Title of Invention | SYNTHESIS FURNACE |
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Abstract | Synthesis furnace (1) with a furnace chamber (3) surrounded by a furnace wall (2) all around, in which several burners (5) are arranged mainly in one plane with the burner outlet direction pointed downwards, whereby at least the outer burners (5) arranged in the region of the furnace wall (2) have a burner outlet direction (R), which is inclined from the centre of the furnace moving away towards the vertical and in which several reaction pipes (4) are arranged mainly perpendicular and parallel to one another, that are heated from outside by the firing burners (5), characterized in that the inclination of the burner outlet direction (R) of the individual burners (5) is different. |
Full Text | "Synthesis Furnace" The invention relates to a synthesis furnace with a furnace chamber surrounded by a wall all around, in which there are several burners mainly arranged on one level, with the burner orifice directed downwards and several reaction pipes arranged mostly perpendicular and parallel to one another, whereby the reaction pipes are heated from outside by the firing burners. Such synthesis furnaces, e.g. for producing ammonia, methanol or hydrogen, are sufficiently well known and are designed for use in big technology often as generic top- fired box furnaces with vertically standing reaction tubes or slotted tubes. These reaction tubes are arranged in series and are charged through from above to below with process gas. This process gas is thereby subjected to a so-called fission process. The process gas is collected below either inside or outside the furnace in exit collectors. In the lanes between the pipe rows the pipes get heated by the burners arranged above in the furnace and firing vertically downwards; the flue gas generated by the burner flows through the furnace from top to bottom and is drawn away through the flue gas tunnel arranged on the floor (e.g. published in: "Ammonia: Principles and Industrial Practice/Max Appl - Weinheim; New York, Chichester; Brisbane; Singapore; Toronto; Wiley-VCH, 1999, ISBN 3-527-29593-3, pages 80-89). In such synthesis furnaces, particularly with a large number of pipe rows, a very un-uniform flow is observed, especially in the outer pipe rows mainly influenced by re- circulation. This re-circulation leads to low flue gas and process gas temperatures in the outer pipe rows as compared to the central rows. This low temperature in the outer rows has a disadvantageous effect on the fission process. Besides, it also leads to flame deflection in the outer burner rows, which hampers the entire heat transfer and increases the material load. In order to avoid these known problems, already various solutions have been suggested (Flue Gas Flow Patterns in Top-fired Steam Reforming Furnaces, P.W. Farnell & W. J. Cotton, Synetix, Billingham, England, 44th Annual Safety in Ammonia Plants and Related Facilities symposium, Seattle, Washington, paper no. 3e, September 27 - 30, 1999). On the one hand, it is suggested that the outer burners be operated with higher air discharge velocities, and on the other hand, that the process gas be distributed in a specific manner in different quantities to the reaction pipes. However, both the solutions have not proved to be satisfactory. It has also been suggested that the burner distance to the furnace wall be increased. However, this solution also does not solve the above mentioned problems. It is therefore the task of this invention to improve the heat distribution and the total heat transfer in a simple design and technically easy to control manner. This task is fulfilled in the case of a synthesis furnace of the type described above, in that at least the outer burners arranged in the region of the furnace wall have a burner outlet direction that is inclined starting from the centre of the furnace and moving away from the vertical. It has been seen that by using this solution, as against the previously described known solutions, the flame deflection of the outer burner rows towards the centre of the furnace can be significantly reduced in a design-wise and control-technically simple manner. One obtains a mainly more uniform flow-off of the flue gases along the reaction pipes, the heat transfer gets improved and the increased material load of the reaction pipes due to "hot spots" in case of synthesis furnaces according to the state-of-the-art technology, gets significantly reduced, so that the life-span of the reaction pipes increases significantly. In order to achieve a good heat distribution or flue gas flow, it is foreseen that the inclination of the burner outlet directions of the individual burners is different. This means that the burners, depending on the suction