Mentioning: 42 - 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 …
process at around 100 C in an autoclave filled with gypsum slurry. In this process, larger In this process, larger hemihydrate crystals can grow with fewer surface defects.
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 …
1. Introduction. Calcium sulfate is the subject of much research due to its wide scope and large-scale of industrial applications [1], [2], [3].It occurs in nature mainly in form of three different phases distinguished by the content of crystal water: dihydrate (DH, CaSO 4 ·2H 2 O), hemihydrate (HH, CaSO 4 ·0.5H 2 O), and anhydrite (AH, CaSO …
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 …
Alpha-calcium sulfate hemihydrate (α-HH) has been used effectively in grafting through its desired features to support bone regeneration. In recent years, many synthetic methods have been proposed. Among them, the autoclave method for manufacturing α-HH is best suited for cost-savings due to its simple operation and …
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.
One-step wet-process phosphoric acid by-product CaSO4 and its purification. ... Alpha-calcium sulfate hemihydrate used as a water-soluble template for the synthesis of ZnO hollow microspheres. ... Effects of different carboxyl additives on the growth habits of hemihydrate gypsum crystals. Construction and Building Materials 2022, 316, 126037.
The pilot plant with a production capacity of 1000 kg/batch was constructed at Xiaoshan Power Plant, Zhejiang Province, China. Fig. 1 shows the schematic diagram of the pilot plant, which mainly consists of a salt solution tank (D 2.0 m × H 2.0 m), a homogenizer (D 2.0 m × H 2.0 m), two stirred bed reactors (D 2.0 m × H 2.0 m), a …
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 …
Here, a dynamic method, or an improved autoclaved process, was used to produce α-calcium sulfate hemihydrate from FGD gypsum. In this process, the …
Pouring time should be controlled in the time before α-hemihydrate decorative gypsum hydration, and the pouring temperature can be slightly lower than the autoclave temperature. The process of ...
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. Typical pressures for the autoclave can be from atmospheric to about 15 psi.
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. Processing gypsum in this way produces more dense crystals with little porosity, and these crystals require less water for setting and produce the dense ...
It can be inferred that in the process of the HH-CSW formation from gypsum, two Ca–O–H bonds of gypsum was broken up and they formed two Ca–O–S bonds, as illustrated in Fig. 10. The formation of two Ca–O–S bonds along the a-axis resulted in the blocking of the H 2 O channel of the a-axis while that of the c-axis was …
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 the conversion process. Under optimal operating conditions, hexahedral column shaped crystals are …
Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, …
Autoclave‐Free Formation of α‐Hemihydrate Gypsum. A. Zurz I. Odler F. Thiemann Katarina Berghöfer. Materials Science. 1991. Flue gas gypsum may be …
Mentioning: 42 - 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 …
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.
In order to utilize the spent CaCl 2 waste from soda plants, in this work a novel process was proposed to directly produce higher strength α-gypsum by the following reaction of CaCl 2 and Al 2 (SO 4) 3 without autoclave equipment at atmospheric conditions: (1) 3 C a C l 2 + Al 2 SO 4 3 + 1.5 H 2 O → Δ 3 C a S O 4 ∙ 0.5 H 2 O + 2 A l …
Several fabrication approaches are commonly adopted to prepare the a-CSH, including autoclave heating and chemical synthesize methods etc. 4,5,[18][19][20][21] Among them, autoclave heating is one ...
Under optimal working conditions the quality of the formed α-hemihydrate gypsum is similar to that of a material produced in an autoclave. Discover the world's research 25+ million members
The kinetics fit an autocatalytic process, with a very small initial [product]o (typically ∼10−4 M, consistent with a high purity gypsum starting material) and a rate …
use of autoclaves and crystal modifiersto convert the crystal structure, one is the SICOWA-ProMineral process, 9 in which stable stackable blocks made from finelydivided FGD gypsum
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 …
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 …
1 Introduction . Calcium sulfate hemihydrate [CaCO 4 ∙ 0.5H 2 O(s)] can be found naturally in very dry climate regions in Egypt, Australia, Death valley and Kuwait as bassanite, but in the presence of water or humid atmosphere it can convert to dehydrate [1, 2]. Therefore, the production of hemihydrate industrially has been studied widely through the dehydration …
DOI: 10.1016/J.CEJ.2011.09.033 Corpus ID: 96659014; α-calcium sulfate hemihydrate preparation from FGD gypsum in recycling mixed salt solutions @article{Guan2011calciumSH, title={$alpha$-calcium sulfate hemihydrate preparation from FGD gypsum in recycling mixed salt solutions}, author={Baohong Guan and Li …
Alpha hemihydrate is formed in an autoclave above 100°C in a water (suspension autoclave) or in a steam autoclave. 5 - 7 This is possible as, above 100°C, …