2001 Progress Report: Multiplexed Diode-Laser Absorption Sensors for Real-Time Measurements and Control of Combustion Systems

EPA Grant Number: R827123
Title: Multiplexed Diode-Laser Absorption Sensors for Real-Time Measurements and Control of Combustion Systems
Investigators: Hanson, Ronald K. , Jeffries, J. B.
Current Investigators: Hanson, Ronald K. , Baer, D. S. , Jeffries, J. B.
Institution: Stanford University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2002)
Project Period Covered by this Report: October 1, 2000 through September 30, 2001
Project Amount: $344,605
RFA: Exploratory Research - Environmental Engineering (1998) RFA Text |  Recipients Lists
Research Category: Sustainability , Land and Waste Management , Engineering and Environmental Chemistry

Objective:

The objective of this research project is to demonstrate novel optical sensors based on semiconductor diode laser technologies, which have been developed for the telecommunications industry. These new lasers, coupled with fiber-optic components, enable simple and inexpensive devices for spectroscopic measurements of important gas-phase atmospheric pollutants. These all-optical sensors are compact and reliable, and allow fast species-specific and sensitive measurements of the target species: CO, a toxic, regulated combustion pollutant; CO2, a major-species combustion product and greenhouse gas; NO and NO2, the important nitrogen-oxide pollutants; NH3, an important combustion effluent from thermal de-NOx and from fuel-bound nitrogen; and H2O, a major-species combustion product. The sensor strategy developed in this program is based on absorption spectroscopy techniques, incorporating new developments in room temperature continuous wave semiconductor diode lasers. The range of available diode laser wavelengths recently has been extended into the infrared spectral region near 2.0 and 2.3 µm, thereby enabling sensitive absorption measurements using the strong, first-overtone vibrational bands of CO and NO, and strong combination bands of NH3, CO2, and H2O. Similar extensions of diode laser wavelengths into the blue and near-ultraviolet region of the spectrum will enable measurements of NO2, and with non-linear wavelength conversion NO. These new lasers operate without cryogenic cooling, and thus promise portable and rugged sensors. The diode-laser absorption sensors also will be used to accurately measure (some for the first time) important spectroscopic parameters of the target species at the probed wavelengths over a range of temperatures and pressures that are relevant to combustion flows.

Progress Summary:

Diode-laser absorption sensors have been developed for fast, sensitive, in situ measurements of gas temperature, and the concentrations of the target species CO, NH3, CO2, and H2O. The sensors employ newly available room temperature, distributed feedback tunable diode lasers that operate near 2.3 µm for CO measurements, 2.0- µm for NH3 and CO2 measurements, and near 1.3-1.4 µm for H2O measurements. The laser wavelength is tuned across the absorption feature for simultaneous, non-intrusive, multi-parameter direct absorption measurements in the combustion and exhaust regions of laboratory combustion facilities. For CO measurements, a detection limit of 1.5 ppm-m was achieved by direct absorption spectroscopy with a 0.1-second total measurement time in the exhaust duct of a laboratory combustor. This detection limit is improved to 0.1 ppm in a 1-m path with wavelength modulation spectroscopy and a 0.4-seconds measurement time. The results of this research suggest that diode laser absorption techniques may be applied for in situ measurement and monitoring of exhaust effluent from a wide variety of industrial processes.

During the past year, field measurements of CO2 and NH3 have been conducted to test the performance biological water re-processor. We conducted a field test of a CO2 and NH3 diode laser absorption sensor near 2 µm at the National Aeronautics and Space Administration (NASA) Johnson Space Center. NASA researchers are developing a biological water processor to recycle waste water during space travel. Small emissions of NH3 indicate this reactor eventually will build up toxic NH3 levels in the confined vehicle. In addition, the CO2 effluent release monitors the health of this reactor. The CO2 levels have a very large dynamic range from a few hundred ppm to more than 10 percent of the effluent. Transitions to monitor these gases were selected, the fundamental spectroscopy quantified, and a real-time remotely monitored sensor was assembled. The performance of this sensor was proven during a 45-hour quasi-continuous field test with remote operation of the sensor.

Future Activities:

Future plans involve extending the capabilities of the sensors for measurements of other combustion species and incorporating the sensors into closed-loop feedback systems for real-time combustion control and emissions compliance.


Journal Articles on this Report : 5 Displayed | Download in RIS Format

Other project views: All 21 publications 7 publications in selected types All 5 journal articles
Type Citation Project Document Sources
Journal Article Wang J, Maiorov M, Jeffries JB, Garbuzov DZ, Connolly JC, Hanson RK. A potential remote sensor of CO in vehicle exhausts using 2.3 μm diode lasers. Measurement Science & Technology 2000;11(11):1576-1584. R827123 (2000)
R827123 (2001)
R827123 (Final)
not available
Journal Article Wang J, Maiorov M, Baer DS, Garbuzov DZ, Connolly JC, Hanson RK. In situ combustion measurements of CO using diode-laser absorption near 2.3 μm. Applied Optics 2000;39(30):5579-5589. R827123 (2001)
R827123 (Final)
not available
Journal Article Webber ME, Baer DS, Hanson RK. Ammonia monitoring near 1.5 μm with diode-laser absorption sensors. Applied Optics 2001;40(12):2031-2042. R827123 (2000)
R827123 (2001)
R827123 (Final)
not available
Journal Article Webber ME, Kim S, Sanders ST, Baer DS, Hanson RK, Ikeda Y. In situ combustion measurements of CO2 by use of a distributed-feedback diode-laser sensor near 2.0 μm. Applied Optics 2001;40(6):821-828. R827123 (2001)
R827123 (Final)
not available
Journal Article Webber ME, Claps R, Englich FV, Tittel FK, Jeffries JB, Hanson RK. Measurements of NH3 and CO2 with distributed-feedback diode lasers near 2.0 μm in bioreactor vent gases. Applied Optics 2001;40(24):4395-4403. R827123 (2001)
R827123 (Final)
not available

Supplemental Keywords:

remote sensing, temperature, waste reduction, pollution prevention, control, atmosphere, combustion, environmental engineering, toxics, pollutants., RFA, Scientific Discipline, Air, Waste, Environmental Chemistry, Environmental Monitoring, Incineration/Combustion, Engineering, Chemistry, & Physics, Environmental Engineering, optical sensors, combustion generated radicals, emissions measurement, air pollution, emission controls, optical sensor, process control, carbon dioxide, fiber laser, combustion, incineration, real time monitoring, emissions contol engineering, laser absorption sensors, combustion contaminants

Relevant Websites:

http://navier.stanford.edu/hanson Exit
http://vonkarman.stanford.edu/tsd/theses.html Exit

Progress and Final Reports:

Original Abstract
  • 1999 Progress Report
  • 2000 Progress Report
  • Final Report