CN107881393B - Anti-coking alloy material, preparation method thereof and anti-coking cracking furnace tube - Google Patents
Anti-coking alloy material, preparation method thereof and anti-coking cracking furnace tube Download PDFInfo
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- 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
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- 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
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- 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
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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- 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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- 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
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- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
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Abstract
The invention relates to the field of anti-coking, in particular to an anti-coking alloy material, a method for preparing the anti-coking alloy material and an anti-coking cracking furnace tube. The anti-coking alloy material comprises an alloy material substrate and a coating layer coated on the surface of the alloy material substrate, wherein the coating layer contains metal oxides and metal sulfides of metal elements in the alloy material substrate, and relative to the volume of the coating layer, the content of the metal oxides is 75.1-85% by volume, and the content of the metal sulfides is 15-24.9% by volume. The anti-coking alloy material can effectively inhibit coking and can keep the anti-coking performance for a long time.
Description
Technical Field
The invention relates to the field of anti-coking, in particular to an anti-coking alloy material, a method for preparing the anti-coking alloy material and an anti-coking cracking furnace tube.
Background
In the ethylene production process, the cracking furnace tube inner wall inevitably generates surface coking and metal matrix carburization, which can cause two adverse effects. On one hand, coking can cause the inner diameter of the furnace tube to be reduced, the pressure drop to be increased, the treatment capacity of the device to be reduced, the thermal resistance of the tube wall to be increased, the heat transfer coefficient of the furnace tube to be reduced and the energy consumption to be increased. For this reason, the coke cleaning process must be performed by shutting down the furnace every 30 to 60 days. This frequent decoking treatment severely reduces production efficiency and increases production costs. On the other hand, carbon deposited on the surface of the furnace tube diffuses into the metal matrix to form carbide, increasing the brittleness of the material and further causing metal powdering. These material damages caused by carburization interact with the thermal cycle in the decoking process, greatly shortening the life of the cracking furnace tube. Therefore, the problem of furnace tube coking is an urgent problem in the ethylene production process.
Over the past 50 years, various approaches have been used to inhibit coking in the radiant coils of pyrolysis furnaces. For example, the coking condition of the radiant coils is improved to some extent by changing the process conditions (low hydrocarbon partial pressure, short residence time, etc.) of the thermal cracking of hydrocarbons, pretreating the cracking feedstock (hydrogenation, aromatics extraction, etc.), introducing enhanced heat transfer members (external nail heads, enhanced heat transfer members, etc.) into the radiant coils, and adding a coking inhibitor into the feedstock.
In addition, a method for pre-oxidizing the cracking furnace tube can be adopted, and the method generally obtains manganese-chromium spinel MnCr on the inner surface of the furnace tube in a low-oxygen partial pressure oxidation mode2O4Protective layer, but its resistanceThe coking capability is unstable, and one important reason is that the manganese chromium spinel oxide layer can not completely cover Fe and Ni elements on the inner surface. In addition, in the liquid cracking furnace using naphtha and diesel oil as raw materials, although the coking is also based on catalytic coking, the polycondensation coking accounts for more than 50% of the total coking amount, and the polycondensation coking can completely cover the oxidation film. Therefore, the oxide film in the liquid cracking furnace tube can only be effective in the initial service stage of the furnace tube because the oxide film is not covered by the polycondensation coking yet, and the oxide film can not exert the efficacy when the cracking furnace is operated to the middle and later stages.
Disclosure of Invention
The invention aims to overcome the defects of insufficient anti-coking performance and/or insufficient anti-coking time of the anti-coking alloy material in the prior art, and provides the anti-coking alloy material, a method for preparing the anti-coking alloy material and an anti-coking cracking furnace tube. The anti-coking alloy material can effectively inhibit coking and can keep the anti-coking performance for a long time.
