MX2008010650A - Catalytic reactor - Google Patents

Abstract

A catalytic reactor having a mixing section (10) connected to a downstream reaction section (12) containing a catalyst (44) to promote a reaction of oxygen and a hydrocarbon fed to the catalytic reactor. The mixing section (10) is provided with a flame arrestor (30) to prevent a stable flame from propagating should any reaction of oxygen and hydrocarbons occur during mixing. The flame arrestor (30) permits flow in both axial and radial directions to promote mixing. Baffle elements (32) and a downstream static mixer (34) can also be used. The catalyst (44) is preferably in the form of monolithic blocks (46) enclosed by a ceramic tube (48) that is maintained as a unitary catalyst assembly (44) thatcan be removed for replacement and installation of the catalyst (44) as a single unit.

Description

CATALYTIC REACTOR Field of the Invention The present invention provides a catalytic reactor having a mixing section for mixing a gas containing oxygen with a hydrocarbon containing gas to produce a mixture and a downstream reaction section for catalytically reacting the mixture for produce a product More particularly, the present invention relates to a reactor in which the mixing section has a flame damper to prevent the formation of a stable flame and the hydrocarbons within the mixture should somehow be ignited. BACKGROUND OF THE INVENTION There are a variety of reactors which have the purpose of reacting oxygen with a hydrocarbon containing current to produce a synthesis gas product containing hydrogen and carbon monoxide. Typical reactors are partial oxidation reactors in which the hydrocarbon species are mixed with an oxygen containing gas and are partially oxidized with the aid of a partial oxidation catalyst. Other reactors also inject steam so that the hydrocarbons can be reacted by known reformed methane vapor reactions. In a reactor like these, the partial oxidation reactions, being exothermic, provide heat to meet the endometric heat requirements of the methane vapor reforming reactions. A ta! The reactor is known as an autothermal reactor. Still other reactors are multi-tubular reactors used for exothermic selective oxidation reactions for the production of ethylene oxide, vinyl acetate and other oxygenated hydrocarbons. Reactors that are designed for partial oxidation reactions contemplate an operation in which the proportions of hydrocarbons and oxygen are selected to produce a substantially complete conversion of the hydrocarbons to a hydrogen and carbon monoxide containing synthesis gas. As such, there is a significant oxygen content in which the auto thermal ignition of hydrocarbons is possible. The reaction of hydrocarbons and oxygen before the catalyst, for any reason is particularly undesirable because it results in unwanted consumption of reactants by total oxidation resulting in a decrease in the required production ranges and deposition of potential carbon in the catalyst . This problem is exacerbated in these reactors because the oxidation reactions occur directly downward in the reaction section at high temperature and in this way, combustion within the reaction section can propagate an undesired reaction inside the chamber. mixture. To combat this problem, the reactors have been designed so that the reactants, namely, hydrocarbons and oxygen are mixtures in a mixing section very quickly so that they do not have time to react before the reaction section is reached, which contains a catalyst to promote the possible reaction. An example of a reactor that is designed to prevent combustion of the reactants in the mixing section can be found in U.S. Patent No. 4,865,820 which describes a partial oxidation reactor in which the mixing chamber is provided with narrow passages. having straight through sections in which any of reactive reactants I is introduced for mixing under turbulent conditions with another reactive stream through the orifices formed in the narrow passage. The resulting turbulent flow has a velocity that exceeds the velocity of the propagated flame due to the recoil of the reactor flame. U.S. Patent No. 5,886,056 has provision for injecting high speed reactant gases through the plurality of isolated passages in a collector injector to reduce the residence time of the reactants within the mixing section to prevent undesirable reaction of the reactants inside the mixing section. In the North American patent No. 6, 471,937, the hot reactant gases are introduced into a nozzle contained in a mixing chamber to produce a supersonic velocity jet that introduces another reaction mixture component into the jet. The reactant mixtures are then introduced into a reaction zone. The residence time within the mixing chamber is sufficiently short and the reactants do not have time to react before entering the reaction zone. The problem with all these reactors is that they are not disposed to an operation in which it is not desired to completely react the hydrocarbons to a synthesis gas. For example, a catalytic partial oxidation reactor can be used as