JPH0637655B2 - Operating method of circulating fluidized bed reduction equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an operating method for reducing ore, particularly iron ore, using a circulating fluidized bed reduction furnace.

[Conventional technology]

The iron manufacturing method using a blast furnace requires large capital investment and requires high quality agglomerated ore and coke in terms of raw fuel. Therefore, the smelting reduction method, which eliminates the restrictions on these facilities and raw fuels, has been drawing attention. The smelting reduction method is composed of two large processes, a smelting reduction furnace and a preliminary reduction furnace. In the preliminary reduction furnace, there is a method of applying a fluidized bed having a particle circulation device, that is, a circulating fluidized bed. Such a circulating fluidized bed reduction method, for example, as described in JP-A-62-228878, charged powdered ore, further introducing a reducing gas that is the main fluidized gas from the bottom of the fluidized bed. In a device having a riser to be formed, a cyclone for solid-gas separation above the riser, and a downcomer continuously connected to the cyclone at the bottom of the riser, a device from a fluidized bed The ore is pre-reduced while circulating through the cyclone to the fluidized bed again.

In this fluidized bed reduction method, since the gas flow velocity is higher than that of other bubbling fluidized beds and the like, there are advantages that the particle size distribution width of the ore particles used can be widened and the productivity is high.

Further, the gas reduction rate of powdered ore is greatly affected by the reduction temperature, and if the reduction temperature is raised, the reduction rate increases and the efficiency becomes high. However, there is a problem that the increase of the reduction temperature causes sticking, the flow of the ore is stopped, and the operation cannot be performed.

This sticking phenomenon is a "chemical device" in a bubbling fluidized bed.
As described in the June 1986 issue, it is considered that during the reduction process, protrusions of metallic iron are generated on the surface of the ore and the sintering causes the particle motion to become inactive and the flow to stop. In the circulating fluidized bed, since the gas flow velocity is high, such sticking does not occur in the riser, which is a fluidized reactor, but when the reduction temperature is raised, sticking is performed by the downcomer, which is the particle moving bed.

This sticking can be avoided by lowering the reduction temperature, but the reduction of the reduction temperature has a drawback that the progress of the reduction reaction is slowed down, resulting in deterioration of productivity and gas basic unit.

[Problems to be Solved by the Invention]

The problem to be solved in the present invention is to find means for preventing the occurrence of sticking without losing the high productivity feature of the circulating fluidized bed reduction method.

[Means for Solving the Problems]

According to the present invention, in the reduction of fine ore by a circulating fluidized bed, coarse ore having a particle diameter of 2 mm or more is contained in an amount of 10 to 40% by weight and 2 to 0.
The grain size is adjusted so that the intermediate grains having a grain size of 5 mm are 15 to 30% by weight, and the average T.Fe content of the charged ore is 65% by weight.
The above problems have been solved by the following. Further, preferably, the T.Fe content of fine particles having a particle size of 0.5 mm or less is 65% by weight.
The following is desirable.

[Action]

 The present invention has been completed based on the following findings.

The generation of clusters in downcomers in a circulating fluidized bed reduction system is affected by the particle size distribution and iron content (T.Fe content) of the charged ore. The influence of the particle size distribution of the ore is as follows. When the particle size distribution width is narrow, coarser particles are less likely to generate clusters, and finer particles of 0.5 mm or less are more likely to generate giant clusters. Such a relationship makes it easier for clusters to form when the iron content of the ore is high, and especially when T.Fe exceeds 65% by weight. Therefore, in the case of ores with high iron content, a certain value of 0.5 mm
If the following fine particles are present, the formation of huge clusters will become noticeable and operation problems will occur.

On the other hand, coarse particles with a diameter of 2 mm or more and intermediate particles with a particle diameter of 2 to 0.5 mm are adjusted to have a particle size distribution of 10 to 40% by weight and 15 to 30% by weight, respectively. Generation can be suppressed. In particular, the intermediate particles have a function to disperse the stress at the particle contact points by being present between the coarse particles, thereby suppressing the formation of clusters. Therefore, if the iron content of the intermediate grains existing between the coarse grains and the fine grains is low, the formation of clusters is further suppressed.

〔Example〕

Figure 1 shows the relationship between iron quality and sticking. Here, the sticking index indicates the proportion of ore that has become equal to or larger than the maximum particle size of the charging raw material due to sticking. T.
It can be seen that sticking tends to occur when the Fe content exceeds 65% by weight. Next, Fig. 2 shows the relationship between ore particle size and sticking. It can be seen that the finer the particles, the easier the sticking.

Fig. 3 shows the change in sticking due to the mixing of the intermediate particles. When the intermediate particles are in the range of 15 to 30% by weight, sticking is suppressed. At this time, if the T.Fe content of the intermediate-grained ore is reduced, the effect of suppressing sticking becomes remarkable.
In the case of the ore mixing ratio of A shown in Fig. 3, the reduction temperature at which the operation was possible without forming clusters was 850 ° C. Further, in the case of the B ore mixing ratio, the reduction temperature at which the operation was possible without forming clusters was 900 ° C or higher.

As described above, the formation of clusters can be suppressed by adjusting the particle size of the charged ore. In addition, the intermediate grain T.Fe
By lowering the content, generation of clusters can be further suppressed.

〔The invention's effect〕

 The following effects can be achieved by the present invention.

(1) Since the occurrence of sticking can be prevented by adjusting the particle size distribution, the reduction temperature of the circulating fluidized bed can be increased and the gas utilization rate can be increased.

(2) The productivity of the circulating fluidized bed can be further increased.

(3) If the circulating fluidized bed is applied to the preliminary reduction process of the smelting reduction method, the preliminary reduction rate can be further increased even with the same gas amount, so that the coal basic unit in hot metal production can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a relation between iron quality and sticking, FIG. 2 is a diagram showing a relation between ore particle diameter and sticking, and FIG. 3 is a diagram showing a change in sticking due to mixing of intermediate grains.

Claims (1)

[Claims] 1. A reducing gas is introduced as a main fluidizing gas into a fluidized bed column charged with a powdered ore having a T.Fe content of 65% by weight or less for fluidized reduction, and the reducing ore is provided above the column. In the circulating fluidized bed reduction method, the coarse particles having a particle size of 2 mm or more are 10 to 40% by weight, and 2 to 0.5 mm.
Of operating a circulating fluidized bed reduction apparatus in which powdered ore having a particle size composition of 15 to 30% by weight is charged.