Multiphase CFD modeling and simulation of gas-solid flow systems including CO2 capture processes.

摘要

Carbon capture and sequestration (CCS) is one of the key technologies needed to reduce the carbon dioxide (CO2) emission and its effects on climate change. The goal of this study is to develop an advanced design and scale-up tool for a regenerable solid sorbent carbon capture process using computational fluid dynamics (CFD). In this study, a systematic methodology was established, starting from investigating the properties of the sorbent and its reaction kinetics, to developing models to design, evaluate, troubleshoot, and scale-up of the reactors that are needed to deploy this technology for an advanced power plant (i.e., integrated gasification combined cycles [IGCC]). To develop a realistic CFD model, the effect of formation of clusters in the system was studied using an energy minimization multi-scale (EMMS) approach and was shown to calculate the fluidized bed expansion with high accuracy. The effect of compaction of particles was also investigated and a model capable of simulating independent experimental data for the angle of repose was presented. In addition, this dissertation provides detailed investigations of a magnesium oxide (MgO)-based sorbent and its performance for CO2 capture from a syngas stream including the development of shrinking core models (SCM). Initially, the regenerator fluidized bed reactor at elevated temperature and pressure was simulated and several case studies were performed. Furthermore, a three-dimensional (3D) CFD simulation of a full-loop circulating fluidized bed was provided based on the developed constitutive relations and coupling them with two-fluid model equations. In order to reduce the computational time, a CFD simulation in a two-dimensional (2D) domain including heterogeneous regeneration and carbonation reactions based on the shrinking core model was performed that can be used for parametric studies and optimization of the CO2 sorption and desorption processes in a circulating fluidized bed (CFB) reactor. In addition, a coupled CFD-PBE (population balance equation) model based on the FCMOM (finite size domain complete set of trial functions method of moments) approach was developed and was shown to have broad application in reaction engineering and reactor design where the poly-disperse nature of the phases has a strong effect on the hydrodynamics of the system such as coal gasifiers. Finally, the base case design for CFB reactors incorporated in the CO2 capture process using techno-economic analysis was developed and the operating and capital costs of the unit were demonstrated. It was shown that capturing CO2 in an IGCC power plant by pre-combustion technology is economically viable and can compete with other available technologies.