EP2869918A1

EP2869918A1 - Reactor for carrying out an exothermic reaction in the gas phase

Info

Publication number: EP2869918A1
Application number: EP13734393.5A
Authority: EP
Inventors: Thomas Bogenstätter; Heribert Deck; Ortwin GROEHL; Thomas WEESER; Jan Ulrich; Jasmina Kessel
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2012-07-05
Filing date: 2013-07-04
Publication date: 2015-05-13
Also published as: MA20150354A1; AU2013285462A1; CL2015000014A1; CA2877979A1; JP2015527186A; MA37710B1; SG11201500006VA; WO2014006164A1; MX2015000248A; CN104428058A

Abstract

The invention relates to a reactor for carrying out an exothermic reaction in the gas phase, which comprises a vessel having an outer wall (13) composed of a metallic material, where an inner shell (17) is accommodated in the interior of the reactor (1) and the inner shell (17) is at a distance of at least 50 mm from the inside of the outer wall (13).

Description

The invention is based on a reactor for carrying out an exothermic reaction in the gas phase, comprising a container with a jacket of a metallic material.

Corresponding reactors are used, for example, in reactions which are carried out at elevated temperatures. Here, the material from which the reactor is made must be selected so that it is stable at the temperatures that prevail inside the reactor. Especially with corrosive media, there is the additional problem that the material is attacked by the media used and due to the high temperatures at which the reaction is carried out, an additional weakening occurs. It should be noted in particular that the jacket of the reactor is generally a supporting part on which additionally loads the mass of the reactor.

For example, a reaction conducted at elevated temperature with corrosive media is the oxidation of sulfur dioxide to sulfur trioxide.

The reactors currently used for this oxidation are usually made of stainless steel. Here, however, it has been shown that the material is damaged due to the temperatures occurring during the oxidation, which leads to a reduction in the creep strength and thus also to a shorter life of the reactor. For example, the generally used stainless steels with the material numbers 1 .4878 or 1.4541 are subject to creep damage at temperatures of more than 560 ° C. The damage results from a change in the mechanical technological material properties, which can lead to failure depending on the progress of the damage.

It is therefore an object of the present invention to provide a reactor which, compared with the reactors known from the prior art, has an increased service life or a higher gas phase temperature when carrying out an exothermic reaction in the gas phase.

The object is achieved by a reactor for carrying out an exothermic reaction in the gas phase, comprising a container with a jacket of a metallic material, wherein an inner shell is accommodated in the interior of the reactor, wherein the inner shell has a distance of at least 50 mm to the inside of the shell.

By using the inner shell, an additional gas layer is formed between the inner shell and the jacket of the reactor. The gas layer has an insulating effect, so that the temperatures acting on the jacket are lower than the temperatures inside the reactor. This avoids that the jacket is exposed to temperatures that adversely affect the stability of the shell, so that the service life of the reactor is increased. In particular, the use of the inner shell avoids that the material of the shell becomes brittle due to the temperatures within the reactor and thus the stability and the strength of the shell decrease. An embrittlement of the inner shell affects by far not so dramatic, since the inner shell has no supporting function. Unlike embrittlement of the shell, embrittlement of the inner shell does not lead to possible failure of the reactor.

The reactor according to the invention is particularly suitable for carrying out exothermic reactions in the gas phase, which are carried out at elevated temperatures, for example at temperatures of more than 300 ° C., preferably at temperatures of more than 500 ° C. In particular, the reactor is suitable for carrying out reactions which contain aggressive media with respect to the material of the jacket, for example for reacting sulfur dioxide with oxygen to form SO 3. The SO3 produced in this way is used, for example, in the production of sulfuric acid.

In one embodiment, the inner shell is made of the same material as the shell. As a material for the production of jacket and inner shell is suitable for example stainless steel. Here, the stainless steel is chosen so that it is stable against the media contained in the reactor. When using the reactor for the production of sulfur trioxide by oxidation of sulfur dioxide, for example, stainless steels with the material numbers 1 .4878 or 1.4541 are suitable. These are stable to the sulfur dioxide and sulfur trioxide contained in the reactor and also have a sufficient long-term stability, when the temperature to which the stainless steel is exposed, can be kept smaller than 560 ° C. Since the inner shell, unlike the jacket, has no supporting function, embrittlement and the concomitant decrease in the strength of the material do not lead to a failure of the reactor. And under normal operating conditions also not to damage the inner shell.

Another advantage of the inner shell is that damage to the inner shell is possible without having to replace the entire reactor. As an alternative to the production of sheath and inner shell of the same material, it is also possible to use different materials for the production of sheath and inner shell. For example, it is possible to use different steels. It is also possible to manufacture the jacket from a steel and the inner shell of a material inert and temperature-stable material compared to the substances contained in the reactor. As a material for the inner shell, for example, non-metals, such as a ceramic or glass can be used. It is also possible to coat the inner shell to reduce the heat radiation. As a coating material for the inner shell is suitable for example high temperature resistant mineral wool.

