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Gypsum is a naturally occurring mineral that has been used by humans for various purposes for thousands of years. It is a versatile mineral with a wide range of applications in construction, agriculture, industry, and even art. In this introduction, we'll explore the definition and composition of gypsum.
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Phospho-gypsum is an industrial solid waste discharged from the phosphate production process. The waste includes complex impurities such as phosphoric acid and its salts, fluoride, and organics. Usually, retarders are mixed in gypsum-based building materials to extend setting time. Although the effects of the impurities on hydration …
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In this paper, the solid waste desulfurization gypsum produced by coal-fired power plants was used as a raw material to prepare calcium sulfate whiskers with high application prospects. Calcium sulfate whiskers with uniform morphology and high aspect ratio can be prepared by hydrothermal method in sulfuric acid solution. A new process …
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To achieve more profitable products, much attention has been paid to the development of FGD gypsum markets in the production of α-calcium sulfate hemihydrate ... D.W. Kirk, S. Tong, Process for the production of α-hemihydrate calcium sulfate from flue gas desulfurization materials, CA Patent 1996 CA2167978. Google Scholar
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of the hemihydrate, and water flowing on its surface may dissolve and wash away the material. This is the reason why gypsum is recommended for indoor applications only. It can, however, be used in external walls if the process includes treatment with silicone or bitumen and if a plaster coating is added.
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The building gypsum is mainly composed of β-hemihydrate gypsum (β-HH). β-HH is widely applied throughout the world due to its easy manufacture, aesthetics, low price and environmental friendliness [6,7]. In addition, it has fine grains, a large specific surface area, and a large level of water consumption for its standard consistency.
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wallboard, gypsum must be partially dehydrated or calcined to produce calcium sulfate hemihydrate (CaSO4 ½H 2O), commonly called stucco. A flow diagram for a typical gypsum process producing both crude and finished gypsum products is shown in Figure 11.16-1. In this process gypsum is crushed, dried, ground, and calcined.
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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 gypsum ...
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An industrially feasible process was proposed to produce α-calcium sulfate hemihydrate (α-HH) from FGD gypsum without any additives. In this process, an AlCl 3 solution was used to promote the …
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It can be inferred that in the process of the HH-CSW formation from gypsum, two Ca–O–H bonds of gypsum was broken up and they formed two Ca–O–S bonds, as illustrated in Fig. 10. The formation of two Ca–O–S bonds along the a -axis resulted in the blocking of the H 2 O channel of the a-axis while that of the c -axis was …
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The main production process for phosphate is shown in Fig. 1. In the wet phosphoric acid process, sulphuric acid is used to treat phosphate rock. Due to the chemical reaction (Eq. ... The crystal of hemihydrate and gypsum in Fig. 12 was marked as number 1 and 2, respectively. After 2 min hydration, the particles were mainly …
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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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An industrially feasible process was proposed to produce α-calcium sulfate hemihydrate (α-HH) from FGD gypsum without any additives. In this process, an AlCl3 solution was used to promote the conversion of calcium sulfate dihydrate (DH) to hexagonal prismatic α-HH with high strength at atmospheric pressure. The phase transition kinetics …
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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. ... In contrast, if water is supplied during the setting process, the gypsum crystals can grow further. For absorption ...
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Phospho-gypsum is an industrial solid waste discharged from the phosphate production process. The waste includes complex impurities such as phosphoric acid and its salts, fluoride, and organics. ... (Peak II). It is evident that hemihydrate gypsum containing Na 2 HPO 4 had a longer peak II than S4 (0.06 wt.% retarder), because the …
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Preparation of α-hemihydrate gypsum crystal is an approach for utilization of phosphogypsum (PG), but the soluble phosphorus impurities in PG have a crucial influence on the performance of α ...
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This process can disrupt the original structure of hemihydrate gypsum. The addition of maleic acid to the salt solution was found to foster anhydrous gypsum formation. In contrast, succinic acid can decrease the crystals' aspect ratio, resulting in the growth of short columns, thereby enhancing the product's strength performance.
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In recent years, the massive accumulation of industrial by-product gypsum, especially flue gas desulfurization (FGD) gypsum and phosphogypsum (PG), not only encroaches on lands but also causes serious environmental pollution. The preparation of α-calcium sulfate hemihydrate (α-HH) from industrial by-product gypsum is an important …
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Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated. This dehydration process is technically performed in three different ways.
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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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Abstract This study demonstrated the use of nesquehonite (MgCO3×3 H2O) in producing plasterboard. Nesquehonite (NQ) can be activated via thermal treatment under …
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Depending on the process of industrial production, hemihydrate occurs in two different forms (α- and β-forms); α-form is prepared by wet method (e.g., …
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The preparation of natural and synthetic gypsum prior to calcination, such as drying and grinding. The various calcination methods for β-hemihydrate and α-hemihydrate are reviewed, such as batch kettle, continuous kettle, submerged combustion kettle, conical kettle, and other calcination equipment.
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This process led to the formation of an amorphous phase (Fig. 5), as described by Morrison et al. [25] while the needle morphology remained somewhat intact, as shown in …
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The process of converting gypsum into alpha hemihydrate involves heating gypsum at a specific temperature to remove water molecules, resulting in a more concentrated and stable form of calcium sulfate. The term "alpha" in alpha hemihydrate refers to the unique crystal structure formed during this dehydration process. The alpha …
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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 …
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This is a two-stage process with calcium sulphate hemihydrate formed in the first stage being transformed to dihydrate gypsum in the second stage prior to discharge as a by-product. The filter acid may be further concentrated by evaporation, if required, for downstream uses. 2. Basics of Hemihydrate (HH) Process 2.1.
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In this article, tricalcium aluminate (C 3 A) was utilized as addition agent for hemihydrate gypsum (HHG) to improve the performance of gypsum pastes, and on that basis, the optimal dosage group of C 3 A was selected for further study on the composite effect with nano-silica (NS). HHG plasters with 0–5% content of C 3 A and besides …
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Lactic acid gypsum (LAG), the by-product from lactic acid preparation, has caused land occupation and environmental pollution. Herein, hemihydrate gypsum (HHG) whisker, an inorganic material with excellent performance, prepared using LAG as the raw material via atmospheric pressure salt solution method was investigated. Nitrate …
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