Enginuity 2009

Sustainability: Engineering a pathway to sustainable manufacturing

Helen LouMeeting society’s present needs without impinging on future generations is the goal of sustainability. For today’s chemical and allied industries, economic globalization, environmental pressure and the depletion of natural resources are tremendous challenges on the path to that goal. And today’s engineers are challenged to find solutions that radically reduce resource use and minimize or eliminate adverse environmental impacts, all while maximizing profitability.

Fortunately, Helen Lou, associate professor of chemical engineering, is guiding the quest for affordable sustainability. She is building a nationally recognized program in the frontier of sustainable manufacturing. She holds two master’s degrees and the Ph.D. from Wayne State University.

Her experience in sustainability is considerable. Lou has served as programming chair, vice chair and chair of the American Institute of Chemical Engineers (AIChE) Sustainability Forum. She also chaired the AIChE Process Development Division, Manufacturing Area, from 2001 to 2005. In her seven years at Lamar, she has established a strong research program and secured more than 20 research grants from the National Science Foundation, Environmental Protection Agency, Texas ATP and other funding agencies. Lou has received six grant awards from the NSF and served as the primary investigator for five of them. These grants cover the research topics of environmentally benign manufacturing, chemical process safety and security, and industrial sustainability. A recognized leader in sustainability, Lou has been working on systematic characterization, analysis, integration and decision-making of industrial systems.

Accurate and efficient computational models can aid engineers’ understanding of industrial systems. Multiscale models are frequently needed when seeking answers. Lou is an expert in many modeling techniques, and her work on such systems ranges from mesoscale to process scale and macroscale (e.g., industrial ecology).

Reaction is the core of chemical processing. Lou’s group has been working on algorithms that can model complex reaction networks in reacting-flow simulations. With Lamar’s high-performance computing facilities, her group has modeled and analyzed complex combustion chemistries involving hundreds of reactions intertwined through complex reaction pathways.

In many cases, detailed multi-dimensional views of a system can provide critical information to guide optimal design and operation; however, the popular process simulators, such as ASPEN, HYSYS and Pro II, can’t simulate phenomena in multiple dimensions. In Computational Fluid Dynamics (CFD) simulation, millions of calculations may be required to simulate the interaction of fluids and gases with the complicated geometries. CFD models empower engineers to simulate flows of gases and liquids, heat and mass transfer, moving bodies, multiphase physics, chemical reaction, fluid-structure interaction and acoustics. Using CFD software, engineers can build a “virtual prototype”' of the system or device and then apply real-world physics and chemistry to the model to predict the performance of that design.

“This helps engineers more easily see the design efficiency and can help them troubleshoot what goes wrong,” Lou said. “It can also help them design clean technologies and make their processes more cost effective.”

Lou has been using Fluent, a leading commercial CFD software package, to design and develop advanced technologies for improving the performance of process units, such as reactors and combustion chambers. Her research combines complex reaction kinetics models with CFD to examine the effects of firing patterns on combustion efficiency and to quantify carbon conversion, pollutant formation, flame structure and temperature uniformity. This research will lead the way towards development of clean combustion systems and fuels for the energy industry and chemical industry, Lou said.

Another research area using CFD is the development of novel technology for inhibiting runaway reactions. Thermal runaway is always related to the generation of hot spots in a reaction system that may eventually lead to an overproduction of undesirable byproducts from competing reactions, product quality degradation and yield decrease, or, most severely, reactor rupture or explosion if the excessive reaction heat is not removed quickly, Lou said.

“We want to develop measures to stop the reaction right away through a very cost-effective inhibition method,” Lou said.

Lou’s research facilitates the investigation of optimal inhibition mechanisms for different reaction kinetics under different local conditions. The influence of reactor geometry; the number, location and size of inhibitor nozzles; different reaction speeds; air sparging strength; and the dynamic changes of different local physical, chemical and hydrodynamic properties of the system such as viscosity and density was simulated to identify the optimal design location, amount and time for automatic inhibitor injection using pressurized air or inert gas.

Lou has pioneered process-scale research on profitable pollution prevention by optimizing the design and operation of chemical production systems. In large-scale chemical manufacturing, unit operations interact closely through mass, energy and momentum transfers. Lou has also initiated research to show that by implementing process safety and security techniques, “chain-reaction” disasters can be avoided. In her research, she identified the inherent vulnerability of process design and operations and the effect of disturbances on the entire process. This research will help facilitate the quantitative evaluation of process safety and security status, the prediction of possible safety and security failures, and the review of design and operation policy to improve operation.

Process integration is a holistic approach to process design and optimization that exploits the interactions between different units to employ resources effectively and minimize costs. Lou’s work in the field, which focuses on mass integration, heat integration and energy integration, has led to successful applications in the chemical and surface-coating industries. Using mathematic programming and pinch technology, she has developed water use and reuse networks to minimize water consumption in the processes and has developed heat-exchanger networks to save energy.

Another important approach for sustainable development is the concept of the Industrial Ecosystem (IE). “In an industrial ecosystem, a group of industries are inter-connected through mass and energy exchanges for mutual benefits,” Lou said. IE converts the industrial process from a linear process to a cyclic process where the waste generated by one industry can be used as a resource by another industry. Several such industrial ecosystems have been developed around the world, including the industrial complex at Kalundborg, Denmark; the industrial complex in the lower Mississippi River corridor; the Dalian Economic and Technological Development Zone in China, and several U.S. ecoparks.

Lou’s research interests also include Life Cycle Analysis (LCA), a procedure to evaluate and analyze the environmental impacts of a product or service by using the complete input and output data about the material and energy involved at various stages of the life cycle, starting from the stage of collecting raw material from earth and ending at the stage when all this material is returned back to earth. “We have to consider all the potential impacts of a product process,” Lou said. “That includes environmental impacts, heath issues and more if we are to create a lifecycle analysis of an industrial ecosystem.”

Lou has combined the use of LCA and IE in the design of optimal industrial ecosystems of the most cost-effective symbiosis for recycle, reuse and resource conservation.