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How to dehydrate gypsum into hemihydrate gypsum

Calcium sulphate hemihydrate hydration leading to

2007-3-1  The hydration of calcium sulphate hemihydrate (CaSO 4 ·0.5H 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 presented.

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Estimation of gypsum hemihydrate content in recycled

2016-1-1  As the results, it was found that the dihydrate gypsum is changed into the hemihydrate gypsum under thermal condition of 90 °C and the hemihydrate gypsum is changed into anhydrite under that of 120 °C with heating of 24 h. The followings were clarified in this paper. The cement density measuring method was available in order to measure the

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A kinetic and mechanistic study into the transformation

2019-4-29  longer for -hemihydrate than for -hemihydrate (Song et al., 2009). NMR studies also found that additives such as citric acid and gypsum seeds do not change the total amount of water needed to convert hemihydrate to dihydrate (Song et al., 2010). One non

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Calcium sulphate hemihydrate hydration leading to

The hydration of calcium sulphate hemihydrate (CaSO 4 ·0.5H 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 presented.

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a-Hemihydrate Gypsum from Flue Gas Desulphurization

In this work, properties of sulphate technogenic raw material flue gas desulphurization (FGD) gypsum have been investigated in order to obtain alpha-hemihydrate gypsum as gypsum binding material.

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Estimation of gypsum hemihydrate content in recycled

2014-10-24  When the above phenomena are reviewed with the formation change of the gypsum related to the masses calculated from the Eqs. (1 3), it is implied that “the recycled gypsum dihydrate transforms to the recycled gypsum hemihydrate through thermal dehydration for 24 h at 90 °C” and “the recycled gypsum hemihydrate transforms to the recycled gypsum anhydrate through the thermal dehydration

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Conversion of gypsum to anhydrite in aqueous salt

The hemihydrate formed will then dehydrate to anhydrite. Results of additional calculations shown in Table 5 explain why gypsum was not dehydrated at 50 and 70 under the conditions of these experiments and why only gypsum, hemihydrate, and natural anhydrite were identified in the solid phases of the solubility experiments.

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Distribution behavior of arsenate into α-calcium sulfate

Transforming gypsum into α-calcium sulfate hemihydrate (α-HH) provides a promising utilization pathway for the abundant amount of chemical gypsum. The transformation follows the route of "dissolution-recrystallization", during which the arsenic pollutant in gypsum is released into the solution, and

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Hemihydrate an overview ScienceDirect Topics

This type of scale results from the deposits of three forms of calcium sulphate; the anhydrite (CaSO 4), the hemihydrate (CaSO 4.0.5H 2 O), and dehydrate calcium sulfate or gypsum (CaSO 4.2.H 2 O). Precipitation is affected by concentration, pH, temperature, and solubility of calcium sulfate which in turn is affected by the presence of other ions.

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Calcium Sulfate Hemihydrate an overview ScienceDirect

Gypsum is the name given to a mineral categorized as calcium sulfate mineral, and its chemical formula is calcium sulfate dihydrate, CaSO 4 ⋅ 2H 2 O. However, a broader definition includes all the calcium sulfates, including calcium sulfate hemihydrate, CaSO 4 ⋅

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-Hemihydrate Gypsum from Flue Gas Desulphurization

hemihydrate gypsum from dihydrate [19]. Fig. 4, a, shows that the α-hemihydrate gypsum obtained without crystallization regulator is composed of densely-arranged intertwined long-needle-shaped crystals. The addition of maleic acid anhydride crystallization regulator stops the crystal growth in

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Crystallization Kinetics of -Hemihydrate Gypsum

2021-7-21  According to the difference in hydration, calcium sulfate can be divided into dihydrate gypsum (CaSO 4 2H 2 O), hemihydrate gypsum (CaSO 4 0.5H 2 O), and anhydrite (CaSO 4 ) [1–3]. Phosphogypsum (PG) is mainly composed of calcium sulfate dihydrate (DH), which is a

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Preparation of Whitening Dihydrate Gypsum and Short

2017-8-29  Using FGD gypsum as the raw material, whitening and large prismatic dihydrate gypsum can be obtained by dissolution-crystallization and decoloring process with α-hemihydrate gypsum whiskers prepared in MgSO 4-CaCl 2-H 2 O solution, which can transform into whitening short columnar α-hemihydrate gypsum. The effects of aging temperature, pH, dosage of sodium dodecyl sulfonate

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Distribution behavior of arsenate into α-calcium sulfate

Transforming gypsum into α-calcium sulfate hemihydrate (α-HH) provides a promising utilization pathway for the abundant amount of chemical gypsum. The transformation follows the route of "dissolution-recrystallization", during which the arsenic pollutant in gypsum is released into the solution, and

get price

a-Hemihydrate Gypsum from Flue Gas Desulphurization

In this work, properties of sulphate technogenic raw material flue gas desulphurization (FGD) gypsum have been investigated in order to obtain alpha-hemihydrate gypsum as gypsum binding material.

get price

Preparation of Whitening Dihydrate Gypsum and Short

2017-8-29  Using FGD gypsum as the raw material, whitening and large prismatic dihydrate gypsum can be obtained by dissolution‐crystallization and decoloring process with α‐hemihydrate gypsum whiskers prepared in MgSO 4 ‐CaCl 2 ‐H 2 O solution, which can transform into whitening short columnar α‐hemihydrate gypsum. The effects of aging temperature, pH, dosage of sodium dodecyl sulfonate

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WHAT IS GYPSUM Gypmak

Dehydrate gypsum is the plaster in nature. After calcination process gypsum dehydrate transform to hemihydrate, AII anhydride (dry plaster) and AIII soluble (unstable gypsum). Hemihydrate, in other words named as stucco is the plaster calcined by losing 1,5 moles of the 2 moles of water.

