NaCl共熔作用提高钙基脱硫剂利用率研究

Study on the effect of NaCl eutectic on improving the utilization rate of calcium-based desulfurizer

为提高煤燃烧过程中钙基吸收剂的脱硫利用率,在固定床实验系统上研究了NaCl添加对石灰石煅烧产物CaO脱硫活性的影响规律,初步获得了NaCl对吸收剂和硫酸化产物层的作用机理。结果表明,在煅烧阶段,采用浸渍法添加NaCl可以调节钙基吸收剂的孔隙结构,这是因为NaCl可以与颗粒表面的吸收剂发生低温共熔,低温共熔形成的液膜可加速液相烧结,从而使吸收剂表面积逐渐降低,随着NaCl的添加量增加(0~6.0 mol%),吸收剂的比表面积降低(4.35~0.75 m^(2)/g)。NaCl添加量4 mol%、8 mol%,可以提高乏吸收剂的脱硫活性,使其钙转化率分别增加13.1%、20.7%,这是由于NaCl与硫酸化产物层的共熔作用改变了脱硫反应中离子扩散的方式,使离子扩散速率显著提高。在硫酸化过程中,NaCl可同时与吸收剂和硫酸化产物发生三相共熔,当NaCl添加量较少时,NaCl与吸收剂的共熔作用对脱硫活性的影响占主导地位,而随着NaCl添加量的增加,NaCl与硫酸化产物的共熔作用对脱硫活性的影响变得越来越重要。

In order to improve the desulfurization utilization rate of calcium-based sorbents during coal combustion,the effect of NaCl addition on the desulfurization activity of CaO calcined limestone was studied in a fixed bed experiment system,and the mechanism of NaCl on the sorbent and sulfide layer was preliminarily obtained.The results show that in the calcination stage,the pore structure of calcium-based absorbent can be adjusted by adding NaCl by impregnation method.This is because NaCl can co-melt with the absorbent on the particle surface at low temperature.The liquid film formed by low temperature co-melting can accelerate the liquid phase sintering,so that the surface area of the absorbent is gradually reduced.With the increase of NaCl content(0~6.0 mol%),the specific surface area of the absorbent is reduced(4.35~0.75 m^(2)/g).The addition of NaCl(4 mol%,8 mol%)can improve the desulfurization activity of spent absorbent,and the calcium conversion rate increased by 13.1%,20.7%,respectively.This is because the eutectic effect of NaCl and sulfurized product layer changed the way of ion diffusion in desulfurization reaction,and the ion diffusion rate increased significantly.In the process of sulfation,NaCl can be three-phase eutectic with absorbent and sulfide products at the same time.When the amount of NaCl added is small,the eutectic effect of NaCl and absorbent on desulfurization activity is dominant.With the increase of NaCl addition,the eutectic effect of NaCl and sulfide products on desulfurization activity becomes more and more important.