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

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

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

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

EXPERIMENTAL ARRANGEMENT Photograph of Experimental Equipment

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

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

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

RESULTS UN-IGNITED RELEASES

RESULTS – UN-IGNITED RELEASES Horizontal ground level release :

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

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

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

RESULTS IGNITED RELEASES

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

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

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

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

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

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

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.