JP2007002305A - Method for smelting molten pig iron using cupola - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for smelting molten pig iron using a cupola having such superior thermal efficiency as to make the efficiency of melting a cold iron source equivalent to or higher than that in a conventional process, even when having replaced some of foundry coke with blast furnace coke without specially changing a facility, in a process of smelting the molten pig iron by melting the cold iron source such as iron slug and pig iron with the use of the cupola. <P>SOLUTION: The method for smelting the molten pig iron includes melting the cold iron source using the coke as a main fuel while using the cupola provided with a tuyere arranged so that an area ratio (S) of tuyeres' heads can be in a range of 32 to 42%, which is defined by the following expression: S=(D<SP>2</SP>/D<SB>0</SB><SP>2</SP>)×100, wherein (D<SB>0</SB>) represents a diameter of an inner wall face of a furnace body in a tuyere part of the cupola; (D) represents an inner diameter of a tuyeres' head face which is formed by connecting the heads of tuyeres; and (S) represents the area ratio (%) of the tuyeres' heads. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing hot metal by melting a cold iron source such as iron scrap and pig iron using copola as a main fuel, and more specifically, it is excellent in thermal efficiency and a part of casting coke is used for a blast furnace. The present invention relates to a hot metal manufacturing method using cupola that can be replaced with coke.

  In a cupola that melts cold iron sources such as iron scrap and pig iron using coke as the main fuel, the coke and cold iron source are charged into a cylindrical furnace at a certain ratio, and air or hot air is fed from the tuyere in this state. , The coke is burned, the cold iron source is melted by the combustion heat of the coke, and the hot metal is taken out from the outlet at the bottom of the furnace.

  In this case, only the coke is packed in the range from the furnace bottom to a certain height above the tuyere, and this is burned to melt the cold iron source charged in the upper part of the coke. The coke that fills the bottom of the furnace is called “bed coke”, and the bed coke burns and wears out. To compensate for this, coke (called “additional coke”) is cooled from the top of the furnace body. The iron source is charged in layers or mixed. Molten iron produced by melting the cold iron source is superheated (also referred to as “superheat”), flows down the gap between the bed coke, and is carburized by the coke to produce pig iron. Note that the charge ratio between the additional coke and the cold iron source is referred to as the coke ratio.

The tip of the tuyere protrudes from the furnace wall and connects the tip of each tuyere arranged in the circumferential direction of the furnace body, for example, as shown in the schematic cross-sectional view of the cupola tuyere in FIG. The circle is called “the inner diameter of the tuyere”. As shown in FIG. 5, the protrusion amount of the tuyere is the percentage of the tuyere surface inner area with respect to the cross-sectional area of the furnace body, where D is the diameter of the tuyere surface inner diameter and D ₀ is the diameter of the furnace wall surface. ((D ² / D ₀ ² ) × 100; this is defined as “a tuyere tip area ratio”). Normally, each tuyere is adjusted so that the tuyere tip area ratio is about 60 to 70%. Has been placed. Dissolution capacity of the cupola, the air blowing amount, will vary with conditions such as coke ratio, essentially depends on the inner wall surface diameter of the tuyere (D _0), the inner wall diameter (D ₀₎ see a large unit time It is known that the amount of dissolution per hit increases (for example, see Non-Patent Document 1).

As coke for forming bet coke, so-called “cast coke”, a coke having a particle size of 120 mm or more and a large diameter is used. When blast furnace coke having a smaller diameter than that of casting coke is used, the reaction interface area increases due to the small diameter, and the reaction between the CO ₂ gas generated by the combustion of coke and coke in the middle stage in the furnace, that is, carbon. A solution reaction (C + CO ₂ = 2CO) is likely to occur. Since the carbon solution reaction is an endothermic reaction, heating of the cold iron source in the furnace is hindered, resulting in a problem that the melting efficiency of the cold iron source is reduced. In addition, when blast furnace coke is used, it is easy to be filled because of its small diameter, the bulk density of bet coke is increased, air and hot air are not easily passed through, and the melting efficiency is reduced. For these reasons, casting coke is usually used in cupolas.

