Radial flow catalytic reactor including heat exchange apparatus within the bed

An improved reactor is disclosed wherein a high temperature product gas discharged from a catalyst bed within the reactor is cooled in a central heat exchanger installed within the reactor by heat exchange with a low temperature feed gas comprising gaseous raw materials for the reaction, and the product gas is thereafter flowed along the inner surface of an outer pressure vessel in order to maintain the outer pressure vessel at a low temperature. Inlet and outlet pipes for a coolant which coolant is circulated through a coolant passage structure which penetrates the catalyst bed in order to absorb the heat of reaction, both penetrate the top cover of the outer pressure vessel so that the coolant passage structure can be readily removed for maintenance and inspection, and the overall design of the reactor is simplified.

FIELD OF THE INVENTION 
This invention relates to improvements in a reactor in which a catalytic 
chemical reaction can be carried out. More specifically, the present 
invention relates to a reactor having an improved internal structure 
effective to prevent the pressure vessel of the reactor from increasing in 
temperature excessively during an exothermic reaction wherein a feed gas 
that contains a large amount of hydrogen, which feed gas remains gaseous 
at the temperature and pressure of the reaction, flows radially through a 
cylindrical catalyst bed of the reactor to produce a product which is 
gaseous at the temperature and pressure of the reaction. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 4 321 234, the entire contents of which are incorporated 
herein by reference, discloses a reactor wherein the heat of reaction is 
removed by coolant that circulates through a number of vertically 
extending cooling tubes which are arranged parallel to the axis of a 
single, cylindrical catalyst bed of the reactor. A feed gas flows in the 
radial direction through the catalyst bed and thereby undergoes an 
exothermic reaction. The heat of reaction causes the coolant within the 
cooling tubes to boil. The coolant is fed through the cooling tubes under 
pressure, at its boiling temperature. After absorbing the heat of 
reaction, the coolant is discharged from the reactor in the form of a 
vapor, or a liquid-vapor mixture of the coolant. In the specification, the 
vapor and the mixture of vapor and liquid are, in combination, called 
merely as a vapor of the coolant. 
U.S. patent application Ser. No. 502,298, now U.S. Pat. No. 4,594,227 filed 
Sept. 8, 1983, the entire contents of which are incorporated herein by 
reference, which corresponds to Japanese patent application No. 
167639/1982, discloses a reactor wherein the annular, cylindrical catalyst 
bed formed in the intercylinder space between a pair of inner and outer 
cylindrical catalyst retainers is subdivided by two or more partition 
walls which extend radially and vertically. By this means, a plurality of 
catalyst beds which are sectorial in horizontal cross section are formed. 
The reactant feed gas is flowed radially through the different catalyst 
beds in a predetermined sequence, while a coolant liquid is fed through 
cooling tubes installed in each of the catalyst beds in the same manner as 
disclosed in U.S. Pat. No. 4 321 234. Using the improved arrangement of 
U.S. Ser. No. 530 298, the temperature distribution in the direction of 
the gas flow in the catalyst beds can be optimized in accordance with the 
purpose and characteristics of the particular reaction that is to be 
performed. In addition, the heat of reaction can be recovered by making 
use of the coolant vapor. The reactor of Ser. No. 530 298 is accordingly 
advantageous for effecting exothermic reactions. 
The present inventors have discovered that the outer pressure vessels of 
the foregoing reactors, according to the prior art, suffer from hydrogen 
embrittlement. Hydrogen embrittlement occurs when the outer pressure 
vessel is exposed to a high temperature, high pressure, feed gas 
containing a large amount of hydrogen. The present invention relates to a 
reactor which retains the advantageous features of the foregoing two prior 
art reactors, and which, in addition, is provided with unique structural 
features that render it less subject to hydrogen embrittlement. 
Hydrogen embrittlement can occur when a high temperature, high pressure, 
feed gas containing a large amount of hydrogen and/or a product gas which 
also contains a substantial amount of residual hydrogen are brought into 
contact with a conventional low carbon steel or alloy steel containing a 
total of 10% by weight or less of alloying components other than iron and 
carbon. The foregoing product gas is formed from the feed gas by bringing 
the feed gas into contact with the catalyst in the catalyst bed. After a 
long period of such contact, the well-known phenomenon called hydrogen 
embrittlement takes place whereby the low carbon steel or alloy steel is 
deteriorated by the action of hydrogen and becomes brittle. 
As used hereinafter, the term "carbon steel" refers to steel consisting 
essentially of 0.02 to 0.6 wt. %, preferably 0.1 to 0.4 wt. % carbon, less 
than 10.0 wt. % preferably less than 5.0 wt. % alloying elements other 
than iron and carbon, and the balance is essentially iron. The term 
"carbon steel" used hereinafter refers to both low carbon steels and alloy 
steels containing up to 10 wt. % of alloying components other than iron 
and carbon. 
As a method for minimizing such hydrogen embrittlement, as disclosed in 
U.S. Ser. No. 530,298 noted above and many other literatures, a low 
temperature feed gas can be fed to a reactor having an outer pressure 
vessel made of carbon steel. Before this low temperature feed gas reaches 
the reaction temperature, it is first flowed along the inner surface of 
the outer pressure vessel in order to reduce heat transfer from the 
catalyst bed of the reactor, which is at a high temperature, to the outer 
pressure vessel, thereby maintaining the temperature of the outer pressure 
vessel at 300.degree. C. or lower, preferably 250.degree. C. or lower. 
Alternatively, an outer pressure vessel can be used which is made of a 
stainless steel containing more than 10 wt. % of alloying elements other 
than iron and carbon. 
According to methods wherein a low temperature feed gas is flowed along the 
inner surface of the outer pressure vessel made of carbon steel, the low 
temperature feed gas can be preheated by causing it to undergo heat 
exchange with high temperature product gas leaving the catalyst bed, using 
a heat exchanger that is installed in the reactor. However, the amount of 
heat needed to preheat the feed gas is less than, the sum of the evolved 
heat of reaction and the heat content of the product gas leaving the 
catalyst bed. Consequently, the product gas flowing out of the reactor is 
normally high in temperature in spite of the heat exchange step, and thus 
it is not possible to use the product gas for the purpose of preventing 
the outer pressure vessel made of carbon steel from increasing in 
temperature by flowing the product gas along the inner surface of the 
outer pressure vessel after the heat exchange step. The foregoing prior 
art procedures fail to eliminate the need to make the outer pressure 
vessel from stainless steel in order to avoid hydrogen embrittlement. The 
use of stainless steel for making the outer pressure vessel, however, 
renders the reactor more expensive. 
When a low temperature feed gas is first flowed along the inner surface of 
the outer pressure vessel as described above, the pressure in the flow 
passage adjacent to the inner surface of the outer pressure vessel is 
higher than the pressure in the central part of the reactor containing the 
catalyst beds by an amount corresponding to the pressure drop that occurs 
due to the flow resistance that the gas encounters as it passes through 
the catalyst bed and the other flow passages in the reactor. This pressure 
drop is normally on the order of 5 to 20 kg/cm.sup.2. The feed gas flowing 
along the inner surface of the outer pressure vessel is upstream of the 
gas that is passing through the catalyst bed in the central part of the 
reactor. Under these circumstances, an external pressure corresponding in 
magnitude to the foregoing pressure drop is exerted on the external 
cylindrical partition wall which separates the chambers that differ in 
pressure. This external pressure tends to collapse the cylindrical 
partition wall or walls inwardly, with the practical effect being that the 
cylindrical partition wall will be deformed by buckling. In order to 
prevent such buckling, the cylindrical partition wall(s) and the radial 
partition wall(s) which aid in supporting the cylindrical partition 
wall(s) must be made thicker. 
