AU2009341533A1 - Method and equipment of producing iron by smelting-reduction - Google Patents

Abstract

A method of producing iron by smelting-reduction comprises the following steps: placing raw material in an iron smelting equipment, heating and reducing it to metal iron, heating the metal iron continuously to make it melt. The raw material is a breathing shell, a half-breathing shell, an open shell or mixture thereof. The iron smelting equipment can be a converter, arc furnace and so on.

Description

METHOD AND APPARATUS FOR PRODUCING IRON BY SMELTING-REDUCTION Technical Field The present invention relates to a method and apparatus for producing iron by smelting-reduction, and particularly to a method and apparatus for producing directly reduced molten steel by a smelting-reduction apparatus with heat reservoirs and molten iron similar to that made by a blast-furnace using natural lump ore or artificial iron lump ore as raw materials. Background Presently, smelting-reduction is an important composing part of steel producing, and it has the main characteristic of reducing ferric oxide in a melting state using a non-coking coal as non-regenerative energy and a reductant. The smelting-reduction also has the advantages of replacing coke by coal, short production process, less environment pollution as well as lower construction investment and production cost etc. Thus, the smelting-reduction is a field which is thought highly of by the industrial insiders, and the iron and steel enterprises in the world are competing for researching and developing the smelting-reduction. At present, the smelting-reduction includes COREX (CN1010323B), DIOS (CN1035136A) and HISELT (CN1037542A), in which the COREX method has been put into the industrial production, while the DIOS and HISELT methods are still in the experimental stage. The COREX has the main characteristic of using ferric oxide pellet or lump ore as raw materials and adopting a two-step method of pre-reduction and final-reduction. The pre-reduction is performed in a shaft furnace, and the final-reduction is completed in a smelting gasifier. Although having achieved a striking success, the COREX still has deficiencies such as low productivity, high coal and oxygen consumption as well as large equipment investment and complex production process etc. Thus, the COREX lacks competitive power as compared with the existing blast furnace iron-making. The applicant of the present invention discloses a three-step metal reduction method in an invention patent application No.200810079321.X. The method fabricates a molded article by mixing metal oxides with a certain amount of carbon, binder, CaO and water, and then places the molded article into a reduction apparatus. The first step of the method is performing the pre-reduction of the molded article in a state isolated from air and oxygen; the second step thereof is collecting evolved gas produced by the reduction process in the first step, and cooling, purifying and pressurizing the evolved gas; the third step thereof is that a final-reducing furnace uses the evolved gas as a reductant or a heat carrier to further reduce material emerged from a pre-reducing furnace, and causes the evolved gas to be in mixed combustion with heat exchanged air or oxygenrich gas, or makes the evolved gas be in mixed combustion with pure oxygen in the final-reducing furnace to heat products of the reducing furnace, thus carrying out a final reduction reaction while melting metal and removing slags, and finally producing molten iron or directly reduced molten steel. The applicant of the present invention provides a method and apparatus for producing iron by smelting reduction through an electric arc furnace in another invention patent application No. 200810079930.5, in which a melting furnace portion includes a 2 furnace body, a furnace cover, an electrode, a charging device and a discharging device. The apparatus further comprises at least a pair of heating furnaces and at least a pair of heat reservoirs; the heating furnaces are connected to a furnace body of the electric arc furnace through connecting ports; each of the heat reservoirs has one end connected to the respective heating furnace and has another end connected to a discharging system, a fan and a gas treatment apparatus. The present invention makes full use of the evolved gas produced by the smelting reduction process, and combusts the evolved gas to heat materials and regenerators in the heat reservoirs, thus bringing the heat from the heat reservoirs into the furnace by means of gas circulation so as to optimize the use of the heat. However, the above technical solution still has such deficiencies that a material molded article is apt to be oxidized and iron slags can not be separated easily in the reduction process. Summary of the Invention In order to eliminate deficiencies of the related art, the present invention provides a method for producing iron by smelting-reduction which causes a material molded article not to be oxidized in a reduction process while having no influence on heat transfer. Thus, the iron making process is optimized, and the molten steel and slags are separated from each other sufficiently to produce high quality steel products. Another object of the present invention is to provide an apparatus for producing iron by smelting-reduction which carries out the above method. The present invention provides a method for producing iron by smelting-reduction through an electric arc furnace, and the method includes: placing a molded article of a raw material into the electric 3 arc furnace; heating the molded article to reduce it into metal iron; and continually heating the products of the reducing furnace to make them molten after a metallization rate at which various iron oxides in the raw material are reduced reaches 40-95%, thus producing directly reduced molten steel or molten iron similar to that made by a blast-furnace. The raw material is a breathing shell, or a semi-breathing shell or an open shell or a mixture thereof. The breathing shell, the semi-breathing shell and the open shell are defined as follows: (1) the breathing shell mainly consists of a core molded article and an outer casing. (D the core molded article is divided into four types: (i) the core molded article is formed by being rolled or pressed into a molded article with a spherical shape or other shapes after an uncoated molded article, that is, iron oxides such as Fe 2

