JPH059530A - Method for operating circulating fluidized bed pre-reduction furnace for powdery ore - Google Patents

Abstract

PURPOSE:To achieve the stabilization of an operation by executing the operation in the suitable range of particle circulating speed in a circulating fluidized bed pre-reduction method for powdery ore. CONSTITUTION:In the operation of a circulating fluidized bed pre-reduction furnace composed of a riser 1, cyclones 10, 11, a downcomer 6 and a particle circulating device 7 for circulating the particles from the downcomer 6 to the riser 1, difference between the particle circulating speed at the inlet side of the first step of cyclone 10 and the particle fly-out speed at the outside of a final cyclone 11, is obtd., and the flow rate of circulating gas 8 blown into the particle circulating device 7 is controlled so that the difference Gs becomes 5-50kg/m<2> (cross sectional area of the riser)&Nsec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a circulating fluidized bed preliminary reduction furnace for powdered ores, and particularly to stabilize the operation of the fluidized bed preliminary reduction furnace and improve productivity.

[0002]

2. Description of the Related Art A fluidized bed preliminary reduction furnace (hereinafter referred to as a riser) that introduces a reducing gas to circulate and fluidize a powdery ore, and a preliminary reduced ore powder discharged together with exhaust gas from the riser. A circulating fluidized bed consisting of one or more cyclones to collect, a downcomer that stores and discharges the preliminary reduced ore powder collected by the one or more cyclones, and a particle circulation device that circulates the preliminary reduced ore powder from the downcomers to the riser. A method of pre-reducing powdery ore using a pre-reduction device is known. As a method of preliminary reduction of powdery ore by such a circulating fluidized bed, when introducing high-temperature exhaust gas generated in a smelting reduction furnace into a riser, the gas flow velocity in the fluidized bed is more important than the particle ejection velocity (particle termination velocity). While introduced at a high speed, the pre-reduced ore powder (hereinafter abbreviated as pre-reduced ore) that has flown out of the riser is collected by a cyclone, and the collected pre-reduced ore is continuously closed in a closed circuit via a particle circulation path. A method of returning to the riser and performing preliminary reduction while circulating and flowing is disclosed in JP-A-1-306515 and JP-A-2-4909.

[0003]

[Problems to be Solved by the Invention] When preliminarily reducing powdery ore in a circulating fluidized bed, improvement of trapping efficiency of pre-reducing reduced ore in cyclone in the circulating fluidized bed is important for stable operation and maintenance of productivity. Will be important. However, in the conventional circulating fluidized bed technology, depending on the riser gas flow rate and the ore brand, ore pulverization occurred, and the collection efficiency in the cyclone decreased. These are mainly because the gas flow rate of the riser, the particle size of the pre-reduction ore, and the ore retention amount in the riser have a large influence on the particle circulation speed of the riser, and they are not operated within an appropriate range. Conventionally, when the particle circulation speed of the riser is excessively high, there was a problem that the ore was worn or markedly pulverized due to thermal cracking, resulting in a decrease in the preliminary reduction rate due to a decrease in particle collection of the cyclone and wear of the cyclone. On the other hand, if the particle circulation speed of the riser is too small, the pre-reduction rate will decrease, or there will be a large amount of ore falling from the lower part of the riser, resulting in unstable operation.
Therefore, an object of the present invention is to provide a circulating fluidized bed pre-reduction method capable of suppressing pulverization of a pre-reduced ore using a circulating fluidized bed, improving cyclone collection efficiency, and stabilizing productivity.

[0004]

According to the present invention, a riser which introduces a reducing gas to circulate and fluidize a powdery ore to preliminarily reduce it and a prereduced ore powder discharged from the riser together with the exhaust gas are collected. Circulating fluidized bed pre-reduction consisting of one or more cyclones, a downcomer that stores and discharges pre-reduced ore powder collected by the one or more cyclones, and a particle circulation device that circulates the pre-reduced ore powder from this downcomer to a riser It is applied to a method of pre-reducing powdery ore using an apparatus.

The present invention is a technique for eliminating the reduction in cyclone particle collection efficiency due to the pulverization of the pre-reducing ore in such a circulating fluidized bed preliminary reduction furnace method, which is the particle circulation speed on the inlet side of the first-stage cyclone. And the particle ejection speed at the exit side of the final stage cyclone, the difference is 5 to 50 kg.
It is characterized in that the circulation amount of the particle circulation device is controlled so that / m ² (riser cross-sectional area) · sec.
This control of the circulation amount is achieved by controlling the amount of gas blown into the particle circulation device.

