PROCESS AND PLANT FOR THE COMBUSTION OF SULFUR TO SULFUR DIOXIDE

Abstract

A reactor for the combustion of sulfur includes reactor walls which form a symmetrical base area b, whereby at least two burners are mounted each with a burner holding device. All burner holding devices have the same distance to each other and each burner holding device has the same distance to the a center point z of the base area b. At least one burner holding device is arranged such that during operation the flame of said burner shows an angle α between 0 and 45° to a center axis a, which is defined as the shortest connection between this burner holding device and the center point z.

Claims

1.-9. (canceled)

10. A reactor for the combustion of sulfur comprising reactor walls which form a symmetrical base area b, and at least two burners each having a burner holding device, whereby the burner holding devices are equidistant with respect to each other and each burner holding device has the same distance to a center point z of the symmetrical base area b, wherein at least one burner holding device is arranged such that during operation the flame of the burner corresponding to the at least one burner holding device comprises an angle α between 0 and 45° to a center axis a, which is defined as a shortest connection between the at least one burner holding device and the center point z.

11. The reactor according to claim 10, wherein the base area b has a square or a circular shape.

12. The reactor according to claim 10, wherein the base area b has the shape of a polygon with at least six sides and the number of sides is a multiple of the number of burners.

13. The reactor according to claim 10, comprising at least three burners.

14. The reactor according to claim 10, wherein the reactor further comprises a first zone wherein heat is transferred via radiation and a second zone wherein heat is transferred via convection at a waste heat boiler.

15. The reactor according to claim 10, wherein the walls comprise membrane walls.

16. The reactor according to claim 10, wherein the reactor comprises two heat exchangers and wherein between the two heat exchangers additional oxygen is introduced or additional burners are positioned.

17. The reactor according to claim 10, further comprising at least one control unit which, on the basis of measured temperatures, adjusts the burner holding device within the angle α in such a way that the heat profile is as homogeneous as possible, this adjustment being carried out on the basis of a stored experimentally determined matrix.

18. A process for the combustion of sulfur, comprising combusting sulfur in at least two burners that are mounted on walls of a combustion chamber, which describes a symmetrical ground plan and wherein the distance between each burner is identical, wherein at least one burner is arranged with respect to its flame direction such that it has an angle α to the axis a of the shortest connection between burner holding device and center point z of a base area b defined by the walls of the combustion chamber.

Description

[0044] The drawings show schematically:

[0045] FIG. 1a shows schematically a first industrially proven arrangement for sulfur combustion, comprising a brick-lined vertical combustion chamber (4) connected to the waste heat boiler located at the top of the combustion chamber,

[0046] FIG. 1b shows schematically a second traditional, popular and industrially proven arrangement for sulfur combustion, comprising a horizontal brick-lined combustion chamber (4), laterally connected to the waste heat boiler (6).

[0047] FIG. 1c shows schematically a third traditional and industrially proven arrangement for sulfur combustion, comprising 2 or more horizontal brick-lined combustion chambers (4) and a single central vertical brick-lined collection chamber (4′) connected to the waste heat boiler (6),

[0048] FIG. 2a shows schematically a first embodiment for sulfur combustion with a burner arrangement according to the invention, without separate combustion chamber, whereas the oxygen supply for the combustion of the sulphur can be either air or oxygen enriched air,

[0049] FIG. 2b shows schematically a second embodiment for sulfur combustion with a burner arrangement according to the invention, without separate combustion chamber, whereas either oxygen enriched air or pure oxygen is used, so that with this arrangement and by recirculation of gas cooled at the waste heat boiler (6) and subsequent further cooling in a heat exchanger e.g. an economizer (11), a very high SO.sub.2 concentration of the gas can be achieved, up to 100%-vol.,

[0050] FIG. 2c shows schematically a third embodiment for sulfur combustion, with a burner arrangement according to the invention, without separate combustion chamber, enabling the sulphur combustion to be substoichiometric with regard to oxygen and hence resulting low NOx generation, whereby non-oxidized S.sub.2-gas containing combustion product is cooled at the waste heat boiler (6) to typically 550° C., prior to addition of an appropriate amount of oxygen (air or enriched air) for completion of the oxidation of the residual S.sub.2-gas, followed by an additional heat exchanger, e.g. boiler element.

[0051] FIG. 2d shows schematically a fifth embodiment for sulfur combustion, with a burner arrangement according to the invention, without separate combustion chamber, whereas the sulphur burners (2, 2″) are arranged for a 2-stage combustion with intermediate cooling of the first (lower) combustion gas by a waste heat boiler (6) and final cooling (15) of the gas following the second (upper) sulphur combustion. Again, oxygen supply can be via air or oxygen enriched air.

[0052] FIG. 3 shows schematically the burner arrangement according to the invention, in this instance arranged at a cylindrical reactor shape.