O

3 , Fe 3 0 4 etc. are mixed with carbonaceous matter such as coal powder and coke powder etc., a carbon content inside the molded article may be the same or may be different, and other substances such as calcium oxide or calcium carbonate etc. is allowed to be added into the molded article so as to make its composition and strength become more suitable; (ii) the molded article with the spherical shape or other shapes in (i) is coated with carbonaceous matter which is allowed to be added with other substances such as calcium oxide or calcium carbonate etc., the coating may be a rolling coating, a pressing coating, a coal powder spraying coating or a dipping coating, and other methods can also be used for coating the carbonaceous matter on the uncoated molded article with respect to the molded articles with different shapes; (iii) the molded article may also be a nonferrous substance or a less ferrous substance such as carbonaceous matter, lime and limestone etc.; (iv) the core 4 molded article is formed by rolling or pressing an uncoated molded article, that is, carbonaceous matter such as coal powder, coke powder, semicoke and petroleum coke etc. or a mixture thereof into a molded article with a spherical shape or other shapes. A carbon content in the molded article may be the same or may be different, and the molded article is allowed to be added with other substances such as calcium oxide or calcium carbonate etc. so as to make its composition and strength become more suitable; moreover, external dimensions of the core molded article may become larger or smaller according to the core molded article's material property, status of a melting furnace and ambience required by the melting furnace, and it is possible that the same melting furnace has core molded articles with different external dimensions and has core molded articles composed of different substances. @ the outer casing is formed by mixing a substance such as limestone, dolomite, lime or calcium carbide etc. or a mixture thereof with some other substances such as various adhesives like silicasol, water glass, phosphoric acid, and aluminum oxide etc.. It is allowed to add some other substances such as metal, metal oxides, carbonaceous matter, organic matter or inorganic matter etc. to the outer casing. These substances are mixed or bonded together in a certain manner to wrap the core molded article. The casing may be a rolling casing, a pressing casing, a powder spraying casing or a dipping casing. It is allowed but not necessary to add other substances into the casing as a framework etc.. And it is allowed but not necessary to adopt artificial perforations on the casing to enhance the breathability. Area of each aperture and its distribution state and number on the casing are determined by the breathing shell's property and material proportioning. The casing should have a certain low temperature intensity or high temperature intensity, and it is allowed to perform a drying process or a sintering process at a suitable temperature after the casing process. The thickness of the outer casing can be determined to be thick or thin according to the material property and proportioning of the whole breathing shell, the outer casing's composition and its material proportioning as well as the melting furnace's status etc.. It is allowed that different parts of the same casing in the same breathing shell adopt an outer casing composed of different thicknesses and different substances. The casings of the breathing shells which are placed in the same melting furnace may adopt outer casings composed of different thicknesses and different substances. When a breathing shell is placed into various melting furnaces to be heated, ambience in the melting furnace can be selected according to characteristics of the breathing shell, i.e. the ambience may be oxidative ambience or reductive ambience or weakly oxidative ambience. Taking a breathing shell mainly containing calcium carbonate as an example, calcium carbonate in an outer casing of the breathing shell is decomposed to discharge C02 at a suitable temperature; the outer casing of the breathing shell still transfers heat from outside of the melting furnace to the core molded article; substances which contain carbon and ferric oxide etc. in the core molded article undergo a reduction reaction to produce gases such as CO, C02, H 2 and hydrocarbon etc.; these gases are discharged from voids left by for example decomposing calcium carbonate in the outer casing of the breathing shell into the melting furnace; in a certain time period and temperature range, the amount of gases in the melting furnace entering the core molded article may present several situations according to property and proportioning of materials of the outer casing and the core 6 molded article of the breathing shell: the first situation is that almost no gas in the melting furnace enters the core molded article in the breathing shell, thus making the core molded article reduced without interference from extraneous gas; the second situation is that a little of gas in the melting furnace enters the core molded article in the breathing shell, thus participating in the reduction reaction in the core molded article; and the third situation is that much gas in the melting furnace enters the core molded article in the breathing shell, thus participating in the reduction reaction therein largely. The breathing shell's outer casing may be in the following state during its temperature is raised from a lower range to a higher range: (D the breathing shell's outer casing can still maintain a complete shape even at a very high temperature, and it can still keep intact after the core molded article finished most of the reduction reaction, even till the core molded article is in a smelted or semi-smelted state or is molten into a liquid state directly, at this time, the melting furnace such as an arc furnace etc. can be used to heat the outer casing so as to make the breathing shell's casing enter liquid metal as a flux, thus achieving iron slags or steel slags separation and producing directly reduced molten steel or molten iron similar to that made by a blast-furnace. The breathing shell's outer casing may be doped with substances with good conductivity such as metal corresponding to the metal oxides of the core molded article or metal oxides or metal compound thereof, so as to facilitate the subsequent heating process; @ the breathing shell's outer casing can not retain a long time or a very high temperature or it is made of carbon-containing material, which may cause cracking and pitting thereof to form a semi-breathing shell, thus exposing a part of the core molded article to the melting furnace's 7 ambience, and the melting furnace's ambience may be selected according to the degree of cracking and pitting, thus enabling the reduction process and the melting process thereafter to be performed in a suitable ambience; @ when heated from a low temperature to a high temperature, the breathing shell's outer casing can hardly retain its shape, and can hardly isolate the core molded article from the melting furnace's ambience effectively, i.e. forming an open shell, at this time, the melting furnace's ambience effects on the core molded article strongly, and the ambience need to meet the reducing and melting requirements, thus enabling metal oxides to be reduced while keeping a reduced state to avoid repeated oxidation. (2) the semi-breathing shell's main structure and composition are the same as those of the breathing shell except that the semi-breathing shell's outer casing is subject to cracking and pitting damages during heating the melting furnace from a low temperature to a high temperature, so that portions of the core molded article corresponding to the damaged positions are exposed to the melting furnace's ambience, while the other parts of the breathing shell are still protected under the outer casing so as to retain a function of isolating the core molded article from the gases in the melting furnace. (3) the open shell: ( the open shell's main structure and composition are the same as those of the breathing shell except that the open shell's outer casing can hardly retain its original shape when heated from a low temperature to a high temperature, and it can hardly isolate the core molded article from the melting furnace's ambience effectively, thus the melting furnace's ambience effects on the core molded article strongly; 0 under the condition that the core molded article does not have an outer 8 casing, the core molded article is mixed with calcium oxide or calcium carbonate or calcium carbide as a lump flux and one or several of substances such as lump coal, coal powder and lump coke etc. in the melting furnace, and the metal oxides are reduced and molten to form directly reduced molten steel or molten iron similar to that made by a blast furnace in the melting furnace's suitable ambience at the corresponding temperature. The open shell may comprise a lump mixture of a core molded article and a lump flux such as calcium oxide. The breathing shell, the semi-breathing shell and the open shell can be heated in a converter, an electric arc furnace, an open hearth, a plasma furnace, a puddling blast furnace, an electric resistance furnace, an induction heating furnace, a submerged arc furnace and a smelting reduction furnace or a combination of the above furnaces. The melting furnace's ambience can be selected according to the characteristics of the breathing shell, the semi-breathing shell and the open shell, i.e. the ambience may be oxidative ambience or reductive ambience or weakly oxidative ambience. As for the breathing shell's outer casing, in the case that almost no gas or a little of gas in the melting furnace enters the core molded article, the melting furnace can choose to heat the breathing shell in oxidative ambience or weakly oxidative ambience, but without excluding the breathing shell being heated in reductive ambience; in the case that much gas in the melting furnace enters the core molded article in the breathing shell through the outer casing, the semi-breathing shell or the open shell should be heated in weakly oxidative ambience or reductive ambience but without excluding they being heated in oxidative ambience. The breathing shell, the semi-breathing shell and the open shell can be heated directly in a converter, an electric arc furnace, an 9 open hearth, a plasma furnace, an electric resistance furnace, an induction heating furnace, a submerged arc furnace and a smelting reduction furnace or a combination of the above furnaces in suitable ambience to be reduced and molten so as to produce directly reduced molten steel or molten iron similar to that made by a blast-furnace; the breathing shell, the semi-breathing shell and the open shell can also be transferred into these melting furnaces after heated to a certain temperature in other furnaces. For example, these shells may be transferred into other melting furnaces which are provided separately or connected to the smelting reduction furnace or the smelting reduction furnace itself is enabled to have the function of these melting furnaces when the core molded article is heated to a certain temperature in the smelting reduction furnace, e.g. brought into a smelted or a semi-smelted state, or when metal oxides have been reduced to a certain degree. For example, inserting an electrode into the smelting reduction furnace for performing electric arc heating, or adding an induction coil in its furnace wall for performing induction heating or blowing-in oxygen for performing smelting similar to that in the converter etc.. A variety of smelting reduction furnaces may be used, for example, a shaft furnace, a rotary furnace and a coking furnace etc.. The shaft furnace may selectively use a blast furnace beam kiln, a sleeve kiln, a double hearth kiln or a shaft kiln with peripheral burners and with air and fuel feeding, and it can also be a specific smelting reduction furnace. Furnace of any type has a common characteristic, i.e. a considerable part of heating fuel comes from flammable gases such as CO, H 2 and hydrocarbon etc. generated by metal reduction of the core molded article of the breathing shell, the semi-breathing shell or the open shell. These flammable gases enter the smelting reduction furnace through a 10 form of a casing coated on the breathing shell and are combusted therein, or these flammable gases are combusted outside the smelting reduction furnace to produce heat energy, which is then carried into the melting furnace by these flammable gases such as CO, H 2 and hydrocarbon etc. or other types of gases or media, or flammable gases produced by the core molded article are used for generating electricity and heating-melting is performed in an electric heating form. And heat energy generated by these fuels accounts for whole or a considerable part of heat required by the reducing and melting process. In the case that the breathing shell's outer casing has fewer pores after heated, the outer casing may be added with a specific substance, for example, a substance with a low melting point, when it is being made, to increase porosity. In the case that the breathing shell's outer casing has more pores after heated, the outer casing may be added with a specific substance when it is being made, for example, substances such as SiO 2 /Al 2 0 3 etc. are added to a substance containing calcium carbonate to reduce porosity under high temperature. Material for making the breathing shell, the semi-breathing shell and the open shell can selectively use powder of lime, limestone, dolomite and calcium carbide etc. with a certain granularity or particles of lime, limestone, dolomite and calcium carbide etc. with a certain granularity. The following process can be performed in various suitable furnaces, and suitable products can also be produced by heating and melting the following materials: the breathing shell can also be applied to a melting-making process of calcium carbide in such a manner that a core molded article is made after mixing coal powder with calcium oxide powder or calcium carbonate powder in a certain form and a certain ratio and then calcium carbonate or Il calcium oxide is coated as an outer layer casing; technology of the breathing shell, the semi-breathing shell and the open shell can also be applied to smelt other metals as well as a calcination process of calcium carbonate or magnesium carbonate; the technology can also be applied to form a casing of substance such as calcium carbonate or magnesium carbonate etc., that is, carbonaceous matter is wrapped inside the casing to form coke with casing's substance containing calcium oxide etc. or semicoke with casing's substance containing calcium oxide, calcium carbonate or magnesium carbonate etc. after calcined in various furnaces at a certain temperature; coke and semicoke can be used in a blast furnace, a cupola furnace and a calcium carbide melting furnace etc. The present invention is particularly suitable for such metal melting process or chemical process, i.e. the casings of the breathing shell, the semi-breathing shell and the open shell serve as a flux or a participant in the whole process, and the reduction reaction or the chemical reaction of the core molded article in the breathing shell demands isolation or at least semi-isolation of the core molded article from gases in the ambience of the melting furnace or the heating furnace or other substances other than the casing substance in the melting furnace in a certain temperature range and within a certain technical time. In the meantime, in many cases, the melting furnace demands that the flammable gases or other gases generated by the reduction reaction or chemical reaction of the core molded article serve as fuel or participant required by the process after they enter the melting furnace through the pores in the casing, and that the products of the reduction reaction or chemical reaction of the core molded article as well as the casing substance and the other substance in the melting furnace are necessary participants in the process. Material 12 of the breathing shell, the semi-breathing shell and the open shell as well as other substances in the melting furnace almost do not participate in the reduction reaction process or chemical reaction process, and the substance which merely has the function of catalyzer accounts for a very small or a smaller proportion in the reduction reaction process or chemical reaction process. The reduction reaction or chemical reaction of the core molded article in most cases demands transfer of the heat in the melting furnace into the core molded article through the casings of the breathing shell, the semi-breathing shell and the open shell, and the transferred heat serves as whole or a considerable part of the heat required by the reduction reaction or chemical reaction, and by controlling the technical process and choosing a suitable combination of devices, it is possible to realize that the proportion of the flammable gases in the flue gas discharged from the melting furnace and its system is very low, and the temperature of the discharged flue gas is also low. Since the arrangement of the devices required in the whole reduction reaction or chemical reaction process is succinct and compact, as an alternative, the whole melting furnace and its important auxiliary facilities can be enclosed into a big container filled with inert gas, and the wall of the container may be made selectively of transparent, opaque or translucent substances. For example, the inert gas is helium. The big container is connected to a gas treatment device which performs dust-removing and purifying treatment of the gases in the container. The filtered gases which largely contain helium return to the container, thus reducing pollution and saving energy, and after the flue gas discharged from a duct is purified to remove harmful substances containing sulfur, the gases rich in C0 2 , N 2 can be used in the intensive agriculture etc., thus providing C02 for the intensive agriculture. It is possible 13 to utilize crops to extract different parts of the crops as the composition of the carbonaceous matter of the material provided by the present invention, thus enabling the whole flow to become a cycled and optimized process and become more environmental friendly. As an alternative, it is possible to adopt the following methods: the outer casing of a core molded article which contains ferric oxide or is carbonaceous matter for the breathing shell, the