Infrared thermography for prediction of spontaneous combustion of sulfide ores

The method of infrared thermography to predict the temperature of the sulfide ores has a large error. To solve this problem, the temperature of the sulfide ores is measured by thermal infrared imager and recording thermometric instrument contrastively. The main factors, including emissivity, distance, angle and dust concentration that affect the temperature measurement precision, are analyzed. The regression equations about the individual factors and comprehensive factors are obtained by analyzing test data. The application of the regression equations improves the precision of the thermal infrared imager. The geometric information lost in traditional infrared thermometry is determined by visualization grid method and interpolation method, the relationship between the infrared imager and geometry information is established. The geometry location can be measured exactly.

Nonlinear characteristics of induced spontaneous combustion process of sulfide ores

To investigate the relationship between nonlinear parameters and spontaneous combustion tendency of sulfide ores, nine different sulfide ore samples were taken from a pyrite mine in China, and induced spontaneous combustion experiment was carried out in the laboratory. Different stages of the induced spontaneous combustion process were studied by integrating wavelet technology and nonlinear dynamics theory. The results show that ignition points of all the ore samples are above 330 ℃, indicating that sulfide ores of the pyrite mine are difficult to combust spontaneously under normal mining conditions. Spontaneous combustion process includes three stages： incubation stage, development stage and approaching stage. The average temperature rising rate of the three stages are 1.0 ~C/min, 2.0 ~C/min and 4.2 ~C/min, respectively. During the spontaneous combustion process, mean values of approximate entropy and correlation dimension increase at first, and then decrease in the following stage. The mean value of the maximum Lyapunov exponent increases with the passage of reaction time. In a whole, correlation among the three nonlinear parameters firstly weakens, then enhances, and the best correlation period is at approaching stage. As ignition point increases, the maximum Lyapunov exponent of approaching stage decreases. Therefore, combustible tendency of sulfide ores could be qualitatively evaluated based on the maximum Lyapunov exponent of this stage.

Locating method of fire source for spontaneous combustion of sulfide ores

in order to achieve a more efficient way to accurately detect the position of the fire source of spontaneous combustion underground mine, a simple fire source locating method, based on infrared scanning system which can determine the point where the highest temperature on the surface of igniting ores occurs, was proposed. First, the differential equations that describe heat flow in ore body were presented and the relationship between the surface temperature distribution and the depth and intensity of inner fire source was established with a relatively simple heat transfer model. With the solution of equation, the expression of the relationship between the surface temperature distribution and the inner fire source was deduced and the mathematical-physical model of heat transfer process was set up. Then, with the model, visualization of fire source on the basis of MATLAB simulation platform was realized. The results show that： 1） within 10 m, when the detecting depth is less than 2 m, the temperature perturbation on ores surface can change rapidly, and then slowly; after 4 m, in contrast, it changes very little, and is even close to zero at 10 m; 2） When it is close to self-ignition duration and the detective depths are 2, 5 and 10 m, respectively, the maximum temperature differences are correspondingly 0.5, 0.04 and 0.005 ℃ in the scope of 1 m×1 m; under the same condition, the maximum temperature differences are 1.391, 0.136 and 0.018 ℃, respectively, in the scope of 2 m×2 m. Therefore, this system can be used to measure the temperature differences on the surface of ore body and determine the highest temperature point directly. Also, it is possible to determine the depth of fire source and its intensity by locating method of fire source indirectly.

Evaluation of spontaneous combustion tendency of sulfide ore heap based on nonlinear parameters

To explore a new evaluation method for spontaneous combustion tendency of different areas in sulfide ore heap, ore samples from a pyrite mine in China were taken as experimental materials, and the temperature variations of the measuring points of simulated ore heap were measured. Combined with wavelet transform and nonlinear parameters extraction, a new method for spontaneous combustion tendency of different areas in sulfide ore heap based on nonlinear parameters was proposed and its reliability was verified by field test. The results indicate that temperature field evolution of the simulated ore heap presents significant spatial difference during self-heating process. Area with the maximum increasing extent of temperature in sulfide ore heap changes notably with the proceeding of self-heating reaction. Self-heating of sulfide ore heap is a chaotic evolution process, which means that it is feasible to evaluate spontaneous combustion tendency of different areas by nonlinear analysis method. There is a relatively strong correlation between the maximum Lyapunov exponent and spontaneous combustion tendency with the correlation coefficient of 0.9792. Furthermore, the sort of the maximum Lyapunov exponent is consistent with that of spontaneous combustion tendency. Therefore, spontaneous combustion tendency of different areas in sulfide ore heap can be evaluated by means of the maximum Lyapunov exponent method.

