Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Process for gasification of solid carbonaceous material
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The present invention relates to a process for
gasification of solid carbonaceous materials, wherein the
solid carbonaceous material is gasified in a gasification
reactor furnace having a molten iron bath. In particular,
5 the present invention relates to a process for operating
- a gasification reactor furnace in such a manner that the form-
ati~n of an adhered rnass ~ue ~o splashes on the l1pper part of':
a furnace, a hood or a lanc~ is avoided, so khat a stable and!;
long-lasting furnace operation can take place.
~enerally speaking, the so-called coal gasification
process in a gasification furnace provided with a molten
iron bath is a process wherein the- heat necessary for the
gasification is supplied from the molten iron. The known
processes for gasifying solid carbonaceous material, e.g.,
15 coal, coke or the like, include a series of processes
`~ disclosed in Japanese patent applications JA-OS 52-41604,
52-41605 and 52-41606, which have been laid open for
inspection. The essential feature of these processes is
that coal is introduced into the furnace either by dropp-
;~ 20 ing the coal onto the bath surface or by introducing coal
by means of carrier gas into the molten iron bath through
an opening located below the bath level, and blowing oxygen
and/or steam into the furnace via a different route to
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different portions of the furnace. Because of this
feature, the coal gasification efficienc~ is low and other
drawbacks are inescapable as follows:
(I) If the coal is dropped on the surface of the molten
; 5 iron, the coal is trapped by the floating slag on the bath
` surface and only a part thereof enters the molten iron by
agitation. Thus some coal is lost because of splashing or
because it continues to float with the slag without being
gasified. The coal utilization efficiency may be as low
as 80~, and the CO2 c~ontent in the resultant gas may not
be depressed below 5 to 6%, resulting in no effective
gasificationO
(II) Sulfur in the floating coal reacts directly with
oxygen to produce Sx thus the expected advantage of
gasification of this type, that no sulfur is contained in
the produced gas, is lost.
(III) Since the positions in which the coal and oxygen are
introduced-are different and separate from each other-, a hot
spot or so-called fire point with a super-high temperature is
for~,ed, e.g., on the surface of the molten iron bath if the oxygen
is top-blown, and loss of the molten iron due to evapor-
ation is large, a large amount of combustible metal iron
containing micro carbon particles is contained in the pro-
duced gas resulting in dangers in dust treatment, and the
furnace operation becomes difficult due to the iron loss.
DE-OS 2443740 discloses a process also falling within
the same essential nature as the abovementioned Japanese
applications, and thus suffers the same disadvantages.
A known process disclosed in JA-OS 55-89395 (applied
~or by the assignee o~ the present application eliminated
these disadvantages in the prior art to a considerable
extent and the utilization efficiency of the carbon in the
solid carbonaceous material is consequently improved.
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According to this Japanese application, oxygen is top-
blown through a non-submerged lance onto a molten iron bath
surface forming a hot spot or so~called fire point with a high
temperature toward which a solid carbonaceous powder is
pneumatically top-blown through a non-submerged lance by
means of a carrier gas. Thereby, the amount of solid
carbonaceous material trapped by the floating slag on the
iron bath is reduced. In a furnace of the type similar to
a converter in which a molten iron bath having a
temperature of 1300 - 1500C is stored, the coal (powdered
coal) and a gasifying agent are top-blown through the
non-submerged lance toward the molten iron, thereby
gasifying the coal. This process using a converter type
furnace facilitates the feeding of coal and the gasifying
agent into the furnace, and is capable of efficiently
gasifying any kind of coal. However, molten iron splashes
from the bath during operation due to the jet of the
gasifying agent, resulting in the formation o~ an adhered
~ass on the upper part of the furnace or hood or the surface
of the lance (on the water cooling pipe~ which causes
difficulty in operation. Once an adhered mass has been
formed, it consistently grows until the throat of the furnace
and hood become blocked, whereon the pressure control in the
furnace is adversely affected, finally leading to an
inoperable condition.
