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In its liquid state, LNG is neither flammable nor explosive.<ref name=CalifEnergyCommission/><ref>[http://www.ferc.gov/o12faqpro/default.asp?Action=Cat&ID=26 Frequently Asked Questions: LNG]] From the website of the [[Federal Energy Regulatory Commission]]</ref> For LNG to burn, it must first vaporize, | In its liquid state, LNG is neither flammable nor explosive.<ref name=CalifEnergyCommission/><ref>[http://www.ferc.gov/o12faqpro/default.asp?Action=Cat&ID=26 Frequently Asked Questions: LNG]] From the website of the [[Federal Energy Regulatory Commission]]</ref> For LNG to burn, it must first vaporize, mix with air in the proper proportions (the [[Flammability limit|flammable range]] is 5 to 15 volume percent<ref>'''Note:''' If there is less than 5 volume % or more than 15 volume % of natural gas vapor in the air, the gas will not burn.</ref>), and then be ignited. | ||
When LNG is released into the atmosphere because of a leak, spill or any other cause (on land or at sea), it immediately begins to vaporize by absorbing heat from the ground or the sea water. At the usual ambient air temperature of about 15 to 40 °C, natural gas is much lighter than air. However, the natural gas vapor formed when LNG vaporizes is very cold (i.e., −160 °C) and therefore much denser than the ambient air, which means that the initial vapor will remain at ground or sea level. The vapor will begin mixing with air and water moisture in the air will be condensed to form a visible vapor cloud. .As the cloud is initially formed, it contains too much natural gas to be flammable. It will linger near ground level until further heat is absorbed and the natural gas rises and mixes with more air. As that occurs, the concentration of natural gas within the cloud will begin to decrease. At some point, the natural gas concentration in the cloud will decrease to the point where the gas is in the flammable range and becomes ignitable. If an ignition sources is present at that point, only the part of the cloud which is within the flammable range will burn. The vapor cloud will not explode unless it is confined. Any part of the cloud that enters a building or becomes confined in a congested area will become explosive if it encounters an ignition source.<ref name=Pitblado>{{cite book|author=John M. Woodward and Robin Pitblado|title=LNG Risk Based Safety: Modeling and Consequence Analysis|publisher=John Wiley and [[American Institute of Chemical Engineers]]|date=2010|id=ISBN 0-470-31764-7}}</ref><ref>[http://www.nyserda.org/Energy_Information/lngstudy.pdf Report On Issues Regarding The Existing New York Liquefied Natural Gas Moratorium] 1998, from the website of the New York State Energy and Research Development Authority (NYSERDA). The report concluded that safety concerns associated with LNG terminal facilities were adequately addressed by existing Federal, State and local statutes and regulations. For those reasons, the study recommended: that the New York State Legislature discontinue the existing moratorium.</ref> | When LNG is released into the atmosphere because of a leak, spill or any other cause (on land or at sea), it immediately begins to vaporize by absorbing heat from the ground or the sea water. At the usual ambient air temperature of about 15 to 40 °C, natural gas is much lighter than air. However, the natural gas vapor formed when LNG vaporizes is very cold (i.e., −160 °C) and therefore much denser than the ambient air, which means that the initial vapor will remain at ground or sea level. The vapor will begin mixing with air and water moisture in the air will be condensed to form a visible vapor cloud. .As the cloud is initially formed, it contains too much natural gas to be flammable. It will linger near ground level until further heat is absorbed and the natural gas rises and mixes with more air. As that occurs, the concentration of natural gas within the cloud will begin to decrease. At some point, the natural gas concentration in the cloud will decrease to the point where the gas is in the flammable range and becomes ignitable. If an ignition sources is present at that point, only the part of the cloud which is within the flammable range will burn. The vapor cloud will not explode unless it is confined. Any part of the cloud that enters a building or becomes confined in a congested area will become explosive if it encounters an ignition source.<ref name=Pitblado>{{cite book|author=John M. Woodward and Robin Pitblado|title=LNG Risk Based Safety: Modeling and Consequence Analysis|publisher=John Wiley and [[American Institute of Chemical Engineers]]|date=2010|id=ISBN 0-470-31764-7}}</ref><ref>[http://www.nyserda.org/Energy_Information/lngstudy.pdf Report On Issues Regarding The Existing New York Liquefied Natural Gas Moratorium] 1998, from the website of the New York State Energy and Research Development Authority (NYSERDA). The report concluded that safety concerns associated with LNG terminal facilities were adequately addressed by existing Federal, State and local statutes and regulations. For those reasons, the study recommended: that the New York State Legislature discontinue the existing moratorium.</ref> | ||
Revision as of 14:39, 28 February 2011
In its liquid state, LNG is neither flammable nor explosive.[1][2] For LNG to burn, it must first vaporize, mix with air in the proper proportions (the flammable range is 5 to 15 volume percent[3]), and then be ignited.
