JPH0914853A - Layer split type fluidized-bet furnace - Google Patents

Abstract

PURPOSE: To realize a low-cost multi-stage fluidized-bed furnace capable of average improving by increasing the in-furnace resident time of ore with a simple structure. CONSTITUTION: The space on a dispersing plate of a prereducing furnace 31 is divided into a plurality of sections by partition walls 12, and a preheating section 32 is provided as one of them. An oxygen inlet 33 is provided at the section 32, the part of reducing gas for fluidizing iron ore is burnt, and the temperature of the gas lowered by the charge of the ore is raised. The temperature of a fluidized bet is raised from 600 deg.C to 750 deg.C by next section by preheating, further raised from 800 to 850 deg.C, and discharged in the state that the prereducing rate is improved. The transfer between the sections is conducted via an opening 13 provided at the wall 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a layer-division type fluidized bed furnace whose inside is divided into a plurality of compartments.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Examined Patent Publication No. 59-199.
Japanese Patent Publication No. 65, Japanese Patent Publication No. 7-5950, Japanese Patent Application Laid-Open No. 1-152225 and the like disclose prior arts using a fluidized bed furnace as a preheating device in a smelting reduction process of iron ore. In the smelting reduction process, as shown in FIG. 13, the iron ore is pre-reduced in the preliminary reduction furnace 1 and finally reduced in the melting furnace 2 to obtain molten iron. Melting furnace 2
Then, oxygen gas (O ₂ ) and coal are introduced together with the solid pre-reduced ore to reduce the pre-reduced iron oxide (FeO _x ) to iron (Fe). During this reduction reaction, a reducing gas containing carbon monoxide (CO) and the like is generated, and this reducing gas is used in the preliminary reduction furnace 1 to reserve iron ore (main component Fe ₂ O ₃ ) from FeO _x to reserve. The reduction is done.

As a reaction process using a fluidized bed furnace,
In addition to the smelting reduction process, direct reduction iron making processes and the like have been earnestly studied, and a fluidized bed furnace that is inexpensive and has a high reaction rate is required.

FIG. 14 shows the relationship between the gas flow rate and the required temperature for fluidizing the preliminary reduction furnace 1 of FIG. 13 and the preliminary reduction rate. In the one-stage flow-rate reactor, the gas flow rate decreases as the preliminary reduction rate is increased, so that the temperature must be raised to obtain a predetermined reaction amount. 1-stage type, 1
In the section type fluidized bed, both the ore that has not reacted at all immediately after being charged and the ore that has stayed in the furnace and has undergone the reaction have been completely mixed and then discharged at a constant flow rate. The average reaction rate becomes low.

A fluidized bed furnace having a plurality of compartments has been proposed as a series multi-stage fluidized bed furnace 3 as shown in FIG. 15, for example. In the serial multi-stage fluidized bed furnace 3, a plurality of dispersion plates 5 are provided above the wind box 4, and the ore sequentially moves downward along the chute 6 in the fluidized bed furnace 3 formed by the dispersion plates 5. react. Japanese Unexamined Patent Publication No. 59-180278 discloses a fluidized bed furnace in which a space on a dispersion plate is divided into a plurality of partitions by partition walls perpendicular to the dispersion plate.

[0006]

As described above, in a fluidized bed furnace that forms only a single fluidized bed, the average reaction rate of the ore discharged becomes low, so that a structure in which a plurality of fluidized bed furnaces are provided is used. Proposed. The configuration shown in FIG. 15 has the following drawbacks because it forms a plurality of fluidized beds in the vertical direction.

[0007] The furnace height increases, and not only the furnace but also the raw material handling equipment such as a hopper conveyor and the exhaust gas treatment equipment such as a duct are expensive.

Since the reducing gas moving from the lower side to the upper side contains a large amount of powdered dust of the granular material, the dust tends to adhere to the fluidized-bed dispersion plate on the upper side.

