摘要
原地爆破浸出采铀工艺是一种高效、经济的铀矿开采技术,它在低品位硬岩型铀矿资源的开发中具有广阔的应用前景。但其引起的井下氡污染已成为迫切需要解决的问题。原地爆破浸出采场铀矿堆中氡的运移规律研究是原地爆破浸出采铀矿山通风防氡、控氡的重要基础研究课题,对于促进铀矿安全生产、实现铀矿资源的绿色开采和铀矿冶工业的可持续发展有着重要的理论意义和工程实际意义。
论文在国家自然科学基金项目《松散破碎射气介质中氡运移的多相多过程耦合作用模型及数值模拟研究》(No.10575048)的资助下,将原地爆破浸出采场铀矿堆抽象为松散破碎射气介质,通过理论分析、模型试验、数值模拟以及某原地爆破浸出采铀采场的工程应用,取得的创新性研究成果如下：
(1)研制出了获得国家发明专利的松散破碎射气介质多功能渗流试验装置。根据原地爆破浸出采场铀矿堆的粒级分布特征,采用Rosin-Rammler分布公式,选配了七组不同级配的试样,采用所研制的试验装置,进行了气液(水)两相渗流试验研究,研究了特征粒径、粒径分布指数对其中气液(水)两相渗流的影响。
(2)利用松散破碎射气介质气液(水)两相渗流试验结果,采用BP神经网络算法,建立了根据特征粒径、粒径分布指数、孔隙率、含水饱和度预测气液(水)两相有效渗透率的人工神经网络(ANN)模型；采用量纲分析方法,建立了根据松散破碎射气介质气液两相模型试验结果预测松散破碎射气介质原型气液两相有效渗透率的方法。
(3)研制并建立了获得国家发明专利的松散破碎射气介质瞬态氡析出能力测量装置及计算方法。根据Rosin-Rammler分布,选配了七组不同级配的试样,采用所研制的试验装置,测量了七组试样的氡浓度随时间的变化,研究了特征粒径、粒径分布指数、矿石含水率、氡浓度对瞬态氡析出能力的影响。
(4)利用瞬态氡析出能力试验结果,采用自适应神经模糊推理系统(ANFIS),建立了根据氡浓度、特征粒径、粒径分布指数和矿石含水率预测瞬态氡析出能力的ANFIS模型；采用量纲分析方法,建立了根据松散破碎射气介质瞬态氡析出能力模型试验结果预测松散破碎射气介质原型瞬态氡析出能力的方法。
(5)基于多孔介质中的气液两相渗流理论、氡运移的扩散-渗流理论、放射性衰变理论以及氡的溶解规律,建立了松散破碎射气介质中氡运移的气液两相耦合数学模型。
(6)采用计算流体力学(CFD)方法进行了某原地爆破浸出采铀矿山的采场铀矿堆中氡运移的数值模拟,得到了铀矿堆中氡的浓度分布和氡的运移析出规律,为原地爆破浸出采铀矿山的控氡、降氡提供了理论依据。
In-place leaching of explosively fragmented uranium ore is an economic and high efficiency mining technique suitable for recovering uranium from low grade hard-rock type uranium ore body. However, the air pollution in place leach stope caused by the radon from the fragmented uranium ore is a sever problem which needs to be solved as soon as possible. The regularity for radon transport in the uranium ore heap to be leached in the underground stope is a fundamental research subject for controlling the air pollution caused by radon by ventlation, which is of great significance both in theory and practice for the safety production, green mining of uranium resource and sustainable development of uranium mining and metallurgy industry.
This dissertation was supported by the National Natural Science Foundation of China project-studies on multi-phase and multi-process coupling model and numercial simulation for radon transport in loose fragmented radioacive medium (No.10575048). The uranium ore heap to be leached in the underground stope was simplified as a kind of radon emanating loose media, and studies were carried out on the radon migration through gas-liquid two-phase fluid in loose fragmented radioactive medium using analytical method, physical modeling, numerical modeling and field test. The main innovative achievments are summed up as follows:
(1) The self-developed apparatus for the research of gas-liquid(water) single-phase and two-phase seepage in loose fragmented radioactive medium was patented in China. Base on the characteristicse of the particle size distribution of the uranium ore heap to be leached in the underground stope, seven samples were prepared with different particle size distributions in obedience with Rosin-Rammler distribution law. The apparatus was used to study the influence of characteristic particle size, particle size distribution index, porosity and saturation of the medium on gas-liquid(water) two-phase seepage。
(2) On the basis of the test results of gas-liquid(water) two-phase seepage, the Artifical Neural Network(ANN) models for predicting gas-liquid(water) two-phase effective permeability were established using BP neural network algorithm from the characteristic particle size, particle size distribution index, porosity and saturation. And the method which could predict gas-liquid two-phase effective permeability of prototype on the basis of model test is established using dimension analysis.
(3) The self-developed apparatus for measuring transient radon emanation capability and proposed method for calculating transient radon emanation capability in loose fragmented radioactive medium was also patented in China. Seven samples were prepared with different particle size distributions in obedience with Rosin-Rammler distribution law, the apparatus was used to measure the variation of radon concentration of seven samples with time, and to study the influence of the radon concentration,characteristic particle size, particle size distribution index and moisture of the medium on the transient radon emanation capability.
(4) The test results on transient radon emanation capability were used to establish the Adapive Neuro-Fuzzy Inference System(ANFIS) models for predicting transient radon emanation capability from radon concentration,characteristic particle size, particle size distribution index and moisture. And the method which could predict transient radon emanation capability of prototype from the model tests was proposed using dimension analysis.
(5) The principles of two-phase flow through a porous medium, radon migration by diffusion and seepage, radioactive decay and regular pattern of radon dissolved in water was used to establish gas-liquid two phase coupling model for radon transport in loose fragmented radioactive medium.
(6) The Computational Fluid Dynamicis(CFD) model was established to simulation the radon migration through gas-liquid two-phase fluid in the uranium ore heap to be leached in the underground stope. The simulation results of radon concentration distribution and emanation in uranium ore heap and the stope provided the theoretical proof for controlling air pollution caused by radon in the stope.
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