Dihydrate gypsum dehydration

Dehydration Pathways of Gypsum and the Rehydration

2019年4月26日  Lou et al studied the dehydration mechanisms of flue gas desulfurization gypsums and pointed out that gypsum dehydration proceeds 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 From atom level to macroscopic scale: Structural mechanism of 1996年7月10日  From Xray diffraction analysis, it appears, that the decomposition reaction of both the natural gypsum and pure calcium sulphate dihydrate proceeds via the hemihydrate The thermal dehydration of natural gypsum and pure calcium 2019年4月26日  In the hightemperature and low water vapor pressure region, gypsum dehydrates to form γCaSO 4 in a singlestep process (CaSO 4 2H 2 O → γCaSO 4); with Dehydration Pathways of Gypsum and the Rehydration

Fast insitu Xray scattering reveals stress sensitivity of gypsum

2021年5月24日  Here, we perform fast, timeresolved synchrotron Xray scattering on natural alabaster samples, finding that a small elastic load accelerates the dehydration reaction 2022年12月8日  Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to Formation of alpha;Hemihydrate Inside of a Gypsum Two–step process in the dehydration of gypsum Supplementary Figure S1 (Fig S1–S4 are available online from https://doi/102465/jmps) shows the TG and DTA curves of Structural evolution of gypsum (CaSO42H2O) during thermal It is found that the dehydration of gypsum to anhydrite proceeds via the hemihydrate and γanhydrite phases and the interplay and behaviour of these phases has been determined by full Structural evolution during the dehydration of gypsum materials

In situ IR spectroscopic and thermogravimetric study of the

The dehydration of gypsum CaSO 42H 2 O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether Naturally occurring crystals are calcium sulfate dihydrate, CaSO 4 2H 2 O, known as gypsum, and anhydrous calcium sulfate, IICaSO 4 When gypsum is heated, dehydration occurs to form hemihydrates, CaSO 4 1/2H 2 O, followed by anhydrite, IIICaSO 4 The hemihydrates and the anhydrite have two modifications, α and β, respectivelyCalcium Sulfate Dihydrate an overview ScienceDirect Topics2022年12月8日  Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world the dehydration process of gypsum and the rehydration of hemihydrate were investigatedFormation of αHemihydrate Inside of a Gypsum 1 Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first stage and the nucleation and precipitation of dihydrate in the second stage 2 Gypsum hydration is strongly influenced by water amount Spread flow test is suitable to determine the water demand for gypsum hydrationGypsum hydration: a theoretical and experimental study

Structural evolution during the dehydration of gypsum materials

It is found that the dehydration of gypsum to anhydrite proceeds via the hemihydrate and γanhydrite phases and the interplay and behaviour of these phases has been determined by full structural ‘Rietveld’ refinement In the study of the pure gypsum system, the hemihydrate structure is shown to be preserved as water is lost1996年7月10日  thermochimica acta ELSEVIER Thermochimica Acta 282/283 (1996) 483492 The thermal dehydration of natural gypsum and pure calcium sulphate dihydrate (gypsum)' DL HudsonLamb", CA Strydom a, JH Potgieter b a Department oJ'Chemistry, University of Pretoria, Pretoria, 0002, South Africa b Technical Services, PPC, PO Box 40073, Cleveland The thermal dehydration of natural gypsum and pure calcium sulphate 2007年12月1日  The structures were identified as crystals formed during the dehydration process of gypsum inside of a gypsum crystal The hypothesis of Fowler et al [13] remarked that αHH is formed as water The dihydrate‐hemihydrate transformation in gypsum2024年10月14日  Consequently, a portion of the dihydrate gypsum may undergo drying and dehydration, forming βhemihydrate gypsum Compared with αHH, βhemihydrate gypsum has a crystal structure mostly composed of loose, fine, and irregular grains, with a larger specific surface area [ 26 ], more rapid hydration, shorter coagulation time, and greater standard consistencyPreparation of Medium–Low Strength Hemihydrate Gypsum from

The dihydrate‐hemihydrate transformation in gypsum

A microscope study has been made of the development of crystals of calcium sulphate hemihydrate produced on, or in, sheets of the dihydrate in the form of selenite by calcining under controlled conditions The crystal forms were shown to be strongly dependent upon both temperature and ambient water vapour pressure A mechanism for the nucleation and growth The dehydration of gypsum CaSO 42H 2 O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO 4 n H 2 O) exist, other than the hemihydrate with n =05, and also to compare the mechanism of the dehydration process when measured by two techniques with In situ IR spectroscopic and thermogravimetric study of the dehydration 2000年4月1日  Calcium sulfate occurs in nature mainly in form of three different minerals distinguished by their degree of hydration: gypsum (CaSO 4 ), bassanite (CaSO 4 ⋅05H 2 O) and anhydrite (CaSO 4 Dissolution and conversions of gypsum and anhydrite2011年9月30日  The effects of pressure on the dehydration of gypsum materials were investigated up to 633 K and 25 GPa by using Raman spectroscopy and synchrotron Xray diffraction with an externally heated diamond anvil cell At 25 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely dehydrates to γ The dehydration process of gypsum under high pressure