It has also been generally necessary to fabricate the interior cylindrical 
and radial partition walls mentioned above from stainless steel, because 
these walls come into contact with gases containing a large amount of 
hydrogen at a high temperature and pressure. Thus, these partition walls 
must be made both thicker and of a more expensive material in order to 
prevent buckling and hydrogen embrittlement. These problems have been 
generally overlooked in the prior art because the prior art reactors have 
been built on a relatively small scale. However, it has recently become 
possible to greatly enlarge the reactor in which a high pressure feed gas 
containing a large amount of hydrogen is used at a high temperature to 
synthesize ammonia, methanol and similar products. When such a reactor is 
built on a large scale, it becomes important to solve the problems of 
hydrogen embrittlement and buckling of the interior partition walls 
without using large amounts of expensive stainless steel.

SUMMARY OF THE INVENTION 
The reactor according to the present invention ameliorates the problems of 
hydrogen embrittlement of the outer pressure vessel and buckling of the 
inner partition walls, but without, however, using an excessive amount of 
expensive stainless steel. According to the invention, the high 
temperature product gas leaving the catalyst bed after completion of the 
reaction is cooled sufficiently by undergoing heat exchange with a low 
temperature feed gas within a heat exchanger installed in the reactor. The 
thus-cooled product gas is thereafter allowed to flow along the inner 
surface of the outer pressure vessel. A feed pipe for the liquid coolant, 
which is to be supplied to the bottoms of the cooling tubes and to flow 
upwardly therein, penetrates into the interior of the reactor through a 
top cover or top wall thereof. This arrangement facilitates maintenance 
and inspection of the interior of the reactor, and allows the product gas 
which has left the catalyst bed and has been cooled by the foregoing heat 
exchange step to flow without interruption along the interior surface of 
the outer pressure vessel. 
DETAILED DESCRIPTION 
The product gas which leaves the catalyst bed and is cooled in the heat 
exchanger, according to the invention, is the most downstream portion of 
the gas that is flowing through the reactor and is, therefore, at the 
lowest pressure within the reactor. By flowing this gas along the inner 
surface of the outer pressure vessel, the pressure difference between the 
flow passage adjacent to the interior of the outer pressure vessel and the 
central chambers of the reactor is reversed as compared to the procedure 
employed in the prior art as described above, so that the partition walls 
which separate the product gas flow space from the central chambers of the 
reactor are subjected to an internal pressure which corresponds in 
magnitude to the pressure drop that the gas undergoes as it flows through 
the catalyst bed. As a result, the force exerted on the partition walls is 
a tensile force instead of a collapsing force, and the problem of buckling 
of these partition walls is thereby avoided. 
This solution to the problem of buckling of the interior partition walls is 
possible only when a substantial portion of the total reaction heat 
generated is removed and recovered as the latent heat of vaporization of 
the coolant which flows through the cooling tubes in the catalyst bed or 
beds, as described in detail in the aforementioned U.S. Pat. No. 4,321,234 
and U.S. Ser. No. 530,298, filed Sept. 8, 1983. Thus, according to the 
present invention, an upright, annular, cylindrical catalyst bed defined 
by the intercylinder space between a pair of inner and outer cylindrical 
catalyst retainers has a multiplicity of vertical cooling tubes extending 
therethrough. 
More particularly, for a highly exothermic reaction, the amount of heat 
required to preheat the low temperature feed gas to the desired reaction 
temperature is generally less than the sum of the heat evolved by the 
reaction and the heat content of the product gas which is discharged from 
the catalyst bed. Consequently, if the gas discharged from the catalyst 
bed is cooled, as disclosed in the prior art, by allowing the low 
temperature feed gas to undergo heat exchange with the high temperature 
product gas in a heat exchanger inside the reactor without removal of 
reaction heat by any other means, for the purpose of merely preheating the 
feed gas, then the sum of the amounts of the heat of reaction and the heat 
content of the high temperature product gas will greatly exceed the heat 
needed to preheat the feed gas. Under such circumstances, it is impossible 
to cool the product gas to a sufficiently low temperature as required in 
the present invention. 
Since most of the total exothermic heat of the reaction is removed as the 
latent heat of vaporization of the coolant in the reactor, according to 
the present invention, there is no significant difference between the heat 
content of the product gas that flows out of the catalyst bed and the 
amount of heat required to preheat the feed gas, so that the gas that 
flows out of the catalyst bed can be cooled to a sufficiently low 
temperature by undergoing heat exchange with the low temperature feed gas. 
Thus, by virtue of the cooling tube arrangement used in the reactor 
according to the present invention, it is possible to use an outer 
pressure vessel made of carbon steel, as defined above. The internal 
partition walls of the reactor, namely, the coaxial cylindrical catalyst 
retainer walls and the radial partition walls extending between these 
retainer walls, can be made of relatively thin stainless steel. 
In the reactors disclosed by U.S. Pat. No. 4,321,234 and U.S. Ser. No. 
530,298, the feed pipe for supplying the coolant to the cooling tubes 
extends through the bottom cover or bottom wall of the reactor. According 
to the present invention, however, in order to allow the cooled product 
gas to flow along the inner surface of the outer pressure vessel, it is 
necessary to isolate the intercylinder space containing the catalyst beds 
from the outer pressure vessel. To achieve this, at least one partition 
wall must be provided at a location spaced from the interior surface of 
the cylindrical portion of the outer pressure vessel and also spaced from 
the interior surface of the bottom wall of the outer pressure vessel. When 
the coolant feed pipe is introduced through the bottom of the reactor, 
this feed pipe must pass through both the partition wall and the bottom 
wall of the outer pressure vessel. It is not impossible to extend a 
coolant feed pipe through a partition wall and a bottom wall. However, in 
the reactor of the present invention, the outer pressure vessel is 
maintained at a relatively low temperature. There may accordingly exist a 
temperature difference of at least 100.degree. C., more likely 
200.degree.-300.degree. C., between the outer pressure vessel and the 
coolant feed pipe, because the liquid coolant is at its boiling 
temperature. There is also a temperature difference of about 100.degree. 
C. between the aforesaid partition wall and the coolant feed pipe. To 
minimize thermal stress of a coolant feed pipe that extends through the 
bottom of the reactor, caused by the foregoing temperature difference, a 
complex and expensive feed pipe structure would be needed, and such an 
arrangement would make maintenance and inspection of the reactor 
inconvenient. To avoid such problems, the coolant feed pipe in the reactor 
according to the present invention extends through the top wall of the 
outer pressure vessel. That is, the coolant feed pipe, according to this 
invention, penetrates through the top wall of the reactor, extends 
downwardly through the catalyst bed, and then connects to manifolds 
provided at the bottom of the catalyst bed to distribute the coolant into 
each of the cooling tubes to flow upwardly therein. When this structure is 
employed, the coolant in the coolant feed pipe will normally boil in the 
portion of the coolant feed pipe which passes through the catalyst bed. In 
this case, it is important to employ a structure wherein the coolant vapor 
generated by this boiling does not interfere with the downward movement of 
the coolant in the coolant feed pipe. 
As a specific structure for this purpose, the portion of the coolant feed 
pipe which passes through the catalyst bed may be covered with a heat 
insulating material. Alternatively, a duplex pipe can be employed so that 
the coolant is fed downwardly inside of the inner pipe of the duplex pipe, 
and the annular space between the inner and outer pipes of the duplex pipe 
is open to the distributing manifold at its bottom end and is connected to 
the discharge outlet for the coolant vapor at its top end. In this annular 
space, the coolant vapor is present close to or at the same temperature as 
the coolant flowing downwardly inside of the inner pipe. Although it is 
possible to separately provide (1) a discharge pipe for the vapor 
generated by the boiling coolant in each of the cooling tubes and (2) the 
foregoing coolant feed pipe through the top cover, the coolant feed and 
discharge pipes are preferably installed as a single duplex pipe 
penetrating the top wall as described above. This improves the simplicity 
of the installation and the efficiency of heat insulation. By this means, 
it becomes easier to install the cooling system which comprises the 
coolant feed pipe, coolant vapor discharge pipe, distributing manifolds, 
cooling tubes and collecting manifolds. This cooling system can be 
installed by suspending it from the upper end of the reactor or by 
mounting it on a floor provided on the partition wall which isolates the 
catalyst bed from the bottom wall of the outer pressure vessel. By this 
means, the cooling system or coolant passage structure is mounted on the 
outer pressure vessel at only one location. As a result, it becomes 
possible to make the reactor structure substantially free from thermal 
stress even if there is a large temperature difference between the outer 
pressure vessel and the coolant passage structure. 
