DD155140A5 - METHOD FOR HIGH-TEMPERATURE TREATMENT OF CARBON-CONTAINING MATERIALS - Google Patents

Abstract

Treating a hydrocarbonaceous material at temperatures of 500 degrees C or higher in a plant made of a nickel-containing refractory steel, the surfaces of the plant exposed to the hydrocarbonaceous material comprising a material made of nickel-free metals, nickel-free alloys, nickel-free oxides or nitrides and silicon carbides is selected, coated or covered, whereby the deposition of carbon on these surfaces is prevented.

Description

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Claimed priority: December 13, 1979, Japan,

Patent application no. 160810/197 9

Applicant: TOYO ENGINEERING CORPORATION

No. 2-5, Kasumigaseki 3-chome, Chiyoda-ku, Tokyo, Japan

-. ^ Procedure for

High temperature treatment of hydrocarbonaceous materials.

Field of application of the invention

The invention relates to improvements in a process in which a hydrocarbon, a mixture of a hydrocarbon and steam and / or an oxygen-containing gas or a mixture of a hydrocarbon and at least one selected from hydrogen, Kohlenmonoxy.d and carbon dioxide member of a chemical reaction such. thermal cracking, steam reforming, partial oxidation, etc .: or other high temperature treatments. Such materials to be treated are referred to simply as hydrocarbonaceous materials hereinafter.

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Characteristic of the known technical solutions

Today, ethylene, hydrogen or a mixture of hydrogen and carbon oxides are produced on a large scale by subjecting a hydrocarbonaceous material to thermal cracking, steam reforming and / or partial high temperature, high pressure oxidation in the presence or absence of a catalyst. During and after such chemical reactions, the hydrocarbonaceous material to be treated is exposed to high temperature. In this case, its hydrocarbon component undergoes thermal decomposition, which leads to deposition of solid carbon. Since this solid carbon tends to accumulate on the surfaces of the reactor and other equipment exposed to the hot gas, it is necessary to shut down the production system and remove the deposited solid carbon in order to reduce its accumulation.

In most cases, as a building material for the plant in which hydrocarbonaceous material is processed at a high temperature, nickel-containing steels which maintain sufficient strength even under such high-temperature conditions are used. The inventors of the present invention found that the solid carbon deposit described above is accelerated by the catalytic action of the nickel contained in these steels.

Object of the invention

It is an object of the invention to provide a process for processing a hydrocarbonaceous material at high temperature which does not cause carbon deposition to a significant degree.

It is also an object of the invention to provide a process for the high-temperature treatment of a hydrocarbonaceous material.

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as to prevent the equipment made of a nickel-containing metallic material used for processing the hydrocarbonaceous material at high temperature from being rendered brittle due to the occurrence of carburization.

Explanation of the essence of the invention

These objects of the present invention are achieved by providing a method of treating a hydrocarbon-containing material at temperatures of 50O ⁰ C or more in a made of a nickel-containing heat-resistant steel apparatus, wherein the hydrocarbon-containing material of the group is selected from a hydrocarbon, a mixture consists of a hydrocarbon and at least one member selected from the group consisting of steam and an oxygen-containing gas and a mixture of a hydrocarbon and at least one member selected from hydrogen, carbon monoxide, carbon dioxide and olefins, with the proviso that it makes it possible to treat the surfaces of the equipment are exposed to the hydrocarbonaceous material, with

(a) a member selected from titanium, cobalt, chromium, iron and alloys thereof,

(b) a member selected from titanium, cobalt, chromium, iron and alloys thereof containing aluminum or aluminum and silicon,

(c) a steel containing no nickel,

(d) an alloyed steel containing aluminum or aluminum and silicon and no nickel,

(e) a member selected from alloys of titanium and niobium and alloys of copper and chromium, or

(f) a member selected from alumina, titania, silica, silicon carbide, silicon nitride, boron nitride and chromium oxide.

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embodiment

Any of the coating materials belonging to the above-mentioned categories (a) to (f) may be used in the practice of the present invention

or to cover the surfaces of the plant / which are exposed to the hydrocarbonaceous material to be treated. These coating materials are explained in greater detail below.

Among the metallic materials belonging to category (a) ', typical examples of the alloys of iron and chromium are an iron-chromium alloy containing 17 to 19% by weight of chromium and 0.3% by weight of carbon contains, and an iron-chromium alloy containing 2 6 to 28 wt .-% chromium and Q _r 1 wt .-% carbon.

Typical examples of the alloys belonging to the category (b) are a titanium-aluminum alloy containing 6% by weight of Al and a Ti-Al-Zr-V alloy containing 6% by weight. Aluminum, 4 wt .-% zirconium and 1 wt .-% vanadium.

