JPH04366387A - Operating method for circulation fluidized bed reactor - Google Patents

Abstract

PURPOSE:To cope with a normal operating condition against an abrupt variation in a particle level in a downcomer without affecting influence to a control by feeding gas from below a cyclone into the cyclone in response to the level in the downcomer, etc. CONSTITUTION:The captioned reactor for introducing reducing gas 2 to a fluidized bed of powderlike ore and reducing it, collects powder discharged together with the gas by cyclones 5, 10 and again circulates it to a reaction fluidized bed. In this case, an auxiliary gas introducing unit 9 is provided under the primary cyclone 5. When a particle level in a downcomer 6 or a particle staying amount in a riser 4 is extremely raised, auxiliary gas is sprayed to feed particles moved down to the downcomer 6 to a downstream side from the primary cyclone 5. When the level is returned to a normal level, spraying of the gas is reduced or stopped. Thus, the level can be controlled without varying an extraction amount of a product from a product discharge port 3 or a circulation amount to the riser 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a fluidized bed reducing apparatus which forms a fluidized bed of powdered ore and introduces a reducing gas into the fluidized bed for reduction.

0002

[Prior Art] In such a fluidized bed reduction device, powdered ore is charged into a reaction tank riser, reducing gas is introduced from the bottom of the riser to form a fluidized bed, and the reduced powder is discharged from the top of the bed along with the gas. There is a circulating fluidized bed reactor that collects ore with a cyclone and returns it to the riser using a downcomer, and is used as a preliminary reduction device for powder ore during the production of pig iron by smelting reduction.

[0003] In this fluidized bed reduction apparatus, methods for maintaining the solid-gas reaction of the fluidized bed formed in the riser under optimal conditions are disclosed in, for example, Japanese Patent Laid-Open Nos. 62-228883 and 1-242726. Discloses a method of adjusting the state of fluidized bed formation by measuring the level of particles in the downcomer and discharging the particles in the downcomer from a plurality of discharge ports provided in the downcomer. has been done.

0004

[Problems to be Solved by the Invention] However, in the above method, when the level of particles in the downcomer increases rapidly, the discharge capacity of the outlet provided in the downcomer is increased to remove a large amount of particles at once. The product discharge pipe must be designed with a large capacity so that the product can be discharged.

[0005] In this way, when the capacity of the powder discharge pipe in the downcomer is increased, the controllability of fluidized bed adjustment is improved under normal operating conditions in which a very small amount of powder is discharged relative to the circulating amount. becomes worse.

The problem to be solved by the present invention is to provide a means for coping with rapid fluctuations in the level of particles in the downcomer in the above-mentioned circulating fluidized bed reactor without affecting control under normal operating conditions. The purpose is to find out.

[0007]

[Means for Solving the Problems] The present invention has solved the problems by causing gas to flow into the cyclone from below the cyclone depending on the particle level in the downcomer or the amount of particles retained in the riser.

As a means for introducing gas, an auxiliary gas blowing nozzle for controlling the circulation amount is provided in the downcomer section directly below the cyclone, and the auxiliary gas is injected through this nozzle while controlling the gas amount with the blowing amount control device. An effective method is to supply At this time, the auxiliary gas is caused to flow from the downcomer to the cyclone due to the pressure difference.

[0009]

[Operation] When the particle level in the downcomer becomes extremely low, the pressure seal collapses, causing a large amount of gas to flow into the downcomer from the riser, resulting in inoperability. On the other hand, when the particle level in the downcomer becomes extremely high,
There is a risk that the cyclone will become blocked by particles.
Operation becomes impossible. Such a change in the level of particles in the downcomer is generally caused by the amount of cyclone capture corresponding to the amount fed to the downcomer compared to the sum of the amount of product withdrawn, which corresponds to the amount discharged from the downcomer, and the amount recycled to the riser. This occurs due to an imbalance in the amount of collected particles. conventionally,
While attempts have been made to prevent fluctuations in the level of particles in the downcomer by changing the amount of particles discharged from the downcomer, the present invention mainly focuses on controlling the amount of particles supplied to the downcomer,
In other words, this problem is dealt with by changing the amount of particles collected by the cyclone.

