Source: http://www.allindianpatents.com/patents/208085-method-and-apparatus-for-manufacturing-metallic-iron
Timestamp: 2017-12-15 06:27:59
Document Index: 252397605

Matched Legal Cases: ['art 207', 'art 207', 'art 207', 'art 207', 'art 207', 'art 207', 'art 207', 'art 207', 'art 207', 'art 207', 'art 207']

Indian Patents. 208085:METHOD AND APPARATUS FOR MANUFACTURING METALLIC IRON
METHOD AND APPARATUS FOR MANUFACTURING METALLIC IRON
"A Method and apparatus for manufacturing iron" A method of making metallic iron in which a compact, containing iron oxide such as iron ore or the like and a carbonaceous reductant such as coal or the like, is used as material, and the iron oxide is reduced through the application of heat, thereby making metallic iron. In the course of this reduction, a shell composed of metallic iron is generated and grown on the surface of the compact, and slag aggregates inside the shell. This reduction continues until substantially no iron oxide is present within the metallic iron shell. Subsequently, heating is further performed to melt the metallic iron and slag. Molten metallic iron and molten slag are separated one from the other, thereby obtaining metallic iron with a relatively high metallization ratio. Through the employment of an apparatus for making metallic iron of the present invention, the above-described method is efficiently carried out, and metallic iron having a high iron purity can be made continuously as well as productively not only from iron oxide having a high iron content but also from iron oxide having a relatively low iron content.
Reduced iron obtained using the above-mentioned methods is charged into an electric furnace
directly as source iron or in the form of briquettes. With the increasing trend of recycling scrap in recent years, this reduced iron is of particular interest, since it may be used as a diluent of impurities contained in the scrap.
A conventional method, however, does not involve separating slag components such as SiCh, AbOa, and CaO contained in the iron ore or the like and in the carbonaceous material (coal or the like), from the molten iron produced. Therefore, the resultant reduced iron has a relatively low iron content (iron purity of metallic iron). In actual practice, these slag components are separated and removed during a subsequent refining process. However, an increase in the amount of slag not only decreases yield of refined molten iron, but significantly increases the running cost of an electric furnace. Therefore, reduced iron is required to be iron rich and have a relatively low content of slag components. In order to meet this requirement, it is necessary for the above-mentioned conventional reducing iron-making methods to use iron-rich iron ore, which narrows the choice of source materials for making iron.
In the method of making metallic iron according to the present invention, iron oxide compacted with a carbonaceous reductant is subjected to reduction through the application of heat to yield
metallic iron, the method having the following aspects:
(1)	A shell containing metallic iron is generated and grown via reduction through the application of heat. The reduction normally is continued until substantially no iron oxide is present within the shell, during which slag aggregates with in the shell.
(2)	A metallic iron shell is generated and grown via reduction through the application of heat, the reduction is continued until substantially no iron oxide is present within the shell, and heating is further continued to allow slag generated within the shell to flow out from inside the shell.
(3)	A metallic iron shell is generated and grown via reduction through the application of beat, the reduction is continued until substantially no iron oxide is present within the shell, and heating is further continued to allow molten metallic iron to separate from molten slag.
(4)	A metallic iron shell is generated and grown via reduction through the application of heat, and the reduction is continued until substantially no iron oxide is present within the shell, during which slag aggregates within the shell, and then the aggregated slag is separated from metallic iron.
When any of aspects (1) to (4) described above is embodied, a maximum temperature of heating for reduction may be controlled to be not less than the melting point of the accompanying slag and not more than the melting point of the metallic iron shell, so as to more efficiently conduct the reaction of generating metallic iron. This reducing step may be solid phase reduction, through
which an iron oxide is reduced, and liquid phase reduction which is continued until substantially no iron oxide, composed mainly of FeO, is present, whereby the purity of the metallic iron obtained can be efficiently improved.
As used herein, the term "reduction is continued until substantially no iron oxide is present within the metallic iron shell" means, on a quantitative basis, that the reduction through the application of heat is continued until the content of iron oxide, composed mainly of FeO, is preferably reduced to 5% by weight or less, more preferably to 2% by weight or less. From a different point of view, this means that the reduction through the application of heat is continued until the content of iron oxide, composed mainly of FeO in the slag separated from metallic iron, is preferably not more than 5% by weight, more preferably 2% by weight or less.
1)	The compact is moved in a horizontal direction.
2)	The compact is placed on an iron belt, comprising walls formed at both edge portions thereof to prevent the compact from falling off the iron belt, and is moved in a horizontal direction.
3)	The compact is placed on a horizontal surface.
4)	The compact is tumbled.
5)	The compact falls downward.
6)	The elongated compact is moved downward in a vertical position.
7)	The elongated compact is moved downward along a sloped surface.
a melting apparatus for melting the shell and the slag; and
a separator for separating the molten iron from the molten slag.
In the above-described apparatus for making metallic iron, when the compact is granular or agglomerate, the above-described thermal reduction apparatus may comprise a mechanism for reducing the compact through the application of heat while moving the compact in a horizontal direction. A preferred embodiment of the mechanism is an endless rotary member, comprising an endless rotary member and a hearth located on the member and used for placing the compact thereon. Separating members may be provided on the hearth at certain intervals to prevent the compact from adhering to another compact. The separating members are preferably formed of a desulfurizing agent, so that desulfurization can also be performed in a process of reduction through the application of heat.
The above-described mechanism may also be embodied in the form of an iron belt, comprising walls formed at both edge portions thereof to prevent the compact from falling off the iron belt,
for conveying thereon the compact in a horizontal direction and for subjecting the compact to reduction through the application of heat during the horizontal conveyance of the compact.
When the compact is granular or agglomerate, another preferred embodiment of the thermal reduction apparatus may comprise a feeding member, comprising a horizontal plane, for intermittently feeding in the compact placed on the horizontal plane, a discharging member for discharging the compact from the feeding member, and a heating mechanism for heating the compact. The discharging member may be a tilting member for making the position of the feeding member alternate between a horizontal position and a sloped position, or a pushing member for pushing out the compact from the feeding member, thereby smoothly discharging the compact.
a mechanism for reducing the compact through the application of heat while tumbling the compact, or
a mechanism of tumbling, comprising a tumbling surface for tumbling the compact thereon and a discharging unit for discharging the compact from the tumbling surface, and a thermal reduction member for heating the compact.
The above-described thermal reduction apparatus and the melting apparatus may be integrated into a thermal reduction-melting apparatus, which comprises a mechanism of tumbling, comprising a sloped tumbling surface for gradually tumbling down the compact along a sloped direction and a discharging section for discharging the compact from the sloped tumbling surface, and a mechanism for reducing and melting the compact through the application of heat. This enables reduction and melting through the application of heat to be performed continuously and efficiently.
In the above-described thermal reduction-melting apparatus, the tumbling surface preferably comprises the interior surface of a channel-like member having an arc-shape, V-shape9 or the like recess and is sloped along the length of the channel-like member. This enables smoother reduction and melting through the application of heat.
A further embodiment of the thermal reduction apparatus which receives the granular or agglomerate compact may comprise a mechanism for allowing the compact to fall downward and for reducing the falling compact through the application of heat. Alternatively, the thermal reduction-melting apparatus integrally comprising the thermal reduction apparatus and the melting apparatus may further comprise a space for allowing the granular compact to fall
downward and a heating member for reducing and melting the granular compact through the sequential application of heat while the granular compact is falling.
When the elongated compact is used, the elongated compact may be continuously fed onto an iron belt through a feeder, so that the elongated compact on the iron belt is continuously conveyed into a thermal reduction apparatus, where the elongated compact is reduced through the application of heat. In this case, the iron belt is also melted in a melting process with metallic iron generated in the reducing process, and collected in the form of molten iron.
Preferably, the apparatus for making metallic iron according to the present invention may further comprises means for feeding an iron belt for conveying the compact thereon, thereby feeding the compact on the iron belt into the thermal reduction apparatus and a melting apparatus for reducing and melting the compact through the application of heat. In this case, when the compact is granular or agglomerate, the iron belt may comprise walls formed at both edge portions thereof to prevent the compact from falling off the iron belt and may convey the compact thereon in a horizontal direction within the thermal reduction apparatus for reducing the compact through the application of heat. When the compact is in an elongated form, there may be provided forming means for continuously forming the elongated compact and for feeding the elongated compact
onto the iron belt, thereby continuously forming the elongated compact and subjecting it to reduction and melting through the application of heat. The iron belt used is melted in the melting apparatus to thereby be merged with metallic iron, generated through reduction, and collected in the form of molten iron.
