Inorganic Chemicals Industry ›› 2025, Vol. 57 ›› Issue (8): 87-93.doi: 10.19964/j.issn.1006-4990.2024-0440

• Environment·Health·Safety • Previous Articles     Next Articles

Effect of compound magnesium salt on performance of desulfurized building gypsum

TIAN Bo(), HAO Jianying(), WANG Shengchang   

  1. School of Materials Science and Engineering,Taiyuan University of Science and Technology,Taiyuan 030024,China
  • Received:2024-08-06 Online:2025-08-10 Published:2024-12-29
  • Contact: HAO Jianying E-mail:102499701@qq.com;haojy2006@163.com

Abstract:

Desulfurized building gypsum is a type of building gypsum made from by-products mainly composed of calcium sulfate dihydrate(CaSO4·2H2O) produced during the wet removal of sulfur dioxide from flue gas using lime,calcium hydroxide,or limestone.Desulfurization building gypsum is made into building gypsum through calcination,but its insufficient mechanical properties seriously limits industrial application.Therefore,improving its strength is the focus of current research.The building gypsum was obtained by calcining desulfurization gypsum at 170 °C for 2 h using a certain proportion of magnesium acetate and magnesium sulfate composite magnesium salt as crystal modifier,and the effects of the proportion and dosage of composite magnesium salt on the properties of building gypsum were studied using X-ray diffractometer and scanning electron microscop.The results showed that using the compound magnesium salt of magnesium acetate and magnesium sulfate as crystal modifier,the Mg2+ in magnesium sulfate could promote crystal growth,corresponding to the best mechanical properties.The appropriate amount of SO42- accelerated the hydration reaction by increasing the supersaturation of the dihydrate gypsum solution,ultimately improving the performance of building gypsum.The introduction of magnesium acetate not only ensured that the Mg2+ concentration was controllable,but also the acetate group could form a surface complex with Ca2+ to achieve precise control of crystal growth.The optimal process parameters were optimized in the experiment.When the dosage was 0.30% and the mass ratio of magnesium acetate to magnesium sulfate was 1∶2,the hydration product of the building gypsum prepared under this condition showed short and thick hexagonal crystals,and the mechanical properties of building gypsum were the best,with 2 h flexural and compressive strengths of 3.90 and 9.82 MPa,respectively,and absolute dry flexural and compressive strengths of 7.40 and 22.50 MPa,respectively.It met grade 3.0 building gypsum standard in GB/T 9776—2022 "Calcined Gypsum",and close to grade 4.0 level..

Key words: desulfurization building gypsum, compound magnesium salt, building gypsum, mechanical properties

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