The coating layer of the prior anti-coking material usually contains as much manganese-chromium spinel oxide as possible, but the inventor of the invention finds that a part of the surface of the alloy material matrix can not form the manganese-chromium spinel oxide because Cr and Mn elements in the cracking furnace tube matrix alloy continuously migrate from the grain boundary or crystal defects of the surface layer to the surface in the oxidation process, but the grain boundary and the crystal defects are not uniformly distributed, and in some areas with smaller grain boundaries or crystal defects, the Cr and Mn elements migrate to the surface little, and the formed manganese-chromium spinel oxide can not completely cover Fe and Ni elements on the surface of the alloy material matrix, so that the catalytic coking of the part of the area is serious. Therefore, the inventor of the invention finds that partial sulfides are formed in the coating layer, and the partial sulfides are mainly FeS and NiS formed by Fe and Ni on the inner surface of the alloy material substrate, so that the surface of the alloy material substrate can be basically and completely covered, and the catalytic coking activity of the cracking furnace tube is remarkably reduced.
The invention provides a coking-resistant alloy material, which comprises an alloy material matrix and a coating layer coated on the surface of the alloy material matrix, wherein the coating layer contains metal oxides and metal sulfides of metal elements in the alloy material matrix, and relative to the volume of the coating layer, the content of the metal oxides is 75.1-85% by volume, and the content of the metal sulfides is 15-24.9% by volume.
The invention provides an anti-coking cracking furnace tube in a second aspect, which is characterized in that the tube wall of the anti-coking cracking furnace tube is made of the anti-coking alloy material, wherein the coating layer is positioned on the inner side of the tube wall of the anti-coking cracking furnace tube.
A third aspect of the present invention provides a method for preparing the anti-coking alloy material of the present invention, characterized in that the method comprises the steps of: and contacting a coating gas with the inner surface of the alloy material substrate at a high temperature of above 500 ℃ so as to react with the inner surface of the alloy material substrate to form a coating layer, wherein the coating gas contains a sulfide gas, water vapor and a carrier gas, and the sulfide gas is contained in an amount of 0.01-0.1 vol%, the water vapor is contained in an amount of 0.001-2 vol%, and the carrier gas is contained in an amount of 97.9-99.989 vol%, based on the total volume of the coating gas.
The anti-coking alloy material provided by the invention can effectively inhibit coking and can keep the anti-coking performance for a long time. The method provided by the invention has simple process, and the formed oxide film and the formed sulfide film can effectively cover Fe and Ni elements on the inner wall of the cracking furnace tube, thereby reducing coking in the operation process and prolonging the operation period of the cracking furnace. The anti-coking alloy material is particularly suitable for cracking furnace tubes. The method can reduce the coke deposited on the inner wall of the cracking furnace tube by more than 50 percent and even more than 70 percent.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a coking-resistant alloy material, which comprises an alloy material matrix and a coating layer coated on the surface of the alloy material matrix, wherein the coating layer contains metal oxides and metal sulfides of metal elements in the alloy material matrix, and relative to the volume of the coating layer, the content of the metal oxides is 75.1-85% by volume, and the content of the metal sulfides is 15-24.9% by volume.
The coating layer of the present invention satisfies the above composition requirements that a superior anti-coking effect can be achieved, and preferably, the content of the metal oxide is 78-82 vol% and the content of the metal sulfide is 18-22 vol%, with respect to the weight of the coating layer.
In the present invention, the composition of the metal sulfide in the coating layer is not particularly limited, and is a metal sulfide formed in a sulfidizing reaction of a metal contained in the alloy material, and thus the metal sulfide in the coating layer may contain a sulfide of a metal element capable of forming a sulfide in various alloy materials, and may include, for example, FeS, NiS, MnS, and Cr2S3One or more of (a). Preferably, FeS and NiS account for 90 wt% or more, more preferably 95 wt% or more of the metal sulfide in the coating layer.