It is also possible to manufacture the jacket from a material other than stainless steel. Again, it is necessary to use a material that is stable to the substances contained in the reactor. Due to the inner shell and the gas phase between the inner shell and the jacket, the temperature to which the shell is exposed is lower than the temperature inside the reactor. Therefore, a material for the jacket can be used, which is less temperature stable than a stainless steel. However, it is preferred to use stainless steel as the material for the jacket. Furthermore, it is particularly preferred to manufacture the jacket and inner shell from the same material.

In a further preferred embodiment, a gap is formed between the inner shell and the bottom and / or top of the reactor. Through the gap gas can flow from the reactor into the gap between the inner shell and jacket. This ensures in particular that the same pressure prevails in the gap between inner shell and jacket as in the reactor. As a result, the inner shell is not loaded from the inside on one side with pressure, but the pressure acts evenly from all sides to the inner shell. The gap between the inner shell and the bottom and / or cover of the reactor is kept so small that, although a pressure equalization takes place, but only a small gas flow through the gap between the inner shell and jacket is generated. The less the gas moves in the gap between inner shell and jacket, the better is the insulating effect by the gas. In contrast, with a uniform gas flow, hot gas is regularly conveyed into the gap, so that the intended effect of insulation through the gap does not occur. With colder gas supplied, it is possible to cool the inner shell and the jacket by the gas flow.

In one embodiment, the reactor contains internals. As internals, for example, trays, structured or unstructured packings or random packings are used. understood. Suitable trays that may be included in the reactor are, for example, trays, bubble-cap trays or any other trays known to those skilled in the art. It is particularly preferred if at least one bottom is received in the reactor as an installation.

In a further embodiment, at least one catalyst bed is contained in the reactor. The catalyst bed can be designed, for example, as a fixed bed or as a fluidized bed. If the catalyst bed is a fluidized bed, preferably at least one bottom is accommodated in the reactor, which serves as a gas distributor in the fluidized bed. Between the granules for the fluidized bed and the overlying floor acting as a ceiling, a sufficiently large distance is left, that when flowing through the fluidized bed granulate with a gas, sufficient turbulence is possible. Preferably, the catalyst bed is a fixed bed. For this purpose, the catalyst forming the fixed bed can rest, for example, on a floor. Unlike a fluidized bed, a fixed bed is independent of the flow direction. So this can for example be flowed through from top to bottom. When a catalyst bed is contained in the reactor, the bottom on which the catalyst rests is, for example, a tray rack or a support plate for the catalyst. In the production of SO3 by oxidation of sulfur dioxide, a catalyst bed in the form of a fixed bed is preferred.

In a particularly preferred embodiment, the reactor is subdivided into several segments, each segment having at least one inlet and at least one outlet and each segment containing a catalyst bed and a gas space above the catalyst bed. The separation of the reactor into several segments is preferably carried out by intermediate floors. The feed is in the case of a catalyst bed designed as a fixed bed, for example above the catalyst bed in the gas space, so that the gas flowing through the catalyst bed can be supplied via the feed. In a gas space below the catalyst bed, the gas flowing through the catalyst bed is collected and can then be removed via a drain from the gas space below the catalyst bed.

When a catalyst bed is used, the chemical reaction usually occurs in the catalyst bed. In a particularly preferred embodiment, the reactor according to the invention is used for the oxidation of sulfur dioxide to sulfur trioxide. For this purpose, gaseous sulfur dioxide and an oxygen-containing gas are supplied and the sulfur dioxide reacts with the oxygen to sulfur trioxide. As the oxygen-containing gas, for example, oxygen or air can be used. If oxygen is used, it may additionally contain an inert gas. Age- natively, it is also possible to further enrich the oxygen in the air. However, the use of air is particularly preferred.

In the oxidation of sulfur dioxide to sulfur trioxide, the gases are added at a temperature in the range of 400 to 460 ° C. The reaction takes place in the presence of a catalyst at an overpressure of 0.4 bar. Due to the exothermic nature of the reaction, the sulfur trioxide leaving the reactor, sulfur dioxide and gas containing oxygen and nitrogen using the air have a temperature of 550 to 650 ° C. Accordingly, temperatures in this area also arise in the reactor. From a temperature of 560 ° C results in using steels 1.4878 or 1 .4541 reduced life by changing the mechanical technological material properties with a decrease in strength. In order to avoid a failure of the reactor, therefore, according to the invention, the inner shell is taken into the reactor. The inner shell forms an insulating layer between the inner shell and the jacket of the reactor, so that the temperature acting on the jacket of the reactor is reduced. For example, it is possible to set the temperature of the jacket through the inner shell to a temperature in the range between 400 and 560 ° C. As a result, the creep strength is not reduced and thus increases the life of the reactor. Since the inner shell, in contrast to the reactor shell has no supporting function, embrittlement of the inner shell does not lead to an operation disturbing damage to the reactor.

