CN1239715C - Method for producing liquid smelting iron in an electric furnace - Google Patents

Abstract

The invention relates to a method for producing a molten iron in an electric arc furnace comprising several electrodes, equipped with a hearth and comprising a bath surface, on top of which a non-foamed liquid slag is arranged. The inventive method comprises the following steps: reducing the metal charge to form a pre-reduced metal charge containing excess free carbon, the pre-reduced metal charge being thermally transferred to a surface of a molten bath within the electric arc furnace in a curtain of inert gas; mixing the surface of the molten pool by injecting gas to prevent crust formation; to produce a melt iron, a pre-reduced metal filler is melted in an electric arc furnace.

Description

Method for producing liquid smelting iron in an electric furnace

The present invention relates to a method of producing liquid smelting iron.

Considerable effort has been expended over the years to develop a reduction/smelting method to replace the blast furnace for the production of liquid smelting iron, especially in the system of small capacity production units, avoiding the preparation of materials, in other words, the direct Utilize ore powder and charcoal. This type of process is of interest, mainly, in that equipment involving large investments, such as those for the production of coke and for the sintering of ore, can be avoided.

Direct reduction using char as a reducing agent (rather than via the liquid phase) makes the most economic sense, especially in countries lacking natural gas resources. However, a disadvantage of these methods is that they produce pre-reduced iron ore with a high sulfur content (0.3-0.6 wt% S).

Of these methods, those using the ore in fine-grained form (fluidized bed or multiple hearth furnace technology) are of particular interest since they involve the least troublesome form of ore. Granules of pre-reduced iron ore can be used, as well as the obtained fine powder form, without any difficulty using the cold or low temperature (<300°C) blast injection process in electric furnaces for steel production.

However, the large use of this type of pre-reduced iron ore particles in electric furnaces for steel production has two problems: it introduces a large amount of sulfur, which cannot be eliminated in the oxidative smelting environment of steelmaking electric furnaces, and It reduces the productivity of the electric furnace because it starts reduction-smelting from a cold state and consumes more energy than that consumed by the main raw material, scrap iron. This leads to excessive energy consumption, with consequent reduction in productivity.

These disadvantages can be avoided by producing smelted iron, instead of steel, in fact, by introducing pre-reduced iron ore particles (pre-reduced fine powder) directly from the reduction furnace, at a temperature of about 1000°C. Into the electric furnaces that produce smelted iron to get rid of the sulfur problem. In fact, feeding pre-reduced iron ore particles into the furnace at 1000°C greatly reduces the energy required for smelting. The production of smelted iron requires a reducing medium capable of reducing sulfur by about 90%. By creating a suitable slag, molten iron can be obtained with a sulfur content of 0.03-0.06%, which is equivalent to standard grade molten iron, which can then be used in all traditional applications of iron smelting, especially as a source of pure iron for electric furnaces.

This is all true, especially when treating waste in fine powder form by reduction, which always provides pre-reduced iron ore with a very high sulfur content. In the following description, "metal fine powder" should be understood as various types of products containing partially oxidized metallic iron. Metal fines are iron ore particles, scrap particles of various types containing partial iron oxide, especially fine particles from filters of blast furnaces and electric furnaces, mill scale scrap or particles (when reheating or rolling Iron oxides formed), rolling or machining tailings, etc.

This type of smelting of fine metal particles for the production of smelted iron has traditionally been carried out in resistively heated slag furnaces, improperly known as submerged arc furnaces (SAF). The fine powder is generally introduced into the cold zone of this type of electric furnace by gravity. However, this type of electric stove has limited power. In fact, the power density of a submerged arc furnace (SAF), expressed in MW/ ^m2 , is four-fifths lower than that of a free-form electric arc furnace. In order to obtain the same production level, the diameter of the submerged arc furnace used is 2 times larger than that of the electric arc furnace.

