MXPA97009584A - Process for the high efficiency catalytic conversion of carb monoxide - Google Patents

Abstract

The present invention relates to: A process for the catalytic conversion of carbon monoxide (CO) to carbon dioxide (CO2), of the type comprising the steps of feeding at a predetermined rate a gaseous flow comprising carbon monoxide to a space, and reactivate the carbon monoxide in the reaction zone to obtain a gaseous flow comprising carbon dioxide, which is distinguished by the preliminary stage of the acceleration of the gaseous flow which comprises carbon monoxide upstream from the space of reaction

Description

PROCESS FOR THE HIGH EFFICIENCY CATALYTIC CONVERSION OF CARBON MONOXIDE Field of the Invention The present invention relates to a process for the high efficiency catalytic conversion of carbon monoxide (CO) to carbon dioxide (C02) of the type comprising the steps of: - feeding a gas stream at a predetermined speed comprising carbon monoxide to a reaction space; - reacting the carbon monoxide in this space to obtain a gaseous flow comprising carbon dioxide. In the description set forth below and in the claims, the term "reaction space" is generally understood to mean the meaning of a space comprising the catalyst-containing media in which the carbon monoxide conversion reaction takes place. according to the following formula: CO + H20 (steam) or C02 + H2 The conversion reaction of carbon monoxide is very important for the industry because it allows obtaining one of the basic reagents for many synthesis reactions (for example the synthesis of the ammonium), ie hydrogen The present invention also relates respectively to a reactor and equipment for the implementation of the above process, as well as to a respective modernization method for a reactor and an apparatus for the catalytic conversion of carbon monoxide. As is known, in the field of catalytic conversion of carbon monoxide the need is even more strongly felt to easily provide the conversion processes implemented, allowing the production capacities to be carried out even higher in costs and low in operation and the energy consumption. BACKGROUND OF THE INVENTION It is known that the industry's requirement for carbon monoxide conversion processes in which gaseous reactants were made to flow with a substantially axial, radial or axial radial movement through a space of reaction comprising at least one catalytic bed. A process of this type is described, for example, in EP-A-0 372 453. Despite the advantages, in some way, the processes according to the prior art all deploy a series of adapters linked to the presence of water -for example in the form of droplets- are entrained in the gaseous flow comprising carbon monoxide. Actually, the water introduced together with the carbon monoxide in the reaction space irreversibly damages the surface layer of the catalyst contained therein making it extremely compact or saturated. This is due, in particular, to the localized thermal shock caused by the immediate evaporation of the water that is in contact with the catalyst at high temperature, and in part to the mechanical impact of the water tapping on the catalyst. The primary consequence of this saturation of the surface layer of the catalyst is a significant pressure drop of the gaseous flux passing through the catalytic mass and a decrease in the activity of the catalyst, with the associated decrease in the conversion production (and here the capacity productive) and high energy consumption. This important disadvantage of the carbon monoxide conversion processes, according to the prior art, has now been known for more than two decades, and only the solution proposed so far consists of the manual removal by a worker of the layer of carbon monoxide. saturated catalyst and its replacement with a new catalyst.

In addition, the formation of the saturated catalyst layer can be very frequent and penalized by the general behavior of the process as previously required in the indicated treatment and very short time intervals generally less than one year (3 to 9 months). As you can easily imagine, the aforementioned solution can not be considered satisfactory for industrial requirements because it involves the detention of the plant indicated for the implementation of the conversion process., and consequently it stops production, high maintenance and operation costs, and a higher energy consumption. SUMMARY OF THE INVENTION The fundamental problem of the present invention is to provide a carbon monoxide conversion process which would allow obtaining high production capacities and whose implementation would not involve high investment and operation costs, high maintenance costs and even higher costs. energy consumption. In particular, the fundamental problem of the present invention is to make available a carbon monoxide conversion process in which the saturation of the catalyst surface would not occur as is done in the process according to the prior art.

