ABSORPTION CHARACTERISTICS OF LNG AS A FUNCTION OF INFRARED WAVELENGTH. Carolina Herrera

Transcription

1 ABSORPTION CHARACTERISTICS OF LNG AS A FUNCTION OF INFRARED WAVELENGTH Carolina Herrera Mary Kay O Connor O Process Safety Center International Symposium October 28, 2009

2 Overview Liquefied Natural Gas Previous experiments Problem statement Motivation Objectives Methodology Conceptual design Conclusions Future work 2

3 Natural Gas Use in 2007 Supply and consumption (Tcf) Source: EIA dot Source: EIA dot Concerns about potential consequences of the release of large quantities of LNG. The more we know, the better 3

4 Test Diameter Substrate Regression Burning rate (m) rate (m/s) (Kg/m 2 s) Esso 18 Trench 1.6* Shell 20 Concrete 2.37* dike US 0.38 Ground 1.94* Bureau of Mines dike AGA 1.8 Ground 5.2*10 5 dike 6.1 Ground 1.5*10 4 dike 24 Ground 2.3*10 4 Gaz de France dike 35 Concrete dike 3.11* ,

5 Evaporation rates Calculation: Calorimeters Radiometers Direct data measurements: Thermocouples Helium purged dip tubes Test Steady state (methane burning period) (s) Heat flux feedback from fire to the pool (kw/m 2 ) Liquid (Kg/m 2 s) Calculated from measured heat feedback * Helium purged dip tube data * Based on methane latent heat of vaporization (510 KJ/Kg) The mean burning rates in Montoir test differed between them by a factor of almost 2.5 5

6 Soot particles Possible explanations: Heat absorption and scattering of methane vapor and liquid droplets on the pool surface LNG Droplets + methane gas Heat reflection back to the fire from the liquid surface Heat absorption of low temperature soot at the bottom of the fire 6

7 Determine the absorption characteristics for LNG in the liquid phase at cryogenic temperatures. Obtain a thermal absorption equation as a function of known parameters Study LNG burning rates primarily as a result of radiant heat 7

8 Phase I Experimental work under controlled conditions in which IR spectroscopy and radiometry techniques will be applied Theoretical modeling of results Phase II Application of the results obtained in phase I. Experimental work under real conditions. 8

9 Energy balance on the pool surface: Q evap Q conv Q rad Q cond Q loss Q cond and Q conv can be neglected: Q evap Q rad Q Q loss can not be assumed to be very small: Q evap Q rad Q rf loss Q tr Q rf Qtr Finally, the mass evaporated was calculated: m Q H evap evap ΔH evap : heat of evaporation 9

10 Incident radiation Reflected Absorbed LNG Absorbs only part of incident radiation. This amount varies with the material, wavelength and temperature: Absorptivity (α) = Incident radiation absorbed A fraction is reflected by the surface. Transmitted total incident radiation Reflectivity (ρ) = Incident radiation reflected The difference is the fraction transmitted. Transmitivity (τ) = ρ + α + τ =1 total incident radiation 10

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13 <overview> 13

14 Investigation of LNG over prediction phenomena will contribute to the understanding of large scale fire scenarios. Results obtained in this research will offer a tool for an improved prediction of the hazards arising when modeling pool fires. Optical properties of materials need to be incorporated when performing indirect calculations of burning rates. 14

15 Conceptual design Liquid cell fabrication Spectrometer Magna 560 FTIR Experimental setup Reproducibility of previous research data Determine direct applicability of LNG optical properties in the determination of LNG burning rates 15

16 Malvos, H., Details of 35 m Diameter LNG Fire Tests Conducted in Montoir, France in 1987 and Analysis of Fire Spectral and Other Data Nedelka, D., The Montoir 35 m Diameter LNG pool fire experiments. International conference on liquefied natural gas Malvos, H., et al., Thermal emission and other characteristics of large liquefied natural gas fires. Process Safety Progress, 2006 Briscoe, F., et al., Spread and evaporation of liquid. Prog. Energy Comb. Sci., 1980 Raj, Phani. Large LNG fire thermal radiation- Modeling issues and hazard criteria revisited. Process Safety Progress, 2005 Raj, Phani. LNG fires: A review of experimental results, models and hazard prediction challenges. Journal of hazardous materials, 2006 Nedelka, D., Calculation of radiation effects from LNG fires. European applied research conference on natural gas, 1990 Raj, Phani., LNG pool fire spectral data and calculation of emissive power. 8 th annual symposium, MKOPSC, 2005 Reid, Robert. Boiling of LNG on typical dike floor materials Johnson, D., et al., Modeling the release, spreading, and burning of LNG, LPG, and gasoline on water. Journal of Hazardous Materials Statistical modeling of thermal radiation transfer in buoyant turbulent diffusion flames. Combustion and Flame Fay, J.A., Model of large pool fires. Journal of Hazardous Materials Koseki, H., Combustion properties of large liquid pool fires. Fire Technology Large hydrocarbon fuel pool fires: physical characteristics and thermal emission variations with height. Journal of Hazardous Materials Luketa-Hanlin, Anay, A review of large-scale LNG spills: Experiments and modeling, Journal of Hazardous Materials Cleaver, P. et al., A summary of some experimental data on LNG safety. Journal of Hazardous Materials Luketa-Hanlin, Anay, A review of large-scale LNG spills: Experiments and modeling, Journal of Hazardous Materials Cleaver, P. et al., A summary of some experimental data on LNG safety. Journal of Hazardous Materials Miller, R.G.J., Laboratory methods in infrared spectroscopy. 1965: Philadelphia, Sadtler Research Laboratories. Wishnow, E.H., A. Leung, and H.P. Gush, Cryogenic multiple reflection absorption cell and Fourier transform spectrometer system for the far infrared. Review of Scientific Instruments, (1): p Kassi, S., et al., The near-infrared ( mu m) absorption spectrum of methane down to 77 K. Physical Chemistry Chemical Physics, (30): p Birnbaum, G., et al., Far infrared absorption in liquid methane: experiment and theory. Molecular Physics, (4): p Buontempo, U., et al., Far Infrared-Absorption Spectrum of N2 in Gas and Liquid-Phases. Journal of Chemical Physics, (6): p Kreith, F. Principles of heat transfer. Second edition. International textbook company Medtherm corporation 16

17 Dr. Sam Mannan Dr. Mentzer Dr. Raj LNG team Kirk Richardson Randy Marek MKOPSC members 17

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