CA2426882A1 - Cylindrical tube for industrial chemical installations - Google Patents
Cylindrical tube for industrial chemical installations Download PDFInfo
- Publication number
- CA2426882A1 CA2426882A1 CA002426882A CA2426882A CA2426882A1 CA 2426882 A1 CA2426882 A1 CA 2426882A1 CA 002426882 A CA002426882 A CA 002426882A CA 2426882 A CA2426882 A CA 2426882A CA 2426882 A1 CA2426882 A1 CA 2426882A1
- Authority
- CA
- Canada
- Prior art keywords
- tube
- tube according
- valleys
- metal tube
- recesses
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000003317 industrial substance Substances 0.000 title description 2
- 238000009434 installation Methods 0.000 title 1
- 239000000956 alloy Substances 0.000 claims abstract description 12
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 7
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 7
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 6
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 6
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 239000007788 liquid Substances 0.000 claims abstract description 4
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 8
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 7
- 239000005977 Ethylene Substances 0.000 claims description 7
- 229930195733 hydrocarbon Natural products 0.000 claims description 7
- 150000002430 hydrocarbons Chemical class 0.000 claims description 7
- 239000004215 Carbon black (E152) Substances 0.000 claims description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 239000011651 chromium Substances 0.000 claims description 4
- BIJOYKCOMBZXAE-UHFFFAOYSA-N chromium iron nickel Chemical compound [Cr].[Fe].[Ni] BIJOYKCOMBZXAE-UHFFFAOYSA-N 0.000 claims description 3
- 238000005336 cracking Methods 0.000 claims description 3
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 2
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 239000010703 silicon Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 20
- 238000005255 carburizing Methods 0.000 description 13
- 238000012360 testing method Methods 0.000 description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
- 238000010000 carbonizing Methods 0.000 description 7
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 150000001247 metal acetylides Chemical class 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000005864 Sulphur Substances 0.000 description 2
- 150000001722 carbon compounds Chemical class 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000000571 coke Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000012925 reference material Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000004939 coking Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- NPURPEXKKDAKIH-UHFFFAOYSA-N iodoimino(oxo)methane Chemical compound IN=C=O NPURPEXKKDAKIH-UHFFFAOYSA-N 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C30/00—Alloys containing less than 50% by weight of each constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
- F16L9/006—Rigid pipes specially profiled
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B21/00—Pilgrim-step tube-rolling, i.e. pilger mills
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
- B21B3/02—Rolling special iron alloys, e.g. stainless steel
Abstract
The invention provides a tube for use in furnaces where gas and liquid media are being passed through the tube from one end to the other while being subjected to substantial heating and decomposition resulting therefrom. The cylindrical tube is made of a stainless iron-nickel-chromium-base alloy comprising in weight-% max 0.08 % C, 23-27 % Cr, 33-37 % Ni, 1.3-1.8 % Mn, 1.2-2 % Si, 0.08-0.25 % N, 0.01-0.15 % rare earth metals, and Fe and usual impurities. The cylindrical tube has a smooth outer surface and an inner surface provided with valleys or recesses extending longitudinally with a smoothly curved bottom profile.
Description
CYLINDRICAL TUBE FOR INDUSTRIAL CHEMICAL INSTALLATIONS
FIELD OF THE INVENTION
The invention relates to a tube to be used in a device for heating of a gas or liquid medium that is transmitted from one end of said tube to the other end thereof while simultaneously being heated such that a chemical reaction occurs. The heating can occur for instance by heating the exterior cylindrical tube wall or by providing heating directly through the walls.
BACKGROUND OF THE INVENTION
In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
In order to obtain an acceptable yield of a product, such as ethylene in an ethylene craclcer, it is necessary to use a tube that is free from craclcs on its inner side. The tube must also be resistant towards exposure of those products that are formed inside such tube. When using materials currently for such tube applications it frequently occurs that oxides axe being formed on the inside of such tubes and that easily come apart therefrom, which reduces the lifetime of such tubes. At the same time there is a problem with carbonizing since a deposit of a carbon compound is formed on the inside of such tube. The larger deposit that is formed, the smaller is the amount of gas that can be passed through such tube. At the same time the heat transformation will decrease which results in an impaired economy.