Since a plurality of fluidized bed furnaces are formed, the gas pressure loss becomes large.

In a large-volume fluidized bed furnace, the diameter of the furnace becomes large and it becomes necessary to support the dispersion plate from below. It is difficult to support the multi-stage upper dispersion plate from below,
Therefore, it is necessary to increase the thickness in order to increase the diameter of the dispersion plate, which increases the cost of the dispersion plate. It also makes maintenance difficult.

Although the utilization rate of the reducing gas is large in the series multi-stage type, it is impossible to arbitrarily select the reducing gas in the molten reduction iron-making process or the like because the reducing gas generated in the process is used. It can be judged only by the size of the preliminary return rate.

Further, Japanese Patent Publication No. 7-5950 proposes a method in which oxygen gas is mixed with reducing gas in order to raise the temperature in the ore by raising the temperature in the fluidized bed. However, in this method, since the gas after the oxygen gas is blown in and partially burned must have a sufficient reducing ability, the amount of the blown oxygen gas is limited, and sufficient temperature rise cannot be performed. Further, in the smelting reduction process, the higher the preliminary reduction rate of the preliminary reduction ore sent from the preliminary reduction furnace to the smelting reduction furnace, the lighter the final reduction load in the smelting reduction furnace becomes. The flow rate of coal charged into the smelting reduction furnace and the gas flow generated in the smelting reduction furnace in correlation therewith is reduced. If the reduction rate is increased in the pre-reduction furnace, the load becomes large, which requires a large amount of heat. Particularly, the sensible heat is mostly covered by the sensible heat of the reducing gas. However, as described above, the reduction gas flow rate decreases as the pre-reduction rate of ore increases, so the gas temperature required at the pre-reduction furnace inlet increases, and the dust contained in the gas softens. Then, it adheres to the dispersion plate or the like and hinders normal operation. JP-A-1-205014, JP-A-1-152225, and the like disclose a method of preheating ore by burning gas discharged from a fluidized bed furnace, but the configuration of equipment becomes complicated. However, there are drawbacks such as increased equipment costs.

In the prior art of JP-A-59-180278, a core is inserted near the center of the furnace to partition the core and the outer wall of the furnace into a plurality of compartments. Multiple sections are connected in series to improve the average reaction rate of ore. However, since it is necessary to provide the core, the area that can be effectively used in the furnace is reduced, and only a uniform reaction can occur in a plurality of divided sections.

It is an object of the present invention to provide a bed-division type fluidized bed furnace capable of causing an efficient reaction without increasing equipment cost.

[0015]

According to the present invention, a high-temperature reducing gas is introduced into a furnace through a dispersion plate in the lower part of the furnace to form a fluidized bed of a granular material to be charged into the furnace. In a fluidized bed furnace for reaction, the inside of the furnace is divided into a plurality of compartments, and a partition wall in which an opening for transferring the granular material to adjacent compartments is formed, and a reducing gas in some compartments And a oxygen supply device for introducing an oxygen-containing gas for partially burning the gas. Further, the present invention is characterized in that the arrangement density of the reducing gas introduction nozzles formed on the dispersion plate is changed in accordance with the divided division. Further, the present invention is characterized in that the section where the oxygen-containing gas from the oxygen supply device is introduced and the reducing gas is partially burned is provided with an exhaust gas passage separate from other sections. Further, the present invention is a fluidized bed furnace in which a high-temperature reaction gas is introduced into the furnace through a dispersion plate in the lower part of the furnace and reacted while forming a fluidized bed of the granular material to be charged into the furnace. , The furnace is divided into a plurality of compartments, the partition wall provided with an opening for the transfer of the granular material to the adjacent compartments, the arrangement density of the reaction gas introduction nozzles formed in the dispersion plate, It is a fluidized bed reactor of the layer-divided type, which is characterized in that it is changed in accordance with the divisions into which it is divided. Further, the present invention is characterized in that the oxygen-containing gas and the fuel are blown into a part of the divided sections. Further, the present invention is characterized in that a section separated from the outer wall of the furnace is provided near the center of the furnace. Further, the present invention is characterized in that the volume of the upper space of the plurality of divided compartments is relatively changed with respect to the bottom area of each compartment.

