The present invention envisages a cooling device for a carbon dioxide methanation catalytic reactor. It applies, in particular, to methanation reactors.
STATE OF THE ART
The methanation reaction is a highly exothermic reaction carried out using catalysts. The efficiency of this reaction is dependent on thermal control of the reactor and optimization of the reactor’s energy recovery.
There are two types of reactors:
- fixed-bed reactors and
- fluidized-bed reactors.
Fixed-bed reactors are simple to design and build but, when they don’t include an internal cooling system, the heat released by the exothermic reactions results in a rise in temperature, with two consequences: a shift in the chemical balances leading to a drop in conversion efficiency, and a risk of catalyst deactivation through high-temperature sintering during the catalyst’s active phase.
The most common methanation reactors are catalytic fixed-bed reactors with heat exchangers between the reactors. However, these reactors do not allow the reaction temperature to be controlled gradually. This drawback results in several reaction stages in series being necessary to be sure of a satisfactory conversion, and therefore very high costs.
In other systems, exchange reactors incorporating cooling for fixed-bed reactors use a tubular or plate heat exchanger type of configuration. In these reactors, the catalyst is arranged in vertical tubes and a heat transfer fluid, eg water, thermal oil or water vapor, is used for cooling via the outside of the tubes, also called “shell side”. These systems have the disadvantage of requiring the construction of a shell that has to withstand very high pressures. The cost of constructing this shell rises significantly when the reactor’s size is increased, or when the reactor requires a higher temperature, which has a significant negative impact on the use of these systems.
In other systems, the bed is cooled by coils arranged either horizontally or vertically. The drawbacks of these coils are detailed at the end of the following section.

The advantage of fluidized-bed methanation reactors is that they have a very uniform temperature, enabling good control of the chemical conversion by removing the heat produced by the reactions, which can only be controlled if a cooling system is incorporated.
In the case of catalytic fluidized-bed methanation reactors, there are systems utilizing a built-in cooling device using the phase change of water to regulate the temperature within the reactor. These systems are based on the use of coils into which the cooling water is introduced and the phase change occurring in the coils.
Some systems utilize tubes in a bundle with no particular orientation to cool two fluidized-bed reactors operating at different pressures.
The use of coils or bundles for phase change cooling poses stratification problems between the liquid phase and the vapor phase:
- when the coils or bundles are not sufficiently inclined relative to the horizontal; or
- when the coils or bundles have loops at their highest point.
In both cases, this interferes with the proper cooling of the reactor, leads to the premature deactivation of the catalyst, and can cause early aging of the cooling system. In these two configurations, one way of reducing the risk of the cooling system malfunctioning is to insert a circulating pump in the cooling device. This equipment increases the capital expenditure and operating costs of the system without providing any guarantee of optimum operation.
The following documents are also known:
- US 4 539 016, published September 3, 1985;
- EP 0 081 948, published June 22, 1983; and
- US 2 394 680, published February 12, 1946.
Document US 4 539 016 relates to the methanation field, and describes a system technically for regulating pressure using a cooling principle utilizing the water–vapor phase change.
However, the device described by US 4 539 016 applies exclusively to the methanation of CO (carbon monoxide).

The description of document US 4 539 016 relates to adjusting and maintaining constant the temperature in a methanation catalytic fluidized bed of a CO – H2 mixture. However, the description is contradictory:
- on the one hand, this document states that the temperature of the fluidized bed must be regulated to obtain the greatest possible methane conversion; and
- on the other hand, this must be done when as far as possible from the theoretical equilibrium temperature (1st column, lines 14–19).
This contradiction lies in the fact that the best conversion rate for the methane mixture to be obtained when the theoretical equilibrium temperature is reached.
In addition, this same document states (1st column, lines 25–31) that the gases can therefore be brought close to the theoretical heterogeneous gas equilibrium corresponding to the selected temperature.
In this document US 4 539 016, the temperature of the fluidized bed is regulated by regulating the pressure of the cooling liquid to a specific value determined and set independently of the temperature inside the methanation reactor.
This characteristic is a major drawback since, under industrial conditions, the flow rate and/or composition of the incoming gases vary, as does the amount of heat to be removed. Given the heat transfer laws, there is therefore a variation in the temperature of the catalytic bed despite the thermosiphon cooling system’s self-regulating tendency.
If the cooling system’s temperature is constant, the temperature gradient must be increased in order to transfer more heat, which results in the temperature in the fluidized bed rising. The larger the resistance to the heat transfer between the fluidized bed and the outer wall of each cooling tube, the truer this is.
Document EP 0 081 948 describes a reactor applicable to different catalytic processes, mainly the synthesis of methanol, but it also includes the methanation reaction of carbon oxides. This document describes the presence of a cooling bundle in the reactor, using phase changing to cool the reactor, and using the thermosiphon phenomenon for circulating the cooling water.
Document EP 0 081 948 has no regulation of the temperature in the reactor, especially when the flow rate or the proportions of the incoming gases change. This interferes with the process by modifying the chemical balances, which are highly

