JPH06319977A - Method and apparatus for continuous granulation of powder - Google Patents

Abstract

PURPOSE:To perform remote operation and automating of granulation process and to improve productivity and quality by a method wherein the relative humidity in a drum is measured and the amt. of feeding of a raw material powder and/or a water soln. is controlled and the relative humidity in the drum is kept cost. CONSTITUTION:A humidity sensor 4 is fixed in a granulation drum 2 of a rotary drum type rotating granulation apparatus. Then, while a granulation drum 2 is rotated, a raw material powder is fed from a hopper 9 through a screw type quantitative feeder 6 and a water soln. of a surfactant is adjusted from a water soln. storing tank 10 through a tube pump 8. In this case, the amt. of feeding of the water soln. is adjusted by means of a tube pump 8 so as to make the relative humidity to be 60-80%. A granulated product with specified properties such as a particle size distribution and a fine pore vol. is granulated stably and for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously granulating powder and a granulating apparatus therefor.

[0002]

2. Description of the Related Art The tumbling granulation method is known as a method for granulating powder at a relatively low cost, and is widely used in fields such as agricultural chemicals, chemical fertilizers, adsorbents, catalysts and ceramics. As a unit operation, "spray the liquid while rolling the dry powder raw material,
It is defined as "operation of forming agglomerates having a substantially spherical shape and having a required strength", and a device such as a rotating dish type, a rotating drum type and their variants are used.

The process of rolling granulation in a rotary drum type rolling granulator is roughly divided into three stages of nucleation, growth and classification. First, the powder raw material charged into the granulator initially forms loose aggregates with water. The agglomerates are tightened by rolling and come into contact with the small pieces to form larger agglomerates (nucleation). The nuclei thus generated have appropriate plasticity, and while being deformed by themselves or being involved while destroying the particles of the other party, they are made spherical by growing rolling and grow into large particles (growth). In the drum, these mixed particles mainly flow unevenly due to the difference in particle size and are continuously discharged (classification). Further, in a rotary drum type granulator having a pressure crushing ball inside the apparatus, the granules are broken or compressed by the pressure crushing ball. As described above, a plurality of phenomena occur at the same time in the rolling granulation in the drum, and in carrying out the same, granulation must be carried out while maintaining a mutual balance. The rotation operation itself in tumbling granulation is only an auxiliary action for performing cohesive compression by the solid phase / liquid phase / gas phase interface phenomenon, and the conditions for carrying out stable granulation with good reproducibility are It depends on the type of raw material (solid phase) and the quantitative ratio with water (liquid phase).
Water is used to activate the interfacial phenomenon, but its adjustment is very difficult, and if the water content is insufficient, it will not be granulated, and if it is too large, large lumps will form. For example, when granulating synthetic zeolite, a binder component such as clay mineral, alumina or silica is added. However, the main component, synthetic zeolite, has a sharp crystal size distribution and poor mutual adhesion. Therefore, even if the binder component is added, the range of the optimum water content for granulation is extremely narrow, and in our experience, it is rare that the width exceeds ± 1% with respect to the optimum water content.
In order to control the green bulk density of the granulated product and obtain a granulated product of a constant quality, good reproducibility cannot be obtained unless the water content is controlled within an accuracy of usually ± 0.3%. The water content of the granulated product is calculated from the water content of the raw material and the supply amount of the raw material and water, and the operating conditions of the rotary drum type rolling granulator are set. However, due to subtle fluctuations in the water content of the raw materials or fluctuations in the amount of feed by the raw material and water supply devices, the state of the internal granulated product fluctuates constantly even if the granulator is operated under certain conditions. Alternatively, it is impossible to maintain a steady granulation state without finely adjusting the water supply amount.

The particle size of the granulated product obtained by the tumbling granulation method is wide, and when a granulated product having a uniform particle size is to be obtained, a classification operation is required. Sugimoto et al., Simultaneous operation of continuous granulation and classification using a horizontally rotating conical vessel (Chemical engineering papers,
8, 530 (1982)). Further, Japanese Patent Application Laid-Open No. 2-68129 proposes a system in which a ball for pressure crushing having a diameter of 50 mm or less is placed in a horizontal rotary conical container and continuous granulation, classification, and simultaneous compaction / crushing operations are carried out. .