The present invention is described in further detail below in examples 
illustrated by the attached drawings, but the scope of the invention is 
not limited to these examples. 
FIG. 1 illustrates a vertical cross section of an exemplary reactor 
according to the present invention wherein a single, annular, cylindrical 
catalyst bed is employed. The substantially cylindrical outer pressure 
vessel 1 has a dome-shaped top cover 2 and a dome-shaped bottom wall 3. A 
substantially cylindrical heat exchanger 4 is mounted inside the outer 
pressure vessel 1 and is coaxial therewith. An annular catalyst bed 6 
surrounds the heat exchanger 4. The inner periphery of the catalyst bed 6 
is radially outwardly spaced from an outer shell 5 of the heat exchanger 
4. The catalyst bed 6 is formed by packing a granular catalyst in the 
annular, intercylinder space between a gas- permeable, cylindrical, inner, 
catalyst retainer 7 provided at a desired radial separation from the outer 
surface of the outer shell 5, and a gas-permeable, cylindrical, outer, 
catalyst retainer 8 which is larger in diameter than the inner catalyst 
retainer 7 and is coaxial therewith. 
Both of the catalyst retainers 7 and 8 comprise a cylinder having a large 
number of holes or perforations extending therethrough over the entire 
vertical surface thereof, whereby reactant gas can freely flow 
substantially horizontally and radially through the catalyst bed 6. From 
one to three sheets of netting or mesh are attached to each of the 
retainers 7 and 8 and covering the holes thereof to prevent the catalyst 
particles from leaking through the holes. The upper end of the annular 
space between the inner catalyst retainer 7 and the outer shell 5 of the 
heat exchanger 4 is sealed by a removable annular closure plate 9 which 
blocks upward flow of the gas. This annular space defines a gas flow 
passage which is divided into a first, inner, annular, cylindrical, gas 
flow passage 12a and a second, inner, annular, cylindrical, gas flow 
passage 12b by a cylindrical wall 11a which is attached in a gas-tight 
fashion at its lower end to the lower part of the outer shell 5 of the 
heat exchanger 4. The wall 11a has a plurality of holes extending 
therethrough near the upper end thereof which allow a uniform vertical 
distribution of the reactant gas through the inner catalyst retainer 7. 
The total surface area occupied by holes on the wall 11a is generally 
smaller than the corresponding area occupied by holes on the inner 
catalyst retainer 7. 
In this example the outer catalyst retainer 8 is spaced a desired radial 
distance inwardly from the cylindrical portion of an inner cup-shaped 
partition wall 10a. The partition wall 10a has an upright cylindrical wall 
portion and a substantially hemispherical bottom wall portion. The 
partition wall 10a separates the catalyst bed 6 from the outer pressure 
vessel 1, including the bottom cover 3 thereof. The annular space between 
the outer catalyst retainer 8 and the partition wall 10a is sealed by 
horizontal, annular top and bottom walls of the outer catalyst retainer 8. 
The partition wall 10a has a large number of holes extending therethrough 
over the vertical surface thereof that faces the outer catalyst retainer 
8. This perforated wall portion 11b is radially outwardly spaced from the 
outer catalyst retainer 8, and causes the reactant gas to flow evenly 
through the catalyst bed 6 over the vertical dimension thereof. The space 
between the inner partition wall 10a and the outer pressure vessel 1 is 
divided into first and second, outer gas flow passages 13a and 13b by a 
second, outer partition wall 10b which is attached in gas-tight fashion to 
the partition wall 10a near the upper end of the wall 10a. The partition 
wall 10b is of substantially the same shape as the wall 10a, but is larger 
in size and of larger wall thickness. The first passage 13a is defined 
between the outer surface of the wall 10a and the inner surface of the 
wall 10b. The second passage 13b is defined between the outer surface of 
the wall 10b and the inner surface of the outer pressure vessel 1. 
The lower end of the cylinder which defines the inner catalyst retainer 7 
is joined at the lower end thereof to the partition wall 10a in a 
gas-tight fashion. The lower end of the outer shell 5 of the heat 
exchanger 4 is also joined to the partition wall 10a so that the 
connection therebetween is gas-tight. In the foregoing structures, the 
components of the heat exchanger 4 housed within the outer shell 5 
thereof, the catalyst retainers 7 and 8, the partition walls 10a and 10b 
and parts connected thereto are suspended from the pressure vessel by 
means of a flange 14 provided at the upper end of the partition wall 10a, 
which flange rests on a shoulder provided near the upper end of the 
cylindrical central portion of the outer pressure vessel 1. The surface of 
the partition wall 10b facing the outer pressure vessel 1 is covered by a 
a layer 43 of heat insulating material to prevent heat from escaping 
outwardly from the partition wall 10b. Although the outer catalyst 
retainer 8 is disposed inside of the partition wall 10a in the embodiment 
shown, it is also possible to change the structure of this portion so that 
the perforated portion of the outer catalyst retainer 8 is made part of 
the partition wall 10a, and the perforate wall 11b projects outwardly of 
the partition wall 10a in the annular space between the outer partition 
walls 10a and 10b. 
A large number of cooling tubes 15 extend vertically through the catalyst 
bed 6. The tubes 15 are arranged in a multiplicity of concentric circles 
which are coaxial with the central vertical axis of the reactor. The 
cooling tubes 15 can be connected so as to define a single cooling zone 
encircling the central axis of the catalyst bed, or they can be connected 
so as to define two or more circumferentially, spaced, separate cooling 
zones, each of which is of sectorial shape in horizontal cross section. 
This will be described hereinbelow with reference to FIG. 6 and it is 
disclosed in greater detail in U.S. Ser. No. 530,298. 
Each cooling zone has at least one coolant feed pipe 22 and at least one 
coolant vapor discharge pipe 23 associated therewith. The lower ends of 
the cooling tubes 15 are connected to secondary distributing manifolds 16 
of a secondary distributing structure. When the cooling tubes 15 are 
connected to form a single cooling zone of annular shape, the manifolds 16 
can be circular in plan view. When the cooling tubes 15 are connected to 
form a plurality of separate, arcuate cooling zones located in 
side-by-side relation, each manifold 16 can be of the same arcuate extent 
as the cooling zone of which it is a part. Each of the secondary 
distributing manifolds 16 is connected by at least one connecting tube 17 
to a primary distribution manifold 18 which comprises a circular tube when 
a single cooling zone is provided or arcuate tubes if multiple cooling 
zones are being employed. 
The upper ends of the cooling tubes 15 are connected to primary collecting 
manifolds 19 in the primary collecting structure, which collecting 
manifolds 19 are arranged in the same way as the distributing manifolds 
16. Each of the primary collecting manifolds 19 is connected by at least 
one connecting tube 20 to a secondary circular collecting manifold 21 
which is arranged in the same way as the distribution manifold 18. 
