Bench-scale system, design

Solox has designed a hybrid solar/electric ultraviolet (UV) oxidation system for remediating organic contaminants in water. While the bench-scale system of this technology worked, according to the vendor, it has not been tested yet at field scale and is not commercially available. All information is from the vendor and has not been independently verified. 

Bench-scale tests were conducted to determine design parameters and operability of Che distillation process for the pilot plant. The column, reboller, and condenser used in the bench-scale system were constructed of fiberglass-reinforced ethylene-chlorotrifluoroethylene. The heat exchangers were spaghetti tube bundles constructed of fluorinated ethylene-propylene copolymer. 

The selection requirements for each of the components of the SCWO system for treating a variety of waste types comes from environmental regulations, waste characteristics, and cost and safety criteria. Similar to the bench-scale experimental design, the major components to be included in the SCWO design involve three main subsystems (influent introduction, reactors, and effluent removal systems). Other auxiliary systems such as heat exchangers and effluent exhaust systems must also be designed. In addition, for scale-up operations, the waste pretreatment and handling systems have to be considered. Fig. 10 shows a schematic of a complete system. 

Work is currently in progress that will identify optimum operating conditions for both reactor stages. This information will be used for the design of a continuous, Integrated, bench-scale system. 

The topics presented in this paper include a description of the bench-scale system, the experimental approach, and the results of degradation testing. Also included are the results of batch precipitation experiments designed to study coprecipitation of adipic acid in scrubber waste solids. 

The design of the bench-scale system was influenced by two important considerations ... 

Once the bench scale system is optimized, design and construct a pilot-scale pressurized bioreactor at significantly increased scale. 

There are only limited reports on hydrothermal gasification in larger than laboratory scale. At PNNL bench-scale systems were developed as early as 1989 (Elliott et al., 1989). This work was used to design a scaled-up mobile reactor system, designed for up to 0.5 t of wet feed per day (Elliott et al., 1994). PNNL demonstrated successfully the continuous gasification of biomass to methane-rich product gas. Initially problems occurred with plugging of the catalyst bed by biomass which was solved by a two-step process where biomass was liquefied in a CSTR before HTG. The design... 

Consider the possibility of scahng up the design of a new system from experimental data obtained in a laboratory-bench scale or a small pilot-plant unit. 

Scale-up techniques for using the results of pilot plant or bench scale test w ork to establish the equivalent process results for a commercial or large scale plant mixing system design require careful specialized considerations and usually are best handled by the mixer manufacturer s specialist. The methods to accomplish scale-up will vary considerably, depending on whether the actual operation is one of blending, chemical reaction tvith product concentrations, gas dispersions, heat transfer, solids suspensions, or others. 

Bench Scale ERS Sizing Tools— Acquisition of Thermal Data— Apparatus Design and Sample Thermal Data for 5 Systems, DIERS/AIChE, 1986, 159 pages. 

One goal of our experimental program with the bench-scale unit was to develop the necessary correlations for use in the ultimate design of large commercial plants. Because of the complexity inherent in the three-phase gas-liquid-solid reaction systems, many models can be postulated. In order to provide a background for the final selection of the reaction model, we shall first review briefly the three-phase system. 

Aqueous, alkaline fuel cells, as used by NASA for supplemental power in spacecraft, are intolerant to C02 in the oxidant. The strongly alkaline electrolyte acts as an efficient scrubber for any C02, even down to the ppm level, but the resultant carbonate alters the performance unacceptably. This behavior was recognized as early as the mid 1960 s as a way to control space cabin C02 levels and recover and recycle the chemically bound oxygen. While these devices had been built and operated at bench scale before 1970, the first comprehensive analysis of their electrochemistry was put forth in a series of papers in 1974 [27]. The system comprises a bipolar array of fuel cells through whose cathode chamber COz-containing air is passed. The electrolyte, aqueous Cs2C03, is immobilized in a thin (0.25 0.75 mm) membrane. The electrodes are nickel-based fuel cell electrodes, designed to be hydrophobic with PTFE. 

The Contalab, initially supplied by Contraves, was purchased by Mettler-Toledo, which is now placing less emphasis on this design than on the RC1. Some comments here are appropriate, however, since it is another type of bench-scale calorimeter, and units continue to be used. Its measuring system is based on the heat balance principle, in which a heat balance is applied over the cooling/heating medium. For this purpose, both the flow rate of the coolant and its inlet and outlet temperatures must be known accurately. Figure 3.12 is a schematic plan of the Contalab. 

The Sikarex safety calorimeter system and its application to determine the course of adiabatic self-heating processes, starting temperatures for self-heating reactions, time to explosion, kinetic data, and simulation of real processes, are discussed with examples [1], The Sedex (sensitive detection of exothermic processes) calorimeter uses a special oven to heat a variety of containers with sophisticated control and detection equipment, which permits several samples to be examined simultaneously [2]. The bench-scale heat-flow calorimeter is designed to provide data specifically oriented towards processing safety requirements, and a new computerised design... 

