Characterization of slag from anthracite gasification in moving bed slagging gasifier. (15th May 2021) - Wang, Ji
Highlights: Anthracite was gasified in pilot scale moving bed slagging gasifier. Residual char had high graphitization degree and pore structure. Gasification reactivity of residual chars depends on its surface areas. Precipitation of metallic iron and invasion of char by slag were observed. Reasons for occurrence of residual char in slag were proposed. Abstract: Gasification has become an effective way to realize clean and efficient utilization of coal. Anthracite is characterized by low grindability index and low gasification reactivity, which is not suitable for fluidized gasifier and entrained-flow gasifiers for low carbon conversion and high crushing cost. However, due to its high thermal and mechanical strength, it is preferred to be gasified in moving bed slagging gasifier. In this work, three slag samples were collected from pilot plant of moving bed slagging gasifier using anthracite as feedstock, and residual char was found in slag. In order to reveal formation mechanism of slag and residual char in the slags, properties of mineral matter and residual char were analysed. Results showed that slag taken from stable operation condition had low contents of residual char and crystalline phases. However, a lot of residual char particles were found in other two slags. Comparing to coal char prepared at 850 °C, residual chars in slags had higher graphitization degree and surface areas. Besides, it presented a higher gasification activity, which mainly depends on its porous structure and surface areas. In addition, formation of metallic iron, interface of char-slag and invasion of char by slag were observed in slag with residual char. It was found that occurrence of residual char in slag from anthracite gasification in moving bed slagging gasifier was strongly influenced by low reactivity of anthracite, unreacted limestone, high molten slag level.