  However, because casting coke is more expensive than blast furnace coke, blast furnace coke is used instead of casting coke to dissolve cold iron sources such as iron scrap for the purpose of reducing manufacturing costs. A method has been proposed.

  For example, Patent Document 1 discloses a carbon solution reaction of coke charged above a level surface of a secondary tuyere in a cupola-type melting furnace having secondary tuyere arranged in a plurality of stages in the height direction of the furnace. In order to suppress, when a coke layer is present in front of each secondary tuyere, powdery limestone or iron ore is blown from each secondary tuyere using an inert gas as a carrier gas, and each secondary tuyere There has been proposed an operation method in which oxygen-containing gas is blown from each secondary tuyere when an iron scrap layer exists in front of the tuyere. According to Patent Literature 1, even if coke for blast furnace is used, the carbon solution reaction is suppressed by blowing inert gas and the thermal efficiency is improved. However, it is necessary to arrange the secondary tuyere in a plurality of stages. Moreover, there is a complication of changing the gas type blown from each secondary tuyere according to the descending of the charge, which is not necessarily efficient.

In Patent Document 2, the amount of additional coke used is reduced by blowing pulverized coal from the lower stage of the two-stage tuyere, using a melting furnace composed of a cupola having upper and lower two-stage tuyere and a front furnace. A melting method that suppresses the carbon solution reaction of coke by reducing and promoting secondary combustion by hot air blown from the upper stage of the second stage tuyere has been proposed. That is, by reducing the charging amount of the additional coke, the chance of contact between the coke and the CO ₂ gas is reduced, and the carbon solution reaction is suppressed. However, pulverized coal does not form bed coke. Therefore, this method has a problem that bed coke is not stably formed. Moreover, there is a problem that a pre-furnace is necessary and the equipment cost becomes extremely high.
Japanese Patent Laid-Open No. 3-111505 Japanese Patent Application Laid-Open No. 7-146072 Revised 4th Edition Casting Handbook, Japan Foundry Association, published on January 20, 1986, p. 225-226

  The present invention has been made in view of the above circumstances, and its object is to make special equipment changes when melting cold iron sources such as iron scrap and pig iron using a cupola to produce hot metal. Even without replacing part of the casting coke with blast furnace coke, the melting efficiency of the cold iron source can be made equal to or higher than the conventional one, and the hot metal can be made with cupola. Is to provide a method.

  The present inventors have conducted intensive research and examinations in order to solve the above problems. The following describes the results of research and examination.

  A plurality of tuyere are installed at substantially equal intervals in the circumferential direction on the side wall of the bottom of the cupola, and air or hot air is blown into the cupola from the tuyere. The coke charged in the cupola is burned by air or hot air blown from the tuyere, so that coke is burned within the range where fresh air containing a large amount of unburned oxygen gas or fresh hot air is blown. Become active. That is, the combustion of coke is activated in a certain predetermined range from the tip of the tuyere, and the temperature of that part becomes the highest.

  Conventionally, from the viewpoint of expanding the range in which this combustion is activated, in other words, the area surrounded by the tuyere inner diameter shown in FIG. 5 described above is 60 to 70% with respect to the cross-sectional area of the furnace body. The amount of protrusion of the tuyere was set so that the tuyere tip area ratio was 60 to 70%. That is, conventionally, it has been considered that by setting the tuyere tip area ratio to 60 to 70%, the range in which the combustion of coke is activated becomes the widest and the dissolution efficiency is improved.

Certainly, by setting the tuyere tip area to 60 to 70%, interference with adjacent tuyere is reduced even if geometrically judged, and the range in which the combustion of coke is activated is increased. Therefore, the high-temperature CO ₂ gas generated by the coke combustion also rises in a wide range in the furnace according to the area of the range in which the coke combustion is activated. The cold iron source charged from the upper part of the furnace body is heated by this gas and eventually dissolves. However, since the high-temperature CO ₂ gas rises over a wide range in the furnace, it rises in contact with the furnace wall, and by contacting the furnace wall, the heat of the high-temperature CO ₂ gas is also taken away from the furnace wall. Usually, the outermost surface of the furnace wall is formed of an iron skin, and the iron skin is water-cooled with shower water or the like.