All of the primary and secondary distributing and collecting manifolds 16, 
18 and 19, 21 extend substantially horizontally, and adjacent secondary 
distributing manifolds 16 and primary collecting manifolds 19 are 
staggered at different vertical heights. It is preferred to position the 
secondary distributing manifolds 16 slightly lower than the lower ends of 
the gas-permeable portions of the catalyst retainers 7 and 8. The primary 
distributing manifold 18 is positioned below its associated secondary 
distributing manifolds 16. The primary collecting manifolds 19 are 
positioned slightly higher than the upper ends of the gas-permeable 
portions of the catalyst retainers 7 and 8. The secondary collecting 
manifold 21 is disposed above the primary collecting manifolds 19. Further 
details regarding the arrangement of cooling tubes, primary and secondary 
distributing structures and primary and second collecting structures are 
given in the aforementioned U.S. Pat. No. 4,321,234 and U.S. Ser. No. 530, 
298. 
The secondary collecting manifold 21 in each cooling zone communicates with 
at least one coolant vapor discharge pipe 23 which extends outside of the 
reactor. A coolant feed (inlet) pipe 22 is provided as an inner pipe 
inside the secondary collecting manifold 21 and the coolant vapor 
discharge pipe 23 located thereabove. The coolant feed pipe 22 penetrates 
vertically through the secondary collecting manifold 21 in each cooling 
zone and extends substantially vertically downwardly through the catalyst 
bed 6 and communicates with the primary distributing manifold 18 at the 
lower end of the cooling zone. In this context, "cooling zone" refers to 
the entirety of the annular catalyst bed when the cooling tubes 15 are 
connected to form a single circular cooling zone and it refers to a 
sectorial subdivision of the annular catalyst bed when the cooling tubes 
are connected to form a plurality of arcuate cooling zones. Several 
cooling zones can be employed even when the annular catalyst bed is not 
subdivided. In this example, the coolant feed pipe 22 that extends between 
the upper end of a primary distributing manifold 18 and the lower end of 
its associated secondary collecting manifold 21 comprises the inner pipe 
of a duplex pipe. The annular space between the inner and outer pipes 22, 
23 communicates at its upper end with the coolant vapor discharge outlet 
and communicates at its lower end with the primary distributing manifold 
18. A duplex pipe is used in order to prevent the coolant from boiling as 
it flows downwardly within the coolant feed pipe 22 due to the generation 
of heat in the catalyst bed, and thus prevent the downward movement of the 
coolant through the pipe 22 from becoming obstructed by the evolved 
coolant vapor. Using the duplex pipe, some liquid coolant and vapor 
thereof at the same temperature as the liquid coolant flow upwardly 
through the annular space between the inner and outer pipes 22, 23 so that 
heat transfer from the high temperature catalyst bed 6 into the coolant 
feed pipe 22 is reduced. As an alternative, the outer pipe of the duplex 
pipe can be replaced by a heat insulating structure comprising an 
insulating layer. 
In the coolant passage structure described above, the coolant passes 
through the coolant feed pipe 22 into the cooling zone and is distributed 
from the primary distributing manifolds 18 through a plurality of 
connecting pipes 17 into the secondary distributing manifolds 16. From the 
manifolds 16 it is further distributed into a large number of cooling 
tubes 15. As the coolant absorbs reaction heat evolved in the catalyst 
bed, the coolant boils and is converted to its vapor in the cooling tubes, 
and the coolant vapor from the cooling tubes is combined in the primary 
collecting manifolds 19 and fed via the pipes 20 to the secondary 
collecting manifold 21 for each cooling zone. The vapor is then discharged 
from the reactor via the annular space between the coolant vapor discharge 
pipe 23 and the coolant feed pipe 22. 
In the shell-and-tube heat exchanger 4, wherein a plurality of tubes 28 are 
arranged substantially vertically parallel to the central vertical axis of 
the reactor, a main gas feed pipe 24 from the outside of the reactor is 
connected, by means of a gas-tight connection, to an upper annular plate 
26 which comprises part of the outer shell 5 of the heat exchanger 4 and 
defines the upper end of the compartment in which heat exchange takes 
place. The pipe 24 opens to the shell side of the heat exchanger 4 within 
the compartment defined by the interior of the outer shell 5. A second gas 
feed pipe 25, the purpose of which will be described hereinbelow, is 
connected to a lower annular plate 27 which defines a bottom wall of the 
heat exchanger 4. The second feed pipe 25 penetrates the partition walls 
10a and 10b from outside of the reactor and opens to the shell side of the 
heat exchanger 4 above the lower annular plate 27. The lower end of the 
outer shell 5 of the heat exchanger 4 is joined to the partition wall 10a 
by means of an outer pipe and bellows which surround the second gas feed 
pipe 25 and are spaced apart therefrom a selected distance. 
The interior structure of the shell-and-tube heat exchanger 4 between the 
upper and lower plates 26, 27 is conventional. A plurality of vertical 
tubes 28, preferably disposed in one or more circular arrays coaxial with 
the vertical central axis of the reactor, extend between the upper and 
lower plates 26, 27 and define the tube side of the heat exchanger 4. The 
shell 5 of the heat exchanger 4 includes a plurality of horizontal baffle 
plates 29 which cause the feed gas fed from the pipe 24 to move in a 
zig-zag path through the interior of the heat exchanger 4 as it flows 
downwardly. The greater part of the fresh feed gas is introduced through 
the main feed pipe 24 and it undergoes heat exchange with a high 
temperature product gas discharged from the catalyst bed which flows 
through the tubes 28. This preheats the fresh feed gas on the shell side 
of the heat exchanger to a temperature at which the reaction is initiated, 
and this feed gas is then passed uniformly in all radial directions from 
the inside to the outside of the catalyst bed 6. To reach the bed 6, the 
feed gas flows through at least one opening 30 formed at the lower end of 
the outer shell 5, then passes through the inner and outer annular gas 
passages 12a and 12b as described above and enters the catalyst bed 6 
through the inner catalyst retainer 7. 
The desired reaction takes place as the gas passes through the catalyst bed 
6 and contacts the catalyst, thereby generating a gaseous product. Most of 
the reaction heat generated by the exothermic reaction is absorbed by the 
coolant that flows through the tubes 15. After the reaction is completed 
and most of the reaction heat has been absorbed by the coolant, the 
product gas, which is still quite high in temperature, flows through the 
outer catalyst retainer 8, thence via the perforate wall 11b into gas 
passage 13a. The gas passage 13a communicates with the tubes 28 of the 
heat exchanger 4 via the annular space between the outer shell 5 and the 
pipe 25 in the lower part of the heat exchanger 4. The high temperature 
product gas flows upwardly through the tubes 28, is cooled by heat 
exchange with the feed gas on the shell side of the heat exchanger 4, and 
is discharged into a chamber at the upper end of the heat exchanger above 
the plate 26. The product gas is then fed through a plurality of 
connecting pipes 33 to the gas passage 13b. In the assage 13b, the product 
gas passes downwardly along the inner surface of the outer pressure vessel 
1 and passes downwardly to a lower chamber located between the bottom 
cover 3 and the outer partition wall 10b. The product gas is then finally 
discharged outside of the reactor through the product gas outlet 34. 
By means of the foregoing interior reactor structure and the 
above-described gas passages, the pressure inside the outer shell 5 of the 
heat exchanger 4 can be kept higher than the pressure outside of the outer 
shell of the heat exchanger. Further, the gas pressure within the inner 
catalyst retainer 7 is higher than the pressure outwardly thereof, and a 
similar pressure relationship can be set up for the outer catalyst 
retainer 8 and the partition walls 10a, 10b. 
In accordance with this reactor pressure distribution, the partition walls 
7, 8 of the reactor can be designed based on tensile strength which is 
used for strength calculations when the inner pressure of a vessel is 
higher than the outer pressure thereof, rather than basing it on buckling 
strength or collapsing strength which is used when the outer pressure of a 
vessel is higher than its inner pressure. This allows thinner plates to be 
used as the reactor partition walls 7, 8 when these partitions are made 
from ordinary platelike materials. 
