| The annual consumption of various minerals used in nationwide industries in China is over 5 billions tons, and 90 percentage of energy and 80 percentage of raw materials needed originate from these minerals. While the development of the national economy continues, unfortunately, the resources with valuable elements are getting depleted, and the portion of difficult- to- treated resources is growing, and the overall recovery of the resources in China is low up to 20% in the comparison with the developed countries. Furthermore, the stockpiled tailings after the treatment occupy the farmland and pollute the surroundings. Thus, in order to fully develop the active effects of mineral resources on industrial feed, national economy, environment and society, it is necessary to build our scientific system for evaluating mineral resources utilization according to the principles of high efficiency, low energy consumption and non-pollution and with the aid of the latest information technology.The present situation of the utilization of iron ores and its evaluation systems is analyzed and summarized. The related data and papers are extensively collected by retrieving papers, enquiring relevant experts and visiting the plants. On the basis of the related industrial production data of four key iron and steel Co. (Panzhihua Iron and Steel Co., Baotou Iron and Steel Co., Jiuquan Iron and Steel Co. and Anshan Iron and Steel Co.), a number of models, such as iron recovery versus the grade of iron concentrate, consumption of iron concentrates versus the grade of iron concentrate, sinter product versus the grade of iron concentrate, consumption of flux versus the grade of iron concentrate and the utilization coefficient of furnace versus the grade of iron concentrate, are established with the help of software Matlab.After the effects of the grade of iron concentrates on the sub-processes of beneficiation, sinter and iron-making (named overall process) are systematically analyzed, it is essential that the optimization of the grade of iron concentrates for overall process (including the three sub-processes) meet the following six objectives: profits obtained and the consumptions of iron ores, flux, coke, electricity and coal. A new methodnamed 'cost method' for optimizing the grade of iron concentrates has been put forward, which weighting factors of the above objectives depend on the cost proportion of an objective in the overall cost and can be calculated mathematically. The weighting factors are dynamically changing according to their prices fluctuations of the selected objectives. Thus the resultant value of its objective function varies and reflects its reality.The fundamentals of Fuzzy mathematics are employed for multi-object optimizations of grade of iron concentrates in overall process. It is shown that the optimal grades of iron concentrate is as follow: 54%TFe for Midi concentrate of Panzhihua Iron and Steel Co., 54%TFe for concentrate of Baotou Iron and Steel Co., 54%TFe for concentrate of Jiuquan Iron and Steel Co., 67.5%TFe for Diaojuntai concentrate of Anshan Iron and Steel Co. and 68.5%TFe for Gongchanglin magnetite concentrate of Anshan Iron and Steel Co. It can be seen that the models fit very well to the production data of the four key plants.The expert system of 'cost methods for optimizing grade of iron ores' and its database which is based on network server (Windows 2000 sever, Web server, SQL sever 2000, and PHP language) has been developed and it can be run on a PC or a network, hence it is possible to extensively share its information and form the decision-making network system for the utilization of iron ores.
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