oxycombustion is the obtaining of a high-purity, low-cost oxygen supply, in order
to save fuel and energy (Chen et al. 2012b).
In this context, photobioreactors could be the key to getting around this problem.
This equipment can provide substantial oxygen (O 2 ) concentrations through water
photolysis reactions during microalgae cultivation. In theory, it is possible to
generate on average 0.73 kg of O 2 for every 1 kg of CO 2 bioconverted, demonstrating the production potential of this substance in photobioreactors (Jacob-Lopes
et al. 2010, 2017).
In addition, these bioprocesses produce several volatile organic compounds
(VOCs), which have considerable energy value, besides releasing, in the photobioreactor exhaust gases, substantial concentrations of unconverted CO 2 , which
could improve the thermal performance of combustion systems (Jacob-Lopes and
Franco 2013).
Therefore, in order to satisfy the oxygen supply required in oxycombustion
systems, a promising technological route has been developed through the integrated
bio-oxycombustion process. This bioprocess refers to the simultaneous production
of two metabolic bioproducts: O 2 and VOCs from the direct conversion of GHG.
These compounds are released with photobioreactor exhaust gases, which can be
subsequently integrated as oxidizers and gaseous fuels, respectively, in industrial
combustion processes. Furthermore, the unconverted CO 2 can be potentially used
as nitrogen diluent. With this in mind, the aim of this chapter is to present a
comprehensive overview of integrated bio-oxycombustion systems with
photobioreactors.
2 Fundamentals of the Oxycombustion
Carbon capture from large point source emitters is a fast-developing technology that
can mitigate the impact of anthropogenic CO 2 production. Oxycombustion has
proven to be a potential capture technology mainly due to its perceived superiority
in relation to efficiency and simplicity (Olajire 2010). Several authors have provided comprehensive information about the different aspects of oxycombustion
technology (Buhre et al. 2005; Wall et al. 2009; Toftegaard et al. 2010;
Scheffknecht et al. 2011; Chen et al. 2012a, b; Yin and Yan 2016; Khalil et al.
2017; Gładysz et al. 2017).
In a conventional combustion system, air is used as the oxidizer, and the coming
CO 2 from the flue gas is diluted by N 2 of air, resulting in a reduced CO 2 concentration per capture (about 15% v/v). In oxycombustion, a combination of
practically pure oxygen (usually 95% v/v) and recycled flue gas is used as the
oxidizer for burning the fuel. Such flue gas is composed mainly of CO 2 and H 2 O,
which is used to control the flame temperature in the burner and fill the volume
removed N 2 , ensuring that there is enough gas to carry heat through the system
(Stanger et al. 2015). Carbon dioxide concentration in the flue gases increases by
272
I. Aguiar Severo et al.
to save fuel and energy (Chen et al. 2012b).
In this context, photobioreactors could be the key to getting around this problem.
This equipment can provide substantial oxygen (O 2 ) concentrations through water
photolysis reactions during microalgae cultivation. In theory, it is possible to
generate on average 0.73 kg of O 2 for every 1 kg of CO 2 bioconverted, demonstrating the production potential of this substance in photobioreactors (Jacob-Lopes
et al. 2010, 2017).
In addition, these bioprocesses produce several volatile organic compounds
(VOCs), which have considerable energy value, besides releasing, in the photobioreactor exhaust gases, substantial concentrations of unconverted CO 2 , which
could improve the thermal performance of combustion systems (Jacob-Lopes and
Franco 2013).
Therefore, in order to satisfy the oxygen supply required in oxycombustion
systems, a promising technological route has been developed through the integrated
bio-oxycombustion process. This bioprocess refers to the simultaneous production
of two metabolic bioproducts: O 2 and VOCs from the direct conversion of GHG.
These compounds are released with photobioreactor exhaust gases, which can be
subsequently integrated as oxidizers and gaseous fuels, respectively, in industrial
combustion processes. Furthermore, the unconverted CO 2 can be potentially used
as nitrogen diluent. With this in mind, the aim of this chapter is to present a
comprehensive overview of integrated bio-oxycombustion systems with
photobioreactors.
2 Fundamentals of the Oxycombustion
Carbon capture from large point source emitters is a fast-developing technology that
can mitigate the impact of anthropogenic CO 2 production. Oxycombustion has
proven to be a potential capture technology mainly due to its perceived superiority
in relation to efficiency and simplicity (Olajire 2010). Several authors have provided comprehensive information about the different aspects of oxycombustion
technology (Buhre et al. 2005; Wall et al. 2009; Toftegaard et al. 2010;
Scheffknecht et al. 2011; Chen et al. 2012a, b; Yin and Yan 2016; Khalil et al.
2017; Gładysz et al. 2017).
In a conventional combustion system, air is used as the oxidizer, and the coming
CO 2 from the flue gas is diluted by N 2 of air, resulting in a reduced CO 2 concentration per capture (about 15% v/v). In oxycombustion, a combination of
practically pure oxygen (usually 95% v/v) and recycled flue gas is used as the
oxidizer for burning the fuel. Such flue gas is composed mainly of CO 2 and H 2 O,
which is used to control the flame temperature in the burner and fill the volume
removed N 2 , ensuring that there is enough gas to carry heat through the system
(Stanger et al. 2015). Carbon dioxide concentration in the flue gases increases by
272
I. Aguiar Severo et al.