JP6273891B2 - Method and apparatus for reducing metal oxide by moving hearth furnace - Google Patents

Description

  The present invention mixes and forms iron ore, metal oxides such as dust generated at steelworks, and carbon materials such as coal and coke, and then performs reduction treatment in a moving hearth furnace to form metal. It relates to a method and a device to obtain.

  Granules such as pellets and briquettes formed by mixing iron ore and metal oxides such as dust generated at steelworks and coals such as coal and coke, and reducing treatment by heating with a burner, In recent years, a method for obtaining reduced iron for metal refining has been actively implemented as a direct reduction method (for example, see Non-Patent Document 1).

  In order to reduce production costs, carbonaceous materials are cheap and have low volatile content (VM), such as subbituminous coal and lignite (hereinafter referred to as “high VM coal”, and low volatile content (VM) such as anthracite. The coal is sometimes referred to as “low VM charcoal”), but when using high VM charcoal, the volatilization rate of volatile matter (VM) is high, Since bursting that bursts due to a sudden rise in pressure occurs, there is a limit to the use of high-VM coal (see, for example, Patent Document 1).

FIG. 1 shows a cross section of a conventional moving hearth furnace. The granulated product 1 charged into the hearth 2 from the charging port 5 is left in the hearth 2 and is carried in the hearth traveling direction. During the progress of the hearth, the granulated material 1 is heated by the burner 3 and when the metal oxide is iron oxide, it becomes reduced iron by the reaction of the following formula, and the reduced iron discharge device 8 causes the furnace to be reduced from the reduced iron discharge port 6. Discharged outside.
C (fixed carbon of carbonaceous material in the granulated product) + O ₂ → CO ₂
C + CO ₂ → 2CO
Fe ₂ O ₃ + 3CO → 2Fe + 3CO ₂

  The combustion exhaust gas from the burner 3 and the gas generated from the granulated material flow in the direction opposite to the hearth traveling direction and are discharged from the exhaust duct 7 '. The gas generated from the granulated product 1 contains a large amount of unburned components (CO) and burns in the burner 3 on the exhaust duct 7 'side, so the temperature in the vicinity of the exhaust duct 7' cannot be controlled low. . Therefore, when the volatilization rate of volatile matter (VM) is increased and the metal oxide is reduced mainly by indirect reduction, it is difficult to use high VM charcoal as a carbonaceous material.

  On the other hand, in order to effectively use the reducing gas (CO) generated from the granulated material, a technique for actively controlling the flow of the generated gas has been proposed (for example, see Patent Document 2). However, even in this technique, since the exhaust gas near the exhaust duct 7 ′ contains a large amount of unburned components (CO), the temperature near the exhaust duct 7 ′ cannot be controlled low, and high VM charcoal is used as a carbon material. It is difficult to use.

  Generally, in direct reduction of iron ore, when the reduction temperature is about 1300 ° C. or less, hydrogen reduction by hydrogen and indirect reduction by CO occur. Hydrogen reduction is significantly faster than indirect reduction (see, for example, Non-Patent Document 2). Since the volatile matter (VM) in the carbonaceous material contains a large amount of hydrocarbons and hydrogen, if the hydrogen reduction is effectively utilized by effectively using the hydrogen component in this, there is a possibility of reducing the basic unit of the carbonaceous material. is there.

JP 09-310111 A JP 2001-107121 A

Takahashi Politics et al .: CAMP-ISIJ, Vol. 14 (2001), p. 149 Whip, Akira Moriyama, “Metallurgy Reaction Engineering”, 1974, p. 231, P.I. 234

  Therefore, the present invention can use charcoal materials containing a wide range of volatile matter (VM) regardless of the amount of volatile matter (VM) contained in the charcoal material. Even when it is used, the problem is to increase the metallization rate by reducing hydrogen consumption by promoting the hydrogen reduction while suppressing the bursting of the granulated product due to the rapid volatilization of the volatile matter (VM), and to reduce the carbon basic unit. An object of the present invention is to provide a metal oxide reduction method and reduction apparatus using a moving hearth furnace that solves the above problem.

  The inventors of the present invention have intensively studied a method for solving the above-described problems. As a result, in the mobile hearth furnace, if a hydrogen reduction zone in which the ambient temperature is set low is provided before the indirect reduction zone in which indirect reduction is performed, even if high VM charcoal is used, volatilization occurs. It was found that hydrogen reduction by the hydrogen component in the volatile component (VM) can be promoted while suppressing bursting of the granulated product due to rapid volatilization of the component (VM).