The aforementioned problem is solved according to the present invention by means of a carbon monoxide conversion process of the aforementioned type, which is characterized in that it comprises the preliminary stage of: accelerating the gaseous flow comprising the carbon monoxide water above the reaction space. Advantageously, thanks to the step of accelerating the gaseous flow comprising carbon monoxide to enter the reaction space, it is possible to obtain the separation of the water suspended therein in droplets of small diameter, for example between 100 μm and 600 μm , to promote at least the partial evaporation of the later in the gaseous feed stream that is generally not saturated with steam. In addition, it has surprisingly been found that following the step of accelerating, water droplets resulting from the separation of all tends to concentrate - for mechanical fluid reasons - towards the center of the feed gas flow to strike only a small circumscribed portion of the catalytic mass contained in the reaction space, while the drop pressure is drastically limited due to the saturation of the catalyst. Finally, as a consequence of the separation of the above mentioned water in small diameter droplets any damage to the catalyst by a mechanical impact is substantially eliminated. Thus, the process according to the present invention advantageously allows on the one hand, at least the partial removal of the water transported in the gaseous feed flow, and on the other hand the drastic reduction of the impact of the catalytic region by this drag as well as its harmful effect. Preferably, the aforementioned acceleration is such that the increase in the velocity of the gaseous flow comprising carbon monoxide by a factor of between 1.5 to 5 times, such that the complete and effective separation of all the water entrained in the gaseous flow is obtained. . Advantageously, the gaseous flow comprises carbon monoxide which passes through the reaction space with a substantially radial or axial / radial movement. In this way, the presence of traces of water in the gaseous feed flow does not cause saturation problems in particular and here the loss of charge, since the portion of the shock of the reaction space by this residual drag is completely secondary and marginal. For the implementation of the aforementioned process, the present invention makes possible a reactor for the high efficiency catalytic conversion of carbon monoxide to carbon dioxide of the type comprising: an external substantially cylindrical coating; - at least one catalytic bed supported within the aforementioned coating; - an inlet nozzle in the communication fluid with the aforementioned coating to feed at least one catalytic bed with the gaseous flow comprising carbon monoxide; characterized in that it further comprises: means for accelerating the gaseous flow supported upstream of at least one catalytic bed. As an alternative, the present invention is advantageously implemented by a device for the high efficiency catalytic conversion of carbon monoxide of the type comprising: a conversion reactor comprising a substantially cylindrical coating and at least one catalytic bed supported on this coating; - a duct for feeding the reactor of the gaseous flow comprising carbon monoxide, and characterized in that it further comprises: means for accelerating the gaseous flow supported in the duct. According to another aspect of the present invention, there is also available a method for the modernization of a reactor for the catalytic conversion of carbon monoxide to carbon dioxide of the type comprising: an external substantially cylindrical coating, - - at least one bed catalytic supported on the aforementioned coating; an inlet nozzle in the communication fluid with the coating for feeding at least one catalytic bed with the gaseous flow comprising carbon monoxide; characterized in that it comprises the step of: - disposing upstream of at least one catalytic bed, means for accelerating the gas flow. According to yet another aspect of the present invention, a method for the modernization of equipment for the catalytic conversion of carbon monoxide to carbon dioxide of the type comprising: a conversion reactor comprising a substantially external coating is also available. cylindrical and at least one bed supported in this coating; - a duct for feeding the reactor a gaseous flow comprising carbon monoxide; and characterized in that it comprises the step of: - arranging in the duct means for accelerating the gaseous flow. Thanks to the aforementioned modernization methods, in a respective form for an existing reactor or equipment, it is possible to obtain a simple carbon monoxide conversion process to be implemented and capable of carrying out the high production capacity in a consumption of energy and low operating cost and in which saturation of the catalyst surface contained in at least one catalytic bed has not occurred. The features and advantages of the method according to the present invention are shown in the description of an embodiment thereof given below so as not to limit the example with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a cross-sectional view of a carbon monoxide conversion reactor according to the present invention. Detailed Description of a Preferred Modality - With reference to Figure 1, the reference number 1, indicates as a gap a reactor for the high efficiency catalytic conversion of carbon monoxide to carbon dioxide. In general, the conversion reaction takes place at temperatures between 180 ° C and 500 ° C and at a pressure between 1 bar and 100 bar. The equipment 1 comprises an external substantially cylindrical coating 2, which is defined within a reaction space 3 in which a catalytic bed 4 is supported, to contain the catalyst 5. In the example of figure 1, the catalyst 5 is all housed in a single catalytic bed 4. But it is possible to provide a reaction space 3 in which the catalyst 5 is distributed in a plurality of catalytic beds 4, for example two or three beds. The catalytic bed 4 is of the axial-radial type with the upper end 6 and the side wall 7 permeable to gas. In the catalytic bed 4, a gas-permeable side wall 8 is also provided in fluid communication with a manifold 9 for the collection of the gas left in the catalytic bed 4. A catalytic bed of this type is described for example in the EP-patent. A-0 372 453.

