Limitations, small-scale testing

Feedstock Development. Most of the research in process in the United States in the early 1990s on the selection of suitable biomass species for energy appHcations is limited to laboratory studies and small-scale test plots. Many of the research programs on feedstock development were started in the 1970s or early 1980s. 

The number of small scale test methods, used for classification purposes, should be limited and based on ISO tests, presumably the Cone Calorimeter /10/ (see Fig. 8) and possibly the ISO Surface Spread of Flame test /11/. 

Definitive answers to these questions are not yet available. Only recently has there been the opportunity to coUect and compare explosive boiling incidents from different industries. Also, most experiments that have been conducted to explore RPT mechanisms have been limited to relatively small-scale tests. Evidence now exists to suggest that the small-scale results may only be indicative of a trigger or initiating step, and other mechanisms need to be introduced to explain large-scale boiling explosions. 

While it appears that the bulk water (or hot fluid) temperature must be above TsKbydrocarbon), the upper limit is impossible to define. [The TJ TsD value of 1.10 used previously is only approximate.] As an example, in small-scale tests, liquid methane will not undergo an RPT when poured on water at any temperature. If the water were at 293 K, T /Tsi = 293/166 = 1.76 i.e., the ratio is far above unity. 

As will be described later in this section, for several types of small-scale tests where RFTs would be expected, an increase in the absolute system pressure had a profound effect in suppressing such incidents. As often noted in previous sections, one current theory to explain RPTs invokes the concept of the colder liquid attaining its superheat-limit temperature and nucleating spontaneously. In an attempt to explain the pressure effect on the superheating model, a brief analysis is presented on the dynamics of bubble growth and how this process is affected by pressure. The analysis is due largely to the work of Henry and Fauske, as attested to by the literature citations. 

One approach for using DOE on more complex processes is to do the majority of the process development on smaller, representative sections of material, such as test panels, rather than on full-scale parts, and then to scale up with a more limited experimental matrix. There is no guarantee that experience on small-scale test panels will directly translate to large parts because dimensions and thickness of the part are important variables in their own right. Another way to save on costs is to start with a satisfactory process and to continue, via careful monitoring of process variations and results, to extend the range of experience. This method is variously called statistical process control or statistical quality control. 

The TRE study was conducted (between 1998 and 2000) for metal refinery that was intermittently non-compliant with toxicity limits (> 50% mortality in 100% final effluent) for Daphnia magna and rainbow trout. Although not classified as a small-scale test, the results from the rainbow trout tests were also included in this case study. Key elements of the study included Phase I TIEs, Source Investigations and Toxicity Treatability Evaluations. The study team included site operations and process representative, toxicologists, chemists and engineers. 

Advantages, Possibilities, and Limitations of Small-Scale Testing of Catalysts for Fixed-Bed Processes... 

It is fairly easy to invent small-scale tests that are confusing as to which aspect of fire they are meant to evaluate and may give dangerous impressions because of ill-conceived presentation of results. Consequently, the established standards. should be adhered to and the limitations of small-scale tests in terms of predicting performance appreciated. 

BS 6336 [6] is a most important standard and discusses the need carefully to access the limitations of small-scale tests in order to avoid possible incorrect or misleading interpretations. Large-scale tests are frequently useful in establishing the performance of a product or material in a specific environment suitable small-scale tests can then be selected to provide quality assurance and control. 

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