  This invention was made | formed based on the said knowledge, and the summary is as follows.

(1) In a method in which a granulated product obtained by mixing a raw material containing a metal oxide and a carbonaceous material is placed on a hearth of a moving hearth furnace and heated to reduce the metal oxide, the moving hearth The furnace is divided into three zones, a first zone, a second zone, and a third zone, in the direction of the hearth from the inlet of the granulated material,
(x) In the first zone, the metal oxide is hydrogen-reduced with the hydrogen component of the volatile matter (VM) contained in the carbonaceous material in the granulated product,
(y) In the third zone, the metal oxide is indirectly reduced with carbon in the granulated product,
(z) A method for reducing metal oxide by a moving hearth furnace, wherein the gas generated in the first zone and the third zone is exhausted in the second zone.

  (2) The atmosphere temperature in the first zone is set based on the amount of volatile matter (VM) in the carbonaceous material, and the reduction of metal oxide by the moving hearth furnace according to (1) above Method.

(3) The metal oxide reduction method using the moving hearth furnace according to (2), wherein the atmosphere temperature in the first zone is set to T (° C.) or less defined by the following formula.
T (° C.) = 1400−8.75 × VM
VM: amount of volatile matter (VM) in the carbonaceous material (mass%)

  (4) The lower limit of the atmospheric temperature of the first zone is (T-50) ° C., wherein the metal oxide reduction method using the moving hearth furnace according to the above (3).

  (5) The metal by the moving hearth furnace according to any one of (1) to (4), wherein the moving hearth furnace is a linear moving hearth furnace or a rotary moving hearth furnace Reduction method of oxide.

(6) A moving hearth furnace in an apparatus for reducing the metal oxide by standing and heating the granulated material formed by mixing a raw material containing a metal oxide and a carbonaceous material to the hearth of the moving hearth furnace However, in the first zone, the first zone and the third zone where the metal oxide is a hydrogen component contained in the granulated material from the inlet of the granulated material in the direction of the hearth , and the metal oxide is reduced by hydrogen. Divided into three zones, a second zone for exhausting the generated gas , and a third zone for indirectly reducing the metal oxide with carbon in the granulated product ,
When the effective length of the moving hearth is L,
(X) the first zone is from 0.3 × L to 0.4 × L from the inlet of the granulated product,
(Z) The second zone is from 0.3 × L to 0.4 × L to 0.6 × L from the inlet of the granulated material, and has an exhaust duct in the zone. A metal oxide reduction device using a moving hearth furnace.

  (7) The metal oxide reducing apparatus according to (6), wherein the moving hearth furnace is a linear moving hearth furnace or a rotary moving hearth furnace.

  According to the present invention, in the direct reduction method of metal oxide, carbon materials containing a wide range of volatile matter (VM) can be used regardless of the amount of volatile matter (VM) contained in the carbonaceous material. Even when inexpensive high VM charcoal is used, hydrogen reduction is promoted while suppressing bursting of the granulated product due to rapid volatilization of volatile matter (VM), and the metalization rate is increased. Can be reduced.

It is a figure which shows the cross section of the conventional moving hearth furnace. It is a figure which shows the temperature dependence of the hydrogen reduction rate constant of iron ore, and an indirect reduction rate constant (estimated by the formula of a nonpatent literature 2). It is a figure which shows the aspect of the test apparatus used in order to investigate the temperature rising behavior of a granulated material, VM (volatile matter) generation | occurrence | production behavior, the influence on reduction | restoration of generated gas, and the presence or absence of explosion. The temperature rise behavior and VM (volatile matter) generation of pellets formed by mixing high VM charcoal and pellets mixed with low VM charcoal when tested at an atmospheric temperature of 1300 ° C using the test apparatus of FIG. It is a figure which shows a behavior. The temperature rise behavior and VM (volatile matter) of pellets formed by mixing high VM charcoal and pellets mixed with low VM charcoal when tested at an ambient temperature of 900 ° C. using the test apparatus of FIG. It is a figure which shows generation | occurrence | production behavior. 3 shows the temperature rise behavior of the pellets formed by mixing high VM charcoal and the change in H ₂ / (H ₂ + H ₂ O) of the generated gas when tested at an ambient temperature of 1300 ° C. using the test apparatus of FIG. FIG. When the test apparatus of FIG. 3 is used and the atmosphere temperature is 900 ° C., the temperature rise behavior of the pellets formed by mixing high VM charcoal and the change in H ₂ / (H ₂ + H ₂ O) of the generated gas are shown. FIG. Using the test apparatus of FIG. 3, the amount of coal (volatile matter) when coal is tested by changing the ambient temperature for pellets formed by mixing and molding four types of coal with different amounts of VM (volatile matter) It is a figure which shows the relationship of an explosion. 3 (Volatile content) volatilization completion time when the pellets formed by mixing and molding three types of coal with different VM (volatile content) amounts as charcoal using the test apparatus of FIG. FIG. It is a figure which shows the cross section of the moving hearth furnace of this invention.

