阅读说明：本技术 抗结焦合金炉管及其制备方法和应用 (Anti-coking alloy furnace tube and preparation method and application thereof ) 是由 王红霞 张利军 郏景省 王申祥 王国清 于 2020-06-23 设计创作，主要内容包括：本发明涉及石油烃热裂解领域,公开了一种抗结焦合金炉管及其制备方法与应用,所述方法包括：将低氧分压气体与合金炉管进行接触反应；其中,所述炉管包括固定于炉管内的强化传热构件；所述低氧分压气体的露点为0℃至10℃。该合金炉管的制备工艺简单,且能够显著减缓裂解炉的结焦,延长液体原料裂解炉的运行周期。(The invention relates to the field of petroleum hydrocarbon thermal cracking, and discloses an anti-coking alloy furnace tube and a preparation method and application thereof, wherein the method comprises the following steps: carrying out contact reaction on the low-oxygen partial pressure gas and the alloy furnace tube; wherein the furnace tube comprises an enhanced heat transfer component fixed in the furnace tube; the dew point of the low oxygen partial pressure gas is 0 ℃ to 10 ℃. The alloy furnace tube has simple preparation process, can obviously slow down coking of the cracking furnace and prolong the operation period of the liquid raw material cracking furnace.)

1. A method for preparing a coking-resistant alloy furnace tube is characterized by comprising the following steps: carrying out contact reaction on the low-oxygen partial pressure gas and the alloy furnace tube;

wherein the furnace tube comprises an enhanced heat transfer component fixed in the furnace tube; the dew point of the low oxygen partial pressure gas is 0 ℃ to 10 ℃.

2. The production method according to claim 1, wherein the dew point of the low oxygen partial pressure gas is 2 ℃ to 8 ℃.

3. The preparation method according to claim 1 or 2, wherein the furnace tube matrix composition comprises, in weight percent: 12 to 50 weight percent of chromium element, 20 to 50 weight percent of nickel element, 0.2 to 3 weight percent of manganese element, 1 to 3 weight percent of silicon element, 0.1 to 0.75 weight percent of carbon element, 5 to 40 weight percent of iron element, 0 to 5 weight percent of trace elements and trace elements;

preferably, the furnace tube matrix comprises the following components in percentage by weight: 20-38 wt% of chromium element, 25-48 wt% of nickel element, 1-2.5 wt% of manganese element, 1-2 wt% of silicon element, 0.1-0.6 wt% of carbon element, 12-35 wt% of iron element, 0-3 wt% of trace elements and trace elements;

preferably, the trace elements are selected from one or more of niobium, titanium, tungsten, aluminum and rare earth;

preferably, the trace elements are selected from sulphur and/or phosphorus.

4. The production method according to any one of claims 1 to 3, wherein the heat transfer enhancement member is selected from at least one of a twisted sheet, an internal fin, and an internal fin.

5. The preparation method according to any one of claims 1 to 4, wherein the length of the enhanced heat transfer member tube is 20 to 80cm, the number of the enhanced heat transfer member tubes is 1 to 200, and the enhanced heat transfer member tubes are distributed on different tube passes of the whole furnace tube.

6. The production method according to any one of claims 1 to 5, wherein the low oxygen partial pressure atmosphere gas is a mixture of CO and water vapor;

preferably, the method further comprises the step of determining the dew point of the low oxygen partial pressure gas.

7. The production method according to any one of claims 1 to 6, wherein the conditions of the contact reaction include: the reaction temperature is 600-1100 ℃, and preferably 800-1050 ℃; the reaction time is 5-72h, preferably 30-60 h.

8. An anti-coking alloy furnace tube produced by the production method according to any one of claims 1 to 7.

9. The anti-coking alloy furnace tube of claim 8, wherein the inner surface of the alloy furnace tube contains an oxide film.

10. The coking resistant alloy furnace tube of claim 9, the oxide film comprising chromium manganese oxide and a metallic element, wherein the chromium manganese oxide has a composition of Mn_xCr_3-xO₄Wherein x is 0.5 to 2;

preferably, the metal element includes an iron element and/or a nickel element.

