JPH0472154B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to high temperature fluidized beds with particle circulation, and more particularly to high circulation rates and devices for improving the controllability of this circulation rate.

[Conventional technology]

The high-speed fluidized bed was developed as a so-called FCC process for catalytic thermal decomposition of light oil or residual oil, etc. Due to its good thermal efficiency and reaction efficiency, it is suitable for combustion gasification reactions of coal and coke, activation of activated carbon, and reduction of fine ore. It is also applied to

However, there are still many unknown points regarding the amount of particle circulation in a high-speed fluidized bed and its controllability, and various proposals have been made.

The first example of these conventional methods is "Chemical Engineering Society, 51st Annual Meeting, Research Presentation Abstracts, C315,
1986, "Horio et al." reports on a coal combustion experiment entitled "High-speed fluid combustion characteristics of coal using a transparent circulating fluidized bed."

In this experimental device, as shown in Figure 7,
High-speed fluidized bed consists of 100 quartz tubes and 10 stainless steel tubes.
The raw coal is fed to the bottom of the riser, fluidized and combusted in the riser, and particles containing unburned coal pass through the first cyclone and pneumatic valve 14 and return to the riser. , and the ash is transferred from the lower part of the pneumatic valve 14 to the hopper 1 via the rotary valve 107.
It was taken out on 08.

As described above, a pneumatic valve is used for the circulation of particles in the first example, and the amount of circulation of particles is regulated by air injection from the horizontal and vertical directions.

In addition, as a second example of the conventional method, “&EC Proc,
Des., & Dev.15, 47 (1976), Yerushalmi, j.et
al.'' reported the radial particle distribution in the cross section of a high-speed fluidized bed.

As shown in FIG. 8, the apparatus used in this experiment has a U-shaped tube 16 connecting an ascending pipe forming a high-speed fluidized bed and a descending pipe forming a moving bed.

An air inlet is provided at the bottom of this U-shaped tube 16, and a butterfly valve 15 is provided at the downhill tube, and by adjusting these, the circulating amount of particles is controlled.

[Problem to be solved by the invention]

Among the above-mentioned conventional technologies, the first example, the inclined tube type circulating fluidized bed with a pneumatic valve at the bottom, is suitable for high-temperature operation because it does not use a mechanical valve, but it There are many curved pipe parts, and there is a problem that a high circulation rate of particles cannot be obtained.

Further, although the circulating fluidized bed of the second example having a U-shaped lower part can achieve a high circulation rate, the circulation rate is controlled by the opening degree of a slide valve or a butterfly valve attached to the downcomer side.

This is because the amount of circulation is greatly affected by the velocity of the fluidizing gas, and it is difficult to control the amount of circulation independently of the fluidizing gas unless a valve is installed.

Therefore, although it is good at low temperatures, at high temperatures it has the drawbacks of deterioration of the valve material and difficulty in controlling the fluidizing gas.

The present invention solves these conventional problems,
In the circulating fluidized bed, a high circulation rate of particles per unit cross-sectional area and unit time of the device is obtained at both low and high temperatures, and with respect to the main fluidizing gas,
The purpose is to obtain a high-speed fluidized bed structure that can independently control the amount of particle circulation and has good controllability of the amount of circulation.

[Means to solve problems]

In order to achieve this objective, the present inventors have conducted intensive research on an apparatus that can obtain a high circulation rate of particles at high temperatures and also have a structure that allows good control of the circulation rate, and as a result has arrived at the present invention.

That is, in the high-speed fluidized bed of the present invention, high-temperature particles are circulated through a circuit consisting of a riser, a solid-gas separation chamber, a downcomer, and an inclined pipe, and a high-speed fluidized bed is formed in the riser. 30± to axis
At an angle of 10 degrees, the inclined pipe is connected from above to a confluence section located below the riser pipe and connected by a path with a cross-sectional area equal to or larger than that of the riser pipe, and the cross-sectional area and slope of the confluence section are The cross-sectional area of each of the downcomer pipe and the downcomer pipe is 1 to 5 times the cross-sectional area of the riser pipe, and the main fluidizing gas outlet is opened at a position above the confluence part, and the This is a high-speed flow device with a high circulation rate, which is characterized by providing a gas outlet at the bottom of the inclined pipe and the confluence section.

Next, the present invention will be explained using examples and drawings.