In FIG. 1, the secondary gas feed pipe 25 which extends upwardly from the 
central portion of the bottom of the reactor is used as an inlet for a 
reducing gas for reduction of the catalyst or as an inlet for a high 
temperature gas for preheating the catalyst bed during start-up of the 
reactor. In normal operation, it can also be used as an inlet for a low 
temperature feed gas to effect fine adjustment of the temperature of the 
feed gas that is preheated in the heat exchanger 4, or it can be used as 
an inlet for an inert gas or product gas adjusted to a desired temperature 
for use as a diluent gas in cases in which the reaction occurring in the 
catalyst bed is extremely vigorous. A closeable outlet 35 is provided on 
the bottom cover 3 as an exhaust port for removing spent catalyst. The 
catalyst is charged into the reactor through an inlet 36 formed on the top 
cover 2 of the reactor and is packed around the tubes 15 comprising the 
coolant passage structure. The mounting structure for the coolant 
passages, heat exchanger, catalyst retainers, partition walls 10a and 10b 
and parts associated therewith can be removed, in this order, from the 
outer pressure vessel 1 after the catalyst is discharged through the 
catalyst outlet port 35 and the top cover 2 has been removed. This 
facilitates maintenance and inspection of the reactor of the present 
invention considerably as compared with prior art reactors. 
FIG. 6 corresponds to FIG. 2 of Ser. No. 530,298 and it is presented to 
schematically illustrate an apparatus for flowing feed gas in series 
through a plurality of sector-shaped catalyst bed sections. Ser. No. 
530,298 discloses many additional embodiments of apparatus of this type 
and reference should be made thereto for any additional details. The 
hereinafter described embodiment of FIGS. 2 and 3 is based on the 
operating principles of the apparatus illustrated in FIG. 6. 
Inside the outer shell 101, there are provided a gas-permeable, outer, 
catalyst retainer 104 and an inner catalyst retainer 105 within the outer 
catalyst retainer 104, both retainers 104 and 105 being coaxial with each 
other and with the central axis of the outer shell. The outer annular 
space defined between the outer shell 101, the outer catalyst retainer 104 
and the bottom and top walls provides an outer gas flow passage. The outer 
gas flow passage 106 is divided by outer dividing walls 115 into passages 
106A and 106B. Inside the inner catalyst retainer 105, there are provided 
an inner circular barrier wall 108, which could be the shell of a 
shell-and-tube heat exchanger, and inner radially extending dividing walls 
116 which extend radially outwardly from the circular barrier wall 108 to 
the inner catalyst retainer 105. The space defined by the inner catalyst 
retainer 105, barrier wall 108 and bottom and top walls is thereby divided 
into a plurality of inner gas flow passages 107 and 107A and 107B by the 
dividing walls 116. The space defined by the outer catalyst retainer 104, 
inner catalyst retainer 105 and bottom and top walls is divided by 
radially extending vertical partition walls 109 into a desired number of 
chambers (4 in the illustrated example) 110, 111, 112 and 113, which are 
respectively sectorial in horizontal cross section, that is, in the shapes 
of segments of an annulus. 
In the example illustrated in FIG. 6, all of these chambers 110, 111, 112 
and 113 are used as reaction chambers and, in each of them, 
heat-exchanging tubes 114 are arranged and a catalyst is packed. In each 
of these chambers, gas is caused to flow in a radial direction. It is 
necessary to determine, in advance, the order of the reaction chambers, 
that is, the order in which the gas is caused to pass in series through 
the reaction chambers 110, 111, 112 and 113, and the direction of the flow 
of the gas in each reaction chamber. 
In the illustrated example, the reaction chambers are used in the order of 
(1) radially outward flow in the first reaction chamber 110, (2) radially 
inward flow in the second reaction chamber 111, (3) radially outward flow 
in the third reaction chamber 112, and (4) radially inward flow in the 
fourth reaction chamber 113. By causing the gas in the first chamber 110 
to flow radially outwardly from the inner gas flow passage 107A to the 
outer gas flow passage 106A, the orders of gas flow through the remaining 
reaction chambers and the direction of flow of the gas in each reaction 
chamber are determined. In each reaction chamber, heat-exchanging tubes 
114 are arranged in a number of partially circular groups, which groups 
are concentric with the common central axis of the shell 101 and the 
catalyst retainers 104 and 105. That is, the heat-exchanger tubes of each 
group are vertically extended in each reaction chamber and equidistantly 
arranged in the circumferential direction on each of a plurality of 
horizontal concentric arcs each of which has a different, desired distance 
from the coxmon axis of the reaction chamber, and length of which depends 
on the arcuate extent of the reaction chamber in which that group of tubes 
is disposed, for example, 90.degree. in the reactor of FIG. 6. 
Furthermore, in order to control the order of flow of the gas through the 
reaction chambers, there are provided the radially outwardly extending 
outer dividing walls 115 which divide the outer gas flow space into outer 
gas flow passages 106A and 106B. The outer dividing walls 115 are radially 
aligned with and define extensions of the partition wall 109 between the 
first and fourth reaction chambers 110, 113 and the partition wall 109 
between the second and third reaction chambers 111, 112. The radially 
extending inner dividing walls 116 that define the inner gas flow passages 
107, 107A and 107B are respectively located on (1) extensions of the 
partition wall 109 between the first and second reaction chambers 110, 
111, (2) the partition wall 109 between the third and fourth reaction 
chambers 112, 113 and (3) the partition wall 109 between the fourth and 
first reaction chambers 113, 110. In accordance with the gas flow path 
established as described above, a feed gas inlet and a reaction product 
gas outlet are respectively provided at the upper or lower ends of the 
inner gas flow passages 107A and 107B, respectively, said inlet being in 
communication with the first reaction chamber 110, and said outlet being 
in communication with the fourth reaction chamber 113. 
FIGS. 2 and 3 illustrate a further embodiment of the reactor of the present 
invention. In this second embodiment, the catalyst bed 6 is subdivided 
into four catalyst beds 6a, 6b, 6c and 6d of equal sectorial size by 
vertical partitions walls which extend radially from the inner catalyst 
retainer to the outer catalyst retainer at 90.degree. angles to each 
other. Each of the separate catalyst beds defined by the partition walls 
constitutes an independent cooling zone which is cooled by a cooling 
passage structure as described above in connection with FIG. 1. 
FIG. 2 shows a vertical section of the reactor of this example, and FIG. 3 
shows a horizontal cross section of this reactor. As shown in FIG. 3, the 
four catalyst beds 6a-6d are defined by the radially extending partition 
walls 37a, 37b, 37c and 37d. FIG. 3 illustrates horizontal cross sections 
through each catalyst bed at different vertical positions. The horizontal 
cross section of the first catalyst bed 6a is taken at height A shown in 
FIG. 2. The second catalyst bed 6b is shown at height B in FIG. 2 with the 
coolant passage structure and top cover 38 being omitted. The third 
catalyst bed 6c is shown at height C in FIG. 2 and showing the coolant 
passage structure and top cover 38 thereof. The fourth catalyst bed 6d, 
including the coolant passage structure associated therewith but without 
the top cover 38, is shown at height B in FIG. 2. 
The reactor of this embodiment is essentially different from the reactor of 
FIG. 1 in that the feed gas flows through the catalyst beds in series from 
the first to the fourth catalyst beds 6a-6d, and flows radially through 
each catalyst bed. Although there are various possible paths by which the 
feed gas can be flowed through the four catalyst beds in series, in this 
embodiment the feed gas flows radially outwardly in the first catalyst bed 
6a, radially inwardly in the second catalyst bed 6b, radially outwardly in 
the third catalyst bed 6c and radially inwardly in the fourth catalyst bed 
6d. 