Known furnaces for the cracking of hydrocarbon are usually provided with cast tubing of nickel-based alloys with high amounts of chromium. This leads to some disadvan-tages because such tube materials are more expensive and further, high nickel content can be a catalyst for undesirable coking.
FIELD OF THE INVENTION
The invention relates to a tube to be used in a device for heating of a gas or liquid medium that is transmitted from one end of said tube to the other end thereof while simultaneously being heated such that a chemical reaction occurs. The heating can occur for instance by heating the exterior cylindrical tube wall or by providing heating directly through the walls.
BACKGROUND OF THE INVENTION
In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
In order to obtain an acceptable yield of a product, such as ethylene in an ethylene craclcer, it is necessary to use a tube that is free from craclcs on its inner side. The tube must also be resistant towards exposure of those products that are formed inside such tube. When using materials currently for such tube applications it frequently occurs that oxides axe being formed on the inside of such tubes and that easily come apart therefrom, which reduces the lifetime of such tubes. At the same time there is a problem with carbonizing since a deposit of a carbon compound is formed on the inside of such tube. The larger deposit that is formed, the smaller is the amount of gas that can be passed through such tube. At the same time the heat transformation will decrease which results in an impaired economy.
Known furnaces for the cracking of hydrocarbon are usually provided with cast tubing of nickel-based alloys with high amounts of chromium. This leads to some disadvan-tages because such tube materials are more expensive and further, high nickel content can be a catalyst for undesirable coking.
Also, the fshape permanenece of such tubes, which normally are characterized as high temperature materials, is not satisfactory in certain applications.
In a cracker, a decomposition of a hydrocarbon occurs. The starting materials could be for instance naphta or propane mixed with water vapor. When the material passes through the tubes in the craclcing furnace the temperature is increased to above 800° C.
Important products that axe being obtained are for instance ethylene and propylene.
Also hydrogen gas, methane, butane and other hydrocarbons are being formed. In order to avoid undesired reactions it is essential that such heating occurs very rapidly and that the obtained products are subjected to quenching - the residence time in the furnace only amounts to some tenths of seconds. The temperature in the furnace can reach 1200° C -and the tube material temperature in the furnace could be above 1100° C. The heating of the furnace room could be obtained by combustion of gases from the cracking process such as hydrogen and methane, and a furnace can be equipped with a large number of gas burners that can be arranged in the floor or in the walls such furnace.
The tubes that are used in the furnace shall have good shape permanence to heat and shall be able to withstand high temperatures. They must also be resistant towards oxidation and corrosion so as to withstand the atmosphere in the furnace room.
The carbon potential inside the tubes in the furnace is very high and the tube material should therefor be able to withstand carburization and carbide formation. Minor amounts of sulphur are often being added to the starting material and therefor the tubes must also have good resi-stance towards sulphur and sulphur compounds.
SUMMARY OF THE INVENTION
The present invention relates to a new type of finned tube to be made of a material that improves resistance towards the environment in furnaces for the craclcing of hydrocarbon external to the tube, as well as the particular environmental conditions occurring inside the tube.
According to one aspect, the present invention provides a metal tube for use in furnaces where gas and liquid formed media is being pressed through such tube from its inlet end to its opposite end while being subjected to substantial heating and decomposition therefrom, the metal tube comprising: a body; a smooth outer surface; and an inner surface with a profile; wherein the body is made of a stainless iron-nickel-chromium base alloy comprising, in weight-%: -max 0.08% C, 23-27% Cr, 33-37% Ni, 1.3-1.8%
Mn, 1.2-2% Si, 0.08-0.25% N, 0.01-0.15% rare earth metals, and normal impurities; and the profile comprises a plurality of valleys or recesses, said valleys or recesses extending longitudinally along the tube, and having a smoothly curved bottom.
