Study on direct alcohol/ether fuel synthesis process in bubble column slurry reactor

Abstract

The recent studies of direct alcohol/ether synthesis process in slurry reactors were reviewed, and the research work in our laboratory was carried out in this paper. a global kinetics model for direct dimethyl ether (DME) synthesis from syngas over a novel Cu-Zn-Al-Zr slurry catalyst was established according to the total of 25 experimental data, and a steady-state one-dimensional mathematical model was further developed in bubble column slurry reactor (BCSR), which was assumed that the bubble phase was plug flow, and the liquid phase was fully mixed flow. The numerical simulations of reactor design of 100000 t/a dimethyl ether pilot plant indicate that higher pressure and lower temperature were favorable to the increase of CO conversion, selectivity of dimethyl ether, product yield and height of slurry bed. The optimal operating conditions for DME synthesis process were obtained: reaction temperature at 240°C, reactor pressure at 5 MPa and reactor diameter of 2.5 m.

Keywords

syngas / alcohol/ether fuel / slurry catalyst / bubble column slurry reactor / global kinetics / mathematical model

References

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Acknowledgments

This work was supported by a grant from the Major State Basic Research Development Program of China (973 Program, No. 2005CB221205).

Notation

A	reactor bed cross-sectional area in Eq. (41), m2
aL	specific surface area of gas-liquid mass transfer, m2·m-3
aS	specific surface area of particles, m2·m-3
Ccat	catalyst mass concentration in slurry phase, kg·m-3
\overline{C_{\mathrm{c}\mathrm{a}\mathrm{t}}}	average mass concentration of catalyst in reactor, kg·m-3
C_{cat}^0	initial mass concentration of catalyst in the gas inlet, kg·m-3
C_{G,j}	concentration of gas phase component j, kmol·m-3
C_{G,j}^{\ast }	equilibrium concentration of gas phase component j at gas-liquid interface, kmol·m-3
C_{L,j}	concentration of liquid phase component j, mol·m-3
C_{S,j}	concentration of liquid phase component j on the surface of catalyst, kmol·m-3
DR	internal diameter of BCSR, m
DG	axial back-mixing diffusion coefficient in gas phase, m2·s-1
DL	axial back-mixing diffusion coefficient in slurry phase, m2·s-1
DS	axial dispersion coefficient of catalyst particles, m2·s-1
dp	average diameter of catalyst particles, m
Fr	Froude number, dimensionless
fj	fugacity of component j, Pa
G	gravitational acceleration, m·s-2
kL,j	liquid mass transfer coefficient of component j at gas-liquid interphase, m·s-1
kS,j	liquid mass transfer coefficient of component j at liquid-solid interphase, m·s-1
L	static bed height, m
Lh	slurry operating bed height, m
M	gas-liquid equilibrium constant
N	transient flux of syngas component in reactor bed, mol·s-1
NT	transient flux of gas in reactor bed, mol·s-1
ri,j	reaction rate of component j involved in chemical reaction I, kmol·kg-1·s-1
rj	reaction rate of component j, kg·m-1·s-1
R	gas constant, kJ·kmol-1·K-1
Reg	Reynolds number of gas phase, dimensionless
Rep	Reynolds number of catalyst particles, dimensionless
SDME	selectivity of dimethyl ether
T	reaction temperature, K
up	hindered sedimentation velocity of catalyst particles, m·s-1
uG	superficial gas velocity, m·s-1
ut	terminal sedimentation velocity of catalyst particles, m·s-1
Vcat	volume fraction of catalyst in slurry phase without syngas in
W	weight of catalyst, kg
Wcat	mass fraction of catalyst particles in slurry phase, wt-%
X	axial dimensionless length, Z/Lh
xTC	total carbon conversion
yj	mole fraction of component j in gas phase
ϵG	gas holdup
μL	viscosity of medical liquid paraffin, Pa·s
μS	viscosity of slurry phase, Pa·s
νi,j	stoichiometric coefficient of component j involved in chemical reaction i
Superscript
*	indicate equilibrium value
0	indicate initial value
Subscripts
cal	calculated value
cat	catalyst
exp	experimental value
G	gas phase
in	at the inlet of reactor bed
j	component: CO, CO2, H2, H2O, CH3OH, CH3OCH3
L	liquid phase
p	catalyst particles
S	solid phase

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