Rod Mill Research Articles

Effect of grinding media on surface property and flotation performance of ilmenite

Grinding is essential for flotation separation, and the shape of grinding media impacts the morphological characteristics of mineral. This study systematically analyzed the surface physicochemical properties of ilmenite ground with ball and rod media using various analytical methods. Particle size analysis and scanning electron microscopy (SEM) revealed that rod-milled products had coarser sizes, greater irregularity, higher elongation, and lower roundness than ball-milled products. X-ray diffraction (XRD) results indicated that the proportion of the {104} crystal surface produced by rod milling was 49.55 %, compared to 47.45 % produced by ball milling. Adsorption and flotation tests confirmed stronger interactions between rod-milled products and sodium oleate (NaOL), leading to a higher recovery than ball-milled products, with the largest recovery difference being 14.15 % at pH 5.0. Furthermore, flotation kinetics analysis indicated that rod-milled products exhibited higher flotation rates than ball-milled products. This study provides valuable guidance for the selection of grinding media in industrial production.

Synthesis and Characterization of Red Pigment from Acid Regeneration Plant (ARP) By-product Via Rod Milling Process

Iron o xide waste from acid regeneration plants (ARP) is often discarded due to its non-profitability. This research aims to introduce a value-added process to convert iron oxide waste into red pigment via rod milling process. The iron oxide waste collected from ARP was grinded with a rod milling machine at 30 rpm for 24 hours. The ground product was then mixed with industrial-grade red pigment in various ratios. The mixed samples were then rod-milled again into ultra-fine particles. A total of seven samples were prepared, applied onto a canvas and analysed by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) methods. From the analyses, the existence, composition, and orientation of iron oxide were established. The waste-derived red pigments were subsequently subjected to particle size analysis on a scanning electron microscopy (SEM) platform, with results showcasing the efficiency of the rod milling process. Colour-related properties of the samples before and after canvas application were investigated using the L*a*b* system with a chromameter. Empirical outcomes indicated that the a* value plays an important role in determining the redness of the sample. Overall, the a* values obtained were above 15 and gradually increased in accordance to the amount of industrial-grade red pigment added. The oil absorptivity of red pigments was also tested via an oil absorptivity test. Notably, the assay signified that particle size and porosity affect the amount of oil that can be absorbed by the pigment.

Increasing of the unit capacity of MF process at Miike Smelter

MF (Mitsui Furnace) is a half shaft blast furnace developed by Mitsui Miike Smelter in the 1960’s to treat vertical retort residue. Currently MF mainly treats various secondary wastes (EAF dust, Secondary Fly Ash, etc.) and recovers zinc and lead as crude zinc oxide, copper and silver as matte, meanwhile other elements such as FeO, CaO, SiO2, Al2O3 are concentrated in slag.There are two steps in the MF process. The first step is pretreatment. In this process, various waste materials are blended in a certain proportion with reductant and dried adding binder in a rotary dryer, then grinded in a rod mill. The grinded materials are made into an oval briquette by briquetting machine. The second step is treatment process. The briquettes fed into the MF are smelted and reduced by blowing air through the tuyeres. By enriching the tuyere air with oxygen generated by the VSA (Vacuum Swing Adsorption) oxygen generator in 2005 and 2012, we have improved the throughput of wastes.By the improvement of oxygen enrichment in the MF, the unit capacity increased significantly. However shortage of the drying capacity in the pretreatment process became a problem. To ensure sufficient drying capacity, we installed one more rotary drier in series in 2016. Additionally in 2018, we installed a granulator after the rod mill to improve the bulk density in briquette. As a result of these efforts, the treatment amount in the whole MF process has increased.The MF can treat various kinds of materials containing various non-ferrous metal-valuables. Through these process improvements, we promote the treatment of wastes containing heavy metals and contributes significantly to the recycling of metal resources.

Comparison of Approaches to Predict Grinding in An Industrial Rod Mill Operating at Low Fillings