Spontaneous combustion tendency of fresh and pre-oxidized sulfide ores

Three representative sulfide ore samples were collected from typical metal mines,and their corresponding pre-oxidized products were obtained under nature environment.The thermal behaviors of each sample at heating rates of 5,10,15 and 20 °C/min in air flow from ambient temperature to 800 °C were studied by simultaneous thermal analysis and the TG/DSC curves before and after the pre-oxidation were compared.By the peak temperature of DTG curves,the whole reaction process for each sample was divided into different stages,and the apparent activation energies were calculated by the Ozawa-Flynn-Wall method.The results show that the reaction process of each sample after pre-oxidation is more complex,with quicker reaction rates,fewer heat production quantities,and higher or lower ignition-points.The apparent activation energies decrease from 364.017-474.228 kJ/mol to 244.523- 333.161 kJ/mol.Therefore,sulfide ores are more susceptible to spontaneous combustion after the pre-oxidation.

Test of oxidation behavior of sulfide ores at ambient temperature for fire control

The coincidence of relevant factors, e.g. oxygen absorption quantity, weight increment, water soluble iron ions and sulfate ion of sulfide ore samples in the oxidation process, was tested through experiment. Based on a large number of tests for a group sample of sulfide ores from a mine, some important conclusions were obtained. The results obtained by the investigation indicate that there is no general interpretation relative to the oxygen absorption and the formation products of sulfate ion and water soluble iron ions during the oxidation process of sulfide ores at ambient temperature. However, the weight increment of the sulfide ore samples in the oxidation process at ambient temperature has a linear relationship with the auantitv of oxvaen absorption.

FAULT TREE ANALYSIS OF SPONTANEOUS COMBUSTION OF SULPHIDE ORES AND ITS RISK ASSESSMENT

A logic fault tree of mine spontaneous combustion of sulphide ores was built by the fault tree analysis (FTA) based on a lot of mechanism investigation of sulphide ore spontaneous combustion in more than ten mines and review of a great amount of relevant

高温高硫矿床矿石自燃危险性的评价

高温高硫矿床开采中矿石自燃危险性的准确评价一直是一个难题 ,探讨了多指标综合评判的新方法。实例分析表明 ,该方法具有较好的效果。

基于层次分析法和集对理论的硫化矿自燃倾向性评定

采用多因素综合鉴定法对某硫铁矿的9个矿样进行了实验室自燃倾向性鉴定,得到了矿样的化学成分分析结果,矿相分析结果,矿样中水溶性铁离子、硫酸根离子含量随氧化时间的变化规律结果,自热性指标、自燃性指标。建立了硫化矿自燃倾向性判定流程的结构图,根据确定的硫化矿石倾向性分级标准,利用AHP方法和集对分析理论确定了该矿9个矿样的同一度和对立度,并进一步分析评价了指标数值与自燃倾向性分级标准之间的数量关系,得到了9个矿样的平均联系度;根据联系度的同异反态势确定联系度所属的集对态势,最后根据集对态势得到了9个矿样的氧化程度及自燃倾向性程度分级,得到了定量化的安全评价结果。该研究方法对硫化矿石自燃的安全评价具有指导意义。

基于未确知测度理论的硫化矿石爆堆自燃危险性评价

运用未确知测度理论,建立采场硫化矿石爆堆的自燃危险性评价模型。选取采场硫化矿石的氧化增重率、水溶性铁离子含量、矿堆中水溶液pH、矿石的含水量、矿物成分的ST值、矿石的自热幅度、矿石的着火点、矿石损失率、矿岩的环境温度、矿石堆的体积共12项指标作为未确知测度模型的判别指标;根据实测数据建立各指标的未确知测度函数,并利用信息熵理论获得各判别指标的权重,依照置信度识别准则进行等级判定,最后得出采场矿石爆堆的自燃危险性评价结果。用该方法对国内4座典型硫化矿山的采场矿石爆堆自燃危险性进行评价,评价结果与矿山实际情况完全相符。因此,这种新方法能够应用到硫化矿山开采时的采场矿石爆堆自燃危险性评价当中,并能解决采场矿石爆堆自燃危险性评价中的诸多因素不确定性问题,对其进行定量评价。

高硫矿山开采中的炸药自爆机理及防治技术

硫化矿床开采中的炸药自爆现象是高硫矿山生产中可能遭遇的典型灾害之一,其严重影响着矿山的安全生产。基于Web of Science、中国知网等信息平台对硫化矿诱发炸药自爆的相关成果进行系统检索,围绕炸药自爆机理、炸药自爆模拟试验、炸药自爆危险性评价方法、炸药自爆防治技术等方面对国内外研究现状进行评价。最后,就硫化矿诱发炸药自爆的宏微观反应特性、多参数耦合作用机理、数学建模与数值分析、危险性判别准则、阻化干预等研究内容进行了展望。