JPH04224611A - Method for controlling holdup quantity of ore in circulating fluidized bed pre-reduction furnace - Google Patents

Abstract

PURPOSE:To control holdup quantity of ore existing in a fluidized bed reaction tower in the subject furnace consisting of a fluidized bed reaction tower 1, cyclone 2, downcomer 3, granular ore circulating device 4, ore supply pipe 6 and ore discharge pipe 7. CONSTITUTION:The gas is supplied from the granular ore circulating device 4 in the circulating fluidized bed pre-reduction furnace and while promoting the fluidity in the system, by temporarily adjusting ore supplying rate and ore discharging rate, control of the holdup quantity of ore in the furnace is easily implemented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the amount of ore retained when powdered ore used in a smelting reduction method is pre-reduced in a circulating fluidized bed pre-reduction furnace.

0002

2. Description of the Related Art FIG. 4 shows an overall flow sheet of an apparatus for melting and reducing powdered ore. The smelting reduction furnace 10 is supplied with carbonaceous material 11 from above, gas 12 is blown into it from below, the carbonaceous material is combusted to generate reducing gas, and preliminary reduced ore (fine ore) is supplied from the preliminary reduction furnace 20. 22 is melted down and the molten metal 14 is discharged. The preliminary reduction furnace 20 introduces the high-temperature reducing gas 13 containing reducing components generated in the smelting reduction furnace 10, supplies fine ore 21 for preliminary reduction, and discharges the preliminary reduction ore 22. Exhaust gas 23 is released. In this pre-reduction furnace 20, as shown in FIG. 1, the ore discharged from the pre-reduction reaction tower 1 is recovered by a cyclone 2, etc., and is circulated back to the pre-reduction reaction tower 1 via a downcomer 3 to increase the pre-reduction rate. A so-called circulating fluidized bed pre-reduction furnace is used.

[0003] When the smelting reduction furnace 10 and the circulating fluidized bed pre-reduction furnace 20 as described above are directly connected to smelt and reduce ore, the pre-reduction of the ore in the pre-reduction furnace 20 depends on the operating state of the smelting reduction furnace 10. It is necessary to change the rate. In this case, adjusting the amount of ore retained in the reaction tower 1 of the circulating fluidized bed pre-reduction furnace is very effective in adjusting the pre-reduction rate.

Conventionally, the control of the amount of ore retained in the reduction reaction tower in a circulating fluidized bed pre-reduction furnace was disclosed in Japanese Patent Application Laid-Open No. 63-57709.
As shown in the publication, this has been carried out by adjusting the circulation rate by sending ore particles from the bottom of the downcomer into the reaction tower using a pneumatic valve.

[0005]

[Problem to be solved by the invention] However, the fluidity of powdered ore changes significantly depending on the ore brand, reduction rate, temperature, particle size distribution, etc., so it is necessary to move the powder using a carrier gas with a pneumatic valve. When controlling the amount of ore retained in the reaction tower by adjusting the circulation rate, it is not possible to grasp the fluidization state of the ore particles circulating in the system, so the controllability of the particle circulation rate is poor. The amount of retention in the system must be adjusted through trial and error. As a result, the adjustment not only takes time but also has poor controllability. The present invention has discovered that a circulating fluidized bed pre-reduction furnace has self-control properties, and provides a method for controlling the amount of ore retention using a simple method.

[0006]

[Means for Solving the Problems] The present invention provides a fluidized bed prereduction reaction tower equipped with an ore supply pipe, an ore discharge pipe, a reducing gas introduction pipe, and a carryover pipe, a cyclone connected to the carryover pipe, and a cyclone connected to the bottom of the cyclone. In a method for controlling the amount of ore retained in a circulating fluidized bed pre-reduction furnace, which comprises a downcomer equipped with an ore discharge pipe or a supply pipe, and a particle circulation device that supplies raw materials from the downcomer to a fluidized bed pre-reduction reaction tower, gas is supplied to the particle circulation device. The amount of ore retained in a circulating fluidized bed characterized by adjusting one or both of the ore supply rate and ore discharge rate while promoting fluidization of the entire system in the circulating fluidized bed pre-reduction furnace. This is a control method. This adjustment may be continuous or intermittent.

The method of the present invention will be explained in detail below with reference to the drawings. FIG. 1 shows an example of a circulating fluidized bed pre-reduction furnace to which the present invention is applied. The ore is fluidized in the reaction tower 1, and the ore particles are blown up by the high-temperature reducing gas 13 rising inside the reaction tower 1, enter the cyclone 2 through the carryover pipe 9, and are separated into solid and gas. Exhaust gas 23 is exhausted. The separated ore descends through the downcomer 3, passes through the particle circulation device 4, and returns to the reaction tower 1 again. In the downcomer 3, the ore particles are descending at a relatively high speed, and although the main stream of the reducing gas rises in the reaction tower 1, pressure loss occurs in the cyclone 2, so some of the reducing gas is transferred to the particle circulation device 4. The water rises inside the downcomer 3 and flows into the cyclone 2. As a result, the present inventors found that the ore particles in the downcomer 3 exhibit a state close to fluidization. Therefore, if the ore is slightly fluidized in the particle circulation device 4, the ore particles will be fluidized throughout the entire system of the circulating fluidized bed pre-reduction furnace including the reaction tower 1 and the downcomer 3. Therefore, the amount of ore in the reaction tower 1 and the amount of ore in the downcomer 3 are balanced. In other words, if the ore particles are brought into a slightly fluidized state in the particle circulation device 4, the entire system of the circulating fluidized bed pre-reduction furnace can be self-controlled without directly controlling the particle circulation amount as in the prior art. As a result, ore corresponding to the amount of ore naturally present in the system will remain in the reaction tower 1. Therefore, the amount of ore present in the reaction tower can be controlled by adjusting the amount of ore present in the entire system of the circulating fluidized bed pre-reduction furnace.