  The present invention will be described below.

The reduction method of metal oxide by the moving hearth furnace of the present invention (hereinafter sometimes referred to as “the reduction method of the present invention”) comprises a granulated product formed by mixing a raw material containing a metal oxide and a carbonaceous material, In the method of reducing the metal oxide by standing on the hearth of the moving hearth furnace and reducing the metal oxide, the moving hearth furnace is moved from the inlet of the granulated material to the hearth traveling direction in the first zone and the second zone. And divided into three bands of the third band,
(x) In the first zone, the metal oxide is hydrogen-reduced with the hydrogen component of the volatile matter (VM) contained in the carbonaceous material in the granulated product,
(y) In the third zone, the metal oxide is indirectly reduced with carbon in the granulated product,
(z) The second zone is characterized in that the gas generated in the first zone and the third zone is exhausted.

The apparatus for reducing metal oxide by the moving hearth furnace of the present invention (hereinafter sometimes referred to as “the present invention reducing apparatus”) moves a granulated product formed by mixing a raw material containing a metal oxide and a carbonaceous material. In an apparatus for heating and reducing metal oxides by standing on the hearth of the hearth furnace, the moving hearth furnace moves from the inlet of the granulated material in the direction of the hearth , and the carbonaceous material in the granulated material is 1st zone for hydrogen reduction of metal oxide, 2nd zone for exhausting gas generated in the 1st zone and 3rd zone, and carbon in the granulated product When the effective length of the moving hearth is L,
(X) the first zone is from 0.3 × L to 0.4 × L from the inlet of the granulated product,
(Z) The second zone is from 0.3 × L to 0.4 × L to 0.6 × L from the inlet of the granulated material, and has an exhaust duct in the zone. To do.

  In the direct reduction method of iron ore, at a reduction temperature of about 1300 ° C. or less, hydrogen reduction is significantly faster than indirect reduction (see Non-Patent Document 2). Therefore, the present inventors have confirmed the temperature dependence of the reduction rate constant in hydrogen reduction and indirect reduction of iron ore.

  FIG. 2 shows the temperature dependence of the hydrogen reduction rate constant and indirect reduction rate constant of iron ore calculated by the formula described in Non-Patent Document 2. From FIG. 2, it can be seen that when the reduction temperature exceeds 600 ° C., the hydrogen reduction rate is significantly faster than the indirect reduction rate.

  The present inventors have conceived that the moving hearth furnace is divided into a hydrogen reduction zone and an indirect reduction zone in order to take advantage of the remarkable difference between the hydrogen reduction rate and the indirect reduction rate. The temperature rising behavior of particles, the generation behavior of volatile matter (VM), the effect on reduction of the generated gas and the presence of explosion were investigated.

  FIG. 3 shows an aspect of the test apparatus used for the above investigation. The test apparatus 10 includes a cylindrical alumina test tube 10b that penetrates the center of the test furnace 10a.

  One end of the alumina test tube 10b is sealed with a sealing plug 11b provided with a porcelain protection tube 12 with a board 14 accommodating the pellet 13 attached to the tip, and a gas tube 15 for sending nitrogen gas into the alumina test tube 10b. The other end is a temperature measuring device 17 incorporating a thermocouple for measuring the atmospheric temperature in the alumina test tube 10b, and a rubber for introducing the atmospheric gas in the alumina test tube 10b to the gas cooling / cleaning device 19. It is sealed with a sealing plug 11 a having a pipe 18.

