mojtaba mokhtarian

The main objective of this contribution is to focus on the portion of the comminution process which deals with the prediction of the energy consumption due to the comminution portion of the milling processes. The comminution energy in mineral processing and cement industry is usually determined by empirical Bond Work Index (BWI), regardless of the mechanical properties of a rock. The BWI is a measure of ore resistance against grinding and is determined by using the Bond grindability test. Determining the BWI value is quite complicated and time consuming. Its value constitutes ore characteristic and is used for industrial commination plants designing and optimization. The BWI is defined as the calculated specific energy (kW h/t) applied in reducing material of infinite particle size to 80% passing 100 µm. The higher the value for BWI, the more energy is required to grind a material in a ball mill. The energy consumed in the process of comminution depends on both the mechanism of comminution and the mechanical properties of the materials being ground. It is interesting to study the effect of the essential ones of these properties on the energy efficiency of grinding process.

Several attempts have been made to obtain and optimize the comminution energy. An efficient Response Surface Method, (RSM)-based method for the BWI approximate value determination, which is based on physico-mechanical tests, is presented in this paper. BWI and some physico-mechanical tests on 8 typical rock samples and its correlation are studied; it would be beneficial to examine this relation based on physical concept. The database including Uniaxial Compressive Strength (UCS), Abrasion (AT), Hardness (HT) and Modulus of Elasticity (ME) are assembled by collecting data from Haffez experiments.

The determination of the BWI from RSM- based multivariate model is almost matched with measured Bond’s work index. As a result of analysis the best equation obtained from RSM-based model is formulized in Equation 1: (1) Standard statistical evaluation criteria are used to evaluate the performances of predictive models.

The performance of the estimator models can be controlled by R2, VAF, RMSE, MAPE, VARE and MEDAE. The RSM- based model with higher VAF as well as lower RMSE, MAPE, VARE, MEDAE shows better performance in comparison to the Haffez single-variable models. AT and ME have the greatest effect on the value of BWI; and also HT has the least impact.

Performance prediction of diamond wire saws and estimation of sawability are important in the cost estimation and the planning rock cutting projects. In this paper, the performance prediction of diamond wire saws in cutting carbonate rocks is considered on 14 different carbonate rocks in stone quarries. Uniaxial compressive strength (UCS), Brazilian tensile strength (BCS), Schmidt hammer value (SHv), Los Angeles (LA) abrasion and production rate (Ph) of diamond wire saws are determined in separated reference. The scope of this study is to evaluate the capability of two different methods in order to predict production rate of carbonate rock using diamond wire saw. A non-linear model presented by Ataei et al. and new proposed non-linear model are presented. An application of Imperialist Competitive Algorithm (ICA) is used to determine the non-linear production rate estimator coefficients. According to the calculated statistical error between the forecasted and real measured values of production rate, ICA-based model has the lower values of MAPE, MAE, VARE, MEDAE and RMSE than the previous model in the literature, while it has the higher value of VAF than the previous model in the literature. It is concluded that the production rate of carbonate rock using diamond wire saw can reliably be estimated using the developed model.

The Rashakan limestone mine as supplier of Urmia cement plant is producing about 3 million tons of limestone ore. The proximity of this mine to the Urmia railway and the main transit road of Urmia-Mahabad, as well as the destructive effects of vibration and noise caused by mine explosions on residential and environmental area, has caused the use of continuous surface miner machines as one of options for continuation of mining operations. Determining the ease of rock mass extraction, which is referred to as the excavatability index, has a vital role in the decision making stage for the selection of methods and extraction machines. This paper investigate the feasibility of mechanized extraction based on the geomechanical characteristics of Rashtkan limestone mine rock mass. In 18 different sections of the of 8 geomechanical zones of the mine, geomechanical parameters including weathering, uniaxial compressive strength (UCS), joint spacing and layers thickness were measured by field and laboratory surveys. Based on the diggability index rating method, the excavatability of the zone (7), (1, 6), (8), (3 and 5) is classified in the hard, relatively hard, easy and very easy excavation classes. In the following, considering the uncertainties in the results of the classification systems, one of the most recent applied classification methods based on continuous rating is used. The results show that the estimation of both continuous and conventional rating methods for the three zones of 1, 6 and 8 is the same and for the zones of 3, 5 and 7, the continuous rating method suggests easier excavation condition. According to the results of this research, the geomechanical conditions of Rashakan limestone rock mass are appropriate for mechanized extraction and the use of continuous surface miner machines. It is recommended that in order to correct selection of the type and capacity of extractive machinery a technical and economic analysis be conducted based on the investment and the operational costs of each of the different options for different types of machines.