Reactor countercurrent

There are essentially three types of coal gasifiers moving-bed or countercurrent reactors fluidized-bed or back-mixed reactors and entrained-flow or plug-flow reactors. The three types are shown schematically in Eigure 2. 

I 9 Structured Reactors, a Wealth of Opportunities 9.2.2.1 Countercurrent Reactors... 

Hydrotreating units in the past were built with one reactor, to meet the 500 ppm S specification however, a second reactor is needed to cope with the actual requirements. Several attempts have been made also to change the operating conditions to improve performance of the units and to achieve the stipulated level of desulfurization. From a co-current fluid-dynamics, the first modification went into countercurrent feeding. In a countercurrent reactor, where hydrogen is fed at one end and the feed in the other, the most difficult to-desulfurize compounds, will react under the higher hydrogen concentration. The countercurrent operation introduces some other problems, such as hot spots and vapor-liquid contact. 

Conventional reactor designs have been optimized to create a basis for comparison. The mechanically agitated vessel achieves the highest yield of 74.4%, followed by the bubble column reactor with a yield of 72.9%, and the co-as well as the countercurrent reactors both achieving a yield of 69.5%. 

Frauhammer J., Friedrich, G., Kolios, G., Klingel, T., Eigenberger G., von Hippel, L., Arntz, D., Flow distribution concepts for new type monolithic co- or countercurrent reactors, Chem. Eng. Technol. 1999, 22, 1012-1016. 

Leybros, J., P. Carles, J-M. Borgard (2009), Countercurrent Reactor Design and Flow Sheet for Iodine-sulfur Thermochemical Water Splitting Process , Int. J. of Hydrogen Energy, forthcoming. 

Figure 25. Equivalence of operation with periodical flow re versa and countercurrent heat exchange A) Fixed-bed reactor with periodic flow reversal, B) Temperature profiles with rapid flow reversal, C) Countercurrent reactor with catalyst at the wall D) Schematic concentration and temperature profiles m both reactors [141...

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. 

For comparison and the completeness of the modeling work, we have also developed a similar model for the cocurrent WGS membrane reactor. Figure 5 illustrates the comparison between the cocurrent and countercurrent WGS membrane reactors in terms of the profiles of CO mole fractions in the H2 products along the reactors under the same conditions. As shown in this figure, the CO concentration in the H2 product was 7.8 ppm for the countercurrent reactor whereas that was 0.77% (7,700 ppm) for the cocurrent reactor. Thus, the countercurrent reactor was much more effective than the cocurrent one. Future work will be on the countercurrent reactor only. 

Continuous heterogeneous reactors Packed-tower countercurrent reactors Fixed-bed catalytic reactors... 

Figure 6.15 Typical temperature crossover in a countercurrent reactor/heat exchanger. [After E. A. Grens and R. A. McKean, Chem. Eng. Sci., 18, 291, with permission of Pergamon Press, Inc., London, England, 1963.]...

Figure 8.14 A countercurrent reactor gas-liquid or liquid-liquid.

Whereas the reacticm in a simple shaft reactor is adiabatic and therefore requires a two-stage operation, the temperature profile along a countercurrent reactor is much more favorable. On entering the ring space between the reactor shell and the catalyst vessel at approximately 230 °C, the gas/steam mix flows downwards and then enters the tubes in the catalyst vessel. As it flows upward through these catalyst surrounded tubes, the mix is heated up to approximately... 

A general esterification reaction consists of reacting an alcohol with an acid in the presence of a catalyst (such as sulfonic acid) to produce the ester and water. This is an equilibrium reaction and leads to low conversion. The catalyst is usually neutralized with inorganic base after the completion of the reaction. If carried out in a countercurrent reactor under two-phase conditions, this reaction has many benefits. For example, conversion of maleic anhydride to dialkyl maleates or fatty acids to fatty acid esters is performed in a column packed with a solid catalyst. Liquid (acid) flows down the column from the top. Alcohol vapor flows upward from the bottom and absorbs water that is formed and carries it up (see Fig. 6.30). The removal of water by the alcohol drives the... 

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

Design of a fixed-bed for highly exothermic reactions is perhaps the most demanding because of the sensitivity problem that these reactions can cause. In the next section the design of a countercurrent reactor/heat exchanger for highly exothermic reactions is considered. 

DESIGN OF A COUNTERCURRENT REACTOR/HEAT EXCHANGER WITH PARAMETRIC SENSITIVITY... 

Design of a Countercurrent Reactor/Heat Exchanger with... 

All gasification processes can be separated into three generic types of reactors (a) moving-bed or countercurrent reactors (b) fluidized-bed or back-mixed reactors (c) entrained-flow reactors (not back-mixed). 

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