Start
Jan 28, 2016 - 17:00
End
Jan 28, 2016 - 18:00
Venue
Room 118 Department of Chemical Engineering
Event Type
Speaker
Dr. Saurabh Joshi Cummins Inc. Columbus IN USA
Title
Catalytic Air Pollution Abatement: Fundamental and Practical Aspects
Abstract: Quality of the environment is a serious concern all over the world. Stringent emission regulations are being imposed by several countries to reduce the harmful emissions from mobile and stationary sources. Monolithic catalysts have been widely used for air pollution abatement due to their several advantages such as high heat and mass transport rates per unit pressure drop smaller transverse temperature gradients and ease of scale-up. This seminar covers fundamental aspects of optimal design of monolithic catalysts as well as an overview of state-of-the-art technologies for air pollution abatement. Monolithic catalyst consists of a large number of long narrow channels (of hydraulic diameter about 1 mm) in parallel through which reacting fluid flows and the catalyst is deposited in the form of a washcoat (of average thickness ~ 40 µm) on the monolith channel wall. The reactants diffuse transverse to the flow direction in the gas phase and through the porous washcoat where they react and the products formed diffuse back into the gas phase. Therefore the detailed mathematical model consists of a system of coupled nonlinear partial differential equations (PDEs) along with highly nonlinear reaction source/sink terms. Although the numerical solution of such detailed models is possible with the present day computers it may be demanding in terms of time and memory requirements especially for real time simulations that may be needed in the control and optimization schemes. Therefore we develop simplified low-dimensional models having same qualitative behavior as the full PDE models and sufficient accuracy for practical applications. These are derived directly by averaging the governing equations and using the concepts of inter and intra-phase mass transfer coefficients. It is shown that the low-dimensional model is more general and superior to the classical two-phase model which use the effectiveness factor concept. These new models are robust and accurate with practically acceptable error speed up the computations by orders of magnitude and can be used with confidence for the real time simulation and control of monolithic catalysts. Further we develop analytical criteria for determining the transition boundary between the operating regimes (such as kinetic washcoat diffusion and external mass transfer controlled) in catalytic monoliths in terms of various reactor and operating parameters. The second part of work elaborates various state-of-the-art experimental techniques utilized for analyzing performance and optimal design of catalytic monoliths. Specifically we demonstrate the use of spatially resolving measurement techniques (Spaci-FTIR) to analyze the distributed performance along the length of a monolithic Cu-zeolite SCR catalyst. The technique was used to study SCR zone length and ammonia storage. The significant finding is that the NH3 storage is nearly complete in the SCR zone and no significant storage occurs beyond the SCR zone. Thus the catalyst utilization can be determined using the fractional storage under the SCR reaction conditions. These findings were utilized for model development catalyst design and control.About speaker: Saurabh Joshi is currently working in the research and technology division of Cummins Inc in Columbus IN USA where his research is focused on automobile air pollution abatement. He received his B.Chem.Engg. degree from ICT Mumbai in 2004. He completed his PhD from University of Houston in 2010 where he developed experimental and modeling techniques for optimal design of monolithic catalysts. Saurabh would like to utilize his academic and industrial research experience to establish a laboratory dedicated to research on air pollution abatement.