semi-breathing shell or the open shell is rich in calcium carbonate, calcium oxide or calcium carbide etc., the core molded article's carbon content can be selected appropriately, and the breathing shell, the semi-breathing shell and the open shell can be chosen differently according to a heating temperature curve which varies with time, so as to produce molten iron similar to that made by a blast-furnace or directly reduced molten steel. In this process, only a part of or a little of acidic substance such as SiO 2 etc. is reduced to a substance such as metal Si, while a part or a most part of the acidic substance such as SiO 2 etc. is combined with a flux such as CaO etc. in the casing to form molten slags to be discharged, thus enabling the subsequent process such as steel-making or iron-making etc. to become simple and convenient, and even using a little of oxygen or not using oxygen in the steel-making. After the reduced products are molten by heating, oxygen or inert gas is blown into an electric arc furnace, a converter, an open hearth, a submerged-arc furnace, a plasma furnace etc. to facilitate slag removing. The inert gas is argon. In order to carry out the above method for producing iron by smelting-reduction, the present invention provides an apparatus for producing iron by smelting-reduction such as an electric arc furnace, a converter, a submerged arc furnace and an induction 14 furnace. The electric arc furnace may have a melting function, and it comprises a furnace body, a furnace cover, an electrode, a charging device and a discharging device. The electric arc furnace further comprises at least a pair of heating furnaces and at least a pair of heat reservoirs; each of the heating furnaces is connected to the furnace body of the electric arc furnace; each of the heat reservoirs has one end connected to the respective heating furnace and has another end connected to a discharging system, a blower and/or a gas treatment device. A gas inlet is disposed at the bottom of the electric arc furnace. The submerged arc furnace comprises a furnace body, a furnace cover, an electrode as well as a heating furnace, a heat reservoir and a gas treatment device coordinated therewith. A gas inlet is disposed at the bottom of the submerged arc furnace, the gas inlet is connected to a gas pipeline, and the electrode is inserted into a lower portion of the melting material directly for the submerged arc operation. The converter comprises a furnace body, a furnace cover, an electrode and a coordinated apparatus. A gas inlet and a desulfurizer-charging port are disposed in the converter's cover; the gas inlet is connected to a gas pipeline. The induction furnace comprises a furnace body, a furnace cover, an induction coil as well as a power supply device and an external heating device coordinated therewith. A gas inlet is disposed in the induction furnace's cover and/or at the bottom of the induction furnace, and a desulfurizer-charging port is disposed in the induction furnace's cover. The present invention has the following advantages: 1. The present invention adopts the technology of a breathing shell, a semi-breathing shell and an open shell, and can apply the 15 breathing shell, the semi-breathing shell and the open shell, which can even serve as materials in the blast furnace iron-making, to almost all of the smelting-reduction apparatus or direct reduction apparatus. That is, the pre-reduction and final-reduction can be preformed quickly at a temperature under which a metal is to be molten approximately or a lower temperature, so as to reduce the pre-reduction time and speed up the pre-reduction process; in the meatime, the materials are not cohesive under this temperature, and can move effectively. The high-temperature gas produced by the final-reduction furnace can be used for heating the materials by direct combustion or by a heat-carrier, which changes the situation in the traditional smelting-reduction technology that the pre-reduction temperature is lower and the pre-reduction time is longer and the high-temperature gas from the final-reduction furnace needs to be largely cooled down before being used in the pre-reduction furnace, thus saving energy source and apparatus investment. 2. The breathing shell's outer casing can be used as a flux in the melting, and it is not necessary to add other fluxes or it is necessary only to add a few of other fluxes, thus saving energy source while making the technical process become more simpler. 3. The breathing shell's outer casing transfers heat to the core molded article effectively for the reduction reaction, while the core molded article produces gases such as CO, H 2 and hydrocarbon etc. in the reduction process, and these gases enter the reduction furnace through pores of the outer casing; in the meantime, only a little of gas in the furnace ambience can be controlled to enter the core molded article so that the reduction reaction of the core molded article can be performed almost without participation of extraneous gas, thus avoiding that the reduced metal is oxidized 16 again. Therefore, the melting furnace or the smelting reduction furnace for heating the breathing shell may adopt oxidative ambience or reductive ambience or weakly oxidative ambience. The combustible gases from the core molded article are combusted to provide all or most of heat required for heating the raw material by the breathing shell, the semi-breathing shell and the open shell; in the meantime, there are less combustible gas in the discharged flue gas, and the temperature of the discharged flue gas is lower. Thus, all these reduce the energy consumption in the reduction process and the melting process. 4. The material of the breathing shell, the semi-breathing shell and the open shell can be molten in many melting furnaces. The present invention gives some examples of heating and melting, in which only fuels including gas which enters the reduction furnace through the casing and gases such as CO, H 2 and hydrocarbon etc. produced by the core molded article are used. The core molded article inside the casing can be in a molten state, a semi-molten state or still be in a solid state but approximate to a smelted state, thus saving energy source, simplifying the apparatus and improving the efficiency. 5. In the reduction process, since the breathing shell, the semi-breathing shell and the open shell are used and the core molded article are isolated from the external environment, the reduction reaction in the casing is not affected. The molded article adopts the casing technology, which protects the material of the core molded article in the casing effectively, prevents the reduced substance from being oxidized in the reduction process while having no affection on the transfer of heat and some substances in the reduction process. The casing adopts the materials of limestone, dolomite and lime etc. and can serve as a flux for 17 producing iron by smelting-reduction or making molten steel by direct reduction. When the breathing shell, the semi-breathing shell and the open shell are adopted for producing molten iron similar to that made by a blast furnace or directly reduced molten steel, it is possible not to use coking, sintering and pelleting processes separately, and it is even possible not to use lime calcination and blast furnace iron-making processes separately, thus saving the fuel and simplifying the technical process. Since the casing is provided outside the molded article, it avoids contact and bonding between the molded articles so as to optimize the operation process. 6. The material of the casing may be alkaline limestone, dolomite, calcium carbide or lime etc., which reacts with the acidic substances in the raw material to generate furnace slags after the casing is broken in the melting process so that the directly reduced molten steel or molten iron can be separated from the slags and other impurities easily. After removing the slags and other impurities, the steel-making process may be preformed in the same melting furnace, i.e. oxygen or inert gases can be sprayed into the melting furnace, and an electromagnetic stirring of the electric arc furnace and the induction heating furnace can also be performed effectively. That is, in the same melting furnace, not only can molten iron or directly reduced molten steel be produced according to the material's different composition and technical process, but also the subsequent steel-making process can be preformed, which saves energy and reduces pollution effectively. 7. The present invention can cancel one or several of coking, sintering, pellet firing, lime calcination and blast furnace iron-making which are separate, and the arrangement of devices required by the whole reduction process or chemical process is 18 succinct and compact, thus saving land resources and reducing pollution source accordingly. In the meantime, the pollution of dioxin, phenol, nitrogen-oxygen compound and sulfur compounds etc. in the traditional technology is largely reduced. The breathing shell's outer casing also reduces discharge of sulphur-containing substance and other harmful substances into the atmosphere effectively so as to reduce emission of dust. 8. In the smelting-reduction and melting process, as a alternative, the following technical process can be performed, that is, only a part of or a little of acidic substance such as SiO 2 etc. is reduced to a substance such as metal Si, while a part or a most part of acidic substance such as SiO 2 etc. is combined with a flux such as CaO etc. in the casing to form molten slags to be discharged, which enables the subsequent process of steel-making or iron-making to become simple and convenient, and even a little of oxygen or no oxygen is used in the steel-making. 9. The flue gas produced by the present invention are rich in C02, and can be used for the intensive agriculture after purified to remove dust thereof, thus providing C02 for the intensive agriculture. It is possible to utilize crops to extract different parts of the crops as the composition of the carbonaceous matter of the material provided by the present invention, thus enabling the whole flow to become a cycled and optimized flow and become more environmental friendly. 10. The present invention adopts the technology of a breathing shell, a semi-breathing shell and an open shell, and can apply the breathing shell, the semi-breathing shell and the open shell to various suitable furnace types; in the meantime, the breathing shell can also be applied to a melting-making process of calcium carbide in such a manner that a core molded article is made after mixing 19 coal powder with calcium oxide powder or calcium carbonate powder etc. in a certain form and a certain ratio and then coating calcium carbonate or calcium oxide as an outer layer casing; technology of the breathing shell, the semi-breathing shell and the open shell can also be applied to smelting of other metals as well as a calcination process of calcium carbonate or magnesium carbonate; the technology can also be applied to form a casing of substance such as calcium carbonate or magnesium carbonate etc., that is, carbonaceous matter is wrapped inside the casing to form coke with casing's substance containing calcium oxide etc. or semicoke with casing's substance containing calcium oxide, calcium carbonate or magnesium carbonate etc. after calcined in various furnaces at a certain temperature; coke and semicoke can be used in a blast furnace, a cupola furnace and a calcium carbide melting furnace etc. The present invention is particularly suitable for such metal melting process or chemical process, i.e. the casings of the breathing shell, the semi-breathing shell and the open shell serve as a flux or a participant in the whole process, and the reduction reaction or the chemical reaction of the core molded article in the breathing shell demands isolation or at least semi-isolation of the core molded article from gases in the ambience of the melting furnace or the heating furnace or other substances other than the casing substance in the melting furnace in a certain temperature range and within a certain technical time. In the meantime, in many cases, the melting furnace demands that the flammable gases or other gases generated by the reduction reaction or chemical reaction of the core molded article serve as fuel or participant required by the process after they enter the melting furnace through the pores in the casing, and that the products of the reduction reaction or chemical reaction of the core 20 molded article as well as the casing substance and the other substance in the melting furnace are necessary participants in the process. Material of the breathing shell, the semi-breathing shell and the open shell as well as other substances in the melting furnace almost do not participate in the reduction reaction process or chemical reaction process directly, and the substance which merely has the function of catalyzer accounts for a very small or a smaller proportion in the reduction reaction process or chemical reaction process. The reduction reaction or chemical reaction of the core molded article in most cases demands transfer of the heat in the melting furnace into the core molded article through the casings of the breathing shell, the semi-breathing shell and the open shell, and the transferred heat serves as whole or a considerable part of the heat required by the reduction reaction or chemical reaction, and by controlling the technical process and choosing a suitable combination of devices, it is possible to realize that the proportion of the flammable gases in the flue gas discharged from the melting furnace and its system is very low, and the temperature of the discharged flue gas is also low. Brief Description of the Drawings Fig. 1 is a schematic diagram of an apparatus for producing iron by smelting-reduction through an electric arc furnace of the present invention; Fig. 2 is a schematic diagram of a flow of a discharging system of the present invention; Fig. 3 is a schematic diagram of an arrangement of a furnace cover and an electrode of the electric arc furnace in the present invention; 21 Fig. 4 is a schematic diagram of an apparatus for producing iron by smelting-reduction through a submerged arc furnace; Fig. 5 is a schematic diagram of an apparatus for producing iron by smelting-reduction through a converter; Fig. 6 is a schematic diagram of an apparatus for producing iron by smelting-reduction through an induction furnace; Fig. 7 is a schematic diagram of an apparatus for producing calcium carbide by a submerged arc furnace. Wherein, 1- electrode; 2- furnace body; 3- furnace cover; 4- blower; 5- heating furnaces (5a, 5b); 6- heat reservoirs (6a, 6b); 7 regenerators; 8- gas treatment device; 9- molten iron/molten steel outlet; 10- gas pipeline; 11- desulfurizer-charging port; 12- cyclone separator; 13- bag dust collector; 14-draught fan; 15- chimney; 16 gas inlet; 17- induction coil; 18- slag cooling device; 19- pig iron or continuous casting billet or rolled metal cooling device; 20- calcium carbide cooling cylinder; 21- calcium carbide outlet. Detailed Description of the Embodiments (Embodiment 1) The apparatus for producing iron by smelting-reduction is an electric arc furnace, and the raw material is a breathing shell. As shown in Fig.1, the apparatus for producing iron by smelting-reduction through the electric arc furnace provided by the present invention comprises a furnace body 2, a furnace cover 3, a charging device and a discharging device, wherein a molten iron/molten steel outlet 9 is provided in a lower portion of the furnace body 2. A gas inlet 16 is provided at the bottom of the electric arc furnace, and the gas inlet 16 is connected to a gas 22 pipeline 10. As shown in Fig.3, three electrode sockets are provided on the furnace cover 3, an electrode 1 is inserted into the sockets respectively, and the three electrode sockets are in a triangular distribution. A pair of heating furnaces 5a, 5b and a pair of heat reservoirs 6a, 6b are provided outside the furnace body 2, and the two heating furnaces are mounted on both sides of the furnace body 2. The heating furnaces are connected to the furnace body 2 of the electric arc furnace through connecting ports, and gases flow back and forth in the connecting ports. Each of the heat reservoirs 6a, 6b has one end connected to the respective heating furnace, and has another end connected to a blower 4, a gas treatment device and a discharging system respectively. The gas treatment device comprises a gas-circulating compressor, a gas cooling and purifying device and a gas storage tank etc. The gas treatment device may be used or may not be used. In order to make full use of residual heat, the apparatus for producing iron by smelting-reduction through the electric arc furnace is further provided with two or more than two slag cooling devices 18 and two or more than two pig iron or continuous casting billet or rolled metal cooling devices 19. Heat of molten slags or continuous casting billets or rolled metals is brought to the furnace body 2 via the heating furnaces 5a, 5b by using circulation of evolved gas. As shown in Fig.2, the discharging system comprises a cyclone separator 12, a bag dust collector 13, a draught fan 14 and a chimney 15. The heating furnaces are provided with combustion-supporting air pipelines and fuel pipelines. The outlet of the blower 4 is divided into four branches, which are connected to the two heating furnaces and the two heat reservoirs respectively, and each of which is provided with a valve. The fuel pipelines connected to the heating furnaces and waste gas 23 discharging pipelines connected to the heat reservoirs are also provided with valves. The two heating furnaces combust fuel and evolved gas alternately, and the two heat reservoirs perform heat-storage and heat-emission alternately. The evolved gas is produced in the reduction process of iron oxides, in which a large amount of CO, H 2 is contained. Each of the heat reservoirs has a regenerator 7 which is a ceramic ball-like body. The furnace body 2 and furnace cover 3 of the electric arc furnace are of a steel structure, and are mounted with a refractory liner. The furnace body 2 and the furnace cover 3 as well as the electrodes 1 and the furnace cover 3 are connected to each other hermetically by means of water cooling jackets. The technical steps of the smelting-reduction iron making process by the electric arc furnace are as follows: (1) Preparation of a breathing shell: mixing iron oxides such as Fe 2

