利用热重分析-X射线衍射分析法研究氧／二氧化碳气氛下石灰石硫化特性

Investigation on Sulfation Characteristics of Limestone Under O_2/CO_2 Atmosphere by TGA-XRD

通过TGA-xRD相定量分析联合对石灰石在O2／CO2气氛中的硫化特性进行了实验研究。结果表明,在O2/CO2气氛下,高CO2浓度使石灰石煅烧反应减慢,系统中较长时间内有高活性CaO产生,同时,由于在CaO／CaCO3界面上CO2的产生使CaSO4产物层扩散阻力降低,这两方面因素导致CaO在O2／CO2气氛下较长时间内维持较高的硫化速率,使得石灰石在O2／CO2气氛下可以取得较高的Ca转化率。1000℃为石灰石在O2／CO2气氛下的最佳硫化反应温度。相同硫化工况下,石灰石在O2／CO2气氛下硫化速率和Ca转化率均随CO2分压升高而升高,表明O2／CO2气氛更适合于高温脱硫。

The sulfation characteristics of limestone under O2/CO2 atmosphere were studied by combined TGA（thermogravimetric analysis） and quantitative X-ray diffraction （XRD） analysis. The experimental results show that high CO2 concentration make the calcination reaction of limestone slowed under O2/CO2 atmosphere. The system keeps on producing nascent CaO. The nascent CaO has high activity because it has bigger specific surface area and porosity without sintering. At the same time, the diffusional resistance through CaSO4 product layer is reduced because of the CO2 being formed at the CaO/CaCO3 interface before the limestone complete decomposition into CaO. The above two factors make CaO keep on a high sulfation rate for a long time under O2/CO2 atmosphere. So the high Ca conversion of limestone can be reached under O2/CO2 atmosphere. The optimal sulfation temperature under O2/CO2 atmosphere is 1000℃. The sulfation rate and Ca conversion increase with CO2 partial pressure under O2/CO2 atmosphere. It suggests that the O2/CO2 atmosphere is in favor of limestone desulfurization at high temperature.