JP3345723B2 - Fluidized bed or tumbling fluidized bed granulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed or a tumbling fluidized bed granulator capable of measuring and controlling the height of a powder bed in tumbling fluidized bed granulation or the like.

[0002]

2. Description of the Related Art FIG. 11 is a sectional view showing a basic structure of a general fluidized bed granulator or a tumbling fluidized bed granulator. In this granulating apparatus, a wire mesh or a rotating plate 2 is disposed in a granulating tank 1, and a pipe 5 for supplying air from a blower 3 through a heater 4 is connected to a lower portion thereof. Granulation tank 1
A spray 6 for supplying water or a binder is provided at the upper part of the. As shown in the figure, a wire mesh or a perforated rotating plate 2 is used.
In some cases, a stirring blade 7 may be provided on the upper portion to stir the granular material.

In the granulation using such a granulating apparatus, as is well known, a powder raw material is put on a wire mesh 2 and air is supplied from below by a spray 6 above to provide a constant humidity. Feed and fluidize the raw material. If a rotating plate is used in place of the wire mesh, the fluidization by the air flow from around the rotating plate and the granulation by the rolling flow accompanied by the rolling are performed. If the rotary plate is a perforated rotary plate, the effect of the air flow from the small holes formed in the rotary plate is added.

[0004] In such tumbling fluidized bed granulation, conventionally, much attention has been paid to the measurement of the height of the powder bed. Actually, the state of fluidization is visually observed at the beginning of the operation of the equipment to check whether it is in a good state of fluidization, and since the subsequent state cannot be observed, the operation is carried out with complete intuition. Was.

However, as the granulation proceeds and the particles are compacted, the adhesion force between the particles increases and the amount of moisture in the particles increases, and depending on the flow rate of the blown air, the flow stops and causes problems such as blockkining and the like. Granulation operation cannot be continued.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to accurately measure the height of a powder layer without causing problems such as blocking and always performing granulation in a good fluidized state. It is an object of the present invention to provide a fluidized bed or a tumbling fluidized bed granulator capable of measuring the height of a powder bed and controlling the height.

[0007]

SUMMARY OF THE INVENTION A rolling fluidized bed granulator according to the present invention comprises a fluidized bed granulating apparatus or a rolling fluidized bed granulating apparatus provided with an upper part for measuring the height of a powder bed. The height of the powder layer was measured by placing an ultrasonic distance measuring device at the height of the sample.

Further, the control of the powder bed by the tumbling fluidized bed granulator according to the present invention is carried out by using the above bed height sensor, for example, a fluidized bed or a tumbling fluidized bed granulator equipped with an ultrasonic distance measuring machine. The value obtained by measuring the height of the body layer is compared with a preset target value, and the difference is fed back to determine the amount of air for fluidization blown from the lower part of the raw material powder to the height of the powder. The purpose of the present invention is to maintain the height of the powder layer at a constant target value by controlling the target value.

As mentioned above, it is important to control the fluidized state of the fluidized bed and its height, but in practice, there has been no suitable measuring means in the past, and adjustments have been made manually and intuitively. .

Generally, it is considered that the height (level) of the powder layer is measured by arranging a beam generator such as a laser precipitator at each height (level) and observing the state of interruption of the beam by an object. It is conceivable to detect the height. However, in this method, a large number of detectors must be arranged in the vertical direction, and an extremely large number of detectors are required. In addition, the upper part of the fluidized bed is a thin layer with a small number of powders and granules, and the powder is moving violently, so it is difficult to accurately grasp the height of the powder bed. .

For the above reasons, there has not been known a granulating apparatus for measuring the height of a powder layer.

In the present invention, an ultrasonic distance measuring device was installed above the granulation tank, and a distance measurement experiment to the upper part of the powder layer was performed. As a result, the distance was measured only by one distance measuring device. It has been found that it is possible to perform measurement up to a portion which is not affected by a portion where the density of the powder is extremely small and the fluctuation is severe. Therefore, by specifying the installation position (height) of the ultrasonic distance measuring device, the height of the fluidized bed or the tumbling fluidized bed can be continuously measured, whereby the fluidization at each time point during granulation can be performed. Can be grasped relatively accurately.