a pre-reformer to react higher hydrocarbons to methane prime. When such a reactor is used as a pre-reformer, the amount of oxygen based on the volume that is introduced in relation to the hydrocarbon feed is one fifth or less. That should be compared to a reactor designed for the complete reaction of hydrocarbons to carbon monoxide and hydrogen in which the range would be half or more. As such, the devices that are described in the patents listed above and that all depend on the drag, and will not work with such a small proportion of oxygen. In any case, the possible combustion mechanism of hydrocarbons is completely different in the pre-reformer case in which the reactants are mixed, a flammable mixture is produced. However, once the mixture is complete, there is not enough oxygen to produce a flammable mixture. In this way, combustion can be produced with mixing, but there is a small danger of combustion once the mixture is complete. Typically in these applications oxygen is introduced as a high velocity jet designed to entrain the flammable gas rapidly so that the flammable mixing zone is minimized. Flame arresters can also be placed after the mixing zone to reduce the effect of overheating in case the mixture accidentally ignites. The flame dampers consist of a set of narrow passages that only allow axial flow. Another problem in any reactor that contains a catalyst is that, eventually, the catalyst would have to be replaced. This can be a very difficult task that can take days to complete. In U.S. Patent 4,865,820, an attempt is made to segregate the catalyst from the insulation used to isolate the reactor walls from the high temperature reactions occurring in this reactor by provision of a reactor having an external pressure vessel containing insulation, an internal refractory and a metal coating containing the catalyst. The upper mixing section can be removed to allow recovery and reinstallation of the catalyst when replacement is required. Even if the catalyst is formed of monolithic blocks, recovering and recharging the catalyst is still problematic.

As will be discussed, the present invention provides a catalytic reactor in which the stable flame propagation within the mixing chamber is inhibited and is designed so that the catalyst can be easily installed and replaced. Brief Description of the Invention According to the present invention, a catalytic reactor is described, having a mixing section for mixing an oxygen containing gas with a hydrocarbon containing gas and a reaction section connected to the mixing section to react a mixture of oxygen containing gas and hydrocarbon containing gas to produce a product. The mixing section includes a mixing chamber having an inlet for the gas-containing hydrocarbon, an oxygen injector located within the mixing chamber for injecting the gas-containing oxygen into the gas-containing hydrocarbon. A flame damper is located at least below the oxygen injector. The flame damper is formed of a mass of porous material that allows mixing in both radial and axial directions of the mixing chamber to promote mixing of the oxygen containing gas and the hydrocarbon containing gas. The flame damper is in contact with the walls of the mixing chamber such as the flow of the oxygen containing gas and the hydrocarbon containing gas is forced to pass through the flame damper before entering the reaction section. In this way, if the combustion of the reactants occurs within the mixing section of a catalytic reactor of the present invention, the propagation of the flame is inhibited. Contrary to previous designs, this flame arrester can be placed close to the oxygen injection so that at least part of the mixture, which is the most dangerous part of the process, is carried out inside the flame damper. . The reaction section includes an internal chamber placed to receive the mixture of oxygen containing gas "and hydrocarbon containing gas.The catalyst is located inside the internal chamber to promote reactions involving mixing.An external pressure vessel is provided together With the thermal insulation between the inner chamber and the external pressure vessel, an outlet penetrates the external pressure vessel and communicates with the internal chamber to discharge a product gas containing the product.The advantage of such an arrangement is that the The catalyst and the reaction that occurs inside it are insulated from the insulation to prevent reaction between the insulation and the catalyst.Thereafter, the external pressure vessel is isolated from the inner chamber in which the reactions occur, operates at a lower temperature for allow the use of less expensive materials for such a pressure vessel and more environment for the personnel and equipment around the catalytic reactor. Preferably, the flame damper is made of metal foam monolith. The metal foam monolith may consist of metallic foam monolith layers and the mixing chamber may subsequently be provided with conductive elements that lie between the layers to then promote the mixture of oxygen containing gas and the hydrocarbon containing