MXPA98004899A - Method and apparatus for directing the oxygen injection with a reagent current within a fluidized bed reactor - Google Patents

Abstract

A system provides an oxygen containing gas and a gaseous reactant stream to a fluidized bed reactor using a sprinkler to introduce the oxygen-containing gas into the reactant gas stream. A feed line couples the sprinkler to the fluidized bed of the reactor and introduces the reactant gas stream and the oxygen-containing gas introduced into contact with the fluidized bed. A controller controls and maintains the quantity of gas containing oxygen and the gaseous reagent over a higher flammability limit, preferably with a safety margin of at least 1

Description

METHOD AND APPARATUS FOR DIRECTING OXYGEN INJECTION WITH A REAGENT CURRENT WITHIN A REACTOR OF FLUIDIZED BED FIELD OF THE INVENTION The invention relates to a method and apparatus for introducing oxygen-containing gas into a reagent stream that is fed to a fluidized bed reactor and more particularly to the injection of oxygen into a reagent feed stream into a bed reactor. fluidized that is used in an anhydride synthesis process BACKGROUND OF THE INVENTION The production of anhydrides involves the partial oxidation of an appropriate hydrocarbon in the presence of a suitable catalyst. The production of commercial maleic anhydride employs feeds from an appropriate reactant stream such as butane or benzene within a partial oxidation reactor, in the presence of air / oxygen and a suitable catalyst maleic anhydride is produced with minor amounts of other oxygenating and carbon oxides. In most cases butane is the preferred supply. When butane is used as a starting material, a separate air for the introduction of air into the fluidized bed To provide oxygen for the conversion of butane to anhydride maltreatment, the prior art has suggested the addition of oxygen or oxygen-containing gas directly to the feed stream or as a separate feed for the reactor Such teachings can be found in the patent d and United States No. 3,899,516 to Dickason, United States Patent No. 4668802 to Contractor, US Pat. Nos. 4,987,239 and 5,126,463 to Ramachandran et al. None of the above-mentioned patents provides any teaching that a deficiency may occur. Oxygen in a fluidized bed reactor at the reagent feed introduction point Dickason teaches the addition of substantially pure oxygen directly to the reactor at high butane concentrations. Contractor teaches the use of a bed transported with air, air enriched with oxygen, or oxygen in the regeneration zone The Ramachandran patents teach that when the pure oxygen feed is present in the partial oxidation reactor, a gaseous flame suppressor mixture, for example, carbon dioxide or a substantially unreacted hydrocarbon can be used. , both Ramachandran patents provide the ap additional potassium downstream from the partial oxidation reactor to recover and recycle the carbon dioxide and the unreacted hydrocarbon feed U.S. Patent No. 3,661,165 to Rainbird et al. describes a sprinkler valve for mixing oxygen with gaseous hydrocarbons in a process component. The Rainbird et al. sprinkler valve includes a number of jets confronting downstream within the hydrocarbon gas flow. The jets introduce oxygen at a rate of jet that is substantially higher than the velocity of the hydrocarbon gas Variations in the mass flow of oxygen are achieved by varying the area of the jet orifices, while maintaining a predetermined pressure drop across the orifices. The patent US Pat. No. 3,702,619 to Son discloses a process and apparatus for supplying a gaseous stream into another gaseous stream in an in-line mixing apparatus. U.S. Patent No. 5,356,213 for US Pat.

