JPH11108561A - Fluidized bed reaction device with interior partition plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the residence time of a particle in a flowing reaction device. SOLUTION: In a fluidized bed reaction device 1 where a supply port 2 of a raw material particle, the supply port of a fluidization gas, and the delivery port 3 of a particle are provided at upper, lower, and side part, respectively, a channel being bent or spirally curved by a partition plate 13 being nearly vertically provided on a gas diffusion plate 7 at the lower part in the flow reaction device 1 is formed, and the residence time of the fluidized raw material particle can be adjusted, the partition plate 13 is set to a position that is higher than that of a splash zone directly above a surface 6 of a dense layer in a fluidized bed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed reactor which is a reactor used for a reaction between a powder and a gas, and more particularly to a method for controlling a residence time distribution of particles in a fluidized bed. The present invention relates to a fluidized bed reactor having a partition plate of the above.

[0002]

2. Description of the Related Art Fluidized bed reactors are widely used for the reaction between powder and gas. Fluidized bed reactors are different from shaft furnaces in that relatively small particles are caused to react by flowing them with a reaction gas.No need to agglomerate the particles and the gas flow velocity Since the starting speed can be increased, a large amount of gas can be introduced per area, and the productivity can be improved.

On the other hand, particles entering a fluidized bed reactor are vigorously stirred by a gas and are in a completely mixed state. Therefore, when particles are continuously supplied and discharged, unreacted or not sufficiently reacted particles are present in the product. Mixed with probability. Therefore, in order to increase the reaction rate of a product to a certain level or more,
It is necessary to greatly reduce the supply speed and discharge speed of the particles, and the productivity is reduced.

In order to compensate for the disadvantages of these fluidized bed reactors, a fluidized bed reactor having a partition plate as shown in FIGS. 3 and 4 has been devised. For example, US Pat.
18,479 and JP-A-8-261658. These prior arts relate to a fluidized bed reactor in which powder is continuously supplied from a particle supply port 22 of a furnace body 21 into a fluidized bed 29 in which the powder is flowing by gas and discharged from a particle discharge port 23. However, a partition plate 26 is provided vertically on the gas dispersion plate 25 so that the supplied powder is not immediately discharged from the particle discharge port 23, and the particles are separated by the partition plate 26. The flow path 24 is formed so as to flow and move in a meandering manner and head toward the particle discharge port 23. That is, the partition plate 26 prevents the particles from being completely mixed, and attempts to create a motion state of the particles that is close to the extrusion flow. In these prior arts, as described in Japanese Patent Application Laid-Open No. 8-261658, the height of the partition plate 26 is set higher than the height at which the fluidized bed is formed, so that the flow path of the bent particles is formed. It has been done.

[0005]

In a fluidized bed, air bubbles that have risen in the fluidized bed burst near the surface of the bed,
A phenomenon in which particles are blown up is observed. For this reason, even if a partition plate is provided to form a flow path for particles, there are particles that jump over the partition plate and are short-circuited to the particle discharge port.In the case of operating conditions with a long particle residence time, the effect of the partition plate is reduced. This causes a problem that the residence time distribution becomes close to a completely mixed state. In order to control the residence time distribution of the particles in the fluidized bed reactor, it is not enough to control the movement of the particles in the fluidized bed part, and the particle concentration in the upper space of the fluidized bed called freeboard is low. It is necessary to prevent particle mixing in the area.

[0006]

SUMMARY OF THE INVENTION The present invention is provided substantially vertically on a gas dispersion plate in a lower portion of a fluidized bed reactor having a supply port for raw material particles, a discharge port for product particles, and a mechanism for supplying a fluidizing gas. In a fluidized bed reactor that forms a curved or helically curved flow path with a partition plate and enables the adjustment of the residence time distribution of fluidized particles, the partition is separated from the height of the splash zone immediately above the surface of the dense layer in the fluidized bed. This is a fluidized bed reactor equipped with a partition plate characterized by having a raised plate.

