MXPA99011413A - Hermetic pressure container for thermal handling cicl - Google Patents

Abstract

An airtight pressure vessel subject to severe thermal cycling through a temperature range that includes temperatures up to approximately 371 ° C. Unlike conventional hermetic pressure vessels that are constructed of horizontally arranged plates, the vessel is constructed of plates that are larger than 4.88 meters in height. As a result, there are no circumferential seams in a critical area of the cylindrical section of the container, providing superior durability.

Description

I '* HERMETIC PRESSURE CONTAINER FOR MAN THERMAL EYE CYCLIC BACKGROUND OF THE INVENTION 5 This invention relates generally to sealed pressure vessels for handling large volumes of a product as the product is treated through a thermal cycle with a higher temperature in excess of about 371 degrees centigrade. In particular, the invention relates to containers of hermetic pressure that could be used to coke delayed oil. Delayed petroleum coking is a process in which a fraction of oil is heated to a temperature at which it is thermally decomposed to provide a solid coke product and a hydrocarbon distillate product. In general, a supply of liquid petroleum is distilled first until the lighter ends have been recovered and a heavy residue remains. This heavy residue is usually pre-heated to a temperature of at least 371 ° C before being fed to a pressure vessel hermetic. In the vessel, it can be further heated to temperatures of up to 538 ° C under high pressure conditions that prevent the petroleum fraction from vaporizing until it is partially decomposed. The decomposition process produces hydrocarbon vapors from The container and a heavy tar continue to decompose until a porous coke remains in the container. Vaporization results in pores and channels in the waste that can be filled with additional residue. Once the container is full, the residue is allowed to cool, forming coke. The coke can then be purged with steam to remove any remaining volatile components. To complete the process, water is added to the container to quench the coke. As the water level progressively increases in the vessel, it shuts off the coke to a temperature below 93 ° C. In order to increase the production speed, the shutdown operation is frequently done as quickly as possible. Unfortunately, the faster the coke is turned off, the greater the wear and tear on the container. One of the main causes of this wear and tear is that the steel plate and the welding material that joins the plate rings that form the container have different resis- tance of transfer point and slip. At circumferential weld locations, thermal cycling causes a permanent tightness that increases progressively, eventually leading to distortion and fracture at or near the welds and frequently leading to the end of the container's useful life. As described in the patent of E. U. , No. 3,936,358, some efforts have been made to reduce wear and tear on the containers by controlling the shutdown regime. Unfortunately, this can reduce the production speed.

More recently, efforts have been made to adjust the composition of the weld material so that its yield point strength matches more closely that of adjacent steel plates. It is expected that closer matching will reduce stresses at the welding sites, extending the life of the vessel. Unfortunately, the containers that use the new welding materials have not been in service long enough to know if this solution will be successful. A need persists for an airtight pressure vessel that can better withstand extreme thermal cycling.

BRIEF DESCRIPTION OF THE INVENTION The invention relates to an airtight pressure vessel having improved resistance to extreme temperature cycling, and thus an improved life when used in operations such as coking delayed oil. Like many containers designed to handle products under severe thermal cycling, the container has a cylindrical section arranged vertically that contains most of the work volume of the container. The cylindrical section is made of large metal plates, generally of the order of plates of 3.05 by 12.2 m. Unlike the previous containers used for these purposes, the metal plates are arranged vertically, instead of horizontally. By arranging the plates in this manner, such that the vertical edges of each metal plate are greater than 4.88 or 6.1 meters in length, it provides a critical section with an extensive height in which there are no horizontal seams. Most conventional plate folding equipment is not capable of bending plates more than 6.1 meters wide. Consequently, while it is relatively easy to bend a plate of 3.05 by 12.2 m such that the edges of 3.05 m remain straight and the edges of 12.2 m are curved, it is more difficult to bend plates as needed for this invention; that is, they have a right edge that is more than 4.88 or 6.1 meters long. It has been found that the distortion and rupture in welds that end the life of hermetic pressure vessels used to coke delayed oil commonly occur in a horizontal (or circumferential) seam within or near the lower part of 4.88 meters above the surface. base of the container. As a result of the elimination of horizontal seams at this location, the most likely point of failure can be eliminated, significantly increasing the expected duration of the container. Alternatively, if the critical section of the container is observed as being in a higher location, the vertically arranged plates can be positioned there.

BRIEF DESCRIPTION OF THE DIAMETERS Figure 1 is an elevation view of one embodiment of a hermetic pressure vessel according to the present invention, with the skirt shown only in fragmentary detail.

