Experimental Releases of Liquid Hydrogen (LH2)

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

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

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 • 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. Energy Technology Institute to investigate the safe use of hydrogen based fuels for power generation