To this end, the present invention provides a mechanism that allows gas to flow in from below the primary cyclone. If it becomes necessary to reduce the amount of particles supplied to the downcomer using this system, an auxiliary gas for controlling the circulating amount with a pressure higher than the internal pressure of the device by at least 1 atm is blown into the downcomer. The particles are transported downstream from the primary cyclone. In addition, if gas flows into the cyclone from below, the collection efficiency of the cyclone will decrease.
The blowing of the auxiliary gas for controlling the circulation amount has an effect more than simply transporting particles upward by gas. Therefore, the effect of reducing the level of particles in the downcomer appears extremely quickly, and the ability to respond to emergencies 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 gas blowing amount, so that the steady state can be achieved. 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 extracted on the particle discharge side from the downcomer and the amount of circulation to the riser are significantly changed. This makes it possible to control the particle level within the downcomer without causing any damage.

[0013]

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

In the figure, this circulating fluidized bed pre-reduction device includes a riser 4 having a raw material supply port 1 provided on the side, a reaction gas inlet 2 and a product discharge port 3 provided at the bottom, and the riser 4. It has an external particle circulation device consisting of a primary cyclone 5 and a downcomer 6 that communicate with the top of the riser 4, and the external particle circulation device communicates with the lower part of the riser 4 through a connecting pipe 8 having a product outlet 7 in the middle. . Also,
Directly 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.

Although the supply of auxiliary gas for controlling the circulation amount is normally stopped, the particle surface level in the downcomer 6 and the amount of particles retained in the riser 4 have increased significantly, and the normal product outlet 7, When a stable state cannot be maintained only by discharging particles from the product discharge port 3, the auxiliary gas introduction device 9 is activated to increase the number of particles discharged to the secondary cyclone 10.

The collected fine ore particles in the secondary cyclone 10 provided following the primary cyclone 5 are temporarily retained in a hopper 12 provided through a discharge pipe 11 and then discharged from an outlet 13.

In the figure, normally the amount of reduced ore discharged from the product discharge port 3 and product take-out port 7 is maintained constant. Under this condition, for example, if the flow rate of the reducing gas introduced from the reaction gas inlet 2 is increased, the riser 4
The amount of powdered ore discharged from the pump to the exhaust system increases, and the amount of powdered ore collected by the primary cyclone 5 increases rapidly. This increases the particle surface level L of the downcomer 6. This downcomer 6 is equipped with a level measuring device using a differential pressure measuring method, and when the measured value exceeds a certain reference value, the auxiliary gas introduction device 9 is activated to provide auxiliary gas for controlling the circulation amount. Inject 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 due to the introduction of the auxiliary gas, so the amount of powder ore collected in the primary cyclone 5 decreases. In this way,
It becomes possible to rapidly reduce the particle level in the downcomer 6.

[0018] When it is found by the level measuring device that the particle level L has reached a predetermined level or less, the gas introduction from the gas introduction device 9 is stopped.

[0019]

[Effects of the Invention] The present invention provides the following effects.

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

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

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

(4) The level of particles in the downcomer and the amount of particles retained in the riser are adjusted by introducing gas, and since no mechanical operation is involved, fewer troubles occur.

(5) It is possible to quickly respond to changes in the amount of cyclone particles collected due to changes in gas amount, particle diameter, etc.

[Brief explanation of drawings]

FIG. 1 shows an overview of a circulating fluidized bed pre-reduction device used to carry out the present invention.

[Explanation of symbols]

1 Raw material supply port 2 Reactant gas inlet 3 Product discharge port 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

Claims (1)

[Claims] Claim 1: In the operation of a circulating fluidized bed reactor in which powder discharged together with gas from a reaction fluidized bed is collected in a cyclone and the collected powder is circulated again to the reaction fluidized bed, A method of operating a circulating fluidized bed reactor in which gas is blown into the cyclone from below the cyclone according to the particle level or the amount of particles retained in the riser.