Effects of Composite Crystal Modifiers on Properties of Calcined Gypsum

Abstract

Abstract: As a kind of solid waste, flue gas desulfurization (FGD) gypsum can be used to prepare calcined gypsum by calcining at high temperature to realize the resource utilization of solid waste. FGD gypsum was used as raw material, calcium oxide and aluminum sulfate were added as composite crystal modifiers, and calcined gypsum was prepared by calcining at 170 ℃ for 2 h. The effects of the composite ratio and dosage of composite crystal modifiers on the properties of calcined gypsum were studied, and the composite crystal conversion mechanism was revealed. The results show that when the content of composite crystal modifier is 1% (mass fraction) and the composite ratio of calcium oxide and aluminum sulfate is 1 ∶1 (mass ratio), the prepared calcined gypsum has the best property. The gypsum block is dense after hydration, and the hydration products are in the form of alternating short columns or fibers. The 2 h flexural and compressive strength of calcined gypsum are 3.6 and 9.7 MPa, the dry flexural and compressive strength are 6.8 and 23.5 MPa, which meets the requirements of grade 3.0 calcined gypsum in Calcined Gypsum (GB/T 9776—2022).

Key words: FGD gypsum, calcined gypsum, composite crystal modifier, aluminum sulfate, calcium oxide, mechanical property

CLC Number:

TU528

HAO Jianying, WANG Shengchang, CHEN Jianing, TIAN Bo. Effects of Composite Crystal Modifiers on Properties of Calcined Gypsum[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(11): 4027-4034.

References

[1] 信翔宇, 陈广立, 张秀芝, 等. 石膏固废再生利用研究进展[J]. 中国粉体技术, 2023, 29(1): 10-18.
XIN X Y, CHEN G L, ZHANG X Z, et al. Research progress on recycling of gypsum solid waste[J]. China Powder Science and Technology, 2023, 29(1): 10-18 (in Chinese).
[2] 黎涛, 于亮, 宋文吉, 等. 烟气脱硫石膏粉化学物相分析[J]. 冶金分析, 2013, 33(2): 28-32.
LI T, YU L, SONG W J, et al. Chemical phase analysis of flue gas desulfurization gypsum powder[J]. Metallurgical Analysis, 2013, 33(2): 28-32 (in Chinese).
[3] LI Y, NI W, DUAN P X, et al. Experimental study and mechanism analysis of preparation of α-calcium sulfate hemihydrate from FGD gypsum with dynamic method[J]. Materials, 2022, 15(9): 3382.
[4] GUO H S, WANG Q P, LI W F, et al. Phase transformation and physical properties of binding materials fabricated from solid waste FGD gypsum by oil bath heating and the micromorphology and formation mechanism of their hydration products[J]. Construction and Building Materials, 2023, 377: 130981.
[5] WU S, WANG W L, REN C Z, et al. Calcination of calcium sulphoaluminate cement using flue gas desulfurization gypsum as whole calcium oxide source[J]. Construction and Building Materials, 2019, 228: 116676.
[6] CAILLAHUA M C, MOURA F J. Technical feasibility for use of FGD gypsum as an additive setting time retarder for Portland cement[J]. Journal of Materials Research and Technology, 2018, 7(2): 190-197.
[7] THYMOTIE A, CHANG T P, NGUYEN H A. Improving properties of high-volume fly ash cement paste blended with β-hemihydrate from flue gas desulfurization gypsum[J]. Construction and Building Materials, 2020, 261: 120494.
[8] WANG Y G, WANG Z F, LIANG F, et al. Application of flue gas desulfurization gypsum improves multiple functions of saline-sodic soils across China[J]. Chemosphere, 2021, 277: 130345.
[9] 茹晓红, 林海燕, 王玉江. 碱度对脱硫建筑石膏性能的影响[J]. 新型建筑材料, 2017, 44(8): 14-17.
RU X H, LIN H Y, WANG Y J. Effect of alkalinity on the performance of flue gas desulfurization calcined gypsum[J]. New Building Materials, 2017, 44(8): 14-17 (in Chinese).
[10] 刘林程, 左海滨, 许志强. 工业石膏的资源化利用途径与展望[J]. 无机盐工业, 2021, 53(10): 1-9.
LIU L C, ZUO H B, XU Z Q. Resource utilization approach of industrial gypsum and its prospect[J]. Inorganic Chemicals Industry, 2021, 53(10): 1-9 (in Chinese).
[11] 高淑娟. 煅烧对脱硫石膏性能的影响[J]. 四川建材, 2016, 42(6): 19-20.
GAO S J. Effect of calcination on properties of desulfurized gypsum[J]. Sichuan Building Materials, 2016, 42(6): 19-20 (in Chinese).
[12] HAO J Y, CHENG G J, HU T, et al. Preparation of high-performance building gypsum by calcining FGD gypsum adding CaO as crystal modifier[J]. Construction and Building Materials, 2021, 306: 124910.
[13] 栾扬, 赵志曼, 李黎山, 等. 复合转晶剂对磷建筑石膏晶体转晶影响的叠加效应研究[J]. 硅酸盐通报, 2018, 37(10): 3086-3090.
LUAN Y, ZHAO Z M, LI L S, et al. Superposition effect of composition medium crystal agent on the crystal transformation of phosphogypsum[J]. Bulletin of the Chinese Ceramic Society, 2018, 37(10): 3086-3090 (in Chinese).
[14] 张康. 改性剂-煅烧联合改性湿氟石膏制备建筑石膏粉的研究[D]. 长沙: 中南大学, 2013.
ZHANG K. Study on preparation of building gypsum powder by modifying wet fluorgypsum with modifier-calcination[D]. Changsha: Central South University, 2013 (in Chinese).
[15] 赵莉, 刘子树, 徐明新, 等. 高含氯脱硫石膏制备石膏砂浆研究进展[J]. 洁净煤技术, 2021, 27(3): 27-35.
ZHAO L, LIU Z S, XU M X, et al. Research progress on the preparation of gypsum mortar from desulfurization gypsum with high chlorine content[J]. Clean Coal Technology, 2021, 27(3): 27-35 (in Chinese).
[16] RESIO L C. Dolomite thermal behaviour: a proposal to establish a definitive decomposition mechanism in a convective air atmosphere[J]. Open Ceramics, 2023, 15: 100405.
[17] WANG X, JIN B, XU Z Y, et al. Effects of AlCl₃ on the crystal morphology of calcium sulfate whisker prepared from FGD gypsum[J]. IOP Conference Series: Materials Science and Engineering, 2019, 472: 012005.
[18] 王宇斌, 文堪, 王森, 等. 同离子效应对半水硫酸钙形貌的调控机理[J]. 高校化学工程学报, 2018, 32(6): 1444-1449.
WANG Y B, WEN K, WANG S, et al. Regulation mechanism of common ion effect on the morphology of calcium sulphate hemihydrate[J]. Journal of Chemical Engineering of Chinese Universities, 2018, 32(6): 1444-1449 (in Chinese).
[19] NGUYEN T T N, LEE M S. Speciation of alumina in aqueous solution and its interaction with silicate ion[J]. Geosystem Engineering, 2019, 22(4): 232-238.
[20] FAN H, SONG X F, LIU T J, et al. Effect of Al³⁺ on crystal morphology and size of calcium sulfate hemihydrate: experimental and molecular dynamics simulation study[J]. Journal of Crystal Growth, 2018, 495: 29-36.