Abstract. The influence of the activity of calcium sulfate dihydrate (CaSO 4 ·2H 2 O) on the hydrothermal formation of CaSO 4 ·0.5H 2 O whiskers was investigated in this paper, using commercial CaSO 4 ·2H 2 O as the raw material. The experimental results indicated that the activity of CaSO 4 ·2H 2 O was improved after calcination of the commercial CaSO 4 ·2H 2 O at 150°C for 6.0 h ...
Pratima Bajpai, in Pulp and Paper Industry, 2015. 3.6.5 Gypsum. Gypsum consists of calcium sulfate crystallized with different degrees of hydration, all of which can be referred to as gypsum. In most cases, gypsum refers to calcium sulfate in the dihydrate form, and the other forms can be distinguished from each other by additional names example hemihydrate, calcined gypsum, and stucco gypsum.
A method and system for calcining gypsum to recover gypsum in a form consisting essentially of calcium sulfate anhydrite is disclosed. The method includes the steps of feeding the ground gypsum material into a first kettle and heating the ground gypsum in the first kettle to the first predetermined temperature. The first predetermined temperature is preferably below 400.degree.
Aug 01, 2005· The focus of this paper is the calcination step investigating only FGD gypsum wallboard; the impact of additives was not tested. Calcination changes the form of calcium sulfate from calcium sulfate dihydrate (CaSO 4 ·2H 2 O) or gypsum to calcium sulfate hemihydrate (CaSO 4 .
wallboard, gypsum must be partially dehydrated or calcined to produce calcium sulfate hemihydrate (CaSO4 ½H 2O), commonly called stucco. A flow diagram for a typical gypsum process producing both crude and finished gypsum products is shown in Figure 11.16-1. In this process gypsum is crushed, dried, ground, and calcined.
Continuous calcination of gypsum is provided by uniformly feeding uncalcined gypsum into the calcining batch in a kettle to a location below the surface but above the uppermost agitator, and allowing calcined gypsum to be discharged from the kettle through a discharge outlet in the wall of the kettle at the top surface of the calcining gypsum.
May 11, 1976· Calcination of gypsum, in its most common commercial form, involves heating gypsum, calcium sulfate dihydrate, and driving off some of the water of crystallization to form stucco, calcium sulfate hemihydrate. On subsequent addition of water to stucco, it will return to a rock-like calcium sulfate dihydrate.
US2418590A US534034A US53403444A US2418590A US 2418590 A US2418590 A US 2418590A US 534034 A US534034 A US 534034A US 53403444 A US53403444 A US 53403444A US 2418590 A US2418590 A US 2418590A Authority US United States Prior art keywords acid anhydrite gypsum kettle hemihydrate Prior art date 1944-05-04 Legal status (The legal status is an assumption and is not a .
EP2061731A1 EP07855582A EP07855582A EP2061731A1 EP 2061731 A1 EP2061731 A1 EP 2061731A1 EP 07855582 A EP07855582 A EP 07855582A EP 07855582 A EP07855582 A EP 07855582A EP 2061731 A1 EP2061731 A1 EP 2061731A1 Authority EP European Patent Office Prior art keywords temperature process plaster pressure steam Prior art date 2006-12-20 Legal status (The .
Gypsum is usually referred to be CaSO 4.2H 2 O. Calcium sulfate dIiydrate undergoes calcination to form hemihydrate (CaSO 4 1/2H 2 O) or anhydrous form (CaSO 4). Initially the calcination process was achieved by heating the raw gypsum material in an open environment, later on with the development in science calcination was achieved by heating ...
A calcining kettle includes a cylindrical housing having a hot air chamber at one end, a dust collecting chamber at an opposite end and a calcining chamber between the hot air chamber and the dust collecting chamber, at least one air pad disposed between the hot air chamber and the calcining chamber, each air pad being supported by air pad supports for passage of hot air therethrough.
Any tea kettle that has seen good use is bound to develop some mineral buildup, which doesn't sound like the easiest thing to clean out. But it's a lot easier than you might think to get even electric kettles as clean as new. Calcium and lime buildups can be dissolved with .
Sep 12, 1978· The process of calcining gypsum which comprises heating a mass of finely ground gypsum in a kettle to a temperature sufficient to convert said gypsum to calcium sulfate hemihydrate, maintaining a substantially continuous supply of gypsum being fed to said kettle, allowing a substantially continuous flow of calcined gypsum at the top of said ...
Abstract: A process is disclosed for making a blend of alpha- and beta-stucco including a slurry calcination step to produce alpha calcium sulfate hemihydrate followed by a fluidized bed calcination step to produce beta calcium sulfate hemihydrate. The process starts with 50-75% gypsum-containing solids slurry, and then steam calcines the slurry in a first reactor to form partially calcined ...
kettle consistency Prior art date 1967-01-11 ... 238000001354 calcination Methods 0.000 description 21; ZOMBKNNSYQHRCA-UHFFFAOYSA-J calcium sulfate hemihydrate Chemical compound ...
Feb 06, 1960· Kelley, Southard and Anderson1 have shown that the thermodynamic properties of calcium sulphate hemihydrate depend on whether the hemihydrate is produced from gypsum calcined in a steam-saturated ...
Calcining. Plaster or stucco is made by calcining the raw gypsum to convert the dihydrate into a hemihydrate, and is known as calcined gypsum. In some plants, landplaster is fed to kettle or flash calciners to produce plaster. Calcining occurs at about 250°-300°.
Kettle calcination continues to be the most commonly used method of pro-ducing (b-hemihydrate. The kettle can be operated on either a batch or a contin- ... Calcium sulfate, CaSO4, has several ...
gypsum kettle which may range between 60 and 200 minutes. Due to the kettle being heated indir-ectly the specific thermal energy requirement is about 20 % higher than when the gypsum is cal-cined directly in the gypsum calcining mill ( Tab 1). The quantity of the water to be evaporated in the calcining process also plays an important role.
Referring to FIG. 3, an exemplary process 300 for the post-calcination treatment of beta calcium sulfate hemihydrate (plaster) is shown. The described process is a batch process; however, it is contemplated that the process may be a continuous or semi-continuous process. ... The kettle calcination temperature was 147° C., operating at a ...
Desulfurization of Calcium Sulfate 163 Figure 35 Fluldizatlon Data—Gypsum 192b Figure 36 Fluldizatlon Data—Gypsum 193 . ix SUMMABI The shortage of Frasch-minable sulfur reserves has led to consideration of other materials as sources of sulfur and sulfuric acid. Naturally occurring calcium sulfate.
Abstract: A method and apparatus is disclosed for the continuous calcining of gypsum material in a high-efficiency, refractoryless kettle preferably heated by a multiple series of separate immersion tube burner coils, each coil operating within a specific calcining zone inside the kettle. The lowest, i.e., initial, burner tube coil is formed with a low profile to permit use of a small initial ...
Apr 24, 2014· A calcining kettle includes a cylindrical housing having a hot air chamber at one end, ... Plaster of Paris is also known as calcined gypsum, stucco, calcium sulfate semihydrate, calcium sulfate half-hydrate or calcium sulfate hemihydrate. It is the hemihydrate form that is mixed with water, then shaped to form a product having an interlocking ...
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.