Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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"Method and device for ignition and for operation of burners in
the gasification of fuels that contain carbon"
The invention is directed at a method for ignition and for
operation of burners in the gasification of fuels that contain
carbon, using at least two gasification burners.
Such a method of procedure, in which multiple dust burners are
ignited by a pilot burner, is shown by DE 10 2005 048 488 Al.
Other methods of procedure for ignition use so-called ignition
lances, for example, as is shown by DE 32 27 155 Al, whereby
passing such movable ignition aids through the firebox walls
brings additional effort with it, and this leads to making such
devices more expensive. Other examples are shown by EP 0 347
002 Bl, EP 0 511 479 Al, US 408,628, US 5,273,212, DD 231 962 A,
or DD 241 457 A.
With regard to the state of the art, reference is furthermore
made to DE 196 41 843 Al, DE 195 29 994 C2, DE 100 24003 Al, DE
100 19 198 Al, DE 734 927 A, EP 0 095 103 El, WO 2008/055829 Al,
or AT 286 072 B.
A disadvantage of the known methods of procedure consists, among
other things, in that the pilot burners or ignition burners
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continue to be kept in operation, and in this connection require
a permanent through-flow of gas and oxygen or air, in order to
prevent them from becoming plugged up by slag or the like. In
this connection, it is particularly problematic to keep
corresponding exit openings on the gasifier wall open at high
slag flow. As has just been mentioned, the use of movable
ignition lances is cost-intensive and problematic for other
reasons. In this connection, access channels for gasification
must be checked before introduction of the ignition burner, and
usually cleaned, seals must be replaced, and more of the like,
whereby this work must be carried out in the pressure-free
state.
If this work must be carried out, the gasifier and the
subsequent gas treatment, including H2S and COS removal, must
first be relaxed and made inert, whereby the fuel gases diluted
with inert gas are usually burned off by way of a flare. After
ignition of the ignition burner, the pressure then has to be
raised slowly, for example 0.5 bar/min, and the inert gas must
be displaced by the gas produced in the gasifier, whereby once
again, the displaced gas, which is mixed with fuel gas, must be
burned off in the flare. This method of procedure is not only
time-consuming, but rather also has a high ignition fuel
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consumption with correspondingly high emission values caused by
the flare.
This is where the invention takes its start, whose task consists
in allowing start of the pressure gasification with short start
times at high pressures, without prior inertization of the gas
space, while avoiding continuous fuel gas consumption in the
pilot burner or ignition burner, whereby in the case of
stationary ignition burners, these are also protected against
contamination.
This t314: maybe accomplished, according to the invention, with a
method of procedure of the type indicated initially, in that one
of the gasification burners is configured as a start-up burner,
for the ignition of which at least one pilot burner serves,
which is ignited by way of an electrical ignition device,
whereby a combustible gas mixture composed of a fuel gas and gas
that contains oxygen is ignited by the pilot burner, in the
start-up burner, whereby after ignition of the start-up burner,
at least one further gasification burner is ignited by this
burner, and the start-up burner is operated further as one of
the gasification burners of the fuel that contains carbon, by
means of a change in medium.
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By means of this ignition, which takes place in the manner of a
cascade, a number of advantages may be achieved, which
particularly make it possible for ignition at high pressure to
be possible, and to eliminate a movable or displaceable
ignition device. In this way, the need to clean the access
channel of the displaceable ignition burner before every start
and to renew the seal of the corresponding channel may be
eliminated. This method of procedure, according to the
invention, may make it possible for a plurality of gasification
burners to be operated as start-up burners, with the use of a
pilot burner during start-up.
A fast pressure increase before ignition of the gasification
burner may be possible without inertization of the gas space,
and emissions during flare burn-off during shut-down and start-
up may be eliminated, to name only a few advantages.
According to one embodiment of the present invention, there is
provided a method for ignition and for operation of burners in
gasification of a fuel that contains carbon, using at least two
gasification burners, wherein: one of the gasification burners
is configured as a start-up burner, for the ignition of which
at least one pilot burner serves, which is ignited by way of an
electrical ignition device, whereby a combustible gas mixture
composed of a fuel gas and gas that contains oxygen is ignited
by the pilot burner, in the start-up burner, whereby after
ignition of the start-up burner, at least one further
gasification burner is ignited by this burner, and the start-up
burner is operated further as one of the gasification burners
of the fuel that contains carbon, by means of a change in
medium.
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According to another embodiment of the present invention, there
is provided a device for carrying out the method above, wherein
a pilot burner is positioned in a center of a gasification
burner and is equipped with a centric nozzle head, which is
surrounded by a burner pipe, which projects beyond a nozzle
head in the flow direction of the fuel gas, whereby at least
one electrical ignition device is provided within the burner
pipe space, wherein a reduction in cross-section of the burner
pipe is provided behind the ignition device in the flow
direction and at least one optical flame monitoring element is
assigned to the burner pipe.
