Grinding Rolls Research Articles

Influence of HPGR operating parameters on the edge and centre product – an industrial trial

ABSTRACT High pressure grinding rolls has been widely used in mineral industries as energy-efficient equipment. During the working life of an HPGR mill, the rolls’ surface wears out, and a concave wear profile (maximum wear in the middle) occurs on the rolls. As a result, a difference between HPGR discharge particle size from the middle and edges is also expected that has yet to be quantified. On the other hand, many operational variables affect the HPGR performance; however, there is an interaction between the operational variables and worn rolls. This work studied the effect of operational variables such as hydraulic pressure, rolls’ rotation speed, level of material in the hopper, and operational gap on the HPGR performance on an industrial scale. In addition, the particle size of HPGR discharge from the middle and edges of the rolls is also investigated. Results indicated that HPGR discharge from the middle of the rolls is always finer than discharge from the edges, while the difference between the discharge size from the middle and edges depended on the other variables. Furthermore, it was concluded that deeper material levels in the hopper and lower rotation speed of the rolls resulted in a finer HPGR discharge. This finding is crucial in optimising the HPGR performance and modifying the design of HPGRs to regulate the distribution of material on the rolls.

The Impact of Enzyme Type, Temperature, and Grinding Roller Interval on Barley Malt-Based Beverages

The Impact of Enzyme Type, Temperature, and Grinding Roller Interval on Barley Malt-Based Beverages

Shape and roundness accuracy prediction of the roll grinding based on improved Elman neural network

Abstract Due to the strong nonlinear relationship between the shape and roundness of the roller and the grinding process parameters, a prediction method for roll shape error and roundness error based on an improved Elman neural network is proposed. During the training process of the Elman neural network, Sine chaotic mapping is used to make the population distribution more uniform, and the sparrow search algorithm is used to obtain the optimal parameters of the Elman neural network. The verification results show that the prediction errors of the roll shape and roundness are both less than 10%, and the accuracy of the prediction model is higher than 85%, which proves the effectiveness of the proposed method.

Failure Analysis of Pulverized Coal Injection (PCI) Mill Grinding Roller Bearing at Blast Furnace

Failure Analysis of Pulverized Coal Injection (PCI) Mill Grinding Roller Bearing at Blast Furnace

The Diatomite Grinding Technology Concept for the Protection of Diatomite Shells and the Control of Product Grading.

Diatomite deposits in Poland are located in the Podkarpackie Voivodeship, and the only active deposit is in Jawornik Ruski. Therefore, it is a unique material. Improved rock processing methods are constantly in demand. In the research presented here, we have used research methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), particle shape analysis, and appropriate sets of crushing machines. Diatomite comminution tests were carried out on test stands in different crushers (jaw crusher, hammer crusher, high-pressure roller press, ball mill) using different elementary crushing force actions: crushing, abrasion, and impact, occurring separately or in combination. The machines were tested with selected variable parameters to obtain products with a wide range of grain sizes ranging from 0 to 10 mm. The ball mill (yield 87%, system C3) and the hammer crusher with HPGR (high-pressure grinding roller) (yield 79%, system D2 + D3) have the greatest impact on diatom shell release and accumulation in the finest 0-5 μm and 5-10 μm fractions. For commercial purposes, it is important to obtain very fine fractions while keeping the shells undisturbed.

Penataan Penjadwalan Preventive Maintenance Semua Mesin Milling Wheat Menggunakan Metode TPM (Total Productive Maintenance)