FIG. 2 is a set of photographs showing cross-sections of pellets subjected to reduction through the application of heat at different temperatures,
FIG. 5 is a graph showing a change in the content of slag constituents with reducing time at a reducing temperature of 1500°C;
FIG. 6 is a graph showing a change in the FeO content of reduced pellets with reducing time at a reducing temperature of 1500°C;
FIG. 7 is a graph showing a change in the carbon content of reduced pellets with reducing time at a reducing temperature of 1500°C; and
FIG. 11 is a schematic cross-sectional view taken along lines Z--Z and Y--Y of FIG. 10;
In the process of studying a new method of making metallic iron, which may replace both indirect iron making methods such as a method using a blast furnace, and direct iron making methods such as the heretofore mentioned SL/RN method, the present inventors found that when
compacts, in grains, pellets, or in any other form, of pulverized iron oxides and carbonaceous reductant are heated in a non-oxidizing atmosphere, the following phenomenon occur. When a compact is heated, the carbonaceous reductant contained in the compact reduces iron oxides in the following manner: the reduction continues from the periphery of the compact, and metallic iron generated during the incipient stage of the reduction diffuse and join together on the surface of the compact to form a metallic iron shell on the periphery of the compact. Subsequently, reduction of iron oxides by the carbonaceous reductant progresses efficiently within the shell, so that a state is established within a very short period of time such that substantially no iron oxide is present within the shell. The thus generated metallic iron adheres to the inner surface of the shell, and the shell grows accordingly. On the other hand, most of the by-product slag, which is derived from both gangue contained it an iron oxide source, such as iron ore, and the ash content of a carbonaceous reductant, aggregates within the metallic iron shell. Thus, metallic iron having a relatively high iron purity and constituting the shell can be efficiently separated from the aggregated slag.
This phenomenon, which occurs during reduction and will be described later with reference to photos, is believed to occur in the following manner. FIGS. 1 (A) to 1 (F) show cross-sectional views of a compact schematically illustrating the phenomenon which occurs when the method of the present invention is carried out. When a compact 1 composed of an iron oxide-containing material and a carbonaceous reductant and having a form shown in FIG. 1 (A) is heated, for example, to a temperature of 1450 to 1500°C in a nonoxidizing atmosphere, the reduction of iron oxides progresses from the periphery of the compact 1, and metallic iron generated diffuses and joins together to form a metallic iron shell la (FIG. 1 (B)). Subsequently, as heating continues, iron oxides within the shell la are quickly reduced, as shown in FIG. 1 (C), through reduction by the carbonaceous reductant present within the shell la and reduction by CO generated by a reaction between the carbonaceous reductant and iron oxides. The thus generated metallic iron Fe adheres to the inner surface of the shell, and the shell grows accordingly. On the other hand, as shown in FIG. 1 (D), most of the by-product slag Sg derived from the above-mentioned gangue and the like aggregates within the cavity defined by the shell la.
The reduction through the application of heat is represented by the following schemes:
Y = yi + y2
Y: chemical equivalent (mol) of carbon required for reduction
yi : amount (mol) of carbon required for reaction represented by scheme (1)
y2: amount (mol) of carbon required for reaction represented by scheme (2)
When compacts are prepared using an iron oxide, containing material and a carbonaceous reductant, the mixing ratio between iron oxides and the carbonaceous reductant is adjusted such that the amount of the carbonaceous reductant is not less than a theoretical equivalent expressed by scheme (3). This allows reduction through the application of heat to progress efficiently.
As described above, according to the present invention, the metallic iron shell la is formed on the periphery of the compact 1 during the incipient stage of reduction through the application of heat, and the reduction progresses further within the cavity defined by the shell la, thereby significantly improving the efficiency of the reduction. Preferably, an ultimate temperature of heating for reduction may be controlled so as to be not less than the melting point of the accompanying slag and not more than the melting point of the metallic iron shell la. If the ultimate temperature of heating is equal to or greater than the melting point of the metallic iron
shell la, generated metallic iron will immediately fuse and aggregate; consequently, the metallic iron shell la will not form and the subsequent reducing reaction will not progress efficiently. Also, if non-reduced molten iron oxide flows out from inside the metallic iron shell la, it may be highly likely to damage the refractory of the furnace. On the other hand, when the ultimate temperature of heating for reduction is controlled so as to be not less than the melting point of the accompanying slag, the by-product slag fuses and aggregates, and metallic iron diffuses and joins together intensively; consequently, the metallic iron shell la grows accordingly while slag Sg is separating from the shell la as shown in FIGS. 1 (C) and (D).
As described above, a key feature of the present invention is that "a metallic iron shell is formed within which a reducing reaction progresses efficiently," which is not employed in conventional indirect and direct iron-making methods and which significantly enhanced reduction through the application of heat. The metallic iron shell la grows as a carbonaceous reductant contained in the compacts progressively reduces the compacts. Once the metallic iron shell la is formed, the carbonaceous reductant and the generated CO continue reduction within the shell la. Hence, the atmosphere for reduction through the application of heat does not need to be reducing, but may be a non-oxidizing atmosphere such as a nitrogen gas atmosphere. This is a significant difference from the conventional methods.
Basically, the above-stated reduction through the application of heat progresses in the form of a solid phase reduction, which does not cause the metallic iron shell la to melt. Conceivably, liquid phase reduction also progresses at the latter or end stage of the reducing reaction for the following reason. The interior of the metallic iron shell la is believed to maintain a highly
reducing atmosphere because of the presence of a carbonaceous reductant and CO generated by the reducing reaction of the reductant, resulting in a significant rise in reduction efficiency. In such a highly reducing atmosphere, metallic iron generated within the shell la is subjected to carburization, so that its melting point gradually reduces. As a result, at the latter or end stage of the reducing reaction, part of the compacts melt, so that iron oxides undergo liquid phase reduction. By setting a relatively low reducing temperature, reduction can be carried out entirely in the solid phase. However, the higher the reducing temperature, the higher the reaction ratio of reduction, and so a relatively high reducing temperature is advantageous to complete the reducing reaction within a short period of time. Hence, it is desirable that the reducing reaction ends with liquid phase reduction.
In the state shown in FIG. 1 (D), iron oxides composed mainly of FeO and contained in the
compact are substantially all reduced to metallic iron (iron oxide content, indicative of the progress of the reduction, is usually not more than 5% by weight and is experimentally confirmed to be not more than 2% by weight or not more than 1% by weight), and some iron oxides composed mainly of FeO and fused into the internal aggregate of molten slag Sg are also mostly reduced (content of iron oxides composed mainly of FeO contained in the slag, indicative of the progress of the reduction, is usually not more than 5% by weight and is experimentally confirmed to be not more than 2% by weight or not more than 1% by weight). Accordingly, metallic iron having a relatively high iron purity can be efficiently obtained by chilling compacts in the state of FIG. 1 (D), crushing their metallic iron shell la with a crusher, and magnetically selecting metallic iron from slag. Alternatively, heating at the same temperature or a higher temperature may be continued subsequently to the establishment of the state of FIG. 1 (D), whereby part or all of the metallic iron shell la is melted so as to separate the slag from metallic iron, which will be described below.
When heating is continued at a slightly higher temperature, as needed, subsequent to the establishment of the state of FIG. 1 (D), part of the metallic iron shell la melts, for example, as shown in FIG. 1 (E). This allows the accompanying slag Sg to flow out from inside the shell la, thereby facilitating the separation of metallic iron from the slag. Alternatively, heating may be continued to establish the state shown in FIG. 1 (E), whereby the entire metallic iron shell la melts and aggregates, in order to be separated from the slag Sg which had previously melted and aggregated. Then, the thus prepared mass in the state shown in FIG. 1 (E) or (F) is processed by a crusher or the like to crush the fragile slag only, leaving metallic iron in agglomerates. The crushed mass is then subjected to screening using a screen having an appropriate mash or to magnetic separation, thereby readily obtaining metallic iron having a relatively high iron purity. In addition, the difference in specific gravity between metallic iron and slag may be used to separate molten metallic iron from molten slag.
The metallic iron shell can be melted not only by heating at a higher temperature subsequently to the completion of the reducing reaction but also by reducing the melting point of the metallic
iron shell through carburization. At the last stage of the reduction progressing within the metallic iron shell, the internal atmosphere, which is strongly reducing, causes reduced iron to be carburized with a resultant reduction in the melting point of the reduced iron. Hence, even by maintaining the reducing temperature, the metallic iron shell can be melted due to the reduction in its melting point.
In the present embodiment, an iron oxide and a carbonaceous reductant and, as needed, a binder, are homogeneously mixed and then formed into agglomerates, grains, briquettes, pellets, bars, or other forms of compacts, and the resulting compacts are subjected to reduction through the application of heat. The amount of the carbonaceous reductant to be mixed in is not less than a theoretical chemical equivalent required for a reducing reaction represented by the aforesaid schemes (1) to (3). The amounts of yi and yi represented by schemes (1) and (2) vary with material conditions (chemical composition, grain size, pellet size, etc.) and reduction
temperature. However, the theoretical chemical equivalent is determined by measuring the CO and CO2 density of gases which is generated in a small reduction apparatus where pellets are reduced at a specified temperature. The pellets are added with carbonaceous reductant slightly more than a necessary amount for an assumed reduction case of scheme (1) only. Preferably, the carbonaceous reductant is used in excess, in consideration of the amount consumed or carburization to lower the melting point of the metallic iron shell.
As heretofore mentioned, preferably, an ultimate temperature during reduction through the application of heat is not less than the melting point of the by-product slag and not more than the melting point of the metallic iron shell. However, it is not necessarily adequate to absolutely predetermine the ultimate temperature because the temperature of slag varies depending on the amount gangue contained in iron ore or other iron oxide sources and depending on the amount of iron oxide contained in the slag. Nevertheless, the reducing temperature falls preferably in the range of 1350 to 1540°C, preferably in the range of 1400 to 1540°C, more preferably in the range of 1430 to 1500°C. Such a temperature range of reduction provides metallic iron having as high an iron purity of not less than 95% by weight in metallization ratio, usually not less than 98% by weight, and in excellent cases not less than 99% by weight.
