ES2275693T3 - A SAFETY CONTAINER OF A FLUIDIZED CATALYTIC RECREATION REACTOR. - Google Patents

Abstract

Fluidized catalytic cracking reactor vessel comprising at its upper end means to separate catalyst particles from an effluent of a dilute phase fluidized catalytic cracking reactor riser, which separation means are fluidly connected to the downstream part of the reactor riser, fluidly connected with means to discharge the cleaned reactor riser effluent from the vessel and fluidly connected to means to discharge the separated catalyst to the lower end of the vessel, the vessel further comprising at its lower end means to discharge catalyst from the reactor vessel, wherein (a) between the side wall of the vessel and the separation means a shield is present, resulting in an exterior space between the vessel wall and the shield and an interior space within the shield, wherein the interior space is in open communication with the lower end of the reactor vessel at its lower end and wherein the exterior space and interior space are fluidly connected by means of one or more openings, and (b) means are present to supply a gas poor in coke precursors to the exterior space.

Description

Safety vessel of a reactor FCC

The invention relates to a container of safety of a fluidized catalytic cracking reactor (FCC) that it comprises means to prevent the formation of coke on the surface of the internal parts of the container and the walls of the container. The invention especially relates to a method for retrofit safety vessels of existing FCC reactors so that a reactor safety vessel is obtained which,  during use, you experience less coke formation in your internal parts and walls of the safety container.

The document US-A-4,961,863 describes a safety vessel of an FCC reactor comprising in its upper end a cyclone means to separate particles from catalyst of an effluent from a cracking elevator reactor fluidized catalytic in dilute phase, said cyclone medium being fluidly connected to the downstream part of the reactor elevator, fluidly connected with means to unload the clean effluent from the lift reactor from the vessel security and fluidly connected with dipleg media (media to forward the particles collected in a catalytic bed cyclone) to discharge the catalyst separated from the lower end of the safety container. A secondary opening will be present gas discharge, usually between or after the medium of separation, to allow the gases present in the container reactor safety are discharged from the vessel of reactor safety together with the clean reactor effluent elevator. These configurations in which these media are fluidly connected, result in times of short and low contacts after cracking, they are called precise or coupled cyclone FCC reactor configurations precise.

During use, coke tends to form, by example, on the surface of the separating means of a container of safety of an FCC reactor for example as in the document US-A-4961863. This is especially the case when an FCC unit is operating with a supply heavier than what he was designed for. This is due to small quantities of coke precursors, for example hydrocarbons heavy ones that have not completely separated from the catalysts in the middle of separation. When these small amounts of coke precursors together with the catalyst are discharged to the lower end of the reactor safety vessel almost immediately separate from the catalyst and flow up in the reactor safety vessel. Coke will form when these coke precursors come into contact with the outside hot, for example from the separating medium.

The problem of excessive coke formation is especially a problem when heavy supplies are processed in FCC reactor safety vessels that have been modified with respect to a conventional design not required in the called precise coupled design. If the coke formation reaches a certain level, large coke fragments can fall towards down towards the lower end of the safety container of the reactor. These large fragments of coke can cause blocking the medium to discharge the catalysts from reactor safety vessel. Due to said blocking the FCC unit will have to close to remove the lock. It has experience that such unscheduled closures occur almost After one or two years of operation. This is very disadvantageous. Especially considering the fact that a unit FCC is supposed to work without an unscheduled shutdown during several years, for example 4 years.

The object of the present invention is provide a safety vessel of an FCC reactor that, When used, it can work for a long time in absence of unscheduled closures due to the problems of coke formation described above.

The object is achieved with the following apparatus.

