Grinding Period Research Articles

Strength characterization and sustainability assessment of coal bottom ash concrete.

Coal bottom ash (CBA) which is waste and environment contaminant has been used in grinded and raw form as replacement of Portland cement (PC) and natural fine aggregates (NFA) in concrete. The combined effect of grinding period (GP) (2-10h), grinded CBA (GCBA) (10-30%), and raw CBA (0-50%) on strength and microstructural characteristics was investigated and optimized along with its sustainability assessment. An enhancement in strength parameters with an increase in GP and replacement of PC and NFA with GCBA and CBA respectively was observed. The microstructural techniques like XRD, SEM, EDS, and FTIR also correlate with the aforementioned behavior. Mathematical models for strength parameters are well fitted and in good agreement with experimental and predicted values. Multi-objective optimization suggested 6.38h grinding, 24.21% GCBA, and 32.96% CBA as the optimum values. CBA-based optimized mix resulted in 19.79% and 22.6% lower carbon footprints and eco-cost than the control mix.

Reviewing mechanical performance of geopolymer concrete containing coal bottom ash

Concrete is one of the most demanding construction materials and also the third-largest emitter of greenhouse gases on the planet. Likewise, cement is a commonly used binder in concrete and its production accounts for nearly 7 percent of global greenhouse gasses resulting it into one of the most non-sustainable options. Geopolymer concrete (GPC) is a type of construction material made with the utilization of the waste products of industries (like fly ash, copper slag, coal bottom ash, etc.). It comprises the process of geopolymerisation with the help of alkali activators particularly made of sodium hydroxide and sodium silicate. Further, Coal Bottom ash (CBA), generated from thermal power plants is generally landfilled and has already created serious threats to the environment. The current review summarizes the present and past research trends of mechanical behavior of GPC made with different amounts of CBA either used as replacement of binder or as fine aggregates. Generally, the mechanical properties of GPC depend on various parameters like alkali solution content, liquid/binder ratio, molarity of NaOH, NS/NH ratio, grinding of CBA and type of curing. The literature indicates that, an increase in various parameters such as NS/NH ratio (1.5–4.9), molarity of NaOH (10 M−16 M) and the grinding period (12 h–36 h) improves the overall mechanical properties. Likewise, an increase in liquid/binder ratio (0.5–1) and alkali content reduces the strength properties of CBA based GPC at different curing regimes. The findings also suggest the adequate potential of CBA to be used as primary/secondary material in Geopolymer concrete. Last, the study briefly highlights the challenges and future scope of application of CBA in developing GPC.

DETERMINING THE CHARACTER OF DISTRIBUTION THE CONTACTING VERTICES OF GRAINS AT THE SURFACE ON THE GRINDING WHEEL, TAKING INTO ACCOUNT THE MULTI-PASSAGE OF PROCESS

The article is devoted to the method of determining the nature of distribution the contacting vertices of grains on the working surface of grinding wheel, depending on the grinding time. The number of contacting grains is determined by the probability of contact. A distinctive feature is the use of a mathematical model that takes into account the change in the distribution of grain vertices as a result of wear of the abrasive tool during the grinding period. Considered the probabilities in three types of wear: abrasion and spallation of the grain's vertices, pull-out grain from the bundles of the wheel. Changing the position of the grain’s vertices under the action of a particular type of wear is determined using random Markov’s processes. The method takes into account the influence of the following factors: characteristics of the abrasive tool, the grinding mode, the material to be processed, the initial distribution of grains on the abrasive tool working surface and the strength of their retention. The results of the study may be used to solve problems related to determining the intensity of heat generation in the contact zone of the grinding wheel and the billet, calculation of cutting power, tool wear and other issues related to the study of the grinding process.

Mathematical simulation of cutting force during grinding using theory of Markov processes

The article presents a cutting force mathematical model which takes into account the grinding wheel working surface wear resulting from abrasion and chipping of grain vertices, pulling of grains out of the wheel bond depending on the grinding time. Wear of grain vertices is considered as a Markov process with discrete time and state, and the process of forming the grinding wheel working surface as a superposition of such Markov processes. The model allows to determine the nature of cutting force distribution in the grinding zone across the contact surface layers of the abrasive tool and the characteristics of changes in the distribution throughout the grinding period. The mathematical model takes into account the influence of the following factors: characteristics of the abrasive tool, the grinding mode, the material to be processed, the initial distribution of grains on the abrasive tool working surface and the strength of their retention. The model includes the probabilities for types of grain vertice wear resulting from abrasion and chipping, pulling of grains out of the abrasive tool bond. The wear type probability calculation is determined by taking into account the actual cutting force of the grain vertex. A change in the grain vertex position resulting from various types of wear after each interaction with the processed material is determined by transition probabilities.