dependent on the temperature, and therefore the conversion rate, but also by causing overheating of the catalyst, which deactivates it.
Document US 2 394 680 describes a method comprising cooling with no phase change. Document US 2 394 680 proposes using different materials as a cooling fluid: molten metals, molten salts and, in its preferred embodiment, steam. This steam enters the exchanger in the saturated state and leaves in the superheated state. This means that, in the reactor, there is a very significant temperature gradient.
OBJECT OF THE INVENTION
The present invention aims to remedy all or part of these drawbacks. To this end, the present invention envisages a cooling device for a carbon dioxide methanation catalytic reactor, which comprises:
- at least one cooling tube passing through the reactor comprising:
- an inlet; and
- an outlet positioned at a higher altitude than the inlet;
- a water tank supplying the tube by gravity, comprising:
- a water outlet, connected to the inlet of the tube;
- a water and steam inlet connected to the outlet of the tube;
- a steam outlet; and
- a water supply inlet;

- a means for measuring the temperature in the catalytic reactor; and
- a means for controlling a water level in the water tank, configured to supply the water tank with water in order to maintain a predefined water level in the tank.
Using tubes for cooling through the liquid–gas phase change of the water, makes it possible to overcome stratification phenomena between water and steam that can be experienced in “horizontal” or “vertical” coils. The chosen configuration enables continuous removal of the steam produced and permanent circulation of the cooling water without using auxiliary pumps. Measuring the temperature in the catalytic reactor makes it possible to regulate the cooling system’s operating pressure, and therefore its temperature, which makes it possible to regulate the temperature in the reactor. Maintaining a minimum pressure requires a minimum

temperature in the cooling system, which prevents the formation of toxic compounds such as carbonyls.
To avoid the problem encountered by document US 4 539 016, the present invention provides for the installation of a regulation loop which takes the actual temperature in the fluidized bed into account, in order to act, if necessary, on the pressure of the cooling system, which modifies its temperature to allow the heat transfer between the fluidized bed and the cooling system to be raised or lowered, so as to keep the temperature of the fluidized bed constant, and therefore at the optimum conversion temperature.
In some embodiments, the regulation system is configured to control the opening or closing of the valve as a function of a difference between the temperature captured and a predefined limit value.
These embodiments allow the cooling device to be regulated such that the temperature measured inside rises or lowers to reach the predefined limit value.
In some embodiments, the device that is the subject of the present invention comprises a pressure sensor inside the cooling device, the regulation system being configured to control the opening or closing of the valve as a function of the temperature and the pressure captured.
These embodiments allow the pressure to be regulated inside the cooling device, the steam thus released being able to be reused by an external device.
In some embodiments, at least one of the tubes is rectilinear and passes through the reactor vertically, each rectilinear tube being configured such that the water circulating in said tube is partially vaporized during the passage in the catalytic reactor.
These embodiments make it possible to overcome the stratification phenomena between water and steam that can be experienced in “horizontal” or “vertical” coils.
In some embodiments, the device that is the subject of the present invention comprises a water distributer connected to each tube.
These embodiments make it possible to limit the number of apertures passing through the wall of the reactor, these apertures being combined to form a water inlet for the water distributer.

