Mesh reactor

Similar studies were made on a mesh microreactor comprising Pd/Al203 and Pt/Al203 catalysts coated on a microstructured mesh [270,271]. The global rate constants were 56 and 1.41/s for the Pd and Pt catalysts, respectively [271]. An activation energy of 46 5 kj/mol was found for the Pt catalyst in the mesh reactor, which corresponds to the value of 39 kj/mol determined for a commercial Pt/ A1203 powder catalyst in a well-behaved batch reactor (see Figure 4.54). 

Accordingly, operation was in the chemical regime, that is, governed by kinetics and not controlled by mass transfer [271]. For the Pd catalyst, however, the activation energies measured in the mesh reactor and in a well-behaved batch reactor with commercial Pd/Al203 powder catalyst were different, being about 0 and 41 kj/mol,... 

Continuous phase contacting, where the fluid phases are separated. Examples are microstructured falling film and mesh reactors. 

Figure 8.7 Mesh reactor (schematic) [12]. (Adapted with permission from Wiley.)...

C. Turner, J. Shaw, B. Miller, et al.. Solvent extraction using micro-mesh reactors, in ProceecUr of the 4th Intematiomd Conference on Microreaction Technology, 2000, pp. 334-340. 

Momentum Transport The liquid film profile and its thickness 5 depend on the flow rate, the surface tension (liquid, gas and reaction plate material property) and on the channel dimensions (width, depth, length, diameter, etc.), which determine the interfacial area. In mesh reactors, the meniscus stability (depending on the surface tension and pore geometry) plays a certain role. We encounter the following parameters ... 

Heat and Mass Transfer Using the film theory, both phenomena mainly depend on the film and gas stream thickness and the type of reaction. Other parameters are the interfacial area, the residence time and the axial dispersion. Good mass and heat transport presume a good fiow equipartition in the channels. In mesh reactors the mesh open area determines the interfacial area. Mass transfer coefficients ki a from 3 to 8 L s and higher values in catalytic systems can be achieved [25]. 

FFMR, falling film microreactor PBMR, packed-bed microreactor MM, micromixer MBC, microbubble column MMR, microstructured mesh reactor SCR, single-channel reactor... 

Prof. Asterios Gavriilidis of University College, London for data on the mesh reactor. 

Wire-mesh reactors can apply rapid heating (100-10 K/s) to small amoimts of particles (<1 g). Therefore, a flat layer of coal particles is placed between two layers of wire-mesh that can be heated by electric current The pressure ranges from 10 to 100 bar and high-resolution data for temperature versus time can be gained. A carrier or reaction gas is forced through the wire-mesh, passing the particles and even gas distribution over the sample is accomplished [60,75]. 

The conditions in wire-mesh reactors fit better to entrained-flow systems and the gathered data are used for modeling the release of volatile matter, that is, the impacting flame formation. Although a small-scale and inexpensive method, investigations using wire-mesh reactors remain a more academic subject compare to TGA, which has been broadly used in industry. 

The mesh reactor is an alternative continuous-phase microcontactor, where the gas and liquid flow through separate channels separated by a thin membrane. To provide stable operation, the fluid interface is immobilized by well-defined openings obtained with a thin mesh [72]. Interfadal forces help to stabilize the fluid interface within the openings, while fluid layers are thin enough to facilitate mass transfer. The meniscus shape at the interface between the two phases defines the available area for mass transfer and is a function of contact angle, pore geometry, and pressure difference between phases. The open area of the micromesh contactor is about 20-25%, which leads to a gas-liquid interfacial area of 2000 well above the values obtained in traditional stirred tank reactors. This... 

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