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  • Author or Editor: I. Dombalov x
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Abstract  

Different physical chemical methods were used to study the thermochemical processes in a system involving a natural phosphate and complex acid salts of ammonium sulphate. The products of decomposition of the double ammonium salt and the products of their interactions with the phosphate were identified. The formation of ammonium and calcium polyphosphates and the disproportionation of P3O 10 5− and P2O 7 4− to PO 4 3− and PO 3 were found to depend on the circumstances of the thermal interactions.

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With a complex of physico-chemical methods for analysis it is proved that in the course of mechanochemical treatment of a Syrian phosphorite and ammonium sulphate mixture new phases have been formed. The thermal analysis proves an increase in the reaction properties of the ammonium sulphate and the Syrian phosphorite which is a prerequisite for the increase in the content of P2O5 assimilated , in the activated phosphorite mixtures and the possibility to use them in the production of NP complex fertilizers.

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Abstract  

Stability of mineral mixed fertilizers processed by effective mixing and compaction, using extrusion technology, is a subject of this study. As new products there is a need to learn the possible changes in the phase ratios and caking processes during long term storage. 7 samples with different nutrient components ratios are investigated after one year kept in a storage facility without conditioning. Applying TG-DTA, electron microscopy and X-ray diffraction methods samples are studied, recording thermal effects and mass losses, type of crystal structures and phase content in the sample. On the base of the results obtained the relationships are discussed and conclusions made about the possibility to safety storage and visible application of the new products as fertilizers in the agriculture for nut ratio of different plant. It is confirmed that the investigated samples, produced on the base of low grade phosphates are stable during long term storage and they could be successfully recommended for practical use in agriculture, using traditional or individual method of fertilization.

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Abstract  

Mechano-chemical activation is a widely used method for increasing the reaction activity of solids and, consequently, to accelerate solid phase reactions and to reduce the temperature of the subsequent thermal decomposition. Thermal decomposition of triboactivated calcium carbonate is a subject of different studies while dolomite decomposition has limited data. The present work represents a study of thermal stability and phase transitions of mechano-chemical activated dolomite under different conditions, namely using various amounts and kind of milling balls and the duration of activation. Temperatures of decomposition of MgCO3 and CaCO3 are specified. The study includes the determination of the thermal stability and the rate of thermal decomposition of activated dolomite.

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Abstract  

The thermal behavior of Tunisia phosphorite and ammonium sulfate mixtures are examined by non-isothermal thermogravimetry in air atmosphere. It has been shown that the thermal stability of mixtures have different behavior after mechano-chemical treatment due to phase changes in the mixtures. New solid phases are confirmed by the stages and rate of mass changes and also by the heat effects observed. New phases are also confirmed by using X-ray diffraction method. Based on the data obtained by the mechanism of chemical transformations is proposed. The kinetics of mechano-activated mixtures decomposition is significantly influenced by the time of treatment and proceeds in few stages. Stage I is attributed to the effect of partially ammonia releasing, when the next stages are associated with the decomposition of apatite structures. Because of the interfacial interactions during mechano-chemical treatment insoluble phosphorous forms from apatite structures are transformed to the soluble forms suitable for plants nutrition. The results have shown that the soluble form can be controlled by the initial components ratio and conditions of treatment on the way to obtain slow releasing nutrition products.

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The thermal stability of barium peroxide obtained via the oxidation of BaO was studied. The investigations were carried out with a Q1500D MOM derivatograph. The flow rate of air or oxygen-argon mixtures was 25–30 l/h. It was found that the thermal properties of the BaO-BaO2 system and of BaO2 depend on the partial pressures of oxygen and water vapour during the process of oxidation of BaO. The most stable BaO2 can be produced from high-purity BaO with a special crystal structure.

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