基于RSM-BBD的多源煤基固废胶结体配比及性能研究

Study on Proportioning and Performance of cemented Body from Multi-source Coal-based Solid Waste Based on RSM-BBD Experiment

本工作采用响应面法(RSM)Box-Behnken Design(BBD)模式对脱硫石膏、气化细渣和炉底渣等多源煤基固废进行配比优选,并研究了最优配比胶结体的力学性能、孔隙结构、热稳定性、微观结构等特性。结果表明:(1)气化细渣掺量对胶结体的1 d强度影响最大,脱硫石膏掺量对胶结体3 d和7 d强度影响最大,两种固废的交互作用对胶结体早期强度影响最显著,表现为负效应;在粉煤灰与矸石质量比为0.4∶1和质量浓度为80%的条件下,获得脱硫石膏、气化细渣和炉底渣的最优质量比为0.2∶0.1∶0.1,并分析了最优配比胶结体的压缩变形和破坏特征。(2)研究了胶结体的微观特性:胶结体内存在密集细颈型封闭孔隙,孔直径范围在5~3.7×10^(5) nm,微孔较少,以中、大孔为主;胶结体在55~65℃和90~120℃区间出现游离水和结晶水的吸热脱水反应,在600~700℃区间出现结构水、羟基水的脱除和水化产物的分解,在800℃累计失重约8%。(3)煤基固废胶结体的水化反应以水泥为主,固废之间未发生化学反应,水化产物为少量短杆状钙矾石相和薄层绒状C-S-H凝胶;钙矾石中少量Al^(3+)被Si^(4+)取代,少量SO_(4)^(2-)被CO_(3)^(2-)取代。

In this work,the mix proportion of multi-source coal-based solid wastes such as desulfurization gypsum,gasification fine slag and furnace bottom slag was optimized by Box-Behnken Design(BBD)model in response surface methodology(RSM),the mechanical properties,pore structure,thermal stability,and microstructure of the cemented body with the optimal mix proportion were analyzed.The results showed that:(1)the content of gasification fine slag has the greatest influence on the one day strength of the cemented body,the content of desulfurization gypsum has the greatest influence on the three days and seven days strength of the cemented body,and the interaction of the two solid wastes has the most significant influence on the early strength of the cemented body,showing a negative effect;under the condition of mass ratio of 0.4∶1 between fly ash and coal gangue and mass concentration of 80%,the optimal mass mix proportion of desulfurization gypsum,gasification fine slag and furnace bottom slag is 0.2∶0.1∶0.1,and then the compression deformation and failure characteristics of the cemented body with the optimal mix proportion are analyzed.(2)The microscopic characteristics of the cemented body were studied.There are dense and narrow-necked closed pores in the cemented body,with pore diameter ranging from 5 nm to 3.7×10^(5) nm and few micropores,mainly medium and large pores.The endothermic dehydration reaction of free water and crystal water occurs at 55—65℃and 90—120℃,the removal of structural water and hydroxyl water and the decomposition of hydration products occur at 600—700℃,and the cumulative mass loss at 800℃is about 8%.(3)The hydration reaction in cemented body is mainly cement,and there is no chemical reaction between coal-based solid wastes.The hydration products are a small amount of short rod-shaped ettringite phase and a thin layer of plush C-S-H gel;a small amount of Al^(3+)in ettringite is replaced bySi^(4+)and a small amount of SO_(4)^(2-)is replaced by CCO_(3)^(2-).