Additionally, in electric arc furnaces, smelting of non-sprayed fine material results in the formation of clumps, often adhered to the furnace walls called linings or berms. This also occurs when smelting finely ground scrap, swarf, grinding swarf, etc.

Excessive use of these materials blocks part of the volume of the converter, preventing the correct introduction of scrap, while the operator must regularly purge the melt through rather large overheated furnaces, which explains the energy loss and reduced productivity. As a result, introduction by gravity of the pre-reduced metal fines into the electric furnace without any special precautions necessarily leads to encrustation and lining formation.

Under normal operating conditions, electric arc furnaces use foamed slag, which is obtained by a combined injection of carbon and oxygen in the conventional smelting of scrap iron in order to form CO gas in the slag. This foaming slag is spontaneous when a carbon-rich (>2% C) pre-reduced material is used, since the pre-reduced iron ore provides both oxygen and carbon. Due to its low density and its insulating properties, the foamy slag acts as a hindrance to the dissolution of the pre-reduced fines. The pre-reduced fines fall on the slag, agglomerate rapidly and form a solid mass which is difficult to melt and, since it is not very dense, leads to the formation of a lining on the furnace walls.

In order to produce smelted iron, carbon has to be used, and it is obvious that carbon can be injected alone, the best way from an economic point of view is to make pre-reduced iron ore with excess carbon. This excess carbon binds to iron in low proportions. However, when producing pre-reduced fines with 5-10% C for the manufacture of smelted iron, this carbon corresponds mainly to particles of free carbon. However, it is difficult to introduce this free carbon into the metal unless it is injected into the melt. In fact, free-form electric arc furnaces (unlike submerged arc furnaces in that they function by means of resistive heating, rather than electric arcs) operate primarily in an oxidizing environment where carbon oxidizes rapidly. If no special precautions are taken, the non-sprayed carbon feed will be lost mainly as gas, so the metal will be depleted of carbon and therefore steel.

It would be advantageous to have an optimized method that enables the direct production of molten iron in an electric arc furnace from pre-reduced metal fines.

The object of the present invention is to provide an optimized method for producing molten iron.

According to the invention, this object is achieved by a method for producing liquid smelting iron in an electric arc furnace comprising several electrodes, equipped with a furnace and having a bath surface covered by liquid non-foaming slag. The method comprises the steps of:

a) reducing metal fines to form pre-reduced metal fines containing excess free carbon.

b) In an inert gas curtain, heat transfer of pre-reduced metal fines to the surface of a molten bath contained in an electric arc furnace.

c) The injection gas is to agitate the surface of the molten pool in such a way as to prevent the formation of crusts.

d) Melting the pre-reduced metal fines in an electric arc furnace to obtain liquid molten iron.

The method provided is to use a free-form electric arc furnace in a very specific way by introducing hot pre-reduced metal fines (preferably directly at the outlet of the reduction furnace, in other words at a temperature greater than 500 °C, In the most preferred embodiment, at a temperature of 800-1100°C) and work on the surface of the molten iron bath covered by a layer of non-foaming liquid slag which can be neutralized by spraying through the furnace The bath surface is agitated by gas (nitrogen, argon) and/or by spraying oxygen-containing gas through one or several lances. The surface of the molten pool is vigorously agitated by jets of gas.

This vigorous agitation, homogenizes the temperature of the metal + slag melt and renews the surface of the slag layer to keep it superheated and liquid and able to absorb pre-reduced metal fines without solidifying and forming impermeable of crusts.

In the case of agitating the surface of the molten pool by injecting neutral or inert gas through the hearth of the electric arc furnace, in the proposed method, the flow rate of the inert gas is preferably between 50 and 150 l/min.t (per minute per ton in the melt liters of liquid metal). In the best version of the present invention, the stirring rate is 80-120l/min.t. These rates must be adjusted as a function of the height of the molten pool surface and the number and location of injection points. Agitation at high speeds is not relevant to normal implementations used in electric arc furnaces. In fact, in the usual way of producing steel in electric arc furnaces, the agitation rate is in the range of 1-10 l/min.t and is only used to homogenize the melt, without even considering the smelting result and the temperature.

