FR2472035A1 - PROCESS FOR HIGH TEMPERATURE TREATMENT OF HYDROCARBON CONTAINING MATERIALS TO AVOID CARBON DEPOSITS ON REACTOR SURFACE - Google Patents

Abstract

PROCESS FOR TREATING AT A HIGH TEMPERATURE OF 500C OR MORE A MATERIAL CONTAINING A HYDROCARBON IN A REFRACTORY STEEL APPARATUS CONTAINING NICKEL, IN WHICH THE SURFACES OF THE APPARATUS IN CONTACT WITH THE MATERIAL CONTAINING HYDROCARBIDE DEPUT FROM METAL ARE COATED NICKEL, AN ALLOY WITHOUT NICKEL, AN OXIDE OR NITRIDE WITHOUT NICKEL OR SILICON CARBIDE, TO AVOID THE DEPOSIT OF CARBON ON THESE SURFACES.

Description

Process for treating high temperature materials

containing a hydrocarbon.

  The present invention relates to a method for treating

  at high temperature hydrocarbon-containing materials.

  More particularly, the invention relates to

  to a process in which a hydrocarbon is subjected to

  bure, a mixture of a hydrocarbon, water vapor and / or

  a gas containing oxygen, or a mixture of a hydro-

  carbide and at least one substance such as hydrogen,

  carbon monoxide and carbon dioxide, at a

  chemical action such as thermal cracking, reforming

  steam, partial oxidation, etc. or other

  at high temperature. To simplify these matters

  to be dealt with will be hereinafter referred to as "ma-

containing a hydrocarbon ".

  To date, to produce ethylene on a large scale,

  hydrogen or a mixture of hydrogen and oxides of car-

  bone, a hydrocarbon-containing material is subjected to

  thermal cracking, steam reforming and / or oxy-

  partial dation at high temperature and high pressure in the presence or absence of a catalyst. During these chemical reactions and before or after them, the hydrocarbon-containing material being handled is subjected to high temperatures.

  high. So the hydrocarbon it contains undergoes a

  thermal composition which causes a solid carbon deposit. As this solid carbon tends to accumulate on the surfaces of the reactor and other devices in contact with

  the hot gas, it is necessary to stop the system of

  and remove the solid carbon deposited to reduce

at least its accumulation.

  In most cases, as building materials for

  high temperature handling apparatus of a

  a hydrocarbon, most commonly used steels are

  kel retaining sufficient mechanical strength even in such

  the conditions of high temperature. The plaintiff has discovered that

  the solid carbon deposition previously described is favored by the

  catalytic conversion of the nickel contained in these steels.

  The object of the invention is therefore to provide a method for

  handle at elevated temperature a material containing a

  hydrocarbon without practically causing carbon deposition.

  It is also intended to provide a process for the treatment of

  temperature of a material containing a hy-

  hydrocarbon, in which it is possible to prevent the apparatus from making a metal material containing nickel and used for handling at high temperature the material containing

  a hydrocarbon, becomes fragile by carburation.

  According to the invention, to achieve these objectives, in

  a process for treating a hydrocarbon-containing material

  at a temperature of 5000C or more in a machine

  made of refractory steel containing nickel, this material

  containing a hydrocarbon being selected from a hydrocarbon

  bure, a mixture of a hydrocarbon, water vapor and / or

  a gas containing oxygen and a mixture of a hydrogen

  carbide and at least one constituent such as hydrogen,

  carbon monoxide, carbon dioxide and

  In one embodiment, the surfaces of the apparatus in contact with the hydrocarbon-containing material are coated with: (a) a component selected from titanium, cobalt, chromium, iron and their alloys; (b) a component selected from titanium, cobalt, chromium, iron and their alloys containing aluminum or aluminum and silicon; (c) a steel not containing nickel,

  (d) alloy steel containing aluminum or aluminum

  luminium and silicon and not containing nickel; (e) a component selected from titanium and niobium alloys and copper and chromium alloys; or (f) a component selected from alumina, titanium dioxide, silica, silicon carbide, nitride,

  silicon, boron nitride and chromium oxide.

  The invention will now be described in detail

  EEA. In the practice of the invention, it is possible to use one

  any of the coating materials belonging to the

  gories (a) to (f) above for coating the surfaces of the ap-

  similar which are in contact with the hydrocarbon-containing material to be treated. These coating materials are going

  now be described in more detail.

