Rod Mill Research Articles

Effect of fine slime on the choice of columbium ore pretreatment flowsheets

The article presents studies of slime formation in processing of Vishnevogorsk columbium ore. The slime formation criterion is assumed as the presence of size grades less than 50 and 5 µm estimated from modern laser granulometer data. The optimal methods and equipment for grinding are chosen depending on rate of slime formation in final products. The studies use centrifugal and rod mills. The rod mill assures the lowest rate of slime formation. Based on the experimental results, the columbium ore pretreatment flowsheet and special ore disintegration methods have been selected. The flowsheet uses crushing machines ensuring the highest rate selectivity—inertia cone crusher and the lowest rate slime formation during milling—rod mill.

Effects of flow rate, slurry solid content, and feed size distribution on rod mill efficiency

ABSTRACTIn this paper the effects of flow rate, slurry solid content, and feed size distribution on the rod mill efficiency have been investigated. It is difficult to achieve highest grinding efficiency without sufficient information on operating parameters and their effects on the system. Several experiments were performed on a continuous rod milling circuit. Two flowsheets arrangements were considered to produce the particles with size <500 µm: an open circuit and a closed one. The flow rate selected at range of 11.5–17 t/h, slurry solid content at range of 27–61%, and feed size distribution at range of 12–30 mm. Results showed that the lowest grinding efficiency was occurred at solid content of 44 wt% and deviation from this optimum amount had positive implications on mill efficiency. Results also revealed an inverse relationship between flow rate and reduction ratio. The results of both open and closed circuits showed that the feed size had no effect on the mill product size (80% passing product size or d80). However, the reduction ratio was found to be sensitive to the feed size. Mathematical models were also developed to predict d80 and reduction ratio as a function of flow rate, solid content, and 80% passing feed size (f80).

Effects of mechanical activation methods on thermo-oxidation behaviors of pyrite

To explore the effects of mechanical activation methods (ball mill, planetary mill and rod mill) on the oxidation and the spontaneous combustion of pyrite, the kinetic curves of non-activated pyrite and mechanically activated pyrite were created by simultaneous thermal analysis. The structural characteristics and changes of mechanically activated pyrite were investigated by X-ray diffraction and SEM, and the relationship between the mean diameter and the grinding time was obtained by using a laser particle size analyzer. The kinetic model of pyrite and the kinetic parameters were deduced using Bagchi method. The relationship between the kinetic parameters indicates that, pyrite activated by ball milling shows the best thermal stability at the same diameter. By comparing and analyzing the X-ray diffraction patterns, results show that different mechanical activation ways played different roles in structural changes of pyrite.

The effect of regrind mills on the separation of chalcopyrite from pyrite in cleaner flotation

Stirred mills have been widely used for regrinding and are more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms and redox environments during grinding. In this study, the effect of regrinding with these two types of mills on the separation of chalcopyrite from pyrite in the cleaner stage was studied. A laboratory rod mill and a laboratory stirred mill were used to regrind rougher flotation concentrates. It was found that chalcopyrite and pyrite exhibited different flotation behavior after regrinding with the rod mill and the stirred mill, resulting in different separability of chalcopyrite from pyrite. The mechanism underpinning this phenomenon was investigated by a range of techniques including dissolved oxygen demand measurements, X-ray photoelectron spectroscopy (XPS) and Time of flight secondary ion mass spectrometry (ToF-SIMS). It was found that the two mills produced different surface oxidation and pyrite activation by copper ions which determined the separation of chalcopyrite from pyrite. This study demonstrates that the selection of a regrind mill should not only depend on its energy efficiency but also the property of surfaces produced for subsequent flotation.