ABSTRACT Several approaches have been proposed over the years that may be used to predict the performance of industrial rod mills. Unfortunately, studies that allow comparing the accuracy in their predictions are very scarce. The work compares four methods for predicting size reduction in an industrial rod mill. These were the Bond work index method (BW) and the Callcott–Lynch (CL) model, both originally proposed for rod mills, besides the Herbst–Fuerstenau (HF) and the Austin–Klimpel–Luckie (AKL) models, first proposed for ball mills, but here adapted and applied to rod milling. A total of 10 industrial surveys were conducted of the industrial mill in dry grinding of coke breeze, covering operation under a variety of conditions, all of which at lower fillings than commonly used in industry (<15%). Since most conditions surveyed were not within the typical operating range for rod mills, simulations using the Discrete Element Method were used to predict the mill power, used as input in both BW and HF models. At first, the fidelity of methods that allow predicting full-scale mill performance solely from bench-scale information, namely BW, HF, and AKL, is compared. Results showed that they all presented high biases in their estimates of product fineness, with AKL predicting finer products whereas BW and HF predicting coarser products. Using then data from a single industrial survey for model calibration (base case), in addition to the bench-scale test results, a comparison of the four approaches became possible. Taking the absolute deviations between measured and predicted P 80 values, it became evident that the HF provided the highest fidelity in the predictions, with mean deviations of 12.8%, AKL with 15.3%, with both BW and CL presenting deviations above 18%. The work thus shows that size-mass balance models that rely on fitting most model parameters from bench-scale tests (HF and AKL) can provide predictions with good confidence when data from an industrial base case are additionally used in fine-tuning the model, even when applied to describing rod milling under unusually low fillings.

INVESTIGATION OF ENERGY - TECHNOLOGY DEVELOPMENT IN ULTRA FINE GRINDING

Ultra-fine grinding refers to the process of reducing materials to extremely small particle sizes, typically in the micron or submicron range. It is commonly used in various industries such as mining, pharmaceuticals, ceramics, and chemicals, where the production of fine particles with specific properties is required.&#x0D; Energy plays a significant role in ultra-fine grinding processes. The reduction of materials to such small sizes requires a considerable amount of energy input. The energy consumption in ultra-fine grinding is typically higher compared to conventional grinding methods due to the higher surface area and increased particle-particle interactions.&#x0D; In the mining sector, with the depletion of high-grade ore deposits, it has become a necessity to operate very low-grade ore deposits with very small particle liberation sizes. In the enrichment of these ores, most of the energy required is spent on grinding. In micronized grinding, conventional mills (such as rod and ball mills) lose their efficiency and become uneconomical. &#x0D; most of the energy spent in conventional mills is used directly in size reduction, and a significant portion is lost as heat and sound without doing any useful work (size reduction). In addition, for grinding below 75 µm , the efficiency of conventional mills is greatly reduced (energy consumption increases excessively), and grinding becomes uneconomical. &#x0D; In this study, alternative fine and ultrafine grinding mills for ore dressing plants are introduced, and information about their working principles is presented. Unlike other studies, information on particle and grinding energy calculations is given. The reasons for the lack of a theory or model to perform newly developed calculations for ultrafine grinding theories are tried to be explained.

An Improved Understanding of Chalcopyrite Leaching Mechanisms: The Influence of Anisotropic Crystal Planes

Chalcopyrite (CuFeS2) particles, exposing anisotropic crystal planes during the grinding process, possess comprehensive surface properties that affect their leaching behaviors. In order to investigate the influence of anisotropic crystal planes on the leaching mechanisms, CuFeS2 particles with anisotropic crystal planes were produced by employing three-head laboratory grinder mill (TM), rod mill (RM), and ball mill (BM) and were then leached in a sulfuric acid solution at pH = 1. Based on the XRD, SEM, XPS, and simulation results, (112), (102), (312), (110), (116), (100), and (001) planes were mainly exposed on the CuFeS2 surface during the crushing and grinding process. In addition, fewer (112), (102), (312), and (110) planes but more (116), (100), and (001) planes were exposed on the CuFeS2 samples in the TM method than in the RM and BM methods. Since the leaching rates were in the order of (001) &gt; (100) &gt; (116) &gt; (110) &gt; (312) &gt; (102) &gt; (112) planes, the Cu extractions followed an order of TM &gt; RM &gt; BM. This study, therefore, provides an excellent theoretical basis for the effect of anisotropic crystal planes on CuFeS2 leaching, further improving the understanding of CuFeS2 leaching mechanisms.

Long-term simulation of an industrial coke breeze grinding circuit

One important application of rod milling is in size reduction of coke breeze, which is used as solid combustible in iron ore sintering plants. The work applies modeling and simulation of an industrial circuit comprised of a flip-flow screen and a rod mill to predict the circuit response in long-term operation, following the strategy used in the plant of replacing the rod charge only when it reaches the end of its life. Initially, the model for rod wear has been calibrated and the mill fillings estimated. Then the mill model has been validated with data from several industrial surveys, showing good agreement between the two. A long-term (approximately three-month) pseudo-dynamic simulation was then carried out to mimic the strategy normally used in plant operation. Additional simulations were then carried out to compare different scenarios of operation, demonstrating the benefit of increasing the rod charge and diameter, in particular when associated with operation of the mill at lower speed in the beginning of the charge life and progressive increase thereafter, besides partially replacing worn rods in their midlife. For instance, simulations showed that an increase in initial mill filling from 15 to 20 %, progressive increase in fraction of critical speed from 0.40 to 0.65 in contrast to operation at constant speed and gradual reduction of throughput from 60.0 to 40.2 t/h resulted in 56 % increase in charge lifetime, 35 % reduction in variability in product quality and 12 % reduction in cost of operation per ton of coke breeze produced.