The present inventors have actually tried to granulate various raw material powders by rolling granulation using this rotary drum type rolling granulation apparatus. The optimization of the granulation conditions such as the number of rotations of the rotary drum type rolling granulator, the amount of balls for pressurization and pulverization, the raw material residence time, and the amount of water was examined. The granulation state inside the drum of the granulator was examined. Varies delicately and has a certain quality as a granulated product. For example, it is not possible to granulate continuously and stably for a long time while controlling granulation properties such as particle size distribution, pore volume, abrasion resistance and bulk density. It was difficult. Up to now, in order to stably obtain the target granulated product using the granulating apparatus, a skilled worker constantly observes the granulated state inside the drum and adjusts the supply amount of the raw material powder or the aqueous solution. The current situation is that a skilled person, for example, does it based on visual experience. Further, depending on the type of raw material powder, the optimum moisture range for granulation is extremely narrow, and in such a case, granulation itself may be quite difficult.

For example, as the water content of the granulated product increases, the particle size of the granulated product gradually increases, and the phenomenon of adhesion to the inner wall of the drum of the granulating device becomes conspicuous. If this state progresses further, the granulated material becomes a large mass, and it becomes difficult to continue the operation of the apparatus. Before such a situation, the skilled person perceives a tendency that the particle size of the granulated product becomes large, and controls the operation by temporarily increasing or decreasing the supply amount of the raw material powder or the supply amount of the aqueous solution or temporarily stopping the operation. Perform a work to maintain a steady granulation state.

On the other hand, as the water content of the granulation product decreases, the particle flow in the cross-sectional direction inside the drum of the granulation device shifts from the cascading state, which is a stable region, to the catalyzing state. Along with this, the particle size of the granulated product becomes small, and the granulated product becomes powdery and light. When this state progresses further, the granulation phenomenon no longer occurs effectively, and the raw material powder finally comes out from the discharge port. It is very difficult for an expert to visually detect that the water content of the granulated product tends to decrease. That is, since the change in the particle size distribution of the granulated product is so small that it is difficult to discriminate it, an accurate determination cannot be made only by visual inspection. Therefore, a skilled person regularly measures the green bulk density, particle size distribution and water content of the granulated material by sampling inspection. When it is determined from the measurement results that the water content of the granulated product tends to decrease, control is performed by increasing or decreasing the supply amount of the aqueous solution or operation is temporarily stopped to maintain a steady granulated state. I'm working. However, since the raw material powder is supplied to the inside of the drum of the granulator and granulated, and there is a residence time of 1 to 2 hours from the granulator to discharge, a response delay occurs,
It was extremely difficult for even an expert to maintain a steady granulation state. Further, it was a very difficult task even for a skilled person to continuously granulate a target granulated product.

[0008]

The object of the present invention is to solve these problems, that is, to granulate target particle size distribution, pore volume, abrasion resistance, bulk density, etc. without requiring a skilled person. The present invention provides a granulating method by a rotary drum type rolling granulator and a granulating apparatus for the granulated product having physical properties, which can be stably and continuously obtained for a long time.

[0009]

That is, according to the present invention, the relative humidity inside the drum is measured in the continuous granulation method of powder by supplying the raw material powder and the aqueous liquid to the rotary drum type rolling granulation device. However, the present invention is directed to a continuous granulation method of powder, which comprises controlling the supply amount of the raw material powder and / or the aqueous liquid to maintain the relative humidity inside the drum at 60 to 80%.

The present invention will be described in detail below.

There is no limitation on the kind of the rotary drum type rolling granulator used in the present invention, but when it is applied to a type in which a pressure crushing ball for promoting compaction and crushing is provided inside the drum. The effects of the present invention are better achieved.

Also in the method of the present invention, the operating conditions of the rotary drum type rolling granulator may be those normally employed except for the adjustment of the relative humidity inside the drum. For example, when a raw material powder such as zeolite, zirconia, alumina, and an agricultural chemical is supplied at 0.3 to 1.0 kg / hr and a ball for pressure crushing is used, the drum rotation speed is usually 40 to 70 rp.
m, and a pressure crushing ball of 0.4 to 1.5 kg may be used. As the aqueous liquid, an aqueous solution containing a commonly used surfactant (nonionic surfactant, cationic surfactant, zwitterionic surfactant), CM
A C aqueous solution, a PVA aqueous solution, a methylcellulose aqueous solution, water, etc. may be adopted depending on the properties of the raw material powder.