In the present invention, the composition of the metal oxide in the coating layer is not particularly limited, and is a metal oxide formed in an oxidation reaction of a metal contained in the alloy material, and thusThe metal oxide in the coating layer may contain oxides of metal elements capable of forming oxides in various alloy materials, and may include, for example, MnO and Cr2O3、MnxCr3-xO4(manganese chromium spinel), etc., preferably, wherein Mn is presentxCr3-xO490% by weight or more, more preferably 95% by weight or more of the metal oxide in the coating layer; where x is from 0.5 to 2, preferably from 1 to 2, and is generally from 1, 1.5 and 2, i.e. Mn1Cr2O4、Mn1.5Cr1.5O4And Mn2Cr1O4。
In the present invention, the thickness of the coating layer may be 0.5 to 5 μm, preferably 1 to 4 μm, and more preferably 2 to 3 μm.
In the present invention, the elemental composition of the alloy material base is not particularly limited, and may include, for example, Fe, Cr, Ni, Mn, Si and C, and trace elements, preferably, where the weight percentage content of Mn and Si satisfies formula (1), and under the condition of the elemental content of Mn and Si of the present invention, the surface of the alloy material base is more likely to form a continuous coating layer, and the total coverage can be secured as much as possible,
more preferably, the weight percentages of Mn and Si satisfy formula (2),
in the present invention, the cracking furnace tubes can be various cracking furnace tubes commonly used in the art, preferably cracking furnace tubes for cracking hydrocarbon organic matter. Preferably, the cracking furnace tube contains 13-44 wt% of chromium, 16-44 wt% of nickel, 0.2-3 wt% of manganese, 0-3 wt% of silicon, 0-0.75 wt% of carbon, 0-5 wt% of total trace elements and trace elements, and 0.25-70.8 wt% of iron; more preferably, the cracking furnace tube contains 30-40 wt% of chromium, 30-42 wt% of nickel, 1.6-2 wt% of manganese, 1.5-3 wt% of silicon, 0.2-0.6 wt% of carbon, 0-2 wt% of trace elements and 10.4-36.7 wt% of iron. The trace element of the invention is at least one of Al, Nb, Ti, W, Mo, La, Ce, Y, Nd, Pr, Gd, Dy and Sm, and the trace element is sulfur and/or phosphorus.
The invention provides a coking-resistant cracking furnace tube, wherein the tube wall of the coking-resistant cracking furnace tube is made of the coking-resistant alloy material, and the coating layer is positioned on the inner side of the tube wall of the coking-resistant cracking furnace tube.
In the invention, the anti-coking cracking furnace tube also comprises an enhanced heat transfer component which is positioned in the anti-coking cracking furnace tube and is connected with the inner wall of the tube wall. The enhanced heat transfer component can change the flowing state of the pyrolysis gas and mainly plays two roles: (1) changing the flow regime of the coating, trace amounts of O in the gas2The sulfide can be fully contacted with the pipe wall, and the coverage rate of the formed coating layer is higher; (2) in the cracking process, after the enhanced heat transfer component changes the flowing state of the cracking gas from laminar flow to turbulent flow, the polycondensation coking on the inner surface of the furnace tube is easily flushed away by the cracking gas flow, because the polycondensation coking is generally loose coke, and the adhesive force on the inner wall of the furnace tube is weak. Therefore, coke attached to the inner wall of the furnace tube containing the heat transfer enhancement component is mainly subjected to catalytic coking, so that the coating layer can fully exert the effect.
In the present invention, the heat transfer enhancing member is not particularly limited, and may be, for example, a twisted piece. The number of the twisted pieces may be 1-10, and the length of each twisted piece may be 20-30 cm. The installation mode of the twisted piece is that the central axis of the twisted piece is superposed with the central axis of the cracking furnace tube, and the edge of the twisted piece is connected with the inner wall of the cracking furnace tube, so that the interior of the alloy material matrix is divided into two parts.
In a third aspect of the present invention, there is provided a method for preparing the anti-coking alloy material of the present invention, wherein the method comprises that the coating layer is obtained by the following method: and contacting a coating gas with the surface of the alloy material substrate at a high temperature of above 500 ℃ so as to react on the surface of the alloy material substrate to form a coating layer, wherein the coating gas contains a sulfide gas, water vapor and a carrier gas, and the sulfide gas is contained in an amount of 0.01-0.1 vol%, the water vapor is contained in an amount of 0.001-2 vol%, and the carrier gas is contained in an amount of 97.9-99.989 vol%, based on the total volume of the coating gas.
