autoclave free formation of a hemihydrate gypsum
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autoclave free formation of a hemihydrate gypsum

Autoclave‐Free Formation of α‐Hemihydrate Gypsum

Download Citation Autoclave‐Free Formation of α‐Hemihydrate Gypsum Flue gas gypsum may be converted to α-hemihydrate by suspending the starting material in inorganic salt solutions of ...

Autoclave‐Free Formation of α‐Hemihydrate Gypsum - Zürz ...

Autoclave‐Free Formation of α‐Hemihydrate Gypsum. Alfred Zürz. Technical University Clausthal, Clausthal‐Zellerfeld, Federal Republic of Germany ... The crystal morphology of the produced α‐hemihydrate gypsum and, thus, its quality depend significantly on the composition of the liquid phase. Additions of different carbonic acids may ...

ChemInform Abstract: Autoclave‐Free Formation of α ...

Read "ChemInform Abstract: Autoclave‐Free Formation of α‐Hemihydrate Gypsum., ChemInform" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.

Autoclave (Alpha Hemihydrate)

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 origin and means self-locking.

Studies on the Preparation of Calcium Sulfate Hemihydrate ...

Various factors effecting the calcination of gypsum such as pressure, time of the autoclaving process and the particle size of gypsum lumps were investigated. The formation of hemihydrate was ...

Dehydration of gypsum in the water suspension

O there is a great probability of formation of a-CaS0 4 III which has a lattice identical with that of the hemihydrate. At a slow dehydration of gypsum in an autoclave CaS0 4 II can be formed according to the reaction (A) also at temperatures under 235—250°C because above 25°C there is no

Preparation of Calcium Sulfate α-Hemihydrate from FGD ...

mM. It was confirmed that the optimum moulding pressure and moisture content of moulded body from FGD gypsum were 30 kgf/cm 2 and between 10% and 15% respectively, which prevent moulded body from collapsing and maximize the capillary effect by given pore volume while autoclaving. Keywords: FGD, gypsum, α-hemihydrate, moulded body, autoclave 1.

Direct transformation of calcium sulfite to α-calcium ...

Jan 01, 2011  Studies on the preparation of calcium sulfate hemihydrate by an autoclave process. J Appl Chem, 18 (10) (1968), pp. 307-312. View Record in Scopus Google Scholar. A. Zürz, I. Odler, F. Thiemann. Autoclave-free formation of α-hemihydrate gypsum. J Am Ceram Soc, 74 (5) (1991), pp. 1117-1124. CrossRef View Record in Scopus Google Scholar

US3579300A - Continuous process for the production of ...

process for producing calcium sulphate alpha-hemihydrate by subjecting a slurry of gypsum and water to superatmospheric pressure sufficient to maintain the water in the liquid state at a preselected mean temperature of at least 130*c., continuously passing the said slurry into a reactor having an inlet and an outlet, injecting into said slurry sufficient steam at a pressure and temperature ...

Preparation of α-calcium sulfate hemihydrate from FGD ...

Jul 01, 2009  To prepare α-calcium sulfate hemihydrate (α-HH) from flue gas desulfurization (FGD) byproduct under atmospheric pressure, the dehydration of FGD gypsum in a concentrated Ca and Mg chlorides solution medium at 95 °C was investigated, and the effects of K + ions were focused on. The crystal water content variation, material phases, and morphological characteristics of the dehydration

Studies on the Preparation of Calcium Sulfate Hemihydrate ...

Various factors effecting the calcination of gypsum such as pressure, time of the autoclaving process and the particle size of gypsum lumps were investigated. The formation of hemihydrate was ...

Autoclaved gypsum plaster from selenite and by‐product ...

The data showed that complete inversion of gypsum into hemihydrate takes place by heating gypsum of particle size 15 to 20 mm 3 at 1.75 kg cm −2 steam pressure for 7 h. The microscopy of plaster revealed formation of well‐defined euhedral prismatic and tabular shaped crystals showing a higher degree of crystallinity than the conventional β ...