When the reaction, for example the oxidation of sulfur dioxide to sulfur trioxide in the presence of a catalyst is carried out and the reactor also contains a fluidized bed, it is particularly preferred if the material of the fluidized bed is catalytically active. For this purpose, on the one hand, the entire fluidized bed granules can be catalytically active or alternatively, in addition to an inert granules, a heterogeneous catalyst may be contained in the fluidized bed, this may for example also be admixed in granular form the inert fluidized bed granules. However, it is particularly preferred if the entire fluidized bed granulate is catalytically active.

For a fixed bed, it is possible to use, for example, a catalytically active packing or catalytically active packing. In this case, it is particularly preferable to manufacture the packing or filling body from a carrier material, onto which the catalytically active material is applied.

In this case, the catalyst used is in each case the catalyst suitable for the reaction to be carried out in the reactor. When a reaction different from the oxidation of sulfur dioxide to sulfur trioxide is carried out in the reactor, it is also possible that the reactor is made of a material other than stainless steel. The material from which the shell of the reactor is made depends on the reaction. Normally, a material is used which is inert to the substances to be reacted in the reactor. Regardless of the material for the jacket, it is further preferred to manufacture the inner shell of the same material as the jacket. Such an inner shell is preferably used when the temperature acting on the material of the shell is so high that damage to the shell may occur.

The inner shell forms an insulating layer between the inner shell and the jacket, so that the temperature acting on the jacket of the reactor can be reduced.

Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

Show it:

FIG. 1 shows a section of a reactor designed according to the invention,

FIG. 2 shows a temperature distribution without an inner shell,

Figure 3 shows a temperature distribution with inner shell. FIG. 1 shows a section of a reactor.

The section shows a right half of a reactor 1, which is divided into two segments 3. In addition to the two segments 3 shown here, other segments 3 may be included. These are then arranged correspondingly above or below.

When the reactor is used for the oxidation of sulfur dioxide to sulfur trioxide, usually each segment 3 has a lower gas space 5, a catalyst bed 7 and an upper gas space 9. The catalyst bed 7 is usually designed in the form of a fixed bed and is located on a floor 1 1. In this case, the bottom 1 1, for example, a rack or a support plate for the catalyst.

In operation, a gas stream is added to the upper gas space 9, which contains the educts necessary for the reaction. From the upper gas space 9, the gas stream is introduced into the catalyst bed 7. In the catalyst bed 7, the reactants of Gas flow converted to the product. The gas containing the product collects in the lower gas space 5 and can be removed therefrom. If complete conversion of the gas does not take place, the gas containing the product in the lower gas space 5 also contains educts.

In an exothermic reaction, heat is released during the reaction, whereby in particular the catalyst bed 7 is heated. Since the hot gas emerges from the catalyst bed 7, at least the jacket below the catalyst bed is also heated.

Usually, a reactor has a metallic shell 13. Due to the high temperature inside the reactor, the jacket 13 is provided on its outside with an insulation 15. Due to the high temperatures occurring in the interior of the reactor during exothermic reactions, the jacket 13 is exposed to a correspondingly high temperature. This can lead to a temperature damage of the material of the shell 13 in some materials. Thus, for example, in the oxidation of sulfur dioxide to sulfur trioxide, the steels 1 .4878 or 1 .4541 usually used for the jacket 13 are subject to creep damage at the temperatures occurring during the reaction, which leads to a reduced lifetime of the entire reactor 1. The reduced service life results from an embrittlement with a decrease in the strength of the shell 13. According to the invention, therefore, an inner shell 17 is accommodated in the interior of the reactor 1, which is positioned at a defined distance from the shell 13. By the inner shell 17 thus a gap between the inner shell 17 and shell 13 is formed. The inner shell 17 is arranged in particular at the positions in which temperatures occur in the reactor, which are above the temperature, which can lead to a time-state damage of the material of the shell 13.

The gap 19 between shell 13 and inner shell 17 is filled with a gas. The gas has an insulating effect, so that the temperature acting on the jacket 13 is lower than without use of the inner shell 17. In this way, the temperature acting on the shell 13 below the critical temperature, which leads to a creep damage, can be maintained.

