2015 AIChE Spring Meeting and 11th Global Congress on Process Safety
(31a) Hydrogen Jet Vapor Cloud Explosion: Test Data and Comparison with Predictions
Hydrogen Jet Vapor Cloud
Explosion: Test Data and Comparison with Predictions
Derek Miller
Air Products
7201 Hamilton Boulevard
Allentown, PA 18195-1501
millerd3@airproducts.com
C.D. Eastwood, Ph.D and J. Kelly Thomas, Ph.D.
Baker Engineering and Risk Consultants (BakerRisk)
3330 Oakwell Court, Suite 100
San Antonio, TX 78218-3024
(210) 824-5960
Releases of hydrogen at elevated pressures form turbulent
jets which may pose vapor cloud explosion (VCE) as well as jet fire hazards.
The turbulence induced by the jet release can lead to flame speeds sufficient
to produce damaging blast loads if the release is not immediately ignited, even
in the absence of confinement or congestion. The VCE hazard posed by such high
pressure hydrogen releases is not well-recognized, and there is no
well-established methodology to predict the associated VCE blast loads.
Air Products commissioned a series hydrogen jet release
tests, aimed primarily at measuring the thermal flux from ignited open air hydrogen
jets. The hydrogen jets were created by depressurizing a high-pressure
hydrogen reservoir through a horizontal vent pipe. Pipe diameters of ¾-inch
and 2-inches were tested at a release pressure of approximately 60 barg, giving
initial flow rates of roughly 8 and 1 kg/s, respectively. For both release
sizes, a single test was performed where the ignition system was not activated
until approximately 2 seconds after the release had been initiated, such that
the resulting flame propagated into a turbulent flammable gas cloud of limited
volume. Blast loads were measured at 10 m and 20 meters off the jet
centerline.
BakerRisk compared the data from the Air Products hydrogen
jet VCE tests with predictions made using the FLACS computational fluid
dynamics (CFD) code. FLACS was first used to evaluate the flammable clouds
resulting from the jet releases up to the time of ignition. FLACS was then run
with a range of grid sizes for the 2-inch release case in order to determine a
grid size which gave reasonable agreement with the measured peak pressure and
pressure history. The grid size giving the best agreement with the 2-inch
release case data was then used to evaluate the ¾-inch release case.
This paper presents the data from these two hydrogen jet
release VCE tests along and the comparison with the FLACS predictions. Based
on these results, the feasibility of using FLACS as a general predictive tool
for the blast loads from such hydrogen releases is discussed.