[0016]

According to the present invention, the fluidized bed is divided into a plurality of compartments by the partition wall, and the partition wall is formed with the openings for transferring the raw material of the granular material to the adjacent compartments. The residence time of the raw material in the furnace is substantially increased, and the average reaction rate until it is discharged to the outside of the furnace is improved. Since the oxygen-containing gas is supplied to some of the sections to partially burn the reducing gas, it is possible to raise the temperature of the fine-grain raw material and improve the reduction rate. Since the temperature of the fine-grain raw material can be raised in the furnace, the temperature of the reducing gas introduced into the fluidized bed furnace can be lowered, and the amount of dust contained in the reducing gas attached to the dispersion plate etc. can be reduced. be able to. The reducing gas partially burned by the oxygen-containing gas does not reoxidize the fine-grained raw material having a high reduction rate, so that the reducing ability is improved.

Further, according to the present invention, by changing the arrangement density of the reducing gas introducing nozzles formed on the dispersion plate, that is, the number of nozzles per unit area and the nozzle diameter, the fine-grain raw material is reduced in each section. It is possible to obtain an optimum flow rate of reducing gas required for use, and it is possible to effectively utilize the reducing gas.

Further, according to the present invention, the reducing gas partially burned by the oxygen-containing gas is discharged by providing a route different from the exhaust gas route of the other zones, so that the calorific value of the exhaust gas from the other zones is discharged. It is possible to maintain the utility value of the exhaust gas without decreasing the exhaust gas.

Further, according to the present invention, the arrangement density of the reaction gas introduction nozzles is changed for each of a plurality of divisions divided by the partition wall on the dispersion plate, and the reaction gas flow rate optimum for the reaction in each division is obtained. Can be improved, and the reaction gas can be effectively used.

Further, according to the present invention, a part of the plurality of divided sections can be heated according to the reaction stage, so that an efficient reaction can be caused as a whole.

Further, according to the present invention, the volume of the upper space of the plurality of divided sections is changed relative to the bottom area of each section, so that the sections having different gas flow rates passing through the dispersion plate are used. A crack can be formed. By changing the cross-sectional area of some sections according to the particle size range of the fluidizable powder or granular material, it is possible to process the powder or granular material with a wide particle size range as a whole.

[0022]

1 shows a schematic structure of a preliminary reduction furnace 11 according to a first embodiment of the present invention. A partition wall 12 is provided in the preliminary reduction furnace 11, and an opening 13 is formed in the partition wall 12. Such a partition wall 12 is erected on the dispersion plate 15 above the wind box 14. A fluidized bed is formed on the dispersion plate 15 by the reducing gas supplied from the wind box 14, and the reduced ore is discharged from the fluidized bed through the chute 16. The chute 17 into which the raw iron ore is charged is the partition wall 12
The section 18 to which the chute 16 for discharging reduced ore is connected among the plurality of sections 18 divided by
The iron ore is charged into the section 18 different from the above through the raw material charging port 19. The reducing gas is supplied to the wind box 14 through the reducing gas supply pipe 20. The reducing gas is, for example, FIG.
The gas generated from the melting furnace in the smelting reduction process as shown in Fig. 4, CO is 46%, CO ₂ is 20%, and H ₂ is 11%.
%, H ₂ O is 18%, N ₂ is 5%, and the temperature is 1
It is 019 ° C. The reducing gas having such a composition is stored in the wind box 14 from the gas inlet 21 through the reducing gas supply pipe 20, and forms the fluidized bed 22 on the dispersion plate 15.