As shown in FIG. 1, the circulating high-speed flow device of the present invention includes a rising pipe 1, a settling chamber 2, a descending pipe 3, and an inclined pipe 5.
and a cyclone separator 4 as a main part, and a main fluidizing gas supply port 6, a fluidized bed lower gas supply port 7, an inclined pipe gas supply port 8, a raw material supply port 9 and a reactant extraction port 10 are attached to this. It consists of

First, a confluence section 12 with the inclined pipe 1 is formed below the ascending pipe 1. As shown in FIG. 2, this merging section 12 has a cylindrical or square tube shape having a cross-sectional area equal to or larger than that of the rising pipe 1, and its upper part is smoothly contracted and connected to the lower end of the rising pipe.

At this junction, the angle θ formed by the axis of the inclined pipe with respect to the vertical axis of the rising pipe 1 is 30±.
The inclined pipe 5 is connected to the confluence part 12 so as to form an angle of 10°. Further, the cross-sectional area of the confluence section 12 is 1 to 5 times the cross-sectional area of the straight pipe section of the riser pipe 1.

A main fluidizing gas blowing pipe 6 is connected to the confluence part 12.
is provided, and the tip of this blow-off pipe 6 is connected to the confluence part 12.
The opening is made at the upper end position 13 or slightly above this, and a gas outlet 8 is provided in the vicinity of the confluence part 12 of the inclined pipe 5.

Furthermore, the respective pipe diameters of the downcomer pipe 3 and the inclined pipe 5 are as follows:
These pipe cross-sectional areas are 1 to 5 of the pipe cross-sectional area of riser pipe 1.
Select so that it is twice as large.

In addition, a gas outlet 7 is provided at the bottom of the confluence section 12,
In addition, a particle feed port 9 is provided at the connection between the confluence section 12 and the riser pipe 1, and a reactant extraction port 10 is provided in the inclined pipe 5 near the connection between the descender pipe 3 and the inclined pipe 5. form a circulation circuit.

[Function] The high-speed fluidized bed apparatus of the present invention configured as described above functions as follows.

First, a predetermined reaction gas is supplied to the lower part of the riser pipe 1 from the opening at the tip of the main fluidizing gas blow-off pipe 6, and then a predetermined amount of particles is supplied from the particle feed port 9 to the riser pipe 1 and settle. The particles are circulated through a circuit consisting of chamber 2, downcomer 3, ramp 5 and merging section 12.

Next, the amount of particles supplied from the particle feed port 9 and the type and amount of gas supplied from the main fluidizing gas blow-off pipe 6 are selected depending on the operational purpose, respectively.
Adjust to the specified conditions.

At this time, the circulation circuit is heated and kept warm by known means (not shown).

In this way, a high-velocity fluidized bed is formed in the riser 1, and the mixed phase of particles and gas undergoes major reactions while rising through the riser 1.

The solid-gas mixed phase is then discharged into settling chamber 2, where coarse particles are separated, and the remaining mixed phase containing fine particles and gas is sent to cyclone separator 4, where it is separated into fine particles and reacted gas. The fine particles flow down the lower part of the cyclone separator and join the coarse particles in the downcomer pipe 3, and the remaining reacted gas is circulated or taken out of the system for separate treatment.

On the other hand, the coarse particles separated in the settling chamber 2 are transferred to the downcomer pipe 3.
The particles flow down inside the inclined pipe 5, then reach the confluence section 12, and are injected into the riser pipe 1 by the fluidizing gas supplied from the main fluidizing gas blow-off pipe 6. This process is repeated, and the particles circulate through the circuit. A predetermined reaction is then carried out.

In such a particle circulation circuit, for example, by using iron sand of a predetermined particle size as the particles and CO gas as the reaction gas, reduced iron is transferred to the reactant extraction port 1.
The CO ₂ gas is recovered from the cyclone separator 4 and discharged to the top of the cyclone separator 4 as a reacted gas.

In the above-mentioned invention, the ascending pipe 1 and the inclined pipe 5 are connected at the confluence part 12 so that their axes form an angle of 30±10°, preferably 30°. This reduces the frictional resistance between the particles and the inner wall of the tube when they descend inside the inclined tube, making it easier for the particles to flow down.

When this angle θ exceeds 40°, the force of restraining the particles against the bottom wall of the inclined tube 5 increases, and the descent of the particles is inhibited. Furthermore, if the angle θ is less than 20°, the particles change direction rapidly from the inclined pipe 5 to the merging portion 12, and the frictional resistance between the particles and the pipe wall due to bending increases, and the movement of the particles is inhibited.

