Explore the vast range of titles available.

Economic and legal conditions of the European power industry enforce higher participation of biomass in the thermal energy mix per power unit, due to the necessity of carbon dioxide emission reduction. One of the most important features dictating the suitability of biomass fuel for utilization in pulverized fuel-fired boilers is its grindability. The grindability of biomass is a difficult parameter to estimate due to its non-uniform morphology and inhomogeneous character. Milling and co-milling of large amounts of biomass can deteriorate the mill output and make it difficult to ensure the proper particle size distribution of the pulverized fuel fed into the combustion chamber. The main objective was to determine whether torrefaction pre-treatments could increase the grindability features of various types of biomass. Investigations of raw and torrefied biomass grindability were performed with the use of a modified Hardgrove Index for alder chips, palm kernel shells, and willow chips. Additionally, semi-industrial scale milling tests were performed, which allowed for the evaluation of torrefied biomass suitability for continuous grinding installations equipped with vertical spindle mills. According to the analysis, an increase in the biomass grindability index after the torrefaction process was shown. Additionally, it was noted that for milling low-density materials (e.g., torrefied biomass), changes in the construction of the industrial mill classifier may be necessary for the proper grinding circuit operation.

This study explores the relationship between maceral composition, coal rank, and the Hardgrove Grindability Index (HGI) of Batu Ayau coal through proximate, petrographic, and HGI analyses. The results indicate a positive correlation between vitrinite composition and HGI values for Batu Ayau coal (R = 0.65), while liptinite and inertinite exhibit negative correlations (R = -0.58 and R = -0.51, respectively). Additionally, volatile matter and calorific value, as representations of coal rank, demonstrate positive correlations with HGI values (R = 0.38 and R = 0.56). The mineral content affects HGI values variably, with a correlation coefficient of 0.25 for Batu Ayau coal, depending on the type of constituent minerals.

The characteristics of HGI fractions of the blend coal were investigated. One rejected coal (A) with three imported coals, Indonesian coal (B), Russian coal (G) and Australian coal (H), and their blends were tested for their grindability indices as per standard ASTM D 409. The fractions obtained from HGI tests were further assessed for its quality using their proximate, ultimate and α-quartz analysis. The reactivity of these fractions was measured with the TGA. The results showed that after pulverization process the blend coals were not of the same blend ratio. The ash content and α-quartz analysis of the fractions reveal disproportionation happening during pulverization of coal. This was supported by the ultimate carbon values of the same parent/blend coals which showed the higher carbon percentage in plus 75 fractions of HGI tests. Thereby, before blending two different coals the characteristics of parent coals needed to be studied and assessed for the optimum blend proportion that can be used for that particular coal.

The substitution of biolubricant for mineral cutting fluids in aerospace material grinding is an inevitable development direction, under the requirements of the worldwide carbon emission strategy. However, serious tool wear and workpiece damage in difficult-to-machine material grinding challenges the availability of using biolubricants via minimum quantity lubrication. The primary cause for this condition is the unknown and complex influencing mechanisms of the biolubricant physicochemical properties on grindability. In this review, a comparative assessment of grindability is performed using titanium alloy, nickel-based alloy, and high-strength steel. Firstly, this work considers the physicochemical properties as the main factors, and the antifriction and heat dissipation behaviours of biolubricant in a high temperature and pressure interface are comprehensively analysed. Secondly, the comparative assessment of force, temperature, wheel wear and workpiece surface for titanium alloy, nickel-based alloy, and high-strength steel confirms that biolubricant is a potential replacement of traditional cutting fluids because of its improved lubrication and cooling performance. High-viscosity biolubricant and nano-enhancers with high thermal conductivity are recommended for titanium alloy to solve the burn puzzle of the workpiece. Biolubricant with high viscosity and high fatty acid saturation characteristics should be used to overcome the bottleneck of wheel wear and nickel-based alloy surface burn. The nano-enhancers with high hardness and spherical characteristics are better choices. Furthermore, a different option is available for high-strength steel grinding, which needs low-viscosity biolubricant to address the debris breaking difficulty and wheel clogging. Finally, the current challenges and potential methods are proposed to promote the application of biolubricant.

This article deals with the development of an alternative method for determining the grindability index of fine-grained materials. This method is inspired by the commercially used VTI method (also known as RTI after the Russian Thermal Energy Institute), which was widely used in Central and Eastern Europe in coal grinding. The disadvantage of the VTI method is that it uses a specific grinding device that otherwise has no other use and nowadays is no longer commonly available. Through the new method, high-energy grinding was performed using a commercially available planetary mill on silicate materials such as limestone, feldspar, corundum, and quartz. The effectiveness of the method was verified on clinker as a representative of widely used materials. The deviation between the grindability index calculated by the origin VTI method and the new developed method was on average approximately 8%; in the case of clinker grinding, it was only 3%. The results showed that the VTI method could be replaced by a new method that uses a modern available planetary mill and laser granulometry to determine the grindability index. The result is a new classification of materials according to their grindability indexes, which is based on the original VTI method.

