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Liquid Hydrogen R&D test report

CM34 – 17/10/12

S WatsonP WarburtonM Courthold

Test programmeStated aim to produce 22 litres of LH2

1.Hydride bed charge2.H2 fill x 33.H2 empty x 34.Hydride bed empty

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Bottle ‘incident’• Small leak from H2 bottle when

connecting• Fixing resulted in a brief but rapid

release…vent system went above LEL• All procedures, alarms and interlocks

worked as expected!

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Hydride bed chargeManufacturer suggested 8 hour charge

• Started with heater-chiller at -15°C• Connected 2 H2 bottles (~16000l)• Regulator set to 1.5 bara• No flow meter in line so only indicator of

progress was bottle pressure• Dropped to <10 bar in ~2 hours

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First H2 fill• Commenced fill at 3am on 30th July• Cooldown rapid – pressure control loop

started after 16 hours• Hydride bed back pressure dropped

faster than expected...• …and heater loop did not initiate• Hydrogen began to freeze• Fill aborted

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Bed pressure starts to drop

H/C temp increased

Control valve stays open

Hydrogen starts to freeze

Second H2 fill• Restarted without empty sequence• Manual control of heater and hydride

bed temperature• Reached 10,000 litres of H2…• …equated to approx 12 litres of LH2

No graph…control system reset and overwrote data!

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Empty sequence• Sequence uses heater to boil off LH2

and return to hydride bed• Very conservative starting conditions,

gradually ramped up• LH2 boil-off completed in approx 15

hours

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Pressure setpoint changed

LH2 all boiled off

Final H2 fill• Automatic control of heater• Manual control of hydride bed temp• Realised that HX temperature must be

lower than expected to condense• Optimised setpoint resulted in steady

condensation rate• Heaters are critical when H2 flow slows

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Hydride bed temp increased Hydride bed temp

maxed

H2 flow beginning to slow; heater

loop now critical

Hydride bed empty• Purge of gas panel with helium• Set hydride bed to max temperature

and pumped directly on it• After approx 12 hours, pressure was

around 100 mbar• Filled with argon to 3 bar and closed

hand valve = back to original state

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Improvements• Sensors for flow in to hydride bed• Improve resolution of temp sensors• Procedural changes

• Vent hydrogen in fault condition• Increased N2 purge flow rate

• Do we need a hydride bed?

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Step IV plan• HAZOP • Design review• Modifications required by above• AFC interface manufacturing• Step IV operation• Commissioning

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End

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