Contribution to the Improvement for Thermal Working Condition of the Toyoha Mine Using Thermal Environmental Analysis

Abstract

Geothermal gradient of Toyoha Mine, which produces Lead-Zinc ore minerals with some silver content, is 20-30 degrees centigrade per 100 meters, and highest rock temperature reaches more than 150 degrees centigrade in the working area. In this situation, countermeasure for hot conditions should be required seriously. In addition to the big diameter long hole drilling for the return air shaft and the cool water spray at the face, thermal environmental analysis has been applied. This paper summarizes the results of thermal characteristics of the mine and some examples of application to the field by thermal environmental analysis. Large scale ventilation network with 304 nodes, 484 roads and 6 fans has been constructed and thermal environmental analysis of the full mine basis has been conducted to match the original state of the mine, and short, middle and long term thermal environment estimation analysis has been conducted. But big differences of the calorific values, which are added in the underground, has been shown between simulations and measured data. In order to grade up the accuracy of the analysis, the estimation of individual thermal origin has studied, i.e. heat from blasted ore and rock, blasting, diesel and electric equipment, and so on. And thermal environmental analyses of the partial basis including heading block and extraction block have been done to set the thermal characteristics. Also suitable heat transmission compensation factor, surface area compensation factor, and others have been considered by case studies. Using the studied results noted above, authors applied this technology to actual field, such as ventilation plan at headings by sensitivity analysis, assessment of thermal condition improvement by some kinds of backfilling at post-extraction block, and support the underground layout design. Finally, it is proved that thermal environmental analysis technology is able to contribute the improvement of safety, productivity, and energy cost saving.