Arpentinier describes an additional sprinkler design that is positioned coaxially with respect to the axis of a channel containing a feed stream. Radial fins are employed in the sprinkler to inject gas in a substantially radial direction towards the outside of the feed stream to allow mixing of the injected gas with the feed flow gas. The prior art cited above does not include teaching of the fluidized-bed reactor performance failures that occur as a result of oxygen deficiencies at the feed-in introduction points. further, the prior art insofar as it includes teachings regarding the introduction of oxygen containing gases at various points in a process does not include teachings of how such an introduction can be achieved in a way to ensure the safety of the process. Therefore, it is an object. of this invention provide an improved system for allowing an oxygen-containing gas to be combined with a gaseous reagent feed stream for a fluidized bed reactor. It is another object of this invention to provide an improved system and method for combining an oxygen-containing gas and gaseous reagents in a manner that avoids explosions, deflagration or other anomalous effects in the process. It is yet another object of this invention to provide an improved method and system for the addition of oxygen to butane in a fluidized bed reactor where there is no Oxygen deficiencies in the feed flow inputs BRIEF DESCRIPTION OF THE INVENTION A system provides an oxygen-containing gas and a gaseous reactant stream to a fluidized-bed reactor. A sprinkler causes an introduction of oxygen-containing gas into the reagent gas stream. A feed line couples the sprinkler to the fluidized bed of the reactor. introduces the reactive gas stream and the oxygen-containing gas introduced directly into contact with the fluidized bed A controller controls the amount of gas containing oxygen and the gaseous reactant so that at the point of feed injection, the fluidized bed catalyst does not experience oxygen deficiency To confirm safety the reagent content of the combined feed and the oxygen stream is maintained above a higher flammability limit preferably with a safety margin of at least 10% In one embodiment the system allows the production of maleic anhydride from a feed stream n that includes butane and oxygen BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a system that modalizes the invention of the present Fig. 2 is a sectional view of a feed pipe including a sprinkler for introducing oxygen into a gaseous feed stream. Fig. 3 is a schematic view of a pair of adjacent jets of the sprinkler of Fig 2 DETAILED DESCRIPTION OF THE PREFERRED MODALITY While the invention will be described hereinafter in the context of the process of production of maleic bed anhydride, those skilled in the art will realize that it is equally applicable to other processes that introduce an oxygen-containing gas. with a stream of reagent fed to a fluidized bed reactor. In Fig. 1, a system for producing anhydride malting using a partial fluidized bed oxidation process is shown. A conduit 10 provides a flow of butane through a control valve 12 a check valve 14 towards a sprinkler 26 An oxygen source is connected by means of a control valve 28 to the sprinkler 26 The sprinkler 26 thus allows the oxygen to be introduced into the mixed gas stream and to pass through the conduit 30 to the feed lines 32 The feed lines 32 are in direct contact with a fluidized bed 34 comprising a particle catalyst that facilitates a reaction that occurs between the butane and oxygen components to produce maleic anhydride. That product is emitted from reactor 38 via conduit 38 where it is subjected to further processing. At the bottom of reactor 36 is a feed of air 38 which provides additional oxygen for the reaction A controller 40 includes control connections for each of the valves 12, 20, and 28 and serves to control the reagent feeds therethrough in accordance with the detected process conditions While a single controller 40 is shown in FIG. 1, those skilled in the art will realize that a plurality of controllers can be used to control the respective valves and other control entities. The process inputs to the controller 40 do not are shown in Figs 2 and 3 The controller 40 (under the control of the operator) ensures that the s oxygen sufficient by the sprinkler 26 within the feed stream to ensure at the injection points within the fluidized bed reactor 36, that sufficient oxygen is present to avoid an oxygen deficiency at such injection points. The controller further ensures that the Mixed concentration of reagents and oxygen is maintained above a maximum flammability limit (UFL) of the mixture. An acceptable safety margin of at least 10%, and preferably 25%, must be maintained. Direct injection Oxygen with the reagents allows the concentration of oxygen in the region of the feed injection that allows an improvement in performance and extension of the useful life The air flow inside the reactor 36 by means of the conduit 38 is also adjusted to ensure that the proper amount of oxygen is introduced into the fluidized bed of the reactor to allow optimum reaction conditions to be achieved. It is vital for the invention that various oxygen supplies are provided to the fluidized bed reactor 36, a supply that ensures an adequate concentration of oxygen in the immediate regions of the feed injection and the second supply of oxygen that ensures the appropriate availability of general oxygen within the fluidized bed to allow the adequate reaction conditions to be reached. before the oxygen feed flow through the sprinkler 26 is maintained at a level to ensure that the upper flammability limit of the mixed reagent gas stream is exceeded The upper and lower flammability limits (UFL and LFL) for a stream of butane feed in 100% oxygen are approximately 49 0 and 1 8, respectively at 3 1 kg «/ cm2g 440 ° C The sprinkler 26 is formed to allow its injectors to be placed in a pattern that achieves the effective distribution of oxygen through the flow of reactive gas The injectors are also placed to prevent the interaction of flammable mixtures occurring within the feed stream In fig 2 the sprinkler 26 is placed inside the duct 30 and is preferably formed in the form of an individual ring 50 which is placed normal to the flow of feed gas To achieve good gas distribution, the inner and outer diameters of the ring 50 are fixed so that there is substantially equal gas flow in the regions 52 and 54 respectively. This arrangement ensures that a low pressure area is not formed in the feed pipe within the ring of injectors (the which would be extracted together with the jets, causing a coalescence thereof and creates a severe problem in the case of an ignition of one of the jets) Therefore, the effective cross-sectional areas of the regions 52 and 54 are made approximately equal by appropriate sizing of the ring 50 Within the ring 50 there is a channel 56 communicating with the valve 28 (see Fi. 1) by means of the inlet 58 A plurality of fixed jets 60 are placed around a ring 50 and are oriented to direct the oxygen effluent from the channel 56 in a downward direction inside the duct 30 A sectional view of a pair of jets 60 and 60"is shown in FIG. 3. Oxygen flows out of jets 