Process Design via CFD Analysis in Carbothermic Aluminium and Slag Fiberization
Dimitrios I. Gerogiorgis (National Technical University of Athens (NTUA), Greece)
Location: Sala de Graus, ETSEQ
Start time: Feb. 17, 2012,
12 p.m.
Abstract
A plethora of novel chemical processes of extreme industrial importance at various sizes cannot be reliably designed via standard modeling simplifications, because accurate models must rely on nonlinear PDE systems describing spatiotemporal variation, flow and reactions. Further challenges perplexing modeling efforts may include poor understanding of physics, high CPU cost but also extreme operating conditions which hinder experimental campaigns.
This talk will present the process and CFD modeling studies we have completed addressing the design of a new carbothermic aluminium reactor and a mineral slag fiberization unit. Carbothermic reduction is a potentially feasible but technically challenging alternative electrochemical process, whose cornerstone principle is the efficient implementation of the high-temperature endothermic reduction reaction between carbon and aluminium oxide, thereby avoiding the prevalent capital- and energy-intensive Hall-Héroult electrolytic process. The ALCOA-ELKEM carbothermic ARP reactor is a multistage and multiphase prototype which has successfully reached production scale and addresses these challenges successfully. Another promising process of considerable interest is the mineral slag fiberization of red mud, which has a strong potential to alleviate environmental pressure issues by transforming a by-product of electrolytic a¬¬¬luminum into mineral wool, and then to various marketable products.
Our ARP reactor CFD simulation and MINLP optimization studies were the first to focus on simultaneous solution of charge, heat, momentum, mass and gas volume fraction balances for working prototypes of the ALCOA-ELKEM ARP reactor during its key development stages. By constructing a multiscale hierarchy and interfacing results from process and CFD models, we have succeeded in providing accurate state variable distributions which were subsequently confirmed by experimental measurements conducted at ELKEM (Norway), as well as in providing design guidelines for water models and ARP campaigns at ALCOA (Pittsburgh).
Currently, our CFD modeling and analysis efforts focus on melt-blowing slag fiberization via an impinging air jet, a process which avoids melt-spinning disadvantages (rotation and wear). Molten red mud slag which precedes pig iron casting flows out of a heated ladle orifice at a high temperature and adjustable flowrate, forming a free-falling vertical stream which visibly radiates its excessive heat: at a given distance, a high-velocity impinging air jet meets the vertical molten slag stream and induces droplet generation and subsequent fiber elongation. CFD modeling and analysis of the molten slag flow under external cooling encompasses all physicochemical phenomena (slag flow, radiative cooling, drop generation, fiber elongation) and considers several temperature-dependent slag transport properties to understand which degrees of freedom (manipulated variables) can be used towards optimizing process design.
About Dimitrios I. Gerogiorgis
Institution: National Technical University of Athens (NTUA), Greece
Dr. Dimitrios Gerogiorgis holds a Diploma in Chemical Engineering with highest honors from the Aristotle University of Thessaloniki, Greece (1999); he then obtained a Masters of Science in Electrical and Computer Engineering (2003) and simultaneously his Doctorate in Chemical Engineering (2004) from Carnegie Mellon University at Pittsburgh, Pennsylvania, USA; he was advised by Professor Erik Ydstie under simultaneous J.W. Fulbright, Alexander Onassis and Carnegie Mellon Doctoral Fellowships. He also received an Eberly Center for Teaching Excellence Development Certificate. Collaborating with the ALCOA Technical Center, he was the first researcher to model in detail and investigate both computationally (CFD) and experimentally (with ALCOA’s G. Carkin) the complex multiphase flow within a novel carbothermic aluminum reactor, receiving several distinctions.
Dr. Gerogiorgis has been awarded a Marie Curie postdoctoral fellowship in order to join the Centre for Process Systems Engineering at Imperial College, London, where he was supervised by Prof. Efstratios Pistikopoulos and worked successfully on several research projects in oil extraction, polygeneration optimization and SOFC control. Following his military service with the Greek Army Ordnance Corps, he joined the MIT Department of Chemical Engineering, where he served as a postdoctoral fellow at the Novartis-MIT Center for Continuous Manufacturing. Working on Quality by Design-oriented synthesis and optimization of novel continuous pharmaceutical processes, he achieved the generation of CPM process design superstructures, investigated their feasibility and viability and developed a systematic methodology for rapid screening of candidate CPM flowsheets via Interval Arithmetic (IA).
He is currently a senior researcher at the National Technical University of Athens (NTUA), focusing on design, CFD analysis and optimization of a novel molten slag fiberization process addressing efficient red mud utilization.
