An Improved High-Pressure Roll Crusher Model for Tungsten and Tantalum Ores

Abstract

An improved approach is presented to model the product particle size distribution resulting from grinding in high-pressure roll crusher with the aim to be used in standard high-pressure grinding rolls (HPGR). This approach uses different breakage distribution function parameter values for a single particle compression condition and a bed compression condition. Two materials were used for the experiments; altered Ta-bearing granite and a calc-silicate tungsten ore. A set of experiments was performed with constant operative conditions, while varying a selected condition to study the influence of the equipment set-up on the model. The material was comminuted using a previously determined specific pressing force, varying the feed particle size, roll speed and the static gap. A fourth group of experiments were performed varying the specific pressing force. Experimental results show the high performance of the comminution in a high-pressure environment. The static gap was the key in order to control the product particle size. A mathematical approach to predict the product particle size distribution is presented and it showed a good fit when compared to experimental data. This is the case when a narrow particle size fraction feed is used, but the fit became remarkably good with a multi-size feed distribution. However, when varying the specific pressing force in the case of the calc-silicate material, the results were not completely accurate. The hypothesis of simultaneous single particle compression and bed compression for different size ranges and with different parameters of the distribution function was probed and reinforced by various simulations that exchanged bed compression parameters over the single particle compression distribution function, and vice versa.The main advantages of HPGR lie in energy savings and the simplicity of the process [7]. However, the particle size reduction ratio is lower than that in some other types of mills, such as ball and rod mills. HPGR are used in various configurations such as pre-grinding, hybrid grinding and finish grinding, among others [4]. This is mainly due to the comminution effect under the action of high-pressure rolls, which generates many more internal fractures of particles than other devices [13][14][15], and also generates material with latent cracks for a second stage of milling or even enough to liberate the ore [4,16]. The favourable influence of HPGR performance on downstream beneficiation operations has also been proved, for example, in the ore flotation process [17]. HPGR also appears to have a less negative impact on the environment in terms of lower dust and noise emissions [18].With regard to the description of the model, the mechanism of breakage by compression and shear is dominant in roll crushers [19]. In HPGR, two main breakage mechanisms are observed: single particle compression and bed compression [20][21][22]. Single particle compression is more efficient, but larger particles cause unnecessary liner wear issues [21] and also result in the separatio...

Understanding Mineral Liberation during Crushing Using Grade-by-Size Analysis—A Case Study of the Penuota Sn-Ta Mineralization, Spain

“…These results are in line with an observation from our SEM-EDS investigation of unconcentrated samples, despite the much more limited number of ore-bearing particles studied. A simple conceptual model for the induced fractionation of minerals during crushing is presented in Figure 12, which is based on the presented results and previous studies [25,31,32]. Fractures and microfractures in matrix minerals possibly control the overall breakage behavior of the rock; as a consequence of this, most of the finer particles are generated from breakage of matrix minerals.…”

“…The case study was performed on two~1 ton samples from the Penouta open pit mine, collected by university of Centres Cientifics i Tecnològics de la Universitat de Barcelona during January 2015, as a part of a multi-partner research collaboration (OPTIMORE, project number 642201) [25,[28][29][30][31][32]. Due to potential mineralogical variations, samples of the mineralized leucogranite were collected from different parts of the open pit.…”

Ore crushing in the high-pressure roller-press as a modelling object under stochastic properties of feed materials

“…Yet, there is no single opinion as to simulating this very characteristic [5] considers simulation of curves of granulometric composition of crush products and notes that crushing results can be controlled by selecting a particular value of pressure on the ore bed. [6] applies the distribution function of disintegration of ore lumps that is associated with the characteristic of the initial material to assessing ore sizes [7] also indicates that besides the ore disintegration distribution, the clearance between rollers has a great impact on the size of crush products. The authors of [8] note that the granulometric composition of products is influenced by the location of rollers.…”

Liberation Characteristics of Ta–Sn Ores from Penouta, NW Spain

“…Gravity separation studies focussed in a particular sector of the Penouta tailings have been reported [35], as well as studies on metallurgical treatments [36]. These studies, along with the previous studies on crushing [37] and milling [32,38], provide a broad understanding of the Penouta ore processing. However, in this study, the mineralogical characteristics of ore materials, tailings, and leucogranite outcropping are characterized.…”