  Nitrogen gas is blown from the gas pipe 15 into the alumina test tube 10b to form a nitrogen atmosphere, and the electrode 16 heats the alumina test tube 10b from the outside.

  When the predetermined temperature is reached, the pellet 13 obtained by mixing and granulating iron ore powder and coal powder having a different volatile matter (VM) amount is left on the board 14 at the tip of the porcelain protection tube 12, and the alumina test tube 10b. In the center of the. A thermocouple is passed through the porcelain protection tube 12, and the tip of the thermocouple is in contact with the pellet 13 so that the pellet temperature can be measured.

  The temperature inside the alumina test tube 10 b is measured by the temperature measuring device 17, and the atmosphere formed by the gas generated from the pellets is collected by the rubber tube 18 and introduced into the gas cooling / cleaning device 19. The atmospheric gas is sent to a gas analyzer (not shown) after cooling and cleaning.

The inventors set the atmospheric temperature to a predetermined temperature, and the temperature rising behavior of the pellets with the passage of time, the generation behavior of volatile matter (VM), and the H ₂ / (H ₂ + H ₂ O of the generated gas. ) Was investigated. Further, the correlation between the atmospheric temperature and the volatile matter (VM) amount of coal and the explosion of the pellets, and the correlation between the volatile matter (VM) generation completion time and the atmospheric temperature were also investigated. In addition, content of the volatile matter (VM) in carbon material can be measured by JISM8812.

  Fig. 4 shows pellets formed by mixing high VM charcoal (VM 37% subbituminous coal) and metal oxide, low VM charcoal (VM 7% anthracite) and metal oxide when tested at an ambient temperature of 1300 ° C. The temperature rise behavior (pellet temperature transition) and volatile matter (VM) generation behavior (VM generation amount transition) of the pellets formed by mixing are shown.

  Up to 1000 ° C, the pellet temperature rise behavior was almost the same for pellets made from high VM charcoal and pellets made from low VM charcoal, but in pellets made from high VM charcoal. Bursting (explosion) occurred at a pellet temperature of 1000 ° C., and neither the pellet temperature nor the amount of VM generated could be measured.

  Fig. 5 shows pellets formed by mixing high VM charcoal (VM 37% subbituminous coal) and metal oxide, low VM charcoal (VM 7% anthracite), and gold seat oxide when tested at an ambient temperature of 900 ° C. The temperature rise behavior (transition of pellet temperature) and the generation behavior of volatile matter (VM) (transition of VM generation amount) are shown. At an atmospheric temperature of 900 ° C., bursting did not occur in pellets using high VM charcoal as a carbon material and pellets using low VM charcoal as a carbon material.

In order to investigate the reduction efficiency of iron ore by hydrogen reduction, the change with time was measured using H ₂ / (H ₂ + H ₂ O) of the generated gas as an index.

FIG. 6 shows the temperature rise behavior of the pellets formed by mixing high VM charcoal and metal oxide when the atmosphere temperature is 1300 ° C. (the transition of the pellet temperature) and the generated gas H ₂ / (H ₂ + H ₂ O) shows the change. At an atmospheric temperature of 1300 ° C, bursting occurs at a pellet temperature of 1000 ° C, and H ₂ / (H ₂ + H ₂ O) at that time is about 25%. Thereafter, the generated volatile matter (VM) is used to reduce iron ore. It was discharged without being used, and H ₂ / (H ₂ + H ₂ O) became 100%.

  At an atmospheric temperature of 1300 ° C., iron ore and coal were separated by the bursting of pellets, and thus it was considered that the contribution to reduction of the generated volatile matter (VM) was reduced.

FIG. 7 shows the temperature rise behavior of a pellet formed by mixing high VM charcoal and a metal oxide (change in pellet temperature) and the generated gas H ₂ / (H ₂ + H) when tested at an ambient temperature of 900 ° C. ₂ O) shows the change. At an atmospheric temperature of 900 ° C., H ₂ / (H ₂ + H ₂ O) decreases to about 0% in 6 minutes, and it can be seen that the generated H ₂ gas was effectively used for the reduction of iron ore. Since bursting did not occur at an atmospheric temperature of 900 ° C., it is considered that volatile matter (VM) was effectively used for reduction.

