BFRL Program - Healthy and Sustainable Buildings

BFRL Project

Measurements and Standards Test Bed for Greenhouse Gas Emissions in the Large Fire Laboratory

Objective: To create a well-characterized and accurate reference measurement system to serve as a testbed for carbon dioxide gas emission measurements.

BFRL Program: Healthy and Sustainable Buildings

What is the problem? Global climate change is recognized as a serious challenge. Several regulatory approaches to reducing greenhouse gas emission are currently under consideration by the Congress. All of these emissions mitigation approaches are heavily reliant on accurate determination of greenhouse gas mass flow rate measurement, generally at or near their source. Current industrial continuous emissions monitoring (CEM) methods for carbon dioxide are often based on a fuel mass balance or inferred from oxygen measurements and may have significantly large uncertainties. Target greenhouse gas emission reductions of 80% relative to 2005 levels are likely. Emission determinations having large errors will make it difficult to judge whether this target is being met regardless of the approach that is finally mandated.

Extension of the capabilities of the NIST Large Fire Laboratory (LFL) will provide an emissions test bed at near industrial-scale for performance evaluation and calibration of instruments of the type generally used for continuous monitoring of point emission sources. Additionally, the test bed may be used for the protocol development assisting documentary standard efforts. A well-characterized CO₂ emission source will also provide a reference for performance evaluation of optical remote sensing technologies currently under development. Ultimately, these new measurements and standards capabilities will lead to improvements in determination of greenhouse gas inventories in the United States. International recognition of U.S. emission measurement capabilities will be enhanced by closely tying these enhanced measurements and standards capabilities to the International System of Units.

Why is it hard to solve? Typical industrial stack emission conditions include a combination of unsteady flow, elevated exhaust gas temperature, and potentially large concentration gradients across a stack. An accurate, well-characterized, and well-controlled flow of carbon dioxide is needed to provide a basis for testing the current generation of industrial monitoring equipment and for the development of a new generation of instrumentation. The largest source of the emission measurement uncertainty in the LFL exhaust stream is the mass flow rate.[1] In the Large Fire Laboratory, the uncertainty of the mass flow measurement is on the order of 10% (reported with an expansion factor of 2). Improving that measurement by an order of magnitude will require new ways of dealing with every part of the mass flow measurement system and the natural gas calibration system.

How is it solved today, and by whom? Carbon dioxide gas emissions from industrial facilities are measured in some facilities today. Monitoring approaches are based on the combination of CO₂ concentration measurements combined with total gas mass flowrate measurement to determine total mass of CO₂ emitted. Manufacturer-claimed accuracy for gas concentration measurements are approximately 2% based on instrumentation and calibration gas uncertainties. However, there is indication that the performance of this instrumentation on known gas streams is several time higher than this value. For flowrate measurements, significantly larger inaccuracies are encountered.

Why NIST? The NIST Large Fire Laboratory is a world leader on quantitative large fire measurements including calorimetry. The study of greenhouse gas emissions is consistent with the NIST's and BFRL’s missions to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security, improve the quality of life, and meet the needs of the U.S. building and fire safety industries.

What is the new technical idea? The general technical approach for this project is to use a well-controlled and well-characterized fire as a source of carbon dioxide. The Large Fire Laboratory’s fume hoods, exhaust duct and stack will be instrumented for precise measurement of gas emission rates. New technologies for open-path remote sensing and stack-mounted measurement systems can then be evaluated using a well-characterized flow of CO₂. Improvements will be made to two parts of the calorimetry system. Work will proceed to improve the measured mass flow of natural gas going to the calibration burner and the measurement of the carbon dioxide mass flow in the exhaust. Specific measurements will be targeted for improvement as part of the development of the experimental plan. Specialized instrumentation to benefit the measurement accuracy will also be identified for procurement. A term appointment or contract will be pursued to bring an expert to assist with the planning and to assist with subsequent measurement development.

What is the research plan? A detailed research plan will be developed this year in consultation with measurement experts in the NIST Chemical Science and Technology Laboratory (CSTL.) Preliminary measurement improvements that will be considered include better calibration gas standards, independent flow measurements for cross validation, optimization of probe locations using detailed mapping experiments, and more accurate calibrations for flow and gas measurement probes and transducers. Computational fluid dynamic modeling will be used to help understand and improve the duct flowfield. The development of a test bed for point emission source monitoring will emphasize improved measurement accuracy and precision for the evaluation and calibration of continuous emissions monitoring instrumentation used by industry, and the development and demonstration of measurement protocols for documentary standards. An aspect of the work could include development of an accreditation program for independent, private sector measurement providers.

[1] R.A.Bryant, T.J.Ohlemiller, E.L.Johnsson, A.Hamins, B.S.Grove, A.Maranghides, G.W.Mulholland, and W.F.Guthrie, NIST 3 Megawatt Quantitative Heat Release Rate Facility: Description and Procedures, , NIST IR 7052 (2004).

Contact:
Matthew Bundy
(301) 975-6880
matthew.bundy@nist.gov

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Last updated: 6/4/2009