The growing search for alternative energy sources is not only due to the present shortage of non-renewable energy sources, but also due to their negative environmental impacts. Therefore, a lot of attention is drawn to the use of biomass as a renewable energy source. However, using biomass in its natural state has not proven to be an efficient technique, giving rise to a wide range of processing treatments that enhance the properties of biomass as an energy source. Torrefaction is a thermal process that enhances the properties of biomass through its thermal decomposition at temperatures between 200 and 300 °C. The torrefaction process is defined by several parameters, which also have impacts on the final quality of the torrefied biomass. The final quality is measured by considering parameters, such as humidity, heating value (HV), and grindability. Studies have focused on maximizing the torrefied biomass’ quality using the best possible combination for the different parameters. The main objective of this article is to present new information regarding the conventional torrefaction process, as well as study the innovative techniques that have been in development for the improvement of the torrefied biomass qualities. With this study, conclusions were made regarding the importance of torrefaction in the energy field, after considering the economic status of this renewable resource. The importance of the torrefaction parameters on the final properties of torrefied biomass was also highly considered, as well as the importance of the reactor scales for the definition of ideal protocols.

Accurate characterization of ore grindability is essential for optimizing mill throughput, reducing energy consumption, and predicting mill performance under varying ore conditions. However, the standard Bond work index (BWI) test remains time-consuming, costly, and requires a large amount of sample. This study evaluates the effectiveness of several rapid, low-cost alternatives, Leeb rebound hardness (LRH), Cerchar abrasivity Index (CAI), portable X-ray fluorescence (pXRF), and hyperspectral imaging (HSI), as proxies for grindability in gold-bearing ores. Sixty-two hand-size rock samples collected from two adjacent Canadian open-pit mines were analyzed using these techniques and subsequently grouped into ten ore groups for BWI testing. LRH and CAI effectively differentiated moderate (<15 kWh/t) from hard (>15 kWh/t) grindability classes, while geochemical features and HSI-based mineralogical attributes also showed strong predictive capability. HSI, in particular, provided non-destructive, spatially continuous data that are advantageous for complex geology and large-scale operational deployment. A conceptual workflow integrating HSI with complementary field measurements is proposed to support comminution planning and optimization, enabling more responsive and timely decision-making. While BWI testing remains necessary for circuit design, the results highlight the value of combining rapid proxy measurements with advanced analytics to enhance geometallurgical modelling, reduce operational risk, and improve overall mine-to-mill performance.

The main theoretical prerequisites for the thermodynamic analysis of the process of grinding rocks are given. The structural-energetic relationships between the regularities of plastic deformation with energy characteristics that occur during the crushing of mineral substances are described. The evaluation of the grindability of rocks in a ball mill under different grinding modes was made. Rational operating modes of the mill have been determined to ensure the required degree of grinding, which makes it possible to significantly reduce the energy consumption of the grinding process. To assess the quantitative content of adsorption centers, a classification of the “indicator of reduced hydration activity” is proposed. (P pga ), allowing the most accurate assessment of the contribution of the surface activity of mineral fillers to the course of the processes of interactions and transformations occurring in a hydrated medium.

Torrefaction of biomass materials has received a tremendous attention over the years due to its ability to produce a high-grade solid biofuel with enhanced durability, excellent grindability, higher bulk density and calorific value, and greater energy density, as compared to the original untreated biomass material. It is a mild pyrolysis treatment technology under inert atmosphere which can improve the chemical and physical properties of raw biomass through the elimination of oxygen, reduction of moisture content, and change of chemical compositions. When raw biomass is mildly pyrolyzed in a default-oxygen or N2 atmosphere at moderate temperatures, the properties of raw biomass including low calorific value, hydrogen-carbon ratio, hygroscopicity, and grindability can be significantly enhanced. In the present review, the operating mechanism of different torrefaction processes including wet, dry, and ionic-liquid-assisted torrefaction is analyzed and discussed. More importantly, the reactor design for commercialization purpose, reaction kinetics and mechanism, economics, and sustainability of biomass torrefaction is discussed in detail. This review is extended to the torrefaction of agro-residue biomass since torrefied agro-residue-based pellets can be produced from agro-residues. The various technological applications of biomass torrefaction are also reviewed and the prospects in ensuring the continuous production of high-grade fuels are summarized.

The carbothermic co-reduction of nickel laterite ore and red mud realized the simultaneous reduction of nickel, iron in laterite ore, and iron in red mud at high efficiency. Nickel and iron in nickel laterite ore and iron in red mud were recovered in the form of ferronickel. The size characteristics of ferronickel particles and grindability of carbothermic reduction products are essential for obtaining good technical indicators. The influence of co-reduction conditions on ferronickel particle size and relative grindability was investigated by a carbothermic reduction test, particle size analysis, and relative grindability determination. The mean size of ferronickel particles increased and the proportion of coarse particles grew with improving carbothermic reduction temperature, increasing appropriately anthracite dosage, and prolonging carbothermic reduction time. However, the relative grindability of carbothermic reduction products deteriorated when reduction temperature was improved and the reduction time was extended. The relative grindability was negatively correlated to the ferronickel particle size. The carbothermic reduction temperature had the most dominant effect on the ferronickel particle size and relative grindability, followed by the anthracite dosage and reduction time. More nickel-bearing and iron-bearing minerals were reduced to metallic state with raising reduction temperature and increasing appropriate anthracite dosage. The fine ferronickel particles agglomerated and merged into bulk ferronickel grains with a prolonged reduction time. The results will provide theoretical guidance for the recovery of nickel and iron by co-reduction of nickel laterite ore and red mud.