MXPA99000623A - Method for the in-situ modernization of a heteroge synthesis reactor - Google Patents

Abstract

A method for the in-situ modernization of a heterogeneous synthesis reactor, comprising the steps of providing a non-perforated cylindrical wall (15) coaxial with respect to the gas outlet wall (8), in a catalytic bed (16) of the radial or axial-radial type, the non-perforated cylindrical wall (15) extends from an upper end (8a) of the gas outlet wall (8) by a portion thereof of a predetermined length, to define a clearance (16) between the gas outlet wall (8) and the non-perforated wall (15), for the passage of a part of the gas leaving the catalytic bed (16), and by the step of providing closure means for the free space (16) between the non-perforated wall (15) the outlet wall of the gas (8), in proximity to the upper end (8a) of the latter, thus avoiding a deviation of the catalytic bed or a recycling to it of the gas that enters or leaves the reactor, respectively. Thanks to the previous steps, the present method allows to operate with a reduced amount of catalyst in the catalytic bed, maintaining however, without changing the characteristics of fluid dynamics and pressure drop.

Description

METHOD FOR THE IN-SITU MODERNIZATION OF A HETEROGENIC SYNTHESIS REACTOR FIELD OF THE INVENTION The present invention relates to a method for the in-situ modernization of a heterogeneous synthesis reactor, in particular for exothermic synthesis, such as the synthesis of ammonia or methanol and the conversion of carbon monoxide, where it includes at least one catalytic bed of the radial or axial-radial type, provided with opposed cylindrical perforated walls for the inlet and outlet of gases. In the description given below and in the following claims, the term "in-situ modernization" is understood as the modification, in the place of its installation, of an existing reactor, to improve its operation and obtain, for example, a production capacity and / or a performance in the conversion comparable to those of a reactor of recent construction. In the terminology of the field, this type of modernization is also called reconversion or restructuring. As is known, in the field of heterogeneous synthesis reactions, in general, it is increasingly perceived P1022 / 99MX the need to adapt the existing synthesis reactors to the catalysts of recent conception with always increasing reaction activity, in order to achieve an improvement in the conversion performance and a reduction in the energy consumption while decreasing Investment costs. In fact, the continuous progress in the realization of catalysts of high activity have caused that (being the production capacity of the reactor the same) the mass of catalyst to be loaded in the respective bed is markedly lower than the maximum volume of filling for the which the bed has been designed, thus allowing savings in the cost of the catalyst.

PREVIOUS TECHNIQUE In previous reactors provided with catalytic beds of the axial type, the adaptation of the reactor to the new catalysts of high reaction activity does not cause special problems, since the catalytic bed (s) can be loaded with an additional amount or less high catalyst without involving substantial modifications in the run of the same (in particular from the point of view of fluid dynamics), except for a different pressure drop that can be regulated P1022 / 99MX any way, adequately modifying the operations of the reactor. In previous reactors comprising catalytic beds of the radial or axial-radial type, the loading of a catalyst mass different from the designed mass involves, on the contrary, severe inconveniences in the run of the catalytic bed (s). A catalytic bed of the radial type only partially filled with catalyst inevitably presents rows of holes in the gas inlet and outlet walls, which are discovered in the upper part of the bed, with the subsequent undesired deviation of the reaction gases that evade the passage through the bed and a corresponding drastic reduction in the conversion efficiency of the reactor. The same problem arises in a catalytic bed of the axial-radial type, where axial cross-linking of the catalyst by the reaction gases is also lacking, which involves a further reduction in the conversion efficiency compared to an optimum loaded catalyst bed. In particular, the presence of a reduced amount of catalyst in the axial-radial bed, in addition to discovering a part of the holes in the perforated gas inlet and outlet walls, prevents the function P1022 / 99 X made by the non-perforated portion of the upper part of the gas outlet wall to axially direct the gases entering the bed. Even when the reconversion of the existing reactors has been increasingly accepted and the objective of the technique is to avoid a costly replacement of these and, at the same time, achieve the maximum conversion performance and the minimum energy consumption compatible with the volume Reaction available, methods have not been proposed until today that allow the adaptation of the existing reactors provided with catalytic beds of the radial or axial-radial type that can satisfy the aforementioned need. Currently, in the absence of valid technical solutions, the radial or axial-radial catalytic beds of the existing reactors are still loaded with conventional catalysts, to the detriment of the improvement in conversion efficiency and energy consumption, which could be achieved using its place, the new catalysts of high reaction activity. In another way, that is, a high activity catalyst, it is always necessary to completely fill the available volume of the radial or axial-radial catalytic bed to avoid the aforementioned drawbacks, consequently it is obtained, together with an increase in the yield of conversion, also an increase in P1022 / 99 X production capacity of the existing reactor that is not always required or desired, this increase may include, for example, a replacement of the device located downstream of the synthesis reactor that would otherwise decrease in size, with the consequent high investment and construction costs related. Furthermore, filling the total available volume in existing catalytic beds that have been suitably designed to contain a conventional catalyst of lower activity requires a high activity catalyst amount, so that it makes the cost of the investment prohibitive. Due to these major drawbacks, the use of high activity catalysts in the above heterogeneous synthesis reactors comprising catalytic beds of the radial or axial-radial type, has not yet had a specific application, even though there is more and more need of it in the field.