Modeling and simulation of dry grinding of coke breeze in rod mills

Limited to less than 5 m in diameter and, as such, no longer found in large-scale circuits, rod mills remain popular in medium- and small-scale plants, primarily owing to their ability to prevent overgrinding. One successful application of rod milling is in size reduction of coke breeze, a material generated from mechanical degradation of coke during handling which is used as solid combustible in iron ore sintering. The work investigates the grinding response of coke breeze in a laboratory rod mill, through experiments conducted with narrow-size feeds under a range of conditions. Data has been described using the size-mass balance model, which demonstrated that coke exhibits non-normalizable breakage response, with an inflexion point at 0.27 mm. The model showed very good ability to predict grinding of different narrow sizes after being fitted form a single test. The validity of the Austin-Klimpel-Luckie scale-up relationship, incorporating an additional correction term for moisture, has then been demonstrated by comparing results from experiments with different rod sizes, mill fillings, interstitial fillings and moisture contents to predictions, with very good agreement. Finally, predictions of product size of an industrial mill operating at different throughputs were also in good agreements to data collected in plant surveys, demonstrating the great potential of the model in optimizing full-scale operations.

Numerical assessment of interstand tensions in continuous hot rolling processes of flat and long products

The paper deals with the calculation of interstand tensions in continuous rolling mills.In the rolling mill industry, continuous measurement and data collection of roll forces, roll torques, temperatures and roll velocities is possible. However, the important process parameter of interstand tensions is not directly measurable and no direct calculation of the interstand tensions is possible. The interstand tensions couple the effects of subsequent roll gaps and should therefore by known for a holistic recalculation of the process. It is straightforward to calculate the effects of the tensions on roll forces, torques and the stock velocity. The inverse problem of calculating the acting interstand tensions including their effects from the process parameters is of greater interest but also of a higher complexity, because the interactions between all the stands in the rolling mill must be regarded. The present paper aims at filling this research gap by presenting a mathematical model to solve the inverse problem by a linearization of the tensions influences in the rolling mill. The present model does not require measured roll forces or torques to find the interstand tensions, only the rotational velocities of the rolls and the rolling parameters (material, temperature, pass schedule or pass design) must be known. Tension-dependent spread is considered by an empirical sub-model. Results are shown for the tension distributions in strip and rod mills. The results indicate that the present friction conditions and the entry size of the rolled stock have a high impact on the tension distributions.

The Optimal Physical Treatment Process for Production of High-grade Iron Concentrate from Waelz Kiln Slag

The aim of this study was to develop a physical treatment method for obtaining iron concentrate with a grade higher than 60% from slag generated in the Waelz Kiln (WK) process. The size of the WK slag used in this work was several millimeters, with T-Fe and ZnO contents of 40.24% and 1.03%, respectively. The slag samples were pulverized in a laboratory rod mill for various grinding times, followed by a magnetic separation test under a low magnetic intensity of 0.05 T initially. The results showed that the highest iron grade was obtained from samples with a grinding time of 10 min. Additionally, for a grinding time of 20 min, the highest grade and recovery ratios were achieved at a magnetic intensity of 0.8 T. Based on these findings, the optimal physical treatment process proposed in this study resulted in iron concentrates with a grade of 61.34% and an enrichment ratio of 1.52.

Statistical distributions for modeling mineral liberation

Using the algorithm and the results of laboratory studies on grinding of loparite ores from the Lovozero deposit in a ball and rod mill, simulation grinding models were designed based on the transformation of a discrete function of the density distribution of outputs of mineral particle size classes. The model’s adequacy was quantitatively analysed carried out by calculating the determination coefficient without taking into account the constant component of the distribution; for a qualitative assessment of the result the authors used the Cheddock scale. The authors studied the minerals disintegration at ball and rod grinding with the following verification of the proposed algorithm. To identify the distribution of loparite by size classes in the initial ore samples and in the samples obtained in the disintegration taking place at different productivity, the X-ray diffraction analysis and the combined (weight, optical and geometric) methods were used.