Therefore, it is difficult to maintain a long-lasting
operation, particularly in a converter type furnace. It
is therefore necessary to interr~pt the operation in order
to remove the adhered mass, resulting in a non-stable
supply of the produced gas.
Accordingly, it is an object of the present invention
to provide a novel process for the gasification of solid
- carbonaceous material wherein the drawbacks aforementioned
in the prior art may be eliminated, at least in part.
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~n particular, it is an object of the present
invention to provide a process for the gasification of solid
carbonaceous ~aterial wherein the formation of an adhered mass
on the upper part of a furnace or hood can be substantially pre-
vented to allow a long-lasting operation of the furnace.
It is a further object of the present invention at
least in one preferred form thereof, to provide a process
for the gasification of solid carbonaceous material that
enables the sulfur content in the produced gas to be
reduced.
According to the invention there is provided a process
for the gasification of solid carbonaceous material in
which particulate solid carbonaceous material is top-blown
onto a molten iron bath located in a furnace through a non-
submerged lance towards a hot spot formed by means of
a jet of a gasifying agent comprising oxygen, the gasify-
ing agent is top-blown through a non-submerged lance, the
solid carbonaceous material is blown by means of a carrier
gas, and a slag-forming material is optionally blown
toward ~he hot spot, thereby gasifying the solid
carbonaceous material, wherein the ratio L/Lo of the
depression depth L of the molten iron bath to the molten
iron bath depth Lo is maintained within the range of
0.05 to 0.15, and the blowing velocity of the solid
carbonaceous material is maintained at 50 to 300 m/sec, so
that the formation of an adhered mass on the upper part of
the furnace or hood is suppressed.
The present invention further provides such a process
as aforementioned with an additional, preferred feature,
wherein the ratio L'/Lo of the penetration depth L' of
the solid carbonaceous material into the molten iron bath
to the molten iron bath depth Lo is maintained at 0.15
to 0.3.
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In the following, a preferred embodiment of the present
invention is disclosed with reference to the accompan~ing
drawings in which:-
Figure 1 is a cross-sectional view of a gasification
reactor furnace for performing an embodiment of the
present invention;
Figure 2 is a longitudinal sectional view of a lance;
and
Figure 3 is a bottom view of the lance of Figure 2.
Figure 1 shows a gasification reactor furnace 1 of the
converter type, which is provided with an exhaust port for steel and/or
slag 2 and a non-submerged lance 4 of the multiple nozzle
type for top blowing the particulate solid carbonaceous
material, oxygen and steam. The furnace contains a molten
iron bath 5 therein. A jet of the gasifying agent, which
is top-blown through the lance 4, produces a hot spot 10
on the iron bath surface within a depression. The
carbonaceous material is blown by means of a carrier gas
towards the hot spot 10, the carbonaceous material thus
being converted to a gas.
At the same time, slag 6 is produced on the molten bath
surface due to residual ash components in the carbonaceous
material. Alternatively or additionally the slag 6 may be
formed from slag-forming materials which are blown into the
bath, preferably together with the carbonaceous material. The
slag-forming material may merely be thrown into the furnace.
The solid carbonaceous material may be any known
material containing substantial amounts of carbon, e.g.,
coal, coke, pitch, coal-tar and the like. In the
following description, the solid carbonaceous material is
~`~ represented by coal (powdered coal) as the preferred
embodiment.
The gasifying agent comprising oxygen may be any gas
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containing substantial amounts of oxygen or a mixture of
such a gas and steam. The oxygen content should be 70~ by
volume or more in order to supply sufficient oxygen
without causing the iron bath to cool. Steam is prefer-
ably added if the oxygen content is 99~ by volume or more.It is most preferred to employ pure oxygen and steam.
However, steam may be employed with an oxygen content of
70~99% by volume if it brings costs down.
Blowing is conducted through a lance or lances,
preferably of the multiple nozzle type which allows at
least the coal and oxygen to be blown through one lance.
Steam may be blown either through the same lance as the
oxygen, or through a separate lance. The optional blowing
of the slag-~orming material is preferably conducted through
the same nozzle as the oxygen or the coal. However, different
arrangements in the blowing technique can be made without
departing from the scope oÉ the present invention.