For the above reasons, in the present invention, the inclined pipe 5 and the rising pipe 1 are
their respective axes meet at an angle of 30±10°, thereby providing a high circulation rate of particles in the high-speed flow circuit.

Furthermore, the cross-sectional area of the merging portion 12 between the inclined pipe 5 and the rising pipe 1 is 1 to 5 times that of the rising pipe, and the upper end of the merging portion 12 and the rising pipe 1 are
Smoothly connect the bottom edge of.

If the cross-sectional area of the confluence section 12 is less than one time the cross-sectional area of the rising pipe 1, particles moving through the inclined pipe 5 and the confluence section 12 will be inhibited from moving due to frictional resistance with these inner tubes. Therefore, a high circulation rate cannot be obtained, and the fluidized bed becomes dilute and the reaction progresses slowly.

In addition, if the cross-sectional area of the confluence section 12 is more than five times the cross-sectional area of the riser pipe 1, the overall fluid resistance of the particles will be reduced, but on the other hand, the amount of particles retained will be excessive, which will affect the uniformity of the reaction and the energy consumption. Unfavorable from the viewpoint of
Moreover, pressure fluctuations become large, making stable operation impossible.

Further, for the same reason as above, the diameters of each of the downcomer pipe 3 and the inclined pipe 5 are selected such that the cross-sectional area of these pipes is 1 to 5 times the cross-sectional area of the riser pipe 1.
As a result, the particles in the downcomer pipe 3 and the inclined pipe 5 are
Facilitates the movement of particles as they descend through these tubes.

Furthermore, in the present invention, the main fluidizing gas blow-off pipe 6 provided below the riser pipe 1 penetrates the confluence section 12 and opens near the confluence section upper end 13.

As a result, the particles in the confluence section 12 receive a suction effect due to the injection of the main fluidizing gas, and their transport into the riser pipe 1 is promoted. At this time, from the gas outlet 7 at the bottom of the confluence section 12, gas is supplied in an amount that is 1 to 2 times the fluidization start speed (U _nf ) in the confluence section to fluidize the particles in the confluence section 12. , which facilitates particle transport into the riser 1 by the main fluidizing gas.

If the amount of this gas is less than 1 times U _nf , the effect of fluidizing the particles in the confluence section will be weak, and if this gas amount is more than twice U nf, good results will be obtained for the flow of particles in the confluence section, but on the other hand, the inclined pipe 5 This is undesirable because it impedes the descent of particles from the merging portion 12 to the merging portion 12.

For this reason, the amount of gas supplied to the gas outlet 7 at the bottom of the merging section is set to 1 of U _nf at the merging section.
〜2 times.

Further, the inclined pipe 5 is supplied with an amount equal to or less than three times the U _nf in the inclined pipe from the gas outlet 8 located close to the confluence section 12, thereby fluidizing the particles moving inside the inclined pipe 5. , which eliminates the drop in descending velocity associated with particle pulsation, known as the static-slip flow phenomenon.

Further, even if the gas supply from the gas outlet 8 is zero, the particles are circulated only by the gas supply from the gas outlet 7, and in this case, controllability is particularly good in a range where the amount of particle circulation is small.

The amount of gas supplied to this gas outlet 8 is adjusted as appropriate depending on the operating conditions, and the upper limit of this gas supply amount is set.
Use 3 times the amount of U _nf . If the amount is more than this, it is not preferable because it inhibits the particles from descending in the inclined pipe 5 and further in the downcomer pipe 3.

By continuously supplying gas below the inclined tube 5 in this way, the descending speed of particles within the tube is increased, and the amount of particle circulation within the system is increased.

The present invention combines each member having the above-mentioned functions, and due to their synergistic effect, there is no mechanically moving part, good controllability, and high-speed flow with high circulation rate over a wide range from low to high temperatures. It is what realizes the layers.

Example 1 The riser section of the fluidized bed is 40A (inner diameter 38.4mm), height 3m, and the downcomer and inclined pipe are 65A (inner diameter 70.3mm).
mm), using the device of the present invention with an inclined tube angle of 30°, iron sand from New Zealand ( _p = 0.16 mm, ρ _s
= 4730Kg/m ³ ) is used, the temperature is 900℃, and the superficial gas linear velocity of the fluidized bed is 7.8m, the amount of gas from the bottom of the fluidized bed is kept constant at 54H/Hr, and the amount of gas from the bottom of the opening is approximately The amount of gas from the gas blowing pipe 8 with an inner diameter of 16.7 mm placed at a position of 15 cm to the inclined pipe is 32, 40, 54,
It was changed to 108N/Hr.

