加压富氧燃烧下SO_3生成特性的动力学机理研究

Dynamics Mechanism Investigation on the Formation of SO_3 During Pressurized Oxy-fuel Combustion

加压富氧燃烧技术由于受燃烧压力和烟气再循环富集SO_2的影响,烟气中SO_3的形成存在加剧的风险。本文通过详细化学反应机理和热力学平衡计算,对0.1~2.5 MPa范围内加压富氧燃烧条件下一些关键因素对SO_3形成的影响进行分析。研究结果表明;加压燃烧显著缩短2SO_2+O_2→2SO_3总包反应体系达到平衡的时间,并促进了SO_3的生成量,压力从0.1 MPa.提高到1.5MPa,对应的SO_3浓度升高到4倍,酸露点温度升高71℃。在高温火焰区(T≥1473K),0.1~2.5 MPa压力范围下,反应体系的平衡时间在1~100 mS的量级,SO_3的生成率在0~6.5%;而在后火焰区(T≤1273 K),反应速率较慢,反应体系的平衡时间在1~1000 s的数量级。通过对火焰区SO_3生成特性的热力学平衡评估发现SO_3的生成量分别与SO_2和O_2的浓度呈1和0.5次方的关系。

The increase of pressure and enrichment of SO2 due to gas flue recycle, significantly intensify the formation of SO3 during pressurized oxy-fuel combustion. By using detailed chemical reaction mechanism and thermodynamic equilibrium calculation, investigation on the influence of key factors on the formation of SO3 was carried out. Results show that, under pressurized oxy-fuel combustion the time reaching to equilibrium of the overall reaction （2SO2＋O2 →2SO3） significantly shortened, and the formation of SO3 is promoted. With pressure increasing from 0.1 MPa to 1.5 MPa, the concentration and partial pressure of SO3 increase to 4 times and 56 times relatively, and the acid due point （ADPT） increased 71℃. In high temperature flame zone （T≥1473 K）, the equilibrium time ranges within 1 and 100 ms and the ratio of SO3 formed ranges within 0 and 6.5%. While in post-flame zone, the reaction rate is slow and the equilibrium time ranges within 1-103 s. The evaluation of SO3 in post-flame zone using thermodynamic equilibrium reveals that the formation of SO3 is proportional to SO2 concentration and the 0.5th power of 02 concentration. Key words pressurized oxy-fuel combustion; SO3; detail reaction mechanism; thermodynamics; dynamics