阅读说明：本技术 合金炉管及其处理方法与应用 (Alloy furnace tube and treatment method and application thereof ) 是由 王红霞 王国清 王申祥 郏景省 张利军 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,公开了一种处理合金炉管的方法、由该方法处理得到的合金炉管。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,所述低氧分压气体的露点为-40℃至40℃。通过采用控制混合气露点来准确控制低氧分压气氛的方法处理合金炉管,在其表面形成致密、稳定的氧化膜,抑制或减缓催化结焦现象,减少炉管渗碳程度,延长炉管使用寿命。(The invention relates to the field of petroleum hydrocarbon thermal cracking, and discloses a method for treating an alloy furnace tube and the alloy furnace tube treated by the method. The method comprises the following steps: carrying out contact reaction on the low-oxygen partial pressure gas and the alloy furnace tube; wherein the dew point of the low oxygen partial pressure gas is-40 ℃ to 40 ℃. The alloy furnace tube is processed by adopting a method of accurately controlling the low-oxygen partial pressure atmosphere by controlling the dew point of the mixed gas, a compact and stable oxide film is formed on the surface of the alloy furnace tube, the phenomenon of catalytic coking is inhibited or slowed down, the carburization degree of the furnace tube is reduced, and the service life of the furnace tube is prolonged.)

1. A method of treating an alloy furnace tube, the method comprising: carrying out contact reaction on the low-oxygen partial pressure gas and the alloy furnace tube;

wherein the dew point of the low oxygen partial pressure gas is-40 ℃ to 40 ℃.

2. The method of claim 1, wherein the low oxygen partial pressure gas has a dew point of 0 ℃ to 20 ℃.

3. The method of claim 1 or 2, wherein the low oxygen partial pressure gas is selected from CO₂、CO、CH₄、C₂H₆、C₃H₈、NH₃、H₂O、H₂、N₂At least one of Ar, He, air and a pyrolysis gas;

preferably, the low oxygen partial pressure gas is selected from CH₄And H₂Gas mixture of O, CO₂And CO, H₂Gas mixture of O and CO and H₂O and H₂At least one of the gas mixtures of (a);

more preferably, the low oxygen partial pressure gas is selected from H₂And H₂A gas mixture of O;

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

4. The method of any one of claims 1-3, wherein the conditions of the contact reaction comprise: the reaction temperature is 600-1100 ℃, and preferably 750-1000 ℃; the reaction time is 5-72h, preferably 20-50 h.

5. The method of any of claims 1 to 4, wherein the base composition of the alloy furnace tube 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, 0 to 5 weight percent of trace elements and trace elements, and 5 to 40 weight percent of iron element.

6. An alloy furnace tube treated by the method of any one of claims 1 to 5.

7. The alloy furnace tube of claim 6, wherein the alloy furnace tube inner surface contains an oxide film.

8. The alloy furnace tube of claim 7, wherein the oxide film comprises chromium manganese oxide and a metallic element, wherein the chromium manganese oxide has a composition of Mn_xCr_3-xO₄And x has a value of 0.5 to 2.

9. The alloy furnace tube of claim 8, wherein the metallic element comprises an iron element and/or a nickel element;

preferably, the content of the metal element in the oxide film is less than 30 wt%, preferably less than 15 wt%.

10. Use of the alloy furnace tube of any one of claims 6-9 for thermal cracking of petroleum hydrocarbons.

Technical Field

The invention relates to the field of petroleum hydrocarbon thermal cracking, in particular to a method for treating an alloy furnace tube, the alloy furnace tube treated by the method and application of the alloy furnace tube.

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. Therefore, the surface state of the furnace tube is modified by a coating technology for forming a protective layer on the inner surface of the furnace tube, and other inert components are used for covering iron and nickel elements in the alloy of the furnace tube, so that the loss of the catalytic coking function of the alloy becomes one of important means for effectively inhibiting the ethylene cracking furnace tube from coking.

The method for forming the protective layer on the inner surface of the cracking furnace tube has two different forms: one method is to form a protective layer on the inner surface of a cracking furnace tube by means of thermal spraying, thermal sputtering, high-temperature sintering, chemical heat treatment, chemical vapor deposition and the like, and the method has the defects that the protective layer is not firmly combined with a furnace tube substrate and is easy to peel off; the other method is to generate an oxide protective layer in situ on the inner surface of the cracking furnace tube by specific atmosphere treatment at a certain temperature, and the method has the advantages that the bonding force between the protective layer and the substrate of the furnace tube is strong and the protective layer is not easy to peel off.