60 'and 60" and creates regions of substantially pure oxygen 70 and 72. Mixed reactive feed gas is present in regions 74, 74' and 74"Within regions 76 and 78 (with double scratching), a mixture of oxygen and reagents occurs that is within the flammable scales. Furthermore, downstream (regions 80 and 82), the gas mixture is non-flammable, even when it contains The separation D between the adjacent jets 60 'and 60"is adjusted so that the flammable regions 76 and 78 do not interact. The limitation of the jet interaction reduces the probability that once the jet is ignited it causes the ignition of another jet and of the jets that coalesce to form an individual jet with a large volume of flame. The orifices of adjacent jets are therefore placed so that the nearby regions of flammable gas mixture do not interact. In addition, the regions of gas mixed from adjacent jets intersect at a point beyond the furthest extension of the flammable regions. The ignition risk is further reduced by decreasing the total combined flammable volume contained within each oxygen jet. This is achieved by reducing to a minimum the diameter of the orifice of each jet which, in turn, tends to increase to the maximum the number of holes to achieve a desired level of oxygen flow. The distance between a center of an orifice to the center of an adjacent orifice is given by D > d0 ^ (2587-UFL) / (100-UFLK where D = center - center distance between the holes, d0 = hole diameter, UFL = upper flammability limit (in percentage) A risk of sustained jet blast is further reduced by ensuring that the oxygen jet velocity is appreciably higher that the velocity of the gaseous fed reagents and the flame velocity of a flammable oxygen reagent mixture Such a jet velocity promotes the flame off, and the ignition occurs To promote the shutdown, the initial oxygen jet velocity is preferably of at least two times either the feed rate of the reagent stream or the flame velocity, whichever is greater In addition the sprinkler is not constructed outside the square-shaped tube or to be held with an angle iron Such structures They include sharp angles that create countercurrents that can improve flame stability. Returning to Fig. 1, the controller 40 operates the valves 12, 20 and 28 to provide approximately four parts of butane and ninety-six parts of air to the fluidized-bed reactor 36. Oxygen injection, by means of the valve 28 and the sprinkler 26, allows a modest reduction in air flow through conduit 28. In addition to ensure that the combined reagent / oxygen flow in conduit 30 is in excess of the upper flammability level, it is preferred that the volumetric flow of the sprinkler 26 does not exceed a relative volumetric flow of 38% oxygen and 62% butane, more preferably, the volumetric effluent does not exceed a relative volumetric flow of 32% oxygen and 68% butane. Instead of decreasing the air flow when oxygen is added to the butane system, the air flow can be maintained at the pre-oxygen addition level. The butane feed rate can be increased without reducing the performance. In this way, direct oxygen injection can be used to promote the production of maleic anhydride. The direct oxygen injection can also be coupled with the air enrichment so that the oxygen is added to the butane feed stream and the air stream. The air flow can be reduced or maintained at the pre-oxygen addition level. By doing so, the production and the production improvements obtained by the addition of oxygen are maximized. If the oxygen flow increases suddenly or the flow suddenly decreases of reagent feed, it is possible that the outlet from the sprinkler 26 can move within a detonable region To control a sudden increase in oxygen flow, the valve 28 is provided with a critical flow orifice that limits the possible flow of oxygen . The orifice is dimensioned so that if the valve 28 fails in the fully open state, the amount of oxygen required to produce a detonation under the normal minimum feed flow rates can not be delivered during the emergency process shutdown, while the oxygen flows to the sprinkler 26 is turned off simultaneously with the process reagents, the oxygen flow will stop simultaneously with the stopping of the reagent flow. Since the oxygen valve 28 is significantly smaller than either of the supply valves 12 and 20, the oxygen flow will stop before the flow of reactants, thus preventing an accumulation of feed concentration to a detrimental level. The controller 40 is operated to stop the flow of oxygen to the sprinkler 26 if the feed reagent pressures fall below a certain level. This is due to a significant drop in the feed flow that can be caused by the feed block and a shut-off response based on the pressure of the valve 28 prevents a possible subsequent detonable mixing between the duct 30, the controller 40 is operated to stop the flow of oxygen to the sprinkler 26 if the temperature of the mixed oxygen reagent stream rises above a certain level. This is due to a significant increase in the temperature of the gas mixture that can originating around by a deflagration near the sprinkler and a shut-off response based on the temperature of the valve 28 will extinguish such deflagration. The valve 28 is also controlled by the controller 40 to ensure that certain minimum oxygen flows to the sprinkler 26. In the operation , the reagent feed should be avoided from the countercurrent inside the sprinkler 26. This is prevented by maintaining an oxygen flow through each sprinkler jet 60; maintaining a jet velocity that is large enough to avoid a convective or diffuse flow of reagent feed into sprinkler 26, and place the jets on the downstream side of the sprinkler 26 Maintenance of oxygen flow through each jet of sprinkler 60 is achieved by ensuring that the pressure drop across the jets 60 is significantly greater than the pressure drop inside the sprinkler 26. In order to prevent the reagent feed from being dispersed within the sprinkler 26, it is preferred that a drop of minimum pressure through each jet 60 is at least 0 0703 kg / cm and preferably 0 703 kg / cm 2 Finally during start-up, a nitrogen purge is used to wash the reagent sprinkler 26 before the flow starts Oxygen During turn-off the sprinkler 26 is flushed of oxygen with a nitrogen purge while maintaining a high enough pressure drop to avoid negative pressure. Current This is necessary since the reagents will flow into the sprinkler 26 after shutdown. While the sprinkler 26 has been shown in the form of a ring, other shapes such as concentric rings, vertical cross sections and vertical pipe are acceptable. However, each structure must meet the requirements set forth above with respect to the most preferred embodiment, that is, the circular sprinkler configuration shown in Fig. 2. Instead of placing the jets directly on the bottom edge below the sprinkler 26, they can be positioned off center, although on the downstream side. This can be beneficial as it allows it to be used a greater number of jets While the description has focused on the use of the invention in a maleic anhydride production process, other gas phase oxidations using fluidized beds can also employ the invention (for example, the processes for the acrylonitrile production, synthesis of italic anhydride, etc.).

