Optimizing CO2 Purification in a Negative CO2 Emission Power Plant

Abstract

In the pursuit of mitigating CO₂ emissions, this study investigates the optimization of CO₂ purification within a negative CO₂ emission power plant using a spray ejector condenser (SEC) coupled with a separator. The approach involves direct-contact condensation of vapor, primarily composed of an inert gas (CO₂), facilitated by a subcooled liquid spray. A comprehensive analysis is presented, employing a numerical model to simulate a cyclone separator under various SEC outlet conditions. Methodologically, the simulation, conducted in Fluent, encompasses three-dimensional, transient, and turbulent characteristics using the Reynolds stress model turbulent model and mixture model to replicate the turbulent two-phase flow within a gas–liquid separator. Structural considerations are delved into, evaluating the efficacy of single- and dual-inlet separators to enhance CO₂ purification efficiency. The study reveals significant insights into the optimization process, highlighting a notable enhancement in separation efficiency within the dual-inlet cyclone, compared to its single inlet counterpart. Specifically, a 90.7 % separation efficiency is observed in the former, characterized by symmetrical flow patterns devoid of wavering CO₂ cores, whereas the latter exhibits less desirable velocity vectors. Furthermore, the investigation explores the influence of key parameters, such as liquid volume fraction (LVF) and water droplet diameter, on separation efficiency. It is ascertained that a 10 % LVF with a water droplet diameter of 10 µm yields the highest separation efficiency at 90.7 %, whereas a 20 % LVF with a water droplet diameter of 1 µm results in a reduced efficiency of 50.79 %. Moreover, the impact of structural modifications, such as the addition of vanes, on separation efficiency and pressure drop is explored. Remarkably, the incorporation of vanes leads to a 9.2 % improvement in separation efficiency and a 16.8 % reduction in pressure drop at a 10 % LVF. The findings underscore the significance of structural considerations and parameter optimization in advancing CO₂ capture technologies, with implications for sustainable energy production and environmental conservation.