Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to apparatus for the catalytic
treatment of gases such as nitrogen and hydrogen with the aid
of a catalyst, using at least one concentric heat exchanger
arranged axially in a pressure vessel and surrounded by a
catalyst bed.
The device may be e~uipped with a centre inlet dome
for feeding gas to the tube bundle of the heat exchanger and
with a deflector arranged such that the gas leaving the heat
exchanger tubes flows radially through the first catalyst bed
from the external to the internal side. D~-PS 27 10 247, for
instance, describes various embodiments of a similar device.
The known devices have a common Eeature: -the gases leaving the
firs~ catalyst bed and fed to the heat exchanger either :Elow
around the upper part of the first catalyst bed to the second
bed or they descend through the outer section of the heat ex-
changer near the catalyst bedsO
In the known devices there are difficulties with re-
gard to the control functions, e.g. when the inlet temperature
required for the second catalyst bed has to be controlled.
Moreover, the known devices often re~uire costly and complicated
components for assembly and disassembl~v.
The aim of the invention is to design a device for
improving the gas stream and temperature control before the gas
streams enter the catalyst beds and for optimiæing the assembly
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and maintenanceO
The present invention provides apparatus for the
catalytic treatment oE nitrogen and hydrogen comprising at least
one heat exchanger axially concentrically arranged in a pressure
vessel and a catalyst bed surrounding the heat exchanger, a
centrally disposed feed dome for feeding the gas to the tube nest
of the heat exchanger and a deflection means for deElection of the
gas leaving the heat exchanger tubes for them to flow through the
first catalyst bed radially from the outside inwardly,
characterized in that provided in the interior of the first tube
nest heat exchanger is a concentric discharge tube for the gas
which leaves the Eirst catalyst bed and which flows from the
bottom upwardly around the heat exchanger tubes as viewed in the
direction of the Eorce of gravity, wherein the discharye tube is
provided with upper collecting openings for said gas.
It has been found that the centre discharge pipe offers
the advantages described below: it is possible to provide a
controlled radial gas stream through the first catalyst bed and
the heat exchanger arranged in the centre of the bed. The tube
bundle of the heat exchanger can be moun-ted concentrically around
the discharge pipe and this conEiguration facilitates the assembly
of the bundles. Moreover, the pipe is suitable for the functions
described below.
The centre discharge pipe can be provided with a feed
line for piping the quench gas into the upper section of the
discharge pipe. This embodiment permits simple control of the
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inlet temperature of the gas flowing through the discharge
pipe and entering the second catalyst bed. In known devices,
this control has to be effected via a chamber not clearly
defined with regard to the flow pattern and, consequently, it
is impossible for the required temperature to be attained in
the whole inlet section of the downstream catalyst bed. The
invention provides for a simple solution to this problem.
It is recommended that at least one quench gas feed
line be provided for the tubular heat exchanger r such Eeed line
passing through the heat exchanger down to the outlet section.
According to the invention, a plurality of such quench gas feed
lines should pass through the tube bundle of the heat exchanyer
and be connected to a common ring line.
This configuration facilitates gas temperature control
at the inlet of the first catalys-t bed, depending on the outlet
temperature of the gases preheated in the first heat exchanger.
The device should be designed such that the concentric
heat exchanger has a lower tubesheet which can be removed from
the top and is supported by a collar at the lower end.
The pressure vessel of known devices which contains
the components mentioned above are often provided with an upper
cover permitting the installation of heat exchangers, catalyst
beds~ etc. from above. The invention provides for a configur-
ation greatly facilitating assembly, because the heat exchanger
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can easily be inserted from the top into the first catalyst
bed and is adequately supported by the collar of the catalyst
bed.
According to a further embodiment, a gasket such as
a labyrinth gasket is placed between the lower tubesheet and
the collar of the catalyst bed. It is possible to mount the
tubesheet onto the collar by means of spacer bolts but other
fixing elements are also suitable.