The initial bench-scale experimental investigations into solvent extraction processes are conducted with small apparatus, such as separating funnels. Following the successful completion of these tests, when the best reagent and other conditions for the system have been established, small-scale continuous operations are run, such as in a small mixer-settler unit. The data so obtained are used to determine scale-up factors for pilot plant or plant design and operation (see Chapters 7 and 8). 

Aspects of coal liquefaction have been much researched, particularly with the re-emeigence of interest caused by the oil crisis in the 1970 s. The type of reactors used in the studies has been various, ranging from small bomb type microautoclaves through larger autoclaves and bench-scale reactors to larger scale pilot or demonstration plants. The use of differently sized and designed high pressure equipment for liquefaction studies further complicates an already complex system and allows only limited comparison of results. 

The process design principles of SLM, non-dispersive extraction, and hybrid hquid membrane systems need to be understood through bench scale experiments using feed solution of practical relevance. While the economic analysis of an ELM process can be performed from small scale experiments, such an analysis is difficult for other LM systems. In particular, availability and cost of hollow fiber membranes for commercial application are not known apriori. A simple rule of thumb for cost scale-up may not be apphcable in the case of an HE membrane. Yet we feel that the pilot plant tests would be adequate to make realistic cost benefit analysis of a liquid membrane process, since the volume of production in )8-lactam antibiotic industries is usually low. 

The literature on extractive distillation is rather sparse. In addition to that on the design and operation of the commercial units, the bench scale work of Griswold and coworkers (21) at the University of Texas and that of Dicks and Carlson (12) at the University of Pennsylvania are noteworthy. Pertinent thermodynamic data on extractive distillation systems have been presented by Wohl (59), and Colburn and coworkers (20, 43) have published vapor-liquid equilibria for several systems. Scheibel (48) has presented an approximate method for design of extractive distillation units. 

Much experimental work has been carried out on ozonation in drinking, waste and process water treatment. And since there is still much to be learned about the mechanisms of ozonation, and many possibilities of utilizing its oxidizing potential many experiments will be carried out in the future. Not only researchers but also designers, manufacturers and users of ozonation systems will continue to do bench-scale testing because ozonation is so system dependent. Most full-scale applications have to be tried out bench-scale for each system considered. That means that there is a need for not only fundamental information about the mechanisms of ozonation, but also information on how to set-up experiments so that they produce results that can be interpreted and extrapolated. 

Because ozonation is so system dependent, most full-scale applications are first tried out bench-scale. That means designers and manufacturers of treatment systems, researchers, as well as potential industrial operators of ozonation must know not only the fundamentals about the mechanisms of ozonation, but also how to set-up experiments so that the results can be interpreted, extrapolated, and applied. 

The idea of using fluidized bed as both uniform light distribution and an immobilizing support for photocatalysts has been originally proposed and theoretically evaluated by Yue and Khan [3]. Experimental application of this idea has been demonstrated by Dibble and Raupp [4] who designed a bench scale flat plate fluidized bed photoreactor for photocatalytic oxidation of trichloroethylene (TCE). Recently, Lim et al. [5,6] have developed a modified two-dimensional fluidized bed photocatalytic reactor system and determined the effects of various operating variables on decomposition of NO. Fluidized bed photocatalytic reactor systems have several advantages over conventional immobilized or slurry-type photocatalytic reactors [7,8]. The unique reac-... 

The major advantage of these fixed-bed systems is that the fixed-bed technology can be simple, and will require minimum scale-up studies. As indicated earlier, this type of design has been successfully scaled-up to commercial size directly from bench-scale pilot plant data many times. 

Examples of the use of models for the design of large-scale systems include the measurement of pressure drop and heat transfer in model heat exchangers, the mixing and rate of reaction in a bench-top batch reactor and the prediction of pressure drops in pipelines. 

For scale-up operations, the selection of the reactor is considered to be the key element in designing SCWO systems. Environmental regulations set the requirement for the destruction efficiency, which in turn sets requirements on the temperature and residence time in the reactor (as an example, the required DRE is 99.99% for principal hazardous components and 99.9999% for polychlorinated biphenyls, PCBs). The reactor parameters for the scale-up designs can be extrapolated from the available bench-scale data. A detailed discussion on available reactor types is given below. 

Cellular foam occurs at low vapor velocities in small columns, where the wall provides foam stabilization. It occurs with some systems or tray designs but not with others and is promoted by surface tension effects such as the Marangoni effect (99). Cellular foam is uncommon in industrial columns. The foam that causes problems in industrial installations is mobile foam, where the bubbles are in turbulent motion. Mobile foam is associated with the froth and emulsion regimes. Cellular foam is encountered in bench-scale and pilot-scale columns. If cellular foam occurs in the test unit, caution is required when scaling up the results. 

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