REACTION CHAMBER AND ASSEMBLY METHOD

Abstract

Described is a reaction chamber (100) configured to house coking reactions comprising a main body (90) with a base portion (B) and a head portion (S), wherein the base portion (B) and the head portion (S) are joined together at their respective joint edges, characterised in that the walls of the main body (90) are made of stainless steel in such a way as to allow a joint between the base portion (B) and the head portion (S), of the main body (90), by welding only the base sheet since no plating is present on the sheet itself and in such a way as to allow the construction of the base portion (B) and the head portion (S), when constructed by coupling and welding a plurality of sheets, by welding only the base sheet since no plating is present on the sheet itself.

Advantageously, the method of assembly of the reaction chamber (100) according to the invention limits the operations necessary to weld only the base sheet since there is no plating on the sheet itself.

Claims

1. A reaction chamber (100) configured to house coking reactions comprising: a main body (90) having a base portion (B) and a head portion (S), wherein said base portion (B) has a conical conformation for conveying the reaction products and wherein said head portion (S) has a substantially cylindrical conformation delimited at the top by a closing cap, said base portion (B) and said head portion (S) being jointed to each other by a plurality of welded joints at respective junction edges, characterized in that said portions of said main body (90) are made of stainless steel in such a way as to allow a junction between sheets forming the three aforementioned portions and the junction between said portions by means of a single welded junction line, so avoiding the plating restoration operation required for clad sheet metal not characterized by carbon and/or low alloy steel metal sheet.

2. The reaction chamber (100) according to claim 1, wherein said stainless steel comprises a balanced percentage of ferritic steel wherein the remaining percentage is austenitic steel.

3. The reaction chamber (100) according to claim 1, wherein said main body (90) comprises a substantially cylindrical lateral casing (L), positioned between said base portion (B) and said head portion (S), said lateral casing (L) being shaped in a substantially cylindrical shape and being joined to both said base portion (B) and said head portion (S), by means of a respective welding line.

4. The reaction chamber (100) according to claim 1, wherein said lateral casing (L), and/or said base portion (B), and/or said head portion (S), comprises a plurality of substantially rectangular sheets (10), said sheets (10) being joined together by means of a respective welding line at each edge line.

5. The reaction chamber (100) according to claim 4, wherein two consecutive sheets (10) are laterally aligned with each other.

6. The reaction chamber (100) according to claim 5, wherein the connections with the external pipes and the connections for the instrumentation are made of stainless steel.

7. The reaction chamber (100) according to claim 4, wherein two consecutive sheets (10) are longitudinally offset from each other.

8. The reaction chamber (100) according to claim 1, comprising an annular element (30), positioned or positionable between said lateral casing (L) and said head portion (S).

9. The reaction chamber (100) according to claim 1, comprising an annular connection element (50), positioned or positionable between said lateral casing (L) and said base portion (B).

10. The reaction chamber (100) according to claim 9, wherein said annular connection element (50) has a Y-shaped cross section.

11. An assembling method for assembling a reaction chamber (100) according to claim 1, comprising the steps of: providing a base portion (B) of a main body (90) of said reaction chamber (100), said base portion (B) having a conical conformation for conveying reaction products; preparing a head portion (S), having a substantially cylindrical conformation delimited at the top by a closing cap; joining an ending edge of said base portion (B) to an ending edge of said head portion (S), wherein said joining operation is carried out by welding the stainless steel base sheet, no plating being placed on the sheet.

12. The method according to claim 11, comprising a step of providing a substantially cylindrical lateral casing (L) and joining said lateral casing (L) between said base portion (B) and said head portion (S), wherein said joining operation is carried out, for each junction edge, by welding the stainless steel metal sheet, no plating being placed on the sheet.

13. The method according claim 11, wherein said base portion (B), and/or said head portion (S), and/or said lateral casing (L), is obtained by a junction operation of a plurality of substantially rectangular plates (10), said sheets (10) being joined together by welding of the single base sheet, no plating being placed on the sheet.

14. The method according to claim 11, wherein said single welding line is made using, as welding material, the same material used to make the chamber.

15. The method according to claim 11, wherein said single welding line is carried out using a nickel alloy as welding material.

16. The method according to claim 11, wherein the welds of the connections to the external pipes are performed using the same material used to make the chamber as the filler material.

17. The method according to claim 11, in which the welds of the connections to the external pipes are carried out using, as welding material, the same material used to make the connection.

Description

DESCRIPTION OF THE DRAWINGS

[0066] Reference will be made to the accompanying drawings, in which:

[0067] FIG. 1 shows a front view of an embodiment of the reaction chamber according to the invention in an operational configuration;

[0068] FIGS. 2-4 show front views of the main portions of the reaction chamber of FIG. 1;

[0069] FIG. 5 shows a front view of an element of the reaction chamber of FIG. 1;

[0070] FIG. 5a shows an enlarged detail of FIG. 5;

[0071] FIG. 6 shows a partially exploded front view of the reaction chamber of FIG. 1 in an assembly configuration;

[0072] FIG. 7a shows a schematic sequence of the welding phases between portions of a prior art reaction chamber;

[0073] FIG. 7b shows a schematic sequence of the welding phases between portions of a reaction chamber, assembled according to an embodiment of the method according to the invention;

[0074] FIG. 8 shows a graphical representation of the temperature trend as a function of time during a coking and decoking cycle.

