Effects of enzyme microcapsule shape on the performance of a nonisothermal packed-bed tubular reactor

The effects of enzyme microcapsule shape (spherical, cylindrical and flat plate) on the performance of a nonisothermal, packed-bed reactor have been modeled as a function of Biot number and Peclet number for mass and heat transfer (Bi(m), Bi(h), Pe(m) and Pe(h)), and dimensionless heat of reaction a. Under the given simulation conditions, only higher values of Bi(m), and Bi(h), (> 2.5) confirm the influence of microcapsule shape on the reactor performance such that the axial and overall conversion and bulk temperature decrease as follows: spherical > cylindrical > flat plate. In terms of the shape-independent modified Biot number, Bi(*) = Bi/{(n + 1)/3}, this order is retained for 2 < Bi(*) < 8. The influence of increasing Pe(m), Pe(h), and α on conversion and bulk temperature also follows the above order. For the flat plate, the exit conversion and temperature are not influenced by Pe(m) and Pe(h) that is, mass transfer and thermal back-mixing effects, respectively. On the other hand, for the spherical and cylindrical microcapsules, overall back-mixing effects are negligible only beyond a critical value of Pe(m) (~7) and Pe(h) (~1.75). The conversion and bulk temperature increase with the increase in α, independent of the microcapsule shape. The spherical and cylindrical microcapsules, unlike the flat plate, cannot be considered isothermal.