Conventional single nozzle lances may be used in a bundle
or a set.
The gasification reactor furnace 1 is preferably of
the converter type as shown in Figure 1, however a furnace
of the open hearth type, e.g., as disclosed in JA-OS
55-89395, may be employed depending upon the scale of
operation. A preferred embodiment of the process using
the converter type furnace 1 is disclosed in the following.
The furnace 1 is operated as herein below disclosed.
Molten iron is charged through an opening 3, the produced
gas is introduced into a gas holder (not shown) through a
hood and duct (not shown) for gas recovery arranged over
the opening 3. Slag may be exhausted through an exhaust port 2
at a kipped position of the furnace 1 or through the opening
(mouth) 2.
` A non-submerged lance 4 with multiple nozzles 4-1, 4-2,
4-3 is shown in Figures 2 and 3 which enables coal
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and its carrier gas, oxygen, and steam to be blown through
one lance via three types of nozzles. The lance 4 incluaes
a center nozzle 4-1, an annular slit nozzle 4-2
encirculating the center nozzle 4-1, and three nozzles 4-3
- 5 located at the apices of a triangle at the peripheral
portion of the annular slit nozzle 4-2. Through the
center nozzle 4-1 is blown a fluid mixture of coal and its
carrier gas is blown through the center nozzle 4-1, steam
is blown through the slit nozzle ~-2 and oxygen is blown
through the peripheral nozzles 4-3. A water cooling
channel 4-4 with a double shell structure extends to the
bottom of the lance where turning chamber 4-5 connects
inlet and outlet channelsO
Coal, oxygen and steam are top-blown through the
non-submerged lance 4 via their respective nozzles onto
the molten iron bath. The coal is blown by means of its
carrier gas toward the hot spot 10 which is formed by
the jet of the gasifying agent, i.e., oxygen and steam.
This causes spla~hes 7 from the iron bath surface, partic-
ularly at the hot spot 10, unless special conditions
apply.
In the prior art devices, the splashes were caught on the
upper part ~f the furnace or hood7 lance and the like and
rapidly cooled thereon to form a solid adhered mass 8,
preventing continuous operation due to blockages at the
mouth 3 and nozzle-portion of the lance. In the prior
art, so-called hardblowing, which is the usual manner of
blowing in converter operation, is considered essential
for gasification with high efficiency of coal utilization,
and such a blockage could hardly be avoided.
Now, according to the present invention, the formation o~
an adhered mass can be suppressed by operating the
furnace under specified conditions without reducing the
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utilization efficiency of the coal. To achieve this, the
so-called L/Lo ratio of the depression depth L of the
iron bath to the iron bath depth Lo (see Figure 1) is
maintained at 0.05 to 0.15, and the blowing velocity of
the solid carbonaceous material is maintained at 50 to 300
m/sec. The ratio L/Lo is preferably maintained at 0.1
to 0.15. This ratio L/Lo is mainly defined by the
penetration depth of the jet of gasifying agent, whereas
the coal blowing velocity is mainly determined by the
carrier gas velocity.
~` Under these conditions, the furnace can be operated
for a long period by eliminating splashing and thus the
deposit and growth of an adhered mass during operation.
It is also preferred to maintain a ratio Ll/Lo of the
penetration depth L' of the solid carbonaceous material
(see Figure 1) into the iron bath to the iron bath depth
Lo within the range from 0.15 to 0.3. This ensures not
only a long-lasting s~able operation of the furnace, but
also yields a produced gas with a minimum amount of sulfur
impurities.
The jet depression ratio L/Lo should not be below
0.05 because the composition of the produced gas
is then adversely affected, whereas the rat~o L/Lo
should not exceed about 0.15 because the formation of the
adhered mass cannot then be su2pressed and furthermore, the
loss of the iron bath would be enhanced due to spitting.
Usually, the ratio L/Lo may be predominantly control]ed
by varying the distance between nozzle (lance end) and the
iron bath surface under preset conditions of the gasifying
agent jet and the coal hlowing velocity during the
operation. However minor control can be effected by also
varying the gasifying agent jet and/or coal blowing
velocity within the prescribed range.
