THERMOCHEMICAL CONVERSION: (CO)GASIFICATION AND HYDROTHERMAL GASIFICATION - Biomass as a Sustainable Energy Source for the Future - page 342

TABLE 10.9 Tar reduction materials based on ECN report by Zwart (2009)
Positive aspects

Negative aspects

Natural rock materials

Calcined
dolomite,
magnesite,
and limestone

Abundant
Inexpensive

High attrition tendency
Variable qualities

Large tar
conversions

Recarbonization with
deactivation

Disposable
Investigated to large
extend

Olivine Attrition resistant

Inexpensive

Lower tar reduction
activity than dolomite

Clay minerals Abundant

inexpensive

Loss of activity at higher T
(>800 C)

Disposal after usage
less problematic

Lower activity than
dolomite

Iron and iron
minerals

Abundant Without H 2 rapid

deactivation

Inexpensive Lower activity than

dolomite

Synthetic materials

Transition metal
catalysts

For example, Ni on
carrier materials
with promoters

Almost complete
tar conversion
900 C, high
activity

Deactivation due to S and
high tar content

Increase CO/H 2
yields

Relatively expensive

Commercial
catalysts available

Disposal

Activated
alumina

High tar conversion,
comparable to
dolomite

Deactivation due to coking

Alkali metals Natural production

in gasifier

Agglomeration

Lower activity compared
to dolomite

FCC catalyst Reasonably cheap Deactivation by coking

Experience in
industrial use

Lower activity compared
to dolomite

Char Inexpensive Consumed in reaction

In situ generation Varying qualities

High tar conversion