FIG. 2 is a sectional view taken along the section line II-II in FIG. However, in FIG. 1, for convenience of description, the positions of the chutes 16 and 17 are changed and displayed. A three-step reaction is carried out through the three sections 18 divided by the partition wall 12 until the iron ore charged is discharged as reduced ore. By this, the partition wall 12
In the case where there is not, the reduction rate of 13% can be increased by 4% to 17% by the partition wall 12 according to the present embodiment. The temperature of the fluidized bed 22 that achieves such a preliminary reduction rate of 17% is 700 ° C., and the height of the fluidized bed 22 is 1100 mm.

FIG. 3 shows a preliminary reduction furnace 1 according to the embodiment of FIG.
1 shows the actual shape of 1. The outer wall 24 of the upper wall portion 23 is provided with the wind box 14 and the dispersion plate 15 and has a diameter larger than that of the portion where the fluidized bed 22 is formed. As a result, the gas flow velocity is reduced, and the height of the fluidized bed 22 is suppressed.
A charging valve 25 is provided in the middle of the chute 17 from the raw material charging port 19, and a discharge valve 26 is also provided in the middle of the chute 16 for discharging the reduced ore to maintain the airtightness in the preliminary reduction furnace 11. . An exhaust duct 27 is connected to the top of the preliminary reduction furnace 11, and a fine material is collected by a cyclone separator 28 and returned to the material charging port 19.

FIG. 4 is an enlarged view of a part of the dispersion plate 15 in the IV section of FIG. A nozzle 29 is arranged in the dispersion plate 15, and reducing gas is ejected from a gap provided in the cap above the dispersion plate 15 to form a fluidized bed 22.

FIG. 5 shows the relationship between the number of stages of the fluidized bed and the residence time. In the case of the single stage type, that is, when n = 1, the time t / t0 based on the average particle retention time t0 for all fluidized beds is used.
When is 0, the maximum ratio is reached, and the ratio decreases as time increases. When the number of stages n increases, the discharge frequency immediately after charging becomes 0 and the residence time increases.

FIG. 6 and FIG. 7 show the structure of the preliminary reduction furnace 31 according to the second embodiment of the present invention. 6 is a longitudinal sectional view, and FIG. 7 is a sectional view taken along the section line VII-VII in FIG. In this embodiment, a preheating section 32 is provided in one of the sections divided by the partition wall 12,
The oxygen gas supplied from the oxygen supply device 34 is blown in through the oxygen introduction port 33 to raise the temperature of the powdery particles to 600 ° C. When it is necessary to keep the reducing gas at 1000 ° C or lower in consideration of the properties of the dust in the reducing gas and the softening temperature due to the components such as coal, when the reducing gas is reduced by 200 to 300 ° C by the iron ore charging, The temperature can be partially raised to approximately 900 ° C., which is optimum for the reaction. However, if the temperature exceeds 900 ° C, some of the ore will stick in the fluidized bed, so the temperature should be kept at around 850 ° C. By increasing the fluidized bed temperature in this way, the preliminary reduction rate can be improved to about 24%.

FIG. 8 shows a schematic structure of a preliminary reduction furnace 51 according to the third embodiment of the present invention. In this embodiment, the exhaust gas from the preheating section 53 divided by the partition wall 52 is discharged separately from the other exhaust gas through the individual exhaust ducts 54 to reduce the latent heat amount (LHV) held by the other exhaust gas. Can be prevented.

FIG. 9 shows a schematic structure of a preliminary reduction furnace 61 according to the fourth embodiment of the present invention. It should be noted in this embodiment that the partition wall 62 forms the section 63 which is separated from the furnace outer wall 24 in the vicinity of the center of the furnace, and therefore, as in the case of the multi-division only by the partition wall 64 extending in the radial direction. The sharp dead point is formed in the central portion, and the flow state is not deteriorated.

