Study of Gypsum Dehydration by Controlled Transformation Rate Thermal Analysis (CRTA)

Badens, Elisabeth; Llewellyn, Philip L.; Fulconis, J.M.; Jourdan, C.; Veesler, Stéphane; Boistelle, R.; Rouquérol, F.

doi:10.1006/jssc.1998.7797

Cited by 48 publications

(25 citation statements)

References 15 publications

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“…The reaction conversion changes and the reaction heat were calculated from the weight changes of the reactants. This reaction occurs between β-CaSO 4 ·1/2H 2 O and γ-CaSO 4 in our experimental temperature range (Badens et al, 1998). Figure 3 shows the reaction equilibrium line of CaSO 4 /CaSO 4 ·1/2H 2 O reversible reaction obtained by the reference (Lee et al, 1986) and the reaction equilibrium plots by our experimental data in different systems.…”

Section: Methodsmentioning

confidence: 70%

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Reaction Characteristics of CaSO4/CaSO4 1/2H2O Reversible Reaction for Chemical Heat Pump

Ogura

Haguro

Shibata

et al. 2007

J. Chem. Eng. Japan

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We had proposed chemical heat pumps using a reversible calcium sulphate/water reaction system for effective waste energy utilization. However, more reaction kinetics studies are necessary for this reaction system, especially for different atmosphere condition and different materials. As a result, the reaction equilibrium line of CaSO 4 in the closed system like CHP system was found to be close to that in the open system. It means that the CHP using CaSO 4 /CaSO 4 ·1/2H 2 O reversible reaction stores under 373 K level thermal energy, and releases the same level hot heat and 273 K level cold heat. Furthermore, the effects of material size on the reaction rates could be calculated by the proposed equations, which enable the effective CHP reactor design.

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Section: Methodsmentioning

confidence: 70%

“…However, more reaction kinetics studies are necessary for this reaction system, especially in a closed system like CHP system for different materials. Although the reaction kinetics of CaSO 4 has been done by some researchers (Badens et al, 1998;Hudson-Lamb et al, 1996;Strydom et al, 1995), those were done in an open system.…”

Section: Introductionmentioning

confidence: 99%

Reaction Characteristics of CaSO4/CaSO4 1/2H2O Reversible Reaction for Chemical Heat Pump

Ogura

Haguro

Shibata

et al. 2007

J. Chem. Eng. Japan

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“…[30][31][32][33][34][35] Thermogravimetric analysis for all samples showed the same profile as that illustrated in Figure 5. The first mass loss between 100 and 250 °C [36][37][38][39][40][41][42] can be ascribed to the release of water molecules of gypsum which occurrs in two steps as described by Equations 1 and 2: Calcium phosphate loses water molecules by dehydration reactions at the same temperature range 38,43,44 , also in two stages, as described by Equations 3 and 4: As the first gypsum dehydration step corresponds to a mass loss of 75%, one can assume that the DTG peak at 134 °C corresponds to this water loss of gypsum. On the other hand, the calcium phosphate dehydration is more difficult to be proven, since the phosphate phase is present at smaller quantities in the fertilizer than the gypsum phase.…”

Section: -Results and Discussionmentioning

confidence: 99%

Characterization of Single Superphosphate Powders – a study of Milling Effects on Solubilization Kinetics

Plotegher

Ribeiro

2016

Mat. Res.

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Conventional single superphosphate (SSP) is known as one of the most important and common sources of phosphorus in agriculture. Despite SSP has been widely produced as a fertilizer, a few studies have been done to describe the fundamental aspects of this P-fertilizer, i.e., phase composition, thermal degradation behavior, and solubility kinetics. Therefore, this paper reports on the detailed characterization of SSP powders by correlating their properties with particle size and surface area. Commercial SSP fertilizers were milled under different conditions and the resulting powders were characterized by X-ray diffraction, thermogravimetric analyses, scanning electron microscopy, FT-IR spectroscopy, and solubilization tests. It was observed that short milling times favored the solubilization kinetics, whereas long milling times were deleterious due to agglomeration effects. It was pointed out that agglomeration plays an important role in phosphate availability. These results provided a deeper understanding of SSP powders in microstructural terms, and may be used as a foundation for the development of novel strategies of alternative production of phosphorus fertilizers.

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“…In the literature, there is a number of studies on kinetics dehydration of gypsum (25,27,(43)(44)(45)(46)(47)(48)(49). In general, all the studies of the CaSO 4 2H 2 O dehydration through DTA or DTG show the presence of two endothermic peaks.…”

Section: ) T O (°C) T E (°C) T P (°C) T O (°C) T E (°C) T P (°C) T O mentioning

confidence: 99%

Thermal dehydration kinetics of phosphogypsum

López¹,

Tayibi²,

García‐Díaz³

2015

Mater. construcc.

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ABSTRACT:Phsophogypsum is a by-product from the processing phosphate rock. Before the use of it in cement industry such as setting regulator is necessary a study of dehydration reaction of phosphogypsum to avoid the false setting during the milling.The aim is to study the thermal behavior of two different phosphogypsum sources (Spain and Tunisia) under non-isothermal conditions in argon atmosphere by using Thermo-Gravimetriy, Differential Thermal Analysis (TG-DTA) and Differential Scanning Calorimetry (DSC).DSC experiments were carried out at temperatures ranging from ambient to 350 °C at different heating rates. The temperatures of conversion from gypsum to hemihydrate and anhydrite states and heat of dehydration were determined. Various methods were used to analyze the DSC data for reaction kinetics determination. The activation energy and frequency factor were calculated for dehydration of phosphogypsum. Activation energy values of the main dehydration reaction of phosphogypsum were calculated to be approximately 61-118 kJ/mol. RESUMEN:Estudio cinético de la deshidratación térmica del fosfoyeso. El fosfoyeso es un subproducto procedente del procesado de la roca fosfato. Una de las posibles vías de reutilización y revalorización es su uso como regulador del fraguado en la industria cementera. Debido a los posibles problemas de falso fraguado asociado a los procesos de deshidratación que tienen lugar durante la molienda del cemento, esta investigación estudió el comportamiento térmico, bajo condiciones no-isotérmicas en atmósfera de argón, de dos fosfoyesos, mediante TG-DTA y DSC.Los ensayos de DSC se realizaron hasta los 350 °C a diferentes velocidades de calentamiento. La temperatura de conversión del yeso a las formas de hemihidrato y anhidrita y el calor de hidratación fueron determinados.Las cinéticas de reacción fueron obtenidas analizando los datos de DSC mediante varios métodos. Se calculó la energía de activación y el factor de frecuencia para las reacciones de deshidratación del subproducto. Los valores de energía de activación de las principales reacciones de deshidratación del fosfoyeso fueron obtenidos, aproximadamente 61-118 kJ/mol.

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Study of Gypsum Dehydration by Controlled Transformation Rate Thermal Analysis (CRTA)

Cited by 48 publications

References 15 publications

Reaction Characteristics of CaSO4/CaSO4 1/2H2O Reversible Reaction for Chemical Heat Pump

Reaction Characteristics of CaSO4/CaSO4 1/2H2O Reversible Reaction for Chemical Heat Pump

Characterization of Single Superphosphate Powders – a study of Milling Effects on Solubilization Kinetics

Thermal dehydration kinetics of phosphogypsum

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