To prevent an unwanted leakage of the catalyst 5, the end 6 is generally equipped with an anticorrosive layer of the known type and not shown. According to the alternative embodiment of the present invention not shown, the catalytic bed 4 can be of the purely radial type with the end 6 impermeable to gas. The reference numbers 10 and 11 respectively indicate a gas inlet nozzle and a gas outlet nozzle disposed at the upper and lower ends respectively of the liner 2. Advantageously, they are properly supported upstream of the catalytic bed 4, means - generally indicated by the reference number 12- to accelerate the feeding of the gaseous flow in the reaction space 3. In the example of Fig. 1, the means 12 are disposed in the gas inlet nozzle 10 and preferably close to the liner 2. This arrangement is particularly preferred because it allows obtaining easy to build means 12, small in size and easy to construct. access for maintenance. At this point, it has been noted that the liner 2 near the gas inlet nozzle 10 is generally of an opening (not shown) called in the industry "manhole" for the inspection and maintenance of the conversion reactor 1. The means 12 comprise a clogging element with a passage diameter smaller than the passage diameter of the gas inlet nozzle 10. Venturi-type or calibrated Venturi-type elements can be used as clogging elements 13 for example. Especially, the results were satisfactorily obtained with an average between the aforementioned diameters of passage between 0.45 and 0.85. Thanks to the acceleration means 12, it is possible to obtain the transport of the water transported in the feed gas flow in droplets of small diameter to at least partially facilitate evaporation of the water and in any case significantly reduce the danger of damage to the catalyst. In Figure 1, the arrows Fg indicate several trajectories followed in the conversion reactor 1 by the gas flow while the reference number 14 indicates the drops of water entering this flow. The gaseous flow composition Fg is fed into the reaction space 3 and comprises carbon monoxide and various vapors during the crossing of the catalytic bed 4 following the conversion reaction, so that the outlet of the reactor 1 comprises mainly carbon dioxide and hydrogen. Due to the acceleration imparted to the gas flow Fg by the means 12, the drops 14 are concentrated in a central area of the reaction space and carry only a small and circumscribed portion of the surface of the catalyst 5. In addition, since the drops 14 are divided into drops of negligible size, their impact with the catalytic mass does not cause particular problems of saturation. According to the catalytic conversion process according to the present invention, the gaseous flow Fg comprising carbon monoxide is fed at a predetermined speed into the reaction space 3, where the carbon monoxide reacts to provide a gaseous flow Fg comprising carbon dioxide. Advantageously, according to a preliminary step of the present process, the flow of gas Fg comprising carbon monoxide is accelerated upstream of the reaction space 3. Thus, the water droplets 14 introduced into the feed gas stream Fg are they divide with at least a partial evaporation of these, such that the formation of a saturated surface layer of the catalyst contained in the reaction space is prevented or at least substantially reduced. The operating conditions of pressure and temperature of the present process are those previously established and correspond to the typical operating conditions of the catalytic carbon monoxide conversion processes according to the state of the art. It is advantageously found that by appropriately increasing the velocity of the gaseous flow Fg it is possible to obtain almost total evaporation of the water droplets 14. In particular, this occurs when the acceleration is such that the velocity of the gas flow Fg increases. by a factor between for example 4 and 5 times. With reference to the reactor of figure 1, the range of increase of the aforementioned speed was obtained by preferably using a Venturi bottleneck element 13 with a proportion of the passage diameter of the element 13 to the passage diameter of the inlet nozzle of gas 10 between 0.45 and 0.50. Thanks to the presence in the reaction space 3 of a catalytic bed 4 of the axial-radial type, the gaseous feed flow Fg is advantageously flowed in the convention reactor 1 with movement - - substantially axial-radial. In this way the double advantage