Sustainable process intensification

Given the very significant advances indicated previously on individual small-scale structured devices on the laboratory scale, the major challenge facing the chemical industry in order to perform sustainable process intensification is not the further development of individual locally structured units but rather the effective integration of those units into complete production systems, exhibiting the required multi-scale features described above. 

Charpentier, J.-C. (2007). In the frame of globalisation and sustainability. Process Intensification, a path to the future of chemical and process engineering (molecules into money). Chemical Engineering Journal, Vol. 134, pp. 84-92. 

Therefore, in this definition process intensification encompasses both novel apparatus and techniques which are designed to bring dramatic improvements in production and processing (Figure 1.8) [25]. As a result, safe, cheaper, compact, sustainable (environmentally friendly), and energy-efficient technologies are obtained. 

Dr Alexei Lapkin is a Senior Lecturer in Chemical Engineering at the University of Bath, UK, where he is also a Deputy Director of the Centre for Sustainable Chemical Technologies. He obtained his Master in Chemistry from the Novosibirsk State University, Russia, and Ph.D. in Chemical Engineering from the University of Bath. His research is focused on process intensification, bioprocessing, design and applications of functional materials. 

The philosophy of process intensification has been traditionally characterized by four words smaller, cheaper, safer, slicker. And indeed, equipment size, land use costs, and process safety are among the most important PI incentives. But process intensification can (and should) also be placed in a broader context—the context of sustainable technological development. Several years ago DSM published a picture symbolizing its own vision of process intensification (32), in which skyscraping distillation towers of the naphtha-cracking unit are replaced by a compact, clean, and tidy indoor plant (see Figure 3). The importance of PI for sustainable development and its role in the company s responsible business has been further stressed in a recent publication by the company s CEO, Peter Elverding (33). Here,... 

More and more chemical companies do recognize the fact that their image, their reputation, plays a very important role in successful business. A proper image of the company is necessary to ensure public support for its activities. A study done in the United States showed that only the tobacco industry and the nuclear energy sector had a worse reputation than the chemical industry. The situation in Europe is probably not very much different. On the other hand, process intensification, deeply anchored in the philosophy of sustainable development, in safe and environmentally friendly processing, presents perhaps the simplest, the most obvious key to the improved image of the chemical industry. 

This chapter is meant for developers and designers of processes, in particular of intensified processes, who want to ensure that their processes contribute to sustainable development. To this end problems with the present technological solutions in relation to the world-scale environment and society are explained in the first section. Then in the second section sustainable development is explained and the role and criteria for sustainable technology are derived. Finally process intensification is assessed on its contribution to sustainable development. 

The LCA results can be used for a sustainability assessment of a new technology by comparing the outcome with the existing technology results. In the conceptual phase of the new technology, a relative assessment can be used to highlight where improvements should be made and where the problem areas are. This is shown in Section 3 on process intensification assessment. 

THE POTENTIAL FOR PROCESS INTENSIFICATION TO CONTRIBUTE TO SUSTAINABLE DEVELOPMENT... 

Elaborate descriptions of process intensification will be found elsewhere in this book. Here a short description suffices, followed by an assessment on its potential to contribute to sustainable development, based on present industrial cases and general features. 

Process intensification consists of the development of novel apparatuses and techniques that, compared to those commonly used today, are expected to bring dramatic improvements in manufacturing and processing, substantially decreasing the ratio of equipment size to production capacity, energy consumption, or waste production and ultimately resulting in cheaper and more sustainable technologies (35). 

Table 7 contains a summary of the potential of process intensification for sustainable development. Some aspects will be explained in the sections that follow. 

Sustainable development item Process intensification improvement potential... 

Membranes and membrane processes are best suited in this context as their basic aspects well satisfy the requirements of process intensification for a sustainable industrial production. In fact, they are precise and flexible processing techniques, able to maximize phase contact, integrate conversion and separation processes, with improved efficiency and with significantly lower energy requirements compared to conventional techniques. 

Innovation is the key issue in today s chemical process industries. The main directions are sustainability and process intensification. Sustainability means in the first place the efficient use of raw materials and energy close to the theoretical yields. By process intensification the size of process plants is considerably reduced. The integration of several tasks in the same unit, as in reactive separations, can considerably simplify the flowsheet and decrease both capital and operation costs. 

Finally, it is worth mentioning that a successful integration of catalytic reaction steps with product separation and catalyst recovery operations will also be dependent on innovative chemical reaction engineering. This will require the widespread application of sustainable engineering principles [48].In this context process intensification , which involves the design of novel reactors of increased volumetric productivity and selectivity with the aim of integrating different unit operations to reactor design, and miniaturization will play pivotal roles [49, 50]. 

However, the integration of PIM also creates synergy in the development of intensified processes, novel product forms, and size dependent phenomena, which in turn provides novel intensified processes. Process intensification-miniaturization is seen as an important element of sustainable development because it can deliver 1) at least a 10-fold decrease in process equipment volume 2) elimination of parasitic steps and unwanted by-products, thus eliminating some downstream processing operations 3) inherent safety because of reduced reactor volume 4) novel product forms 5) energy, capital, and operating cost reduction, and an environment friendly process 6) plant mobility, responsiveness, and security and 7) a platform for other technologies. 

The combination of process intensification and process miniaturization is an important element of sustainable technology and a platform for advancement in multidisciplinary science and engineering. There are now several examples of intensified processes being utilized in industry, as apparent from patent activity. Some of these intensified processes are confined to a single unit operation, while others integrate several intensified unit operations in the more efficient production of existing/improved/novel products. 

Pekdemir, T. Keskinler, B. Yildiz, E. Akay, G. Process intensification in wastewater treatment ferrous iron removal by a sustainable membrane bioreactor system. J. Chem. Technol. Biotechnol. 2003, 78, 773-780. 

A large variety of books and review papers is thus available, but often they either do not employ a comprehensive approach or are not consistent with the approach of sustainable industrial chemistry that is the core of this book. In addition, for educational purposes, it is useful to overview the main methods and tools available to develop a novel and innovative sustainable industrial chemistry. This chapter is dedicated to catalysis as key tool for sustainability and process intensification. 

Methods and Tools of Sustainable Industrial Chemistry Process Intensification... 

Eurther examples and concepts are discussed in the following sections, but already this introduction evidences the possibilities and opportunities for a sustainable industrial chemistry that derive from the application of process intensification equipment and methodology. 

Figure 3.3 PI provides radically innovative principles in process and equipment design that can benefit process and chain efficiency, capital and operating expenses, quality, wastes, process safety and more, and align perfectly with the Triple-P philosophy of sustainable industrial chemistry. Source adapted from EU Roadmap for Process Intensification (www.creative-energy.org).

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