(184b) CFD Modelling of Thermal and Hydraulic Characteristics of a Rotating Packed Bed Reactor Used for CO2 Capture

As part of the nationally determined contributions (NDCs) defined within the United Nations Framework Convention on Climate Change (UNFCCC), an ambitious approach from each country is required to decrease the world’s greenhouse gas emissions owing to their obligations towards the Paris Agreement. The prime share of these greenhouse gas emissions is coming from the power generation and industrial sector which alone encompasses 69.8% of the total gas emissions worldwide. In this context, pre and post-combustion carbon capture technologies have gained a lot of attention to mitigate climate changes along with meeting demands of the ever-rising power requirements around the globe with its 85% dependence on fossil fuel thermal power generation. Although research is being done to create greener power cycles, yet to meet the ambitious but essential goal set by the EU, carbon capture from the environment itself has become imperative. This novel idea is facing its own frontiers however, cost and size issues for example still need to be addressed. Rotating packed bed (RPB) reactor based on the process intensified (PI) technology could be a promising and cost-effective carbon capture technique. Experimental studies on the rotating packed bed reactors available in the literature provide vital information, nevertheless, constraints of cost and time confine the availability of enough experimental data required to understand complex flow patterns within RPB and to be used in the engineering design process to further improve its performance. High-end computational resources could be employed at this point to make up for the limited availability of experimental data. While CFD studies on the flow characteristics within RPB are available in the literature, investigations on the heat and mass transfer phenomena are rare. Since MEA solvents heat up during the carbon absorption process inside the RPB reactor evaluation of its heat transfer characteristics becomes a vital inquiry for its design as well as to address its intercooling requirements. Apart from thermal characteristics associated with RPB, hydraulic performance calculations bear equal significance as the pressure inside the RPB fluctuates incessantly subjected to varying flow area and centrifugal forces in the radial direction. The present investigation, therefore, focuses on the development of a CFD model so as to investigate the fluid flow and heat transfer characteristics inside the rotating packed bed reactor. The developed model is based on the volume of fluid (VOF) approach while its validation is accomplished using existing experimental data. Once model is validated, response surface method (RSM) is engaged to analyze the effect of control parameters associated with the RBP, i.e., liquid-gas flow rate ratio, inlet air-water temperature ratio, packing porosity, and rotational speed of rotor on the response parameters including heat transfer rates, liquid side Nusselt number, temperature drop, and pressure drops with its application to carbon capture. To implement the response surface methodology, the design of the experiment is carried out using a central composite design (CCD) technique while required data for RSM is generated using validated CFD model for various combinations of control parameters. Results suggest that the upsurge in the temperature of concentrated monoethanolamide (MEA) solvents is high enough to require intercooling. Moreover, granting all defined control parameters affect thermal and hydraulic characteristics associated with rotating packed bed, the impact of the inlet mass flow ratio and rotational speed is substantial and thus needs consideration in the design of RPBs. Finally, optimal ranges of the control parameters are reported based on the correlations developed using response surface methodology that will be helpful in further refining the design of rotary packed bed reactors.