By forming a tube with a high strength stainless steel with good resistance towards oxide flaking and carbonizing, the chemical resistance, and the economy of such tubing and furnaces have been improved in a special way. This has brought about a tube having very good heat transfer properties combined with substantially improved resistance toward too quickly appearing carbonizing, carburization and oxide flalcing due to the products produced during such transfer of materials within the tube.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The obj ects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings in which lilce numerals designate like elements and in which:
Fig. 1 shows a cylinder with a formation in accordance with the invention.
Fig. 2 shows a cross section of the cylinder embodiment in Fig. 1.
Fig. 3 shows the weight change during oxidation in air and 1000° C as a function of the exposure time of said tubes.
Fig. 4 shows schematically how the carburizing profile was measured on rod shaped specimen for analyzing the carbide content.
Fig. 5 shows the measurement results of the carburizing in terms of area function of carbides.
DETAILED DESCRIPTION OF THE INVENTION
In Fig. 1, a tube 10 is designated having an entry end portion through which a gas formed medium such as hydrocarbon and steam shall be urged towards the exit end portion while undergoing a chemical reaction.
In the embodiment as shown, the inner surface 11 of the tube 10 is provided with re-cesses 13 and ridges 14 of a sinusoidal shaped contour, while the outer surface 16 is substantially smooth or arcuate, see Fig. 2. The ridges 14 and the recesses 13 are provided with a rounded profile to avoid fatigue cracks.
In accordance with an alternative embodiment, the interiorly provided recesses 13 of the cylinder 10 can be helically provided in the longitudinal direction of said cylinder.
Alternatively, instead of being cylindrical in its entire length said tube can be conically shaped from its inlet end to its outlet end.
It has been found that the shape permanence to heat is improved by the use of tubes as aforesaid if the tubes are made by pilger rolling over a mandrel in principle in the manner as shown and described in U.S. Patent No. 4,095,447. Alternatively, however, such tubes could be made in the manner described in LT.S. Patent No.
5,016,460.
Instead of pilger rolling over a mandrel drawing over a mandrel can be applicable.
The steel material to be selected for such cylinder 10 is a stainless iron-nickel-chromium base alloy with an austenitic structure and otherwise strictly controlled and optimized amounts of alloy constituents. The alloy contains, in weight %, max 0.08%
C, 23--27% Cr, 33-37% Ni, 1.3-1.8% Mn, 1.2-2% Si, 0.08-0.25% N, 0.01-0.15%
rare earth metals and Fe and normal impurities. The amount of rare earth metals axe preferably 0.03-0.10% which promotes the formation of a thin elastic adherent oxide film when the material is exposed to oxidizing environment at high temperatures. The amount of nitrogen should preferably be 0.13-0.18%, and the amount of silicon should preferably be 1.3-1.8%.
By the above given choice of material, it is possible to achieve unexpectedly superior, substantially longer, usage time pexiods without interruption for exchanging tubes while simultaneously also achieving a substantially smaller amount of deposits of carbon compounds on the inner tube side, which furthermore improves the usage economy since smaller amounts of deposits on the tubes enables larger amount of hydrocarbon and steam to be transported through the tubes, for instance in connection with the manu-facture of ethylene.
A further improvement can be achieved by providing a chromium oxide layer on the inner tube surfaces which will prevent the diffusion of carbon into the material by oxidation of said tubes before they are put into usage.
Fig. 3 illustrates the results of a study of the tendency toward oxide flaking in tubes made of Sanicro 39 type material according to the invention put in relation to some conventional materials that are being used in corresponding applications. For reference purposes this study included both forged and cast alloys which are well established materials for cracker tubes in ethylene furnaces, for instance a material marketed by International Nickel Inc. under the designation INCO 803, one material marketed by Sumitomo Metals Ltd under designation HK4M and a cast alloy with designation HP45-Nb. The analysis of the various reference materials is given in the table below.
Alloy Cr Ni Si Mn C N Nb Ti Al HP45-Nb 23.636.91.4 1.220.17 0.046 1.2 -- --Inco 25.835.30.650.900.0750.013 -- 0.55 0.52 HK4M 25.324.50.411.120.21 0.017 -- 0.46 0.33 Sanicro3924.934.81.5 1.4 0.0480.166 -- -- -- REM=0.05 The diagram in Fig. 3 shows the weight change during oxidation in air at 1000 D C as a function of the exposure time for the tubes.