In some embodiments, individual pilot burners can be ignited,
thereby making it possible to use the combustible mixture
produced by the corresponding gasification burners and the
flame formed from it to subsequently ignite the gas/oxygen
mixture
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from other gasification burners. In this connection, the power
and stability of the ignition flames are increased. These can
then ignite further carbon burners, whereby the regulation and
monitoring concept of the start routine is greatly simplified.
A further embodiment of the method of procedure according to the
invention consists in that the pilot burner, after ignition of
the start-up burner, additionally has a gas mixture applied to
it that contains CO2 and/or steam and/or oxygen, if applicable
also inert gas, in order to prevent it from clogging, so that
the pilot burner is fully integrated into the gasification
system.
It is also advantageous if the pilot burner is first ignited at
=
less than 50% of the power of the gasification burner that is
operated as a gas burner, and at an oxygen excess number of 0.8
to 1.2, whereby it can also be provided that to accelerate the
ignition of the mixture that contains oxygen, in the gasifier,
the pilot burner has a fuel excess/oxygen excess number < 0.8
applied to it.
An aid in ignition of the gasifier consists in monitoring the
ignition flame of the pilot burner, whereby the flame is
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monitored in such a manner that the ignition element of the
pilot burner is shut off when the flame is recognized.
If the flame is monitored using an ionization flame monitor, the
ignition element of the pilot burner can be used as a
corresponding electrode, as one embodiment of the invention also provides.
According to one enbooliment of the invention, an optical flare mnitorcanbe
used, or the change in the electrical resistance of the ignition
element can be used to recognize the flame.
In one embodiment, the task fornalated above is accomplished with a device, in
that
the pilot burner is equipped with a centric nozzle head, which
is surrounded by a burner pipe, which projects beyond the nozzle
head in the flow direction of the fuel gas, whereby at least one
electrical ignition device is provided within the burner pipe
space, and a reduction in cross-section of the burner pipe is
provided in the flow direction behind it.
With this embodiment, it is possible to use an electrically
heated ceramic glow element, for example. The reduction in
cross-section in the burner pipe ensures a production of spin in
the nozzle region, so that hot gas is passed back into the
surroundings of the nozzle orifice, and the colder mixture of
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freshly supplied gases is ignited, and, in addition, a higher
turbulence level can be set in order to bring about simple
ignition. In this way, the flame can be stabilized by means of
the corresponding constrictions.
As was already mentioned further above, it is important to
monitor the nem of the pilot burner, whereby according to one embodiment of
the
invention, at least one flame monitoring element is assigned to
the burner pipe, for example an optical flame monitoring device
with a fiberglass line to a corresponding electronic component.
As will be described further below, the burner according to one embodiment of
the
invention has ring-shaped channels, whereby gas that contains
oxygen is fed in through the first ring-shaped channel of the
start-up burner, both during the ignition process and during
normal operation, in such a manner that the orifice of the pilot
burner is surrounded by a clean gas. If the pilot burner has a
gas mixture applied to it after ignition, in order to prevent it
from becoming clogged, this has the advantage that the fuel
excess can react with the oxygen from the first ring channel.
Further characteristics, details, and advantages of embodiments of the
invention are evident from the following description and using
the drawing. This shows, in
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Fig. 1 a section through a pilot burner according to one embodiment of
the
invention, in a simplified representation,
Fig. 2 a top view of the pilot burner according to the arrow
II in Fig. 1, and in
Fig. 3 a gasification burner with a centrally integrated
pilot burner.
The device for ignition and for operation of burners in the
gasification of fuels that contain carbon, designated in general
with 1, is essentially formed by a pilot burner, represented
schematically and in simplified manner in Fig. 1, and designated
with 2, which burner has a fuel gas nozzle 3 to which the
corresponding fuel gas is supplied at 4, whereby the fuel gas
nozzle 3 is equipped with an air feed 5 that surrounds the fuel
gas nozzle 3 concentrically. In the flow direction of an
ignition flame, not shown in the figures, the nozzle head
designated with 6 is surrounded by a burner pipe 7.
As can be seen in Fig. 1, an electrical ignition element, for
example a glow element 9, which is connected with a
corresponding power source by way of an electrical line 10, for
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igniting the fuel gas/air mixture, projects into the pipe space
8 formed by the burner pipe 7. In order to produce stable
flames and optimal burner behavior, a constriction, indicated in
general with 11, projects into the space formed by the burner
pipe 7, in the orientation of the flame that is formed, in order
to thereby bring about swirling or circulation of the gas, as
indicated with an oval circle 12 in Fig. 1, with a broken line.
The pilot burner 2 is preferably situated in the central channel
of the gasification burner, and is thereby protected from dirt
by means of the gas that flows out through the inner ring
channel. In addition, the central pilot burner channel can be
flushed by means of a gas.