(PDF) The thermal dehydration of natural gypsum

thermochimica acta ELSEVIER Thermochimica Acta 282/283 (1996) 483492 The thermal dehydration of natural gypsum and pure calcium sulphate dihydrate (gypsum)l a,*, CA Strydom DL HudsonLamb aDepurtment of Chemistry, 2021年12月13日  Dihydrate gypsum is the dominant phase composition in PG, it is a stable phase at room temperature but can be converted into αhemihydrate gypsum (αCaSO 4 05H 2 O) [16] and βhemihydrate gypsum (βCaSO 4 05H 2 O), also called building gypsum [17] according to different heating methods αhemihydrate gypsum is prepared in a pressurized Dehydration behaviour and impurity change of phosphogypsum during 2020年7月3日  The objective of this research was to understand the dehydration mechanism of technical dihydrate and the variation of the physical properties of βhemihydrate after the first hydration The conversion of gypsum into a recycled product has been interesting for many researchers due to its reaction reversibility, cycle The Mechanism of the First Hydration‐Dehydration Cycle of Pure 2010年10月26日  Methods The dehydration process of FGD gypsum was performed with simultaneous TG/DSC analysis (NETZSCH STA 409 Luxx, Selb/Bavaria, Germany) at N 2 atmosphere with a gas flow of 20 mL min −1Nonisothermal analysis was carried out at different heating rate (2−20 K min −1)Isothermal analysis was conducted in the temperature range of Dehydration behavior of FGD gypsum by simultaneous TG and

Raman spectroscopy of the dehydration process of gypsums

2015年2月5日  The dehydration process of a synthetic gypsum indicates that it has an interstitial gypsum phase dehydrating in a similar way to the interstitial phase found in the Terra Alba gypsumDownload scientific diagram Structures of a) gypsum, b) hemihydrate, and c) insoluble anhydrite with view in cdirection from publication: Crystallization and Phase Stability of CaSO4 and CaSO4 Structures of a) gypsum, b) hemihydrate, and c) insoluble 2014年7月12日  The dehydration process of gypsum rock was studied under concentrated solar energy by using a Fresnel lens with power density of 260 Wcm 2 Temperatures higher than 700 C were attained for 1 min Dehydration of Gypsum Rock by Solar Energy: Preliminary Study2024年6月15日  The temperature at which the gypsum binder (calcium sulfate hemihydrate) is industrially produced, between 80 and 180 °C, is often mentioned in the literature [14,15,16,17]However, dehydration from gypsum to basanite (CaSO 4 05H 2 O) starts at a much lower temperature The dehydration temperature depends on the measurement method, New insight into the phase changes of gypsum

Study of gypsum by PDSC Journal of Thermal Analysis and

2012年3月18日  Calcium sulfate dihydrate has been widely characterized by both differential scanning calorimetry and thermogravimetry (TG) Two dehydration processes were reported to be partially overlapping High resolution TG and water vapor self generated atmosphere pinhole lid strategies were used to increase the resolution of both dehydration processes In this study, Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again Formation of αHemihydrate Inside of a Gypsum 2009年6月1日  The dehydration of pure and waste gypsums has been examined using in situ synchrotron angledispersive Xray diffraction Pure gypsum was studied under a number of defined environments; various Structural evolution during the dehydration of Depending on the mill temperature, the gypsum becomes partially or completely dehydrated to hemihydrate or anhydrite respectively According to [8] the temperatures at which gypsum dehydration to hemihydrate can take place lie 2 Gypsum dehydration during cement production ZKG