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide a method for modernizing a heterogeneous synthesis reactor of the type comprising at least one radial or axial-radial bed that allows the use of newly designed catalysts, which have always greater P1022 / 99MX reaction activity, to achieve an improvement in conversion performance and a reduction in energy consumption, in a simple and reliable way and to lower investment and operation costs. The problem is solved by a method of the type set forth in the foregoing, characterized in that it comprises the following steps: providing a non-perforated cylindrical wall, coaxial to the gas outlet wall in the catalytic bed, the non-perforated cylindrical wall is extends from an upper end of the gas outlet wall by a portion thereof of a predetermined length, to define a gap between the gas outlet wall and the non-perforated wall, for the passage of a part of the gas that leaves the catalytic bed; providing means for closing the free space between the non-perforated wall and the gas outlet wall, in proximity to the upper end of the latter, thereby avoiding, respectively, a deviation of the outgoing gases by evading the passage through the catalytic bed or a recycling of incoming gas to the catalytic bed. The method according to the present invention allows, advantageously, a partial loading of the existing radial or axial-radial catalytic bed (s), thus allowing an effective use of the P1022 / 99MX new catalysts of high activity, without adversely affecting the operation of the beds, keeping unchanged, in particular, the fluid dynamics and the pressure drop characteristics of the same In fact, thanks to the presence of a With a non-perforated wall of predetermined length near the upper area of the gas outlet wall and the simultaneous formation of a free space between the non-perforated wall and the gas outlet wall, it is advantageously possible to achieve a double objective, which It is exposed below. On the other hand, the non-perforated wall allows the gas fluid entering the beds to be directed towards the catalytic bed, thus avoiding the formation of undesirable deviations, that is, preventing the gas from flowing directly through the perforations of the gas. gas outlet wall, which remain uncovered due to only partial filling of the catalytic beds, without going through the catalyst. On the other hand, the presence of the free space allows the flow of gas that has passed through the catalytic mass to escape through all the perforations of the gas outlet wall, in order to maintain the pressure drop in the bed without change (s). ) catalytic (s). Particularly satisfactory results have been achieved by providing a non-perforated wall that is P1022 / 99MX extends by a portion comprised between 5% and 50% of the length of the gas outlet wall, respectively defining a substantially annular free space having a thickness comprised between 0.5 and 10.0 cm. In this way, it is possible to load even relatively small amounts of high activity catalyst, without the risk that the catalytic bed deviates undesirably from the synthesis gas, while maintaining fluid dynamics and drop characteristics unchanged. of pressure that follow the conversion. With reference to the present invention, it should be emphasized that the ability to conceive a partial load of the catalyst in a catalytic bed of the radial or axial-radial type (without adversely affecting the operation thereof) contrasts fully with the teachings constants of the prior art according to which the use of radial or axial-radial catalytic beds inevitably includes a complete filling thereof with catalyst, to prevent the reaction gases from being diverted and not passing through the beds. In fact, due to the intrinsic characteristics of these beds, partial loading of a radial or axial-radial catalytic bed was inconceivable in accordance with the prior art. Only after the investigation of P1022 / 99 X applicant, it has been possible to solve the aforementioned technical problem by proposing a modernization of existing radial or axial-radial catalytic beds, which allows (contrary to the teaching of the prior art) a partial load thereof . The features and advantages of the invention are set forth in the description of an example of the instrumentation of a modernization method according to the invention, which is described below by way of illustration, without being limiting, and with reference to the accompanying drawings .