Preparation of New Backfill Cementitious Materials with Unclassified Tailings-Rod Milling Sands

According to an orthogonal experimental design and neural network prediction models, a new kind of backfill cementitious materials of unclassified tailings- rod milling sands is prepared with unclassified tailings partly replaced rod milling sands as aggregates, iron slag powder as the active materials as well as desulphurized ash and quicklime as the main stimulator. Hydration products and microstructures of the backfill cementitious materials are analyzed by XRD and SEM. The results show that with addition of 30% unclassified tailings, the compressive strength of the backfill cementitious materials cured for 3 days, 7 days and 28 days reaches 1.73 MPa, 4.22 MPa and 6.93 MPa, and the corresponding increment is 8.13%, 51.8% and 34.0% respectively in comparison with the ordinary cement, and these strength values can meet the backfill strength index of Jinchuan Nickel mine. The hydration products of the new backfill cementitious materials are mainly C-S-H gel and flocculent CSH gel, which form dense gel and bond the aggregates together resulting in the high mechanical strength of the materials. Therefore, utilization of 30% unclassified tailings can be achieved for the nickel mine company through producing this new backfill cementitious materials.

Simple Mechanical Beneficiation Method of Coarse Fly Ash with High LOI for Making HVFA Mortar

This study focusses on the effect of milling of fly ash obtained from four different sources on the properties of high volume fly ash (HVFA) mortar. Two fly ash samples with low loss-on-ignition (LOI) were taken from a coal-fired power plant, while the other two with high LOIs were obtained from a textile factory and from a paper mill, respectively. Milling was performed using a rod mill at a certain period of time. The workability of HVFA mortar with constant water to cementitious ratio was controlled by adjusting the superplasticizer content. The results show that the specific gravity of fly ash increases after milling. Utilizing milled fly ash ends up with significant strength increase of HVFA mortar, especially those utilizing high LOI fly ash. This shows that milling is an excellent fly ash beneficiation technique, especially on the one with high LOI value.

Ergonomic Study and Design of the Pulpit of a Wire Rod Mill at an Integrated Steel Plant

This paper presents ergonomic study and design of the pulpit in a wire rod mill at an integrated steel plant. The mill was facing problem of less productivity of workers due to lack of proper work posture and working conditions. The study data were collected from the interview of seven operators involved with the pulpit. Relevant ergonomic tools were used for assessing the survey data for identifying the risk factors involved with these operators. Ergonomically improved pulpit was proposed for reducing the musculoskeletal disorders (MSDs) thereby increasing the productivity of the plant.

A one-parameter model for describing the residence time distribution of closed continuous flow systems characterized by nonlinear reaction kinetics: Rod and ball mills

For evaluation of the performance of a continuous flow reactor, a description of the residence time distribution (RTD) of the reactants is required in the form of a suitable mathematical expression. For closed reactors, the analytic expression obtained from the well known axial dispersion model is too complicated for practical use. The \ wo-parameter empirical model that involves one large and two small perfectly mixed sub-reactors along with a small plug flow sub-reactor provides an accurate description of RTD in the form of a relatively much simpler mathematical expression. However, due to the lack of specification of the sequence in which the sub-reactors are arranged, this model cannot be used for modeling of systems characterized by nonlinear reaction kinetics. Therefore, in this paper we propose a new one-parameter empirical model that meets both the requirements. The model involves partitioning the process unit into a number of unequal-volume perfect mixers arranged in a definite order. The first perfect mixer at the feed end is the largest, and the volumes of the successive smaller perfect mixers form a geometric progression, the inverse of the common ratio being the sole parameter of the model. Several sets of available experimental RTD data on two closed reactors, rod mills and ball mills, were analyzed using the proposed model. In most cases the model was found to fit the experimental data on a par with the dispersion and two-parameter models. Moreover, the proposed order of arrangement of different perfect mixers could be validated by demonstrating that the simulated trend of variation in the particle size distribution along the mill matches closely with that observed in practice.

