In situ combustion measurements of CO, H_(2)O, and temperature with a 1.58-μm diode laser and two-tone frequency modulation

摘要

An optical near-infrared process sensor for electric are furnace pollution control and energy efficiency is proposed. A near-IR tunable diode laser has performed simultaneous in situ measurements of CO (1577.96 nm), H_(2)O (1577.8 and 1578.1 nm), and temperature in the exhaust gas region above a laboratory burner fueled with methane and propane. The applicable range of conditions tested is representative of those found in a commercial electric are furnace and includes temperatures from 1250 to 1750 K, CO concentrations from 0 to 10%, and H_(2)O concentrations from 3 to 27%. Two-tone frequency modulation was used to increase the detection sensitivity. An analysis of the method's accuracy has been conducted with 209 calibration and 105 unique test burner setpoints. Based on the standard deviation of differences between optical predictions and independently measured values, the minimum accuracy of the technique has been estimated as 36 K for temperature, 0.5% for CO, and 3% for H_(2)O for all 105 test data points. This accuracy is sufficient for electric are furnace control. The sensor's ability to nonintrusively measure CO and temperature in real time will allow for improved process control in this application.