PT X is a factory that processes wheat into flour with roll mill as the main equipment. The wheat used is a blend of Indian wheat and Australian wheat. Indian wheat has a hard texture that can cause the roll grinding to become damaged or dull, increased working amperes,bearing jams, broken belts and motor overload which causes downtime. When a machine or component breaks down, the production process in the company will be disrupted and may come to a halt, so the target is not achieved and endangers to the company. To keep production machines and equipment working, maintenance processes are carried out properly and regularly. Additionally, the company can implement preventive maintenance steps to prevent and reduce machine downtime. Preventive maintenance is a planned maintenance strategy to prevent potential breakdowns. To reduce the high machine downtime, preventive maintenance is solution . The method chosen in this research is Total productive Maintenance. Based on research results, the overall equipment effectiveness (OEE) values were 85.8% in January, 87.18% in May, 86.69% in June, 85.25% in November, and 85.51% in December. The OEE values that did not meet the standard occurred in February (81.92%), March (81.34%), April (84.73%), July (83.77%), August (79.03%), September (77.05%), and October (81.72%). The biggest factor that causing losses of overall equipment effectiveness is caused by the high value of the six big losses, particularly the reduced speed losses, which stand at 9%.

Effects of Two Different Methods of Teeth Grinding on Dental Injuries, Skin Lesions, Growth and Behaviour of Suckling Piglets Compared to a Non-Treated Control Group.

Teeth grinding in suckling piglets is performed on many farms to protect the piglets' littermates and the sow's udder from injuries caused by the piglets' canines and third incisors. In this study, the effects of two teeth-grinding methods on the piglets' dental health and welfare were investigated. The piglets of a litter were evenly assigned to a treatment: one-third of littermates were ground with a roller grinding head (RG), one-third with a teacup grinding head (TCG), and one-third were not ground at all (CG). A random sample of 100 animals each from the RG and TCG treatment was examined for tooth injuries, i.e., dental pulp openings. Additionally, behavioural analysis was performed (n = 650 piglets), and skin lesions, growth and mortality were determined (n = 1565 piglets). TCG piglets had a lower risk (p < 0.001) of pulp opening than RG piglets (0.08 ± 0.31 vs. 2.67 ± 1.67 opened pulps per piglet). Mortality, growth, skin lesions and behaviour of piglets were not influenced by treatment (p > 0.05). This study showed that both teeth-grinding methods led to pulp openings. If teeth grinding cannot be avoided on a farm, using the teacup grinding head is recommended concerning animal health and welfare.

Changes of surface properties of sucrose particles during grinding in a cocoa butter-based suspension and their influence on the macroscopic behavior of the suspension

Chocolate mass is a cocoa butter-based suspension, which mainly consists of sugar and cocoa particles dispersed in a continuous lipid phase. During chocolate manufacturing, sugar particles have to be ground to sizes below 25–30 µm. Such a fine grinding is carried out either by five roll refiners or by ball mills. Despite obtaining similar particle size distributions at the end, the grinding procedures result in different chocolate mass properties. The reasons for that are not fully understood, so far. Therefore, changes in particle sizes and surface properties of sucrose particles as well as their interactions with surrounding cocoa butter during the different grinding processes were investigated including atomic force microscopy techniques to characterize local surface states. It was found that especially the alteration of surfaces during continued grinding differed. In the case of roller grinding, surface states became more inhomogeneous and different surfaces states at microscopic level existed in parallel. More homogenous surfaces but with a higher degree of amorphous states were formed during grinding in the ball mill. Variations in macroscopic behavior of the suspension can be explained by the differences in interaction of particles with each other and with the surrounding lipid phase.

Critical Assessment of Novel Developments in HPGR Technology Using DEM.

Advances in high-pressure grinding roll (HGPR) technology since its first commercial application in the cement industry include new roll wear protection techniques and new confinement systems. The latter contribute to reductions in the edge effects in an attempt to reach a more homogenous product size along the rolls. Additional advances in this technology have been made in recent years, while modeling and simulation tools are also reaching maturity and can now be used to subject such novel developments to detailed scrutiny. This work applies a hybrid approach combining advanced simulations using the discrete element method, the particle replacement model and multibody dynamics to a phenomenological population balance model to critically assess two recent advances in HPGR technology: spring-loaded cheek plates and the offset roller press. Force and torque controllers, included in the EDEM 2022.1 software, were used to describe the responses of the geometries in contact with the granular material processed. Simulations showed that while the former successfully reduced the lateral bypass of the material by as much as 65% when cheek plates became severely worn, the latter demonstrated lower throughput and higher potential wear but an ability to generate a finer product than the traditional design.

