BURNER AND METHOD FOR PARTIALLY OXIDIZING LIQUID, CARBON-CONTAINING FUEL

Abstract

A burner for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas a well as the process in which this burner is used, wherein the parts of the outlet orifice of the burner directed towards the combustion chamber are wholly or partly provided with a coating or with a diffusion layer for protection against thermal load and/or corrosion.

Description

FIELD OF THE INVENTION

This invention relates to a burner for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas, and to the process for producing synthesis gas by partial oxidation of said fuels, in which the burner according to the invention is used.

PRIOR ART

A known process for the partial oxidation of liquid, carbonaceous feedstocks for the production of synthesis gas for example is the Lurgi process as described in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Volume 15, Chapt. 3.2.2.

In such processes, the hydrocarbonaceous feedstock stream, e.g. heavy oil, together with the oxygen-containing oxidizing agent, e.g. air enriched with oxygen, and possibly a moderator (mostly steam or carbon dioxide) is converted into a synthesis gas chiefly consisting of carbon monoxide and hydrogen in a reactor space (combustion chamber) at temperatures of 1200 to 1500° C. and high pressures, between 30 and 75 bar.

The reactor is equipped with one or more burners which in general are installed at the head of the reactor such that their flame is vertically guided into the reactor from top to bottom, so that only the lower end of the burner throat protrudes into the combustion chamber and is exposed to the high temperatures and the corrosive atmosphere of the combustion chamber. Such burner is described in DE 198 60 479 C1 and in DE 199 31 373 A1.

The high temperatures and corrosive gases obtained in these processes for producing synthesis gas limit the durability of the burners. Therefore, at least the components of the burners subjected to high loads are fabricated from so-called superalloys. These are high temperature resistant alloys, such as high-carbon nickel-chromium-iron alloys. Fundamental statements on superalloys can be found in Rompps Chemie-Lexikon, 8th edition, Franckh'sche Verlagshandlung, Stuttgart.

Beside the selection of particularly robust construction materials numerous constructive methods have been developed to extend the service life of the burners.

In EP 0 545 281 B1 it is proposed to line the end face of the burner throat with a layer composed of individual ceramic platelets arranged one beside the other.

In EP 1 284 234 A2 it is proposed to divide the inner burner tube into two halves releasably connected with each other, wherein only the lower half facing the end face of the burner is made of a particularly high temperature resistant and high-melting metal alloy. The end face of the outer burner tube is equipped with a space for the passage of a cooling medium and in addition the burner throat protruding into the reactor is surrounded with cooling coils.

DE 601 20 674 T2 proposes the installation of an annular heat shield on the end face of the burner throat, which is made of a material with a high melting point.

What is disadvantageous in the previously proposed solutions for extending the service life of the burner is the fact that they intervene in the construction of the burner throat, so that in the construction a compromise must be found between the actual function of the burner and the measures for protecting the same against corrosion.

DESCRIPTION OF THE INVENTION

Therefore, it has been the object to find a solution for extending the service life of the burner, which rather does not intervene in the construction of the burner and can be carried out economically.

The solution of the object according to the invention substantially can be derived from the characterizing features of claim 1 in conjunction with the features of the generic part. Further advantageous aspects of the invention can be taken from the sub-claims. This invention also relates to a process for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas, in which the burner according to the invention is used.

This object is solved in that the parts of the outlet orifice directed towards the combustion chamber are wholly or partly provided with a coating or with a diffusion layer for protection against thermal load and/or corrosion.

This inventive solution of the object was induced by the proven practice in the construction of hot gas turbines to provide the parts exposed to high temperatures and corrosive gases with a protective ceramic layer, as is reported e.g. in DE 35 43 802 A1.

PREFERRED ASPECTS OF THE INVENTION

In accordance with a preferred aspect of the invention the burner according to the invention is provided with a coating of an adhesive layer and a heat insulation layer, which each are applied by a thermal spraying method, such as plasma spraying, wherein the adhesive layer consists of the metal mixture MCrAlY (M represents at least one of the elements Ni, Co, Pt or Pd) and wherein the heat insulation layer preferably consists of an oxidic spraying material, in particular of ZrO₂. This combination of materials was found to be particularly effective with regard to the extension of the service life of the burner.

In a further aspect of the invention it is provided that by alitizing, chromizing or siliconizing merely a diffusion layer is produced in the surface of the workpiece. The separate heat insulation layer is omitted, which contributes to the constructive simplicity of the burner according to the invention.

In accordance with a particularly preferred aspect of the invention the burner designed according to the invention is wholly or partly provided with a combination of a coating for protection against thermal load and a diffusion layer on its parts of the outlet orifice directed towards the combustion chamber. In this way, a particularly marked extension of the service life and the related operating cost advantages are achieved.

This invention also relates to a process for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas, which is characterized in that at least one burner according to at least one of claims 1 to 4 is used. Details of the procedure and constructive details of the burner are known to the skilled person and described already for example in the documents DE 19931373 A1, DE 19860479 C1, DE 10152686 A1 and DE 10156980 A1, the disclosure of which is herewith included in the present application by reference.

