TY - BOOK
T1 - Gasification reactivity and ash sintering behaviour of biomass feedstocks
AU - Moilanen, Antero
AU - Nasrullah, Muhammad
PY - 2011
Y1 - 2011
N2 - Char gasification reactivity and ash sintering properties
of forestry biomass feedstocks selected for large-scale
gasification process was characterised. The study was
divided into two parts: 1) Internal variation of the
reactivity and the ash sintering of feedstocks. 2)
Measurement of kinetic parameters of char gasification
reactions to be used in the modelling of a gasifier. The
tests were carried out in gases relevant to pressurized
oxygen gasification, i.e. steam and carbon dioxide, as
well as their mixtures with the product gases H2 and CO.
The work was based on experimental measurements using
pressurized thermobalance. In the tests, the temperatures
were below 1000 °C, and the pressure range was between 1
and 20 bar. In the first part, it was tested the effect
of growing location, storage, plant parts and debarking
method. The following biomass types were tested: spruce
bark, pine bark, aspen bark, birch bark, forestry
residue, bark feedstock mixture, stump chips and hemp.
Thick pine bark had the lowest reactivity (instantaneous
reaction rate 14%/min) and hemp the highest (250%/min);
all other biomasses lay between these values. There was
practically no difference in the reactivities among the
spruce barks collected from the different locations. For
pine bark, the differences were greater, but they were
probably due to the thickness of the bark rather than to
the growth location (see Ch. 3.4). For the spruce barks,
the instantaneous reaction rate measured at 90% fuel
conversion was 100%/min for pine barks it varied between
14 and 75%/min. During storage, quite large local
differences in reactivity seem to develop. Stump had
significantly lower reactivity compared with the others.
No clear difference in the reactivity was observed
between barks obtained with the wet and dry debarking,
but, the sintering of the ash was more enhanced for the
bark from dry debarking. Char gasification rate could not
be modelled in the gas mixture of H2O + CO2 + H2 + CO,
similarly as it can be done for coal. The reasons were
assumed to be that in the carbon dioxide gasification,
the gasification rate was negatively dependent on the CO2
pressure, the opposite of what is observed in steam
gasification and the dependence of the gasification
reaction rate on the conversion had three patterns.
Normally it increases with the conversion, but it may
also decrease or go through a minimum. According to the
sintering tests, the ash residues were not totally
sintered but they consisted of molten particles
(spheres), unreacted char particles and powdery ash. The
strongest sintering was observed for hemp, spruce bark
obtained by dry debarking, and aspen bark. Increased
pressure and CO2 resulted in intensified sintering, as
has been observed in earlier studies.
AB - Char gasification reactivity and ash sintering properties
of forestry biomass feedstocks selected for large-scale
gasification process was characterised. The study was
divided into two parts: 1) Internal variation of the
reactivity and the ash sintering of feedstocks. 2)
Measurement of kinetic parameters of char gasification
reactions to be used in the modelling of a gasifier. The
tests were carried out in gases relevant to pressurized
oxygen gasification, i.e. steam and carbon dioxide, as
well as their mixtures with the product gases H2 and CO.
The work was based on experimental measurements using
pressurized thermobalance. In the tests, the temperatures
were below 1000 °C, and the pressure range was between 1
and 20 bar. In the first part, it was tested the effect
of growing location, storage, plant parts and debarking
method. The following biomass types were tested: spruce
bark, pine bark, aspen bark, birch bark, forestry
residue, bark feedstock mixture, stump chips and hemp.
Thick pine bark had the lowest reactivity (instantaneous
reaction rate 14%/min) and hemp the highest (250%/min);
all other biomasses lay between these values. There was
practically no difference in the reactivities among the
spruce barks collected from the different locations. For
pine bark, the differences were greater, but they were
probably due to the thickness of the bark rather than to
the growth location (see Ch. 3.4). For the spruce barks,
the instantaneous reaction rate measured at 90% fuel
conversion was 100%/min for pine barks it varied between
14 and 75%/min. During storage, quite large local
differences in reactivity seem to develop. Stump had
significantly lower reactivity compared with the others.
No clear difference in the reactivity was observed
between barks obtained with the wet and dry debarking,
but, the sintering of the ash was more enhanced for the
bark from dry debarking. Char gasification rate could not
be modelled in the gas mixture of H2O + CO2 + H2 + CO,
similarly as it can be done for coal. The reasons were
assumed to be that in the carbon dioxide gasification,
the gasification rate was negatively dependent on the CO2
pressure, the opposite of what is observed in steam
gasification and the dependence of the gasification
reaction rate on the conversion had three patterns.
Normally it increases with the conversion, but it may
also decrease or go through a minimum. According to the
sintering tests, the ash residues were not totally
sintered but they consisted of molten particles
(spheres), unreacted char particles and powdery ash. The
strongest sintering was observed for hemp, spruce bark
obtained by dry debarking, and aspen bark. Increased
pressure and CO2 resulted in intensified sintering, as
has been observed in earlier studies.
KW - biomass
KW - fuel
KW - gasification
KW - reactivity
KW - ash
KW - sintering
KW - pressure
KW - bio diesel
M3 - Report
SN - 978-951-38-7748-4
T3 - VTT Publications
BT - Gasification reactivity and ash sintering behaviour of biomass feedstocks
PB - VTT Technical Research Centre of Finland
CY - Espoo
ER -