In the present invention, when the anti-coking alloy material is in the form of an anti-coking cracking furnace tube, the method comprises that the coating layer is obtained by the following method: and at the high temperature of more than 500 ℃, introducing the coating gas into the cracking furnace tube, and forming a coating layer on the inner surface of the cracking furnace tube by reacting the coating gas with the inner surface of the cracking furnace tube.
In the present invention, when the contents of sulfide gas and water vapor in the coating gas satisfy the above ranges, a superior coating effect and anti-coking effect can be achieved, and more preferably, the content of sulfide gas is 0.02 to 0.08 vol%, the content of water vapor is 0.2 to 1.8 vol%, and the content of carrier gas is 98.12 to 99.78 vol%, based on the total volume of the coating gas; further preferably, the content of the sulfide is 0.02 to 0.04 vol%, the content of the water vapor is 0.5 to 1.5 vol%, and the content of the carrier gas is 98.46 to 99.48 vol%.
In the present invention, the sulfide itself may be a gas, or may be a liquid at room temperature, but may be entrained by an introduced carrier gas at room temperature or under heating to enter a gas. The sulfide may be selected from H, for example2S、SO2、SF6、COS、CS2、CH3SH、CH3CH2SH、CH3SCH3、CH3CH2SCH2CH3、CH3S-SCH3And CH3CH2S-SCH2CH3In (1)One or more, preferably H2S、SF6、CH3SH、CH3SCH3And CH3S-SCH3One or more of (a).
In the present invention, the carrier gas may be a carrier gas conventional in the art, and may be selected from, for example, H2、N2One or more of Ar and He, most preferably H2. Since the above-mentioned gas is expensive and difficult to obtain in industrial purity, a by-product gas generated during industrial operation can be used as a carrier gas, and the carrier gas may further contain other impurity gases, such as a hydrocarbon cracked gas, e.g., CH4、C2H6、C3H8、C2H4、C3H6、C2H2And C3H4One or more of (a). The impurity gas may account for 50% by volume or less, preferably 40% by volume or less, more preferably 30% by volume or less of the carrier gas.
The present invention is not particularly limited in the manner of obtaining the coating gas, and for example, the coating gas may be obtained by directly mixing a sulfide gas, water vapor and a carrier gas, or may be obtained by passing a carrier gas through an aqueous solution containing a sulfide soluble in water, or may be obtained by passing a carrier gas through a sulfide and water in a liquid state in this order.
The conditions for treating the inside surfaces of the cracking furnace tubes with a gas mixture containing sulfide gas, water vapor and a gas having a low partial pressure of oxygen are not particularly limited in the present invention, as long as the coating film of oxides and sulfides can be formed on the inside surfaces of the tubes, thereby facilitating the inhibition or alleviation of coking of the cracking furnace tubes, and for example, the treatment conditions generally include a treatment temperature of 800-. In addition, although the desired oxides and sulfides can be obtained by controlling the treatment temperature and the treatment time within the above ranges, it is preferable that the treatment temperature is 850 ℃ and 1150 ℃ and the treatment time is 10 to 100 hours, more preferably 20 to 60 hours, in order to obtain oxide films and sulfide films having higher coverage and better anti-coking effect.
In the present invention, the presence of the carrier gas allows the water vapor content to be greatly reduced, thereby creating an environment with a low oxygen partial pressure. The low oxygen partial pressure environment is a reducing environment in which the oxygen partial pressure is low, so that the oxidation process occurs very slowly, and a dense coating film of oxides and sulfides is formed on the surface of the material. The pressure of the low oxygen partial pressure gas can be 0-0.3MPa, preferably 0.05-0.2 MPa; wherein the oxygen partial pressure may be 1.1X 10-15～1×10-9Pa, preferably 1.1X 10-15～1×10-13Pa. In the present invention, the oxygen partial pressure refers to the pressure occupied by oxygen present in the low oxygen partial pressure gas, and the oxygen in the low oxygen partial pressure environment is mainly derived from oxygen-containing compounds (such as H)2O) oxygen generated by decomposition.
