Laboratory and pilot plant reactors

Heat loss to atmosphere Small-diameter laboratory and pilot plant reactors Commercial units... 

Model Reaction. The benzene hydrogenation on nickel-kiesel-guhr has been selected as a model reaction. This reaction is well understood and can serve as a typical representative of hydrogenation reactions. Butt (4 5) and Pexider et al.(11) have studied this reaction in laboratory and pilot plant reactors respectively. Pexiderfs data have been obtained from a nonadiaba-tically operated reactor. The reaction rate expression has ... 

Cocurrent downflow with slug or Taylor flow has been most widely used. Other possible designs, e.g., cocurrent upflow and froth flow, have to our knowledge been tested only in laboratory and pilot plant reactors. Consequently, we will focus on downward slug flow, and the main areas of interest are scale-up, liquid distribution, space velocity, stacking of monoliths, gas-liquid separation, recirculation, and temperature control. 

The modeling of single channels in Section 11 of this chapter is accurate for circular channels, but most reactors contain square or sinusoidal channels. There are very few measurements of film thickness and mass transfer in square and sinusoidal channels. In reactor design we have to rely on reaction rale measurements in laboratory and pilot plant reactors, and scale up the results to industrial size. 

Sie, S.T. Scale effects in laboratory and pilot-plant reactors for trickle-flow processes. Rev. Inst. Franc. Pet. 1991, 46, 501. 

A similar situation can arise for pore diffusion rate-limited processes. In this situation the physical structure of the solid support must be altered to improve catalyst performance, that is, to increase overall-Changing the chemical composition of the solid-supported catalyst will not alter /coveraii- All the data produced by the laboratory and pilot plant reactors will scatter in one region of the plot, which is the pore diffusion rate constant for the process. 

LABORATORY AND PILOT PLANT REACTOR DESIGN AND OPERATION... 

The behavior of several configurations of trickle-bed laboratory and pilot plant reactors have been studied and reported in... 

EXAMPLES OF LABORATORY AND PILOT PLANT REACTORS USED FOR TRICKLE BED REACTIONS... 

Scahng up will probably continue to be a problem since large reactors carmot be as efficient as small laboratory reactors. However, it may be possible to make laboratory or pilot-plant reactors that are more similar to large-scale reactors, allowing more rebable validation of the simulations and process optimization. The time from laboratory-scale to full-scale production should be shortened from years to months. 

Figure 4.25 Specialty plates for laboratory and pilot plant micro reactor modules of modified CYTOS systems (left). Standard off-the-shelf CYTOS system (right) [55].

Collect together all the kinetic and thermodynamic data on the desired reaction and the side reactions. It is unlikely that much useful information will be gleaned from a literature search, as little is published in the open literature on commercially attractive processes. The kinetic data required for reactor design will normally be obtained from laboratory and pilot plant studies. Values will be needed for the rate of reaction over a range of operating conditions pressure, temperature, flow-rate and catalyst concentration. The design of experimental reactors and scale-up is discussed by Rase (1977). 

Identify the predominant rate-controlling mechanism kinetic, mass or heat transfer. Choose a suitable reactor type, based on experience with similar reactions, or from the laboratory and pilot plant work. 

Scale-up can also have a significant effect on the basic process control system and safety systems in a reactive process. In particular, a larger process will likely require more temperature sensors at different locations in the process to be able to rapidly detect the onset of out-of-control situations. Consideration should be given to the impact of higher-temperature gradients in plant-scale equipment compared to a laboratory or pilot plant reactor (Hendershot 2002). 

The deactivation of methanol-synthesis catalyst was studied in laboratory and pilot-plant slurry reactors using a concentrated, poison-free, CO-rich feedstream. The extent of catalyst deactivation correlated with the loss of BET surface area. A model of catalyst deactivation as a function of temperature and time was developed from experimental data. The model suggested that continuous catalyst addition and withdrawal, rather than temperature programming, was the best way to maintain a constant rate of methanol production as the catalyst ages. Catalyst addition and withdrawal was demonstrated in the pilot plant. 

A fluidized-bed reactor is to be designed to destroy 99.99% of a unique liquid hazardous waste. Based on laboratory and pilot plant studies, researchers have described the waste reaction by a first-order reversible mechanism. Their preliminary findings are given below. 

Ti02 is used extensively in both laboratory and pilot plant studies. Other oxides, such as Z1-O2, Sn02, WO2, and M0O3 are much less active and, as a result, do not have the same application prospects as Ti02 (Formenti and Teichner, 1979). Davydov et al., (1999) indicate that proper ranking of photo catalysts requires careful uncoupling of the intrinsic catalyst properties from the reactor configuration and the radiation field. 

Preparatory work for the steps in the scaling up of the membrane reactors has been presented in the previous sections. Now, to maintain the similarity of the membrane reactors between the laboratory and pilot plant, dimensional analysis with a number of dimensionless numbers is introduced in the scaling-up process. Traditionally, the scaling-up of hydrodynamic systems is performed with the aid of dimensionless parameters, which must be kept equal at all scales to be hydrodynamically similar. Dimensional analysis allows one to reduce the number of variables that have to be taken into accoimt for mass transfer determination. For mass transfer under forced convection, there are at least three dimensionless groups the Sherwood number, Sh, which contains the mass transfer coefficient the Reynolds number. Re, which contains the flow velocity and defines the flow condition (laminar/turbulent) and the Schmidt number, Sc, which characterizes the diffusive and viscous properties of the respective fluid and describes the relative extension of the fluid-dynamic and concentration boundary layer. The dependence of Sh on Re, Sc, the characteristic length, Dq/L, and D /L can be described in the form of the power series as shown in Eqn (14.38), in which Dc/a is the gap between cathode and anode Dw/C is gap between reactor wall and cathode, and L is the length of the electrode (Pak. Chung, Ju, 2001) ... 

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