JP2009280833A - Low-temperature iron-making method allowing high speed smelting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-temperature iron-making method allowing high speed smelting, in which reducing reaction time required for the smelting is drastically shortened and the outer operation for adjusting gas composition in a furnace is unnecessary, and the use amount of reduction-material needed to the iron-making and discharge of carbon dioxide are drastically reduced without lowering the durability of the furnace. <P>SOLUTION: Iron-oxide and carbon, are finely crushed to make powdery materials, and after mixing the powdery iron-oxide and carbon at a prescribed ratio, the powder mixture is stored in the furnace as it is or in a solid state of packing together, and is heated and held at 800-1200°C in a state of allowing only the gas discharge, and thus, iron is refined in a furnace atmosphere of high concentration of carbon monoxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an improvement of the low-temperature iron manufacturing method for producing iron directly from a mixture of carbon (mainly coke, coal, charcoal) and iron oxide (mainly Fe2O3, Fe3O4), specifically, reduction required for smelting High-speed smelting that can significantly shorten the reaction time, eliminates the need for external operations to adjust the gas components in the furnace, and reduces the amount of reducing material used and the amount of carbon dioxide required for iron making It relates to a possible low-temperature iron manufacturing method.

  In conventional iron making methods, as in the Tatara method, a large amount of air or oxygen is blown into a mixture of iron ore and coal contained in the furnace, and a high temperature exceeding 1500 ° C is achieved by the combustion heat of coal. At the same time, it is based on the principle of making iron by taking the oxygen contained in iron ore using the reducing power of carbon monoxide generated by incomplete combustion of coal.

  Conventionally, a shaft that heats iron ore powder at a low temperature around 1000 ° C., which is considerably lower than the melting point of iron, while continuously supplying carbon monoxide, hydrogen, or a reducing gas that is a mixture thereof. A furnace and a high-temperature fluidized bed method have also been proposed.

  In addition, as a steelmaking method performed at a low temperature, a reduction gas is continuously blown into a mixture of iron ore and coal accommodated in a rotary kiln, and a reaction by heating at 950 to 1050 ° C. takes 10 to 20 hours to produce 100 tons per day. The method of producing sponge iron on the scale of is also carried out in India.

  However, the technology using such a reducing gas, when the reducing gas reduces iron ore, itself becomes inert carbon dioxide or water vapor that acts to inhibit the reduction of iron ore, reducing the amount in the furnace gas. Since the ratio of the gas is reduced, the progress of the reduction reaction is slow, and there is a problem that the component of the gas in the furnace must always be adjusted by an external operation in order to continue the reduction reaction. .

  Moreover, in the steelmaking method that uses coal as a reducing material as well as the heat source as described above and the ironmaking method that supplies the reducing gas externally, only a large amount of reducing material is wasted. In addition, since the amount of carbon dioxide emission is very large, there are concerns about adverse effects on the environment.

  In addition, conventionally, a material obtained by compressing and solidifying coal powder and iron ore powder (referred to as pellets), which is a reducing material, is stored in a furnace heated to a temperature exceeding 1000 ° C. and heated. Only in the initial stage, oxygen necessary for combustion is supplied and coal is used as a heat source, and after the reduction of iron ore has progressed more than a certain level, the supply of oxygen is stopped and inert gas is blown in, and coal is used as a reducing material. There is also reported a technique for producing a flocculent solid iron called sponge iron by reducing iron ore by heating at about 1200 ° C. to 1400 ° C. using only as (see Patent Document 1).

  However, with respect to the above-described conventional technology, the object is mainly iron making by low-temperature, solid-phase reaction. However, by flowing an inert gas over the raw material, it is a monoxide that is a reducing gas generated from the raw material. If carbon and carbon dioxide that reacts with coal to generate carbon monoxide are washed away, there is a possibility that the reduction rate of iron ore will be reduced.

In addition, when the method of heating the raw material at a high temperature of 1200 ° C. or more as described above is adopted, the inside of the furnace is easily eroded by molten pig iron. There is also a problem that causes deterioration of durability.
Japanese Patent Laid-Open No. 7-238307 (page 2-9, FIG. 1-8)

  The present invention has been made in view of the problems as described above, and the object of the present invention is to greatly reduce the reduction reaction time required for smelting and to adjust the gas components in the furnace. Providing a low-temperature ironmaking method that can be smelted at high speed, which can significantly reduce the amount of reducing materials used and the amount of carbon dioxide required for steelmaking without reducing the durability of the furnace. There is to do.

