Concept selection phase

Using the TRACE/SNAP modeling tool, the SNPP model was developed in a modular fashion. Model builders built and tested stand alone versions of the reactor, HRS, recuperator, gas cooler, turbine and compressor. The SNAP GUI was effective in joining the pieces as well as duplicating large sections. For example, the second Brayton and heat rejection loops were copied and pasted within SNAP from the first loops. The TRACE plant model originally included component models that were developed during the concept selection phase. In order to provide the most current model, most of these sub-models were updated to post-concept selection versions. 

Safety aspects are considered in two phases (Fig. 11). In the rule based synthesis some safety related rules are applied in process concept selections. These include rules such as separate corrosive or hazardous components first or avoid using chemically incompatible substances in the same process. ... 

The UOP Ebex process has been available for license since the 1970s. This process is a rejective simulated moving bed process where the ethylbenzene is the least adsorbed member of the mixed xylenes and is recovered in high purity in the raffinate stream [47]. Other liquid phase simulated moving bed concepts selective for ethylbenzene have been considered. These would ostensibly require less adsorbent circulation per unit feed because ethylbenzene is typically at <20% concentrahon in mixed xylenes [48, 49]. A process is disclosed by Broughton [50] that produces a pure m-xylene stream along with a pure ethylbenzene stream. 

Phase 2. Technology review and design concept selection. This includes... 

These results are directly compatible with models of human information processing (Rasmussen, 1983). Calculation is, in most cases, a skill-and-rule-based activity and requires relatively little mental effort. In contrast to this, selection and evaluation, as well as the activities around task clarification, are more rule-and knowledge-based tasks that require higher mental effort. According to the stress-strain concept, these phases result in a higher strain level. 

The material selection phase of design, like the concept phase, is based upon accumulated knowledge via literature searches and/or personal design experiences with performance of materials in previous... 

With the concept selection completed, a design must be executed. This is accomplished in the system and detail design phases. Elements here are highly dependent on the nature of the product, so that the process here is less explicitly described than the previous steps. This activity is greatly influenced by several of the issues mentioned previously, so a framework will be laid here and then these ancillary issues will be discussed along with ways they might interact with the design itself. 

Provided that field development is judged to be feasible, one development alternative is selected and further matured in the Concept study phase. The aim is to provide an adequate decision basis for investment approval to be made by the board of directors. The aims of the SHE activities in the first two phases are to ensure that the selected concept is feasible with respect to SHE and that the authorities and Norskoil s SHE goals and requirements are met in a cost-efficient way. It is not necessary to choose the best concept from a SHE point of view, but the rationale for making the selection has to be documented. 

The project screens different development concepts. Risks that may make a concept unfeasible or result in high extra costs are focused on in special studies. An independent consultant carries out coarse Risk and emergency-preparedness analysis (REPA) for the two development alternatives that are considered (NORSOK Standard Z-013, see Norsk Standard, 1998). They are a standard production ship and a standard semi-submersible PDQ platform. The aim is to get a total overview of the risks involved for concept selection and to check compliance with the acceptance criteria. It is important to remember that the REPA and the acceptance criteria evaluate the integrity of passive and embedded barriers in particular. These are to a large extent determined in the early project phase. 

Occupational accidents are not a major concern in concept selection. The risk of this type of accidents is mainly decided by the detailed design solutions developed in later phases. Early on, the project focuses on some basic characteristics of the different development alternatives that have impHcations for the possibility of developing acceptable solutions in later phases. They include ... 

A substantial amount of work was initiated by the NRPCT to select and develop a concept fora gas-Brayton space reactor for the Prometheus project. The three major technical reports - the feasibility study, the concept selection report, and the close-out report - have been formally issued and stored in the Office of Scientific and Technical Information (OSTI) Science Research Connection database. These reports can inform future developers of space reactors on the work completed during this phase of the Prometheus program. 

The way to take advantage of an in-depth knowledge of processes is to review complete products or subassemblies and consider how individual parts should be defined within them. In other words, process selection should ideally be integrated into a product s concept development phase so that maximum manufacturing flexibihty is preserved from the outset. Components can thus be defined within the product-as-a-system framework to uncover unique benefits that may be associated with a particular process (2). 

For the Berry phase, we shall quote a definition given in [164] ""The phase that can be acquired by a state moving adiabatically (slowly) around a closed path in the parameter space of the system. There is a further, somewhat more general phase, that appears in any cyclic motion, not necessarily slow in the Hilbert space, which is the Aharonov-Anandan phase [10]. Other developments and applications are abundant. An interim summai was published in 1990 [78]. A further, more up-to-date summary, especially on progress in experimental developments, is much needed. (In Section IV we list some publications that report on the experimental determinations of the Berry phase.) Regarding theoretical advances, we note (in a somewhat subjective and selective mode) some clarifications regarding parallel transport, e.g., [165], This paper discusses the projective Hilbert space and its metric (the Fubini-Study metric). The projective Hilbert space arises from the Hilbert space of the electronic manifold by the removal of the overall phase and is therefore a central geometrical concept in any treatment of the component phases, such as this chapter. 

Holdup and Flooding At this point it is useful to introduce the concepts of holdup and flooding in column contactors. It is normal practice to select the phase which preferentially wets the internals of the column as the continuous phase. This then allows the dispersed phase to exist as discrete droplets within the column. If the dispersed phase were to preferentially wet the internals, this could cause the dispersion to prematurely coalesce and pass through the column as rivulets or streams which would decrease interfacial area and therefore column efficiency. 

In common with all multidimensional separations, two-dimensional GC has a requirement that target analytes are subjected to two or more mutually independent separation steps and that the components remain separated until completion of the overall procedure. Essentially, the effluent from a primary column is reanalysed by a second column of differing stationary phase selectivity. Since often enhancing the peak capacity of the analytical system is the main goal of the coupling, it is the relationship between the peak capacities of the individual dimensions that is crucial. Giddings (2) outlined the concepts of peak capacity product and it is this function that results in such powerful two-dimensional GC separations. 

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