Combustion of Lithium Particles in N₂—Reaction Rates

ABSTRACT

The combustion of single lithium particles (d_p < 200 µm) with N₂ was investigated in a laminar flow reactor. A particle sampling probe was used to extract and quench particles at various residence times. Burnout of the extracted particles was analyzed using X-ray diffraction and ultimate analysis (carbon, hydrogen, and nitrogen; CHN) to determine the burnout constituents. The burnout consists mainly of Li₃N and Li as well as some impurities (LiOH, Li₂O, Li₂CO₃) due to the experimental and analytical procedures. Scanning electron microscopy images report on the structural change of the particles during reaction. The resulting trend of lithium conversion depending on the particle residence time was used to calculate reaction rates for the reaction of lithium particles with nitrogen.

KEYWORDS:

• Energy storage
• Lithium combustion
• Metal combustion
• Particle sampling

Acknowledgments

The authors acknowledge the helpful comments of the anonymous reviewers who improved the manuscript.

Funding

This work was supported by the Federal Ministry of Education and Research (BMBF) under project number 03EK3007D and by the Ruhr University Research School PLUS, funded by Germany’s Excellence Initiative [DFG GSC 98/3].

Nomenclature

Ap	=	particle surface (spherical particle) (m2)
cp	=	heat capacity, calculated for the mass fraction of Li and Li3N (J/kg*K)
d	=	diameter (m)
dp	=	particle diameter (m)
d10/50/90	=	characteristic diameters (10/50/90% quantil) (m)
∆Hmelt	=	melting enthalpy of lithium (kJ/mol)
mp	=	particle mass (kg)
	=	conversion rate molLi/(m2s)
Nu	=	Nusselt number
t	=	time (s)
Tgas, Tg	=	gas temperature (K)
Tign	=	ignition temperature (K)
Tp	=	particle surface temperature (K)
Tw	=	wall temperature (K)
V(dp)	=	particle volume correlated to particle size dp
X	=	mole fraction (mol/mol)
	=	reacted fraction of lithium by calculation (mol/mol)
	=	measured fraction of lithium (mol/mol)
Y	=	mass fraction (kg/kg)
ε	=	emissivity
λ	=	thermal conductivity (W/(m*K)
M	=	molar mass (kg/mol)
ρp	=	particle density (kg/m3)
σ	=	Stefan–Boltzmann constant (5.67*10–8 W/(m2 K4)

Additional information

Funding

This work was supported by the Federal Ministry of Education and Research (BMBF) under project number 03EK3007D and by the Ruhr University Research School PLUS, funded by Germany’s Excellence Initiative [DFG GSC 98/3].