Bond Grindability Tests Research Articles

Investigating the Characterization and Grindability Behaviour of Farin-lamba Cassiterite toward Effective Tin Oxide Production

Cassiterite has been an essential source of tin; its exploration and exploitation have become a priority worldwide. The effective beneficiation of cassiterite depends mainly on its grindability and effective liberation. The Modified Bond's grindability test is a method used to determine the work index, which is crucial in estimating the energy needed to grind an ore. This is crucial during mineral processing, as a slight deviation would affect the company's operating expenditure (OPEX). This study investigates the work index for Farin-Lamba cassiterite with reference to silica sand sourced from Igbokoda. The test ore (cassiterite) was analyzed using Energy Dispersed X-ray fluorescence spectrometer (ED-XRS), Petrographic Analysis, and Scanning Electron Microscope equipped with an Energy Dispersive Spectrum (SEM-EDS) to understand their chemical and mineralogical characteristics in relation to their grindability. The test ore and the reference material (silica sand) underwent comminution using 500g of each to a 100% passing 500 μm array of sieves arranged in (√2) series from 500μm to 63μm onto an automatic sieve shaker. The chemical and mineralogical analysis revealed the presence of gangue such as SiO2 and Al2O3, which increases the energy needed during communition; further, the presence of rough and large grain size in the ore also increases the energy needed for communition. The results were subjected to Gaudin Schuman's equation to determine the ore's work index, which was 14.664 KWh/ton for the test ore, which is standard for cassiterite, which ranges from 10-15 kWh/ton. Further, the energy needed for comminution was calculated to be 33.7272 Kwh, providing valuable insights into the energy efficiency of the grinding process. The evaluation of the grindability of Farin-Lamba cassiterite in relation to the reference ore not only contributes toward understanding the ore processing dynamics but also provides information needed for the optimization of energy consumed during the process of tin oxide production.

MICROWAVE ACTED MICRO GRINDING OF ŞIRNAK ASPHALTITE SLIME, LIGNITE SLIME

In terms of the advanced technological developments in energy production the low quality coals need the most feasible technologies. it is possible to produce coal-derived products from low quality coals. On the contrary of environmental concerns of low quality coal burning, coal preparation, grinding and washing of various type of low quality coals need feasible evaluation. The grinding systems are needed in today's modern technology. In this fine grinding study, Hardgrove and Bond grindability tests are practiced over Şırnak shale, Şırnak asphaltites and bottom ash. Grinding tests ere carried out to certain weight samples conditioned in microwave oven at the fine size values in the product. The duration period are changed after grinding for 60 and 90 minutes. Şırnak asphaltite and Şırnak shale were dry milled in two different horizontal and vertical roller mills in different micro-grinders and the fineness values of 20 μm and 45 μm are determined and compared. The unit energy consumption for different types of clinker production in industrial mills has been calculated and presented comparatively. The differences in the grindability of raw materials and the amount of energy consumed in cement production were determined by experimental and industrial tests. The easiest to grind is Şırnak asphaltite and shale, while the most difficult to grind is marl. As a result of the HGI and Bond tests, they are the decisive tests in industrial-scale grinding of cement. Since materials that are easy to grind are evaluated, it has been observed in this study that clinkers with additives produced using claystone are more advantageous. Micronized grinding of soft limestone instead of marly limestone has proven to be easy. The particle size functions in the micro pulp are defined in the vertical ball mill. In the production of additive Portland cement, micronized grinding of oak charcoal and fly ash with microwave requires less energy and can be grinded more easily.

A Review of Alternative Procedures to the Bond Ball Mill Standard Grindability Test

Over the years, alternative procedures to the Bond grindability test have been proposed aiming to avoid the need for the standard mill or to reduce and simplify the grinding procedure. Some of them use the standard mill, while others are based on a non-standard mill or computation techniques. Therefore, papers targeting to propose a better alternative claim to improve validity, to reduce test duration, or to propose simpler and faster alternative methods for determining the Bond work index (wi). In this review paper, a compilation and critical analysis of selected proposals is performed, concluding that some of the short procedures could be useful for control purposes, while the simulation-based procedures could be interesting within a process digitalisation strategy.

