3.1 Thermochemical Conversion Technologies
63
Table 3.2 Comparison of the
physical properties of bio-oil
and heavy fuel oil.
Regenerated with permission
from ACS Publications [27]
Properties
Bio-oil Heavy fuel oil
Moisture content (wt%)
15–30
0.1
Specific gravity
1.2
0.94
Elemental composition (wt%, d.b. a )
C
54–58
85
H
5.5–7.0 11
O
35–40
1.0
N
0–0.2
0.3
Ash
0–0.2
0.1
HHV (MJ/kg)
16–19
40
Viscosity at 50 °C (cP)
40–100 180
a Dry basis
Pyrolysis products from bio-feedstocks include syngas (mainly composed of
CH 4 , H 2 , CO or CO 2 ), liquid bio-fuels (bio-oils or bio-crude oils) and biochar
[6, 23]. Bio-oil is a dark brown, viscous and energy-dense liquid containing a
variety of compounds such as alkanes, aromatic hydrocarbons, phenols, oxygenated
compounds, ketones, esters, amines, etc. [26]. It is considered as a promising renewable alternative to petroleum crude oil for power or heat generation and extraction
of valuable chemicals. Bio-oils are carbon neutral, and commonly contain much
lower nitrogen and sulfur content if compared with most of fossil fuels, which hence
generate less SO x and NO x emissions than fossil fuels in combustion. However, biooils have undesirable compounds such as water, aldehydes and acids that cause poor
fuel properties such as high acidity and poor chemical and thermal stability due to
their higher oxygen content and viscosity than petroleum fuels. Thus, crude bio-oils
need to be upgraded by either catalytic operations (hydrogenation, cracking, emulsification) or other methods [26]. Table 3.2 shows the comparison of the properties
of bio-oil and heavy fuel oil.
The other valuable product of biomass pyrolysis is biochar, containing mainly
carbon and some volatiles and ash. It could be used as a soil amendment to improve
crop yields and as an adsorbent agent for removal of certain pollutants in water
filtration applications, due to its cation exchange capacity [26, 28]. Since biochar
has a highly porous structure, it could improve water retention and increase the
surface area of soil leading to improved efficiency of nutrient use [29, 30]. Also, the
porous structure and adsorption properties of biochar make it ideal for the growth
and reproduction of soil microorganisms [31].
Pyrolysis processes are flexible for installation, do not require waste separation
and they have minimum environmental issues [23]. Some of the advantages of this
process include [32]:
– Capability to utilize renewable resources as well as waste and residual biomass
as the feedstock;
63
Table 3.2 Comparison of the
physical properties of bio-oil
and heavy fuel oil.
Regenerated with permission
from ACS Publications [27]
Properties
Bio-oil Heavy fuel oil
Moisture content (wt%)
15–30
0.1
Specific gravity
1.2
0.94
Elemental composition (wt%, d.b. a )
C
54–58
85
H
5.5–7.0 11
O
35–40
1.0
N
0–0.2
0.3
Ash
0–0.2
0.1
HHV (MJ/kg)
16–19
40
Viscosity at 50 °C (cP)
40–100 180
a Dry basis
Pyrolysis products from bio-feedstocks include syngas (mainly composed of
CH 4 , H 2 , CO or CO 2 ), liquid bio-fuels (bio-oils or bio-crude oils) and biochar
[6, 23]. Bio-oil is a dark brown, viscous and energy-dense liquid containing a
variety of compounds such as alkanes, aromatic hydrocarbons, phenols, oxygenated
compounds, ketones, esters, amines, etc. [26]. It is considered as a promising renewable alternative to petroleum crude oil for power or heat generation and extraction
of valuable chemicals. Bio-oils are carbon neutral, and commonly contain much
lower nitrogen and sulfur content if compared with most of fossil fuels, which hence
generate less SO x and NO x emissions than fossil fuels in combustion. However, biooils have undesirable compounds such as water, aldehydes and acids that cause poor
fuel properties such as high acidity and poor chemical and thermal stability due to
their higher oxygen content and viscosity than petroleum fuels. Thus, crude bio-oils
need to be upgraded by either catalytic operations (hydrogenation, cracking, emulsification) or other methods [26]. Table 3.2 shows the comparison of the properties
of bio-oil and heavy fuel oil.
The other valuable product of biomass pyrolysis is biochar, containing mainly
carbon and some volatiles and ash. It could be used as a soil amendment to improve
crop yields and as an adsorbent agent for removal of certain pollutants in water
filtration applications, due to its cation exchange capacity [26, 28]. Since biochar
has a highly porous structure, it could improve water retention and increase the
surface area of soil leading to improved efficiency of nutrient use [29, 30]. Also, the
porous structure and adsorption properties of biochar make it ideal for the growth
and reproduction of soil microorganisms [31].
Pyrolysis processes are flexible for installation, do not require waste separation
and they have minimum environmental issues [23]. Some of the advantages of this
process include [32]:
– Capability to utilize renewable resources as well as waste and residual biomass
as the feedstock;