As for the by-product slag, its content of iron oxides composed mainly of FeO can be reduced to not more than 5% by weight, usually not more than 2% by weight, or under more adequate conditions of reduction through the application of heat, not more than 1% by weight. This feature is advantageous to prevent damage to the refractory wall of a furnace caused by direct contact with molten iron oxide. According to the heretofore mentioned conventional reducing iron-making methods, when iron oxides contained in iron ore or the like are subjected to reduction through the application of heat using a carbonaceous material, or when metallic iron obtained through reduction is separated from accompanying slag, a considerable amount of iron oxides composed mainly of FeO is left unreduced in the slag, causing damage to the refractory of the furnace. According to the present invention, iron oxides composed mainly of FeO contained in slag are mostly reduced, so that almost no iron oxide or only a very small amount of iron oxide,
if any, is left unreduced in the slag. Thus, the problem of damage to the refractory of a furnace does not occur, not only at the reducing step, but also at the subsequent slag separating step.
Coal powder (carbonaceous reductant), iron ore (iron-containing material), and binder (bentonite), each having a composition shown in Table 1 and an average grain diameter of not more than 45|im, were mixed in the mixing ratio shown in Table 1. The resulting mixture was formed into substantially spherical pellets having 17 mm diameters. The thus formed pellets were subjected to reduction through the application of heat in a non-oxidizing atmosphere (nitrogen gas atmosphere) for 20 minutes at 1400°C, 1450 °C, and 1500 °C, followed by cooling. The cross-sections of the reduced pellets were observed. FIG. 2 shows typical photographs of their cross-sections. In the tables "T." stands for "total", and "M." stands for "metallic".
As seen from Fig. 2, in pellets subjected to reduction through the application of heat at a temperature of 1--100°C and 14:"30"C. a
metallic iron shell is formed on their surface while metallic iron adheres to the internal surface of the shell as it accumulates, and slag-agglomerates separately from the shell in an internal space defined by the shell. In a pellet subjected to reduction through the application of heat at a temperature of 1500nC, it.seems that once formed, the metallic
iron shell nielted after the reducing reaction had completed."and lhen
the molten metallic iron and molten slag solidified to mutually separated metallic iron having metallic luster, and a vitreous mass, respectively (the corresponding photograph in Fig. 2 show only metallic iron obtained by removing slag after crushing). Table 2 shows the chemical composition of the reduced pellets, and Table 3 shows the chemical composition of the vitreous slag.
Reducing* time: 20 minutes
As seen from Table 2, in pellets subjected to reduction nt a temperature of 1500°C, solidified metallic iron (see Fig. 2) having an
elliptical shape and metallic luster contains almost no slag constituents.
and the reduced metallic iron having a metallization ratio of not less than 99% by weight is substantially completely separated from I In* slag. On the other hand, in pellets subjected to reduction at a temperature of 1400°C or 1450°C, a metallic iron shell still remains, and their choniM ,,1
compositions seem to indicate that reduction of iron oxide is insufficient. However, as seen from Fig. 2, in those pellets, a metallic iron shell is already separated from aggregated slag within the shell. This implies that granular metallic iron having a relatively high iron purity can be obtained by: crushing reduced pellets and collecting metallic iron through magnetic separation; continuing heating at a higher temperature to melt part of the metallic iron shell to thereby allow molten slag to flow out from inside the shell, followed by separation of metallic iron from slag; or continuing heating at a higher temperature to melt the entire metallic iron shell and then allowing molten melnllic iron and molten slag to aggregate separately from each other.
Fig. ?) shows a change.in appearance of a pellet observed when reducing time is varied from ."? minutes through 15 minutes nl ;i reduein^ temperature of 1500°C. Table 4 shows the chemical composition of each
reduced pellet corresponding to each reducing time. Figs. 1 to 7 show a change in metallization ratio, content of slag constituents, iron oxide content, and carbon content, respectively, with reducing time.
As seen from Fig". 3, 3 minutes after healing has started, no particular change in appearance is observed with the pellet. However, as seen from Table 4, reduction of iron oxide is considerably progressed in the pellet. 5 minutes after heating has started, the pellet surface ' exhibits an apparent metallic luster indicative of a metallic iron shell being formed. In addition, the T. Fe content of the metallic iron is in
excess of 90% by weight. 6 minutes later, the T. Fe content of the metallic iron is as high as not less than 98% by weight as shown in Table 4.
At this point of time, it is observed that part of the metallic iron shell melts to allow molten slag to flow out from inside the shell. 9 minutes later, most of the metallic iron shell melts and aggregates in a fried egg like shape, in which metallic iron agglomerates in the position corresponding to the yolk, and vitreous slag aggregates around the metallic iron in the position corresponding to the white of the egg. After this point of time, the shape of the metallic iron and slag varies somewhat, but as seen from Table 4, the T. Fe concentration in the metallic iron shows almost no further increase. This indicates that the reducing reaction of iron oxides contained in a pellet progresses quickly and is almost completed while the metallic iron shell is formed and, once the metallic iron shell is formed, under an enhanced reducing condition established within the shell, after which the separation of the metallic iron from slag progresses with time. As seen from Table 4 and FIGS. 4 to 7, 6 minutes after reduction through the application of heat starts, the slag and FeO content of the obtained metallic iron is reduced to a very low level, whereby metallic iron having a metallization ratio of not less than 99% is obtained.
As will be easily understood, if the compact composed of an iron oxide-containing material and a carbonaceous reductant contains as much carbonaceous reductant as equal to or greater than the equivalent required for reducing iron oxides contained in the compact, then when the compact is heated at a temperature of about 1400°C or higher, a metallic iron shell will form on the periphery of the compact at the incipient stage of heating, and subsequently iron oxide will be quickly reduced within the metallic iron shell, while molten slag is separated from metallic iron. When the reducing temperature is increased to 1500 °C, a reducing reaction and the separation of metallic iron from slag progress within a very short period of time, whereby metallic iron having a very high iron purity is obtained at a relatively high yield.
FIG. 8 shows a flow chart illustrating an embodiment of the present invention. Pulverized iron
oxide-containing material and pulverized carbonaceous reductant, together with binder, are mixed and formed into pellets or other forms of compacts. The thus formed pellets or the like are subjected to reduction through the application of heat at a temperature of not less than 1400 °C in a furnace. During the reducing step, a metallic iron shell is formed during the incipient stage of reduction, and then a reducing reaction progresses within the shell while molten slag aggregates within the shell. At the separating step, reduced masses are chilled to solidify, and then the resulting solidified masses are crushed, followed by collection of metallic iron through magnetic separation or the like. Alternatively, heating may be further continued to melt metallic iron so as to separate molten metallic iron from molten slag utilizing a difference in the specific gravity between them. If needed, the collected metallic iron may be refined to remove impurities such as sulfur and phosphorus and in addition, the carbon content of the metallic iron can be adjusted.
The amount of a carbonaceous reductant contained in the compact must be at least an amount required for reducing iron oxide, preferably plus an amount required for carburizing reduced iron, so that generation of reduced iron (metallic iron) can be accompanied by carburization. Solid (unmolten) reduced iron, composing a shell, has a porous form and thus is likely to be re-oxidized. This re-oxidization can be prevented by the presence of the carbonaceous reductant in the compact more than the above-described "amount required for reducing source iron oxide + amount required for carburizing reduced iron." This is because the CO gas generated from the compact establishes a non-oxidizing atmosphere around the compact. That is, the compact most preferably contains the carbonaceous reductant in "amount required for reducing source iron oxide + amount required for carburizing reduced iron + amount of loss associated with oxidation."
In the above-described process, a carbonaceous reductant is previously contained in the compact in "amount required for reducing source iron oxide" plus "amount required for carburizing reduced iron + amount of loss associated with oxidation." However, the carbonaceous reductant may be contained in the compact in "amount required for reducing source iron oxide," and the carbonaceous reductant may be additionally supplied from outside in "amount required for carburizing reduced iron + amount of loss associated with oxidation" during reduction through the application of heat. Alternatively, the carbonaceous reductant may be contained in the
compact in "amount required for reducing source iron oxide + amount required for carburizing reduced iron," and the carbonaceous reductant may be additionally supplied from outside in "amount of loss associated with oxidation" during reduction through the application of heat. In such a manner, the carbonaceous reductant may be additionally supplied to compensate a shortage. In any of these cases, the carbonaceous reductant in "amount required for reducing source iron oxide" allows a metallic iron shell to be generated in a good manner while slag aggregates inside the shell.
A carbonaceous reductant in "amount required for carburizing reduced iron" or "amount of loss associated with oxidation" may be additionally supplied while metallic iron (reduced iron) is being melted. In this case, carburization advances during the melting process, and the CO gas generated from the carbonaceous reductant maintains a non-oxidizing atmosphere around the compact, thereby preventing metallic iron from being re-oxidized.
Through the employment of such a sloped floor, the compacts smoothly move within the melting
apparatus toward the subsequent separator. As the compacts move downward on the sloped floor, their degrees of melting increase and become substantially uniform (no -mixed presence of the compacts of different degrees of melting), thereby efficiently melting the compacts.