Use of drilling performance to improve rock-breakage efficiencies: A part of mine-to-mill optimization studies in a hard-rock mine

In a hard-rock mine, blasting is an important rock-breakage process that impacts energy consumption both in downstream comminution processes and mine productivity. Optimizing the blast fragmentation to improve rock-breakage efficiencies during crushing and grinding is key to mine-to-mill (MTM) optimization. This study explores the use of monitoring while drilling (MWD) data to achieve this goal. Representative penetration rates (PRs) were extracted from blastholes to estimate intact rock properties and predict the breakage efficiencies that directly affect comminution energy consumption. Two intact rock properties, tensile strength (TS) and Bond work index (BWI), were correlated with the PR data to predict these efficiencies in crushing and grinding, respectively. Because of the complexity of the raw MWD data and effects of various disturbances, the MWD data was preprocessed and normalized to achieve a representative PR value at each blasthole. This preprocessing entailed defining valid PR ranges from the MWD data that could eliminate the noise related to discontinuity features in the rock mass structure as well as errors in operator behaviors. The PR data was also normalized using the adjusted penetration rate (APR) to minimize the effects of mechanical factors such as drill feed force, torque, and rotational speed. To correlate the representative APR value with intact rock properties, TS and BWI, various laboratory experiments were conducted: drilling tests using a high-precision coring machine, Brazilian disc tests, and Bond grindability tests. Based on the results of these experiments, models were developed to predict rock-breakage efficiencies during crushing and grinding based on APR. The result of this study can be used to obtain blast energy designs that consider comminution energy consumption and efficiency in the downstream rock-breakage processes.

A Bond Work index mill ball charge and closing screen product size distributions for grinding crystalline grains

Ball mill charge size distributions originally specified for Bond grindability tests to determine the Bond Work index (BWi) are not commercially available. Those proposed to date do not match all of Bond's (1961) original specifications of total ball mass, number and surface area. An alternative mill ball charge is proposed that closely approximates Bond's original total ball mass, number of balls and ball surface area.Results of 30 Bond Work index tests of six pure materials (calcite, magnesite, labradorite (feldspar), quartz, andalusite and glass) using closing screen apertures (P1) values of 500, 250, 125, 90 and 63μm are analysed. The samples were selected on the basis of having distinct hardness's (Mohs hardness 3 to 7.5), being relatively free of crystallographic defects and having distinct cleavage properties The 80 percentile size of the fines produced (P80) concur with those of published values.The trend based of P80 values for P1 values of 150 to 44μm recommended by Bond poorly fit with published P1 values >250μm. It is demonstrated that the BWi test P1 values of mono-mineralogical or mono-material samples determines the P80 value obtained. Based on test results of this investigation a polynomial exponential equation relating P80 to P1 values with an R2 correlation factor of 0.9977 is presented. This relation is independent of the tested material hardness and crystallographic defects and planes of weakness.

The Bond work index of limestone and andesite mixtures

This paper investigates grinding of mineral mixtures with different grindabilities in the Bond ball mill. Understanding the ore mixture grinding is of great importance in mineral processing. The energy required for crushing and grinding is presented by the Bond work index and is determined by means of Bond grindability test. This paper presents the experimental results of the Bond work index values obtained by the standard method on limestone and andesite samples, as well as composite samples made up from these ore in different weight ratios. Comparatively are shown the Bond work index values that are obtained by the mass fraction of components that make up the composite samples calculation and their differences from the real value. During the Bond work index value determining, changes in the composition of the grinding products and circulating mill charge were monitored.