When the alloy material is subjected to high-temperature oxidation treatment only by using mixed gas of water vapor and carrier gas, a part of the inner surface can not form manganese-chromium spinel oxide, because Cr and Mn elements in the matrix alloy of the cracking furnace tube can continuously migrate from the grain boundary or crystal defects of the surface layer to the surface in the oxidation process, but the distribution of the grain boundary and the crystal defects is not uniform, in some areas with small grain boundary or crystal defects, the Cr and Mn elements migrate to the surface very little, and the formed manganese-chromium spinel oxide can not completely cover Fe and Ni elements on the inner surface of the cracking furnace tube (because Fe and Ni are difficult to be oxidized under the condition of low oxygen partial pressure), so that the catalytic coking of the part of the area is serious. The coating gas also contains sulfide, and the sulfide can vulcanize Fe and Ni which are not covered to generate FeS and NiS, so that the coking phenomenon of the cracking furnace tube is remarkably relieved.
The method of the invention uses a relatively low water vapor content and the coating gas used in the method of the invention favors the formation of higher levels of manganese chromium spinel compared to coating gases with higher water vapor content, but the temperature is less easily controlled in industrial operations and is subject to temperature runaway and is therefore not generally used for on-line coating.
The coating layer obtained by the method of the invention has firm combination because of containing a large amount of ionic bonds formed by oxygen and sulfur and the metal on the inner surface of the furnace tube, and is not easy to strip under the huge scouring action of the cracking gas flow. The coating layer of the invention has the same main components with the matrix alloy, so the thermal expansion coefficient of the coating layer is very close to that of the matrix, the thermal stress generated between the coating layer and the matrix is small, and the coating layer can meet the requirement of long-term use of the hydrocarbon cracking furnace tube.
The present invention will be described in detail below by way of examples.
Example 1
This example was conducted by using 35Cr45Ni alloy material coupons having dimensions of 5X 2mm and an elemental composition as shown in Table 1. The coupon is first weighed to record the initial weight. Then suspending the weighed metal hanging pieces in a furnace tube, introducing coating gas into the furnace tube to coat the hanging pieces, wherein the coating gas contains 2 volume percent of CH41% by volume of H2O, 0.02 vol.% H2S and 96.98 vol% H2The flow rate is 200ml/min, the treatment temperature is 950 ℃, and the treatment time is 30 h. A coated coupon was obtained and was designated I1.
Example 2
This example was conducted by using 35Cr45Ni alloy material coupons having dimensions of 5X 2mm and an elemental composition as shown in Table 1. The coupon is first weighed to record the initial weight. Then suspending the weighed metal hanging pieces in a furnace tube, and introducing coating gas into the furnace tube to coat the hanging pieces, wherein the coating gas contains 20 vol% of C3H80.5 vol.% H2O, 0.08 vol.% CH3SH and 79.42 vol% N2The flow rate is 200ml/min, the treatment temperature is 1050 ℃, and the treatment time is 40 h. A coated coupon was obtained and was designated I2.
Example 3
This example was conducted by using 35Cr45Ni alloy material coupons having dimensions of 5X 2mm and an elemental composition as shown in Table 1. The coupon is first weighed to record the initial weight. Then suspending the weighed metal hanging pieces in a furnace tube, and introducing coating gas into the furnace tube to coat the hanging pieces, wherein the coating gas contains 8 vol% of C2H41.5 vol.% H2O, 0.03 vol% CS2And 90.47 vol% Ar at a flow rate of 200ml/min, a treatment temperature of 850 ℃ and a treatment time of 60 h. A coated coupon was obtained and was designated I3.
Example 4
The procedure is as in example 1, except that different doctor blades are used, the elemental composition of which is shown in Table 1. The finished coated cracking furnace tube was obtained as I4.
