Improved surface morphology by reforming of oxygen functional groups of Indian coal upon irradiating with microwave radiations

The high-rank coal reserves are limited and getting depleted at an escalating rate to meet the demands of growing population. This concern has compelled the scientific community to use the young high ash coals. The coal water slurry fuel is one promising way to use low-quality coal as an economical liquid fuel. Due to poor physico-chemical and surface properties of such coals, these systems appear to be unsustainable. This research presents a sustainable solution to use the existing low-quality coals efficiently without any modification in the already installed systems. The Indian coal possessing high moisture and oxygen functional groups was successfully irradiated with microwaves, resulting in the improvement of morphological, physical, chemical and rheological characteristics. These changes are due to the elimination of the Hydroxyl (-OH-) and Carboxyl (-COOH-) groups, which are observed to contribute the most to the hydrophilicity of the coal particles. The morphological investigations reveal the breaking up of the bigger particles into fines upon microwave irradiation. The treated coals exhibit physico-chemical and surface properties similar to high-rank coals but still possess high ash that does not pose any issue with the normal operation of the system.