Baffle plate installed in catalyst inlet region of catalyst cooler with side inlet

Abstract

To provide a baffle plate that prevents erosion of rows of tubes of a beam close to a catalyst inlet.SOLUTION: There is provided a baffle plate 100 installed in a catalyst inlet region of a catalyst cooler 200 with side inlet, wherein the baffle plate is fixed in front of the first row of tubes of a beam 220 closest to the catalyst inlet region of the catalyst cooler 200, positioned so as to deflect gases entrained by the catalyst flow that enter a shell of the catalyst cooler 200 through the upper section of the inlet nozzle 210, and direct the gases to pass between the baffle plate 100 and the shell of the catalyst cooler 200 to the diluted phase 230 of the shell, in a region above the top 241 of a catalyst bed 240.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to the technical field of fluid catalytic cracking (FCC) technology. More specifically, the present invention relates to a means for improving the uptime and reliability of catalyst coolers in residual fluid catalytic cracking (RFCC) units. [Background technology]

[0002] Processing the residue in an RFCC unit results in very high coke yields. While fluid catalytic cracking (FCC) units have coke yields of 4-6% w / w, RFCC units can achieve values ​​as high as 8-12% w / w.

[0003] Due to the high coke load in RFCC units, the energy release in the regenerator is high and far exceeds the energy demand of the converter. To cope with this excess energy, RFCCs are equipped with so-called "catalyst coolers," which are devices designed to cool the bed. Without them, processing loads with high residue content would be impossible.

[0004] A catalyst cooler removes heat from the hot catalyst bed through water-filled beams (feixe com agua), similar to a heat exchanger. Natural or forced circulation of water through the interior of the beams removes excess heat from the catalyst and returns it to the regenerator at a lower temperature. The energy absorbed by the water generates high-pressure saturated steam, which is used by the RFCC unit itself and / or other units in the refinery. The amount of heat removed by the catalyst cooler is controlled by a valve at the outlet, regulating the catalyst circulation and, therefore, the thermal load of the equipment.

[0005] FCC catalysts are extremely abrasive, so beam erosion and the resulting holes in the tubes are a constant concern for designers of this type of equipment. Figures 1, 2, and 3 show typical schematics of catalyst coolers from different designers, KBR, UOP, and Stone & Webster, respectively.

[0006] The KBR design, designed with a single beam, as shown in Figure 1, was intended to be a simpler, lower-cost alternative. A drawback of this design is that if a tube is punctured, the catalyst cooler will be completely lost. KBR attempts to solve this problem by applying a hard coating to the first and second rows of tubes, which are typically most susceptible to erosion due to their proximity to the catalyst inlet in the shell. While applying a highly erosion-resistant coating extends the tube life, industrial practice has shown that these coatings have limited durability and can fail after 36 to 48 months of operation, depending on the operating conditions of the catalyst cooler.

[0007] The UOP design was devised to try to avoid the aforementioned problems, with the catalyst entering through the top of the unit, as shown in Figure 2. Unlike the KBR and Stone & Webster models, in the UOP model the catalyst flow does not enter laterally across the beam.

[0008] Stone & Webster attempted to solve the erosion problem by inserting multiple beam assemblies, allowing for independent isolation, as shown in Figure 3. Thus, if a perforated tube is identified, the RFCC unit does not need to be shut down; simply block the water inlet to the assembly where the perforated tube is located and continue to operate. Because the heat load on the catalyst cooler is reduced, refiners need to adjust the feed quality by reducing the RFCC feed flow or processing lighter residues. While this is not ideal, such a configuration allows refiners to gain some time to plan beam shutdown and repair. However, this flexibility comes at the cost of a more complex and expensive deployment. Because this is a temporary solution to the problem and involves revenue loss, it should only be resolved after the unit has been shut down and the beam has been repaired.

[0009] Corrosion problems are particularly significant in catalyst coolers where the catalyst enters the cooler through the side of the shell. While this configuration offers several advantages, it also creates significant erosion problems in the first row of tubes near the catalyst inlet. Severe erosion in the first and second rows of tubes can lead to holes in the catalyst cooler beams, resulting in unscheduled shutdowns of the RFCC and significant loss of revenue. This lack of reliability in equipment prevents long-term operation, which is desirable for increased profitability.