The thermal reduction apparatus 123 is followed by a melting apparatus 112, located at an end of conveyance on the hearths 146 (downstream of the conveying member). The melting apparatus
112	has, as a melting mechanism, a melting burner 161 for heating the interior of the melting
apparatus 112 enclosed by a furnace wall 106 made of refractory. The melting apparatus 112 also
has a sloped floor 151 for leading the compacts 104 to the next process (separator 113). A weir
152 is located between the melting apparatus 112 and the following separator 113. The separator
113	collects molten iron 154 and molten slag 153. The separator 113 has a slag outlet 155 and a
molten iron outlet 156.
A pulverized mixture, composed of a carbonaceous reductant such as coal or the like and iron oxide such as iron ore or the like, is compacted to grains, for example. The thus-formed compact contains the carbonaceous reductant in "amount required for reducing source iron oxide+amount required for carburizing reduced iron+amount of loss associated with oxidation."
The melting compacts 104 stay behind the weir 152, and a molten substance overflows the weir
152 to be collected in the separator 113.
Since the molten slag 153 and the molten iron 154 are different in specific gravity, they separate one from the other in the separator 113 such that the molten slag 153 collects on the molten iron 154 to form two layers. The thus-separated slag 153 is released from the slag outlet 155 while the molten iron 154 is released from the molten iron outlet 156.
In a method of making metallic iron according to Embodiment 3 of the present invention, a granular or agglomerate compact (hereinafter may be referred to as a compact) of iron oxide
which contains a carbonaceous reductant is reduced through the application of heat, thereby making metallic iron. Specifically, the above-mentioned compact is reduced through the application of heat while being placed on a horizontal surface. In the course of this reduction, a shell composed of metallic iron is generated and grown, and slag aggregates inside the shell. This reduction is continued until substantially no iron oxide is present inside the shell. Subsequently, the compact in the form of the shell with a slag aggregate contained inside is discharged from the horizontal surface, followed by further heating for melting. The resulting molten substance is separated into molten slag and molten iron.
Like Embodiment 2, the amount of a carbonaceous reductant contained in the compact must be at least an amount required for reducing iron oxide, preferably plus an amount required for carburizing reduced iron. More preferably, the amount of a carbonaceous reductant is "amount required for reducing source iron oxide+amount required for carburizing reduced iron+amount of loss associated with oxidation."
Further, like Embodiment 2, a carbonaceous reductant may be contained in the compact in "amount required for reducing source iron oxide," and the carbonaceous reductant may be additionally supplied from outside in "amount required for carburizing reduced iron + amount of loss associated with oxidation" during reduction through the application of heat. Alternatively, the carbonaceous reductant may be contained in the compact in "amount required for reducing source iron oxide + amount required for carburizing reduced iron," and the carbonaceous
reductant may be additionally supplied from outside in "amount of loss associated with oxidation" during reduction through the application of heat. In such a manner, the carbonaceous reductant may be additionally supplied to compensate a shortage.
Further, as previously described, a carbonaceous reductant in "amount required for carburizing reduced iron" or "amount of loss associated with oxidation" may be additionally supplied while metallic iron (reduced iron) is being melted. In this case, carburization advances during the melting process, and the CO gas generated from the carbonaceous reductant maintains a non-oxidizing atmosphere around the compact, thereby preventing metallic iron from being re-oxidized.
A powdery desulfurizer may be used which is attached to the surface of the compact. This prevents the compacts from sintering together to become a relatively large agglomerate or sinteringly adhering to a furnace wall. In addition, since the powdery desulfurizer adhering to the compact is charged into the melting apparatus, desulfiirization can be performed within the melting apparatus. Examples of such a desulfurizer include limestone.
FIGS. 10 and 11 show Embodiment 3 of a metallic iron-making apparatus according to the present invention, wherein FIG. 10 shows a horizontal section of the apparatus as viewed from above, and FIG. 11 shows a sectional view of the apparatus taken along lines Z--Z and Y--Y of FIG. 10.
The apparatus of making metallic iron has a thermal reduction apparatus 223, a melting apparatus 212, and a separator 213. The thermal reduction apparatus 223 is composed of preparatory compact chambers 202 and 209 and a thermal reduction furnace 210. The thermal reduction apparatus 223 has a cart (feeding member) 207 to carry the compacts 204, and the cart 207 moves between the preparatory compact chambers 202 and 209 and the thermal reduction furnace 210. The cart 207 has a tilting member (not shown) for alternating the position of a compact-carrying plane (hearth) between a horizontal position and a sloped position. The
preparatory compact chambers 202 and 209 have feed ports 217 and 218, respectively, for feeding the compacts 204 therethrough from the exterior of the preparatory compact chambers 202 and 209. The thermal reduction furnace 210 has a reducing burner 211 (thermal reduction mechanism) and an exhaust gas outlet 221 for releasing a generated exhaust gas.
A pulverized mixture, composed of a carbonaceous reductant such as coal or the like and iron oxide such as iron ore or the like, is compacted in advance. As in the above-described Embodiment 2, The thus-formed compact contains the carbonaceous reductant in "amount required for reducing source iron oxide+amount required for carburizing reduced iron+amount of loss associated with oxidation." Furthermore, in Embodiment 3, a powdery desulfurizer such as powdery limestone or the like adheres to the compact surface.
The compacts 204 are fed into the preparatory compact chamber 202 through the feed port 217 to be placed on the cart 207 (in a horizontal position). The cart 207 carrying the compacts 204 moves into the thermal reduction furnace 210. The compacts 204 are reduced through the application of heat within the thermal reduction furnace 210, whose maximum temperature is regulated by the reducing burner 211 so as to be not less than the melting point of generated slag and not more than the melting point of a metallic iron shell. During this reduction, the cart 207 maintains its horizontal position, i.e. the compacts 204 are reduced through the application of
heat while being placed on a horizontal plane (hearth).
In this thermal reduction process, reduction first advances at the peripheral portion of the compact 204, thereby forming a shell composed of metallic iron. Subsequently, through reduction by carbon monoxide, which is generated inside the shell from the carbonaceous reluctant itself and through pyrolization of the carbonaceous reductant, a reducing reaction of iron oxide efficiently advances inside the shell. Accordingly, generated metallic iron aggregates to grow the shell, and generated slag also fuses to aggregate. That is, as reduction advances, the compact 204 generates and grows the metallic iron shell while slag aggregates inside the shell. As a result, in this thermal reduction process, a metallization ratio considerably increases, and the amount of iron oxide mixed into the slag considerably decreases.
Upon substantial end of reduction, the compact 204 is composed of the metallic iron shell and a slag aggregate inside the shell. At this stage, the cart 207 is sloped by the tilting member (as
represented by the dotted line of FIG. 11). Since at least the shell of the compact 204 is in a solid state, the compacts 204 move downward on the sloped hearth of the cart 207 to be discharged from the thermal reduction furnace 210 into the melting apparatus 212. The emptied cart 207 returns to the preparatory compact chamber 202 to be fed again with the compacts 204 through the feed port 217.
In the apparatus of making metallic iron of FIGS. 10 and 11, the thermal reduction apparatus 223 uses a tilting member, as a discharging member, which changes the position of the cart 207 (a feeding member) from a horizontal position to a sloped position to thereby discharge the compacts 204 from the thermal reduction apparatus 223 into the melting apparatus 212. The discharging member is not limited thereto, but may be, for example, a pushing member for pushing out the compacts 204 on the cart 207 to thereby discharge the compacts 204 from the thermal reduction apparatus 223. Alternatively, an iron support may be placed on the cart 207, and the compacts 204 may be placed on the support, so that the compacts 204, together with the iron support, may be discharged from the thermal reduction apparatus 223. Such a method that the compacts 204 are discharged by the pushing member or together with the iron support can smoothly lead the compacts 204 into the meting apparatus 212 even when the compacts 204 agglomerate to a considerably large size.
In Embodiment 4, a granular or agglomerate compact (hereinafter may be referred to as a compact) of iron oxide which contains a carbonaceous reductant is reduced through the application of heat, thereby making metallic iron. Specifically, the above-mentioned compact is rolled to be uniformly heated so as to be efficiently be reduced. In the course of this reduction, a shell composed of metallic iron is generated and grown, and slag aggregates inside the shell. This reduction is continued until substantially no iron oxide is present inside the shell. Subsequently, the compact in the form of the shell with a slag aggregate contained inside is further heated to be melted, followed by separation into molten slag and molten iron. Since the compacts are rolled, the compacts are prevented from sintering together to become a relatively large agglomerate or sinteringly adhering to a furnace wall during reduction through the application of heat,
FIG, 12 is a schematic sectional view showing an embodiment 4 of an apparatus of making
metallic iron according to the present invention. FIG. 13 shows a sectional view of the apparatus of making metallic iron taken along line A--A of FIG. 12. In FIGS. 13 and 12, reference numeral 301 denotes a thermal reduction-melting apparatus, and reference numeral 302 denotes a separator. The thermal reduction-melting apparatus 301 and the separator 302 are constructed of or lined with refractory.
