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  • Author or Editor: B. Pacewska x
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The stages of thermal decomposition of basic aluminium-ammonium sulfate (BAAS) in hydrogen atmosphere were studied with use of differential thermal analysis (DTA), thermogravimetric (TG), X-ray diffraction phase analysis (XRD), and chemical analyses. It has been found that hydrogen greatly influences the process of the desulfurization of the investigated compound: this process occurs at lower temperatures as compared to the desulfurization process in air. The final decomposition product of the basic salt at 1223 K isγ-Al2O3. The experimental part is preceded by the thermodynamic analysis of the desulfurization process of BAAS in hydrogen atmosphere, and its results have been correlated with experimental tests.

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Abstract  

The present work is an attempt to use the waste water stream, containing considerable amounts of aluminium chloride, for the manufacture of mineral–carbon sorbents. The use of the wastewater has given a possibility of obtaining a suitable mineral matrix of aluminium hydroxide for the sorbents. Atactic poly(propylene) (APP) have been used as the necessary carbon raw material. The modification of aluminium hydroxide was attained by preliminary mixing with the organic component, followed by carbonisation. Optimum conditions for obtaining Al(OH)3 have been determined and the effect of the amount of carbon matter on the properties of the materials obtained has been evaluated. The studies have enabled to trace the changes in the structure and properties of the sorbents obtained.

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A mathematical model of the thermal decomposition of basic aluminium ammonium sulfate has been developed. The construction of the model consisted in simulation of TG and DTG curves, with the use of kinetic parameters identified on the basis of results obtained in measurements of the rate of thermal dissociation of the compound under isothermal and non-isothermal conditions.

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Abstract  

Thermal analysis, mass spectrometry, infrared spectrophotometry, X-ray phase analysis, scanning electron microscopy, and sorption methods were used in the study of thermal transformations of the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium. It has been found that the process of aluminium nitrate hydrolysis under the conditions applied and in the presence of ammonia gives boehmite as the main product, with some admixture of a basic salt.Aluminium oxide obtained from the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium at 550°C has a crystalline -Al2O3 structure. Its specific surface, as determined by low-temperature adsorption of nitrogen, exceeds 200 m2g–1. Features of the products are well developed mesopore structure and considerable ability of benzene adsorption. Calcination of the obtained aluminium oxide for 2 h at 900°C reduces its specific surface to about 110 m2 g–1.

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The process of obtaining a special aluminium oxide by means of the thermal dissociation of a basic aluminium-potassium sulfate in the presence of carbon (soot) and water vapour was studied. Under these conditions, the dissociation of the basic salt occurs at a lower temperature than in presence of air. K2O-Al2O3 and/or Al2O3 are formed as fine-grained reaction residues, depending on the final temperature. The technologically useful range of temperatures for the process was established.

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Practical aspects of the studies of stages of thermal dissociation of solids, of the kinetics of the stages, and of utilization of general regularities of the process for verification of kinetic studies are discussed.

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Abstract

A study was made of the effect of an atmosphere of H2+CO (a 3∶1 molar mixture) on the mechanism and the kinetics of desulfuration of basic aluminium-ammonium sulfate under variable pressures of hydrogen and carbon monoxide. The temperature region of the process, the nature of almost all the solid intermediates, and the equations and kinetic parameters relating to the rate of desulfurization of the compound for α<0.6 were determined. Despite the complexity of the process, the results permitted determination of the temperature and the composition of the gas phase necessary for the process of desulfuration to occur and for aluminium oxides with the required properties to be obtained.

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Abstract  

Investigations of physico-chemical properties of three kinds of fly ash and their influence on cement hydration were performed in this work. Thermal analysis, microcalorimetry, infrared absorption and others were used. It was confirmed that the kind of coal and combustion conditions essentially influence physico-chemical properties of fly ash and in consequence influence cement hydration. Investigated fly ashes show in cement system so-called pozzolanic activity. Fly ash from combustion of brown coal in fluidized furnace revealed better activity compared to other investigated ones. This work is an introduction to more extensive investigation of fly ash activation.

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