Abstract Mineral deposits have shown decreasing ore grade and increasing complexity, which has led mining projects to experience increased capital and operating costs. Preconcentration is an alternative to minimize such costs. Notwithstanding the resulting rise in ore grade and reduction in feed mass, the generated tailings may contain significant amounts of the material of interest. In order to improve the mineral liberation at this stage, selective comminution proposes to explore different comminution mechanisms. This investigation compared three different crushing methods (jaw crusher, impact crusher, and high-pressure roller mill) for three different types of ores and the response of their products to pre-concentration, using a gravity method that was evaluated through heavy-liquid separation of the -6.35+3.35 mm crushed fraction. This fraction represents approximately 15% of the total sample, and is used as an indication of the gangue rejection potential for the -12+1.18 mm fraction. Copper and polymetallic ores showed good pre-concentration results for this size range at laboratory scale, with metallurgical recoveries greater than 90% and a rejection of over 20% of mass. Iron ore showed a 97% metallurgical recovery and 10% mass rejection. The impact crusher proved to be the best option for selective comminution for the polymetallic ore, with the highest metallurgical recovery. Finally, no significant differences were observed when using any of the three crushing mechanisms for the copper and iron ore. complexity costs interest stage jaw highpressure high pressure mill preconcentration, preconcentration pre concentration, concentration heavyliquid heavy liquid 6.35+3.35 635335 6 35 3 -6.35+3.3 15 sample 12+1.18 12118 12 1 18 -12+1.1 scale 90 20 97 10 Finally 6.35+3.3 63533 -6.35+3. 12+1.1 1211 -12+1. 9 2 6.35+3. 6353 -6.35+3 12+1. 121 -12+1 6.35+3 635 -6.35+ 12+1 -12+ 6.35+ 63 -6.35 12+ -12 6.35 -6.3 -1 6.3 -6. - 6. -6

Abstract A considerable portion of energy consumption and, as a consequence, operational costs in mineral processing, is associated with comminution. High Pressure Grinding Rolls (HPGR) are appealing for their energy efficiency and resulting lower operating costs. This article evaluates this technology as an alternative to the conventional fused alumina comminution route of a specific plant comprising a complex roll crushing circuit. Two fused alumina samples, called BT and TB, were submitted to HPGR (open circuit) and physical characterization (DWT, BBWI, bulk density, specific gravity) tests. In addition, simulations were conducted using JKSimMet® 6.0 software, aiming to predict the performance of a closed circuit equipment and scale-up of an industrial-scale unit. Product size distributions of the open circuit HPGR tests and closed circuit HPGR simulations were compared with the product size distribution required by the industrial comminution circuit. The required throughput was also evaluated. Results show that the alternative HPGR route provides a remarkable potential for circuit simplification, while considerably reducing the number of comminution equipments from 13 to 1, which facilitates operational control and possibly reduces operating costs.

Abstract Pre-concentration consists of the preliminary discarding of a fraction of the mineral processing plant feed which contains little or none of the mineral of interest, reducing the mass to be processed in downstream operations (e.g. milling, concentration and dewatering), as well as the capital and operational costs. In this context, this study investigates the performance of density and sensor-based sorting separation methods in the removal of carbonate gangue of a zinc ore, in size fractions typical of crusher products, using sink and float tests with heavy liquids, jig stratification and laboratory scale ore sorting tests using an X-Ray Transmission (XRT) sensor. The best results were obtained through sink and float in heavy liquids, which indicated the possibility of discarding 30% of the feed mass, removing over 60% of the carbonates (CaO and MgO) and losing only 2% of the zinc. The ore sorting tests also presented positive results, with approximately 93% of metallurgical recovery in 70% of the mass for both size fractions tested. The jig stratification results were worse, since the zinc content discarded with this method was high. The results indicate significant reduction potential for Capex and Opex costs using pre-concentration strategy.

Abstract A pilot scale test program was conducted to evaluate the size reduction performance of HPGR (High Pressure Grinding Rolls) operating in different circuit configurations. For this purpose a series of pilot-HPGR locked cycle tests were performed with medium and high pressures to simulate the HPGR operation in closed circuit with a screen, with partial product recycle, and with edge recycle. Logged instrumentation data such as roller speed, working gap, operating pressure, and power draw were used in combination with material test results such as particle size distributions, flake density, flake thickness, and bulk density of the feed for calculation of HPGR operational parameters. The paper reports the results from the pilot HPGR test work. The analysis reported herein includes an evaluation and comparison of different circuit configurations of the HPGR operation in terms of energy consumption, capacity and product fineness and also discusses the benefits of various circuit arrangements.

A Mina do Sossego, localizada na região sudeste do Estado do Pará, foi a primeira usina da Vale a operar um moinho SAG para processar minério de cobre e ouro. Nos primeiros três anos de operação, foram estudadas alternativas para aumento de produção, principalmente focadas em aspectos operacionais da moagem SAG. Em seguida, foram realizados estudos visando a identificar o desempenho do circuito em função dos diferentes tipos de minérios alimentados. Uma caracterização completa do minério foi realizada em conjunto com a calibração de modelos matemáticos baseados em amostragens conduzidas no circuito industrial. O simulador foi então usado para prever níveis de produção associados a cada tipo de minério, assim como determinar configurações otimizadas para o circuito. Esse artigo descreve em detalhes os principais aspectos da otimização do circuito, assim como o método para prever a produção em função das características do minério e do circuito.

Sossego was the first Vale SAG mill operation to process copper-gold ore. It is located in the State of Para, southeastern Amazon region of Brazil. In the first three years of continuous operation, Vale investigated different alternatives for improving the circuit’s performance by investigating operating conditions, mainly focusing on the SAG mill. It was decided to further assess the performance of the comminution circuit as a function of ore characteristics. A comprehensive ore characterization program was then conducted, together with the calibration of mathematical models on the basis of surveys carried out at the industrial circuit. The simulator was then used to predict the throughput associated to each ore type, as well as to establish the optimized circuit configuration and tailored operating conditions. This paper describes in detail the main aspects of optimizing the industrial circuit performance, as well as the successful method for predicting the production as a function of ore characteristics and circuit configuration.