11. Use of the anti-coking alloy furnace tube of any one of claims 8-10 in a liquid feedstock cracking furnace.

Technical Field

The invention relates to the field of petroleum hydrocarbon thermal cracking, in particular to an anti-coking alloy furnace tube and application thereof.

Background

Ethylene is one of the most important basic raw materials in the petrochemical industry. The current method for producing ethylene mainly adopts a tubular furnace cracking technology and is widely applied worldwide. An unavoidable problem in the ethylene production process is coking and carburization of the cracker during service. Coking in the cracking process can reduce the inner diameter of the furnace tube, increase the pressure drop in the tube and shorten the operation period of the cracking furnace; when the temperature of the tube wall reaches an allowable limit or the pressure drop reaches a certain degree, the furnace is stopped for coke cleaning operation. Coking on the inner wall of the furnace tube hinders the normal operation of the cracking reaction, affects the ethylene yield, reduces the production efficiency, and easily causes the inner wall of the furnace tube to carburize at high temperature, thus leading to the weakening of the material performance of the furnace tube.

At present, in order to ensure the high-temperature strength of the ethylene cracking furnace tube, the material used for the furnace tube mainly comprises elements such as Fe, Cr, Ni and the like, and simultaneously contains trace elements such as Mn, Si, Al, Nb, Ti, W, Mo and the like. The existing research shows that at high temperature, Fe and Ni elements have obvious catalytic action on the coking of hydrocarbon on the surface of a FeCrNi alloy cracking furnace tube. In addition, heavier hydrocarbon feedstocks are also associated with significant free radical coking and polycondensation coking during cracking. In the existing literature, in order to reduce catalytic coking, researchers try to prepare inert coatings on the inner wall surfaces of cracking furnace tubes by using various technologies to reduce the contact of hydrocarbons and Fe and Ni active components on the inner surfaces of the cracking furnace tubes. On the other hand, researchers also use measures such as adding components in the cracking furnace tube, reducing the pressure in the cracking tube, reducing the residence time, reducing the cracking temperature, optimizing the cracking raw material, adding a coking inhibitor and the like to reduce the free radical coking and the polycondensation coking in the cracking process.

A series of patents of treating the inner surface of a cracking furnace tube under an atmosphere of low oxygen partial pressure to obtain a chromium-manganese spinel oxide film are disclosed by NOVA chemical company, canada, including US5630887A, US6436202B1, US6824883B1, US7156979B2, US7488392B2, and the like. The disclosed material shows that the technology has good coking inhibition effect in a gas cracking furnace which takes light hydrocarbons such as ethane and propane as raw materials, but has poor coking resistance effect in the cracking process of liquid raw materials. Because the coking of the gas cracking furnace is mainly catalytic coking, Fe and Ni elements with catalytic coking activity in the furnace tube can be isolated from the hydrocarbon coking source by the oxide film. In the case of a liquid cracking furnace using naphtha, diesel oil, or the like as a raw material, although coking is also based on catalytic coking, the amount of polycondensation coking is 50% or more of the total coking amount, and the polycondensation coking can completely cover the oxide film. Therefore, the oxide film in the liquid cracking furnace tube is only effective in the initial service period of the furnace tube because the oxide film is not covered by the polycondensation coking yet, and the oxide film can not exert the effect when the cracking furnace is operated to the middle and later periods. In addition, the technical solution disclosed in the above patent does not relate to how to control the mixed gas to obtain the low oxygen partial pressure atmosphere. In fact, whether in engineering or in the laboratory, an atmosphere of low oxygen partial pressure is difficult to obtain, and obtaining a stable atmosphere of low oxygen partial pressure by means of a flow control device is very difficult and difficult to achieve.

Disclosure of Invention

The invention aims to solve the problems that the operation period of a liquid raw material cracking furnace is short due to coking and the preparation of an oxide film in the furnace tube is difficult in the prior art, and provides an anti-coking alloy furnace tube and a preparation method and application thereof.

