基于PGNAA/XRF融合的高精度煤炭重金属成分在线检测新方法及其物理机理研究

With the continuous development of China's industrialization process, the demand of the energy grows rapidly. The energy production and consumption structure of our country has been dominated by the coal; the wide use of the coal causes the release of heavy metals into the environment. This will bring serious pollution to the environment. At present, energy conservation and emission reduction have become a severe problem that needs to be solved urgently. In order to improve the utilization of coal resources and reduce the emission of the harmful heavy metal material, the real-time on-line analysis of the material composition could be used to provide necessary scientific data. Due to the limit of the flux of the neutron source and the measuring time, the prompt gamma neutron activation analysis (PGNAA) online analytical technology can’t able to realize the high precision measurements of the heavy metals by itself. On the basis of the previous research, this project proposes a new program. While the prompt gammas are used to measure the main elements such as oxygen and carbon, the secondary X-ray fluorescence are fully used to analysis the heavy metals at the same time. Through the technology fusion of the PGNAA and XRF, the main elements and the high precision measurements of the heavy metals in coal can be realized at the same time. Using the Monte Carlo method, the structure, performance and the measurement process of the system will be simulated to research the influence law and the physical mechanisms of the parameters on the performance of the system. The factors that affect the detection efficiency of the X-ray fluorescence will be the emphasis of the study. By the experimental and theoretical method, the effect of the particle size and geometric factors of material on the analysis precision of heavy metal elements will be studied. The empirical formula of the element content and the intensity of the gamma and X-ray is developed by the results of the simulation and experiment. The research work of this project will provide the basis of the theory and practice for improving the of quantitative analysis accuracy of the heavy metal elements in coal.

节能减排是我国经济社会发展中亟需解决的问题。通过实时在线分析物料成分，可为提高煤炭资源利用率、降低重金属排放提供必要的科学数据支持。由于中子源通量和测量时间的限制，单一的瞬发γ中子活化（PGNAA）在线分析技术无法实现煤炭中微量重金属的高精度测量。本项目在已有研究基础之上，提出在利用PGNAA中瞬发γ射线信息的同时，充分利用瞬发γ射线激发的特征X荧光信息的新方法，通过PGNAA和XRF技术的融合，对煤炭中主要元素测量的同时实现重金属的高精度测量。利用蒙特卡洛方法研究系统的结构、性能和测量过程，重点研究影响瞬发γ射线激发的X荧光探测效率的主要因素，建立系统各物理参数与系统性能的理论关系；从实验和理论两方面入手，研究物料的粒度、几何因素等对重金属元素分析精度影响的物理机制；分析实验和模拟结果，建立元素含量与特征γ、X能谱信息的相关模型，为提高煤炭中重金属元素的测量精度提供理论和实践上的依据。

随着我国社会的发展，能源的需求越来越大。煤炭是我国能源的支柱，伴随着煤炭的燃烧，煤炭中的微量重金属有可能进入环境，这些微量重金属元素对人类和环境的危害都很大，是需要重视的问题。利用瞬发伽马中子活化技术可实现煤炭工业现场中煤炭元素成分的实时在线检测，但对应低含量、中子截面较小的重金属元素，PGNAA的检测精度较低。本项目通过PGNAA和XRF技术的融合，提高煤炭中重金属的检测精度，通过项目的实施，主要取得的结果如下：研究了PGNAA中荧光产生的物理机制，结果表明PGNAA过程中，中子与物质相互作用产生的带电粒子、伽马射线，这些次级粒子分别通过与物质的内转换、光电效应，可产生物料中元素的特征X荧光，但主要的X荧光来源于次级低能伽马与元素的相互作用；设计并优化PGNAA-XRF联合检测混合样品中重金属元素的实验装置，分析实验结果，由混合样品中Hg和Pb元素之间的特征伽玛和X荧光与其浓度的关系，拟合给出了PGNAA-XRF联合检测方法测量元素含量的经验公式，由此证明了PGNAA与XRF联合检测方法的可行性，且该方法可显著降低样品中中子截面低的重金属Pb的检测限；利用使用硅漂移探测器(SDD)测量DT中子发生器产生的中子与煤炭中的元素相互作用产生的光谱，测量结果表明能谱中明显测到Pb元素的特征X荧光峰，但由于基体效应，在工业物料表面不平整时，荧光计数率较低；为提高物料中元素分析精度，对基体效应中物料的颗粒度进行了研究，同时对X荧光的解谱方法进行了研究，从而提高物料中元素分析精度。