Microreactors system design

The presence of gas-phase reactions resulted in reduced CH4 emissions at transient operation and steady state and in corresponding increased CO emissions. This suggests care when designing microreactor systems with models using only heterogeneous chemistry. 

The authors developed a multi-layered microreactor system with a methanol reforma- to supply hydrogen for a small proton exchange membrane fiiel cell (PEMFC) to be used as a power source for portable electronic devices [6]. The microreactor consists of four units (a methanol reformer with catalytic combustor, a carbon monoxide remover, and two vaporizers), and was designed using thermal simulations to establish the rppropriate temperature distribution for each reaction, as shown in Fig. 3. 

TeGeotenhuis, W. E., Wegeng, R. S., VanderWiel, D. P., Whyatt, G. A., ViSWANATHAN, V. V, ScHIELKE, K. P., Sanders, G. B., Peters, T. A., Microreactor system design for NASA in situ propellant production plant on mars, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 343-3350 (5-9 March 2000), AIChE Topical Conf Proc., Atlanta, USA. 

Fig. la-e. Selected microreactors, a Stainless steel microreactor system designed by Ehrfeld Mikrotechnik. b Glass microreactor (Watts and Haswell 2005). c Stainless steel microreactor of the CYTOS Lab system (http //www.cpc-net.com/cytosls.shtml). d Silicon-based microreactor designed by Jensen (Ratner et al. 2005). e Glass microreactor of the AFRICA System... 

As the ability to generate more samples per imit time increases with improvements in the capabilities of combinatorial and microreactor systems, there is a growing need for a faster analytical response. To keep the Development Cycle (react, analyze, handle data, and design next experiment) functioning at a productive rate there is need to characterize samples and convert the corresponding analyhcal data into valuable information. This information will then feed the Design of Experiment part of the cycle. Significant effort has been put into approaches to speed up the ability to analyze samples and this has often been aided by miniaturization of the analytical equipment. 

DARPA (Defense Advanced Research Program Agency) provides additional funding for DuPont/MIT collaborative research effort to prove that a microreactor system can be designed for safe, parallel operation... 

We designed this system to allow various 1 mL scale continuous process equipment types (e.g., reactors, separators) to be modularly inserted. The microreactor... 

Full factorial designs with M levels can be used for estimating polynomials of order at most M -1. Naturally, these designs are feasible only with very few variables, say maximum 3, and typically for only few levels, say at most 4. For example, a 44 design would contain 256 which would be seldom feasible. However, the recent development in parallel microreactor systems having e.g. 64 simultaneously operating reactors at different conditions can make such designs reasonable. 

FIGURE 42.3 A modular microreactor system for the direct fluorination of ethyl acetoacetate by fluorine gas. The design allows for multiple channels to be supplied from single reservoir sources and a multichannel device to be constructed in a facile manner from a disposable channel plate. (Taken from Chambers, R.D., et al.. Lab on a Chip, 2005, 5 191-198. With permission.)... 

Quiram DJ, Jensen KF (2007) Integrated microreactor system for gas-phase catalytic reactions. 3. Microreactor system design and system automation. Ind Eng Chem Res 46 8319-8335... 

By applying MF techniques, the reaction heat can be controlled by varying the thickness and thermal conductivity of the wall. Geometrical parameters and construction materials are the key selection criteria in designing the microreactor systems, whilst for microsystems which perform chemical reactions, separations, analyses, and sensing devices, the channels, cavities, valves and electrodes all need to be designed and selected properly. 

The development of the microreactor system started with the notion that at that time standard solutions were not commercially available. Therefore, cooperation with the Institut fur Mikroverfahrenstechnik (IMVT), part of the Forschungszentrum Karlsruhe (FZK) in Germany, was set up. IMVT was able to provide the detailed design knowledge needed and it was able to manufacture small-scale units. DSM provided the engineering knowledge in the field. 

Figure 1.8 Parallel microreactor system (the so-called CYTOS Pilot System) designed and commissioned by CPC for Clariant in 2001, for the manufacturing of diazo pigments. Source Reprinted from Ref [50], Copyright (2007), with permission from Elsevier.

There have been also advancements in the pharmaceutical industry. Thus, DSM designed a microreactor system to produce a few hundred tons of naproxcinod per year [86]. 

The pyrolysis chamber consists of a glass tube designed to contain the microreactor system during a pyrolysis experiment. The upper part of the chamber is connected with a hammer assembly through a kolvar tube sealed to the glass. The lower part is designed to hold the... 

Another erample involves the design of a gas-phase microreactor system for the OTddation of CH4 and NH3 ]65]. The system utilizes the fabrication, assembly, and system integration principles from the computer industry. The reactor boards consist of several reactor channels and control functions for the gas flow rate and reaction temperature (Figure 11.13). The different reactor boards are highly modular and fit in the slots of a computer framework. 

This chapter is organized as follows. The numerical model is firstly presented, followed by an assessment of characteristic time scales which are relevant for the adopted quasisteady approach. The impact of pressure, solid material properties, equivalence ratio, inlet velocity, surface radiation heat transfer, and gas-phase chemistry on the transient microreactor response is then elaborated. Based on the outcome of the previous computations, implications for the design of microreactor systems are outlined. 

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