Prediction of Particle Size Distribution of Mill Products Using Artificial Neural Networks

High energy consumption in size reduction operations is one of the most significant issues concerning the sustainability of raw material beneficiation. Thus, process optimization should be done to reduce energy consumption. This study aimed to investigate the applicability of artificial neural networks (ANNs) to predict the particle size distributions (PSDs) of mill products. PSD is one of the key sources of information after milling since it significantly affects the subsequent beneficiation processes. Thus, precise PSD prediction can contribute to process optimization and energy consumption reduction by avoiding over-grinding. In this study, coal particles (−2 mm) were ground with a rod mill under different conditions, and their PSDs were measured. The variables studied included volume% (vol.%) of feed (coal particle), vol.% rod load, and grinding time. Our supervised ANN models were developed to predict PSDs and trained by experimental data sets. The trained models were verified with the other experimental data sets. The results showed that the PSDs predicted by ANN fitted very well with the experimental data after the training. Root mean squared error (RMSE) was calculated for each milling condition, with results between 0.165 and 0.965. Also, the developed ANN models can predict the PSDs of ground products under different milling conditions (i.e., vol.% feed, vol.% rod load, and grinding time). The results confirmed the applicability of ANNs to predict PSD and, thus the potential contribution to reducing energy consumption by optimizing the grinding conditions.

Setting, bleeding, and hardening strength properties of coarse aggregate backfill slurry

This work systematically investigates the effects of coarse aggregate (CA) type, dosage, and slurry concentration on the backfill slurry's setting, bleeding, and hardening strength properties. Rod milling sand (RMS) and waste rock (WR) were selected as CA, the backfill slurry's concentration ranged from 76% to 79%, its replacement rate of tailings with RMS and WR was between 40% and 60%, and its cure period was 3, 14 and 28 days. Then, the fresh backfill slurry was subject to setting and bleeding experiments, and the hardened backfill slurry was submitted to UCS tests. Finally, a CPB curing time of 28 days was chosen for microstructure experiments to reveal the mechanism of the effect of slurry concentration and CA dosage on CPB hardened strength. The results showed that the initial and final setting times reduce as concentration increases and increase as tailings/CA (T/CA) decreases. The effect of concentration and CA dosage on the bleeding properties of backfill slurry is not apparent. Increasing the slurry concentration increases the amount of C-S-H gel inside the CPB, which improves its mechanical behavior. The CPB has optimal physical properties when the slurry concentration is 77%− 78%, and the amount of WR is 50%. The study results can provide a theoretical basis for the preferential selection of backfill materials in mines.

Development of process flow scheme on a low-grade calcareous graphite ore by split flotation technique

ABSTRACT The low-grade calcareous graphite ore contains 14.5% Fixed Carbon (FC), 71.82% ash, and 13.68% volatile matter plus moisture content. The primary liberation size, 210 µm was determined by the mesh of grind. In order to upgrade the ore, the sample was ground wet in a rod mill to obtain a coarse product of 210 µm size. It is further subjected to rougher flotation followed by one-stage cleaning of rougher float to reject the maximum amount of gangue minerals with a minimum amount of graphite losses at this size range. The first stage cleaner float was sieved over 150 µm size to separate +150 and −150 µm size fractions. These size fractions were subjected to grinding for further liberation of graphite values and thereby subjected to multistage cleaning separately to produce high-grade graphite concentrates. Three-stage grinding, and multistage cleanings were involved in the split flotation process to produce a high-grade flake and fine graphite concentrate. The combined graphite concentrate produced using the split flotation technique was 85.56% FC with a weight yield of 13.0% & recovery of 76.6%, comparatively more than 80.68% FC with a weight yield of 12.4% & recovery of 68.8% in the direct flotation technique results.

Comparison of simulation model and plant data of a crushing-grinding circuit

Increasing complexity of ore deposits requires operations to be continuously improving their cost competitiveness. Mathematical modelling and process simulation techniques are useful tools to understand the process, define bottlenecks and increase process efficiencies. This paper presents a crushing and grinding circuit of a chromite ore gravity separation plant’ simulation model results and actual plant operating data. Throughout the study, jaw crusher, ball and rod mill summary equipment characteristics, breakage and selection functions employed, comparison of particle size distribution curves of site process streams to model results are presented. Simulation work is completed by using METSIM® software. The paper also showcases ease of flow diagram and process data presentation by the utilisation of the adequate simulation approach.