In order to ensure optimum efficiency of the agitation, the surface of the molten metal pool must have a defined minimum height, preferably at least 0.3 m, to ensure a strong agitation of the metal melt. It needs to be avoided that agitating gases injected through the furnace simply pass through the "holes" of the metal melt without vigorously agitating it. Obviously, this minimum height can vary as a function of the shape of the electric arc furnace and the positioning of the gas injection means, which are preferably perforated bricks or uniform nozzles.

In a preferred embodiment of the invention, the means for injecting the agitating gas are located near the outer edge of the furnace chamber of the electric arc furnace, in other words transversely with respect to the bottom of the melt, so as to maintain or have a tendency to agglomerate at the edge of the furnace The pre-reduced metal fine powder particles are directed towards the hottest central region located between the electrodes.

Alternatively, or in addition to agitation of the bath surface by injection of inert gas through the hearth of the electric arc furnace, agitation of the bath surface can also be performed by injection of oxygen-containing gas through one or several injectors. Gaseous CO bubbles are formed by reacting with C in the molten iron by injecting an oxygen-containing gas (hereinafter referred to as "raw oxygen") into the surface of the molten pool using penetrating injection. This release of CO creates turbulence in the liquid metal, ensuring vigorous agitation of the molten pool surface and slag.

To protect the pre-reduced metal fines falling into the furnace, the metal fines may be surrounded by a curtain of inert gas, preferably nitrogen or argon. This curtain of inert gas, preferably having an annular shape, minimizes re-oxidation of the furnace-induced laterally deflected particles and pre-reduced metal fines before they reach the slag layer and bath surface layer, respectively. It is best to use a nitrogen flow of 50-200Nm ³ /h to form a protective curtain, so as to protect about 10-60t/h of pre-reduced metal fine powder containing about 50% metallized Fe, and transfer it in an amount of 60-100% . These values depend on many factors, such as the geometry of the furnace, the height of the fine powder droplet, and disturbances in the electric arc furnace, among others, and the results can be adopted.

Preferably, the transfer of the pre-reduced metal fines takes place in the central zone of the electric arc furnace located between the electrodes.

According to a preferred embodiment of the present invention, the fully reduced metal fines are mixed with charcoal, preferably with a diameter of 2-20 mm, before being fed into the electric arc furnace. The amount of carbon used depends on the amount of carbon in the pre-reduced metal fines. A 7-15% excess of carbon is required, preferably an excess of about 10%. In this way, smelted iron can be obtained with 3-3.5% C, 0.01-0.05% Si and 0.03-0.06% S, depending on the sulfur content in the char.

According to another preferred embodiment of the present invention, step a) comprises the following steps:

a1) introducing fine metal powder into a multi-hearth furnace comprising several superimposed hearths and depositing it in the upper hearth of the multi-hearth furnace,

a2) The fine metal powder is gradually transferred to the lower furnace,

a3) Introduce a carbon reducing agent sufficient to reduce the metal fine powder to one or several lower furnaces, and ensure that there is an excess of free carbon,

a4) heating the multi-chamber furnaces, when they come into contact with the carbon reducing agent, reducing the metal fines and, at a suitable temperature, generating gas from the carbon reducing agent,

a5) In the multi-hearth furnace, the excess gas generated by the carbon reducing agent is burned off, and the heat generated is used to dry or preheat the fine metal powder. a1) Metal fines are introduced into a multi-hearth furnace comprising several superimposed hearths, where they are deposited in the upper chamber of the multi-hearth furnace.

According to another preferred embodiment of the present invention, a slagging agent is added in step a) and/or step b). These slagging agents are preferably selected from lime, fluxes and magnesia, and mixtures thereof.

At the end of step a) there is a carbon excess of 7-15%, preferably an excess of about 10%.

