Process Cycle Optimisation

Setting the product composition of a pharmaceutical preparation, so as to effect an efficient and economical drying cycle, will probably always be beyond the remit of the process engineer. However, bearing in mind the complexities of the freeze-drying process, its optimisation should be given due consideration even by those responsible for product development. 

As such, ToFSIMS (often in combination with XPS) is a useftil tool for process/coating optimisation. Coatii durability can also be studied by these techniques, as a fimction of, for example, washing (e.g. time, temperature, detergents, wash cycles) and ageii (e.g. shelf life, exposure to ultra-violet/sun). 

Unlike polyurethane-RIM processes, nylon-RIM reactions are endothermic and require temperatures of 130-140°C. In contrast to the polyurethane-RIM systems, this enables thick wall parts to be made. Cycle times of 2-3 minutes are comparable to those for polyurethane-RIM. In the development stage, current work is concerned with reducing moulding times and optimising moulding conditions. 

As an example, Baitz et al7 focused on different technologies and peripheral system conditions to reduce dust and heavy metal emissions from a refinery. They stressed that the knowledge of the sensitive life cycle parameters and a suitable database, and thus the possibility to quantify impacts, enables a sustainable decision-making in process design and process optimisation. 

The ECO method was developed to aid environmental impact and cost optimisation of chemical synthesis pathways or processes suitable for the research and development (R D) stage. In order to represent terms of ecological as well as economic sustainability, three objective functions which incorporate (i) energy demand (EF), (ii) risks concerning human health and the environment (EHF) and (iii) costs (CE), were defined. Their calculation follows the life cycle approach and is based on the data available already in R D. Because the application of a comprehensive LCA is both, too complex and based on data which are partially not available at the R D stage, the determination of the three objective functions is based on the SLCA approach extended by economic issues. The key objectives are introduced below. 

Azapagic, A. Clift, R. (1999) The Application of Life Cycle Assessment to Process Optimisation. Computers and Chemical Engineering, 23(10), 1509-1526. 

Azapagic, A. (1999) Life Cycle Assessment and Its Application to Process Selection, Design and Optimisation. Chemical Engineering Journal, 73(1), 1-21. 

Kniel, G.E., Delmarco, K., Petrie, J.G. (1996) Life Cycle Assessment Applied to Process Design Environmental and Economic Analysis and Optimisation of a Nitric Acid Plant. Environment Progress, 15(4), 221-228. 

Baitz, M., Wolf M.A., Faltenbacher, M. (2001) Life-Cycle Related Technical-Environmental Multi-Parameter Trade-Off Optimisation of Processes. Journal of Advances in Science, 13(3), 199-202. 

Insertion and -elimination. A catalytic cycle that involves only one type of elementary reaction must be a very facile process. Isomerisation is such a process since only migratory insertion and its counterpart P-elimination are required. Hence the metal complex can be optimised to do exactly this reaction as fast as possible. The actual situation is slightly more complex due to the necessity of vacant sites, which have to be created for alkene complexation and for P-elimination. 

With a good description of the mass transfer processes occurring in a CDPF now in place, it should be possible to predict the effects of PGM zoning and non-uniform aging on the performance of a CDPF. To illustrate the way in which this model can help in optimising the placement of the PGM washcoat in a CDPF systems, simulations were carried out over the European drive cycle for ... 

The Bunsen section is central to the cycle, not only because it objectively is the section which produces the two acids that are independently processed in the other two sections, but also because its optimisation is key for the whole cycle efficiency. Indeed, the Bunsen reaction does not actually proceed as written above, but requires large amounts of excess water and excess iodine (Norman, 1982) ... 

The efficiency of the cycle was evaluated to be close to 39%, a value which is not far from what would be expected from alkaline electrolysis using the 50% efficiency electricity produced by a V/HTR. There may be some room for possible process improvements, especially in terms of Bunsen section optimisation, but recent thermodynamic data will more likely lead to a revision of the efficiency to a lower value. Furthermore, Figure 3 demonstrates that efficiency is not the dominant factor for cycle competitiveness. 

General Atomics (GA) and the Commissariat a Ytnergie Atomique (CEA) have been working on sulphur-iodine cycle flow-sheeting for several years, leading to sometimes differing efficiency estimates. They have undertaken to understand and reconcile these differences, and have come to consider in more detail the effect of the VHTR characteristics on the optimisation of the sulphur-iodine flow sheet. This paper will present the outcome of these studies, and stress the interplay between nuclear reactor and chemical process. 

Many variations are possible for each section of the HyS cycle (Brecher, 1977) the temperatures and other operating conditions can be optimised, with a wide variety of solutions in matter of chemical engineering to perform unit operations and to exchange heat. Each section is strongly dependant on the other, meaning that an output may be the input of the next section. Any change in one section may influence directly the whole process. 

Innovative analytical tools and methods have been developed, and dedicated instrumented devices now give access to the necessary reliable data, essential for the optimisation of the process and for the analysis of the potential of the cycle. 

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