As appears from the diagram in Fig. 3 the obtained result shows that the oxides being formed more easily come apart from these reference materials when compared with the material Sanicro 39 selected according to the invention.
The carburizing tests were carried out so as to be similar to the ethylene environment present in the aforementioned cracker applications by providing shifting carburizing and oxidizing environments. The carburizing occurred in a gas mixture comprising carbon monoxide, hydrogen gas and methane in a mixture which was at a temperature of 1050° C and gave an oxygen potential corresponding to 10-15 atm and a carbon activity > 1. After being exposed for 120 hours to this carbonizing environment the coke that had been formed was talcen out by introducing air to combust the coke. The time period for the carburizing/oxidizing cycle varied bet-ween 135-140 hours. The total testing time was 1104 hours corresponding with 8 cycles as set forth above. The temperature was kept constant at 1050° C during the entire first test. The geometry of the test rods was 8 mm x 8 mm x 20 mm.
After the test was completed the test rods were taken out and a cross section thereof was studied by looping upon how the area fraction of carbides varied along a selected line.
The cross section of said test rods had a squaxe shaped outer surface and with this test rod design it was found that the carbonizing was much depending on where on this outer surface the measurement was made. Areas close to corners and edges appeaxed to be more sensitive to carbonizing than those surfaces that were planax. In Fig.
4, it is shown the position of the lines that are analyzed in the cross section of the test rod. The first line (Prof 10) was located 0.8 mm (10% of the edge length) into the material along the outer surface. The second Line (Prof 50) was located 4 mm from a corner whilst being extended through the center of the test rod.
In Fig. 4 it is schematically shown how carburizing vaxies depending on whether the location is close to an edge or extending far into a planar surface.
This figure also schematically shows how the carburizing depth varies depending on the distance from a corner. The grey marked axea represents the carburized area and the white field represents the noncarburized area. It should be noted that the carbonizing depth is larger in the corners of the test rod.
In Fig. 5 the results from the area fraction analysis of carbides are presented. The x-axis represents the distance from the start point at one outer surface (0-8 mm) and the y-axis shows the measured area fraction of carbides (%). The diagram shows that Sanicro 39 and HP45-Nb are not affected by carburizing from planar surfaces (Prof 50) and out of these two Sanicro 39 appeared with the best resistance towards carburizing in the area close to the corners or the edges (prof 10). The alloy 803 was affected by massive carburizing in the comer areas and also appeared with strong carburizing on the planar surfaces. The alloy HI~4M was subjected to carburizing to its maximum through the entire material.
While the present invention has been described by reference to the above-mentioned embodiments, certain modifications and variations will be evident to those of ordinary slcill in the art. Therefore, the present invention is limited only by the scope and spirit of the appended claims.
In a cracker, a decomposition of a hydrocarbon occurs. The starting materials could be for instance naphta or propane mixed with water vapor. When the material passes through the tubes in the craclcing furnace the temperature is increased to above 800° C.
Important products that axe being obtained are for instance ethylene and propylene.
Also hydrogen gas, methane, butane and other hydrocarbons are being formed. In order to avoid undesired reactions it is essential that such heating occurs very rapidly and that the obtained products are subjected to quenching - the residence time in the furnace only amounts to some tenths of seconds. The temperature in the furnace can reach 1200° C -and the tube material temperature in the furnace could be above 1100° C. The heating of the furnace room could be obtained by combustion of gases from the cracking process such as hydrogen and methane, and a furnace can be equipped with a large number of gas burners that can be arranged in the floor or in the walls such furnace.
The tubes that are used in the furnace shall have good shape permanence to heat and shall be able to withstand high temperatures. They must also be resistant towards oxidation and corrosion so as to withstand the atmosphere in the furnace room.
The carbon potential inside the tubes in the furnace is very high and the tube material should therefor be able to withstand carburization and carbide formation. Minor amounts of sulphur are often being added to the starting material and therefor the tubes must also have good resi-stance towards sulphur and sulphur compounds.