화력발전소 매립 석탄재의 분쇄가 지오폴리머의 강도에 미치는 영향

Abstract Bottom ash from coal fired power plants is not widely used due to a broad range of particle sizes and a high carbon contentfor producing geopolymers. The effect of mechanical activation on compressive strength of bottom ash- based geopolymers wasexamined by rod and planetary-ball milling to encourage full-fledged recycling of bottom ash, the main component of pond ash.The amount of amorphous component in the milled ash samples did not change significantly after the mechanical activation. Itis presumably because needle-shaped mullite crystals, which is a major crystalline phase and grown in a glassy matrix, possesshigh strength and toughness, and therefore, they could endure external shocks and remain almost intact. Milling operation, how-ever, decreased the particle size and improved the homogeneity of ash, thereby leading to increase reactivity of milled ash withalkali activators. Rod milling produced a relatively narrow particle size distribution of the milled ash particles; however, it was · Received : July 16, 2014 · 1st Revised : September 1, 2014 · 2nd Revised : October 24, 2014 · Accepted : November 6, 2014Corresponding Author : Sujeong Lee (E-mail : crystal2@kigam.re.kr)Mineral Resources Research Division, Korea Institute of Geoscience & Mineral Resources, 124 Gwahang-no, Yuseong-gu,Daejeon, 305-350 KoreaTel : +82-42-868-3125 / Fax : +82-42-868-3418ⓒThe Korean Institute of Resources Recycling. All rights reserved. This is an open-access article distributed under the termsof the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permitsunrestricted non-commercial use, distribution and reproduction in any medium, provided the original work is properly cited.

Dynamic image analysis of calcite particles created by different mills

In this study, particle shapes of calcite mineral ground by different mills namely ball, rod and autogenous mills were measured using a new 3D analysis with random orientation technique (by Micromeritics® Particle Insight Dynamic Image Analyzer). The results were expressed by the shape parameters such as circularity, ellipse aspect ratio (EAR), bounding rectangle aspect ratio (BRAR) and feret aspect ratio (FAR). More than 6400 particles were measured for each mill product with a 99% statistical accuracy. The results showed that, the highest aspect ratio (EAR, BRAR and FAR) and the lowest circularity were obtained by autogenous mill. However, the highest circularity and the lowest aspect ratio were obtained by rod milling. These differences in shape were attributed to the different grinding mechanisms acted in the mills employed. The results of the 3D dynamic image analysis were also compared with previous study for the same mineral based on 2D SEM technique. Although different techniques were used for shape analysis, the results were in good agreement with each other. This approach will find various applications for calcite characterization, preparation and utilization processes as well as for other minerals.

Modeling the Laws that Determine the Quality of Rolled Rounds During the Rolling Operation

It is proposed that results obtained from the experimental-theoretical solution of a three-dimensional problem on the plastic flow of metal be used to determine the main reasons for variations in the output of usable metal products. The results were obtained on the basis of models of quality. Modeling was performed to analyze a technology for rolling a broad range of structural-grade carbon-steel rounds that then undergo cold extrusion and upsetting. The rounds are rolled on a light-section mill and a rod mill at the EVRAZ ZSMK combine. It is shown that under the given production conditions the value of the integral index of rolled-product quality which characterizes the output of usable metal over long periods of time is determined mainly by simultaneous processes that involve the healing (or deepening) of surface defects, the formation of cracks on the surface of the semifinished products, nonuniform wear of the grooves of the rolling-mill passes, and depletion of the reserve ductility of the metal in the region where it comes into contact with the grooves. The results have been used to substantiate corrective measures taken in the multi-stage manufacture of rolled products at the combine. The measures were substantiated within the context of the combine’s existing quality-control system.

Effects of Temperature and Cross Section Variations on the Vibrational Behavior of Finished Wire Blocks

Because of the great speed range in a finishing block of a wire rod mill, the reduction of torsional vibrations makes it possible to achieve closer rolling tolerances. The components transmitting the torque like gear box, coupling etc. can generate non-smooth or alternating torques which affect the product quality. To study the influences of torsion vibrations on the product quality, the dynamic interactions of the block and rolling process are simultaneously analyzed by a simulation model. As an example, a three stand arrangement is considered. The real transmission system is idealized as a structurally discrete torsional vibration model. The generalized rotational coordinates with a large number of rotational degrees of freedom can be reduced among others constants by means of gear ratios. Euler-Lagrange equations are applied to create the coupled equations of motion, which together constitute an ordinary differential equation of order 28. The rolling and main drive torques are defined as excitation for vibration on the right side of the equation system. A DC motor is selected as main drive and the voltage circuit equation of motor is integrated into the system of differential equations. The armature current and its interaction are consequently simulated. The rotational speed of rolls and motor, as well as roll torques, longitudinal stresses in rod and section widths are shown in diagrams as the result and thereby the torsional vibration of the essential elements of the system are studied for different temperatures and cross-sectional variations.