is obtained: on the one hand the compensation of the pressure drop caused by the bottleneck element 13 and on the other hand a secondary and marginal area of the surface of the catalyst 5 is made available which will be sacrificed if it is necessary in case of saturation of it. In fact, the pressure drops resulting from the crossing by the gaseous flow Fg of the catalytic mass are significantly reduced with respect to a purely axial crossing of the catalytic bed, such that it is capable of facing without particular limitations in the production capacity, even in the high pressure drops caused by the passage of the gaseous flow Fg through the bottleneck element 13. Furthermore, as shown in figure 1, the water droplets 14 are transported to a smaller and marginal zone of the catalytic bed 4, that is, the central area of the axial part of the bed 4, such that any damage to the remaining part of the catalyst 5 is prevented and consequently prevents the formation of additional undesired pressure drops in the catalytic bed 4. In the case of a purely radial catalytic bed, the same advantages are obtained from the point of view of pressure drop, with respect to a radial layer - - axial, but the use of the catalytic layer and thus, the production capacity of the reactor, are less under equal conditions because there is a non optimal use of the catalytic mass due to the lack of the axial component. According to a particularly advantageous embodiment of the present invention, the acceleration means 12 comprise a Venturi element 13, which provides the desired increase in velocity of feed gas Fg with a minimum pressure drop in relation to the pressure drop caused by the bottleneck elements of the calibrated disc type or similar. According to an alternative implementation of the process according to the present invention, equipment (not shown) of the type comprising: a conversion reactor having a substantially cylindrical outer envelope and at least one catalytic bed supported on the envelope; - a duct for feeding to the reactor a gaseous feed stream comprising carbon monoxide. The duct generally has the function of connecting the reactor with a process heater disposed upstream of the reactor. By the term "process heater" it is intended to understand heater for the production of steam by means of indirect heat exchangers between a heating flow comprising carbon monoxide and a water flow. Generally these heaters are of the tube-nest type with two ends of the tubes fixed to respective tube plates. Advantageously, the equipment comprises means for accelerating the gaseous flow Fg of feed supported in the duct. The acceleration means preferably comprise a bottleneck element having a pitch diameter smaller than the passage diameter of the duct. Preferably, the ratio between the step diameters mentioned above is between 0. 45 and 0.85 and the bottleneck element is a Venturi. Regarding the problem of catalyst saturation, the advantages obtained with the equipment of this type are comparable with those described above with reference to the reactor of figure 1. In this case, since the means of acceleration of the gas stream of feed are within of a duct, its insertion and maintenance are very difficult. The present invention also provides respective methods of modernization of a reactor and equipment for the catalytic conversion of carbon monoxide. Advantageously, these methods comprise the step of disposing upstream of the reaction space means for proper acceleration of the feed gas stream comprising carbon monoxide. In this way, it is possible to convert in a technically simple manner and with a low implementation cost, existing reactors or equipment to obtain the advantages mentioned above and eliminate the disadvantages indicated with reference to the prior art. Preferably, the acceleration means are housed in a gas inlet nozzle or in a feed duct and comprising a bottleneck element, for example of the Venturi type having a pitch diameter smaller than the pitch diameter of the element that contains them. The numerous advantages carried out by the present invention are clear from the above discussion, in particular the possibility of effectively neutralizing if none of the problems is totally eliminated from the saturation of the surface of the catalyst contained in the reaction space by means of a easy conversion process to implement and give a high production capacity with low operating costs and low consumption of - - Energy .