The thermal reduction-melting apparatus 301 is composed of a channel-like member 303 and a cover member 304. The channel-like member 303 has an arc-shaped inner surface, i.e. a sloped surface for tumbling 308 and is sloped along the length of a channel (in a right-left direction of FIG. 12). The channel-like member 303 is supported by support rollers 307 and rocks in the direction of arrow B. Therefore, the sloped surface for tumbling 308 rocks accordingly. Rolling on the rocking sloped surface for tumbling 308, compacts 305 gradually move downward along the direction of inclination (toward the right of FIG. 12). A burner 306 serving as a thermal reduction-melting member is provided in the thermal reduction-melting apparatus 301 on the bottom side of the slope (at the right-hand side of FIG. 12). The burner 306 establishes a thermal reduction atmosphere (the left-hand region of FIG, 12) and a melting atmosphere (the right-hand region of FIG. 12) within the thermal reduction-melting apparatus 301. In FIG. 12, reference numeral 309 denotes an exhaust gas outlet for releasing an exhaust gas generated by the burner 306.
The compacts 305 are formed by compacting a mixture, composed of a carbonaceous reductant such as coal or the like and iron oxide such as iron ore or the like. The thus-prepared compacts 305 are charged into the thermal reduction-melting apparatus 301 through a feed port 310. As described above, the compacts 305 gradually move downward along the direction of inclination (toward the right of FIG. 12) while tumbling, during which the compacts 305 are reduced and melted through the application of heat of the burner 306. A resulting molten substance 315 is discharged through a discharging section 311, formed at the bottom end portion of the sloped surface for tumbling 308, into the separator 302. The internal temperature of the thermal reduction-melting apparatus 301 is regulated such that the thermal reduction region has a
temperature of less than the melting point of a generated metallic iron shell and not less than the melting point of generated slag and such that the melting region has a temperature at which both reduced metallic iron and the generated slag melt.
In the above-described Embodiment 4, the compacts 305 are reduced and melted through the
application of heat within the thermal reduction-melting apparatus 301 having the sloped surface for tumbling 308. Alternatively, the thermal reduction-melting apparatus 301 may be constructed as a thermal reduction apparatus wherein the burner 306 is only used as a thermal reduction member for reducing the compacts 305 and the compacts 305 undergoes only reduction through the application of heat. In this case, the separator 302 may be provided with a burner, an electric heating apparatus or the like to thereby have functions of a melting apparatus, or a melting apparatus may be provided between the thermal reduction apparatus and the separator so as to perform melting within the separate melting apparatus. In addition, a plurality of the burners 306 may be provided such that some burners 306 are used to maintain a thermal reduction atmosphere while other burners 306 are used to maintain a melting atmosphere. The separator 302 may preferably be provided with a heating burner or an electric heating apparatus for further heating molten slag S and molten iron F to a higher temperature to thereby increase their fluidity, so that molten slag S and molten iron F can be more readily separated one from the other, thereby more facilitating their separate release.
The amount of a carbonaceous reductant contained in the compact 305 must be at least an amount required for reducing iron oxide, preferably plus an amount required for carburizing reduced iron, so that generation of reduced iron can be accompanied by carburization. Solid (unmolten) reduced iron, composing a shell, has a porous form and thus is likely to be re-
oxidized. This re-oxidization can be prevented through containment of an additional amount of the carbonaceous reductant in the compact 305 since the CO gas generated from the compact 305 establishes a non-oxidizing atmosphere around the compact 305. That is, the compact 305 most preferably contains the carbonaceous reductant in "amount required for reducing source iron oxide+amount required for carburizing reduced iron + amount of loss associated with oxidation."
In the above-described proposal, a carbonaceous reductant is previously contained in the compact in "amount required for reducing source iron oxide + amount required for carburizing reduced iron + amount of loss associated with oxidation." However, like Embodiment 2 or the like, the carbonaceous reductant may be contained in the compact in "amount required for reducing source iron oxide," and the carbonaceous reductant may be additionally supplied from outside in "amount required for carburizing reduced iron + amount of loss associated with oxidation" during reduction through the application of heat. Alternatively, the carbonaceous reductant may be contained in the compact in "amount required for reducing source iron oxide+amount required for carburizing reduced iron," and the carbonaceous reductant may be additionally supplied from outside in "amount of loss associated with oxidation" during reduction through the application of heat. In such a manner, the carbonaceous reductant may be additionally supplied to compensate a shortage.
While metallic iron (reduced iron) is being melted, the thermal reduction-melting apparatus 301 may be replenished with a carbonaceous reductant to compensate a shortage of the carbonaceous
reductant, so that the CO gas generated from the carbonaceous reductant maintains a non-oxidizing atmosphere around the compacts 305, thereby preventing metallic iron from again being oxidized. Thus, it is preferable that during the melting of metallic iron, a carbonaceous reductant be additionally fed in the amount of compensating a shortage or that the carbonaceous reductant is previously contained in the compact 305 in excess of a required amount, so that even when some iron oxide remains due to incomplete reduction in a reducing process, the remaining iron oxide can completely be reduced in a melting process.
In Embodiments 5 to 7, a granular or agglomerate compact of iron oxide which contains a carbonaceous reductant is reduced through the application of heat, thereby making metallic iron. Specifically, the above-mentioned compact is reduced through the application of heat while falling downward. In the course of this reduction, a shell composed of metallic iron is generated and grown, and slag aggregates inside the shell. This reduction is continued until substantially no iron oxide is present inside the shell. The compact in the form of the shell with a slag aggregate contained inside is further heated to be melted in the course of the fall, followed by separation into molten slag and molten iron. Further, by adding a preceding process of continuously forming the granular compacts to the process of reduction through the application of heat, it becomes possible to continuously perform a series of processes of preparing granular compacts
serving as material for metallic iron, reducing the compacts through the application of heat, and separating metallic iron generated through the reduction from slag.
In a section located underneath the section of reduction through the application of beat, further heating is performed to melt the metallic iron shell. The resulting molten substance falls into a separator located underneath, where molten iron and molten slag are separated one from the other due to their different specific gravities. Thus, highly reduced metallic iron can be efficiently obtained in the form of molten iron. Furthermore, since iron oxide is intensively reduced in the thermal reduction process, the amount of iron oxide mixed into the accompanying molten slag is significantly small. Therefore, the refractory of a melting apparatus can accordingly be prevented from damagingly being melted by iron oxide mixed into the molten slag.
FIG. 14 shows a schematic sectional view of Embodiment 5 of the present invention, illustrating a typical method and apparatus for making metallic iron. In FIG. 14, reference numeral 401 denotes a screw-shaped conveying apparatus; numeral 402 denotes a reducing-melting furnace having a space of falling for conducting heating, reduction, and melting; numeral 403 denotes a heating section for indirectly heating the reducing-melting furnace 402 from outside; and numeral 404 denotes a separator furnace for receiving molten slag and molten metallic iron, falling from above, and for separating them one from the other. For use in this apparatus of
making metallic iron, a mixture, composed of a carbonaceous reductant such as coal or the like and iron oxide such as iron ore or the like and, as needed, a binder, is compacted to grains, thereby forming granular compacts D. The granular compacts D are fed into the conveying apparatus 401, so that they are continuously charged from the tip portion of the conveying apparatus 401 into the top portion of the reducing-melting furnace 402.
Slag, generated in the course of generation of metallic iron, melts inside the metallic iron shell of the granular compact D at a lower temperature than metallic iron does. The thus-molten slag and
the metallic iron shell fuse together in a separated state. As the granular compact D falls further downward within the reducing-melting furnace 402 and is heated further, the metallic iron shell also melts. The molten metallic iron, together with the molten slag, falls into the separator furnace 404 located underneath. In the separator furnace 404, molten slag S having a smaller specific gravity separately floats on the surface of molten iron F. Thus, the molten slag S is released from the separator furnace 404 at a location in the vicinity of the surface of the molten iron F while the molten iron F is released from the bottom portion of the separator furnace 404.
In FIG. 14, reference numeral 406 denotes exhaust gas outlets. Exhaust gases may be released through the corresponding exhaust gas outlets 406 without any utilization thereof. However, since the exhaust gases have a high temperature and contains combustible gas, they may be utilized as fuel gases to be fed to burners 405 located at the heating section 403, resulting in a reduced fuel consumption associated with heating. In the above description, the reducing-melting
furnace 402 is indirectly heated from outside. However, burners may be mounted inside the reducing-melting furnace 402 for directly heating the granular compacts D.
FIG. 15 shows a schematic sectional view of Embodiment 6 of the present invention, which is constructed such that the falling speed of granular compacts D can be reduced with no requirement to mount falling-speed control members or the like. In Embodiment 6, a separator furnace 404 is integrally formed at the bottom portion of a reducing-melting furnace 402. Furthermore, a high-temperature non-oxidizing gas is fed into the thus-constructed furnace at positions just above the boundary between the reducing-melting furnace 402 and the separator furnace 404, thereby forcibly suspending the falling granular compacts D by an ascending current of the non-oxidizing gas. As a result, the residence time of the granular compacts D within the reducing-melting furnace 402 can be increased. In this case, while the suspended granular compacts D are subjected to reduction through the application of heat, a metallic iron
shell is formed on the surface of the granular compact D, and a reducing reaction advances inside the shell. Subsequently, when the thus-formed metallic iron is melted through the further application of heat, molten iron fuses together to grow. The thus-grown molten iron falls downward. Accordingly, by adequately regulating the flow rate of the non-oxidizing gas in accordance with the resistance of the granular compacts D against the ascending current, the residence time of the granular compacts D within the reducing-melting furnace 402 can be regulated as desired. Therefore, while the granular compacts D are resident within the reducing-melting furnace 402, reduction through the application of heat can sufficiently be advanced. This application of heat for reduction may be attained by direct heating through the feed of a high-temperature non-reducing gas or by indirect heating through the use of burners or the like arranged around the reducing-melting furnace 402.