Figure 2 is a similar elevation view of an alternative embodiment of a hermetic pressure vessel according to the present invention. Figure 3 is a similar elevation view of another alternative embodiment of a hermetic pressure vessel according to the present invention. Figure 4 is a similar elevation view of a conventionally constructed pressure vessel used to coke oil, and Figure 5 is an enlarged plan view of the container of Figure 1 taken through lines 5-5 of FIG. Figure 1 D ESCR I PTION DETAIL OF THE I NVENTION Figure 1 shows an example of an airtight pressure vessel that offers a longer duration under severe thermal cyclic conditions. The container (10) illustrated is designed to coke oil, and includes a base (12), a cylindrical section (14), an upper part (16), and a skirt (18). The container may be from about 9.15 to 39.65 or more meters high, and have a diameter from about 3.66 to 15.25 or more meters. It has an internal volume of at least approximately 930.25 cubic meters. The container can withstand cyclic handling of a product through a temperature range of about 371 to 538 degrees centigrade to less than about 93.3 degrees centigrade. As illustrated, the container can withstand pressures up to the range of 3.52 to 10.55 kg / cm2 man. As illustrated, the base (12) has angled sides (2) that allow the processed coke to be easily removed from the container through a base opening (22). The base is also shown having a steam inlet (23) to add energy to the product to remove any remaining volatile components before the coke is turned off, and a feed inlet (24) to feed petroleum distillate and quench water to the container. As illustrated, the base includes a transition section in the form of a ball joint (26) leading to the cylindrical section (14) of the container. The precise configuration of the base is not essential to the invention and, for other types of hermetic pressure vessels in which the cylindrical section is otherwise closed at the bottom, a separate base such as illustrated may not be necessary. The cylindrical section (14) of the container (10) is the most important. As seen in Figure 4, a hermetically sealed container (10 ') constructed in a conventional manner used to coke oil is constructed using steel plates arranged horizontally, resulting in a series of circumferential seams (30) between rows of adjacent plates. The final distortion and fracture at or near the circumferential seams within or near the first 4.88 meters of the cylindrical section usually terminates the life of the container. Such circumferential seams have been removed from the critical area of the container (10) at hermetic pressure illustrated in Figure 1, resulting in a container with a longer shelf life. As illustrated, the cylindrical section (14) is constructed of a series of raised plates (40) that are 3.5 meters wide and more than 6.1 meters in length.

To accommodate the internal pressures of 3.52 to 10.55 kg / cm2 man, the plates are approximately 3.81 centimeters thick. Plates of other widths and thicknesses could also be used. As best seen in Figure 5, the plates (40) are joined together by vertical welds (42). As illustrated in Figures 1 and 2, the cylindrical section (14) is directly attached to the base (12) by the ball joint (26). Alternatively, as shown in Figure 3, if the critical section (48) of the container is at a higher location, the plates (40) could rest on a lower ring of plates (44). Conventionally, 1.52 to 4.88 meter metal plates are used to build airtight pressure vessels of the type contemplated herein. The 3.05-meter-wide plates are some of the most commonly used. When such plates are arranged horizontally, there are three circumferential seams within a 6.1 meter section of the cylindrical section. As a consequence, using plates with vertical edges greater than 6.1 meters offers the advantage of eliminating at least two circumferential seams. In order to provide optimum resistance to internal pressure, the cylindrical section (14) has a round, and preferably circular, cross section. In order to form the desired circular cross section, the vertical steel plates (40) have been curved across their extensive length (as seen in Figure 5) instead of their widths (as in conventional containers). Although potentially more difficult or expensive, this can be done by press-forming the plates, or possibly in other forms. As a result of the use of vertical plates (40) instead of plates arranged in a conventional manner, the only welds within the critical section (48) of the indic cylindrical section are the vertical welds (42) between adjacent plates raised. Unlike welds in circumferential seams, it has been found that these vertical welds are relatively durable even under extreme conditions of oil coking. As illustrated in Figures 1 and 3, an upper ring (46) of steel plates arranged in a conventional manner is disposed above the raised metal plates (40). It may be preferred, from a durability point of view, to use metal plates that extend the full height of the cylindrical section (14), as seen in Figure 1, thus eliminating all circumferential seams within that section. From an economic point of view, this may not be practical for particularly high containers. Since tension problems are less significant in other parts of the container, advantages can be derived as long as there are no circumferential seams in the critical section (48) subject to severe thermal cycling. In some circumstances, it may be useful to tape the plates (40) to provide a reduced thickness above the lower edge of the indian cylindrical section (14). This can be useful where the upper portions of the cylindrical section do not need to be as strong as the lower portions. Alternatively, with plates having a constant thickness, the thickness of the vertical weld (42) between adjacent plates can be reduced in the upper portions of the container, where less resistance is needed. As yet another alternative, transitional sections such as ball joints can be formed between one or both ends of the raised plates and any other plates or portions of the base or the upper part, as desired. As illustrated, the cylindrical section (14) of the container (10) is covered by a cover (16). The upper part is domed in a conventional manner, and provides a volume for the steam produced during extreme thermal cycling. Other configurations may also be useful. As illustrated, the upper part has a recovery outlet (60) for extracting hydrocarbon vapors from the container during petroleum coking, and a separate orifice (62) that can provide access for an auger to be used when extracting coke from the coke. container. The recovery outlet and orifice may not be necessary if the container is to be used for other purposes. The skirt (18) is wound around the container, extending between the patella (26) in the upper part of the base (12) and the floor (80), and is used to support the container (10) in its upright position. The preceding detailed description has been given for clarity of understanding only. Unnecessary limitations should not be understood from this, since they would be obvious modifications for those experts in the technique.

