Note: Descriptions are shown in the official language in which they were submitted.
WO 2011/131323 PCT/EP2011/001928
"Apparatus for supplying multiple burners with fine-grained
fuel"
The invention is directed at an apparatus for supplying multiple
burners with fine-grained fuel, of the type indicated in the
preamble of claim 1.
In the thermal conversion of solid fuels, such as, for example,
different coals, peat, hydrogenation residues, waste materials,
garbage, biomasses, and flue dust, or a mixture of the stated
substances, under elevated pressure, there is the need to bring
the substances used, which are stored under normal pressure and
ambient conditions, to the pressure level of the thermal
conversion, in order to allow conveyance into the pressurized
reactor. Possible thermal methods can be, for example,
combustion under pressure or gasification under pressure,
according to the fluidized bed method or entrained flow method.
Metering of fine-grained fuel from a storage container for
transport to the burners is a prerequisite for optimal gasifier
operation.
One possibility of metering consists in that the storage
container is fluidized, similar to a fluidized bed (EP 0 626 196
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Al/DE 41 08 048 Al). This variant has the disadvantage that for
one thing, greater amounts of gas are required for fluidization,
and, for another, the pressure at the exit in the conveying pipe
is sensitively determined by the properties of the fluidized
bed. The fluidization state and the fluidized bed height have a
direct effect on the exit pressure. If non-homogeneous, in
other words bubble-forming fluidization is involved,
pressure/density fluctuations additionally occur, which
influence the exit pressure and thereby the exit mass stream.
Another possibility of allowing solids discharge from a
container consists in providing conical run-out geometries,
taking the bulk material properties into consideration. Solids
run-out from a cone can be supported by means of adding gas by
way of or at the cone walls (US 2006/0013660, US 4,941,779),
whereby gas is supplied to the discharge cone by way of porous
elements. The amount of gas is generally smaller than the
amount that would be required for fluidization, but sufficient
to eliminate the wall friction of the bulk material and/or to
prevent local deposits leading to bridge formation. In this
connection, as described, the solid is drawn off from a bulk
material layer (DE 10 2008 012 731 Al, DE 10 2008 014 475 Al).
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By means of adding gas into the conveying line or the container
cone run-out directly at the beginning of the conveying line, an
attempt is made to adjust a solids stream density that is as
constant as possible.
The latter method is the preferred variant in the gasification
systems described, in which fine-grained fuel must be handled
both under atmospheric pressure and under high pressure. In
this connection the required gas amount is limited, in contrast
to full fluidization, and, at the same time, it is possible to
do without mechanical installations.
In the case of great systems power, a separate discharge cone is
generally provided for each burner line. In the case of great
solids withdrawal streams, the amount of gas to be supplied to
ensure discharge by way of the cone is clearly lower than the
amount of gas added to adjust the conveying density in the dense
stream, i.e. gas must be added to the solid below the cone, for
example, for further dense stream conveying. Furthermore,
additional gas is generally required in the container to
maintain the pressure.
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It is the task of the invention to reduce the required excess
gas amounts and to be able to do without separate discharge
cones per burner line, without giving up the uncoupling of the
burner lines.
This task is accomplished, according to the invention, with an
apparatus of the type indicated initially, by means of the
characterizing characteristics of claim 1.
It is evident that loosening of the fine-grained fuel to be
conveyed is positively influenced by means of the gas-permeable
wall regions of the discharge cone, whereby at the same time,
multiple solids lines that lead to the burners, in each
instance, can be charged with fuel.
Embodiments of the invention are evident from the dependent
claims. In this connection, it can particularly be provided
that the solids discharge lines in the cone are provided below
the gas-permeable wall surfaces in the direction of gravity. By
means of this measure, it is guaranteed that each of the burner
lines can be charged with correspondingly loosened fuel.
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The configuration of the cone wall can be carried out very
differently. One of the apparatuses according to the invention
consists in that the gas-permeable wall surfaces in total form
the wall surface of an element of the discharge cone shaped as a
truncated cone.