FIG. 2 is a view showing an experimental apparatus for confirming that the height of the powder layer can be measured by an ultrasonic measuring machine. The ultrasonic measuring device 10 is installed at a height h ₁ (320 mm) from the position 11, and the distance h ₂ from this installation position to the upper part of the powder layer is determined by the ultrasonic measuring device, and the difference (h ₁ −h) ₂ ) The height H of the powder layer was determined.

On the other hand, an image of the powder layer is taken by a television camera 12 as shown in FIG.
The actual height of the powder layer was determined.

A comparison of the results of the two measurements revealed that the two measured values agreed very well.

Further, in the present invention, as can be seen from the results of various experiments described later, the height of the powder layer and the granulation conditions, particularly the amount of air supplied from the lower part of the granulation tank, have a fixed relationship. The detected value of the height of the powder layer in the method is fed back, and the granulation conditions according to the height of the powder layer, specifically, by controlling the amount of air, maintain the desired powder layer during granulation. It is something that you get.

[0017]

Next, the apparatus of the present invention will be described based on an embodiment.

FIG. 1 shows an ultrasonic distance measuring device 10 installed in a granulation tank 1 of the conventional rolling fluidized bed granulator shown in FIG. It is placed at a height of h ₁ from the surface 11 in FIG.

Using such a device, the height of the powder layer can be measured while performing tumbling fluidized granulation.

That is, in the same manner as in a general fluidized bed or tumbling fluidized bed granulation method, raw material powder is put on a wire mesh or a rotating plate (porous rotating plate) 2 and air is sent from a lower portion at an appropriate flow rate. Granulation is performed by spraying water or a binder liquid from a spray. Here by measuring the distance h ₂ of then to the powder layer upper by ultrasonic distance measuring 10 detects the height H of the powder layer. Here, since the distance is measured by the ultrasonic distance measuring device, the appropriate height of the powder layer can be measured as described above.

Next, the control of the height of the powder layer in the apparatus of the present invention will be described.

FIG. 3 shows the height H of the powder layer and the dimensionless flow velocity u / umf of air (u is the air velocity, um
f is a graph showing the relationship with the fluidization start speed) and is based on the experimental results. In FIG. 3, the curve a indicates that the moisture value is 1.
Similarly, the curve b is 15.0 w (%), the curve c is 17.5 w (%), and the curve d is 19.0 w (%). From this figure, it can be seen that it is necessary to increase the amount of air in order to maintain a constant powder layer height H. This is due to the fact that as the water content increases, the granulation proceeds, the particles are compacted, and the adhesion between the particles increases. Further, from this figure, it can be seen that the powder layer height at the time of fluidization is almost the same regardless of the moisture value.

From the above results, it can be seen that the powder layer height can be maintained at a constant value by controlling the amount of air supplied from the lower part of the granular material. Further, good fluidization can be obtained by the value of the height of the powder layer.

In the control of the height of the powder layer in the apparatus of the present invention, a target value of H is set as shown in FIG. 4, and the measured value of H is compared with the measured value of the ultrasonic distance measuring apparatus. Thus, the value of H is controlled to the target value by controlling the flow rate of the air based on the above experimental results. In this way, the difference from the target value is fed back, and the flow rate of the air is controlled so that the difference becomes zero, that is, the height of the powder layer is controlled to the target value.

FIGS. 5 and 6 show the results of experiments using the control method of the present invention. FIG. 5 shows the results of controlling the amount of water, and FIG. 6 shows the results of controlling the height of the powder layer.

As shown in FIG. 5, the amount of water can be controlled. In other words, in the low moisture region (W ≦ 8%), the layer height is lowered,
In the high moisture region (W ≧ 8%), the result is obtained by controlling the bed height to 120 mm. As is clear from this figure,
Up to the desired water content, the bed height is lowered, and by controlling the layer height to a predetermined layer height (for example, 120 mm) by increasing the water content, granulation with a desired water content becomes possible. It is possible to obtain granules having a bulk density of

From FIG. 6, it can be seen that granulation can be performed while maintaining a predetermined layer height, so that a good granulation operation can be performed without blocking or the like.

FIG. 7 shows the relationship between the height of the powder layer and the rotation speed N of the stirring blade. The curve a shows u / umf = 2.27,
Curve b is u / umf = 4.53, and curve c is u / umf =
6.80, curve d is u / umf = 9.07. As is clear from this figure, the lower the wind speed is, the more easily the influence of the stirring blades occurs, and the bed height H decreases as the rotation speed N increases.