  Means adopted by the present inventor for solving the above-described problems will be described as follows.

  That is, in the present invention, iron oxide and carbon are finely pulverized and granulated, and the powdered iron oxide and carbon are mixed at a predetermined ratio, and then the mixed powder is directly or collectively. Refining iron in a furnace atmosphere with a high concentration of carbon monoxide by heating and holding at a temperature of about 800 ° C to 1200 ° C in a solidified form in a furnace where only gas can be discharged. There is a feature in the point.

  Further, in order to solve the above problems, the present invention may employ technical means of adding liquid paraffin as a binder material in the step of mixing iron oxide and carbon in addition to the above means as necessary. it can.

  Moreover, in order to solve the said subject, in addition to the said means, this invention fills the heat transfer container with the solid body which mixed and solidified iron oxide and carbon, and accommodates in a furnace. Technical means can be employed.

  In the present invention, the reaction in which wustite (FeO) generated in the iron ore reduction process is reduced by carbon monoxide at about 700 ° C. or more proceeds unless the carbon monoxide is at a concentration several times higher than that of carbon dioxide. In the absence of oxygen or reducing gas that promotes the generation of carbon dioxide by carbon combustion or reaction with iron oxide, there is a risk that the concentration of carbon monoxide may be reduced. Without any external supply of active gas, the iron oxide and carbon are heated and held in a temperature range of about 800 ° C to 1200 ° C in a state where they are in close contact with each other as finely and closely as possible. It can be manufactured.

  Specifically, when heating is performed in the furnace from 800 ° C. to 1200 ° C., the actual smelting time can be shortened to within one hour.

  This is because the present invention uses finely pulverized and mixed iron oxide and carbon as raw materials, so that carbon monoxide and carbon dioxide generated during the reduction reaction form fine channels inside the mixed powder. This is because the generated gas reacts with iron oxide or carbon one after another in the channel and the reduction proceeds efficiently.

  As a result, even if the raw material is in a solid state that is densely compressed in a large amount, the flow of gas inside the solid body is secured by the expansion pressure of the generated gas, so that the reduction reaction proceeds efficiently. Therefore, the feature of the present technology that does not require any external gas supply is based on this principle.

  In the present invention, the inside of the furnace during heating is in a state in which only gas can be discharged. From this gas outlet, carbon monoxide generated by direct reaction between iron oxide and carbon, or reaction between carbon dioxide and carbon. At the same time, carbon dioxide generated by the reduction of iron oxide is released to the outside of the furnace, and as the reduction reaction of iron oxide proceeds, the amount of carbon monoxide generated gradually becomes larger than that of carbon dioxide. Even without adjusting the components, the atmosphere in the furnace can be naturally shifted to a high concentration state of carbon monoxide.

  Furthermore, in the present invention, since there is no consumption due to carbon combustion or external supply of reducing gas, the amount of reducing material used can be greatly reduced, and carbon combustion or excessive reducing gas is introduced into the atmosphere. Since it is possible to prevent generation of useless carbon dioxide generated by being discharged and to suppress the generation amount of carbon dioxide throughout the entire iron manufacturing process, it is very friendly to the environment.

  On the other hand, in the present invention, the mixture of solid ore and carbon remains solid at a temperature lower than the melting temperature of iron (high temperature of 1500 ° C. or higher, or 1200 ° C. or higher in the case of pig iron rich in carbon). Since the iron making proceeds by reaction, no melt is generated in the iron making process, and deterioration due to erosion of the wall of the furnace, which is a major problem in the conventional iron making method, can be greatly reduced.

  In short, the present invention is a technology that can realize a significant reduction in reaction time, omission of external operations, improvement in furnace durability, reduction in the amount of reducing material used, and reduction in carbon dioxide emissions in the iron making process. Its practical value is very high.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described in more detail with reference to specific examples as follows.

“Example 1”
In this Example 1, hematite (based on Bengala, Fe2O3) is used for iron oxide, Bincho charcoal is used for carbon, and 15 g of Bincho charcoal is powdered for 80 g of hematite. (Hematite: about 200 mesh, Bincho charcoal: about 100-300 mesh) Mixing was performed, and this was compression molded to prepare a sample that was a high-density solid.

  Next, after storing the sample divided into about 10 grams in an electric furnace, the inside of the furnace was evacuated and argon gas was introduced until the pressure became 1 atm. And kept at high temperature.

  As a result, the sample in the furnace is only iron by heating in less than 1 hour, which is much shorter than the smelting time required in conventional ironmaking technology (only alpha iron was detected by the X-ray diffraction method) It was confirmed that

  When the ratio of carbon to 80 grams of iron oxide in the sample is changed to 10-18 grams, or when the particle size of iron oxide and carbon is changed to about 1 centimeter, the mixed powder of iron oxide and carbon remains as it is. Even when housed in the furnace in this state, the reduction reaction was completed within 1 hour, and the same effect could be obtained.

  It was also confirmed that the actual smelting time could be shortened within one hour when the furnace heating temperature was changed from 800 ° C to around 1200 ° C.

  The reason why the smelting time could be shortened in this way is that the gas was not supplied into the furnace and only the gas was discharged. As a result, the concentration of carbon monoxide in the gas components in the furnace became several times that of carbon dioxide. In order to verify the causal relationship between the change in the gas components in the furnace and the reduction reaction time of iron oxide, carbon monoxide and carbon dioxide, which began to be generated from the sample when the heating temperature exceeded 700 ° C, were examined. The total amount of the mixed gas was collected, and the amount of gas generated per hour and the ratio of carbon monoxide and carbon dioxide were measured.

  First, only carbon monoxide and carbon dioxide were detected during the reaction, but there was a lot of carbon dioxide in the early stage of the reaction, and a lot of carbon monoxide was detected in the later stage, and the reaction temperature was 950 ° C. The results showed that on average, the ratio of carbon monoxide and carbon dioxide was almost equal.

  At this time, the more carbon dioxide is generated, the greater the reduction effect of iron oxide by carbon, but as the reduction of iron ore proceeds, the amount of carbon monoxide with less oxygen binding to carbon increases. The trend was confirmed.

  Because of the above phenomenon, the concentration of carbon monoxide in the furnace naturally increases, so the atmosphere in the furnace is shifted to a state in which the reduction reaction proceeds well without any special adjustment from the outside of the furnace. The

  In addition, since no oxygen or reducing gas is supplied to burn carbon in the furnace, the amount of reducing material used and the amount of carbon dioxide emitted can be greatly reduced.

  By the way, the amount of reducing material such as carbon required to produce one ton of iron is a measure of the efficiency of the iron making process and can be expressed as the reducing material ratio (previously this was called the coke ratio) The value in the blast furnace method in recent years is an example that is considered to be the most efficient, and is about 500 kilograms of coke, that is, about a reducing material ratio of about 500.

  On the other hand, compared with this, the reducing agent ratio in Example 1 (which can be compared with the coke ratio because charcoal is used) is about 250-300, which is about half of that, and carbon combustion occurs by blowing air or oxygen from outside. It was proved that iron production could be carried out with the minimum amount of carbon necessary for the iron oxide reduction reaction.

  And since this reducing material ratio is proportional to the amount of carbon dioxide emission in iron making, halving the reducing material ratio has the same meaning as halving the amount of carbon dioxide emission in iron making.

  On the other hand, since the heating temperature of the furnace is set to 1200 ° C. or less at which the melting of pig iron begins, no melt is generated in the iron making process, so the problem of deterioration due to erosion of the wall of the furnace is also eliminated.

“Example 2”
Next, a second embodiment of the present invention will be described. In this Example 2, heating is started in a state in which the inside of the furnace containing the sample is kept in the atmosphere, and only the gas is discharged by blocking the entry of the gas from the outside. It was confirmed that almost the same result as in Example 1 was obtained.

“Example 3”
Next, Embodiment 3 of the present invention will be described. In this Example 3, a small amount of liquid paraffin was added to the sample as a binder material at the time of mixing iron oxide and carbon, and compression molding was carried out. By using pellets having a high internal bonding force produced by this method, It was confirmed that the reduction reaction was further promoted.