From the viewpoint of reducing the heat taken away by the furnace wall as much as possible, the present inventors have expanded the tuyere protrusion amount, that is, the tuyere tip area ratio, although the range in which coke combustion is activated may be narrowed. The test operation was conducted such that the hot melt zone was brought closer to the reactor core and the hot CO ₂ gas was mainly raised in the center of the furnace. And the amount of heat removal by the furnace body cooling water at that time and the melting efficiency were investigated.

  Figure 1 investigates the amount of heat removed from the cooling water at the tuyere, the lower part of the furnace body, and the upper part of the furnace body when the tuyere tip area ratio is 60% and when the tuyere tip area ratio is 38%. The results are shown. As shown in FIG. 1, when the amount of protrusion of the tuyere is increased (the tuyere tip area ratio = 38%), the amount of heat removed by the cooling water at the tuyere increases, but the amount of heat removed at the lower part of the furnace body is greatly increased Compared to the case where the conventional tuyere tip area ratio is 60%, the total amount of heat removed to the tuyere and the side wall is about 0.3 Gcal / hr, which is about 10% lower than the ratio. It was done.

FIG. 2 shows the relationship between the tuyere tip area ratio obtained by the test operation and the dissolution amount per unit time. In FIG. 2, the dissolved amount when the tuyere tip area ratio is 60% is displayed as an index with the reference (1.0) as the dissolution amount. As shown in FIG. 2, by setting the tuyere tip area ratio to 32 to 42%, the amount of dissolution per unit time is 1.05 to 1 compared to the case where the conventional tuyere area ratio is 60 to 70%. It was found that it can be increased 10 times. This is because the high-temperature CO ₂ gas rises mainly in the center of the furnace body, so that the heat of the CO ₂ gas transmitted to the furnace wall is reduced and the heat of the CO ₂ gas is effectively used as a cold iron source. This is because it was transmitted and the heating of the cold iron source was promoted. When the tuyere tip area ratio is less than 32%, the reason why the dissolution efficiency is decreased is considered to be that the range in which coke combustion is activated becomes too narrow and the generated CO ₂ gas is reduced.

  In addition, since the thermal efficiency in the furnace is improved, even if about 30 to 40% of the coke used is switched from the casting coke to the blast furnace coke, the increase in the endothermic amount due to the carbon solution reaction by the blast furnace coke is sufficient. I found out that I can make up for it. In other words, even if about 30 to 40% of the coke to be used is switched from casting coke to blast furnace coke, it not only compensates for the increase in heat absorption due to the carbon solution reaction caused by blast furnace coke, but also improves thermal efficiency beyond that. It was obtained and the knowledge that the dissolution efficiency could be improved was obtained.

Furthermore, a blow lance capable of injecting gas at a flow rate higher than the speed of sound is arranged inside the tuyere, and oxygen gas is blown into the furnace at a flow rate higher than the speed of sound from this blow lance so that the center of the furnace body Even if the temperature of the CO ₂ gas that rises further increases and about 60% of the coke used is switched from casting coke to blast furnace coke, the amount of increase in the endotherm due to the carbon solution reaction by the blast furnace coke is sufficiently increased. The knowledge that it can supplement was obtained.

The present invention has been made on the basis of the above knowledge, and the method for producing hot metal by the cupola according to the first invention is characterized in that the diameter of the wall surface of the furnace body at the tuyere of the cupola is D ₀ , The tuyere arranged so that the tuyere tip area ratio defined by the following formula (1) is in the range of 32 to 42%, where D is the diameter of the tuyere surface inner diameter connected to the tip. Using the provided cupola, hot metal is produced by melting a cold iron source using coke as a main fuel. However, S in Formula (1) is a tuyere tip area ratio (%).