effect of adjacent burner flames on the respective own flame, are arranged at a corresponding angle of inclination (opposed to the suction effect of adjacent burners). It is thereby foreseen that the inclination of the burner exit directions of the burners, starting from the centre of the furnace, increases outwards towards the furnace walls. Whereas the centrally arranged burners do not have any inclination, the inclination of the burner rows increases towards the outside to a maximum value. It has also been proved to be particularly useful if the angle of inclination, starting from the centre, lies between 0 to 10°, preferably between 0 to 5°. In order to realise the inclination of the burners, design-wise it can be foreseen that the burners with inclined burner exit direction are installed altogether inclined and/or their burner orifice is arranged in an inclined manner. It is also foreseen that the inclination of the burner outlet direction is adjustable, i.e. during operation of the synthesis furnace these can be altered for adapting to the respective conditions/patterns. For this, it is particularly foreseen that for setting the inclination a control system is foreseen, that takes into consideration the operation parameters of the synthesis furnace. The invention is described in details below on the basis of the drawing. The following are shown: Fig. 1 A principle diagram of a synthesis furnace; Fig.2a The temperature distribution in a synthesis furnace according the state-of-the-art technology; Fig.2b The temperature distribution in a synthesis furnace as per the invention; Fig.3a Flow patterns in a synthesis furnace according to the state-of-the-art technology; Fig.3b Flow patterns in a synthesis furnace as per the invention; and Fig.4 A diagram in which the heat flow density for the outermost pipe row over the pipe length for a synthesis furnace according to the state-of-the-art technology and the synthesis furnace as per the invention is shown. A synthesis furnace is generally denoted in fig. 1 by the reference sign 1. This synthesis furnace is designed as box-type or square-type and has a furnace chamber 3 surrounded by a furnace wall 2 all around. Within this furnace chamber 3 several reaction pipes 4 are arranged, mainly arranged perpendicular and parallel to one another, through which process gas is introduced from above, which is not shown in more details. This process gas flows from top to bottom through the reaction pipes 4 and is collected in the lower region of the furnace or outside it in exit collectors that have not been shown. In the region between the reaction pipes 4 or pipe rows formed by these, several burners 5 are arranged in the upper region of the chamber 3 mainly on one level. However, these burners 5 have a burner outlet direction pointing downwards; in fig. 1, for each burner 5 a vertical burner axis 6 has been drawn with dashed line. Now it is important that at least the outer burners 5 arranged in the region of the furnace wall 2 have a burner outlet direction R, which is inclined moving away from the centre of the synthesis furnace 1 against the vertical. This angle of inclination is denoted by a in fig. 1 and defined opposite to the allied vertical burner axis 6. It is obvious that, contrary to the two dimensional depiction in fig. 1, this inclination can also stretch or stretch additionally, depending on the arrangement of the burners, towards the centre of the furnace chamber 3 in the plane stretched transverse to the shown drawing plane. The centre of the furnace chamber 3 is thereby situated in the region of the plane supporting the central reaction pipes 4m. It is particularly advantageous, if not only the burner outlet directions R of the outer burners 5 are inclined, but also those of the central and inner burners, whereby the arrangement is made in such a way that the inclination increases starting from the inner burners towards the furnace wall 2; the inclination y of the inner burners is clearly lesser than the inclination P of the central burners and this again is lesser than the inclination a of the outer burners. The angle of inclination a of the outer burners lies at approx. maximum 10°, preferably 5°; the angle of inclination p and y are suitably selected lesser. The inclination of the burners 5 can be realised in different ways; on the one hand, it can be foreseen that the burners are installed altogether inclined or only their burner orifice or burner nozzle is inclined. It is particularly advantageous if the inclination of the burners 5 can be adjusted, especially also during operation; in this case a control system (not shown) can be foreseen for the synthesis furnace 1, which takes up an adjustment of the inclinations under consideration of the operation parameters of the