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This paper presents the modeling and simulation of an industrial-scale chemical looping combustion (CLC) power plant, including all process units (reactors, flue gas treatment units, heat integration, steam cycle, and CO2 compression train). A model of a 525 MWth CLC power plant was built using a rigorous representation of the solid fuel and oxygen carrier. Petcoke was considered the main fuel of interest in this study, and it is compared with other solid fuels. The flue gas compositions obtained with the model show that cleanup units are mandatory to comply with CO2 quality requirements. High levels of flue gas treatment, including 97.1% deNOx and 99.4% deSOx, are needed to achieve typical specifications for captured CO2. This is mainly due to the high level of contaminants in the fuel, but also to the absence of nitrogen in the CLC flue gas, thus resulting in higher concentrations for all substances. The high level of flue gas treatment is thus one of the important challenges for solid fuel combustion in CLC. The overall CO2 capture efficiency of the plant is estimated to be as high as 94%. Regarding the energy balance, a process net efficiency of 38% is obtained. Comparing the results with other available technologies shows that CLC exhibits one of the highest net plant efficiencies and carbon capture rates. CLC is thus a promising technology to produce clean energy from solid fuels. Finally, based on a sensitivity analysis, it is shown that process efficiency is mainly affected by the design and performance of the CLC furnace, the steam injection rate in the fuel reactor, the char separation efficiency, and the excess oxygen in the air reactor., SCOPUS: ar.j, info:eu-repo/semantics/published

Predicting bubble properties in fluidized beds is of high interest for reactor design and modeling. While bubble sizes and velocities for low velocity bubbling fluidized beds have been examined in several studies, there have been only few studies about bubble behavior at superficial gas velocities up into the turbulent regime. For this reason, we performed a thorough investigation of the size, shape and velocity of bubbles at superficial gas velocities ranging from 0.18 m/s up to 1.6 m/s. Capacitance probes were used for the determination of the bubble properties in three different fluidized bed facilities sized of 0.1 m, 0.4 m and 1 m in diameter. Particles belonging to Geldart’s group B (Sauter mean diameter: 188 µm, solid density: ρs = 2600 kg/m3) were used. Correlations for the determination of bubble phase holdup, vertical bubble length and bubble velocity are introduced in this work. The shape of bubbles was found to depend on superficial gas velocity. This implies that at large superficial gas velocities the horizontal size of a bubble must be much smaller in comparison to its vertical size. This leads to a decrease of pressure fluctuations, which is observed in the literature as a characteristic of transitioning into a turbulent regime., Predicting bubble properties in fluidized beds is of high interest for reactor design and modeling. While bubble sizes and velocities for low velocity bubbling fluidized beds have been examined in several studies, there have been only few studies about bubble behavior at superficial gas velocities up into the turbulent regime. For this reason, we performed a thorough investigation of the size, shape and velocity of bubbles at superficial gas velocities ranging from 0.18 m/s up to 1.6 m/s. Capacitance probes were used for the determination of the bubble properties in three different fluidized bed facilities sized of 0.1 m, 0.4 m and 1 m in diameter. Particles belonging to Geldart’s group B (Sauter mean diameter: 188 µm, solid density: ρs = 2600 kg/m3 were used. Correlations for the determination of bubble phase holdup, vertical bubble length and bubble velocity are introduced in this work. The shape of bubbles was found to depend on superficial gas velocity. This implies that at large superficial gas velocities the horizontal size of a bubble must be much smaller in comparison to its vertical size. This leads to a decrease of pressure fluctuations, which is observed in the literature as a characteristic of transitioning into a turbulent regime.

This study explores the effects of rotational mechanisms on the characteristics of the leading edge vortex (LEV) by comparing translating and revolving flexible wings that are started from rest. Tomographic particle image velocimetry (tomographic-PIV) technique was employed to acquire three-dimensional flow fields for the revolving wings, while planar flow fields for the case of translating wings were acquired via 2D2C-PIV measurements. The comparison of flow fields between the two motion kinematics reveals similar behavior of the vortical structures yet the LEV circulation in the translating wings has higher values. The LEV centroid in the revolving cases stays above the leading edge, while in the translating wings, it always remains at a lower position. The effect of high flexibility results in the retention of LEV closer to the wing surface for both cases., Aerodynamics

This study explores the effects of rotational mechanisms on the characteristics of the leading edge vortex (LEV) by comparing translating and revolving flexible wings that are started from rest. Tomographic particle image velocimetry (tomographic-PIV) technique was employed to acquire three-dimensional flow fields for the revolving wings, while planar flow fields for the case of translating wings were acquired via 2D2C-PIV measurements. The comparison of flow fields between the two motion kinematics reveals similar behavior of the vortical structures yet the LEV circulation in the translating wings has higher values. The LEV centroid in the revolving cases stays above the leading-edge, while in the translating wings, it always remains at a lower position. The effect of high flexibility results in the retention of LEV closer to the wing surface for both cases., Aerodynamics

Increasing number of air travellers in recent years and the emergence of multi-airport cities throughout the world has made the behaviour of travellers regarding the choice of the origin airport even more important. Analysis of this behaviour helps for a better future planning and development of competing airports as an important element of their demand prediction. In this paper, particular emphasis is stressed on the behaviour of resident and non-resident passengers in choosing between the origin airport through the empirical case study of the two airports of Tehran multi-airport system, namely Imam Khomeini (IKIA) and Mehrabad International Airport (MIA) in Iran. The 24- hour and one-week survey was conducted in May 2011 and a total number of 2980 questionnaires were collected from the two airports. Binary Logit was used to model the origin airport choice of resident and non-resident travellers from the city of Tehran. Results show that the difference in the two groups is affected by “age”, “Income”, “Travel Destination”, “Trip Purpose” and “Marital Status”. Further model results show that variables “Public Access”, “Flight Frequency” and “Airport Tax” are more important for non-resident air travellers in choosing their origin airport.