Research on on-site installation process of grinding roller of SLM5600 Vertical roller mill

SLM5600 vertical roller mill is widely used in 6000t/d cement clinker production line, the main parts of SLM series mill is a whole disc and three grinding roller, the roller in addition to the regular change with the liner accident, also need to regularly check and change with the bearing and oil seal and the wear bushing, by SLM5600 roller mill Department of heavy cement plant machinery maintenance conditions are limited, many manufacturers can only be shipped back to my company roller for repair and replacement parts, resulting in long period of maintenance, repair costs, provide a set of field assembly roller assembly process in this paper, according to the process maintenance workers on-site replacement parts and grinding roller assembly.

Investigating the benefits of using HPGR prior to cyanidation of low grade gold ore

AbstractIt is known that the cracked structure of the particles has positive effects in leaching processes. In this respect, high pressure grinding rolls (HPGR) provides some advantages such as increasing leaching efficiency and reducing leaching time by creating more cracked particles compared to other crushers. Although there are studies on the advantages of HPGR on different ores, these have not been fully demonstrated in low grade gold ores, and leaching kinetics have not been examined in detail in the studies conducted in this context. In this study, first of all, crack formation in a low grade gold ore by crushing with HPGR and jaw crusher was investigated. Then, bottle roll tests were performed in different size fractions and different cyanide concentrations along with column leaching of the pelletized ore in a single test condition. As a result of the studies, it was determined that 2–3 times more cracked particles were formed in HPGR depending on the particle size. It was shown that the modified Kelsall model explains the kinetics better than other kinetic models tested. In summary, it was revealed that maximum gold extractions are almost same for HPGR and jaw crushers. However, the fast dissolution kinetic constant was found to be around 25% higher for HPGR than for the jaw crusher in bottle roll tests while this ratio was approximately 30% higher in column leaching tests, suggesting a distinct influence of the crushing method on the dissolution kinetics.

Effect of material bed compression on white fused corundum product particle shape and bulk density

Comminution of corundum is a challenging task, as it has outstanding mechanical strength and is highly abrasive and is consequently applied as a blasting and polishing agent in the abrasive industry. Thus, the selection of the best comminution methods to achieve the required dispersity properties has great importance. For this, first we must understand the effects of different type of stresses and their influence on the corundum particle fractions. Laboratory scale material bed compression experiments in a piston press were carried out to examine the effect of the pressure and material bed height on the product's particle size distribution, bulk density, and particle shape. The results showed that outstanding yield, high bulk density, and spherical particle shape can be achieved by particle bed breakage in a piston press, so the high-pressure grinding roll (HPGR) technology is a promising comminution method for corundum.

The Effect of HPGR and Conventional Crushing on the Extent of Micro-Cracks, Milling Energy Requirements and the Degree of Liberation: A Case Study of UG2 Platinum Ore

Comparative high pressure grinding rolls (HPGR) and cone crusher pilot-scale tests were conducted using Upper Group 2 (UG2) platinum-bearing ore in order to determine the impact of micro-cracks in HPGR products toward energy requirements in ball mills and the degree of liberation. The ball mill was fed with HPGR and cone crusher products of similar particle size distributions (PSDs). Qualitative analysis of the degree of micro-cracking on the HPGR and cone crusher products performed using scanning electron microscope (SEM) and image analysis software showed that an HPGR product had more micro-cracks than the equivalent cone crusher product. Milling energy requirements were evaluated using size-specific energy consumption indices calculated based on three grind sizes of 300 µm, 150 µm and 75 µm. The effect of residual micro-cracks in the products of HPGR and cone crusher on the milling size-specific energy requirement is inconclusive. The kinetic parameter k in the cumulative rate kinetic model for ball milling cone crusher products and for ball milling HPGR products were similar. Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) was used to determine the degree of liberation of various mineral phases in the mill products. At a coarser grind size (P80 of 300 µm), the sulfides in the mill products pre-crushed using the cone crusher have consistently poorer liberation than in the equivalent HPGR pre-crushed sample. However, at a finer grind size (P80 of 75 µm), the sulfides in the mill products pre-crushed using the cone crusher and using an HPGR showed similar liberation.