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows schematically, a longitudinal section of an existing reactor to carry out heterogeneous synthesis reactions, suitably modified in accordance with the modernization method of the present invention.

DETAILED DESCRIPTION OF A PREFERRED MODE With reference to Figure 1, the reference number 1 indicates a complete heterogeneous synthesis reactor. Reactors of this type are especially suitable for carrying out synthesis reactions Exothermic heterogeneous P1022 / 99MX at high pressure and temperature (20-300 bar, 180-550 ° C), for the production of, for example, ammonia or methanol or for the conversion of carbon monoxide into carbon dioxide. The reactor 1 is composed of a tubular shell 2, provided in the upper part of a nozzle 3 for the entrance of the reaction gases and in the lower part of a nozzle 4 for the exit of the reaction products. The shell 2 is also provided in the upper part of a nozzle 5 to allow the passage of a worker into the reactor 1 to perform the various operations of assembly and maintenance thereof. Nozzles of this type are generally known to those skilled in the art as "inspection records". Inside the shell 2 a catalytic bed 6 of the axial-radial type is obtained, laterally defined by the perforated cylindrical walls of gas inlet and outlet 7 and 8, respectively, and below by the bottom of the shell 2. Catalytic bed 6 is not closed at the top to allow it to be traversed axially by a portion of the reaction gases. To prevent unwanted leaks in the catalyst, can be installed in the catalytic bed 6, containment networks P1022 / 99MX (generally known to those skilled in the art and therefore, not shown). In the example of Figure 1, the gas inlet wall 7 is placed near the shell 2, while the gas outlet wall 8 is placed in the middle part of the reactor 1. Between the shell 2 and the wall 6 of gas inlet a free space 9 is obtained to allow a radial crossing of the bed 6 by the reaction gases. The gas outlet wall 8 is also closed at the top by a hermetic lid 10, of a known type. A chamber 11, extended, coaxially towards the catalytic bed 6, between the wall 8 and the lid 10, is finally provided in the reactor 1, to direct the reaction products leaving the bed to the nozzle 4, through the which are finally evacuated. The dashed line 12 shown in proximity to the upper end of the gas inlet wall 7 delimits the upper level that can be reached by the catalyst inside the catalytic bed 6 and defines, together with the side walls 7 and 8 and the bottom of shell 2, the volume of reaction available in reactor 1. The volume has been calculated based on the reaction activity of the catalyst commercially available at the time of reactor design 1, for P1022 / 99MX reach a predetermined production capacity. Therefore, before being modernized in accordance with the present invention, reactor 1 still had a catalytic bed 6 whose volume was completely occupied by a conventional catalyst. Conversely, the interrupted line 13 indicates the level reached by the catalyst in the reactor 1 advantageously modernized in accordance with the present invention. The catalyst inside the bed 6 is indicated as 14 - as a whole - and has a reaction activity to provide a reactor production capacity equivalent to the designed capacity, but occupying a volume substantially smaller than the volume of the catalytic bed 6. In other words, thanks to the higher reaction activity, the mass of the catalyst 14 charged to the reactor once the catalyst is modernized according to the invention, turns out to be - the production capacity being the same - much smaller that the catalyst mass used before the modernization, including consequently, savings in the cost of the catalyst. The arrows F in Figure 1 indicate the various routes followed by the gas through the catalytic bed 6.

