CA1170456A - Process for gasification of solid carbonaceous material - Google Patents
Process for gasification of solid carbonaceous materialInfo
- Publication number
- CA1170456A CA1170456A CA000383473A CA383473A CA1170456A CA 1170456 A CA1170456 A CA 1170456A CA 000383473 A CA000383473 A CA 000383473A CA 383473 A CA383473 A CA 383473A CA 1170456 A CA1170456 A CA 1170456A
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- Canada
- Prior art keywords
- blown
- coal
- lance
- iron bath
- carbonaceous material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Carbon Steel Or Casting Steel Manufacturing (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
Abstract:
The invention provides a process for the gasification of solid carbonaceous materials such as coal. Powdered coal is top-blown onto a molten iron bath stored in a furnace through a non-submerged lance toward a hot spot formed by means of a jet of oxygen and steam top-blown through a non-submerged lance. The coal is blown by means of a carrier gas and optionally flux is also added to the bath or blown toward the hot spot. The ratio L/Lo of the depression depth L of the molten iron bath to the molten iron bath depth Lo is maintained from 0.05 to 0.15, and the blowing velocity of the solid carbonaceous material is maintained from 50 to 300 m/sec so as to suppress the formation of an adhered mass on the upper part of the furnace, hood or lance.
The invention provides a process for the gasification of solid carbonaceous materials such as coal. Powdered coal is top-blown onto a molten iron bath stored in a furnace through a non-submerged lance toward a hot spot formed by means of a jet of oxygen and steam top-blown through a non-submerged lance. The coal is blown by means of a carrier gas and optionally flux is also added to the bath or blown toward the hot spot. The ratio L/Lo of the depression depth L of the molten iron bath to the molten iron bath depth Lo is maintained from 0.05 to 0.15, and the blowing velocity of the solid carbonaceous material is maintained from 50 to 300 m/sec so as to suppress the formation of an adhered mass on the upper part of the furnace, hood or lance.
Description
- ~ ~7~)~56 Process for gasification of solid carbonaceous material `:
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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~ 5 -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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g 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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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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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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~ 5 -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 . ~ .
:
4 ~ ~
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 ;.~
,.
.
. , .
7 3 ~
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.
3 ~ 7 ~
g 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, . .
~ ~7~4~
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.
.
.
~ :~ 7 ~
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 -.'' ' .
,~
~ ~ 7~
:.
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.
.
.
~ ~7~6 Table 1 .
CO C2 ¦ H2 N2 2 Total S
I _ .
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., .
,~ .
. . .
''~" ' ' , ' ' ' , ' . .
Claims (10)
1. A process for the gasification of solid carbon-aceous material in which particulate solid carbonaceous material is top-blown onto a molten iron bath located in a furnace through a non-submerged lance toward a hot spot formed by means of a jet of a gasifying agent comprising oxygen, the gasifying 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 added to the iron bath or blown toward the 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 hood or lance is suppressed.
2. A process as defined in claim 1, wherein the ratio L'/Lo of the penetration depth L' of the solid carbon-aceous material into the molten iron bath to the molten iron bath depth Lo is maintained at 0.15 to 0.3.
3. A process as defined in claim 1 or 2, wherein the ratio L/Lo is maintained at 0.1 to 0.15.
4. A process as defined in claim 1 or 2, wherein the ratio L/Lo is adjusted by changing the distance between the molten iron bath surface and a lance end, or by changing the velocity of the gasifying agent.
5. A process as defined in claim 1 or 2, wherein the gasification agent consists essentially of oxygen or a mixture of oxygen and steam.
6. A process as defined in claim 1 or 2, wherein the solid carbonaceous material is selected from coal, coke, pitch, coal-tar and mixtures thereof.
7. A process as defined in claim 1, wherein the solid carbonaceous material is blown through a multi-nozzle lance through which the gasifying agent is also blown.
8. A process as defined in claim 7, wherein the solid carbonaceous material is blown through a center nozzle of the multi-nozzle lance.
9. A process as defined in claim 7, wherein steam is also blown through a nozzle of the multi-nozzle lance for blowing coal and oxygen.
10. A process as defined in claim 9, wherein steam is blown through an annular slit nozzle or multi-nozzles encircling a center nozzle.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000383473A CA1170456A (en) | 1981-08-07 | 1981-08-07 | Process for gasification of solid carbonaceous material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000383473A CA1170456A (en) | 1981-08-07 | 1981-08-07 | Process for gasification of solid carbonaceous material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1170456A true CA1170456A (en) | 1984-07-10 |
Family
ID=4120650
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000383473A Expired CA1170456A (en) | 1981-08-07 | 1981-08-07 | Process for gasification of solid carbonaceous material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1170456A (en) |
-
1981
- 1981-08-07 CA CA000383473A patent/CA1170456A/en not_active Expired
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