Note: Descriptions are shown in the official language in which they were submitted.
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This invention relate~ to ooal gasification plant, and more
partioularly to a burner and quenching chamber arrangement for uee
in a slagging coal gasifier of the kind (hereinafter referred to as
the kind specified) in which coal or other carbonaceous fuel is
introduced into the top of a colu~n-like gasifying vessel and is
gasified under high pressure and temperature by means of oxygen and
steam introduced near the fuel bed through tuyeres. ~he residual
ash collects as a molten slag and iron in the hearth of the gasifier
ve~elfrom which it is periodically disc_arged (commonly known as
slag-tapping) downwardly through a slag tap outlet or orifice in the
hearth into water cont~;ned in a quenching chamber. ~sually, the
pool of molten slag and iron is maintained in the he~I~h by directing
hot combustion products from a burner located beneath the slag tap
orifice up the ~ap orifice to retain the slag and iron in the hearth,
the tapping of the molten slag and iron being initiated and controlled
by stopping or reducing the burner output and reducing the pressure
in the quench;ng chamber by controlled venting to atmosphere through
a venting system 80 as to produce a differential pressure between the
quenching chamber and the gasifier vessel.
2~ Examples of such slagging gasifier plant are those disclosed in
- Un~ted K~ngdom Patent Specification No. 977,122, the Gas Council Research
Communications No's GC 50 and GC 112.
.
Some forms of slag-tap burners designed for use in such gasifiers
are of the tangential nozzle mix type, that is to say, of the kind in
which combustible products are separately supplied to the burner and
mixed externally of the burner parts to produce a stable flame.
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Diffioulties have been experienced in the upper regions of the
quenching chamber above the water level using these forms of burners
in that they tended to direot part of the flame downwards into the
region ab~ve the water level causing overheating of the quenohing chamber
walls and other areas of the upper ohamber.
Another diffioulty experienced with such burners is that the
combustion products from the burner, circulating above the water level
before passing through the slag tap hole, tend to cool the products and
therefore, upon passing through the hole, cools the m~lten slag and forms
solid slag within the tap.
An object of the present invention is to provide an improved quench
chamber and burner arrangement less subject to the difficulties mentioned
above.
~ coording to the present invention in the operation of a coal slagging
gasifier in which coal or other carbonaceous fuel is introduced into
the top of a column-like gasifying vessel and is gasified under high
pres~ure and temperature by means of oxygen and steam introduced near
a fuel bed through tuyeres, the gasification process producing a residual
ash which collects as a molten slag and iron in a hearth of the gasifier
vessel from which it is periodically discharged down w dly through a slag
tap orifice into the hearth into water contained in a quenchLng chamber
arranged 80 that a pool of molten slag and iron is maintained in the
hearth by directing hot combustion products from a burner located within
the quench chamber adjacent the underside of the slag tap orifice up the
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tap orifice to retain the slag and iron in the hearth, the tapping
of the molten slag and iron being initiated and oontrolled by
stopping or reduoing the burner output and reduoing the pressure
in the quenohing ohamber by oontrolled venting to atmosphere through
a venting system 80 as to produoe a differential pressure between
the quenohing ohamber and the gasifier vessel, the improvement wherein
a seoondary supply of oombustion-sustaining gas oontaining at least
some of the oxygen required for oombustion at the burner is provided
from a positionwdthin the ohamber above the level of water therein
and remote from the burner whereby the flow path of the oombustion-
sust~;n;ng gaR is arranged to oiroulate in the quenoh oha~ber
between the slag tap and the water level and to provide a layer of
gas intermediate of the walls of the ohamber and the Froduots of
oombustion from the burner, and also whereby the upward flow towards
the slag tap orifioe of the oombustion-sustaining gas restriots the
downward flow ~f the oombustion produots from the burner and cools the
quenohing ohamber walls.
It is an advantage to enable the burner to be operated with the
oombustion-sustaining gas belng supplied remote from the burner and
wherein, preferably, the oombustion-sustaining gas oontains from 10-90%
of the oxygen required for oombustion at the burner.
It is possible to operate the burner wherein the oombugtion-8u8t~;n;ng
gaB i8 a mixture of oarbon dioxide and oxygen or air and the gas is
supplied at about ambient temperature.
Preferably, an apparatus for performing the operation inoludes a
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burner adjacent the underside of the slag removsl orifice within the
quench chamber, and means for supplying said combustion-sustaining gas
to the burner, in a flow path which circulated the space in the chamber,
said means being arranged within the chamber above the water level and
remote from the burner.
It is an advantage for the combustion-sustaining gas to travel along
the entire length of the space between the water level and the slag tap,
and therefore preferably, the combustion-sustaining gas is supplied from
positions adjacent the walls of the chamber and immediately above water level.
Preferably, the combustion-sustain;ng gas is supplied from a supply
means which i8 a tubul æ ~nnulus provided with a plurality of port holes
equi-spaced around its surface.
Preferably also, the tubular annulus is located within and adjacent
the wall of the chamber and above the ~ater level.
During the slag-tapping operations it is desirable that the ring
should not be fouled from the falllng slag and, therefore, preferabl~
the ring is shielded from falling ælag during a tapping operation,
during the operation of the gasifier.
Preferably the burner is a ring nozzle mixing type.
Also preferably, the burner comprises sep æate chamber~ for a
fuel gas and for a primary air supply, each chamber having at least
one inlet and a plurality of outlet ports æranged around the inner
periphery of the ring.
