Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
  • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
  • C10G9/16—Preventing or removing incrustation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
  • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
  • C10G9/18—Apparatus
  • C10G9/20—Tube furnaces
  • C10G9/203—Tube furnaces chemical composition of the tubes
• • 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
  • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium

Definitions

• the present invention relates to steels intended to manufacture reactors, furnaces, pipes or certain of their elements used in particular in petrochemical processes, these steels having an improved resistance to coking.
• the invention also relates to the manufacture of reactors, furnaces, pipes or some of their elements, using these steels.
• coke The carbonaceous deposit that develops in furnaces during the conversion of hydrocarbons.
• This deposit of coke is harmful in industrial units. Indeed, the formation of coke on the walls of the tubes and reactors leads in particular to a reduction in heat exchanges, significant blockages and therefore increases in pressure drops. To keep a constant reaction temperature, it may be necessary to increase the temperature of the walls, which risks causing damage to the alloy constituting these walls. There is also a decrease in the selectivity of the installations and therefore in the yield.
• EP-A-0 190 408 describes an austenitic steel for coal gasification devices.
• Application JP 03-104843 is known, which describes an anti-coking refractory steel for an ethylene steam cracking furnace tube. But this steel contains more than 15% chromium and nickel, and less than 0.4% manganese. This steel is developed to limit the formation of coke between 750 ° C and 900 ° C for the steam cracking of naphtha, ethane or diesel.
• the steels of the invention may also contain from 0.25 to about 0.5% by weight of titanium.
• the invention also relates to a method for manufacturing plant elements intended for petrochemical processes taking place at temperatures between 350 and 1100 ° C., in which, to improve the resistance to coking of said elements, they are manufactured in all or part of it, using steel as defined above.
• These steels can be used to manufacture installations using petrochemical processes, for example, catalytic or thermal cracking and dehydrogenation.
• Another application may relate to a process of steam cracking of products such as naphtha, ethane or a gas oil, which leads to the formation of light unsaturated hydrocarbons, in particular ethylene, etc. at temperatures from 750 ° C. to 1100 ° C.
• the steels according to the invention can be used to manufacture whole tubes or plates intended for the manufacture of furnaces or reactors.
• the steels according to the present invention can be produced by the conventional foundry and molding methods, then shaped by the usual techniques to manufacture sheets, grids, tubes, profiles, etc. semi-finished products can be used to build the main parts of reactors or only accessory or auxiliary parts.
• the steels according to the invention can also be used for covering the internal walls of furnaces, reactors or pipes, by at least one of the following techniques: co-centrifugation, plasma, electrolytic, "overlay”. These steels can then be used in powder form to coat the internal walls of the reactors, grids or tubes, in particular after installation of the installations.
• the steels used in the examples have the compositions indicated below (% by weight): STEELS VS Yes Mn Or Cr S P Al Ti AS 0.06 0.5 1.1 10 17.5 0.015 ⁇ 0.04 0.07 0.5 F1 0.37 2.31 10.25 D1 0.04 1.9 1.8 12.5 19.3 0.001 0.02 0.06 0.005 D2 0.2 3.6 0.8 14.5 18.5 0.015 ⁇ 0.04 1.0 ⁇ 0.01 C1 0.06 5 1.2 10 17.5 0.015 ⁇ 0.04 0.07 0.5 C2 0.06 3.5 1.2 10 17.5 0.015 ⁇ 0.04 0.07 0.5 C3 0.05 3 1.2 12 17.5 0.015 ⁇ 0.04 0.06 0.35 C4 0.05 2.5 1.2 12 17.0 0.05 ⁇ 0.04 0.06 0.35
• AS is a standard steel commonly used for the manufacture of reactors or reactor components. Steels F1, D1 and D2 are also presented for comparison.
• the isobutane dehydrogenation reaction makes it possible to obtain isobutene.
• a side reaction is the formation of coke.
• the coke deposit consists mainly of coke of catalytic origin.
