煤灰氧化物与钙基固硫产物的高温多相反应机理

高温下常规固硫产物CaSO4的不稳定与分解是导致层燃炉和煤粉炉内固硫效率低下的主导因素，研究不同矿物质体系中硫酸钙的高温热变化行为具有重要意义。文中以化学纯矿物为研究对象，采用TG-DTG-DSC热综合分析法研究了煤灰氧化物SiO2、Al2O3、Fe2O3、CaO对CaSO4高温稳定性的影响；并采用高温反应器、XRD等试验设备及测试方法分析了CaO、SiO2、Al2O3、Fe2O3与CaSO4所组成的二元、三元矿物组分的固相反应过程。结果表明，CaO的加入对CaSO4的分解影响并不明显，SiO2、Fe2O3、Al2O3对CaSO4的分解总体表现为促进作用。SiO2在高温下易与CaO发生固相反应形成硅酸二钙和硅酸钙使得CaSO4的初始分解温度降低，在1200℃以后硫硅酸钙的形成对CaSO4的分解有一定的延缓作用。Fe2O3的加入由于铁离子的扩散效应促进了CaSO4的分解。Al2O3对CaSO4分解的影响具有两重性，Al2O3在CaSO4分解初期易与CaO发生固相反应形成铝酸钙促进CaSO4分解，但在CaSO4分解后期形成硫铝酸钙在一定程度上抑制了CaSO4的分解。

Heterogeneous Reactions Mechanism of Oxides in Coal Ash and Calcium-based Desulfurization Residues at High Temperature

It is valuable to study the thermal behavior of CaSO4 in different minerals system at high temperature because the decomposition of CaSO4 is main reason for the low desulfurization efficiency using calcium-based sorbents in pulverized coal fired boilers and grate furnaces. The effects of oxides in coal ash such as SiO2, Al2O3, Fe2O3, CaO on CaSO4 stability at high temperature were investigated by means of TG-DTG-DSC, and the solid state reactions of binary and ternary system consisting of CaO,SiO2,Al2O3, Fe2O3,CaSO4 were conducted with the facilities and methods such as high temperature reactor, XRD. The experimental results show that there is no remarkable effect on CaSO4 stability when doping with CaO, but SiO2, Fe2O3, Al2O3 can accelerate the decomposition of CaSO4 due to different mechanism such as solid reactions and diffusion action. SiO2 causes early decomposition of CaSO4 due to the formation of calcium silicate and dicalcium silicate during the reaction of CaO and SiO2 at high temperature, and the formation of calcium sulphosilicate above 1200℃ helps to retard CaSO4 decomposition. Fe2O3 can promote CaSO4 decomposition for the Fe ionic diffusion action. The effect of Al2O3 on CaSO4 decomposition is dual, the formation of calcium aluminate generated by the reaction of CaO and Al2O3 accelerate CaSO4 decomposition at the first stage, and then the decomposition of CaSO4 is restrained after the formation of calcium sulphoaluminate.