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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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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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Flue gas desulfurization (fgd) is a waste incineration process that employs limestone slurry (CaCO 3) as a scrubber to remove SO 2 from exhaust gases, thereby reducing pollutant emissions. CaCO 3 reacted with SO 2 to form calcium sulphite (CaSO 3), which was then oxidized to form anhydrite (CaSO 4) and gypsum (CaSO 4 ⋅2H 2 O), …
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Semantic Scholar extracted view of "Utilization of phosphogypsum to synthesize α-hemihydrate gypsum in H3PO4–H2O solution" by Long Chen et al. Skip to search form Skip to main ... ion concentration are important for improving the conversion rate of α-HH–DH and the purity of DH products in the production of wet process …
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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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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 …
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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 …
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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 …
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1. Introduction. Phosphogypsum (PG) is a by-product of phosphoric acid production by treating phosphate ore (apatite) with sulfuric acid, which is comprised of dihydrate gypsum (CaSO 4 ·2H 2 O, DH) and various impurities (such as P 2 O 5, F −, organic matter, or even heavy metal ions, etc.) (Tayibi et al., 2009, Zeng et al., …
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The calcium sulphate dihydrate gypsum (CaSO 4 ·2H 2 O) is the most common sulphate evaporite mineral on our planet 1.Sulphate evaporites play an important role in Earth's sulphur cycle and are ...
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The gypsum-hemihydrate transformation has been long studied as a laboratory analogue for seismogenic dehydration reactions during subduction 8,9 and as …
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1. Introduction. Phosphogypsum (PG) is the main solid waste in the phosphorus chemical industry. In the wet process production of phosphoric acid, which is a mainstream process of the phosphorus chemical industry, 4.5–5.5 tons of PG is emitted for each ton of P 2 O 5 production [1], [2], [3].The PG is mainly composed of dihydrate …
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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 …
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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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Gypsum and anhydrite are naturally occurring minerals, however the hemihydrate and anhydrite can be obtained by calcination which is a process of chemical alteration by heating the dihydrated gypsum at temperatures of 125 °C-180° C and higher than 300 °C, respectively, as shown in Fig. 11 [30,31,20,32].
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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 …
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A microscopic mechanism of efflorescence on hemihydrate gypsum: insight into the formation and diffusion of sodium impurities in hemihydrate gypsum crystals. Colloids Surf. A Physicochem. Eng. ... a physical–chemical coupling production process. Chin. J. Chem. Eng., 28 (8) (2020), pp. 2221-2226, 10.1016/j.cjche.2020.05.021.
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In this paper, the dihydrate–hemihydrate recrystallization method was employed to produce β-hemihydrate gypsum. The effects of thermodynamic conditions such as temperature, sulfuric acid concentration, and phosphoric acid concentration on the removal of F and P impurities were investigated. Kinetic studies revealed that the …
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Hemihydrate gypsum (CaSO 4 ·0.5H 2 O, HH) is a kind of air-hardening cementitious material, which is widely applied in building and decoration materials, ... Kudo Y. Process for Production α-Form Gypsum Hemihydrate. 4842842. U.S. Patent. 1989 June 15; 13. Duan Z., Qin H., Li G., Tang X., Wen Z. Research on crystal form modifying …
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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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α-hemihydrate gypsum is synthesised by mild method from cleaner phosphogypsum. ... "Wet method" is an economic process of preparing phosphoric acid and is widely applied in phosphate fertiliser industry. ... (which is widely used in industrial production) for ease of utilisation. In the water-washing pre-treatment, the traditional …
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One process of forming alpha-hemihydrate gypsum involves placing calcium sulfate dihydrate in an autoclave in the presence of saturated steam at elevated pressure over an extended period of time. This method can be used for autoclaving of lump or ground gypsum. ... As described herein, reference has been made to the production of alpha ...
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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. ... 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 …
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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, …
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This work develops a new class of salt solution method to prepare alpha-calcium sulfate hemihydrate (α-HH) from flue gas desulfurization (FGD) gypsum in trace K 2 SO 4-contained 4.0 M Ca(NO 3) 2 aqueous solution at 95 °C under atmospheric pressure. The driving force for the phase transition is provided by the concentrated Ca(NO 3) 2 …
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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., autoclaving) and β-form is prepared by dry methods (e.g., calcining) from calcium sulphate dihydrate [16], [17], [18], [19].In the laboratory [19] β-hemihydrate is prepared from the dihydrate …
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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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DOI: 10.1021/acs.iecr.0c03305 Corpus ID: 224895914; Unraveling a Sustainable Process for the Production of High-Strength α-Gypsum Using Soda Residues and H2SO4 @article{Wang2020UnravelingAS, title={Unraveling a Sustainable Process for the Production of High-Strength $alpha$-Gypsum Using Soda Residues and H2SO4}, …
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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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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.
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