On-line H{sub 2}S monitoring using near-infrared tunable diode laser spectroscopy

The purpose of this project is to evaluate and demonstrate the technique of frequency-modulated, tunable diode laser spectroscopy for the monitoring of H{sub 2}S gas in geothermal plant emissions. The geothermal power industry has an interest in the development of real-time techniques for monitoring these emissions, since improved measurement capabilities could lead to considerable cost savings through the optimization of the chemicals used for abatement. There are several locations throughout the plant at which this measurement could be performed. They vary from the main stream line which operates at a temperature of about 350 F (175 C) and a pressure of 100 psig to the cooling stack with a temperature of 80--100 F (27--38 C) at ambient pressure. Gas concentrations range from 0.1 ppm to 1,000`s of ppms. The technical goal of this effort was to perform a series of scoping experiments to determine the effect of elevated pressure, temperature and water vapor on the sensitivity of this spectroscopic technique for the detection of H{sub 2}S. The results of these experiments are presented, and the deployment options and system designs are discussed