Further, the present invention is characterized in that the partition plate is made higher than the height of the splash zone just above the surface of the dense layer in the fluidized bed, which is obtained from the space of the partition plate and the superficial velocity of the gas by the relationship of the formula (1). I do.

[0008] ^{H = Dw (0.4Dw -0.36 -0.1)} exp (0.75Uo Dw -0.23) ··· (1) Here, H is the splash zone height (m), Dw is of the partition plate Interval (m), Uo is gas superficial velocity (m / s)
It is.

A splash zone in the field of a fluidized bed is an area in the vicinity of the surface of a dense layer in a fluidized bed in which the phenomenon of rising and falling of coarse particles ejected at the time of rupture of bubbles formed of a reaction gas is present (for example, , "Reaction Engineering of Fluidized Bed" (published in Baifukan 1984, p. 155).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, particles in a fluidized bed reactor are provided with a bent or spiral flow path formed between a partition plate and a device wall or an adjacent partition plate. In addition to moving according to the amount of particles supplied or discharged to the free board, the particles blown up on the free board are also separated by a partition plate having an upper end above the splash zone, so that the particles fall again into the same area, so that the partition plate is removed. It is possible to prevent the particles from jumping and shortcut to the discharge port.

The splash zone can be actually measured by collecting the ejected particles using a specially designed particle sampler, but it is convenient if estimation can be made based on operating conditions. As a result of an experiment by the inventors, it was found that the height of the splash zone had little dependence on the particle properties, gas properties, and the like, and was greatly affected by the spacing between the partition plates and the superficial gas flow velocity. That is, it was found that the height of the splash zone was increased by increasing the interval between the partition plates and by increasing the superficial velocity of the gas. For this reason, many experiments were repeated, and the height of the splash zone when the spacing of the partition plates and the gas superficial gas velocity were changed was determined in the experiment by referring to the experiments and examination results of other researchers, and the A relational expression for calculating the height of the splash zone as a function of the interval and the gas superficial velocity was obtained. As a result, it was concluded that the height of the partition plate in the present invention should be higher than the distance H determined by the equation (1) further above the surface of the dense layer in the fluidized bed. Above this height, almost no increase in the particles injected during the rupture of the gas bubble formed of the reaction gas near the surface of the dense layer in the fluidized bed is observed, and it is not possible to jump over the partition plate and mix into the adjacent region. As a result, it is possible to prevent particles from shortcutting to the outlet.

[0012]

FIG. 1 shows the configuration of a vertical section of a fluidized bed reactor according to one embodiment of the present invention. FIG. 2 is a sectional view a of FIG.
The configuration of the horizontal section of -a 'is shown. A particle supply port 2 and a particle discharge port 3 are provided on the left and right sides of the rectangular fluidized bed reactor 1. Since the particles 4 in the fluidized bed flow so as to overflow to the discharge port and are discharged to the product hopper 5, the level of the surface 6 of the dense layer in the fluidized bed substantially coincides with the position of the opening of the particle discharge port 3. The particle supply port 2 is open to a free board space 9 above the dense layer in the fluidized bed.

An example in which the present invention is applied to a fluid reduction device for iron ore will be described below. From the particle supply port 2, for example, iron ore (iron oxide) via the raw material hoppers 10a and 10b
Supply. When it travels to the particle outlet 3, it reacts with carbon dioxide gas, which is the fluidizing gas 8 blown into the fluidized bed via the gas dispersion plate 7, is reduced and becomes metallic iron, and is discharged from the particle outlet 3. Is done. The reacted gas rises in the freeboard space 9 inside the fluidized bed reactor 1 and is discharged outside the system through the exhaust gas duct 11 and the cyclone 12.