ИСПОЛЬЗОВАНИЕ ОПАЛ-КРИСТОБАЛИТ-ТРИДИМИТОВОГО НАПОЛНИТЕЛЯ В ТЯЖЕЛОМ БЕТОНЕ

Opal-cristobalite-tridimite micro-filler (OCTMF) as a component of dense aggregate concrete (DAC), obtained by grinding of sedimentary siliceous rock – abiomorphic silicite fractions of 0.315-0.63 mm was studied considered. The chemical-mineral composition and microstructure of the of OCTMF particles were determined. Comparative analysis of the relationship between particle size distribution, average particle diameter, specific surface area of OCTMF particle and grinding period in shock-abrasive and cavitation mills was carried out. The conductometric express method was applied to study the effect of the OCTMF specific surface area on hydration activity of cement system. The optimal value of OCTMF specific surface area was (880–900 m2/kg), achieved as a result of cavitation dispersion for 5–10 minutes, that provides increasing in t hydration activity of cement system by 52–54 %. The effect of the consumption of components on strength of the DAC after 28 days of hardening was determined using mathematical statistics method. That allows predicting this parameter by varying the component composition of the concrete mix. An assessment of the OCTMF efficiency was made. It was established, the maximal effect of the OCTMF is at concentration up to 5 % (by wt. of cement), that provides an increasing the design compressive strength of DAC up to 126 %.

Modification of Steel Roller Composition to Curb Excessive Wear

Incorporation of roller presses in the grinding circuits of cement manufacturing plants was borne out of the dire need to reduce the power consumed by ball mills in its finish grinding process. This study evaluated the wear phenomena of a roller press installed in a cement plant. Two improvised wear measuring devices (IWMDs) were constructed on a laboratory scale with chevron lines created on each of the rollers. One of the IWMDs had 1.00% chromium and 0.20% molybdenum exhibiting the exact properties of the existing roller press. The other IWMD had 1.10% chromium and 0.22% molybdenum. The IWMDs were subjected to grinding operation with the same raw material of sized media fed at 0.2 tonnes/h for a continuous grinding period of about 6 h per day. Wear measurements were taken on the lines monthly for trending and up till the end of 733 h test running. The chevron lines on the IWMD with Xuper 646 XHD chipped off after 17.5 h of operation, while that with chevron lines made with AbraTec 6710 XHD was in operation for a cumulative period of 733 h within 7 months. Results on the AbraTec 6710 XHD model showed a maximum of 0.04 mm/tonne average wear within a span of 7 months compared to the chipped-off lines and an average wear rate of 1.75 mm/tonne on the Xuper 646 XHD IWMD having characteristics of the existing equipment. The AbraTec 6710 XHD IWMD indicated its suitability for clinker–limestone grinding roller press compared with Xuper 646 XHD.

Effects of Grinding Process on the Properties of the Coal Bottom Ash and Cement Paste

The grinding process is necessary to convert original coal bottom ash (CBA) into a powder form. The aim of this study is to evaluate the grinding process effects on physical properties of CBA, it influences on consistency and setting time of cement paste and to predict it potentiality based on chemical characteristics to reduce the alkali-silica reaction (ASR) in concrete. The CBA is the by-product of coal based thermal power plant. Due to high production of electricity in Malaysia, the excess amount of CBA has been produced annually and it causes the environmental problems. Therefore, it is necessary to come up with advanced solutions for that pollution. This study considered the different grinding periods i.e. 2, 10, 20, and 40hrs as to produce different particle fineness. It was perceived through the laboratory findings that the more the grinding period, finer the particle sizes. Besides that, cement paste with 10, 20 and 30% of ground CBA as a substitute of ordinary portland cement (OPC) by weight was prepared, it was observed that the consistency of OPC paste increases with the addition of ground CBA. Moreover, initial and final setting time of cement paste containing ground CBA was observed higher than the OPC paste. Hence, based on experimental analysis and energy efficiency scenario, grinding period of 20hrs with specific surface area 3835.75 cm2/g is suggested for the future studies.