In addition, as is evident from Fig. 2, an optical flame
monitoring element 13 can also be provided on the burner head 6,
which element is surrounded by a protective pipe 14. In this
connection, the sudden constriction 11 is not shown separately
in Fig. 2, so that the elements 5 and 13 can be shown.
From Fig. 3, it is evident that the pilot burner 2 can represent
an integral component of a gasification burner, indicated in
general with 15, whereby the individual ring spaces and feed
spaces of the gasification burner are reproduced in simplified
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manner here. This gasification burner 15 can be operated as a
start-up burner, as has been described above.
In Fig. 3, the ring space or ring channel for primary oxygen is
indicated with 16; 17 indicates the ring channel for the fuel,
for example a gas or a dust suspension, 18 designates the ring
channel for the secondary oxygen, and 19 designates the ring
channel for inert or low-oxygen gas, for example N2, CO2, steam,
or steam + 02. Finally, in Fig. 3, 20 also designates the outer
pipe of the gasification burner, 21 designates the orifice of
the gasification burner, and 22 designates the orifice of the
pilot burner.
Example for an advantageous media change in the pilot burner and
the adjacent channels of the gasification burner.
Channel Ignition Normal operation
process
4 Fuel gas No gas or a gasification medium or an
inert gas
Gas that - No gas, if the burner is directed
contains downward, for example
oxygen - advantageously, a gasification medium
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that contains either 02 and/or 002 or
steam
- or a fuel gas that was supposed to be
broken down in the gasifier
16 Gas that Gas that contains oxygen
contains
oxygen
17 Fuel gas Pneumatically conveyed fuel
18 Gas that Gas that contains oxygen
contains
oxygen
There is also the possibility of having inert gas flow through
the ring channels 16 to 19 to flush the channel, in each
instance. In this way, for example, inert gas can flow through
the channe116, and thus prevent contamination in the region of
the orifice of the pilot burner 22.
The size of the back-flow region 12 oval/circle can be
influenced by means of the L/D ratio.
A monitoring element 13 for flame monitoring can be a lens
system that has flushing air applied to it to prevent
contamination, or also for cooling. This system can be
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surrounded with a protective pipe (Fig. 2, 14 protective pipe).
A monitoring element can also be implemented by means of a
suitable light guide system.
The monitoring element can be integrated parallel to the nozzle
channel of the fuel gas line.
Another implementation possibility exists in such a manner that
this monitoring element is integrated centrally within the fuel
gas feed channel, so that flame monitoring takes place through
the nozzle channel.
The monitoring element can recognize the flame of the pilot
burner, for one thing, and, in the event that the pilot burner
is shut off, can also be used to recognize a flame of the carbon
burner, operated as a gas burner, by means of using the signal.
In this connection, the method of effect of the device according
to one embodiment of the invention is the following:
Fuel gas and the air required for combustion are supplied to the
pilot burner 2 or the central nozzle 3. This gas mixture flows
into the interior of the burner pipe 7, designated as 8, into
which the electrical ignition element, for example a glow
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element, designated as 9, projects, whereby the position of such
a glow element is determined in such a manner that optimal
ignition of the fuel/air mixture is guaranteed. This can be a
location through which there is weak flow, for example, at which
back-flow of the fuel gas/oxygen mixture takes place before
ignition, or of the hot waste gas after ignition.
Not shown is the possibility that multiple glow elements 9 can
be provided, which, as already mentioned above, can also be used
to measure the ionization stream.
The burner pipe 7 can stabilize the flame within the pipe with a
sudden constriction 11, whereby part of the hot waste gases are
deflected by means of the constriction, and the circulation 12
is reinforced. As a result, the fresh, cold mixture of the
supplied gases is reliably heated above the ignition temperature
with the circulating hot waste gases. The flame penetrates from
the burner pipe 7 into the gasification space, and there then
ignites a combustible gas mixture of fuel gas and oxidation
media, which flow out of the ring channels 16 to 19 of the
gasification burner during the ignition phase. After the
gasification burners have been ignited, gasification media such
.as CO2, steam, or mixtures with oxygen can be passed to the
combustion space not only by way of the fuel gas feed line of
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the pilot burner 4, but also by way of the air feed line 5,
thereby ensuring that no dust deposits or caking form in the
pilot burner.
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Of course, the invention is not restricted to the exemplary
embodiments that are shown. Further embodiments are possible
without departing from the basic idea. For example, alternative
injection of the corresponding media into the pilot burner can
be modified and adapted to the cases of use, in each instance,
the pilot burner can be operated at a fuel gas excess, the
combustion media in the pilot burner can be formed by air or
oxygen with nitrogen or CO2 or with steam, in order to avoid soot
formation at sub-stoichiometric combustion, for example, but the
air can also be enriched with oxygen, the oxygen feed can be
supplied with and without spin, and the like.