The solid carbon reducing agent is selected from charcoal or liquid or solid petroleum products. When the carbon reducing agent is in the multi-hearth furnace, the contained volatile components are removed, and part of the sulfur is also removed.

Part of the excess carbon is consumed in step d).

In addition, excess free carbon can be used to terminate reduction reactions and carburize molten iron.

According to another aspect of the invention, the production efficiency of an electric arc furnace can be increased, the power of the arc being limited by the arc voltage due to the available "submerged" arc length.

Instead of using the air that naturally enters the EAF to "burn uselessly" and risk solidifying the metal fines and forming an impermeable crust, in order to increase the productivity of the electric arc furnace, with maximum energy efficiency, use It is also advantageous to reduce the excess carbon of the metal fines.

Obviously, if it is desired to increase the production capacity of the electric arc furnace for smelting iron per hour, it is necessary to increase the flow rate of the metal fines introduced into the electric arc furnace. This increase in the flow rate of the metal fines also increases the risk of crust formation.

This object is achieved by the above-mentioned method for the production of liquid smelting iron in an electric arc furnace, wherein one or several post-combustion nozzles - which are connected to one or several primary oxygen injections - constitute the burner, which Power is comparable to an electric arc. These injectors deliver the injection of afterburning gas preferably between the arcs, and in a preferred embodiment onto the electrode ring ("electrode spacing ring").

The post combustion gas injection is advantageously positioned such that the slag is pushed towards the central portion of the arc furnace between the electrodes. This enhances the agitation of the slag in a suitable manner and makes it possible to maintain sufficient agitation of the superheated slag permanently in the area receiving the metal fines. The high turbulence in the superheated slag in this zone enables the flow rate of metal fines to be increased without risk of crust formation. Indeed, without such injection of post-combustion gas, the disturbance of the slag is achieved by agitating the surface of the molten pool by injecting neutral gas through the hearth of the electric arc furnace and/or by injecting raw oxygen onto the surface of the molten pool through one or several injectors. rather indirectly. In fact, the post-combustion gas is directly injected into the slag layer, so that the movement of slag in the electric arc furnace can be better controlled and positioned, so as to accelerate the melting of metal fine powder and reduce the push and adhesion of non-melted metal fine powder to the furnace wall. on the danger.

One of the advantages of the process of the present invention is the optimization of the operation of the two reactors, in fact the fact of producing pre-reduced smelt iron with an excess of free carbon increases the rate of reduction and increases the level of metallization.

In order to obtain this excess of free carbon, an appropriate amount of carbon reducing agent needs to be added during the reduction stage.

Another advantage of the excess free carbon in the pre-reduced iron ore is based on the fact that inside the reduction chamber of the reduction reactor, the temperature is very high and, as a result, the carbon reducing agent, which happens to be char, is carried out to a large extent Devolatilization and desulfurization. As a result, devolatilized charcoal dissolves more readily in the iron melt during the smelting stage than non-devolatilized charcoal. In addition, since the carbon reducing agent is subjected to very high temperatures and is inside the reduction reactor, the sulfur content is significantly reduced. Smelted iron obtained in this way has a very low sulfur content. It is obvious that coke can be used instead of char when smelting pre-reduced iron ore particles. for best carbon solubility. However, using coke instead of char increases production costs and does not solve the sulfur problem. In fact, coke contains no volatile substances, however, it contains approximately the same amount of sulfur as the charcoal used to produce it.

Excess carbon is burned off in the smelting furnace, thus saving electricity during pellet smelting.

The fact that the carbon reducing agent is only added to the upper chamber of the multi-hearth furnace enables it to use the waste heat of the gas to dry and preheat the pellets or iron ore and completely burn off the carbon monoxide without the need for a separate post-combustion step. Also, the higher temperatures in these upper chambers will reduce the amount of sulfur in the free carbon even more.

Therefore, the unexpected advantages of the present invention do not lie in the juxtaposition of the two known methods, but in the mutual cooperation between the two methods.

