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1. Introduction. Gypsum, an important mineral resource, is widely used in the chemical industry [1], agriculture [2], medical treatment [3], building materials [4], food [5], and other fields, which mainly come from natural and industrial by-products.In the field of chemical industry, gypsum is commonly used as a raw material for the production of …
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Alpha high‐strength hemihydrate gypsum (CaSO 4 ·0.5H 2 O, α‐HH) with a large‐size columnar crystal (average size: 135.31 µm, maximum size: 500 µm) is successfully prepared via a NaCl ...
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Sustainability of gypsum products as a construction material. N. Lushnikova, L. Dvorkin, in Sustainability of Construction Materials (Second Edition), 2016 β-Hemihydrate binder. β-Hemihydrate (also known as plaster of Paris) is the most commonly used gypsum binder in construction.It is produced in an apparatus connected to air. Different equipment is …
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The preparation technology of α-HH includes autoclave method, pressurized hydrothermal method and atmospheric hydrothermal method. The …
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Here, a dynamic method, or an improved autoclaved process, was used to produce α-calcium sulfate hemihydrate from FGD gypsum. In this process, the attachment water of the mixture of FGD …
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1. Introduction. Gypsum is a material in which the amount of water of crystallization varies with its surrounding conditions, such as temperature or humidity, and can be classified into three groups, namely, calcium sulfate anhydrite (CaSO 4), calcium sulfate hemihydrate (CaSO 4 ∙1/2H 2 O), and calcium sulfate dihydrate (CaSO 4 ∙2H 2 …
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Natural fibrous gypsum is a kind of high-quality gypsum resources, whose high-value added utilization pathway is to be transformed to α-calcium sulfate hemihydrate (α-HH), a cementitious material that can react with water to form pastes with mechanical strength.In this work, α-HH was prepared from natural fibrous gypsum in KCl mediated …
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Pressure solution method and high temperature method are used to hydrothermal treatment desulfurization gypsum which is added crystal modifier preparing crystal α-hemihydrate decorative gypsum in ...
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a-hemihydrate products with commercially available ma- terials, an autoclave-made a-hemihydrate gypsum product and a plaster of Paris (P-hemihydrate) were included in …
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Alpha-calcium sulfate hemihydrate (α-HH) has been prepared from flue gas desulfurization (FGD) gypsum with salt solution method under atmospheric pressure. X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC), optical micrograph, X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometry …
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ZG is a global Gypsum autoclave manufacturers, exporters & suppliers. Gypsum autoclave that have been found wide industrial application area. Gypsum autoclave are a precious possession that is designed and fabricated to last for lifetime. People are buying Gypsum autoclave as investment and identity marker.
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The synthesis of hemihydrate gypsum (α-HH) crystals with a low aspect ratio is of great significance to practical production for the effective utilization of flue gas desulfurization (FGD) gypsum. In this work, the hexagonal prismatic α-HH crystals with controllable morphology were prepared in Glycerol-NaCl-Water solutions with maleic …
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The effects of phosphoric acid (H3PO4) in pressurized aqueous solution on the dehydration of CaSO4·2H2O to form α-hemihydrate gypsum (α-HH) phase and the …
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1. Introduction. Calcium sulfate is the subject of much research due to its wide scope and large-scale of industrial applications [1], [2], [3].It occurs in nature mainly in form of three different phases distinguished by the content of crystal water: dihydrate (DH, CaSO 4 ·2H 2 O), hemihydrate (HH, CaSO 4 ·0.5H 2 O), and anhydrite (AH, CaSO …
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1 a) Represents the solubility curves of gypsum, anhydrite, and hemihydrate while b) represent both nucleation and growth processes [11, 12] ... 3 In-situ ultrasonic speed velocity during the hydration of different types of hemihydrate:a) steam autoclave α-HHb) β-HH. 4 Heat evolution curves of: a) pure steam autoclave α-HH and b) β-HH.
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Moulding gypsums are products made of calcium sulphate hemihydrate with optional factory additives, where very pure brilliant raw gypsum is used in their manufacture. Physically different hemihydrates are produced depending on the calcination process used: Alpha hemihydrate in the autoclave, or beta hemihydrate in the boiler plant or in the ...
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use of autoclaves and crystal modifiersto convert the crystal structure, one is the SICOWA-ProMineral process, 9 in which stable stackable blocks made from finelydivided FGD gypsum
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Similar results can be achieved by recrystallization from gypsum slurry around 100 °C in an autoclave or under a water steam atmosphere. ... This theory of the formation of α-hemihydrate inside ...
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Similar results can be achieved by recrystallization from gypsum slurry around 100 °C in an autoclave or under a water steam atmosphere.
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The industrial application of PG is mainly focused on building gypsum (β-CaSO 4 ·0.5H 2 O) [5], α-hemihydrate gypsum (α-CaSO 4 ·0.5H 2 O, α-HH) [6], [7], cement retarder [8], sulfuric acid co-production cement [9], soil conditioner [10] and so on. Among which, the preparation of α-HH using PG is one of the most profitable …
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Flue-gas desulphurization (FGD) gypsum is a highly prevalent industrial by-product worldwide, which can be an excellent alternative to natural gypsum due to its high content of CaSO4·2H2O. …
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DOI: 10.1016/J.CEJ.2011.09.033 Corpus ID: 96659014; α-calcium sulfate hemihydrate preparation from FGD gypsum in recycling mixed salt solutions @article{Guan2011calciumSH, title={$alpha$-calcium sulfate hemihydrate preparation from FGD gypsum in recycling mixed salt solutions}, author={Baohong Guan and Li …
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Several fabrication approaches are commonly adopted to prepare the a-CSH, including autoclave heating and chemical synthesize methods etc. 4,5,[18][19][20][21] Among them, autoclave heating is one ...
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Indeed, different autoclaves and different raw gypsum sources will result in a different hemihydrate surface. The authors suggest showing the hemihydrate solubility …
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The first industries for the autoclave production of alpha–hemihydrate by this method were built in Germany (Guilini) in 1962 and Japan (Nitto) in 1973 [1 – 4]. ... 15, 361 (1964). Forester J.: Chem. Ing. Tech. 44, 969 …
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Calcium Sulfate Hemihydrate, also known as plaster of Paris, is a material made from gypsum that has been used for centuries in construction and various medical applications, including bone repair and growth factor release. ... (17 psi) of pressure, in steam for 5 to 7 hours in an autoclave. Processing gypsum in this way produces more dense ...
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Flue gas gypsum may be converted to α-hemihydrate by suspending the starting material in inorganic salt solutions of high concentration or in diluted sulfuric acid and maintaining the suspension ...
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For the time being, α-HH is commercially produced by autoclave methods such as the SICOWA-ProMineral autoclaving process [13] and the Omega process [14]. However, these traditional processes are run at elevated temperature and high pressure and hence are energy-intensive. ... Preparation of α-calcium sulfate hemihydrate from …
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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 …
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Hemihydrate gypsum with controllable aspect ratio were synthesized at different maleic acid concentration. • The phase conversion process was observed with …
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