Improved thermal shock performance of Al2O3–C refractories due to nanoscaled additives

http://skheiri.persiangig.com/1-s2.0-S0272884212012837-main.pdf

Nano-bonded refractory castables

This study presents a new lightweight periclase-magnesium alumina spinel castable (LPSC) for the working lining of steel ladles using porous periclase-spinel aggregates to replace conventional dense magnesia aggregates. The porous periclase-spinel aggregates were produced by an in-situ decomposition technique resulting in an apparent porosity of 23.3% and a median pore size of 5.66 μm. Scanning electron microscopy revealed a better porous aggregate/matrix interface bonding in the LPSC, which significantly improved its strength and thermal shock resistance. Additionally, the higher amount of micropores of the porous aggregates in the LPSC absorbed more penetrated slag from the matrix, which enhanced the slag resistance. Thus, compared with conventional castables, the LPSC had a lower bulk density of 9.2–10.8% and a lower thermal conductivity of 18.8% (1000 °C) while at the same time a higher strength, thermal shock resistance and slag resistance was achieved.

Energy efficient lightweight periclase-magnesium alumina spinel castables containing porous aggregates for the working lining of steel ladles

In this study, the catalytic performance of the CeO2 promoted Ni-MgO-Al2O3 catalysts with different preparation methods was studied in carbon dioxide reforming of methane (CDRM) for the production of synthesis gas. The nitrogen adsorption/desorption (BET), X-ray diffraction (XRD), temperature-programmed reduction and oxidation (TPR and TPO), scanning electron microscopy (SEM) techniques were used to characterize the samples. The obtained results showed that the Ce addition to Ni-MgO-Al2O3 catalyst with the high specific surface area has a significant influence on the metal crystallite size, reduction properties, and coke deposition. The CeO2-Ni-MgO-Al2O3 catalyst with cerium content of 3 wt.% prepared by the impregnation method possessed the highest resistance against carbon formation in CDRM. In addition, the catalytic results confirmed that the feed ratio (CO2/CH4) and GHSV affected the catalytic activity. However, the CH4 and CO2 conversions improved when the cerium was added to Ni-MgO-Al2O3 catalysts.

CeO2 Promoted Ni-MgO-Al2O3 nanocatalysts for carbon dioxide reforming of methane

In gasifiers the reaction of a carbon feedstock with oxygen and water takes place to produce synthetic gas. The decrease of the operation temperature at the refractory lining by an innovative gasification technology permits the development of new chrome oxide free materials fulfilling economical as well as ecological aspects. Considering this aspect, spinel-containing refractory castables with increasing spinel content have been investigated according to their thermomechanical properties, phase formation as well as their resistance against corrosion attack by molten coal slag under gasification-similar conditions. In order to determine the influence of spinel and cement in the alumina-spinel castables, increasing spinel amounts and cement types has been added to alumina. In particular, MA-spinel cement has been applied. It has been shown, that the addition of MA-spinel cement to spinel-rich alumina improves the corrosion resistance against molten slag remarkably.

M.A.L. Braulio

Papers

Spinel-containing alumina-based refractory castables