In laboratory-scale reactors

Thus, for this reaction, a substantial temperature difference exists between the solid surface and the bulk fluid. It has a far greater influence on the observed rate than the corresponding concentration difference. Differences of this magnitude can clearly lead to complications in the analysis of data obtained in laboratory scale reactors. If such differences will exist at the operating conditions to be employed in a commercial scale reactor, the design engineer must be sure to take them into account in his analysis. 

The effectiveness of a fixed-bed operation depends mainly on its hydraulic performance. Even if the physicochemical phenomena are well understood and their application in practice is simple, the operation will probably fail if the hydraulic behavior of the reactor is not adequate. One must be able to recognize the competitive effects of kinetics and fluid dynamics mixing, dead spaces, and bypasses that can completely alter the performance of the reactor when compared to the ideal presentation (Donati and Paludetto, 1997). The main factor of failure in liquid-phase operations is liquid maldistribution, which could be related to low liquid holdup in downflow operation, or other design problems. These effects could be critical not only in full-scale but also in pilot- or even in laboratory-scale reactors. 

As mentioned earlier, both chemical (catalyst, surfactants, stabilizers) and physical (fluid dynamics, energy dissipation rates, circulation time and so on) factors control the performance of the suspension polymerization reactor. It is first necessary to examine the available experimental data to clearly understand the role of these chemical and physical factors. The available data indicates that the yield of usable polymer beads in laboratory scale reactor is more than 85%. Laboratory experiments were then planned to examine the sensitivity of the yield to various parameters of the polymerization recipe under the same hydrodynamic conditions. These experiments showed that the yield is relatively insensitive to small deviations in the chemical recipe. Analysis of the available data on pilot and plant scale indicated a progressive decrease in the yield of usable polymer beads from laboratory to pilot to plant scale. This analysis and some indirect evidence suggested that it may be possible to re-design the plant-scale reactor hardware to generate better fluid dynamics and mixing to increase the yield of particles in the desired size range. 

Despite the large number of reports, almost without exception, the reported yields of ammonia were very low typically nanomoles of ammonia were said to be synthesized in laboratory-scale reactors. Some workers have... 

Process kinetic analysis in laboratory-scale reactors (V = 10-501)... 

The same type of oscillations seen in laboratory-scale reactors have been reported for industrial copolymerization reactors (Keane, 1972). In a model of vinyl acetate polymerization in an industrial-scale reactor, Teymour and Ray (1992b) discovered a wide range of dynamical behavior, including a perioddoubling route to chaotic oscillations. Oscillations in temperature ranged in amplitude from 70 to 140 °C. The extent of conversion oscillated from about 0.5 to almost 1. Obviously, behavior of this type would be detrimental to the operation of a plant. 

We can use Eqs. (4.11.19) and (4.11.20) to estimate whether we have to limit the adiabatic temperature rise (ATad) by dilution with inerts to avoid pronounced radial and axial temperature gradients in laboratory-scale reactors. As an example, we take a typical value for the term RT /Ea of 60 K (e.g., for 600 K and EA = 50kJ mol ), a value for L/c/r of 10, a reactor length L of 50dp, and Da of 1. We also consider that the reactor diameter should be equivalent to at least 10 particle diameters, which is already needed to exclude wall effects [see Eq. (4.11.16)]. Therefore, according to Eq. (4.11.19) the influence of... 

The rate constants included in the kinetic expressions, rate equations, can seldom be estimated theoretically based on fundamental theories, such as collision and transition state theories, but an experimental determination of the reaction rates in laboratory-scale reactors is usually unavoidable. Based on experimentally recorded reactant and product concentrations, it is possible to estimate the numerical values of rate constants. Below we will give a brief introduction of the procedures involved in the data acquisition and estimation of kinetic parameters. 

Our ultimate objective is to produce automatically with laboratory-scale reactors polymers with pre-defined molecular characteristics in reasonable amounts for test purposes. Whatever control is exercised over the chemistry of a polymerization to introduce novel structural features into polymer chains, the final molecular weight distribution (MWD) of the product is always of importance hence attention has been given to... 

