Introduction Reactive flow
Reactive flows are flows that are chemically reactive. All types of fluid flows with chemical reactions occurring within the fluid phase, at the interphase between different fluid phases or at interphases to solids. Reactive flow finds its applications in many areas including catalytic cracking in chemicals process, combustion in IC engine, CO2 capture process, polymerization, etc. Simulation of reactive flows is becoming increasingly important because it allows researchers to gain insight into processes with difficult conditions, such as high temperature and pressure. In this way, the effort and costs for prototypes and field test can be reduced to a minimum.
CFD case studies
A gas-phase polypropylene polymerization fluidized bed is more attractive due to the fact that it can be operated with a high solid loading, requires neither drying nor separation of polymers from solvents and has relatively low environmental impact. Nevertheless, heat transfer in a gas-phase fluidized bed is limited, especially in a high-solid-loading mode of operation, due to highly exothermic polymerization and poor heat transfer in the gas phase of the system.
The goal of this project is to create models on two levels and show how useful they are for simulating a fluidized bed reactor for propylene polymerization. The operational variables investigated to improve productivity and change product attributes are catalyst feed rate, operating temperature, hydrogen feed, reactor size, and superficial velocity. Local distributions of phase movements and local temperature distributions will also be investigated in order to avoid polymer overheating, hot spots, and the possibility of melting. This research is unique and will contribute in the better understanding of propylene polymerization in fluidized bed reactors, as well as the examination of both a laboratory and an industrial reactor.
Contour of bed temperature for different reactor scales obtained using (a) Set I with weight space time similarity, and (b) Set II with hydrodynamic similarity
Contour of weight average molecular weight in the fluidized bed for various hydrogen feed concentrations
The sulfur dioxide (SO2) and carbon dioxide (CO2) emissions from fuel combustion in a coal-fired power plant constitute a significant source of damage to the environment. Therefore, SO2 and CO2 should be captured before being released into the atmosphere. However, the competitiveness between SO2 and CO2 for calcium carbonate(CaCO3)/calcium oxide (CaO) solid sorbents is still unclear. In this study, unsteady state computational fluid dynamics simulation in a riser of an industrial scale circulating fluidized bed boiler integrated with heterogeneous combustion, carbonation, calcination, and desulfurization reactions using a mixed feeding of CaCO3/CaO solid sorbents was developed in a two-dimensional model to investigate the competition between SO2 and CO2 capture.
Due to the concern on the environmental impact of the CO2 emission from the combustion process, a computational fluid dynamics model has been developed to investigate CO2 capture of flue gas in circulating fluidized bed reactor (CFBR) and circulating fluidized bed downer (CFBD). The adsorption model of solid sorbent was implemented to predict the removal percentage of CO2 in continuous process. The understanding of various operating conditions and cooling system specification play roles in the removal efficiency. The outcomes offer a better system design and propose optimal conditions for better removal of CO2