(359e) Significance of Flow Mal-Distribution and Channel Imperfections in Structured Monolith-Based Adsorption Processes

Structured adsorbents offer the advantage of extremely low-pressure drops, even at high gas superficial velocities. However, channel imperfections and inlet-flow mal-distribution often add to the intrinsic dispersion in structured adsorbent systems. Traditionally, these structured adsorbent systems are assumed to consist of identical channels and in order to match the breakthrough curve, an ‘effective’ diffusivity is often estimated. Since the root cause of the excess dispersion is not addressed, employing the effective diffusivity while modelling a complete cycle results in erroneous predictions. Here, these effects are modelled by considering a corrugated-structured, monolithic adsorbent system to be composed of a finite number of sectors and each sector to further consist of a finite ‘types’ of channels. The different sectors and the types of channels allow us to account for inlet flow mal-distribution and channel imperfections, respectively. The flow distribution and fraction of different type of channels are determined in order to match the observed breakthrough curve. Only introducing both flow distribution effects and different channel types it is possible to reproduce the experimental response. This is to be contrasted with using a simple column model and determining an effective mass transfer coefficient to capture the spread of the breakthrough curve.

Full cycle predictions are then performed for CO₂ capture from a dried flue gas stream. Comparisons between the ‘real’ monolith and an ‘ideal’ monolith with the actual mass transfer coefficient and with the apparent coefficient that matches the breakthrough curve are discussed. The full cycle simulations of the ‘real’ monolith are shown to reproduce correctly experimental results¹.

¹Mohammadi, N., 2017. CO₂ capture from flue gas by a PSA process using a novel structured adsorbent. Doctoral Thesis. The University of South Carolina