Note: Descriptions are shown in the official language in which they were submitted.
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A Gas Synthesis Reactor
The invention relates to a gas reactor, for example, for
the synthesis of ammonia, mainly consisting of a pressure vessel
housing at least two heat exchangers, these heat exchangers being
arranged axially in sequence one behind the other, and substan-
tially concentrically in each catalyst bed.
Various reactor configurations for exothermal catalytic
gas reactions are known, for instance for the synthesis of ammonia
and methanol. Such devices normally comprise a pressure vessel,
the walls of which must not be exposed to the high reaction temp-
eratures if possible. It is recommended that the whole of the
pressure vessel walls have a uniform, and relatively low, tempera-
ture.
West German Patent 3,343,114, for example, describes a
reactor vessel with two catalyst beds, the process gas enters the
reactor at the bottom, rises in the shell, by-passing the internal
catalyst beds, then flows downwards through the heat exchangers
and finally through the first catalyst bed. With regard to
reactor shell cooling, West German OLS 3,14~,778 describes a
similar configuration. In this case, the process gas inlet is
also located at the bottom. The gas rises in the shell, then
descends in a concentric downpipe and flows through the first heat
exchanger. This vessel also houses two catalyst beds in a common
shell. This applies also to West German patent 2,710,247 which
describes a configuration wherein synthesis gas is supplied at the
vessel top, the gas flowing downwards and cooling the vessel wall.
Two catalyst beds are used, the cold synthesis gas flowing back to
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the heat exchanger at ~he bottom and then penetratlng the first
atalyst bed.
This invention seeks to provide a simple configuration
which permits an optimization of the process gas stream flow in
such a reaction vessel, thus improving the gas pre-heating and
ensuring an optimum cooling of the vessel wall. A speclal feature
of this invention is that it allows for the incorporation of more
than two catalyst beds in the reactor vessel.
Thus this invention provides either a lateral radial or
l~ a bottom inlet pipe ~or 1;he channel o~ a second heat exchanger,
this inlet pipe being required for the distribution of at least a
part of the loop gas which is used for shell coollng. If there
are more than ~wo heat exchangers, this invention will then be
applied to the last in the series, which generally is at the
bottom of the reactor shell.
As used in the followin~ discussion and claims, the
terms "first heat exchanger", "second heat exchanger" as well as
"first, second, third catalyst bed" are intended to mean that the
upper heat exchanger is the "first", and the surrounding catalyst
bed is the "first bed" in the vertical pressure vessel, the heat
exchanger below is the "second" and the related bed is the "second
bed", etc. It is of course possible to combine the first and
second heat exchanger such that they form a single heat exchanger.
This invention provides a gas reactor comprising in
combination a pressure vessel; an inner shell spaced and separated
from the pressure vessel to provide a gas flow space therebetween;
at least two heat exchanger series connected and installed
concentrically within each of at least ~wo catalyst beds; and
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means to feed process gas and loop cooling gas; wherein the second
heat exchanger is provided with a channel adapted to receive at
least a part stream of the cooling loop yas whereby this stream
flows countercurrently in the second heat exchanger with the
process gas, thereby cooling the process gas.
In a preferred embodiment the reactor includes radial
channels communicating between the gas flow space and the second
heat exchanger channel.
In a further preferred embodiment the reactor comprises
three catalyst beds, a gas collection space communicating with the
gas flow space below the third catalyst bed, and a gas feed
channel linking ~he gas collection space to the second heat
exchanger inlet channel and passing through a central outlet pipe
of the third catalyst bed.
In another preferred embodiment at least one of the loop
gas feed means is connected to a point between the first and
second heat exchangers, thus permitting mixing of at leas~ two
sources of loop gas before mixed loop gas passes into the first
heat exchanger.
The invention additlonally provides a gas reactor
comprising a pressure vessel, an inner shell spaced and separated
from the pressure vessel to provide a gas flow space therebetween,
at least two heat exchangers connected and installed
concentrically within each of at least two catalys~ beds loca~ed
within said inner shell, at least first and second separately
controllable, loop gas feed means to said heat exchangers, at
least one of said heat exchangers receiving loop gas from both
first and second loop gas feed means, whereby said loop gas flows
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countercurrently to process gas flowing through the heat
exchangers, thereby cooling said process gas.
The invention provides for a relatively simple
configuration. Since a part stream of the gas coaling the shell
is admitted at the vessel top and descends in the vessel - thereby
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partly cooling the vessel wall - it is possible to feed at least
some of this gas to a channel leading to the second exchanger, via
a lateral or bottom inlet; the heat exchanger being of a relative-
ly simple conventional construction. Thus this gas does not pass
through a third heat exchanger. ~ccording to an embodiment of the
invention, the reactor has three catalyst beds arranged axially
one below the other. The loop gas is used for cooling the entire
shell and then it flows through a concentric riser from the
collecting chamber below the third catalyst bed into the feed
channel of the second heat exchanger. This configuration offers
the possibility of heating the concentric riser with the aid of
loop gas, if required; the riser passes through the third catal~st
bed, preferably concentrically.