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The coal penetration depth ratio L'/Lo is determined
predominantly by the coal blowing velocity, the term "coal
penetration depth" is to be construed as the depth to
which the particulate solid carbonaceous material
penetrates into the iron bath in the form of particles
(solid). The coal penetration ratio L'/Lo should not
exceed about 0.3 because the coal is then too intensively
blown into the iron bath, resulting in increased splashing
due to vigorous gasification, whereas the ratio L7L/o
should not be below about 0.15 because the desulfurization
efficiency then decreases, resulting in an increase of
sulfur in the resultant gas. This lower limitation also
corresponds to the coal blowing velocity wherein, at a low
velocity, the coal does not penetrate sufficiently into
the iron bath, which produces a low coal gasification
efficiency.
Generally, in a converter operation for steel-making,
the ratio L/Lo of the oxygen jet penetration
depth L to the iron bath depth Lo is determined depend-
ing upon the purpose of each operation, as movements inthe iron bath greatly affect the condition of blowing,
whereas the ratio L/Lo is determined in order to
eliminate the detrimental effects caused by the adhered
mass on gasification of coal without adversely affecting
other factors in the result.
The coal blowing velocity is limited within the rangefrom
50 to 300 m/sec at the nozzle because at a lower veloci`ty the
sulfur in the coal is not trapped sufficiently in the iron
bath and slag, and slag-formation of the ash component is
insufficient, whereas at a higher velocity abrasion of the
nozzle is enhanced and blowing energy costs become greater.
The iron bath is approximately maintained at a
temperature from 1300 to 1600C preferably around 1500C,
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during operation. However, the temperature should be
determined in relation with the nature of slag and carbon
- content in the iron bath.
A resultant coal utilization efficiency of about 96~
can be achieved, which is as high as the best of those in
the prior art with a greater L/Lo ratio (see JA-OS
55-89395 Ex. 2, maximum efficiency: 96.1%; Ex.l, L/Lo :
0.58-0.79). In order to further enhance the coal utiliz-
ation efficiency, an auxiliary lance as disclosed in the
above JA-OS may be employed, i.e., by blowing steam,
oxygen, or the like without coal onto the iron bath at a
separate position.
The oxygen je' velocity in the present invention
amounts approximately from 1 ~ Mach measured at the nozzle
end, and the steam is blown about at 1 Mach.
The carrier gas for blowing the coal encompasses oxygen,
steam, air, N2, Ar, CO2, recycled make-gas, combustion
exhaust gas generated in a discharging chamber of produced
slag, and coke oven gas.
The depth of the iron bath Lo is adopted generally
according to conventional converter technology depending
upon the size and type of furnace to be employed.
However, Lo in the present invention ranges from 0.6 to
1.0 m for a 15 t furnace, preferably from 0.7 to 0.9 m.
In the present invention, an additional step of
blowing slag forming material or flux toward the hot
spot in the manner disclosed in JA-OS 55-89395 can be
`~ employed. Examples of fluxes are burnt lime powder,
.` limestone, calcined dolomite, converter slag powder,
fluorspar, soda ash as a slagging agent. The
essential purpose of slag forming is absorption of or
reaction with sulfur present in coal. Such flux may be
blown together with oxygen, steam or the carrier gas for
coal, pre~eraàly blown throagh the same nozzle as the coal.
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General conditions for operation of the process for
coal gasification as set forth in JA OS 55-89395 or
corresponding Canadian Patent Application No. 342,653
assigned to the same assignee to which the present
application is to be assigned, subject to particular
conditions as disclosed herein may be applied. Some
standard feeding rates are as follows: The coal feeding
rate amounts to about 0.3 t/pig t hr. The oxygen blowing
rate is approximately 610 Nm3/coal t. The steam
blowing rate is around 150Kg/coal t at 300C at a
pressure from 2 to 6 Kg/cm2G. The flux-blowing rate
is around 47 Kg.coal-t which, however, varies depending upon
the nature of the coal. The feeding rates of the coal and
gasifying agent may be increased by up to 4 to 5 times the
standard rates. The carbon content in the iron bath
ranges approximately from 1 ~ 2~ by weight.
