Bench-scale experimentation using

A turbine type agitator is commonly used for liquid-solid systems. Mixing rates depend on the forces required to suspend all solid particles. Minimum levels can be determined for (1) lifting the particles, and (2) for suspending them in an homogeneous manner [200]. Similar requirements apply to liquid-liquid systems. For cases where two poorly miscible fluids of about equal volume are used in the reaction, the mixer is placed at the interface. For a bench-scale experimental system of about 2 liters capacity, the minimum rotational speed to obtain well-dispersed system is 300 to 400 rpm [201], depending on the type of mixer. This rotational value decreases as the vessel volume increases. 

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). 

Acar et al. (1996 1997) showed that ionic migration could be used for injection and transport of anionic and cationic additives. In a bench-scale experimental setup, ammonium hydroxide (NH4OH) was introduced at the anode compartment and sulfuric acid (H2S04) at the cathode compartment. The electric field caused migration of nitrate ion from anode towards the cathode and sulfate ion from cathode towards the anode. The study reported transport rates of 5 to 20 cm/day in fine sand and kaolinite soil specimens and consequent soil saturation of ammonium and sulfate ions. The study concluded that ion migration under dc fields can be used to inject nutrients, electron acceptors/donors to enhance in situ bioremediation. 

On the basis of the bench-scale experimental results, methanol will be used as the extraction medium. Let us consider a process in which dried sludge is repeatedly washed with fresh methanol. The bench-scale experiments suggest a solvent mass to sludge mass ratio of approximately 3, 15—30 minutes of contact time per cycle and 10 wash... 

The reactor model was applied to simulate the behavior of the bench-scale unit used for the kinetic experiments at stable catalyst conditions, which is after the initial deactivation period. Molar concentration profiles of sulfur, nitrogen, and metals in the liquid and solid phases in both reactors (Rj and Rj) are presented in Figure 8.10. Experimental values are also included for comparison. As observed, the model allows for tracking the evolution of each chemical lump, showing a good agreement with the experimental data. It can be noticed that there is a concentration gradient... 

Use of Literature for Specific Systems A large body of experimental data obtained in bench-scale laboratoiy units and in small-diameter packed towers has been published since the early 1940s. One might wish to consider using such data for a particular chemically... 

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. 

Experimental results showed the packing media used in a bench-scale biotrickling filter... 

A bench-scale settler was used in an experimental study to assess continuous biodesulfurization operation to separate oil and water + biocatalyst [260], The design was based on a viton tubing settler surface placed at an angle to allow separation of the multi phase mixture. The device was reported to operate with over 95% efficiency for first 24 hours after which the performance reduced drastically. 

Equipment to be Used for the Analysis of Hazards The need for experimental thermodynamic and kinetic data is clear by now. The equipment designed to provide this information for the chemicals involved are described in Chapter 2, and include the DSC, DTA, ARC, Sikarex, SETARAM C-80, and DIERS technology. Kinetic data for the desired reaction are preferably obtained with instrumented bench-scale equipment such as the RC1. This type of equipment is discussed in Section 3.3. 

These factors are introduced in the experimental plan at the bench-scale before the pilot--plant stage. On the bench-scale, glass or steel laboratory reactors of about 1 to 2 L will be used for MSSR and a 30 cm diameter and 2 m height for BSCR. 

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-... 

Development of technology is generally done using laboratory scale units. Experimental data can be obtained with less expense and with more accuracy and flexibility than by attempting to do the same test on a commercial scale. In the laboratory, smaller quantities of feedstock and catalyst are needed and lower manpower and capital costs are incurred. By necessity, bench scale units must process feedstocks which are at least as difficult as those processed commercially. 

The choice of experimental reactor is important to the success of the kinetic modeling effort. The short bench-scale reaction tubes sometimes used for studies of this sort give little or no insight into best mathematical form of the kinetic model, conduct the reaction over varying temperatures and partial pressures along the tube, and inevitably operate at velocities that are a small fraction of those to be encountered in the plant-scale reactor. Rate models from laboratory reactors of this sort rarely scale-up well. The laboratory differential reactor suffers from velocity problems but does at least conduct the reaction at known and relatively constant temperature and partial pressures. However, one usually runs into accuracy problems because calculated reaction rates are based upon the small observed differences in concentration between the reactor inlet and outlet. 

Testing in bench-scale equipment is a valuable experimental method for investigation of the impact of deactivation on the catalyst performance when full-size catalyst pellets, industrial mass velocity and pressure are used. Bench-scale testing is often... 

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