P1022 / 99MX In accordance with a first step of the modernization method of the present invention, a substantially cylindrical and non-perforated wall 15 is provided which is coaxial with the gas outlet wall 8 in the catalytic bed 6. The non-perforated wall 15 protrudes from an upper end 8a of the gas outlet wall 8 by a predetermined portion thereof, to define an annular free space 16 between the gas outlet wall 8 and the non-perforated wall 15, for the passage of a part of the gas leaving the catalytic bed 6, as indicated by the arrows F in Figure 1. In a further step of the present method, the means of closing the free space 16 between the non-perforated wall 15 and the wall 8 of gas outlet, in proximity to the upper end 8a of the latter, thus avoiding the diversion of the incoming gases or recycling to the catalytic bed of the gases leave the reactor respectively. Thanks to the steps of providing a non-perforated wall near the upper end of the gas outlet wall and of defining a clearance between the walls for the passage of the reacted gases, it is advantageously possible to load the catalytic bed with amounts of catalyst substantially lower than the designed quantities, without adversely affecting the performance P1022 / 99MX of the same, maintaining without changes, in particular, its characteristics of fluid dynamics and pressure drop. In fact, even when the level of the catalyst 14 remains well below the upper end 8a of the gas outlet wall 8 (interrupted line 13), thereby leaving some holes in the wall uncovered, the non-perforated wall 15 prevents the gas assets cross the catalytic bed 6 without penetrating the catalytic mass, and the free space 16 allows all the holes in the wall 8 to be used as outputs for the reaction products. If the non-perforated wall 15 were in direct contact with the gas outlet wall 8 (without the formation of the free space 16), a catalytic bed with the same characteristics of fluid dynamics would be obtained as those of the non-modernized bed, but By reducing the number of holes available for the output of the reaction products, the pressure drop would be increased. In the example of Figure 1, the non-perforated wall 15 advantageously extends by a portion comprised between 20% and 40% in length of the gas outlet wall 8. In practice, the wall 15 preferably extends over a length to reconstruct in the catalytic bed 6, only partially loaded with the catalyst 14, a predominantly axial crossing area.

P1022 / 99MX of the reaction gases. If the catalytic bed 6 were of a radially only type, the wall 15 would arrive barely beyond the interrupted line 13 that defines the level reached by the catalyst 14, to ensure a substantially radial crossing of the catalytic bed. Moreover, the free space 16 is preferably defined to have a thickness comprised between 1 and 5 cm. In any case, the thickness of the free space 16 must be large enough to allow the gas to cross without causing an additional pressure drop. Advantageously, the free space 16 is closed in the vicinity of the upper end 8a of the gas outlet wall, to avoid undesired deviations of the gaseous reactants entering the catalytic bed 8 or the recycling of the reaction products to the bed . In order to simplify as much as possible the instrumentation of the present method of modernization, the non-perforated wall 15 is suitably supported by the gas outlet wall 8. For example, the wall 15 can be removably attached to the wall 8 through special support means hooked to the wall, in proximity to its upper end 8a. In particular, in accordance with a modality Preferred P1022 / 99MX of the invention, shown in Figure 1, the non-perforated wall 15 (whose diameter is larger than that of the gas outlet wall 8) is advantageously supported by a gas-tight horizontal spacer 17 projecting above the upper end 8a of the wall 8 gas outlet and tilts on it. The wall 15 and the separator 8 advantageously form a kind of gas-tight glass (made, for example, of a non-perforated plate), which rests inverted on the lid 10 of the gas outlet wall 8. At the conclusion of the steps, a reactor 1 is obtained which makes it possible to carry out heterogeneous synthesis reactions with high conversion yields and with a low energy consumption, in the following way: The gaseous reactants, enter the reactor 1 through the nozzle 3, are fed to the catalytic bed 6 which comprises a high activity catalyst 14. Depending on the type of reaction, the temperature and pressure of the gaseous reactants fed to the catalytic bed 6 are regulated downstream of the reactor 1. The gaseous reactants cross the catalytic bed with a centripetal axial-radial flow. Thanks to P1022 / 99MX the presence of the non-perforated wall 15, it is possible to axially deviate the flow of gaseous reactants, avoiding unwanted deviations of the catalytic bed 6. The reaction products obtained in the catalytic bed 6 cross the gas outlet wall 8 and they are then collected in chamber 11, to then finally exit reactor 1 through nozzle 4. A (minimum) part of the reaction products flows advantageously along space 16, thus allowing to take advantage also of the part of the wall 8 circumscribed by the wall 15 for the exit of gases. Thus, it is possible, (the production capacity of the already existing reactor being the same) to load the catalytic bed 6 only partially with a catalyst of high reaction activity, obtaining savings in the cost of the catalyst and maintaining, at the same time, the characteristics of fluid dynamics and pressure drop of the catalytic bed that has not been changed. If an increase in the production capacity of the existing reactor were required (which would include the need for full exploitation of the available volume of the catalytic bed 6, loading it with a high activity catalyst), it would suffice to remove the wall from the reactor not perforated 15 and, consequently, also the separator 17 that supports it, to return P1022 / 99MX to the catalytic bed 6 to its original configuration. The present invention can be advantageously applied in particular in the fields of heterogeneous synthesis reactions, where technological progress has allowed the development of new catalysts which always have increasing reaction activities. A very interesting field is undoubtedly the field of ammonia synthesis, where thanks to the present method, it is now possible to effectively modernize existing reactors to use high activity catalysts, such as catalysts with graphite support. based on ruthenium. Another particularly interesting field is the field of carbon monoxide conversion, where already existing reactors (for example, those of the type shown in Figure 1) can be advantageously loaded with reduced volumes of high activity catalysts, such as for example catalysts comprising copper for high temperature conversion. However, the modernization method according to the present invention is not limited to the type of reactor described above in relation to Figure 1, but can also be applied to reactors comprising a plurality of supported radial or axial-radial beds, example, inside a P1022 / 99MX appropriate cartridge. Further, for the purposes of implementing the present method, it does not matter whether the catalytic bed is crossed by the reaction gases with a centripetal or centrifugal flow. In the last example, the gas outlet wall 8 would be near the shell 2 and the non-perforated wall 15 would have a diameter smaller than the diameter of the wall 8. The present invention can also be obviously used, when a reduction is desired in the production capacity of the existing reactor and, therefore, when a reduction in the mass of the conventional catalyst (low yield) to be charged in the reactor is required. From what has been stated in the foregoing, the many advantages achieved by the present invention become evident; it is possible to load only partially a catalytic bed of the radial or axial-radial type of an already existing reactor, thereby obtaining a saving in the cost of the catalyst, without adversely affecting the operation of the reactor.