In the method of the present invention, the relative humidity inside the drum of the granulator is 60 to 80%, preferably 67 to 76%.
Need to maintain. If the relative humidity is less than 60%, the water content becomes excessive and the granulation product and the balls for pressurization and crushing become thick so that continuous granulation becomes difficult. If the relative humidity exceeds 80%, the granulation phenomenon does not occur effectively and the final As a result, the raw material powder comes out from the outlet. Therefore, when the relative humidity rises and is likely to be higher than 80%, the amount ratio of the aqueous liquid / raw material powder is increased, that is, the amount of the aqueous liquid supplied is increased and / or the amount of the raw material powder is decreased. On the other hand, when there is a risk that the relative humidity will drop and become lower than 60%, the amount ratio of the aqueous liquid / raw powder is reduced, that is, the supply amount of the aqueous liquid is reduced and / or that of the raw powder is increased. The relative humidity inside the drum must be maintained within the range of 60-80%. Relative humidity inside the drum can be automatically controlled by incorporating a circuit that uses the relative humidity as an input signal and raises or lowers or turns on and off the output to the powder supply device and / or the liquid supply device. However, it is easier to adjust the amount ratio of the aqueous liquid / raw material powder by keeping the supply amount of the raw material powder constant and varying only the supply amount of the aqueous liquid whose flow rate is easier to adjust.

The relative humidity measuring device may be any hygrometer as long as it accurately measures the relative humidity inside the drum of the granulating device. In recent years, a small-sized humidity sensor using a polymer humidity sensor or the like has been commercially available as a device for simply and accurately measuring the relative humidity in the atmosphere, and is suitably used for the purpose of the present invention. There are no particular restrictions on the location where the detection part of the hygrometer is installed inside the drum, except for the vicinity of the raw material supply port and product discharge port, which are usually susceptible to the atmosphere from the outside of the drum. For example, as shown in FIG. 1, it may be installed near the center of the drum ((4) in the figure is the detection unit of the hygrometer). In addition, the granulated material that has been scattered over a long period of time may adhere to the detection part of the hygrometer, and the relative humidity inside the drum may not be measurable because of too much adhesion, so it does not hinder the measurement. It is preferable to attach a protective wire net or the like to the detector.

[0015]

The mechanism of the effect expression of the present invention is presumed to be as follows.

In the drum, the particles collide with each other to be consolidated and sheared and ground. The mechanical energy used for this consolidation and shearing is converted into heat. Further, depending on the type of powder raw material, there are some that generate heat of adsorption or heat of crystallization upon contact with an aqueous liquid. The amount of heat (per amount of raw material powder) generated by these is substantially constant when the amount ratio of aqueous liquid / raw material powder is above a certain level. Therefore, in that range, the higher the amount ratio of the aqueous liquid / raw material powder is, the smaller the temperature rise value of the raw material powder / aqueous liquid mixed phase due to the above heat is, and the increase in the temperature causes the water to be transferred to the air phase inside the drum. Has a small amount of evaporation, and the increase in absolute humidity of the air phase is also small. Since the temperature of the air phase does not rise as much as that of the raw material powder / aqueous liquid mixed phase, the relative humidity inside the drum becomes lower as the amount ratio of the aqueous liquid / raw material powder becomes larger. The smaller the powder amount ratio, the higher the relative humidity inside the drum.

The present inventors have found that the relative humidity inside the drum has a close relationship with various granulation characteristics of the powder, and it is the relative humidity and the amount ratio of the aqueous liquid / raw powder described above. It is recognized that it is due to the close relationship of. For example,
As shown in FIG. 2 showing the results of Example 1, the obtained granulated product has a linear relationship between the green bulk density and the relative humidity, and as shown in Table 1, the obtained granulated product is To 120 ° C
After fluidized and dried for 30 minutes, use an electric muffle furnace for 6 minutes.
As a result of measuring the physical properties by firing for 2 hours in the range of 00 ° C to 700 ° C, wear resistance, pore volume, particle size distribution and bulk density are closely related to the bulk density of the granulated granules. It was confirmed to be in. That is, if the green bulk density is light, the abrasion resistance is low, the pore volume is porous, the particle size distribution is small, and the bulk density is also light. When the green bulk density is heavy, the abrasion resistance is high, the pore volume is small, and a dense granule can be obtained. In this way, by controlling the relative humidity inside the drum of the granulating apparatus, it becomes possible to control these physical properties of the product granulated product, and it becomes possible to stably obtain the target granulated product. It was.