In order to achieve the above object, a first aspect of the present invention provides a method for manufacturing a coking-resistant alloy furnace tube, the method comprising: carrying out contact reaction on the low-oxygen partial pressure gas and the alloy furnace tube;

wherein the furnace tube comprises an enhanced heat transfer component fixed in the furnace tube; the dew point of the low oxygen partial pressure gas is 0 ℃ to 10 ℃.

The invention provides a coking-resistant alloy furnace tube prepared by the preparation method.

The third aspect of the invention provides an application of the anti-coking alloy furnace tube in a liquid raw material cracking furnace.

Through the technical scheme, the anti-coking alloy furnace tube and the preparation method and application thereof provided by the invention have the following beneficial effects:

the invention solves the problems of coking and carburization of the furnace tube by forming the oxide film on the surface of the alloy furnace tube, namely, the furnace tube is treated by adopting the low-oxygen partial pressure atmosphere, so that the oxide film is generated on the surface of the furnace tube in an in-situ growth mode, and the obtained oxide film has strong bonding force with the furnace tube and is suitable for long-term use.

Furthermore, the invention applies the low oxygen partial pressure technology to the hydrocarbon cracking furnace tube containing the enhanced heat transfer component, has obvious effect of inhibiting the liquid cracking furnace from coking, and greatly prolongs the running period of the liquid cracking furnace.

Detailed Description

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 discloses a preparation method of an anti-coking alloy furnace tube, which is characterized by comprising the following steps: carrying out contact reaction on the low-oxygen partial pressure gas and the alloy furnace tube;

wherein the furnace tube comprises an enhanced heat transfer component fixed in the furnace tube; the dew point of the low oxygen partial pressure gas is 0 ℃ to 10 ℃.

In the invention, the inventor researches and discovers that an oxide film can be formed on the inner surface of the furnace tube by carrying out a contact reaction on the furnace tube containing the enhanced heat transfer member and low-oxygen partial pressure gas, so that the obtained alloy furnace tube can reduce free radical coking and polycondensation coking, and inhibit or slow down the catalytic coking phenomenon of the furnace tube.

Furthermore, in the invention, the oxide film is tightly combined with the inner surface of the furnace tube, so that the coking of the inner wall of the furnace tube can be inhibited, the carburization degree of the furnace tube is slowed down, and the decoking period and the service life of the furnace tube are prolonged.

In the present invention, the low oxygen partial pressure atmosphere means a reducing atmosphere in which the oxygen partial pressure is low, so thatThe oxidation process is very slow, which is beneficial to generating a compact oxide film on the surface of the material. The oxygen partial pressure refers to the pressure occupied by oxygen present in the atmosphere, and in a low oxygen partial pressure atmosphere, oxygen in the atmosphere is mainly derived from oxygen-containing compounds (such as H)₂O) oxygen generated by decomposition.

In both engineering and laboratory environments, a low oxygen partial pressure atmosphere is difficult to obtain, and obtaining a stable low oxygen partial pressure atmosphere by a flow control device is difficult and difficult to achieve. The present inventors have surprisingly found, through theoretical analysis and extensive experiments, that the object of accurately controlling the low oxygen partial pressure atmosphere can be achieved by controlling the dew point of the mixed gas, for example, when the dew point of the low oxygen partial pressure gas is controlled to 0 ℃ to 10 ℃, thereby obtaining an effective method for performing low oxygen partial pressure treatment on the alloy furnace tube.

In the present invention, the dew point refers to the temperature at which saturated water vapor in the air starts to condense and condense, and at a relative humidity of 100%, the temperature of the surrounding environment is the dew point temperature.

In the present invention, the method further comprises the step of determining the dew point of the low oxygen partial pressure gas.

In the invention, the method further comprises testing the dew point of the low-oxygen partial pressure gas (by using a commercially available dew point tester) before the low-oxygen partial pressure gas is subjected to contact reaction with the alloy furnace tube, so that the low-oxygen partial pressure gas in contact with the alloy furnace tube has the dew point defined by the invention.

