Dehydration Pathways of Gypsum and the Rehydration
2019年4月26日 Some researchers have argued that gypsum undergoes a two-stage dehydration process, where β-CaSO 4 0.5H 2 O is formed first and then γ-CaSO 4 is obtained by further dehydration of β-CaSO 4 0.5H 2 O. McAdie studied the gypsum
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(PDF) Dehydration Pathways of Gypsum and the
2019年4月30日 In the high-temperature and low water vapor pressure region, gypsum dehydrates to form γ-CaSO 4 in a single-step process (CaSO 4 2H 2 O → γ-CaSO 4 ); with increasing water vapor pressure,...
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The thermal dehydration of synthetic gypsum - ScienceDirect
1995年12月20日 The Sestak-Berggren equation [16] gives the best description (correlation coefficient = 0.954, Durbin-Watson value = 0.116) of the dehydration during the last
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Dehydration Pathways of Gypsum and the Rehydration
2019年4月4日 Some researchers have argued that gypsum undergoes a two-stage dehydration process, where β-CaSO 4 0.5H 2 O is formed first and then γ-CaSO 4 is
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Dehydration Pathways of Gypsum and the Rehydration Mechanism
2019年4月26日 In the high-temperature and low water vapor pressure region, gypsum dehydrates to form γ-CaSO 4 in a single-step process (CaSO 4 2H 2 O → γ-CaSO 4 );
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From atom level to macroscopic scale: Structural mechanism of gypsum ...
2022年4月1日 The first step is dehydration: heated to 100–200 °C, gypsum (CaSO 4 2H 2 O) releases water as vapor [ 1, 2] and, depending on temperature and water vapor partial
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525. The dehydration of gypsum. Part I. A study of the
The dehydration of gypsum. Part I. A study of the thermal decomposition of gypsum by the adsorption of oxygen and of nitrogen at –183°
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Kinetics of Gypsum Dehydration - Springer
2017年8月25日 According to the thermal curves, the gypsum dehydration comports two steps described by the following equations:
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Mechanism and kinetics of gypsum–anhydrite
2011年6月1日 Below 100 °C, the mechanism consists of a direct dehydration step of gypsum to anhydrite (with no intermediate hemihydrate formation), resulting in the
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The Dehydration Kinetics of Gypsum in a Fluidized Bed Reactor
2000年10月1日 The gypsum is dehydrated tocalcium sulphate hemihydrate (hereafter abbreviated to hemihydrate) before use.
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Calcium Sulfate Dihydrate - an overview ScienceDirect Topics
In addition, synthetic gypsum is recovered via flue-gas desulfurization in some coal-fired electric power plants and used interchangeably with natural gypsum in some applications. 19.2.1 Definition of gypsum. Gypsum is a sulfate mineral composed of calcium sulfate dihydrate and has the chemical formula CaSO 4 2H 2 O. It exists as massive ...
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Mechanism and kinetics of gypsum–anhydrite
2011年6月1日 Based on these observations, the gypsum–anhydrite transformation mechanism under these conditions consists of step-wise dehydration of gypsum to hemihydrate and then to anhydrite. Since anhydrite is the stable phase under these conditions, and it has the lowest solubility level, the bulk of solution will reject its
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Thermal analysis application: Gypsum - Linseis
2023年10月15日 The double-step dehydration of calcium sulphate-dihydrate appears between 100°C and 300°C. The first step is the forming of half-hydrate (CaSO4 ∙ 2H2O to ... The chemical formula of Gypsum is
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chemical equation dehydration of gypsum
Dehydration Pathways of Gypsum and the Rehydration 2019年4月26日 Dehydration of gypsum has been investigated in isothermal conditions within the 348-403 K range with a temp. increase of 5 K. Dehydration proceeds through the CaSO42H2O → CaSO40 ...
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Fast in-situ X-ray scattering reveals stress sensitivity of gypsum ...
2021年5月24日 The dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, and due to the global use of plaster ...
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The thermal dehydration of natural gypsum and pure calcium sulphate ...
1996年7月10日 For natural gypsum, and a-values in the range of 0 and 0.2, the 3-dimensional diffusion equation of Jander .(a) _ C1- (1- a)t/3]2 = kt appears to fit the data best; the correlation coefficient value is only 0.726 and the equation gives an average activation value of 88 18 kJ mol- t and an average In A value of 7.7 2.7.
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Novel approach to thermal degradation kinetics of gypsum: application ...