In some embodiments, the device that is the subject of the present invention comprises a steam collector connected to each tube.
These embodiments make it possible to limit the number of apertures passing through the wall of the reactor, these apertures being combined to form a water outlet for the water collector.
These embodiments make it possible to regulate the water’s circulation speed in the device.
In some embodiments, at least one tube is positioned near an inner wall of the reactor.
In some embodiments, at least one wall of the reactor is formed by at least one tube.
These embodiments make it possible to form the wall of the reactor from cooling tubes.
These embodiments can be utilized in the case of reactors operating at a pressure close to atmospheric pressure.
In some embodiments, at least one tube comprises fins.
These embodiments increase the area of contact between the tube and the inside of the catalytic reactor.
BRIEF DESCRIPTION OF THE FIGURES
Other advantages, aims and particular features of the invention will become apparent from the non-limiting description that follows of at least one particular embodiment of the device that is the subject of the present invention, with reference to drawings included in an appendix, wherein:
- figure 1 represents, schematically and in a side view, a first particular embodiment of the device that is the subject of the present invention;
- figure 2 represents, schematically and in a top view, a second particular embodiment of the device that is the subject of the present invention; and
- figure 3 represents, schematically and in a side view, a third particular embodiment of the device that is the subject of the present invention.
DESCRIPTION OF EXAMPLES OF REALIZATION OF THE INVENTION

The present description is given in a non-limiting way, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous way.
It is now noted that the figures are not to scale.
Figure 1, which is not to scale, shows a cross-section view of an embodiment of the device 10 that is the subject of the present invention. This cooling device 10 for a carbon dioxide methanation catalytic reactor 105 comprises:
- at least one cooling tube 110 passing through the reactor 105 comprising:
- an inlet 115; and
- an outlet 120 positioned at a higher altitude than the inlet 115;
- a water tank 125 supplying the tube 110 by gravity, comprising:
- a water outlet 130, connected to the inlet 115 of the tube 110;
- a water and steam inlet 135 connected to the outlet 120 of the tube 110;
- a steam outlet 140; and
- a water supply inlet 145;

- a means 150 for measuring the temperature in the catalytic reactor 105; and
- a means 155 for controlling a water level in the water tank 125, configured to supply the water tank 125 with water in order to maintain a predefined water level in the tank 125.
The catalytic reactor 105 is, for example, a cylinder comprising an inlet 107 for gas to be treated and an outlet 109 for treated gas. This reactor 105 is, for example, configured to perform a methanation reaction.
This catalytic reactor 105 is preferably a fluidized-bed reactor.
In some variants, such as the one shown in figure 3, the reactor 305 comprises two portions. A first portion is configured to receive a fluidized bed and has a smaller diameter in relation to the larger second portion. The first portion is an expansion area for the fluidized bed, while the second portion is a disengagement area.
This reactor 105, or 305, is traversed by at least one tube, 110 or 310 respectively. Each tube 110, or 310, is, for example, a channel, one wall of which is thermally conductive. One side of the wall is positioned in contact with the inside of the reactor 105, or 305, while the other side of the wall is positioned in contact with

water or water vapor, or a liquid water/water vapor mixture, circulating in the tube 110, or 310, depending on the operation of the device 10.
When the device 10 is in operation, a portion of the water contained in the tube 110 is transformed into steam by heat exchange between the reactor 105 and the wall of the tube 110, then between the wall of the tube 110 and the water contained in the tube 110. This steam moves vertically towards the top of the tube 110 with the water contained in the tube 110.
The water enters into the tube 110 by a water inlet 115, this inlet 115 being, for example, an aperture of the tube 110 connected to a water supply channel.
The water exits from the tube 110 by an outlet 120, this outlet 120 being, for example, an aperture of the tube 110 connected to a water and/or steam removal channel.
Each cooling tube 110 is preferably vertical or close to vertical with no 180° return bends. Preferably, only the water supply of each tube 110 and the collection of the water/steam mixture exiting from each tube 110 are carried out with non-vertical tubes, 170 and 175.
The device 10 also comprises a water tank 125. This water tank 125 is, for example, a sealed water container. This water tank 125 comprises four openings:
A first opening is a water outlet 130, connected to the inlet 115 of the tube 110. This water outlet 130 comprises a channel 132 for transporting water from the opening of the tank 125 through to the inlet 115 of the tube 110. The channel 132, referred to as “cold outlet”, is known to the person skilled in the art as “downcomer”. This channel 132 does not enter the reactor 105. Preferably, this first opening is positioned on a lower portion of the tank 125 when this tank 125 is fixed in position. In this way, gravity causes the outlet 130 to be supplied with water with no additional apparatus required.
A second opening is a water and steam inlet 135 connected to the outlet 120 of the tube 110. This inlet 135 comprises a channel 137 for transporting fluid from the outlet 120 of the tube 110 through to the opening of the tank 125. Preferably, this second opening is positioned on an upper portion of the tank 125 when this tank 125 is fixed in position. In this way, the water and the steam crossing the opening are separated by the effect of gravity and, if necessary, by means of conventional gas/liquid separation equipment such as:

