A Compilation of Current LNG Technology

Transcription

1 A Compilation of Current LNG Technology John L. Woodward, Ph.D. Baker Engineering & Risk Consultants San Antonio, TX and Robin M. Pitblado, Ph.D. Det Norske Veritas, Houston, TX B E R C AKE R NGI NE E RI NGAND I S K ONS UL T ANT S

2 LNG Risk-Based Safety: Modeling and Consequence Analysis; Woodward and Pitblado, John Wiley & Sons/ AIChE, 2010, 374 pages B E R C AKE R NGI NE E RI NGAND I S K ONS UL T ANT S

3 Sampling Two Year Effort Updated summary of LNG risk analysis literature, compilation of data. Important historical developments in LNG technology. Compile experimental data on evaporation, fires, dispersion; models for each. Unresolved technical issues: cascading failures, fire engulfment of carrier, mechanism of spread on water, pool fire

4 Motivation Proportions of membrane carriers

5 Two Types of Carriers Moss Sphere Carriers; high centered

6 Historic Lessons Learned: eg Sloshing Damage Learned cargos must be discharged completely (with minimal heel), limiting flexibility.

7 Historically LNG Carriers Have Survived Grounding

8 Claims Made by LNG Opponents LNG Vapor cloud will be 127 miles long from full tank spill on water; Modern models converged on 1.5 miles. An LNG tanker holds 3,000,000 gal (11,360 m 3 ) Energy equivalent to 5 Hiroshima atom bombs; Burning rates-> 11 to 31 min cf 100 ms nuclear.

9 Driving Risk Analyses: Hole Size EU Project HARDER assembled data from 3000 collisions -> 6.6 to 7.4 knots for two LNG carriers to penetrate. Pitblado et al used ABAQUS FEM code predicted penetration energy. Terrorist threats, CFD modeling

10 FEM Prediction of Bow Intrusion from Collision with LNG Carrier

11 Explosive Laden Boat Attack Threat

12 Predicted Penetration of Inner Hull from Explosive Laden Boat Attack

13 Three Categories of Spills

14 Spill Under Water Pressures Inner Hull After initial P equilibrium, equal volume exchange flow at constant pressure.

15 Change in Inflow Mechanism for Breach Below Water Level Discharge rate drops as pressure builds, then constant pressure, equal volume exchange.

16 Vertical Height (m) Above Water Level-> Jet Plume Side View (Fraction LFL, LFL, UFL) for Algeria LNG Inner Hull 0.10D m AboveW, BD/D2.5 Cloud 1 ** Maximum Flammable Mass D:\SS3GDEV\Plant\LNGDEMO.SS3 Cloud Centerline UFL LFL.5fraction LFL Downwind Distance (m) 04/22/2009 SS3G V DLL:18/04/09 05:50 PM Inner hull breach above water level could jet past outer hull and penetrate into water, increasing potential for RPT.

17 Possible Technology Transfer to Predict RPT Energy Large RPT energy increase at high spill rate (Coyote). Hicks-Menzies model explosion efficiency from water on molten metal.

18 Alternate LNG Spread Models Standard: LNG sinks into water by Δ Supercritical: LNG skitters on film of vapor MODEL Max Pool Radius, m Evap Time, s Supercritical Standard Ratio SuperC/Std

19 Fire Length, m Pool Fire Modeling Issues Extrapolation to large pool diameters leads to very high flames, not yet seen in nature Pool D, m Thomas Gb=0.18 Possible Cox & Chitty Gb=0.18 Thomas Gb=0.135 Moorhouse Gb=0.18

20 Possible Mechanism Change: Mass Fire Coherent Fire Longer Distance to 5 kw/m 2 Mass Fire Shorter Distance to 5 kw/m 2

21 Radiant Flux varies with Pool Size 10 m Pool Diameter, 300 gpm Spill Rate Montoir Test, 35 m Pool Diameter on Concrete

22 Structure of Pool Fires Swirl and Lighthouse Model (Radiating Bright Spots)

23 z/l Pool Fire Models Improving E(z), kw/m2 E(z) Data1 Data2 Data3 Eave Three-zone model of Raj accounts for vertical profile in Surface Emissive Power. Improves distance prediction to 5 kw/m 2.

24 Modeling Effect of Waves & Carrier Travel- Limits Hazard Out of Harbors LNGMAP model by Spaulding et al shows spill pool moving with tanker path.

25 Fire Engulfment of Moss Carrier- SIGGTO-sponsored CFD work Heat flux needed to buckle weather cover with size of breach (inverse to duration of fire). Only holes < 3 m 2 can heat cover to melt pt.

26 Future LNG Research Needs: GAO Survey of Experts Large-scale tests to establish whether change of mechanism occurs giving shorter fire plumes with large pool fires (mass fire). Is cascading effect of LNG carrier tanks even possible? (RPT in double hull space; Ignition in double hull space; Fire/cryogenic stressing of structural members). Which mechanism best describes LNG spread on water?