Chemical Looping Combustion

Chemical looping combustion (CLC) is an encouraging technology for hydrogen and power co-generation with efficient CO2 capture. Utilization of the captured CO2 is a much more important task to realize negative CO2 emissions. The objective of the work is to explore a case study of carbon dioxide utilization (CDU) in the form of formic acid synthesis using the captured CO2 and co-generated H2 from coal direct chemical looping (CDCL) power plant. Steady-state simulations are performed on the power and H2 co-generation CDCL plant integrated with formic acid synthesis and presented a comparison of overall performance of the CDCL plants with and without CDU integration. The simulation results revealed that the formic acid synthesis integrated CDCL plant avoids release of 62.49 kg.CO2/GJ of fuel input into the environment and utilizes the captured CO2 completely with the net electrical efficiency penalty of 5.8%.

Mitigate the degree of technological obsolescence on combustion and heating systems due to industrial processes, imply the necessity to venture, analyze, adopt and adapt new technologies, characterized by high efficiency, productivity and low environmental impact. The predesign of a lab scale batch fluidized bed reactor was made, based on scientific research data related to chemical looping combustion, chemical looping reforming and desulfurization of coal with limestone. It was conceived determining the varying operation conditions at which the solid oxygen carrier would suffer in a continuous CLC process.
The development of the model is featured by the solid bed particles (OC) which better works for the studied reactions and the supply of gas streams. The correlations used for the equipment specification were reported based on the parameters defined for batch fluidized bed reactors and the kunii-Levenspiel model.
Finally, the possible configurations were analyzed varying the reactor diameter from 0.05 – 0.07 m; the aim of the project is to select a configuration that meets the minimum criteria to operate independently the three reaction systems (Chemical Looping Combustion, Chemical Looping Reforming and Desulfurization of coal with limestone) under the fixed operation conditions and rules of thumb of batch fluidized beds in the equipment design activity.

Key Words:

Batch Fluidized bed reactor
CLC
OC
CLR
Desulfurization of coal with limestone

Nine different concepts for natural gas fired power plants with CO2 capture have been investigated, and a comparison is made based on net plant efficiency and emission of CO2. The cycles are one post-combustion, six oxy-fuel and two pre-combustion capture concepts. A 400MW combined cycle plant is applied as a reference case. A common basis for the comparison of all

Integrating biomass energy generation with carbon capture will result in "car-bon neutral" to "carbon negative" technology. Countries like India and China possess significant reserves of limestone. Calcium looping (CaL) technology can prove to be a promising option for carbon capture in these countries. The present work aims at improving the performance of CaL-integrated biomass-fired power plant (BFPP) by exploring different looping configurations. In this study, (i) standalone BFPP, (ii) conventional CaL (single stage), and (iii) double CaL-integrated BFPP have been systematically evaluated. A comparative performance evaluation of these three plants in terms of energy, exergy and ecological assessment, has been carried out. A detailed parametric study and unit-wise exergy analysis of the best configuration among the three are presented to identify the scope for further improvement in efficiency and energy savings. KEYWORDS biomass power generation, carbon negative technology, calcium looping, CO 2 capture, energy analysis, exergy analysis, sugarcane bagasse, system integration 1 | INTRODUCTION Energy plays a very critical role in socioeconomic development of any country. The countries like China, India, and Brazil are emerging as major economies, and the energy demand in these countries are rising at a rapid pace. Figure 1 shows the energy consumption statistics from different fuel sources for these countries. 1 Biofuels and oils products are the major energy sources for India whereas for China, the primary sources of energy are coal and oil products. Figure 1 emphasizes that biofuels plays a substantial role in meeting the energy demand of these countries. At present, coal is the primary source of energy for India's electricity generation. As per the Energy Statistics report 2018, Indian coal-based thermal power plants contribute to about 70.83% (267.13 GW) of electricity generation. 2 Coal-based thermal power plants are associated with massive greenhouse gas (GHG) emissions. In order to limit climate change, India is adopting policies and exploring various carbon mitigation techniques including renewable energy production that will create additional carbon space by reducing GHG emissions intensity to 33% to 35% by the year 2030. 3 Hence, it is imperative to promote the use of renewable energy sources for various positive reasons 4 such as low GHG emissions, inexhaustible energy, stable energy prices, and grid independent electricity production that can easily reach out rural areas. 5

CO2 capture and storage from energy conversion systems is one option for reducing power plant CO2 emissions to the atmosphere and for limiting the impact of fossil-fuel use on climate change. Among existing technologies, chemical looping combustion (CLC), an oxy-fuel approach, appears to be one of the most promising techniques, providing straightforward CO2 capture with low energy requirements.This paper provides an evaluation of CLC technology from an economic and environmental perspective by comparing it with to a reference plant, a combined cycle power plant that includes no CO2 capture. Two exergy-based methods, the exergoeconomic and the exergoenvironmental analyses, are used to determine the economic and environmental impacts, respectively. The applied methods facilitate the iterative optimization of energy conversion systems and lead towards the improvement of the effectiveness of the overall plant while decreasing the cost and the environmental impact of the generated produc...

