Economics and Scale-Up

Not everything is gloomy. Supercritical CO2 (SCCO2) already has several profitable commercial - not chemical related - applications (see Section 6.2) [5, 6]. 

Some years ago, Beckman and co-workers listed a series of desirable process characteristics (1) and key constraints (2) that they believed were prerequisites for 

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If one considers these key points, it can be seen that decaffeination exhibits characteristics 1 a), 1 c) and 1 d), and constraints 2 b) and 2 d) are also obeyed. The whole situation was succinctly captured by SCF pioneer Val Krukonis, who stated, There is no point in doing something in a supercritical fluid just because it s neat. Using the fluids must have some real advantage. And in this case, advantage does not just mean technical or scientific elegance . 

The key point is that, in general, the phase behavior of a given reaction system wiU not be known prior to the development of that process. Moreover, in those cases where data are available in the literature, they often refer to mixtures far more dilute than would be used in a commercial process. In such a process, energy and plant costs will clearly dictate that the reaction mixture should contain the minimum amount of SCF (see Beckman s constraint 2 e). This contrasts with SCF extraction, where the concentration of the extract dissolved in the SCF is determined, at least in part, by the mass-transport kinetics on the matrix material. All of these factors mean that the phase behavior of the reaction mixture wiU usuaUy have to be determined by experimental methods. 

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The ultimate goal of process development is to achieve feasibility where it is possible to produce amino adds on a large scale at a production cost per kg of amino add comparable to, or cheaper than, the processes currently used by other companies. If we presume that the technical performance (fermentation and recovery) are sorted out on a laboratory scale and scaling up looks promising, then it is time to find out whether it is possible to operate economically on a large scale. 

The scope of coverage includes internal flows of Newtonian and non-Newtonian incompressible fluids, adiabatic and isothermal compressible flows (up to sonic or choking conditions), two-phase (gas-liquid, solid-liquid, and gas-solid) flows, external flows (e.g., drag), and flow in porous media. Applications include dimensional analysis and scale-up, piping systems with fittings for Newtonian and non-Newtonian fluids (for unknown driving force, unknown flow rate, unknown diameter, or most economical diameter), compressible pipe flows up to choked flow, flow measurement and control, pumps, compressors, fluid-particle separation methods (e.g.,... 

This outline of the many factors that have to be investigated for the design and operation of an SX-EW plant is perhaps typical of the development of an SX process on which little or no prior work has been done. Today, with the knowledge and experience available, processes similar to those already in operation may be designed and scaled up more economically. The Bluebird Mines operation took about 4 years from initial bench-scale tests to plant operation. 

On the other hand, the manufacturer may determine that the advantages of process scale-up are compromised by the increased cost of production on a larger scale and/or the potential loss of interest or investment income. Griskey (1) addresses the economics of scale-up in some detail in his chapter on engineering economics and process design, but his examples are taken from the chemical industry. For a more extensive discussion of process economics, see Ref. 2. 

Remer DS, Mattos FB (2003) Cost and scale-up factors, international inflation indexes and location factors. International Journal of Production Economics 84 1-16... 

In this article, we first review the methods of growing amorphous silicon for solar cells. The next part covers the material properties that are relevant to the development of efficient, stable a-Si H solar cells. In Part IV, we discuss the fabrication, performance, and scale-up of a-Si H solar cells, and in Part V, we consider the economics of these cells for various applications. We conclude with some projections for the future of a-Si H photovoltaics. 

The differences cannot be easily explained. The selection rules are often heavily influenced by economical considerations alone. The technological parameters are flux, recirculation rate, chemical compatibility, pore size or molecular weight cutoffs, pressure and temperature limitations, and cleane-ability. Once the feasibility has been established, the engineering design and scale-up come into play. 

For the economic analysis, the design and scale up of commercial reactor systems it becomes more important to use modem mathematical modelling tools and therefore it is necessary to get more insight into the macro kinetic aspect as well as the understanding of the behaviour of the phase equilibrium. As well for investigating the aspects of choosing the optimal catalyst it is necessary to have a suitable technology available. 

Power consumption of the mixer motor for endpoint determination and scale-up is widely used (Leuenberger and subsequent work, HoW and subsequent work, Landin et al. Faure et and many others because the measurement is economical, does not require extensive mixer modifications, and is well correlated with the granule growth. 

It has been suggested in the literature [34] that filtration devices producing Taylor or Dean vortices can help depolarization of the solute build up on membranes. This seems to be an attractive way because of excellent bulk fluid mixing, high wall shear rates and weakly decoupled cross-flow with transmembrane flux. Unfortunately there are some severe limitations on a technical and economical point of view with such devices. Build up and scale up of these modules are expensive with difficulties in repairing and changing membranes. A good compromise between economic and technical constraints has been described by Charpin et al. [39]. It consists in the preparation of mineral (metal... 

The overall objective of chemical production activities is to reproduce the process that has been transferred from process development to meet the current and future market requirements for the drug product. Particular emphasis is placed on issues related to process safety, environmental issues, equipment requirements, and production economics. The scale-up factor from the pilot plant to commercial production is usually rather small (approximately 1-20). As a result, the informa-... 

This book on "Environmental Oriented Electrochemistry" concentrates on the Electrochemistry/Environment relationship including, among others, chapters on design and operation of electrochemical reactors and separators, process simulation, development and scale-up, optimization and control of electrochemical processes applied to environmental problems, also including economic analysis, description of unique current and future applications, in addition to basic research into developing new technologies. 

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