JPH01247519A - Outside circulating type fluidized bed furnace - Google Patents

Abstract

PURPOSE:To improve treating efficiency by arranging plural number of baffle plates in a riser so as to cross rising of fluidized gas to interrupt granule rising while getting on the fluidized gas. CONSTITUTION:The plural number of baffle plats 11 crossing the rising stream of the gas in the inner part of the riser 1 parallel arranging a down comer 2, are arranged as zigzag-state to furnace height direction. Reducing gas blown into the riser 1 is flowed as showing with the arrow mark 13. The fire ore floated in the gas is collided to the bottom face of the baffle plate 11 and separated from the gas stream to circulate the inner part of the riser 1. In this result, the fire ore quantity discharged through derivating tube 3 is made to little and concn. of the fire ore in the furnace can be maintained to high. By this method, the fire ore is actively brought into contact with the fluidized gas and the treatment of preheating, drying, pre-reduction, etc., can be efficiently executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an external circulation fluidized bed furnace used when treating particulate materials such as fine ore with heated gas.

[Conventional technology]

The smelting reduction method is attracting attention as an alternative to the conventional hot metal production technology using a blast furnace. The smelting reduction furnace used in this method can be used [without restrictions on $=l,
It was developed for the purpose of producing molten iron-based alloys using smaller-scale equipment. Furthermore, in order to effectively utilize the reducing power and heat of the exhaust gas generated in the smelting reduction furnace, a method has been developed in which raw ore is preheated and pre-reduced in a fluidized bed furnace as a fluidizing gas.

In addition, an external circulation type fluidized bed furnace is known in which fluidizing gas is blown into the riser constituting the fluidized bed furnace at a high superficial velocity to perform preheating, preliminary reduction, etc. of fine ore at high speed (Unexamined Japanese Patent Publication No. Publication No. 56-105409). In this case, as the superficial velocity of the fluidizing gas increases, the proportion of fine ore that is scattered to the outside from the riser also increases. Therefore, the scattered fine ore is separated and captured from the exhaust gas by a cyclone provided in a downcomer that constitutes an extra-furnace circulation path, and is returned to the fluidized bed furnace.

Regarding this type of fluidized bed furnace, the present inventors have developed a furnace in which a plurality of protrusions are provided in the circumferential direction in order to improve the contact state between the powder and the fluidizing gas inside the riser. It was developed and filed as Japanese Patent Application No. 61-288672. Also,
A furnace with multiple expansion/contraction parts in the direction of the furnace height,
It was filed as Japanese Patent Application No. 1986-286600.

[Problem to be solved by the invention]

However, since the protrusions proposed in Japanese Patent Application No. 61-288672 extend in the direction of the furnace height, a bag-like space is created between adjacent protrusions. The reducing gas that is blown into the furnace as a fluidizing gas is the furnace! In the vicinity, the flow follows this bag-like space, making it easier to rectify the gas flow near the furnace wall, reducing the downward flow of particles generated near the furnace wall, and suppressing the tendency for internal circulation in the riser to increase. , the opportunity for the granular material to come into contact with fresh fluidizing gas is reduced.

Furthermore, in the evaporator disclosed in Japanese Patent Application No. 61-286600, if the rate of change in cross-sectional area of the contracting part and the expanding part is doubled or more, and if the flow of the reducing gas is not made into a sufficiently contracted/expanded flow, the internal circulation of particles will be prevented. It is not possible to increase the amount. That is, in the reduction section, it is necessary to rapidly increase the speed of the reducing gas so that the particles have a large slip with the reducing gas. On the other hand, in the expansion section, it is necessary to sufficiently expand the flow of the reducing gas to reduce the gas velocity and reduce the particle transport ability. Therefore, the diameter and height of the riser become very large.

Incidentally, fine ore charged into a fluidized bed furnace equipped with an extra-furnace circulation path rises within the riser in a state where it is fluidized by reducing gas. At this time, near the top of the riser, the speed difference between the fine ore and the reducing gas, that is, the slip speed, becomes almost zero. Therefore, the fine ore is quickly discharged from the riser along with the gas, and the amount of particles circulating inside the riser is reduced. As described above, since the particle concentration in the riser is low and the particle residence time is short, the reduction rate of fine ore is slow and the efficiency of reducing gas utilization is poor. Here, by increasing the circulation amount of fine ore, the concentration of fine ore in the riser can be increased to a certain extent. However, this requires a large-scale external circulation device.