[0008]

[Operation] As described above, the ore particles are in a fluidized state in the reaction tower 1, and in the downcomer 3, the slightly fluidized particles are in a state where they flow easily like water. Therefore, if the particles are fluidized or nearly fluidized in the particle circulation device 4, if there are many particles in the downcomer 3, the particles will flow to the reaction column 1 side until the pressure is balanced. However, if there are many particles on the reaction column 1 side, the particles will move to the downcomer side until the pressure is balanced. Therefore, if the amount of ore present in the entire system of the circulating fluidized bed pre-reduction furnace is increased, the amount of ore present in the reaction tower will increase, and if the amount of ore present in the entire system is decreased, the amount of ore present in the reaction tower will be reduced. I can do it. In other words, the reaction tower 1 and the downcomer 3 act like a liquid communication pipe for the ore particles in a fluidized state.

[0009] It is difficult to align the levels of the powder that normally exists in the communicating pipe on the left and right sides. If the levels on the left and right sides of the communicating tube are changed after fluidizing the powder, the position will change in the direction of balance, making it easier to match the levels. Specifically, the amount of ore in the reaction tower can be changed as follows. When increasing the amount of retained ore, the ore discharge rate from the discharge pipe 7 is kept constant and the supply pipe 6 is temporarily closed.
The ore feeding speed may be increased, or the ore discharging speed may be decreased and the ore feeding speed may be increased at the same time, or the ore discharging speed may be reduced while maintaining the ore feeding speed. On the other hand, if you want to reduce the amount of ore, it is obvious that you can do the exact opposite.

As shown in FIG. 2, the particle circulation device 4 includes a dispersion plate 43 provided at the bottom of a cylinder 42.
On the other hand, a powder inflow pipe 41 from the downcomer is connected above the dispersion plate 43, and a powder outflow pipe 44 to the fluidized bed reactor is connected above it. It may be an installed device. When fluidizing gas 45 is blown into this particle circulation device to fluidize the powder in the cylinder 42, the powder flows in the direction of the arrow 46, for example, when the level of the powder on the downcomer side is high.

[0011]

[Example] Fig. 3 shows an example in which the amount of ore retained in the reaction tower was controlled by the method of the present invention in a circulating fluidized bed pre-reduction furnace using a reaction tower with an inner diameter of 700 mm and a height of 7.3 m. The main test conditions are as follows. Reduction temperature: 680-770℃ Ore: Harmonic mean diameter of Brazilian iron ore: 165 μm Reducing gas amount: 3764 Nm3 /H Reducing gas composition:
H2 = 14.6%, CO = 40.7%, CO2 = 0.
8%, H2 O = 0.6%, N2 = 43.3%. Flow rate of N2 flowed to slightly fluidize the ore in the circulation device = 0.
65m/s As shown in Figure 3, the ore supply rate and ore discharge rate can be reduced by simply flowing gas at a rate of 0.65m/s without controlling the circulation rate of ore particles at all using the particle circulation device. It is clear that it is possible to accurately and stably adjust the amount of ore in the reaction tower by adjusting.

0012

[Effects of the Invention] According to the present invention, in a circulating fluidized bed pre-reduction furnace, the particle circulation rate can be adjusted without adjusting the particle circulation amount using a particle circulation device.
By simply adjusting the ore feed rate and ore discharge rate, the amount of ore in the reaction tower can be accurately and stably controlled.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a circulating fluidized bed pre-reduction furnace in which the present invention is implemented.

FIG. 2 is a configuration diagram of a particle circulation device.

FIG. 3 is a graph showing changes in the amount of ore in the reaction tower, the ore feeding rate, and the ore discharge rate when the present invention is carried out.

FIG. 4 is an overall flow sheet of the melting reduction apparatus.

[Explanation of symbols]

1 Reaction tower 2 Cyclone 3 Downcomer 4 Particle circulation device 5 Reducing gas introduction pipe 6 Ore supply pipe 7 Ore discharge pipe 8 Coarse particle extraction pipe and emergency extraction pipe 9 Carryover pipe 10 Melting reduction furnace 20 Pre-reduction furnace 41 Particles from the downcomer Inlet pipe 42
Particle supply pipe 43 to reaction tower Gas distribution plate

Claims (1)

[Claims] Claim 1: A fluidized bed prereduction reaction tower, a cyclone connected to its carryover pipe, a downcomer connected to the bottom of the cyclone and equipped with an ore discharge pipe or a supply pipe, and a fluidized bed prereduction reaction tower from the lower end of the downcomer. In a method for controlling the amount of ore retention in a circulating fluidized bed pre-reduction furnace comprising a particle circulation device that supplies raw materials, gas is supplied to the particle circulation device to promote fluidization of the entire system in the circulating fluidized bed pre-reduction reactor. A method for controlling the amount of ore retained in a circulating fluidized bed, the method comprising adjusting the ore supply rate and/or ore discharge rate.