Comminution test method using small drill core samples

Comminution tests aim to measure the comminution properties of ore samples to be used in designing and sizing the grinding circuit and to study the variation within an ore body. In the geometallurgy context this information is essential for creating a proper resource model for production planning and management and process control of the resource’s exploitation before and during production.Standard grindability tests require at least 10kg of ore sample, which is quite a lot at early project stages. This paper deals with the development of a method for mapping the variability of comminution properties with very small sample amounts. The method uses a lab-scale jaw crusher, standard laboratory sieves and a small laboratory tumbling mill equipped with a gross energy measurement device. The method was evaluated against rock mechanics tests and standard Bond grindability test. Within this approach textural information from drill cores is used as a sample classification criterion.Experimental results show that a sample of approximate 220g already provides relevant information about the grindability behavior of iron ores at 19% mill fillings and 91% fraction of the critical mill speed. The gross energy measured is then used to calculate an equivalent grinding energy. This equivalent energy is further used for predicting the variations in throughput for a given deposit and process.Liberation properties of the ore connected to grindability elaborates energy required for grinding and significances of it when deciding to move to higher grinding energy considering the improvement of liberation of the desired mineral. However, high energy significantly enhanced the degree of liberation of magnetite and is expected to improve the concentrate grade after downstream treatment. The higher the magnetite content the better is the liberability of magnetite and the lower the energy required to liberate the desired mineral. Liberability of magnetite is also affected by texture classes containing low magnetite content. A methodology that combines this information has been developed as a practical framework of geometallurgical modeling and simulation in order to manage technical and economic exploitation of resource at early, project stages and during mining operations.

Comparisons of Dry Grinding Kinetics of Lignite, Bituminous Coal, and Petroleum Coke

The objective of this study was to analyze dry grinding kinetics of three different solid fuels in terms of selection and breakage distribution functions values using a batch laboratory ball mill. For this purpose, first, standard Bond grindability tests were made for three different fuel samples. Second, experiments were carried out with eight different mono-sizes between 1.7 and 0.106 mm formed by a √2 sieve series fraction. Then, parameters of Si and B i,j equations were determined from the size distributions at different grinding times. Finally, the kinetic model parameters (Si , aT , α, γ, β, and φ j ) were compared for three different fuel samples, and the relationship between proximate analysis values (ash, moisture, etc.) with the Bond grindability value (Gbg ) and breakage parameters were examined. From the results of the test, the validity of the relationships between Bond grindability and proximate analysis has been not confirmed with good correlation coefficients. The reason for this negative result could be attributed to a difference of the geological origin of solid fuels. However, relationships between breakage parameters of grinding kinetic and proximate analysis values of solid fuel samples were obtained for γ value. Additionally, it was found that the bituminous coal was easier to grind than lignite and petroleum coke, taking into account the quite different values of the model parameters. However, petroleum coke was given finer than other fuel in respect to finer size fraction.

Determination of the Bond work index on samples of non-standard size

The Bond work index, Wi, is defined in a Bond ball mill on the samples of standard size −3.327+0mm. In practice, it is possible to find materials of non-standard size that are finer than 3.327mm.In this work, a procedure for the calculation of the Bond work index is suggested for cases when the Bond grindability test is conducted on samples of non-standard size.

Estimation of the Bond grindability index from chemical analysis values and modulus of mixture of raw material of marls

In this study, the relationships between Bond grindability index (Gbg) and chemical constituents were investigated on marl samples from the AS cement factory (Burdur/Turkey). First, standard Bond grindability tests were carried out for marl samples. Then, chemical analysis values were performed for six different marl samples. Second, the modulus of mixture of raw materials (lime saturation factor, cementation index, saturation factor, cementation index, alumina modulus, lime and silica modulus, hydraulic modulus, silica modulus) was calculated. Finally, the relationships between the Bond grindability (Gbg) with chemical analysis values (calcium oxide, silicon dioxide and loss on ignition) and modulus of a mixture of raw materials were examined. The validity of the obtained relationship equations have been confirmed with correlation coefficients (r2) of as high as 0·954, outside silica modulus through a simple regression analysis of marl samples. From these relationships, the Bond grindability index of marl samples can be determined with good accuracy.

Comparison with Some Porous Materials and the Effects of Powder Filling on Breakage Parameters of Diatomite in Dry Ball Milling

In this study, a comparison of breakage parameters with some porous materials (pumice, trass, and amorphous silica) and the effects on breakage kinetics of powder filling of diatomite were investigated on at batch grinding conditions. For this purpose, first, standard Bond grindability tests were performed for four porous samples. Second, eight different mono-size fractions of all samples were carried out between 1.7 mm and 0.106 mm formed by a sieve series. Then, Si and Bi,j equations were determined for the size distributions at different grinding times, and the model parameters (Si, aT, α, γ, φj, and β) were tested for four different porous materials. Finally, model parameters were discussed for four different powder filling (3.5, 7, 10.5, and 14%) of diatomite samples. From the results of test, the validity of the relationships between Bond grindability and breakage parameters has been not confirmed with good correlation coefficients. The reason of this negative result could be attributed to different of the geological origin of porous materials. In addition, the results of the effect of powder filling on the grinding were found different than other investigators.

