Experimental Study on Product Characteristics of Typical Pulverized Coal Preheated by a Self-Preheating Burner

As the major primary energy source in China, coal has been proved to be capable to improve its physical and chemical characteristics by the pretreatment of the self-preheating burner. In this study, the effects of altering operating conditions including preheating temperature ( T p ) and primary air equivalence ratio ( λ p ) on preheating characteristics of three typical pulverized coal were investigated on a bench-scale test rig. The high-temperature coal gas compositions along the axis of the riser and at the outlet of the self-preheating burner were measured, and the coal char and coal tar produced in the preheating process were collected and analyzed separately. The results indicated that with the significant release of volatile and the occurrence of chemical reactions, cracks and micropores emerged on the surface of the particles, making the pore structure on the surface more developed, and T p had the most significant effect on the structure of coal particles. Additionally, there were evident differences in the corresponding operating conditions when the preheating characteristics of the three typical coal reached optimally. And preheating had the strongest influence on the degree of anthracite modification. With respect to coal tar, the increase of T p and λ p further promoted its secondary cracking and oxidation, resulting in a decrease in production yield. In this study, for bituminous coal and lignite, a large amount of coal tar were produced during preheating and the highest production yields could reach 5.74% and 6.15%, respectively. While for anthracite, the production yield was intensely low due to its own coal properties, all below 1.02%.