EP0627012B1 - Process for desulphurising irons melts with minimal slag production and suitable device therefor - Google Patents

Abstract

PCT No. PCT/DE93/00165 Sec. 371 Date Aug. 29, 1994 Sec. 102(e) Date Aug. 29, 1994 PCT Filed Feb. 25, 1993 PCT Pub. No. WO93/17131 PCT Pub. Date Sep. 2, 1993.The invention relates to a method and apparatus for desulphurizing iron with minimal slag formation, comprising the steps of melting and heating, to a temperature of about 1400 DEG to 1800 DEG C., a slag having the following chemical composition: 20% max SIO2; 30% max/Al2O3; about 5-40% SiO2+Al2O3+TiO2 combined; 2% max FeO; 1.5% max MnO; about 25-65% CaO+MgO+BaO+Na2O+K2O; 20% max MgO; 10% max Na2O+K2O; 60% max CaF2; about 50-85% CaO+MgO+BaO+Na2O+K2O+CaF2; percentages by weight; where the ratio of the percentage by weight of CaO plus MgO divided by the percentage by weight of SiO2 plus one-half Al2O3 is at least two and where the ratio of the percentage by weight of Na2O plus K2O to SiO2 is no more than one; then mixing the sulphur-containing hot metal with this bath of molten slag so as not to exceed 10 parts molten iron per part slag by weight. The desulphurized molten iron is then drawn from beneath the slag bath. The process may be accomplished using a low shaft furnace according to the present invention comprising a furnace body lined with carbon bricks or carbonaceous, basic or high-alumina refractory bricks and having a discharge pipe extending down to the bottom of the furnace chamber for discharging the desulphurized molten iron from beneath the slag bath.

Description

The invention relates to a process for the desulfurization of molten iron with minimal slag accumulation and a device suitable therefor.

Pig iron, as it comes from the blast furnace, usually contains 0.03% - 0.08% sulfur. It is state of the art to reduce the sulfur content of the pig iron before further processing in the steel plant, depending on the intended use of the steel produced, by means of various desulfurization processes to contents of less than 0.01% or less than 0.005%.

For the desulfurization of the pig iron, carbide-containing desulfurizing agents or, increasingly, mixtures containing metallic magnesium. used. Soda desulphurization is also still in use.

In JP-A-54/114 415 it was proposed to desulfurize cast iron with a slag of alkali metal oxides, fluorides and aluminum oxide heated by means of electrodes by pouring the liquid cast iron out of a refractory material through a sieve located above the slag and the resulting metal drops desulphurized when passing through the layer of sip. The desulfurized cast iron collects at the bottom of the furnace and is discharged through a slide. The used slag must be replaced by fresh slag.

In the journal Metals, Vol. 2, No. 20, January 1968, a method for desulfurization and dephosphorization of cast iron is described. A lime aluminate slag heated by electrodes is used for desulfurization, but is not regenerated.

Pig iron desulphurization produces large quantities of sulfur-containing slags, which also contain around 50% iron. The accumulation of spent, iron-containing desulphurization slag from the hot metal desulphurization of a large blast furnace with a daily production of 10,000 tons of hot metal amounts to about 300 tons per day.
The recovery of the iron from the slag is labor intensive and expensive.

Since it is no longer possible to deposit large quantities of sulfide-containing slags, which give off the toxic and malodorous hydrogen sulfide gas when exposed to water, in densely populated areas, very expensive, wet-chemical treatment processes for these slags have been developed (DE 3837249A1).

Unused carbide can also be contained in the spent desulfurization slag, which releases toxic and explosive acytylene gas when exposed to water.

In the desulfurization process according to the prior art, there is a considerable drop in temperature due to the blowing in of desulfurization mixtures by means of an immersion lance in the torpedo or charging pan. In the worst case, this can lead to the freezing of large quantities of pig iron, which is associated with considerable financial losses.

The object of the invention was to provide a process for the desulfurization of molten iron which avoids the disadvantages mentioned, and to provide an apparatus for carrying out the process.

