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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 of FGD gypsum …
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This study explored the production of a medium–low strength α-hemihydrate gypsum (α-HH) from phosphogypsum using an autoclaved method. The influence of slurry concentration, spreading thickness, crystallizing agents, slurry pH, autoclaving temperature, and autoclaving time on the properties of α-HH was investigated.
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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 conversion of calcium sulfate dihydrate (DH) to hexagonal prismatic α-HH with high strength at atmospheric pressure.
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process (x = 2, gypsum as the final crystal form) and the nondihydrate process (also known as the hemihydrate process because hemihydrate is involved, although it is not necessarily the final crystal form). The dihydrate process is the earliest developed industrial phosphoric acid production technology.
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On this basis, the influence mechanisms of H 3 PO 4 on the preparation and performance of hemihydrate gypsum were revealed. The research in this paper can provide guidance for green, low-cost, and high-value utilization of phosphogypsum resources.
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When gypsum is heated at about 150– 160 °C, it loses approximately three-quar-ters of its water in a partial dehydration process and becomes hemihydrate gypsum (CaSO 4•1⁄2H2O) or calcined gypsum; it is also known as beta gypsum (alpha gypsum is made by processing batches of gypsum under elevated pressure).
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This article addresses the microstructure and related mechanical properties of gypsum produced from β-hemihydrate using information of its hydration process, from fresh paste to hardened gypsum. The water demand of the investigated β-hemihydrate was determined applying the spread flow test.
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According to Lavoisier and Le Chatelier, 9 the reaction is a process of dissolving hemihydrate to create a super saturated solution of gypsum, from which gypsum is formed. This is possible due to the lower solubility of gypsum compared to hemihydrate. This theory is proven by Figure 4a - 4i and it shows why gypsum can act as an accelerator.
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In particular, the present system is an improved method of dispersing, mixing, and conveying dry additives to a wall board manufacturing process. [0002] Gypsum board is commonly employed in drywall construction of interior walls and ceilings and also has other applications.
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To produce plasters or wallboard, gypsum must be partially dehydrated or calcined to produce calcium sulfate hemihydrate (CaSO4 1⁄2H 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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In particular, the present system is an improved method of dispersing, mixing, and conveying dry additives to a wall board manufacturing process. [0002] Gypsum board is commonly employed …
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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 temperature (323–363 K), …
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production process are critical to the acid filtration efficiency. In this work, a thermodynamically consistent definition of supersaturation is derived and modeled using the …
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On this basis, the influence mechanisms of H 3 PO 4 on the preparation and performance of hemihydrate gypsum were revealed. The research in this paper can provide …
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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 protein ...
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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 approaches because α-HH is a …
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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 …
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This study explored the production of a medium–low strength α-hemihydrate gypsum (α-HH) from phosphogypsum using an autoclaved method. The influence of slurry …
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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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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 hydration. An excess of water is needed for good workability for the gypsum plasterboard production but
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Calcium sulfate hemihydrate (β-CaSO 4 ·0.5H 2 O) is the most widely used gypsum building material [16].However, the commertial hemihydrate phosphogypsum that is heated at 100-180℃ directly is not as popular as desulfurization gypsum due to its lower performance [3].The commercial hemihydrate phosphogypsum contains impurities, such as …
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This study evaluated the feasibility to recycle TG to produce α-hemihydrate gypsum via microwave hydrothermal method, wherein tricarballylic acid (TA) was employed as modifier to modulate the crystallization of α-HH.
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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.
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When gypsum is heated at about 150– 160 °C, it loses approximately three-quar-ters of its water in a partial dehydration process and becomes hemihydrate gypsum (CaSO 4•1⁄2H2O) or …
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Depending on the production 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
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production process are critical to the acid filtration efficiency. In this work, a thermodynamically consistent definition of supersaturation is derived and modeled using the mixed-solvent-electrolyte framework in OLI software for gypsum in an acid mixture.
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Production of high-strength gypsum (α-CaSO 4 ∙1/2H 2 O) from commercial reagents like sulfuric acid and quick lime is obviously economically ineffective due to the high cost and low profit of ...
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The first describes the process of water leaving the structure of gypsum to form hemihydrate or anhydrite. The second depicts the temperature-dependent solubility of the …
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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) [1,2,3].Phosphogypsum (PG) is mainly composed of calcium sulfate dihydrate (DH), which is a byproduct from the wet process of phosphoric acid production.
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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 conversion of …
WhatsApp: +86 18221755073
This article addresses the microstructure and related mechanical properties of gypsum produced from β-hemihydrate using information of its hydration process, from fresh …
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The first describes the process of water leaving the structure of gypsum to form hemihydrate or anhydrite. The second depicts the temperature-dependent solubility of the calcium sulphates in water. The third illustrates the hydration energy of hemihydrate as it …
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This study evaluated the feasibility to recycle TG to produce α-hemihydrate gypsum via microwave hydrothermal method, wherein tricarballylic acid (TA) was employed as …
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