Also, in Embodiments 5 to 7, as described above in other Embodiments, the carbonaceous reductant contained in the above-described granular compact D is consumed, first, through reduction of iron oxide in a reducing process, and then through carburization of metallic iron, generated through the reduction. Solid reduced iron to undergo a melting process has a porous
form and thus is likely to be re-oxidized. In order to prevent the reduced iron from being re-oxidized, the carbonaceous reductant must be contained in the granular compact D sufficiently against re-oxidization, so that the CO gas generated through combustion of the carbonaceous reductant establishes a non-oxidizing atmosphere around the granular compact D falling within the reducing-melting furnace 402. To attain this end, the granular compact D must contain the carbonaceous reductant in at least "amount required for reducing source iron oxide + amount consumed for carburizing reduced iron + amount of loss associated with oxidation within the furnace." In addition, in order to prevent reduced iron from being re-oxidized, the carbonaceous reductant or the CO gas may be additionally supplied in the amount of compensating a shortage into the lower portion of the reducing-melting furnace 402 or the separator furnace 404.
In Embodiments 8 and 7, an elongated compact of iron oxide which contains a carbonaceous reductant is reduced through the application of heat, thereby making metallic iron. Specifically, the above-mentioned elongated compact is reduced through the application of heat while being moved downward in a vertical position. In the course of this reduction, a shell composed of metallic iron is generated and grown, and slag aggregates inside the shell. Subsequently, the metallic iron shell with a slag aggregate contained inside is further heated to be melted in the course of downward movement, followed by separation into molten slag and molten iron. Further, by adding a preceding process of continuously forming the elongated compact to the process of reduction through the application of heat, it becomes possible to continuously perform a series of processes of preparing the elongated compact serving as material for metallic iron, reducing the elongated compact through the application of heat, and separating metallic iron generated through the reduction from slag.
In a section located underneath the section of reduction through the application of heat, further heating is performed to melt the metallic iron shell. The resulting molten substance, composed of molten iron and molten slag, falls into a separator located underneath, where molten iron and molten slag are separated one from the other due to their different specific gravities. Thus, highly
reduced metallic iron can be efficiently obtained in the form of molten iron. Furthermore, since iron oxide is intensively reduced in the thermal reduction process, the amount of iron oxide mixed into the accompanying molten slag is significantly small. Therefore, the refractory of a melting apparatus can accordingly be prevented from damagingly being melted by iron oxide mixed into the molten slag.
FIG. 17 shows a schematic sectional view of Embodiment 8 of the present invention, illustrating a method and apparatus for making metallic iron. In FIG. 17, reference numeral 501 denotes a material hopper; numeral 502 denotes compacting-feeding rollers (having functions of both a compacting apparatus and a feeding apparatus); numeral 503 denotes a thermal reduction furnace; and numeral 504 denotes a separator furnace serving as a separator. A mixture E, composed of a carbonaceous reductant such as coal or the like and iron oxide such as iron ore or the like and, as needed, a binder, is fed into the hopper 501 in the direction of arrow H. The compacting-feeding rollers 502 continuously compact the mixture E into an elongated compact G having a certain shape (usually a plate shape, a square bar shape, or a round bar shape) and certain dimensions, and feed the elongated compact G, maintained in a vertical position, into the thermal reduction furnace 503. The "vertical position" basically means a hanging position, but may somewhat (for example, .±5°) incline at a feeding section due to accuracy of a feeding apparatus without departing from the spirit of the present invention.
The thermal reduction furnace 503 has burners 505 serving as a heating member. As the elongated compact G lowers within the thermal reduction furnace 503, the elongated compact G is directly heated by flames of the burners 505. As a result, reduction advances from the surface of the elongated compact G toward the interior thereof, thereby forming a shell, composed mainly of metallic iron generated through reduction, on the surface as previously described. Carbon monoxide generated from a carbonaceous reductant and through pyrolization of the carbonaceous reductant establishes an intensive reducing atmosphere within the shell, thereby sharply accelerating reduction of iron oxide inside the shell. Therefore, by properly controlling the lowering speed of the elongated compact G and heating conditions in accordance with the
length of the thermal reduction furnace 503, the intensive reducing atmosphere established within the metallic iron shell efficiently reduces iron oxide inside the shell, thereby obtaining a metallization ratio of not less than 95%, or in some cases of not less than 98%.
The present invention may be embodied such that the aforementioned mixture is compacted to the elongated compact G merely through the application of pressure. Preferably, as shown in FIG. 17, the mixture is compacted through the application of pressure while being surrounded by a support mesh K made of iron, so that there is no risk that the elongated compact G would break while it is continuously lowering. The support mesh K is finally melted together with metallic iron, generated through reduction through the application of heat, and falls into the separator furnace 504. Therefore, the support mesh K is desirably made of iron. In place of an exterior reinforcement through the use of the support mesh K, an iron core (a stranded wire, or an iron wire having a rugged surface for increasing the effect of support may also be acceptable) may be
inserted as reinforcement in the central portion of the elongated compact G. EMBODIMENT 9
FIG. 18 shows a schematic sectional view of Embodiment 9 of the present invention. Embodiment 9 is basically similar to Embodiment 8 except that a mixture E, composed of a carbonaceous reductant, iron oxide, and a binder, is fed to compacting-feeding rollers 502 through a screw feeder 501a and that a thermal reduction furnace 503 is indirectly heated by burners 505 arranged therearound.
The carbonaceous reductant contained in the above-described elongated compact G is consumed, first, through reduction of iron oxide in a reducing process, and then through carburization of metallic iron, generated through the reduction. Solid reduced iron to undergo a melting process has a porous form and thus is likely to be re-oxidized. In order to prevent the reduced iron from being re-oxidized, as previously described, the carbonaceous reductant must be contained in the granular compact D sufficiently against re-oxidization, so that the CO gas generated through combustion of the carbonaceous reductant establishes a non-oxidizing atmosphere around the elongated compact G moving downward within the thermal reduction furnace 503. To attain this end, the elongated compact G must contain the carbonaceous reductant in at least "amount required for reducing source iron oxide + amount consumed for carburizing reduced iron+amount of loss associated with oxidation within the furnace." In addition, in order to prevent reduced iron from being re-oxidized, the carbonaceous reductant or the CO gas may be additionally supplied in the amount of compensating a shortage into the lower portion of the
thermal reduction furnace 503 or the separator furnace 504.
In the above-described Embodiments 8 and 9, the elongated compact G is not subjected to any treatment before it is charged into the thermal reduction furnace 503. In order to reduce the length of the thermal reduction furnace 503 to thereby shorten time required for reduction through the application of heat, the elongated compact G may be prereduced before it is charged into the thermal reduction furnace 503. In this case, a prereducing apparatus must be provided upstream of the thermal reduction furnace 503. Also, as shown in FIG. 18. a submerged weir 508 may be provided within the separator furnace 504, thereby efficiently separating molten iron F and molten slag S one from the other.
In a method of making metallic iron according to Embodiment 10 of the present invention, a granular (including pellet-like) or agglomerate compact of iron oxide which contains a carbonaceous reductant is conveyed on an iron belt and reduced through the application of heat, thereby making metallic iron. In the course of this reduction, a shell composed of metallic iron is generated and grown on the surface of the compact, and slag aggregates inside the shell.
Subsequently, the compact in the form of the shell with a slag aggregate contained inside is further heated while being conveyed on the iron belt, so that the metallic iron shell, slag, and the iron belt used for conveyance are melted. The resultant molten substance is separated into molten slag and molten iron. According to the present embodiment, there can also be performed continuously a series of processes of reducing the compact through the application of heat, melting generated metallic iron and slag through the further application of heat, and separating molten iron and molten slag one from the other.
FIG. 19(a) is a schematic cross-sectional view showing an apparatus for making metallic iron for carrying out the above-described method. In FIG. 19(a), reference numeral 601 denotes an iron belt; numeral 602 denotes an annealing furnace; numeral 603 denotes a forming section; numeral 604 denotes a material hopper; numeral 605 denotes a thermal reduction furnace; numeral 606 denotes a melting furnace; and numeral 607 denotes a separator furnace.
The present embodiment uses an iron belt 601 as means for conveying material compact. The iron belt 601 is annealed to be softened while passing through the annealing furnace 602. The thus-annealed iron belt 601 is formed at the forming section 603 into a gutter-like shape with both edges bent upright (see a partial transverse cross-section shown in FIG. 19(b)). The thus-formed iron belt 601 is continuously fed into the thermal reduction furnace 605. A mixture, composed of a carbonaceous reductant such as coal or the like and iron oxide such as iron ore or the like and, as needed, a binder, is compacted to a certain form such as pellets, thereby forming material compacts. The thus-prepared material compacts are placed onto the iron belt 601 through the material hopper 604 located at the upstream side of the thermal reduction furnace 605. The material compacts are continuously fed on the iron belt 601 toward the right of FIG. 19. Heating burners (not shown) are provided on side walls or ceiling portion of the thermal reduction furnace 605 so as to sequentially dry and reduce the material compacts through the application of heat. As previously described, in this thermal reduction process, reduction progresses from the surface of each compact due to a solid reductant contained in the compact, thereby forming a shell, composed mainly of metallic iron generated through reduction, on the
surface of the compact. In addition, carbon monoxide generated from a carbonaceous reductant and through pyrolization of the carbonaceous reductant establishes an intensive reducing atmosphere within the shell, thereby sharply accelerating reduction of iron oxide inside the shell. Therefore, by properly determining the moving speed of the iron belt 601, heating conditions, etc. in accordance with the length of the thermal reduction furnace 605, the intensive reducing atmosphere established within the metallic iron shell efficiently reduces iron oxide inside the shell, thereby obtaining a metallization ratio of not less than 95%, or in some cases of not less than 98%.
