This work firstly shows that the observed crystallization inside of gypsum during dehydration is the formation of alpha-hemihydrate.
The α form material is also produced by heating gypsum, but this material is heated to 123 °C under approximately 1.2 kg/cm 2 (17 psi) of pressure, in steam for 5 to 7 hours in an autoclave.
Alcohol–water solution-mediated transformation of gypsum into α-hemihydrate (α-HH) whiskers provides a green alternative for the high-value-added recycling of flue gas desulfurization (FGD) gypsum. However, the role of non-lattice cations during the transformation is still unclear. We report an evolution from "boosting–retarding" to …
The alpha- and beta-forms of calcium sulphate hemihydrate, CaSO4.1/2H (2)O, were characterized using thermal, X-ray diffraction, optical and electron microscopy techniques.
Herein, cleaner PG is prepared with "HCl H 2 SO 4 method", and thus is used to synthesise α-hemihydrate gypsum (α-HH) in CaCl 2 solution under atmospheric pressure. …
Alpha hemihydrate is a crystalline form of calcium sulfate (CaSO 4 ), commonly known as plaster of Paris. This substance is derived from gypsum, a mineral composed of calcium sulfate dihydrate. The process of converting gypsum into alpha hemihydrate involves heating gypsum at a specific temperature to remove water …
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 …
Autoclave‐Free Formation of α‐Hemihydrate Gypsum. Flue gas gypsum may be converted to α-hemihydrate by suspending the starting material in inorganic salt …
pH is one of the most important parameters that determine the crystallization process, but it is always neglected in the preparation of α-calcium sulfate hemihydrate (α-HH) from calcium sulfate dihydrate (DH) with the hydrothermal method. Flue gas desulfurization (FGD) gypsum, which is mainly composed of DH, was used as raw …
An autoclave can be defined as an instrument used to clean any equipment and keep germs and bacteria-free. It is used in Laboratories, data centers, research centers, …
Download Citation | Autoclave‐Free Formation of α‐Hemihydrate Gypsum | Flue gas gypsum may be converted to α-hemihydrate by suspending the starting material in …
Results of the testing of α-hemihydrate manufactured of FGD gypsum, obtained in hydrothermal conditions at 130°C during 3 h of isothermal curing in rotary autoclave demonstrante that compressive strength of gypsum dry samples reached 67 MPa ( Leškevičiene, 2013 ).
As early as the 1990s, Germany has industrially produced α-hemihydrate gypsum from FGD gypsum by the autoclave process, which treated the feedstock at around 150°C under pressurized steam (0.14~0.28 Mpa) for 4~6 hours, and operated a plant with annual production capacity 240000 tons (Engert and Koslowski, 1998).
With systems such as mill calcining systems for combined grinding and calcining, the rotary kiln, the kettle, and the rotary tubular calciner, as well as continuous autoclaves for the production of alpha hemihydrate, Grenzebach supports its customers so they can optimally process gypsum to ensure that the finished product has the desired qualities.
For the first time, α-calcium sulfate hemihydrate (α-HH) was successfully prepared from calcium sulfate dihydrate (DH) in methanol–water solution under atmospheric pressure. The effect of methanol concentrations (40–73 mol%) on the transition from DH to α-HH were investigated at temperatures (60°–75°C) within a reaction time of 36 h. The …
On the other hand, an alpha-hemihydrate with larger crystals is formed inside of the gypsum crystal during a recrystallization, like is observed during the formation of alphahemihydrate in a steam autoclave.
Normally, the surface area of suspension autoclave alpha-hemihydrate is smaller compared to the steam autoclave alpha-hemihydrate, which is in turn lower than that of …
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 …
The purified FGD gypsum was mixed with distilled water in a ball mill at a rate of 300 rpm for 4 h. Next, the slurry was placed in a double-walled jacket autoclave. Distilled water was added to ensure a solid to liquid ratio of 1:20–1:30, while 0.01 M H 2 SO 4 and 1.5 wt% CuCl 2 were added to the slurry.
Autoclave (Alpha Hemihydrate) Gypmak. Autoclave (Alpha Hemihydrate) The chemical structure of alpha gypsum (CaSO4 + 1 / 2H2O) is the same as the beta plaster There are differences in crystal structure resulting from the production process For the production of alpha plaster high pressure autoclave kiln is used Autoclave is a word of Greek ...
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 at boiling, or near boiling temperature for a period of time. The crystal …
The influence of fluorine and phosphorus impurity and content on the dehydration reaction process of phosphogypsum and its crystalline micromorphology is assessed during the preparation of α‐type gypsum hemihydrate in the reversed‐phase microemulsion system and its mechanism.
Mentioning: 39 - Flue gas gypsum may be converted to a-hemihydrate by suspending the starting material in inorganic salt solutions of high concentration or in diluted sulfuric acid and maintaining the suspension at boiling, or near boiling temperature for a period of time. The crystal morphology of the produced a-hemihydrate gypsum and, thus, its quality …
Modeling of the kinetics of the synthesis process for calcium sulfate alpha-hemihydrate from gypsum formed by flue gas desulfurization (FGD) is important to produce high-performance products with…
The hydrothermal method is efficient in synthesizing alpha calcium sulfate hemihydrate (α-CSH) particles from flue gas desulfurization gypsum. This study investigates the effects of LiCl·H 2 O solution with different carboxylates on …
Similar results can be achieved by recrystallization from gypsum slurry around 100 °C in an autoclave or under a water steam atmosphere. However, in contrast, the …
DE1771497A1 - Process for the production of gypsum components from alpha hemihydrate - Google Patents ... hemihydrate seed crystals additional autoclave Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as …
pH is one of the most important parameters that determine the crystallization process, but it is always neglected in the preparation of {alpha}-calcium sulfate hemihydrate ({alpha}-HH) from calcium sulfate dihydrate (DH) with the hydrothermal method. Flue gas desulfurization (FGD) gypsum, which is mainly composed of DH, was …
