ETANKFIRE backgroundToday, ethanol is used both for low blending in gasoline and for flexi fuel cars running on E85. In Europe, 5% of ethanol has been used in gasoline for a number of years; but from 2011, the acceptable proportion of ethanol in low blended fuels will increase to 10%. In the US, 10% ethanol is already used in gasoline and there are ongoing discussions concerning increasing this figure to 15%.
The obvious consequence of increasing the volume of low blended ethanol is that the volumes of bulk ethanol transported, handled and stored will increase dramatically in coming years. However, experience of tank fire fighting involving ethanol or other water miscible fuels, is very limited and those few tank fires that have occurred have resulted in burn out rather than extinguishment.
Limited fire test data available for water miscible fuels
Some test data concerning foam fire fighting of ethanol fuels and other water miscible products are available, even for reasonably large scale scenarios. Unfortunately all such data relates to spill fire scenarios, i.e., relatively thin fuel layers and cannot be immediately extrapolated to large storage tank fire scenarios.
Similarly, existing test standards for alcohol resistant foam concentrates (ISO 7203-3, EN 1568-4, UL162, etc) all employ thin fuel layers and short pre-burn times, i.e., represent spill fires. Even spill fires pose serious fire fighting issues and the general conclusion from the various large scale tests and standard test methods is that the use of alcohol resistant (AR) foams is a fundamental requirement to obtain extinguishment of water miscible fuels. However, the tests have also shown that AR foams will fail unless gentle foam application onto the burning fuel surface can be achieved. For more information is available in SP report 1981:20 and 1990:36, links to the right.
As tank fires are usually extinguished using large capacity foam monitors, gentle application is not possible and therefore extinguishment cannot be expected. Further, a tank fire will present a more severe situation compared to a spill fire due to the large fuel depth and, consequently, the dilution effect from the fire fighting foam will be limited. In most situations, the pre-burn time will also be longer than that expected in a spill fire, thereby increasing the temperature of the fuel and creating hot steel surfaces making extinguishment even more difficult.
A very important and related issue is that the burning behavior of a large scale ethanol fire might be significantly different from that of a petroleum fire. Fire tests in a 200 m2 pool fire indicate that the heat flux from the acetone/ethanol fire is approximately twice that of gasoline. The same observation was made during the Port Kembla tank fire. This indicates that the radiation from a fire in ethanol fuels might be significantly higher compared to that generated by gasoline, which will increase the risk of escalation of a fire incident even further. Clearly, relevant experimental data is needed to validate computer models, thereby improving our ability to make reliable risk assessments in ethanol tank storage facilities.