JPH0637653B2 - Operation method of fluidized-ore reduction furnace for fine ore - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for maintaining high efficiency operation of a fluidized bed reduction furnace for ores, especially iron ores.

[Conventional technology]

In recent years, the steelmaking method using the conventional blast furnace has a large amount of capital investment,
In addition, a smelting reduction ironmaking method has emerged that has solved problems such as restrictions on raw material selection that require high quality agglomerated ore and coke. The smelting reduction ironmaking process is composed of two large units, a smelting reduction furnace and a preliminary reduction furnace, and a method of applying a fluidized bed having a particle circulation device to the preliminary reduction furnace is common. This fluidized-bed reduction furnace basically collects iron ore and a fluidized bed reaction tower into which a reducing gas is charged, and ore discharged together with gas from the reaction tower with a cyclone for gas-solid separation, and a reaction. It has a structure consisting of a descending connecting pipe that is recharged at the bottom of the tower.

However, since such a fluidized-bed reduction reactor reacts in a dilute fluidized bed in which fine ore is suspended, the utilization efficiency of the reducing gas is poor and the productivity per volume of the reaction tower is low,
There is also a drawback that it is difficult to obtain a product having a stable reduction rate.

Therefore, various operating methods have been proposed for securing productivity in the fluidized-bed reduction furnace and obtaining a product with a stable reduction rate.

For example, Japanese Patent Laid-Open No. 63-57709 discloses a method of controlling the reduction rate by changing the product extraction rate, ore circulation flow rate, reducing gas supply rate, and reducing gas inlet degree.

Further, Japanese Patent Application Laid-Open No. 1-115447 discloses a method of controlling a flow rate of a circulating gas or a particle circulation rate to stably maintain a fluid state against fluctuations and changes in operating conditions.

By these disclosed operation methods, it is possible to maintain the operation state so as not to make a large change in the reduction rate and the flow state of the charged ore.

[Problems to be Solved by the Invention]

However, such a control method is merely aimed at stable operation of the furnace, and is not considered to obtain a highly efficient operating state in which the processing capacity of the reduction furnace is fully used. Inferior operation will continue.

The problem to be solved in the present invention is to establish a highly efficient operation method of a circulating fluidized-bed reduction reactor which can maximize the capacity and the reducing function of the introduced reducing gas as well as the stable operation.

[Means for Solving the Problems]

INDUSTRIAL APPLICABILITY According to the present invention, by maintaining the particle volume fraction in the fluidized bed of a fluidized-bed reduction reactor within a specific range, the reducing gas introduced into the fluidized bed can be most effectively used for the reduction of ores, and the productivity is improved. It was completed based on the knowledge that
Alternatively, both are controlled to maintain the particle volume fraction within the range of approximately 4 to 15%.

[Action]

The operation efficiency of the reducing furnace, which is represented by the utilization rate of the reducing gas introduced into the fluidized bed, shows a high value when the ore particle volume fraction in the reaction fluidized bed is within a specific range.

When the volume fraction of the ore particles is small, there are few particles that react with the reducing gas in the fluidized bed, so the gas does not react sufficiently and is discharged out of the furnace, resulting in a sharp drop in efficiency. The allowable limit is about 4%.

When the volume fraction of particles in the fluidized bed is large, the amount of particles in the fluidized bed is large, but the dispersion of the particles becomes poor and the particle aggregates are unevenly distributed. Due to insufficient contact, the gas does not react sufficiently with the iron particles and is discharged outside the furnace, resulting in a sharp drop in efficiency. The allowable limit is about 15%.

Then, the ore particle volume fraction can be maintained within that range by adjusting either or both of the gas flow rate of the fluidized-bed reduction reactor and the particle circulation flow rate.

〔Example〕

FIG. 1 is a diagram schematically showing an operating form of the present invention. The fluidized-bed reduction furnace 10 is composed of a rising pipe 1 forming a reaction layer and a descending pipe 2 forming a route for returning the partially reduced particles to the rising pipe 1 again.

Referring to the figure, the powdered ore 4 supplied from the raw material supply port 3
Is reduced by forming a fluidized bed by the reducing gas 5 supplied from below the rising pipe 1. After the reaction, the reducing gas 5 enters the cyclone 6, and the particles entrained in the gas return to the ascending pipe 1 via the descending pipe 2.

In the process, a part of the product is taken out of the downcomer 2 as a product 7,
Alternatively, it is collected from the product outlet 8 at the bottom of the fluidized bed. The pressures of the lower part and the upper part of the rising pipe 1 during the operation are detected by the pressure detectors 9a and 9b attached at the respective positions.

