A Study on Effect of Temperatures on the Flammability of Biodiesel Vapour Mixtures for Accident Prevention

Biodiesels are widely used as an alternative fuel resulting from higher global energy
demands as they are environmental friendly. Study on fire and explosion is very
important mainly in industrial activities due to previous cases that have been reported
involving biodiesel. In general biodiesel is considered to be much safer than fossil
fuels as it is much less flammable due to its high flash point. However, biodiesel will
combust if it is heated up to over 150°C. Therefore, this study is conducted to
investigate the flammability of biodiesel vapor mixtures at different range of
temperature varying from 50°C-200°C. Biodiesel produced by chemically reacting
lipids with an alcohol via transesterification process was analyzed using Gas
Chromatography Mass Spectrometry (GC-MS) to examine the composition of the
sample. Total components vaporized from biodiesel sample differ at different
temperatures. The results from GC-MS indicated that there are three components
vaporized from biodieselliquid sample at 150°C and six components at 200°C. Mole
fractions of components in the vapor phase were calculated using modified Raoult' s
law. The fugacity coefficients were predicted using ThermoSolver software based on
Peng-Robinson method, while the activity coefficients were calculated using
COSMO software. Lower Flammability Limit (LFL) and Upper Flammability Limit
(UFL) for individual components were calculated using the flammability limit
dependence on temperature equation (Zabetakis, S.Lambiris, & Scott, 1959). While
LFL and UFL values for the mixture (LFLmix and UFLmix) were determined using Le
Chatelier equation (Chatelier, 1891). Limiting Oxygen Concentrations (LOCs) were
determined using equation proposed by Hansen and Crowl (Hansen & Crowl, (June
2010)). The LFLmix, UFLmix, and LOCmix values were used to construct the
flammability diagram and to determine the flammability of biodiesel vapor mixture
at 50°C, 100°C, 150°C and 200°C. From the flammability diagram, it shown that
biodiesel vapor mixture is not flammable at lower temperature; 50°C and 1 00°C but
as the temperatures increase; 150°C and 200°C the biodiesel became flammable. The
findings of this study may assist in minimizing frre hazards associated with presence
of organic compound vapors derived from biodiesel.