GB2088892A

GB2088892A - Process for Gasification of Solid Carbonaceous Material

Info

Publication number: GB2088892A
Application number: GB8124221A
Authority: GB
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1980-12-01
Filing date: 1981-08-07
Publication date: 1982-06-16
Also published as: DE3131293A1; GB2088892B; FR2495178B1; AU535363B2; FR2495178A1; AU7391281A; DE3131293C2

Abstract

In a process for gasification of solid carbonaceous material such as coal powdered, coal is top-blown by a carrier gas onto a molten iron bath stored in a furnace through a non-submerged lance toward a hot spot formed by means of jet of oxygen and steam top-blown through a non-submerged lance and flux is optionally added into the furnace by the lump or blown toward the hot spot, thereby coal being gasified. The ratio L/L0 of the depression depth L of the molten iron bath to the molten iron depth L0 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 forming of adhered mass on the upper part of the furnace or hood. A mixing gas may be blown through bottom nozzles to stir the molten iron bath. <IMAGE>

Description

SPECIFICATION Process for Gasification of Solid Carbonaceous Material The present invention relates to a process for gasification of solid carbonaceous material, wherein the solid carbonaceous material is gasified in a gasification reactor furnace with molten iron bath.

Particularly, the present invention relates to a process for operating the gasification reactor furnace which enables to prevent forming of adhered mass due to splash on the upper part of a furnace a hood, or a lance, and to stablize the furnace operation and a long-lasting operation.

Generally speaking, so-called coal gasification process by using gasification furnace with molten iron bath is a process wherein heat necessary for the gasification is supplied from the molten iron.

Among known processes for gasifying solid carbonaceous material, e.g. coal, coke or the like there are disclosed a series of processes in Japanese patent application openlayings JA-OS 52-41604, 52- 41605 and 52-41606. Essential nature of those processes consist in introducing coal into a furnace either by dropping coal onto a bath surface or by introducing coal by the aid of carrier gas into the molten iron bath through an opening mounted below the bath level, and blowing oxygen and/or steam into the furnace through different way and to different portions in the furnace from the manner and portion by and to which the coal is introduced.Due to such features coal utilization efficiency at gasification is low and other drawbacks are inescapable as follows: (I) As, if the coal is dropped on the molten iron, the coal is caught by the floating slag on the bath surface then a part thereof being dissolved into the molten iron by agitation, the loss of coal by splashing away or by floating with slag without being gasified will increase, the coal utilization efficiency will be as low as not more than 80%, CO2 content in the resultant gas will not be able to be depressed below 5 to 6%, resulting in no effective gasification.

(II) Sulfur in the floating coal will directly react with oxygen to produce SOx thus expected advantage of the gasification of this type that no sulfur would be contained in the produced gas will be lost.

(III) Since the portion of coal introduction and that of blowing an oxygen jet are different and apart from each other, hot spot or so-called fire point with a super-high temperature will be formed, e.g., on the surface of the molten iron bath if oxygen is top-blown, loss of the molten iron due to its evaporation will be large, a large amount of combustible metal iron containing micro carbon particles will be contained in the produced gas resulting in danger in dust treatment, and the furnace operation would become difficult due to the iron loss.

DE-OS 2443740 discloses a process also falling within the same essential nature as abovementioned JA-OS, therefore being inescapable from abovementioned disadvantages.

A known process disclosed in JA-OS 55-89395 applied by the assignor of the present application to a considerable extent eliminated such disadvantages in the prior art aforementioned and the utilization efficiency of C of the solid carbonaceous material was improved. According to this JA-OS, 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 careous powder is pneumatically top-blown through a non-submerged lance by the aid of a carrier gas. Thereby, the amount of the solid carbonaceous material caught by the floating slag on the iron bath was reduced.

In a furnace of a type usually similar to a converter in which molten iron bath of 1300-1 5000C is stored, the coal (powdered coal) and a gasifying agent are top-blown through the non-submerged lance toward the molten iron thereby the coal being gasified. This process using the converter type furnace facilitates feeding of coal and gasifying agent into the furnace, and is capable of gasifying any kind of coal to the advantage. However, the molten iron will be splashed from the bath during operation due to a jet of the gasifying agent resulting in forming adhered mass on the upper part of the furnace or hood, or surface of the lance (on water cooling pipe) on its rapid cooling, which would raise difficulty in the operation.Once an amount of the adhered mass having been formed, it will consistently grow until a throat of a furnace and hood will be likely to be blocked, whereon the pressure control in the furnace is strongly inhibited leading to a condition inoperable.