• the steel F1 has a ferritic structure, the steels C1 and C2 an austeno-ferritic structure and the steels C3 and C4 an austenitic structure.
• the chromium and nickel contents of steels C3 and C4 were adjusted using the equivalence coefficients of Guiraldenq and Pryce, in order to locate these steels in the austenitic single-phase domain of the Schaeffer diagram.
• Alloys C1, C2, C3 and C4 have the ability to develop a stable and inert oxide layer vis-à-vis catalytic coking phenomena.
• the presence of silicon in these alloys promotes the formation of an outer and substantially continuous layer practically consisting solely of chromium oxide without Cr_Ni_Fe spinel oxides.
• This chromium oxide layer is separated from the metal substrate by an oxide zone rich in silicon.
• the atmosphere of the chemical reaction, for example of dehydrogenation of isobutane is then practically only in contact with a chromium oxide layer catalytically inert vis-à-vis the coking phenomenon.
• the microbalance makes it possible to continuously measure the gain in mass on the sample.
• FIG. 1 shows a graph having the time in hours on the abscissa and the ordinate the mass of coke which forms on the sample during the reaction, mass given in grams per square meter (g / m 2 ).
• Curve 1 relates to AS steel, curve 2 to F1 steel, curves 3 and 3b respectively to steels D1 and D2, all 4 curves to steels C1, C2, C3 and C4.
• Figure 2 shows the coking curves during several successive coking / decoking cycles.
• the decoking was carried out in air at 600 ° C, for the time necessary to burn the deposited coke (5 to 10 minutes).
• Curve 6 represents coking for AS steel in the first cycle
• curve 5 represents coking for AS steel sample after 20 coking / decoking cycles.
• Curves 7 represent the coking / decoking curves after 20 cycles for steels C3 and C4.
• steels C3 and C4 After 20 coking / decoking cycles, steels C3 and C4 have the same resistance to coking. Their surface chromium oxide layer has not evolved and it has retained its very low original catalytic activity with regard to coking. On the other hand, for standard steel which contains practically no silicon, after 20 coking / decoking cycles, the carbon deposition rate after 6 hours of testing has been multiplied by four.
• the protective layer of standard steel is not stable: during successive decoking, there is an enrichment of this layer with catalytic metallic element such as iron or nickel.
• a second test was carried out with a steam cracking reaction of hexane at a temperature of about 850 ° C.
• the protocol for preparing the steel samples and for testing is the same as for Example 1.
• FIG. 3 shows the coking of a steel sample AS, represented by curve 8, clearly superior to curves 9 and 10 representing respectively the coking of samples of steels C4 and C3.
• the C3 and C4 alloys which contain in particular silicon have a lower coking rate than that of standard steels.
• Column 1 corresponds to the temperature of the sample, column 2 to the stress at the elastic limit, column 3 to the stress at break, column 4 to the elongation at break.
• Column 5 corresponds to the breaking stress in the creep test after 10,000 hours, column 6 after the 100,000 hours, and column 7 to the stress for an elongation of 1% in the creep test after 10,000 hours.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Orthopedics, Nursing, And Contraception (AREA)
• Materials For Medical Uses (AREA)
• Absorbent Articles And Supports Therefor (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 1994
  • 1994-12-20 FR FR9415453A patent/FR2728271A1/fr active Granted
• 1995
  • 1995-12-18 DE DE69522783T patent/DE69522783T2/de not_active Expired - Fee Related
  • 1995-12-18 EP EP95402864A patent/EP0718415B1/fr not_active Expired - Lifetime
  • 1995-12-18 NO NO19955144A patent/NO314807B1/no not_active IP Right Cessation
  • 1995-12-18 AT AT95402864T patent/ATE205889T1/de not_active IP Right Cessation
  • 1995-12-19 RU RU95121106A patent/RU2146301C1/ru not_active IP Right Cessation
  • 1995-12-20 KR KR1019950053030A patent/KR100391747B1/ko not_active IP Right Cessation
  • 1995-12-20 JP JP33094095A patent/JP3906367B2/ja not_active Expired - Fee Related
  • 1995-12-20 CN CN95121455A patent/CN1080323C/zh not_active Expired - Fee Related
  • 1995-12-20 US US08/575,546 patent/US5693155A/en not_active Expired - Lifetime

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