FIG. 10 shows a schematic structure of a preliminary reduction furnace 71 according to the fifth embodiment of the present invention. In this embodiment, not only the oxygen-containing gas but also the fuel is supplied to the preheating section 73 partitioned by the partition wall 72, and the preheating section 7
3 is heated. As the fuel, a liquid fuel such as natural gas or petroleum, or a circulating gas obtained by cooling and removing dust from exhaust gas can be used. Combustion of fuel and oxygen-containing gas
It may be performed immediately before blowing into the fluidized bed, or may be performed after blowing into the fluidized bed.

11 and 12 show the structure of a preliminary reduction furnace 81 according to the sixth embodiment of the present invention. FIG. 12 shows FIG.
The sectional view seen from the section line XII-XII of FIG. What should be noted in this embodiment is that the furnace outer wall 84 of the section 83 partitioned by the partition plate 82 partially swells to reduce the flow velocity for forming the fluidized bed.
Dispersion plate 15 of section 83 in which outer wall 84 of the furnace is swollen
The area occupied on the top is relatively small as shown in FIG. 12, and the iron ore charged from the raw material charging port 19 is 0.1
When it has a particle size distribution of 10 mm,
Fine grains of 0.1 to 0.5 mm migrate from the top of the partition wall 82, are pre-reduced, and are discharged as fine grain pre-reduction ores. Further, the scattered fine grains are collected by the cyclone 85 and returned to the section 83 as a circulation fine grain ore.
The flow velocity of such fine grain section 83 is, for example, 1
m / s. On the other hand, coarse particles of iron ore of 0.5 to 10 mm are fluidized at a flow velocity of 4.8 m / s,
It is discharged as coarse grain pre-reduction ore. According to this example, iron ore having a wide range of particle size distribution of 0.1 to 10 mm can be treated comprehensively, and inexpensive raw materials can be effectively used.

In each of the above embodiments, the preliminary reduction furnace for iron ore in the smelting reduction process has been described, but the layer-division type fluidized bed furnace according to the present invention can also be used as the reduction furnace in the direct reduction ironmaking process. it can. Further, the layer-separated fluidized bed furnace according to the present invention can be used for a general ore preheating process, a firing reaction process and the like. In addition, openings 13 that allow the fluidized bed to be moved between sections.
Can also be formed as a notch such as the upper edge of the partition wall.

[0033]

As described above, according to the present invention, by dividing the inside of the flow furnace into a plurality of parts, it is possible to obtain the same effect as that of the series multistage type, and the residence time of the granular material in the furnace. Can be increased to improve the average reaction rate. Since the height of the furnace does not increase unlike the series multi-stage type, a process with low equipment cost and operating cost can be realized with simple equipment. Since the reducing gas is partially burned in some sections, it is possible to improve the reduction rate and lower the temperature of the reducing gas at the inlet of the fluidized bed furnace to prevent dust from adhering to the dispersion plate or the like. Moreover, since the partially burned gas does not reoxidize the ore whose reduction rate has already been improved, the reducing ability of the furnace can be improved.

Further, according to the present invention, the arrangement density of the reducing gas introducing nozzles can be changed to distribute the reducing gas at an optimum ratio for each division, and the reducing gas can be effectively used.

Further, according to the present invention, the partially burned exhaust gas can be discharged separately from the exhaust gas of the other zones, so that the calorific value of the exhaust gas of the other zones is not reduced, and the exhaust gas Value can be maintained.

Further, according to the present invention, the inside of the fluidized bed furnace is divided into a plurality of sections, and the distribution of the reaction gas for forming the fluidized bed furnace is determined by the arrangement density of the gas introduction nozzles formed on the dispersion plate. Since it can be adjusted, the reaction gas can be effectively used.

Further, according to the present invention, since the oxygen-containing gas and the fuel are blown into a part of the compartment, the compartment can be effectively heated, and the efficient reaction is promoted as a whole. You can

Further, according to the present invention, since the compartment separated from the outer wall of the furnace is provided near the center of the furnace, even if the number of compartments in the furnace becomes large, a separate section does not occur near the center of the furnace, Can be effectively used.