The particle volume fraction in the fluidized bed in such a fluidized-bed reduction reactor is estimated by the following equation.

Particle volume fraction (%) = 100 (P1-P2) / L / ρs where P1: rising tube lower pressure (kg / m ² ) P2: rising tube upper pressure (kg / ² ) L: pressure detecting end 9a Distance from 9b (m) ρs: Particle density in the fluidized bed (kg / ³ ).

FIG. 2 is a diagram showing the relationship between the gas utilization rate and the volume fraction of ore particles in the fluidized bed of the fluidized-bed reduction reactor shown in FIG.

The gas utilization rate shown in the figure is shown as the difference between the oxidation degree of the reducing gas at the inlet and outlet of the fluidized bed, that is, [(CO ₂ + H ₂ O) / (CO + CO ₂ + H ₂ + H ₂ O)]. Can be used as an index of efficiency effectively used for reduction.

The main operating conditions at this time are temperature 820 to 820 in the fluidized bed.
860 ° C., degree of oxidation of inlet gas 12-18%, product reduction rate 40-50%, particle circulation speed 50-250 kg / m ² / s,
The gas flow rate is 5 to 9 m / s.

When the particle volume fraction in the fluidized bed is within the specific range A, the gas utilization rate is 13 to 18% and the production rate is 5 to 9t-Fe /
m ² / h was obtained. All of these values were 1.5 times or more outside the specific range A.

The range of particle volume fraction for obtaining high gas utilization rate and production rate is in the range of approximately 4% and approximately 15% in any dimension furnace or operation under any conditions. That is, the gas utilization rate when the particle volume fraction is within the specific range A is 1.5 times or more as compared with when it is outside the specific range A, and the production rate is 2 t-F.
e / m ² / h or more can be obtained.

On the other hand, the volume fraction of the ore particles in the fluidized bed in the fluidized-bed reduction reactor has a unique relationship with the gas flow velocity in the fluidized bed and the circulating flow rate of the ore. FIG. 3 shows the relationship between the particle volume fraction, the gas flow velocity in the fluidized bed, and the circulating flow rate of ore. As shown in the figure, the particle volume fraction in the fluidized bed increases due to the decrease in the gas flow velocity, and decreases in the opposite case. Further, the particle volume fraction increases as the particle circulation flow rate increases.

Therefore, from the relationship between FIG. 2 and FIG. 3, the factors of the gas flow velocity in the fluidized bed and the circulating flow rate of the ore or both are maintained within the specific range A of the particle volume fraction for obtaining the above high operation efficiency. Can be a controlling factor for

FIG. 4 shows the operation sequence of the fluidized-bed reduction reactor having the structure shown in FIG. 1, and shows the relationship between the circulation flow rate of ore particles and the gas flow rate, the particle volume fraction, the ore reduction rate, and the production rate. .

As shown in the figure, it is possible to control the particle volume fraction in the fluidized bed by the gas flow velocity and the particle circulation flow rate, and it is possible to control the operation efficiency of the fluidized bed by the gas flow velocity and the particle circulation flow rate. I understand.

〔The invention's effect〕

The following effects can be achieved by the operation method of the fluidized-bed reduction reactor of the present invention.

(1) The reaction can be performed in a region where the reducing gas and the ore are in good contact with each other. As a result, it is possible to operate the reduction furnace with the maximum efficiency.

(2) The efficient operation can be maintained and the reduction furnace can be operated with high efficiency.

(3) Return will proceed smoothly and productivity will be improved.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an operating form of the present invention. FIG. 2 shows the relationship between the volume fraction of ore particles and the reducing gas utilization rate, and FIG. 3 is a diagram showing the relationship between the volume fraction of ore particles, the gas flow velocity, and the particle circulation flow velocity. FIG. 4 is a diagram showing an operating state of the fluidized-bed reduction reactor shown in FIG. 1: Upcomer pipe, 2: Downcomer pipe 3: Raw material supply port, 4: Fine ore 5: Reduction gas, 6: Cyclone 7,8: Product outlet 9a, 9b: Pressure detector, 10: Flow reduction furnace

Front Page Continuation (72) Inventor Tatsuhiko Egashira 59, 46 Nakahara, Tobata-ku, Kitakyushu, Fukuoka Prefecture 59 Nippon Steel Co., Ltd. Machinery & Plant Division

Claims (1)

[Claims] 1. A fluidized reduction of fine ore in which a particle volume fraction in a fluidized-bed reduction reactor is maintained within a range of 4 to 15% by adjusting a gas flow rate in a fluidized-bed reduction fluidized bed and a circulation flow rate of ore or both. How to operate the furnace.