Dehydration of gypsum in the water suspension

O there is a great probability of formation of a-CaS0 4 III which has a lattice identical with that of the hemihydrate. At a slow dehydration of gypsum in an autoclave CaS0 4 II can be formed according to the reaction (A) also at temperatures under 235—250°C because above 25°C there is no

Preparation of Calcium Sulfate α-Hemihydrate from FGD ...

mM. It was confirmed that the optimum moulding pressure and moisture content of moulded body from FGD gypsum were 30 kgf/cm 2 and between 10% and 15% respectively, which prevent moulded body from collapsing and maximize the capillary effect by given pore volume while autoclaving. Keywords: FGD, gypsum, α-hemihydrate, moulded body, autoclave 1.

Direct transformation of calcium sulfite to α-calcium ...

Jan 01, 2011  Studies on the preparation of calcium sulfate hemihydrate by an autoclave process. J Appl Chem, 18 (10) (1968), pp. 307-312. View Record in Scopus Google Scholar. A. Zürz, I. Odler, F. Thiemann. Autoclave-free formation of α-hemihydrate gypsum. J Am Ceram Soc, 74 (5) (1991), pp. 1117-1124. CrossRef View Record in Scopus Google Scholar

THERMAL TREATMENT OF THE PHOSPHOGYPSUM

raised pressure in autoclave allows for obtaining the gypsum binder of high quality [7]. This method was used to obtain an extremely strong gypsum binder from the mixture of ground gypsum stone and the admixture that controls crystallization of hemihydrate gypsum [8]. The mixture with 1-2 % of water was pressed under 12-18 MPa pressure.

Promotion of conversion activity of flue gas ...

Jan 16, 2020  The massive accumulation of flue gas desulfurization (FGD) gypsum produced in the wet limestone-gypsum flue gas desulfurization process not only encroaches on lands but also causes serious environmental pollution. The preparation of α-hemihydrate gypsum (α-HH) is an important way to achieve high-value utilization of FGD gypsum. Although the glycerol-water solution approach can be

autoclave process gypsum to alpha hemihydrate

Review of Global Gypsum Conference Exhibition 2019. Oct 24 2019 0183 32 Three technologies currently exist for the production of alpha hemihydrate gypsum from phosphogypsum the autoclave process the hydrothermal process and the normal pressure salt process but each has its own disadvantages including high energy costs low product strength and large amounts of waste water...

[PDF] Production of gypsum products from waste battery ...

Production of gypsum products from waste battery acid. Lead-acid batteries are the largest worldwide use of lead. Conventional recycling (95% in UK) produces harmful by-products. Recent environmental legislation has led to increased costs, due to the energy required, and the requirement to

US3410655A - Production of alpha-calcium sulfate ...

US3410655A US52963266A US3410655A US 3410655 A US3410655 A US 3410655A US 52963266 A US52963266 A US 52963266A US 3410655 A US3410655 A US 3410655A Authority US United States Prior art keywords hemihydrate temperature calcium sulfate dihydrate alpha Prior art date 1965-04-24 Legal status (The legal status is an assumption and is not a legal conclusion.

Calcium sulfate - Wikipedia

Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO 4 and related hydrates.In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant.One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum.It has many uses in industry. All forms are white solids that are poorly soluble in water.

ALPHA PLASTER PRODUCED BY PRESSURELESS METHOD

gypsum to alpha- hemihydrate can be effected in a mixed solution based on NaCl and KCl. This, however, must contain at least 25 % NaCl. Effect of the mixed solution concentration on the kinetics and morphology of hemihydrate The effect of concentration was tested on the mixed solution 4 composed of 25 % NaCl and 75 % KCl, see

Characterization and precipitation mechanism of α-calcium ...

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 (EDS), and scanning electron microscopy (SEM) have been ...

ECO-BALANCE FEATURES AND SIGNIFICANCE OF

Gypsum cement from E–PGK 11.46 0.32 22 71 Gypsum cement from E–PGM 11.65 0.32 18 65 2. Materials and methods Autoclave cellular concrete plant (YTONG) ecobalance evaluation method (Hums 1994) was used for analytical investigations. According to this method, the analytical investigations were conducted in 3 steps:

Preparation of Calcium Sulfate α-Hemihydrate from FGD ...

mM. It was confirmed that the optimum moulding pressure and moisture content of moulded body from FGD gypsum were 30 kgf/cm 2 and between 10% and 15% respectively, which prevent moulded body from collapsing and maximize the capillary effect by given pore volume while autoclaving. Keywords: FGD, gypsum, α-hemihydrate, moulded body, autoclave 1.