Effective separation and recovery of iron and chromium from laterite residue in the presence of calcium chloride

In nitric acid pressure leaching (NAPL) for the treatment of limonitic laterite ores, the comprehensive utilization of leach residue is significant for resource recovery and environmental protection. In this work, the recovery and separation of iron and chromium from NAPL residue by metallization reduction roasting−magnetic separation with calcium chloride as additive was studied. The following optimum parameters were obtained: 1100 °C roasting temperature, 25 % reductant dosage, 40 min roasting time, 7 % calcium chloride dosage, 200 mT magnetic field intensity, and 40 s rod mill time (D50 = 7.20 µm). Under these optimum conditions, 81 wt% iron content in the concentrate and 7.4 wt% chromium in the tailings were obtained. The corresponding recovery rates of iron and chromium were 95 % and 64 %, respectively. The microstructure and composition of leach residue and process products were investigated by SEM, EDS, and XRD to study the phase transition and polymerization of substances during roasting. The results showed that iron was mainly enriched in the magnetic concentrate, and chromite and silicate minerals dominated the tailings. Analysis of the action of calcium chloride in the reduction roasting revealed that calcium chloride was beneficial for the liberation of Fe from fayalite and the migration and polymerization of iron.

Developing an Automated System to Control the Rolled Product Section for a Wire Rod Mill with Multi-Roll Passes

The key priority of metallurgical industry development is expanding the range and improving the quality of bar products and their major component, steel wire. Continuous wire rod mills with multi-roll passes have been developed and implemented over the past decades. These include mills with four-roll passes with mutually perpendicular rolls. The specific feature of mills with complex passes is the impossibility of conduct and the direct measurement of the workpiece dimensions in several directions during rolling. The paper studies the development of a system for indirect control over complex section geometry by adjusting the interstand space tension with simultaneous compensation for changes in rolling forces. The paper contribution is the first justification of a technique for the control over the indirect rolled product section on mills with multi-roll passes based on theoretical and experimental research. Analytical and experimental dependencies between the metal pressure on the rolls and the semifinished rolled product temperature, rolling speed, and single drawing have been obtained for various steel grades. The impact of process factors on the rolled product section geometry when rolling in stands with four-roll passes has first been studied. The automated control system implementing the proposed technique has passed pilot tests on a continuous five-stand mill. The processes occurring in closed-loop speed and torque control systems under controlling and disturbing effects have been experimentally studied. Implementing the proposed algorithms indirectly confirmed the reduced impact of tension and pressure on the section geometry.

Data-Driven Roll Pass Design of Wire Rod Mills

The classical approach for roll pass design of a wire rod mill employs an iterative technique incorporating spread calculation and rectangular equivalent pass methods. This method comes to its limits in terms of computational efficiency and numerical stability when a complete pass design for a wire rod mill with lots of different final dimensions and materials must be designed. To improve the pass design technique, a fast data-driven method for pass design based on synthetic data generated by the classical pass design model was created. The results are compared to the original training data, as well as newly generated test data. It is shown that the artificial neural network (ANN) is able to predict appropriate oval groove geometries with good precision.

A Kinetic Model for Size Reduction in a Pilot Scale Tower Mill: Model Verification

Mark Duffy produced a complete set of grinding data on a pilot-scale tower mill. Here these data are analyzed in terms of grinding kinetics. The results show that the data can be fitted with a simple first-order breakage model, which is not normally observed in any grinding system, including other types of grinding machines such as tumbling ball mills and rod mills. The model has only two parameters, making it possible to determine the parameters using simple search methods. The results show that larger particles break faster than smaller particles, as is usually observed in all mills. Statistical analysis of the data showed that one of the parameters could be fixed for seven of the nine tests.

Study on maceral characteristics and separation of low-rank coal

ABSTRACT This paper studies the characteristics of Shenhua low-rank coal, including industrial analysis, element analysis, density composition, particle-size composition, maceral characteristics and enhanced gravity. The separation characteristics of Shenhua low-rank coal maceral were examined by manual enrichment, screening enrichment and centrifugal heavy-liquid separation. After manual enrichment, vitrinite content was 31.06% higher than vitrinite content in raw coal, and inertinite content was increased by 13.50% compared with raw coal. The screening results show that vitrinite is easily broken into small pieces to be enriched in coarser particle size (0.125–0.074 mm), and inertinite is easily enriched in fine particle size (−0.045 mm); Centrifugal heavy-liquid separation showed that product in range of −1.30 g/cm3 was taken as pure vitrinite and product in range of 1.36–1.40 g/cm3 was regarded as purer inertinite. Finally, using rod mill products as feed material of enhanced gravity separation to study effect of feed speed, rotation frequency and recoil water on vitrinite recovery, vitrinite recovery of 71.81% and vitrinite content of 68.72% are obtained respectively under the optimal conditions of 30 Hz rotation frequency, 0.03 MPa recoil water pressure and 15 ml/s feed speed.