NZ272891A - Hot gas line of multi-layer construction, incorporating bellows compensation for thermal expansion - Google Patents

Description

New Zealand No. International No. 272891 PCT/ TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates: 08.09.1994; Complete Specification Filed: 30.08.1995 Classification:^) F16L51/02; F16L59/02; F16L9/00 Publication date: 24 November 1997 Journal No.: 1422 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention: Hot gas line for gases containing hydrogen and carbon monoxide Name, address and nationality of applicant(s) as in international application form: METALLGESELLSCHAFT AKTIENGESELLSCHAFT, joint Stock Company of Reuterweg 14, D-60323 Frankfurt am Main, Federal Republic of Germany 272891 COMPLETE SPECIFICATION "HOT GAS LINE FOR GASES CONTAINING HYDROGEN AND CARBON MONOXIDE" We, METALLGESELLSCHAFT AKTIENGESELLSCHAFT, a joint Stock Company incorporated under the laws of the Federal Republic of Germany, of Reuterweg 14, D-60323 Frankfurt am Main, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: (followed by page 1«'/ A 7685 - la Mota 11gcsol1schaft AG Reuterweg 11-60323 Frankfurt-on-Main Caso No. 9*1 00 26<■— Hot Gas Line for Gases Containing Hydrogen and Carbon Monox i de DESCRIPTION This invention relates to a hot gas line for conducting a product gas, which contains hydrogen and carbon monoxide and is the result of a reaction of gaseous, liquid, or solid fuels and is at temperatures in the range from 600 to 1500°C, which hot gas line comprises an outer sheath tube, an inner protective tube, which is subdivided into sections, and a protective layer, which consists of a heat-insulating protective compound and is disposed between the protective tube and the sheath tube.

Product gases which are conducted through hot gas lines of that kind may consist, e.g., of raw synthesis gases. Such gases may be produced, e.g., by a cracking of natural gas, by a gasification of liquid hydrocarbons, or by a gasification of coal. Suitable processes and reactors for such processes have been described in Ullmanns Encyclopedia of Industrial Chemistry, 5th edition, Volume A12, pages 192 to 208. They include, inter alia, a tubular heater, details fo which are known from DE-A-43 27 176.

The hot gas line which conducts hot product gases, June £9, 1994 272831 which contain H2 and CO, comprises a protective tube, which is divided into sections, so that length changes of the protective tube caused by temperature changes will not be restricted and will not result in a deflection or destruction of the protective tube. For this reason the protective tube cannot be designed to be perfectly gastight but an open butt joint is required between two sections of the tube so that the tube sections can elongate in response to a temperature rise.

It has been found that small side streams of the hot gas can constantly escape through the open butt joints of the hot gas line and can flow as far as to the inside surface of the sheath tube so that hot spots will undesirably result on the sheath tube after a prolonged operation. Besides, the carbon monoxide will attack the sheath tube, which is usually made of steel, so that the formation of carbides will result in metal dusting, by which the tube will be weakened and may even be destroyed.

For this reason it is an object of the invention so to design the hot gas line described first hereinbefore that the protective tube can be designed to be as gastight as possible but can readily change in length. This is accomplished in accordance with the invention in that at least one section of the protective tube comprises a compensator, which consists of metal bellows,, which will take up the length change of the. section of the protective tube.

A further feature of the invention resides in that the protective tube section which is provided with a compen sator is secured to the sheath tube by at least one annular joint, which acts as a gas barrier. The joint which is provided between the protective tube section and the sheath tube and acts as a gas barrier will ensure that a constant gas flow, even at a very low rate, cannot occur in the region between the sheath tube and the protective tube section.

A compensator will generally be provided near a portion of the protective tube in which length changes of the protective tube section will occur in different directions.