Further, the method comprises the step of monitoring the dew point of the low oxygen partial pressure gas in the contact reaction system in real time during the contact reaction by using a commercially available dew point meter.

Furthermore, the inventor researches and discovers that the enhanced heat transfer component arranged in the furnace tube changes the flowing state of the low-oxygen partial pressure gas in the process of the contact reaction of the furnace tube and the low-oxygen partial pressure gas, and trace O in the low-oxygen partial pressure gas₂Can be fully contacted with the tube wall to completely oxidize the tube wall, and the coverage rate of the formed oxide film is higher.

In contrast, the furnace tube without the enhanced heat transfer member is subjected to low oxygen partial pressureIn the treatment, the gas is in laminar flow contact with the pipe wall, and the gas flow is O₂The oxidation reaction of the tube wall is not basically participated, the tube wall can not be completely oxidized, so the coverage rate of the formed oxide film is lower.

In addition, by the enhanced heat transfer component, in the cracking process, after the enhanced heat transfer component changes the flowing state of the cracking gas close to the tube wall from laminar flow to turbulent flow, the polycondensation coking on the inner surface of the furnace tube is easily flushed by the cracking gas flow, because the polycondensation coking is generally loose coke and has weak adhesion force on the inner wall of the furnace tube. Therefore, coke attached to the inner wall of the furnace tube containing the heat transfer enhancing component is mainly subjected to catalytic coking, so that an oxidation film formed by low oxygen partial pressure can fully exert the effect of the coke, and the operation period of the cracking furnace is remarkably prolonged.

Further, in the present invention, the dew point of the low oxygen partial pressure gas is 2 ℃ to 8 DEG C

According to the invention, the furnace tube base body can adopt a nickel-chromium alloy furnace tube which is common in the prior art.

Preferably, the furnace tube matrix comprises the following components in percentage by weight: 12 to 50 weight percent of chromium element, 20 to 50 weight percent of nickel element, 0.2 to 3 weight percent of manganese element, 1 to 3 weight percent of silicon element, 0.1 to 0.75 weight percent of carbon element, 5 to 40 weight percent of iron element, 0 to 5 weight percent of trace elements and trace elements.

Further, the furnace tube matrix comprises the following components in percentage by weight: 20-38 wt% of chromium element, 25-48 wt% of nickel element, 1-2.5 wt% of manganese element, 1-2 wt% of silicon element, 0.1-0.6 wt% of carbon element, 12-35 wt% of iron element, 0-3 wt% of trace elements and trace elements.

According to the invention, the trace elements are selected from one or more of niobium, titanium, tungsten, aluminum and rare earth;

according to the invention, the trace elements are selected from sulphur and/or phosphorus.

In the present invention, the heat transfer enhancing member may be a member capable of changing a fluid flow state and improving a heat transfer coefficient, which is conventional in the art, for example, preferably at least one selected from the group consisting of twisted pieces, internal ribs, and internal fins.

In the present invention, the alloy furnace tube for the cracking furnace provided with the enhanced heat transfer member can be obtained by a method conventional in the art. For example, alloy furnace tubes for cracking furnaces are typically cast by centrifugal casting, while tubes with enhanced heat transfer members within the tubes have different forms of processing, such as: the furnace tube with the twisted sheet or the inner fin component in the tube is generally obtained by adopting a static casting mode; and the furnace tube with the inner fin component in the tube is formed by welding fins in the furnace tube.

Further, alloy furnace tubes for cracking furnaces provided with a heat transfer enhancing member are also commercially available, for example, plum blossom tubes (tubes provided with inner fins inside) by Kellogg corporation, MERT tubes (tubes provided with inner fins inside) by Kubota, twisted sheet tubes (tubes provided with twisted sheets inside) by china petrochemical industry, and the like.

According to the invention, the length of the enhanced heat transfer component pipes is 20-80cm, the number of the enhanced heat transfer component pipes is 1-200, and the enhanced heat transfer component pipes are distributed on different pipe passes of the whole furnace pipe.

