Preparation of Large-grained anhydrite(VI) γ-CaSO₄ with FGD gypsum

ABSTRACT

Large-grained anhydrite(VI) γ-CaO₄ was prepared in autoclave method by using flue-gas desulfurization gypsum as materials. The influence of slurry concentration, succinic acid and sodium chloride content, reaction temperature, reaction time, pH value, 1,4-butanediol was investigated. The research shows that large-grained anhydrite(VI) γ-CaSO₄ with length of 120 μm and length–diameter ratio of 1, dry compressive strength of which is similar to α40 grade, was obtained at slurry concentration of 18 wt%, succinic acid of 0.02 wt%, NaCl content of 3.0 wt%, 1,4-butanediol of 0.712 wt% after three times washing under 120°C without change of pH value. After five times circulation of mother liquid, the morphology and performance of product had no significant difference with initial product.

KEYWORDS:

• FGD gypsum
• gypsum–anhydrite
• high strength
• low crystal modifier content
• organic additive

Highlights

1. Design a new method of high pressure salt solution for preparing large-grained anhydrite(VI) γ-CaSO₄.

2. Anhydrite(VI) γ-CaSO₄ with length of 120 μm and length–diameter ratio of 1 was prepared at slurry concentration of 18 wt%, succinic acid of 0.02 wt%, NaCl of 3.0 wt%, 1,4-butanediol of 0.712 wt%, reaction temperature of 120°C, reaction time of 150 min, and without adjusting pH value, which the dry compressive strength achieved α40 grade.

3. After five cycle times of mother liquid, there has no obvious difference between the last and initial anhydrite(VI) γ-CaSO₄ gypsum morphology.

Additional information

Funding

This work was supported by Research Fund Program of Guangdong Provincial Key Lab of Green Chemical Product Technology: Grant Number [GC201816] and Nature Science Foundation of Hebei Province, China: Grant Number [B2017202268].