  Of the metallic materials belonging to the category

  (a), typical examples of iron and chromium alloys are an iron-chromium alloy containing 17 to 19% by weight of chromium and 0.3% by weight of carbon, and an iron-chromium alloy containing 26 to 28% by weight of chromium

and 0.1% by weight of carbon.

  Typical examples of alloys

  category (b), a titanium-aluminum alloy

  holding 6% by weight of aluminum and a Ti-Al-Zr-V alloy

  holding 6% by weight of aluminum, 4% by weight of zirconium and

1% by weight of vanadium.

  A typical example of alloy of category (d) is a Fe-Cr-Al-Si alloy containing 23% by weight of

  chromium, 1.5% by weight of aluminum and 1.5% by weight of silicon

  cium. The titanium and niobium alloys of category (e) may contain 91 to 99% by weight of titanium, 1 to 3% by weight of niobium and 0 to 2% by weight of each of the other components such as zirconium, aluminum and tantalum. Copper and chromium alloys of category (e) may consist of 95 to 99% by weight

  of copper, 1 to 3% by weight of chromium and 0 to 2% by weight of

  very components such as beryllium.

  There is no particular limitation to the process

  whereon the surfaces of the apparatus in contact are

  with the hydrocarbon-containing material, a material

  belonging to any of the categories (a)

  to (e) above. However generally this is done

  garment according to the casting method of casting a melt of the metallic material onto the surface to be covered with previously formed construction material into tubular, plate or other elements; the method in which a device producing high temperatures such as an acetylene torch, an electric arc, etc. is used. for a melt of the metallic material to adhere to the surfaces to be covered with construction material; a method in which a melt of the metallic material is sprayed and deposited on the surfaces to be covered with the construction material, for example by a flame spraying or plasma spraying method, the chemical vapor deposition method according to which vaporizing a metal compound into contact with the surfaces to be coated with the building material and performing a chemical reaction to deposit the metal thereon; the physical vapor deposition method according to which one ionizes in a high vacuum a vapor of a metal or a

  metal compound and provides the ions obtained with

  kinetics in an electric field to lead them into a plasma or other space where they are directly

  deposited on the surfaces to be coated with the construction material

  chemical reaction causing the deposit

  metal; or the so-called plating process according to which

  brick separately from tubes, plates or other elements of the metallic material and are pressure-joined to

  surfaces to be coated with the building material

fashioned.

  When using high temperature elements

  coated with a metallic material belonging to

  In any of the above categories (a) to (e), there is a slight degree of interdiffusion or mixing of components between the nickel-containing building material and the coating material. It is therefore desirable for the coating material to have a thickness of at least 100 μm to withstand prolonged use. The resulting shaped and coated construction material can further be subjected to bending, flaring, welding or

  other operations to make a device or device

  any desired shape. However, if the building material is in the form of a molded part, it is desirable not to subject the building material

  covered with bending, flaring or other work.

  The process used to coat the building material

  The use of a non-metallic material of the above-mentioned category depends on the nature of the non-metallic material. (A) If the nonmetallic material is an oxide, the coating can be carried out by the sputtering process in which the oxide is melted and sprayed onto the surfaces to be coated with the building material, for example by flame spraying or plasma spray; or the firing process in which a suspension of the oxide is applied to the surfaces to be coated with the building material and then fired at elevated temperature. However, in the latter case, it is desirable to cook the oxide in combination with a mixture consisting of various proportions of oxides selected from silica, alumina, boron oxide, calcium oxide, oxide zinc, barium oxide, zirconium oxide and the like to lower the melting temperature of the oxide below that of the building material and thus avoid melting or alteration of the building material. Nevertheless, the temperature at which the coated building material obtained according to this cooking method can be used is limited to the melting temperature of the layer

coating.

  (B) If the nonmetallic material is silicon carbide, silicon nitride or boron nitride, the coating may be applied by a method in which a melt is applied to the surface to be coated with the building material. a solution of a compound containing silicon-carbon, nitrogen-boron or nitrogen-silicon bonds and then a chemical reaction is carried out in air or in an inert gas at elevated temperature to deposit the desired compound; the spraying process described above in which a powder or a rod of silicon carbide, boron nitride or silicon nitride is melted and sputtered onto the surfaces to be coated with the construction material with

  a plasma torch, the vapor deposition process

  previously described chemical composition or the deposition process

  by physical vaporization previously described.

  The construction material coated with the non-metallic material of Class (f) may be in the form of tubes, plates or other elements as is the case with the metallic materials of the classes (a) to (e) above. When using such a non-metallic material, it is necessary

  that the thickness of the coating is not less than 10 μm.