A safety vessel of a reactor fluidized catalytic cracking comprising at its upper end a means for separating catalyst particles from an effluent of a diluted phase of a catalytic cracking elevator reactor fluidized, said separation means being connected in a manner fluid with the part downstream of the elevator reactor, connected to fluid way with the medium to discharge the clean effluent from the lifting reactor from the safety vessel and connected to fluidly with a separate catalyst discharge medium to the lower end of the safety container, comprising additionally the safety container at its lower end a means for discharging the catalyst from the container of reactor safety, in which

(a) between the side wall of the container security and the separation medium is present a layer protective, which results in an outer space between the wall of the safety vessel and the protective layer and a space interior inside the protective layer, where the interior space is in open communication with the lower end of the container reaction at its lower end and in which outer space and the interior space are fluidly connected by a or more openings, and

(b) means are present to provide a poor gas in coke precursors to outer space.

With the present apparatus in accordance with the invention, a lower coke formation is obtained. Unwanted be limited in any way by the following theory it is believed that the Coke formation reduction is attributed to the fact that coke precursors that are discharged from the separator medium to bottom end of reactor safety vessel, cannot enter said outer space due to the overpressure obtained by adding additional gas Poor in coke precursors. In this way, large areas stagnant, present in outer space, will contain significantly less coke precursors resulting in a lower coke formation resulting in a lower coke formation

The resulting trajectory of the precursors of coke from the lower end of the safety container of the reactor to the secondary gas discharge opening within the interior space will be shorter than in an apparatus without a layer protective Therefore a shorter residence time will be obtained of coke precursors and consequently will also be formed Less coke in the interior space. Due to the presence of the protective layer will occur more turbulence inside the interior space, thereby reducing the coke formation

The protective layer of the apparatus according to the invention is present between the side wall of the container of Security and the means of separation. The resulting interior space is in open communication with the lower end of the container reactor safety so that the vapors, precursors of coke and optional separation gas present at the end bottom of the safety container can freely enter the interior space from below. The outer space is connected from fluid way through one or more openings with the interior space. These openings may be present in the protective layer. Preferably, this opening is formed by a space between the side wall of the reactor safety vessel and the lower end of the protective layer. In this configuration the protective layer and side walls of the safety container of the reactor do not join, which is advantageous due to the advantages Obvious construction. Because both outer space and the interior space are fluidly connected with end bottom of the reactor safety vessel, the space interior and outer space are fluidly connected in accordance with this invention.

The protective layer may be composed of a substantially vertical wall, i.e. tube or box type, which extends from the roof of the safety vessel to a position at the lower end of the safety container and that horizontally close the separation means. Preferably the protective layer comprises side walls of tube type and a ceiling, the ceiling being located just above the separation means.  This is advantageous because it reduces the volume of the interior space resulting in greater turbulence and less time to residence of the coke precursor flow within the space inside.

Poor gas in additional coke precursors that is added to outer space will flow through the opening or openings in the protective layer towards the interior space and towards the secondary gas discharge opening. The gas velocity in this opening or openings in the protective layer should be high enough to prevent coke precursors enter outer space from the lower end of the safety vessel Preferably, this gas velocity it is between 1 and 5 m / s and more preferably it is greater than 2 m / s. This gas speed can be achieved by adjusting the volume of the gas poor in coke precursors that is added to outer space and / or adjusting the area of the openings in the protective layer. By example a protective layer that has an opening that opens towards the lower end of the reactor safety vessel, such as described above, it can be advantageously modified adding a section of lower protective layer that tilts towards the side wall of the safety vessel reducing from this way the area of the annular (type) opening.

The separation means to separate the catalytic cracking elevator reactor effluent catalyst diluted phase fluidized can be any means known by a specialist in the technique. A particular reference is made to "Fluid catalytic cracking technology and operation", Joseph W. Wilson, PennWell Publishing Company, Tulsa, 1997, pages 104 to 112 illustrating different separation means suitable for use in combination with the present invention. Means of separation preferably they are a combination of a primary separator and secondary. Suitably the primary separators are separators horizontal cyclone type in which the effluent is supplied tangentially towards a horizontally mounted cylinder. Saying horizontal cyclone separator or double drum separator se described for example in the document US-A-4,961,863 mentioned previously. Another very suitable primary separator is a cyclone vertical provided with or without a dipleg. Vertical cyclones provided with a dipleg are the most used primary separators usually in FCC processes as illustrated in the book of general text mentioned above. Vertical cyclones without a dipleg are described for example in the document EP-A-643122. Separators secondary are properly a vertical cyclone or a separator of whirlwind. The vertical cyclones provided with a dipleg are the secondary separators most commonly used in FCC processes as illustrated in the general textbook that has been made reference above.

