Crushing and milling

The comminution of ores consumes a high portion of energy. Therefore, different pretreatment methods of ores prior to their comminution are considered to reduce this energy. However, the results of pretreatment methods and their technological development are scattered in literature. Hence, this paper aims at collating the different ore pretreatment methods with their applications and results from published articles, conference proceedings, and verified reports. It was found that pretreatment methods include thermal (via oven, microwave, or radiofrequency), chemical additive, electric, magnetic, ultrasonic, and bio-milling. Results showed that the chemical pretreatment method has been used at an industrial scale since 1930, mainly in cement production. The microwave pretreatment results showed positive improvements at pilot scale mining applications in 2017. The results of ore pretreatment using electric and ultrasonic methods showed up to 24% and 66% improvement in energy consumption, respectively. The former and the latter have been piloted for gold and carbonate ore, respectively. Findings also showed that magnetic, radiofrequency, and bio-milling methods have not led to significant reductions in comminution energy. Based on energy reduction, safety, costs, stage of application, and downstream benefits, microwave and electrical pretreatment methods may be focused for applications in the mining industry.

In 1978 two quernstones were given on loan to the National Museum of Ireland for recording purposes. The larger of the two was found "about 30 years" previously by Mr. Richard Carolan, Roughgrange, Drogheda, who recognised its importance and preservgd it. The stone is now on display in the Millmount Museum, Drogheda.

Over a century of mining native copper in Michigan’s Copper Country has produced several million tons of workable metal and an even greater amount of waste. The remaining rock, tailings, and slag each represent a separate step in the process of hard rock mining, providing tangible links to industrial landscape narratives at both regional and site-specific scales. Recently, the Keweenaw National Historical Park’s Advisory Commission funded a survey of over 350 separate sites of copper mine waste, ranging from multi-acre tailings deposits to slag heaps occupying less than 50 sq. ft. This work resulted in the development of a classification and scoring rubric designed to identify waste sites of greatest
historical significance, authenticity, and integrity. These findings offer insight into understanding and appreciating the residues of extractive practice that in this case, due to the benign nature of the unalloyed copper mined there, pose a lesser threat to the environment compared with most hard rock mining activities.

Brittle spheres are crushed and fragmented between two rigid platens dynamically. More than 140 plaster spheres with two different strengths (37 and 59 MPa) and three different sizes (50, 60 and 75 mm) were tested. The impact energies varied from 10 J to over 300 J with impact velocities ranging from 1 to 9 m/s. Twelve different failure patterns are identified, depending on the number of fragments and severity of crushing around the axis of compression. In general, fragments resulted from the double dynamic impact are of two different sizes, namely larger fragments resulted from primary fractures (mainly passing through a diameter of the sphere) and smaller fragments resulted from secondary fractures (do not pass through a diameter of the sphere). The number of smaller fragments increases with the impact energy. The cumulative mass of all fragments of size larger than d [i.e. R(d)] can be fitted into a power law of d (or the so-called Gates-Gaudin-Schuhmann distribution), but there are two distinct slopes of the double-log scale plot of R(d) versus d. The power index n of the larger-fragment-fit is, in general, larger than that of the smaller-fragment-fit. Typically, n ranges from 0.8 to 1.6 and decreases with the impact energy and strength of the sphere. The diameter of the end crushing zone is found approximately proportional to m 1/4 r 1/4 v 1/2 , where m is the mass of the impactor, r is the radius of the sphere and v is the impact velocity. In addition, taking into account of kinetic energy loss, crushing modulus as well as specific fracture energy were obtained for the spheres. D

For static compressions of spheres, a new stress analysis for isotropic elastic spheres compressed between two¯at rigid platens is proposed by incorporating the Hertz contact stress. The predictions of the failure load for various sizes and strengths of spheres agree very well with our static experiments on a brittle plaster material. For dynamic compressions of spheres, a simple crushing analysis illustrates that the size of the contact zone can be estimated quite accurately in terms of the size of the sphere, the dynamic hardness, and the impact energy. Although the maximum contact force at failure is larger in the static case than that in the dynamic case, the energy required for fragmentation of the solid spheres is larger under dynamic test than under static test. Comparisons of the static and dynamic tests show that the impact energy required for fragmentation of a sphere can be approximated as 1.5 times of that for the static test. As expected, the impact energy for fragmentation increases monotonically with the size and strength of the spheres. The contact time at failure, however, does not exhibit a clear trend with the changes in size and strength of the spheres. Ó

The comminution of ores consumes a high portion of energy. Therefore, different pretreatment methods of ores prior to their comminution are considered to reduce this energy. However, the results of pretreatment methods and their technological development are scattered in literature. Hence, this paper aims at collating the different ore pretreatment methods with their applications and results from published articles, conference proceedings, and verified reports. It was found that pretreatment methods include thermal (via oven, microwave, or radiofrequency), chemical additive, electric, magnetic, ultrasonic, and bio-milling. Results showed that the chemical pretreatment method has been used at an industrial scale since 1930, mainly in cement production. The microwave pretreatment results showed positive improvements at pilot scale mining applications in 2017. The results of ore pretreatment using electric and ultrasonic methods showed up to 24% and 66% improvement in energy consumptio...

A milling of composite material (CM), containing boron-tungsten fibre and aluminium matrix (CM Al-W-B) is investigated. In order to obtain a powder with determined particle size a multi-stage milling has been done. The milled material consists of  luminium matrix alloy, boron and tungsten particles. A morphology of CM Al-W-B particles is described. The mechanism of milling and relationship between energy spent for disintegration are presented.

A waste of composite material (CM), containing boron-tungsten fibre and aluminium matrix (CM Al-W-B) is investigated. A method of grinding has been used for processing of Al-W-B CM waste. This method has been carried out in several stages in order to obtain a powder with determined particle size. The milled material contains aluminium matrix alloy, boron and tungsten. The morphology of CM Al-W-B particles is described. The mechanism of disintegration and relationship between energy spent for disintegration, and a degree of milling of CM Al-W-B powder, are described. Possible applications of Al-W-B composite powder as a source material for obtaining a new composite ceramics by self-propagating high-temperature synthesis (SHS) are noted.