Claims (19)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as property and therefore the contents of the following are claimed as novelty: CLAIMS 1. A process for the high efficiency catalytic conversion of carbon monoxide (CO) to carbon dioxide ( C02), of the type comprising the steps of: feeding at a predetermined rate a gaseous flow comprising carbon monoxide to a reaction space; reacting the carbon monoxide in the reaction space to obtain a gaseous flow comprising carbon dioxide; characterized in that it comprises the preliminary step of: accelerating the flow of gaseous gas comprising carbon monoxide from the reaction space. Process according to claim 1, characterized in that the acceleration is such that the velocity of the gaseous flow comprising carbon monoxide is increased by a factor between 1.5 to 5 times. Process according to claim 1, characterized in that the gaseous flow comprises carbon monoxide passing through the reaction space with a substantially radial or axial-radial movement. 4. A reactor for the high efficiency catalytic conversion of carbon monoxide (CO) to carbon dioxide (C02) of the type comprising: an external substantially cylindrical shell; at least one catalytic bed supported within the coating; an inlet nozzle in fluid communication with the liner to feed at least one catalytic bed with a gaseous flow containing carbon monoxide; characterized in that it further comprises: means for accelerating the gaseous flow supported upstream of at least one catalytic bed. 5. A reactor according to claim 4, characterized in that the means are arranged in the nozzle. 6. A reactor according to claim 4, characterized in that the means comprise a bottleneck element having a passage diameter smaller than the passage diameter of the nozzle. 7. A reactor according to claim 4, characterized in that the ratio between the passage diameter of the bottleneck element and the passage diameter of the nozzle is between 0.45 and 0.85. 8. A reactor according to claim 6, characterized in that the bottleneck element is a Venturi. 9. A reactor according to claim 4, characterized in that at least one catalytic bed is of a radial or axial-radial type. 10. Equipment for the high efficiency catalytic conversion of carbon monoxide (CO) to carbon dioxide (C02) of the type comprising: a conversion reactor comprising a substantially cylindrical coating and at least one catalytic bed supported on this coating; a duct for feeding the gas flow reactor comprising carbon monoxide; and characterized in that it further comprises: means for accelerating the gaseous flow supported in the duct. 11. An equipment according to claim 10, characterized in that the means comprise a bottleneck element having a passage diameter smaller than the passage diameter of the duct. 12. A device according to claim 11, characterized in that the ratio between the passage diameter of the bottleneck element and the passage diameter of the duct is between 0.45 and 0.85. 13. An equipment according to claim 11, characterized in that the bottleneck element is a Venturi. 14. A method for the modernization of a reactor for the high efficiency catalytic conversion of carbon monoxide (CO) to carbon dioxide (C02) of the type comprising: an external coating - substantially cylindrical; at least one catalytic bed supported within the coating; an inlet nozzle in fluid communication with the liner to feed at least one catalytic bed with a gaseous flow containing carbon monoxide; further characterized in that it comprises the steps of: disposing upstream of at least one catalytic bed, means to accelerate the gas flow. 15. Method according to claim 14, characterized in that the means are arranged in the nozzle. 16. Method according to claim 15, characterized in that the means are arranged close to the coating. Method according to claim 14, characterized in that the means comprise a bottleneck element having a passage diameter smaller than the passage diameter of the nozzle. 18. Method according to claim 16, characterized in that the bottleneck element is a Venturi. 19. A method for the modernization of equipment for the catalytic conversion of carbon monoxide (CO) to carbon dioxide (C02) of the type comprising: a conversion reactor comprising a - - substantially cylindrical coating and at least one catalytic bed supported in this coating; a duct for feeding the gas flow reactor comprising carbon monoxide; and characterized in that it comprises the step of: arranging in the duct means for accelerating the gaseous flow.