In an adequately more commercial FCC process of a primary separator fluidly connects to the end downstream of the fluidized catalytic cracking elevator reactor in dilute phase. In turn, more than one secondary separator can fluidly connect to a primary separator. This crowd of separators that may be present at the top of a reactor safety vessel results in an area larger outer surface on which the coke formation Locking up most of this area surface with the protective layer according to the apparatus of the present invention gives rise to an opportunity to train considerably less coke as explained previously.

The gas outlet of a primary separator can discharge the catalyst-poor gaseous effluent in the part upper inner space. This gas will enter through an opening of secondary inlet gas inlet also located in the interior space. The cyclone gas inlet opening secondary will also serve as secondary discharge opening of gas.

Preferably the gas outlet duct of the primary separator and gas inlet pipe of the separator secondary are fluidly connected in a configuration of FCC coupled precisely. The secondary gas discharge opening as described above is properly present in the conduit that connects the primary and secondary separators. Optionally the secondary gas discharge opening can be present in the gas outlet duct of the separator secondary.

Preferably an area of separation at the bottom of the safety vessel from reactor. In this separation zone low point hydrocarbons of boiling present in the catalyst as discharged into the safety container or at the end of the container lower security are separated by contact with a means of suitable separation, which preferably comprises steam, in a fluidized bed of dense catalyst phase. The middle of separation is the fluidized medium of said fluidized bed. The gas separation and hydrocarbons enter the interior space to unload them from the security container by opening secondary gas discharge. Optionally, a different separation safety container to separate additionally the hydrocarbons of the catalyst obtained in the reactor safety vessel. This last configuration in sometimes called FCC configuration of three containers of safety, the third vessel being the regenerator. In a configuration of three safety vessels the poor gas in coke precursors, which is added to outer space, is preferably the separation gas comprising hydrocarbons as obtained in the different separation vessel. It has been discovered that the content of coke precursors in this gas stream is low enough to use the gas for this purpose.

In addition to the analyzed option of the configuration of three safety vessels the poor gas in coke precursors can be any inert gas, for example nitrogen or low boiling hydrocarbons. Preferably steam is used.

The reactor safety vessel can used properly to process heavier supplies. These Heavy supplies are characterized because they have a content of Conradson carbon of more than 1% by weight and in which more than 40% in volume of its components has a boiling point of more 475 ° C.

The invention also relates to a method for reset a safety vessel of a cracking reactor existing fluidized catalyst comprising at its upper end a means for separating catalyst particles from an effluent of a phase fluidized catalytic cracking elevator reactor diluted, a means to discharge the clean effluent from the reactor elevator from the safety vessel and a means to unload the catalyst separated to the lower end of the vessel security and at its lower end a means to download the catalyst from the reactor safety vessel, in which a protective layer is added to the reactor safety vessel existing to reach a reactor safety vessel as described above. The security vessels of an existing FCC reactor, for example, designed for a Light supply, can be advantageously set back with this simple method to reach an FCC unit that can handle heavier supplies. Typical FCC processes that can set back with this method are described for example in the book General text mentioned above pages 24 to 42. This Re-setting method is especially advantageous because adding a simple element, the protective layer, problems can be avoided with coke without having to take more rigorous measures, such as for example replace the entire reactor safety vessel by a reactor specially designed for a more supply heavy.

The invention will be further illustrated using Figure 1.