Performance comparison of stirred media mill and ball (BOND) mill in bauxite grinding

Nowadays, the demand for a finer grind in mineral processing has set new challenges within the industry, particularly for grinding technology. Apart from a finer grind, energy efficiency is also a key driver in optimizing grinding technology. With increasing need for fine and ultrafine grinding, stirred media mills became an alternative for conventional ball mills. In this study, samples of bauxite whose chemical composition and Hardgrove Index values are known were ground to micronized size by a laboratory scale stirred media mill and its performance was compared with a laboratory scale ball (Bond) mill. Stirred media mill decreased bauxite d50 size from 780 to 5 µm in 3 min. But, the ball mill has reduced to 455 µm at the end of the same grinding period. In addition, the energy consumed by the ball mill for similar fineness (5 µm) was approximately 300 kWh/t energy, whereas the stirred media mill consumes approximately 174 kWh/t energy. As a result, the stirred mill consumed less energy because it could grind in a shorter time.

Effect of grinding period on physical properties of modified bitumen using palm oil fuel ash (POFA)

Malaysia is having rapid economic development in recent years, and this has placed high performance demand on its highway infrastructure. The increased in number of traffic has led to severe pavement deterioration. Due to this, better and stronger pavement materials are needed in order to cater the increasing number of axle loading. Palm oil fuel ash (POFA) which comes from the ash of burning mesocarp of the palm oil fruitlets has been used as a modifier to improve the properties of bitumen. POFA is a biomass that had pozzolanic properties (siliceous material). By using POFA in bitumen, it will promote sustainability and lesser landfill to dump this waste. The objective of this research is to evaluate the effect of grinding period of POFA and different percentage of POFA towards physical properties of modified bitumen. A few sets of samples of POFA modified bitumen at different grinding time and POFA content have been prepared and tested with penetration test and softening point test. The microstructural characteristics of POFA were also investigated by using Field Emission Scanning Electron Microscope (FESEM). From the result, it shows that grinding time and POFA content does not influence the physical performance of the bitumen.

궤도의 성능향상을 위한 탄성구성요소로 통합된 상부구조 설계

Track elastic components can be technically and economically efficient when integrated well into track superstructure of a railway network. In such cases, the elastic rail pad is larger than a 800m radius curve provides smooth rail branching and allows for high-speed operation (). High track resistance causes the tamping intervals to stand out because the constantly increasing share of the sleeper pad further extends the increase of the tamping interval and the long grinding period; the engineering and construction of the small curve radius track provides some measures for reducing the solid sounds. Installation of elastic mats under the ballast can have a good effect, particularly in the context of protection against dust during construction or extensive renovation measures when laying new lines. However, such a process requires special attention and proper installation.

Particle characteristics and hydration activity of ground granulated blast furnace slag powder containing industrial crude glycerol-based grinding aids

This paper investigates the viability of industrial crude glycerol (C-GLY) as grinding aids of the granulated blast furnace slag (GBFS). The effects of C-GLY on the particle characteristics and hydration activity of GBFS are studied. The results show that C-GLY can effectively optimize the particle characteristics of ground GBFS. Both the sieve residue and angle of repose of GBFS powder with 0.08wt% C-GLY are obviously reduced and the specific surface area is improved. The particle size distribution of GBFS powder with C-GLY becomes narrow and particle content of less than 32μm is obviously increased. In the initial grinding period, the uniformity coefficient of GBFS powder is reduced by C-GLY, while the uniformity coefficient is increased in the latter grinding period. Additionally, 7d and 28d hydration degree of ground GBFS (50min grinding time) paste with C-GLY are improved by 4.9% and 5.8%, respectively. For the different grinding time, all the activity indexes of different ground GBFS powder are effectively improved by C-GLY. And the uniformity and compactness of hydration products of blended cement paste containing ground GBFS with C-GLY are also improved. By contrast, the action effects of C-GLY on the grinding performance and hydration activity of GBFS are close to that of TEA and better than that of glycerol. Due to the huge cost advantage of C-GLY, its comprehensive performance is better than that of other grinding aids, selecting C-GLY as GBFS grinding aids is feasible.

