Reactors microstructured heat exchanger-reactor

Besides microstructured heat exchanger/reactors constructed in the form of plates as shown in Figure 5.1, shell and tube micro heat exchangers are available. An example is shown in Figure 5.6. The heat transfer within the reactor tubes can be estimated with the asymptotic Nu or with Equation 5.12 for short channels. The outer heat transfer coefficient depends on the flow regime, the arrangement of the tubes, and the presence of baffles [8, 13]. For small-scale systems, capillaries submerged in constant temperature baths are commonly used. In this case, the main heat transfer resistance is mostly located at the outer side of the reactor. 

Figure15.2 (a) Photograph and (b) schematic representation ofa microstructured heat exchanger/reactor (Forschungszentrum Karlsruhe [1]). Channel length L= 14 mm, width W= 100 tm, height H= 78 Xm.

M. Wichert, R. Zapf, V. Hessel, H. Lowe, Fuel processing in integrated microstructured heat-exchanger reactors. f Power Sources 2007, 171 (1), 198-204. 

Kolb, G., Schiirer, )., Tiemann, D., Wichert, M., Zapf, R., Hessel, V., and Lowe, H. (2007) Fuel processing in integrated microstructured heat-exchanger reactors. J. Power Sources,... 

Figure 2.2 Schematic illustration of a microstructured heat exchanger/reactor. (Adapted from Ref [4] with permission from Elsevier.)...

Eichtner, M., Benzinger, W., Hass-Santo, K., Wunsch, R., Schubert, K., Functional coatings for microstructure reactors and heat exchangers, in Ehrfeld, W. (Ed.), Microreaction Technology 3rd International Conference on Microreaction Technology, Proc. of IMRET 3,... 

FIGURE 1 Photograph (left) and schematic illustration (right) of a microstructured heat exchanger or reactor (Forschungszentrum Karlsruhe [25]). Channel dimensions length, L — 14 mm, width, b = 100 pm, height, e — 78 pm. (Adapted with permission from Elsevier.)... 

K. Schubert, W. Bier, J. Brandner, M. Fichtner, C. Franz, G. Linder, Realization and testing of microstructure reactors, micro heat exchangers and micromixers for industrial application in chemical engineering, in W. Ehrfeld, I.H. Rinard, R.S. Wegeng (Eds.), Proceedings of 2nd International Conference on Microreaction Technology (IMRET 2), AIChE, New Orleans, 1998, p. 88. 

Fig. 6.13 Example of a heavy-pilot microstructured heat exchanger integrated 5 kW i reactor-heat exchanger system for selective oxidation to achieve gas purification of H2-rich reformer gas for fuel cells. (Source IMM.)...

On the basis of the experimental results, the authors predicted a reactor performance for MBE production of up to 12000kgm h depending on pressure and temperature even at moderate temperature differences in the microstructured heat exchanger. This corresponds to a PI of two orders of magnitude compared to a standard batch slurry reactor with a typical specific productivity of 125 kgm h ... 

Table 5.6 Specifications of the microstructured reformer/burner heat-exchanger reactors of 100 Wei and 5 kWei power equivalent as assumed by Delsman et al. for their calculations [386].

Figure 7.31 shows a microstructured plate heat-exchanger reactor developed by Kolb et al. [312], which was designed for a power equivalent of 2 kW of the corresponding fuel cell. The temperature profile, which was determined experimentally in... 

A Pt/AljOj coated microstructured reactor/heat exchanger for the controlled H2/02-reaction in the explosion regime, in Ehreeld, W., Rinaed, I. H., Wegeng,... 

Rebrov, E. V., Duinkerke, S.A., de Croon, M. H. J. M., Schouten, J. C., Optimization of heat transfer characteristics, flow distribution, and reaction processing for a microstructured reactor/ heat-exchanger for optimal peformance in platinum catalyzed ammonia oxidation, Chem. Eng. 93 (2003) 201-216. 

A chip-type micro reactor array comprises parallel mixer units composed of inverse mixing tees, each followed by a micro channel that it is surrounded by heat exchange micro channels (so called channel-by-channel approach similar to the tube-in-tube concept). Such an integrated device was developed as a stack of microstructured plates made of a special glass, termed Foturan (Figure 4.26). The integrated device was attached to PTFE tubes of various lengths. 

Internal heat exchange is realized by heat conduction from the microstructured reaction zone to a mini channel heat exchanger, positioned in the rear of the reaction zone [1,3,4], The falling film micro reactor can be equipped, additionally, with an inspection window. This allows a visually check of the quality of film formation and identification of flow misdistribution. Furthermore, photochemical gas/liquid contacting can be carried out, given transparency of the window material for the band range of interest [6], In some cases an inspection window made of silicon was used to allow observation of temperature changes caused by chemical reactions or physical interactions by an IR camera [4, 5]. 

Rebrov EV, Croon MHJM, Schouten JV. Design of a microstructured reactor with integrated heat-exchanger for optimum performance of a highly exothermic reaction. Catalysis Today 2001 69 183-192. 

Janicke, M. T., Kestenbaum, H., Hagendorf, U., Schuth, F., Fichtner, M., Schubert, K., The controlled oxidation of hydrogen from an explosive mixture of gases using a microstructured reactor/heat exchanger and Pt/Al203 catalyst,/. Catal. 2000, 191, 282-293. 

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