The design equations for a CSTR do not require that the reacting mixture has constant physical properties or that operating conditions such as temperature and pressure be the same for the inlet and outlet environments. It is required, however, that these variables be known. Pressure in a CSTR is usually determined or controlled independently of the extent of reaction. Temperatures can also be set arbitrarily in small, laboratory equipment because of excellent heat transfer at the small scale. It is sometimes possible to predetermine the temperature in industrial-scale reactors for example, if the heat of reaction is small or if the contents are boiling. This chapter considers the case where both Pout and Tout are known. Density and Q ut wiU not be known if they depend on composition. A steady-state material balance gives... 

The use of glutaric dialdehyde as a coupling agent bound the enzymes trypsin or glucose-6-phosphate dehydrogenase to the surface. A large part of the enzymic activity was retained (Fig. 4), and the activity was such that the particle-enzyme conjugate could be used in laboratory scale continuous-flow reactors. 

Low contamination levels are readily achieved in laboratory scale UHV systems. Very high costs inhibit the use of UHV in industrial scale systems, however, so another, local-UHV approach has been proposed, viz. the plasma box reactor [152]. The substrate is mounted in a box, which is surrounded by a shell, which is pumped to a low pressure. The process pressure in the box is maintained by a throttle valve. As the pressure in the box is larger than the pressure in the surrounding shell, contaminants diffuse outwards and the incorporation of contaminants in the deposited layer is low. 

Another advantage of the micro-LC approach is that the required sample size is minimal, so the sample can be drawn from a 1-1 laboratory scale reactor without influencing the reactor composition. The ISCO pLC-500 microflow syringe pump has proven to be reliable and reproducible in evaluations in our laboratory. Capillary liquid columns have been fabricated on planar devices such as silicon to form a miniaturized separation device.19... 

Apparatus. Since all the polymer modification reactions presented in this paper involved gas consumption, an automated gas consumption measuring system was designed, fabricated and used to keep constant pressure and record continuously the consumption of gas in a batch type laboratory scale reactor. Process control, data acquisition, and analysis was carried out using a personal computer (IBM) and an interface device (Lab-master, Tecmar Inc.). 

Equation 8.3.4 may also be used in the analysis of kinetic data taken in laboratory scale stirred tank reactors. One may directly determine the reaction rate from a knowledge of the reactor volume, flow rate through the reactor, and stream compositions. The fact that one may determine the rate directly and without integration makes stirred tank reactors particularly attractive for use in studies of reactions with complex rate expressions (e.g., enzymatic or heterogeneous catalytic reactions) or of systems in which multiple reactions take place. 

Coughlin MF, Kinkle BK, Bishop PL (2003) High performance degradation of azo dye Acid Orange 7 and sulfanilic acid in a laboratory scale reactor after seeding with cultured bacterial strains. Water Res 37 2757-2763... 

Measurement of biofilm activity can be performed based on laboratory reactor experiments or with a technique combining biofilm growth taking place in a sewer followed by measurements in laboratory scale (Raunkjaer et al., 1997 Bjerre et al., 1998). Huisman et al. (1999) developed a sewer in situ biofilm respiration chamber. It includes a DO sensor and a chamber that can be pressed onto the sewer wall. It is designed to achieve an even and unidirectional flow distribution over the entire measurement area. Pure oxygen is injected for oxygenation. 

Figure 7.4 Collection of commercial Raman probes designed for different installations (a) laboratory scale probe with interchangeable immersion or noncontact optics, shown with immersion option (b) probe shown in (a) installed in laboratory fermentation reactor (c) production scale immersion probe (d) probe shown in (c) installed in a glass reactor (e) gas phase probe with flow through cell (f) probe shown in (e) installed in process piping (g) wide area illumination (WAI) noncontact probe after completion of a pharmaceutical tablet coating operation. Adapted, with permission. Copyright 2004 Kaiser Optical Systems, Inc.

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