Further developments, advantages and possible applications of the invention can also be taken from the following description of embodiments and the drawings. All features described and/or illustrated form the invention per se or in any combination, independent of their inclusion in the claims or their back-reference.

In the drawing:

FIG. 1 shows the arrangement of the burner according to the invention in the combustion chamber,

FIG. 2 shows the position and the layered structure of the protective layer according to a first preferred aspect of the invention,

FIG. 3 shows the position and the layered structure of the protective layer according to a second preferred aspect of the invention,

FIG. 1 shows how the throat (1) of the burner extends through the reactor wall (3) into the combustion chamber (4) of the reactor with the lower end of the outer burner tube (2). In this example, the throat of the burner (1) is constructed of two concentric tubes. The inner tube (5) conveys a mixture (6) of carbonaceous fuel and steam, the outer tube (2) conveys the oxygen (7) necessary for the combustion and/or partial oxidation, which is possibly mixed with steam or carbon dioxide. FIG. 1 shows the inner (5) and outer (2) tube ends of the burner throat by way of example as straight tube pieces. Other tube shapes are, however, also possible, such as tubes conically tapering towards the tube end or widening tubes. It is also possible that the outer tube (2) is provided with a cooling chamber (9) in which a coolant is contained. In this example shown in FIG. 1 the end face of the outer tube (2) directed into the combustion chamber (4) is provided with a protective layer (8) which according to the invention can be a coating or a diffusion layer. Of course, the lower end face of the inner tube (5) can also be provided with such protective layer, which is not shown in FIG. 1.

As indicated in FIG. 1, the protective layer (8) can not only cover the end face, but also the surfaces in the inner or outer region of the tube or tubes of the burner throat.

FIG. 2 shows the layered structure of the protective layer ((8) in FIG. 1) according to claim 2.

In the aspect of the invention according to claim 2, an adhesive layer (11) and a heat insulation layer (13) each are applied onto the workpiece (10) by a thermal spraying method, such as plasma spraying, wherein the adhesive layer (11) consists of the metal mixture MCrAlY (M represents at least one of the elements Ni, Co, Pt or Pd) and wherein the heat insulation layer (13) preferably consists of an oxidic spraying material, in particular of ZrO₂. The surface (12) of this adhesive layer (11) additionally is enriched with aluminum and silicon atoms in its surface by a diffusion treatment, by so-called alitizing/siliconizing.

Thermal coating methods, such as plasma spraying, useful for the solution of the object are described in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Volume 21, Chapt. 5.

The fact that the durability of the protective layer is improved by priming by means of an adhesive layer of this type is known to the skilled person for example from U.S. Pat. No. 4,321,310. In the development of the present invention MCrAlY spraying material with the trade name SICOAT 2464 has been used successfully.

FIG. 3 shows the structure of the protective layer ((8) in FIG. 1) according to claim 3.

The variant of the invention according to claim 3 consists in that a coating of the workpiece (10′) is omitted and instead the surface to be protected merely is subjected to a diffusion treatment, wherein aluminum and/or silicon and/or chromium atoms diffuse into the surface (12′). These processes are known to the skilled person as alitizing, siliconizing and chromizing. The fundamentals of the used diffusion treatment are described in Rompps Chemie-Lexikon, 8th edition, Franckh'sche Verlagshandlung, Stuttgart.

INDUSTRIAL APPLICABILITY

The present invention provides a burner which is characterized by a high resistance to thermal and corrosive loads.

LIST OF REFERENCE NUMERALS

(1) burner throat

(2) outer burner tube

(3) reactor wall

(4) combustion chamber

(5) inner burner

(6) mixture of carbonaceous fuel and steam

(7) oxygen

(8) protective layer

(9) cooling chamber

(10), (10′) workpiece

(11) adhesive layer

(12), (12′) surface of the adhesive layer

(13) heat insulation layer

Claims

1. A burner for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas, whose outlet orifice is directed into a combustion chamber, wherein the parts of the outlet orifice directed towards the combustion chamber are wholly or partly provided with a coating or with a diffusion layer for protection against thermal load and/or corrosion.

2. The burner according to claim 1, wherein the coating consists of an adhesive layer and a heat insulation layer, which each are applied by a thermal spraying method, such as plasma spraying, wherein the adhesive layer consists of the metal mixture MCrAlY (M represents at least one of the elements Ni, Co, Pt or Pd) and wherein the heat insulation layer preferably consists of an oxidic spraying material, in particular of ZrO2.

3. The burner according to claim 1, wherein by alitizing, chromizing or siliconizing merely a diffusion layer is produced in the surface of the workpiece.

4. The burner according to claim 1, wherein the parts of the outlet orifice directed towards the combustion chamber are wholly or partly provided with a combination of a coating for protection against thermal load and a diffusion layer.

5. A process for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas, wherein at least one burner according to claim 1 is used.