Commercial reactors, linear velocity

One goal of catalyst designers is to constmct bench-scale reactors that allow determination of performance data truly indicative of performance in a full-scale commercial reactor. This has been accompHshed in a number of areas, but in general, larger pilot-scale reactors are preferred because they can be more fully instmmented and can provide better engineering data for ultimate scale-up. In reactor selection thought must be given to parameters such as space velocity, linear velocity, and the number of catalyst bodies per reactor diameter in order to properly model heat- and mass-transfer effects. 

Both reactors used 38.1 mm 0 tubes. The commercial reactor was 12 m long while the length of the laboratory reactor was 1.2 m. Except for the 10 1 difference in the lengths, everything else was the same. Both reactors were simulated at 100 atm operation and at GHSV of 10,000 h-1. This means that residence times were identical, and linear gas velocities were 10 times less in the lab than at the production unit. Consequently the Re number, and all that is a function of it, were different. Heat transfer coefficients were 631 and 206 in wattsWK units for the large and small reactors. 

The scheme of commercial methane synthesis includes a multistage reaction system and recycle of product gas. Adiabatic reactors connected with waste heat boilers are used to remove the heat in the form of high pressure steam. In designing the pilot plants, major emphasis was placed on the design of the catalytic reactor system. Thermodynamic parameters (composition of feed gas, temperature, temperature rise, pressure, etc.) as well as hydrodynamic parameters (bed depth, linear velocity, catalyst pellet size, etc.) are identical to those in a commercial methana-tion plant. This permits direct upscaling of test results to commercial size reactors because radial gradients are not present in an adiabatic shift reactor. 

Fixed-Bed Demonstration Plant. The major objective of the demonstration test was to verify the bench unit results in a larger plant operating at conditions similar to a commercial-size reactor. The linear velocity of the reactant is the only variable which is significantly different between a bench-scale unit and a commercial-size reactor. The other operating conditions are normally the same for both reactors. 

The theoretical RTD responses in Fig. 19-7a are similar in shape to the experimental responses from pilot and commercial reactors shown in Fig. 19-8. The value of n in Fig. 19-8 represents the number of CSTRs in series that provide a similar RTD to that observed commercially. Although not shown in the figure, a commercial reactor having a similar space velocity as a pilot reactor and a longer length typically has a higher n value than a pilot reactor due to greater linear velocity. 

Stepan was the first to develop and conunercialize a continuous falling film SO3 sulfonation process. The design is a multitubular unit. The company operates about 12 falling film SO3 sulfonation units in the United States, not only for the production of linear alkyl benzene sulfonates, but substantial amounts of fatty alcohol and fatty alcohol ethoxylates are also sulfated. Other key commercial reactor designs are by Chemithon, Ballestra SpA, Lion, Mazzoni SpA, and Meccaniche Modeme. Several features are common to all falling-film systems. Fatty alcohol and alcohol ethoxylates are reacted at a rate of about 0.3 kg/h/mm with SO3 concentration at about 2-3%. Liquid residence times are estimated at 10-30 s and most units operate with gas velocities in the range of hurricane wind velocities (121-322 km/h). ° Linear alcohols and linear alcohol ethoxylates are by far the easiest to sulfate. Caution is required with branched alcohols as color and conversion can suffer. 

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