Effect of Organic Diacid Carbon Chain Length on Crystal Morphology of α-Calcium Sulfate Hemihydrate in Preparation from Flue Gas Desulphurization Gypsum

2012 ◽  
Vol 253-255 ◽  
pp. 542-545 ◽  
Author(s):  
Xian Feng Liu ◽  
Jia Hui Peng ◽  
Jian Xin Zhang ◽  
Jin Dong Qu ◽  
Mei Li
Keyword(s):  
Hydrothermal Method ◽  
Flue Gas ◽  
Atmospheric Pressure ◽  
Calcium Sulfate ◽  
Crystal Morphology ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Key Technology ◽  
Calcium Sulfate Hemihydrate ◽  
Flue Gas Desulphurization

Modifying crystal morphology was the key technology of the preparation of α-calcium sulfate hemihydrate from flue gas desulphurization gypsum using the hydrothermal method under atmospheric pressure. For exploring crystal modifier, the crystal morphology of α-calcium sulfate hemihydrate in preparation from flue gas desulphurization gypsum with various organic diacid was studied, by polarizing microscope profile observation. The results showed, When the space between two carboxyls was triplicate length of C-C, the organic diacid had the best effect of modifying crystal morphology.

Effect of Butane Diacid on Crystal Morphology and Reaction Process of α-Calcium Sulfate Hemihydrate in Preparation from Flue Gas Desulphurization Gypsum

2013 ◽  
Vol 838-841 ◽  
pp. 2681-2684 ◽  
Author(s):  
Xian Feng Liu ◽  
Jia Hui Peng ◽  
Ming Zheng Chen ◽  
Leng Bai ◽  
Liu Liu
Keyword(s):  
Flue Gas ◽  
Calcium Sulfate ◽  
Crystal Morphology ◽  
Reaction Process ◽  
Crystal Plane ◽  
Crystal Water ◽  
Water Testing ◽  
Film Layer ◽  
Calcium Sulfate Hemihydrate ◽  
Flue Gas Desulphurization

Modifying crystal morphology was the key technology of the preparation of α-calcium sulfate hemihydrate from flue gas desulphurization gypsum using the hydrothermal method under atmospheric pressure. For exploring the mechanism of butane diacid effect on crystal morphology of α-calcium sulfate hemihydrate in preparation from flue gas desulphurization gypsum, the crystal morphology, convert ratio, and reaction process of α-calcium sulfate hemihydrate were studied by scanning electron microscope observation, and crystal water testing. The results showed, firstly, crystal modifier made the growth rates of crystal in all directions equal and made the crystal into hexagonal short column, by selectivity adsorbing on (111) crystal plane of α-calcium sulfate hemihydrate to form buffer film layer which hindered combining and growing of crystallization unit on the crystal plane of c-axis direction. Secondly, butane diacid was a good crystal modifier. When adding butane diacid of optimal amount of 0.02%~0.05%, the crystal morphology of α-calcium sulfate hemihydrate was satisfactory, the crystal length-diameter ratio was 1:1, but the convert ratio was only 91%~93%.

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.

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.

scholarly journals Excess molar volumes of 1,3 propanediol + (C1-C5) alkan-1-ols: Application of cubic EOS

2012 ◽  
Vol 77 (3) ◽  
pp. 363-370 ◽  
Author(s):  
Mohammad Almasi ◽  
Ladan Khosravi
Keyword(s):  
Atmospheric Pressure ◽  
Full Range ◽  
Excess Molar Volumes ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Structural Factors ◽  
Pressure Measurements ◽  
Molar Volumes ◽  
Pure Compounds ◽  
Vibrating Tube Densimeter

Densities of the binary mixtures consist of methanol, ethanol, 1- propanol, 1-butanol and 1-pentanol with 1,3 Propanediol were measured at temperatures (293.15, 298.15, 303.15 and 313.15) K and atmospheric pressure. Measurements have been made over the full range of compositions and for the pure compounds by using a vibrating tube densimeter. Excess molar volumes have been obtained from these experimental results and were fitted to a Redlich-Kister type expansion. The results were interpreted in terms of molecular interactions and structural factors of the alcohols. It was observed that an increase of the alcohol carbon chain length led to lower interactions on mixing. The Peng-Robinson-Stryjek-Vera (PRSV) equation of state has been used to correlate the binary excess molar volumes.

Retracted Article: Effect of ethylene glycol on hydrothermal formation of calcium sulfate hemihydrate whiskers with high aspect ratios

RSC Advances ◽  
2015 ◽  
Vol 5 (62) ◽  
pp. 50544-50548 ◽  
Author(s):  
Wenpeng Zhao ◽  
Yumin Wu ◽  
Jun Xu ◽  
Chuanhui Gao
Keyword(s):  
Ethylene Glycol ◽  
Hydrothermal Method ◽  
Calcium Sulfate ◽  
Aspect Ratios ◽  
Retracted Article ◽  
Calcium Sulfate Hemihydrate

A facile ethylene glycol-assisted hydrothermal method was developed to synthesis HH whiskers with high aspect ratios.

Sign in / Sign up

Export Citation Format

Share Document