Research On Multi-objective Ore Blending Optimization In Open-pit Phosphate Mine Based On Improved Nsga-Ⅱ Algorithm

With the rapid development of China’s industry,the demand for mineral resources has sharply increased.Phosphate ore,as a non-renewable chemical raw material,is widely used in industrial sectors such as construction,agriculture,metallurgy,chemical industry,and environmental protection,deeply affecting national security and economic development.How to utilize limited phosphate rock resources to produce mineral products that meet quality requirements is an urgent problem that every mining enterprise needs to solve at present.However,optimizing ore blending technology is the key to solving this challenge.This article focuses on the problem of varying characteristics of phosphate rock and large fluctuations in raw ore grade caused by geological conditions in mines,which makes it difficult for the quality of selected ore to meet the actual needs of the beneficiation plant.Therefore,a study on multi-objective optimization of phosphate ore blending is carried out.The main tasks include:（1）The existing research on ore blending optimization is summarized.Firstly,the current research status of ore blending optimization at home and abroad was summarized from two aspects:the ore blending optimization problem model and the method for solving the ore blending problem model.The contributions and shortcomings of existing research were elaborated.Finally,an overview was provided of the basic theory of open-pit ore blending and the related theories of multi-objective optimization,laying a theoretical foundation for the establishment and solution technology of multi-objective ore blending optimization models for open-pit phosphate mines.（2）A multi-objective ore blending optimization model for open-pit phosphate mine is constructed.In this study,based on the analysis of existing ore blending problems,the optimization objectives are to minimize the total ore grade deviation of selected ore and the total energy consumption of production operations during the implementation of the ore blending plan phase,in view of the characteristics of different phosphate rock characteristics and large fluctuations in raw ore grades caused by mine geological conditions.Based on the actual production situation of the mine,a multi-objective optimization model for open-pit phosphate ore blending is established with the production capacity of shovel loading,transportation,crushing equipment,ore output,and harmful impurities such as MgO and SiO₂ content in phosphate rock as constraints for the optimization model.（3）The multi-objective ore blending optimization model solving algorithm for open-pit phosphate mines has been designed.Considering that the ore blending optimization model is a multi-objective nonlinear optimization problem with numerous constraints,an improved NSGA-Ⅱ algorithm,named SDN-NSGAⅡ,is designed based on the classic NSGA-Ⅱ algorithm.The designed SDN dominance（Niching based Strengthened Dominance）replaces the traditional Pareto dominance relationship in NSGA-Ⅱ,which fully considers the information of local optimal solutions in each region to determine the dominance relationship between candidate solutions by making full use of the convergence information,distribution information,and feasibility information of the solution.Finally,simulation results and numerical analysis on a series of standard test problem sets validate the effectiveness of the proposed algorithm in solving multi-objective optimization.（4）Taking a phosphate open-pit mine in Kunming,Yunnan as an application example,the actual production data collected from the open-pit mine is incorporated into the established multi-objective phosphate ore blending optimization model,and the proposed algorithm is used to optimize the problem.The optimization results show the superiority of the proposed algorithm for solving multi-objective phosphate ore blending optimization problems and the practicality of the proposed model.