Effect of DROF Process on the Temperature Field and Roll Force

The key technology of direct rolling of free heating for bar and rod mill (DROF) was briefly introduced. Compared with the traditional process, the DROF can reduce energy consumption and emission, so as to decrease the production cost. It is very important to understand temperature field of continuous casting billet (CC-billet) to carry out the research on DROF technology. In order to reduce the loss of heat, the insulation cover is used, so it can effectively reduce the roll force and motor power. The rolling parameters, such as roll force and power, in former 4 stands of roughing mills were investigated by finite element method (FEM). The results show that the average temperature of the CC-billet after 300s from the cutting time can still be over 970°C, it can meet the need of direct rolling.

The Orthogonal Test and Optimal Decision for the Development of New Backfill Cementing Materials Based on the Rod Milling Sand

The experiment uses lime, desulfurization ash, slag and other solid wastes with mirabilite and NaOH as the admixture for Jinchuan mine rod milling sand to get a new backfill cementing materials that can replace the cement materials. There obtains the influence of activators to strength of the new backfill cementing materials’ body through the orthogonal experiment. The MATLAB genetic programming is exploited for getting the regression function of compressive strength and shrinkage rate for the new backfill cementing materials. Using the genetic algorithm to optimize the constrained regression functions that can get the best combinations of the activators, Finally. The results show that the compressive strengths (28d, 7d, 3d) of new backfill cementing materials are 6.73MPa, 4.03MPa and 1.00MPa when the lime, desulfurization ash, mirabilite, NaOH and slag are 7.05%, 16.32%, 3.062%, 1.08% and 72.48%. The optimal results conform to the requirements of the Jinchuan mine filling strength, which lays a foundation for further industrial test of new backfill cementing materials in Jinchuan mine.

The effect of particle breakage mechanisms during regrinding on the subsequent cleaner flotation

Stirred mills have been widely used for regrinding, and are acknowledged to be more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms during grinding. In this study, the effect of regrinding by both mills on surface properties and subsequent mineral flotation was studied, using chalcocite as the mineral example. A rod mill and a stirred mill with the same stainless steel media were used to regrind rougher flotation concentrates. Different chalcocite flotation recovery was achieved in the cleaner stage after regrinding in tumbling and stirred mills. The factors contributing to the different recovery included particle size, the amount of created fresh surfaces, surface oxidation and the redistribution of collector carried from rougher flotation. All the factors were examined. It was determined that the predominating factor was the different distribution of collector resulting from different particle breakage mechanisms in the stirred and tumbling mills, in line with ToF-SIMS analysis. In the tumbling mill, the impact particle breakage mechanism predominates, causing the collector to remain on the surface of newly produced particles. In the stirred mill, the attrition breakage removes collector from the surface, and decreases particle floatability. Furthermore, the type of grinding media in the stirred mill also influences the subsequent flotation, again due to the change of particle breakage mechanisms. The results of this study demonstrate that the selection of regrinding mills and grinding media should not only depend on the required energy efficiency, but also on the properties of the surfaces produced for subsequent flotation.