In order to guarantee better installation and, if applicable,
better replaceability if damage occurs, the invention also
provides that the discharge cone is formed from multiple
elements, connected with one another, particularly elements
shaped as truncated cones.
It has proven to be practical if, as the invention also
provides, the cone is provided with a closure bottom that is
gas-permeable at least in certain regions.
In a further embodiment, it can be provided, according to the
invention, that a double-walled element shaped as a truncated
cone is directly assigned to the storage container for the fine-
grained fuel, with a gas-permeable inner wall made of a sintered
metal, a perforated metal sheet or the like, whereby such a
design, in itself, is known for a total cone from the document
US 2006/0013660 mentioned above.
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In order to also facilitate and optimize the solids discharge,
it can also be provided, according to the invention, that the
solids discharge lines have an angle less than 90 relative to
the vertical axis of the cone, directed downward in the
direction of gravity, whereby a possibility of such a
configuration can consist in that the solids discharge lines are
positioned at a right angle to the related cone wall.
Depending on the fuel, it can be practical if an inner stirring
device is assigned to the closure bottom. Such an inner
stirring device has a number of advantages. It can serve to
support fluidization by means of mechanical loosening, can allow
uniformization of the fluidized or loosened solids density, and
can bring about a reduction in the bubbles that can occur in the
case of fluid gas feed.
In a further embodiment, it is provided, according to the
invention, that the closure bottom and/or the lower region of
the discharge cone, in the direction of gravity, is provided
with media feed lines, particularly for loosening the solid in
the cone interior. With this embodiment, it is possible to also
meter additives into the actual fuel, for example substances
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that influence the ash melt behavior, for example mineral,
organic substances, but also ashes, slag or the like, whereby
the slag can be recirculated.
Further details, characteristics, and advantages of the
invention are evident on the basis of the following description
and using the drawing. This shows, in
Fig. 1 a fundamental sectional representation through a
discharge cone according to the invention,
Fig. 2 and 3 top views, according to Arrow II/III in Fig. 1,
of two embodiment variants of the discharge cone,
and in
Fig. 4 and 5 in the representation of Fig. 1, two variants of
the discharge cone configuration.
The discharge cone 1 shown in Fig. 1 is divided into segments,
which is advantageous from the aspect of production technology,
and consists of an inner cone 2 that forms the fluidization
region, the solids discharge region 3, and the cone bottom 4.
The discharge cone can also be structured, according to the
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invention, as a component (not shown here) that has the
properties according to the invention.
The fluidization region is formed by a pressure-resistant outer
mantle 5, the inner cone 2 that lies within it, the fluidization
means feed 7, and the two connection flanges 8a and 8b.
The discharge cone 1 is connected with a solids container, not
shown in the figures, by way of the connection flange 8a. The
wall of the inner cone 2 is structured as a permeable wall
region 6 for the fluidization means, and the opening angle
relative to the vertical or to the direction of gravity (arrow
"g") is described by the angle al.
The fluidization means (arrow 9) that flows through the
fluidization means feed 7 distributes itself in the fluidization
means distribution space 10 formed between the outer mantle 5
and the inner cone 2. From there, it flows through
correspondingly gas-permeable regions of the inner cone 2. The
solid (arrow 11) that enters into the discharge cone 1 from
above, with gravity, is loosened at the inner cone 6 by the
supplied fluidization means and flows into the solids discharge
region 3 that follows below the fluidization means region 2.
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The solids discharge region 3 consists of the two connection
flanges 12 and 13, the cone wall 14 with the opening angle a2
relative to the vertical, and the solids discharge lines 15.
The solids discharge region 3 is connected with the discharge
flange 8b of the fluidization region of the discharge cone 1 by
way of the connection flange 12. The loosened solid enters into
the solids discharge region 3 and is drawn off by way of the two
solids discharge lines 15 shown in this exemplary embodiment of
Fig. 1.
The opening angles al and a2 of the cone walls, in each instance,
can be of different sizes, for example in order to vary the
construction height of the discharge cone 1.