Therefore, according to that process it was difficult to maintain a long-lasting operation particularly on using the conventer type furnace, also it was necessary to break or stop the operation in order to remove the adhered mass resulting non-stable supply of the produced gas, which is drawn to drawbacks of that process.

Slag floating on the molten iron bath level formed from ash in the coal or blown flux will increase.

In the prior art, mixing effect to the molten iron bath due to the jet of the gasifying will be diminished if the slag layer gets thick. Then the coal utilization efficiency will be depressed as the gasifying agent attains less contact with the molten iron bath resulting in less coal diffusion therein. Therefore it was difficult in the prior art to attain a high coal utilization efficiency without causing to form the adhered mass.

Accordingly, there is much to be desired in the prior art aforementioned, and it is an object of the present invention to provide a novel process for gasification of solid carbonaceous material wherein the drawbacks aforementioned in the prior art may be eliminated.

Particularly, it is an object of the present invention to provide a process for gasification of solid carbonaceous material wherein forming adhered mass on the upper part of a furnace or hood can be prevented to allow long-lasting operation of the furnace.

It is a further object of the present invention to provide a process wherein a high utilization efficiency of C is attained without causing to form mass.

It is still an object of the present invention, to provide such process for gasification of solid carbonaceous material that enables to depress sulfur content in the produced gas to a possible minimum amount.

The present invention provides a process for gasification of solid carbonaceous material in which pulverized solid carbonaceous material 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 a gasifying agent comprising at least oxygen, the gasifying agent is top-blown through a non-submerged lance and the solid carbonaceous material being blown by means of a carrier gas, and slag-forming material is optionally blown toward the hot spot, thereby the solid carbonaceous material being gasified, wherein the ratio L/LO of the depression depth L of the molten iron bath to the molten iron bath depth L0 is maintained from 0.05 to 0.1 5, and the blowing velocity of the solid carbonaceous material is maintained from 50 to 300m/sec so as to suppress forming of adhered mass on the upper part of the furnace or hood. For further improving coal utilization efficiency, a stirring gas is blow through at least one nozzle which opens below the level of the molten iron bath to stir the molten iron bath.

The present invention further provides such a process as aforementioned with an addition feature, wherein the ratio L'/Lc of the penetration depth L' of the solid carbonaceous material into the molten iron bath to the molten iron bath depth L0 is maintained from 0.15 to 0.3.

In the followings, the preferred embodiment of the present invention is disclosed by hand of accompanying drawings which, however, are shown for better illustration and not for limitation thereof.

Brief Description of the Drawings Fig. 1 shows a cross sectional view of a gasification reactor furnace for performing an embodiment of the present invention, Fig. 2 shows a longitudinal sectional view of a lance, Fig. 3 shows a bottom view of Fig. 2, and Fig. 4 shows a cross sectional view of a furnace according to another embodiment.

Fig. 1 shows a gasification reactor furnace 1 of a converter type, which is provided with an exhaust port for steel and/or slag 2 and a non-submerged lance 4 of a multiple nozzle type for top blowing the pulverized solid carbonaceous material, oxygen and steam, and is storing an appropriate amount of 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, toward the hot spot 10 the carbonaceous material being pneumatically blown by means of a carrier gas, whereon the carbonaceous material is converted to gas, i.e., gasified.

At the same time, slag 6 is produced on the molten bath level due to residual ash components in the carbonaceous material on its gasification. Alternatively or additionally the slag 6 is formed from the slag-forming material which is blown, preferably, together with the carbonaceous material. The slagforming material may be thrown into the furnace.

The solid carbonaceous material in the present invention encompasses known material containing substantial amount of carbon, e.g., coal, coke, pitch, coal-tar and the like. Hereinbelow, the solid carbonaceous material is represented by coal (Dowdered coal) as a preferred embodiment.

The gasifying agent comprising at least oxygen encompasses a gas substantially containing oxygen or a mixture gas of oxygen and steam. The oxygen content should be 70% by volume or more in order to supply sufficient oxygen without causing the iron bath to coal. Steam is preferably added if oxygen is 99% by volume or more. Most preferred is to employ pure oxygen and steam. However, steam may be employed at an oxygen content of 7099% by volume provided that it brings cost down.

