JPH03197610A - Method for operating circulating fluidized bed reduction apparatus - Google Patents

Abstract

PURPOSE:To raise reduction temp. in a circulating fluidized bed and to improve utilizing rate of gas by introducing reduction gas into a fluidized bed tower charged with powdery ore having a specific value or lower of T.Fe content and a prescribed grain size constitution to execute fluidizing reduction and circulatively supplying the reduced ore into lower part from upper part of the tower. CONSTITUTION:At the time of executing fluidizing reduction by introducing the reduction gas in the circulating fluidized bed as the essential fluidizing gas, the grain size of charged powdery ore is regulated so as to be 10-40wt.% coarse grain having >=2mm grain diameter and 15-30wt.% intermediate grain having 2-0.5mm grain diameter. Further, the average T.Fe content in the charged ore is regulated to <=65wt.% and desirably, the T.Fe content of the fine grain having <=0.5mm diameter is made to <=65wt.%. As the development of sticking can be prevented with the regulation of grain size distribution as above, the reduction temp. in the circulating fluidized bed can be raised and the utilizing rate of gas can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application 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 a large capital investment and requires high-quality agglomerate ore and coke in terms of raw materials and fuels.

For this reason, the smelting reduction method that eliminates these restrictions in terms of equipment and raw materials and fuels is attracting attention. The smelting reduction method consists of two major processes: a smelting reduction furnace and a pre-reduction furnace. The preliminary reduction furnace has a fluidized bed with a particle circulation device,
In other words, there is a method of applying a circulating fluidized bed. Such a circulating fluidized bed reduction method is described, for example, in Jikai 11B62-228878.
As described in the publication, it has a riser that charges fine ore and further introduces reducing gas, which is the main fluid gas, from the bottom of the riser to form a fluidized bed, and above the riser there is a solid-gas In a device that is equipped with a cyclone for separation and a downcomer connected to the lower part of the riser, fine ore from the fluidized bed is pre-reduced while being circulated through the cyclone and back to the fluidized bed. Ru.

This fluidized bed reduction method has the advantage that the particle size distribution width of the ore particles used can be widened because the gas flow rate is higher than in other bubble fluidized beds, and productivity is high.

Further, the gas reduction rate of fine ore is greatly influenced by the reduction temperature, and the higher the reduction temperature, the higher the reduction rate and the higher the efficiency. However, there is a problem in that an increase in the reduction temperature causes sticking to occur, stopping the flow of ore and making it impossible to operate.

This sticking phenomenon occurs in ``Chemical Equipment J'' in the bubble fluidized bed.
As described in the June 1986 issue, it is thought that during the reduction process, metallic iron protrusions are formed on the surface of the ore and sintered, thereby making particle movement inactive and stopping the flow. In a circulating fluidized bed, the gas flow rate is high, so such sticking does not occur in the riser, which is a fluidized reactor, but when the reduction temperature is increased, sticking occurs in the downcomer, which is a particle movement bed.

This sticking can be avoided by lowering the reduction temperature, but this has the disadvantage that lowering the reduction temperature slows down the progress of the reduction reaction, resulting in deterioration of productivity and gas consumption.

[Problem to be solved by the invention]

The problem to be solved by the present invention is to find a 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) In the reduction of fine ore using a circulating fluidized bed, the present invention is characterized in that the charged fine ore contains 10 to 40% by weight of coarse particles having a particle size of 21111 or more and a particle size of 2 to 0.5a. The particle size is adjusted so that the intermediate grains having 15 to 30% by weight have an average T of the charged ore,
The above problem was solved by setting the Fe content to 65% by weight or less. Further, it is preferable that the T and Pa contents of the fine particles having a particle size of 1.5 mm or less be 65% by weight or less.

[Effect]

The present invention was completed based on the following findings.

The occurrence of clusters in the downcomer in the circulating fluidized bed reduction equipment depends on the particle size distribution of the charged ore and the iron content (T, Fe).
content). The influence of ore particle size distribution is as follows. When the particle size distribution width is narrow, coarse particles are less likely to form clusters, and fine particles of 0.5 mm or less are more likely to form giant clusters. This unpleasant relationship is such that the higher the iron content of the ore, the easier it is to form clusters, and T
, When Fe exceeds 65% by weight, the formation of clusters becomes particularly noticeable. Therefore, in the case of ores with high iron content, −
If fine grains of 0.5 mm or less are present above the window, the formation of giant clusters becomes noticeable and operational troubles occur.

On the other hand, by adjusting the particle size distribution so that the coarse particles with a diameter of 2 or more and the intermediate particles with a particle diameter of 2 to 0.5 mm are within the ranges of 10 to 40% by weight and 15 to 30% by weight, respectively. Cluster generation can be suppressed. In particular, intermediate grains have the function of dispersing stress at grain contact points by being present between coarse grains, 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 generation of clusters will be further suppressed.

〔Example〕

Figure 1 shows the relationship between iron content and sticking. Here, the sticking index indicates the proportion of ore whose diameter exceeds the maximum particle size of the charged raw material particles due to sticking. T
, it can be seen that when Fe exceeds 65% by weight, sticking tends to occur. Next, Figure 2 shows the relationship between ore particle diameter and sticking. It can be seen that fine particles are easier to stick.

Figure 3 shows the change in sticking due to the mixing of intermediate grains. There is an effect of suppressing sticking when the amount of intermediate grains is in the range of 15 to 30% by weight. At this time, T, P of the intermediate grain ore
When the e content is lowered, the effect of suppressing sticking becomes more pronounced. In the case of ore mixing ratio A shown in Figure 3, the reduction temperature at which operation can be performed without cluster formation is 85.
It was 0°C. Furthermore, in the case of the ore mixing ratio B, the reduction temperature at which operation could be performed without cluster formation was 900° C. or higher.

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

〔Effect of the invention〕

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 a circulating fluidized bed is applied to the pre-reduction process of the smelting reduction method, the pre-reduction rate can be increased even with the same amount of gas, so the coal consumption rate in hot metal production can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between iron content and sticking, FIG. 2 is a diagram showing the relationship between ore particle size and sticking, and FIG. 3 is a diagram showing changes in sticking due to mixing of intermediate grains.

Claims (1)

[Claims] 1.T. A reducing gas is introduced as the main fluidizing gas into a fluidized bed tower charged with fine ore with an Fe content of 65% by weight or less to cause fluidized reduction, and the reduced ore is taken out from the top of the tower and sent to the bottom of the tower. In the circulating fluidized bed reduction method, the amount of coarse particles with a particle size of 2 mm or more is 10 to 40% by weight, and 2 to 0% by weight.
．． A method for operating a circulating fluidized bed reduction apparatus in which fine ore having a particle size composition of 15 to 30% by weight of 5 mm particles is charged.