Impact of inherent minerals on the yield and properties of char from pyrolysis of the lignite with high ash content

In order to investigate the impact of inherent minerals on pyrolysis for lignite with high ash content,some py- rolysis experiments were conducted in Drop Tube Reactor and Thermogravimetric analyzer at 800 -1 200 ℃ . Lignite samples containing different ash and mineral compositions were prepared by separation,acid demineralization and min- eral addition. Results show that the inherent minerals could reduce the pyrolysis reactivity of lignite and increase the char yield at low temperature (800 ℃ );AAEM played a major role. While at high temperature (≥1 000 ℃ ),the in- herent minerals reduced the char yield by in-situ catalyzed steam-gasification. The reduction in char yield was directly related to the ash and internal water content of coal samples,as well as the total amount of basic metals. Raman analy- sis showed the inherent minerals can disorder the microcrystalline structure of char and inhibit the fracture of cross- linking bonds. The surface of char was increased by Ca as the main role of inherent mineral composition. With the py- rolysis temperature increasing,the excessive mineral will inhibit the further expansion of porosity for chars.