Preparation of α-calcium sulfate hemihydrate from …
process, the precipitate may be anhydrite (n=0), hemihydrate (n=0.5) or dihydrate (n=2) of calcium sulfate. And the classical dihydrate technique is the main process to produce phosphoric acid in fertilizer industries. Additionally, anhydrite and hemihydrate gypsum are unstable, with the extension
Preparation of α-High-Strength Hemihydrate …
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 …
Gypsum hydration: a theoretical and experimental study
Gypsum hydration: a theoretical and experimental study. Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent …
11.16 Gypsum Manufacturing
soil conditioner, industrial and building plasters, and gypsum wallboard. To produce plasters or 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 ...
No. 4710 February 6, 1960 NATURE 375
A sample of hemihydrate was prepared by heating 800 gm. of a washed natural gypsum for 5 hr. in a glass container filled to a depth of. 3 in. (oven temp. 170° C.). The sample was cooled and then ...
Crystallization Kinetics of -Hemihydrate Gypsum …
gypsum (CaSO4 2H2O), hemihydrate gypsum (CaSO4 0.5H2O), and anhydrite (CaSO4) [1–3]. Phosphogypsum (PG) is mainly composed of calcium sulfate dihydrate (DH), which is a byproduct from the wet process of phosphoric acid production. It is estimated that every ton of phosphoric acid produces about 4.5 to 5.5 tons of PG [4,5] in the world. A large
Effect of Soluble Phosphorus on the Mechanical Properties …
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-hemihydrate gypsum. In this article, different forms of soluble phosphorus (H3PO4, H2PO4− and HPO42−) on the setting time and mechanical …
What is the Difference Between Alpha and Beta Hemihydrate
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 …
Hemihydrate
Depending on the process these products are: gypsum dihydrate, gypsum hemihydrate or anhydrite with more or less calcium sulfite or calcium sulfite hemihydrate. • At high …
Crystallization kinetics of large-sized columnar α-hemihydrate gypsum …
Direct production of high-strength α-calcium sulfate hemihydrate (α-HH) with no additives was accomplished by the reaction of aluminum sulfate and waste CaCl 2 discarded from Solvay soda plant. For scaling-up this new process, the crystallization kinetics of α-HH was experimentally investigated under varying conditions including …
Autoclave‐Free Formation of α‐Hemihydrate …
Here, a dynamic method, or an improved autoclaved process, was used to produce α-calcium sulfate hemihydrate from FGD gypsum. In this process, the …
Preparation of α-High-Strength Hemihydrate from …
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 …
Formation of α-Hemihydrate Inside of a Gypsum …
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 …
Revealing maleic acid role in the preparation of α-hemihydrate gypsum …
The applications of gypsum in China are primarily twofold: the preparation of high-strength gypsum, construction gypsum, composite cementing materials, and others, and the preparation of gypsum building products like gypsum board and gypsum blocks. Among these, α-hemihydrate gypsum (α-HH) is a high-end gypsum product, mainly …
Alpha Gypsum: k-sentials
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 ...
ALPHA GYPSUM POWDER VS BETA GYPSUM POWDER – …
1.Hemihydrate gypsum has two forms: α and β, both of which are rhombic crystals, but their physical properties are different. α-type hemihydrate gypsum has good crystallinity and firmness. β-type hemihydrate gypsum is a flaky and cracked crystal with excellent crystals. Its specific surface area is much larger than that of α-type ...
Efficient removal of impurities from phosphogypsum
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.
Hydration reaction and microstructural …
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 hemihydrate, and a …
Gypsum hydration: a theoretical and experimental study
Gypsum hydration: a theoretical and experimental study. Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs in two formations of α- and β-type. Among them β-hemihydrate is mainly used to produce gypsum plasterboard since ...
Hydration reaction and microstructural characteristics of hemihydrate
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 hemihydrate, and a few fibrous gypsum crystals were observed under different hydration condition, which confirmed that gypsum precipitated at the very beginning. ... The process of gypsum …
Direct transformation of FGD gypsum to calcium sulfate hemihydrate …
A new process of desulfurization gypsum activated by high-energy grinding to reduce the reaction temperature and sulfuric acid concentration was developed. Through the comparison of product morphology, the best grinding time was determined to be 3.5 h. ... Insight into the effect of maleic acid on the preparation of α-hemihydrate gypsum …
Formation of α-Hemihydrate Inside of a Gypsum Crystal …
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 investigated.
Hydration characteristics and mechanism analysis of β
The production of gypsum plaster starts from the thermal dehydration of gypsum (CaSO 4 ·2H 2 O, calcium sulfate dihydrate), at about 100–180 °C. During the process of heating, 75% crystallization water in calcium sulfate dihydrate is lost, and calcium sulfate hemihydrate (CaSO 4 ·0.5H 2 O) is finally formed, which is also referred …
Effect of Soluble Phosphorus on the Mechanical …
Preparation of α-hemihydrate gypsum crystal is an approach for utilization of phosphogypsum (PG), but the soluble phosphorus impurities in PG have a crucial …
Synthesis and Characterisation of Hemihydrate Gypsum
This study combined inorganic α-hemihydrate gypsum (α-HHG) with organic polyacrylamide (PAM) hydrogel to create a novel α-HHG/PAM composite material. Through this facile composite strategy, this fabricated material exhibited a significantly longer initial setting time and higher mechanical strength compared to α-HHG. The …
Microstructure and mechanical properties of β …
Therefore topics such as the hydration induced properties, and especially the behavior of the β-hemihydrate upon hydration to produce gypsum (plasterboard) is still …
Preparation of α-High Strength Gypsum from Flue Gas …
The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD) gypsum is a good way to realize the comprehensive utilization of FGD gypsum.To obtain α-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD …
Utilization of phosphogypsum to synthesize α-hemihydrate gypsum …
Phosphogypsum (PG) is a kind of industrial solid waste with high impurity content and low utilization rate. In this study, α-hemihydrate gypsum (α-HH) was synthesized from PG in H 3 PO 4 –H 2 O solution (wet-process phosphoric acid solution and phosphoric acid solution) under atmospheric pressure. The crystal morphology of α …
Autoclave‐Free Formation of α‐Hemihydrate Gypsum
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 …
Materials | Free Full-Text | Experimental Study and …
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. The preparation of α-calcium sulfate hemihydrate is a high-value pathway for the efficient use of FGD gypsum. Here, a dynamic method, or an improved …