Industrial multitubular reactor

Figure 10.9. Temperature profiles in an industrial multitubular reactor, showing that hot spot temperature is 100°C higher than the temperature close to the reactor inlet (real plant data).

Vinyl chloride is made from ethylene and chlorine with Cu and K chlorides. The Stauffer process employs 3 multitubular reactors in series with 25 mm (0.082 ft) ID tubes (Naworski and Velez, in Leach, ed.. Applied Industrial Catalysis, vol. 1, Academic Press, 1983, p. 251). 

In addition to the harmonization of the underlying physical and chemical processes, the catalytic-plate heat exchanger offers a cost-effective alternative to both conventional multitubular reactors and catalytic microreactors for industrial... 

In industrial practice, the laboratory equipment used in chemical synthesis can influence reaction selection. As issues relating to kinetics, mass transfer, heat transfer, and thermodynamics are addressed, reactor design evolves to commercially viable equipment. Often, more than one type of reactor may be suitable for a given reaction. For example, in the partial oxidation of butane to maleic anhydride over a vanadium pyrophosphate catalyst, heat-transfer considerations dictate reactor selection and choices may include fluidized beds or multitubular reactors. Both types of reactors have been commercialized. Often, experience with a particular type of reactor within the organization can play an important part in selection. 

Operating conditions for industrial catalysts in multitubular reactors. 

The different industrially established fixed-bed reactor configurations of the adiabatic, the multistage and the multitubular reactor types represent a mature and versatile class of reactors for heterogeneously catalyzed gas phase reactions. Companies specialized in their... 

An important issue for packed bed reactors is temperature control. Insufficient heat removal may lead to local overheating of the catalyst pellets with the consequence of rapid deactivation. Therefore, multitubular reactors with up to 35 000 parallel tubes are used in chemical industry for the temperature control of highly exothermic reactions. 

Many microreactors are at the research level but a few are already commercially available. Microwave-assisted flow processing in microreactors (MAFP) [93] or radiofrequency-heated flow reactors [94,95] are promising alternatives for conventionally heated, multistep production of fine chemicals in batch reactors. Realization of MAFP at an industrial scale requires a proper design of multitubular reactors integrated with microwave heating [96]. 

Based on the available open Hterature, industrial technologists have not generally reported the development of state-of-the-art reactor models that combine intrinsic reaction kinetics, transport effects, and fluid hydrodynamics across the required range of temporal and length scales. If available, they have been kept as company confidential for business reasons. However, Shin and coworkers (2007) describe a hybrid model for a multitubular reactor used in terephthaldehyde manufacture that couples a commercial CFD... 

For industrial processes on a large scale, two different constructions of packed beds are very common multibed and multitubular reactors. These reactors are illustrated in Figures 5.5 and 5.6. 

The most difficult problem to solve in the design of a Fischer-Tropsch reactor is its very high exothermicity combined with a high sensitivity of product selectivity to temperature. On an industrial scale, multitubular and bubble column reactors have been widely accepted for this highly exothermic reaction.6 In case of a fixed bed reactor, it is desirable that the catalyst particles are in the millimeter size range to avoid excessive pressure drops. During Fischer-Tropsch synthesis the catalyst pores are filled with liquid FT products (mainly waxes) that may result in a fundamental decrease of the reaction rate caused by pore diffusion processes. Post et al. showed that for catalyst particle diameters in excess of only about 1 mm, the catalyst activity is seriously limited by intraparticle diffusion in both iron and cobalt catalysts.1... 

Patil, N.G., Benaskar, F., Rebrov, E.V., Meuldijk, J., Hulshof, LA., Hessel, V., and Schouten, J.C. (2012) Continuous multitubular milli-reactor wilh a Cu thin film for microwave assisted fine-chemical synthesis at industrial scale. Ind. Eng. Chem. Res., 51,14344-14354. 

The solid catalysts are mostly applied as bulk materials, mixtures of active constituents and inert diluent and eggshell catalysts using more or less inert cores of alumina or silica These compositions are available as tablets, spheres, extrudates or spr -dried finer particles depending on the reactors to be used. Fixed bed multitubular and fluidized bed reactors are used. Outstanding industrially operated examples are the conversions of propene to acrylonitrile or 3-picoline to nicotinonitrile, for example. Scheme 7.4 depicts various examples on reactants, nitrile products and their subsequent uses. 

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