Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including heat exchanger for reaction chamber or reactants...
Patent
1996-07-30
1999-09-14
Scheiner, Laurie
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including heat exchanger for reaction chamber or reactants...
422194, 422198, 422200, B01J 804, F28D 804, F28D 700
Patent
active
059519533
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of Application
The present invention relates to a mixing assembly for gaseous flows at different temperatures, in particular for heterogeneous exothermic synthesis reactors comprising a plurality of superimposed catalytic beds and in which at least one of the beds is provided with a gas permeable wall for outlet of a flow of hot gas, said assembly including:
a baffle extending below and parallel to said gas permeable wall with which it defines an air space for collection of said hot gas flow;
an annular opening for outlet of said hot gas flow from said air space defined between said baffle and a side wall supporting said at least one bed associated with the reactor;
a perforated distributor for a cooling gas flow supported below said baffle at a predetermined distance from said annular opening.
In the description given below and in the followings claims, the term: hot gas, is understood to mean a partially reacted gas or gas mixture leaving a catalytic bed of a synthesis reactor, in which it has reacted exothermically. By way of example, in the exothermic heterogeneous synthesis reaction of methanol said gas has a temperature generally between 240.degree. C. and 290.degree. C.
On the contrary, the term: cooling gas, is understood to mean a cooling gas having a temperature lower than that of the partially reacted gas leaving the catalytic bed. Usually said gas consists of a predetermined part of reagent gasses and, again in the case of methanol synthesis, has a temperature generally between 60.degree. C. and 200.degree. C.
In the terminology of the field the cooling gas is also indicated by the term `quench gas`.
As known, during performance of an exothermic heterogeneous synthesis reaction it is necessary to cool the hot gas flow leaving each catalytic bed so as to bring the temperature back to a value such as to allow reaching the maximum conversion yield in the next bed.
2. Prior Art
For this purpose, the reactors assigned to this type of synthesis are provided with devices or mixing assemblies designed to cool the partially reacted gas mixtures flowing through a single catalytic bed or between a plurality of superimposed catalytic beds.
Thus for example in European patent application EP-A-0 359 952 of this applicant there is described an exothermic heterogeneous methanol synthesis reactor, in which are supported a plurality of superimposed catalytic beds in mutually spaced relationship between which are provided respective mixing assemblies for intermediate cooling of the reaction products by a flow of quench gas.
Said mixing assembly comprises a baffle extending below and parallel to the gas permeable bottom of at least one catalytic bed with which it defines an air space for collection of a hot gas flow leaving said at least one bed.
An annular opening for outlet of said hot gas flow from said air space is defined between said baffle and the side wall of the reactor supporting said at least one bed.
Below said baffle at a predetermined distance from the annular opening is supported a perforated distributor for a cooling gas flow.
Mixing of the hot synthesis gas flow with a cooling gas flow takes place in the peripheral zone of the reactor near the side wall supporting the catalytic beds.
If on one hand this type of assembly allows obtaining a certain degree of mixing of the gaseous flows, on the other hand it is not possible to achieve substantially complete mixing of the hot gases and cold gases before they enter in contact with the next catalytic bed.
In addition, the device in accordance with the prior art is not able of correcting and uniforming any local flow rate and temperature unevenness of the hot gases leaving said annular opening.
This local unevenness in flow rate and temperature are due to the fact that the hot gas flow coming from a bed containing a generally granular catalytic mass is subject to uncontrolled variations in flow rate and, if there are very extensive so-called catalyst "packing" phenomena, in temperature as well.
In other words, the mixing assembly ju
REFERENCES:
patent: 2632692 (1953-03-01), Korin et al.
patent: 3254967 (1966-06-01), Wentworth
patent: 3480407 (1969-11-01), Wentworth et al.
patent: 3946104 (1976-03-01), Forster et al.
patent: 4859425 (1989-08-01), Zardi
patent: 4946657 (1990-08-01), Zardi
Methanol Technology, 6147 Nitrogen (1994) Jan./Feb., No. 207, London, GB, "Meeting today's challenges" pp. 24-30.
Pagani Giorgio
Zardi Umberto
Methanol Casale S.A.
Parkin Jeffrey S.
Scheiner Laurie
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