The object is achieved by a method having the features of claim 1; the device is described in claim 9.

With the invention, a process for the desulfurization of molten iron was found, which can be used for pig iron as well as for cast iron, which does not have the serious disadvantages of the usual desulfurization processes for molten iron, since almost no sulfur-containing slag is produced from the outset and also desulfurized can be.

Another advantage of the process according to the invention is that there is also no need for expensive processing of a high iron-containing slag.

In principle, the process according to the invention can do without the expensive desulphurization agents based on carbide or magnesium, which makes it considerably cheaper than the processes currently used which correspond to the prior art.

In the method according to the invention, the pig iron is not desulfurized in the torpedo pan or charging pan of the steelworks, as is customary, but instead it is e.g. a specially developed downhole furnace electrically heated by means of graphite or carbon electrodes or a correspondingly adapted ladle furnace or electric furnace. Resistance heating in this furnace melts such large quantities of basic slag that a weight ratio of molten iron to slag of less than 10, preferably less than 5, and particularly preferably less than 2.5 for continuous desulfurization, is maintained in the desulfurization process.

A downhole furnace suitable for the process can be tilted and has a pouring device which allows the desulfurized iron melt to be drawn off under the desulfurization slag. This is preferably achieved by means of a pouring pipe, which extends down to the bottom of the working space of the furnace. Opposite the pouring pipe there is an inlet channel for the pig iron to be desulfurized. A nozzle or a sink can be attached to the bottom of the furnace below the inlet channel for the pig iron. But there can also be several nozzles or flushing stones on the floor or on the side walls of the invention Downhole furnace be attached. For better swirling of pig iron and desulphurization slag, there can be a funnel under the inlet channel, but above the floor nozzle, in which the incoming, sulfur-containing pig iron is intensively mixed with the desulphurisation slag that shoots up from below in the funnel. Much of the desulfurization work is already being done.

The furnace is expediently lined with carbon pounding mass, coal stones or in particular on the furnace floor and where predominantly liquid iron comes into contact with the lining with carbon-containing, basic or high-alumina refractory stones.

Other melting units can also be used for the process according to the invention. The prerequisite for this is that there is the possibility of melting slag by means of electrodes and pouring the iron either continuously or discontinuously separately from the slag. Melting units which can be used for the methods according to the invention after appropriate adaptation are ladle furnaces or e.g. Electric ovens with an eccentric floor cut.

The refractory lining described is also useful for ladle ovens or electric ovens which have been adapted for the method according to the invention.

The desulfurization process can be carried out by first melting a basic slag in the furnace and then pouring in the sulfur-rich pig iron. The reverse order, especially when using a pan oven, is also possible and useful.

= mind. 2 $\frac{{\text{Na}}_{\text{2}}{\text{O + K}}_{\text{2}}\text{O}}{{\text{SiO}}_{\text{2}}}$

= max. 1 sowie rohstoffbedingte Verunreinigungen.The chemical analysis of the slag used is as follows: SiO ₂ = Max. 20% by weight Al ₂ O ₃ = Max. 30% by weight SiO ₂ + Al ₂ O ₃ + TiO ₂ = 5 - 40% by weight FeO = Max. 2.0% by weight MnO = Max. 1.5% by weight CaO + MgO + BaO + Na ₂ O + K ₂ O = 25-65% by weight MgO = Max. 20% by weight Na ₂ O + K ₂ O = Max. 10% by weight CaF ₂ = 0 - 60% by weight CaO + MgO + BaO + Na ₂ O + K ₂ O + CaF ₂ = 50-85% by weight $\frac{\text{CaO + MgO}}{{\text{SiO}}_{\text{2nd}}{\text{+ 0.5Al}}_{\text{2nd}}{\text{O}}_{\text{3rd}}}$

= at least 2 $\frac{{\text{N / A}}_{\text{2nd}}{\text{O + K}}_{\text{2nd}}\text{O}}{{\text{SiO}}_{\text{2nd}}}$

= Max. 1 as well as impurities due to raw materials.

sowie rohstoffbedingte Verunreinigungen.The preferred composition of the slag has the following chemical analysis:

as well as impurities due to raw materials.