A typical example of the alloys belonging to category (d) is an Fe-Cr-Al-Si alloy containing 23% by weight chromium, 1.5% by weight aluminum and 1.5% by weight. - contains% silicon.

The alloys of titanium and niobium belonging to category (e) may consist of 91 to 99% by weight of titanium, 1 to 3% by weight of niobium and 0 to 2% by weight of other components such as zirconium , Aluminum and tantalum exist. The alloys of copper and chromium belonging to 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 other constituents such as beryllium.

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The method by which the surfaces of the equipment exposed to the hydrocarbonaceous material are coated or covered with a metallic material belonging to any one of the above enumerated categories (a) to (e) is not particularly limited. However, this coating is usually by the so-called casting process, in which a melt of the metallic material is poured over the surfaces to be covered from the building material, which has been previously formed into tubes, plates or other moldings; dur.ch the method in which a means for generating high temperatures such as an acetylene burner, an electric arc, etc. is used to cause a melt of the metallic material to adhere to the surfaces of the building material to be covered; by the method of spraying a melt of the metallic material onto the surfaces to be covered from the building material and depositing them thereon, such as by the flame spraying method or the plasma jet method; by the chemical vapor deposition method, wherein a vapor of a metallic compound is brought into contact with the surfaces to be coated from the building material and subjected to a chemical reaction to deposit the metal thereon; by the physical vapor deposition method in which a vapor of a metal or its compound is ionized in a high vacuum and kinetic energy is given to the resulting ions in an electric field, and these ions are then introduced into a plasma space or other space where they are be deposited directly on the surfaces to be coated from the building material or subjected to a chemical reaction to deposit the metal on the surfaces; or by

the so-called plating process, at -. r

the tubes, plates or other shaped body made separately from the metallic material and to the surfaces to be covered of the previously formed building material by application of. Pressure bound ^ be / performed.

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When the molded articles coated with a metallic material belonging to any one of the aforementioned categories (a) to (e) are used at a high temperature, a small degree of inter-diffusion or mixing of components occurs between the nickel-containing building material and the coating material. It is therefore desirable that the coating material have a thickness of not less than 100 μm to endure long-term use. The resulting molded and coated building material may further be subjected to bending, pipe working, welding, and other processing to produce equipment or parts thereof having desired shapes. However, when the building material is in the form of castings, it is desirable to stop subjecting the coated building material to bending, pipe widening or other processing techniques.

The method for coating the building material with a non-metallic material belonging to the aforementioned category (f) depends on the kind of the non-metallic material.

(A) When the non-metallic material is an oxide, the coating may be carried out by the so-called spraying method in which the oxide is melted and coated on the surfaces to be coated from the building material e.g. sprayed by flame spraying or plasma jet method; or the coating is carried out by the so-called baking method, in which a suspension of the oxide is applied to the surfaces to be coated from the building material and then baked at a high temperature. In the latter case, however, it is desirable to heat the oxide in combination with a mixture consisting of varying proportions of oxides of silicon oxide; Alumina, boric oxide, calcium oxide, zinc oxide, barium oxide, zirconia and the like are selected for the purpose of lowering the melting temperature of the oxide to a value

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Lower, which is lower than that of the building material 1st, and thereby prevent melting or alteration of the building material. Nevertheless, the temperature at which the coated building material obtained by this baking process can be used is limited to the melting temperature of the covering layer.

(B) When the non-metallic material is silicon carbide, silicon nitride or boron nitride, the coating may be carried out by a method in which a melt or a solution of a compound that is silicon-on-carbon, nitrogen-on-boron or nitrogen-on-silicon bonds is applied to the surfaces to be coated from the building material and 'then subjected to a chemical reaction in air or in an inert gas at high temperature to deposit the desired compound thereon; or it may be melted by the above-described spraying method in which a powder or a rod of silicon carbide, boron nitride or silicon nitride is sprayed onto the surfaces to be coated from the building material by the plasma jet method or by the above-described chemical vapor deposition method or by the above described physical vapor deposition method can be performed.

When the surfaces to be coated of the building material are coated according to the category (f), the building material may be in the form of pipes, plates or any other shaped articles as in the case of the metallic materials corresponding to the above-mentioned categories (a) to (e ) are present. When such a non-metallic material is used, a covering layer having a thickness of not less than 10 μm is required. Advantageously, however, the thickness of the cover layer is not greater than 1 millimeter. The reason is, namely, if a system with an excessively thick covering layer is subjected to a heating process step or the like,

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Not only does the covering layer have the total coefficient of heat transfer to affect the heat flow therethrough, but it also tends to split due to the difference in the thermal expansion coefficients between the building material and the coating material.