[0053] FIG. 1a shows a possible design of a reactor for sulfur combustion. Liquid sulfur is introduced into the burner 2 via lines 1, 1′. An oxygen-like gas, often air, is fed into the burners 2 via lines 3, 3′. This sulfur is burnt in a vertical combustion chamber 4, which has a brick lining of 5.

[0054] The resulting heat is then conducted in a heat exchanger 6. The resulting sulfur dioxide is discharged with a line 7.

[0055] FIG. 1b essentially corresponds to this design, whereby the horizontal combustion chamber 4 is arranged here lateral to the waste heat boiler heat exchanger 6.

[0056] FIG. 1c shows an arrangement with a central vertical collection chamber 4′ and two horizontal combustion chambers 4 arranged symmetrically to it, followed by the waste heat boiler 6.

[0057] Contrary to the above, subject of this invention is the omission of a separate sulfur combustion furnace or chamber, while the burner(s) are directly firing into the lower empty part of the membrane wall water tube boiler. Said empty lower part of the waste heat boiler being the radiation chamber (high temperature), whereas the upper part of the boiler contains the convection part.

[0058] FIG. 2a shows a somehow more complex structure that can only be achieved by adjusting the burners 2 in accordance with the invention. Again, sulfur is fed to the burners 2 via line 1, 1′ and air or oxygen enriched air via line 3, 3′.

[0059] The decisive factor is that no brick-lined combustion chamber 4 can be found here, but the burners 2 are arranged in the same housing as the waste heat boiler and its associated heat exchangers.

[0060] This design essentially corresponds to that of FIG. 2b, where parts of the resulting sulfur dioxide are first fed via line 7 and line 10 to a heat exchanger 11 and then to a compressor 12, before they are recirculated via line 16 in lines 3′ and 3′. Such a recirculation of cooled gas can be used in order to achieve even higher SO.sub.2 concentrations, up to 100%-vol.

[0061] FIG. 2c shows a structure in which air or oxygen-enriched air is introduced into the system via lines 13 and 14 above the first heat exchanger 6, which then completes the combustion. A second heat exchanger 15 is located above this said gas/air input. Said 2-stage combustion is therefore proposed, arranged in the same full-length membrane casing. Sub-stoichiometric combustion with oxygen deficiency does apply to the lower sulfur burner(s) 2, resulting in SO.sub.2 containing gas which also contains gaseous un-burned sulfur S.sub.2 which is typically cooled down to 550 to 700° C. at the heat exchanger 6, prior to the addition of the said air/oxygen enriched air. By addition of the said air, the said S.sub.2 gas is subsequently fully oxidized to SO.sub.2. So, not only the combustion temperature at the first combustion stage be kept comparatively low, but the formation of NOx is also prevented/reduced due to the limited oxygen content.

[0062] FIG. 2d alternatively shows the arrangement of two further burners 2″ and corresponding sulfur supply lines 1″. Thus, both combustion temperatures, i.e. first and second stage can be kept at a lower level and both, low NOx figures can be achieved as well as higher SO.sub.2 concentrations of the total combustion gas.

[0063] FIG. 3 shows a burner arrangement according to the invention. The burner walls 23 form a base area with a center point z. The burner holding devices 22 are mounted on the wall(s) 23, whereby each burner 22 is mounted at the same distance from all other burners 22.

[0064] The central axis a is defined as the shortest connection from a burner mounting device 22 to the center point z. At least one of the burner holding device 22 is arranged such that the burner flame describes an angle α to the axis during operation.

[0065] At least parts of the reactor wall(s) 23 is/are equipped with tubes 25 as membrane wall 24.

[0066] This arrangement causes the entire combustion air and combustion gas to move/swirl in a circle, thus improving the mixing of the gas and uniformity of the flow when entering the downstream convection part. As a result, heat transfer in an area next to the burners 2 is dominated by radiation while above/downstream said radiation area a convection zone is established.

[0067] The angle of obliquity a can vary from zero or a few degrees to a substantial figure, e.g. 15°. Obviously, this concept can be applied to all other shapes of membrane walls.

[0068] List of Reference Numerals

[0069] 1, 1′, 1″ line

[0070] 2, 2′, 2′″ burner

[0071] 3, 3′, 3″, 3′″ line

[0072] 4, 4′ combustion chamber

[0073] 5 burner

[0074] 6 heat exchanger

[0075] 7 line

[0076] 9, 10 line

[0077] 11 heat exchanger

[0078] 12 compressor

[0079] 13, 14 line

[0080] 15 heat exchanger

[0081] 16 line

[0082] 22, 22′ burner holding device

[0083] 23 reactor wall

[0084] 24 membrane wall

[0085] 25 tubes

[0086] a center line

[0087] b base area

[0088] z center point

[0089] α angle