Blowing is conducted through a lance or lances, preferably, of a multiple nozzle type which at least allows to blow coal by means of a carrier gas and oxygen through one lance. Steam may be blown either through the same lance with oxygen or a separate lance. The optional blowing of the slagforming material is preferably effected through the same nozzle for oxygen or coal blow. However, different arrangements in the blowing technic through the lance can be made without departing from the gist of the present invention. Conventional single nozzle lances may be used in a bundle or a set.

The gasification reactor furnace 1 is preferably of a converter type as shown in Fig. 1, however a furnace of an open hearth type, e.g., as disclosed in JA-OS 55-89395 may be employed depending upon the scale of operation. Hereinafter is being disclosed a preferred embodiment using the converter furnace 1.

The furnace 1 is operated as hereinbelow disclosed. Molten iron is charged through a mouth 3, the produced gas is introduced to a gas holder (not shown) through a hood and duct (not shown) for gas recovery arranged over the mouth 3. Slag may be exhausted through an exhaust port 2 at a kipped position of the furnace 1, or through the mouth 3.

A non submerged lance 4 with multiple nozzles 4-1, 4-2, 4-3, is shown in Figs. 2 and 3 which enables to blow coal and the carrier gas, oxygen and steam through one lance via three types of nozzles. The lance 4 includes a center nozzle 4-1, an annular slit nozzle 4-2 encirculating the center nozzle 4-1, and three tri-angularly located nozzle 4-3 at the peripheral portion of the annular slit nozzle 4-2. Through the center nozzle 4-1 is blown a mixture fluid of coal and the carrier gas, through the slit nozzle 4-2 is blown steam, and through the peripheral nozzles 4-3 is blown oxygen, respectively. A water cooling channel 4-4 with double shell structure is provided extending to the lance bottom whereat turning chamber 4-5 connects inlet and outlet channels.

On gasification of coal, coal, oxygen and steam are top-blown through the non-submerged lance 4 via respective nozzles onto the molten iron bath (iron bath hereinafter). Thereon, the coal is blown by means of the carrier gas toward the hot spot 10 which is formed through the jet blow of the gasifying agent, i.e., oxygen and steam, whereas splash 7 of iron bath is splashed from the iron bath surface, particularly at the hot spot 10.

According to the prior art, the splash was caught on the upper part of the furnace or hood, lance and the like and rapidly cooled thereon to form solid adhered mass 8, resulting in a serious trouble barring continuous operation due to the likelihood of blockage at the mouth 3 and nozzle-portion of the lance. In the prior art, so-called hardblowing as is a usual manner of blowing in converter operation, would have been considered essential for the gasification with high efficiency of coal utilization and such blockage could hardly be obviated.

Now, according to the present invention, such forming of the adhered mass can be suppressed by operating the furnace under specified condition without deteriorating the utilization efficiency of coal, i.e., so-called L/L0 ratio of the depression depth L of the iron bath to the iron bath depth L0 is maintained from 0.05 to 0.1 5, and the blowing velocity of the solid carbonaceous materials is maintained from 50 to 300 m/sec. The ratio L/L0 is preferably maintained from 0.1 to 0.15. This ratio L/L0 is mainly defined by the penetration depth of a jet of gasifying agent, whereas the coal blowing velocity is mainly determined by the carrier gas velocity on blowing.

Under those conditions the furnace can be operated for a long period by eliminating splashing thus deposit and growth of the adhered mass during the operation.

Most preferred is to hold also another ratio L'/L0 of the penetration depth L' of the solid carbonaceous material into the iron bath to the iron bath depth L0 within a range from 0.15 to 0.3.

According to holding such conditions, the present invention enables not only long-lasting stable operation of the furnace but also yielding of a produced gas with a minimum impurity amount of sulfur.

The jet depression ratio L/L0 should not be below 0.05 because, then, composition of the produced gas is deteriorated, whereas the ratio L/L0 should not exceed about 0.15 because, then, formation of the adhered mass can not be suppressed, furthermore, the loss in the iron bath would be enhanced due to spitting. Usually, the ratio L/L0 may be dominantly controlled by varying the distance from the nozzle (lance end) and the iron surface under a preset condition of gasifying agent jet and coal blowing velocity during an operation. However minor control can be effected by varying also the gasifying agent jet and/or coal blowing within the prescribed range.