These problems are not limited to the preliminary reduction of fine ore, but are common to preheating and drying of powder and granules, and to fluidized bed furnaces equipped with an external circulation system, such as coal-fired high-speed fluidized bed furnaces. be.

Therefore, the present invention provides a baffle plate in the furnace that crosses the upward flow of the fluidizing gas, thereby blocking the powder and granules from rising inside the furnace on the fluidizing gas, and moving the powder and granules into a fresh flow. The purpose is to increase treatment efficiency by actively contacting the chemical gas.

[Means to solve the problem]

In order to achieve this objective, the external circulation type fluidized bed furnace of the present invention has a plurality of baffle plates installed in the internal space of the riser provided with the downcomer to prevent the powder and granules accompanied by the fluidizing gas from rising. is provided so as to cross the upward flow of the fluidizing gas.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained using examples with reference to the drawings.

FIG. 1 is a schematic diagram showing a first embodiment of a fluidized bed furnace in which the present invention is applied to preliminary reduction of fine ore.

In this fluidized bed furnace, a downcomer 2 is attached to a riser l that constitutes a fluidized bed main body. This downcomer 2 is
The upper part is connected to the riser 1 by an outlet pipe 3 and the lower part by an inlet pipe 4. The fine ore charged into the riser 1 from the charging pipe 5 is fluidized by the reducing gas blown from the gas injection tuyere 6 opened at the bottom of the riser 1.
Rise inside riser-1.

The fine ore discharged from riser 1 accompanied by gas is
It is fed into the cyclone 7 through the outlet pipe 3. The fine ore separated into solid and gas by the cyclone 7 is returned to the riser 1 from the introduction pipe 4 through the downcomer 2. On the other hand, the gas separated from the fine ore by the cyclone 7 is discharged to the outside of the system via the exhaust pipe 8 as exhaust gas.

In the circulation path of the fine ore that circulates through the riser 1 → outlet pipe 3 → cyclone 7 → downcomer 2 → introduction pipe 4 → riser 1, a fine particle extraction pipe 9 is installed in the middle of the downcomer 2, and the melting and reduction furnace is operated. Depending on the condition, fine-grained reduced ore is extracted continuously or intermittently. Further, a coarse grain removal pipe IO is provided at the lower part of the riser 1, and when the amount of coarse grain powder ore staying in the riser 1 increases, the coarse grain powder ore is taken out from the riser 1 as appropriate.

In the fluidized bed furnace of this embodiment, a plurality of baffle plates 11 are provided inside the riser 1 across the upward flow of gas. The baffle plate 11 has a substantially triangular cross section so that the fine ore that rises with the gas easily collides with it and prevents the growth of the fine ore deposited on the upper surface. Further, as shown in the plan sectional view of FIG. 2, it has an annular cross section that is concentric with the inner wall of the riser l. It is fixed to the inner wall of the riser 1 by appropriate means such as a support arm 12.

The baffle plates 11 are arranged in multiple stages in the furnace height direction of the riser 1, as shown in FIG. By providing the baffle plates 11 in a staggered manner in the vertical direction, the lower baffle plates 11 are prevented from overlapping with the upper baffle plates 11.

As a result, the reducing gas blown into the riser l is
It flows in the furnace as shown by arrow 13. Therefore, the fine ore floating in the gas collides with the bottom surface of the baffle plate 11, is separated from the gas flow, and circulates inside the riser 1. As a result, the amount of fine ore discharged via the outlet pipe 3 is reduced, and the concentration of fine ore in the furnace can be maintained high.

The position of this baffle plate 11 is preferably within a range of 0.8XR from the center of the riser 1, where R is the inner diameter of the riser 1. That is, in this range, fine ore is rising along with the flow of reducing gas. Therefore, the concentration of fine ore in the riser 1 is increased by preventing the fine ore from rising with the baffle plate 11 and allowing it to fall by gravity. In addition,
In the range from 0.8XR to the furnace wall, fine ore descends along the inner surface of the furnace wall, and even if the baffle plate 11 is provided here, it is not effective in preventing the fine ore from rising. Further, as shown in FIG. 1, by providing the baffle plates 11 in a staggered manner in the direction of the furnace height, the fine ore falls over the entire cross section of the riser 1, and the fine ore concentration is uniformly increased.