  The relationship between the volatile matter (VM) amount of coal and the ambient temperature and explosion was investigated. Fig. 8 shows the amount of volatile matter (VM) and explosion when coal pellets formed by mixing four types of coal with different amounts of volatile matter (VM) with metal oxide are tested at different ambient temperatures. The relationship is shown.

As shown in FIG. 8, explosion does not occur below the temperature (T) of the following straight line.
T (° C.) = 1400−8.75 × VM
VM: Coal volatile matter (VM) amount (%)

  In addition, the amount of volatile matter (VM) in the coal was changed, and the time when volatile matter (VM) volatilization was completed was investigated. Fig. 9 shows three types of coal with different amounts of volatile matter (VM) (brown coal (VM: 50%), high VM coal (VM: 37% subbituminous coal), low VM coal (VM: 7% anthracite coal)) The volatile matter (VM) volatilization completion time when the pellets formed by mixing each of the above with a metal oxide was tested while changing the ambient temperature is shown.

  From FIG. 9, it can be seen that in an atmosphere having an atmospheric temperature of 900 ° C., volatilization of the volatile matter (VM) is completed in 5 to 7 minutes regardless of the amount of volatile matter (VM). Further, it can be seen that when the ambient temperature rises, the volatilization completion time of the volatile matter (VM) is shortened.

  Based on the above test results, the present inventors, in a moving hearth furnace that reduces a metal oxide by heating a granulated material formed by mixing a raw material containing a metal oxide and a carbonaceous material, (i) The first zone that can promote hydrogen reduction by hydrocarbons and hydrogen in the volatile matter (VM) in the carbonaceous material while setting the atmosphere temperature low and preventing bursting of the granulated material, indirect reduction by carbon The present invention has been achieved in which a transition / exhaust zone is provided in front of the third zone to be performed, and (ii) a transition / exhaust zone having an exhaust duct for exhausting gas generated in both zones is provided between the two zones.

  In FIG. 10, the cross section of the moving hearth furnace of this invention is shown. Although the cross section of the mobile hearth furnace is shown in FIG. 10 in a straight line shape, the mobile hearth furnace of the present invention can have a first zone, a second zone, and a third zone described below. Any floor furnace may be used. Therefore, the moving hearth furnace of the present invention is not limited to a linear type, and may be, for example, a rotary moving hearth furnace.

  In the mobile hearth furnace shown in FIG. 10, the granulated material 1 charged into the hearth 2 from the charging port 5 and placed in the hearth 2 is conveyed in the hearth traveling direction while being burner 3. And the reduction of the metal oxide proceeds in the granulated product 1. Temperature control is performed in the three zones, the first zone, the second zone, and the third zone, and the hydrogen reduction in the first zone, the exhaust in the second zone, and the indirect reduction in the third zone are optimized.

  The first zone is a hydrogen component in the volatile matter (VM) contained in the carbonaceous material in the granulated product, while preventing the bursting of the granulated product due to rapid volatilization of the volatile matter, and the metal oxide is hydrogen reduced. , A zone that completes volatilization of volatile matter (VM) in coal.

The atmosphere temperature T (° C.) of the first zone is
T = 1400-8.75 × VM (mass%)
VM: Coal volatile matter (VM) amount (%)
Set as follows. By this temperature setting, bursting of the granulated product due to rapid volatilization of the volatile matter (VM) can be prevented.

  When using high VM charcoal as the carbon material, it is preferable to set the atmosphere temperature in the first zone low, and when using low VM charcoal as the carbon material, it is preferable to set the atmosphere temperature in the first zone high. The lower limit of the atmospheric temperature in the first zone is not particularly limited, but if it is too low, the reduction rate is lowered and the productivity is lowered, so (T-50) ° C. or higher is preferable.

When high VM charcoal is used as the charcoal, reduction of the metal oxide proceeds mainly by the following hydrogen reduction in the first zone.
CH ₄ → C + 2H _{2
Fe 2 O 3 + 3H 2 (} H 2 produced by the decomposition of H ₂ and CH ₄ in VM) → 2Fe + 3H ₂ O
2C (C generated by decomposition of CH ₄ in VM) + O ₂ → 2CO
Fe ₂ O ₃ + 3CO → 2Fe + 3CO ₂

  When low VM charcoal is used as a charcoal material, since bursting is difficult to occur, the temperature of the first zone can be set high, and the reduction of metal oxide by indirect reduction of the carbonaceous material in the granulated product by indirect reduction also proceeds. .