The gaseous reactant stream, such as naphthalene or ortho-xylene in the form of a gaseous stream, can be used for the oxidative production of phthalic anhydride using the inventive system and process as described herein. In other embodiments, the production of nicotinonitrile can be produced by reacting 3-methyl pyridine with ammonia in the presence of a catalyst. In yet another embodiment, isophthalonitrile can be produced by reacting metaxylene and ammonia in the presence of a catalyst. In certain cases, inert gases may be added either to oxygen or reagent feed streams to reduce the upper fire limit and thereby increase the maximum allowed oxygen concentration in the feed stream. It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications may be devised by those skilled in the art without departing from the invention. Accordingly, it is intended that the present invention encompass all such alternatives, modifications and variants that fall within the scope of the appended claims.

Claims (1)

1. CLAIMS A system for providing a mixture of an oxygen containing gas and a gaseous reactant stream selected from the group consisting of butene butene and benzene to a fluidized bed reactor to produce a maleic anhydride comprising a) a source of a first gas containing oxygen coupled to the reactor b) the reactive gas stream, c) sprinkler means for introducing a second oxygen-containing gas into the reactive gas stream, d) feeding means coupling the sprinkler means to a fluidized bed of the reactor, to introduce the reactive gas stream and the second oxygen-containing gas introduced directly into contact with the fluidized bed, and e) control means for controlling the feed of the second oxygen-containing gas to the sprinkler means to introduce sufficient oxygen within the reactive gas stream at a feed injection point to maintain an effective amount of oxygen not to produce the maleic anhydride 2 The system as described in claim 1, wherein the first oxygen-containing gas is air. The system as described in claim 1, wherein the first oxygen-containing gas is oxygen. The system as described in claim 1, wherein the fluidized bed comprises a catalyst for converting the gaseous reactant stream and the oxygen-containing gas to a maleic anhydride. The system as described in claim 1, wherein the control adjust the gaseous reactant feeds to the reactive gas stream and the second oxygen-containing gas to ensure that a combined reagent gas stream and the second oxygen-containing gas is maintained above a higher flammability limit. 6 A method for providing a mixture of a gas containing oxygen and a stream of gaseous reactant selected from the group comprising butane, butene and benzene to a fluidized bed reactor for producing maleic anhydride, comprising the steps of a) introducing an oxygen-containing gas into the gaseous reactant stream. b) feeding the gaseous reactant stream and the second gas containing oxygen introduced directly into contact with the fluidized bed reactor; and c) controlling the feed of the oxygen-containing gas so that it introduces sufficient oxygen into the gaseous reactant stream at a feed injection point to maintain an effective amount of oxygen directed to produce the maleic anhydride. 7 The method as described in claim 6 wherein the gaseous reactant stream comprises butane, the oxygen-containing gas is oxygen and the fluidized-bed reactor. the method comprising adding a catalyst to convert the butane and oxygen to a maleic anhydride. The method as described in claim 6, wherein further the control step maintains the feed of the gaseous reactant stream and the oxygen an upper flammability limit 9 The method as described in claim 6, wherein in addition the control stage maintains a combined stream of oxygen and gaseous reactant stream over an upper flammability limit. oxygen-containing gas and a gaseous reactant stream to a fluidized-bed reactor to produce an anhydride, comprising the steps of a) introducing an oxygen-containing gas into the gaseous reactant stream; b) feeding the gaseous reactant stream and the second gas containing oxygen introduced directly into contact with the fluidized bed reactor; and c) controlling the feed of the oxygen-containing gas so that it introduces sufficient oxygen into the gaseous reagent stream at a feed injection point to maintain an effective amount of oxygen directed to produce the anhydride