Facile preparation of α-calcium sulfate hemihydrate whisker …
LAG is the ideal raw material to replace natural gypsum to produce hemihydrate gypsum (HHG) whiskers, realizing the high-value utilization of industrial by-product gypsum. ... Preparation and surface modification of anhydrous calcium sulfate whiskers from FGD gypsum in autoclave-free hydrothermal system energy sources, …
Influence of dehydration method on the morphology of hemihydrate gypsum
Fig. 6 - SEM analysis of hemihydrate gypsum, hemihydrate phosphogypsum, and processed hemihydrate phosphogypsum obtained in the autoclave (a-c) and microwave reactor (d-f).
Studies on the preparation of calcium sulphate hemihydrate …
To enable further work to be carried out on the hydration of hemihydrate plasters, materials purer than the available commercial plasters and with reproducible properties were required. As a first stage in the attempted preparation of such materials, the process variables in the autoclave dehydration of gypsum were investigated.
Crystallization Kinetics of α-Hemihydrate Gypsum Prepared …
α-Calcium sulfate hemihydrate (α-HH) is an important cementitious material, which can be prepared by hydrothermal method from calcium sulfate dihydrate (DH) in an electrolyte solution. Study of the conversion kinetics of DH to α-HH in NaCl solution is helpful for understanding the control process. In this paper, X-ray diffraction (XRD) …
Preparation of hemihydrate gypsum with controllable …
DOI: 10.1016/j.jcrysgro.2021.126360 Corpus ID: 241731164; Preparation of hemihydrate gypsum with controllable morphology in Glycerol-NaCl-Water solutions with maleic acid @article{Chen2021PreparationOH, title={Preparation of hemihydrate gypsum with controllable morphology in Glycerol-NaCl-Water solutions with maleic acid}, …
Autoclave‐Free Formation of α‐Hemihydrate …
Under optimal working conditions the quality of the formed α-hemihydrate gypsum is similar to that of a material produced in an autoclave. References. 1 E. Eipeltauer, " Preparation of Crude Gipseous Rock and …
[PDF] Preparation of α-calcium sulfate hemihydrate from …
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 …
Studies on the Preparation of Calcium Sulfate Hemihydrate …
Investigations were carried out to produce an autoclaved gypsum plaster (α-hemihydrate) by heating the naturally occurring selenite and by-product phosphogypsum under steam pressure in an autoclave.
Preparation of Calcium Sulfate α-Hemihydrate from FGD …
This study was performed to investigate the formation process of calcium sulfate α-hemihydrate from FGD gypsum produced at thermal power plant burning bituminous coal. The experimental results showed that calcium sulfate α-hemihydrate with a large aspect ratio was produced in the temperature range of 120 °C and 140 °C in the absence of …
Effect of Fluorine and Phosphorus Impurities in …
In this study, phosphogypsum (PG) is simulated by doping fluorine and phosphorus ions in an analytically pure reagent of gypsum dihydrate. 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 …
Autoclave‐Free Formation of α‐Hemihydrate Gypsum
Effect of particle size on the transformation kinetics of flue gas desulfurization gypsum to α-calcium sulfate hemihydrate under hydrothermal conditions. ... Autoclave-free method is commonly ...
Transformation of Flue-Gas-Desulfurization Gypsum to (α …
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 desulfurization (FGD) gypsum. In this work, the hexagonal prismatic α-HH crystals with controllable morphology were prepared in Glycerol-NaCl-Water solutions with maleic …
Facile preparation of high-strength α-CaSO4·0.5H2O
Crystal modifier is a significant factor in preparation of α-hemihydrate gypsum (α-HH) from phosphogypsum (PG). The influence of maleic acid, reaction …
Hemihydrate
Sustainability of gypsum products as a construction material. N. Lushnikova, L. Dvorkin, in Sustainability of Construction Materials (Second Edition), 2016 β-Hemihydrate binder. β-Hemihydrate (also known as plaster of Paris) is the most commonly used gypsum binder in construction.It is produced in an apparatus connected to air. Different equipment is …
Effect of Ethylenediaminetetraacetic Acid on the Preparation …
Phosphogypsum shows different properties with natural gypsum and flue gas desulfurization gypsum due to the existence of a variety of impurities, including phosphorus, fluorine, organic compounds and other ingredients.It has been a barrier for the application of phosphgypsum.In order to explore the ways for its application,the effect …
Effect of pH on the Preparation of α‐Calcium Sulfate Hemihydrate …
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.
