|
(11) | EP 1 493 967 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||
| (54) | Incineration system and bluff body therefor |
| (57) The invention concerns an incineration system, e.g. for the combustion of waste and
to collect incineration heat therefrom for the production of e.g. steam or heat. This
system has a bluff body (14) containing a longitudinally extending supply channel
for injection of a fluid, such as a gas or liquid, into the flue gases in e.g. the
combustion chamber or post-combustion chamber through mutually spaced nozzles. Said
supply channel is subdivided into two or more subchannels (16). Preferably, a said
sub-channel (16) debouches at another zone to obtain differences in fluid injection
from said bluff body in its circumeferential and/or longitudinal direction. |
[0001] This invention relates to an incineration system, e.g. for the combustion of waste and to collect incineration heat therefrom for the production of e.g. steam or heat. It also relates to a bluff body (also called nozzle bar) for use in such incineration system.
[0002] From the patent literature several incineration systems are known with a built-in bluff body. Exampes are disclosed in EP-A-0286077 (Temelli); DE-A-3038875 (Temelli); DE-A-4401821 (Kummel), the disclosure of which is inserted here by reference. Generally, a bluff body is installed near the combustion chamber exit and the post-combustion chamber connecting thereto and is used to subdivide and cool the flow of flue gases and inject a process gas, such as secundary air. By this, the combustion is optimised towards e.g. efficiency or complete combustion.
[0003] The object of this invention is to further develop the known incineration system, particularly its bluff body. The advantages of this invention are versatile and concern e.g. one or more of the following improvements: efficiency, durability, maintainability, ease of construction, efficiency, complete combustion, reliability, manufacture, retrofit.
SUBDIVISION INTERNAL SPACE
[0004] In one aspect the invention relates to a bluff body containing a longitudinally extending supply channel for injection of a fluid, such as a gas or liquid, into the flue gases in e.g. the combustion chamber or post-combustion chamber through mutually spaced nozzles of said bluff body, wherein said supply channel is subdivided into two or more co-extending, mutually separated sub-channels, each debouching at another zone of the external surface of the bluff body to obtain differences in fluid injection from said bluff body in its circumeferential and/or longitudinal direction, wherein said sub-channels are non-concentric or the one sub-channel is present outside the other sub-channel. Each sub-channel can separately be controlled.
EXTERNAL SHAPE
[0005] In another aspect the invention relates to a bluff body having a cross-sectional shape such that in its mounted position, it has an almost constant width over a substantial part of its height, while it is substantially symmetrical relative to a horizontal axis.
EXAMPLES
[0006] The invention is further illustrated by non-limiting embodiments, shown in the annexed drawing, showing in:
Fig. 1 a cross sectional view of a part of a waste incinerator;
Fig. 2 a cross sectional view of a bluff body;
Fig. 3 a perspective, cut away view of another bluff body;
Fig. 4 a cross sectional view of several designs of the bluff body.
[0007] Fig. 1 shows an incinerator containing a bluff body 14, which is located above the fire grate 10 from below which primary air (arrow A) and from the left of which waste (arrow B) is supplied. Flue gases flow upwards (arrow C), the heat of which is taken up by steam pipes in the front and back walls 11 of the plant. The bluff body 14 is positioned such that it influences the incineration process in the combustion zone 12 or post-combustion zone 13 by its position, shape and/or injection of fluid jets 8. The bluff body 14 offers a more or less streamlined object inside the upward flow of flue gases. Further details of the incinerator or the bluff body 14 in general can be obtained from e.g. any of the above cited patent publications.
[0008] It should be appreciated, that generally the incinerator contains a combustion zone 12 with a grate 10 and with a waste supply (arrow B) disposed above said grate and with a flue gas exhaust (arrow C). Between the combustion zone and the flue gas exhaust there is an approximately horizontal connection opening 17 with a cross-section of flow approximately symmetrical relative to the axis of the exhaust C and provided between the combustion zone 12 and the flue gas exhaust C above the merge point of the waste supply B. The bluff body 14 is disposed inside said connection opening 17 such that the bluff body 14 extends transversely to the direction of flue gas flow.