= mind. 2 sowie rohstoffbedingte Verunreinigungen.The particularly preferred composition of the slag according to the invention has the following chemical composition: SiO ₂ = 5 - 15% by weight Al ₂ O ₃ = Max. 25% by weight SiO ₂ + Al ₂ O ₃ + TiO ₂ = 25 - 40% by weight TiO ₂ = Max. 5% by weight FeO = Max. 0.7% by weight MnO = Max. 0.5% by weight CaO + MgO = 50 - 65% by weight MgO = Max. 5% by weight CaF ₂ = 7 - 30% by weight CaO + MgO + CaF ₂ = 55-75% by weight Na ₂ O + K ₂ O = Max. 0.5% by weight $\frac{\text{CaO + MgO}}{{\text{SiO}}_{\text{2nd}}{\text{+ 0.5Al}}_{\text{2nd}}{\text{O}}_{\text{3rd}}}$

= at least 2 as well as impurities due to raw materials.

The slag melts in such a way that a part of the slag is liquefied after an arc is ignited between graphite or carbon electrodes. As soon as a slag bath is present, the electrodes are immersed in the liquid slag, which is then heated by resistance heating.

The remaining quantities of the required slag are dissolved in the slag bath formed in this way.

The liquid slag is brought to a temperature of 1400-1800 ° C, preferably 1500-1700 ° C, particularly preferably 1550-1650 ° C.

The sulfur-containing iron melt is then allowed to flow evenly into this hot slag. The iron melt is desulfurized very quickly. The desulfurization reaction is particularly rapid if, for example, a gas consisting of argon, nitrogen or air or a mixture of these gases is blown in through a sink or one or more floor nozzles, whereby hot slag is flushed against the inflowing iron melt. In addition, an iron melt, which has already settled on the furnace floor, is stirred vigorously. It can give off the remaining sulfur to the hot slag. The reaction of the iron melt with the slag can be intensified by means of a funnel in the inlet which is covered by the liquid slag and into which the sulfur-containing iron melt runs. To do this, hot slag is pumped up through the funnel using a gas jet. The hot slag is swirled with the incoming molten iron. It transports the molten iron out of the funnel at the top.

Gases such as air and / or water vapor can also be blown into the slag melt or through the slag melt into the iron melt by means of one or more lances immersed in the slag melt from above, thereby accelerating the desulfurization process.

In order to further accelerate the desulfurization reaction, the usual desulfurization agents for pig iron, e.g. based on carbide or lime can be blown in with the gas.

Such a measure can be expedient, for example, if an iron melt with a particularly high sulfur content and / or to an extremely low final content has to be desulfurized in the shortest possible time.

To correct the slag composition, blowing in a small amount of the desulfurizing agent can also be useful. This is especially true when some blast furnace slag runs with the pig iron in the downhole furnace.

As a result of the favorable conditions for the desulfurization of the pig iron, the process runs very quickly, so that after the furnace has been tilted, desulphurised iron melt can be poured out continuously from the pouring pipe. In this case, desulfurization takes place in one pass.

However, a mode of operation is also possible in which the pig iron is poured into the downhole furnace and the desulphurization takes place at the same time. Subsequently, the sulfur is desulphurized and then the pig iron is poured out by tilting the downhole furnace. If the pouring hole has become blocked, it must be burned up using an electrode, for example.

It is also possible to use a correspondingly adapted ladle furnace or electric furnace for the method according to the invention.
When using a ladle furnace, the ladle is first filled with pig iron rich in sulfur, and then with the help of electrodes, such a quantity of liquid slag is melted on the pig iron that the weight ratio of iron to slag does not fall below 10: 1.
During the melting of the slag until the end of the desulfurization process, the pig iron is stirred by blowing gases through one or more sink stones at the bottom of the pan.
After the slag has melted, it is blown into the melt by means of one or more water-cooled Lan air or air and water or water vapor immersed in the slag.
The process is continued until the desired sulfur content of the pig iron is reached.
The desulphurized pig iron is then poured out through a slide located on the bottom of the pan.
Fresh, sulfur-rich pig iron is then poured into the pan and the next batch is desulphurized.

The slag is usually exhausted when its sulfur content has exceeded about 6-8% by weight. In this way, 750 t to 1000 t of pig iron can be desulfurized from an initial sulfur content of 0.05% to a final sulfur content of 0.01% with a downhole furnace containing 5 t of desulphurization slag. In a blast furnace that produces 10,000 t of pig iron per day, this is the case after approx. 1 1/2 to 2 1/2 hours.

However, especially when using fluorine-containing desulphurization slags, e.g. by blowing oxygen, air, water vapor or their mixtures into the slag, a part of the sulfur which is surprisingly large for the person skilled in the art is removed from the slag already during the desulfurization process, without the slag thereby losing its desulfurization effect.

For example, by blowing air or mixtures of air and water vapor intensively into the slag by means of one or more lances, a sulfur breakdown of approximately 1% by weight per hour can be achieved in the slag. This means that 25 times the tonnage of pig iron, based on the weight of the desulfurization slag, can be desulfurized every hour from an initial content of 0.05% by weight to a final content of 0.01% by weight sulfur, without the sulfur content in the Slag rises.

With a downhole furnace according to the invention, which contains 20 t of slag with a composition according to the invention, about 500 t of pig iron per hour can be desulfurized from 0.05 to 0.01% for days.

• 1) Eine Entfernung des Schwefels aus einer Entschwefelungsschlacke in diesem Umfang wurde bisher noch nicht beschrieben.
• 2) Nach herrschender Lehrmeinung verliert eine Schlacke mit hohen Gehalten an Schwefel, welche oxidierend behandelt wird, nicht nur ihre Fähigkeit zu entschwefeln, sondern wirkt im Gegenteil auf Eisenschmelzen mit niedrigem Schwefelgehalt rückschwefelnd.

This result is completely surprising for the person skilled in the art for two reasons:

• 1) A removal of the sulfur from a desulfurization slag to this extent has not been described so far.
• 2) According to the prevailing doctrine, a slag with a high sulfur content, which is treated with an oxidizing agent, not only loses its ability to desulphurize, but on the contrary has a sulfurizing effect on molten iron with a low sulfur content.

But even in the melting process according to the invention alone, without additional blowing in of oxygen, air or water vapor or their mixture into the slag, the slag loses part of its sulfur content.

Quite surprisingly, a considerably larger amount of pig iron can be desulfurized than is possible due to the sulfur solubility of the slag.

When the desulfurization slag has been saturated with sulfur, i.e. if the desired level of desulfurization is no longer achieved, the slag can be subjected to a regeneration process. For this purpose, the hot metal inflow is first stopped and the hot metal is poured out completely.

The subsequent regeneration of the slag is carried out by oxidation, if appropriate after adding SiO ₂ and / or Al ₂ O ₃ . The slag can be oxidized by blowing in air and / or oxygen or by adding an oxidizing agent such as iron oxide, iron ore and / or manganese ore. The sulfur content of the oxidized melt can be reduced, for example, from 6% to below 0.20% within a few minutes.

A reducing agent (for example coal, coke, lignite coke, peat coke or charcoal) is then applied to the melt and the oxides from the desulfurization slag are reduced by overheating the melt. Other reducing agents such as Aluminum can be used to reduce the slag's heavy metal oxides.

As soon as the heavy metal oxides have been reduced, ie that a so-called white slag is present, the desulfurization process for pig iron can be started again.

The oxidation process produces SO ₂ , which can be converted to gypsum, for example, in a conventional scrubber by reacting with hydrated lime in the exhaust gas stream from the furnace. This gypsum from the conversion of the flue gases with lime can be easily processed or deposited.

The method according to the invention is therefore very environmentally friendly. In relation to the state of the art, only a fraction of the desulfurization slag used is obtained and even this can be processed into low-sulfur, high-quality desulfurization slag. In addition, small amounts of gypsum are produced, which can be landfilled or processed without any problems.

A small amount of slag is unavoidable because the pig iron containing sulfur cannot be separated quantitatively from the blast furnace slag that is running before the desulfurization process. In order to keep the chemical analysis of the desulphurization slag at an optimal composition, small amounts of lime, fluorspar and possibly alumina must be added to the desulphurization slag depending on the amount and chemical analysis of the blast furnace slag.

For this reason, some desulphurization slag has to be poured off from time to time.

The best time for this is after the oxidation and reduction process of the slag. At this point, the slag is low in sulfur and has its maximum desulfurization power. Such a slag can advantageously be used, for example, in a ladle furnace as a high-quality and inexpensive slag raw material.

In the desulphurization process according to the invention for molten iron, there is therefore no slag which would have to be deposited or subjected to another elaborate treatment process.

Another advantage of the process according to the invention is that the pig iron is heated up during the desulfurization process.

With sufficient transformer power, the downhole furnace according to the invention can even be used for the additional melting and desulfurization of scrap iron. This can e.g. proceed in such a way that a certain amount of cut iron scrap is continuously charged in the furnace according to the invention.

It is in the nature of the process according to the invention that problems such as the drop in temperature due to the blowing in of desulfurization mixtures by means of an immersion lance, as is customary in the prior art, cannot occur.

The cumbersome, time-consuming and associated with further temperature losses associated with the spent, sulfur-containing slag after the desulfurization process by blowing in desulfurizing agents according to the prior art is omitted in the inventive method, since the desulfurized pig iron in the downhole furnace according to the invention clean from the spout pipe Desulfurization slag is separated.

On the other hand, about 5% of the original amount of high sulfur-containing slag remains during the deslagging process after the hot metal desulfurization according to the prior art desulphurized pig iron back, which leads to a corresponding sulfurization of the crude steel when it is subsequently refined with oxygen in the converter.

A not to be overlooked advantage of the desulfurization process according to the invention is that the downhole furnace described can be easily inserted at different points in the production process between the blast furnace and the converter, since due to its special construction principle between the inlet channel for the sulfur-containing and the pouring hole for the desulfurized pig iron only very little height is needed.

1 shows a possible embodiment of the downhole furnace according to the invention. The downhole furnace is electrically heated by means of graphite electrodes 1. It can be tilted and has a pouring spout 2 which extends down to the bottom of the working space of the furnace. The pouring pipe enables the desulfurized iron melt 3 to be drawn off under the desulfurization slag 4. Opposite the pouring pipe there is an inlet channel 5 for the pig iron to be desulfurized. A nozzle 6 is attached to the bottom of the furnace, below the feed channel for the pig iron. For better swirling of pig iron and desulphurization slag, there is a funnel 7 below the inlet channel, but above the floor nozzle, in which the incoming, sulfur-containing pig iron is intensively mixed with the desulphurization slag shooting up from below in the funnel.

The following examples serve to further explain the invention:

For the examples, an experimental furnace with an elliptical furnace kettle was used, which was lined with carbon stamping paste and a capacity of 400 mm in length, 260 mm in width and 240 mm deep. The furnace had a graphite tube with an outside diameter of 100 mm and an inside diameter of 30 mm on the pouring side, which reached down to the bottom of the melting chamber. In this vessel, 20 kg of desulphurization slag were melted using 2 electrodes with a diameter of 100 mm.

To get a faster result, i.e. In order to achieve the sulfur saturation of the slag as quickly as possible, the slag pyrite was added to the sulfurization.

After reaching a slag temperature in the range of 1500 ° C to 1650 ° C, 10 kq of cast iron was added and at full capacity, i.e. fused further with 15 V and 750 A.

Once all of the cast iron had melted, the slag and cast iron were kept at temperature for half an hour. Depending on the test variant, either slag and melt were stirred with a graphite rod for 5 minutes at the end of the half-hour test time (Examples 1 and 4) or air or air plus water vapor was blown into the slag during the half hour melting time (Examples 2 and 3). The blowing rate of the gases was chosen so that the slag was stirred vigorously, but without large quantities of slag spouting out of the test furnace.

The desulfurized cast iron was then poured through the graphite tube.

Samples of the slag and desulphurized cast iron were taken for chemical analysis.

In some cases cast iron breakage was added again after the pouring and the test was repeated one or more times. The cast iron used for the tests contained 0.21% by weight of S, 3.17% by weight of C, 2.06% by weight of Si and 0.27% by weight of Mn.

The test results are summarized in Table 1 at the end of the description. In addition to the sulfur contents of the slags (S found) found by analysis, the calculated sulfur contents of the slags (S calculated) are also given. The calculated sulfur content of the slag results from the initial content of the respective slag, i.e. from the sulfur content found in the previous test plus the calculated increase in the S content from the desulfurization of the cast iron during the test.

example 1

After the slag had melted down and a slag temperature of 1650 ° C. had been reached, cast iron was melted down with 0.21% S (Pr.Nr.O). After the cast iron had melted down, the slag temperature was kept at 1650 ° C. for half an hour.

At the end of the half-hour test period, cast iron and slag were stirred with a graphite rod for 5 minutes. The cast iron was then tapped and slag and cast iron samples taken.

Sample No. 0 indicates the S content of the cast iron used.

The sulfur values of the desulfurized cast iron were between 0.010 and 0.017% by weight (Pr.No. 1-3). The calculated sulfur losses of the slags were 0.38% by weight based on the test period of half an hour.

After the end of the desulphurization tests, 40% manganese ore - based on the weight of the slag - was added to the slag and the slag was desulphurized (Pr.Nr.4).

Then 7% brown coal coke was added to the slag and the manganese or iron oxide was largely reduced from the slag (Pr.Nr.5).

Example 2

In this experiment, compressed air was blown into the slag using a lance. The sulfur content of the desulfurized cast iron was between 0.001 and 0.003% by weight (Pr.No. 1-4). The calculated sulfur losses of the slags fluctuated between 0.31 and 0.59% by weight (Pr.No. 2-4) based on the test duration of half an hour.
The slag temperature was 1520 ° C.
After the end of the desulfurization tests, the 5 content of the slag could be reduced to 0.13% by weight by adding 40% manganese ore. (Pr.No. 5).

Example 3

In Example 3, compressed air and steam were blown into the slag using a lance. The sulfur content of the desulfurized cast iron was between 0.002 and 0.003% by weight (Pr.No. 1-3). The calculated S losses of the slags fluctuated between 0.49 and 0.56% by weight (Pr No. 2-3) based on the test duration of half an hour.

The slag temperature was 1530 ° C.

Example 4

In this test, cast iron and slag were stirred with a graphite rod for 5 minutes at the end of the half-hour test period.

The desulfurization effect of the slag, the chemical analysis of which was outside the composition according to the invention, was not satisfactory. The S content of the cast iron after the desulfurization process was between 0.044 and 0.059% by weight. (Pr No. 1-4)
The slag temperature was 1630 ° C.

Claims (13)

1. Process for desulphurising molten iron, characterised in that a slag (4) with the chemical composition: SiO₂ = max. 20 wt.% Al₂O₃ = max. 30 wt.% SiO₂ + Al₂O₃ + TiO₂ = 5 - 40 wt.% FeO = max. 2.0 wt.% MnO = max. 1.5 wt.% CaO + MgO + BaO + Na₂O + K₂O = 25 - 65 wt.% MgO = max. 20 wt.% Na₂O + K₂O = max. 10 wt.% CaF₂ = 0 - 60 wt.% CaO + MgO + BaO + Na₂O + K₂O + CaF₂= 50 - 85 wt.% $\frac{\text{CaO + MgO}}{{\text{SiO}}_{\text{2}}{\text{+ 0.5Al}}_{\text{2}}{\text{O}}_{\text{3}}}$

   

   = min. 2 $\frac{{\text{Na}}_{\text{2}}{\text{O + K}}_{\text{2}}\text{O}}{{\text{SiO}}_{\text{2}}}$

   

   = max. 1 and impurities which depend on the raw materials used, in a tiltable low-shaft furnace or an electrical furnace adapted for the process according to the invention or pan furnace, is brought to a temperature of 1400 - 1800°C by resistance heating the slag (4) using electrodes (1) immersed in the slag and desulphurising the sulphur-containing molten iron (3) with this slag and either batchwise or continuously running it off below the desulphurising slag (4), wherein the ratio of molten iron (3) to slag (4) should not exceed the value of 10:1 in parts by weight and the desulphurising slag (4) is regenerated continuously and/or batchwise.
2. Process according to Claim 1, characterised in that a slag (4) with the following chemical composition:

   

   

   and impurities, which depend on the raw materials, is used.
3. Process according to Claim 1, characterised in that a slag (4) with the following chemical composition: SiO₂ = 5 - 15 wt.% Al₂O₃ = max. 25 wt.% SiO₂ + Al₂O₃ + TiO₂ = 25 - 40 wt.% TiO2 = max. 5 wt.% FeO = max. 0.7 wt.% MnO = max. 0.5 wt.% CaO + MgO = 50 - 65 wt.% MgO = max. 5 wt.% CaF₂ = 7 - 30 wt.% CaO + MgO + CaF₂ = 55 - 72 wt.% Na₂O + K₂O = max. 0.5 wt.% $\frac{\text{CaO + MgO}}{{\text{SiO}}_{\text{2}}{\text{+ 0.5Al}}_{\text{2}}{\text{O}}_{\text{3}}}$

   

   = min. 2 and impurities, which depend on the raw materials, is used.
4. Process according to Claim 1, characterised in that the temperature of the desulphurising slag (4) is between 1500 and 1700°C.
5. Process according to Claim 1, characterised in that the removal of sulphur from the desulphurising slag (4) takes place using air, oxygen, water or steam, iron oxide, iron ore or manganese ore, individually or in any combination.
6. Process according to Claim 1, characterised in that the ratio of molten iron (3) to slag (4) is maintained at a maximum of 5:1 parts by weight.
7. Process according to Claim 1, characterised in that in the case of continuous desulphurisation, the ratio of molten iron (3) to slag (4) is maintained at a maximum of 2.5:1 parts by weight.
8. Process according to Claim 1, characterised in that air, oxygen, steam or mixtures thereof are blown from above into the molten slag or through the molten slag into the molten metal using one or more lances.
9. Device for performing the process for desulphurising molten iron according to Claim 1 containing a fusion unit in which slag (4) can be fused by resistance heating using immersed electrodes (1), characterised in that it is a tiltable fusion unit with a drainage pipe (2) which reaches into the molten iron when the fusion unit is tilted.
10. Device according to Claim 9 for performing the process for desulphurising molten iron according to Claim 1, characterised in that it is a tiltable low-shaft furnace heated by electrodes (1) and that its lining consists of carbon monolithic lining material and/or carbon bricks, whereas carbon-containing, basic or alumina-rich, refractory bricks may be provided for the base of the furnace and it has a drainage pipe (2) extending down to the base of the working space.
11. Low-shaft furnace according to Claim 10, characterised in that a hopper (7) for swirling and partially desulphurising the sulphur-containing molten iron with hot, liquid slag supplied from the base of the hopper is located in the working space, on the molten iron (3) inlet side.
12. Low-shaft furnace according to Claim 10, characterised in that at least one scouring brick and/or at least one gas injection nozzle (6) are provided in its base and/or in its side walls.
13. Device according to Claim 9 for performing the process for desulphurising molten iron according to Claim 1, characterised int hat it is a pan furnace whose refractory lining consists of carbon mcnolithic lining material and/or carbon bricks, whereas wherever mainly liquid iron comes into contact with the lining, carbon-containing, basic or alumina-rich, refractory bricks are used.

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