脱硫建筑石膏是以石灰、氢氧化钙或石灰石湿法脱除烟气中二氧化硫时产生的以二水硫酸钙（CaSO₄·2H₂O）为主要成分的副产品为原料制成的建筑石膏。脱硫石膏通过煅烧后制成脱硫建筑石膏，但其力学性能不足的问题严重限制了工业化应用，因此提升改善其强度是当前研究的重点方向。研究以一定比例的乙酸镁和硫酸镁复合镁盐作为转晶剂，脱硫石膏于170 ℃下煅烧2 h制得脱硫建筑石膏，采用X射线衍射仪和扫描电子显微镜等技术手段研究了复合镁盐的比例及掺量对脱硫建筑石膏性能的影响。结果表明：以乙酸镁和硫酸镁复合镁盐作为转晶剂，硫酸镁中的Mg²⁺可以促进晶体生长，样品力学性能最优；适量的SO₄^2-能够通过提高二水石膏溶液的过饱和度而加速水化反应，最终改善建筑石膏性能；乙酸镁的引入，不仅确保了Mg²⁺浓度可控，而且乙酸根离子还能与Ca²⁺发生表面络合，实现对晶体生长的精准调控。优化实验条件确定了最佳工艺参数，当掺量为0.30%（质量分数），乙酸镁和硫酸镁质量比为1∶2时，该条件下制备的建筑石膏的水化产物呈现六棱柱状短粗晶体，建筑石膏的力学性能最佳，2 h抗折和抗压强度分别为3.90 MPa和9.82 MPa，绝干抗折和抗压强度分别为7.40 MPa和22.50 MPa，满足GB/T 9776—2022《建筑石膏》中3.0级标准并接近4.0级水平。

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 SO₄^2- 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..