P1022 / 99MX

Claims (10)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. The method for the in-situ modernization of a heterogeneous synthesis reactor, which includes an external shell comprising at least one catalytic bed of the radial or axial-radial type, provided with opposed, cylindrical, perforated walls for the inlet and outlet of gases, the method comprising the steps of: providing a cylindrical, non-perforated wall , coaxial to the gas outlet wall in the catalytic bed, the cylindrical wall, not perforated, extends from an upper end of the gas outlet wall by a portion thereof of a predetermined length, to define a clearance between the gas outlet wall and the non-perforated wall, for the passage of a part of the gas leaving the catalytic bed; - providing means for closing the gap between the non-perforated wall and the gas outlet wall, in proximity to the upper end of the latter, thereby avoiding, respectively, a deviation of the incoming gas evading passage through a catalytic bed or a recycling of the outgoing gas to the catalytic bed.
1. P1022 / 99MX
2. 2. The method according to claim 1, characterized in that the non-perforated wall extends over a portion comprised between 5% and 50% of the length of the gas outlet wall.
3. 3. The method according to claim 1, characterized in that the free space has a thickness comprised between 0.5 and 10 cm. The method according to claim 1, characterized in that the non-perforated wall is supported by the gas outlet wall. The method according to claim 4, wherein the gas outlet wall has a diameter smaller than the diameter of the gas inlet wall and the non-perforated wall respectively, characterized in that the non-perforated wall is supported by a separator horizontal gas-tight protruding above the upper end of the gas outlet wall and leaning over it. 6. A heterogeneous synthesis reactor of the type comprising: an outer shell; at least one catalytic bed of the radial or axial-radial type, provided with opposite walls, cylindrical, perforated, for the entrance and exit of gases, extended in the shell; P1022 / 99MX characterized in that it further comprises in the catalytic bed: a non-perforated cylindrical wall coaxial to the gas outlet wall in the catalytic bed, the non-perforated cylindrical wall extends from an upper end of the gas outlet wall by a portion thereof of a predetermined length, to define a gap between the gas outlet wall and the non-perforated wall, for the passage of a part of the gas leaving the catalytic bed; means for closing the free space between the non-perforated wall and the gas outlet wall, in proximity to the upper end of the gas outlet wall, thereby avoiding, respectively, a gaseous reactant of the incoming gas evading the passage through the gas. catalytic bed or recycling of the outgoing gas to the catalytic bed. The reactor according to claim 6, characterized in that the non-perforated wall extends for a length comprised between 5% and 50% of the length of the gas outlet wall. The reactor according to claim 6, characterized in that the free space is substantially annular and has a thickness comprised between 0.5 and 10 cm. 9. The reactor according to claim 6, P1022 / 99MX characterized in that the non-perforated wall is supported by the gas outlet wall. The reactor according to claim 9, wherein the gas outlet wall has a smaller diameter than the diameter of the gas inlet wall and the non-perforated wall respectively, characterized in that the non-perforated wall is supported by a separator horizontal gas-tight protruding above the upper end of the gas outlet wall, and tilts on it. P1022 / 99MX