- chicanes;
- cyclones; and/or
- mist eliminators.
A third opening is a steam outlet 140. This outlet 140 can comprise a steam transport channel supplying an external device or a flue equipped with a valve 160 as described below.
The steam produced by the evaporation of water in each tube 110 allows the heat from the exothermic reaction to be recovered, directly in the form of heat, in the form of matter, or in the form of energy via a turbine, for example. In general, an external device can be connected to the outlet 140 for steam from the tank 125.
In some preferred embodiments, the device 10 comprises a means 146 for measuring the water level in the tank 125. This measurement means 146 is, for example, an external level sensor connected to the tank 125 by taps.
The steam leaving the device is compensated for by inputting an equivalent quantity of feed water into the tank 125.
A fourth opening is a water supply inlet 145. This inlet 145 is connected to a water supply channel from an external water distribution network.
The tank 125 is positioned such that the surface of the water in the tank 125, when the water in this tank 125 is at the lowest point, this lowest point corresponds to the highest point of a tube 110 in the reactor 105. In this way, thanks to the channel 132 and regardless of the geometry of the channel 132 or tank 125, the presence of water in this tank 125 means there is water in at least one tube 110.
In some variants, The device 10 comprises a plurality of tanks 125, each supplied by and supplying one or more tubes 110.
Therefore, as can be understood, each tube 110 is continually supplied by a thermosiphon function that ensures a natural, self-regulating circulation of the cooling water. The more heat there is to be removed from the reactor 105, the more steam bubbles are formed, which increases the circulation flow rate of the water and steam and therefore the renewal of water in contact with the cooling tubes 110.
The means 150 for measuring the temperature inside the catalytic reactor 105 is, for example, a temperature sensor positioned inside the reactor 105 in the catalyst layer.

In some variants, the device 10 comprises a plurality of measurement means 150.
The control means 155 of the water tank 125 is, for example, a microcontroller-type electronic circuit, configured to command a control means (not shown) of the water inlet 145 to open or close the water inlet 145 as a function of a level measured by the means 146 for measuring the water level in the tank 125.
The regulators, 156 and 157, are, for example, grouped together in a microcontroller-type electronic circuit to control the opening or closing of the steam outlet 140 by the valve 160.
In some embodiments, such as that shown in figure 1, the device 10 comprises:
- a steam outlet valve 160 positioned on the outlet 140 for steam from the tank 125; and
- a system 158 for regulating the pressure inside the water tank as a function of the reactor temperature measured by the temperature measurement means, this regulation system 158 being configured to control the opening or closing of the valve as a function of the reactor temperature measured by the temperature measurement means 150 in order to increase or reduce the pressure in the tank.
The pressure regulation system 158 is made up of:
- a regulator 156, as described below;
- a regulator 157 as described below; and
- the valve 160.
The regulation system 158 is configured to control the opening or closing of the valve 160 as a function of the reactor temperature measured by the temperature measurement means 150 in order to increase or reduce the pressure in the tank 125. Thus, when the pressure in the tank 125 must be reduced, the valve 160 is opened so that steam escapes from the tank 125.
In some embodiments, such as that shown in figure 1, the regulation system 158 is configured to control the opening or closing of the valve 160 as a function of a difference between the temperature captured and a predefined limit value. In these embodiments, the pressure inside the circuit formed by the tank 125 and the tubes