Accordingly, the present invention enables the formation of
an adhered mass on the upper part of the furnace or on the hood
or lance to be suppressed by ~eans of controlling the L/Lo
ratio o~ the gasifying agent jet penetration depth L to the
iron bath de~th Lo and the coal blowing velocity. This makes it
possible to employ a conventional converter type furnace
for gasification of solid carbonaceous material with the
important advantage of a long and stable supply of the
`` 25 produced gas containing a small amount of sulfur.
The invention is illustrated further by the following
Examples which should not be construed as limiting the
scope of the present invention.
In the Example, the percentages are based on material
weights unless otherwise stated.
Example 1 15 tons of molten iron (1500C, C:1.5%, S:l.l ~,
P:0.3 %) was stored in a converter type furnace with a
maximum inner diameter (horizontal) of 2.3 m, a mouth
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diameter of 1.3 m, an effective height of 4 m, and a
chamber volume of 13 m3, into which coal ~C~
(C:77.6%, ~I:4.~ %, N:1.8 %, 0:2.5 %, S:0.8 %, ash:~ 2.9 %)
was fed at a rate of 3.5 ton/hr to gasify the coal. A
lance as shown in Figures 2 and 3 was used for blowing
coal, oxygen and steam into the furnace. The multi-nozzle
lance included a center nozzle of 15.7 mm diameter, a slit
nozzle of 3 mm width, and three peripheral nozzles of 12.1
mm diameter. Coal was blown through the center nozzle at
200 m/sec velocity, and at a 3~5 ton/hr feeding rate.
Steam was blown at Mach 1 at a 400 Kg/hr rate through the
slit nozzle Oxygen was blown at 2 to 3 Mach at a rate of
2000 Nm3/hr. The oxygen jet penetration depth ratio
L/Lo was maintained variable within the range from 0.05
to 0.15 during the operation. The coal penetration depth
ratio L'/Lo was adjusted within a range from 0.15 to
0.30. Lo was 0.85 m.
A five day continuous running operation was
successfully carried out under the above conditions. The
average composition of the resultant produced gas is shown
in Table 1. The average coal utilization efficiency
`~ amounted to 96% without additional blowing for increasing
the efficiency.
After the operation was ceased, the inside of the
furnace was inspected with respect to the formation of an
adhered mass on the wall and lance. No substantial
deposition which would cause any disturbance of the
control of the chamber pressure was found. Only a slight
deposit was found on the lance, this deposit being
insufficient to cause any possibility of blocking the
nozzle. Only slight abrasion in nozzles was observed.
The distance between the iron bath surface and the
lance end ranged from 1400 to 1500 mm during the operation.
Excess slag was discharged from tlme to time.
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Table 1
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CO C2 ¦ H2 N2 2 Total S
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62.3 2.0 l' 34.1 1 4 0.02 ~ 100 ppm
Example 2
Flux composed of burnt lime powder and fluorspar was
blown through the same nozzle as the coal at feeding rates
of 150 to 280 Kg/hr for the burnt lime powder and 0 - 40
Kg/hr for the fluorspar. The same conditions as in
Example 1 were employed. Gasification was continuously
carried out for 5 days, and almost the same results
were~;observed as in Example 1.
Reference Test
A five hour operation was carried out under the same
conditions as in Example 1 except for the L/Lo ratio and
the coal blowing velocity which were varied outside the
ranges of Example 1, i.e. a conventional L/Lo ratio from
0.2 to 0.3 was maintained. This ratio range is usual in
the blowing operation for converter steel - making
within which the decarburization efficiency of oxygen is
not decreased. The distance between the iron bath surface
and the lance end ranged from 850 to 1000 mm.
After five hours of operation under the above
conditions, the operation had to be termina,ted due to an
adhered mass deposited on the upper part o~ the ~urnace', the
hood and the lance. Thus, the practical advanta~e of the
present lnvention over the prior art is eminently demonstrated.,
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