Among the various moldings made of the above-described building material and coated with the above-described coating material, pipes are particularly important because they are often used as reactors, heat exchangers, and the like, and therefore very often the situation becomes hot exposed to hydrocarbonaceous material. Therefore, depending on the flow path on which a hydrocarbonaceous material passes through a reactor or heat exchanger, it may often be necessary not to coat only one surface of the tube, but both surfaces of the tube.

There is no particular limitation on the hydrocarbon that is treated in the practice of the present invention. Specific examples of the hydrocarbon may include hydrocarbons having a small number of carbon atoms, e.g. Methane, ethane, etc., to hydrocarbons having a large number of carbon atoms, such as heavy oil, which is obtained as a distillate by subjecting reduced crude to vacuum distillation. Generally speaking, the hydrocarbon treated in the practice of the present invention has an atomic H / C ratio of 2.0 to 4.0. The present invention is particularly effective when applied to the treatment of the above-mentioned heavy oil.

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The above-described hydrocarbon may be used alone in the form of a gas or a liquid. Alternatively, it may be used in admixture with steam and / or an oxygen-containing gas or in admixture with hydrogen, carbon monoxide, carbon dioxide and / or olefins (they may be a product gas obtained by treating a hydrocarbon or a mixture of a hydrocarbon and steam and or an oxygen-containing gas has been obtained). The content of hydrocarbon in such mixtures is usually in the range of 10 to 60 wt .-%.

The term "treating" as used herein means not only subjecting a hydrocarbonaceous material to a chemical reaction such as thermal cracking, steam reforming, partial oxidation, etc., but also providing a feed stream and a product stream and after this chemical reaction is processed.

In the practice of the invention, the hydrocarbonaceous material is treated at temperatures of 500 ^° C. or more. Furthermore, this treatment is preferably carried out at a pressure of 6 to 100 kg / cm G (about 7 to 101 bar absolute). As the building material for the equipment for treatment under such severe conditions, nickel-containing materials such as nickel-containing heat-resistant steels are used in the usual cases.

According to a basic feature of the present invention, when a hydrocarbonaceous material is treated at temperatures of 500 ^° C. or more, and when it is subjected to, in particular, a chemical reaction such as thermal cracking, steam reforming, partial oxidation, etc. in the presence or absence of a catalyst, the deposition can occur and accumulation of "solid carbon on the surfaces of the reactor containing the hydrocarbon

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Material is exposed to be significantly reduced. When the settled and accumulated solid carbon is left as it is, it hinders the passage of a fluid containing the hydrocarbon and causes an increase in the pressure loss. Moreover, in cases where it is necessary to remove or supply the heat of reaction to carry out the aforesaid chemical reaction, the deposited and accumulated solid carbon also causes a marked drop in the overall heat transfer coefficient, making it difficult to continue the operation. As a countermeasure, therefore, it is necessary to periodically shut down the large system or to partially stop its operation and to remove the deposited carbon by any known means. When the present invention is applied, the frequency of this carbon removal can be reduced to 2/3 less than was necessary in the conventional case.

Another feature of the present invention is that the carburization of the nickel-containing building material can be greatly reduced. It is well known that the so-called carburizing phenomenon occurs when a carbon steel or an alloy steel containing nickel, chromium, iron and the like is exposed to carbonaceous substances such as hydrocarbons, carbon oxides, etc. at temperatures of 700 ° C or more. This means that its carbon component penetrates and diffuses into the microstructure of the steel, thereby reducing its strength to such a degree that the steel is no longer suitable for the application. It is believed that such carburization is not only due to the penetration and diffusion of the deposited carbon into the microstructure of the steel but is also attributable to the presence of a gaseous carbonaceous substance. In this way, the invention makes it possible, the working time or life of molded parts such

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Extend reactor pipes, pipes, etc., which would otherwise have to be replaced at intervals of 2 to 3 years.

The present invention produces appreciable effects when applied to parts, fittings or equipment made of a nickel-containing heat-resistant steel used at temperatures of 500 ° C or more, and especially to their surfaces exposed to a stream of hydrocarbonaceous material are applied. Although these parts, fittings and equipment may have any desired shapes, the invention is particularly important for tubular parts used as reactors. The reason for this is that the flow of hydrocarbonaceous material in the reactor usually reaches a maximum temperature, the deposition of carbon is most likely to occur there, due to the necessity of removing or supplying a large amount of the reaction heat, and the reduction of the overall heat transfer coefficient , caused by the deposited carbon, leads to the greatest difficulties.

