JP2981015B2 - Operating method of circulating fluidized bed reactor - Google Patents

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 fluidized bed reducing apparatus for forming a fluidized bed of fine ore and introducing a reducing gas into the fluidized bed to reduce the fluidized bed.

[0002]

2. Description of the Related Art As such a fluidized bed reducing device, powdered ore is charged into a reactor riser, a reducing gas is introduced from below the riser to form a fluidized bed, and the reduced powder discharged together with the gas from the upper part thereof is discharged. There is a circulating fluidized bed reactor in which the ore is collected by a cyclone and then returned to the riser by a downcomer, and is used as a pre-reduction device for powdery ore in the production of pig iron by smelting reduction.

In this fluidized bed reduction apparatus, as a method for maintaining the solid-gas reaction of a fluidized bed formed in a riser under optimum conditions, for example, Japanese Patent Application Laid-Open Nos. 62-228883 and 1-2242726. As described in the above, a method of adjusting the formation state of the fluidized bed by measuring the particle level in the downcomer and discharging the particles in the downcomer from a plurality of outlets provided in the downcomer is disclosed. Have been.

[0004]

However, in the above-mentioned method, when the particle level in the downcomer rises rapidly, the discharge capacity of the outlet provided in the downcomer is increased so that a large amount of particles can be collected at one time. In order to be discharged, the capacity of the product discharge pipe must be designed large.

[0005] As described above, when the capacity of the powder discharge pipe in the downcomer is increased, the controllability for the fluidized bed adjustment under normal operating conditions in which a very small amount of powder is discharged with respect to the circulating amount. Gets worse.

The problem to be solved in the present invention is a means for responding to the rapid fluctuation of the particle level in the downcomer in the circulating fluidized bed reactor without affecting the control under normal operating conditions. Is to find out.

[0007]

According to the present invention, according to the level of particles in a downcomer or the amount of particles retained in a riser, air is blown into the cyclone from immediately below the cyclone.
By Rukoto to control the amount of gas circulation quantity control gas to solve the problem.

[0008] As a means for flowing the gas, a down-commer section just below the cyclone is provided with a nozzle for blowing an auxiliary gas for controlling the amount of circulation , and a particle level in the down-comer is controlled.
Alternatively, it is effective to supply the auxiliary gas through this nozzle while controlling the gas amount by the blowing amount control device in accordance with the amount of particles retained in the riser . At this time, the auxiliary gas is to continue to flow from immediately below the downcomer cyclone to the cyclone by a pressure difference.

[0009]

When the particle level in the downcomer is extremely reduced, the pressure seal collapses, causing a large amount of gas to flow from the riser to the downcomer, resulting in inoperability.
On the other hand, when the particle level in the downcomer rises extremely,
There is a risk that the cyclone will be blocked by particles,
Operation becomes impossible. Such a change in the particle level in the downcomer is generally caused by the sum of the product withdrawal amount corresponding to the amount discharged from the downcomer and the circulation amount to the riser, and the cyclone trapping amount corresponding to the supply amount to the downcomer. This is caused by an imbalance in the amount of collected particles. Conventionally, while trying to prevent the fluctuation of the particle level in the downcomer by changing the emission amount from the downcomer, in the present invention, the amount of particles supplied to the downcomer, that is, the amount of collected particles of the cyclone To deal with it.

For this purpose, the present invention provides a mechanism that allows gas to flow from below the primary cyclone. When it becomes necessary to reduce the amount of particles supplied to the downcomer using this, an auxiliary gas for controlling the circulation amount having a pressure higher than the internal pressure of the apparatus by 1 atmosphere or more is blown, and the gas is lowered to the downcomer. The incoming particles are transported downstream from the primary cyclone. Also, if gas flows into the cyclone from below the cyclone, the efficiency of trapping the cyclone decreases,
The blowing of the circulation amount control auxiliary gas has an effect more than the upward transport of particles by gas alone. Therefore, the effect of lowering the level of particles in the downcomer is manifested very quickly, and emergency response can be greatly improved.

On the other hand, when the particle level in the downcomer returns to the normal control level, the amount of particles supplied to the downcomer can be increased by reducing or stopping the amount of gas blown. Can be easily migrated.