Other aspects and characteristics of the invention will become clearer from the following detailed description of the preferred embodiment as an example, with reference to the sketches given in the appendix. As follows:

Fig. 1 is a schematic diagram of an electric arc furnace for producing liquid molten iron according to a first embodiment of the present invention.

Fig. 2 is a schematic diagram of an electric arc furnace for producing liquid molten iron according to a second embodiment of the present invention.

FIG. 3 is a plan view of the electric arc furnace according to FIG. 2 .

Fig. 1 shows a schematic diagram of an electric arc furnace for producing liquid molten iron according to a first embodiment of the present invention.

It shows an electric arc furnace 10, comprising a converter 12, covered by 14, through which dome 14 is penetrated three electrodes 16 capable of producing an arc of about 20 cm each and a power of about 4 MW. Between these three electrodes 16 is placed a device 18 for delivering pre-reduced metal fine powder. This device 18 comprises, on the one hand, a feed chute for feeding the pre-reduced metal fines into the furnace 12 and, on the other hand, a nitrogen curtain 20 capable of spraying around the pre-reduced metal fines falling into the furnace. Nozzle.

The point of impact of the pre-reduced metal fines is located between the three electrodes 16 , in other words, at the hottest point within the electric arc furnace 12 . At the moment of impingement floating on the layer of non-foamed slag 22 on the liquid melt 24, the pre-reduced metal fines are immediately incorporated therein and melt rapidly.

The hearth 26 of the converter 12 is equipped with several porous bricks 28 through which a high-speed flow of agitating gas 30 is injected, and the turbulence generated by the injection of this gas 30 passes through the liquid melt 24, thereby preventing the agglomeration of the pre-reduced metal fine powder or form crusts.

Fig. 2 shows a schematic diagram of an electric arc furnace for producing liquid molten iron according to a second embodiment of the present invention. Fig. 3 shows a plan view of the electric arc furnace.

In an electric arc furnace 10' with center loading by gravity, three post-combustion nozzles 32 are provided, connected to three primary oxygen injectors 32' between the arcs on the electrode ring ("electrode spacing ring"), The formed burner has a power comparable to that of an electric arc. The original oxygen injection 34 from the injector 32' is a penetrating injection and is located in the bath surface 24. As the oxygen penetrates into the liquid metal, the oxygen reacts with the carbon contained in the melt and releases CO gas. This release of CO creates large disturbances within the bath surface and in the dross layer.

Post-combustion lances 32 each inject into slag bed 22 a post-combustion oxygen stream 36, or stream of secondary oxygen, which is weaker and less penetrating than primary oxygen injection 34 , CO from the bath surface 24 is burned off with the injection of raw oxygen. CO is burned off inside the slag layer 22 . This leads to local overheating of the slag. In order to enhance agitation of the slag and push the slag back into the center of the arc furnace, the injection of post-combustion oxygen is positioned so that the resulting pulses enter the slag opposite those of the arc. Arrows 38 in FIG. 3 indicate the slag movement caused by the arc on the one hand and the slag movement caused by the injection of post-combustion oxygen 36 on the other hand. This makes it possible to speed up the smelting of the pre-reduced metal fines, and thus prevents these fines from agglomerating and being pushed and stuck to the furnace wall of the electric arc furnace.

Example 1

For a given electrical power, limited to 12MW for example, use of additional free carbon and oxygen, thus enabling the use of any technique: either melting at least double the flow rate of metal fines or (DRI), or supplying less metallized metal Fine powder or (DRI) into the furnace, thus increasing the productivity of the reduction furnace.

In the case of a multi-hearth furnace, the production of 54 or 57 t/h of DRI with a metallization level of 60% can be ensured by having a furnace with 50% of the capacity required to produce 50 t/h of DRI at a metallization level of 90% .

Also, the last column in Table 1 shows the possibility of adding additional carbon in the form of excess free carbon in the DRI.

Table 1: Data table of molten iron fed DRI into a 1000°C furnace smelted with 3% C, flowing at 1500°C. DRI Fe level (%) Amount of Metallization (%) DRI free C (%) DRI flow rate (t/h) Smelting iron flow rate (t/h) Electrical power (MW) Oxygen flow rate (Nm ³ /h) Additional C flow rate (t/h) 80 90 8 50 40 12 0 0 80 90 8 125 100 12 3000 2.4 74 60 8 54 40 12 3600 2.6 71 60 12 57 40 12 3600 0

Label description:

10 electric arc furnace

12 Converter

14 vault

16 electrodes

18 transfer device

20 nitrogen curtain

22 Slag layer

24 liquid metal melt

26 Hearth

28 perforated bricks

30 inert gas

32 post-combustion nozzles

32' original oxygen injector

34 Original Oxygen Injection

36 Post-combustion oxygen injection

38 Slag movement

Claims (130)

1. method of in electric arc furnace, producing liquid smelting iron, this electric arc furnace contains several electrodes, is equipped with burner hearth, and contains the weld pool surface that is covered by non-foam liquid slag, and this method may further comprise the steps:

A) the reducing metal fine powder contains the prereduction lemel of excessive uncombined carbon with formation.

B) in the noble gas curtain, under greater than 500 ℃ temperature, make the heat of prereduction lemel transfer to weld pool surface in the electric arc furnace.

C) to avoid forming crust by the stirring weld pool surface of jet flow stream.

D) in electric arc furnace the lemel of melting prereduction to obtain liquid smelting iron.

2. according to the method for claim 1, feature is to rely on gravity to carry out the transfer of prereduction lemel.

3. according to the method for claim 1, feature is that the transfer of prereduction lemel is to carry out in the zone between the electrode at electric arc furnace.

4. according to the method for claim 2, feature is that the transfer of prereduction lemel is to carry out in the zone between the electrode at electric arc furnace.

5. according to the method for claim 1, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 50-150l/min.t, and reach the stirring of weld pool surface.

6. according to the method for claim 2, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 50-150l/min.t, and reach the stirring of weld pool surface.

7. according to the method for claim 3, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 50-150l/min.t, and reach the stirring of weld pool surface.

8. according to the method for claim 4, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 50-150l/min.t, and reach the stirring of weld pool surface.

9. according to the method for claim 5, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 80-120l/min.t, and reach the stirring of weld pool surface.

10. according to the method for claim 6, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 80-120l/min.t, and reach the stirring of weld pool surface.

11. according to the method for claim 7, feature is by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 80-120l/min.t, and reach the stirring of weld pool surface.

12. method according to Claim 8, feature are by the burner hearth through electric arc furnace, to spray neutral gas with the speed of 80-120l/min.t, and reach the stirring of weld pool surface.

13. according to the method for claim 1, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

14. according to the method for claim 2, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

15. according to the method for claim 3, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

16. according to the method for claim 4, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

17. according to the method for claim 5, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

18. according to the method for claim 6, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

19. according to the method for claim 7, feature is by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

20. method according to Claim 8, feature are by through one or several injector, to spray oxygen-containing gas in weld pool surface, and reach the stirring of weld pool surface.

21. according to the method for claim 1, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

22. according to the method for claim 2, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

23. according to the method for claim 3, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

24. according to the method for claim 4, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

25. according to the method for claim 5, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

26. according to the method for claim 6, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

27. according to the method for claim 7, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

28. method according to Claim 8, feature are that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

29. according to the method for claim 13, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

30. according to the method for claim 14, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

31. according to the method for claim 15, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

32. according to the method for claim 16, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

33. according to the method for claim 17, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

34. according to the method for claim 18, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

35. according to the method for claim 19, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

36. according to the method for claim 20, feature is that step a) comprises the steps:

A1) lemel is incorporated into and has in the multiple hearth furnace of several stacked burner hearths, and it is deposited in the upper strata burner hearth of multiple hearth furnace,

A2) lemel is transferred to down in one deck burner hearth gradually,

A3) in one or several lower floor's burner hearth, add carbonaceous reducing agent, and guarantee that excessive uncombined carbon is arranged with the amount that is enough to the reducing metal fine powder,

A4) heating multiple hearth furnace, and make lemel contact and be reduced with carbonaceous reducing agent, produce gas by carbonaceous reducing agent,

A5) burn the excess air that produces by carbonaceous reducing agent, and with the heated drying and the preheating lemel of generation.

37. according to the method for claim 1, feature is to add slag former in step a) or step b).

38. according to the method for claim 2, feature is to add slag former in step a) or step b).

39. according to the method for claim 3, feature is to add slag former in step a) or step b).

40. according to the method for claim 4, feature is to add slag former in step a) or step b).

41. according to the method for claim 5, feature is to add slag former in step a) or step b).

42. according to the method for claim 6, feature is to add slag former in step a) or step b).

43. according to the method for claim 7, feature is to add slag former in step a) or step b).

44. method according to Claim 8, feature are to add slag former in step a) or step b).

45. according to the method for claim 13, feature is to add slag former in step a) or step b).

46. according to the method for claim 14, feature is to add slag former in step a) or step b).

47. according to the method for claim 15, feature is to add slag former in step a) or step b).

48. according to the method for claim 16, feature is to add slag former in step a) or step b).

49. according to the method for claim 17, feature is to add slag former in step a) or step b).

50. according to the method for claim 18, feature is to add slag former in step a) or step b).

51. according to the method for claim 19, feature is to add slag former in step a) or step b).

52. according to the method for claim 20, feature is to add slag former in step a) or step b).

53. according to the method for claim 21, feature is to add slag former in step a) or step b).

54. according to the method for claim 22, feature is to add slag former in step a) or step b).

55. according to the method for claim 23, feature is to add slag former in step a) or step b).

56. according to the method for claim 24, feature is to add slag former in step a) or step b).

57. according to the method for claim 25, feature is to add slag former in step a) or step b).

58. according to the method for claim 26, feature is to add slag former in step a) or step b).

59. according to the method for claim 27, feature is to add slag former in step a) or step b).

60. according to the method for claim 28, feature is to add slag former in step a) or step b).

61. according to the method for claim 29, feature is to add slag former in step a) or step b).

62. according to the method for claim 30, feature is to add slag former in step a) or step b).

63. according to the method for claim 31, feature is to add slag former in step a) or step b).

64. according to the method for claim 32, feature is to add slag former in step a) or step b).

65. according to the method for claim 37, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

66. according to the method for claim 38, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

67. according to the method for claim 39, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

68. according to the method for claim 40, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

69. according to the method for claim 41, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

70. according to the method for claim 42, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

71. according to the method for claim 43, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

72. according to the method for claim 44, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

73. according to the method for claim 45, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

74. according to the method for claim 53, feature is that slag former is selected from lime, flux and magnesium oxide, and their mixture.

75. according to the method for claim 1, feature is that excess carbon is 7-15%.

76. according to the method for claim 2, feature is that excess carbon is 7-15%.

77. according to the method for claim 3, feature is that excess carbon is 7-15%.

78. according to the method for claim 4, feature is that excess carbon is 7-15%.

79. according to the method for claim 5, feature is that excess carbon is 7-15%.

80. according to the method for claim 6, feature is that excess carbon is 7-15%.

81. according to the method for claim 7, feature is that excess carbon is 7-15%.

82. method according to Claim 8, feature are that excess carbon is 7-15%.

83. according to the method for claim 13, feature is that excess carbon is 7-15%.

84. according to the method for claim 21, feature is that excess carbon is 7-15%.

85. according to the method for claim 37, feature is that excess carbon is 7-15%.

86. according to the method for claim 65, feature is that excess carbon is 7-15%.