This review reports recent advances on chemical-looping combustion (CLC). CLC is a promising technology for fossil fuel combustion preventing CO2CO2 dilution with flue gases, mainly nitrogen. In CLC, the solid oxygen carrier supplies the stoichiometric oxygen needed for CO2CO2 and water formation, and this leads to a free nitrogen mixture. As a result, the requirement of CO2CO2 separation from flue gases, a major cost for CO2CO2 capture, is circumvented. Furthermore, formation of NOxNOx is also reduced. A good oxygen carrier for CLC shall readily react with the fuel gas and shall be reoxidized upon being contacted with oxygen. An oxygen carrier is typically formed by a metal oxide and an inert binder, which provide, respectively, oxygen storage, fluidizability and mechanical strength. Over the last 10 years, several research groups have been researching oxygen carriers which are both active and stable under fluidized bed conditions. While Fe, Ni, Cu, Mn and Co oxides are potential oxygen carrier materials, recent studies show that Ni is best suited for CLC. Few studies have been devoted to the solid-state kinetics of both reduction and oxidation with either a nucleation–nuclei growth or unreacted shrinking core models being considered. In order to implement CLC, two interconnected fluidized bed reactors (the fuel and air reactor) with the oxygen carrier circulated between units have been proposed. While reactor design, modeling and hydrodynamics are matters that have been analyzed by several research groups; these topics still require more attention and investigation. Preliminary economic assessments, have suggested that CLC holds great promise for combustion processes, having the potential for achieving very efficient and low cost CO2CO2 capture. Even with these favorable prospects, commercial scale-up of CLC still depends nowadays on the availability of highly performing and stable oxygen carriers.

In chemical looping combustion (CLC), a solid oxygen carrier circulates between two fluidised bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In this paper, CLC is integrated in a natural gas fired combined cycle (NGCC). In this system, nickel- and iron-based oxygen

Through continuous flow reactor experiments, materials characterization and theoretical calculations, we provide new insights into the reduction of hematite (α-Fe2O3) nanoparticles by methane (CH4) during chemical looping combustion (CLC). Across CLC-relevant temperatures (500 to 800 oC) and gas flowrates (2.5 to 250 h-1), decreasing α-Fe2O3 particle size (from 350 to 3 nm) increased the duration over which CH4 was completely converted to CO2 (i.e., 100% yield). We attribute this size-dependent performance trend to the greater availability of lattice oxygen atoms in the near-surface region of smaller particles with higher surface area-to-volume ratios. All particle sizes then exhibited a relatively rapid rate of reactivity loss that was size- and temperature-independent, reflecting a greater role for magnetite (Fe3O4), the primary α-Fe2O3 reduction product, in CH4 oxidation. Bulk (X-ray diffraction; XRD) and surface (X-ray photoelectron spectroscopy; XPS) analysis revealed that oxygen carrier reduction proceeds via a two-stage solid-state mechanism; -Fe2O3 reduction to Fe3O4 followed the unreacted shrinking core model (USCM) while subsequent reduction of Fe3O4 to wüstite (FeO) and FeO to iron metal (Fe) followed the nucleation and nuclei growth model (NNGM). Atomistic thermodynamics modeling based on density functional theory supports that reduction initiates via the UCSM, as partially reduced α-Fe2O3 surfaces exhibited a wide range of stability relative to bulk Fe3O4. Reduction and reoxidation cycling experiments were also performed to explore more practical aspects related to the long-term performance of unsupported -Fe2O3 nanoparticles as oxygen carriers for CLC.

A series of chemical-looping combustion (CLC) tests were conducted in a thermogravimetric analysis (TGA) reactor to investigate the potential of a Chinese sulfur-containing lean iron ore as the oxygen carrier. Two main products of solid-fuel pyrolysis and gasification, namely, CH 4 and CO, were selected as the reducing gases. Consecutive reduction−oxidation cycles were first carried out in the TGA reactor to evaluate the cyclic stability and agglomeration tendency of the oxygen carrier. The effects of the temperature, fuel gas concentration, and reaction gas composition on the reduction reaction were further investigated. Increasing the reaction temperature or fuel gas concentration enhanced the reduction rate and reaction degree of the oxygen carrier. Meanwhile, CO showed much higher reduction reactivity than CH 4. A comparison of the rate index of the iron ore used with those of high-grade minerals indicated that the iron ore had adequate reactivity for its application in solid-fuel CLC technology. The side reaction of carbon deposition was also discussed. Finally, the shrinking-core model with chemical reaction control was adopted to determine the chemical kinetics.

This paper presents part-load evaluation of a natural gas-fired chemical looping combustion (CLC) combined cycle with CO2 capture. The novel combined cycle employs an air-based gas turbine, a CO2-turbine and a steam turbine cycle. In this combined cycle, the CLC reactors replace combustion chamber of the gas turbine. The proposed combined cycle has a net plant efficiency of about 52.2% at full-load, including CO2 compression to 200bar. The part-load evaluation shows that reducing the load down to 60% results in an efficiency drop of 2.6%-points. However, the plant shows better relative part-load efficiency compared to conventional combined cycles. The pressure in CLC-reduction and -oxidation reactors is balanced by airflow control, using a compressor equipped with variable guide vanes. A combination of control strategies is discussed for plant start-up and shutdown and for part-load when airflow reduction is not practically possible with current generation of compressors. The results show that the combined cycle has a promising efficiency even at part-load; however, it requires an advanced control strategy.