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Power Generation and Refrigeration
Published in Marc J. Assael, Geoffrey C. Maitland, Thomas Maskow, Urs von Stockar, William A. Wakeham, Stefan Will, Commonly Asked Questions in Thermodynamics, 2022
Marc J. Assael, Geoffrey C. Maitland, Thomas Maskow, Urs von Stockar, William A. Wakeham, Stefan Will
However, there are also some significant practical challenges. Identifying optimal and practically viable redox systems for chemical looping combustion is one of the biggest challenges for this technology. The main constraints are the metallurgical limits of materials operating at the high temperatures set by Tc,ox and the thermal stability and volatility of the oxides. In general, Tc,ox increases with the boiling point of the elements, so that systems that best meet the metallurgical constraints are quite volatile with less stable oxides. Cadmium was an early contender for a viable system but its toxicity and high cost make it an unlikely practical system. Zinc by contrast is non-toxic and much cheaper, with a reasonable balance of Tc,ox and Tc,red, so it is a more attractive option.
Trigeneration Systems
Published in Sotirios Karellas, Tryfon C. Roumpedakis, Nikolaos Tzouganatos, Konstantinos Braimakis, Solar Cooling Technologies, 2018
Sotirios Karellas, Tryfon C. Roumpedakis, Nikolaos Tzouganatos, Konstantinos Braimakis
Wang and Fu (2016) carried out a thermodynamic analysis of a solar-hybrid trigeneration system integrated with methane chemical-looping combustion. The process of chemical-looping combustion occurs without the reaction of air with fuel. It is a technology that is used for capturing CO2 at decreased energy consumption ranges. The system proposed by the authors involved CaS and CaSO4 materials for the chemical-looping system. A number of parametric investigations were carried out in order to estimate the energy and exergy efficiencies at different design conditions and variable operation parameters. The authors estimated that the optimal solar heat collection temperature was equal to 900°C, and that the optimal pressure ratio of the compressor used for the chemical looping was equal to 20. The optimized energetic and exergetic efficiencies of the system were equal to 67% and 55%, respectively. Lastly, the authors remarked that additional research in the fields of CO2 capture and utilization and solar heat storage is necessary in order to improve its feasibility and stability.
Natural Gas Reforming to Industrial Gas and Chemicals Using Chemical Looping
Published in Subhas K Sikdar, Frank Princiotta, Advances in Carbon Management Technologies, 2020
Dawei Wang, Yitao Zhang, Fanhe Kong, L-S Fan, Andrew Tong
Chemical looping processes using a metal-based oxygen carrier to perform redox reaction with a carbon-based fuel can be categorized into 2 types of systems: Chemical looping combustion (CLC) for power generation with CO2 capture and chemical looping reforming (CLR) for chemical and industrial gas production. The Lewis and Gilliland process represents a CLC system where the carbon fuel is fully oxidized to CO2. CLR systems can be further divided based on the product from the CLR reactor. The Lane Producer and HYGAS processes represent CLR processes for H2 production. The DuPont VPO and ARCO processes each represent CLR for selective oxidation systems where the metal oxide oxygen carrier serves to selectively oxidize the reactants to a desired product. CLR for syngas production systems represent chemical looping processes where a carbon-based gaseous fuel, such as natural gas, is partially oxidized to syngas (Fan et al., 2015; Luo et al., 2014; Ryden et al., 2008; Nalbandian et al., 2011; Dai et al., 2006). CLR for selective oxidation systems rely on a multifunctional metal oxide, which possesses catalytic and oxygen transfer properties, to selectively convert hydrocarbon feedstock to chemicals. In the reducer reactor, a catalytic metal oxide reacts with a hydrocarbon feedstock to selectively produce chemicals and reduced catalytic metal oxide. In the combustor reactor, the reduced catalytic metal oxide is regenerated by oxidation with air (Keller and Bhasin, 1982; Contractor, 1999). By directly producing chemicals in the reducer, the generation of syngas as an intermediate is not necessary. A simplified flow diagram of CLR is shown in Figure 1.
A review of application and development of combustion technology for oil sludge
Published in Journal of Environmental Science and Health, Part A, 2022
Zhiqiang Gong, Haoteng Zhang, Yonglong Juan, Lingkai Zhu, Wei Zheng, Junqi Ding, Maocheng Tian, Xiaoyu Li, Jianqiang Zhang, Yizhi Guo, Guoen Li
Chemical looping combustion is a new type of flameless combustion technology, in which the chemical reaction of traditional combustion is broken down into two separate gas/solid redox reactions with the help of oxygen carrier. The fuel has no direct contact with the air, and the oxygen in the air is transferred to the fuel through oxygen carrier. Since the gas products of chemical looping combustion contain only CO2 and water vapor, and the concentration of CO2 is very high. CO2 with a high purity can be obtained by simple cooling and drying. In addition, since the reaction temperature is relatively low and the fuel is not in contact with air, the thermal NOx and rapid NOx are not produced, and production of fuel NOx are inhibited. Therefore, chemical looping combustion is also a clean combustion method to control NOx emission.[129]
Exergy cascade release pathways and exergy efficiency analysis for typical indirect coal combustion processes
Published in Combustion Theory and Modelling, 2019
Qiuhui Yan, Tiantian Lu, Jieren Luo, Yanwan Hou, Xiaohong Nan
Chemical-looping combustion technology can capture CO2 before, after and during combustion according to the need, directly or indirectly obtain electricity, syngas, hydrogen and a variety of chemicals, and the generated CO2 will not be diluted by N2, and the separation of CO2 does not require any energy. Shen et al. investigated a chemical looping combustion process for coal using inter-connected fluidised beds with inherent separation of CO2 [47]. Results show that the CO2 capture efficiency will reach its equilibrium of 80% at the fuel reactor temperature of 960°C. The separation efficiency is high and the energy consumption is low, so Chemical-looping combustion has a good economic benefit.