products was higher than ball mill products resulting from high micro fissured structure. Despite high liberation of particularly alite mineral in HPGR grinding, the compressive strength of ball mill products was slightly higher than HPGR products for narrow size samples. Finally, particle size distribution effect on strength was more obvious for distribution samples; generally ball milling gave higher strength values.

Application of model predictive control in ball mill grinding circuit

Grinding circuit needs to be stably controlled for high recovery rate of mineral ore and significant reduction of production cost in concentrator plants. Ball mill grinding circuit is essentially a multi-input–multi-output (MIMO) system with strong coupling among process variables. Simplified model with multi-loop decoupled PID control usually cannot maintain a long-time stable control in real practice. The response tests between four controlled variables (namely, product particle size, mill solids concentration, sump level and circulating load) and four manipulated variables (namely, fresh ore feed rate, mill feed water flow rate, pump speed and dilution water flow rate) are carried out to construct a four-input–four-output model of grinding circuit. Based on this modeling, constrained model predictive control (MPC) is adopted to handle such strong coupling system and evaluated in an iron ore concentrator plant. The variables are controlled around their set-points and a long-term stable operation of the grinding circuit close to their optimum operating conditions is achieved. More than three years’ operation in industry demonstrates the effectiveness and practicality of this control strategy.

Supervisory expert control for ball mill grinding circuits

Stable control of particle size in ball mill grinding circuits is of great importance for the recovery of the valuable minerals, and the maximization of mill capacity is another main consideration in concentration plants. A supervisory expert control strategy is proposed to control product particle size and to improve fresh ore feed tonnage in grinding circuits. Expert control in supervisory level is developed to optimize the set–points for controllers in regulatory level. Mill solid concentration variable–ratio control, sump dilution water flowrate single–loop control and sump level loose control are carried out in regulatory level to reach the control targets. While the set–point modification by expert control for dilution water controller demonstrates good dynamic performance, the set–point adjustment for feed rate controller ensures a long-term stableness of particle size even ore hardness has changed. An increase of 10% in feed tonnage was achieved relative to other grinding circuits of similar capacity, running in parallel. More than four year’s operation demonstrates the control strategy’s practicality and reliability.

Fine grinding in a horizontal ball mill

The fine grinding of ores is increasing due to the depletion of coarse grained, easily processed ore bodies and the increased need to process disseminated, fine grained deposits. The main reason ball mills are not utilised for fine grinding is the perceived poor energy efficiency generally experienced when grinding to fine sizes. However there is a trend towards ball mill grinding for product sizes below the traditional ball mill cut-off of 45 μm. The effect of ball size on the feed and product size distributions in a fine grinding situation was studied. The grinding tests identified a number of trends for fine grinding, including: • Efficient grind curves forming the same shape as for traditional grinding (exponential decay). • The results supporting the claim that fine material is best ground with small media and coarse material with larger media. • The smallest charge was most efficient at treating the finer feeds. • The smaller charges were very ineffective and inefficient for grinding of the coarser feeds. • Efficient grind was undertaken by smaller charges than that recommended by Bond’s ball sizing formula, and • Operating work index analysis confirming the results of the P 80-energy analysis.