Figure 1 shows a safety container of a fluidized catalytic cracking reactor (1) that is part of an FCC configuration of three security vessels. He reactor safety vessel (1) comprises at its end top the downstream part of a cracking elevator reactor fluidized catalytic in dilute phase (2). In this part waters Below (2) two primary cyclone separators are shown horizontal (3). These separators (3) are supplied tangentially the effluent towards a mounted cylinder horizontally (4). A primary cyclone is connected so fluid with two secondary cyclones (6) of which only show one. The gas outlet openings (5) of the separators Primary (3) fluidly connected to the gas inlets (not shown) of the secondary cyclones (6). The cyclones Secondary (6) are vertical cyclones provided with a dipleg (7). Primary cyclones are also provided with a dipleg (8). The gas outlets (9) of the secondary cyclones are connected to a discharge conduit (10) through which the Clean effluent from the lifting rector leaves the safety vessel of the reactor (1). In the conduit that connects the primary cyclones and secondary is a secondary gas discharge opening (not shown) through which the gas entering the space inside from below can be unloaded from the container reactor safety through the gas outlet ducts (9) and (10) The reactor safety vessel (1) is provided additionally at its lower end with a conduit (11) for unload the catalyst from the safety container of the reactor to separation vessel (not shown). To the extreme bottom of the reactor safety vessel (1), is present a separation zone (12) provided with means (13) for supply separation gas to the fluidization medium. About this part or all of the separation means (3, 6), is present a protective layer (14) having an opening (15) at its end lower. The protective layer (14) has a flat roof (18), walls verticals (19) and an inclined lower wall section (20). The protective layer (14) encloses an interior space (16) from a outer space (17). Both exterior and interior spaces are communicated with the lower end (21). A supply duct (22) is present to supply poor gas in precursors of coke from the different separation vessel (not shown) to outer space (17). This gas will leave outer space (17) through a discharge opening (23) and will flow through the lower end (21) of the reactor safety vessel (1) and from the opening (15) to the interior space (16).

Preferably the gas outlet opening of the conduit (22) is arranged so that the poor gas in Coke enters tangentially into the safety container (1). This it is advantageous because a good mixture of poor gas is achieved in coke in outer space (17).

Claims (7)

1. Safety vessel of a reactor fluidized catalytic cracking (1) comprising at its end superior means for separating catalyst particles from a effluent from a fluidized catalytic cracking elevator reactor in diluted phase (2), said separation means being connected to fluid way with the downstream part of the elevator reactor (2), fluidly connected with a means to discharge the effluent clean of the safety vessel lift reactor (10) and fluidly connected with a means to download the catalyst separated to the lower end of the safety vessel (7, 8), the security container further comprising its lower end a means to discharge the catalyst from the reactor safety vessel (11), in which (a) between the side wall of the container safety and the separation medium is present a protective layer  (14), which results in an outer space (17) between the wall of the safety container and the protective layer (14) and a space inside (16) inside the protective layer (14), in which the interior space (16) is in open communication with the end bottom (21) of the reactor safety vessel at its end bottom and in which space (17) and interior space (16) are fluidly connected by one or more openings, Y (b) means (22) are present to supply a gas poor in coke precursors to outer space (17). 2. Apparatus according to claim 1, in which the opening that contacts the outer space (17) and the interior space (16) is formed by an opening between the wall side of the reactor safety vessel (1) and the end bottom of the protective layer (14), said opening (23) being open to the lower end of the safety container of the reactor. 3. Use of a security container of a reactor according to any one of the claims 1-2, in which a coke-poor gas is supplied to outer space (17) with a speed such that the precursors of coke cannot enter the outer space (17) due to a overpressure obtained by adding coke-poor gas. 4. Use according to claim 3 in the that the poor gas in coke precursors is an inert gas that is steam or nitrogen 5. Use according to claim 3, in the that the gas stream obtained in a separation vessel Different is used as poor gas in coke precursors. 6. Use in accordance with any one of the claims 3-5, wherein the gas velocity of the gas that leaves the outer space when it passes through the openings is greater than 2 m / s. 7. Use in accordance with any one of the claims 3-6, wherein the supply to fluidized cracking process has a carbon content Conradson of more than 1% by weight and in which more than 40% by volume of its components have a boiling point of more 475 ° C.