O

3 , Fe 3 0 4 etc. with coal powder, and adding an appropriate amount of water to make a pellet, i.e. a core molded article; and coating an outer layer of the core molded article with limestone powder and other specific substances as its material and with specific material such as silica sol etc. as an adhesive to form a pellet casing, i.e. a breathing shell. (2) Drying the breathing shell in which the core molded article is wrapped, and then placing the breathing shell into the electric arc furnace. (3) Using an external heating method to heat the breathing shell, and reducing the core molded article at a certain temperature or a certain group of suitable temperatures within a range of 300-1800 'C , wherein the evolved gas is produced continuously in this process. 24 (4) Activating the electrodes of the electric arc furnace to break up the breathing shell by arc heating when a metallization rate of the core molded article in the breathing shell reaches 40-95%, so as to melt the reduced matter in the breathing shell. (5) Performing slag-iron separation to produce molten iron or directly reduced molten steel. The operation process provided by the present invention is: placing the raw material into the furnace body 2 of the electric arc furnace, activating the heating furnace 5b first to heat the regenerator 7 thereof, and then causing flue gas to flow to a discharging system via a valve. When reaching a set temperature, a flue gas outlet of the heat reservoir 6b switches its gas flow direction, air enters the heating furnace 5b via the valve and the heat reservoir 6b, and the regenerator in the heat reservoir emits heat to heat combustion-supporting air. The produced flue gas enters the furnace body 2 of the electric arc furnace through connecting ports to heat the molded article of a breathing shell and performs reduction reaction; the produced evolved gas enters the heating furnace 5a together with the flue gas, and is combusted in the heating furnace 5a after mixed with air with an appropriate flow coming via the valve. The flue gas enters the heat reservoir 6a to transfer heat to the regenerator 7 thereof, and then flows to a discharging system via a valve. When reaching a set temperature, a flue gas outlet of the heat reservoir 6a switches its gas flow direction, combustion-supporting wind enters the heat reservoir 6a via the valve to pre-heat the combustion-supporting air, and then enters the heating furnace 5a to be combusted after mixed with fuel coming via the valve. The flue gas and the evolved gas enter the furnace body 2 of the electric arc furnace through the connecting ports on the right side, and then enter the heating furnace 5b 25 through the connecting ports on the left side, and are combusted in the heating furnace 5b after mixed with air with an appropriate flow coming via the valve. Then the flue gas enters the heat reservoir 6b to transfer heat to the regenerator therein before flowing to the discharging system via the valve. The operation of switching gas flow direction of the two heating furnaces 5a, 5b and the two heat reservoirs 6a, 6b is controlled by setting a temperature at the flue gas outlets of the heat reservoirs. When a flue gas outlet of a certain heat reservoir reaches a set temperature, its gas flow direction is switched automatically. At this time, the heating furnace on this side alters from combusting the evolved gas to combusting fuel. The whole process is controlled automatically, and the switching operation is carried out by switching each of the valves. When starting the heating, it is possible to use the slag cooling devices 18 and the pig iron or continuous casting billet or rolled metal cooling devices 19 as an air pre-heating device, the pre-heated air as a heat-carrier or combustion-supporting gas is in mixed combustion with the evolved gas produced after the breathing shell is heated in a melting furnace to heat the breathing shell and the corresponding regenerator. The operation process of the apparatus for producing iron by smelting-reduction through the electric arc furnace is as follows: by the above progress, flammable gases rich in CO, H 2 and hydrocarbon etc. are produced from the material of the breathing shell, the semi-breathing shell or the open shell, and these flammable gases provide almost all or a considerable part of heat required to heat the materials in the melting furnace to a certain temperature or a certain group of suitable temperatures within a range of 300-1800'C, and iron oxides in the materials are reduced 26 into metal iron. In the above process, when a metallization rate of metal oxides in the raw material within the furnace reaches 40-95% (the reduced metal iron in the breathing shell may be in a solid state, a liquid state or a semi-smelted state), an electrode is used to melt the metal iron by arc heating, and sufficient electromagnetic stirring is performed. The broken outer casing rich in fluxes such as calcium oxide etc. reacts with acidic matter in the raw material, so that slagging and slag-iron separation are performed to produce molten iron or directly reduced molten steel. The molten iron or directly reduced molten steel flows out from a molten iron/molten steel outlet 9. As an alternative, it is also possible to blow-in oxygen or argon to perform molten steel melting or molten iron melting directly after pouring out molten slags. In the above technical process, arc heating by the electrodes can be operated intermittently according to the furnace's state, and the intermittent time may be 0-100% of the reduction and melting time. Introduction of oxygen or argon from the top or the bottom of the furnace can select to input, not to input or to input one of oxygen and argon according to the status of the smelted or semi-smelted molten iron or directly reduced molten steel. It is possible to select to make all molten iron or directly reduced molten steel be in liquid state in the whole process, and almost all molten iron or directly reduced molten steel is discharged out of the furnace body before adding material to perform smelting again. It is also possible that a part which is smelted of molten iron or directly reduced molten steel is discharged out of the furnace body while substances which are smelted incompletely still remain in the furnace to be heated continuously. In the meantime, an appropriate method of adding material is selected to add material. In the melting process, the melting furnace adopts an electrode to perform arc 27 reduction-melting heating or performs fuel reduction-melting heating by introducing combustion-supporting air or oxygen containing gases, and the two kinds of reduction-melting heating can be performed separately or simultaneously. Height-diameter ratio of the furnace body 2 can selectively be slender or squat according to the material's situation and the furnace's status, and the furnace's specific height and diameter are determined by the furnace's status, the material's property and the furnace's productive capacity etc.. The number of the heat reservoirs around the furnace body 2 can be a pair or more pairs selectively. The regenerators in the heat reservoirs can be high temperature resistant refractory pellets and refractory bricks or refractory regenerators with a honeycomb shape or other shapes. The regenerators can adopt a suitable high temperature resistant metal product or a suitable high temperature resistant non-metal product such as carbonaceous matter etc. partially or totally. The slag cooling devices 18 are loaded with separable slags; the pig iron or continuous casting billet or rolled metal cooling devices 19 are loaded with pig iron or continuous casting billets or rolled metals (in the case that suitable above products or by-products exist). In most cases, when the melting furnace is just charged with materials, air (air pipelines associated therewith are not marked in Fig.1) or other oxygen-containing gases or gases rich in CO, H 2 or C02 etc. in the gas treatment device is introduced to cool slags or pig iron or continuous casting billets or rolled metals properly, and then the heated gases as a heat carrier or a combustion-supporting gas are input to the melting furnace for heating the materials. The slag cooling devices 18 and the pig iron or continuous casting billet or rolled metal cooling devices 19 can selectively not be used according to the actual situation. After the flue gas discharged from 28 a pipe is purified to remove harmful substances such as sulphur-containing substance etc., gases rich in C02, N 2 can be used in the intensive agriculture etc.. (Embodiment 2) The apparatus for producing iron by smelting-reduction is a submerged arc furnace, and the raw material is a semi-breathing shell. As shown in Fig.4, the apparatus for producing iron by smelting-reduction through the submerged arc furnace comprises a furnace body 2, a furnace cover 3, an electrode 1 as well as heating furnaces 5a, 5b, heat reservoirs 6a, 6b and a gas treatment device 8 coordinated therewith. A gas inlet 16 is provided at the bottom of the submerged arc furnace, and the gas inlet 16 is connected to a gas pipeline 10. The gas treatment device comprises a gas-circulating compressor, a gas cooling and purifying device and a gas storage tank etc.. The gas treatment device may be used or may not be used. In order to make full use of residual heat, the apparatus for producing iron by smelting-reduction is further provided with two or more than two slag cooling devices 18 and two or more than two pig iron or continuous casting billet or rolled metal cooling devices 19. Heat of slags or continuous casting billets or rolled metals is brought to the furnace body 2 via the heating furnaces 5a, 5b by using circulation of evolved gas. The apparatus for producing iron by smelting-reduction through submerged arc furnace as described in Embodiment 2 differs from the apparatus for producing iron by smelting-reduction through the electric arc furnace as described in Embodiment 1 in that the electrode in Embodiment 2 is inserted into a lower portion of the melting material directly so as to perform 29 the submerged arc operation. The technical steps of the smelting-reduction iron making process by the submerged arc furnace are as follows: (1) Preparation of the semi-breathing shell: mixing iron oxides such as Fe 2 0 3 , Fe 3 0 4 etc. with coal powder, and adding an appropriate amount of water to make a pellet, i.e. a core molded article; coating an outer layer of the core molded article with limestone powder, ironstone powder and other specific substances as its material and with specific material such as water glass etc. as an adhesive to form the semi-breathing shell. The semi-breathing shell differs from the breathing shell in that an outer casing of the semi-breathing shell is floppy and can not resist a high temperature above 1000'C, so that the outer casing is broken in the smelting reduction process. (2) Placing the semi-breathing shell in which the core molded article is wrapped into the submerged arc furnace, wherein the semi-breathing shell is mixed with lump coal having a certain granularity. (3) Using an external heating method to heat the semi-breathing shell, and reducing the materials in the melting furnace at a certain temperature or a certain group of suitable temperatures within a range of 300-1800 'C , wherein the evolved gas is produced continuously in this process. (4) Activating the electrode of the submerged arc furnace to perform arc heating when a metallization rate of the molded article in the furnace reaches 40-95%, so as to melt the reduced matter by arc heating. (5) Performing slag-iron separation to produce molten iron or directly reduced molten steel. 