The solids discharge region 3 is connected with the connection
flange 16 of the cone bottom 4 by way of the connection flange
13. The cone bottom 4 possesses an additional fluidization
means feed 17. The fluidization means (arrow 9a) can be
introduced into the solids discharge region 3 by means of a gas
distribution apparatus 18 of the cone bottom 4. The gas
distribution apparatus 18 is advantageously represented, in Fig.
1, as a centrally disposed nozzle, whereby bridges or blockages
= 5
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are loosened up and the density of the gas/solid mixture to be
conveyed can be adjusted to the desired range.
The gas distribution apparatus 18 can also be configured, for
example, as one or more porous elements in the bottom, as a
perforated distributor, or as a multiple nozzle arrangement.
Which of the variants is to be used is decisively determined, in
an individual case, by the bulk material properties of the solid
to be conveyed.
Fig. 2 shows a schematic top view of an exemplary embodiment of
the invention, with three exits for the solids discharge lines
15, the gas distribution apparatus 18 disposed centrally in the
bottom, and the inner cone 6, which is configured entirely from
a material that is permeable for the fluidization means, in this
example. The discharge cone 1 is fixed in place on the
container run-out by way of screw connections, by way of the
connection flange 8a.
Fig. 3, just like Fig. 2, shows a schematic top view of an
exemplary embodiment of the invention, with the difference that
the inner cone 6' is equipped only in certain segments with
material that is permeable for the fluidization means. If the
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bulk material properties of the material to be conveyed permit
this, the amount of gas to be supplied by means of the reduced
permeable surface can be further reduced.
In an advantageous embodiment, the non-permeable regions of the
inner cone 6 are produced from steel or stainless steel, and
connected with the permeable surfaces, which consist of sintered
metal, by means of welds, for example. In this connection, the
fluidization regions disposed in segments are preferably
disposed directly above the outlets of the solids discharge
lines 15, in order to guarantee stable solids feed.
Furthermore, in this advantageous arrangement, a fluidized
region lies opposite a non-fluidized region, in each instance,
so that the risk of blockage due to bridge formation can be
minimized. In this way, by means of configuring segments of the
inner cone 6 from material not permeable for fluidization means,
the gas consumption can be further reduced, without endangering
the discharge.
In Fig. 4 and 5, two variants of the apparatus according to the
invention are shown, whereby the functionally equivalent
elements bear the same reference numbers.
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In a modification of the exemplary embodiment according to Fig.
1 to 3, Fig. 4 additionally shows a stirrer 19 in the solids
discharge region 3', the drive shaft 20 of which is passed
through a flange bottom 22, which is fixed in place on the
flange 13, by way of a shaft seal 21. In addition, gas feeds 23
are provided, which can be equipped with a nozzle 24, for
example, in order to guarantee optimal gas distribution.
However, this nozzle can also be structured by way of an open
pipe as a typical fluidized bed bell nozzle, or as a porous
material.
In Fig. 5, a variant is shown in which an additive can be
metered in, for example, for which purpose the solids discharge
region 3 is provided with a solids feed connector 25. The
solids feed is indicated by an arrow 26. The feed of the solid
can be promoted if the feed is disposed, as shown in Fig. 5, in
the region of the stirrer 19.
Of course, the exemplary embodiments of the invention as
described can still be modified in many different aspects,
without departing from the basic idea. For example, not only
the solids discharge lines 15 but also the solids introduction
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line 25 can be positioned at different locations and in
different numbers; depending on the design, the gas feed
connectors can also be configured to be double-walled, in order
to supply solids centrally and gases on the outer wall side, and
more of the like.
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Reference Symbol List:
1 discharge cone
2 fluidization region
3 solids discharge region
4 cone bottom
outer mantle
6, 6' gas-permeable wall region (inner cone)
7 fluidization means feed
8a, 8b connection flange
9, 9a arrow
fluidization means distribution space
11 arrow
12 connection flange
13 connection flange
14 cone wall
solids discharge line
16 connection flange
17 fluidization means feed
18 gas distribution apparatus
19 stirrer
distribution shaft
21 shaft seal
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22 closure bottom
23 gas feed
24 nozzle
25 solids feed line
26 arrow
"g" direction of gravity