DEM analysis of wear evolution and its effect on the operation of a lab-scale HPGR mill

Wear due to compression and abrasion from particles is a critical issue for high pressure grinding rolls (HPGR) mills. Understanding the evolution of wear provides useful insight on its mechanisms and helps to mitigate the issue so mills are operated at their optimal states. This work presented numerical simulations based on the discrete element method (DEM) to analyse the formation and evolution of wear of a lab-scale HPGR mill and to investigate how wear affects mill performance and particle breakage. By coupling the DEM model with the Archard wear model and surface re-meshing, the simulated wear patterns were comparable with those observed in practice, showing a parabolic wear profile wear along the rolls with more severe wear in the centre. In addition, the rear part of the stud, compared with the middle and front parts, experienced more significant wear due to the combined effect of compression and abrasion. While increasing wear had no visible effect on throughput, it reduced mill power draw due to weaker compressive force from the rolls to particles. Furthermore, analysis on particle breakage showed that increasing wear reduced particle breakage and produced coarser products. Increasing wear also caused less damage to particles, suggesting more cycles are required to achieve targeted products.

Optimization Model of the Cold Rolling Roll Grinding Volume Based on Nonlinear Fatigue Accumulation Regulation

Optimization Model of the Cold Rolling Roll Grinding Volume Based on Nonlinear Fatigue Accumulation Regulation

Research on wheat flour‐making technology based on discrete elements

AbstractThe operating characteristics of a mill's rolling distance and roller speed during wheat‐milling were studied to provide a reference for optimizing the operating parameters of the mill. The high‐performance discrete element method software (EDEM) was used to establish a roller‐crushing system for wheat flour production. Numerical simulations of wheat flour production were performed using this system. It was found that increasing the roller distance of the flour mill machine could reduce the wear of the grinding rolls and the power of the grinding roll system, which reduced the crushing rate of wheat during the milling process. Increasing the grinding roll speed can reduce the wear of the grinding rolls but will increase the wheat‐crushing rate. At a constant fast roller speed, increasing the speed ratio increased the wheat‐crushing rate which reduced the power of the grinding roller system. During the grinding roll wear process, the obtuse and sharp angles gradually disappear. A comparison of the simulation and experimental results shows that the discrete element method can accurately predict the wear of the grinding roll.Practical ApplicationsThe milling machine is a key piece of equipment used for making wheat flour. The rolling distance, speed, and speed ratio of grinding rolls are important operating parameters during mill operation. Selecting specific parameters will directly affect the quality of wheat‐milling and the economic efficiency of the milling enterprise. This study adopted a discrete element method to study the effects of these parameters on wheat milling, providing a good reference for the technical personnel of milling enterprises.

Influence of magnetite concentrate morphology on oxidation and sintering rates of pellet during induration