Unexpected electrocatalytic activity of the milled mixture containing PdCl2 and multi-walled carbon nanotubes towards ethanol oxidation reaction

A novel finding, that the ground mixture containing PdCl2 and multi-walled carbon nanotubes (MWCNTs) (denoted as PdCl2/MWCNTs) has an unexpected electrocatalytic activity towards ethanol oxidation reaction (EOR), is reported for the first time in this work. The influence of grinding periods on the properties of the resultant PdCl2/MWCNTs mixture is preliminarily investigated. The resultant samples are thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results indicate that although the crystallinities of the prepared samples decrease with increasing the grinding period, no novel phase is displayed in the prepared samples. The electrocatalytic activity of the resultant samples for EOR is studied by using cyclic voltammetry (CV) and chronoamperometry (CA). And it is revealed that the electrocatalytic activity of the resulting mixture for EOR is closely related to the grinding period and the best electrocatalytic activity towards EOR is exhibited by the 15 min-ground mixture. The work described in this work provides a novel concept that the ground mixture containing palladium salts and MWCNTs can also be employed as electrocatalysts for EOR.

The Investigation of Grindability of Refractory Wastes in Their Recycling

The ceramic industry is one that stands out in the use of industrial tailings, replacing pure raw materials by some of these materials. Refractory wastes are ground and used in certain proportions in refractory production. This study is aimed at determining the grindability of recycling of refractory wastes and their kinetic behavior. The breakage behaviors were determined experimentally by using the mono-size fraction technique. The mono-size samples of –2360 + 1700 μm, –1180 + 850 μm, and –425 + 300 μm were ground batchwise for the selected periods to determine the Si. At the end of each grinding period, using the material at different mono-size groups, we determined the particle size distributions and breakage behaviors of the products. Depending on the grinding periods in both of the mills, energy consumption and d80 values of grinding products obtained by various grinding periods were determined. It was found that as the size group decreases, the breakage speed decreases in the ball mill and increases in the stirred mill. An increase in the grinding period results in an increase in energy consumption, but there is no significant change in d80 size in grinding of refractory waste in the ball mill. However, it was found that d80 size decreases significantly with increasing grinding period in the stirred mill.

The investigation of breakage kinetics of vitrified sanitary ware wastes in laboratory scale ball and stirred mills

ABSTRACTThis study is aimed to determine the grindability and kinetic behavior on grinding of vitrified sanitary ware wastes. The specific rates of breakage (Si) and the model parameters were determined through kinetic experiments to understand the grinding mechanisms of vitrified wastes. The breakage behaviors were determined experimentally by using mono-size fraction technique. The mono-sized samples of −2360 + 1700 µm, −1180 + 850 µm, and −425 + 300 µm were ground batchwise for the selected periods to determine the Si. At the end of each grinding period, using the material at different mono-size groups, particle size distributions and breakage behaviors of the products were determined. Depending on the grinding periods in both of the mills, energy consumptions and d80 values of grinding products obtained by varying grinding periods were determined. It was acquired that as the size group decreases breakage speed gets slower in the ball mill and increases in the stirred mill. An increase in the grinding period results in an increase in energy consumption, but there is no significant change in d80 size in grinding of vitrified waste in the ball mill. However, it was found that d80 size significantly decreases depending on the increasing grinding period in the stirred mill.

A laboratory scale application of the attainable region technique on a platinum ore

We investigated the effects of slurry density, grinding time and grinding energy on the grindability of a typical platinum ore in a tumbling ball mill on a laboratory scale. We then used the Attainable Region (AR) method to find ways of reducing the grinding period and grinding energy required to achieve a specific result; and also of maximizing the amount of material in the desired size range. No work on utilizing the AR technique to optimize the size reduction of a PGM ore in slurry has been published as yet, although researchers have used the method for comminution carried out under dry conditions only. The investigation reported in this paper is not intended to set out ideal operating parameters for industrial mills, but aims to show how the AR technique can be used to develop some ways of improving mill performance. The experimental results we obtained proved that this method could be successfully applied to identifying opportunities for higher efficiency in milling a typical industrial ore. In our particular case, a solids concentration of 33% by mass, milled for between 15 and 30minutes, gave us the maximum amount of material in the intermediate size class.

