Objectives: N2O is widely used
in the chemical
industry and laboratories; however, several fire/explosion accidents
have been reported in facilities that handle N2O. This
study aimed (i) to experimentally investigate the lower and upper
flammability limits (LFL and UFL, respectively), limit nitrous oxide
concentration (LN2OC), and minimum inerting concentrations
(MICs) of fuel–N2O–diluent mixtures and (ii)
to computationally estimate the UFLs of fuel–N2O–diluent
mixtures. Methods: Herein, methane and n-propane and
nitrogen (N2), argon (Ar), and carbon dioxide (CO2) were used as fuels and diluents, respectively. The LFL, UFL, LN2OC, and MICs of the fuel–N2O–diluent
mixtures were experimentally determined using a closed cylindrical
vessel, and their UFLs were computationally estimated based on the
laws of conservation energy and mass and adiabatic flame temperatures. Results: Flammability-limit experiments revealed the following:
(i) the LFLs of the CH4–N2O–diluent
and C3H8–N2O–diluent
mixtures were 2.5 and 1.4 vol %, respectively, (ii) the UFLs of the
CH4–N2O–diluent and C3H8–N2O–diluent mixtures were
40.5 and 24.0 vol %, respectively, (iii) a nearly linear relationship
between the UFL and diluent concentration was found, and (iv) the
order of MICs in N2O atmosphere was consistent with the
inerting ability of the diluents. Calculations based on overall combustion
reactions and the laws of energy and mass conservation using six and
five chemicals successfully estimated the UFLs of the CH4–N2O–diluent and C3H8–N2O–diluent mixtures with mean absolute
percentage errors of ≤2.8% and ≤4.1%, respectively. Conclusions: The semiempirical model suggested herein allows
accurate estimation of the UFLs of the tested fuel–N2O–diluent mixtures. These findings would contribute to reducing
accident-induced losses in the chemical industry and laboratories
handling N2O.