This study investigates the influence of the morphology of concentrate on the oxidation and sintering rates of magnetite pellets during induration and its impact on the indurated pellets' quality. Various morphologies of concentrates were obtained by ball milling (BM) and high-pressure grinding rolls (HPGR). Pelletizing and induration processes were carried out at different temperatures and times. After a comparative study of the physical characteristics of concentrate powders, the effect of morphology was evaluated through thermal behavior during induration. The physical, microstructural, and strength properties of pellets were also investigated. The HPGR concentrate had angular and elongated-shaped particles with a broad particle size distribution, while the BM particles had a more rounded morphology, and their size distribution was narrower. Results showed that BM and HPGR magnetite pellets are oxidized between 270 and 950 °C. HPGR pellets oxidize slower than BM pellets. Cold compressive strength (CCS) was increased by induration time, although porosity was reduced. HPGR pellets had less porosity than BM pellets; however, their CCS was significantly higher. For pellets indurated at 1200 °C, the difference in CCS between HPGR and BM pellets increased with an increment in the induration time and reached 80 kg/pellet in 20 min. The microstructural analysis took place on the concentrate powder and pellets fracture surface. It was found that HPGR powder sinters faster than BM powder due to its angular shape and broad particle size distribution.

Research of grinding efficiency and main duct wear of pendulum mill based on CFD-DEM co-simulation

Pendulum mill is a widely used grinding equipment in powder processing industry. Less in-depth studies have been carried out especially for grinding efficiency and wear. Through theoretical analysis, the main influencing parameters were screened, among which spindle speed and spade degree mainly affect the grinding efficiency, but wind velocity mainly causes the main duct wear. The Fluent-DEM co-simulation method is used for the study of the complex physical field of mill operation. The simulation shows that grinding efficiency increases with spindle speed, but the increase from 110 to 120 rev/min is not significant, so the choice of spindle speed should consider both grinding efficiency and energy consumption. The spade degree determines the spade position, the closer the spade is to the grinding roller, the higher the grinding efficiency. Wind velocity has little effect on grinding efficiency, but it does affect the likelihood of particles entering the main duct and causing wear. Multi-objective optimization determines a spindle speed of 110 rev/min and a spade angle of −12° at a wind velocity of 46 m/s to achieve maximum grinding efficiency and minimum wear. This study provides a digital analysis basis for optimizing the operating parameters of the pendulum mill.

Double Extended Sliding-Mode Observer-Based Synchronous Estimation of Total Inertia and Load Torque for PMSM-driven Spindle-Tool Systems

This paper proposes a double extended sliding mode observer-based (DESMO-based) synchronous estimation method of total inertia and load torque for complex PMSM-driven spindle-tool systems with time-varying properties. The novel DESMO is designed by extending double recursive equations from a sliding mode observer of the motor speed to observe the total inertia and the load torque simultaneously, and the corresponding convergence conditions are analyzed in theory. Additionally, a robust activator is introduced to suppress the coupling effect of the observation errors between the total inertia and the load torque. The simulation results show that, compared with two existing methods, the proposed DESMO-based method has satisfactory robustness to the modeling errors and small sensitivity to the algorithm parameters. Furthermore, experiments were performed on a roller grinding machine, and the results validate the effectiveness of the proposed method, especially the robustness to the time-varying friction torque and the sampling noise.

Online prediction of pressing iron ore concentrates in an industrial HPGR. Part 2: Digital assistant

Besides the recent advances in high-pressure grinding rolls (HPGR) technology, the good track record demonstrates the potential growth in its applications in the future. In this regard, challenges are emerging driven by technology improvements and the increasing demand for a proper understanding of the operation and optimization of the grinding process in different scenarios. To fill this gap, new dynamic modeling and simulation approaches have been evolving to capture information of the process in real-time using online tools. However, proper application of these models as online digital assistants is still missing. The present work applies the online modeling approach proposed by the authors in the first part of this series as a digital assistant. The digital assistant receives real-time information of an industrial-scale HPGR pressing of iron ore concentrates and uses the Modified Torres and Casali model to predict the main HPGR performance variables. At first, a quantitative description of the HPGR hydro-pneumatic pressurizing system is calibrated and validated describing the relationship between hydraulic pressure and gap in the industrial machine. Feasibility of applying the online model as a digital assistant was demonstrated from two simulation case studies by providing setpoints of hydraulic pressure based on real-time changes in HPGR feed BSA, with the aim of reducing the variabilities of the HPGR product BSA and absorbing a coarser feed BSA.