110 is regulated so that the temperature inside the reactor 105 rises or falls to reach to predefined limit value.
In some embodiments, such as that shown in figure 1, the device 10 comprises a pressure sensor 165 inside the cooling device. This pressure sensor 165 is, for example, a pressure sensor positioned inside the circuit formed by the tank 125 and the tubes 110. The regulation system 158 is configured to control the opening or closing of the valve 160 as a function of the temperature and the pressure captured.
In some embodiments, such as that shown in figure 1, at least one of the tubes 110 is rectilinear and passes through the reactor 105 vertically, each rectilinear tube 110 being configured such that the water circulating in said tube 110 is partially vaporized during the passage in the catalytic reactor 105.
“Partially vaporized” means an order of magnitude of the order of five percent of vaporized water on output from each tube 110.
In some embodiments, such as that shown in figure 1, the device 10 comprises a water distributer 170 connected to each tube 110. This distributer 170 is, for example, a hollow channel, one opening of which is positioned outside the reactor 105 and, for each tube 110, one opening is positioned inside the reactor 105, the cavity of the channel linking the outside opening and each inside opening.
In some embodiments, such as that shown in figure 1, the device 10 comprises a steam collector 175 connected to each tube 110. This collector 175 is, for example, a hollow channel, one opening of which is positioned outside the reactor 105 and, for each tube 110, one opening is positioned inside the reactor 105, the cavity of the channel linking the outside opening and each inside opening.
Preferably, only the distributer 170 and/or the collector 175 are the only channels not being close to the vertical, unlike the tubes 110 and, where applicable, the channel 132, which are preferably vertical.
In some embodiments, such as that shown in figure 1, at least one tube 110 is positioned near an inner wall 185 of the reactor 105.
In some embodiments, such as that shown in figure 2, at least one wall 215 of the reactor 205 is formed by at least one tube 210.
In some embodiments, such as that shown in figure 1, at least one tube 110 comprises fins 190. Externally, at least one cooling tube 110 can be equipped with

fins over all or part of the length of the tube 110 to increase the contact surface with the catalyst and the gases. In addition, at least one cooling tube 110 can be grooved internally.
Figure 2 shows, schematically, in cross-section and a top view, a particular embodiment of a reactor 205 equipped with tubes 210 of a cooling device that is the subject of the present invention. In this embodiment, the tubes 210 are incorporated into the wall 215 of the reactor 205 and form all or part of it.
Figure 3 shows, schematically, in cross-section and a side view, a particular embodiment of a reactor 305 equipped with tubes 310 of a cooling device that is the subject of the present invention. This reactor 305 is a catalytic fluidized-bed reactor 305.
Therefore, as can be understood by reading the present description, the cooling device operates through a thermosiphon mechanism. This thermosiphon comprises:
- a tank 125;
- a cold downcomer 132;
- a distributer 170 if the device 10 comprises such a distributer 170;
- each tube 110 or 310; and
- a collector 175 if the device 10 comprises such a collector 175.
The thermosiphon operates as follows: the tank 125 is partially filled with water such that each cold downcomer 132 is permanently completely filled with water, as well as the water distributer 170; this assembly forms a permanent column of water. Each cooling tube, 110 or 310, initially partially or completely filled with water is heated by the heat of the reaction occurring in the reactor 105. A portion of the water contained in each tube, 110 or 310, is evaporated, forming steam bubbles. The mixture obtained has a lower density than the water present in the tank and the cold downcomers. As a consequence, a mass imbalance is created, and the water/steam mixture is pushed by the water coming from the tank 125. The water/steam mixture rises via the collector 175 up to the tank 125. This mixture is separated into two phases: the liquid phase is stored in the bottom of the tank 125 and returns to each cooling tube, 110 or 310, and the gas phase is removed as a function of the pressure to be maintained in the cooling system.
Given the heat exchanges, firstly between the water in each tube, 110 or