The inner shell 17 is preferably made of the same material as the shell 13th The gas contained in the gap 19 between shell 13 and inner shell 17 is preferably the gas supplied to the reactor. For this purpose, it is possible, for example, to provide a gap 21 between an intermediate bottom 23, by which the segments 3 are divided and the inner shell 17. Through the gap 21, gas can then escape from the gap 19 between the inner shell 17 and the jacket 13. On the opposite side, for example, the gap 19 is open to the upper gas space 9. If an additional bottom between the upper gas space 9 and catalyst bed 7 is provided, it is preferable to provide the inner shell 17 in the region of the catalyst bed 7 and the lower gas space 5 and to provide an inlet gap between the bottom separating the catalyst bed 7 to the upper gas space 9, through which the gas can enter into the gap 19 between inner shell 17 and shell 13. Usually, however, no bottom is provided above the catalyst bed 7, so that the gas can enter directly from the upper gas space 9 into the gap 19 between inner shell 17 and shell 13.

If cold gas enters the gap, it is not necessary to keep the gas flow as low as possible, because then the gas itself also has a cooling effect.

A temperature distribution without inner shell is shown by way of example in FIG.

Here, once the temperature of the gas inside the reactor is shown and once the temperature on the jacket. The temperature profile in the interior is denoted by reference numeral 25 and the temperature profile at the jacket by reference numeral 27. On the x-axis, the position in the segment 3 from the inlet of the gas to the exit is shown and on the y-axis, the temperature.

The gas is supplied at a temperature of 450 ° C, flows through the upper gas space 9 until reaching the catalyst bed 7. In the catalyst bed 7 begins the chemical reaction, which leads to an increase in temperature due to their exotherm. The temperature rises up to 630 ° C. The gas is removed from the lower gas space 5 at a corresponding temperature. In the upper gas space 9 of the second segment, the gas supply takes place again at a temperature of 450 ° C and the temperature increases in the catalyst bed again. Due to the sulfur dioxide already converted in the first segment, the maximum temperature in the second segment is lower than in the first segment and the temperature only rises to 560 ° C.

Due to the high temperature of the gas stream, the metal of the jacket also heats up. However, by convective heat transport and heat conduction, the maximum temperature at the jacket is lower than the temperature inside the gas stream. To- the temperature in the region of the lower gas space 5 decreases until it reaches the upper gas space 9 of an underlying segment, since the jacket is cooled in the region of the upper gas space 9 of the following segment. Due to heat conduction, this leads to a decrease in temperature in the lower gas space 5 of the segment lying above it. 3

However, the maximum temperature at the jacket due to the temperature in the gas stream, when using the steel jacket when using the reactor for the oxidation of sulfur dioxide to sulfur trioxide, is above the critical temperature at which a rupture damage of the steel occurs.

FIG. 3 shows, by way of example, the temperature profile in the gas stream and in the jacket when an inner shell is used. The temperature profile in the gas flow corresponds to that which occurs even without the use of the inner shell. By using the inner shell 17, however, the temperature acting on the jacket 13 is significantly lower. In this example, the temperature maxima are approx. 525 ° C in the upper segment and approx. 500 ° C in the lower segment. This will keep the temperatures below the critical temperature at which the creep strength of the steel from which the jacket 13 is made will be reduced.

LIST OF REFERENCE NUMBERS

1 reactor

3 segment

5 lower gas space

7 catalyst bed

9 upper gas space

1 1 floor

13 coat

15 insulation

17 inner shell

19 gap

21 gap

23 intermediate floor

25 temperature history inside

27 Temperature profile on the jacket

Claims

claims

1 . Reactor for carrying out an exothermic reaction in the gas phase, comprising a container with a jacket (13) of a metallic material, characterized in that inside the reactor (1) an inner shell (17) is accommodated, wherein the

Inner shell (17) has a distance of at least 50 mm to the inside of the shell (13).

2. Reactor according to claim 1, characterized in that the inner shell (17) is made of the same material as the jacket (13).

3. Reactor according to claim 1 or 2, characterized in that between the inner shell (17) and the bottom and / or cover of the reactor (1), a gap (19) is formed.

4. Reactor according to one of claims 1 to 3, characterized in that in the reactor (1) at least one bottom is received.

5. Reactor according to one of claims 1 to 4, characterized in that in the reactor (1) a catalyst bed (7) is formed.

6. Reactor according to one of claims 1 to 5, characterized in that the reactor (1) is subdivided into a plurality of segments (3), each segment (3) having at least one inlet and at least one outlet, and each segment (3) a catalyst bed (7) and a gas space (9) above the catalyst bed contains.

7. Reactor according to claim 5 or 6, characterized in that the catalyst bed (7) contains a heterogeneous catalyst.

8. Reactor according to claim 6 or 7, characterized in that in each case for the subdivision of two segments (3) an intermediate bottom (23) is received in the reactor (1).

9. Use of the reactor according to any one of claims 1 to 8 for carrying out an exothermic reaction in the gas phase, wherein the reaction is carried out at a temperature of more than 300 ° C.

10. Use of the reactor according to one of claims 1 to 8 for carrying out a reaction for the conversion of sulfur dioxide with oxygen to SO3.