Improvement of grinding characteristics of Indian coal by microwave pre-treatment

The influence of microwave pretreatment on the grindability of high-ash Indian coal was investigated. Scanning electron microscope analysis characterized the micro fractures in microwave treated coal samples, which may be due to the thermal stress cracking resulting from the microwave pretreatment. X-ray diffraction analysis showed that the microwave treated coal had a higher peak compared to the untreated coal indicates that the crystallinity increased with the microwave exposure time. The calculation of the Hardgrove grindability index indicated an increase in the ease of grinding or an increase in the grindability index of the microwave treated coal. Bond grindability tests showed that the work index decreased 15.4% after a microwave exposure time of 120 s. Grindability tests showed that the microwave treated coal ground much more rapidly initially than the untreated coal, with the specific rate of breakage (S 1) increasing by an average of 15%. The results showed that the rates of breakage of both microwave untreated and treated coal samples were dependent on particle size.

Application of Box–Behnken design and response surface methodology for modeling of some Turkish coals

The aim of our research was to apply Box–Behnken experimental design and response surface methodology for modeling of some Turkish coals. As a base for this study, standard Bond grindability tests were initially done and Bond work indexes ( W i ) values were calculated for three Turkish coals. The Box–Behnken experimental design was used to provide data for modeling and the variables of model were Bond work index, grinding time and ball diameter of mill. Coal grinding tests were performed changing these three variables for three size fractions of coals (−3350 + 1700 μm, −1700 + 710 μm and −710 μm). Using these sets of experimental data obtained by mathematical software package (MATLAB 7.1), mathematical models were then developed to show the effect of each parameter and their interactions on product 80% passing size ( d 80). Predicted values of d 80 obtained using model equations were in good agreement with the experimental values of d 80 ( R 2 value of 0.96 for −3350 + 1700 μm, R 2 value of 0.98 for −1700 + 710 μm and R 2 value of 0.94 for −710 μm). This study proved that Box–Behnken design and response surface methodology could efficiently be applied for modeling of grinding of some Turkish coals.

Variation of back‐calculated breakage rate parameters in Bond‐mill grinding

The variation of breakage rates with grinding environment is important in the analysis and simulation of various grinding processes. In particular, computer simulation of the labor‐intensive experimental Bond grindability test requires reliable estimates of breakage rate and distribution parameters from a minimum amount of experimental work. This paper was aimed at studying the variation of breakage rate parameters in the Bond mill. Batch kinetic experiments with monosize feeds and standard locked‐cycle Bond grindability tests with natural size feeds were carried out on cement clinker and trass samples. Using the cumulative‐basis, size‐discretized population balance model (PBM) of batch grinding and invariant breakage distribution parameters determined from monosize short‐time grinding experiments, the breakage rate parameters were back‐calculated by minimizing the sum of squares of relative deviations between the simulated and experimental product size distributions. The back‐calculated rate parameters were found to be varying depending on either grinding time or the feed size distribution. No single set of parameters was found to be representative of the whole grinding path in the Bond grindability test, and therefore attempts to simulate the Bond test with 1 set of parameters resulted in incorrect computed work index values.

Wet bond mill test

The Bond grindability test is currently used in the minerals industry to provide data fundamental to the design of commercial milling installations. In some instances it was found that the work index for the fine limiting sizes (such as 53 μm) was abnormally high. Observations of the test procedure suggested that the dry screening procedure seemed likely to give rise to errors. Other alternative modified Bond test procedures were discussed to solve this problem. Wet Bond milling and screening tests were carried out to avoid incomplete screening of the circulating load at fine sizes. Because the work index required for dry milling was greater than for wet milling, in order to calculate the standard Bond index, the Bond index obtained from wet milling had to be multiplied by 1.3. The results from the dry and wet tests correlated very well.