synthesis furnace 1. By means of this extended design of the burners 5, the flame deflection of the outer burner rows towards the centre gets significantly reduced; one obtains a uniform or more uniform flow-off of the flue gas along the reaction pipes, the heat transfer gets improved and the increased material load due to "hot spots" gets clearly reduced. These advantages as compared to the state-of-the-art technology can be clearly seen in figures 2a and 2b on the one hand, and in 3a and 3b on the other hand. Fig. 2a shows a very un-uniform temperature distribution in a traditional synthesis furnace without burner inclination. As against that, an extended design according to the invention can be identified in fig. 2b, in which the outer burners or their burner outlet direction is inclined by 5° and one can see a clearly more homogeneous temperature distribution. One can see similar behaviour pattern also in the flow condition shown in figures 3a and 3b. Fig. 3a shows the flow patterns for a traditional synthesis furnace without burner inclination and fig. 3b with burner inclination, that too for an inclination by 5° in the outer burners. The undesirable dead zones (white empty surfaces) get significantly reduced in the design as per the invention. In fig. 4 the heat flow density for the outermost pipe row is plotted over the pipe length, in dashed-line for a synthesis furnace according to the state-of-the-art technology and in a continuous line for a synthesis furnace as per the invention with outer burners inclined by 5°. It can be clearly seen that the heat flow density over the pipe length is much more uniformly distributed in a synthesis furnace according to the invention. WE CLAIM: 1. Synthesis furnace (1) with a furnace chamber (3) surrounded by a furnace wall (2) all around, in which several burners (5) are arranged mainly in one plane with the burner outlet direction pointed downwards, whereby at least the outer burners (5) arranged in the region of the furnace wall (2) have a burner outlet direction (R), which is inclined from the centre of the furnace moving away towards the vertical and in which several reaction pipes (4) are arranged mainly perpendicular and parallel to one another, that are heated from outside by the firing burners (5), characterized in that the inclination of the burner outlet direction (R) of the individual burners (5) is different. 2. Synthesis furnace as claimed in claim 1, wherein the inclination of the burner outlet directions (R) of the burners (5), starting from the centre of the furnace, increases outwards towards the furnace walls (2). 3. Synthesis furnace as claimed in claim 1 or one of the following claims, wherein the angle of inclination, starting from the centre, lies between 0 to 10°, preferably between 0 to 5°. 4. Synthesis furnace as claimed in claim 1 or one of the following claims, wherein the burners (5) with inclined burner outlet direction (R) are altogether installed inclined and/or their burner orifice is arranged inclined. 5. Synthesis furnace as claimed in claim 4, wherein the inclination of the burner outlet directions (R) is adjustable. 6. Synthesis furnace as claimed in claim 5, wherein for setting the inclination a control system is foreseen that takes into account the operating parameters of the synthesis furnace. Synthesis furnace (1) with a furnace chamber (3) surrounded by a furnace wall (2) all around, in which several burners (5) are arranged mainly in one plane with the burner outlet direction pointed downwards, whereby at least the outer burners (5) arranged in the region of the furnace wall (2) have a burner outlet direction (R), which is inclined from the centre of the furnace moving away towards the vertical and in which several reaction pipes (4) are arranged mainly perpendicular and parallel to one another, that are heated from outside by the firing burners (5), characterized in that the inclination of the burner outlet direction (R) of the individual burners (5) is different. |
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Patent Number | 247515 | ||||||||
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Indian Patent Application Number | 1547/KOLNP/2006 | ||||||||
PG Journal Number | 16/2011 | ||||||||
Publication Date | 22-Apr-2011 | ||||||||
Grant Date | 13-Apr-2011 | ||||||||
Date of Filing | 06-Jun-2006 | ||||||||
Name of Patentee | UHDE GMBH | ||||||||
Applicant Address | FRIEDRICH-UHDE-STRASSE 15 44141 DORTMUND | ||||||||
Inventors:
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PCT International Classification Number | B01J8/06; C01B3/38 | ||||||||
PCT International Application Number | PCT/EP04/011442 | ||||||||
PCT International Filing date | 2004-10-13 | ||||||||
PCT Conventions:
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