The present invention will now be further illustrated by the following examples. However, these examples are not intended to limit the scope of the invention.

example

Ethane was subjected to steaming in reactor tubes with an inner diameter of 27 mm and a length of 800 mm. These reactor tubes were made of nickel-containing steel (Fe-2Q% Ni-25% alloy), and their inner surface was covered with the respective coating materials shown in Table 1. The ratio of ethane to steam was 7: 3, and the reactor tube was maintained at a temperature of 700 C or 1100 ° C by external heating. After operating for 10 hours

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A pressure of 1 kg / cm G (about 2 bar absolute) and a feed rate of 100 cm / min was continued, the conditions of carbon deposition on the inner surface of the reactor tube were examined. The results thus obtained are summarized in Table 1.

Table 1

Coating material on the inner surface of reactor tubes and conditions of carbon deposition.

Test tube no. Coating material on the inner tube Test temperature Condition of Kohlenstoffab storage on the inner pipe surface shape surface OC deposited amount (mg / cm ² / 10h) thin coating 1 chrome 1000 1.0 thin coating 2 Fe-28% Cr-Leg. 1000 2.1 rußartig 3 Ti-6% A1 alloy 700 0.3 thin coating 4 Fe-23% Cr-1.5% Al-1.5% Si alloy 1000 2.1 rußartig 5 Ti-2% Nb-alloy 700 0.3 rußartig 6 Cu-1% Cr alloy 700 <0.1 thin coating 7 · alumina 1000 2.0 thin coating 8th titanium dioxide 1000 1.4 thin coating 9 silica 1000 1.6 thin coating 10 silicon carbide 1000 1.2 thin coating 11 silicon nitride 1000 1.4 thin coating 12 boron nitride 1000 1.4 thin coating 13 chromium 1000 1.0 thin coating ί4 None 1000 3.4

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As apparent from the data shown in Table 1, a remarkable degree of carbon deposition was observed on the uncovered inner surface of a pipe made of a nickel-containing steel even in the case of steam cracking of ethane, which is a light hydrocarbon. This carbon deposit was significantly reduced by covering this surface with a nickel-free metallic or non-metallic material. Among others, it was found that chromium, a titanium-niobium alloy and a copper-chromium alloy were particularly excellent coating materials.

Claims (3)

22 6 027 invention claim A process for treating a hydrocarbonaceous material at temperatures of 50O ⁰ C or more in a plant made of a nickel-containing heat-resistant steel, wherein the hydrocarbonaceous material is selected from the group consisting of a hydrocarbon, a mixture of a hydrocarbon and at least one selected from the group consisting of steam and an oxygen-containing gas and a mixture of a hydrocarbon and at least one member selected from hydrogen, carbon monoxide, carbon dioxide and olefin, characterized in that the surfaces of the equipment exposed to the hydrocarbonaceous material are selected from (a) a member selected from titanium, cobalt, chromium, iron and alloys thereof; (b) a member selected from titanium, cobalt, chromium, iron and alloys thereof containing aluminum or aluminum and silicon; (c) a steel containing no nickel; (d) an alloyed steel containing aluminum or aluminum and silicon and containing no nickel; 2 2 6 0 2 7 (e) a member selected from alloys of titanium and niobium and alloys of copper and chromium, or (f.) a member selected from aluminum oxide, titanium dioxide, silicon oxide, silicon carbide, silicon nitride, boron nitride and chromium oxide, coated or covered. 2. A process for reacting a hydrocarbon with steam and / or an oxygen-containing gas at high pressure in a reactor made of a nickel-containing heat-resistant steel to form a gaseous mixture containing hydrogen. and carbon monoxide, characterized in that the surfaces of the reactor which are exposed to the hydrocarbon with (a) a member selected from titanium, cobalt, chromium, iron and alloys thereof; (b) a member selected from titanium, cobalt, chromium, iron, and alloys thereof containing aluminum or aluminum and silicon? (c) a steel containing no nickel; (d) an alloyed steel containing aluminum or aluminum and silicon and containing no nickel; (e) a member selected from alloys of titanium and niobium and alloys of copper and chromium, or (f) a member selected from aluminum oxide, titanium dioxide, silicon oxide, silicon carbide, silicon nitride, boron nitride and chromium oxide. 226027 3. The method according to item 2, characterized in that the surfaces of the reactor which are exposed to the hydrocarbon, with a member selected from chromium, a titanium-niobium alloy and a copper-chromium alloy, coated.