Dehydration of Gypsum Rock by Solar Energy: Preliminary Study

source as solar thermal energy for obtaining plaster from the calcination of gypsum rock In order to study the influence of the grain size in the transformation of dihydrate phase (gypsum) into hemihydrate phase (bassanite) Figure 1 Handmade gypsum furnace In 1996年7月10日  DOI: 101016/00406031(95)028196 Corpus ID: ; The thermal dehydration of natural gypsum and pure calcium sulphate dihydrate (gypsum) @article{HudsonLamb1996TheTD, title={The thermal dehydration of natural gypsum and pure calcium sulphate dihydrate (gypsum)}, author={D L HudsonLamb and Christien A Strydom The thermal dehydration of natural gypsum and pure calcium 2022年12月6日  The dehydration of gypsum proceeded through one step, ie, CaSO42H2O → γCaSO4 (γanhydrite) dissolution and of gypsum (calcium sulfate dihydrate, DH) precipitationStructural evolution of gypsum (CaSO42H2O) during thermal dehydration2024年5月15日  As one of the extensively used inorganic cementitious material, hemihydrate gypsum (HH, CaSO 4 05H 2 O) has two forms, namely βHH and αHH β phase is a dehydration product of calcium sulfate dihydrate (DH, CaSO 4 2H 2 O) in dry air at 105–180 °C and has a longer history of application, whilst αHH can be produced by wet calcination Effect of sodium fluoride on the crystal regulation of high

Novel approach to thermal degradation kinetics of gypsum

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 different 2021年12月13日  Dihydrate gypsum is the dominant phase composition in PG, it is a stable phase at room temperature but can be converted into αhemihydrate gypsum (αCaSO 4 05H 2 O) [16] and βhemihydrate gypsum (βCaSO 4 05H 2 O), also called building gypsum [17] according to different heating methods αhemihydrate gypsum is prepared in a pressurized Dehydration behaviour and impurity change of phosphogypsum during Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigatedDehydration of Gypsum Rock by Solar Energy: Preliminary Study2007年3月1日  The hydration of calcium sulphate hemihydrate (CaSO 4 05H 2 O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO 4 2H 2 O) has been the subject of several investigations over a long period and a vast amount of data is widely distributed throughout in the literature In this review article an overall picture of the subject is presentedCalcium sulphate hemihydrate hydration leading to gypsum

Structural evolution of gypsum (CaSO42H2O) during thermal dehydration

Keywords: Gypsum, Hemihydrate, Soluble anhydrite, Dehydration, In situ high–temperature synchrotron X– ray diffraction INTRODUCTION Calcium sulfate dihydrate, gypsum CaSO 42H 2O, is the most common sulfate mineral Therefore, considerable attention has been paid to the dehydration of gypsum Numerous studies on the mechanisms and products of2024年7月1日  Ingenious approach for retrieving valuable metals from gypsum via dehydration–rehydration twostep phase transition Author links open overlay panel Jiayi Zheng a e 1, Changzhou Weng a 1, Chen Tian b, (CaSO 4 2H 2 O, dihydrate) [14], [15], with a weak interaction between water molecules and the crystal frame (only a few Ingenious approach for retrieving valuable metals from gypsum 2018年1月1日  D – dihydrate gypsum CaSO 4 The plaster is an aerial binder obtained through the dehydration of gypsum (CaSo4 2H2O) and forming semyhidrated calcium sulphate (CaSO4 ½ H2O) Influence of dehydration method on the morphology of hemihydrate gypsum PDF On Jan 1, 2009, QL Yu and others published Gypsum hydration: A theoretical and experimental study Find, read and cite all the research you need on ResearchGateGypsum hydration: A theoretical and experimental study

Highquality gypsum binders based on synthetic calcium sulfate

2021年8月25日  A XRD pattern of βcalcium sulfate hemihydrate (Fig 1, a), a SEM image (Fig 1, b), and the dependence of the strength of gypsum on the temperature of its dehydration (Fig 1, c) are shown in Fig 1The XRD pattern of βcalcium sulfate hemihydrate is fully assigned by the XRD pattern of hemihydrate as reported in reference [26]From Fig 1, c it follows that the 2014年3月31日  The process of rehydration of calcium sulphate hemihydrate (CaSO4 05H2O) to the crystallization of gypsum which is chemically known as calcium sulphate dihydrate (CaSO4 2H2O) is based on the Synthesis, Dehydration, and Rehydration of Calcium Sulfate (Gypsum 2011年3月1日  Temperature measurements at preselected board locations indicated three distinct stages of gypsum dehydration; free moisture evaporation, transformation of calcium sulfate dihydrate to calcium (PDF) Scrutinizing Gypsum Board Thermal Performance at Dehydration 2021年1月15日  Due to the combination of the processes of binder production (dehydration of ground gypsum dihydrate with the elimination of 15 water molecules) and the finished product (the reaction of semi Obtaining gypsum products from gypsum dihydrate in a

In situ IR spectroscopic and thermogravimetric study of the dehydration

1990年3月1日  Abstract The dehydration of gypsum CaSO42H2O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO4nH2O) exist, other than the hemihydrate with n=05, and also to compare the mechanism of the dehydration process when measured by two

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