基于反应动力学的煤中钠对SO_3生成的影响研究

Reaction kinetics study on SO_3 formation with presence of sodium in the coal

为研究煤中钠对SO_3生成的作用规律,基于Gibbs自由能最小原理,使用反应动力学计算方法研究了常规空气燃烧方式下煤中钠对SO_3生成的影响,分析了含钠气相化合物的形成转化与SO_3生成和消耗的关系。研究结果表明:常规燃烧方式下,当烟气中不含有NaCl时,沿整个烟气流程中SO_3的气相生成量最多;当烟气中含有Na Cl时,NaCl蒸气初始体积分数越高,沿整个烟气流程中SO_3气相生成量越少;烟气处于高温段时,气相含钠物相的生成与转化对SO_3体积分数基本没有影响;烟气处于低温段时,气相NaHSO_4的形成消耗了SO_3,使其体积分数减少至0;气相Na_2SO_4的形成对SO_3体积分数没有影响,主要受亚硫酸盐前驱体气相生成的控制;烟气中的钠对H、O、OH自由基浓度分布基本不产生影响。因此,常规燃烧方式下钠对SO_3生成有抑制作用。

On the basis of the minimum Gibbs free energy principle, this paper investigates the influence of sodium in coal on the formation of SO3 during conventional air combustion by using the reaction kinetics method. The relationship between the formation and transformation of gaseous sodium compounds and the formation and consumption of SO3 were analyzed. The results indicate that, in the conventional combustion mode, when the flue gas does not contain NaC1, the amount of SO3 vapor produced is the most along the flue gas flow. When the flue gas contains NaC1, the higher the initial volume fraction of NaC1 vapor, the smaller the amount of SO3 vapor produced along the flue gas flow. When the flue gas temperature is high, the formation and conversion of gaseous sodium phase has no effect on the volume fraction of SO3. When the flue gas temperature is low, the formation of NaHSO4 in gas phase consumes SO3, which reduces the volume fraction to zero. The formation of gaseous Na2SO4 has no effect on the volume fraction of SO3 and is mainly controlled by the gas phase formation of sulfite precursors. The distribution of H, O, and OH free radicals in the flue gas is not affected by sodium. Therefore, in the conventional combustion mode, sodium has an inhibitory effect on the formation of SO3.