Development of a Micro-electromechanical Photoacoustic Spectrometer for Industrial Applications and the Study of SO2 at High Temperatures

本课题旨在开发一种结合光声光谱与微机电（MEMS）技术的高灵敏度气体传感器。结合传感器的研制，将研制一种新型高温气相谱仪，用于测量电磁波谱中红外区域气体的谱参数，如谱线强度和碰撞加宽系数，以及它们的温度依赖性。传感器的开发最初将针对一个特定的应用，即在天然气和煤气化获得的气体脱硫过程中测量硫化物气体种类。煤气化和天然气可能是大规模固体氧化物燃料电池的燃料，这是许多正在考虑减少二氧化碳排放的分布式发电策略之一。如果没有脱硫过程，燃料源中的硫化物气体会毒害燃料电池的电极，最初会降低效率，但最终会导致系统故障。使用原位光学技术监测进入燃料电池的气体的硫化物种类含量，将提供故障安全解决方案，并降低故障风险。在标准的激光光谱学中需要光学探测器，然而，在中红外中，这些探测器昂贵且需要温度稳定。光声光谱的使用消除了光学探测器的必要性，使得气体传感器可以很容易地适应于监测广泛的气体种类，传感器的主要限制是适当的光源的可用性。使用MEMS设备来检测由激光-气体相互作用引起的声信号，提供了进一步的优势，因为它坚固耐用，开发成本低，具有谐振频率和高q因子，非常适合在工业环境中运行。这将使许多未来的应用成为目标，包括爆炸物检测、气体泄漏检测、医疗诊断、大气监测和燃烧产物分析。

This proposal aims to develop a highly sensitive gas sensor, combining photo-acoustic spectroscopy with micro-electromechanical (MEMS) technology. In conjunction with the sensor development, a new high temperature gas spectrometer will be developed to measure the spectral parameters of gas species, such as linestrength and collisional broadening coefficients, and their temperature dependence in the mid infra-red region of the electromagnetic spectrum. The sensor development will initially target a specific application, the measurement of sulphide gas species during the desulphurisation of natural gas and gas obtained from coal gasification. Coal gasification and natural gas are the likely fuel for large-scale Solid Oxide Fuel Cells, one of the many distributed power generation strategies being considered to reduce carbon dioxide emissions. Without the desulphurisation process, the sulphide species gases present in the fuel source will poison the electrodes of the fuel cell, initially reducing efficiency but ultimately leading to system failure. Monitoring the sulphide species content of the gas entering the fuel cell using an in-situ optical technique will provide a fail-safe solution and reduce the risk of failure. In standard laser spectroscopy optical detectors are needed, however, in the mid-IR these detectors are expensive and need to temperature stabilised. The use of photoacoustic spectroscopy eliminates the necessity for an optical detector, allowing the gas sensor to be easily adapted to monitor a wide-range of gas species, with the major limitation of the sensor being the availability of an appropriate optical source. The use of a MEMS device to detect the acoustic signal, induced by the laser-gas interaction, provides further advantages as it is robust, cheap to develop with a resonant frequency and high Q-factor, making ideal for operation in industrial environments. This will allow a number of future applications to be targeted including explosives detection, gas leak detection, medical diagnostics, atmospheric monitoring and combustion product analysis.