30 In the process of producing iron by smelting-reduction using the semi-breathing shell, the outer casing of the reduced semi-breathing shell is broken in the melting process, and the broken casing substance can be used as a flux and a slagging agent, which is beneficial to improve quality of the reduced product and for the slag-iron separation. As shown in Fig.4, the heat reservoirs 6a, 6b accumulate heat in a manner of switching their gas flow directions alternately. Oxygen-containing gases pass through the heat reservoir 6b to be combusted together with fuel in the heating furnace 5b and the melting furnace, and the evolved gas which is discharged from the material of the semi-breathing shell out of the casing continuously is combusted as well. Flue gas and unutilized gases such as unburned evolved gas etc. enter the opposite heating furnace 5a. Oxygen-containing gases with an appropriate flow are selected to be mixed and combusted together with combustible substance in the evolved gas. A regenerator 7 in the heat reservoir 6a is heated to accumulate heat, and the cooled flue gas is discharged via a discharging system. Only a little of combustible gas exists in the discharged flue gas, and the discharged flue gas has a low temperature. Thereafter, oxygen-containing gases enter the heating furnace 5a through the heat reservoir 6a to be combusted together with fuel in the heating furnace 5a. The materials in the melting furnace are heated to produce flue gas and evolved gas, which enter the heating furnace 5b together and are mixed and combusted with oxygen-containing gases with an appropriate flow therein. A regenerator 7 in the heat reservoir 6b is heated to accumulate heat, and the cooled flue gas enters a gas discharging system. Only a little of combustible gas exists in the discharged flue gas, and the discharged flue gas has a low temperature. By circulating in turn, the oxygen-containing 31 gases which enter the heating furnaces are always high-temperature gases, thus heat efficiency of the system is improved. The flammable gases rich in CO, H 2 and hydrocarbon etc. are generated from the material of the breathing shell, the semi-breathing shell or the open shell, and these flammable gases provide almost all or a considerable part of heat required for heating the materials in the melting furnace to a certain temperature or a certain group of suitable temperatures within a range of 300-1800'C, and iron oxides in the materials are reduced into metal iron. In the above process, when a metallization rate of metal oxides in the raw material within the furnace reaches 40-95% (the reduced metal iron in the semi-breathing shell may be in a solid state, a liquid state or a semi-smelted state), an electrode is used to melt the metal iron by arc heating, and sufficient electromagnetic stirring is performed. The smelting-reduction iron making process is performed on the semi-breathing shell in the furnace body, the outer casing of the reduced semi-breathing shell is broken in the melting process, and the broken casing substance can be used as a flux and a slagging agent, which is beneficial to improve quality of the reduced product and for the slag-iron separation. Molten iron or directly reduced molten steel is produced, and the molten iron or directly reduced molten steel flows from a molten iron/molten steel outlet 9. As an alternative, it is also possible to blow-in oxygen or argon to perform molten steel melting or molten iron melting directly after pouring out slags on the molten iron or directly reduced molten steel from the top of the furnace. In the above technical process, submerged arc electric heating can be operated intermittently according to actual situation of the whole process, and the intermittent time may be 0-100% of the reduction and melting time. Introduction of oxygen or argon 32 from the top or the bottom of the furnace can select to input, not to input or to input one of oxygen and argon according to the status of the smelted or semi-smelted molten iron or molten steel. It is possible to select to make all molten iron or directly reduced molten steel be in liquid state in the whole process, and all of molten iron or directly reduced molten steel is discharged out of the furnace body. It is also possible that a part which is smelted of molten molten iron or directly reduced molten steel is discharged out of the furnace body while substances which are smelted incompletely still remain in the furnace to be heated continuously. In the meantime, an appropriate method of adding material is selected to add material. In the melting process, the melting furnace adopts an electrode to perform arc reduction-melting heating or performs fuel reduction-melting heating by introducing combustion-supporting air or oxygen containing gases, and the two kinds of reduction-melting heating can be performed separately or simultaneously. In order to reduce oxygen content, impurities and carbon content in molten steel, it is possible to adopt an argon blowing technology after molten slags in the melting furnace are poured out. Argon blowing has a function similar to that of vacuum treatment, i.e. deoxidation, decarburization, degasification as well as molten steel stirring and impurities removing etc.. Argon in use can be byproduct in the oxygen-making industry. Pure argon contains less other gas. After argon is blown into molten steel, it neither participates in chemical reaction nor is dissolved in the molten steel. When air bubbles are formed after argon is blown into molten steel, these air bubbles become nothing else but small vacuum chambers for various gases dissolved in steel, in which partial pressures of other gases are all zero nearly. In this case, gases such as hydrogen and nitrogen etc. in the molten steel diffuse 33 continuously towards the argon gas bubbles, and partial pressures of gases such as hydrogen and nitrogen etc. in the gas bubbles will increase gradually. However, since the gas bubbles receive reduced static pressure and endure thermal expansion in their floating-up process, partial pressures of hydrogen and nitrogen can still retain at a lower level, so that the gas bubbles are capable of absorbing hydrogen and nitrogen etc. continuously. Finally, these gases float out of the molten steel along with argon gas bubbles to be removed. In this case, pure molten iron or pure directly reduced molten steel is obtained. Height-diameter ratio of the furnace body 2 can selectively be slender or squat according to the material's situation and the furnace's status, and the furnace's specific height and diameter are determined by the furnace's status, the material's property and the furnace's productive capacity etc.. The number of the heat reservoirs around the furnace body 2 can be a pair or more pairs selectively. The regenerators in the heat reservoirs can be high temperature resistant refractory pellets and refractory bricks or refractory regenerators with a honeycomb shape or other shapes. The regenerators can adopt a suitable high temperature resistant metal product or a suitable high temperature resistant non-metal product such as carbonaceous matter etc. partially or totally. The slag cooling devices 18 are loaded with separable slags; the pig iron or continuous casting billet or rolled metal cooling devices 19 are loaded with pig iron or continuous casting billets or rolled metals (in the case that suitable above products or by-products exist). In most cases, when the melting furnace is just charged with materials, air (air pipelines associated therewith are not marked in Fig.4) or other oxygen-containing gases or gases rich in CO, H 2 or C02 etc. in the gas treatment device is introduced to cool slags or 34 pig iron or continuous casting billets or rolled metals properly, and then the heated gases as a heat carrier or a combustion-supporting gas are input to the melting furnace for heating the materials. The slag cooling devices 18 and the pig iron or continuous casting billet or rolled metal cooling devices 19 can selectively not be used according to the actual situation. After the flue gas discharged from a duct is purified to remove harmful substances such as sulphur-containing substance etc., gases rich in C02, N 2 can be used in the intensive agriculture etc.. (Embodiment 3) The apparatus for producing iron by smelting-reduction is a converter, and the raw material is an open shell. As shown in Fig.5, the apparatus for producing iron by smelting-reduction through the converter comprises a furnace body 2, a furnace cover 3, an electrode as well as heating furnaces 5a, 5b, heat reservoirs 6a, 6b and a gas treatment device 8 coordinated therewith. A gas inlet 16 and a desulfurizer-charging port 11 are provided in the furnace cover of the converter, and the gas inlet 16 is connected to a gas pipeline 10. In order to make full use of residual heat, the apparatus for producing iron by smelting-reduction is further provided with two or more than two slag cooling devices 18 and two or more than two pig iron or continuous casting billet or rolled metal cooling devices 19. Heat of slags or continuous casting billets or rolled metals is brought to the furnace body 2 via the heating furnaces 5a, 5b by using circulation of evolved gas. The technical steps of the smelting-reduction iron making process by the converter are as follows: (1) Preparation of the open shell: mixing iron oxides such as Fe 2 0 3 , 35 Fe 3 0 4 etc. with coal powder, doping 5% of limestone powder and some other specific substances, and adding an appropriate amount of water to make a pellet, i.e. the open shell. The open shell is a pelleted molded article containing carbon and not having an outer casing, which is doped with lime or limestone powder. (2) Placing the open shell into the converter, and evenly doping an appropriate amount of lime block, lump coal having a certain granularity and some other specific substances. (3) Using an external heating method to heat the open shell, and reducing the materials in the melting furnace at a certain temperature or a certain group of suitable temperatures within a range of 300 - 1800 C , wherein the evolved gas is produced continuously in this process. (4) Activating the electrode of the converter to perform arc heating when a metallization rate of the molded article in the furnace reaches 40-95%, so as to melt the reduced matter by arc heating. (5) Performing slag-iron separation to produce molten iron or directly reduced molten steel. After molten slags are poured out, highly-pure oxygen is introduced into the furnace from a top port, and the highly-pure oxygen is blown to a molten pool at a high speed. High-speed oxygen jet flow impacts the molten pool directly, which performs strong stirring on the molten pool on one hand, and causes strong mutual breaking between the oxygen jet flow and the molten pool on the other hand, thus increasing contact areas between different phases rapidly. These physical phenomenons create excellent conditions for chemical reactions in the furnace, and bring about radical changes to oxygen transfer mechanism, oxygen transfer speed as well as transfer speed of various elements in the molten pool and reaction 36 interfaces thereof. Oxygen is blown into the smelted pig iron to oxidize impurities such as silicon and manganese etc.. A large amount of heat is produced in the oxidation process, which enables a temperature in the furnace reach an enough high temperature. Therefore, it is not necessary for a converter to use additional fuel for steel-making. Steel-making by a converter is performed in the converter. At the beginning, the converter is in a horizontal orientation, and then oxygen is blown into molten pig iron while rotating the converter. At this time, a drastic reaction takes place on a surface of the molten pig iron so that iron, silicon and manganese are oxidized to produce slags. The reaction spreads all over in the furnace by convection of molten steel and molten slags. When only slight silicon and manganese are left in the molten steel, carbon begins to be oxidized so as to produce carbon monoxide to make the molten steel boiling severely. A large blaze appears at a converter mouth due to combustion of escaped carbon monoxide. Finally, phosphor is also oxidized to produce ferrous phosphate, which then reacts with quick lime to produce stable calcium phosphate and calcium sulfide which become slags all together. When phosphor and sulphur are reduced gradually, the blaze fades. When a brown steam of ferroferric oxide appears at the converter mouth, it indicates that the steel-making has been completed. At this time, oxygen-blowing should be stopped immediately, the converter is rotated to be in a horizontal orientation, molten steel is poured into a ladle, and a deoxidizing agent is added to perform deoxidation. As an alternative, oxygen can also be blown-in from the bottom of the furnace. The present invention adopts an oxygen top-blowing converter, but not excluding an oxygen side-blowing converter and an oxygen 37 bottom-blowing converter. The blown-in oxygen is high-pressure industrial pure oxygen, which can further improve production efficiency and steel quality. This is a steel-making method which mainly uses liquid-state pig iron as material and does not need additional heat sources. The main characteristic of steel-making by the converter is: a metal with composition and temperature which satisfy the tapping requirement can be produced depending on physical heat of liquid-state pig iron in the converter and heat produced by the chemical reaction of each component (such as carbon, manganese, silicon and phosphor etc.) of the pig iron with oxygen blown into the furnace. Furnace material is mainly the open shell, and a small amount of the breathing shell and the semi-breathing shell or lump coal having a certain granularity may be added. The converter can be divided into an alkalic converter and an acidic converter according to property of refractory material of a furnace lining thereof; the converter can be divided into a bottom-blowing converter, a top-blowing converter and a side-blowing converter according to position where oxygen is blown-in; and the converter can be divided into an air converter and an oxygen converter according to the type of the blown-in gas. The converter provided by the present invention is an oxygen converter, wherein the open shell is used as the raw material and the furnace is an alkalic converter. The converter may adopt nozzles or porous bricks to blow-in oxygen from the bottom thereof, which can improve a stirring force of the molten pool largely and have advantages of bottom-blowing and top-blowing concurrently. The main advantage of the converter steel making process, as compared with other steel making processes, is that without additional energy sources, it accomplishes the tasks of decarbonization and impurities removing 38 merely depending on the exothermic oxidation reaction between oxygen blown into the molten pool and various elements in molten pig iron, and heats molten steel to the tapping temperature