Simulation of bond grindability test by using cumulative based kinetic model

Bond Grindability Tests are used to provide basic data for designing industrial comminution circuits. The Bond Work Index (W i) of an ore is determined by Bond Grindability Tests that indicate resistance the to comminution. The work index is very important but its determination is time consuming and requires skilled staff and 10 kgs of specially prepared feed sample. Consequently attempts have been made to correlate Bond Tests to classical batch grinding tests. In this study, computer simulation of the Bond Grindability Test was made by using a Cumulative Based Kinetic Model. Standard Bond Grindability Test procedure was carried out to determine the actual work indices of six samples. Batch grinding tests were also performed to determine model parameters. After validation of the model, computer simulations were carried out and the results were compared.

Evaluating high pressure milling for liberation enhancement and energy saving

A programme of laboratory based studies has been undertaken to evaluate the extent of liberation enhancement and energy saving that might be expected when utilising high pressure rolls comminution. This route has been compared to that achieved by conventional grinding for the final preparation of a base metal ore for feed to a flotation circuit. Bond grindability tests were undertaken to estimate expectation of energy requirements for a close circuit mill and direct interpolation allowed an estimate of mill energy required for de-agglomeration following high pressure rolls crushing. The energy input to a simulated high pressure rolls mill was measured directly from work input to samples of the ore. The extent of mineral liberation was assessed directly by evaluating the results obtained from flotation release analysis of the ground samples. The results obtained suggest that a similar degree of liberation may be obtained by the high pressure route but at a coarser product size compared to a conventional route. The energy saving as a consequence of a coarser product and the use of high pressure rolls may be as high as 30%. Despite the marginally lower overall recovery obtained the results from a limited test programme suggest that the high compression route may offer significant scope for improved process efficiency.

The Powder Technology of Standard Grindability Tests

ABSTRACT An analysis is made of the way in which particles are captured and stressed in the Bond Grindability test (ores, cement clinker) and the Hardgrove Grindability lest (coals). The deficiencies of the test results for scale-up to full-scale mills and pulverizers are illustrated by experimental data, and some alternative test procedures are suggested. The concepts are extended to the tests developed for scale-up of grinding in high pressure grinding rolls, and comparisons are made. It is accepted that these standard tests of long standing are useful because of empirical correlations to observed experience, but their limitations must be understood. The Bond Work Index (Wi) and the Hardgrove Grindability Index (HGI) are poorly correlated, but a good correlation is obtained if the Bond test values are obtained from a Bond mill fitted with lifters.

Microwave-assisted grinding

The US Bureau of Mines has conducted studies on the use of rapid microwave heating to stress-fracture ore samples. Iron ores containing hematite, magnetite, and goethite were subjected to microwave energy in batch operations at 3 kW and heated to average maximum temperatures between 840 and 940 degrees C. Scanning electron microscope (SEM) photomicrographs verified fracturing along grain boundaries and throughout the gangue matrix. Standard bond grindability tests showed that microwave heating reduced the work index of iron ores by 10 to 24%. When a continuous feed belt in a microwave applicator was used, samples heated more uniformly and quickly than in batch operations. In a microwave chamber designed to simulate a continuous throughput operation at 3 kW, the grindability of a taconite ore was improved by 13% at a bulk temperature of 197 degrees C. Because stress cracking occurred at a lower temperature, less energy was consumed, thereby improving the cost effectiveness of microwave-assisted grinding. To further improve the economics of microwave fracturing, preliminary tests were conducted to increase heating rates by using higher microwave powers. To appraise the economic feasibility of microwave-assisted grinding, the beneficial effects in the grinding circuit and in the extractive operation were considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Computer simulation of the bond grindability test : Lewis, K A; Pearl, M; Tucker, P Miner EngngV3, N1/2, 1990, P199–206 (Paper to the International Communication Symposium, Camborne, 13–15 September 1989)

Computer simulation of the bond grindability test : Lewis, K A; Pearl, M; Tucker, P Miner EngngV3, N1/2, 1990, P199–206 (Paper to the International Communication Symposium, Camborne, 13–15 September 1989)