As a result, as shown in Figure 3, the circulating amounts of iron sand based on the cross-sectional area of the fluidized bed were 225, 320, 390, and 520 kg/
^m2 ． It became s.

Note that _p : average particle diameter ρ _s : true density of particles Example 2 Using the same apparatus of the present invention as in Example 1, 17 kg of α-alumina particles ( _p = 0.21 mm, ρ _s = 3970 Kg/m ³ ) were used. Therefore, the superficial gas linear velocity of the fluidized bed is 6.9 at a temperature of 900℃.
m/s, the amount of gas from the bottom of the fluidized bed is 71N.
/Hr or 142N/Hr, and the gas amount to the inclined tube was varied as 30, 52, 72, 107, and 145N/Hr.

The circulating amount of α-alumina particles based on the cross-sectional area of the fluidized bed is 40, 62, 95, 135, and 200 kg/h as shown in Figure 4 when the gas amount from the bottom of the fluidized bed is 71 N/Hr.
^m2 ． It became s. A similar effect was also observed when the amount of gas from the bottom of the fluidized bed was 142N/Hr.

Example 3 The apparatus had the same configuration as Example 1, and the influence on the particle circulation amount was examined when the cross-sectional area of the confluence section and the angle of the inclined tube were changed.

The results are shown in FIGS. 5 and 6, and for both the iron sand and α-alumina particles, under the condition that the gas flow rate of the fluidized bed and the gas flow rate from the gas blowing pipes 7 and 8 are constant, When the angle of the inclined pipe was less than 20° or more than 40°, the amount of particle circulation decreased.

In addition, if the ratio of the cross-sectional area of the confluence section to the cross-sectional area of the riser pipe is less than 1, the particle circulation rate will decrease, the vacancy rate in the riser pipe will increase, and the progress of the reaction will be extremely slow.
At higher temperatures, pressure fluctuations in the fluidized bed became large, making stable operation impossible.

〔Effect of the invention〕

The present invention has developed a highly durable device that does not have mechanical elements in a circulating fluidized bed that circulates high-temperature powder or granular material.

In addition, despite the simple structure, a high circulation rate of particles can be obtained, and the controllability of the circulation rate is good, making it extremely useful in practice.

With the present invention, the particle circulation rate can be reduced to 200Kg/m ² . s or more,
For fine ore, 520Kg/m ² . It has now become possible to achieve a particle circulation amount of more than 1.5 seconds.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the overall assembly of the present invention, Fig. 2a,
b is an enlarged explanatory view of the confluence section of the present invention, FIGS. 3 and 4.
Figure 5 is a graph showing the relationship between the particle circulation speed and the amount of gas blown into the inclined pipe when iron sand and α-alumina particles are used in the present invention, and Figure 5 is a graph showing the relationship between the angle of the inclined pipe and the amount of particle circulation. , FIG. 6 is a chart showing the relationship between the ratio of the merging section cross-sectional area to the riser pipe cross-sectional area and the void ratio and pressure fluctuation, and FIGS. 7 and 8 are assembly illustrations of the conventional example, respectively. 1... Ascending pipe, 2... Sedimentation chamber, 3... Descending pipe, 4... Cyclone separator, 5... Inclined pipe, 6... Main fluidizing gas blow-off pipe, 7... Gas blow-off port, 8... Gas blow-off port, 9... Particles Feedro, 10... Reactant extraction port, 11... Descending pipe and inclined pipe connection part, 12... Merging part of rising pipe and inclined pipe, 13... Merging part upper surface, 14... Pneumatic valve, 15... Butterfly valve, 16
...U-shaped tube.

Claims (1)

[Claims] 1. In a circulating fluidized bed in which high-temperature particles are circulated through a circuit consisting of a riser, a solid-gas separation chamber, a downcomer, and an inclined pipe to form a high-speed fluidized bed within the riser, the angle is 30±10° to the vertical axis of the riser. At an angle of The cross-sectional area of each downcomer pipe is equal to 1 of the cross-sectional area of the riser pipe.
~5 times, the main fluidizing gas outlet is opened above the confluence part, and the gas outlet is provided in the inclined pipe near the confluence part and at the lower part of the confluence part. High circulation rate high speed flow device.