Facile preparation of high-strength α-CaSO4·0.5H2O
Crystal modifier is a significant factor in preparation of α-hemihydrate gypsum (α-HH) from phosphogypsum (PG). The influence of maleic acid, reaction temperature, time, and solid–liquid ratio on the preparation of high-strength α-HH from PG was systematically studied herein. The optimum condition for α-HH prepared by …
Characterization and precipitation mechanism of α …
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 …
Understanding gypsum in 3 diagrams
Beta hemihydrate is formed when gypsum is heated up to around 100°C in a normal open kettle or rotary kiln. Alpha hemihydrate is formed in an autoclave above …
Formation of α-Hemihydrate Inside of a Gypsum Crystal …
None of the experiments were performed in an autoclave; gypsum crystals were only heated in a furnace and the crystal seems to be acting as an autoclave. Through several experiments, it was clearly shown that the new-formed crystals inside of the gypsum crystal are alpha-hemihydrate and the experimental proof for Fowler et al. theory was provided.
Gypsum hydration: a theoretical and experimental study
consumption of hemihydrate and formation of dihydrate. 1. Ultrasonic results indicate gypsum hydration reaction consists of two stages: the 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
Preparation of α-hemihydrate gypsum from …
Using FGD gypsum as the raw material, short columnar-shaped α-calcium sulfate hemihydrate can be prepared with succinic acid in hydrothermal autoclave method with a low salt content.
(PDF) Experimental Study and Mechanism Analysis of
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 autoclaved process, was used to produce α ...
Preparation of α-hemihydrate gypsum whiskers from …
A substantial stockpile of phosphogypsum (PG) not just consumes land resources, but also poses environmental contamination risks. Herein, the conversion of PG into high-value α-hemihydrate gypsum (α-HH) whisker by the atmospheric pressure salt solution method with simple process, high efficiency and low energy consumption was …
ChemInform Abstract: Autoclave-Free Formation of α-Hemihydrate Gypsum.
Download Citation | ChemInform Abstract: Autoclave-Free Formation of α-Hemihydrate Gypsum. | ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was ...
Formation of α-Hemihydrate Inside of a Gypsum Crystal …
None of the experiments were performed in an autoclave; gypsum crystals were only heated in a furnace and the crystal seems to be acting as an autoclave. …
Preparation of calcium sulfate whiskers from FGD gypsum …
The purified FGD gypsum, approximately 29.5 g, was first wet-milled at a rate of 300 rpm for 240 min (polyethylene bottle, ZrO 2 medium) in a ball mill (QM-3SP2, Nanjing University Instrument Co., China), while maintaining the mass ratio of purified FGD gypsum to distilled water at 1:1. After ball milling, the slurry was transferred into a …
Studies on the preparation of calcium sulphate hemihydrate …
To enable further work to be carried out on the hydration of hemihydrate plasters, materials purer than the available commercial plasters and with reproducible properties were required. As a first stage in the attempted preparation of such materials, the process variables in the autoclave dehydration of gypsum were investigated. Methods …
Preparation of hemihydrate gypsum with controllable …
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 …
Mechanism and kinetics of gypsum–anhydrite
Contrary to the gypsum behavior at 90 °C, in the experiments performed at elevated temperatures inside the autoclave, the transformation process proceeded faster, and a different transformation mechanism was observed.In the experiments performed at 150 °C, more than 90% of gypsum transformed to hemihydrate after 2 h retention time, …