Design of 3D-printed structures for improved mass transfer and pressure drop in packed-bed reactors

Abstract

Packed-bed reactors are one of the simplest and most widely used reactors in chemical processes. Although simple, the random packing of solid particles can lead to inadequate heat and mass transfer, high pressure drop caused by suboptimal fluid pathways. A combination of a structure with random packing provides simplicity with designed fluid paths to alleviate mass transfer problems. In this paper, we introduce a simplified approach to developing structure-directed random packing (a 3D printed structure surround by randomly packed spherical particles), to improve the interfacial gas–liquid area and reduce pressure drop. The random filling of particles was simulated to minimise the void fraction differences between the near-wall and away-from-wall regions. Conventional structures based on sheets made the void distribution less uniform and also created vertical channels. We developed an alternative set of structures based on short vertical pillars suspended by horizontal supports. The pillars were discontinuous and did not create consistent vertical channels, while the horizontal supports created horizontal channels to enhance radial mass and heat transfer. These structure-directed random packing enhanced void uniformity and modestly (3%) increased gas–liquid interfacial area compared to the randomly packed reactors. Importantly, the pressure drop was reduced by up to 30%. The structure-directed random packings present an opportunity for more efficient scrubbing applications with 20% lower pumping energy consumption compared to randomly packed beds.