of 1600 'C or higher. After blow-melting of the converter is completed, slight superfluous dissolved oxygen generally being 0.01-0.08% exists in the molten steel, and the content of which is mainly determined by carbon content of the resulting molten steel. Deoxidation must be performed to produce qualified steel products. The deoxidation is adding elements having larger oxygen affinities and alloys thereof as deoxidizing agents to molten steel, and reducing oxygen content of steel to below a prescribed limit by virtue of the principle that deoxidated products are not dissolved in molten steel but released, floated upward and departed from molten steel. After the open shell is added into the melting furnace, a fuel-heating process is performed that oxygen-containing gases pass through the heat reservoir 6b to be combusted together with fuel in the heating furnace 5b and the melting furnace, the evolved gas which is discharged from the material of the open shell continuously is combusted as well. Flue gas and unutilized gases such as unburned evolved gas etc. enter the opposite heating furnace 5a. Oxygen-containing gases with an appropriate flow are selected to be mixed and combusted together with combustible substance in the evolved gas. A regenerator 7 in the heat reservoir 6a is heated to accumulate heat, and the cooled flue gas enters a discharging system. Only a little of combustible gas exists in the discharged flue gas, and the discharged flue gas has a low temperature. Thereafter, oxygen-containing gases enter the heating furnace 5a through the heat reservoir 6a to be combusted 39 together with fuel in the heating furnace 5a. The materials in the melting furnace are heated to produce flue gas and evolved gas, which enter the heating furnace 5b together and are mixed and combusted with oxygen-containing gases with an appropriate flow therein. A regenerator 7 in the heat reservoir 6b is heated to accumulate heat, and the cooled flue gas enters a cyclone separator 12 and a bag dust collector 13 and is discharged from a chimney 15. The discharged flue gas also contains a little of combustible gas, and the discharged flue gas has a low temperature. By circulating in turn, the oxygen-containing gases which enter the heating furnaces are always high-temperature gases, thus heat efficiency of the system is improved. The flammable gases rich in CO, H 2 and hydrocarbon etc. are generated from the material of the breathing shell, the semi-breathing shell or the open shell, and these flammable gases provide almost all or a considerable part of heat required for heating the materials in the melting furnace to a certain temperature or a certain group of suitable temperatures within a range of 300-1800'C, and iron oxides in the materials are reduced into metal iron. In the above process, when a metallization rate of metal oxides in the raw material within the furnace reaches 40-95% (the reduced metal iron in the open shell may be in a solid state, a liquid state or a semi-smelted state), an electrode is used to melt the metal iron by arc heating, and sufficient electromagnetic stirring is performed. The broken outer casing rich in fluxes such as calcium oxide etc. reacts with acidic matter in the raw material, and slagging and slag-iron separation are performed to produce molten iron or directly reduced molten steel. The molten iron or directly reduced molten steel flows out from a molten iron/molten steel outlet 9. As an alternative, slag water is poured out after the 40 slag-iron separation, and then the electrode is adjusted suitably. Highly-pure oxygen is introduced into the furnace from a top port, and the highly-pure oxygen is blown into molten pig iron or directly reduced molten steel so as to oxidize impurities such as silicon and manganese etc.. A large amount of heat is produced in the oxidation process, which enables a temperature in the furnace to reach an enough high temperature. Therefore, it is not necessary for a converter to use additional fuel for steel-making, thus directly reduced molten steel or molten steel which has a purity higher than the directly reduced molten steel is produced. In the above technical process, arc heating by the electrode can be operated intermittently according to the furnace's status, and the intermittent time may be 0-100% of the reduction and melting time. Introduction of oxygen or argon from the top or the bottom of the furnace can select to input, not to input or to input one of oxygen and argon according to the status of the smelted or semi-smelted molten iron or directly reduced molten steel. It is possible to select to make all molten iron or directly reduced molten steel be in liquid state in the whole process, and all of molten iron or directly reduced molten steel is discharged out of the furnace body. It is also possible that a part which is smelted of molten molten iron or directly reduced molten steel is discharged out of the furnace body while substances which are smelted incompletely still remain in the furnace to be heated continuously. In the meantime, an appropriate method of adding material is selected to add material. In the melting process, the melting furnace adopts an electrode to perform arc reduction-melting heating or performs fuel reduction-melting heating by introducing combustion-supporting air or oxygen containing gases, and the two kinds of reduction-melting heating can be performed separately or simultaneously. 41 Height-diameter ratio of the furnace body 2 can selectively be slender or squat according to the material's situation and the furnace's status, and the furnace's specific height and diameter are determined by the furnace's status, the material's property and the furnace's productive capacity etc.. The number of the heat reservoirs around the furnace body 2 can be a pair or more pairs selectively. The regenerators in the heat reservoirs can be high temperature resistant refractory pellets and refractory bricks or refractory regenerators with a honeycomb shape or other shapes. The regenerators can adopt a suitable high temperature resistant metal product or a suitable high temperature resistant non-metal product such as carbonaceous matter etc. partially or totally. The slag cooling devices 18 are loaded with separable slags; the pig iron or continuous casting billet or rolled metal cooling devices 19 are loaded with pig iron or continuous casting billets or rolled metals (in the case that suitable above products or by-products exist). In most cases, when the melting furnace is just charged with materials, air (air pipelines associated therewith are not marked in Fig.5) or other oxygen-containing gases or gases rich in CO, H 2 or C02 etc. in the gas treatment device is introduced to cool slags or pig iron or continuous casting billets or rolled metals properly, and then the heated gases as a heat carrier or a combustion-supporting gas are input to the melting furnace for heating the materials. The slag cooling devices 18 and the pig iron or continuous casting billet or rolled metal cooling devices 19 can selectively not be used according to the actual situation. After the flue gas discharged from a duct is purified to remove harmful substances such as sulphur-containing substance etc., gases rich in C02, N 2 can be used in the intensive agriculture etc.. 42 (Embodiment 4) The apparatus for producing iron by smelting-reduction is an induction furnace, and the raw material is a mixture of the breathing shell, the semi-breathing shell and the open shell. As shown in Fig.6, the apparatus for producing iron by smelting-reduction through the induction furnace comprises a furnace body 2, a furnace cover 3, an induction coil 17 as well as a power supply device, heating furnaces 5a, 5b, heat reservoirs 6a, 6b and a gas treatment device 8 coordinated therewith. A gas inlet 16 is provided in the furnace cover 3 and/or at the bottom of the induction furnace, and a desulfurizer-charging port 11 is provided in the furnace cover 3. In order to make full use of residual heat, the apparatus for producing iron by smelting-reduction through the induction furnace is further provided with two or more than two slag cooling devices 18 and two or more than two pig iron or continuous casting billet or rolled metal cooling devices 19. Heat of slags or continuous casting billets or rolled metals is brought to the furnace body 2 via the heating furnaces Sa, 5b by using circulation of evolved gas. The technical steps of the smelting-reduction iron making process by the induction furnace are as follows: (1) Preparation of the breathing shell, the semi-breathing shell and the open shell: preparing the breathing shell, the semi-breathing shell and the open shell according to the steps (1) of embodiments 1-3 respectively, and doping 5% of limestone powder and some other specific substances. (2) Placing the breathing shell, the semi-breathing shell and the open shell into the induction furnace, wherein the shells are mixed with lump coal having a certain granularity. (3) Using an external heating method to heat the shells, and 43 reducing the materials in the melting furnace at a certain temperature or a certain group of suitable temperatures within a range of 300-1800 'C , wherein the evolved gas is produced continuously in this process. (4) Activating the induction furnace to melt the materials in the melting furnace by electromagnetic induction heating when a metallization rate of metal oxides in the raw material within the furnace reaches 40-95%. (5) Performing slag-iron separation to produce molten iron or directly reduced molten steel. Steel-making by the induction furnace is a steel-making method of heating and melting metal by the inductive electrothermal effect, which is particularly applicable to smelt high-quality steel and alloy with high-grade raw materials. A vacuum induction furnace equipped with a vacuum system is especially an important apparatus for smelting high-quality alloy. The characteristics of the steel-making process by the induction furnace are: ( heat reaches a metal molten pool first, then is transferred to the molten slags, thus the molten slags have a lower temperature; 0 the molten pool receives strong electromagnetic stirring. The lower is frequency of an electric source and the higher is power thereof, the more powerful is the electromagnetic stirring. Thus, frequency and power are main factors for limiting the maximum specific power; @ as compared with arc heating, induction heating generates neither a hot spot nor an electric arc, thus causing less pollution and a uniform temperature; @ carbon is not added, thus local overheating is prevented. Moreover, its operation is simple and burning loss of alloy is less. The induction furnace has a channel structure, a working principle of which is similar to that of a 44 transformer. The channel induction furnace has an iron core mounted in a primary winding thereof so as to reduce flux leakage and improve power factor. A secondary winding of the induction furnace is a molten channel filled with molten metal. When an alternating current passes through the induction coil, the molten metal in the molten channel produces an induction electromotive force so as to produce Joule heat for heating furnace burden. Energy is transformed in the molten channel before transmitted to the molten pool, and the molten channel has a very high heat load. Desulfuration and deoxidization can be performed simultaneously due to technical operation requirements of the induction furnace. As for an induction furnace having a load with a very low power factor, decarbonization and dephosphorization are not performed generally, therefore good material must be selected and a capacitor is adopted to improve power factor. The breathing shell, the semi-breathing shell and the open shell are mixed with each other to be placed into the induction furnace. The heat reservoirs 6a, 6b accumulate heat in a manner of switching their gas flow directions alternately. Oxygen-containing gases pass through the heat reservoir 6b to be combusted together with fuel in the heating furnace 5b and the melting furnace, the evolved gas which is discharged from the material of the breathing shall, the semi-breathing shell or the open shell out of the casing continuously is combusted as well. Flue gas and unutilized gases such as unburned evolved gas etc. enter the opposite heating furnace 5a. Oxygen-containing gases with an appropriate flow are selected to be mixed and combusted together with combustible substance in the evolved gas. A regenerator 7 in the heat reservoir 6a is heated to accumulate heat, and the cooled flue gas enters a cyclone separator 12 and a bag dust collector 13 and is discharged 45 via a chimney 15. Only a little of combustible gas exists in the discharged flue gas, and the discharged flue gas has a low temperature. Thereafter, oxygen-containing gases enter the heating furnace 5a through the heat reservoir 6a to be combusted together with fuel in the heating furnace 5a. The materials in the melting furnace are heated to produce flue gas and evolved gas, which enter the heating furnace 5b together and are mixed and combusted with oxygen-containing gases with an appropriate flow therein. A regenerator 7 in the heat reservoir 6b is heated to accumulate heat, and the cooled flue gas enters the cyclone separator 12 and the bag dust collector 13 and is discharged from the