  The hot metal melting method using the cupola according to the second invention is the first invention, wherein a blowing lance capable of injecting gas at a flow velocity equal to or higher than the speed of sound is disposed inside the tuyere, and the sound velocity exceeding the speed of sound from the blowing lance. It is characterized in that oxygen gas is blown into the furnace at a flow rate of 5.

  According to a third aspect of the present invention, there is provided a hot metal smelting method using a cupola according to the second aspect, wherein the blowing lances are installed in a plurality of tuyere and oxygen gas is alternately injected from each blowing lance. It is.

  According to a fourth aspect of the present invention, there is provided a hot metal smelting method using a cupola according to any one of the first to third aspects, wherein coke for blast furnace is used in combination with coke for casting. .

According to the present invention, when a cold iron source is melted using a cupola to produce molten iron, the tuyere is arranged so that the tuyere tip area ratio is in the range of 32 to 42%. The high-temperature CO ₂ gas generated by combustion rises mainly in the center of the furnace, reducing the amount of heat taken by the side wall of the furnace body out of the heat of the CO ₂ gas, and is charged into the furnace accordingly. The amount of heat applied to the cold iron source is increased, and the cold iron source can be efficiently dissolved. In addition, since the heat efficiency in the furnace is increased, the increase in the endothermic amount due to the carbon solution reaction when blast furnace coke is used can be sufficiently compensated, and 30 to 40% of the coke used is inexpensive. Even so, a high dissolution efficiency can be maintained. In particular, when oxygen gas is blown from a blowing lance that can be injected at a flow rate higher than the sonic speed, the thermal efficiency in the furnace further increases, and about 60% of the coke used is inexpensive for blast furnaces. Can be coke. As a result, it has been achieved that the manufacturing cost of hot metal by cupola is greatly reduced, and an industrially beneficial effect is brought about.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 3 is a schematic side sectional view of the cupola used in carrying out the present invention, FIG. 4 is a schematic enlarged side sectional view of the tuyere part shown in FIG. 3, and FIG. 5 is a tuyere of the cupola shown in FIG. FIG.

  As shown in FIG. 3, the cupola 1 includes a furnace body 2 having an outer shell made of a cylindrical steel plate, and a refractory brick is applied to the bottom (furnace bottom) of the furnace body 2 inside the steel plate. A refractory brick layer 3 is formed, and a raw material inlet 4 having an openable / closable upper lid 5 is formed at the top of the furnace body 2. An exhaust hole 6 for exhaust gas exhaust is installed in the lower part of the raw material inlet 4. The exhaust hole 6 is connected to the exhaust duct 13, and the exhaust gas generated inside the furnace body 2 is sucked through the exhaust hole 6 and the exhaust duct 13 by a dust collector (not shown) connected to the exhaust duct 13. It has come to be. A plurality of water-cooled tuyere 9 are arranged in the circumferential direction of the furnace body 2 through the refractory brick layer 3 at the bottom of the furnace body 2. The tuyere 9 is connected to the tuyere conduit 8, and the tuyere conduit 8 is connected to the wind box 7 arranged around the circumference of the furnace body 2. The wind box 7 is connected to a hot stove (not shown) or a blower (not shown), and hot air or air supplied from the hot stove or blower is supplied to the wind box 7, tuyere conduit 8, tuyere 9. Is blown into the interior of the furnace body 2. The refractory brick layer 3 on the bottom surface of the furnace body 2 is inclined, and the inclined downstream side is a tapping bath 11. A skinma 10 for separating hot metal and slag is installed on the way to the hot spring 11. The outer surface of the steel plate constituting the furnace body 2 is cooled by cooling water (shower water). In the cupola 1 shown in FIG. 3, the side wall portion of the furnace body 2 is composed of only a steel plate except for the bottom portion. .

