Addition Of Magnesite Research Articles

Study of Dendromass Ashes Fusibility with the Addition of Magnesite, Limestone and Alumina

The fusibility of ash from woodchip combustion is characterised in the present work. The impact of the increase in MgO, CaO, and Al2O3 content in the bio-ash on the classification of ash into categories according to slagging and fouling indices was evaluated. The ash was characterized based on the chemical composition using slagging and fouling indices. However, these ash composition changes did not assign the ash into categories of the indices FU, SR, RS, and B/A (fouling, slagging, slag viscosity, basicity), with less ash inclination to slagging and fouling. The indices were primarily derived for ashes from coal combustion. The indices values characterizing the ash were compared with measured results of ash melting according to STN ISO 540. The measured ash fusibility values showed that the addition of magnesite, limestone, and alumina to dendro-ashes increases the DT (temperature of deformation), HT (temperature of hemisphere), and the AFI (ash fusibility index). There is no conformity between the values of the indices and the measurement of ash fusibility temperatures. In terms of temperatures in the combustion chamber, the measured sintering (Tsin) and DT are suitable for evaluating the tendency of ash to slagging and fouling as well as an accretion of ash particles sticking to the lining.

Preparation and characterization of solar absorption and thermal storage integrated ceramics from calcium and iron-rich steel slag

Solar absorption and thermal storage integrated ceramics (SATS ceramics) are new thermal storage materials that directly absorb sunlight, which improve the solar-to-thermal conversion efficiency. In this paper, SATS ceramics were developed by using calcium and iron-rich steel slag as the starting material. On the basis of composition characteristics of steel slag and performance requirements of SATS ceramics, the target phases of magnesioferrite spinel (MgFe2O4) and monticellite (CaMgSiO4) were designed and successfully synthesized in the SATS ceramics by the addition of magnesite and quartz. Phase composition, microstructure, physical properties, thermal shock resistance, solar absorptance and thermal storage performance were investigated. The results show that SATS ceramics with the addition of magnesite and quartz possess better properties than the ceramics prepared from 100 wt% steel slag. Particularly, the solar absorptance and thermal storage density of the SATS ceramics with the target phase of MgFe2O4 are 84.7% and 1057.57 kJ kg−1 (25–800 °C), which increased by 3.04% and 21.87% compared to reference sample, respectively. In addition, it still presents higher strength of 64.83 MPa after 30 thermal shock cycles (25–800 °C) than the other samples, indicating good thermal shock resistance. Surprisingly, the utilization rate of steel slag reaches up to 97.89 wt%. This work not only develops a low-cost SATS ceramics, but also provides a new high-value utilization approach to steel slag.

Kaolinite-Magnesite Based Ceramics. Part I: Surface Charge and Rheological Properties Optimization of the Suspensions for the Processing of Cordierite-Mullite Tapes

The present study aimed at investigating the influence of the concentration of sodium silicate and sodium hexametaphosphate on the dispersion of an aqueous kaolinitic clay slurry regarding further use for the tape casting process. The zeta potential of the kaolinitic clay slurry matched the requirements for tape casting. The addition of magnesite in the kaolinitic slurries tended to increase the zeta potential towards the required limit values. Despite this, the further addition of surfactants allowed improving the zeta potential in agreement with the tape casting conditions. Accordingly, the rheological behavior, under continuous and oscillatory flow conditions, of various mixtures of magnesite and a kaolinitic clay was studied. Regarding the pH and the zeta potential measurements, the E–F attraction prevailed at low pH value, and F–F or E–E attraction was predominant at high pH value. All slurries exhibited a shear thinning behavior, which was well-correlated by the Herschel–Bulkley model. It appeared that the best stability for the kaolinitic clay slurries was obtained while using 0.4 mass% and 1.2 mass% of sodium hexametaphosphate and sodium silicate, respectively. An increase in the magnesite concentration above 6 mass% led to a complex behavior with low cohesion energy due to the occurrence of soluble complexes.

Improvement of Oxidizing Roasting of Molybdenite Concentrate by Addition of Magnesite

The results of the thermodynamic modeling are presented for oxidizing roasting of refractory molybdenite (MoS2) with magnesite (MgCO3). The phase and chemical compositions of the MoS2–MgCO3–O2 system and its changes are determined depending on the temperature and quantity of the additive agent. The modeling reveals feasibility of thermochemical decomposition of molybdenite with the formation of waterand soda-soluble compounds MgMoO4 and MgSO4, which is an evidence of efficiency of magnesium carbonate in the capacity of an additive agent. The optimal conditions of the thermochemical decomposition of molybdenite determined theoretically from thermodynamic calculations are proved experimentally.

Improvement of Oxidizing Roasting of Molybdenite Concentrate by Addition of Magnesite

Improvement of Oxidizing Roasting of Molybdenite Concentrate by Addition of Magnesite

Refractory Porous Materials Based on Secondary Resources and Phosphate Compounds

Results are provided for a study of porous ceramic materials prepared in the course of chemical and exothermic reactions based on a system containing secondary resources (chamotte scrap, mullite-containing waste, aluminum smelting slag), aluminium phosphate binder, aluminum refractory clay, and various additives. Temperature dependences are established for heat capacity and thermal conductivity in the range 30 – 1000°C for the material obtained. It is shown that the optimum overall aluminum and slag content in a mixture for preparing porous materials is 10 – 20%. It is established that addition of magnesite and chrome-magnesite, and also ammonium dihydrophosphate, makes it possible to control density and strength of the materials obtained.

Investigation on the Alkali Resistance Property of Theoretical Composition Magnesia Alumina Spinel Bricks

Using alumina-rich MgAl2O4 spinel AR78 and 97 fused magnesite as raw materials, brine as the binder, magnesia alumina spinel bricks close to theoretical composition have been prepared. The phase composition and microstructure of the specimens were analyzed and characterized. The alkali resistance property of specimens was researched using static crucible method. The erosion mechanism of alkali vapor to specimens was studied by XRD, SEM and EDS. The results show that: (1) The alkali resistance property of MgAl2O4 spinel bricks were improved obviously when the addition of magnesite is more than 7%. (2) The alkali resistance property of MgAl2O4 spinel bricks is the best when the addition of magnesite is 10.3%.

Tarred dolomite-magnesite unfired refractories for steel converters with top oxygen blow

Tarred dolomite-magnesite refractories based on preserved dolomite, finely ground magnesite, coal-tar pitch and anthracite oil, are suitable for lining steel converters with top oxygen blast. For the first time in the Soviet Union unfired tarred dolomite converter refractory has been obtained with an addition of magnesite which is not inferior in service to ordinary fired brick PSh used for lining converters. It is possible to transport the bricks if they are preserved from hydration.