Experimental and numerical comparison of structured packings with a randomly packed bed reactor for Fischer–Tropsch synthesis

The potential of four structured packings has been explored for application in highly exothermic multiphase reactions such as the Fischer–Tropsch synthesis where removal of reaction heat is a major issue in the packed bed reactor type. Efficient heat removal is extremely critical to keep the catalytic activity and selectivity in the desired range. Structured internals can play a very important role in improving heat transport and allow solutions that were previously impossible. The catalyst size and shape can be tailored such that an optimal combination of reaction kinetics, pressure drop and heat transfer characteristics is obtained. A dedicated set-up was designed and built to measure the radial heat transport in two-phase flow at ambient pressure in the absence of reaction. The structured packings – especially open and closed cross flow structures (OCFS and CCFS) – exhibit radial heat transport superior over that of packed bed of glass beads, and at lower energy dissipation. A 2D reactor model for Fischer–Tropsch synthesis, based on heat and mass balances including gas–liquid, liquid–solid and intraparticle diffusion transport, is used to compare the performance of a tubular fixed bed reactor either packed with spherical particles or equipped with the OCFS packing. The simulations indicate that a reactor with a structured packing can be operated with at least twice the reactor diameter compared to the packed bed reactor without any significant loss in the STY. A structured bed reactor can considerably contribute to process intensification.