2019年10月14日 Gypsum of chemical formula CaSO 4 2H 2 O, also called calcium sulfate dihydrate, is a versatile material used in several sectors of activity such as cement industry, plaster manufacturing and agriculture [1, 2].It is also found in the formulation of many useful products like paper, glass and paints [3, 4].Gypsum production is carried out in two
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Gypsum hydration: a theoretical and experimental study
2019年12月3日 Substituting the values of α-hemihydrate into equation (4) for full hydration an expression of the void fraction is obtained which is the same as Schiller /9/, who proposed this equation also assuming the volume keeps constant during hydration. An expression is obtained to describe the void fraction of gypsum generated with β-
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Gypsum: Types, Properties, Advantages Disadvantages
2023年10月14日 Gypsum is a soft sulfate naturally occurring, white powdered mineral composed of calcium sulfate di-hydrate with the chemical formula CaSO. 42H2O. It is widely mined and is used as a fertilizer and main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall.
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(PDF) Dissolution and conversions of gypsum and
2000年4月1日 Gypsum dissolves by a simple two-phase dissociation. Anhydrite, when dissolved, forms a solution of calcium sulfate, which at common temperatures and pressures is in equilibrium with the solid ...
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Synthesis, Dehydration, and Rehydration of Calcium Sulfate (Gypsum ...
2014年3月31日 Calcium sulphate hemihydrate (CaSO 4 0.5H 2 O), commonly known as plaster of Paris, is used extensively in the construction, ceramics, and medical industries. There are two varieties of plaster ...
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Heat and mass transfer through gypsum partitions
2016年4月11日 Specifically, we deal with the response of gypsum partitions subjected to fire exposures. While models do currently exist [2-4], most utilize a single energy conservation equation. To approximate the effects of mass transport through and chemical dehydration of the materials that comprise the core of the gypsum wallboard, the
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The kinetics of the precipitation of gypsum, CaSO42H2O
2020年9月3日 To improve the chemical model, further pieces of information had to be gathered. Firstly, we studied the observed conductivity data in more details. In Fig. 6, the conductivity of the undersaturated gypsum solutions are compared with the initial and final conductivity of our reaction mixtures at various starting concentrations.
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Moisture transport and dehydration in heated gypsum, an
2011年9月15日 Abstract. Nuclear magnetic resonance (NMR) is used to non-destructively measure the moisture and dehydration profiles in gypsum during one sided heating to temperatures of 400 °C reflecting the conditions during fire. The temperature and moisture profiles are recorded simultaneously. The gypsum used in the experiments was
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Kinetics of Gypsum Dehydration - Springer
2017年8月25日 KINETICS OF GYPSUM DEHYDRATION D. Fatu Department of Physical Chemistry, Blv. Elisabeta 4-12 Bucharest, 70346 Romania (Received June 6, 2000; in revised form January 25, 2001) Abstract The kinetics of gypsum dehydration in non-isothermal conditions with constant heating rate as well in quasi-isotherm, quasi-isobar
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Structural evolution of gypsum (CaSO42H2O) during thermal dehydration ...
2022年12月6日 The volumetric thermal expansion coefficient of gypsum is 1.31 × 10–4 K–1. The site occupancy of Ow in β-hemihydrate continuously decreases from 0.8 and reaches approximately 0.5 at ...
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Thermal behaviour and kinetics of dehydration of gypsum in
2009年1月11日 Thermal behaviour and kinetics of dehydration of gypsum in air have been investigated using in situ real-time laboratory parallel-beam X-ray powder diffraction data evaluated by the Rietveld method. Thermal expansion has been analysed from 298 to 373 K. The high-temperature limits for the cell edges and for the cell volume, calculated using
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Dehydration Pathways of Gypsum and the Rehydration
2019年4月4日 Over the past decades, many studies have proposed the existence of various subhydrates with a general chemical formula of CaSO 4 nH 2 O, where the numerical value of n ranges from 0 to 0.67. 25,28 If the dehydration product CaSO 4 nH 2 O occurs upon the heating of gypsum, then the dehydration reaction of gypsum can be
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Temperature and humidity dependent formation of CaSO4
2020年4月1日 The temperature and humidity dependent formation of different crystalline phases CaSO 4 xH 2 O with 0 ≤ x ≤ 2 was investigated by in situ X-ray powder diffraction using a Bruker D8 diffractometer equipped with an Anton Paar CHC + cryo−/ humidity chamber. By isothermal measurements over time ranges up to 60 h at temperatures
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