[0006]

The operation of the present invention will be described with reference to FIG. FIG. 2 is a flow sheet of a circulating fluidized bed preliminary reduction furnace to which the present invention is applied. The reducing gas 2 from a smelting reduction furnace (not shown) is discharged from the riser 1 while fluidizing and reducing the powdery ore in the riser 1, and the cyclones 10 and 11 separate and discharge entrained powder. The separated powder is stored in the downcomer 6,
A part is discharged out of the system, and a part is circulated to the riser 1 through the circulation device 7. This circulation amount is controlled by adjusting the circulation gas 8. In FIG. 2, the particle circulation speed Gs in the riser 1 is represented by the amount of powder on the outlet side of the riser, that is, the particle circulation speed Gsa on the first stage cyclone, under the condition that the particle collection efficiency in the cyclone 10 and the cyclone 11 is 100%. It In actual operation, the particle collection efficiency of cyclone 10 and cyclone 11 is not 100%, but riser 1
The particle circulation speed that continuously circulates through the downcomer 6 and the circulation device 7 via the cyclone 10 is the inlet side particle circulation speed Gsa of the first stage cyclone minus the final stage cyclone side particle ejection velocity Gsb Circulating fluidized bed The particle circulation speed in the preliminary reduction furnace system. Further, although the particle circulation speed Gs is affected by the amount of the reducing gas 2 in the riser 1, that is, the gas flow velocity in the riser 1 and the particle diameter of the ore,
The amount of particle circulation to the riser 1 is from the particle circulation device 7 to the riser 1.
The rate of ore circulation itself to (1) is rate limiting. Therefore, the amount of particles circulated to the riser 1 is determined by the particle circulation gas 8 of the particle circulation device 7.
Controlled by the amount of. On the other hand, the cause of pulverization of ore particles is abrasion between particles and grinding due to contact of refractory materials such as risers and cyclones with ore particles in the circulation system. Ore pulverization due to these factors is suppressed by maintaining the net particle circulation velocity Gs as low as possible, and the cyclone collecting efficiency is also improved.
However, when the particle circulation speed Gs is low, it is difficult to secure the amount of ore retained in the riser, which is disadvantageous in terms of productivity. On the other hand, if the particle circulation speed Gs is too high, ore powdering proceeds, cyclone collection efficiency decreases, and operation becomes unstable.

Therefore, according to the research by the inventors, the particle circulation velocity Gs in the riser = 5 to 50 kg / m ² · sec is an appropriate range. Here, m ² is the cross-sectional area of the riser.
The circulating fluidized bed using powdered ore has a method of collecting the pre-reduced ore that has flown out of the riser with one or more stages of cyclones and continuously returning it to the riser through a particle circulation device in a closed circuit. , It is important that the amount of pre-reduction ore retained in the riser is kept at a certain level and does not fluctuate, and therefore the cyclone collection efficiency is not reduced. In the circulating fluidized bed, the gas flow velocity in the riser, the particle size of the pre-reduction ore and the amount of retention in the riser have a great influence on the particle circulation speed Gs in the riser. Further, in the circulating fluidized bed, there is a phenomenon in which the pre-reduced ore is pulverized due to abrasion or thermal cracking of the ore in the riser, reduction pulverization, etc. In particular, when the gas flow velocity in the riser is high and the amount of stay is large, the particle circulation velocity Gs in the riser is too high and Gs is 5
If it exceeds 0 (kg / m ² · sec), the pulverization of the pre-reduced ore will be further promoted, and the particle collection efficiency in the cyclone will decrease, and at the same time, a large amount of reduced ore that has not been much reduced will fly out of the system. Therefore, the preliminary reduction rate is not improved as a whole.

Further, if the particle circulation velocity Gs in the riser is excessively large, the cyclone is greatly worn and there is a problem in maintaining the equipment. On the contrary, when the particle circulation velocity Gs in the riser is too small and is less than 5 (kg / m ² · sec), the gas flow velocity in the riser is low, or the amount of staying in the riser is small, and the preliminary reduction rate is not improved. Further, when the gas flow velocity is low, the amount of ore falling from the lower part of the riser to the lower gas inlet part is large, which causes a problem of unstable operation. Therefore, the present invention at least determines the difference between the particle circulation speed on the inlet side of the first-stage cyclone and the particle ejection velocity on the outlet side of the final-stage cyclone,
This difference is 5 to 50 kg / m ² (riser cross-sectional area) sec
By controlling the flow rate of the circulating gas blown into the particle circulation device so that it falls within the appropriate range, the powdering of the pre-reduction ore is suppressed, the particle collection efficiency and pre-reduction rate of the cyclone are improved, and the operation is stabilized. Can be planned.

