46
material to conduct or transfer heat (expressed in W m-K
−1
) (Capareda 2014).
According to Czernik (2010), biomass with large particle size has low thermal conductivity that results in slow heat and a mass transfer rate.
The chemical composition of the biomass may be used to evaluate the thermal
degradation of the biomass and residues/pollutants (i.e, ash, NOx, SOx), which may
be generated. Proximate analysis provides information on the behavior of the feedstock when it is heated (i.e., how much goes off as gas or vapors and how much
remains as fixed carbon). It includes the measurement of volatile matter, fixed carbon, and ash. Volatile matter (VM) is the material expelled from the biomass when
exposed to 950 °C for 7 min in an oxygen-free environment. It includes volatile
carbon, combined water, net hydrogen, nitrogen, and sulfur. VM is important in
thermal conversion since high amounts lead to more combustible gases during combustion or more gaseous (condensable and non-condensable) products during gasification and pyrolysis.
Fixed carbon (FC) is the material expelled after burning the moisture- and
VM-free biomass to 575 °C for 4 h until the material becomes grayish white
(Capareda 2014). FC fraction in the residual biomass usually increases as volatiles
are released during thermal degradation (Maguyon and Capareda 2013). Char, the
residue after pyrolysis, has typically high amounts of FC and ash. Ash is the residue
which remains after complete combustion of the feedstock which can be used for
other purposes such as cement aggregate replacement, fertilizer additive, etc. As can
be seen in Table 4.2, rice straw FC widely varies among different samples but the
range is comparable with other biomass used for thermal conversion such as rice
husk and wheat straw. Volatile content is relatively lower compared to other biomass
while ash content is relatively higher. Herbaceous biomass such as rice straw has
typically higher ash content (up to 25%) compared to woody biomass. This may be
attributed to the physiological ash, which results from intrinsic biomass properties
such as plant type, maturity and anatomical fractions. High ash contents result in
lower energy yields, catalyst impairment, and slag formation during thermal
Table 4.2 Proximate analysis of various biomass
Biomass
Components (% wt)
Sources
Volatiles
Fixed carbon Ash
Rice straw
60.55–
78.07
6.93–16.75
14.11–
22.70
Migo (2019), Biswas et al. (2017),
Fu et al. (2012)
Rice husks
73.41
11.44
15.14
Biswas et al. (2017)
Corn cob
91.16
6.54
2.30
Biswas et al. (2017)
Wheat straw
83.08
10.29
6.63
Biswas et al. (2017)
Coffee hulls
77.50
11.00
11.5
Huang et al. 2011
Bamboo leaves 70.30
18.70
11.00
Huang et al. 2011
Sugarcane
bagasse
87.00
4.20
8.80
Huang et al. 2011
Sugarcane peel 77.30
10.10
12.60
Huang et al. 2011
M. C. Maguyon-Detras et al.
material to conduct or transfer heat (expressed in W m-K
−1
) (Capareda 2014).
According to Czernik (2010), biomass with large particle size has low thermal conductivity that results in slow heat and a mass transfer rate.
The chemical composition of the biomass may be used to evaluate the thermal
degradation of the biomass and residues/pollutants (i.e, ash, NOx, SOx), which may
be generated. Proximate analysis provides information on the behavior of the feedstock when it is heated (i.e., how much goes off as gas or vapors and how much
remains as fixed carbon). It includes the measurement of volatile matter, fixed carbon, and ash. Volatile matter (VM) is the material expelled from the biomass when
exposed to 950 °C for 7 min in an oxygen-free environment. It includes volatile
carbon, combined water, net hydrogen, nitrogen, and sulfur. VM is important in
thermal conversion since high amounts lead to more combustible gases during combustion or more gaseous (condensable and non-condensable) products during gasification and pyrolysis.
Fixed carbon (FC) is the material expelled after burning the moisture- and
VM-free biomass to 575 °C for 4 h until the material becomes grayish white
(Capareda 2014). FC fraction in the residual biomass usually increases as volatiles
are released during thermal degradation (Maguyon and Capareda 2013). Char, the
residue after pyrolysis, has typically high amounts of FC and ash. Ash is the residue
which remains after complete combustion of the feedstock which can be used for
other purposes such as cement aggregate replacement, fertilizer additive, etc. As can
be seen in Table 4.2, rice straw FC widely varies among different samples but the
range is comparable with other biomass used for thermal conversion such as rice
husk and wheat straw. Volatile content is relatively lower compared to other biomass
while ash content is relatively higher. Herbaceous biomass such as rice straw has
typically higher ash content (up to 25%) compared to woody biomass. This may be
attributed to the physiological ash, which results from intrinsic biomass properties
such as plant type, maturity and anatomical fractions. High ash contents result in
lower energy yields, catalyst impairment, and slag formation during thermal
Table 4.2 Proximate analysis of various biomass
Biomass
Components (% wt)
Sources
Volatiles
Fixed carbon Ash
Rice straw
60.55–
78.07
6.93–16.75
14.11–
22.70
Migo (2019), Biswas et al. (2017),
Fu et al. (2012)
Rice husks
73.41
11.44
15.14
Biswas et al. (2017)
Corn cob
91.16
6.54
2.30
Biswas et al. (2017)
Wheat straw
83.08
10.29
6.63
Biswas et al. (2017)
Coffee hulls
77.50
11.00
11.5
Huang et al. 2011
Bamboo leaves 70.30
18.70
11.00
Huang et al. 2011
Sugarcane
bagasse
87.00
4.20
8.80
Huang et al. 2011
Sugarcane peel 77.30
10.10
12.60
Huang et al. 2011
M. C. Maguyon-Detras et al.