The coal penetration depth ratio L'/LO is determined predominantly by the coal blowing velocity, the term "coal penetration depth" is to be construed the depth up to which the pulverized solid carbonaceous material penetrate into the iron bath in a form of a particle (solid). The coal penetration ratio L'/LO should not exceed about 0.3 because, then, the coal is too intensively blown into the iron bath resulting in increased splashing due to agitatingly vivid gasification, whereas the ratio L'/LO should not be below about 0.15 because, then, the desulfurization efficiency would decrease resulting in sulfur increase in the resultant gas.This lower limitation corresponds also to the coal blowing velocity wherein at a low velocity the coal would not penetrate enough into the iron bath accompanied by a lower coal gasification efficiency.

Generally in the converter operation for steel making the ratio L/L0 of the oxygen jet penetration depth L to the iron bath depth L0 is determined depending upon purpose of each blowing, as movement in the iron bath greatly affect the condition of blowing, whereas the ratio L/LO is determined in order to eliminate the detrimental effect caused by the adhered mass on gasification of coal without deteriorating other factors in the result.

The coal blowing velocity is limited within a range from 50 to 300m/sec at the nozzle because at a less velocity the sulfur in the coal would not be caught sufficiently into the iron bath and slag, and slag-formation of ash component would be insufficient, whereas at a greater velocity abrasion of the nozzle would be enchanced and blowing energy cost would become greater.

During operation, slag formed from ash in the coal or blown flux will gradually increase and accumulate on the iron bath resulting in thick floating slag layer. The thick slag layer will affect mixing the iron bath by the oxygen jet, which will cause less diffusion of coal in the iron bath and less gasification efficiency.

In order to eliminate this problem, the present invention provides stirring means for the iron bath by blowing a stirring gas into the iron bath, i.e. by blowing the stirring gas through a nozzle (or nozzles) which opens (open) below the iron bath level. So-called bottom-blowing nozzle and/or a nozzle mounted through a side wall below the iron bath level is/are used for stirring the iron bath. The stirring gas encompasses inert gas (e.g., N2, Ar of the like), oxidizing gas (air, oxygen, CO2 etc), and hydrocarbon gas (methane, ethane etc). This mixing gas may be a conventional gas which is so-called bottom-blow stirring gas. Preferably, the stirring gas comprises considerable amount of oxidizing gas which will serve to prevent the nozzle from blocking. Thus, e.g., a mixture gas of CO2 1 +oxygen 1 is preferred.The stirring gas is blown at a rate of 0.6-1 ONm3/hr pig-ton at a pressure from 2 to 8 Kg/cm2G. Due to this bottom-blowing, the iron bath 5 is stirred and the gasifying agent which is topblown and then present in the slag contacts with the iron bath at increased contacting possibility, which leads to an enhanced gasification efficiency.

Fig. 4 shows an embodiment of the reactor furnace with stirring nozzles at the furnace bottom.

Preferably, nozzles are arranged at the bottom of furnace within an area locating below the region where the gasifying agent forms the jet. Bottom Er/or side-blowing nuzzles with holes can be replaced with porous refractory nozzles (for bubbling) which are conventional in steel making.

According to the stirring by means of the bottom-blowing, the coal utilization efficiency amounts up to 98% without causing splash increase, enabling a long-lasting operation.

The iron bath is approximately maintained at a temperature from 1300 to 1 6O00C preferably around 1 5000C during operation, which, however, should be determined in relation with the nature of slag and C content in the iron bath.

Without such stirring 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/L0 ratio (see JA-OS 55-89395 Ex. 2, maximum efficiency: 96.1% Ex. 1, L/LO: 0.580.79). In order to further enhance the coal utilization efficiency 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 portion.

The oxygen jet velocity in the present invention amounts approximately from 1-3 Mach measured at the nozzle end, and the steam is blown about at 1 Mach.

The carrier gas for blowing coal encompasses oxygen, steam, air, N2, Ar and CO2, recycled makegas, combustion exhaust gas generated in a discharging chamber of produced slag, and coke oven gas.

The depth of the iron bath L0 is adopted generally according to conventional converter technology depending upon the size and type of furnace to be employed. However, L0 in the present invention ranges from 0.6 to 1.0 m for a 15 furnace preferably from 0.7m to O.9m.

