a simultaneous decrease in furnace gas flow around the product. Considering an
oxycombustion furnace operating at a temperature of 1000 °C, and combustion air
composed of 95% oxygen, fuel reduction is about 68%. This shows a fuel saving of
approximately 35% in relation to a conventional combustion system. Additionally,
the control of parameters such as air supply (fuel/air ratio), removal of combustion
gases, carrier gas velocity, vapor pressure, and oxygen purity assists in fuel supply
to achieve optimum energy efficiency in the furnace.
The remarkable advantages of oxycombustion show the feasibility of its
implementation in power generation industries, despite their current operation only
on pilot-scale. Meantime, original research and review articles have highlighted
many barriers associated with the main operating parameters of the technology,
which must be overcome to achieve industrial scale, as shown in Table 3.
4 Oxygen Produced by Photosynthesis
Green plants and photosynthetic microorganisms, such as cyanobacteria and
microalgae, perform photosynthesis. Commonly, it is necessary mainly CO 2 , which
is converted into organic compounds, and light energy to carry out photosynthesis,
releasing oxygen molecules and water through a sequence of different chemical
reactions in distinct cellular compartments. This mechanism can be subdivided into
two stages: light reactions or photochemical step, which occur only when the cells
are illuminated, and dark reactions or carbon fixation step, which are not directly
influenced by light, also occurring in the dark (Fay 1983).
During photosynthesis, more specifically in light reactions, there is the formation
of highly energetic compounds, such as ATP (adenosine triphosphate) and NADPH
Table 2 Heating value, oxygen supply, and estimated CO 2 emissions for combustion of different
fuels (Griffiths and Barnard 1995; Cengel 2003)
Fuel
Heating value
(MJ/kg)
O 2 supply
kg O2 =kg fuel
À
Á
CO 2 emissions
kg fuel =kg CO2
À
Á
Methane
50.00
2.00
2.75
Ethane
47.80
3.73
1.46
Propane
46.35
3.63
1.00
Butane
45.75
3.58
0.75
Ethanol
27.70
2.08
0.95
Natural gas
47.00
2.11
2.63
Gasoline
44.40
3.50
0.38
Diesel oil
43.40
3.46
0.19
Petroleum coke
29.00
2.69
3.30
Coal
23.00
2.50
2.89
278
I. Aguiar Severo et al.
oxycombustion furnace operating at a temperature of 1000 °C, and combustion air
composed of 95% oxygen, fuel reduction is about 68%. This shows a fuel saving of
approximately 35% in relation to a conventional combustion system. Additionally,
the control of parameters such as air supply (fuel/air ratio), removal of combustion
gases, carrier gas velocity, vapor pressure, and oxygen purity assists in fuel supply
to achieve optimum energy efficiency in the furnace.
The remarkable advantages of oxycombustion show the feasibility of its
implementation in power generation industries, despite their current operation only
on pilot-scale. Meantime, original research and review articles have highlighted
many barriers associated with the main operating parameters of the technology,
which must be overcome to achieve industrial scale, as shown in Table 3.
4 Oxygen Produced by Photosynthesis
Green plants and photosynthetic microorganisms, such as cyanobacteria and
microalgae, perform photosynthesis. Commonly, it is necessary mainly CO 2 , which
is converted into organic compounds, and light energy to carry out photosynthesis,
releasing oxygen molecules and water through a sequence of different chemical
reactions in distinct cellular compartments. This mechanism can be subdivided into
two stages: light reactions or photochemical step, which occur only when the cells
are illuminated, and dark reactions or carbon fixation step, which are not directly
influenced by light, also occurring in the dark (Fay 1983).
During photosynthesis, more specifically in light reactions, there is the formation
of highly energetic compounds, such as ATP (adenosine triphosphate) and NADPH
Table 2 Heating value, oxygen supply, and estimated CO 2 emissions for combustion of different
fuels (Griffiths and Barnard 1995; Cengel 2003)
Fuel
Heating value
(MJ/kg)
O 2 supply
kg O2 =kg fuel
À
Á
CO 2 emissions
kg fuel =kg CO2
À
Á
Methane
50.00
2.00
2.75
Ethane
47.80
3.73
1.46
Propane
46.35
3.63
1.00
Butane
45.75
3.58
0.75
Ethanol
27.70
2.08
0.95
Natural gas
47.00
2.11
2.63
Gasoline
44.40
3.50
0.38
Diesel oil
43.40
3.46
0.19
Petroleum coke
29.00
2.69
3.30
Coal
23.00
2.50
2.89
278
I. Aguiar Severo et al.