Two kinds of typical modification methods

hydrochloric acid potassium manganate modification and sodium hydroxide modification are chosen. These modification methods may change the physical and chemical characteristics of kaolin by using the strong acidity and strong oxidizing of hydrochloric acid potassium manganate

and the strong basicity of sodium hydroxide. And these changes may improve the particulate matter (PM) captured efficiency of kaolin. A typical coal chose in the experiment burns with the raw and modified kaolin in an electrical heated drop-tube furnace

and the particle size distribution of particulate matter is obtained. According to the experimental results

the acid modification can significantly improve the capture efficiency of PM0.2 (particles with the aerodynamic diameter less than 0.2 μm) by kaolin

but the alkali modification inhibit the capture of PM0.2. According to the characterization analysis

for the acid modification kaolin

the Al—OH bond

Al—O—Si bond

Si—O bond and Si—O—Si bond of kaolin are significantly weaken

which can promote the reaction between kaolin and alkali metals

and thus the capture efficiency of PM0.2 is promoted. For the alkali modification kaolin

the Si—O bond and Si—O—Si bond of kaolin are weaken

but the Al—OH bond and Al—O—Si bond of kaolin are strengthened. The strengthened functional groups inhibit the sectional capture processes of alkali metals by kaolin

reducing the capture efficiency of PM0.2.