1. Experimental Releases of Liquid Hydrogen (LH2) Phil Hooker Mark Royle / Deborah Willoughby

2. CONTENTS Background Experimental Arrangements Results / Findings
What was done and why it was done
Experimental Arrangements
Equipment / Experimental conditions / monitored parameters
Results / Findings
Un-ignited Releases / Ignited Releases

3. BACKGROUND
There is limited information available regarding the consequences of LH2 spills in the context of the anticipated future LH2 distribution systems (e.g. onto concrete)
A facility was designed and built with which LH2 could be released and parameters monitored and recorded
A number of experiments were carried out in which LH2 was released and either allowed to disperse without being ignited, or ignited after a known release period

4. EXPERIMENTAL ARRANGEMENTS
Schematic of Experimental Equipment LH 2
Tanker
Purge supply
Vent stack
Vapour line to vent H2 N2
Water drain PI
Vacuum
insulated
flexible
liquid line
Release point
(1" nominal bore)
Valve remote PLC
Liquid bypass
line to vent
Note: Valves in tanker subsystem greatly simplified
full system specification property of BOC
All remote valves nitrogen actuated

5. EXPERIMENTAL ARRANGEMENT
Photograph of Experimental Equipment

6. EXPERIMENTAL ARRANGEMENT
Equipment
LH2 delivered in road tanker by BOC
LH2 fed to release point via 25mm dia. vacuum insulated hose
Vent stack for releasing excess gaseous hydrogen
Valve station to switch between release and bypass to vent
Valves actuated remotely
All equipment located on concrete pad
Weather monitoring station situated at test site
Measuring equipment / cameras positioned as required

7. EXPERIMENTAL ARRANGEMENT
Experimental conditions
Pressure in LH2 road tanker nominally 1 bar g
LH2 flow rate approximately 60 litres / minute
Release time varied from approx. 30 seconds to more than 5 minutes
Where ignition required, chemical igniters fired within the gas cloud

8. EXPERIMENTAL ARRANGEMENT
Monitored parameters
Meteorological conditions monitored for all releases
Un-ignited releases :
Hydrogen concentration within cloud (determined from temperature measurements at 30 points and assuming adiabatic mixing)
Temperature on the surface of and within the substrate (24 thermocouples on surface and three embedded thermocouples at 10mm, 20mm and 30mm depth)
Video footage of cloud, pool and ground accumulations
Ignited releases :
Thermal radiation using 6 fast response radiometers
High speed video recordings for determining flame speed
Thermal imaging camera recordings
Overpressure using three Kuhlite pressure transducers

9. RESULTS
UN-IGNITED RELEASES

10. RESULTS – UN-IGNITED RELEASES
Horizontal ground level release :

11. RESULTS – UN-IGNITED RELEASES
Horizontal ground level release –
Surface temperature :

12. RESULTS – UN-IGNITED RELEASES
Horizontal release at 860mm :

13. RESULTS – UN-IGNITED RELEASES
Vertical release from 100mm :

14. RESULTS
IGNITED RELEASES

15. RESULTS – IGNITED RELEASES
Horizontal ground level release :
< 1 minute release, windy conditions

16. RESULTS – IGNITED RELEASES
Horizontal ground level release :
4.5 minute release, windy conditions

17. RESULTS – IGNITED RELEASES
Horizontal ground level release :
4.5 minute release, windy conditions

18. RESULTS – IGNITED RELEASES
Attempts to reproduce the detonation were
unsuccessful even for releases > 6 minutes
under still weather conditions
=> no overpressure measurements achieved

19. CONCLUSIONS Release of LH2 in contact with concrete surface can :
produce a liquid pool once concrete is sufficiently cooled
cause sub-cooling due to vaporisation
produce a solid deposit of oxygen and nitrogen once the concrete is sufficiently cooled
The release of LH2 from a leak consistent with the failure of a 1 inch transfer line at 1 bar g produces a flammable mixture at least 9 metres downwind from the release point
Under certain circumstances oxygen enrichment, and subsequent detonation, appears to occur

20. ACKNOWLEDGEMENTS
Mark Royle and Deb Willoughby for starting the project, designing and installing the experimental equipment, defining the experimental programme and carrying out much of the experimental work
Jonathan Hall for assisting with the experimental work with enthusiasm and professionalism
Stuart Hawksworth for providing guidance and direction
BOC for assistance in the design of the experimental equipment and in co-operation regarding the supply of the LH2

21. ANNOUNCEMENT
Energy Technology Institute to investigate the safe use of hydrogen based fuels
for power generation
New modelling and large-scale experimental work to identify the bounds of safe design and operation of high efficiency CCGT (combined cycle gas turbine) and CHP (combined heat and power) systems operating on a range of fuels with high and variable concentrations of hydrogen.
Goals are to increase the range of fuels that can be safely used in power and heat generating plant by:
Indentifying the boundaries of safe design and operation of power generation systems using hydrogen based fuels; and
  identifying improvements in the detailed design and instrumentation of hydrogen fuelled power systems in order to deliver more robust and inherently safer system designs.
Outcomes will benefit manufacturers and operators of all powerplants which may potentially utilise fuel containing high or variable levels of hydrogen such as gas feeds from landfill and anaerobic digestors.
The project will be led by the Health and Safety Laboratory (HSL) in collaboration with Imperial Consultants.