SUMMARY OF THE INVENTION
The present invention relates to a new type of finned tube to be made of a material that improves resistance towards the environment in furnaces for the craclcing of hydrocarbon external to the tube, as well as the particular environmental conditions occurring inside the tube.
According to one aspect, the present invention provides a metal tube for use in furnaces where gas and liquid formed media is being pressed through such tube from its inlet end to its opposite end while being subjected to substantial heating and decomposition therefrom, the metal tube comprising: a body; a smooth outer surface; and an inner surface with a profile; wherein the body is made of a stainless iron-nickel-chromium base alloy comprising, in weight-%: -max 0.08% C, 23-27% Cr, 33-37% Ni, 1.3-1.8%
Mn, 1.2-2% Si, 0.08-0.25% N, 0.01-0.15% rare earth metals, and normal impurities; and the profile comprises a plurality of valleys or recesses, said valleys or recesses extending longitudinally along the tube, and having a smoothly curved bottom.
By forming a tube with a high strength stainless steel with good resistance towards oxide flaking and carbonizing, the chemical resistance, and the economy of such tubing and furnaces have been improved in a special way. This has brought about a tube having very good heat transfer properties combined with substantially improved resistance toward too quickly appearing carbonizing, carburization and oxide flalcing due to the products produced during such transfer of materials within the tube.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The obj ects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings in which lilce numerals designate like elements and in which:
Fig. 1 shows a cylinder with a formation in accordance with the invention.
Fig. 2 shows a cross section of the cylinder embodiment in Fig. 1.
Fig. 3 shows the weight change during oxidation in air and 1000° C as a function of the exposure time of said tubes.
Fig. 4 shows schematically how the carburizing profile was measured on rod shaped specimen for analyzing the carbide content.
Fig. 5 shows the measurement results of the carburizing in terms of area function of carbides.
DETAILED DESCRIPTION OF THE INVENTION
In Fig. 1, a tube 10 is designated having an entry end portion through which a gas formed medium such as hydrocarbon and steam shall be urged towards the exit end portion while undergoing a chemical reaction.
In the embodiment as shown, the inner surface 11 of the tube 10 is provided with re-cesses 13 and ridges 14 of a sinusoidal shaped contour, while the outer surface 16 is substantially smooth or arcuate, see Fig. 2. The ridges 14 and the recesses 13 are provided with a rounded profile to avoid fatigue cracks.
In accordance with an alternative embodiment, the interiorly provided recesses 13 of the cylinder 10 can be helically provided in the longitudinal direction of said cylinder.
Alternatively, instead of being cylindrical in its entire length said tube can be conically shaped from its inlet end to its outlet end.
It has been found that the shape permanence to heat is improved by the use of tubes as aforesaid if the tubes are made by pilger rolling over a mandrel in principle in the manner as shown and described in U.S. Patent No. 4,095,447. Alternatively, however, such tubes could be made in the manner described in LT.S. Patent No.
5,016,460.
Instead of pilger rolling over a mandrel drawing over a mandrel can be applicable.
The steel material to be selected for such cylinder 10 is a stainless iron-nickel-chromium base alloy with an austenitic structure and otherwise strictly controlled and optimized amounts of alloy constituents. The alloy contains, in weight %, max 0.08%
C, 23--27% Cr, 33-37% Ni, 1.3-1.8% Mn, 1.2-2% Si, 0.08-0.25% N, 0.01-0.15%
rare earth metals and Fe and normal impurities. The amount of rare earth metals axe preferably 0.03-0.10% which promotes the formation of a thin elastic adherent oxide film when the material is exposed to oxidizing environment at high temperatures. The amount of nitrogen should preferably be 0.13-0.18%, and the amount of silicon should preferably be 1.3-1.8%.
By the above given choice of material, it is possible to achieve unexpectedly superior, substantially longer, usage time pexiods without interruption for exchanging tubes while simultaneously also achieving a substantially smaller amount of deposits of carbon compounds on the inner tube side, which furthermore improves the usage economy since smaller amounts of deposits on the tubes enables larger amount of hydrocarbon and steam to be transported through the tubes, for instance in connection with the manu-facture of ethylene.