  Inside the tuyere 9, as shown in FIG. 4, a blowing lance 12 for injecting oxygen gas at supersonic speed is installed. A laval nozzle 12 </ b> A capable of injecting a gas such as oxygen gas at supersonic speed is installed at the tip of the blowing lance 12. Incidentally, the Laval nozzle 12A is a nozzle having a shape composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. The reduced portion is a throttle part, the enlarged part is a skirt part, and the squeezing part to the skirt part. The transition part and the narrowest part is called a throat. The oxygen gas supplied to the blowing lance 12 passes through the throttle part, the throat, and the skirt part in this order, and is compressed by the throttle part. It expands and is injected into the furnace body 2 from the tip of the blowing lance 12 as a supersonic oxygen jet. However, in order to obtain supersonic speed, it is necessary to set the throat diameter, the outlet diameter of the skirt portion, and the pressure of the supplied oxygen gas to predetermined values.

  As shown in FIG. 5, a plurality of tuyere 9 are installed at almost equal intervals in the circumferential direction of the furnace body 2 (six in FIG. 5), and the blowing lances 12 are installed in all tuyere 9. It is not carried out, but it is installed in some of the tuyere 9 (three in FIG. 5) so that it may become substantially equal intervals in the circumference direction of the furnace main body 2. FIG. The number of tuyere 9 is usually determined according to the capacity of the furnace body 2. In FIG. 5, the blowing lances 12 are not installed in all tuyere 9, but there is no problem even if they are installed in all tuyere 9. In addition, the blowing lance 12 may be installed at only one place in the circumferential direction of the furnace body 2, but in order to make the melting state inside the furnace body 2 uniform, at least two places, desirably three or more places. It is preferable to install in.

Further, as shown in FIGS. 4 and 5, the tuyere 9 is disposed so as to protrude from the inner wall surface 3 a of the refractory brick layer 3 to the inside of the furnace body 2. In the cupola 1 used in the present invention, each tuyere 9 has a diameter (D ₀ ) of the inner wall surface 3 a of the refractory brick layer 3 and a diameter (D) of the inner diameter of the tuyere surface connecting the tips of the tuyere 9. Therefore, the tuyere tip area ratio calculated by the above-described equation (1) is arranged in the range of 32 to 42%.

  Using the cupola 1 configured as described above, the present invention is carried out as follows.

  First, inside the furnace body 2 in the range from the furnace bottom to a predetermined position above the tuyere 9, coke is charged from the raw material charging port 4 to form bet coke, and on this bet coke, coke and A cold iron source such as iron scrap, pig iron (cold iron), and generated scrap is charged at a predetermined ratio. The coke and the cold iron source charged on the bed coke are mixed with each other and charged in layers, or the coke and the cold iron source charged into the furnace body 2 As long as the ratio is within a predetermined range, either is acceptable. In addition, as required, a limestone for adjusting the basicity of the slag to be produced, a slag-forming agent such as quick lime, a hot metal component to be produced, especially an Fe-Si alloy for adjusting the Si content, etc. Alloy iron is charged from the raw material inlet 4.

  As a matter of course, coke for casting having a particle diameter of 120 mm or more can be used as the coke to be used. However, since coke for casting is expensive, coke for blast furnace, which is cheaper than coke for casting, is used in combination. It is preferable to do. However, there are various sizes of blast furnace coke, and among them, it is preferable to use blast furnace coke having a relatively large particle size and a particle size of about 50 to 70 mm. As long as the cupola 1 having the above-described configuration is used, it has been confirmed from experience that 40 to 60% of coke to be used can be switched to coke for blast furnace. Therefore, at least 20% or more, preferably 40% or more Is preferably blast furnace coke.

Next, the coke at the bottom of the furnace is ignited, and air or hot air is sent from the tuyere 9 to burn the coke. CO ₂ gas generated by the combustion of coke rises inside the furnace body 2 and is discharged out of the furnace via the exhaust hole 6 and the exhaust duct 13. The cold iron source is heated by the heat of the generated CO ₂ gas and eventually melts, and the generated molten iron flows down the gap between the bed cokes and reaches the bottom of the furnace. The molten iron is heated (superheated) while flowing down the gap between the bet coke, and the carbon in the coke is transferred to the molten iron to produce molten iron. After the molten iron is separated from the slag by the skinma 10, the molten iron is poured into the hot metal storage container or the holding furnace through the hot water tap 11. The components of the hot metal to be melted are, for example, about C: 3 to 4% by mass, Si: 1 to 3% by mass, and Mn: about 0.2 to 0.5% by mass. The holding furnace is a container that temporarily stores the molten iron before it is cast, and the inner wall is made of a refractory material and can heat the molten metal accommodated by low frequency induction or the like. It is.