Claims (19)

1. REVIVAL NAMES 1. An airtight pressure vessel with a capacity of at least about 930.25 cubic meters to handle cycling of a product through a temperature range of up to approximately 371 degrees centigrade, the pressure vessel comprising: a base; a cylindrical section disposed vertically attached to the base, the section comprising a set of metal plates having vertical edges, the vertical edges of each metal plate abutting the base which is greater than 4.88 meters in length, resulting in the section that has no horizontal seams within the first 4.88 meters above the base.
2. 2. An airtight pressure vessel as recited in claim 1, wherein the base comprises means for cooling the product.
3. 3. An airtight pressure vessel as recited in claim 1, wherein the pressure vessel further comprises a steam inlet for adding energy to the product in the vessel.
4. 4. A sealed pressure vessel as recited in claim 1, the container further comprising a domed upper part.
5. 5. An airtight pressure vessel as recited in claim 1, wherein the cylindrical section has a circular cross section.
6. 6. An airtight pressure vessel as recited in claim 1, wherein the metal plates are 1.52 - 6.1 meter wide metal plates that have been formed by pressing along their length to a radius of 2.44. - at 1 5.25 meters.
7. 7. An airtight pressure vessel as recited in claim 1, wherein a transition section is formed at one end of indi- cated cylindrical plates vertically arranged.
8. 8. An airtight pressure vessel as recited in claim 1, wherein the plates are tapered, with a greater thickness at the base and a lower thickness above the base.
9. 9. An airtight pressure vessel as recited in claim 1, wherein the vertical edges of each metal plate abutting the bottom edge of the cylindrical section are at least about 6.1 meters in length, resulting in the Cylindrical section has no horizontal seams within the first 6.1 meters above the base.
10. 10. An airtight pressure vessel as recited in claim 1, wherein the vertical weld seams between the plates have a relatively greater thickness at the base and a lower thickness below the base. eleven .
11. An airtight pressure vessel as recited in claim 1, comprising in and further: means for feeding petroleum distillate to the pressure vessel; and means for extracting hydrocarbon vapors from the pressure vessel.
12. 12. A sealed pressure vessel with a capacity of at least about 930.25 cubic meters for cyclic handling of a product through a temperature range of up to approximately 371 degrees centigrade, the container comprising a cylindrical section disposed vertically , the section comprising a set of metal plates having vertical edges, the vertical edges of each metal plate being greater than about 6.1 meters in length, resulting in the section having no horizontal seams within a critical section of 6.1 meters
13. 13. A sealed pressure vessel as recited in claim 12, wherein the container further comprises a base under the cylindrical section with means for cooling the product.
14. 14. An airtight pressure vessel as recited in claim 12, and further comprising means for adding steam to the vessel.
15. 15. An airtight pressure vessel as recited in claim 12, and further comprising means for extracting hydrocarbon vapors from the container.
16. 16. An airtight pressure vessel as recited in claim 12, and further comprising a domed top portion.
17. 17. An airtight pressure vessel as recited in claim 12, wherein the cylindrical section has a circular cross section.
18. 18. An airtight pressure vessel as recited in claim 12, wherein the metal plates are 1.52 - 6.1 meter wide metal plates that have been formed by pressing along their length to a radius of 2.44. - at 15.25 meters.
19. 19. An airtight pressure vessel as recited in claim 12, wherein a transition section is formed at one end of the cylindrical plates arranged vertically.