[0010] Therefore, considering the various solutions that have been tested recently, new means are needed to reduce the erosion of tubes in the beams of the catalytic cooler of a residual fluid catalytic cracking (RFCC) unit in order to solve the erosion problem and therefore increase the operating time of the catalytic cooler.

[0011] (latest technology) In the state of the art, there are several documents addressing particle distribution and erosion phenomena in catalyst coolers of fluid catalytic cracking units.

[0012] The main objective of the paper "Investigation on distribution of particles in the inlet region of an FCC external catalyst cooler with different inlet structures" is to optimize the heat exchange in the catalyst cooler, an aspect that, according to the paper, is compromised by the poor distribution of catalyst particles entering the cooler.

[0013] The authors emphasize that poor distribution of hot particles entering the shell creates temperature differences on the metal surface of the beam's tubes, which can lead to localized stresses within the tubes, which can result in cracks and / or fractures within the tubes, which can lead to cooling water leakage. Furthermore, poor distribution of catalyst particles can also lead to the formation of "dead zones", areas of low fluidization inside the cooler.

[0014] To solve this problem, the authors propose introducing a flow divider plate at the cooler inlet to reduce the velocity and simultaneously divide the flow. Two different designs were tested, one dividing the flow into two parts and the other into three parts, both of which aim to obtain a more uniform distribution of catalyst particles in the radial cross section of the cooler.

[0015] The literature suggests that reducing the temperature differential can even reduce tube failure, but does not alleviate the erosion problem, and directing the catalyst flow in a particular direction can even exacerbate it. Failure due to erosion is different from failure due to thermal differentials. Erosion is caused by catalyst particle impact on the beam or by gas cavitation at the top of the bed, while high stress cracks are caused by temperature differentials within the tubes.

[0016] Furthermore, the document provides the understanding that the gases separated in the feed pipe of the cooler inlet pipe have an upward direction and therefore cannot contribute to the erosion process observed in the beams of the catalytic cooler.

[0017] The article "State-of-the-Art Review of Fluid Catalytic Cracking (FCC) Catalyst Regeneration Intensification Technologies" presents a review of the state of the art as it applies to the design of FCC regenerators.

[0018] This document demonstrates the use of baffles and other internal components inserted into the bed of a regenerator operating at low velocity to 1) improve the radial distribution of catalyst in the bed, 2) prevent the formation of large diameter bubbles, 3) minimize catalyst resistance at the top of the bed, 4) minimize gas bypass toward the center of the vessel, and 5) promote efficient heat exchange of energy dissipated by the combustion of coke in the catalyst inventory.

[0019] However, the use of baffles in the bed to reduce bubble energy, combined with a description of erosion caused by catalyst recirculation induced by high velocity jets in the air distributor nozzles of FCC regenerators, does not explain the erosion problem observed in the beams of catalyst coolers. This paper only briefly touches on the problem and, being a technology review, does not propose any new solutions.

[0020] U.S. Patent No. 9,587,824 discloses a catalyst cooler for cooling regenerated catalyst in a regenerator associated with a fluid catalytic cracking unit. The catalyst cooler includes a first passage for conveying hot regenerated catalyst away from the regenerator and a second passage for returning cooled regenerated catalyst to the regenerator. The catalyst cooler also includes at least one heat exchanger. The second passage may be disposed within the first passage, or the first and second passages may each occupy a portion of the horizontal cross section of the catalyst cooler.

[0021] It should be noted that U.S. Patent No. 9,587,824 represents improvements introduced by designer UOP in catalyst cooler design, however, it is notable that this configuration has no similarity to the present invention as it is not a side entry configuration.

[0022] Chinese Patent Application No. 113041963 discloses a prelift catalyst distribution plate structure with a riser pipe, the lower part of which is a riser pipe lower cylinder, a prelift section cylinder, a steam extraction steam ring pipe, and a steam extraction steam nozzle arranged in the riser pipe. The steam extraction steam ring pipe and the steam extraction steam nozzle are arranged below the prelift section cylinder, the spiral distribution plate is arranged in the prelift section cylinder, an anti-wear lining used to reduce catalyst wear for the spiral distribution plate is arranged on the top of the spiral distribution plate, and the catalyst overflow holes of the distribution plate are evenly distributed in a staggered pattern.

[0023] It should be noted that Chinese Patent Application No. 113041963 relates to a mixer of two streams of low and high temperature catalyst sent to the reaction section through a riser, therefore this document is irrelevant to the present invention.