  When hot metal begins to be melted, bet coke is consumed, and the source of cold iron in the furnace body 2 is reduced. To compensate for this, the raw material charging is performed under the condition of a predetermined coke ratio. The inlet 4 is charged with coke and cold iron sources, and, if necessary, limestone and other iron making agents and Fe-Si alloys, etc., and the height of the charge inside the furnace body 2 is set to a substantially constant position. Continue operation while holding.

By using the coke as the main fuel and melting the cold iron source in this way, the tuyere 9 protrudes into the interior of the furnace body 2, so that the high-temperature CO ₂ gas generated by the combustion of the coke is mainly the furnace body. 2 rises, the amount of heat taken by the side wall of the furnace body 2 out of the heat of the CO ₂ gas decreases, and the amount of heat applied to the cold iron source charged in the furnace body 2 increases accordingly. Thus, the cold iron source can be efficiently dissolved. In addition, since the heat efficiency in the furnace is increased, the increase in the endothermic amount due to the carbon solution reaction when blast furnace coke is used can be sufficiently compensated, and 30 to 40% of the coke used is inexpensive. Even so, a high dissolution efficiency can be maintained.

In this operation, it is preferable to blow oxygen gas into the furnace body 2 through the blow lance 12 at supersonic speed. By blowing oxygen gas at supersonic speed, the oxygen gas reaches the position of the coke existing in the center of the furnace body 2, the combustion of the coke existing in the center is promoted, and the temperature of the center of the furnace body 2 is increased. This is because the temperature of the CO ₂ gas rising in the central portion of the furnace body 2 is further increased and the melting of the cold iron source is promoted. As a result, it is possible to further increase the use of blast furnace coke, and even if about 60% of the coke used is used as blast furnace coke, a high melting efficiency can be maintained.

  However, by blowing oxygen gas from the blowing lance 12, the melting efficiency of the cold iron source in the cupola 1 is improved, and a melting capacity higher than the production capacity of the casting equipment in the lower process may be obtained. In this case, the manufacturing cost increases on the contrary due to an increase in the temperature drop of the hot metal due to the extension of the holding time (lead time) and countermeasures therefor. Therefore, it is preferable to match the hot metal production capacity of the cupola 1 with the production capacity of the lower process.

  One method for varying the melting ability of the cupola 1 while blowing oxygen gas from the blowing lance 12 is to increase or decrease the amount of oxygen gas supplied from the blowing lance 12. That is, if the oxygen gas supply amount is decreased, the melting capacity of the cold iron source is decreased accordingly. However, if the amount of oxygen blown from the blow lance 12 is reduced beyond the limit determined by the throat diameter of the Laval nozzle and the outlet diameter of the skirt portion, a supersonic oxygen jet cannot be obtained. If a supersonic oxygen jet cannot be obtained, the combustion of the central coke cannot be promoted, and the stable use of the blast furnace coke is hindered.

  Therefore, in such a case, the amount of air blown from one blower lance 12 is not changed, that is, an oxygen jet blown at a supersonic speed is secured, and several of the blower lances 12 are alternately used. It is preferable to blow into. For example, by blowing from only one of the three blowing lances 12 and sequentially switching the blowing lance 12, or by blowing from two of the three blowing lances 12 and sequentially switching the blowing lance 12 The melting ability can be adjusted while promoting the combustion of the central coke while preventing the coke combustion zone from becoming uneven in the circumferential direction. In this way, it is possible to cope with changes in the order quantity. It should be noted that some of the plurality of blowing lances 12 may be selected, and the oxygen jet may be blown only from the selected blowing lances 12, but in this case, the melting state in the furnace becomes non-uniform, and the charge is charged. This hinders the smooth descent of the door and may cause shelves and the like.