A heat exchanger 4 is centrally installed coaxially with the central 
vertical axis of the reactor in the same manner as described in connection 
with FIG. 1. A cylindrical gas-permeable inner catalyst retainer 7 is 
coaxial with the heat exchanger 4 and outwardly spaced therefrom. The 
annular space 12 is subdivided by four radially, vertically extending 
partition walls into four gas passages 12a, 12b, 12c and 12d associated 
with the catalyst beds 6a-6d, respectively. The inner catalyst retainer 7 
includes a central perforated cylindrical portion and a pair of 
cylindrical nonperforated end portions disposed vertically above and below 
the perforated portion as shown in FIG. 2. An annular, horizontal closure 
plate 9 is provided between the cylindrical outer shell 5 of the heat 
exchanger 4 and the top end of the inner catalyst retainer 7, and the 
lower end of the catalyst retainer 7 is mounted on the inner surface of 
the partition wall 10a, the foregoing connections being gas-tight. The 
annular horizontal closure plate 9 also serves as a flange for mounting a 
top cover 38 over each of the catalyst beds 6. 
The cylindrical gas-permeable outer catalyst retainer 8 is installed 
radially outwardly of the inner retainer 7 so that the top edge of the 
outer retainer 8 is at the same height as the top edge of the inner 
retainer 7. Like the inner retainer 7, the outer retainer 8 includes a 
central cylindrical perforated portion and a pair of cylindrical 
nonperforated end portions above and below the central perforated portion. 
The upper end of the outer retainer 8 is joined to the flange 14 which is 
in the same plane as the closure plate 9, and the lower portion of the 
outer retainer 8 comprises part of the partition wall 10a which separates 
the bottom cover 3 from the catalyst bed 6. 
The flange 14 has a plurality of vertically extending spaced-apart gas 
passage holes 39 around its circumference. The partition walls 37a-37d 
which define the catalyst beds 6a-6d extend radially between the inner and 
outer catalyst retainers 7, 8 in the positions shown in FIG. 3. The upper 
ends of the partition walls 37a-37d are connected to four corresponding 
horizontal, radially extending flange portions 14a which are integral with 
the closure plate 9 and the annular flange 14. The lower ends of the 
partition walls 37a-37d are joined in a gas-tight fashion to the partition 
wall 10a. 
The cylindrical outer partition wall 10b disposed radially outwardly of the 
perforated portion of the outer catalyst retainer 8 defines therewith an 
annular cylindrical space 40. The upper and lower ends of the partition 
wall 10b are joined gas-tight to the foregoing upper and lower 
nonperforated portions of the outer catalyst retainer 8. The outer surface 
of the partition wall 10b is covered with a layer of heat insulating 
material 43. The cylindrical gas passages 12 and 40 are used to allow the 
reactant gas to flow in the circumferential direction inside the inner 
catalyst retainer and in the circumferential direction outside the outer 
catalyst retainer, respectively. For example, the gas passage 12 allows 
reactant gas to flow from the second catalyst bed 6b to the third catalyst 
bed 6c, and the gas passage 40 allows the gas to flow from the first 
catalyst bed 6a to the second catalyst bed 6b. Each of the gas passages 
comprising one quarter of the original unsubdivided passages 12 and 40 are 
designated 12a-12d and 40a-40d respectively for the passages associated 
with the respective catalyst beds 6a-6d. 
To allow the gas to flow through the catalyst beds alternately radially 
inwardly and outwardly and also to allow it to flow uniformly in both 
circumferential and vertical directions in each catalyst bed, the spaces 
12 and 40 in this embodiment are designed as follows. First, a gas passage 
inner partition wall 41a, which is an extension of the partition wall 37a, 
is provided between the gas passages 12a and 12b to prevent direct gas 
flow therebetween. A perforated outer plate 11a, which is an extension of 
the partition wall 37a, is provided between the gas passages 40a and 40b 
to allow flow therebetween. A gas passage partition wall 41b, which is an 
extension of the partition wall 37b, is provided between the gas passages 
40b and 40c to prevent direct gas flow therebetween. A perforated inner 
plate 11b, which is an extension of the partition wall 37b, is provided 
between the gas passages 12b and 12c to allow gas flow therebetween. A gas 
passage inner partition wall 41c, which is an extension of the partition 
wall 37c, is provided between the gas passages 12c and 12d to prevent 
direct gas flow therebetween. A perforated outer plate 11c, which is an 
extension of the partition wall 37c, is provided between the gas passages 
40c and 40d to allow gas flow therebetween. A gas passage inner partition 
wall 41d, provided on the extension of the partition wall 37d, prevents 
direct gas flow between the passages 12d and 12a. Finally, a gas passage 
outer partition wall 41e provided on the extension of the partition wall 
37d cuts off gas flow between the gas passages 40d and 40a. By means of 
the partition walls 41a-41e and plates 11a-11c, the gas flow follows the 
path indicated by the arrows in FIG. 3 and passes in succession through 
the catalyst beds 6 a, 6b, 6c and 6d. 
The coolant passage structure of this embodiment is substantially the same 
as shown in FIG. 1, and detailed description thereof will be omitted. Each 
coolant passage structure associated with each cooling zone, namely the 
sectorial spaces which contain the catalyst beds 6a-6d, can be removed 
upwardly from each of the catalyst beds 6a-6d after removal of the top 
cover 2 and catalyst bed cover 38. The heat exchanger 4 is of the 
shell-and-tube type as in FIG. 1, and is designed so that the fresh feed 
gas can be flowed downwardly through the tubes 28. The feed gas fed into 
the reactor through the main inlet 24 enters the tops of a large number of 
tubes 28 in the heat exchanger 4 and is preheated by heat exchange with 
the high temperature product gas that flows from the fourth (final) 
catalyst bed 6d, through the opening 32 and thence through the shell side 
of the heat exchanger 4. The thus-preheated feed gas is discharged into 
the gas passage 12a through an opening 30 provided in the outer shell 5 
positioned below the lower annular plate 27 of the heat exchanger 4. The 
gas passes radially outwardly from the gas passage 12a through the inner 
catalyst retainer 7 and first catalyst bed 6a to the gas passage 40a. The 
catalytic reaction proceeds partially during the passage of the reactant 
gas through the first catalyst bed 6a. 
From the gas passage 40a, the partially reacted gas enters the gas passage 
40b through the perforated resistance plate 11a. Thereafter, it passes 
radially inwardly through the second catalyst bed 6b to the gas passage 
12b. The reaction proceeds further during the passage of the gas through 
the second catalyst bed 6b. The gas then passes from the gas passage 12b 
through the perforated resistance plate 11b into the gas passage 12c. 
Thereafter, the gas stream passes radially outwardly through the third 
catalyst bed 6c to the gas passage 40c, and the reaction proceeds further 
as the gas passes through the third catalyst bed 6c. The further reacted 
gas then passes from the gas passage 40c through the perforated resistance 
plate 11c to the gas passage 40d. Thereafter, it passes radially inwardly 
through the fourth catalyst bed 6d to the gas passage 12d. The reaction 
proceeds to completion as the reactant gas passes through the fourth 
catalyst bed. 
The resulting high temperature product gas passes into the gas passage 12d 
and flows through an opening 32 into the shell side of the heat exchanger 
4 near the bottom thereof. The product gas then flows upwardly in a zig 
zag fashion past the baffles 29 and is cooled by heat exchange with the 
feed gas flowing through the cooling tubes 28. The product gas then flows 
into an upper chamber of the reactor through at least one opening 31 near 
the upper end of the heat exchanger 4 in the outer shell 5 thereof. The 
thus-cooled product gas in the upper chamber flows downwardly through the 
holes 39 in the annular flange 14, through the cylindrical gas passage 13 
along the inner surface of the outer pressure vessel 1 and finally is 
discharged through the gas outlet 34 at the bottom of the reactor vessel 
1. 
