آخرین محصولات

Hydrothermal recrystallization of alpha calcium hemihydrate from gypsum

Recristallisation hydrothermale d'hemihydrate de calcium alpha à partir de gypse : effet de la température et du taux de solide sur la cinétique et la morphologie du produit Yi Rong, Alain Gaunand, Fabien Baillon, Fabienne Espitalier, Philippe Accart To cite this version: Yi Rong, Alain Gaunand, Fabien Baillon, Fabienne Espitalier, Philippe Accart.

Gypsum p2 Flashcards

Gypsum is heated in an autoclave, where it is exposed to high- pressure steam at 125 degrees C- alpha hemihydrate Wet/Autoclave calcination Water:powder ratio: 0.28-0.30 A lower W:P ratio results in a denser, stronger material with a better …

Dental gypsum Flashcards

Study with Quizlet and memorize flashcards containing terms like Requirements for model, Gypsum chemical name, Chemical name received in lab and more.

Autoclave‐Free Formation of α‐Hemihydrate Gypsum

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 Its Conversion into Its Various Hemihydrate Plaster Forms " (in Ger.), Zem.–Kalk–Gips, 11, 264, 304 ( 1958 ).

CN101691286B

The invention discloses an alpha-type semi-hydrated gypsum autoclave, which comprises a horizontal autoclave body. The horizontal autoclave body is provided with a feed end cover and a discharge end cover. A cavity wall of a cavity of the horizontal autoclave body is provided with a hot oil heating device. The hot oil heating device is connected to the outside of the horizontal …

processus d autoclave gypse à alpha hémihydrate.md

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Autoclave‐Free Formation of α‐Hemihydrate Gypsum

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 depend significantly …

US3579300A

US3579300A US847022A US3579300DA US3579300A US 3579300 A US3579300 A US 3579300A US 847022 A US847022 A US 847022A US 3579300D A US3579300D A US 3579300DA US 3579300 A US3579300 A US 3579300A Authority US United States Prior art keywords slurry gypsum reactor hemihydrate pressure Prior art date Legal …

Gypsum autoclaves from Maschinenbau SCHOLZ

Curing under steam atmosphere is a key process for the production of α-hemihydrate from raw gypsum stone. The α-hemihydrate is used to produce moulding plasters, gypsum building materials and special plasters with outstanding properties.Characteristics here are the high compressive and tensile strength, which can still be influenced by optimised process control in …

DE1771497B2

DE1771497B2 DE DE1771497A DE1771497B2 DE 1771497 B2 DE1771497 B2 DE 1771497B2 DE DE DE DE 1771497 A DE1771497 A DE 1771497A DE 1771497 B2 DE1771497 B2 DE 1771497B2 Authority DE Germany Prior art keywords hemihydrate calcium sulfate gypsum production water Prior art date …

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.

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 high concentration or in diluted sulfuric acid and maintaining the …

DENTMAT LEC

Study with Quizlet and memorize flashcards containing terms like GYPSUM, Calcium Sulfate Dihydrate CaSo4 ∙ 2H20, White to grayish and more. ... form of Alpha Hemihydrate that is harder and stronger and less likely to chip or abrade. 1. Calcined under steam pressure in an autoclave at a temperature of 120-130ᴼC 2. Dehydrated in water in an ...

Gypsum Flashcards

Study with Quizlet and memorize flashcards containing terms like accuracy, dimensional stability, strength, and abrasion resistance, gypsum, hydrous calcium sulfate and more.

GYPSUM Flashcards

Alpha Hemihydrate is produced by calcining gypsum under steam pressure at 120-130°C, resulting in a prismatic, regular, and white product used for cast stone. ... Dehydration in water with 0.5% sodium succinate in an autoclave. 3. Dehydration in a boiling solution of 30% calcium chloride in a kettle. ... Hemihydrate, and how is it produced ...

US5015449A

US5015449A - Process for making construction grade calcium sulfate alpha-hemihydrate from moist finely divided gypsum obtained from a power plant flue gas desulfurization - Google Patents

Preparation of α High-Strength Gypsum from FGD Gypsum …

This paper introduced the characteristics of α high-strength gypsum preparation from FGD gypsum by autoclaved semi-dry process. The compositions of the product in different stages …

Understanding gypsum in 3 diagrams

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, …

Preparation of Medium–Low Strength Hemihydrate Gypsum …

This study explored the production of a medium–low strength α-hemihydrate gypsum (α-HH) from phosphogypsum using an autoclaved method. The influence of slurry …

Sci-Hub | Autoclave-Free Formation of alpha-Hemihydrate …

Autoclave-Free Formation of alpha-Hemihydrate Gypsum. Journal of the American Ceramic Society, 74(5), 1117–1124. doi:10.1111/j.1151-2916.1991.tb04351.x

Gypsum: cast and die material Flashcards

Study with Quizlet and memorize flashcards containing terms like define cast, define die, what are the requirements for cast and die materials? and more.

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 high concentration or in diluted sulfuric acid and maintaining the suspension at boiling, or near boiling temperature for a period of time.

Effect of modifiers on crystalizing habit and mechanical …

α-Hemihydrate gypsum (α-HH) was prepared by autoclaving phosphogypsum (PG) in the presence of potassium sodium tartrate, succinic acid, potassium sulfate and …

Exam 2

1. hemihydrate mixes with water and forms a thick fluid suspension [ hemihydrate is MORE SOLUBLE than dihydrate] "Hemihydrate is soluble in water at the rate of 0.8g/100 ml.This compares with dihydrate which is only soluble in water at the rate of 0.2g/100 ml." 2. as the hemihydrate dissolves, a saturated solution forms--> since dihydrate is LESS SOLUBLE than …

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

DE1771497A1

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 to the accuracy ...

PROCESS FOR PRODUCING ALPHA-HEMIHYDRATE GYPSUM

What is claimed is: 1. A process for producing alpha-hemihydrate gypsum from dihydrate gypsum, comprising: feeding a slurry comprising the dihydrate gypsum and water into a heating tube; heating the heating tube at a temperature effective to generate steam and pressure from the water, wherein the steam and pressure are effective to convert the dihydrate …

CN101691286A

The invention discloses an alpha-type semi-hydrated gypsum autoclave, which comprises a horizontal autoclave body. The horizontal autoclave body is provided with a feed end cover and a discharge end cover. A cavity wall of a cavity of the horizontal autoclave body is provided with a hot oil heating device. The hot oil heating device is connected to the outside of the horizontal …

GYPSUM Flashcards

Study with Quizlet and memorize flashcards containing terms like Gypsum, setting reaction, Calcination and more. ... • Referred as type 3 or hydrocal • Calcined under steam pressure in an autoclave at a temperature of 120-130C ... alpha hemihydrate. type 4 (die stone) high strength, low expansion. type 5 (improved impression)

Process for producing alpha-hemihydrate gypsum

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.

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