The separation of chalcopyrite and chalcocite from pyrite in cleaner flotation after regrinding

In this study, the differences between the separation of chalcopyrite and chalcocite from pyrite in cleaner flotation after regrinding were investigated. In the rougher flotation prior to regrinding, high chalcopyrite and chalcocite recovery were obtained in conjunction with high pyrite flotation recovery due to the activation of pyrite by copper ions during primary grinding. The rougher flotation concentrate was reground in a rod mill before cleaner flotation. It was found that chalcopyrite and chalcocite exhibited different flotation behavior and also affected pyrite flotation differently in cleaner flotation. The mechanism underpinning these phenomena was investigated by a range of techniques including the polarization of mineral electrodes, X-ray photoelectron spectroscopy (XPS) analyses and ethylene diamine tetraacetic acid (EDTA) extraction. It was found that the flotation behavior of both copper minerals and their effect on pyrite flotation after regrinding were governed by their electrochemical activities and galvanic coupling with pyrite.

Foam Glass from Mechanoactivated Zeolite-Poor Rock

The possibility of making foam glass from zeolite-poor rock is examined. Mechanoactivation of the crushed rock or the addition of opoka rock to alkaline zeolite-containing compositions significantly increases the foaming intensity. In addition the macro- and microporous structure of the foam material obtained from rock conventionally crushed in a rod mill differs from that of the foam material made from mechanically activated rock powder.

Experiment on Decarburization of High Carbon Fly Ash and Preparation of Concrete

The raw fly-ash applied in this study has an ignition loss of 17.30 %. The results of floatation experiment show 4.40 % coal content of tailing ash. The screen analysis results on decarburized fly ash shows that the content of +45 μm is above 12 %, failing to meet the quality of Grade I fly ash determined in the standard of China. Therefore, the decarburized fly ash was processed by grinding to meet the required quality. The analysis of the main constituents of different grinding methods conducted for tail fly ash shows that fly ash obtained by open circuit ball mill are the most suitable one used as admixture of concrete. Comparisons were made on the compressive strength and bending strength of 7d and 28d under the conditions of non-grinding and five ways of grinding. The test results show that grinding can improve the compressive strength of fly ash concrete. By way of closed-circuit grinding rod mill, concrete, can fly ash concrete strength be increased remarkablely.

Treating landfill gas hydrogen sulphide with mineral wool waste (MWW) and rod mill waste (RMW)

Hydrogen sulphide (H2S) gas is a major odorant at municipal landfills. The gas can be generated from different waste fractions, for example demolition waste containing gypsum based plaster board. The removal of H2S from landfill gas was investigated by filtering it through mineral wool waste products. The flow of gas varied from 0.3l/min to 3.0l/min. The gas was typical for landfill gas with a mean H2S concentration of ca. 4500ppm. The results show that the sulphide gas can effectively be removed by mineral wool waste products. The ratios of the estimated potential for sulphide precipitation were 19:1 for rod mill waste (RMW) and mineral wool waste (MWW). A filter consisting of a mixture of MWW and RMW, with a vertical perforated gas tube through the center of filter material and with a downward gas flow, removed 98% of the sulfide gas over a period of 80days. A downward gas flow was more efficient in contacting the filter materials. Mineral wool waste products are effective in removing hydrogen sulphide from landfill gas given an adequate contact time and water content in the filter material. Based on the estimated sulphide removal potential of mineral wool and rod mill waste of 14g/kg and 261g/kg, and assuming an average sulphide gas concentration of 4500ppm, the removal capacity in the filter materials has been estimated to last between 11 and 308days. At the studied location the experimental gas flow was 100 times less than the actual gas flow. We believe that the system described here can be upscaled in order to treat this gas flow.

Study on the Milling Technologies of Super-Slender Rod

t is well known that slender rod machining operation is a very difficult problem due to its low stiffness. During slender rod machining process, the deflection, vibration, cutting heat and cutting force of the machined part are the main reasons affecting the product quality. Based on the analysis of current research status of slender rod milling technology, process scheme, milling strategy, clamping fixture and tool designing is carried out in this work. In a roughing milling stage, we create a new strategy of square rod milling, called equilateral milling strategy to eliminating deflection. In finish-milling top waveform stage, a way using semicircle profile cutter to finish was applied. Complex interpolated movement is transform into simple two-dimension curved movement to shorten machine time and increase of efficiency in the way. In addition, machined surface with burnishing effect, high precision and high surface quality is obtained.