In FIG. 19, reference numeral 608 denotes an exhaust gas outlet. An exhaust gas may be released through the gas outlet 608 without any utilization thereof. However, since the exhaust gas has a high temperature and contains combustible gas, it may desirably be utilized as a fuel gas to be fed to the burners of the thermal reduction furnace 605 and melting furnace 606, or as a heat source for preheating the combustion air. Material compacts fed from the material hopper 604 are preferably in the form of pellets and pre-dried, more preferably further pre-reduced since the length of the thermal reduction furnace 605 is reduced through the use of pre-reduced compacts. A compacting apparatus for preparing the material compacts in the form of pellets or the like may be disposed in the vicinity of the hopper 604, so that the material compacts prepared in the
compacting apparatus are fed into the hopper 604. Through the employment of this arrangement, a process of preparing material compacts and a process of reduction through the application of heat is combined into a continuous process.
FIG. 20(a) is a schematic cross-sectional view showing an apparatus for making metallic iron for carrying out the above-described method. In FIG. 20(a), reference numeral 601 denotes an iron
belt; numeral 603 denotes a forming section; numeral 609 denotes a screw feeder; numeral 605 denotes a thermal reduction furnace; numeral 606 denotes a melting furnace; and numeral 607 denotes a separator furnace.
An elongated compact is continuously prepared and placed on the iron belt 601 so as to be conveyed on the iron belt 601 into the thermal reduction furnace 605. That is, as shown in FIG. 20, the screw feeder 609 is combined with the forming section 603. A mixture, composed of a carbonaceous reductant, iron oxide, and binder, is fed into the screw feeder 609, which feeds the mixture toward the forming section 603. Being fed with the mixture and the iron belt 601, the forming section 603 forms the kneaded mixture into an elongated form having a certain cross-section and placed on the iron belt 601 (see a partial transverse cross-section shown in FIG. 20(b)), and feeds the thus-formed elongated compact, together with the iron belt 601, into the thermal reduction furnace 605. The elongated compact may have a flat plate or bar shape, but is preferably shaped such that elongated projections and depressions are formed in a longitudinal direction in order to increase the surface area for efficient drying and reduction through the application of heat.
The thermal reduction furnace 605 comprises an upstream drying section and a downstream thermal reduction section. Heating burners (not shown) are provided on side walls and ceiling portions of the drying and thermal reduction sections so as to sequentially dry and reduce the elongated compact through the application of heat. As previously described) in this thermal reduction process, reduction progresses from the surface of the elongated compact due to a solid reductant contained in the elongated compact, thereby forming a shell, composed mainly of metallic iron generated through reduction, on the surface of the elongated compact. In addition,
carbon monoxide generated from a carbonaceous reductant and through pyrolization of the carbonaceous reductant establishes an intensive reducing atmosphere within the shell, thereby sharply accelerating reduction of iron oxide inside the shell. Therefore, by properly determining the moving speed of the iron belt 601, heating conditions, etc. in accordance with the length of the thermal reduction furnace 605, the intensive reducing atmosphere established within the metallic iron shell efficiently reduces iron oxide inside the shell.
The actual design of the above-described apparatus for making metallic iron may be adequately modified so long as no deviation from the above-stated gist of the present invention is involved. Of course, such modifications are encompassed by the technological scope of the present invention. In operation, the above-described conditions and settings (operating temperature, the amount and form of use of a carbonaceous reductant, utilization of an exhaust gas. etc.) may adequately be selected.
In a method of making metallic iron according to Embodiment 12 of the present invention, a number of elongated compacts of iron oxide which contains a carbonaceous reductant are continuously prepared in parallel by a number of compacting apparatuses disposed in parallel. The thus-prepared elongated compacts are continuously fed in parallel along a sloped surface
into a heat-drying-reducing furnace, and reduced through the application of heat therein. Subsequently, metallic iron generated through reduction and accompanying slag are led into a melting furnace. The resultant molten substance is led into a separator, where molten iron and molten slag are separated one from the other, thereby obtaining metallic iron.
In the present embodiment, as shown in FIGS. 21 and 22, the heating furnace 703 having a sloped surface, sloping down toward the separator furnace 704, is provided on one side or both sides (on one side in FIGS. 21 and 22) of the elongated separator furnace 704. Each heating furnace 703 is provided with a heating burner apparatus and a number of the compacting devices 702 across the width thereof (in a direction perpendicular to the paper surface of FIG. 21) at the upper end portion thereof as shown in FIG. 22. Each heating furnace 703 prepares plate- or barlike elongated compacts 705, feeds these elongated compacts 705 into the heating furnace 703 along the sloped surface of the heating furnace 703. Moving downward along the sloped surface, the elongated compacts 705 are dried and reduced through the application of heat. As previously described, in this thermal reduction process, reduction progresses from the surface of each elongated compact 705 due to a solid reductant contained in the elongated compact 705, thereby forming a shell, composed mainly of metallic iron generated through reduction, on the surface of the elongated compact 705. In addition, carbon monoxide generated from a carbonaceous reductant and through pyrolization of the carbonaceous reductant establishes an intensive reducing atmosphere within the shell, thereby sharply accelerating reduction of iron oxide inside the shell.
The actual design of the above-described apparatus for making metallic iron may be adequately modified so long as no deviation from the above-stated gist of the present invention is involved. Of course, such modifications are encompassed by the technological scope of the present invention. In operation, the above-described conditions and settings (operating temperature, the amount and form of use of a carbonaceous reductant, utilization of an exhaust gas, etc.) may
adequately be selected.
When the present invention is embodied as described above in Embodiments 2 to 12, in a thermal reduction process, slag generated must melt at a lower temperature than does metallic iron generated through reduction in order to successfully reduce iron oxide in a solid-phase state, as previously described. To meet this requirement, the composition of slag components (gangue components mixed in iron ore, generally used as source iron oxide, and a carbonaceous reductant) contained in a compact (or an elongated compact) must be controlled such that the melting point of generated slag is lower than that of reduced iron before and after carburization. Therefore, it may be desirable in some cases that AI2O3, SiCh, CaO, etc. be added to a source mixture of the compact (or the elongated compact) in a compacting process to thereby reduce the melting point of generated slag.
The present invention is not limited to the above-described embodiments. Numerous modifications and variations of the present invention are possible ill light of the spirit of the present invention, and they are not excluded from the scope of the present invention.
As has been described above, according to the present invention, compacts of iron oxide containing a carbonaceous reductant are subjected to reduction through the application of heat, at the incipient stage of which a metallic iron shell is formed. Once the metallic iron shell is formed, iron oxides are reduced under an enhanced reducing condition which is established within the metallic iron shell, whereby the reducing reaction progresses quickly and efficiently. Therefore, the method of the invention can efficiently produce, via reduction through the application of heat and in a short period of time, metallic iron having such a high iron purity, with a metallization ratio of not less than 95%, or in some cases of not less than 98%, which cannot be attained by conventional direct iron making methods. The thus obtained metallic iron having a relatively high iron purity and accompanying slag may be solidified by chilling and
then crushed to separate metallic iron from slag magnetically or by any other screening method or may be melted by further heating so as to separate one from the other through a difference in their specific gravities.
1.	A method for manufacturing metallic iron, comprising the steps of heating a first compact, thereby forming a reduced compact; wherein said first compact comprises iron oxide, and a carbonaceous reducing agent; and said reduced compact comprises a shell, comprising metallic iron, and molten slag, inside said shell. Wherein the heating is at a temperature such that the iron oxide is reduced to metallic iron and the shell is separated from the molten slag.
2.	The method as claimed in claim 1, wherein substantially no iron oxide is present within said shell.
3.	The method as claimed in claim 1, comprising heating said reduced compact, thereby allowing said slag to flow out from inside said shell.
4.	The method as claimed in claim 3, wherein during said heating part of said shell is melted, thereby separating molten slag from said metallic iron.
5.	The method as claimed in claim 4, wherein during said heating said metallic iron is carburized, thereby reducing the melting point of said metallic iron.
6.	The method as claimed in claim 1, comprising heating said reduced compact, thereby melting said metallic iron and separating said metallic iron from said slag.
7.	The method as claimed in claim 6, wherein during said heating said metallic iron is carburized, thereby reducing the melting point of said metallic iron.
8.	The method as claimed in claim 1, comprising allowing said slag to form aggregates, and separating said aggregates from said metallic iron.
9.	The method as claimed in claim 1, wherein said heating is performed at a maximum temperature of not less than the melting point of said slag, and not more than the melting point of said metallic iron.