And further preferably, the inner periphery of the ring bu~ner
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i9 provided with slopingwalls through which said ports are formed,
and arranged in use 80 that th`e fuel gas and the outlet supply are
arranged to provide oonverging streams ofruell gas and primary air
supply in the spaoe defined by the ring.
~ o enable the invention to be more olearly understood, and solely
by way of example, one embodLment of the invention will be desoribed
with referenoe to the aooompanying diagTammatio drawings, in which:-
Figure 1 is a general longitudinal sectional elevation
of part of a slagging gasifier,
Figure 2 is an enlarged longitu~;n~l sectional elevation
of the upper region of a quenching chamber,
Figures 3 and 4 are flow diagrams showing flow patterns
of circulatory gases in the upper part of
the quenching chamber, and
Figure 5 is a side sectional elevation ofa burner.
Referring first to Figure 1, a gasifier has refractory-lined
pressurised gasifioation ohamber 1 into whioh coal is fed from the top.
Oxygen and steam are introduoed into the ohamber 1 through tuyeres
2 to promote gasifioation of the ooal. In use of the gasifier, a pool
of molten slag oolleots in a sloping hearth 3 and is periodioally passed
via a slag outlet or .tap 4 into a ~ater reservoir 5 oont~;ned in a quench
ohamber 6 where it-i~ quenohed before being transferred to a look hopper
(not shown~ in the form of a dense small granlned frit. ~he quenoh
~hamber 6 is attaohed to the bottom end of the gasifioation ohamber 1
through the intermediary of a spaoing member or sandwioh flange 7.
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Referring also to Figure 2 and Figure 5 a metal tube 8 is fixed
to, and extends upwardly from the flange 7 and is fixed at its upper
end to an annular metal block 9 which supports a ring like burner 10
c~ncentrically beneath the slag tap 4.
Preferably, the burner (to be describea fully later) is of the
nozzle mixing ring type and consists generally of a gas ring 11 having
gas outlets 12 and an air ring 13 having air outlets-14. The burner
is supported by a metal ring 19 which Lncludes flange 20. ~he flange
20 ( and therefore the ring 19) is removably secured to the metal block
9 by bolts 21.
In the use of the gasifier, secondary combustion-sustaining gases or
gas miYtUres are supplied to the burner 10 from a tubular ring 15
having outlet ports 16 at any suitable equi-spaced positions around the
ring. The flow path of these gases flow upwards towards the burner 10
and produce flow paths as shown in ~igure 4. The gases or gas mixtures
circulate around the upper part of the quench chamber 17 and region 18
which is the region defined by the sandwich flange 7 and metal tube 8.
Difficulties have~previously been experienced in gasifiers in
that part of the combustion products from the slagtap burner have
mov4d down into the regions 17 and 18 and caused over-heating of the walls
surrounding the regions. This downward flow of part of the combustion
products from the burner is shown in Figure 3. In accordance with the
invention, the upward flow of gases and gas mixtures from the tubular
ring 15 tends to restrict the downward flow of the combustion products from
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the burner and thus avoids, to a great extent, any heating of
the walls surrounding the regions 17 and 18. Furthermore, the gases
flowing from the tubular ring 15 act as a cooling effect upon these
walls.
A preferred arrangement of the aforementioned slag tap burner 10
is shown in Figure 5 and comprises a body 22 having ~nnular gas and air
passageæ 23 and 24, dispo~ed one above the other, which are respectively
supplied with gas and air through inlets 25 and 26. _n inner annular
sloping wall 28 of the burner body 22 has a plurality of spaced gas and
air outlet ports 12 and 14 formed in two arrays, one above the other,
each array communicating with the respective gas or air passage 23, 24.
During slag tapping operations, slag falls through the slag tap orifice
27 and passes through the centre of the burner 10. Difficulties have
occurred in the past where the slag has fouled the burner and caused
damage to it. ~he preferred ring burner described above having a sloping
face 28 avoids the molten slag path and thus no fouling of the burner
takes place.
A further advantage of the present invention is tnat the burner
can be arranged to operate in separate modes, that is to say, it may be
operated between gas rich and oxygen rich mixture conditions.
If the burner is operated on a gas mixture lacking in oxygen,
carbon formation will take place and this is useful in that the flame
can produce a carbon layer on the underside of the slag tap to form a
protective coating which prevents attack of the underside by iron produced
by the gasification process.
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A still further advants~e of the arrangement is that when the
burner is in an oxygen enriohed mode, the excess oxygen reacts with the
carbon dissolved in the slag thus producing an exothermic reaction which
increases the temperature of the molten produots in the hearth. This
obviously increase~ the activity of the reactionary constituents in the
gasffication process.
Another advantage of the arrangement is that when the burner i~
turned down prior to a slag tapping operation, it is preferable that the
primary air supplied from the air outlet ports 14 is reduced to a low
limit and that the oxygen required to retain combustion at the burner 10
i8 -supplied by the secondary combustion-sustaining gas ring 15. The
reason for this is that when the air i~ supplied to the burner from the
primary air supply, it causes an excessive amount of thrust up thr~ugh the
slag orifice which results in a dispersion of the slag stream during a
1~ slag tapping operation. If the oxygen is supplied from the secondary
gas supply ring 15, this dispersion is very much reduced.
Another further advantage of the arrangement i8 that in a burner
having oxygen supplied by a primary and a secondary supply means, the
flame from the burner has more stability and is of a firmer appearance.
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