Contribution of single coal property to the changes of structure and reactivity of chars from blending coking

Abstract

This study investigates the contribution of single coal in blends on the properties of the char produced. Three kinds of coals with varying rank and caking ability were used for the preparation of the chars at 1150 °C in muffle furnace. Char reactivity towards carbon dioxide (CRI) and char strength after reaction (CSR) were tested through the fixed-bed reactor in a laboratory scale and the tumbler, respectively. X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen adsorption test were applied to obtain the information for the chemical and physical structures of the char. The study results show that the CRI of char increases with the increase of subbituminous coal content in blends for its role in increasing the surface area and decreasing the crystallite height (Lc) of the chars; the increase of fat coal content in coal blends causes the decrease of the CRI of chars for its contribution to the more ordered crystallite structure and less surface area. The contribution of single coal property in blends to the CSR of chars is just contrary compared to its contribution to the CRI of the chars. Coal blends with high volatile yield and low GR.I value would cause higher surface area and lower crystallite height of char. The CRI of the char can be well predicted by GR.I value and volatile yield of the coal blends quantitatively: CRI(%)=-0.029GR.I+1.995Vdaf−57.937, which is of certain theoretical guiding significance for gasification of char from coal blends.