A further improvement can be achieved by providing a chromium oxide layer on the inner tube surfaces which will prevent the diffusion of carbon into the material by oxidation of said tubes before they are put into usage.
Fig. 3 illustrates the results of a study of the tendency toward oxide flaking in tubes made of Sanicro 39 type material according to the invention put in relation to some conventional materials that are being used in corresponding applications. For reference purposes this study included both forged and cast alloys which are well established materials for cracker tubes in ethylene furnaces, for instance a material marketed by International Nickel Inc. under the designation INCO 803, one material marketed by Sumitomo Metals Ltd under designation HK4M and a cast alloy with designation HP45-Nb. The analysis of the various reference materials is given in the table below.
Alloy Cr Ni Si Mn C N Nb Ti Al HP45-Nb 23.636.91.4 1.220.17 0.046 1.2 -- --Inco 25.835.30.650.900.0750.013 -- 0.55 0.52 HK4M 25.324.50.411.120.21 0.017 -- 0.46 0.33 Sanicro3924.934.81.5 1.4 0.0480.166 -- -- -- REM=0.05 The diagram in Fig. 3 shows the weight change during oxidation in air at 1000 D C as a function of the exposure time for the tubes.
As appears from the diagram in Fig. 3 the obtained result shows that the oxides being formed more easily come apart from these reference materials when compared with the material Sanicro 39 selected according to the invention.
The carburizing tests were carried out so as to be similar to the ethylene environment present in the aforementioned cracker applications by providing shifting carburizing and oxidizing environments. The carburizing occurred in a gas mixture comprising carbon monoxide, hydrogen gas and methane in a mixture which was at a temperature of 1050° C and gave an oxygen potential corresponding to 10-15 atm and a carbon activity > 1. After being exposed for 120 hours to this carbonizing environment the coke that had been formed was talcen out by introducing air to combust the coke. The time period for the carburizing/oxidizing cycle varied bet-ween 135-140 hours. The total testing time was 1104 hours corresponding with 8 cycles as set forth above. The temperature was kept constant at 1050° C during the entire first test. The geometry of the test rods was 8 mm x 8 mm x 20 mm.
After the test was completed the test rods were taken out and a cross section thereof was studied by looping upon how the area fraction of carbides varied along a selected line.
The cross section of said test rods had a squaxe shaped outer surface and with this test rod design it was found that the carbonizing was much depending on where on this outer surface the measurement was made. Areas close to corners and edges appeaxed to be more sensitive to carbonizing than those surfaces that were planax. In Fig.
4, it is shown the position of the lines that are analyzed in the cross section of the test rod. The first line (Prof 10) was located 0.8 mm (10% of the edge length) into the material along the outer surface. The second Line (Prof 50) was located 4 mm from a corner whilst being extended through the center of the test rod.
In Fig. 4 it is schematically shown how carburizing vaxies depending on whether the location is close to an edge or extending far into a planar surface.
This figure also schematically shows how the carburizing depth varies depending on the distance from a corner. The grey marked axea represents the carburized area and the white field represents the noncarburized area. It should be noted that the carbonizing depth is larger in the corners of the test rod.
In Fig. 5 the results from the area fraction analysis of carbides are presented. The x-axis represents the distance from the start point at one outer surface (0-8 mm) and the y-axis shows the measured area fraction of carbides (%). The diagram shows that Sanicro 39 and HP45-Nb are not affected by carburizing from planar surfaces (Prof 50) and out of these two Sanicro 39 appeared with the best resistance towards carburizing in the area close to the corners or the edges (prof 10). The alloy 803 was affected by massive carburizing in the comer areas and also appeared with strong carburizing on the planar surfaces. The alloy HI~4M was subjected to carburizing to its maximum through the entire material.
While the present invention has been described by reference to the above-mentioned embodiments, certain modifications and variations will be evident to those of ordinary slcill in the art. Therefore, the present invention is limited only by the scope and spirit of the appended claims.