[0009] In the incinerator according to fig. 1, a post-combustion zone is present directly downstream of the connection opening 17 and the bluff body 14. Different from earlier embodiments, this post-combustion zone is NOT Venturi tube-like, however such embodiment of the post-combustion zone also belongs to the invention.
[0011] Fig. 2 shows the bluff body 14 more in detail. As known as such, it is a hollow elongated body, extending in widthwise direction of the incinerator (direction normal to the plane of the paper of fig. 2) and delimited by membrane walls 1 provided by cooling tubes through which water is circulated from headers 15 connected to the natural circulation system 9 of the boiler. This cooling function, cool the flue gases in the combustion and/or post-combustion zone and the improvement of the combustion process, is also minimizing the fouling of the boiler heat surfaces.
[0012] As fig. 2 shows, the inner space of the bluff body 14 is subdivided into four segments 16 by separation panels 2, 4, yielding four separated sub channels 16 extending in the longitudinal direction of the bluff body 14. The panels 2, 4 have a simple connection 5, 6, mutually and to the membrane walls 1, such that these panels can easily be disassembled for e.g. repair or to get human access to the internal space of the bluff body 14. The connection 5, 6 can e.g. be provided by guide rails in which the edges of the panels 2, 4 are inserted and then fixedly bolted.
[0013] Through known as such openings or nozzles (not shown) in the membrane walls 1, fluid from the sub channels 16 can be injected as the fluid jets 8. These fluid jets can have any desired orientation (e.g. upward or downward). Preferably, the jets 8 at one level provide a more or less gap-free grating.
[0014] In fig. 3 a bluff body 14 is subdivided into six segments 16, wherein only a part of the membrane walls 1 are shown. By designing the sub channels 16 at the lowest level shortened as shown, it is possible to design three different injection zones with mutually in-line fluid jets 8 along the length of the bluff body 14 if fluid is supplied 7 from both longitudinal ends. In this embodiment the sub channels 16 at central level expand in the area where the sub channels 16 at lowest level are absent. The sub channels 16 can be connected to supply means such that individual supply with fluid for all or part of the sub channels 16 is possible.
[0015] Fig. 4 shows different arrangements of the partition walls 2-4, such that e.g. ten or even more sub channels 16 can easily be obtained. In stead of being plane as shown, the partition walls 2-4 can also be non-plane.
[0016] In an alternative, one or more of the sub channels 16 can be used for purposes different from guiding a fluid flow.
[0017] Installing two or more bluff bodies next to each other is possible, to e.g. further improve the incineration process. With the sub channels 16, different fluid types can separately and individually controlled added.
[0018] It is for this invention not required that each sub channel 16 is designed to provide fluid jets 8 or that the different injection zones are in line along the lenght of the bluff body or that fluid jets at a specific level and/or direction are injected along the complete length of the bluff body. E.g. the sub channels 16 at the upper level in fig. 3 can be used to inject fluid jets 8 (not shown) at that particular level along the complete length or part of the length of the bluff body.
[0019] The external cross-sectional shape of the bluff body 14 differs from the prior art. It can generally be defined as having parallel side walls and being symmetrical both in a horizontal and vertical sense, thus being double symmetrical. It is also within the field of this invention, if the side walls are outwardly bulged.
PRISMA COOLING CIRCUIT
[0020] Alternatively, by way of further improvement, it is proposed to design the water supply of the membrane walls 1 of the bluff body 14 different from the prior art. According to the prior art (viz. fig. 5 which schematically shows the prior art water circulation system of the boiler with the steam drum 20 and (for reasons of clarity) only one boiler side wall 19 and one boiler front or back wall 11), the membrane walls 1 are a part of the water/steam circulation system of the cooled boiler side walls 19 of the plant. This situation can be illustrated by fig. 2, showing a lower and upper pipe stud 9, mutually in line. These pipes are part of a vertical boiler side wall 19 containing a plurality of parallel, upward extending such pipes to delimit the combustion chamber. Such wall 19 is typically prefabricated and to connect the membrane wall 1 to the circulation system of the wall 19, the pipe part 9', integrally extending between the upper and lower pipe studs 9, is removed from one or several adjacent pipes and the remaining studs 9 are sealed with sealing caps 18 and connected to the membrane wall 1 as fig. 2 shows, such that the water/steam flows according to the full and dashed lines. Thus the supply and exhaust pipes connecting to the headers or manifolds 15 are directly heated by the incinerating process.