According to the invention, the low oxygen partial pressure atmosphere gas is a gas mixture of CO and water vapor.

According to the invention, the conditions of the contact reaction include: the reaction temperature is 600-1100 ℃, and preferably 800-1050 ℃; the reaction time is 5-72h, preferably 30-60 h.

The invention provides a coking-resistant alloy furnace tube prepared by the preparation method.

According to the present invention, the inner surface of the alloy furnace tube contains an oxide film.

In the invention, the inventor researches and discovers that the reasons that the alloy furnace tube can slow down or inhibit the coking and carburization phenomena of the alloy furnace tube at high temperature are as follows: after the alloy furnace tube is in contact reaction with the low-oxygen partial pressure gas by adopting the technical scheme of the invention, because the activity of the oxide formed by the reaction of Cr and Mn elements in the furnace tube and oxygen is higher than that of Fe and Ni elements, the Cr and Mn elements on the surface of the furnace tube are slowly oxidized under the condition of very low oxygen partial pressure, but the Fe and Ni elements are not basically oxidized, and because the oxygen partial pressure of the atmosphere is very low, the oxidation process is very slow, and further an oxide film which is strong in bonding force with a substrate of the furnace tube and compact is generated on the inner surface of the alloy furnace tube in situ, and the oxide film can cover the Fe and Ni elements which have catalytic action on the coking of the furnace tube, so that the coking and carburization phenomena of the alloy furnace tube are slowed down or inhibited, and the operation period of the alloy furnace tube is prolonged.

According to the present invention, the oxide film includes chromium manganese oxide and a metal element. Wherein the chromium manganese oxide consists of Mn_xCr_3-xO₄Wherein x is 0.5-2.

According to the present invention, the metal element in the oxide film includes an iron element and/or a nickel element.

In the present invention, the content of the metal element is less than 30 wt%, preferably less than 15 wt%, and more preferably less than 10 wt% with respect to the total weight of the oxide film.

In the invention, the oxide film on the inner surface of the alloy furnace tube obtained by the method has low contents of iron element and nickel element, so that the catalytic coking in the hydrocarbon cracking process can be inhibited, the running period of the cracking furnace is prolonged, and the long-term use requirement of the cracking furnace tube is met.

In a third aspect, the invention provides the use of the anti-coking alloy furnace tube of the invention in a liquid feedstock cracking furnace.

In the present invention, the liquid feedstock for cracking is at least one selected from the group consisting of naphtha, condensate, hydrocracked tail oil, and diesel.

In the present invention, the cracking reaction of the liquid raw material may be carried out according to a conventional cracking process in the prior art.

The present invention will be described in detail below by way of examples. In the following examples of the present invention,

the element composition of the furnace tube is measured by adopting an X-ray energy spectrum analysis (EDS) method;

the dew point of the low-oxygen partial pressure gas is measured by adopting a detection method of a commercially available dew point tester;

the coking amount of the furnace tube adopts an infrared instrument to measure CO and CO in the burnt gas on line₂The concentration and the volume of the scorching gas are measured on line by adopting a wet gas flowmeter and then calculated;

cracking feedstockThe naphtha has the following physical properties: distillation range of 32.8-173.8 deg.C, specific gravity D₂₀0.7058 g/ml.

Example 1

The industrial cracking furnace radiation section furnace tube with the material of the furnace tube being 35Cr45Ni is processed by the atmosphere of low oxygen partial pressure gas. The furnace tube alloy comprises the following elements in percentage by weight: cr: 32.55, Ni: 42.60, Fe: 21.12, Mn: 0.98, Si: 1.41, Nb:0.64, C: 0.53, others: 0.17. the method is characterized in that twisted sheet tubes integrally manufactured with a furnace tube are axially arranged in the furnace tube of the radiation section of the cracking furnace at intervals, the axial length of each twisted sheet twisted for 180 degrees is one pitch, the distance between two adjacent twisted sheets is 15 pitches, the length of each twisted sheet tube is 35cm, the number of the twisted sheet tubes is 100, and the twisted sheet tubes are distributed on different tube passes of the whole furnace tube. The low-oxygen partial pressure gas is a gas mixture of CO and water vapor, wherein the dew point of the mixed gas is 5 ℃, the treatment temperature is 900 ℃, the treatment time is 50 hours, and an oxidation film containing elements such as Cr, Mn, Ni, Fe, O, Si and the like is formed on the inner wall surface of the radiant section furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 9.93 wt% with respect to the total weight of the oxide film.