FIG. 8 is a diagram showing the relationship between the apparent density ρa and the stirring blade rotation speed N when the wind speed is changed. Regardless of the wind speed, ρa changes depending on the rotation speed N.
Ρa and dimensionless wind speed u / umf obtained based on FIG.
An empirical formula that quantifies the relationship between the rotation speed N of the stirring blade and the rotation speed N is shown below.

Ρa = 5.85 × 10^-2 N^Three-3.00N^Two
+ 2.77 × 10^Threeu / umf + 468.5 where 0 ≦ N ≦ 15 rps, 0 ≦ u / umf ≦ 9 where the shape factor Ψ and angle of repose when the wind speed is changed
Fig. 9 and Fig. 9 show the relationship between φ and the stirring blade rotation speed N.
As shown in FIG. Where the short axis r of the 50 particles₁
And the major axis r_TwoAnd the ratio r₁/ R_TwoThe average of_eAnd

FIG. 9 shows that N ≦ 10.0r. p. s. Then N
As the value of 増 加 increases, the rolling and consolidation effects of the stirring blades increase, the value of Ψ _e increases, the sphericity increases, and FIG.
It can be seen from the above that when the value of N is above, the value of Φ decreases and the fluidity improves. 7, 8, and 9, a, b.
c is for u / umf = 4.53, 6.80, 9.07, respectively.

N> 10.0r. p. s. In this case, it can be seen that the rotation speed of the stirring blade is high and the particles are pressed against the wall surface of the granulation tank by centrifugal force, so that it is difficult to receive an effective rolling consolidation effect.

By taking into account the above points, it is possible to form granules having a predetermined consolidation by controlling the bed height of the present invention by combining the rotation of the stirring blades.

[0034]

The fluidized-bed or tumbling-fluidized-bed granulator according to the present invention can measure the height of the powder bed and can control the height of the bed to a set constant height, and therefore can block the powder. Good granulation can be performed without causing the like. Further, by selecting a set value (target value) of the layer height, a powder having a desired bulk density and particle size can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

Fig. 2 Measurement of layer height by ultrasonic measuring machine

FIG. 3 is a graph showing the relationship between bed height and flow velocity.

FIG. 4 is a schematic diagram of a powder layer height automatic control system.

FIG. 5 is a diagram showing an example of moisture control according to the present invention.

FIG. 6 is a diagram showing an example of powder layer height control according to the present invention.

FIG. 7 is a diagram showing a relationship between a powder layer height and a stirring blade rotation speed.

FIG. 8 is a diagram showing the relationship between the apparent density of the powder and the rotational speed of the stirring blade.

FIG. 9 is a diagram showing the relationship between the shape factor of the granular material and the rotation speed of the stirring blade.

FIG. 10 is a diagram showing the relationship between the angle of repose of the granular material and the rotation speed of the stirring blade.

FIG. 11 is a cross-sectional view of a conventional granulation apparatus.

[Description of Signs] 1 Granulation tank 2 Wire mesh or rotating plate 3 Blower 4 Layer height sensor 11 Reference plane

Claims (4)

(57) [Claims] 1. A layer height which is higher than a reference surface of a granulating apparatus including a wire mesh or a perforated rotating plate, an air supply pipe disposed under the rotating plate, and a liquid supply spray disposed above. The height of the powder layer is measured by arranging a sensor and determining the distance from the layer height sensor to the upper part of the powder layer during granulation .
Fluidized bed or tumbling fluidized bed granulator that controls the amount of air from the pipe 2. The fluidized or tumbling fluidized-bed granulating apparatus according to claim 1, wherein said bed height sensor is an ultrasonic distance measuring machine. 3. The amount of air from the air supply pipe is controlled based on the difference between the measured value of the height of the powder layer by the above-mentioned layer height sensor and a predetermined target value to set the height of the powder layer. 3. The granulating apparatus for a fluidized bed or a tumbling fluidized bed according to claim 1, wherein the target value is always maintained. 4. The apparatus for granulating a fluidized bed or a tumbling fluidized bed according to claim 1, wherein a stirring blade having a variable rotation speed is disposed above the wire mesh or the rotating plate.