[0024] In view of the prior art disclosure, the features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. Summary of the Invention

[0025] The present invention discloses a baffle plate (100) installed in the catalyst inlet region of a lateral entrada catalyst cooler (200), the baffle plate (100) being fixed in front of the first row of tubes in the beam (220) closest to the catalyst inlet region of the catalyst cooler (200) and positioned to deflect gases entrained by the catalyst flow entering the shell of the catalyst cooler (200) through the upper section of the inlet nozzle (210). [Brief explanation of the drawings]

[0026] To complement this description and to provide a better understanding of the features of the invention, a set of figures is presented, showing preferred embodiments in an illustrative and non-limiting manner.

[0027] [Figure 1] A typical diagram of a catalytic cooler from the designer KBR is shown.

[0028] [Figure 2] A typical diagram of a catalyst cooler from the designer UOP is shown.

[0029] [Figure 3] A typical diagram of a catalytic cooler from designer Stone & Webster is shown.

[0030] [Figure 4] The erosion areas of the coating area of ​​the tube rows closest to the catalyst inlet are shown, highlighting the critical erosion areas observed on the first and second rows of tubes in the beam (220).

[0031] [Figure 5] Shows cavitation marks on one of the first row of tubes.

[0032] [Figure 6] As an example, gas entrainment from the regenerator into the interior of the shell of the baffle-less catalytic cooler (200) of the present invention is shown.

[0033] [Figure 7] As an example, gas entrainment from the regenerator into the interior of the shell of a catalytic cooler (200) with baffle plates (100) of the present invention is shown.

[0034] [Figure 8] FIG. 10 is a cross-sectional top view revealing details of the installation of a baffle plate in a catalyst cooler.

[0035] [Figure 9] A cross-sectional view of a catalyst inlet nozzle (210) of a catalyst cooler (200) is shown illustrating the gas bypass and collection areas in the upper passage of the inlet nozzle as a result of the positioning of the baffle plate (100).

[0036] [Figure 10] An exemplary attachment of the baffle plate (100) to the first row of tubes of the beam (220) closest to the catalyst inlet region of the catalyst cooler is shown.

[0037] [Figure 11] 1 shows the installation of a prototype baffle plate in the catalyst cooler of Applicant's RFCC unit.

[0038] [Figure 12] A photograph of the final state of the first row of tubes of a catalytic cooler operating in a conventional configuration without plates (left side) is shown compared to the final state of the first row of tubes of a catalytic cooler operating with plates (right side).

[0039] [Figure 13] 1 shows a graph of the heat load of a catalyst cooler before and after the installation of a baffle plate. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention relates to a baffle plate (100) installed in the catalyst inlet region of a side entry catalyst cooler (200).

[0041] The purpose of the baffle plate (100) is to prevent erosion of the rows of tubes in the beam (220) closest to the catalyst inlet, more specifically, to prevent erosion of the critical region in the first and second rows of tubes in the beam (220) closest to the catalyst inlet nozzle (210) in the shell of the catalyst cooler (200), as shown in Figure 4.

[0042] The critical erosion region coincides with the top region (241) of the catalyst bed (240) in the catalytic cooler (200). As shown in Figure 5, marks on the metal surface of the first row of tubes of the beam (220) in this region indicate a cavitation process caused by the eruptions and implosions of gas bubbles at the top of the bed.

[0043] The fact that erosion is only observed in the rows close to the catalyst inlet nozzles (210) in the shell also indicates that the gas flow causing this phenomenon does not come from the fluidizing air injected under the beam (220), but rather from gases coming from the regenerator, which are being drawn into the catalyst cooler (200) by the catalyst flow itself coming from the catalyst inlet nozzles (210), as shown in Figure 6.

[0044] The drag phenomenon is well known in the literature for FCC unit standpipes and can reach values ​​as high as 1-1.5 kg / ton of circulating catalyst. Depending on the operating conditions of the catalyst cooler, the gas drag due to the catalyst flow can reach a flow rate of 50%-75% of the fluidizing air flow injected at the bottom of the shell. The problem is that instead of being distributed over the entire cross-sectional area, it is concentrated at a single point, i.e., at the shell inlet (210), adjacent to the first and second rows of tubes in the beam (220).