10.	The method as claimed in claim 1, wherein during said heating said iron oxide is reduced first by solid phase reduction, followed by liquid phase reduction, and said heating is continued until substantially no iron oxide is present.
11.	The method as claimed in claim 1, wherein said reduced compact comprises 5% by weight or less of FeO.
12.	The method as claimed in claim 11, wherein said reduced compact comprises 2% by weight or less of FeO.
13.	The method as claimed in claim 1, wherein said slag comprises 5%, by weight or less of FeO.
14.	The method as claimed in claim 13, wherein said slag comprises 2% by weight or less of FeO.
15.	The method as claimed in claim 1, wherein said shell is closed and continuous.
16.	The method as claimed in claim 1, wherein said heating is performed at a temperature of 1350-1540°C.
17.	The method of any one of the preceding claims wherein an object is provided comprising:
(a)	a shell comprising metallic iron, and
(b)	slag, inside said shell.
18.	The method as claimed in claim 17, wherein said slag is molten.
19.	The method as claimed in claim 17, wherein said slag comprises 5% by weight or lessofFeO.
20.	The method as claimed in claim 17, wherein said slag comprises 2% by FeO.
21.	The method as claimed in claim 1, wherein said first compact is in the form of grains or aggregates and undergoes reduction through the application of heat while being moved in a horizontal direction.
22.	The method as claimed in claim 21, wherein said first compact is placed on an iron belt having edge portions comprising walls formed at said edge portions thereof to prevent said first compact from falling off said iron belt, and said first compact undergoes reduction through the application of heat while being moved in a horizontal direction.
23.	The method as claimed in claim 1, wherein said first compact is in the form of grains or aggregates and undergoes reduction through the application of heat while being placed on a horizontal plane.
24.	The method of Claim 1, wherein said first compact is in the form of grains or aggregates and undergoes reduction through the application of heat while being rolled.
25.	The method as claimed in claim 1, wherein said first compact is in the form of grains or aggregates and undergoes reduction through the application of heat while falling downward.
26.	The method as claimed in claim 1, wherein said first compact is in an elongated form, and undergoes reduction through the application of heat while being moved downward in an upright position.
27.	The method as claimed in claim 26, wherein said first compact is continuously formed into an elongated form and fed to a section where reduction is performed through the application of heat.
28.	The method as claimed in claim 26, wherein said first compact comprises iron mesh serving as a support therefor.
29.	The method as claimed in claim 26, wherein said first compact comprises an iron bar or wire serving as a core thereof.
30.	The method as claimed in claim 1, wherein said first compact is in an
elongated form and undergoes reduction through the application of heat while being
moved downward along a slope.
31.	The method as claimed in claim 30, wherein said first compact is continuously fed on an iron belt to a section where reduction is performed through the application of heat to a temperature of 1350-1540° C.
32.	An apparatus for manufacturing metallic iron by reducing a compact of iron oxide containing a carbonaceous reducing agent comprising:
a heat-melting apparatus for melting the shell and slag; and a separator for separating the molten iron from the molten slag.
33.	The apparatus as claimed in claim 32, wherein the compact is in the form of grains or aggregates and said thermal reduction apparatus comprises a mechanism for reducing the compact through the application of heat while moving the compact in a horizontal direction.
34.	The apparatus as claimed in claim 33, wherein said mechanism comprises an endless rotary member and a hearth located on said member and used for placing the compact thereon.
35.	The apparatus as claimed in claim 34, wherein said hearth is provided with separating members at certain intervals on said hearth to prevent the compact from adhering to another compact.
36.	The apparatus as claimed in claim 35, wherein said separating members includes a desulfurizing agent.
37.	The apparatus as claimed in claim 32, wherein said heat-melting apparatus comprises a sloped floor for melting the compact by application of heat while tumbling or sliding the compact thereon.
38.	The apparatus as claimed in claim 32, wherein the compact is in the form of grains or aggregates and said thermal reduction apparatus comprises a mechanism for reducing the compact through the application of heat while the compact is placed on a horizontal plane.
39.	The apparatus as claimed in claim 38, wherein said thermal reduction apparatus comprises a feeding member having a horizontal plane for intermittently feeding the compact placed on said horizontal plane, a discharging member for discharging the compact from said feeding member, and a heating mechanism for heating the compact.
40.	The apparatus as claimed in claim 39, wherein said discharging member is a tilting member for making the position of said feeding member alternate between a horizontal position and a sloped position.
41.	The apparatus as claimed in claim 39, wherein said discharging member is a pushing member for pushing out the compact from said feeding member.
42.	The apparatus as claimed in claim 39, wherein an iron support is placed on said feeding member and adapted to be discharged together with the compact.
43.	The apparatus as claimed in claim 39, wherein separating members are provided on said feeding member at certain intervals to prevent the compact from adhering to another compact.
44.	The apparatus as claimed in claim 43, wherein said separting members includes a desulfurizing agent.
45.	The apparatus as claimed in claim 39, wherein said heat-melting apparatus comprises a sloped floor for melting the compact by application of heat while tumbling or sliding the compact thereon.
46.	The apparatus as claimed in claim 32, wherein the compact is in the form of grains or aggregates and said thermal reduction apparatus comprises a mechanism for reducing the compact through the application of heat while tumbling the compact.
47.	The apparatus as claimed in claim 46, wherein said thermal reduction
apparatus comprises a tumbling mechanism and a thermal reduction member for heating
the compact, said tumbling mechanism comprising a surface for tumbling the compact
thereon and a discharging unit for discharging the compact from said surface.
48.	The apparatus as claimed in claim 47, comprising a thermal reduction-melting apparatus, comprising an integrated unit of said thermal reduction apparatus and said heat-melting apparatus, wherein said thermal reduction-melting apparatus comprises a tumbling-mechanism and a mechanism for reducing and melting the compact through the application of heat said tumbling mechanism including a sloped surface for gradually tumbling down the compact along a sloped direction and a discharging unit for discharging the compact from said sloped surface.
49.	The apparatus as claimed in claim 47, wherein said surface of tumbling is formed of the interior surface of a channel-like member.
50.	The apparatus as claimed in claim 49, wherein the interior surface of said channel-like member has an arc-shape, V-shape, or U-shape.
51.	The apparatus as claimed in claim 47, wherein said surface comprises the interior surface of a channel-like member having an arc-shape, V-shape, or U-shape and is sloped along the length of the channel-like member.
52.	The apparatus as claimed in claim 32, wherein the compact is in the form of grains or aggregates and said thermal reduction apparatus reduces the compact through the application of heat while the compact is falling downward.
53.	The apparatus as claimed in claim 52, comprising a thermal reduction-melting apparatus, comprising an integrated unit of said thermal reduction apparatus and said heat-melting apparatus, wherein said thermal reduction-melting apparatus
comprises a space of falling for allowing the compact in the form of grains to fall downward and a heating member for reducing and melting the compact in the form of grains through the sequential application of heat while the compact in the form of grains is falling.
54.	The apparatus as claimed in claim 53, wherein said separator comprises a submerged weir for receiving molten slag and molten iron falling from above on one side thereof and for releasing the molten slag from one side thereof and the molten iron from the other side thereof.
55.	The apparatus as claimed in claim 32, wherein the compact is in an elongated form, and said thermal reduction apparatus reduces the compact through the application of heat while moving the compact downward in an upright position.
56.	The apparatus as claimed in claim 32, wherein the compact is in an elongated form, and said thermal reduction apparatus comprises a downward sloped surface for reducing the compact through the application of heat while moving the compact downward along said downward sloped surface.
57.	The apparatus as claimed in claim 55, wherein there is provided an apparatus for continuously forming an elongated compact on the material feed side of said thermal reduction apparatus.
58.	The apparatus as claimed in claim 32, comprising means for feeding an iron belt operable to convey the compact thereon, the compact placed on said iron belt being subjected to reduction and melting through the application of heat.
59.	The apparatus as claimed in claim 58, wherein the compact is in the form of
grains or agglomerates, and said iron belt has edge portions and comprises walls formed
at said edge portions thereof to prevent the compact from falling off said iron belt and
conveys the compact thereon in a horizontal direction within said thermal reduction
apparatus for reducing the compact through the application of heat.
60.	The apparatus as claimed in claim 58, wherein the compact is in an elongated
form, comprising forming means for continuously forming the compact in an elongated
form and for feeding the compact in an elongated form onto said iron belt.
1854-mas-1997-abstract.pdf
1854-mas-1997-claims duplicate.pdf
1854-mas-1997-claims original.pdf
1854-mas-1997-correspondence others.pdf
1854-mas-1997-correspondence po.pdf
1854-mas-1997-description complete duplicate.pdf
1854-mas-1997-description complete original.pdf
1854-mas-1997-drawings.pdf
1854-mas-1997-form 1.pdf
1854-mas-1997-form 26.pdf
1854-mas-1997-form 3.pdf
1854-mas-1997-form 4.pdf
1854/MAS/1997
3-18 WAKINOHAMA-CHO, 1-CHOME,CHUO-KU KODE 651.
1 TAKIJA NEGAMI C/O KOBE STEEEL LTD,8-2, MARUNOUCHI 1-CHOME, CHIYADA-KU TIKYO 100.
21 B 13/00
1 8-257117 1996-09-27 Japan