chimney 15. The discharged flue gas also contains a little of combustible gas, and the discharged flue gas has a low temperature. By circulating in turn, the oxygen-containing gases which enter the heating furnaces are always high-temperature gases, thus heat efficiency of the system is improved. The flammable gases rich in CO, H 2 and hydrocarbon etc. are generated from the material of the breathing shell, the semi-breathing shell or the open shell, and these flammable gases provide almost all or a considerable part of heat required for heating the materials in the melting furnace to a certain temperature or a certain group of suitable temperatures within a range of 300-1800'C, and iron oxides in the materials are reduced into metal iron. In the above process, when a metallization rate of metal oxides in the raw material within the furnace reaches 40-95% (the reduced metal iron in the shells may be in a solid state, a liquid state or a semi-smelted state), the induction furnace is activated to melt the materials in the melting furnace by electromagnetic induction heating, and sufficient electromagnetic stirring is performed. The broken outer casing rich in fluxes such as calcium 46 oxide etc. reacts with acidic matter in the raw material, and slagging and slag-iron separation are performed to produce directly reduced molten steel or molten iron similar to that made by a blast furnace. After molten slags are poured out, argon or oxygen can be introduced to perform melting so as to produce pure molten steel or pure molten iron. In the above technical process, electromagnetic induction heating can be operated intermittently according to the furnace's status, and the intermittent time may be 0-100% of the reduction and melting time. Introduction of oxygen or argon from the top or the bottom of the furnace can select to input, not to input or to input one of oxygen and argon according to the status of the smelted or semi-smelted molten iron or directly reduced molten steel. It is possible to select to make all molten iron or directly reduced molten steel be in liquid state in the whole process, and all of molten iron or directly reduced molten steel is discharged out of the furnace body. It is also possible that a part which is smelted of molten molten iron or directly reduced molten steel is discharged out of the furnace body while substances which are smelted incompletely still remain in the furnace to be heated continuously. In the meantime, an appropriate method of adding material is selected to add material. In the melting process, the melting furnace performs electromagnetic induction reduction-melting heating or performs fuel reduction-melting heating by introducing combustion-supporting air or oxygen containing gases, and the two kinds of reduction-melting heating can be performed separately or simultaneously. Height-diameter ratio of the furnace body 2 can selectively be slender or squat according to the material's situation and the furnace's status, and the furnace's specific height and diameter are determined by the furnace's status, the material's property and the furnace's productive capacity etc.. The number of 47 the heat reservoirs around the furnace body 2 can be a pair or more pairs selectively. The regenerators in the heat reservoirs can be high temperature resistant refractory pellets and refractory bricks or refractory regenerators with a honeycomb shape or other shapes. The regenerators can adopt a suitable high temperature resistant metal product or a suitable high temperature resistant non-metal product such as carbonaceous matter etc. partially or totally. The slag cooling devices 18 are loaded with separable slags; the pig iron or continuous casting billet or rolled metal cooling devices 19 are loaded with pig iron or continuous casting billets or rolled metals (in the case that suitable above products or by-products exist). In most cases, when the melting furnace is just charged with materials, air (air pipelines associated therewith are not marked in Fig.6) or other oxygen-containing gases or gases rich in CO, H 2 or C02 etc. in the gas treatment device is introduced to cool slags or pig iron or continuous casting billets or rolled metals properly, and then the heated gases as a heat carrier or a combustion-supporting gas are input to the melting furnace for heating the materials. The slag cooling devices 18 and the pig iron or continuous casting billet or rolled metal cooling devices 19 can selectively not be used according to the actual situation. After the flue gas discharged from a duct is purified to remove harmful substances such as sulphur-containing substance etc., gases rich in C02, N 2 can be used in the intensive agriculture etc.. (Embodiment 5) The apparatus for producing iron by smelting-reduction is a submerged arc furnace, and the raw material is a breathing shell, so that calcium carbide is produced. As shown in Fig.7, the apparatus for producing calcium carbide by 48 the submerged arc furnace comprises a furnace body 2, a furnace cover 3, an electrode 1 as well as heating furnaces 5a, 5b, heat reservoirs 6a, 6b and a gas treatment device 8 coordinated therewith. A calcium carbide outlet 21 is provided at the bottom of the furnace body 2. The gas treatment device may be used or may not be used, and the gas treatment device comprises a gas-circulating compressor, a gas cooling and purifying device and a gas storage tank etc.. Each of the heating furnaces can be connected to the furnace body 2 at one point or multiple points, and a connection angle between them can be selected according to the material's property and the furnace's status. The technical steps of producing calcium carbide by the submerged arc furnace are as follows: (1) Preparation of the breathing shell: a core molded article of the breathing shell is an uncoated molded article of coal powder, coke powder, semicoke and petroleum coke etc. or carbonaceous matter or a mixture thereof by being rolled or pressed into pellets, or it can be a molded article with other shapes. A carbon content in the molded article may be the same or may be different, and the molded article is allowed to be added with other substances such as calcium oxide powder or calcium carbonate powder having a certain granularity so as to make its composition and strength become more suitable. An outer casing of the breathing shell is formed of a substance such as limestone, dolomite etc. or a mixture thereof, in which carbonaceous matter such as carbon black and graphite etc. or some other substances can be doped. These substances are mixed or combined with a specific adhesive in a certain manner so as to coat the core molded article. The casing may be a rolling casing, a pressing casing, a powder spraying casing or a dipping casing. It is allowed but not necessary 49 to add other substances into the casing as a framework etc.. And it is allowed but not necessary to adopt artificial perforations on the casing to enhance the breathability. Area of each aperture as well as its distribution state and number on the casing are determined by the breathing shell's property and material proportioning. And it is allowed to perform a drying process at a suitable temperature after the casing process. (2) Placing the breathing shell into the submerged arc furnace. (3) Utilizing stock gas which is a by-product in producing calcium carbide, and partial extra fuel added if necessary, to heat the breathing shell, wherein the breathing shell is calcined at a suitable temperature controlled within 900-1200 'C to produce calcium oxide, the core molded article is heated at this temperature, and the breathing shell is heated up to 1200-1800'C. (4) After limestone in the outer casing of the breathing shell in the furnace body is decomposed, when gas fuel is used to heat the breathing shell to a suitable temperature within 1200-1800'C, activating the submerged arc furnace to make the materials in the furnace react sufficiently to produce calcium carbide by submerged arc heating of an electrode. (5) Calcium carbide flows out from a calcium carbide outlet 21, and enters a calcium carbide cooling cylinder 20 via a chute to be cooled and broken therein. As shown in Figs.7, 2 and 3, the heating furnaces 5a, 5b use a fuel which may be a gas fuel, a liquid fuel or a solid fuel, or a combination of these fuels. The material of the breathing shell loaded in the furnace body is heated and calcined. The heat reservoirs 6a, 6b accumulate heat in a manner of switching their gas flow directions alternately. Oxygen-containing gases pass 50 through the heat reservoir 6b to be combusted together with fuel in the heating furnace 5b and the melting furnace. Flue gas and unutilized gases such as unburned evolved gas etc. enter the opposite heating furnace 5a. Oxygen-containing gases with an appropriate flow are selected to be mixed and combusted together with combustible substance in the evolved gas. A regenerator 7 in the heat reservoir 6a is heated to accumulate heat, and the cooled flue gas enters a cyclone separator 12 and a bag dust collector 13 and is discharged via a chimney 15. Only a little of combustible gas exists in the discharged flue gas, and the discharged flue gas has a low temperature. Thereafter, oxygen-containing gases enter the heating furnace 5a through the heat reservoir 6a to be combusted together with fuel in the heating furnace 5a. The materials in the melting furnace are heated to produce flue gas and evolved gas, which enter the heating furnace 5b together and are mixed and combusted with oxygen-containing gases with an appropriate flow therein. A regenerator 7 in the heat reservoir 6b is heated to accumulate heat, and the cooled flue gas enters the cyclone separator 12 and the bag dust collector 13 and is discharged from the chimney 15. The discharged flue gas also contains a little of combustible gas, and the discharged flue gas has a low temperature. By circulating in turn, the oxygen-containing gases which enter the heating furnaces are always high-temperature gases, thus heat efficiency of the system is improved. The flammable gases rich in CO, H 2 and hydrocarbon etc. are generated from the material of the breathing shell, the semi-breathing shell or the open shell, and these flammable gases provide almost all or a considerable part of heat required for heating the materials in the melting furnace to a certain temperature or a certain group of suitable temperatures within a 51 range of 300-1800'C. The material in the breathing shell may be in a solid state, a liquid state or a semi-smelted state, and an electrode is used to perform arc heating so as to produce calcium carbide so that the materials in the submerged arc furnace is heated to a certain temperature or a certain group of suitable temperatures within a range of 1800-2300"C. In the process of producing calcium carbide, the submerged arc furnace adopts an electrode to perform arc heating or performs fuel heating by introducing combustion-supporting air or oxygen containing gases, and these two kinds of heating can be performed separately or simultaneously. Height-diameter ratio of the furnace body 2 can selectively be slender or squat according to the material's situation and the furnace's status, and the furnace's specific height and diameter are determined by the furnace's status, the material's property and the furnace's productive capacity etc.. The number of the heat reservoirs around the furnace body 2 can be a pair or more pairs selectively. The regenerators in the heat reservoirs can be high temperature resistant refractory pellets and refractory bricks or refractory regenerators with a honeycomb shape or other shapes. The regenerators can adopt a suitable high temperature resistant metal product or a suitable high temperature resistant non-metal product such as carbonaceous matter etc. partially or totally. Flue gas or stock gas which is generated by the reaction for producing calcium carbide can also be stored after purified by a gas treatment device 8 (in the case that the gas treatment device exists), thereby to be used as a fuel for calcining the breathing shell in the apparatus for producing calcium carbide by the submerged arc furnace. Calcium carbide flows out from the calcium carbide outlet 21, and enters the calcium carbide cooling cylinder 52 20 via a chute to be cooled and broken therein. A certain amount of pore-forming agent which does not influence performance of calcium carbide can be doped in a calcium carbide liquid in the cooling cylinder 20, so as to make cooling media or cooling wind pass through the pores thus formed, or it is also possible not to add pore-forming agent. In most cases, when the melting furnace is just charged with materials, inert gases (such as nitrogen etc.), air or other oxygen-containing gases or gases rich in CO, H 2 and C02 etc. in the gas treatment device are introduced to cool calcium carbide properly, and then the heated gases are input to the melting furnace so as to be used for heating etc. as a heat carrier. The cooling cylinder 20 for cooling the heating gas can also selectively not be used according to the actual situation, wherein air introduction pipelines are not marked in the drawings. After flue gas discharged from a pipe is purified to remove harmful substances such as sulphur-containing substance etc., gases rich in C02, N 2 can be used in the intensive agriculture etc.. 53