Example 4
Next, a fourth embodiment of the present invention will be described. In Example 4, a mixture of iron oxide and carbon was stored in a ball mill (zirconia balls and alumina pot) with a ball-to-sample ratio of about 1 to 100, and a sample that had been pulverized for several hours was used. Using this sample, a reaction experiment similar to that of Example 1 was performed. As a result, the reaction time was reduced in proportion to the pulverization time.

  Specifically, when pulverization with a ball mill was performed for 4 hours, the reaction time was reduced to about one third as a result of heating at 950 ° C. under the same conditions as in Example 1.

  Further, if a pulverizing apparatus such as a ball mill is used, iron oxide and carbon can be granulated to an arbitrary particle size, so that the smelting time can be adjusted.

  The present invention is generally configured as described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made within the description of “Claims”. Since the progress of the iron oxide reduction reaction is determined by the residence time in the furnace, by devising the design of the furnace, the powder mixture is continuously mixed in the furnace as a continuous transport system using a conveyor instead of a batch system. Alternatively, iron that has been reduced may be automatically taken out at the same time as the solid body is accommodated.

  In addition, the iron obtained by the reduction reaction becomes spongy and expands several times more than the original solid, particularly when the reaction temperature is low. In order to prevent the direct reaction with carbon from becoming difficult, it is possible to add restraint to prevent expansion by filling the heat transfer container with solid material made by mixing raw material iron oxide and carbon. It is.

  In addition, it is important that the heat transfer container used at this time has a gap that allows the mixed gas of carbon monoxide and carbon dioxide generated according to the reduction reaction to be released to the outside of the container. It is also important that this gap is of such a size that gas in the external atmosphere does not enter the inside of the container.

  Further, in the present invention, since air, oxygen, or non-reducing gas is not blown from the outside, which is essential in the conventional iron manufacturing method, supply of energy necessary for reduction of iron oxide is not performed. It is necessary to supply from a heat source (that is, in order to keep the inside of the furnace at about 800 ° C. to 1200 ° C., it is necessary to supply energy in accordance with the amount of heat absorbed as iron making proceeds).

  As an external energy supply source, using a nuclear reactor, an industrial waste incinerator, a solar furnace, etc., and using the heat output from the energy source as it is as an external heat source, it is useful for effective use of energy.

  Even when these heat sources are not used, the same coke and coal as in the conventional iron making method can be used by indirectly transferring the heat to the raw material in the furnace (such as through a heat transfer material). The heat of combustion of fuel from fossil fuels such as heavy oil can also be used as an external heat source.

  Even in this case, in this method in which the fuel is burned without contacting the raw material ore or the like, the combustion generated gas does not interfere with the reduction of the ore, so the amount of carbon dioxide generated throughout the entire process is greatly reduced. Any of the above is within the technical scope of the present invention.

  In recent years, measures to reduce carbon dioxide emitted in the industry due to the serious global warming, which is one of the environmental problems, are urgently required all over the world. Attention has been focused on low-temperature iron manufacturing methods that can reduce carbon dioxide emissions compared to large conventional high-temperature iron manufacturing methods. Moreover, when adopting a low-temperature type iron making method, it is necessary to clear a practical problem that iron can be produced efficiently and in large quantities.

  Under such circumstances, the low-temperature iron making method capable of high-speed smelting of the present invention can significantly reduce the amount of carbon dioxide emitted into the atmosphere by effectively utilizing an external energy source as compared with the conventional case. In addition, since it is a useful technology that has also achieved a reduction in smelting time, which is a major problem in practical use, demand in the market is great and its industrial utility value is very high.

Claims (3)

  After the iron oxide and carbon are finely pulverized and granulated, the powdered iron oxide and carbon are mixed at a predetermined ratio, and then the mixed powder is solid as it is or solidified. A high speed characterized by refining iron in a furnace atmosphere with a high concentration of carbon monoxide by heating and holding at a temperature of about 800 ° C. to 1200 ° C. in a state where only gas can be discharged in a furnace A smeltable low-temperature iron manufacturing method.   2. The low-temperature iron making method capable of high-speed smelting according to claim 1, wherein liquid paraffin is added as a binder material in the step of mixing iron oxide and carbon.   The low-temperature iron making method capable of high-speed smelting according to claim 1 or 2, wherein a solid body obtained by mixing and solidifying iron oxide and carbon is filled in a heat transfer container and accommodated in a furnace.