Multiscale process engineering

These factors can also be organized as a multiscale optimization problem by their operations, which is seen in table 11.5. The chemistry of manufacturing is mostly concerned with the nanometer to micrometer scales of molecules and colloids, and process engineering is mostly concerned with the millimeter to meter scales of components and equipment. The systems of plants and markets operate in the kilometer scale, and the global environment operates in the thousand kilometer scale. 

Since the advent of efficient and robust simulation and optimization solution engines" and flowsheeting software packages that allow for relatively easy configuration of complex models, numerous integrated, high fidelity, and multiscale process model applications have been deployed in industrial plants to monitor performance and to determine and capture improvements in operating profit. 

The main objective of this work is to discuss recent developments in molecular simulation, multiscale simulation and multiscale systems engineering, and how these developments enable the targeted design of processes and products at the molecular scale. The control of events at the molecular scale is critical to product quality in many new applications in medicine, computers and manufacturing. 

Korekazu Ueyama, K. (conference chair) 1st International symposium on multiscale multiphase process engineering (MMPE), Kanazwawa City, Japan, 2011. http //www.mmpe.jp. 

The engineering context of the need for multiscale representation of process trends can be best seen within the framework of the hierarchical... 

Fig. 14.11 Schematic representation of fiber spinning process simulation scheme showing the multiple scale simulation analysis down to the molecular level. This is the goal of the Clemson University-MIT NSF Engineering Research Center for Advanced Engineering Fibers and Films (CAEFF) collaboration. CAEFF researchers are addressing fiber and film forming and structuring by creating a multiscale model that can be used to predict optimal combinations of materials and manufacturing conditions, for these and other processes.

Bakshi, B. R. and Hau, J.L., A multiscale and multiobjective approach for environmentally conscious process retrofitting, AlChE Sustainability Engineering Conference Proceedings, Austin, TX, November, pp. 229-235, 2004. 

In the area of nanomaterials and thin films, product quality is judged from the sharpness of interfaces, crystallinity, defects, polymorphism, shape, uniformity in particle-size distribution, film texture, etc. Engineering product quality demands linking of phenomena at very different scales and has attracted considerable interest over the last few years (Alkire and Verhoff, 1998 Christ-ofides, 2001 Raimondeau and Vlachos, 2002a). A recent review of multiscale simulation of CVD processes for various materials is given in Dollet (2004). 

The first objective is represented by the need to increase the productivity and selectivity of both existing and new processes through intelligent operations and multiscale control of processes. This objective is sustained by the important results obtained thanks to the synthesis of a new class of engineered porous supports and catalysts. So the catalytic reactions and separation processes that use these materials can be efficiently controlled. 

In general, previous experimental values and computational data can be used to estimate the kinetic parameters needed for a KMC-based simulation. These parameters may be improved and adjusted after KMC simulation, if an initially identified reaction mechanism is shown to be insufficient to capture the experimental behavior. Most importantly, the DFT+KMC multiscale simulation approach establishes a well-defined pathway for taking atomistic-level details and reaching lab-level experimental results, which can be used to accelerate the discovery process and enhance engineering design. 

On the other hand, well engineered manufacturing operations depend on the availability of manipulated variables for real-time feedback control. These variables usually operate at macroscopic length scales (e.g. the power to heat lamps above a wafer, the fractional opening of valves on flows into and out of a chemical reactor, the applied potential across electrodes in an electrochemical process). The combination of a need for product quality at the molecular scale with the economic necessity that feedback control systems utilize macroscopic manipulated variables motivates the creation of methods for the simulation, design and control of multiscale systems. 

Future trends in electrochemical engineering will be influenced by the need to develop molecular-based discoveries into new and improved products and processes. What is needed is to develop a multiscale systems approach that builds upon the traditional base of continuum-scale mathematical models. 

More recently, techniques have been developed for utilizing multiscale simulation models to perform systems engineering tasks, such as parameter estimation, optimization and control (e.g. see reviews by [9, 10] and [11], and references cited therein). This incorporation of models that couple molecular through macroscopic length scales within systems engineering tools enables a systematic approach to the simultaneous optimization of all of the length scales of the process. 

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