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2 to Basic Chemicals and Fuels
Published in Ashok Kumar, Swati Sharma, 2 Utilization, 2020
Saeed Sahebdelfar, Maryam Takht Ravanchi
Basically, CO2 capture can be classified into four main types: (i) pre-combustion, (ii) post-combustion, (iii) oxy-fuel combustion, and (iv) chemical looping combustion (CLC) capture (Cuellar-Franca and Azapagic, 2015). In the pre-combustion method, the fuel is first reformed to syngas (CO+H2), then treated by WGS, followed by the removal of CO2 (>20%, which facilitates its separation) and combustion of H2. Post-combustion capture involves the removal of CO2 from the flue gas (typically 3%–15% CO2) as in the conventional energy generation systems. In the oxy-fuel combustion process, the fuel (coal) is burnt with nearly pure O2 (>95%) mixed with steam or recycled flue gas (RFG).
Power-to-fuel
Published in Anoop Kumar Shukla, Onkar Singh, Meeta Sharma, Rakesh Kumar Phanden, J. Paulo Davim, Hybrid Power Cycle Arrangements for Lower Emissions, 2022
Alper Can Ince, Can Ozgur Colpan, Mustafa Fazıl Serincan
The integration of the CO2 capture process into a plant becomes a significant environmental and engineering task to reduce CO2 emission that comes from flue gas. In fact, the plant integrated with the capture process leads to producing more CO2 per kWh when compared to the power station without the capture process. However, more than 85% of the CO2 can be captured (Kanniche et al. 2010). The CO2 capture strategies from flue gas can be classified according to the location of conversion where the carbon source (e.g., fuel, raw material) converts the CO2 rich gas such as post-conversion, pre-conversion, and oxy-fuel combustion (Mondal, Balsora, & Varshney 2012). The CO2 capture process is followed by separation techniques such as absorption, membrane, cryogenic separation, adsorption, and chemical looping to obtain pure CO2 (Song et al. 2018). The key comparison for these techniques is presented in Table 13.3. One of the important disadvantages of CO2 capture techniques is the requirement of high energy and thus, total plant energy efficiency is reduced significantly. Here, the membrane separation technique offers lower energy requirements, while the cryogenic separation technique is challenging in terms of high energy penalty. Moreover, the membrane technique suffers from high capacity and stability. In the absorption technique, solvent degradation, corrosion, and high cost are the main problems. One of the most mature processes is the pre-combustion process where the CO2 is captured after following two different routes: steam reforming or partial oxidation and water-gas shift reaction. Then, CO2 is separated through the solvents. Another important process is the post-combustion process, where CO2 is captured after the combustion of fossil fuels. In the oxy-fuel combustion process, the combustion of fuel is done with pure oxygen to produce high CO2 rich gas. The process is followed by condensation to obtain CO2. Several reviews studies that address CO2 capture process such as pre-combustion (Babu et al. 2015; García et al. 2011; Jansen et al. 2015), post-combustion (Samanta et al. 2012; Y. Wang et al. 2017), and oxy-fuel combustion (Habib et al. 2011; Wu et al. 2018) have been published in the last decade.
Numerical Investigation of the Effect of CO2/H2O Composition in Oxidizer on Flow Field and Combustion Behavior of Oxy-pulverized Coal Combustion
Published in Combustion Science and Technology, 2021
The oxy-fuel combustion process is associated with steam enrichment during flue gas recycling. The steam volume concentration in the range of 22 and 37 vol % are found in recycled flue gas for dry and wet recycle oxy-fuel combustion, respectively (Becher et al. 2011). Under dry recycle mode of oxy-fuel combustion, moisture from the flue gas is removed. Wet recycle oxy-fuel combustion mode utilizes recycled flue gas without prior removal of moisture. Carlos and Seepana and Jayanti (Carlos 2007; Seepana and Jayanti 2010) proposed oxy-steam variant of oxy-coal combustion technology, in which whole recycled flue gas is replaced with pure steam. In oxy-steam combustion, high temperature produced by combustion is moderated by steam rather than CO2. The recycle system is not necessary for oxy-steam combustion. Based on its compact system configurations and more CO2 capture efficiency, oxy-steam combustion technology is regarded as next-generation oxy-fuel combustion technology.
Thermal decomposition and kinetic modeling of torrefied Cryptomeria japonica in a CO2 environment
Published in Biofuels, 2018
Kanit Manatura, Jau-Huai Lu, Keng-Tung Wu
Few studies have been conducted using CO2 as the environment gas in pyrolysis [see 9]. Carbon dioxide has not been used very often and may offer some advantages: (1) CO2 can be recycled from carbon capture technologies without any net impact on greenhouse gas emissions [10]; (2) CO2 can replace N2 in a typical oxy-fuel combustion process, affecting the behaviors of coal combustion including coal devolatilization, ignition, char burnout, and ash transformation [11]; (3) flue gas from oxy-fuel combustion contains abundant CO2 content (at a temperature of about 500°C) that can be recirculated into the gasification chamber to enhance the overall process efficiency. Additionally, using CO2 as an agent gas in syngas production may increase the carbon conversion rate and reduce the formation of tar [12,13].