[0018]

The control method of the present invention enables continuous granulation in a rotary drum type rolling granulator while maintaining a steady granulation state, which was impossible even by an expert. It has become possible to control the physical properties of materials. As a result, it has become possible to perform rolling granulation of a narrow range of an appropriate amount of an aqueous liquid for granulation such as zeolite, which has been difficult to granulate with a rotary drum type rolling granulator. As described above, the control method of the present invention has a remarkable effect on the stable control of rolling granulation using the granulating apparatus. Further, the granulation process can be remotely controlled or automated, and the productivity and quality thereof can be markedly improved.

[0019]

【Example】

 Example 1 It was carried out in the steps shown in the flow sheet of FIG.

Rotating drum type rolling granulator (GRC25 type, manufactured by Shinto Kogyo Co., Ltd., large inner diameter 250 mm, small inner diameter 110 mm, length 300 mm) (1) was used as a crushing ball for zirconia (15 mm in diameter). Thing 64
A total of 72 pieces (total weight 1.1 kg) were put in (3 pieces) (8 pieces having a diameter of 30 mm). Humidity sensor (manufactured by Shinei Co., Ltd.,
The sensor part of the TRH-CZ type (4) was fixed so that it was located 20 cm inside the small diameter end of the granulating drum (2). The drum driving motor (5) was started, the granulating drum (2) was rotated at 60 rpm, and Y-type zeolite with a water content of 20 wt% (HSZ-320NAA manufactured by Tosoh Corporation) and clay with a water content of 20 wt% ( (Montmorillonite type) was mixed continuously at a ratio of 8: 2 based on an absolute dry basis, and the raw material powder was continuously fed from a raw material powder hopper (9) to a screw type constant quantity feeder (6) at 0.6 kg / hr. Supplied to. Nonionic surfactant (Leodol L manufactured by Kao Atlas Co., Ltd.)
120, same below) 2wt% aqueous solution storage tank (10)
The tube pump (8) was adjusted to 0.35 kg / hr. The supply amount of the aqueous solution was adjusted by the tube pump (8) so that the relative humidity inside the granulating drum (2) of the granulating apparatus became 75%. That is, when the relative humidity in the granulator was about to fall below 75%, the supply of the aqueous solution was reduced, and when it exceeded 75%, the supply of the aqueous solution was increased. After 1 hour, the granules began to be discharged. After a further 1 hour, the granulated state reached a steady state. After that, continuous operation was performed for 8 hours, but a stable granulated state could be maintained.
The green bulk density of the obtained granulated product was 0.70 kg / l. Next, the supply amount of the aqueous solution was adjusted so that the relative humidity in the granulating drum was 73%. After maintaining the relative humidity for 2 hours, the green bulk density of the sampled granules was measured. As a result, a green bulk density of 0.75 kg / l
was gotten. By the same method, the supply amount of the aqueous solution was adjusted so that the relative humidity in the granulating drum was 71%. After maintaining the relative humidity for 2 hours, the bulk density of the sampled granules was measured. As a result, a green bulk density of 0.80 kg
/ L was obtained. Similarly, the relative humidity in the granulation drum is set to 6
The supply amount of the aqueous solution was adjusted to 9%, the relative humidity was maintained for 2 hours, and then the bulk density of the sampled granules was measured. As a result, a green bulk density of 0.85 kg / l
was gotten.

Each of the obtained granules was heated at 120 ° C. for 3 times.
Table 1 shows the results of measuring physical properties by fluidizing and drying for 0 minutes and then baking at 600 to 700 ° C. for 2 hours. The particle size distribution is shown in FIG.