  By producing the hot metal in this manner using the cupola 1, it is possible to significantly reduce the manufacturing cost of the hot metal.

The present invention was implemented using a cupola having a nominal capacity of 20 ton / hr shown in FIGS. The diameter (D ₀ ) of the inner wall surface of the firebrick layer of the cupola used was 2100 mm, and the diameter (D) of the tuyere surface inner diameter connecting the tips of each tuyere was 1300 mm. That is, the tuyere tip area ratio calculated by the above-described equation (1) was 38%. Hot air heated to about 600 ° C. was blown from the tuyere thus arranged at a flow rate of 180 to 240 Nm ³ / min.

  In addition, oxygen gas was blown from the blowing lance at a flow rate of 1.8 times the speed of sound. When oxygen gas is simultaneously blown from three blowing lances, when blowing from two of the three blowing lances, when blowing from one of the three blowing lances, and from any blowing lance The case of not blowing was carried out. When blowing from one of the three blowing lances, each blowing lance was blown for 1 minute, and the blowing lances were switched in the circumferential direction. In the case of blowing from two of the three blowing lances, the same operation was performed, but blowing was always carried out from two blowing lances, and one blowing lance was blown continuously for 2 minutes. As coke to be used, when coke for blast furnace having a particle size of 50 to 70 mm and coke for casting having a particle size of 120 mm or more are used in combination and oxygen gas is blown from a blowing lance, 60% of the coke to be used is reduced. When blast furnace coke was used and oxygen gas was not blown from the blow lance, 40% of the coke used was blast furnace coke.

  As a result of melting the cold iron source using this cupola and melting the molten iron, when oxygen gas was not blown from the blowing lance, the melting capacity was 20 tons / hr, which was equivalent to the nominal capacity. When oxygen gas was blown from all the blowing lances, a melting capacity of 28 tons / hr could be obtained. Moreover, no adverse effect was caused by using the blast furnace coke, whether oxygen gas was blown or not blown from the blowing lance.

It is a figure which shows the result of having investigated about the amount of heat removal of cooling water in the case where a tuyere tip area ratio is 60% and 38%. It is a figure which shows the relationship between the tuyere tip area ratio obtained by test operation, and the amount of melt | dissolution per unit time. It is a schematic sectional side view of the cupola used when implementing this invention. It is a general | schematic expanded side sectional view of a tuyere part shown in FIG. It is a schematic plane sectional view in the tuyere part of the cupola shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cupola 2 Furnace main body 3 Refractory brick layer 4 Raw material inlet 5 Upper lid 6 Exhaust hole 7 Wind box 8 Tuyere conduit 9 Tuyere 10 Skinma 11 Hot water spout 12 Blow lance 13 Exhaust duct

Claims (4)

The tip of the tuyere defined by the following equation (1) where D ₀ is the diameter of the inner wall of the furnace wall at the tuyere of the cupola, and D is the diameter of the inner diameter of the tuyere surface connecting the tips of each tuyere A cupola having a tuyere arranged so that the area ratio is in a range of 32 to 42%, and using a coke as a main fuel, a cold iron source is melted to produce molten iron. Method of making hot metal with
S = (D ² / D ₀ ² ) × 100… (1)
However, S in Formula (1) is a tuyere tip area ratio (%).   2. The blow lance capable of injecting gas at a flow velocity higher than the sonic velocity is disposed inside the tuyere, and oxygen gas is blown into the furnace from the blow lance at a flow velocity higher than the sonic velocity. Of hot metal with cupola.   The method for producing hot metal with a cupola according to claim 2, wherein the blowing lances are installed in a plurality of tuyere and oxygen gas is alternately injected from each blowing lance.   The method for producing hot metal by using a cupola according to any one of claims 1 to 3, wherein coke for blast furnace is used in combination with coke for casting as coke to be used.

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