Reactivity of heat-treated coals in hydrogen

✍ Scribed by Akira Tomita; Om P. Mahajan; Philip L. Walker Jr

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 1017 KB
• Volume: 56
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(77)90133-8

✦ Synopsis

Reactivities

of eighteen 40 x 100 mesh U.S. coals charred to 1000°C have been measured in H2 at 2.7 MPa and 980°C. The char-hydrogen reaction usually occurs in two stages: a slow induction period followed by a constant-rate region. Reactivities of various chars in the initial stage (Ri) decrease, in general, with increasing carbon content of the parent coals, whereas reactivities in the constant-rate region (R,) are essentially independent of the rank of the parent coals. Reactivities of chars in H2 differ markedly from those in air and CO2. Results of surface-area measurements of chars and activation energies for the hydrogasification reaction suggest that during the induction period the reaction is diffusion-controlled whereas in the constant-rate region it is chemically controlled. Upon removal of mineral matter, Ri values generally decrease but Rc values show a random variation. Removal of mineral matter from coals prior to their carbonization brings about profound changes in surface area and porosity of chars. The effect of char particle size on reactivity is considered.