[0045] Therefore, the present invention identifies the need to prevent the gas flow drawn into the catalyst cooler (200) from the regenerator from entering the region of the beam, thereby eliminating the "explosion" of bubbles at the top (241) of the catalyst bed (240) that would cause cavitation processes on the walls of the tubes of the beam (220), especially in the first and second rows near the inlet nozzle (210).

[0046] For this purpose, an innovative concept is proposed that allows capturing part of the separated gas and directing it into a confined area by means of a baffle plate (100), so that the gas eruptions in the bed (240) do not cause cavitation processes near the surface of the tubes of the beam (220) of the catalytic cooler (200).

[0047] More specifically, the installation of the baffle plate (100) captures a large portion of the gas entering the upper generator of the inlet nozzle (210) of the catalyst cooler (200), directing the gas flow away from the hottest region of the beam (220) and distributing it primarily to the dilute phase (230) of the shell, where the tube walls are cooler and therefore more resistant to erosion. Thus, the installation of the baffle plate prevents the implosion of bubbles at the top (241) of the catalyst bed (240) from reaching the tubes of the beam (220). The bubble implosion occurs in a separate area from the beam (220) and is confined between the baffle plate (100) and the shell of the catalytic cooler (200), thus eliminating the cavitation phenomenon on the beam (220) surface, as shown in Figure 7.

[0048] Preferably, the surface of the baffle plate (100) facing the gas jets at the top (241) of the catalyst bed (240) is protected with a layer of at least 1 inch (25.4 mm) of erosion-resistant refractory (110), preferably Class "A", secured to a hexagonal mesh, as shown in FIG.

[0049] The baffle plate (100) is positioned so that the reduction in the passage area of ​​the catalyst inlet nozzle (210) preferably does not exceed 30%, as shown in more detail in Figure 9. Its insertion into the inlet nozzle may be 20% to 40% of the total height of the ellipse formed by the nozzle adjacent to the catalyst cooler shell (200), which is sufficient to provide effective collection of the gases entering the upper section of the inlet nozzle (210).

[0050] Additionally, the baffle plate (100) may have a sufficient overall height so that release of gas collected in the inlet nozzle (210) occurs within the dilute phase (230) of the catalyst cooler at a point sufficiently far from the top (241) of the catalyst bed (240), preferably below the height of the vent (250).

[0051] The baffle plate (100) is secured to the first row of tubes in the beam (220) closest to the catalyst inlet region of the catalyst cooler (200) by a support grid 120 supported on the tubes by fasteners welded directly to the tubes, as shown in Figures 8 and 10.

[0052] It should also be appreciated that in a preferred configuration, there are open passages for the exit of gas along each side of the baffle plate (100), allowing some of the gas to exit the containment region between the baffle plate (100) and the shell of the catalyst cooler (200) through the sides, thus reducing the upward flow of gas within this space and, as a result, reducing the resistance of the catalyst to the dilute phase (230).

[0053] The side passages can each be designed to have a passage area that is 50% to 150% of the cross-sectional passage area that exists between the baffle plate (100) and the shell of the catalyst cooler (200). This feature can have the advantage of avoiding very high velocities observed in the gas release zone through these outlets. When gas is captured by the baffle plate (100), it always tries to flow towards the dilute phase (230) by the path of least resistance.

[0054] In a second configuration, the baffle plate (100) can alternatively extend to the shell of the catalyst cooler (200), eliminating the side passages entirely (configuration not shown). In this configuration, the gas collected by the baffle plate (100) is routed entirely to the dilute phase (230), increasing the upward velocity within the space confined by the plate (100). Projects using such a configuration must be designed to maintain this velocity within acceptable limits. This alternative configuration has the advantage of eliminating the risk of gas being vented through the side passages, creating new erosion points within the beam (220), and is primarily recommended for new projects. In these cases, the baffle plate (100) can be secured directly to the shell of the catalyst cooler (200) without the need to secure it to the first row of tubes within the beam (220). For retrofitting an existing catalyst cooler, securing the baffle plate (100) to the first row of tubes and providing side passages can be simpler and less expensive.

[0055] Thus, one skilled in the art will appreciate that the baffle plate (100) of the present invention solves a significant erosion problem in the first few rows of beams in a side entry catalytic cooler (200). This innovation has the potential to significantly increase revenue for refiners by extending RFCC operation, thus eliminating the problem of pitting during operation that resulted in unscheduled unit shutdowns with significant production losses.

