Investigation On The Mechanism Of Spontaneous Combustion Of Sulphide Ores And The Key Technologies For Preventing Fire

Spontaneous combustion of sulfide ores is one of the major hazards in safe mining of sulfurous ore deposits. For a long time, many researchers have made a lot of investigation in the theory and technology of preventing the spontaneous combustion of sulfide ores. Because the spontaneous combustion of sulfide ores is a complex process, there are still many problems which has not been fundamentally resolved.On the basis of referring the relevant literatures and the former research results over the world, in this dissertation some topics on the mechanism, potential, mathematical model and prevention technology of sulfide ore during spontaneous combustion were systematically researched by approaches of theoretical analysis, experiment simulation and in-situ test. The obtained achievements have been successfully applied in practice.The main research contents and the achievements in the dissertation are as follow:(1) The process of spontaneous combustion and the oxidation mechanism of sulfide ores at ambient temperature were investigated systemically with the methods both in theory and experiments. Depending upon referring the oxygen adsorption theory, bio-oxidation theory, chemical thermodynamics and electrochemistry and based on all kinds of analysis results, a more reliable and systematical theoretical framework on describing the oxidation mechanism of sulfide ores were completed by comparison and deduction. Moreover, the self-heating effect of sulfide ores was analyzed through tentative study, and a new comparative methodology of testing was invented.(2) The appraisal method of spontaneous combustion tendency, the fire index system and the risk standards for sulfide ores were put forward. By systematically analyzing the existing appraisal methods, a new comprehensive method for testing the spontaneous combustion tendency of sulfide ores in laboratory was developed and the assessing flowchart, the fire index and the appraisal method were expounded. The method was used in practical case and was approved to be correct. Based on the results, the coincidence among all relevant factors during oxidation of sulphide ores at ambient temperature was analyzed. The evaluation standards of spontaneous combustion tendency of sulfide ores and the risk of spontaneous combustion tendency of sulphide ores were constructed.(3) The hydrodynamic theory of porous medium and the heat and mass transfer theory were used in the study. The mathematical models of spontaneous combustion of sulphide ore pile were set up. Depending on that sulfide ore pile was taken as a continuous porous medium and according to the Darcy law, infiltrative equation and conservation of mass, the mathematical model of air flowing in sulfide ore pile was set up. By taking that sulfide ore pile as combustive porous media with inner heat source and according to the heat transfer mechanism in combustive porous media, the corresponding heat transfer model in sulfide ore pile was established. According to the laws of heat generation, transfer and equilibrium of sulfide ore pile, the thermodynamic model to forecast the safe period of sulfide ores pile was built.(4) Systematical technical measures aimed to prevent the sulfide ore spontaneous combustion were developed by direction of the investigation fruits. Effects of the inhibitor, water, ventilation and ore fragementation on the spontaneous combustion were analyzed and their functions in preventing fire of sulphide ores were assessed through theoretical analysis and tentative study. Also, a new method named oxidation-weight-increment was explored at the first time for evaluating the low-temperature oxidation speed of sulphide ores and the effect of inhibitor. It was approved to be effective in practice.(5) The main research achievements were successfully used in Dongguashan Copper Mine. The applications include that the comprehensive lab test method was used to assess the spontaneous combustion tendency of 13 sulfide ore samples in the Mine and that an effective reagent was applied in real project according to the cause of spontaneous combustion of sulfide ores pile in stope. The mathematical model to forecast the safe period of sulphide ores pile in stope was established and the period on the practical conditions of stope was calculated by testing the self-heating flux of sulfide ores. At the same time, the scientific means were suggested for the spontaneous combustion prevention of sulphide ore piles in the Mine. The applications indicated that the research results are effective and feasible, so these results in the dissertation can widely be applied in many other relevant mines.