Further, according to the present invention, since the gas flow rate can be changed in a plurality of divisions, it is possible to process the raw materials of the granular material having different particle diameters in parallel, and the range of the particle size distribution as a whole is A wide range of powdery and granular materials can be processed, and inexpensive materials can be efficiently processed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of a preliminary reduction furnace according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

3 is a vertical sectional view of a preliminary reduction furnace 11 according to the embodiment of FIG.

4 is a partial cross-sectional view of the dispersion plate 15 shown in FIG.

5 is a graph showing an effect of division according to the embodiment of FIG.

FIG. 6 is a partial vertical sectional view of a preliminary reduction furnace 31 according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along section line VII-VII of FIG. 6;

FIG. 8 is a partial vertical sectional view of a preliminary reduction furnace 41 according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view of a preliminary reduction furnace 51 according to a fourth embodiment of the present invention.

FIG. 10 is a partial vertical sectional view of a preliminary reduction furnace 61 according to a fifth embodiment of the present invention.

FIG. 11 is a schematic vertical sectional view of a preliminary reduction furnace 81 according to a sixth embodiment of the present invention.

FIG. 12 is a cross-sectional view taken along the line XII-XII of FIG. 11;

FIG. 13 is a simplified cross-sectional view showing the basic configuration of the iron ore smelting reduction process.

FIG. 14 is a graph showing the relationship between the pre-reduction rate, gas flow rate and required temperature in a single type fluidized bed furnace.

FIG. 15 is a vertical cross-sectional view showing a schematic configuration of a series multi-stage fluidized bed furnace.

[Explanation of symbols]

 11, 31, 51, 61, 71, 81 Pre-reduction furnace 12, 52, 62, 64, 72, 82 Partition wall 13 Opening 14 Wind box 15 Dispersion plate 16, 17 Chute 18, 53, 63, 73, 83 Section 19 Raw material inlet 20 Reducing gas supply pipe 21 Gas inlet 22 Fluidized bed 27,54 Exhaust duct 28 Cyclone separator 29 Nozzle 32 Preheating section 33 Oxygen inlet 84 Outer wall of furnace

Claims (7)

[Claims] 1. A fluidized bed furnace in which high-temperature reducing gas is introduced into the furnace through a dispersion plate in the lower part of the furnace to react while forming a fluidized bed of a granular material to be charged into the furnace. , The partition wall that divides the furnace into multiple compartments and has openings for the transfer of the granular material to the adjacent compartments, and some compartments for partially burning the reducing gas A layered-type fluidized bed furnace comprising: an oxygen supply device for introducing an oxygen-containing gas. 2. The layer-division type fluidized bed furnace according to claim 1, wherein the arrangement density of the reducing gas introduction nozzles formed on the dispersion plate is changed in accordance with the division into which the gas is divided. 3. An exhaust gas passage separate from other divisions is provided in the division where the oxygen-containing gas from the oxygen supply device is introduced and the reducing gas is partially combusted. Item 1. A bed-divided fluidized bed furnace according to item 1 or 2. 4. A fluidized bed furnace in which a high-temperature reaction gas is introduced into the furnace through a dispersion plate in the lower part of the furnace to react while forming a fluidized bed of the granular material to be charged into the furnace. , The furnace is divided into a plurality of compartments, the partition wall is provided with an opening for the transfer of the granular material to the adjacent compartment, the arrangement density of the reaction gas introduction nozzles formed in the dispersion plate, A bed-division type fluidized bed furnace characterized by being changed in accordance with the division into which it is divided. 5. The oxygen-containing gas and the fuel are blown into a part of the divided compartments.
The layer-divided fluidized bed furnace according to any one of 1. 6. The layer-division type fluidized bed furnace according to claim 1, further comprising a partition provided near the center of the furnace, the partition being separated from the outer wall of the furnace. 7. The layer division according to claim 1, wherein the volume of the upper space of the plurality of divided divisions is changed relative to the bottom area of each division. Type fluidized bed furnace.