57
4.5 Comparison of Thermal Conversion Technologies
Comparisons of thermal conversion methods will be discussed in this section based
on energy conversion, technological maturity, and potential environmental issues
that may arise from their operation.
4.5.1 Energy Conversion
The energy conversion efficiency, or thermal efficiency, is the ratio of the energy
generated from the fuel using the selected thermal conversion process and the net
calorific value of the fuel. The energy conversion efficiencies of thermal processes
are summarized in Table 4.7. On average, about a 60% energy conversion efficiency
can be achieved using rice straw as a biomass feedstock. In the study conducted by
Nam et al. (2015), energy recovery was accounted for the energy contained in the
three pyrolysis products. Higher energy recovery was recorded for char in the
bench-scale auger-type and fixed-bed pyrolyzer, while in the fluidized-bed reactor
bio-oil was the main energy product. Park et al. (2014) also reported that char contained most of the biomass energy recovered under slow pyrolysis. The energy efficiency for gasification, on the other hand, ranged from 52 to 61%, which is still
comparable with other thermal technologies. Lower energy yield was reported by
Darmawan et al. (2017); however, this result was obtained using a simulated process only.
Table 4.7 A comparison of thermochemical conversion technologies using rice straw
Thermal conversion
process
Scale
Rice straw
feed rate
Energy
conversion
efficiency, %
Reactor
temperature,
°C
Sources
Direct combustion
Bench
scale
20–
30 kg h
−1
60–85
300–500
Migo (2019)
Pyrolysis (using
batch and fluidized
bed reactors)
Bench
scale
N/A
64.6–75
500
Nam et al.
(2015)
Slow pyrolysis
Lab scale
N/A
80–90
>400
Park et al.
(2014)
Gasification (using
fluidized bad reactor)
Bench
scale
3.6–5.4
52–61
700–850
Calvo et al.
(2012)
Gasification (using
entrained flow and
torrefied biomass)
Simulated
process
12.4 t/h
43
1200
Darmawan
et al. (2017)
Gasification (in the
presence of K 2 CO 3 )
Lab scale
N/A
750
Baloch et al.
(2016)
4 Thermochemical Conversion of Rice Straw
4.5 Comparison of Thermal Conversion Technologies
Comparisons of thermal conversion methods will be discussed in this section based
on energy conversion, technological maturity, and potential environmental issues
that may arise from their operation.
4.5.1 Energy Conversion
The energy conversion efficiency, or thermal efficiency, is the ratio of the energy
generated from the fuel using the selected thermal conversion process and the net
calorific value of the fuel. The energy conversion efficiencies of thermal processes
are summarized in Table 4.7. On average, about a 60% energy conversion efficiency
can be achieved using rice straw as a biomass feedstock. In the study conducted by
Nam et al. (2015), energy recovery was accounted for the energy contained in the
three pyrolysis products. Higher energy recovery was recorded for char in the
bench-scale auger-type and fixed-bed pyrolyzer, while in the fluidized-bed reactor
bio-oil was the main energy product. Park et al. (2014) also reported that char contained most of the biomass energy recovered under slow pyrolysis. The energy efficiency for gasification, on the other hand, ranged from 52 to 61%, which is still
comparable with other thermal technologies. Lower energy yield was reported by
Darmawan et al. (2017); however, this result was obtained using a simulated process only.
Table 4.7 A comparison of thermochemical conversion technologies using rice straw
Thermal conversion
process
Scale
Rice straw
feed rate
Energy
conversion
efficiency, %
Reactor
temperature,
°C
Sources
Direct combustion
Bench
scale
20–
30 kg h
−1
60–85
300–500
Migo (2019)
Pyrolysis (using
batch and fluidized
bed reactors)
Bench
scale
N/A
64.6–75
500
Nam et al.
(2015)
Slow pyrolysis
Lab scale
N/A
80–90
>400
Park et al.
(2014)
Gasification (using
fluidized bad reactor)
Bench
scale
3.6–5.4
52–61
700–850
Calvo et al.
(2012)
Gasification (using
entrained flow and
torrefied biomass)
Simulated
process
12.4 t/h
43
1200
Darmawan
et al. (2017)
Gasification (in the
presence of K 2 CO 3 )
Lab scale
N/A
750
Baloch et al.
(2016)
4 Thermochemical Conversion of Rice Straw