Exchanger monolithic reactor-heat

Wei, J. and Degnan, T. F., "Monolithic Reactor-Heat Exchanger" Proc. ISCRE5 ACS Symposium Series 65, American Chemical Society Washington, D.C., 1978, p. 83. 

A novel monolithic reactor-heat exchanger has been constructed and operated in five different modes. Experiments were conducted with the oxidation of carbon monoxide over copper chromite pelleted catalysts. The experimental temperatures of reactants and coolants, and concentrations agree with computations with a cell model. Virtually flat temperature profiles can be obtained in the co-current mode. 

Experimental analyses of the heat transfer characteristics of the monolithic reactor-heat exchanger were carried out in the absence of reaction to define the NTU values in equations (1), (2), eind (3). Experiments were performed in which the coolcint pass flow rate was varied independently of the reaction pass flow rate, to produce j-factors vs Reynolds number, in good agreement with both the Graetz solution and data from an experimental study by Kays et al (] ) of a crossflow of similar design. 

The NTU values in equations (1) and (2) describing the heat loss from the monolithic reactor-heat exchanger chambers and crossflow shapes were evaluated using data obtained in stop flow experiments. Overall heat transfer coefficients based on the chamber wall area varied from 0.3 BTU/hr. ft °F to 0.55 BTU/hr. ft °F depending on the position in the reactor. 

The monolithic reactor-heat exchanger was run successively as an adiabatic reactor, a countercurrent reactor-heat exchanger and a cocurrent reactor-heat... 

Static mixing catalysts Operation Monolithic reactors Microreactors Heat exchange reactors Supersonic gas/liquid reactor Jet-impingement reactor Rotating packed-bed reactor... 

The whole set-up for partial oxidation comprises a micro mixer for safe handling of explosive mixtures downstream (flame-arrestor effect), a micro heat exchanger for pre-heating reactant gases, the pressure vessel with the monolith reactor, a double-pipe heat exchanger for product gas cooling and a pneumatic pressure control valve to allow operation at elevated pressure [3]. 

In many situations, the monolith reactor can be represented by a single channel. This assumption is correct for the isothermal or adiabatic reactor with uniform inlet flow distribution. If the actual conditions in the reactor are significantly different, more parallel channels with heat exchange have to be simulated (cf., e.g. Chen et al., 1988 Jahn et al., 1997, 2001 Tischer and Deutschmann, 2005 Wanker et al., 2000 Young and Finlayson, 1976). In this section we will further discuss effective single channel models. 

Figure 21 Configuration of a cocurrent downflow monolith reactor with free gas recirculation. Only liquid is recirculated, and an external heat exchanger can be scaled independent of the reactor to deliver the required heat duty.

Cross-flow monoliths have been explored by Degnan and Wei (11-12) as cocurrent and countercurrent reactor-heat exchangers. Four cross-flow monoliths in series were employed the individual blocks were analyzed by a one-dimensional approximation. They found good agreement between theory and experiment. 

The cleaning of flue gases from stationary sources is another field in which the application of monolithic catalysts will certainly rise. There will be no versatile catalyst for cleaning all off-gases. Therefore tailor-made catalysts with zeoliths of various types for specific applications will be developed. Incorporated-type monolithic catalysts are likely to prevail in this field. Since cleaning usually requires a set of equipment items in series (e.g., converter, heat exchangers), multifunctional reactors (reverse-flow reactors, rotating monoliths) will become more common. 

When the heat transfer is considered, the slurry reactors are more efficient, due to large liquid holdup and a relatively high flow velocity of the reaction mixture at the heat exchange surface. Also, it is relatively easy to arrange heat-exchanging devices in the slurry reactors as compared to monolith reactors. 

Cubic/monolithic corrosive liquids, acids, bases, or used as catalyst/heat exchanger for reactors. Usually made of graphite or carbon that has high thermal conductivity, area 1 to 20 m. Ceramic monoliths are used as solid catalyst for highly exothermic gas-catalyst mass transfer-controlled reactions. 

Options are forced draft or induced draft. Use forced draft with louvers when temperature control is critical. Forced draft has less fan power easy access for maintenance easy to use hot air recirculation but has greater susceptibility to air maldistribution and to inadvertent hot air recirculation low potential for natural circulation and the tubes are exposed to the elements. Induced draft high fan power needed, not easy access for maintenance limitation on exit air temperature less chance of air maldistribution or unwanted hot air recirculation better protection from the elements process stream temperatures < 175 °C. Cubic/monoUthic corrosive liquids, acids, bases or used as catalyst/heat exchanger for reactors. Usually made of graphite or carbon that has high thermal conductivity. Area 1-20 m. Ceramic monoliths are used as solid catalyst for highly exothermic gas-catalyst mass transfer[Pg.69]

Technologies Reactors spinning disk reactor, static mixer reactor, microreactors, heat exchange reactors, monolithic reactors, oscillatory flow reactors, trickle bed reactors... 

Simultaneous operation of the monolith reactor as a multichannel heat exchanger... 

A comparison of the size estimated for the components of the three systems described above is shown in Table 5.16. This revealed that the second generation microchannel reactor was about 50% smaller than the monolithic reactor of the first generation. The microchannel reformer size of the third generation system amounted to only 16% of the size of the monolith. The water-gas shift reactors, contributing considerably to the overall size of the first and second generation systems, became obsolete in the third generation, as did most of the heat-exchangers. 

However, monolithic reactors and plate heat-exchangers are more suitable than fixed-beds for the rapid start-up and transient operation requirements of fuel processors on the smaller scale [57]. 

Figure 6.9 Reactor heads forthe upgrading of ceramic monoliths to heat-exchangers as developed by Frauhammer et al. [463].

The pelleted copper chrome catalyst was metered into each of the large sinusoidal ducts of the reaction pass of each of the four monoliths comprising the reactor-heat exchanger. A h layer of quartz chips at each of the reaction pass faces of the cross-flows guaranteed that the reaction was confined to the volume of the monolith where heat exchange could take place. 

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