Claims (9)
1. A metal tube for use in furnaces where gas and liquid formed media is being pressed through such tube from its inlet end to its opposite end while being sub-jected to substantial heating and decomposition therefrom, the metal tube comprising:
a body;
a smooth outer surface; and an inner surface with a profile; wherein the body is made of a stainless iron-nickel-chromium base alloy comprising, in weight%:
max 0.08% C, 23-27% Cr, 33-37% Ni, 1.3-1.8% Mn, 1.2-2% Si, 0.08-0.25% N, 0.01-0.15% rare earth metals, and normal impurities; and the profile comprises a plurality of valleys or recesses, said valleys or recesses extending longitudinally along the tube, and having a smoothly curved bottom.
a body;
a smooth outer surface; and an inner surface with a profile; wherein the body is made of a stainless iron-nickel-chromium base alloy comprising, in weight%:
max 0.08% C, 23-27% Cr, 33-37% Ni, 1.3-1.8% Mn, 1.2-2% Si, 0.08-0.25% N, 0.01-0.15% rare earth metals, and normal impurities; and the profile comprises a plurality of valleys or recesses, said valleys or recesses extending longitudinally along the tube, and having a smoothly curved bottom.
2. The tube according to claim 1, wherein each of the plurality of valleys or recesses are straight whilst extending longitudinally along the cylinder.
3. The tube according to claim 1, wherein each of the plurality of valleys or recesses and each of the plurality of peaks extend helically from an inlet end to an opposite end of said tube.
4. The tube of claim 1, further comprising a chromium oxide layer on the inner surface.
5. A hydrocarbon cracking furnace comprising a tube according to claim 1.
6. A metal tube according to any of the claims 1-5, c h a r a c t e r i z e d in that the amount of rare earth metals is 0.03-0.10%.
7. A metal tube according to any of the claims 1-6, c h a r a c t e r i z e d in that the amount of silicon is 1.3-1.8%.
8. A metal tube according to any of the claims 1-7, c h a r a c t e r i z e d in that the amount of nitrogen is 0.13-0.18%.
9. The usage of a metal tube according to any of the preceding claims in a furnace for the fabrication of ethylene.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE0004336-4 | 2000-11-24 | ||
| SE0004336A SE0004336L (en) | 2000-11-24 | 2000-11-24 | Cylinder pipes for industrial chemical installations |
| PCT/SE2001/002602 WO2002042510A1 (en) | 2000-11-24 | 2001-11-23 | Cylindrical tube for industrial chemical installations |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2426882A1 true CA2426882A1 (en) | 2002-05-30 |
Family
ID=20281972
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002426882A Abandoned CA2426882A1 (en) | 2000-11-24 | 2001-11-23 | Cylindrical tube for industrial chemical installations |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US20020096318A1 (en) |
| EP (1) | EP1339890A1 (en) |
| JP (1) | JP2004514788A (en) |
| KR (1) | KR20030051833A (en) |
| BR (1) | BR0115397A (en) |
| CA (1) | CA2426882A1 (en) |
| EA (1) | EA004604B1 (en) |
| NO (1) | NO20032334D0 (en) |
| SE (1) | SE0004336L (en) |
| WO (1) | WO2002042510A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT410550B (en) * | 2002-01-23 | 2003-05-26 | Boehler Edelstahl | Material used as a tool material in the glass industry, especially as a molding material for machine pressed glass consists of an alloy containing carbon, silicon, chromium, nickel and nitrogen |
| DE202004016252U1 (en) * | 2004-08-12 | 2005-12-22 | Schmidt + Clemens Gmbh & Co. Kg | Composite pipe, for use in steam cracking of hydrocarbons or in rotary furnaces or refuse incinerators, comprises outer spun pipe and coaxial inner pipe which is made by compressing powder |
