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INTRODUCTION

VAPOUR CLOUD EXPLOSIONS FROM THE IGNITION OF METHANE/HYDROGEN/AIR MIXTURES IN A CONGESTED REGION Mark Royle (1) Les Shirvill (2) and Terry Roberts (1) (1) Health and Safety Laboratory (2) Shell Global Solutions. INTRODUCTION.

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INTRODUCTION

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  1. VAPOUR CLOUD EXPLOSIONS FROM THE IGNITION OF METHANE/HYDROGEN/AIR MIXTURES IN A CONGESTED REGIONMark Royle(1) Les Shirvill(2) and Terry Roberts(1)(1) Health and Safety Laboratory (2) Shell Global Solutions

  2. INTRODUCTION NATURALHY – potential for hydrogen distribution within existing natural gas pipeline networks • This work funded by Shell Hydrogen B.V. • Hydrogen mixed with methane • Change in explosive properties

  3. AIM • Measure over-pressures produced by premixed clouds in a repeated pipe congestion array • Determine the amount of hydrogen which can be added to methane without a large increase in explosion overpressure

  4. EXPERIMENTAL PROGRAMME • Perform experiments igniting mixtures of methane, hydrogen and air in a repeated pipe congestion rig. • Measure the overpressures produced by the different mixtures.

  5. EXPERIMENTAL PROGRAMME • Mixtures chosen • 100% hydrogen • 25% methane 75% hydrogen • 50% methane 50% hydrogen • 75% methane 25% hydrogen • 100% methane • Nominal equivalence ratio – 1.1 for methane mixtures. 1.2 for 100% hydrogen.

  6. CONGESTION RIG • 3 m x 3 m x 2 m metal framework structured to consist of 18 one cubic metre units • Bottom units fitted with 9 layers of vertical bars • Top units fitted with 7 layers of criss-crossed horizontal bars • Rig wrapped in plastic film to hold in gas

  7. TEST FACILITY

  8. Measurements within congestion rig • Temperature • Humidity • IR methane analyser • Paramagnetic oxygen analyser • 8 x electro-chemical oxygen sensors

  9. CONCENTRATION ETC. SENSORS

  10. OVER-PRESSURE MEASUREMENTS • 13 x Kulite piezo-resistive pressure sensors • 2 x Bruel & Kjaer 8103 hydrophones • 1 x Bruel & Kjaer sound pressure level meter

  11. PRESSURE SENSORS

  12. Gas mixtures • Certified gas mixtures used (hydrogen / methane) made to order by BOC. • Gas mixture injected into rig via air amplifiers to entrain air • Oxygen and methane concentration monitored until required equivalence ratio obtained

  13. CONCENTRATION DATA

  14. Test name Certified proportion of hydrogen in mixture (%) Nominal equivalence ratio Actual* equivalence ratio NATHY_01 100 1.2 1.28 NATHY_02 0 1.1 1.06 NATHY_03 50.9 1.1 1.06 NATHY_04 25.5 1.1 1.09 NATHY_05 75 1.1 1.1 TRIAL EQUIVALENCE RATIOS * Calculated from mean depleted oxygen concentration

  15. PHOTOGRAPHS 2nd frame after ignition 25% hydrogen 51% hydrogen 100% methane 75% hydrogen 100% hydrogen

  16. PRESSURE DATA AT 16 METRES

  17. DETONATION OF HYDROGEN • For 100% hydrogen • Pressure 3.03 bar just inside and 4.58 bar just outside rig • Plastic shredded into narrow strips (20.5 + 6.7 mm) • Groethe et al. (2002) found: • 21 mm for a 20% hydrogen no-obstacle detonation test • explosive charge initiation • 13 mm for a 30% hydrogen with obstacle test • spark initiation with 10.9% volume repeated pipe blockage (c.f. 4.4%) • 8 mm for a 30% hydrogen no-obstacle detonation test • explosive charge initiation

  18. MAXIMUM PRESSURESInside and near rig (parallel to wall)

  19. MAXIMUM PRESSURESFar field (away from wall)

  20. SUMMARY OF MAXIMUM PRESSURES Hydrogen Maximum Maximum Maximum Maximum concentration pressure pressure just pressure inside pressure on wall outside rig the rig At 32 m (%) (kPa) (kPa) (kPa) (kPa) 0 14.8 11.4 11.8 1.2 25.5 19.3 13.7 13.7 1.4 50.9 98.0 42.8 44.0 8.6 171.3 66.1 75.0 13.0 79.3 100 614.5 457.7 303.2 16.5

  21. EFFECT OF H2 MASS

  22. CONCLUSIONS • For 100% hydrogen transition to detonation occurred at the corners of the rig • Only 0.02 bar difference between 0% & 25% H2 • 0.12 bar ca. 0.14 bar • 50% hydrogen gives ca. 3.5 times the pressure given by methane • 0.44 bar inside rig

  23. CONCLUSIONS (2) • Explosion effects from the mixtures correlate reasonably with mass of hydrogen in the mixture. • Results suggest maximum overpressures generated in large scale trials by methane hydrogen mixtures containing up to 25% (volume) hydrogen may not be much more than those generated by methane alone.

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