gas. The oxygen injector may comprise an inlet pipe projected into the mixing chamber and a circular distributor having openings for discharging oxygen containing gas. If necessary, a static mix can be placed under the flame damper to then promote the mixture of oxygen containing gas and hydrocarbon containing gas. To facilitate installation and recovery of the catalyst from the inner container, the catalyst may comprise a large number of monolithic blocks located within the assembly comprising a ceramic tube and an integral part for retaining the large number of monolithic blocks within the ceramic tube as a simple unit so that the assembly can be installed and retrieved from the inner container as a single unit. Preferably, the catalyst is of substantial cylindrical configuration and the integrating part comprises two opposite end plates of annular configuration and press rolls connected to the two opposite end plates. The final plates are configured to retain the ceramic tube between the end plates and thus the large number of monolithic blocks inside the ceramic tube and between the end plates. In this regard, the ceramic tube can be separable along its length to facilitate the installation of the large number of monolithic blocks and the attachment of the end plates by the press rolls. Brief Description of the Drawings While the description concludes with the claims distinctly, pointing to the matter that the Applicant sees as his invention, it is believed that the invention would be better understood when taken in relation to the accompanying drawings, in which : Figure 1 is a schematic, sectional view of a catalytic reactor according to the present invention; Figure 2 is a bottom plan view of an oxygen injector for use within the mixing section of the catalytic reactor of Figure 1; Figure 3 is a perspective view of an assembly of a catalyst containing a ceramic tube and its integral part to be used in relation to the catalytic reactor shown in Figure 1; Figure 4 is a schematic, elevational view of monolithic catalyst sections retained in the catalyst tube and its integral part retaining the catalyst tube and thus the monolithic catalyst section as a unit assembly; and Figure 4A is a fragmentary exploded end view of catalyst tube halves showing portions of intermediate edges for receiving the press rolls. Detailed Description of the Invention With reference to Figure 1, a catalytic reactor according to the present invention is illustrated. The catalytic reactor 1 is of cylindrical configuration and is provided with a mixing section 10 and a reaction section 12. The mixing section 10 functions to mix an oxygen containing gas, which may be, for example, oxygen or air enriched with oxygen with a hydrocarbon containing gas such as natural gas. The resulting mixture is then reacted within the reactant section 12. It is contemplated that the function of the catalytic reactor at very high temperatures, pressures and superimposed levels, namely, up to about 860 ° C, 40 bar (g) and space velocities of up to 200,000 hr "1.However, this is only for purposes used as examples and a reactor substantially in the form of a catalytic reactor 1 could be used under less severe operating conditions.The mixing section 10 is provided with an inlet 14 for introducing the gas containing hydrocarbon into a mixing chamber 16 of the mixing section 10. A known flow distributor 18 can be provided to distribute the gas containing hydrocarbon in the mixing chamber 16. The flow distributor 18 can be in the form of a circular plate having openings suspended by the feet 19 from the upper flange 20. The upper flange 20 can be connected by the known threaded fasteners, not shown, to a lower flange 22 in turn connected to a lower portion 24 of the mixing section 10 to allow the mixing chamber .16 to be opened for maintenance purposes. An oxygen injector 26 is also provided within the mixing chamber 16 for injecting gas containing oxygen as streams indicated by arrow "A". The oxygen injector 26 is suspended from an inlet pipe 28 also connected to the upper flange 20 and passes through a cut-off recess (not shown) provided within the flow distributor 18. With reference to Figure 2, the oxygen injector 26 is formed by a ring-like distributor having openings 29 for distributing the gas-containing oxygen through the mixing chamber 16. Other configurations, such as cruciform arrangements of pipes, centrally connected and having openings , is another possible configuration. A flame damper 30 is located below the oxygen injector 20 to prevent the formation of a stable flame before the mixing of the oxygen and hydrocarbons is completed to a mixing step in which a flammable mixture is formed. Preferably, the flame damper 30 is formed of a metal sponge material such as can be obtained from Porvair Advanced Materials located at 700 Shepherd Street, Hendersonville, NC, USA. Such materials have a very open structure and with relatively small pore sizes between approximately 10 and 100 pores per 6.45 square centimeters, with pores having diameters of less than 1 