87. according to the method for claim 1, feature is that carbonaceous reducing agent is a charcoal.

88. according to the method for claim 2, feature is that carbonaceous reducing agent is a charcoal.

89. according to the method for claim 3, feature is that carbonaceous reducing agent is a charcoal.

90. according to the method for claim 4, feature is that carbonaceous reducing agent is a charcoal.

91. according to the method for claim 5, feature is that carbonaceous reducing agent is a charcoal.

92. according to the method for claim 6, feature is that carbonaceous reducing agent is a charcoal.

93. according to the method for claim 7, feature is that carbonaceous reducing agent is a charcoal.

94. method according to Claim 8, feature are that carbonaceous reducing agent is a charcoal.

95. according to the method for claim 13, feature is that carbonaceous reducing agent is a charcoal.

96. according to the method for claim 21, feature is that carbonaceous reducing agent is a charcoal.

97. according to the method for claim 37, feature is that carbonaceous reducing agent is a charcoal.

98. according to the method for claim 65, feature is that carbonaceous reducing agent is a charcoal.

99. according to the method for claim 75, feature is that carbonaceous reducing agent is a charcoal.

100. according to the method for claim 1, feature is that carbonaceous reducing agent removes volatile matter in step a).

101. according to the method for claim 2, feature is that carbonaceous reducing agent removes volatile matter in step a).

102. according to the method for claim 3, feature is that carbonaceous reducing agent removes volatile matter in step a).

103. according to the method for claim 4, feature is that carbonaceous reducing agent removes volatile matter in step a).

104. according to the method for claim 5, feature is that carbonaceous reducing agent removes volatile matter in step a).

105. according to the method for claim 6, feature is that carbonaceous reducing agent removes volatile matter in step a).

106. according to the method for claim 7, feature is that carbonaceous reducing agent removes volatile matter in step a).

107. method according to Claim 8, feature are that carbonaceous reducing agent removes volatile matter in step a).

108. according to the method for claim 13, feature is that carbonaceous reducing agent removes volatile matter in step a).

109. according to the method for claim 21, feature is that carbonaceous reducing agent removes volatile matter in step a).

110. according to the method for claim 37, feature is that carbonaceous reducing agent removes volatile matter in step a).

111. according to the method for claim 65, feature is that carbonaceous reducing agent removes volatile matter in step a).

112. according to the method for claim 75, feature is that carbonaceous reducing agent removes volatile matter in step a).

113. 7 method according to Claim 8, feature is that carbonaceous reducing agent removes volatile matter in step a).

114. according to the method for claim 1, feature is that excess carbon is consumed in step d).

115. according to the method for claim 2, feature is that excess carbon is consumed in step d).

116. according to the method for claim 3, feature is that excess carbon is consumed in step d).

117. according to the method for claim 4, feature is that excess carbon is consumed in step d).

118. according to the method for claim 5, feature is that excess carbon is consumed in step d).

119. according to the method for claim 6, feature is that excess carbon is consumed in step d).

120. according to the method for claim 7, feature is that excess carbon is consumed in step d).

121. method according to Claim 8, feature are that excess carbon is consumed in step d).

122. according to the method for claim 13, feature is that excess carbon is consumed in step d).

123. according to the method for claim 21, feature is that excess carbon is consumed in step d).

124. according to the method for claim 37, feature is that excess carbon is consumed in step d).

125. according to the method for claim 65, feature is that excess carbon is consumed in step d).

126. according to the method for claim 75, feature is that excess carbon is consumed in step d).

127. 7 method according to Claim 8, feature is that excess carbon is consumed in step d).

128. according to the method for claim 100, feature is that excess carbon is consumed in step d).

129. according to each method in the claim 1～128, feature is, excess carbon is by through one or several jet pipe, sprays to contain oxygen afterfire gas and flow in the slag and consume.

130. according to the method for claim 129, feature is that the location of the injection of afterfire gas will make the mobile electrode towards electric arc furnace of slag.

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