Such length changes in different directions may occur adjacent to tees and bends. Unless elastic metal bellows are provided, it will be necessary in such critical regions to provide two open butt joints which are closely spaced apart in order to allow for length changes of the tube sections in two different directions. Experience has shown that disturbing hot spots will preferably occur in such regions of known hot gas lines in such cases. Because the protective tube section is provided in accordance with the invention with at least one metal bellows compensator in such a critical region, the number of open butt joints can be decreased and the gas barrier will prevent a constant flow of hot gas to the inside surface of the sheath tube.

Because the protective tube designed in accordance with the invention will effectively protect the sheath tube, the sheath tube may be made at low cost from a relatively low-grade steel, such as plain carbon steel. The sections of the (followed by page 4a) 272 891 protective tube and the metal bellows are preferably made of alloy steel (such as Alloy 800). The heat-insulating protective compound will consist in most cases of a commercially available ramming compound, which has a certain porosity.

More particularly, the present invention consists in a first hot gas line for conducting a product gas which contains hydrogen and carbon monoxide and is a result of a reaction of gaseous, liquid or solid fuels and is at temperatures in the range from 600°C to 1500PC, and a second hot gas line connected to said first hot gas line, both lines being joined by a tee, both hot gas lines comprising an outer sheath tube, an inner protective tube being subdivided into sections, and a porous heat-insulating protective compound disposed between the protective tube and the sheath tube, each two neighbouring sections of said protective tube being separated by a gap, said gap ranging from said protective tube through said protective compound to the inside of said sheath tube, the protective tube section in the tee being composed of a first pipe inside said first hot gas line and a second pipe inside said second hot gas line, both pipes forming a tee and being gastightly connected to each other, said first pipe having two end portions and both end portions being connected to said sheath tube by a conical metal ring, each ring being gastightly connected to said first pipe and said sheath tube and forming a gas barrier, said first pipe in the vicinity of its two end portions containing compensators consisting of metal bellows, said compensators taking up the length changes of said first pipe, and said second pipe having no connection to the sheath tube of the second hot gas line.

Brtoodiments showing features of the hot gas line will be ex-plained with reference to the drawing, in which Figure 1 is a schematic showing of two reactors provided with hot gas lines and Figure 2 is a longitudinal sectional view showing a tee, which is included in a hot gas line and provided with a tubular sensing port.

Figure 1 illustrates one of the numerous ways in which hot gas lines may be employed. In a tubular heater 1, which comprises "numerous tubes 2, which are filled with a granular catalyst (such as a nickel catalyst),natural gas from line 3 is reacted at temperatures in the, range from 700 N.Z. PATENT OFFICE I - 3 SFP iq07 - 4a - 27 2 8 9 1 to 1000°C with steam from line 4 to produce a raw synthesis gas. The tubes 2 are disposed in a combustion chamber 5, which is flown through by hot combustion gas and is provided with numerous burners 6, only one of which is shown in Figure 1.

Tije burners 6 are supplied with fuel, such as natural gas, and with air by means known per se, which are not shown.

The hot product gas formed in the tubes 2 is rich in hydrogen and carbon monoxide and is collected and together with further natural gas from line 9 is supplied to an auto-thermic cracking reactor 10 through a first hot gas line 8.

N.Z. PATENT OFFICE - s sfp m i I 9 7 p 8 9 1 The reaction in the reactor 10 is effected with oxygen supplied through line 11 and steam supplied through line 12 and takes place on a bed 13 formed by a granular catalyst, which may also consist of a nickel catalyst. Hot product gas at a temperature in the range from 800 to 1300°C is withdrawn in a second hot gas line 14. That product gas is a raw synthesis gas, which usually contains at least 60% by volume H2 + CO and is processed further, e.g., for use in the synthesis of ammonia or methanol. In a modification of the process illustrated in Figure 1, raw synthesis gases may be produced without the use of a catalyst in that carbonaceous materials are gasified in known manner.