A further embodiment provides for easy installation
of the ring tube and quench gas tubes, these components being
attached to the f]anges of the sleeve pipes in the heat ex-
changer and removable from above. Moreover, the quench gas
tube for the downstream catalyst bed can be removed upwards
with the aid of an assembly plate fitted to the head of the
stationary centre discharge pipe.
The invention also provides for a centre discharge
pipe head which has an inlet opening and is attached to the
pipe by means of a flexible connector removable from above.
The figures indicated below illustrate, by way of
example only, the configuration of one preferred embodiment.
Figure l is a longitudinal sectional view of the
device according to the invention;
Figures 2 and 3 are enlarged views of the upper section
of the heat exchanger; and
Figures 4 and 5 are enlarged views of the lower section
of the first heat exchanger.
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Device 1 according to Figure 1 consists of vertical pressure
vessel 2 sealed by means of pressure cover 3 and a supporting
structure 4 not shown in detail.
The pressure vessel contains two concentric catalyst
beds 5 and 6, catalyst bed 5 housing the concentric tubular
heat exchanger 7.
The gases to be treated, such as nitrogen or hydrogen,
enter the pressure vessel via upper nozzle 8 and flow through
inlet dome 9 into heat exchanger 7. After passing through the
heat exchanger tubes, the gases leave via annular space 10,
ascending in the outer section of catalyst bed 5 in order to be
sent through said catalyst bed and again through heat exchanger
7. The gases finally enter centre discharge pipe 12 via upper
collecting openings 11, the arrows in Figure 1 indicating the
gas stream. Pipe 12 discharges into lower channel 13 of the
second catalyst bed 6.
A characteristic feature of the invention is described
below: Two quench gas feed lines 14 and 15 are connected to
cover 3 of pressure vessel 2. Quench gas feed line 14 discharges
into ring line 16, a section of which is shown in Figure 3.
Downpipes 17 communica-ting with the ring line 16 pass through
entire tube bundles of heat exchanger 7 and end in annular space
10 as illustrated in Figure 1. Hence, it is possible to feed
quench gas via 16 and 17 to the annular space where it is mixed
with the gases prior to entering the first catalyst bed.
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Quench gas li.ne 15 communicates with the head of
centre discharge pipe 12 and permits the admixture of quench gas
to the gases entering through upper collecting openings 11. This
configuration is suitable for controlling the gas stream to the
second catalyst bed 6.
An optimum interchangeability is obtained by mounting
concentric tubular heat exchanger 7 onto lower collar 18/18a of
the first catalyst bed 5, see Figures 4 and 5. The embodiment of
Figure 4 shows the collar 18 slightly inclined towards the centre,
thus forming a bearing surface for the lower tubesheet 19 of heat
exchanger 7. As shown in Figure 4, the contact sur~ace has a
labyrinth gasket 20.
According to the further embodiment shown in Figure 5,
collar l~a is almost horizontal and standard gasket 20a is used for
tubesheet l9a fixed by means of spacer bolts 21, the spacer tube
being marked 22.
Combinations of labyrinth gaskets and spacer bolting
are also feasible.
As shown in Figures 2 and 3, the upper bolting is
arranged between stationary discharge pipe 12 and a separate
sleeve pipe 23 which are connected by means of flexible joint 24.
The upper quench gas pipe 15 is also fixed to heat exchanger 7 by
means of bolts screwed from above. A similar connection is used
between ring line 16/downpipe 17 and heat exchanger 7. In this
case, a flexible sealing element 25 i5 also installed. The
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flexible sealing element 25 and/or 24 may consist of an expansion
joint or a stuffing box bu-t the invention provides also for other
suitable types.
It must be noted that sleeve pipe 26 is not used for
gas so that it has an insulating effect which is desirable.
It is of course possible to modify and/or re-design
the embodiments described above without departing from the basic
concept of the invention. Thus, the invention is by no means
limited to the bearing and sealing devices shown in the Fi-~u~`s
but is only limited by the scope of the appended cla:ims.