mm. Preferably, the material should have 80 pores per 6.45 square centimeters and a pore diameter of about 0.25 mm. The selected material can be a high nickel alloy such as Inconel 600 or Hastelloy C-276. The sponge material will transmit a flow pattern that is radial and axial to help promote mixing in these directions. In some flow rates the flame filter formed from sponge material may be sufficient to mix the oxygen containing gas and the hydrocarbon containing gas. The flame retardant 30 for the type of high flow conditions for which the catalytic reactor 1 is designed, is preferably formed of six to twelve layers of 2.54 centimeters (illustrated as six layers 30a, 30b, 30c, 30d, 30e and 30f) to allow the conductive plates 32 to be placed between the section to then promote radial flow and increase the mixture of oxygen and hydrocarbons. In the illustration, the conductive plates 32 alternate between an annular plate type diverting the flow inward towards a central opening thereof and a disc-like plate that diverts the outward flow around the disc-like plate. Other configurations are possible, which act to divert the flow and thus increase the mixture. In addition, it is possible for a layer of flame arresting material of any type to be placed on top of the oxygen injection point. Optionally, to promote the subsequent mixing, a mixing element 34 can be provided to then mix the oxygen containing gas and the hydrocarbon containing gas. It should be noted that there are many different types of static mixing elements that could work in the present invention and all are easily obtained from many different manufacturers. In any static mixer, the conductive elements cause the mixture to flow to change the direction and in this way, then mix them together. It should be noted that a suitable static mix could be the static mixers of Chemineer Kenics®, KM model series from North Andover, MA, USA. A similar static mixer is in the form of a cylindrical sheath having knife-like conductive elements to provide improved mixing. An optional feature is to provide instrument portals 35, 36 and 38 in which thermocouples and sample ports can be provided for, measuring gas composition and temperature.

The reactants, after they have been mixed as described above, then flow in the reaction section 12. The reaction section 12 includes an internal chamber 42 which contains a catalyst assembly 44 located within the internal chamber 42. The inner chamber 42 can be formed from a steel alloy which is suitable for atmospheres which carburize high temperatures, such as RA 602 CA alloy which is obtained from Rolles Alloys of Temperante, MI, USA. The internal chamber 42 is not a pressure vessel but can be exposed to high temperature and pressure levels and speeds described above. With reference to Figures and 4, a catalyst assembly 44 may contain a catalyst made from monolithic sections 46 of substantially cylindrical configuration that are retained within the assembly formed of a removable ceramic tube 48 and an integral part consisting of end plates 49. and ring configuration 50 and press rolls 51a and 51b which would be discussed in greater detail below. Preferably, at the top and bottom of the large number of the monolithic catalyst sections 46, the coating blocks 53 are provided to retain the heat within the catalyst. These are very well known in the art and are typically fabricated from a ceramic such as alumina, cordierite or metallic foam. Monolithic catalyst sections 46 are typically fabricated from cordierite or other high temperature material that supports a precious metal catalyst suitable to promote the catalytic reactions of interest, for instantaneous partial oxidation reactions of a gas containing hydrocarbon. The ceramic tube 48 is preferably formed by two sections 48a and 48b, which can be separated along the longitudinal axis of this tube. In practice, the monolithic catalyst sections 46 are placed within a tube half 48, for example 48a, together with the liner blocks 53. The two sections 48a and 48b of the tube 48 are then assembled. The end plates 49 and 50 are then placed at the other end of the tube and the press rolls 51a and 51b are screwed into the end plate 50 by screwed-in provisions 52 and 54. The threaded ends 55 and 56 of the press rolls 51a and 51b are then extended through the openings provided in the end plate 49 and held in place by the nuts 57 and 58 which are screwed into the press rolls to hold the end plates 49 and 50 in position. The end plates 49 and 50 are provided with side walls 59 and 60, respectively, receiving ends of the halves 48a and 48b of the tube 48 and thus maintain the halves 48a and 48b in an assembled state like the tube 48. With Specific reference to Figure 4, the longitudinal edges of each of the halves 48a and 48b of the tube 48 is provided with an elongated recess of the semicircular cross section 62 along the longitudinal edges thereof for receiving the press rolls 51a and 51b nested on and within the longitudinal edges of the halves 48a and 48b of the tube 48. It should be noted that the end