Carrying out hydrocarbon steam cracking reaction in an industrial cracking furnace treated in a low-oxygen partial pressure gas atmosphere, wherein the cracking raw material is naphtha, and the physical properties of the naphtha are as follows: distillation range of 32.8-173.8 deg.C, specific gravity D₂₀0.7058 g/ml; the cracking conditions are as follows: the outlet temperature of the furnace tube is 830 ℃, and the water-oil ratio is 0.55. The operation period of the cracking furnace reaches 230 days.

Example 2

A small HP40(Cr25Ni35) furnace tube containing 1-section twisted sheet tube is subjected to low-oxygen partial pressure preoxidation treatment, and the element composition of the furnace tube alloy is as follows: cr: 25.1, Ni: 35.2, Mn: 1.0, Si: 1.5, C: 0.4, p < 0.03, S < 0.03, and the balance Fe (wt%).

The gas mixture of CO and water vapor is used as the low-oxygen partial pressure atmosphere treatment gas, wherein the dew point of the gas mixture is 5 ℃, the flow rate of the low-oxygen partial pressure gas is 400ml/min, the treatment temperature is 950 ℃, the treatment time is 30 hours, and a gas mixture mainly containing Cr, Mn, Ni and Ti is formed on the inner wall surface of the furnace tube,Fe. O, Si, etc. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 11.27 wt% with respect to the total weight of the oxide film.

Carrying out hydrocarbon steam cracking reaction in a small furnace tube treated in a low-oxygen partial pressure atmosphere, wherein the cracking raw material is naphtha, and the physical properties of the naphtha are as follows: distillation range of 32.8-173.8 deg.C, specific gravity D₂₀0.7058 g/ml; the cracking conditions are as follows: the cracking temperature is 845 ℃, and the water-oil ratio is 0.5. The coking amount of the furnace tube of the invention is reduced by 95.21 percent compared with the coking amount of the HP40(Cr25Ni35) furnace tube which does not contain the strengthening heat transfer component and is not processed by low oxygen partial pressure.

Example 3

A small-scale furnace tube similar to that of example 2 was subjected to a low-oxygen partial-pressure pre-oxidation treatment, except that the dew point of the mixed gas of CO and steam was 8 ℃ and that other treatment conditions were similar to those of example 2, and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si, etc. was formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 12.88 wt% with respect to the total weight of the oxide film.

The hydrocarbon steam cracking reaction is carried out in a small furnace tube treated in the low-oxygen partial pressure atmosphere, and the cracking raw material and the cracking conditions are the same as those in the example 2. The coking amount of the furnace tube of the invention is reduced by 90.15 percent compared with the coking amount of the HP40(Cr25Ni35) furnace tube which does not contain the strengthening heat transfer component and is not processed by low oxygen partial pressure in the prior art.

Example 4

A small-scale furnace tube similar to that of example 2 was subjected to a low-oxygen partial-pressure pre-oxidation treatment except that the dew point of the mixed gas of CO and steam was 2 ℃ and other treatment conditions were the same as those of example 2, and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si, etc. was formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 13.29 wt% with respect to the total weight of the oxide film.

The hydrocarbon steam cracking reaction is carried out in a small furnace tube treated in the low-oxygen partial pressure atmosphere, and the cracking raw material and the cracking conditions are the same as those in the example 2. The coking amount of the furnace tube of the invention is reduced by 86.38 percent compared with the coking amount of the HP40(Cr25Ni35) furnace tube which does not contain the strengthening heat transfer component and is not processed by low oxygen partial pressure.

