JPH03100112A - Method for operating circulating fluidized reduction furnace of powdery ore and reduction furnace - Google Patents

Abstract

PURPOSE:To preven the variation of powdery ore level in a downtake tube and to improve the working efficiency of a fluidized reduction furnace by directly fitting a supplying device for powdery iron ore to the downtake tube in the circulating fluidized reduction furnace composed of an uptake cylinder and the downtake tube for the powdery iron ore. CONSTITUTION:At the time of pre-reducing the powdery iron ore in the circulating fluidized bed type pre-reduction furnace 10, the powdery iron ore 4 is charged from a lower charging hole 3 in the uptake cylinder 1 and pre-reduced in the solid phase with reducing gas 5 supplied from the lower part in the pre-reduction furnace 10, and the powdery ore separated from gas with a cyclone 6 is descended in the downtake tube 2. The reduced ore is discharged from an outlet 7 and unreducing powdery ore is again returned back in the uptake cylinder 1 and pre-reduced. In this case, when quantity of the circulating powdery ore in the downtake 2 becomes little, the reducing gas 5 blown into the uptake cylinder 1 is caused to flow into the downtake tube 2, and collecting efficiency of the cyclone 6 is reduced and the fluidized bed in the uptake cylinder 1 becomes unstable. Hereby, this condition is detected with a level meter 11, and the powdery ore in a hopper 13 is supplied into the downstream tube 2 from a powdery ore supplying device 9 arranged in the downtake tube 2, and blowby of the reducing gas 5 to the downtake tube 2 is prevented and the operational condition is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reduction furnace and a method for operating a reduction furnace for circulating and reducing fine ore such as iron ore.

[Conventional technology]

In recent years, the iron manufacturing method using blast furnaces requires large capital investment, and
A smelting reduction iron-making process has emerged that solves problems such as restrictions on raw material selection that require high-quality agglomerate ore and coke.

The fluidized reduction furnace used for preliminary reduction in this smelting reduction ironmaking method consists of a reaction tower consisting of a riser tube in which iron ore and reducing gas are charged and a fluidized bed reaction is carried out, and the ore discharged from the reaction tower together with gas is It has a structure consisting of a downcomer pipe that collects gas with a cyclone for solid separation and reinjects it into the lower part of the reaction tower.

In the operation of such a fluidized bed reduction reactor, when the particle level in the particle downcomer decreases, the gas blown into the riser will flow to the particle downcomer, reducing the collection efficiency of the cyclone, and the flow of particles in the riser will also stop. It becomes stable.

Therefore, to stabilize the operation of a circulating fluidized bed, it is necessary to prevent large fluctuations in particle levels in the downcomer.

Various means for dealing with this have been disclosed.

For example, Japanese Utility Model Application No. 62-160295 discloses that a particulate retention part with a large cross-sectional area is provided in the middle of the downcomer pipe, and in order to ensure smooth circulation, a product with a particle size composition similar to that of the feed material is discharged. In addition, in the specification of Japanese Patent Application No. 63-69239, detection devices using pressure gauges are installed at two points at the control level of the fluidized powder in the downcomer, and as a result, as the level in the downcomer decreases, the reaction is detected. A method of operating a reduction furnace that increases the amount of feedstock fed to the column is disclosed.

[Problem to be solved by the invention]

When adjusting the level of ore powder in the downcomer,
Absorbing level fluctuations by increasing the amount of particles stagnant in the particle downcomer where the reaction does not proceed increases the wasteful particle stagnation area in the circulation system, which not only reduces the efficiency of the device, but also increases the amount of particles in the stagnation area. This causes a drop in particle temperature, which is unfavorable in terms of thermal efficiency.

In addition, an operating method that increases the amount of raw material supplied to the reaction tower as the level in the downcomer decreases has the disadvantage that it cannot respond to sudden changes in the level in the downcomer.

The problem to be solved by the present invention is that the accumulation of circulating ore in the downcomer is small, and the powder in the downcomer can be removed without affecting the raw material supply to the reaction tower, and therefore without particularly affecting the overall operating conditions. The goal is to find a way to keep the ore level constant.

[Means to solve the problem]

The present invention has achieved this objective by detecting the surface level of ore particles in the downcomer and supplying ore powder directly into the downcomer when the detected level falls below a certain level.

[Effect]

The particle surface level is recovered by detecting the particle surface level in the particle downcomer pipe and temporarily supplying fine ore from a supply mechanism having a relatively large fine ore supplying capacity that can quickly respond when the level decreases. This prevents gas from blowing into the particle downcomer pipe, making stable reduction operation possible at all times.

〔Example〕

The present invention will be explained below based on the embodiment shown in FIG.

In the figure, a fluidized-bed reduction furnace 10 includes a riser 1 that forms a reaction layer and a downcomer 2 that forms a route for returning the partially reduced particles to the riser 1 again.

Referring to the same figure, powder ore 4 supplied from raw material supply port 3
is reduced by forming a fluidized bed by the reducing gas 5 supplied from below the riser 1. The reducing gas 5 after the reaction enters the cyclone 6, and the particles entrained in the gas return to the riser pipe 1 via the downcomer pipe 2.

In the process, some of the products are the lower part of the downcomer pipe 2,
Alternatively, it is collected from the product outlet 8 at the bottom of the fluidized bed. Further, 9 indicates a supply mechanism that directly supplies fine ore to the downcomer pipe 2. The supply mechanism 9 includes a level meter 11 attached to the downcomer pipe 2, and a fine ore hopper 13 having an opening/closing mechanism 12 that opens and closes in response to a signal from the level meter 11.

As the level meter 11, for example, Japanese Patent Application No. 63-692
By using the two-point level detection method disclosed in the No. 39 application, more precise level control becomes possible.

This supply mechanism 9 opens the opening/closing mechanism 12 of the fine ore hopper 13 to supply ore into the downcomer pipe 2 when the particle surface level in the downcomer pipe becomes below the control lower limit level as determined by the level meter 11 .

When the ore level in the downcomer pipe 2 exceeds the control level, the opening/closing mechanism 12 is closed and the supply of fine ore is stopped.

As a result, it is possible to quickly respond to a drop in the ore level in the downcomer pipe 2, minimize level fluctuations, and stabilize the operation of the circulating fluidized reduction furnace.

〔Effect of the invention〕

The following effects can be achieved by the present invention.

(1) Since it is possible to prevent particle surface level fluctuations and blow-through in the downcomer pipe while keeping the particle downcomer capacity small, stable operation is possible without changing the basic structure of the circulating fluid reduction reactor.

(2) Since the residence time of particles in the downcomer tube can be reduced, the drop in particle temperature can be reduced, and the operating efficiency of the entire apparatus can be increased, thereby improving thermal efficiency.

(3) Stable operation is maintained, reduction progresses smoothly, and productivity improves.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. 1: Ascending pipe 2: Descending pipe 3: Raw material supply port 4: Powder ore 5: Reducing gas 6: Cyclone 7.8: Product outlet 9: Fine ore supply mechanism

Claims (1)

[Claims] 1. The surface level of ore particles in the downcomer is detected, and when the detected level drops below a certain level, fine ore is directly supplied into the downcomer from an external system to reduce the ore particles in the downcomer. A method of operating a circulating fluidized-bed reduction furnace for fine ore to adjust the surface level. 2. A circulating fluidized ore reduction furnace for fine ore, which is provided with a detection mechanism that detects the surface level of ore particles in the downcomer, and a supply mechanism that supplies fine ore into the downcomer based on a signal from the detection mechanism.