plates 49 and 50 could be designed to position the press rolls 51a and 51b on the outside of the tube 48, and thus retaining halves 48a and 48b of tube 48 as a whole. However, this would be a less robust installation than illustrated. In addition, a tube that is not formed of halves of sections is possible. However, a similar tube would be more difficult to load with a catalyst. The entire assembly of components such as the catalyst assembly 44 can then be inserted as a unit into an internal chamber 42 with a final plate 49 placed in the upper part of the inner chamber 42. As can be seen, that is advantageous because the catalysts must be removed and replaced as a unit after the catalyst life has reached an end and is thus spent. It should be noted that the ceramic tube 48 is preferably manufactured from Pirolite available from Rex Materials Group of Fowlerville, MI, USA and may have a thickness of 1.25 cm. Subsequently, a layer of ceramic insulation could be used around the sections of the monolithic catalyst 46 and around the catalyst assembly 44. It should be noted later that while the aforementioned assembly is preferred, the embodiments of the present invention can be practiced without the use of the ceramic tube 48 and the components of the integral part. In fact, the present invention contemplates that a sediment catalyst could be used in the place of a monolithic catalyst illustrated here and described. Another advantage of the catalytic reactor 1 is that the catalyst contained within the sections of the catalyst 46, is isolated from an insulating material 60 that surrounds the inner chamber 42. In many reactors, that is not the case and the insulation, which is normally again formed of alumina that wears out over time. In addition, reactions between reactant IOS and alumina can degrade the catalyst. The insulation provided by the ceramic tube 48 and the internal chamber 42 helps prevent this. As can be seen, the internal chamber 42 is not pressed for air and there may be a leak. With specific reference again to Figure 1, to retain the integrity of catalytic reactor 1, an external pressure vessel 63 is provided to contain the insulation 64 and inner chamber 42. Preferably, the insulation 64 is low density ceramic such as FIBERFRAX ® LDS that can be obtained from Unifrax in Niagara Falls, NY, USA. Approximately 15 centimeters of this insulation in an operating reactor at approximately 860 ° C should be sufficient to produce temperatures of less than about 200 ° C on the external surface of the external pressure vessel 63. Since the external pressure vessel 63 is insulated of the inner chamber 42, where the reaction takes place, can be made of stainless steel such as 316 and 304. For high pressures of about 40 bar (g) inside the external pressure vessel 63, the wall thickness of less 2.54 cm are possible due to relatively low operating temperatures. The lower part of the external pressure vessel 63 can be filled with PLICAST® LWI insulation 22 65 which is available from Plibroco Company of Chicago, IL, USA, which is mold ceramics which is more appropriate to support the weight of the inner chamber 42. A set of flanges 66 and 68 are provided to connect the reaction section 12 to mix the section 10 by threaded connectors, not shown in the drawing, but very well known in the art. Also, as is well known, a high temperature packing material can be provided to seal the connection between the mixing section 10 and the reaction section 12. This packing can be a high temperature packing FLEXITALLIC available from Flexitaliic Group Inc. of Houston TX, USA. When the catalyst is to be removed or installed, the flanges 66 and 68 are separated and the catalyst assembly 44 is simply removed. Preferably, a platform 70, supported by the supports 72, 74 and 76 is welded into the pressure vessel 58 and the L-shaped support sections 78 are, in turn, welded to the platform 70 to support the inner vessel 42. Although the two support sections are illustrated, in practice three, equally spaced around the inner chamber 44 are used. The catalytic reactor 1 can be supported by a support 80 connected to the external pressure vessel 63. An outlet 82 is provided for discharge a product gas as indicated by arrow "B". The outlet 82 includes a frustoconical section 84 established within the external pressure vessel 63, an elbow 86 and a straight section 88. This provides communication between the internal chamber 42 and penetrates the external pressure vessel 63. An outlet section 90 of the pressure vessel 63 of cylindrical configuration is provided to include the straight section 88. The outlet section includes an insulation section 60 that also wraps the cross section 88. A connection flange 92 can be provided to connect the catalytic reactor 1 to the equipment of the procedure directed downwards. While the present invention has been described with reference to the preferred embodiments, as can occur to those skilled in the art, various changes, additions and omissions can be made without departing from the spirit and scope of the present invention.

