Grantee Research Project Results
Final Report: Monitoring Multiple Volatile Organic Compounds With Cost-Effective Optical Remote Sensing Instrumentation
EPA Contract Number: EPD04017Title: Monitoring Multiple Volatile Organic Compounds With Cost-Effective Optical Remote Sensing Instrumentation
Investigators: Nelson, Loren D.
Small Business: OPHIR Corporation
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2004 through August 31, 2004
RFA: Small Business Innovation Research (SBIR) - Phase I (2004) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , SBIR - Air Pollution , Small Business Innovation Research (SBIR)
Description:
This Phase 1 effort has been very successful. All tasks identified in the proposal have been accomplished. The Phase 1 research exceeded the tasks identified in the proposal by including laboratory demonstrations of three Volatile Organic Compounds (VOCs): toluene (identified in the proposal), methyl isobutyl ketone (MIBK) and kerosene. Characterizing three VOCs provided additional information on the spectral wavelength requirements for future sensors, which would not have been obtained without this additional effort.
Phase 1 laboratory testing has demonstrated that a correlation radiometer can be constructed from spectral gratings, totally eliminating the conventional gas cell. When detecting hazardous and toxic gases, this is a very important step since it allows the removal of the gas cell from the radiometer. The laboratory demonstration also brought to light several important drawbacks of the synthetic spectral grating approach. Specifically: (1) the lack of a long-term manufacturing source, (2) the optical inefficiency produced by the spectral gratings and its impact on the final system cost, and (3) the limited number of trace gas species that can be addressed with a single CD-like disk.
The Phase 1 effort has successfully addressed and eliminated each of these deficiencies by adopting an adaptive correlation mask technology to replace the currently developed synthetic spectral gratings. The adaptive correlation mask also enables a very cost-effective trace gas sensor to be developed. It can utilize broadband optical sources and can address very broad spectral regions, all with the same sensor hardware. The adaptive correlation mask technology is superior to synthetic spectral gratings since: (1) they are already mass produced (over 1.5 million units shipped) and offer a tremendous volume-buy cost savings over one-off pricing, (2) can achieve high optical efficiency (~88%), and (3) can be adapted to provide optical correlation masks for a vast number of trace gases, with identical hardware. This last point is very important to the gas detection industry. One sensor will be capable of monitoring all gases with absorption spectra in the 2 to 10 μm spectral region. This not only provides cost-effective hardware, sensor manufacturing and calibration costs will be reduced as well, due to the commonality of the manufacturing and calibration processes.
Next, Phase 1 successfully demonstrated that an adaptive correlation mask radiometer will be capable of detecting toluene and MIBK with a Minimum Detectable Concentration of roughly 1.5 to 1.8% of full scale. Phase 2 will likely improve on this performance level by identifying specific “gas” and “blank” correlation mask states for enhanced detection and sensitivity. This level of performance is comparable to commonly available, existing state-of-the-art industrial trace gas detection sensors dedicated to only one or two trace gases.
Finally, the Phase 1 research identified specific hardware required to construct a Phase 2 prototype sensor. A preliminary design was completed and a Phase 2 Program Plan was established to construct and test the adaptive correlation mask radiometer at multiple wavelength bands.
Summary/Accomplishments (Outputs/Outcomes):
The EPA Phase 1 research focused on “proving the concept” of an optical remote-sensing system for detecting, identifying and quantifying volatile organic compounds in air. The Phase 1 effort built on Ophir’s existing Active Gas Correlation Radiometer technique, but explored methods to remove the gas cell from the radiometer. This is an important step when toxic or Hazardous Air Pollutants (HAPs) are to be monitored.
The Phase 1 effort successfully explored synthetic spectral gratings for the application of a correlation radiometer monitoring VOCs. In addition, the Phase 1 effort identified a superior method and hardware from which to construct synthetic spectra for correlation radiometers. Phase 1 sensor performance modeling demonstrated that this approach will meet or exceed the measurement performance of current industrial gas monitors capable of monitoring only one or two trace gas species.
Finally, the Phase 1 research provided a preliminary sensor design and Project Plan for the construction and testing of the prototype. Due to the success of the Phase 1 research, it is recommended that this prototype sensor be constructed and tested in Phase 2.
Conclusions:
The Phase 1 research has successfully demonstrated that an Active Correlation Radiometer can be constructed from hardware that produces a synthetic spectrum of the trace gas of interest. This system is cost-effective and can be mass-produced, providing a low cost sensor that is capable of detecting a large number of trace gases. Such a sensor would find broad support in the industrial gas monitoring market.
Supplemental Keywords:
Monitoring, volatile organic compounds, air, pollution,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Environmental Chemistry, Chemicals, Monitoring/Modeling, Analytical Chemistry, Environmental Monitoring, Atmospheric Sciences, chemical characteristics, Toluene, microanalyzer, optical remote sensing, HAPS, microsensors, air quality model, aromatic compounds, Volatile Organic Compounds (VOCs), aerosol analyzers, atmospheric chemistryThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.