[0009]

FIG. 1 shows an embodiment according to the present invention. Riser 1
800 to 11 discharged from a smelting reduction furnace (not shown)
The reducing gas 2 at 00 ° C. is introduced. Powdered ore is hopper 3
Is cut out by the feeder 4, part of which is inserted into the lower portion of the riser 1 via the supply pipe 5a, and part of which is inserted into the downcomer 6 via the supply pipe 5b. The powdered ore in the downcomer 6 is continuously supplied from the downcomer 6 to the riser 1 by blowing a circulation gas 8 into the particle circulation device 7. Riser 1
The pre-reduced ore 9a that has been pre-reduced therein jumps out from the riser 1 and most of it is collected by the first-stage cyclone 10 and charged into the downcomer 6. Through the particle circulation device 7 in which the circulation gas 8 is blown from the downcomer 6, it is re-introduced into the riser 1 to continuously circulate in a closed circuit,
Perform preliminary reduction. Furthermore, the fine powder pre-reduction ore 9b that could not be collected by the first-stage cyclone 10 is collected by the second-stage (final-stage) cyclone 11 and passed through the transport pipe 12 to the downcomer 7
Will be introduced to. The fine powder pre-reduction ore 9b that could not be collected by the cyclone 11 in the second stage (final stage) jumps out of the system together with the exhaust gas. Next, sampling pipes 13a and 13b are installed on the inlet side of the first-stage cyclone 10 and the outlet side of the second-stage (final-stage) cyclone 11, respectively, and the preliminary reduction ores 9a and 9b are provided.
And sampling devices 14a and 14b, respectively.
After obtaining the amount of pre-reduced ore collected at each measurement point position, the calculation / control device 15 calculates the passing amount of the pre-reduced ore 9a, 9b at each measurement point position, and the particle circulation velocity Gsa, Gsb at each sampling point. Then, the particle circulation velocity Gs in the riser is calculated from Gsa-Gsb, and the circulation gas 8 blown into the particle circulation device 7 is circulated so that the obtained Gs falls within the range of 5 to 50 kg / m ² · sec. The circulating fluidized bed preliminary reduction is performed while controlling with the gas control device 16. Further, the preliminary reduction ore in the circulating fluidized bed preliminary reduction furnace system is cut out from the lower part of the downcomer 6 by the discharge device 17, and is supplied to the smelting reduction furnace via the discharge pipe 18.

Next, the powdery ore is preliminarily reduced by using the preliminary reducing apparatus shown in FIG. 1 having a riser having a diameter of 0.7 m and a height of 7.3 m. : 1.2
m, furnace volume: 7.7 m ³ , upper and lower tuyeres: each was supplied to a smelting reduction furnace having 3 to perform smelting reduction. The results of this operation test are shown in Table 1 together with the test conditions. As shown in Table 1,
In the conforming examples 1 and 2 in which the particle circulation speed Gs in the riser was controlled to be in an appropriate range, the pre-reduction ore pulverization was suppressed, and the particle collection efficiency of the first-stage and second-stage (final-stage) cyclones was improved. A high preliminary reduction rate could be obtained. Contrary to this,
In Comparative Examples 1 and 2 which were operated at the particle circulation velocity Gs in the riser which was not appropriate, the pulverization of the pre-reduced ore became large and the first stage and 2
Particle collection efficiency of the cyclone at the stage (final stage) decreases,
The pre-reduction rate became low. In addition, there were inconveniences such as large wear in the cyclone and a large amount of ore falling from the riser.

[0011]

According to the present invention, by controlling the particle circulation speed Gs of the riser within an appropriate range, it is possible to suppress the pulverization of the pre-reduced ore and improve the cyclone collection efficiency, so that the operation can be stabilized. Therefore, there is an effect that the productivity of the pre-reduction ore can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a circulating fluidized bed preliminary reduction device according to an embodiment of the present invention.

FIG. 2 is a flow sheet illustrating the operation of the present invention.

[Explanation of symbols]

 1 riser 2 reducing gas 3 ore hopper 4 feeder 5a, 5b ore supply pipe 6 downcomer 7 particle circulation device 8 circulation gas 9a, 9b preliminary reduction ore 10 first stage cyclone 11 final stage cyclone 12 transport pipe 13a, 13b sampling device 14a, 14b Sampling device 15 Arithmetic / control device 16 Circulating gas control device 17 Discharge device 18 Discharge pipe

Claims (1)

Claim: What is claimed is: 1. A riser for introducing a reducing gas to preliminarily reduce while circulating and fluidizing a powdery ore, and one or more stages for collecting the preliminary reduced ore powder discharged from the riser together with the exhaust gas. Cyclone, a downcomer that stores and discharges the pre-reduced ore powder collected by this one or more cyclones, and a particle circulation device that circulates the pre-reduced ore powder to the riser from this downcomer. In operation, find the difference between the particle circulation velocity on the inlet side of the first-stage cyclone and the particle ejection velocity on the outlet side of the final-stage cyclone, and make this difference 5 to 50 kg / m ² (riser cross-sectional area) · sec. A method for operating a circulating fluidized bed preliminary reduction furnace for powdery ores, comprising controlling the amount of circulation of the particle circulation device.