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Dehydration Pathways of Gypsum and the Rehydration

The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results

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Thermal analysis of calcium sulfate dihydrate sources used

2016-7-27  The core composition of gypsum wallboard is calcium sulfate dihydrate (CaSO 4 ·2H 2 O) with varying impurities, additives, or both. This study compares here two commercially calcined sources of hemihydrate (CaSO 4 ·½H 2 O) from a natural source and a synthetic by-product of flue gas desulfurization and neutralization to reagent grade hemihydrate. Two common ingredients, borax and

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Gypsum Flashcards Quizlet

Hemihydrate mixed with water to reform the dehydrate form this reaction with water is reversible. Procedures of Gypsum. Indirect. Indirect. Full of gypsum particles makes reaction faster contaminants can accelerate the setting. Gypsum Setting Stages.

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Influence of Gypsum on the Hydrothermal Reaction of

ture (Fig. 3a) . Gypsum is known to dehydrate into hemihydrate by thermal treatment at 97†Ž and then to anhydrite by 160†Ž treatment7) . In this experiment, using the mixtures with gyp-sum, hydroxyl ellestadite was formed from hemi-hydrate at temperatures lower than 160†Ž and

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Crystallization Kinetics of -Hemihydrate Gypsum

2021-7-21  According to the difference in hydration, calcium sulfate can be divided into dihydrate gypsum (CaSO 4 2H 2 O), hemihydrate gypsum (CaSO 4 0.5H 2 O), and anhydrite (CaSO 4 ) [1–3]. Phosphogypsum (PG) is mainly composed of calcium sulfate dihydrate (DH), which is a

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WHAT IS GYPSUM Gypmak

Dehydrate gypsum is the plaster in nature. After calcination process gypsum dehydrate transform to hemihydrate, AII anhydride (dry plaster) and AIII soluble (unstable gypsum). Hemihydrate, in other words named as stucco is the plaster calcined by losing 1,5 moles of the 2 moles of water.

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Availability of Density Measuring Methods Estimating

2014-5-22  As a result, it was found that the dihydrate gypsum is changed into the hemihydrate gypsum under thermal condition of 90°C and the hemihydrate gypsum is changed into anhydrite under that of 120°C with heating of 24 hours. The followings are clarified in this paper: (1) The cement density measuring method was available in order to measure the

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Gypsum hemihydrate–cement blends to improve

The gypsum loses water when burnt at different temperatures as follows: calcium sulfate hemihydrate (CaSO 4 $0.5H 2 O) is formed when gypsum is heated at temperatures between 100 C and 180 C [17

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A New Precipitation Pathway for Calcium Sulfate

2011-9-20  Supplementary Information 3 Figure S1: Raman spectra of reference samples (a) calcium sulfate hemihydrate and (b) calcium sulfate dihydrate. The peaks correspond to the ν1 symmetric stretch of sulfate (1019 cm-1 in hemihydrate and 1012 cm-1 in gypsum), the ν 2 symmetric bending of sulfate (435 cm-1 and 495 cm-1 in hemihydrate, and 419 cm-1 and 497 cm-1 in gypsum), the ν

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A facile method of transforming FGD gypsum to α-CaSO 4

2017-8-1  Without KCl (Fig. 1a), the transformation from FGD gypsum to α-HH began at 360 min and completed within 420 min.When 1% KCl (by weight of FGD gypsum) (Fig. 1b) was added into

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Reuse of phosphogypsum as hemihydrate gypsum: The

2021-8-10  During hemihydrate gypsum hydration, the proportion of free P was higher, which mainly existed as H 3 PO 4 and H 2 PO 4-, but P species on dihydrate gypsum surface contained a higher HPO 4 2-proportion, which was caused by Ca 2+ weakening the binding +

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The path to gypsum is four steps long EARTH Magazine

2016-11-7  The path to gypsum is four steps long. Gypsum forms through a four-stage process, beginning with the formation of bits of nanocrystalline calcium sulfate that gradually assemble into larger aggregates, according to new research. Credit: James St. John, CC BY 2.0. Drywall and plasters made from both natural and manufactured gypsum are commonly

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Gypsum + Model Trimming Flashcards Quizlet

Comes in variety of colors. Modified Alpha Hemihydrate, Particles are dense, for die contruction like inlay, and crowns. The Setting Reaction of Gypsum is made by mixing _______ and ________. This produces the dehydrate Gypsum. After mixing heat is released called ______ reaction. Then crystals are fromed. Calcium Sulfate Hemihydrate and water

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