In the foregoing embodiment the reaction heat generated by the progress of 
the reaction during the passage of the gas through each catalyst bed is 
absorbed by the coolant in the same manner as in the embodiment of FIG. 1. 
The linear gas velocity in each catalyst bed is increased by dividing a 
single cylindrical catalyst bed, as in FIG. 1, into at least two 
horizontally sectorial catalyst beds through which the reactant gas flows 
radially in series. In this case, the same amount of gas is brought into 
contact with the same amount of catalyst to cause the reaction, as in the 
case of a single cylindrical catalyst bed. The heat transfer resistance 
from the reactant gas to the cooling tubes 15 in each catalyst bed is 
decreased, and the overall heat transfer coefficient in the absorption of 
the reaction heat by the cooling tubes is increased, so that the number of 
cooling tubes as well as the ratio of the volume occupied by cooling tubes 
to the total catalyst bed volume can be decreased on the whole as compared 
to the reactor shown in FIG. 1. 
FIG. 4 illustrates an alternative embodiment of a heat exchanger 4 which 
may be used in the present invention as described in FIGS. 1-3. The heat 
exchanger 4 of FIG. 4 is a shell and tube type heat exchanger, but differs 
from the one shown in FIGS. 1 and 2 in that each tube 28 is of helical 
shape. The helical tubes 28 are arranged on a multiplicity of concentric 
circles of different diameters. Small diameter spacer rods 42 are set at 
desired intervals in the circumferential direction between radially 
adjacent spiral tubes, thereby maintaining radially adjacent spiral tubes 
at predetermined distances from each other and securing a gas flow space 
for the reactant gas flowing on the shell side. The shell and tube heat 
exchanger having such spiral tubes has a large heat transfer area in a 
relatively small shell space, and is thus preferred for use as a heat 
exchanger in the present invention. 
A first advantage of the present invention is that, in a reactor which 
contains a gas containing a large amount of hydrogen at relatively high 
temperatures and pressures, carbon steel can be used as the material for 
fabricating the outer pressure vessel 1 because the outer pressure vessel 
1 is maintained at a relatively low temperature. Moreover, cylindrical and 
radial partition walls made of relatively thin material can be used in the 
reactor according to the invention. Since the partition walls used inside 
the outer pressure vessel unavoidably come into contact with gas 
containing a large volume of hydrogen at high temperatures and pressures, 
it is necessary to use stainless steel in fabricating the partition walls 
in order to prevent hydrogen embrittlement. However, the reactor of the 
present invention can be constructed at less cost than conventional 
reactors because less stainless steel is needed. This advantage is 
especially great when a very large reactor must be constructed. A specific 
exemplary design will be described below in view of this advantage. 
A second advantage of the present invention is that the maintenance and 
inspection of the reactor is reduced in complexity because both the 
coolant feed pipe and the coolant vapor discharge pipe pass through the 
top cover of the reactor, thereby enabling the coolant passage structure 
to be removed upwardly. This allows maintenance, inspection and repair of 
the reactor to be remarkably facilitated. 
A third advantage of the present invention is that carbon steel can 
frequently be used to fabricate the coolant passage structure in spite of 
the hydrogen embrittlement problem with such steels. More specifically, 
boiling coolant passes through the coolant passage structure under 
pressure, but the coolant temperature is far lower than that of the gas 
flowing through the catalyst bed. Moreover, the heat transfer resistance 
between the metal which constitutes the cooling passage structure and the 
coolant is far less than the heat transfer resistance between the metal 
and the gas flowing through the catalyst bed, so that the surface 
temperature of the cooling tubes is slightly higher than the coolant 
temperature but far lower than the gas temperature. As a result, the 
coolant passage structure may frequently be made from carbon steel, even 
when stainless steel is required for the partition walls and the like as 
described above. 
When carbon steel is used in the coolant passage structure, it is important 
to keep the surface of the coolant passage structure at a temperature of 
350.degree. C. or lower, preferably 330.degree. C. or lower. The lower 
limit of the coolant passage structure surface temperature is about 
100.degree. C., if the coolant vapor generated is to be effectively used. 
At a surface temperature of 350.degree. C. or lower, the formation of iron 
nitride on the surface of the coolant passage structure made from carbon 
steel, and the resulting embrittlement, can be avoided. Thus, the reactor 
can be safely operated even when ammonia is produced using the reactor 
according to the present invention from a gaseous mixture consisting of 
hydrogen and nitrogen as gaseous starting materials. 
A number of embodiments other than the ones illustrated in FIGS. 1-4 are as 
follows. In FIGS. 2 and 3, the catalyst bed is divided into four equal 
catalyst beds by four radially extending vertical partition walls. 
However, there are many ways to divide a cylindrical catalyst bed. For 
example, such a catalyst bed can be divided into two or three beds instead 
of four beds, or can be divided into beds which are different in size from 
each other. The optimum catalyst bed arrangement varies with the type of 
reaction, performance of the catalyst, size of the reactor and similar 
factors, and must be determined in accordance with these factors. 
Generally, however, the reactor is preferably divided into from two to 
four catalyst beds. If the number of catalyst beds is excessively large, 
the structure of the reactor becomes corresponding excessively complex. It 
is also preferable to flow the reactant gas in series through at least two 
divided catalyst beds, because the aforementioned advantages of serial 
flow through divided catalyst beds are not achieved by flowing it through 
two such catalyst beds in parallel. It is occasionally preferable to flow 
the gas in parallel through some of the divided catalyst beds, and then 
flow the gas in series through the remainder of the catalyst beds. 
It is sometimes desirable to not install a coolant passage structure in the 
catalyst bed through which the reactant gas flows first, when multiple 
catalyst beds are being employed. More particularly, if the reaction has 
an optimum temperature substantially equal to the heat generated by the 
reaction in the adiabatic catalyst bed, then the gas temperature can be 
increased to the desired temperature by omitting cooling tubes from the 
catalyst bed or using a smaller number of cooling tubes in the first 
catalyst bed. This arrangement can reduce or eliminate the need to preheat 
the gaseous raw materials. 
In the examples described above, the product gas cooled by undergoing heat 
exchange with the gaseous raw materials flows downwardly along the inner 
surface of the outer pressure vessel of the reactor. However, it is 
possible to flow the product gas upwardly along the inner surface of the 
outer pressure vessel by changing the arrangement of the partition walls 
in the reactor. Such a modification can be readily carried out by those 
skilled in the art. 
In the distributing manifolds for the liquid coolant, a structure utilizing 
an annular plate as used in the heat exchanger 4 can be used to split the 
coolant into each of the cooling tubes, and may further be used in the 
collecting manifold for collecting the coolant vapor vaporized by 
absorption of reaction heat and feeding it to the coolant vapor discharge 
pipe. However, when an annular plate structure is used in both liquid 
coolant manifolds, it is necessary to use an annular plate having a 
through hole for passage of the granular catalyst when the catalyst is 
charged into or discharged from the reactor as described in U.S. patent 
application Ser. No. 530,298, hereinabove incorporated by reference. 
Moreover, there is frequently a large difference between the pressure of 
the reactant gas and the pressure of the coolant, so that it is necessary 
to use a thick plate to fabricate the annular plate in the coolant 
structure. Accordingly, it is generally preferred to design the manifolds 
utilizing tubular members as illustrated in FIGS. 1-3. The above mentioned 
annular plate may be called also as a tube sheet. 
It is further possible to discharge only coolant vapor that does not 
contain coolant liquid through the discharge pipe 23. It is advantageous 
to use an ordinary shell-and-tube type heat exchanger having a tube-plate 
structure as the heat exchanger for exchanging heat between the product 
gas and the fresh feed gas, in view of the relatively small pressure 
difference between the shell side and the tube side. Among such shell and 
tube heat exchangers, those in which the tubes are arranged spirally 
within the shell, as described above, are preferred since these heat 
exchangers have a large heat transfer area and a comparatively small shell 
volume. 