Comparative example 1
The procedure is as in example 1, except that the coating gas does not contain H2S, i.e. 2% by volume of CH in the coating gas41% by volume of H2O and 97% by volume of H2. The finished coated coupon was finally obtained and was designated as D1.
Comparative example 2
The procedure is as in example 1, except that the coating gas contains 2% by volume of CH43% by volume of H2O, 0.02 vol.% H2S and 94.98 vol% H2. The finished coated cracking furnace tube was obtained as D2.
TABLE 1
Test example
(1) The coating layers coated on the surfaces of the cracking furnace tubes I1-I4 and D1-D2 which are coated and obtained in examples 1-4 and comparative examples 1-2 are respectively observed under an XL-30 field emission environment scanning electron microscope of FEI company, under the electron microscope, the metal oxide is in a whisker shape, the metal sulfide is in a flaky shape, the volume contents of the metal oxide and the metal sulfide can be estimated, ten fields of view are taken for the coating layer of each furnace tube for estimation, the average value is taken, and the volume content ratio of the obtained metal oxide and the metal sulfide is recorded in a table 2.
TABLE 2
| Metal sulfide (%) | Metal oxide (%) | Is not covered (%) | ||
| Example 1 | I1 | 18 | 82 | 0 |
| Example 2 | I2 | 22 | 78 | 0 |
| Example 3 | I3 | 19 | 81 | 0 |
| Example 4 | I4 | 16 | 80 | 4 |
| Comparative example 1 | D1 | - | 88 | 12 |
| Comparative example 2 | D2 | 31 | 69 | 0 |
(2) Coking test
The control example is set first: the test was carried out using the same hanger as in example 1. The coupon is first weighed to record the initial weight. Then hang the metal lacing film who weighs in the stove intraductal and carry out the schizolysis coking experiment, the process of schizolysis coking experiment includes: and starting to heat after the protection of He gas is introduced, wherein the time from the initial room temperature to the cracking reaction temperature of 860 ℃ is 90 min. After the temperature is raised to the cracking temperature, the introduction of He gas is stopped, and simultaneously 2% C is added2H6+98％N2The gas is saturated with water vapor in a water bath at 20 ℃ and then is introduced into a reaction furnace tube to carry out cracking reaction, and the cracking and coking reaction time is 20 hours. And after the cracking and coking experiment is finished, stopping heating and feeding, introducing He gas for protection, and naturally cooling to room temperature. And taking the metal material hanging pieces out of the furnace tube, weighing, subtracting the initial weight from the obtained weight to calculate the coking amount, and recording the coking amount data in a table 3.
The coated coupons I1 to I4 and D1 to D2 obtained in examples 1 to 4 and comparative examples 1 to 2 were subjected to the above-mentioned coking test in the same manner as in the comparative examples, and the coking data are shown in Table 3.
