Modification of Caking and Coking Properties of Shenmu Subbituminous Coal by Low-temperature Rapid Pyrolysis Treatment under CO 2 Atmosphere

We used low-temperature rapid pyrolysis (LTRP) treatment under CO 2 atmosphere to upgrade the caking and coking properties of Shenmu subbituminous coal (SM). Some physicochemical properties of all samples were studied. The modification mechanism was explored according to elemental, FT-IR, oxygen-containing functional group, and vitrinite reflectance analyses. The treated samples were also used for coal-blending coking. Coking indices (mechanical strength, coke reactivity index (CRI), and coke strength after reaction (CSR)) were also evaluated. The results showed that LTRP treatment greatly improved the caking and coking properties of SM, and the optimum temperature was 450°C. The thermal shock of LTRP treatment weakens the molecular structure of coal, which is conducive to the effusion of small molecules in coal; therefore, the precursors of caking components increase. In addition, a relatively high temperature could remove some oxygen-containing functional groups and reduce their negative effects on caking property; some compounds with suitable molecular structures were therefore formed, increasing the production of metaplast. The crucible coking experiments showed that the changes in CRI and CSR between the cokes prepared from the blends with and without the upgraded SM treated at 450°C were slightly, confirming the feasibility of applying the modified SM in coal-blending coking.