Claims (13)

1. A method for producing iron by smelting-reduction, comprising: placing a raw material into an iron smelting apparatus and heating the raw material to reduce it into metal iron; heating metal iron continuously to make it molten when a metallization rate of various iron oxides in the raw material reaches 40-95%, thus producing directly reduced molten steel or molten iron similar to that made by a blast-furnace, characterized in that: the raw material is a breathing shell, or a semi-breathing shell or an open shell or a mixture thereof; the breathing shell, the semi-breathing shell and the open shell are defined as follows: (1) the breathing shell mainly consists of a core molded article and an outer casing: (D the core molded article is divided into three types: (i) the core molded article is formed by being rolled or pressed into a molded article with a spherical shape or other shapes after iron oxides such as Fe 2 0 3 , Fe 3 0 4 etc. are mixed with carbonaceous matter such as coal powder and coke powder etc.; (ii) the molded article with the spherical shape or other shapes in (i) is coated with carbonaceous matter which is allowed to be added with other substances, the coating may be a rolling coating, a pressing coating, a coal powder spraying coating or a dipping coating; (iii) the molded article may be made of a nonferrous substance or a less ferrous substance such as carbonaceous matter, lime and limestone etc.; @ the outer casing is made by mixing limestone, dolomite, lime or calcium carbide etc. or a mixture thereof with adhesives; it is allowed to add some other substances such as metal, metal oxides, carbonaceous matter, organic matter or inorganic matter etc. to the 54 outer casing; the adhesives are silica sol, water glass, phosphoric acid or aluminum oxide etc; the casing may be a rolling casing, a pressing casing, a powder spraying casing or a dipping casing; and it is allowed to perform a drying process or a sintering process after the casing process; (2) the semi-breathing shell's structure and composition are the same as those of the breathing shell except that the semi-breathing shell's outer casing is subject to cracking and pitting damages during a melting furnace is heated from a low temperature to a high temperature, so that portions of the core molded article corresponding to the damaged positions are exposed to the melting furnace's ambience; (3) the open shell: @ the open shell's structure and composition are the same as those of the breathing shell except that the open shell's outer casing can not retain its original shape when raised from a low temperature to a high temperature; 0 the core molded article is mixed with calcium oxide or calcium carbonate or calcium carbide as a lump flux and substances such as lump coal and lump coke etc. in the melting furnace.

2. The method for producing iron by smelting-reduction according to claim 1, characterized in that: the breathing shell, the semi-breathing shell and the open shell are heated in a converter, an electric arc furnace, an open hearth, a plasma furnace, an electric resistance furnace, an induction heating furnace, a submerged arc furnace or a smelting reduction furnace.

3. The method for producing iron by smelting-reduction according to claim 2, characterized in that: the breathing shell, the semi-breathing shell and the open shell are heated directly under 55 suitable ambience of the melting furnace to be reduced and molten, so as to produce direct reduced molten steel or molten iron similar to that made by a blast-furnace; or the breathing shell, the semi-breathing shell and the open shell are transferred into the melting furnace to be molten after heated to a certain temperature in other furnaces.

4. The method for producing iron by smelting-reduction according to claim 3, characterized in that: the melting furnace's ambience can selectively be an oxidative ambience, a reductive ambience, or a weakly oxidative ambience according to the characteristics of the breathing shell, the semi-breathing shell and the open shell.

5. The method for producing iron by smelting-reduction according to claim 1, characterized in that: in the case that the breathing shell's outer casing has fewer pores after heated, the outer casing can be added with a substance with a lower melting point to increase porosity of the outer casing; in the case that the breathing shell's outer casing has more pores after heated, substances such as SiO 2 /AI 2 0 3 etc. can be added to a substance containing calcium carbonate to reduce the outer casing's porosity under a high temperature.

6. The method for producing iron by smelting-reduction according to claim 1, characterized in that: the breathing shell can be applied to produce calcium carbide in such a manner that the core molded article is made after mixing coal powder with calcium oxide powder in a certain ratio and coating calcium carbonate or calcium oxide as the outer casing; the breathing shell, the semi-breathing shell and the open shell can be applied to smelting of other metals as well as 56 a calcination process of calcium carbonate and magnesium carbonate.

7. The method for producing iron by smelting-reduction according to claim 1, characterized in that: in the process of heating metal iron to make it moten, only a part of or a little of acidic substance such as SiO 2 etc. is reduced to a substance such as metal Si, while a part or a most part of acidic substance such as SiO 2 etc. is combined with a flux such as CaO etc. in the casing to form molten slags to be discharged.

8. The method for producing iron by smelting-reduction according to any one of claims 1-7, characterized in that: after the reduced metal iron are molten by heating, oxygen or inert gas is blown into an electric arc furnace, a converter, an open hearth, a submerged arc furnace, a plasma furnace or an induction furnace etc. to facilitate slag removing; and the inert gas is argon.

9. An electric arc furnace apparatus for carrying out the method for producing iron by smelting-reduction according to claim 1, comprising: a furnace body (2), a furnace cover (3), an electrode (1), a charging device and a discharging device, at least a pair of heating furnaces (5a, 5b), and at least a pair of heat reservoirs (6a, 6b); the heating furnaces are connected to the furnace body (2) of the electric arc furnace; each of the heat reservoirs has one end connected to the respective heating furnace and another end connected to a discharging system, a blower (4) and/or a gas treatment device (8) respectively, characterized in that: a gas inlet (16) is provided at the bottom of the electric arc furnace, and the gas inlet is connected to a gas pipeline (10); the electric arc 57 furnace apparatus is further provided with two or more than two slag cooling devices (18) and two or more than two pig iron or continuous casting billet or rolled metal cooling devices (19).

10. A submerged arc furnace apparatus for carrying out the method for producing iron by smelting-reduction according to claim 1, comprising: a furnace body (2), a furnace cover (3), an electrode (1) as well as heating furnaces (5a, 5b), heat reservoirs (6a, 6b) and a gas treatment device (8) coordinated therewith, characterized in that: a gas inlet (16) is provided at the bottom of the submerged arc furnace, and the gas inlet is connected to a gas pipeline (10); the electrode (1) is inserted into a lower portion of the melting material directly; the submerged arc furnace apparatus is further provided with two or more than two slag cooling devices (18) and two or more than two pig iron or continuous casting billet or rolled metal cooling devices (19).

11. The submerged arc furnace apparatus according to claim 10, characterized in that: a calcium carbide outlet (21) is provided at the bottom of the furnace body (2); the submerged arc furnace apparatus is further provided with two or more than two calcium carbide cooling cylinders (20).

12. A converter apparatus for carrying out the method for producing iron by smelting-reduction according to claim 1, comprising: a furnace body (2), a furnace cover (3), an electrode (1) and an external heating device, characterized in that: a gas inlet (16) and a desulfurizer-charging port (11) are provided in the furnace cover of the converter, and the gas inlet is connected to a gas pipeline (10); the converter apparatus is further provided with two or more 58 than two slag cooling devices (18) and two or more than two pig iron or continuous casting billet or rolled metal cooling devices (19).

13. An induction furnace apparatus for carrying out the method for producing iron by smelting-reduction according to claim 1, comprising: a furnace body (2), a furnace cover (3), an induction coil (17) as well as a power supply device and an external heating device coordinated therewith, and characterized in that: a gas inlet (16) is provided in the furnace cover (3) and/or at the bottom of the induction furnace; a desulfurizer-charging port (11) is provided in the furnace cover (3); the induction furnace apparatus is further provided with two or more than two slag cooling devices (18) and two or more than two pig iron or continuous casting billet or rolled metal cooling devices (19). 59