FIG. 3 is a diagram for explaining a second embodiment in which a baffle plate 11 is provided near the connecting portion 3a of the outlet pipe 3 to the riser 1. In the upper part of the riser 1, that is, in the vicinity of the connection f13a, the slip speed is almost zero, so the fine ore suspended in the gas is easily carried out from the riser 1 by the gas flow. Therefore, by providing the baffle plate 11 in this portion, the fine ore is allowed to collide with the baffle plate 11, thereby promoting solid-gas separation.

As shown in FIG. 4, the riser 1 and the cyclone 7 may be connected by an outlet pipe 3 extending in the Chinese direction. In this example, an inclined plate is arranged as a baffle plate 11 at the connection portion of the outlet pipe 3 to the riser l. This baffle plate 11 narrows the flow path cross-sectional area of the outlet pipe 3,
Fine ore floating in the gas flowing into the outlet pipe 3 collides with the baffle plate 11. As a result, the fine ore is separated from the gas stream and falls from the baffle plate 11 back into the riser 1.

FIG. 5 is a graph specifically showing the effect of this baffle plate 11. Note that the baffle plate 11 in this case was arranged within the riser l in the positional relationship shown in FIG. As is clear from FIG. 5, by providing the baffle plate 11, it was possible to reduce the porosity inside the lid 1 by about 5%. Note that the porosity here represents the existence rate of particles, and is expressed as a ratio of the internal volume of the riser 1 excluding the space occupied by the particles in the furnace. As the porosity decreases, the concentration of fine ore in the riser 1 increases, and the catalytic reaction with the injected reducing gas is efficiently carried out.

For example, a reducing gas with an oxidation degree of 10% is introduced at 2Nm'/
When fine ore with an average particle size of 130 units was reduced by blowing at a flow rate of 150 kg/m's and an external circulation rate of 150 kg/m's,
Reduced ore with a reduction rate of 60% was obtained after a treatment time of 2.5 hours. Further, the degree of oxidation of the exhaust gas discharged from the exhaust pipe 8 was about 30%. On the other hand, when fine ore was reduced under the same conditions without providing the baffle plate 11, it took about 3 hours to obtain reduced ore with a reduction rate of 60%, and the degree of oxidation of the exhaust gas was 25%. Met.

As is clear from this comparison, in this example, the preliminary reduction of the fine ore was carried out quickly and the efficiency of use of the reducing gas was high.

It goes without saying that the present invention is not limited to the preliminary reduction of fine ore described above, but is similarly applicable to preheating of powder or granules, drying, and a single coal-fired high-speed fluidized bed furnace.

〔Effect of the invention〕

As explained above, in the present invention, the baffle plate provided inside the riser prevents the powder and granules accompanied by the fluidizing gas from rising. Therefore, the concentration of the powder in the riser is maintained high, the powder is brought into frequent contact with the fluidizing gas, and processes such as preheating, drying, preliminary reduction, etc. are performed efficiently.

Furthermore, since the amount of powder discharged from the riser is reduced, it is possible to use a cyclone provided in the downcomer that is smaller than the capacity of the fluidized bed furnace.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a fluidized bed furnace in a first embodiment of the present invention, FIG. 2 is a plan cross-sectional view of a part of the leide, and FIGS. 3 and 4 are for explaining other embodiments. , and the fifth
The figure is a graph specifically expressing the effects of the present invention. ■=Riser 2: Downcomer 3: Outlet pipe 3a: Connection part 4: Inlet pipe
5: Charge pipe 6: Gas blowing tuyere 7: Cyclone 8; Exhaust pipe
9: Fine grain extraction pipe 10: Coarse grain extraction pipe
11: Baffle plate 12: Support arm 13: Gas flow patent applicant Nippon Steel Corporation representative
Masu Kobori (2 idiots) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Gas flow velocity (m15)

Claims (1)

[Claims] 1. In the internal space of the riser where the downcomer is attached,
1. An external circulation type fluidized bed furnace, characterized in that a plurality of baffle plates are provided across the upward flow of the fluidizing gas to prevent the powder particles accompanying the fluidizing gas from rising.