Facile one‐pot low‐temperature solid‐state approach towards phase transformation of nanoCdS

Nanocadmium sulphide (CdS) has been prepared by the one-pot solid-state method from cadmium chloride (CdCl2) and sodium sulphide (Na2S) without any capping agent. The grinding period plays a major role in transforming CdS from the cubic (zinc blende) to the hexagonal (wurtzite) phase, hitherto unreported at the lowest temperature of 200°C by the solid-state approach. The compounds are characterised by powder X-ray diffraction, UV–visible absorption spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy techniques. On the basis of the results, it has been observed that with only grinding and without subsequent heat treatment, the compounds named with their grinding period as subscript have either zinc blende – CdS(30 min) or mixed zinc blende/wurtzite – CdS(2,4, 6 and 8 h) structures. However, when subjected to heat treatment at 200°C, there is a complete phase transformation to the wurtzite structure achieved only with the CdS(8 h) compound, while the rest of the compounds show similar phases as the compounds prepared without annealing. The photocatalytic efficiency of CdS compounds on methyl orange follows the order, CdS(cubic) > CdS(mixed phase → cubic + hexagonal) > CdS(hexagonal), with cubic phase CdS showing greater efficiency than mixed and hexagonal phases.

Эффективные и экологически безопасные технологии удаления пней на вырубках

Shredding of stumps below the soil surface is constrained by intense abrasion of the cutting elements as a result of their interaction with the soil particles. Therefore, to solve this problem is to remove the stump from the upper soil layer. To perform this operation as a working bodies rip-strip off elements are encouraged to use in the form of pieces of rope that will not only prepare the ground around the stump, but also clear it from adhering soil. Application of this technology will reduce the abrasion and increase grinding period of cutting elements of machines for grinding stumps, thereby increasing their productivity.

Research on Mechanochemical of Silica and its Composite Powders

Silca and its composite powders added different amount of microsilica were ground in a planetary ball mill (QM-3SP4) at various grinding period with addition of a certain number of grinding aid. The effects of mechano-chemical on particle size, crystal size and lattice deformation in grinding process were analyzed. The phase compositions and size compositions of the treated powders were investigated by X-ray Diffraction (XRD) and Laser Particle Size Analyzers. With the increase of grinding time, the particle size decrease, the specific surface area increase, and the more amount of microsilica added, the smaller particle size the powders had after grinding. The XRD results showed that the diffraction peak intensity of powders weaken and gradually widen. The surface of the particle happened to amorphization, and occurred grain refinement and lattice distortion. Comparing with other treated powders, the change of the powders with the microsilica addition of 5% was larger. Even though the grinding time reached to 30h, the crystal transformation of SiO2has not been detected.

Grinding wheel wear monitoring based on wavelet analysis and support vector machine

A novel grinding wheel wear monitoring system based on discrete wavelet decomposition and support vector machine is proposed. The grinding signals are collected by an acoustic emission (AE) sensor. A preprocessing method is presented to identify the grinding period signals from raw AE signals. Root mean square and variance of each decomposition level are designated as the feature vector using discrete wavelet decomposition. Various grinding experiments were performed on a surface grinder to validate the proposed classification system. The results indicate that the proposed monitoring system could achieve a classification accuracy of 99.39% with a cut depth of 10 μm, and 100% with a cut depth of 20 μm. Finally, several factors that may affect the classification results were discussed as well.

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

The structure and particle size of solid fossil fuels have effects on linear or nonlinear movements encountered in breakage rate, besides petrography types, in-organic materials, extensive network of pores, macro chemical forms, etc. Nonlinear breakage behavior in mono size groups of −3,350 + 2,360 μm, −2,360 + 1,700 μm, and −1,180 + 850 μm was a result of heterogeneous structure of the material along with being coarser for grinding medium. The part having low-ash content (coal-like) in the heterogeneous structure was exposed to faster breakage than the part having high-ash content (shale-like). As a result, over-sieve material was composed of shale, which is more difficult to grind, breakage behavior slowed down, and there occurred a deviation in linear breakage behavior with increasing grinding period. Linear breakage behavior in mono size groups of −425 + 300 μm and −212 + 150 μm was considered as a result of homogeneity of the material along with its adequate fineness for grinding medium. Variation of particle size in grinding is an important parameter in terms of breakage behavior. Maximum breakage rate was reached for −425 + 300 μm size group in the stirred mill. The ratio of “grinding medium size/size of the material ground” (6.0/0.425) was calculated as approximately 14. A decrease in this ratio, i.e., an increase in particle size of material, caused engagement difficulties of particles by balls. An increase in the ratio, however, resulted in a pillowing effect of fine materials in the medium and, thus, a decrease in breakage rate.