Pilot scale preparation of α-calcium sulfate hemihydrate from FGD gypsum in Ca–K–Mg aqueous solution under atmospheric pressure

Fuel ◽  
2012 ◽  
Vol 98 ◽  
pp. 48-54 ◽  
Author(s):  
Baohong Guan ◽  
Bao Kong ◽  
Hailu Fu ◽  
Jie Yu ◽  
Guangming Jiang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Atmospheric Pressure ◽  
Calcium Sulfate ◽  
Pilot Scale ◽  
Fgd Gypsum ◽  
Scale Preparation ◽  
Calcium Sulfate Hemihydrate

Influence of Seed Crystal and Modifier on the Morphology of α-calcium Sulfate Hemihydrate Prepared by Salt Solution Method in Pilot Scale

2010 ◽  
Vol 168-170 ◽  
pp. 8-12
Author(s):  
Bao Kong ◽  
Bao Hong Guan ◽  
Liu Chun Yang
Keyword(s):  
Salt Solution ◽  
Calcium Sulfate ◽  
Solution Method ◽  
Pilot Scale ◽  
Seed Crystal ◽  
Flue Gas Desulfurization ◽  
Fgd Gypsum ◽  
Mixed Salts ◽  
Spherical Crystals ◽  
Calcium Sulfate Hemihydrate

Preparation of α-calcium sulfate hemihydrate (α-HH) from flue gas desulfurization (FGD) gypsum is of great value in effectively utilizing the FGD gypsum. This paper focuses on the effect of seed crystal and some modifiers on the morphology of α-HH on a 500-1000 kg/batch setup based on a salt solution method established on the previous work. The pilot tests were carried out in a Ca-Mg-K chloride solution medium at 94 oC (±2 oC) under atmospheric pressure. The results show that a small amount of seeds is advantageous to prepare short-prism α-HH but results in needle-like and spherical crystals in the case of more than 1% addition. The well-shaped α-HH crystals can also be obtained by adding appropriate amounts of crystal modifiers like Fe3+ and the mixed salts of Al3+ and organics.

The Effect of Process Conditions on the Preparation of α-Calcium Sulfate Hemihydrate from FGD Gypsum Using the Hydrothermal Method under Atmospheric Pressure

2011 ◽  
Vol 250-253 ◽  
pp. 881-889 ◽  
Author(s):  
Xian Feng Liu ◽  
Jia Hui Peng ◽  
Chen Yang Zou ◽  
Leng Bai ◽  
Mei Li
Keyword(s):  
Hydrothermal Method ◽  
Reaction Temperature ◽  
Salt Concentration ◽  
Atmospheric Pressure ◽  
Calcium Sulfate ◽  
Ph Value ◽  
Fgd Gypsum ◽  
Rate Of Reaction ◽  
Percent Conversion ◽  
Calcium Sulfate Hemihydrate

This paper studies the laws of crystal growth, percent conversion and the rate of reaction of α-calcium sulfate hemihydrate from FGD gypsum under different conditions using the hydrothermal method under atmospheric pressure. The crystal morphology was observed by using SEM, polarizing microscope profile, and percent conversion and the rate of reaction were obtained by assaying crystal water content and calculating. The results showed, (1) with the increase of reaction temperature, the dehydration rate increased and the formed α-calcium sulfate hemihydrate crystal had a larger particle size; (2) with the increase of salt concentration or slurry concentration, the formed α-calcium sulfate hemihydrate crystal was smaller, percent conversion and the rate of reaction was nearly unchanged; (3) with the increase of pH value of solution, the rate of reaction increased and percent conversion was nearly unchanged, and with pH value ranging from 5 to 7 the formed α-calcium sulfate hemihydrate crystal was crassitude. In conclusion, the perfect technological parameters were as follows: reaction temperature ranging from 95°C to 100°C, salt concentration ranging from 15% to 20%, slurry concentration ranging from 15% to 20%, pH value ranging from 5 to 7, and reaction time not exceeding 90min.

Preparation of α-calcium sulfate hemihydrate from FGD gypsum in K, Mg-containing concentrated CaCl2 solution under mild conditions

Fuel ◽  
2009 ◽  
Vol 88 (7) ◽  
pp. 1286-1293 ◽  
Author(s):  
Baohong Guan ◽  
Liuchun Yang ◽  
Zhongbiao Wu ◽  
Zhuoxian Shen ◽  
Xianfa Ma ◽  
...  
Keyword(s):  
Calcium Sulfate ◽  
Fgd Gypsum ◽  
Mild Conditions ◽  
Calcium Sulfate Hemihydrate ◽  
Cacl2 Solution

Direct transformation of FGD gypsum to calcium sulfate hemihydrate whiskers: Preparation, simulations, and process analysis

Particuology ◽  
2015 ◽  
Vol 19 ◽  
pp. 53-59 ◽  
Author(s):  
Miao Miao ◽  
Xin Feng ◽  
Gangling Wang ◽  
Shaomei Cao ◽  
Wen Shi ◽  
...  
Keyword(s):  
Calcium Sulfate ◽  
Process Analysis ◽  
Direct Transformation ◽  
Fgd Gypsum ◽  
Calcium Sulfate Hemihydrate

EFFECT OF WATER VAPOR ON THE FORMATION OF MODIFICATIONS

1965 ◽  
Vol 43 (9) ◽  
pp. 2522-2529 ◽  
Author(s):  
R. A. Kuntze
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Atmospheric Pressure ◽  
Calcium Sulfate ◽  
Water Vapor Pressure ◽  
Exothermic Peak ◽  
Vapor Pressures ◽  
Ambient Water ◽  
Rate Of Heating ◽  
Calcium Sulfate Hemihydrate

The two recognized forms of calcium sulfate hemihydrate can be identified by the position of a relatively small exothermic peak in their differential thermograms. Hemihydrates prepared at various water vapor pressures up to 760 mm Hg were found to produce this exothermic peak in a position which is characteristic for the β-form. These results indicate that α-hemihydrate cannot be made at atmospheric pressure, as was previously suggested on the basis of heat solution measurements. The typical differential thermogram of α-hemihydrate is only obtained with material made by dehydration in solution or by autoclaving. The effect of ambient water vapor pressure on the position of the three peaks that occur in the differential thermogram of CaSO4•2H2O has also been studied. It was found that the incipient temperature of the second endothermic peak, corresponding to the transition of hemihydrate to soluble anhydrite, is displaced independent of the rate of heating from 145 °C to 187 °C with increasing water vapor pressures up to 760 mm Hg. This indicates that, for each temperature, a threshold water vapor pressure exists, above which soluble anhydrite cannot be formed.

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