JPH0637656B2 - A method for suppressing sticking during reduction of fine ore by a circulating fluidized bed. - 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.

[Prior Art] The ironmaking method using a blast furnace requires a large amount of 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 circulating 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 produced on the surface of the ore and the sintering causes the particle motion to become inactive and to stop the flow. 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 solve the problems associated with the occurrence of sticking in the circulating fluidized bed reduction method without lowering its productivity and to establish an operation method having high stability.

[Means for Solving the Problems]

The present invention is a circulating fluidized bed reduction method in which T.
It is characterized in that carbonaceous materials are mixed in the ore according to the amount of Fe.

The mixing ratio (C% by weight) of the carbonaceous material at that time is C% by weight = 2.5 (T.Fe-60) ± 5 where C% by weight ≧ 0, the unit of T.Fe is calculated as% by weight. Is.

[Action]

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

The generation of clusters in the downcomer in the circulating fluidized bed reduction device is greatly affected by the iron content (T.Fe content) of the ore charged, and the higher the iron content, the more easily clusters are formed, and the T.Fe content increases. If it exceeds 65% by weight, the formation of clusters becomes remarkable. This causes operational troubles.

On the other hand, the mixing of carbonaceous material into the charged ore has the effect of suppressing the formation of clusters. When the amount of carbonaceous material mixed in the ore satisfies the above calculation formula, its effect is great.

〔Example〕

A circulating fluidized bed reduction apparatus having the mechanism shown in FIG. 1 was used to reduce fine ore having a particle size of 2 mm or less.

The results are shown in Table 1.

In FIG. 1, 1 is a raw material supply port, 2 is a reducing gas, 3 is an ascending pipe, 4 is a cyclone, 5 is a descending transfer pipe, and 6 and 7 are product outlets.

Ore A with a T.Ff of 57% can be reduced to a high reduction rate without mixing carbonaceous materials, and the gas utilization rate is as high as 17% (NO.
1). Therefore, it is not necessary to mix carbonaceous materials in an ore with a low iron grade such as ore A. Ore B has a high T.Fe content of 68%, but in this case, the reduction at 900 ° C hardly progresses without sticking carbonaceous materials due to sticking (NO.2). The reduction rate can be increased by lowering the reduction temperature to 800 ° C in order to avoid sticking, but this leads to a reduction in gas utilization rate and a consequent reduction in productivity. (NO.
6). Then, when the carbonaceous material is mixed, it becomes as follows. In other words, when the carbonaceous material content is 10%, the gas utilization rate can be kept high, but the reduction rate is low at 35% (NO.3). 20% carbonaceous material
When mixed, the reduction rate can be 70% and no reduction in gas utilization rate is observed (NO.4). Further mix the carbonaceous material
At 30%, the reduction rate will be over 90%, but the gas utilization rate will decrease (NO.5). Therefore, in order to keep the gas utilization rate high and increase the reduction rate, there is a range of carbonaceous material mixing. Further, if the iron content of the ore becomes lower, the amount of carbonaceous material to be mixed can be reduced accordingly.

〔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 circulating fluidized bed reduction apparatus. 1: Raw material supply port, 2: Reduction gas 3: Ascending pipe, 4: Cyclone 5: Descent transfer pipe, 6, 7: Product outlet

Claims (1)

[Claims] 1. A method for suppressing sticking during powder ore reduction by a circulating fluidized bed in which a carbonaceous material is mixed into the ore according to the amount of T.Fe in the charged iron ore, wherein the carbonaceous material is the ore and the carbonaceous material. The mixing ratio (C wt%) is calculated by the following formula C wt% = 2.5 (T.Fe-60) ± 5 where C wt% ≧ 0, the unit of T.Fe is the amount calculated by wt%. Method for suppressing sticking during reduction of fine ore by bed.