In the present invention, additional step of blowing slag forming material or flux toward the hot spot in a manner as disclosed in JA-OS 55-89395 can be employed. Such flux encompasses 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, preferably blown through the same nozzle as the coal.

General conditions for the operation of the process for coal gasification as set forth in JA-OS 5589395 or corresponding U.K. patent application No. 79 44387 by the same applicant as of the present application except for particular conditions as disclosed herein may be applied. Some standard feeding rates are as follows: The coal feeding rate amounts to about O.3t/pig t Hr. Oxygen blowing rate is approximately 61 ONm3/coal t, steam blowing rate is around 150 Kg/coal tat 3O00C at pressure from 2 to 6 Kg/cm2G. Flux blowing rate is around 47Kg/coal t which, however, varies depending upon nature of coal. The feeding rates of coal and gasifying agent may be increased up to 4 to 5 times of that standard rates. C content in the iron bath ranges approximately from 12% by weight.

Accordingly, the present invention enables to accomplish high coal utilization efficiency as well as to suppress the forming of adhered mass on the upper part of the furnace or hood, or lance by means of controlling the L/L0 ratio of the gasifying agent jet penetration depth L to the iron bath depth L0 and coal blowing velocity, thus also enabling to employ a conventional converter type furnace for gasification of the solid carbonaceous material with a great advantage of long and stable supply of the produced gas including a lowest amount of sulfur. - Examples ("%" represents weight ratio if not otherwise indicated.) Example 1 15 ton molten iron (15000C, C:1.5%, S:1.1%,P::0.3%) was stored in a converter type furnace with a maximum inner diameter (horizontal) of 2.3m, and chamber volume of 1 3m3, into which coal (C:77.6%, H:4.8%, N:1.8%, 0:2.5%, S:0.8%, ash:2.9%) was fed by a rate of 3.5 ton/hr to gasify the coal. A lance as shown in Figs. 2 and 3 was used for blowing coal, oxygen and steam. The multi-nozzle lance includes a center nozzle of 1 5.7 mum diameter, a slit nozzle of 3mm width, and three peripheral nozzles of 12.1 mm diameter. Coal was blown through the center nozzle at 200m/sec velocity, and by 3.5ton/hr feeding rate. Steam was blown at 1 Mach by 400Kg/hr rate through the slit nozzle. Oxygen was blown at 2 to 3 Mach by a rate of 2000Nm3/hr. The oxygen jet penetration depth ratio L/L0 was maintained variable within a range from 0.05 to 0.15 during operation. The coal penetration depth ratio L'/LO was adjusted within a range from 0.15 to 0.30. LO was 0.85m.

5 day-continuously running operation under above conditions was successfully carried out to gasify the coal. 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 operation was ceased, the inside of the furnace was inspected with respect to the forming of adhered mass on the upper part of the furnace or hood, and lance. No substantial deposition which would cause to disturb the control of chamber pressure was found. On the lance, there was confirmed only a slight deposition without forming such deposition that would cause to block the nozzles. Only slight abrasion in nozzles was observed.

The distance between the iron bath surface and the lance end ranged from 1400 to 1500mm during the operation. Excess slag was discharged time to time.

Table 1 (molar /OJ

CO cho CO2 H2 N2 2 Total B 62.3 2.0 34.1 1.4 0.02 100ppm Example 2 Flux of burnt lime powder and fluorspar was blown through the same nozzle with the coal at feeding rates of 1 50 to 280Kg/hr for the burnt lime powder and 0OKg/hr for the fluorspar. The same conditions as in Example 1 were maintained. Gasification was continuously operated for 5 days and almost the same results were observed as in Example 1.

Reference Test 5 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 ware varied outside of the range of Example 1 to gasify coal, wherein 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- < naking within which decarburization efficiency of oxygen is not decreased. The distance between the iron bath surface and the lance end ranged from 850 to 1000mm.

After 5 hour operation under above conditions, the operation was forced to be ceased due to the adhered mass deposited on the upper part of the furnace, hood and lance. Thus the practical advantage of the present invention has turned out evidently over the prior art.