C (fixed carbon of carbonaceous material in the granulated product) + O ₂ → CO ₂
C + CO ₂ → 2CO
Fe ₂ O ₃ + 3CO → 2Fe + 3CO ₂

  In both cases where high VM charcoal is used as charcoal and low VM charcoal is used as charcoal, volatilization of volatile matter (VM) is completed in the first zone, so the second zone and In the third zone, the atmospheric temperature can be set high, and as a result, iron oxide can be efficiently reduced by indirect reduction of the carbonaceous material in the granulated product with fixed carbon.

  The reduced iron is discharged out of the furnace from the reduced iron discharge port 6 by the reduced iron discharge device 8 as in the case of the conventional mobile hearth furnace (see FIG. 10). In order to prevent reoxidation of the reduced iron, the atmosphere needs to be a reducing atmosphere in the third zone. An exhaust duct is provided in the second zone. The reason for providing the exhaust duct in the second zone will be described later.

  The first zone that completes volatilization of the volatile matter (VM) contained in the carbonaceous material in the granulated material and reduces the metal oxide to hydrogen with the hydrogen component in the volatile matter (VM) reduces the effective length of the moving hearth to L As above, it is assumed to be 0.3 × L to 0.4 × L from the inlet of the granulated product.

The first band and the boundary of the second band region is more than 0.3 × L~0.4 × L, when the range of the second band region to a predetermined range, the indirect reduction in carbon in granule in The range of the 3rd zone which performs is narrowed, and the metalization rate of a metal oxide falls. Preferably, it is 0.35 × L from the inlet of the granulated product.

  The second zone is a transition / exhaust zone that smoothly connects the ambient temperature of the first zone and the ambient temperature of the third zone and includes an exhaust duct that exhausts the gas generated in the first zone and the third zone. The second zone is from 0.3 × L to 0.4 × L to 0.6 × L from the charging inlet, and the exhaust gas duct is disposed in this zone.

  When the boundary between the second zone and the third zone exceeds 0.6 × L from the inlet, the atmosphere in the third zone becomes oxidizing, and the reduced metal is re-oxidized and the metallization rate is reduced. The boundary between the second band and the third band is up to 0.6 × L. Preferably, it is up to 0.5 × L from the inlet of the granulated product.

  The burner flue gas and granulated gas generated in the first zone flow in the same direction as the hearth travel direction and are discharged from the exhaust duct (see “7” in FIG. 10) arranged in the second zone. In addition, since it does not enter the third zone where indirect reduction with carbon is performed, indirect reduction in the third zone is not inhibited.

Since the hydrogen reduction rate constant is significantly larger than the indirect reduction rate constant (see Fig. 2), when high VM charcoal is used as the charcoal, most of the hydrogen components in the gas generated in the first zone are used for reduction. The unburned component is only CO generated by the decomposition of CH ₄ and the temperature rise is small. Therefore, the atmospheric temperature can be easily controlled by burner combustion control.

  In addition, when using low VM charcoal as a carbon material, it is also possible to raise the atmospheric temperature of a 1st zone and to perform indirect reduction in a 1st zone.

  The burner combustion exhaust gas and granulated product generated gas in the third zone flow in the direction opposite to the hearth traveling direction, and from the exhaust duct (see “7” in FIG. 10) arranged in the second zone. Discharged. By flowing the gas generated in the third zone in the direction opposite to the hearth traveling direction and exhausting in the second zone, reoxidation of the metal obtained by reduction in the third zone can be prevented.

  In the moving hearth shown in FIG. 10, the exhaust duct is approximately 0.35 × L from the inlet so that it can cope with the case where the atmosphere temperature in the first zone is 900 ° C. (see FIG. 9). Placed in position.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

Example 1
The granulated material was manufactured by mixing high or low VM charcoal and iron ore. This granulated product was left standing on the hearth of the moving hearth furnace shown in FIG. 10 and subjected to reduction treatment to produce reduced iron.

  High VM charcoal (VM: 37%) and iron ore were mixed to produce a granulated product. This granulated product was left standing on the hearth of the moving hearth furnace shown in FIG. 10 and subjected to reduction treatment to produce reduced iron. At this time, the atmosphere temperature in the first zone is set to 900 ° C., the temperature in the third zone is set to 1300 ° C., and the atmosphere temperature in the second zone is increased from 900 ° C. to 1100 ° C. so as to rise smoothly to 1300 ° C. Set.