Claims (10)

1. A catalytic reactor comprises: a mixing section for mixing an oxygen containing gas with a hydrocarbon containing gas and a reaction section connected to the mixing section to react the mixture of the oxygen containing gas and the hydrocarbon containing gas to produce a product; the mixing section includes a mixing chamber having an inlet for the hydrocarbon containing gas, an oxygen injector placed inside the mixing chamber for injecting the oxygen containing gas into the hydrocarbon containing gas and the flame damper placed at least below the oxygen injector; a flame damper being formed of a mass of porous material that allows mixing in both radial and axial directions of the mixing chamber to promote mixing of the oxygen containing gas and the hydrocarbon containing gas and the flame damper in contact with the walls of the mixing chamber so that the flow of the oxygen containing gas and the hydrocarbon containing gas, is forced to pass through the flame damper before entering the reaction section; and the reaction section includes an inner chamber positioned to receive the mixture of the oxygen containing gas and the hydrocarbon containing gas, a catalyst located inside the inner chamber to promote the reactions involving the mixture, an external pressure vessel, thermal insulation enters the inner chamber and the external pressure vessel and an outlet that penetrates the external chamber and is in communication with the inner chamber to discharge a product gas containing the product.

2. The reactor according to claim 1, wherein the flame damper is manufactured from a metal foam monolith.

3. The reactor according to. claim 2, wherein the metal foam monolith consists of metallic foam monolith layers and the mixing chamber further has conductive elements located between the layers to then promote mixture of oxygen containing gas and the hydrocarbon containing gas. The reactor according to claim 1, wherein the injector comprises gas comprises an inlet pipe projecting into the mixing chamber and a circular distributor having openings for discharging the oxygen containing gas. 5. The reactor according to claim 1, further comprising a static mixer located below the flame damper. The reactor according to claim 1, wherein the catalyst comprises a large number of monolithic blisters located in the assembly comprising a ceramic tube and an integral part for retaining the large number of monolithic blocks within the ceramic tube as a unit simple so that the assembly can be installed and retrieved from the internal container as a single unit. The reactor according to claim 6, wherein the catalyst is of substantially cylindrical configuration and the integrating part comprises two final annular shaped end plates and press rolls connected to the opposite end plates, the end plates are of appropriate size to retain the ceramic tube between the final plates and in this way the large number of monolithic blocks inside the ceramic tube and between the final plates. 8. The reactor according to claim 7, wherein the ceramic tube is separated along its length to facilitate the formation of the large number of monolithic blocks and the attachment of the end plates by the press rolls. 9. The reactor according to claim 8, wherein the flame damper is formed by metal foam monolith layers and the mixing chamber further has conductive elements that are located between the layers to promote mixing of the oxygen containing gas and hydrocarbon containing gas. 10. The reactor according to claim 9, further comprising a static mixer located below the flame damper.