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The chemical looping combustion (CLC) process involves the combustion of gaseous fuel through heterogeneous chemical reaction with the oxygen carriers, usually granular metal oxides, in the fluidized bed fuel reactor. It has been recognized that the reaction kinetics of granular metal oxide in the fuel reactor affects the gas−solid flow behavior significantly. This work explores the improvement in one of the most widely adopted kinetic models describing the reduction kinetics, the "chemical control shrinking core model", in which oxide oxygen carriers are assumed to consist of spherical particles. In the analysis, the effects of gas diffusion in the product layer and geometrical irregularity of the oxygen carrier particles on the reaction kinetics are negligible. The work presented in this paper attempts to account for the effects of the gaseous reactant diffusion and particle shape on reaction kinetics by modifying the kinetic model so as to achieve better prediction of the conversion rate in the reduction for the oxygen carriers. The nondimensional form of the derived kinetic model is also discussed. A semiempirical relation is proposed to account for the effect of diffusion changes on the conversion during the reaction. The modeling results have clearly shown that inclusion of the gas diffusion in porous particles can provide better prediction of the reaction kinetics, especially the time for the complete conversion. The shape factor also has a noticeable influence on the conversion rate of oxygen carriers and the time for complete conversion.
Mobile laser scanning (MLS) has been widely used in three-dimensional (3D) city modelling data collection, such as Google cars for Google Map/Earth. Building Information Modelling (BIM) has recently emerged and become prominent. 3D models of buildings are essential for BIM. Static laser scanning is usually used to generate 3D models for BIM, but this method is inefficient if a building is very large, or it has many turns and narrow corridors. This paper proposes using MLS for BIM 3D data collection. The positions and attitudes of the mobile laser scanner are important for the correct georeferencing of the 3D models. This paper proposes using three high-precision ultra-wide band (UWB) tags to determine the positions and attitudes of the mobile laser scanner. The accuracy of UWB-based MLS 3D models is assessed by comparing the coordinates of target points, as measured by static laser scanning and a total station survey.
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