Influence of Gypsum on the Hydrothermal Reaction of Lime ...

starting mixtures, hemihydrate dehydrated form of the gypsum reacted with lime and quartz to form hexagonal prisms of hydroxyl ellestadite which grew radially, and inhibited the formation of C-S-H and tobermorite. This inhibition resulted in the delay of the eleva-tion of the strength.

ECO-BALANCE FEATURES AND SIGNIFICANCE OF

Gypsum cement from E–PGK 11.46 0.32 22 71 Gypsum cement from E–PGM 11.65 0.32 18 65 2. Materials and methods Autoclave cellular concrete plant (YTONG) ecobalance evaluation method (Hums 1994) was used for analytical investigations. According to this method, the analytical investigations were conducted in 3 steps:

THERMAL TREATMENT OF THE PHOSPHOGYPSUM

raised pressure in autoclave allows for obtaining the gypsum binder of high quality [7]. This method was used to obtain an extremely strong gypsum binder from the mixture of ground gypsum stone and the admixture that controls crystallization of hemihydrate gypsum [8]. The mixture with 1-2 % of water was pressed under 12-18 MPa pressure.

Investigation of hydration mechanisms ... - Cement Lime Gypsum

Investigation of hydration mechanisms of alpha and beta hemihydrate. All authors. 1 a) Represents the solubility curves of gypsum, anhydrite, and hemihydrate while b) represent both nucleation and growth processes [11, 12] All authors. 2 SEM images of different types of hemihydrates: a) α-HH steam autoclave and c) β-HH with low and high ...

Characterization and precipitation mechanism of α-calcium ...

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 (EDS), and scanning electron microscopy (SEM) have been ...

autoclave process gypsum to alpha hemihydrate

Review of Global Gypsum Conference Exhibition 2019. Oct 24 2019 0183 32 Three technologies currently exist for the production of alpha hemihydrate gypsum from phosphogypsum the autoclave process the hydrothermal process and the normal pressure salt process but each has its own disadvantages including high energy costs low product strength and large amounts of waste water...

[PDF] Production of gypsum products from waste battery ...

Production of gypsum products from waste battery acid. Lead-acid batteries are the largest worldwide use of lead. Conventional recycling (95% in UK) produces harmful by-products. Recent environmental legislation has led to increased costs, due to the energy required, and the requirement to

ALPHA PLASTER PRODUCED BY PRESSURELESS METHOD

gypsum to alpha- hemihydrate can be effected in a mixed solution based on NaCl and KCl. This, however, must contain at least 25 % NaCl. Effect of the mixed solution concentration on the kinetics and morphology of hemihydrate The effect of concentration was tested on the mixed solution 4 composed of 25 % NaCl and 75 % KCl, see

Review of Global Gypsum Conference Exhibition 2019 ...

Oct 24, 2019  Three technologies currently exist for the production of alpha hemihydrate gypsum from phosphogypsum: the autoclave process, the hydrothermal process and the normal pressure salt process, but each has its own disadvantages, including high energy costs, low product strength and large amounts of waste water.

Dehydration Pathways of Gypsum and the Rehydration ...

gypsum is stable in the low-temperature and high water vapor pressure region and does not dehydrate to form any calcium sulfate hemihydrate. Finally, the rehydration mechanism of soluble ... necessary to make a correction for the Gibbs free energy of formation of γ-CaSO 4. Kevin

GyPSum - Elotex

Large joint-free gypsum based floor leveling compounds speed up the finishing process, ideal for use with underfloor ... from autoclave production. ... from rotary kiln or kettle production. Formation starts at temperatures of around 100° C. Fast formation of hemihydrate phases. used for plastering applications. Anhydrite II ( CaSO 4) comes in ...

Gypsum products - SlideShare

Dec 18, 2016  • Dental stone: Dental stones may be produced byone of two methods. If gypsum is heated to about125ºC under steam pressure in an autoclave a more regular and less porous hemihydrate is formed This is sometimes referred to as an α-hemihydrate. Alternatively, gypsum may be boiled in a solution of a salt such as CaCl2.

Pilot scale preparation of α-calcium sulfate hemihydrate ...

Download Free PDF. Download Free PDF. Pilot scale preparation of α-calcium sulfate hemihydrate from FGD gypsum in Ca–K–Mg aqueous solution under atmospheric pressure. Fuel, 2012. Guangming Jiang. Jie Yu. Baohua Kong. Bao-hong Guan.

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