  The hearth speed was adjusted so that the reduction time was 20 minutes. The metallization rate was 93%. There was no bursting of the discharged reduced granulate.

  Next, low VM charcoal (VM: 7%) and iron ore were mixed to produce a granulated product. This granulated product was left standing on the hearth of the moving hearth furnace shown in FIG. 10 and subjected to reduction treatment to produce reduced iron. At this time, the atmospheric temperature from the first zone to the third zone was set to 1300 ° C. The hearth speed was adjusted so that the reduction time was 18 minutes. The metallization rate was 92%. There was no bursting of the discharged reduced granulate.

  As described above, according to the present invention, in the direct reduction of the metal oxide, regardless of the amount of volatile matter (VM) contained in the carbonaceous material, the carbonaceous material containing volatile matter (VM) in a wide range is used. Even when inexpensive high VM charcoal is used, the bursting of the granulated product due to rapid volatilization of the volatile matter (VM) is suppressed, the metallization rate is increased, and the carbon material basic unit is reduced. Can be reduced. Therefore, the present invention has great applicability in the steel industry.

DESCRIPTION OF SYMBOLS 1 Granulated material 2 Hearth 3 Burner 4 Burner 5 Charge inlet 6 Reduced iron discharge port 7, 7 'Exhaust duct 8 Reduced iron discharge device 10 Test device 10a Test furnace 10b Alumina test tube 11a, 11b Sealing plug 12 Porcelain protection Tube 13 Pellet 14 Board 15 Gas tube 17 Temperature measuring device 18 Rubber tube 19 Gas cooling / washing device

Claims (7)

In a method of reducing the metal oxide, the granulated product formed by mixing the raw material containing the metal oxide and the carbonaceous material is placed on the hearth of the mobile hearth furnace and heated. Divided into three zones, the first zone, the second zone, and the third zone, in the direction of hearth progression from the inlet of the granulated material,
(x) In the first zone, metal oxide is reduced by hydrogen with volatile hydrogen components contained in the carbonaceous material in the granulated product,
(y) In the third zone, the metal oxide is indirectly reduced with carbon in the granulated product,
(z) A method for reducing metal oxide by a moving hearth furnace, wherein the gas generated in the first zone and the third zone is exhausted in the second zone.   The method for reducing metal oxide by a moving hearth furnace according to claim 1, wherein the atmosphere temperature in the first zone is set based on the amount of volatile components in the carbonaceous material. The method for reducing metal oxide by a moving hearth furnace according to claim 2, wherein the atmosphere temperature in the first zone is set to T (° C) or less defined by the following formula.
T (° C.) = 1400−8.75 × VM
VM: Amount of volatile matter in the carbonaceous material (% by mass)   The lower limit of the atmospheric temperature in the first zone is (T-50) ° C, and the metal oxide reduction method using a moving hearth furnace according to claim 3.   The metal oxide reduction by the moving hearth furnace according to any one of claims 1 to 4, wherein the moving hearth furnace is a linear moving hearth furnace or a rotary moving hearth furnace. Method. In an apparatus for reducing the metal oxide by placing the granulated material formed by mixing the raw material containing metal oxide and carbonaceous material on the hearth of the moving hearth furnace and heating it, the moving hearth furnace Gas generated in the first zone, the first zone, and the third zone, in which the metal oxide in the granulated material contains hydrogen components contained in the granulated material in the direction of the hearth in the direction of the hearth , and reduces the metal oxide to hydrogen. Is divided into three zones, a second zone for exhausting the gas , and a third zone for indirectly reducing the metal oxide with carbon in the granulated product ,
When the effective length of the moving hearth is L,
(X) the first zone is from 0.3 × L to 0.4 × L from the inlet of the granulated product,
(Z) The second zone is from 0.3 × L to 0.4 × L to 0.6 × L from the inlet of the granulated material, and has an exhaust duct in the zone. A metal oxide reduction device using a moving hearth furnace.   The apparatus for reducing metal oxide by a moving hearth furnace according to claim 6, wherein the moving hearth furnace is a linear moving hearth furnace or a rotary moving hearth furnace.

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