TABLE 3
| Hanging piece | Comparative example | I1 | I2 | I3 | I4 | D1 | D2 |
| Amount of coke (g) | 4.7273 | 0.4653 | 0.5269 | 0.4417 | 0.6042 | 1.1280 | 0.4829 |
As can be seen from Table 3, the coking amount of the first coking of the cracking furnace tube coated by the method is generally below 1g (mostly below 0.55 g) in the coking test, and the coking amount is reduced by more than 80% compared with the control example, so that the coating layer can effectively inhibit the coking of the furnace tube. The coking amount of the first coking of the comparative example 1 is up to 1.1g and is far higher than that of the invention, which proves that the coking resistance of the obtained furnace tube is far lower than that of the invention when the method without sulfide in the prior art is adopted; comparative example 2, although the coke content was also lower, the resulting manganese chromium spinel was relatively less and sulfide was relatively more due to the higher water vapor content in the coating gas, resulting in a relatively shorter life against coking.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention. It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition. In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (13)
1. The anti-coking alloy material is characterized by comprising an alloy material matrix and a coating layer coated on the surface of the alloy material matrix, wherein the coating layer contains metal oxides and metal sulfides of metal elements in the alloy material matrix, and the content of the metal oxides is 75.1-85% by volume and the content of the metal sulfides is 15-24.9% by volume relative to the volume of the coating layer; the metal oxide in the coating layer contains 90 wt% or more of MnxCr3-xO4X is 0.5-2;
the preparation method of the anti-coking alloy material comprises the following steps of: contacting a coating gas with the surface of the alloy material substrate at a high temperature of above 500 ℃ so as to react on the surface of the alloy material substrate to form a coating layer, wherein the coating gas contains a sulfide gas, water vapor and a carrier gas, and the sulfide gas is contained in an amount of 0.01-0.1 vol%, the water vapor is contained in an amount of 0.001-2 vol%, and the carrier gas is contained in an amount of 97.9-99.989 vol%, based on the total volume of the coating gas; the time of the surface contact is 20-60 hours;
the alloy material matrix contains 13-44 wt% of chromium element, 16-44 wt% of nickel element, 0.2-3 wt% of manganese element, 0-3 wt% of silicon element, 0-0.75 wt% of carbon element, 0-5 wt% of total content of trace elements and 0.25-70.8 wt% of iron element; the trace element is at least one of niobium, titanium, tungsten, aluminum and rare earth, and the trace element is sulfur and/or phosphorus.
2. The coking-resistant alloy material of claim 1, wherein the metal sulfides in the coating layer include FeS, NiS, MnS, and Cr2S3One or more of (a).
3. The anti-coking alloy material of claim 1, wherein the elemental composition of the alloy material matrix includes Fe, Cr, Ni, Mn, Si, and C, wherein the weight percent of Mn and Si satisfies formula (1),
4. the anti-coking alloy material according to claim 3, wherein the weight percent content of Mn and Si satisfies formula (2),
5. an anti-coking cracking furnace tube, characterized in that the tube wall of the anti-coking cracking furnace tube is made of the anti-coking alloy material according to any one of claims 1 to 4, wherein the coating layer is located on the inner side of the tube wall of the anti-coking cracking furnace tube.
6. The anti-coking cracking furnace tube of claim 5, wherein the anti-coking cracking furnace tube further comprises an enhanced heat transfer member located inside the anti-coking cracking furnace tube and connected to the inner wall of the tube wall.
7. The anti-coking cracking furnace tube of claim 6, wherein the enhanced heat transfer members are twisted pieces.
8. A method for preparing the anti-coking alloy material according to any one of claims 1 to 4, characterized in that the method comprises that the coating layer is obtained by the following method: contacting a coating gas with the surface of the alloy material substrate at a high temperature of above 500 ℃ so as to react on the surface of the alloy material substrate to form a coating layer, wherein the coating gas contains a sulfide gas, water vapor and a carrier gas, and the sulfide gas is contained in an amount of 0.01-0.1 vol%, the water vapor is contained in an amount of 0.001-2 vol%, and the carrier gas is contained in an amount of 97.9-99.989 vol%, based on the total volume of the coating gas; the time of the surface contact is 20 to 60 hours.
9. The method of claim 8, wherein the sulfide gas is present in an amount of 0.02 to 0.08 vol%, the water vapor is present in an amount of 0.2 to 1.8 vol%, and the carrier gas is present in an amount of 98.12 to 99.78 vol%, based on the total volume of the coating gas.
10. The method of claim 8, wherein the oxygen partial pressure in the coating gas is 1.1 x 10-13～1×10- 9Pa。
11. The method of claim 8, wherein the sulfide gas is selected from H2S、SO2、SF6、COS、CS2、CH3SH、CH3CH2SH、CH3SCH3、CH3CH2SCH2CH3、CH3S-SCH3And CH3CH2S-SCH2CH3One or more of (a).
12. The method of claim 11, wherein the sulfide gas is selected from H2S、SF6、CH3SH、CH3SCH3And CH3S-SCH3One or more of (a).
13. The method of claim 11 wherein the carrier gas is selected from H2、N2One or more of Ar and He.
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