Example 5

A small-scale furnace tube similar to that of example 2 was subjected to a low-oxygen partial-pressure pre-oxidation treatment except that the dew point of the mixed gas of CO and steam was 10 ℃ and other treatment conditions were the same as those of example 2, and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si, etc. was formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 14.80 wt% with respect to the total weight of the oxide film.

The hydrocarbon steam cracking reaction is carried out in a small furnace tube treated in the low-oxygen partial pressure atmosphere, and the cracking raw material and the cracking conditions are the same as those in the example 2. The coking amount of the furnace tube of the invention is reduced by 81.46 percent compared with the coking amount of the HP40(Cr25Ni35) furnace tube which does not contain the strengthening heat transfer component and is not processed by low oxygen partial pressure.

Example 6

A small-scale furnace tube similar to that of example 2 was subjected to a low-oxygen partial-pressure pre-oxidation treatment except that the dew point of the mixed gas of CO and steam was 0 ℃ and other treatment conditions were the same as those of example 2, and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si, etc. was formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 15.89 wt% with respect to the total weight of the oxide film.

The hydrocarbon steam cracking reaction is carried out in a small furnace tube treated in the low-oxygen partial pressure atmosphere, and the cracking raw material and the cracking conditions are the same as those in the example 2. The coking amount of the furnace tube of the invention is reduced by 75.69 percent compared with the coking amount of the HP40(Cr25Ni35) furnace tube which does not contain the strengthening heat transfer component and is not processed by low oxygen partial pressure.

Comparative example 1

The radiant coils of an industrial cracking furnace of the same type as in example 1 were used except that the low oxygen partial pressure atmosphere treatment was not carried out. The hydrocarbon steam cracking reaction was carried out in the industrial cracking furnace, and the cracking raw material and cracking conditions were the same as in example 1. The operating cycle of the cracking furnace is 100 days.

Comparative example 2

The radiant coils of an industrial cracking furnace of the same type as in example 1 were fabricated, except that the radiant coils were not provided with twisted pieces and were not subjected to the atmosphere treatment of a low oxygen partial pressure gas, and the operating period of the cracking furnace was 55 days.

Comparative example 3

A small-scale furnace tube similar to that of example 2 was subjected to a low-oxygen partial-pressure pre-oxidation treatment except that the dew point of the mixed gas of CO and steam was 20 ℃ and other treatment conditions were the same as those of example 2, and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si, etc. was formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 17.62 wt% with respect to the total weight of the oxide film.

The hydrocarbon steam cracking reaction is carried out in a small furnace tube treated in the low-oxygen partial pressure atmosphere, and the cracking raw material and the cracking conditions are the same as those in the example 2. The coke formation of the small furnace tube was reduced by 33.90% compared to the prior art HP40(Cr25Ni35) tube which did not contain twisted pieces and which was not subjected to low oxygen partial pressure treatment.

Comparative example 4

A small-scale furnace tube similar to that of example 2 was subjected to a low-oxygen partial-pressure pre-oxidation treatment except that the dew point of the mixed gas of CO and steam was-10 ℃ and other treatment conditions were the same as those of example 2, and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si, etc. was formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is Mn_1.5Cr_1.5O₄The total content of the iron element and the nickel element was 19.01 wt% with respect to the total weight of the oxide film.

The hydrocarbon steam cracking reaction is carried out in a small furnace tube treated in the low-oxygen partial pressure atmosphere, and the cracking raw material and the cracking conditions are the same as those in the example 2. The coke formation of the pilot tube was reduced by 24.55% over the prior art HP40(Cr25Ni35) tubes which did not contain twisted pieces and which were not subjected to low oxygen partial pressure treatment.

Comparative example 5

The same tube as the small test tube of example 2, except that no twisted piece was included and low oxygen partial pressure treatment was not performed, the hydrocarbon steam cracking reaction was performed in the small test tube, and the cracking raw material and cracking conditions were the same as in example 2. The coking amount of the small test tube is 100 percent.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.