[0021] Now (viz. fig. 6 providing a similar view as fig. 5) it is proposed for the first time to arrange that the fluid inlet and outlet of the membrane wall 1 of the bluff body 14 is not connected to a relevant pipe 9 of a boiler side wall 19 (and also not connected to a relevant pipe 9 of a boiler front or back wall 11), such that it is not part of the circulation system of the wall 11. In stead, the membrane wall 1 is connected to supply 21 and exhaust tubes 22 separate from the pipes of the wall 19. Indeed, as fig. 6 shows, these tubes belong to the water circulation system of the boiler, such that the heat taken up from the membrane wall 1 will be removed from the fluid circulating within these tubes, brought externally from the zone directly heated by the incinerating process within the combustion chamber and related chambers, e.g. the post combustion and flue exhaust. As a sub circuit separated from the sub circuits of the boiler walls 11, 19, it is directly connected to the common steam drum 20 of the boiler system. In this manner the fluid capacity can be optimised for the membrane wall 1, separate from walls 11, 19.
[0022] Preferably, the connection of the membrane wall 1 to the separate fluid circuit takes place by providing that the manifolds 15 extend through the opposite side walls 19 of the plant such that the supply (lower manifold 15) and exhaust (upper manifold 15) is possible from both longitudinal ends of the bluff body, and the tubes 21, 22 connecting to these manifolds 15 are outside the heated walls and so are protected against direct heating by the incinerating process.
[0023] The invention also covers embodiments based on one or more features from a disclosed embodiment in isolation or combined with one or more features of another disclosed embodiment. The subject matter of claims 4-8 is also applicable to a general bluff body and is not restricted to the bluff body with sub divided supply channel.
1. An incineration system, e.g. to collect incineration heat, has a bluff body (14) with
a longitudinally extending supply channel for injection of a fluid, into the flue
gases in e.g. the combustion chamber or post-combustion chamber through mutually spaced
nozzles, which supply channel is subdivided into two or more sub-channels (16).
2. A system according to claim 1, wherein a said sub-channel (16) debouches at another
zone to obtain differences in fluid injection from said bluff body in its circumeferential
and/or longitudinal direction.
3. A system according to claim 1 or 2, wherein said sub-channels are non-concentric or
the one sub-channel is present outside the other sub-channel.
4. A system according to claim 1, 2 or 3, said bluff body has a sectional shape with
substantially parallel walls, e.g. it has an almost constant width over a substantial
part of its height, while it is substantially symmetrical relative to a horizontal
axis, preferably being substantially symmetrical both in a horizontal and vertical
sense.
5. A system according to any of claims 1-4, having a post-combustion zone NOT Venturi
tube-like.
6. A system according to any of claims 1-5, with separation panels (2, 4), providing
simply mounted (5, 6) sub channels (16), e.g. by guide rails in which the edges of
the panels 2, 4 are inserted.
7. A system according to any of the preceeding claims, with the membrane wall (1) connected
to tubes (21, 22) separate from the pipes of the wall (19), e.g. as a sub circuit
separated from the sub circuits of the boiler walls (11, 19) and directly connected
to the common steam drum (20) of the boiler system.
8. A system according to any of the preceeding claims, and the manifolds (15) extend
through the opposite side walls (19) of the plant such that the supply and exhaust
is possible from both longitudinal ends of the bluff body, and the tubes (21, 22)
connecting to these manifolds (15) are outside the heated walls.