| GB201012737D0 (en) | 2010-07-29 | 2010-09-15 | Airbus Operations Ltd | Improvements to aircraft refuel system piping |
| DK3384981T3 (en) * | 2017-04-07 | 2024-04-08 | Schmidt Clemens Gmbh Co Kg | TUBES AND DEVICE FOR THERMAL SPLITTING OF CARBON HYDRIDS |
| IL269775B2 (en) * | 2017-04-07 | 2024-04-01 | Schmidt Clemens Gmbh Co Kg | Pipe and Device for Thermally Cleaving Hydrocarbons |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3813911A (en) * | 1972-10-18 | 1974-06-04 | Superior Tube Co | Tube rolling mill for producing tubing with various internal configurations |
| GB1557872A (en) * | 1976-09-15 | 1979-12-12 | Shevchenko A A | Others method of continuous tube rolling and rolling mill therefor |
| US4478275A (en) * | 1983-07-25 | 1984-10-23 | Thermacore, Inc. | Abrasion resistant heat pipe |
| US4827074A (en) * | 1988-04-08 | 1989-05-02 | Idemitsu Petrochemical Co., Ltd. | Method of thermally decomposing hydrocarbon and thermal decomposition tube |
| SE462395B (en) * | 1988-11-18 | 1990-06-18 | Avesta Ab | AUSTENITIC JAERN-NICKEL-CHROME BAS-ALLOY WITH GOOD HIGH-TEMPERATURE PROPERTIES AND APPLICATION OF THIS |
| US5016460A (en) * | 1989-12-22 | 1991-05-21 | Inco Alloys International, Inc. | Durable method for producing finned tubing |
| SE469754B (en) * | 1990-05-14 | 1993-09-06 | Kanthal Ab | OVEN BEFORE CRACKING THE PULP |
| SA05260056B1 (en) * | 1991-03-08 | 2008-03-26 | شيفرون فيليبس كيميكال كمبني ال بي | Hydrocarbon processing device |
| US5655599A (en) * | 1995-06-21 | 1997-08-12 | Gas Research Institute | Radiant tubes having internal fins |
| BR9811468A (en) * | 1997-06-10 | 2000-09-19 | Exxon Chemical Patents Inc | Pyrolysis oven with a "U" radiant spiral with internal fins |
| US5944981A (en) * | 1997-10-28 | 1999-08-31 | The M. W. Kellogg Company | Pyrolysis furnace tubes |
| US5985048A (en) * | 1998-04-07 | 1999-11-16 | Semitool, Inc. | Method for developing an enhanced oxide coating on a component formed from stainless steel or nickel alloy steel |
| GB2340911B (en) * | 1998-08-20 | 2000-11-15 | Doncasters Plc | Alloy pipes and methods of making same |
| US6644358B2 (en) * | 2001-07-27 | 2003-11-11 | Manoir Industries, Inc. | Centrifugally-cast tube and related method and apparatus for making same |
-
2000
- 2000-11-24 SE SE0004336A patent/SE0004336L/en unknown
-
2001
- 2001-11-23 KR KR10-2003-7006638A patent/KR20030051833A/en not_active Application Discontinuation
- 2001-11-23 CA CA002426882A patent/CA2426882A1/en not_active Abandoned
- 2001-11-23 JP JP2002545210A patent/JP2004514788A/en active Pending
- 2001-11-23 BR BR0115397-8A patent/BR0115397A/en not_active Application Discontinuation
- 2001-11-23 EP EP01997570A patent/EP1339890A1/en not_active Withdrawn
- 2001-11-23 EA EA200300603A patent/EA004604B1/en not_active IP Right Cessation
- 2001-11-23 WO PCT/SE2001/002602 patent/WO2002042510A1/en not_active Application Discontinuation
- 2001-11-26 US US09/991,703 patent/US20020096318A1/en not_active Abandoned
-
2003
- 2003-05-23 NO NO20032334A patent/NO20032334D0/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| US20020096318A1 (en) | 2002-07-25 |
| EA004604B1 (en) | 2004-06-24 |
| WO2002042510A1 (en) | 2002-05-30 |
| JP2004514788A (en) | 2004-05-20 |
| EA200300603A1 (en) | 2003-10-30 |
| NO20032334L (en) | 2003-05-23 |
| NO20032334D0 (en) | 2003-05-23 |
| WO2002042510A8 (en) | 2002-07-04 |
| SE0004336D0 (en) | 2000-11-24 |
| SE0004336L (en) | 2002-05-25 |
| KR20030051833A (en) | 2003-06-25 |
| EP1339890A1 (en) | 2003-09-03 |
| BR0115397A (en) | 2004-07-06 |
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