Upgrading deashed Huadian oil shale using low-temperature pyrolysis treatment and its application in coal-blending coking

A deashed oil shale (OSA) was treated using low-temperature pyrolysis treatment (LTPT) to modify its caking index (G). The treated OSA was characterized by Fourier transform infrared spectrometry, solid-state C-13 nuclear magnetic resonance (C-13 NMR) spectrometry, and Raman spectrometry to shed light on the mechanism of G improvement. Furthermore, one industrial coal blend and the pyrolyzed OSA with a high G (OSA400) were used to perform crucible coking experiments. The coke reactivity (CR) and coke strength after reaction (CSR) indices, thermogravimetric and derivative thermogravimetric curves, pore volumes, and Raman spectra of the resulting cokes were analyzed. The results showed that LTPT significantly increased the G of OSA but there was no benefit in going above 400 degrees C. the G was modified because of the generation of caking components, the characteristics of which are of medium-sized molecules with suitable molecular structures (e.g., bridge bonds, chain lengths, and functional groups), caused by LTPT. Additionally, the changes in CR and CSR indices between the cokes obtained from the blends with and without OSA400 were within 2.0%, which is acceptable.

Automated summary

Low-temperature pyrolysis treatment significantly increased the caking index of oil shale, leading to improved combustion performance. The generation of caking components with suitable molecular structures played a key role in enhancing the properties of the oil shale.