According to a further embodiment, the first heat ex-
changer incorporated into the first catalyst bed is equipped with
a concentric channel for piping the gas for temperature control,
which communicates with the channel of the first heat exchanger.
Moreover, the channel below the first heat exchanger is also used
as a mixing chamber for the loop gas and the gas for temperature
control.
According to another embodiment of the invention, the
device is equipped with an upper and a lower inlet nozzle for a
part stream of loop gas for shell cooling, the part streams of
cooling gas being fed via a radial inlet to the channel of the
second heat excha~ger. In this case, it is possible to feed part
streams of the loop or process gas to the pressure vessel (at top
and bottom) and to cool the shell with the aid of dif~erent
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streams.
A particular advantage of the construction is that
provision can be made for the different, separa~ely controllable,
sources of loop gas whlch can be used to control heat emitted by
the different stages of the catalyst beds due to the process
configuration.
The invention will now be described by way of reference
to the attached figures wherein:
Figure 1 represents a cross-sectional view of a reactor
according to this invention (schematic drawing); and
Figure 2 represents a modified construction of the
reactor device shown in E'igure 1.
In these figures it is to be noted that the heat
exchangers are shown diagrammatically. The dotted lines indicate
the channels, normally a tube bank or the like, for one gas flow,
whilst the arrows indicate the other, counter current, gas flow.
Device 1 in Eigure 1 comprises a pressure vessel 2,
housing three catalyst beds arranged concentrically to the centre-
line 3 of ~he reactor. The reactor contains three catalyst beds,
a first 4, a second 5, and a third 6. The first heat exchanger 7
is mounted inside the first catalyst bed 4, and the second heat
exchanger 8 is mounted inside the second bed S; the two heat
exchangers are series-connected. The catalyst and the heat :
exchangers are arranged in shell 9 sized such that the external
face of the shell and the internal face of the reactor wall 2 form
an annular spa~e 10 which extends from the top to the boktom of
the reactor, to provide a gas flow space.
Feed nozzle 11 for the start-up device and process-gas
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feed nozzle 12 are installed in the upper part of the reactor. In
the arrangement shown in Figure 1, feed nozzle 13 for the gas
required for temperature control is located in the upper section
of the reactor. The gas used for temperature control gas flows
through downcomer 14 in the centre of the reactor 1 through the
first heat exchanger 7 into channel 15. The second heat exchanger
8 has a channel 16 filled via the lower inlet 17 as illustrated in
Figure 1. The outlet nozzle of the reactor device is marked 18.
The process operates in such a reactor as follows.
The process or synthesis gas enters the reactor 1 via
inlet nozzle 12 and flows through annular space 10 between reactor
wall 2 and shell 9 of the catalyst beds, wi~h their incorporated
heat exchangers. The shell-cooling gas collects in chamber 19
below the third catalyst bed and flows through riser 17 into
channel 16 of the second heat exchanger 8. It has to be mentioned
that the heat exchangers are numbered in accordance with the
related catalyst beds. The gas in channel 16 passes through heat
exchanger 8 and enters channel 15 of the first heat exchanger 7;
this channel communicates with downcomer 14 for gas required to
control the temperature. Channel lS thus serves as a mixing
chamber for the gas flows in downcomer 14 and the second heat
exchanger 8. This mixed gas then passes upwardly through heat
exchanger 7, and serves to cool the process gas flowing counter-
currently therein. On leaving heat exchanger 7, the gas mixes
with any gas entering through the startup nozzle 11, and then
passes to the first catalyst bed 4. The gas then leaves the bed 4
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to flow through the heat exchanger 7 a second time, in counter
current flow to the incoming loop and process gas as noted above.
A similar flow pattern also occurs in the catalyst bed 5, and its
adjacent heat exchanger 8. The process gas finally passes through
the third catalyst bed 6, and leaves the reactor through the outer
shell of the concentric pipes 17 to the exit nozzle 18. In the
pipes 17 heat transfer will also take place between the process
gas and loop gas flowing countercurrently therein.
Figure 2 shows a slightly modified construction, the
modifications being described below. Device la in Figure 2 is
equipped with two inlet nozzles 12a and 12b. Each of these con~
veys into the reactor a part stream of the loop gas entering the
shell. In this case. channel 16a of the second heat exchanger 8a
is filled via radial inlets 17a with the gas descending from the
upper shell part and rising from the lower part. The downstream
process section then corresponds to Figure 1. In this configura-
tion the concentric exit channel 17 is also not used.
It is of course possible to modify the configuration
described above and yet to maintain the basic configuration.
~ence, the device need not have three catalyst beds, i.e. it may
also be divided into four beds with three incorporated heat ex-
changers, etc. According to the invention, the reactor can also
be operated with only one heat exchanger 8 and beds 5 and 6. With
this configuration it is essential that at least a part stream of
the process gas be fed through a riser and/or radial inlets, in
order to be able to maintain adequate temperature control.