The NOVA chemical company in canada proposes a technical scheme of treating the inner surface of a cracking furnace tube under low oxygen partial pressure by using a mixed gas of hydrogen and water vapor as a treatment atmosphere to obtain a chromium-manganese spinel oxide film, and applies for a plurality of patents including US5630887A, US6436202B1, US6824883B1, US7156979B2, US7488392B2 and the like. However, the technical solution disclosed in the above patent does not relate to how to control the mixture 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 alloy furnace tube for ethylene cracking is coked and carburized and the low-oxygen partial pressure atmosphere is difficult to realize and control when an oxide film protective layer in the alloy furnace tube is prepared in the prior art, and provides a method for treating the alloy furnace tube and the alloy furnace tube treated by the method. The alloy furnace tube is processed by adopting a method of accurately controlling the low-oxygen partial pressure atmosphere by controlling the dew point of the mixed gas, a compact and stable oxide film is formed on the surface of the alloy furnace tube, the phenomenon of catalytic coking is inhibited or slowed down, the carburization degree of the furnace tube is reduced, and the service life of the furnace tube is prolonged.

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

wherein the dew point of the low oxygen partial pressure gas is-40 ℃ to 40 ℃.

The second aspect of the invention provides an alloy furnace tube obtained by the above method.

In a third aspect, the present invention provides the use of the above alloy furnace tube for thermal cracking of petroleum hydrocarbons.

By adopting the technical scheme, the method for treating the alloy furnace tube and the alloy furnace tube treated by the method 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 a substrate of the furnace tube and is suitable for long-term use.

Furthermore, the dew point is adopted to realize the accurate control of the low-oxygen partial pressure gas, so that an oxide film with a compact and stable structure is formed on the surface of the alloy furnace tube, the catalytic coking phenomenon is obviously inhibited or slowed down, the carburization degree of the furnace tube is reduced, and the service life of the furnace tube is prolonged.

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 method for treating an alloy furnace tube in a first aspect, 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 dew point of the low oxygen partial pressure gas is-40 ℃ to 40 ℃.

The invention solves the problems of high-temperature 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 a substrate of the furnace tube and is suitable for long-term use.

It is known in the art that an atmosphere of low oxygen partial pressure is difficult to obtain, either in engineering or in a laboratory, and obtaining a stable atmosphere of low oxygen partial pressure by means of a flow control device is very difficult and difficult to achieve. The inventor of the invention skillfully finds the aim of accurately controlling the atmosphere with low oxygen partial pressure by controlling the dew point of the mixed gas through theoretical analysis and a large number of experiments.

In the present invention, the dew point is a temperature at which saturated moisture 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.

According to the invention, the dew point of the low oxygen partial pressure gas is preferably 0 ℃ to 20 ℃.

In the present invention, the low oxygen partial pressure atmosphere refers to a reducing atmosphere in which the oxygen partial pressure is low, so that the oxidation process occurs very slowly, and a dense oxide film is favorably formed 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.

According to the invention, the low oxygen partial pressure gas is selected from CO₂、CO、CH₄、C₂H₆、C₃H₈、NH₃、H₂O、H₂、N₂At least one of Ar, He, air and pyrolysis gas.

According to the invention, the low oxygen partial pressure gas is selected from CH₄And H₂Gas mixture of O, CO₂And CO, H₂Gas mixture of O and CO and H₂O and H₂At least one of the gas mixtures of (a).

According to the invention, the low oxygen partial pressure gas is selected from H₂And H₂A gas mixture of O.

According to the invention, the conditions of the contact reaction include: the reaction temperature is 600-1100 ℃, and preferably 750-1000 ℃; the reaction time is 5-72h, preferably 20-50 h.

In the present invention, the flow rate of the low oxygen partial pressure gas is 100-.

In the present invention, the contact reaction may be carried out in a reactor capable of maintaining a certain atmosphere, which is conventional in the art, for example, the contact reaction may be carried out in at least one of a tube furnace, a shaft furnace and an atmosphere box furnace.

According to the invention, the base components of the alloy furnace tube comprise, 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, 0 to 5 weight percent of trace elements and trace elements, and 5 to 40 weight percent of iron element.

The second aspect of the invention provides an alloy furnace tube treated by the method.

According to the invention, the inner surface of the alloy furnace tube contains an oxide film. In the present invention, the oxide film is formed by in-situ growth.

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 a chromium manganese oxide and a metal element, wherein the chromium manganese oxide has a composition of Mn_xCr_3-xO₄And x has a value of 0.5 to 2.

According to the invention, the metal element mainly comprises an iron element and/or a nickel element.

According to the invention, the content of said metal element in the oxide film is less than 30 wt%, preferably less than 15 wt%.

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 present invention provides a use of the alloy furnace tube described above in thermal cracking of petroleum hydrocarbons, which may be gaseous hydrocarbons or liquid hydrocarbons.

Preferably, the gaseous hydrocarbon is at least one of ethane, propane, butane and liquefied petroleum gas.

Preferably, the liquid hydrocarbon is at least one of naphtha, condensate, hydrocracked tail oil, and diesel.

In the present invention, the thermal cracking reaction can be performed according to the conventional thermal cracking process of petroleum hydrocarbon 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.

Example 1

The HP40(Cr25Ni35) small-scale furnace tube is subjected to low-oxygen partial-pressure pre-oxidation treatment, and the element composition (wt%) of the furnace tube alloy is as follows: cr: 25.1, Ni: 35.2, Mn: 1. si: 1.5, C: 0.4, P less than 0.03, S less than 0.03 and the balance of Fe.

By means of H₂And H₂O as a low oxygen partial pressure atmosphere treating gas, wherein the dew point of the gas mixture is 10 ℃ and is lowThe flow rate of oxygen partial pressure gas is 400ml/min, the treatment temperature is 950 ℃, the treatment time is 30 hours, and an oxidation film mainly containing Cr, Mn, Ni, Fe, O, Si and other elements is formed on the inner wall surface of the furnace tube. The chromium manganese oxide in the oxide film is MnCr₂O₄In the oxide film, the contents of iron and nickel were 3.76 wt% and 4.58 wt%, respectively.

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 91.85 percent compared with the coking amount of the prior HP40(Cr25Ni35) furnace tube which is not treated by low oxygen partial pressure.

Example 2

The same small furnace tube as in example 1 was subjected to a low oxygen partial pressure pre-oxidation treatment except that H was used₂And H₂The dew point of the O gas mixture was 20 ℃ and other processing conditions were the same as in example 1, 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 MnCr₂O₄In the oxide film, the contents of iron and nickel were 5.23 wt% and 4.87 wt%, respectively.

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 1. The coking amount of the furnace tube of the invention is reduced by 87.65 percent compared with the coking amount of the prior art HP40(Cr25Ni35) furnace tube which is not treated by low oxygen partial pressure.

Example 3

The same small furnace tube as in example 1 was subjected to a low oxygen partial pressure pre-oxidation treatment except that H was used₂And H₂The dew point of the O gas mixture was 0 ℃ and an oxide film mainly containing Cr, Mn, Ni, Fe, O, Si and the like was formed on the inner wall surface of the furnace tube under the same treatment conditions as in example 1. The chromium manganese oxide in the oxide film is MnCr₂O₄In the oxide film, the contents of iron and nickel were 6.48 wt% and 5.69 wt%, respectively.

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 1. The coking amount of the furnace tube of the invention is reduced by 80.65 percent compared with the coking amount of the prior art HP40(Cr25Ni35) furnace tube which is not treated by low oxygen partial pressure.

Example 4

The same small furnace tube as in example 1 was subjected to a low oxygen partial pressure pre-oxidation treatment except that H was used₂And H₂The dew point of the O gas mixture was 40 ℃ and other treatment conditions were the same as in example 1, 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 MnCr₂O₄In the oxide film, the contents of iron and nickel were 11.02 wt% and 8.28 wt%, respectively.

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 1. The coking amount of the furnace tube of the invention is reduced by 51.87 percent compared with the coking amount of the prior art HP40(Cr25Ni35) furnace tube which is not treated by low oxygen partial pressure.

Example 5

The same small furnace tube as in example 1 was subjected to a low oxygen partial pressure pre-oxidation treatment except that H was used₂And H₂The dew point of the O-gas mixture was-40 ℃ and other treatment conditions were the same as in example 1, 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 MnCr₂O₄In the oxide film, the contents of iron and nickel were 15.89 wt% and 13.95 wt%, respectively.

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 1. The coking amount of the furnace tube of the invention is reduced by 32.58 percent compared with the coking amount of the prior art HP40(Cr25Ni35) furnace tube which is not treated by low oxygen partial pressure.

Comparative example 1

The same small furnace tube as in example 1 was subjected to a low oxygen partial pressure pre-oxidation treatment except that H was used₂And H₂The dew point of the O gas mixture was 50 ℃ and other treatment conditions were the same as in example 1, 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 MnCr₂O₄In the oxide film, the contents of iron and nickel were 20.13 wt% and 19.78 wt%, respectively.

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 1. The coke formation of the pilot tube was 19.69% less than the coke formation of the prior art HP40(Cr25Ni35) tube which had not been subjected to the low oxygen partial pressure treatment.

Comparative example 2

The same small furnace tube as in example 1 was subjected to a low oxygen partial pressure pre-oxidation treatment except that H was used₂And H₂The dew point of the O-gas mixture was-50 ℃ and other treatment conditions were the same as in example 1, 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 MnCr₂O₄In the oxide film, the contents of iron and nickel were 25.09 wt% and 24.95 wt%, respectively.

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 1. The coking amount of the small-scale furnace tube is reduced by 13.48 percent compared with the coking amount of the HP40(Cr25Ni35) furnace tube which is not treated by low oxygen partial pressure in the prior art.

Comparative example 3

The same small scale furnace tube as that of example 1 was not subjected to the low oxygen partial pressure pre-oxidation treatment, and the hydrocarbon steam cracking reaction was carried out in the small scale furnace tube, and the cracking raw material and the cracking conditions were the same as those of example 1. 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.