Heat exchange catalytic reactor

Details Heat exchange catalytic reactor Heat exchange catalytic reactor

1998-07-09

2000-03-21

Flanigan, Allen

Heat exchange

Casing or tank enclosed conduit assembly

With distinct flow director in casing

165DIG401, 422201, B01J 806

Patent

active

060391138

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a heat exchange catalytic reactor of the shell-and-tube type wherein a reactant stream contacts a catalyst and undergoes a catalytic reaction while heat is exchanged between the reactant stream and a heat exchange medium.
In many catalytic reactions, whether exothermic, such as hydrogenation, shift, methanation, ammonia synthesis or methanol synthesis reactions, or endothermic reactions such as the reverse shift or steam reforming reactions, it is desirable that the temperature of the reactant stream is controlled during the reaction.
Thus it may be desirable in an exothermic reaction to remove heat from the reactants so as to prevent an unacceptable temperature rise which might cause the reaction to run-away and/or become less selective. To that end it is well known to employ a heat exchange reactor wherein a suitable heat exchange medium is passed in heat exchange with the catalyst bed. Usually the heat exchange medium flows counter-current to the flow of the reactants: examples of heat exchange reactors are disclosed in GB 1 578 270 and U.S. Pat. No. 4,321,234. In some cases, for example as described in the aforesaid U.S. Pat. No. 4,321,234, the heat exchange medium is a fluid which changes state as a result of the heat exchange. For example boiling water or methanol may be used as a heat exchange medium. While such systems may enable good control of the temperature, it is necessary to select a heat exchange medium that undergoes the state change at the desired temperature. While the temperature at which the change of state occurs may be altered by changing the pressure, to achieve the necessary temperature with a given heat exchange medium, it may be necessary to employ such a pressure that the pressure differential between the heat exchange medium and the reactants imposes engineering problems. Furthermore such systems employing a change of state of the heat exchange medium of necessity involve the use of condensers or evaporators elsewhere in the heat exchange medium loop. These add to the expense.
Systems wherein the heat exchange medium does not change state generally offer less precise control of temperature unless the heat exchange medium flow rate is very high. We have devised an alternative system using a heat exchange medium that does not undergo a change of state during the heat exchange.
The type of heat exchange reactor with which the invention is concerned is the so-called shell-and-tube arrangement. The reactants stream, or the heat exchange medium, flows through the tubes and is hereinafter referred to as the tube fluid. The other of the heat exchange medium and the reactants stream flows through the shell space and is hereinafter termed the shell fluid. The reactor has a plurality of tubes extending longitudinally through an elongated shell from a tube fluid inlet region to a tube fluid outlet region. The tube fluid is fed to the tube fluid inlet region via a tube fluid inlet, and passes through the tubes to the tube fluid outlet region from whence the tube fluid is removed via a tube fluid outlet. The shell often has a plurality of baffles, for example as described in the aforesaid GB 1 578 270. to cause the shell fluid to flow through a tortuous, e.g. zig-zag, path from a shell fluid inlet past the exterior surfaces of the tubes, to a shell fluid outlet. However the flow of shell fluid is generally co-current or counter-current to the flow of the tube fluid in the sense that at any point in the tubes, apart from possibly the tube fluid inlet and outlet zones, the tube fluid is brought into heat exchange with shell fluid that has been subject to heat exchange downstream of that point in the case of counter-current flow and upstream of that point in the case of co-current flow. The catalyst may be disposed in the tubes, in which case the reactants will form the tube fluid and the heat exchange medium will form the shell fluid. Alternatively the catalyst is disposed in the shell space so that the reactants form the shell fluid and the heat exchange medium passes

REFERENCES:
patent: 1869973 (1932-08-01), Lucke
patent: 3731733 (1973-03-01), Trepaud
patent: 3958630 (1976-05-01), Smith
patent: 4147209 (1979-04-01), Persson
patent: 4904455 (1990-02-01), Karafian et al.
patent: 5382271 (1995-01-01), Ng et al.

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