Basic Information
Abstract Number: 990-6    
Author Name: Ruth E Lindley Affiliation: Cascade Technologies Ltd
Session Title: Analytical Applications of Broadly Tunable Lasers
Event Type: Organized Contributed Session
Event Title: Quantum Cascade Laser Based Gas Analyzer for Process Applications
Presider(s): Crocombe, Richard A Start Time: 09:55 AM ( Slot # 7 )
Date: Tuesday, March 13th, 2012 Location: 308A
Keywords: Analysis, Laser, Process Control, Spectroscopy

Abstract Content
Cascade Technologies have developed a quantum cascade laser based analyser for use in a variety of process applications. The technique used to measure the concentrations of gaseous species in the process gas stream is absorption spectroscopy, utilizing the strong fundamental absorption bands that occur in the mid infrared to achieve sub-ppm detection limits. The analyser is based on a self contained detection engine incorporating up to four quantum cascade lasers housed in individual modules, a dual path cell and two MCT (Mercury Cadmium Telluride) detectors to monitor the light output from each path. The four laser beams are combined into a small area and then split into two parts prior to injection into the cell, and typically each laser is used to measure between 1 and 3 components, depending on the application. The dual path cell is used to enhance the dynamic range of the system, and is typically operated at temperatures between 50 and 200 deg C. The pressure is maintained at sub-atmospheric pressure to minimise broadening effects and allow the spectral features of the gas of interest to be easily distinguished from any cross-interferents that absorb in the same region. The process analyser has an inbuilt pressure control system, pump and gas conditioning and filtration. The concentration data can be read by connecting a monitor, or on a data logger using Modbus over TCP/IP or 4-20 mA outputs. The analyser can be used to detect a wide variety of molecules, including NO, NO2, CO, CO2, SO2, N2O, NH3, H2O, CH4 and other hydrocarbons, amongst others. It may be used in applications such as process control, exhaust gas measurement and environmental monitoring. An ATEX version of this system is currently under development.