A more general structural model which includes the induction time for gas—solid reactions—I. Nonporous solids

✍ Scribed by M.D. Shieh; C. Lee

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 849 KB
• Volume: 47
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(92)85151-z

✦ Synopsis

This paper presents a more general structural model for gas-solid reactions which include the induction time. The work was done by introducing the concept of "surface activation" and carrying out a very tedious derivation. For simple geometries such as infinite slabs, long cylinders, and spheres, we obtained the following relationship between the conversion and time: r** = CI,,(J4 + 0; P,*(x) where r** = (W&(4/& v,)(Ce -GlK,Nr--rt,Jf -exp( -~/kdl~ with g/.(x) = 1 -(1 -x)rI's i 1 -3(1 -x)s13 + 2(1 -x), & = 3 for a sphere P/.(x) = x + (1 -x) In (1 -x), f = 2 for a long cylinder X2, f, = 1 for an infinite slab 0: = (W2RM V,/-&)(l + l/K,).

The quantity C$ which incorporates both structural and kinetic parameters is the characterization of the system. When 63 approaches zero, the overall rate is controlled by the chemical reaction. When 0: is large, the overall rate is controlled solely by the diffusion of the gaseous reactant within the grain.