Abstract

Highly exothermic catalytic reactions face the situation, where very large heat transfer rates at high temperatures are required for safe operation. This high temperature requires an efficient heat exchange and highly sophisticated control systems for temperature, pressure and flow. Catalyst deformation, softening and sintering is expected. Normal and circulated fluidized beds cannot provide the required large areas. This study suggests a unique design of a micro-tube circulating fluidized bed reactor, MTCFB, where the riser column consists of a bottom double pipe and an upper shell and tube heat exchangers. The tube bundle consists of small micro-size tubes of 6.0 mm I.D.  This design provides large mass and heat transfer rates with perfect mixing. A cold-model experiments were carried out to examine the performance of the MTCFB. Small pressure drop, less than 2.0 % of the atmospheric pressure, across the grid and the top riser in absence and in presence of bed particles, was noticed at high gas velocities as 8.0 m/s. Gas-solid flow for MTFB excluding cyclone and downer, and MTCFB, was examined, in terms of elutriation and circulation rates, respectively. Fluidization run smoothly with high reproducibility for bed particles up to 2.5 kg, irrespective of the mode of operation.