Thermal behaviour and kinetics of dehydration of gypsum in air from in situ real-time laboratory parallel-beam X-ray powder diffraction

Ballirano, Paolo; Melis, Elisa

doi:10.1007/s00269-008-0285-8

Cited by 64 publications

(58 citation statements)

References 37 publications

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“…Giustling-Brounsthein (D4) The difference in DTG and DTA profiles, among two PG, indicates the influence of sample origin, chemical composition and traces on dehydration behavior (28). The most obvious discrepancy is the temperature, at which gypsum begins to dehydrate.…”

Section: Thermal Behaviour Of Phosphogypsummentioning

confidence: 99%

“…Most literature reported that gypsum dehydration undergoes a two-step process, via hemihydrate (25,28,(42)(43)(44), while some reports showed that γ-CaSO 4 is directly produced during gypsum dehydration of γ-CaSO 4 upon cooling with humidity air (45 (48) reported that under non-isothermal conditions and in two steps, via hemihydrate in "autogenous P H 2 O ", the dehydration of the gypsum contained in the "flue gas desulfurization gypsum (FGDG) occurs in one step (CaSO 4 2H 2 O→γ-CaSO 4 ), when the P H 2 O is negligible.…”

Section: Thermal Behaviour Of Phosphogypsummentioning

confidence: 99%

“…The temperature and the kinetic dehydration of hydrated calcium sulfate could be influenced by different parameter such as origin sample, chemical composition and crystalline structure, (27,28).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Thermal Behaviour Of Phosphogypsummentioning

confidence: 99%

Section: Thermal Behaviour Of Phosphogypsummentioning

confidence: 99%

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Thermal dehydration kinetics of phosphogypsum

López¹,

Tayibi²,

García‐Díaz³

2015

Mater. construcc.

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“…The (force) fitted data are then used to determine the dimensionality of the single 'rate-determining step ' (e.g. Bray and Redfern 2000;Cattaneo et al 2003;Perrillat et al 2005;Ferrage et al 2007;Carbone et al 2008;Ballirano and Melis 2009;Chollet et al 2009;Inoue et al 2009;Tokiwai and Nakashima 2010;Gualtieri et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

2013

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a much higher apparent E a characterised by an initial stage of around 290 kJ/mol. Afterwards, the apparent E a comes down to around 250 kJ/mol at α ~ 65 % before rising up to around 400 kJ/mol. The delivered kinetic data have been investigated by the z(α) master plot and generalised time master plot methods in order to discriminate the reaction mechanism. Resulting data verify the multi-step reaction scenarios (reactions governed by more than one rate-determining step) already visible in E a versus α plots.Keywords Serpentine dehydroxylation · Generalised master plot · Chrysotile · Brucite · Thermogravimetry · In situ high-temperature X-ray powder diffraction

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“…1 filter paper; the filter cake was thoroughly rinsed with water, dried at mild temperature (i.e 60° C; to prevent thermal conversion of gypsum [19]) for 24 h and characterized by XRD and high-vacuum SEM. Throughout the experiments, sub-samples of the suspensions were collected from the reactor at regular intervals and filtered using 0.45µm PALL acrodisc PSF GxF/GHP membranes (Microsep (Pty) Ltd, South Africa).…”

Section: Direct Aqueous Carbonation Experimentsmentioning

confidence: 99%