[0056] Finally, it is understood that the baffle plate (100) of the present invention is applicable to any catalyst cooler design that allows for catalyst inlet from the side of the shell, such as in the KBR and Stone & Webster designs.

[0057] (Results of the present invention) A prototype of the baffle plate (100) was installed in one of the catalyst coolers of the RFCC unit at the test site, as shown in Figure 11. The RFCC unit had multiple catalyst coolers, and the baffle plate (100) was installed in only one unit.

[0058] The purpose of the test was to compare the erosion pattern of the beam equipped with the baffle plate (100) with that observed in a conventional beam without a plate. For comparison purposes, both beams were subjected to the same operating conditions. After 42 months of continuous operation, the RFCC was shut down for scheduled maintenance, allowing the catalytic cooler beam to be inspected. Figure 12 shows the final condition of the first row of tubes of a catalytic cooler operating in a conventional configuration without a plate (left) compared with the final condition of the first row of tubes of a catalytic cooler operating with a plate (right). It can be seen that in the traditional configuration (without a plate), the tubes underwent a severe erosion process, while in the configuration with the baffle plate (100), the tubes completed operation virtually unscathed. The present invention completely eliminated cavitation.

[0059] It is noteworthy that the installation of the baffle plate (100) did not result in any degradation in the performance of the catalyst cooler that received it, and it performed similarly to the other catalyst coolers and its own past history throughout the test period. Figure 13 shows a graph of the heat load on the catalyst cooler before and after the installation of the baffle plate. For the same load flow rate in the RFCC, no change in the heat removal capacity of the catalyst cooler was observed. The graph shows the results for a 4000m 3 Two similar conditions are highlighted, before and after the installation of the baffle plate, at an RFCC loading of 1000 kcal / d. In both cases, the catalyst cooler was able to remove approximately 30 Gcal / hr.

[0060] Thus, one skilled in the art will be able to grasp the knowledge presented and reproduce the invention as described in the pointed out embodiments and other variations that are covered by the appended claims.

Claims

1. A baffle plate (100) installed in a catalyst inlet region of a side entry catalyst cooler (200), said baffle plate (100) comprising: a first row of beams (220) secured to the front of the tubes of the first row of beams (220) closest to the catalyst inlet region of the catalyst cooler (200); A baffle plate (100) positioned to deflect gases entrained by the catalyst flow entering the shell of the catalytic cooler (200) through the upper section of an inlet nozzle (210), and direct the gases through a gap between the baffle plate (100) and the shell of the catalytic cooler (200) into the dilute phase (230) of the shell in an area above the top (241) of a catalyst bed (240).

2. 2. The baffle plate (100) of claim 1, characterized in that it has a sufficient overall height so that release of the gas collected in the inlet nozzle (210) occurs within the dilute phase (230) of the catalytic cooler at a point sufficiently far from the top (241) of the catalyst bed (240), preferably below the height of a vent (250).

3. The baffle plate (100) of claim 1, wherein the catalyst inlet nozzle (210) passage area reduction does not exceed 30%.

4. 2. The baffle plate (100) of claim 1, wherein the insertion of the baffle plate (100) into the inlet nozzle (210) is 20% to 40% of the total height of an ellipse formed by the nozzle adjacent the shell of the catalytic cooler (200).

5. 2. The baffle plate (100) of claim 1, wherein the baffle plate (100) is secured to the first row of tubes of the beam (220) by a support grid (120), the support grid (120) being supported on the tubes by the installation of fasteners welded directly to the tubes.

6. 2. The baffle plate (100) of claim 1, wherein the entrained gas includes bubbles coming from a regenerator, the bubbles being drawn into the interior of the shell of the catalyst cooler (200) by the catalyst flow itself.

7. 2. The baffle plate (100) of claim 1, wherein the face of the baffle plate (100) facing the gas jets at the top (241) of the catalyst bed (240) is protected with at least a 1 inch (25.4 mm) layer of erosion-resistant refractory (110).

8. 2. The baffle plate (100) of claim 1, further comprising an open passage for the outlet of gas along each side of the baffle plate (100), the side passages each being designed to have a passage area that is 50% to 150% of the cross-sectional passage area that exists between the baffle plate (100) and the shell of the catalytic cooler (200).

9. The baffle plate (100) of claim 1, further comprising the baffle plate (100) extending to the shell of the catalyst cooler (200).

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