The coolant used in the present invention should have a high thermal 
decomposition temperature, should be resistant to oxidation, and should be 
liquid at room temperature. Liquids such as water, a mixture of diphenyl 
and diphenyl oxide, alkylbenzene, alkylnaphthalene and the like are 
preferred. In using these materials as the coolant, the cooling system is 
maintained at a selected pressure so that the coolant will boil at the 
desired temperature. Changing the boiling pressure of the coolant in each 
of the coolant passage structures changes the temperature in the catalyst 
bed in which the coolant passage structure is installed. Moreover, in the 
reactor according to the present invention, the optimum temperature 
distribution for effecting the desired reaction can be established in the 
direction of flow of the reactant gas through each catalyst bed by 
arranging the cooling tubes in a particular formation in each catalyst 
bed. As a result, when the specific reaction, composition of the feed gas, 
reaction pressure and similar factors have been determined, a minimum size 
reactor can be designed according to the invention to produce the product. 
The reactor of the present invention can be made smaller than prior art 
reactors, yet can produce the same amount of gaseous product per unit time 
as larger prior art reactors. 
In the catalyst beds of the reactor of this invention, it is preferred to 
pack a noncatalytic granular packing material having a slightly smaller 
particle size than the catalyst, such as alumina granules, below the upper 
face of the secondary distributing manifold 16 and above the lower face of 
the primary collecting manifold 19 in order to conserve the catalyst. 
Further, a heat insulating material is effectively attached on the outer 
surface of the partition walls nearest the outer pressure vessel in order 
to lower the temperature of the outer pressure vessel. However, if a 
noncatalytic granular packing material is packed in the lower and upper 
sections of each catalyst bed as described above, the use of a heat 
insulating layer on the outer surface of the bottom and uppermost parts of 
the partition wall nearest the outer pressure vessel can be omitted, as 
shown in FIG. 2. 
The reactor of this invention is excellent for effecting reactions wherein 
a feed gas containing a large amount of hydrogen is contacted with a solid 
catalyst under relatively high gas pressures, such as the preparation of 
ammonia from a gaseous mixture of hydrogen and nitrogen, the production of 
lower and middle aliphatic monohydric alcohols such as methanol, ethanol, 
propanol, butanol and the like and mixtures thereof from a gaseous mixture 
of hydrogen and carbon monoxide and/or carbon dioxide, or the production 
of aliphatic saturated hydrocarbons containing 1 to 10 carbon atoms from 
the same gaseous mixture as used to prepare the foregoing alcohols, and 
the production of aliphatic saturated hydrocarbons by the hydrogenation of 
lower and medium olefins containing 1 to 10 carbon atoms. 
EXAMPLE 
A reactor according to the invention was used to conduct a reaction wherein 
a gaseous mixture containing 75 mol % hydrogen and 25 mol % nitrogen was 
contacted with a solid catalyst at a pressure of 150 kg/cm.sup.2 G to 
produce ammonia. FIG. 5 illustrates a process flow chart for this 
synthetic process. 
In FIG. 5, a reactor 51 is the same reactor as described in FIG. 1 above, 
except that the reactor 51 is equipped with a heat exchanger as 
illustrated in FIG. 4. A feed gas is fed through a pipe 67 into the main 
feed gas inlet 24 of the reactor 51. Product gas containing gaseous 
ammonia resulting from the catalytic reaction occurring in the reactor, as 
described above, is discharged through the gas outlet 34 and passes 
through a pipe 59 to a water cooler 52 wherein part of the produced 
ammonia is condensed and liquefied. The remaining gas is then fed through 
a pipe 60 into a low temperature heat exchanger 53 to be cooled by heat 
exchange with liquid ammonia therein. The gas further cooled by the low 
temperature heat exchanger 53 condenses and liquefies most of the 
remaining ammonia, and the gas-liquid mixture is then fed through a pipe 
61 to a separator 54 wherein the condensed liquid ammonia is separated and 
discharged through a pipe 62 as a product. The uncondensed, unreacted gas 
is fed through a pipe 63 to a compressor 55 wherein it is pressurized 
together with fresh feed gas supplied through a pipe 64, and the resulting 
mixture is recycled to the reactor 51 through the pipes 66, 67. 
During start-up of the reactor, the greater part of the gas from the 
circulating compressor 55 passing out of the pipe 66 is introduced into a 
heater 56 wherein it is heated to a predetermined temperature by 
combustion of a fuel supplied to a pipe 68. Thereafter, the thus-preheated 
gas is fed through a pipe 65 into the reactor at the secondary inlet 25 
thereof, and passes out of the outlet 34 to create a gas circulation 
through the pipes 59-63 as described above. 
After the catalyst bed has reached a predetermined temperature, the flow of 
feed gas is rechanneled from the secondary inlet 25 to the main inlet 24 
and the reactor is brought to its normal state of operation. 
Water is used as the coolant in this example. Pressurized water is boiled 
when it absorbs reaction heat in the cooling tubes 15 and passes out of 
the reactor as a vapor-liquid mixture through the pipe 23 and is fed 
through a pipe 69 to a separator 58 wherein steam and liquid water are 
separated. The steam is discharged through a pipe 71 to be conducted 
elsewhere for a desired purpose. The unvaporized water separated in the 
separator 58 is recirculated to the coolant feed pipe 22 through a pipe 70 
by means of a pump 57. Circulation of the unvaporized water can also be 
carried out by gravity feed without use of the pump 57. Fresh boiler feed 
water in an amount equivalent to the steam discharged through the pipe 71 
is supplied through a pipe 72 and combined with the unvaporized water from 
the separator 58. 
Both the outer pressure vessel and the coolant passage structure of the 
reactor in this example are made of carbon steel. The partition walls and 
other parts of the reactor are made of stainless steel. Requirements such 
as gas volume and dimensions such as the size of the reactor according to 
this example are as follows: 
______________________________________ 
Inner diameter of the cylindrical central 
3,650 mm 
portion of the outer pressure vessel 
Length of the cylindrical central portion 
17,400 mm 
of the outer pressure vessel 
Inner diameter of inner catalyst retainer 
1,730 mm 
Outer diameter of outer catalyst retainer 
3,350 mm 
Packing height of catalyst 
15,000 mm 
Outer diameter of each cooling tube 
38 mm 
Total number of cooling tubes 
500 
Number of cooling zones 6 
Heat transfer area of gas heat exchanger 
4,000 m.sup.2 
Feed gas volume at the inlet of heat 
500,000 Nm.sup.3 /hr 
exchanger 
Feed gas temperature at the inlet of the 
50.degree. C. 
heat exchanger 
Feed gas temperature at the inlet of the 
400.degree. C. 
catalyst bed 
Product gas temperature at the outlet of 
500.degree. C. 
the catalyst bed 
Product gas temperature at the outlet of 
70.degree. C. 
the heat exchanger 
Pressure of cooling water in cooling 
120 kg/cm.sup.2 G 
tubes 
Amount of liquid ammonia produced 
41,600 kg/hr 
Pressure of steam generated 
120 kg/cm.sup.2 G 
Amount of steam generated 
80,000 kg/hr 
______________________________________ 
According to another design, the partition walls in the reactor were 
arranged so that cool feed gas entering the reactor is flowed along the 
inner surface of the outer pressure vessel and then into the heat 
exchanger to be preheated by the effluent gas from the catalyst bed. In 
this case, the partition walls, catalyst retainers and other parts made of 
stainless steel were about 40 metric tons larger in total weight than the 
corresponding parts in the reactor of this example of the invention. All 
of the partition walls, catalyst retainers and other parts are made of 
stainless steel in this comparative reactor so that the cost required to 
fabricate the reactor is considerably greater than the cost of the reactor 
according to the present invention.