[0075] The similar parts will be indicated in the various drawings with the same numerical references.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0076] A reaction chamber according to a first embodiment of the invention is denoted in its entirety with the numeral 100.

[0077] The reaction chamber according to the invention is configured to house coking reactions and comprises a main body 90 having a base portion B and a head portion S.

[0078] As shown in FIG. 2, the head portion S has a substantially cylindrical shape and is delimited at the top by a closing cap.

[0079] The closing cap also has an outlet connection or opening for the escape of cracking vapours from the head of the reaction chamber to be further processed in the processing plant, for example, to be conveyed to a fractionating column located downstream of the reaction chamber.

[0080] As shown in FIG. 4, the base portion B has a conical shape to convey the reaction products, in particular petroleum coke.

[0081] In a configuration not shown in the drawings, the base portion B and the head portion S are joined together at the respective junction edges.

[0082] Advantageously, the walls of the main body 90 are made of integral non-plated stainless steel (Martensitic, Ferritic, Austenitic or Austenitic-Ferritic, the so-called duplex) in such a way as to allow a joint between the base portion B and the said head portion S and between the sheets making up the portions B and S by welding sheets in the longitudinal and circumferential direction by welding only the base sheet since there is no plating on the sheet itself and in particular by using a single welding material (that is, a material with the same chemical composition apart from the tolerances allowed by the various reference standards), since the anti-corrosion layer does not have to be restored if the plated sheet is used.

[0083] Preferably, the stainless steel used for making the walls of the main body 90, is Martensitic steel S.S. 410S or S.S. 405S, which has a lower thermal expansion than austenitic stainless steel and comparable to carbon steel.

[0084] Advantageously, the same stainless steel used to make the walls of the main body 90, is used to make the welding lines between the joined portions.

[0085] In alternative embodiments, stainless steel with a balanced percentage of ferritic and austenitic steel (so-called Duplex steel) is used for the walls of the main body 90.

[0086] The use of stainless steel advantageously guarantees a high ductility value, thus being able to contain and avoid the propagation of any cracks.

[0087] In the preferred embodiment shown in FIGS. 1 and 6, the main body 90 of the reaction chamber 100 according to the invention, comprises a substantially cylindrical lateral casing L, positioned between the base portion B and the head portion S

[0088] In particular, the lateral casing L is shaped in a substantially cylindrical manner and is joined to both the base portion B and the head portion S by means of respective welding lines.

[0089] In view of its considerable overall size, each part of the main body 90 mentioned above comprises a plurality of substantially rectangular sheets 10.

[0090] For example, the lateral casing L, the base portion B and the head portion S are all are made from a plurality of sheets 10 which are joined together by a respective welding line at each edge line.

[0091] The construction of the plating of the coke drum is generally made by coupling several plates both laterally to form a single skirt and by coupling several skirts to complete an entire plating.

[0092] To allow the reaction chamber 100 to be anchored to the ground or to a support structure in an operating condition, for example shown in FIG. 1, where the reaction chamber is positioned along a direction substantially vertical to the ground, a cylindrical skirt is used.

[0093] In different embodiments the connection between the cylindrical plating, the skirt and the conical plating is made by means of a Y shaped element.

[0094] The support element G is shaped in such a way as to support the reaction chamber at least along a circumferential area. The expansion of the walls of the main body 90 during the thermal operating cycles could lead to an accumulation of stresses at the above-mentioned support area since the support element, called skirt, is outside the reaction chamber and is therefore not subject to the same thermal expansion because it is not in direct contact with the product to be treated at high temperature.

[0095] In order to prevent the formation of cracks in the above-mentioned support area, the main body 90 may comprise an annular connection element 50, positioned or which can be positioned between the lateral casing L and the base portion B.

[0096] Preferably, as shown in FIG. 4, the annular connection element 50 is positioned at an end edge of the base portion B.

[0097] In particular, as shown in FIG. 5, the annular connection element 50 has a Y shaped transversal cross-section.

[0098] Therefore, advantageously, as shown in the enlargement of FIG. 5a, the support element G is coupled to a free end of the Y section, the function of the Y ring is to distance the welding of the skirt G from the connection zone of the plating with the cone, an area subject to high stress concentration due to the geometric shape of the zone itself, reducing the possible formation of cracks at the welds between the three elements plating/conical bottom/skirt.

[0099] Moreover, the Y shaped connection is generally formed from a forged ring or a ring obtained by calendering then machined by machine tools, allows a better control of the geometrical shape and the geometrical tolerances of the connection itself.