[0014] At this time, if unreacted iron oxide derived from the raw material is mixed with the metallic iron of the product, it is not preferable because the required power in the next melting step increases and the yield of iron decreases.
Therefore, a curved or spirally curved flow path is formed by a partition plate provided almost vertically on a gas dispersion plate in the lower part of the fluidized bed reactor, and the fluidized particles move in the flow path. In this case, particles having extremely short residence time are eliminated, and the residence time distribution width can be reduced. Five partition plates 13 are installed in the fluidized bed reactor vertically with respect to the gas dispersion plate 7 to form a bent channel, and the upper end of the partition plate is located higher than the splash zone just above the surface of the dense layer in the fluidized bed. (FIG. 2). For example, when the gas superficial velocity is 0.8 m / s,
When the partition plates 13 are installed at intervals of 200 mm, (1)
Since the height of the splash zone determined by the equation was about 290 mm, a partition plate was provided in which the upper end of the partition plate was located 400 mm above the surface of the dense layer in the fluidized bed. In order to clarify the effect of the present invention, Table 1 shows the difference in operation results from the comparative example in which the upper end of the partition plate was set at a position lower than the splash zone immediately above the surface of the dense layer in the fluidized bed.

[0015]

[Table 1]

Here, Embodiments 1 and 2 and Embodiment 3
4 and 4 are examples in which the feed rate of the raw material, that is, the production rate is changed in the same apparatus. In the case of the comparative example, the production rate cannot be increased to 0.5 to 0.7 (t / m ² / h) or more when trying to obtain 90% which is the standard of the product reduction rate, but to a level higher than the splash zone. In the example in which the partition plate was extended, the reduction rate increased at the same production rate, and a product with a reduction rate of 90% was obtained even when the production rate was increased.

[0017]

According to the present invention, the particles in the fluidized bed, which are originally in a completely mixed state, are hardly mixed with the particles in the freeboard as well as in the concentrated layer in the fluidized bed, so that the particles become close to an extruded flow. Unreacted particles can be prevented from being mixed into the product, so that the reaction rate of the product can be increased, and at a constant reaction rate, the feed rate can be increased, so that effects such as an improvement in productivity are obtained. The industrial effect is extremely large.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a configuration of a vertical cross section of a fluidized bed reactor according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a horizontal cross section taken along line aa ′ of FIG. 1;

FIG. 3 is an explanatory view showing a configuration of a horizontal section of a conventional fluidized bed reactor.

FIG. 4 is an explanatory diagram showing a configuration of a vertical cross section taken along line bb ′ of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fluidized bed reactor 2 particle supply port 3 particle outlet 4 particles in fluidized bed 5 product hopper 6 dense layer surface in fluidized bed 7 gas dispersion plate 8 fluidizing gas 9 free board space 10a, 10b raw material hopper 11 exhaust gas duct 12 cyclone DESCRIPTION OF SYMBOLS 13 Partition plate 21 Furnace body 22 Particle supply port 23 Particle discharge port 24 Flow path 25 Gas dispersion plate 26 Partition plate 27 Bubbling nozzle 28 Emitted gas 29 Fluidized bed 32, 42 Gas outlet

Claims (2)

[Claims] An inlet for raw material particles, an outlet for product particles,
A bent or helically curved flow path is formed by a partition plate provided almost vertically on a gas dispersion plate in the lower part of the fluidized bed reactor having a fluidized gas supply mechanism, and the residence time distribution of the fluidized particles is measured. In a fluidized bed reactor that enables adjustment,
A fluidized bed reactor having a partition plate therein, wherein the height of the partition plate is higher than the height of the splash zone immediately above the surface of the dense layer in the fluidized bed. 2. The height of the partition plate is set higher than the height of the splash zone immediately above the surface of the dense layer in the fluidized bed, which is obtained from the space of the partition plate and the superficial velocity of the gas according to the relationship of equation (1). A fluidized bed reactor equipped with the partition plate described in the above. H = Dw (0.4Dw ^-0.36 -0.1) exp (0.75Uo Dw ^-0.23 ) (1) where H is the height of the splash zone (m), and Dw is the interval (m) of the partition plate. ), Uo is the superficial velocity of gas (m / s)
It is.