  However, it is desirable that the thickness of the coating layer does not exceed 1 mm since, when an apparatus carrying a too thick coating layer is subjected to heating or the like, the coating layer reduces the overall transfer coefficient of heat, which hinders

  the passage of heat through it and it also tends to

  flake as a result of the difference in thermal expansion coefficient between the building

and the coating material.

  Of the various elements made of the aforementioned construction material and coated with the above-mentioned coating material, the tubes are particularly important because they are often used as reactors, heat exchangers, and the like and, therefore, are frequently

  contact with a hot material containing a hydrocarbon.

  Therefore, depending on the flow path of a hydrocarbon-containing material in a reactor or heat exchanger, it is often necessary to coat not only one of the

  tube surfaces but both surfaces.

  There is no particular restriction on hydro-

  carbide which is treated in the practice of the invention.

  For example, these hydrocarbons can range from hydro-

  carbides having a small number of carbon atoms,

  such as methane, ethane, etc. hydrocarbons

  as a large number of carbon atoms such as the heavy oil obtained as a distillate in the vacuum distillation of crude reduced. In general, the hydrocarbon which is treated in the practice of the invention has an H / C atomic ratio of 2.0 to 4.0. The invention is particularly effective when applied to the treatment of the aforementioned heavy oil.

2472035.

  -7- It is necessary to use the hydrocarbon previously

  described singly as a gas or a liquid.

  Alternatively, it may be used in admixture with water vapor and / or oxygen-containing gas or in admixture with hydroaene, carbon monoxide, carbon dioxide and / or olefins (such as for example, the gas obtained by treating a hydrocarbon or a mixture of hydrocarbon, water vapor and / or an oxygen-containing gas). The hydrocarbon content of these mixtures

  is generally between 10 and 60% by weight.

  In this description, the term "treat"

  not only indicates that a hydrocarbon-containing material is subjected to a chemical reaction such as thermal cracking, steam reforming, partial oxidation, etc., but also that it is handled in the form of a current feed or product stream before and

after this chemical reaction.

  In the practice of the invention, the hydrocarbon-containing material is treated at

  5000C or more. Moreover, this treatment is preferably carried out

  at a pressure of 6 to 100 bar. As the material of construction of the treatment apparatus under these severe conditions, nickel-containing materials are generally used, such as refractory steels.

nickel.

  According to one of the features of the invention, when treating a hydrocarbon-containing material with

  temperatures of 5000 ° C or more and, in particular,

  subject to a chemical reaction such as thermal cracking, steam reforming, partial oxidation, etc. in the presence or absence of a catalyst, deposition and accumulation of solid carbon on reactor surfaces in contact with the hydrocarbon-containing material can be greatly reduced. If the solid carbon deposited and accumulated is left in place, it hinders the passage of a fluid containing the hydrocarbon and causes an increase in the pressure drop. In addition, in the case where it is necessary to eliminate or provide heat to perform any of the above chemical reactions, the deposition and accumulation

2472035.

  Solid carbon dioxide causes a net decrease in the overall coefficient of heat transfer, which makes it difficult to continue the operation. It is therefore necessary to stop the system on a large scale at regular intervals to remove carbon deposited by any of the well-known methods. When operating according to the invention, the frequency of these carbon removal operations can be reduced to two-thirds

  of the frequency necessary in the prior art.

  Another feature of the invention is that the carburization of the nickel-containing building material can be greatly reduced. It is well known that when a carbon steel or alloy steel containing nickel, chromium, iron and the like is contacted with carbon-containing substances such as hydrocarbons, carbon oxides and the like. at temperatures of 700OC or more, a carburization phenomenon occurs. The constitutive carbon of these substances infiltrates and diffuses into the microstructure of steel reducing its mechanical strength to a point

  such that steel is no longer suitable for use. We consider-

  that this carburation is not only due to the infiltration

  carbon diffusion in the microstructure of steel, but also to the presence

  a substance containing carbon in the gaseous state.

  So, the invention makes it possible to extend the service life

  such as reactor tubes,

  tions, etc. who otherwise should be replaced at

intervals of two or three years.

  The invention makes it possible to obtain particular results

  Particularly important when applied to nickel-refractory steel elements used at temperatures of 5000 ° C. and above, and in particular whose surfaces are in contact with a stream of hydrocarbon-containing material. Although these elements and devices can

  have any desired shape, the tubular elements

  used as reactors are particularly important. Indeed, it is in a reactor that the current

2472035.

  Of hydrocarbon-containing material generally reaches its maximum temperature, that carbon deposition is particularly likely to occur due to the need for the supply or removal of a significant amount of heat of reaction and o the decrease in the overall coefficient of heat transfer caused by

  the deposited carbon causes the greatest discomfort.

  The invention is illustrated by the nonlimited example

next.

Example

  Ethane is steam cracked in reaction tubes having an internal diameter of 27 mm and a length of 800 mm. These reaction tubes are made of a nickel steel (20% iron alloy and 25% nickel) and their inner surface is covered with the coating materials indicated in the table below. The ratio of ethane to water vapor is 7/3 and the temperature of the reaction tubes is maintained at 7000C or 11000C by external heating. After ten hours of continuous operation at a pressure of 1 bar with a feed rate of 10 cm3 / min, the state of carbon deposits on the inner surfaces of the reaction tubes is examined. The results obtained are grouped together

in the table below.

- 10 -

Board

  Coating material of inner surface of reaction tubes and state of carbon deposits N Tempering material - Degree of carbon deposition on the surface of the inner surface of the tubes of the over-test tube Integral face test form (oc) top dp 0 tubes (mg / cm2.10h) tubes 1 chrome 1000 1.0 Film 2 Alloy Fe-28% Cr 1000 2, 1 Film 3 Alloy Ti-6% Al 700 0.3 Suie 4 Alloy Fe-23% Cr-1000 2.1 Film 1.5% Al-1.5% Si Alloy Ti-2% Nb 700 0.3 Soy 6 Alloy-Cu-1% Cr 700 <0.1 Soy 7 Alumina 1000 2.0 Film 8 Dioxide 1000 1.4 Titanium Film 9 Silicon 1000 1.6 Film 1000 Carbide 1.2 Silicon Film 11 1000 Nitride 1,4 Silicon Film 12 Boron Nitride 1000 1,4 Film 13 Oxide chromium 1000 1.0 Film 14 None 1000 3.4 Film As the values in the table clearly show, there is a considerable degree of carbon deposition on the uncoated inner surface of an elaborate tube nickel steel even in the case of cracking ethane which is a light hydrocarbon. This carbon deposit decreases considerably when the surface of a non-metallic metallic or non-metallic material is coated.

  of nickel. Among others, chromium, a titanium-

  niobium and a copper-chromium alloy constitute

  particularly excellent coating.

Claims (3)

  A process for treating a hydrocarbon-containing material at temperatures of 5000 ° C or more in a nickel-containing refractory steel apparatus, which hydrocarbon-containing material is selected from a hydrocarbon, a mixture of a hydrocarbon, a water vapor and / or an oxygen-containing gas or a mixture of a hydrocarbon and at least one component selected from oxygen, carbon monoxide, carbon dioxide and an olefin, characterized in that the surfaces of this apparatus which are in contact with the hydrocarbon-containing material are coated with: (a) a comoosant selected from titanium, cobalt, chromium, iron and their alloys; (b) a component selected from titanium, cobalt, chromium, iron and their alloys containing aluminum or aluminum and silicon; (c) a steel not containing nickel;   (d) an alloy steel containing aluminum or aluminum   and a component selected from titanium and niobium alliaa and copper and chromium alloys; or (f) a component selected from alumina, titanium dioxide, silica, silicon carbide, nitride   silicon, boron nitride and chromium oxide.   2. Process for reacting a hydrocarbon with water vapor and / or a high pressure oxygen-containing oxygen in a refractory steel reactor   containing nickel to produce a gas mixture   with hydrogen and carbon monoxide,   in that the reactor surfaces which are in contact with the hydrocarbon are coated with (a) a component selected from titanium, cobalt, chromium, iron and their alloys; (b) a component selected from titanium, cobalt, chromium, iron and their alloys containing aluminum or aluminum and silicon; I2 (c) a steel not containing nickel   (d) an alloy steel containing aluminum or aluminum   minium and silicon and containing nickel nas; (e) a component selected from titanium and niobium alloys and copper and chromium alloys; or <f) a component selected from alumina, titanium dioxide, silica, silicon carbide, nitride   silicon, boron nitride and chromium oxide.   3. Process according to claim 2, characterized in that the surfaces of the reactor which are in contact with the hydrocarbon are coated with chromium, an alloy   titanium-niobium or a copper-chromium alloy.