310, and secondly the catalytic fixed bed or fluidized bed and the gases, this device 10 can regulate the temperature in the fluidized-bed or fixed-bed reactor, 105 or 305, by regulating the pressure of the tank 125. This regulation requires an exact water phase change temperature that varies very little between the top and bottom of each preferably vertical tube, 110 or 310. To achieve this regulation, one or more temperature measurements are taken in the catalytic reactor, 105 or 305. This temperature measurement is used by the regulator 157, such as a control means, which compares the temperature measured to the predefined set-point limit value. The regulator 157 sends an output signal to a second regulator 156, such as a control means, which compares the signal from the first regulator with the pressure measurement of the thermosiphon. Depending on the pressure difference, the second regulator acts on the steam outlet valve 160 to change the operating pressure of the cooling device 10 assembly, to obtain the desired temperature in the catalytic fixed-bed or fluidized-bed reactor, 105 or 305.
The liquid–gas phase change is a phenomenon operating at a fixed temperature for a given pressure. As a consequence, the temperature is uniform over the entire length of each tube, 110 or 310, used for heat exchange. This property is utilized to impose a fixed temperature in the catalytic reactor, 105 or 305, which enables a better conversion for the chemical reactions occurring in it. In addition, this temperature within the reactor, 105 or 305, can be regulated by changing the operating pressure of the cooling device 10, which in practice changes the temperature of the liquid–gas phase change.
The device, 10 or 30, can be produced in two configurations:
If the catalytic reactor, 105 or 305, operates at a pressure close to atmospheric pressure, the side walls of the reactor, 105 or 305, can be formed fully or partially of vertical cooling tubes, 110 or 310. In this case the configuration consists of joining each tube, 110 or 310, forming the wall of the reactor, 105 or 305, by iron plates, called “fins”. Other vertical tubes, 110 or 310, can be used inside the reactor 105 to present the exchange surface and cooling required for the reaction to operate. The advantage of this configuration is that there is no difference in temperature between the walls of the reactor, 105 or 305, and other cooling tubes, 110 or 310, placed inside the reactor, 105 or 305.
If the catalytic reactor, 105 or 305, operates at a pressure far from the

atmospheric pressure, it is preferable to produce the reactor, 105 or 305, according to best practices for pressurized equipment and to incorporate the tubes, 110 or 310, of the vertical tube cooling device 10 within the reactor, 105 or 305. The proposed configurations have the following advantages:
- because it is the phase change that absorbs the heat, the cooling fluid has a constant temperature for a given pressure, which makes it possible to be isothermal;
- most of the exchange surface is preferably vertical, which prevents steam from accumulating in each tube, 110 or 310, and therefore the stratification phenomena between water and steam;
- the principle of natural circulation, via the thermosiphon mechanism, utilized by the device, 10 or 30, means that a circulation pump does not necessarily have to be used;
- they can be applied to fixed-bed or fluidized-bed reactors, 105 or 305; and
- they allow a minimum temperature to be maintained in the reactor 105, which boosts the reaction kinetics and prevents the formation of toxic compounds such as carbonyls.

CLAIMS
1. Cooling device (10) for a carbon dioxide methanation catalytic reactor (105),
comprising:
- at least one cooling tube (110) passing through the reactor comprising:
- an inlet (115); and
- an outlet (120) positioned at an altitude higher than the inlet;
- a water tank (125) supplying the tube by gravity, comprising:
- a water outlet (130), connected to the inlet of the tube;
- a water and steam inlet (135) connected to the outlet of the tube;
- a steam outlet (140); and
- a water supply inlet (145);

- a means (150) for measuring the temperature in the catalytic reactor;
- a means (155) for controlling a water level in the water tank, configured to supply the water tank with water in order to maintain a predefined water level in the tank;
- a steam outlet valve (160) positioned on the outlet (140) for steam from the tank (125); and
- a system (158) for regulating the pressure inside the water tank as a function of the reactor temperature measured by the temperature measurement means, this regulation system (158) being configured to control the opening or closing of the valve as a function of the reactor temperature measured by the temperature measurement means (150) in order to increase or reduce the pressure in the tank.
2. Device (10) according to claim 1, wherein the regulation system (158) is
configured to control the opening or closing of the valve (160) as a function of a
difference between the temperature captured and a predefined limit value.
3. Device (10) according to one of claims 1 or 2, which comprises a pressure sensor
(165) inside the cooling device, the regulation system (158) being configured to
control the opening or closing of the valve (160) as a function of the temperature and
the pressure captured.

4. Device (10) according to one of claims 1 to 3, wherein at least one of the tubes (110) is rectilinear and passes through the reactor (105) vertically, each rectilinear tube being configured such that the water circulating in said tube is partially vaporized during the passage in the catalytic reactor.
5. Device (10) according to one of claims 1 to 4, which comprises a water distributer (170) connected to each tube (110).
6. Device (10) according to one of claims 1 to 5, which comprises a steam collector (175) connected to each tube (110).
7. Device (10) according to one of claims 1 to 6, wherein at least one tube (110) is positioned near an inner wall (185) of the reactor.
8. Device (10) according to claim 7, wherein at least one wall (185) of the reactor (105) is formed by at least one tube (110).
9. Device (10) according to one of claims 1 to 8, wherein at least one tube (110) comprises fins (190).