Example 3 Operation was carried out for five days under the same conditions as in Example 1 subject to bottom-blow stirring as follows: The furnace was equipped with a bottom-blowing nozzle of 6mm hole diameter located at the furnace bottom. Through the bottom-blowing nozzle a mixture gas of CO2 and oxygen (1+1 by volume) was blown at 6-7Kg/cm2G pressure and a rate of 4-5Nm3/hr.pig.ton. The average composition of the resultant gas is shown in Table 2. An average coal utilization efficiency of 98% was accomplished (average gas generation rate of 7500Nm3/hr).

No substantial difference from Example 1 was observed with respect to the adhered mass formation.

Table 2 (molar %J

CO |Co2 1C02 H2 N2 2 Total B 62.5 62.5 2.0 33.9 1.4 10.02 80 ppm Example 4 The same step as in Example 2 was additionally taken in the operation otherwise under the same conditions as in Example 3. After five day continuous operation, the same results were observed as in Example 3.

Claims

1. A process for the gasification of solid carbonaceous material in a furnace, the process comprising: Top blowing a gasifying agent containing oxygen through a non-submerged lance towards a molten iron bath in the furnace to form a hot spot, top blowing pulverised solid carbonaceous material by means of a carrier gas and through a non-submerged lance towards the hot spot, and optionally introducing slag forming material into the region of the hot spot, wherein a ratio L/LO is maintained within the range 0.05 to 0.1 5 where L is the depression depth of the molten iron bath and L0 is the depth of the molten iron bath, and wherein the blowing velocity of the solid carbonaceous material is within the range of about 50 to 300m/sec so as to suppress formation of an adhered mass on at least the upper part of the furnace or a furnace hood.

2. A process for gasification of solid carbonaceous material in which pulverized solid carbonaceous material is top-blown onto a molten iron bath stored in a furance through a nonsubmerged lance toward a hot spot formed by means of a jet of a gasifying agent comprising at least oxygen, in which the gasifying agent is top-blown through a non-submerged lance, the solid carbonaceous material being blown by means of a carrier gas, and slag-forming material is optionally added into the furnace by the lump or blown toward the hot spot, thereby the solid carbonaceous material being gasified, wherein the ratio L/LO of the depression depth L of the molten iron bath to the molten iron bath depth L0 is maintained from 0.05 to 0.1 5, and the blowing velocity of the solid carbonaceous material is maintained from 50 to 300m/sec so as to suppress the formation of adhered mass in the furnace, and wherein a stirring gas is blown through at least one nozzle which opens below the level of the molten iron bath to stir the molten iron bath.

3. A process as defined in Claim 1 or 2, 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 L0 is maintained from 0.1 5 to 0.3.

4. A process as defined in Claim 1 or 2, wherein the ratio L/L0 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 is oxygen or a mixture of oxygen and steam.

6. A process as defined in Claim 1 or 2, wherein the solid carbonaceous material is coal, coke, pitch, coal-tar or a mixture of any two or more thereof.

7. A process as defined in Claim 1 or 2, wherein the solid carbonaceous material and the gasifying agent are top blown through a multi-nozzle lance.

8. A process as defined in Claim 7, wherein the solid carbonaceous material is blown through a centrally disposed nozzle of the multi-nozzle lance.

9. A process as defined in Claim 5, wherein steam is also blown through a nozzle of the multinozzle lance for blowing coal and oxygen.

10. A process as defined in Claim 9, wherein steam is blown through an annular slit nozzle or a plurality of individual nozzles encircling a center nozzle.

1 A process as defined in Claim 2, wherein the stirring gas is an inert gas, an oxidizing gas, a hydrocarbon gas or a mixture of any two or more of said gases.

12. A process as defined in Claim 11, wherein the inert gas is N2, Ar or a mixture thereof.

13. A process as defined in Claim 11, wherein the oxidizing gas is air, oxygen, steam, CO2 or a mixture of any two or more of the aforesaid.

14. A process as defined in Claim 11, wherein the hydrocarbon gas is methane, ethane or a mixture thereof.

1 5. A process as defined in Claim 11 , wherein the stirring gas is blown at a rate of 0.6 1 0Nm3/hr.pig.ton.

1 6. A process as defined in Claim 2, wherein the stirring gas is blown through a bottom nozzle.

1 7. A process as defined in Claim 2, wherein the stirring gas is blown through a nozzle locating at a side wall of the furnace.

18. A process as defined in Claim 11, wherein the stirring gas is a mixture of CO2 and oxygen.

1 9. A process substantially as hereinbefore described.

20. Apparatus for carrying out the process of any one of claims 1 to 19, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.