基于声发射检测的气送煤粉粒度分布在线测量技术研究

On-line continuous measurement of the size distribution of pulverized coal in power plant is essential for the safe, reliable, economical and low-emission operation of the boiler. Currently, sizing of pulverized coal is achieved through manual sample collection and subsequent laboratory analysis. The off-line results cannot be used for on-line adjustment of the pulverizer and combustion optimization of the boiler. A variety of on-line techniques has been attempted worldwide, but none of them has been successfully deployed in the industrial field due to inadequacies in accuracy, price, reliability and durability. The objective of this project is to develop an on-line particle sizing technique through acoustic emission (AE) detection. Information about particle size can be extracted from the elastic stress wave generated by the particle collision with a metallic probe and the particle velocity obtained from a correlation-based electrostatic velocimetry. Theoretical modeling, simulation analysis and experimental studies will be conducted to uncover the underlying mechanism of AE signal generation, propagation and reception. Algorithms for feature extraction and size inversion will be proposed. Three prototype instruments will be developed and tested in both laboratory and coal-fired power plant. The instruments to be developed in this project are simple in structure, low in cost, suitable for hostile industrial environment, low in maintenance requirement and durable for long-term operation. The theoretical and experimental studies to be carried out, which are of great value for both scientific research and industrial application, will provide theoretical foundation and technical support for this novel on-line particle sizing instrument.

煤粉粒度分布的在线连续测量对保证锅炉的安全、可靠、经济和低污染运行具有十分重要的现实意义。现有的测量手段主要依靠人工采样和离线分析，无法用于锅炉的在线调整与燃烧优化，而国内外所尝试的各种在线测量方法由于精度、价格、可靠性、耐用性等原因而无法实际应用。本项目旨在研究基于声发射信号的煤粉粒度分布在线测量技术，通过检测颗粒与探头碰撞产生的弹性应力波，结合静电相关测速技术，对煤粉粒度进行在线连续测量。本项目通过理论建模、仿真分析、实验测试等途径深入揭示颗粒碰撞声发射信号的产生、传播与接收机理，提出声发射信号特征参数提取与粒径反演算法，完成在线测量系统的设计与实现，并在实验室与燃煤电厂进行样机的实验测试。所研制的测量系统结构简单、成本低、可适应恶劣工业环境、对维护要求低、且具有良好的耐用性。拟开展的理论与实验研究将为新型粒度分布在线测量仪表提供理论基础和技术支撑，具有重要的科学研究和应用价值。

燃煤电厂一次风管内煤粉颗粒与侵入式波导杆碰撞产生的声发射信号含有颗粒粒径信息，通过对该信号进行分析能够实现煤粉粒度分布的在线连续测量。基于上述原理，本项目提出基于声发射检测的煤粉粒度分布在线测量方法，通过理论建模、仿真分析、系统研制、实验测试等途径对测量机理、测量方法与系统测量性能等方面进行了深入研究。本项目取得的主要研究成果包括：1）建立了声发射信号产生与传播的有限元模型，搭建了单颗粒碰撞实验装置，验证了仿真模型的有效性；开展了系统的仿真研究，阐明了声发射信号特征与颗粒粒径、碰撞速度、材料性质等因素的依赖关系。2）根据Stronge非弹性碰撞理论建立颗粒粒径的反演模型，结合静电传感器提供的颗粒碰撞速度信息，实现了单颗粒粒径的准确测量。3）研制了声发射与静电传感器一体化探头，提出了气固两相流条件下连续脉冲声发射信号的峰值提取方法，实现了气送粉体粒度分布的在线测量。4）提出了基于声发射信号能量的气送粉体质量流量测量方法，通过解耦颗粒速度信息，实现了质量流量的准确测量。5）研制了工业现场实验样机，通过融合声发射与阵列式静电传感器数据，实现气送煤粉流速、浓度、粒度和质量流量的多参数同时测量。本项目所开展的理论与实验研究有力支撑了新型粒度分布在线测量仪表的研制，能够为燃煤锅炉的优化控制提供测量数据，推动我国智慧电厂的建设与发展。