In the present invention, since the particle level in the downcomer is controlled on the particle supply side to the downcomer, the amount of product withdrawn from the downcomer on the particle discharge side and the amount circulated to the riser are particularly changed. Without this, control of the particle level in the downcomer becomes possible.

[0013]

FIG. 1 shows an outline of a circulating fluidized bed pre-reduction apparatus to which the present invention is applied.

Referring to FIG. 1, the circulating fluidized bed pre-reduction apparatus includes a riser 4 having a raw material supply port 1 provided on a side surface, a reaction gas introduction port 2 provided on a bottom and a product discharge port 3, and a riser 4 having the same. Has a primary cyclone 5 and a downcomer 6 communicating with the top of the riser. The external particle circulation device communicates with the lower part of the riser 4 by a connecting pipe 8 having a product outlet 7 in the middle thereof. . Also,
Immediately below the primary cyclone 5 of the external particle circulation device, an auxiliary gas introduction device 9 for controlling the amount of circulation is provided.

The supply of the auxiliary gas for controlling the circulation amount is normally stopped, but the surface level of the particles in the downcomer 6 and the amount of the particles retained in the riser 4 are greatly increased. If the stable state cannot be maintained only by discharging the particles from the product discharge port 3, the auxiliary gas introducing device 9 is operated to increase the particles discharged to the secondary cyclone 10.

The collected ore particles in the secondary cyclone 10 provided after the primary cyclone 5 are temporarily stored in a hopper 12 provided through a discharge pipe 11 and then discharged from a discharge port 13.

In FIG. 1, normally, the amount of reduced ore discharged from the product outlet 3 and the product outlet 7 is kept constant. In this state, for example, when the flow rate of the reducing gas introduced from the reaction gas introduction port 2 is increased, the riser 4
The amount of fine ore discharged from the exhaust system to the exhaust system increases, and the amount of fine ore collected by the primary cyclone 5 sharply increases. Thereby, the particle surface level L of the downcomer 6 increases. The downcomer 6 is provided with a level measuring device based on a differential pressure measuring method. When the measured value exceeds a certain reference value, the auxiliary gas introducing device 9 is operated to control the auxiliary gas for controlling the circulation amount. Blow gas. The blown gas flows toward the primary cyclone 5 due to the pressure difference. As a result, in the primary cyclone 5, the differential pressure decreases on the collection side by the introduction of the auxiliary gas, so that the amount of collected fine ore in the primary cyclone 5 decreases. In this way,
The particle level in the downcomer 6 can be rapidly reduced.

When it is found by the level measuring device that the particle level L has reached the specified level or less, the gas introduction from the gas introducing device 9 is stopped.

[0019]

According to the present invention, the following effects can be obtained.

(1) The particle level of the downcomer and the amount of particles retained in the riser can be adjusted while keeping the amount of reduced ore discharged from the lower part of the riser and the downcomer constant.

(2) Since the amount of the reduced ore discharged from the lower portion of the riser and the downcomer can be stabilized at a certain level, the stable operation of the reaction layer is possible.

(3) The particles in the downcomer can be rapidly extracted, which is extremely effective as an emergency measure.

(4) The particle level of the downcomer and the amount of retained particles in the riser are adjusted by gas introduction, and there is no mechanical operation.

(5) It is possible to quickly respond to a change in the amount of cyclone particles collected due to a change in the gas amount, particle diameter, and the like.

[Brief description of the drawings]

FIG. 1 shows an outline of a circulating fluidized bed pre-reduction apparatus used for carrying out the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 raw material supply port 2 reaction gas inlet 3 product outlet 4 riser 5 primary cyclone 6 downcomer 7 product outlet 8 connecting pipe 9 auxiliary gas introduction device 10 secondary cyclone 11 discharge pipe 12 hopper 13 outlet

(56) References JP-A-1-118090 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F27B 15/00 C21B 11/00

Claims (1)

(57) [Claims] In the operation of a circulating fluidized bed reactor in which powder discharged together with gas from a reaction fluidized bed is collected by a cyclone, and the collected powder is circulated again to the reaction fluidized bed, a downcomer is used. be in accordance with the particle level or riser inside the particle retention amount of control the amount of gas circulation quantity control gas which blows towards the cyclone from just below the cyclone
A method for operating a circulating fluidized bed reactor, comprising: