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The performance of an oxygen carrier for Chemical Looping Combustion varies with the support material used. NiO oxygen carriers were prepared using 60 or 70 wt% NiO and different raw support materials (γ-Al2O3, pseudoboehmite, α-Al2O3, γ-Al2O3 mixed with MgO, hydrotalcite, MgAl2O4, and γ-Al2O3 with added graphite) by the mechanical mixing method. Reactivity tests were conducted using a thermogravimetric analyzer (TGA) at 950˚C. The oxygen carriers prepared using γ-Al2O3, γ-Al2O3 mixed with a small amount of MgO, hydrotalcite, and MgAl2O4 showed high oxygen transfer capacity, high oxygen utilization, and a high oxygen transfer rate. Graphite addition to γ-Al2O3 did not increase the surface area or reactivity. The use of pseudoboehmite as a support led to a significant decrease in oxygen transfer capacity and severe agglomeration of the oxygen carriers during the redox reaction. The increase in MgO content in the raw support materials decreased the reduction reactivity. The oxygen carriers prepared with α-Al2O3 showed less oxygen transfer capacity than the other oxygen carriers. The differences in the reactivity according to the support type were explained by the relative strength of NiO-support interaction obtained from the temperature-programmed reduction analysis. The reactivity test results in this work indicate that γ-Al2O3 and hydrotalcite could be desirable raw support materials to prepare highly reactive NiO oxygen carriers with high NiO content. Les performances des materiaux transporteurs d’oxygene varient en fonction du support utilise dans le procede de combustion en boucle chimique. Differents materiaux a base d’oxyde de Nickel ont ete synthetises avec des concentrations elevees en NiO, comprises entre 60 et 70 %, sur differents supports (γ-Al2O3, pseudobohemite, α-Al2O3, γ-Al2O3 melangee avec MgO, hydrotalcite, MgAl2O4 et γ-Al2O3 additivees avec du graphite) par melange mecanique. Des tests de reactivite ont ete conduits dans une thermobalance (ATG) a 950˚C. Les materiaux supportes avec γ-Al2O3, γ-Al2O3 melangee avec MgO, l’hydrotalcite et MgAl2O4 ont une capacite de transfert d’oxygene elevee et une reactivite elevee. L’addition de graphite dans l’alumine γ n’ameliore ni la surface specifique ni la reactivite. Avec la pseudo-bohemite, on observe une decroissance de la capacite de transfert d’oxygene et l’agglomeration du materiau pendant la phase de reduction. L’ajout de MgO conduit a une baisse de la reactivite en reduction. Avec l’alumine α, la capacite de transfert est reduite. Les differences de reactivite peuvent etre expliquees par les interactions entre NiO et le support, a partir d’analyses en reduction par temperature programmee. Les tests de reactivite conduits dans cette etude suggerent que les supports a base de γ-Al2O3 et d’hydrotalcite sont les plus appropries pour preparer les transporteurs d’oxygene contenant de l’oxyde de Nickel a haute concentration pour la combustion en boucle chimique.

The theoretical model for the analysis of grounding system encased in the foundation region in a horizontal muitilayer soil is presented. By means of fictitious conductivity concept, the effects of foundation are replaced by a set of equivalent current sources. The analysis of grounding system can be carried out by combining the moment method with additional equivalent current sources. The main advantage of the proposed approach is that it can be linked with the existing codes easily. The results are compared with those found in the literature and obtained by other popular software. Index Terms--Fictitious conductivity, foundation grounding, integral equation, method of moment (MoM).