[0100] Depending on the specific production requirements and the volume of charge to be treated, the reaction chamber 100 will have more or less bulky dimensions. As the overall dimensions vary, the wall thickness of the main body 90 will also vary. The thickness of a stainless steel sheet used for the walls of the reaction chamber 100 according to the present invention calculated according to the formulas of known design standards for pressure vessels may be slightly greater (for example, about 10% greater) than the thickness of a plated sheet with a carbon steel base plate or low alloy steel base plate of known type, so that the structural strength values of the integral stainless steel sheet are still comparable to those of the plated sheet. Under the design temperature and pressure conditions generally adopted for plants of the type in question, the order of magnitude of the thickness of a ferritic stainless steel sheet could be between about 20-70 mm.

[0101] Even though, under the design conditions at which coke drums generally work, the wall thicknesses of integral (un-plated) stainless steel coke drums may be slightly greater than the thicknesses resulting from plated carbon or low-alloy steel sheets, it should be noted that under current market conditions the price of the construction material is very similar when comparing the two construction solutions, so that the price of the reaction chamber material (coke drums) is practically not increased compared to the price of the material of coke drums according to the prior art, due to technical improvements made by the use of integral stainless material (according to the invention).

[0102] The welded joints of the reaction chamber 100 are advantageously made of a nickel alloy, or the welding is carried out using stainless steel electrodes, in order to uniform the welded joints to the rest of the structure and avoid discontinuity of stresses due to the use of materials with a different expansion coefficient on the walls of the main body 90.

[0103] As mentioned above, the method of assembly of the reaction chamber 100 according to the invention avoids many of the non-destructive tests and machining which must be performed on the welding of plated sheets of known type.

[0104] Advantageously, the connections to the external pipes (openings) are also made of integral stainless steel and therefore do not require restoration of plated material (it should be noted that generally in the prior art the connections are also made of plated material and therefore material which needs restoration of plating material or the connections are obtained from forged material which needs a nickel alloy or stainless steel plating through the process of deposition of filler material as described above (electroslag, submerged arc or coated electrode or cored wire).

[0105] The method of assembling a reaction chamber 100 according to an embodiment of the invention comprising the steps of preparing a base portion B and a head portion S, as defined above, of a main body 90 of the reaction chamber 100. Advantageously, the method described here makes it possible to limit the operation of welding between sheets to only welding between stainless steel sheets, avoiding, as happens in current constructions, the restoration of anti-corrosion material after the welding of the carbon steel or low alloy steel material (generally a nickel alloy welding).

[0106] In particular, in the example described here, the assembly method also includes a step of preparation of a lateral casing L, the so-called plating, which is substantially cylindrical, and of joining of the lateral casing L between the base portion B and the head portion S. Advantageously, the joining of the casing L is carried out, for each junction edge, by means of a homogeneous welding line which avoids the restoration of anti-corrosive material as previously described.

[0107] Advantageously, each portion of the main body 90, for example, the base portion B, the head portion S and the lateral casing L (the so-called plating), is obtained by a welded joining operation of a plurality of substantially rectangular sheets 10 wherein each welded joint is made by a homogeneous welding line which avoids the restoration of anti-corrosion material as described previously

[0108] Preferably, the edges of the portions to be joined are machined for example by caulking to allow the filler material used for welding to be accommodated.

[0109] Advantageously, all the non-destructive testing and post-welding stress relief heat treatment operations which must be carried out to assemble plated sheets of known type formed from carbon or low alloy steel base plate are eliminated, allowing a reduction in manufacturing costs as well as manufacturing time.

[0110] As shown in the comparison between FIG. 7a and FIG. 7b, the method according to the invention makes it possible to significantly reduce the number of steps required to obtain edge welding.

[0111] Advantageously, since there is no plated material in the reaction chamber and in the assembly method described here, all the drawbacks linked to the presence of the plated material and to the materials used to restore the plated material are eliminated.

[0112] A further advantage of the use of integral material and the absence of the plating with base plate made of carbon steel or low alloy steel or is that the heat treatments which in the prior art must be carried out at the end of the assembly to relieve stresses are also eliminated, and these heat treatments can be very lengthy, even lasting several days.

[0113] In addition, as mentioned above, the use of integral material, and in particular stainless steel, makes it possible to significantly reduce the construction time from 15-20 months (order of magnitude related to the current 2019 delivery time of plated sheets and the workload of the manufacturer) for reaction chambers of known type (which include plated sheets) to about 12 months or less (order of magnitude related to the current 2019 delivery time of the plated sheets and the workload of the manufacturer) for reaction chambers according to the invention.

[0114] For this reason, advantageously, according to the invention, the welding operations are carried out faster than the welding of plated sheets and the manufacturing method, which is also the object of the invention, makes it possible to minimise not only the reaction chamber manufacturing time but also the plant downtimes required to carry out maintenance and/or repair operations of the chamber.

[0115] In fact, the reaction chambers working generally in creep and fatigue mode continuously even for several months are subject to the occurrence of cracks on the base material and these cracks are subject to propagation within the same material, and must therefore be repaired by sealing by welding with filler material; this operation can only be carried out during plant downtime and requires a long times also because of the subsequent heat treatment for post-welding stress relief repair which is no longer necessary according to the invention.

[0116] This invention is described by way of example only, without limiting the scope of application, according to its preferred embodiments, but it shall be understood that the invention may be modified and/or adapted by experts in the field without thereby departing from the scope of the inventive concept, as defined in the claims herein.