Small-scale tests

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes. 

First carry out a small-scale test, placing about 0 5 g. of the mixture in a test-tube, adding about 5 ml. of 10% aqueous NaOH solution, and shaking the mixture well. It will be readily seen whether the neutral substance (which remains undissolved) is solid or liquid. Then repeat the extraction on a largo scale as follows ... 

The scale-up of filtration centrifuges is usually done on an area basis, based on small-scale tests. Buchner funnel-type tests are not of much value here because the driving force for filtration is not only due to the static head but also due to the centrifugal forces on the Hquid in the cake. A test procedure has been described with a specially designed filter beaker to measure the intrinsic permeabiHty of the cake (7). The best test is, of course, with a small-scale model, using the actual suspension. Many manufacturers offer small laboratory models for such tests. The scale-up is most reHable if the basket diameter does not increase by a factor of more than 2.5 from the small scale. 

Laboratory experiments using rodents, or the use of gas analysis, tend to be confused by the dominant variable of fuel—air ratio as well as important effects of burning configuration, heat input, equipment design, and toxicity criteria used, ie, death vs incapacitation, time to death, lethal concentration, etc (154,155). Some comparisons of polyurethane foam combustion toxicity with and without phosphoms flame retardants show no consistent positive or negative effect. Moreover, data from small-scale tests have doubtful relevance to real fine ha2ards. 

Effects on Visible Smoke. Smoke is a main impediment to egress from a burning building. Although some examples are known where specific phosphoms flame retardants increased smoke in small-scale tests, other instances are reported where the presence of the retardant reduced smoke. The effect appears to be a complex function of burning conditions and of other ingredients in the formulation (153,156,157). In a carehil Japanese study, ammonium phosphate raised or lowered the smoke from wood depending on pyrolysis temperature (158). Where the phosphoms flame retardant functions by char enhancement, lower smoke levels are likely to be observed. 

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. 

While research has developed a significant and detailed filtration theory, it is still so difficult to define a given liquid-solid system that it is both faster and more accurate to determine filter requirements by performing small-scale tests. Filtration theoiy does, however, show how the test data can best be correlated, and extrapolated when necessary, for use in scale-up calculations. 

Scaling Up Test Results The results of small-scale tests are determined as dry weight of sohds or volume of filtrate per unit of area per cycle. This quantity multiplied by the number of cycles per day permits the calculation of either the filter area reqiiired for a stipulated daily capacity or the daily capacity of a specified plant filter. The scaled-up filtration area should be increased by 25 percent as a factor of uncertainty. In the calculation of cycle length, proper account must be made of the downtime of a batch filter. 

For estimating filtration rate (therefore, operating pressure and size of the filter), washing characteristics, and other important features, small-scale tests such as the leaf or pressure bomb tests described earlier are usually essential. In the conduct and interpretation of such tests, and for advice on labor requirements, maintenance schedule, and selection of accessory equipment the assistance of a dependable equipment vendor is advisable. 

If the yields are accepted without full-scale testing, questions can and should arise as to how much contingency exists in the yields (since after all, they were obtained by correlations of similar coals, or perhaps by small-scale tests for your coal, for example). For at least one study, initially presented yields of this sort were found to represent a conservative case and upon request, yields were revealed that were closer to licensor expectations with no contingency. Some design contingency must be provided, but to do this intelligently, any yield contingency must be identified. 

Small scale test runs prior to preparative irradiation experiments may be carried out in tubes which are either taped to the lamp housings (immersion wells) depicted in Figures 13-1 and 13-2 or placed in turntable reactors ( merry-go-rounds ). These arrangements permit the simultaneous irradiation of several samples, but only a fraction of the available light emission is used. In Figure 13-4 a simple reactor is shown which focusses almost all the emitted light into one sample which can be scaled up also to semi-preparative volumes. In this way the necessary irradiation time can be reduced sharply. 

The temperature for methane and butane calculated with the isothermal model is a factor 1.4 times greater than the average temperature measured by Lihou and Maund (1982) in their small-scale tests, although higher local maximum temperatures were measured. In this model, combustion is stoichiometric, thus leading to very high fireball temperatures which, in turn, lead to high radiation emissions. Effective surface emissions measured experimentally were one-half the value calculated from this model, because combustion is not stoichiometric and emissivity is less than unity. 

In order to achieve uniform solid suspension or pickup of solid particles off the bottom, the upward velocities of the fluid streams in all portions of the vessel must exceed the terminal setding velocity of the particular particles. This can be determined by small scale tests. 

Although all these complicating factors cannot be reproduced in small-scale tests, it will be of value to summarise the main knowledge that has been gained from long-period burial trials conducted in the United States and in Great Britain . The subject will be considered under two heads effect of metal composition and effect of the soil. 

The Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (UL 94) has methods for determining whether a material will extinguish, or burn and propagate flame. The UL Standard for Polymeric Materials-ShortTerm Property Evaluations is a series of small-scale tests used as a basis for comparing the mechanical, electrical, thermal, and resistance-to-ignition characteristics of materials. 

Explosibility of Dusts in Small-Scale Tests and Large-Scale Industrial Plant , InstrChem-Engrs(London), JChemE SympSeries No 25 (1968) 11) E.K. Dabora, K.W. Ragland ... 

Carey, W. F. and Williamson, G. J. Proc. Inst. Mech. Eng. (Steam Groupi 163 (1950) 41. Gas cooling and humidification design of packed towers from small scale tests. 

A frequent sizing technique, which is useful when the reaction kinetics and heat of reaction are not known, is to conduct small scale tests. Then scale up to large equipment is done by providing a vent with similar vent area per mass of contents. 

With such modeling efforts, coupled with some small-scale tests, we can assess the hazards of a polymer reaction by knowing certain physical, chemical and reaction kinetic parameters. 

At present there is no small-scale test for predicting whether or how fast a fire will spread on a wall made of flammable or semiflammable (fire-retardant) material. The principal elements of the problem include pyrolysis of solids char-layer buildup buoyant, convective, tmbulent-boundary-layer heat transfer soot formation in the flame radiative emission from the sooty flame and the transient natme of the process (char buildup, fuel burnout, preheating of areas not yet ignited). Efforts are needed to develop computer models for these effects and to develop appropriate small-scale tests. 

A lot of attempts have been made to describe the time dependence of the attrition rate in batch fluidized bed processes. Gwyn (1969) studied the degradation of catalysts in a small-scale test apparatus and defined the elutriated particles as the only attrition product. He described the increase of the elutriated mass, Wel, with time, t, based on the initial solid bed mass, Wbed 0, by the now widely known Gwyn equation ... 

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