Details of the hot gas line 8 or 14 will be explained with reference to Figure 2, which shows the particularly critical region in which two lines are joined by a tee. The main components of the hot gas line consist of the sheath tube 17, the heat-insulating protective compound 18, and the protective tube, which is composed of a plurality of sections 20, 21, 22, 23, and 24. The section 22 of the protective tube is a tes, which comprises a horizontal pipe 22a and a vertical pipe 22b. The sections are separated by a gap, which is constituted by an open butt joint 25. Adjacent to each of the open butt joints 25, the ends of the tube sections are covered by a tubular portion 26 and a conical metal ring 27 is provided. That metal ring 27 is joined to one tube section and to the sheath tube 17, e.g., by welding, to act as a gas barrier in the region between the protective tube and the sheath tube.

A tubular sensing port 36 is provided in the section 21 of the protective tube and is joined at one end to the protactive tube and at the other end to the sheath tube 17. A portion of that tubular sensing port constitutes a compensator 37, which will take up length changes resulting from temperature changes. If that compensator 37 were not provided, an open butt joint would be required through which hot gas might escape and flow as far as to the inside surface of the sheath tube. This is now prevented at that point.

The protective tube section 22 which consists of a tee comprises in its horizontal pipe 22a two compensators 28, each of which consists of annular metal bellows. The two compensators 28 will take up the length changes which result in the horizontal pipe 22a of the protective tube section 22 from temperature changes. The two ends of that horizontal pipe 22a are fixedly joined by metal rings 27 to the sheath tube 17. In case of length changes of the vertical pipe 22b of the tube section 22 its free end can move into the open butt joint 25 provided adjacent thereto.

As is apparent from the drawing a small amount of the hot gas flowing in the direction of arrows 30, 30a, 31, 3'la, and 31b may enter the open butt joints 25 and may flow approximately as far as to the inside surface of the sheath tube. But the conical joining ring 27 associated with each section of the protective tube will prevent a constant follow- 272891 up flow of additional hot gas because that ring will act as a gas barrier. The small amount of hot gas which is present in the open butt joint 25 will deliver its heat content outwardly to the sheath tube so that a stagnant cushion of cooled gas will be formed, by which a flow of additional hot gas into the open butt joint will substantially be prevented and, as a result, that gas can exert only a negligibly small effect on the sheath tube. Besides, an elastic filler consisting, e.g., of ceramic fibers may be provided in the open butt joints 25; this has not been shown in the drawing for the sake of clarity.

To decrease the pressure drop in the flowing gas, the compensators 28 are covered by a guide tube 35, which has smooth surfaces and has an angled rim 35a, which is welded to the section 22a of the protective tube.

Claims (3)

WHAT WE CLAIM IS: -8 - 27 2 89 1

1. A first hot gas line for conducting a product gas which contains hydrogen and carbon monoxide and is a result of a reaction of gaseous, liquid or solid fuels and is at temperatures in the range from 600°C to 1500°C, and a second hot gas line connected to said first hot gas line, both lines being joined by a tee, both hot gas lines comprising an outer sheath tube, an inner protective tube being subdivided into sections, and a porous heat-insulating protective compound disposed between the protective tube and the sheath tube, each two neighbouring sections of said protective tube being separated by a gap, said gap ranging from said protective tube through said protective compound to the inside of said sheath tube, the protective tube section in the tee being composed of a first pipe inside said first hot gas line and a second pipe inside said second hot gas line, both pipes forming a tee and being gastightly connected to each otiier, said first pipe having two end portions and both end portions being connected to said sheath tube by a conical metal ring, each ring being gastightly connected to said first pipe and said sheath tube and forming a gas barrier, said first pipe in the vicinity of its two end portions containing compensators consisting of metal bellows, said compensators taking up the length changes of said first pipe, and said second pipe having no connection to the sheath tube of the second hot gas line.

2. A hot gas line according to claim 1 and substantially as herein described with reference to any embodiment disclosed.

3. A hot gas line substantially as herein described with reference to any embodiment shown in the accompanying drawings. tsy trie authorised agents END OF CLAIMS N.Z. PATENT OFF'CE ~ 3 SEP 1997