Thermal decomposition of calcium carbonate

✍ Scribed by G. Narsimhan

• Publisher: Elsevier Science
• Year: 1961
• Tongue: English
• Weight: 964 KB
• Volume: 16
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(61)87002-4

✦ Synopsis

The process of thermal decomposition of calcium carbonate has been treated as one governed by simultaneous heat and mass transfer, under quasi steady state conditions, to the decomposition interface. It is believed that the surface chemical reaction is very fast and as such does not interfere in the determination of the overall decomposition rate. Rigorous expressions, based on heat transfer rate, have been derived, based on the system properties, for the prediction of decomposition times for definite geometric shapes such as spheres and cylinders. The good agreement observed between the actual and predicted values bears out the soundness of the decomposition scheme assumed for the process. The expression derived are :

Spheres : OD = mH (0.33 +m 0.17 kFl)

Cylinders : BD = aH (040 + 0.25 kH)

Based on an analysis of simultaneous heat and mass transfer rates the following correlation is obtained :

This equation bears very close resemblance to the theoretical expression for the evaporation of small spheres into quiet air. This equation may be rearranged to provide:

which is a modified form of the usual correlation for simultaneous heat and mass transfer based on Chilton-Colburn analogy. The mathematical treatment has been extended to a two-phase solid system (Mg CO,-Ca CO,) characterized by finite but different equilibrium decomposition temperatures. The mathematical analysis involves the solution of simultaneous differential equations. This has been done numerically by the modified Runge-Kutta method with the help of an IRM computer. The confirmation of the proposed equation must await future experimental data for the two-phase system.