Mitigation of tars produ
ced during biomass gasifi
cation
continues to be a te
chni
cal barrier todeveloping systems. This effort
combined the measurement of tar-reforming
catalyst dea
ctivationkineti
cs
and the produ
ction of syngas in a pilot-s
cale biomass gasifi
cation system at a singlesteady-state
condition with mixed woods, produ
cing a gas with an H
2-to-CO ratio of 2
and 13%methane. A slipstream from this pro
cess was introdu
ced into a ben
ch-s
cale 5.25
cm diameterfluidized-bed
catalyst rea
ctor
charged with an alkali-promoted Ni-based/Al
2O
3 catalyst. Catalyst
conversion tests were performed at a
constant spa
ce time
and five temperatures from 775 to875
C. The initial
catalyst-reforming a
ctivity for all measured
components (benzene, toluene,naphthalene,
and total tars) ex
cept light hydro
carbons was 100%. The residual steady-state
conversion of tar ranged from 96.6% at 875
C to 70.5% at 775
C. Residual steady-state
conversions at 875
C for benzene
and methane were 81%
and 32%, respe
ctively. Catalyti
cdea
ctivation models with residual a
ctivity were developed
and evaluated based on experimentallymeasured
changes in
conversion effi
cien
cies as a fun
ction of time on stream for the
catalyti
creforming of tars, benzene, methane,
and ethane. Both first-
and se
cond-order models wereevaluated for the reforming rea
ction
and for
catalyst dea
ctivation. Comparison of experimental
and modeling results showed that the reforming rea
ctions were adequately modeled by eitherfirst-order or se
cond-order global kineti
c expressions. However, se
cond-order kineti
cs resultedin negative a
ctivation energies for dea
ctivation. A
ctivation energies were determined for first-order reforming rea
ctions
and catalyst dea
ctivation. For reforming, the representative a
ctivationenergies were 32 kJ/g·mol for ethane, 19 kJ/g·mol for tars, 45 kJ/g·mol for tars plus benzene,
and 8-9 kJ/g·mol for benzene
and toluene. For
catalyst dea
ctivation, representative a
ctivationenergies were 146 kJ/g·mol for ethane, 121 kJ/g·mol for tars plus benzene, 74 kJ/g·mol forbenzene,
and 19 kJ/g·mol for total tars. Methane was also modeled by a se
cond-order rea
ction,with an a
ctivation energy of 18.6 kJ/g·mol
and a
catalyst dea
ctivation energy of 5.8 kJ/g·mol.