Example 2 The raw material powder was Y-type zeolite (HSZ-manufactured by Tosoh Corporation).
320NAA) and alumina (water content 20 wt%) were mixed at a ratio of 8: 2 in an absolute dry basis weight ratio, and a supply amount of a nonionic surfactant 2% aqueous solution was 0.3 kg /
Granulation was performed in the same manner as in Example 1 except that the hr was used. The volume of the aqueous solution supplied was adjusted with a tube pump so that the relative humidity in the granulating drum was 76%, and the relative humidity was maintained for 2 hours, and then the bulk density of the sampled granulated product was measured. As a result, a green bulk density of 0.70 kg / l was obtained. Thereafter, the green bulk density obtained by adjusting the amount of the aqueous solution supplied by the tube pump so that the relative humidity in the granulation drum was 73% was 0.75 kg / l. The green bulk density obtained by controlling the relative humidity at 67% was 0.80 kg / l. Each of the obtained granules was fluidized and dried at 120 ° C. for 30 minutes, and then 600-
Table 1 shows the results of measuring the physical properties by baking at 700 ° C. for 2 hours.

Example 3 The raw material powder was zirconia TZ-3YS (manufactured by Tosoh Corporation).
(Moisture content 0.5 wt%) is used, the supply amount is 0.6 kg / hr for the raw material powder, and 0.06 kg / water for the aqueous solution.
After adjusting to hr, granulation was performed in the same manner as in Example 1.
The supply amount of the aqueous solution was adjusted with a tube pump so that the relative humidity in the granulation drum was 67 to 74%. Relative humidity 7
The granulated product obtained by controlling the content to 4% has a green bulk density of 1.
It was 8 kg / l. Similarly, the green bulk density obtained by controlling the relative humidity at 70% is 2.2 kg / l, and the green bulk density obtained at a relative humidity of 67% is 2.8 kg.
It was / l. Thus, it was confirmed that the close relationship between the relative humidity and the green bulk density can be applied to powders other than zeolite.

Comparative Example 1 The same procedure as in Example 1 was carried out until the granulation state reached a steady state, and thereafter the amount of the aqueous solution was increased so that the relative humidity in the granulator was intentionally set to 58%. . After 1 hour, the particle size of the granulated product gradually increases, and the phenomenon of adhesion to the pressure crushing balls and the inner wall of the drum becomes conspicuous, and excess water can be visually confirmed. As a result of continuing the operation for another 30 minutes without reducing the supply of the aqueous solution, the granules were not discharged from the drum and adhered to the balls for pressure crushing, and the granules also became a lump, making it impossible to continue the operation. Became. The resulting granules were fluidized and dried at 120 ° C. for 30 minutes, and then 600
Table 1 shows the results of measuring the physical properties by baking at ˜700 ° C. for 2 hours.
Shown in.

Comparative Example 2 The same procedure as in Example 1 was carried out until the granulation state reached a steady state, and thereafter the supply of the aqueous solution was reduced so that the relative humidity in the granulator was intentionally set to 82%. . After 1 hour, the particle size of the granulated product gradually becomes smaller and the green bulk density becomes 0.56k.
It became light as g / l. As a result of continuing the operation for another 30 minutes, powdering became violent in the rotary drum, the granulation phenomenon no longer effectively occurred, and finally powder came out from the discharge port. The obtained granulated product is 30 at 120 ° C.
Table 1 shows the results of measuring the physical properties by performing partial fluidization drying and baking at 600 to 700 ° C. for 2 hours.

[0026]

[Table 1]

[Brief description of drawings]

FIG. 1 is a flow sheet showing steps of Examples and Comparative Examples.

FIG. 2 is a graph showing the relationship between the relative humidity inside the granulating drum of Example 1 and the green bulk density of the granulated product.

FIG. 3 is a graph showing the relationship between the relative humidity inside the granulating drum and the particle size distribution of the granulated product in Examples and Comparative Examples.

[Explanation of symbols]

 (1) Rotating drum type rolling granulator (2) Granulating drum (3) Zirconia ball (4) Hygrometer (5) Drum drive motor (6) Screw type constant feeder (7) Vibration feeder (8 ) Tube pump (9) Raw powder hopper (10) Aqueous solution storage tank

Claims (3)

[Claims] 1. In a continuous granulation method of a powder by supplying a raw material powder and an aqueous liquid aqueous solution to a rotary drum type rolling granulation device, the relative humidity inside the drum is measured to measure the raw material powder and / or the aqueous liquid. The continuous granulation method of the powder characterized by maintaining the relative humidity inside a drum at 60 to 80% by controlling the supply amount of the powder. 2. The granulating method according to claim 1, wherein the powder is zeolite and the relative humidity is 67% to 76%. 3. A rotary drum type rolling granulator, wherein a hygrometer is installed inside the drum of the rotary drum type rolling granulator.