When LNG is released into the atmosphere because of a leak, spill or any other cause (on land or at sea), it immediately begins to vaporize by absorbing heat from the ground or the sea water. At the usual ambient air temperature of about 15 to 40 °C, natural gas is much lighter than air. However, the natural gas vapor formed when LNG vaporizes is very cold (i.e., −160 °C) and therefore much denser than the ambient air, which means that the initial vapor will remain at ground or sea level. The vapor will begin mixing with air and water moisture in the air will be condensed to form a visible vapor cloud. .As the cloud is initially formed, it contains too much natural gas to be flammable. It will linger near ground level until further heat is absorbed and the natural gas rises and mixes with more air. As that occurs, the concentration of natural gas within the cloud will begin to decrease. At some point, the natural gas concentration in the cloud will decrease to the point where the gas is in the flammable range and becomes ignitable. If an ignition sources is present at that point, only the part of the cloud which is within the flammable range will burn. The vapor cloud will not explode unless it is confined. Any part of the cloud that enters a building or becomes confined in a congested area will become explosive if it encounters an ignition source.[4][5]
There are possible hazards associated with LNG other than fire or expliosions:[4]
- Rapid Phase Transition: The sudden vaporization or phase transition from liquid to vapor that has occurred upon occasion when LNG has been spilled into water has caused a physical explosion. No injuries have occurred from an RPT of LNG but equipment has been damaged. The explosive overpressures caused by RPTs have not been well measured as yet, but indications are that the overpressures have not been high enough to cause personnel injury. *
- Asphyxiation: For human death to occur from asphyxiation, the LNG vapors must reduce the normal oxygen concentration in the air (about 21 volume percent) to less than 6 volume percent. This would occur when the concentration of LNG vapors in the air is about 71 volume percent. Breathing is impaired when the oxygen level in the air is reduced to less than 15 volume % and vomiting occurs when the oxygen level is below 10 volume %, which correspond to the concentration of LNG vapors in the air being about 28 and 52 volume percent respectively.
- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namedCalifEnergyCommission - ↑ Frequently Asked Questions: LNG] From the website of the Federal Energy Regulatory Commission
- ↑ Note: If there is less than 5 volume % or more than 15 volume % of natural gas vapor in the air, the gas will not burn.
- ↑ 4.0 4.1 John M. Woodward and Robin Pitblado (2010). LNG Risk Based Safety: Modeling and Consequence Analysis. John Wiley and American Institute of Chemical Engineers. ISBN 0-470-31764-7.
- ↑ Report On Issues Regarding The Existing New York Liquefied Natural Gas Moratorium 1998, from the website of the New York State Energy and Research Development Authority (NYSERDA). The report concluded that safety concerns associated with LNG terminal facilities were adequately addressed by existing Federal, State and local statutes and regulations. For those reasons, the study recommended: that the New York State Legislature discontinue the existing moratorium.