JPH0418224B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a disc of a rotary spray disc used in a spray drying device for drying slurry and producing powder. [Prior art] Ceramic material powders such as alumina and silica are
It is produced by pulverizing the raw materials, adding water, and then subjecting the slurry to predetermined treatments such as iron removal, and then drying it in a spray dryer. This spray drying apparatus has a configuration in which slurry is supplied from above to a rotary spray disk rotated at high speed within a drying cylinder to spray it in the outer circumferential direction, and at the same time hot air is blown into the drying cylinder. Conventionally, the rotary spray disc has a keyway 50 in the center hole, as shown in FIG.
A disk 50 has an upper surface that is smoothly curved from a cylindrical center portion 50a where b is formed toward a disk-shaped outer peripheral portion 50c, and an outer peripheral portion 50 of the disk.
A large number of blades 51 arranged radially at equal intervals on the upper surface of c and an annular guide plate 53 fixed to the upper end of the blades 51 are brazed to each other, and both sides of the blades 51 are provided with abrasion prevention material. For this purpose, a cemented carbide plate 52 was brazed. [Problems to be Solved by the Invention] However, in the conventional rotary sprayer, most of the supplied slurry flows while adhering to the upper surface of the disk 50, and the liquid flows approximately tangentially from the outer peripheral edge of the disk 50. Since the particles were sprayed in the form of droplets, they were not sufficiently dispersed in the axial direction and were not dried efficiently, and a portion of the particles adhered to the inner circumferential wall of the drying cylinder. For this reason, the drying capacity of the drying device was not fully utilized, and the recovery rate of ceramic material powder was also low. The inventor also found that when the rotary spray disc B is used for a long period of time, the drying ability and recovery rate improve somewhat over time, and the reason for this is that as shown in FIG. When the flowing slurry turns from the vertical direction to the horizontal direction, the upper surface of the dike is scraped as shown in a, so part of the slurry flows along the scraped surface and scatters in the direction of arrow F2, while the rest scatters in the direction of arrow F2. It was discovered that the droplets were scattered from the outer periphery of the disk as in F1, and as a result, the ejected droplets were somewhat dispersed in the axial direction (vertical direction) and became smaller particles. An object of the present invention is to provide a spray drying disk in which sprayed and scattered slurry droplets can be widely dispersed in the vertical direction, thereby improving drying efficiency and improving the recovery rate of ceramic material powder. [Means for solving the problem] In order to achieve the above object, the spray drying disk of the present invention supplies slurry to the upper surface of the rotating disk, applies centrifugal force to the slurry, scatters it in the outer circumferential direction, and dries it. In the spray drying disk, a structure is adopted in which the upper surface of the disk is provided with irregularities. [Operations and Effects of the Invention] Since the spray drying disk of the present invention has irregularities on the top surface of the disk, the sprayed and scattered droplets of slurry can be widely dispersed in the vertical direction, which improves drying efficiency and improves the quality of ceramic materials. An improvement in the powder recovery rate can be achieved. [Example] The spray drying disk of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a perspective view including a partially cutaway view of a spray drying disk according to the present invention, in which 1 is a disk body having a shaft hole 1a for fitting a rotary shaft, and the appearance as a whole has an upside-down funnel shape. On the outer slope of the disk body, a plurality of step-like unevennesses 1b and 1c are formed concentrically with respect to the axis.
Further, an annular groove 1d is provided at the upper end of the flat bottom surface, and screw holes 1e are provided at regular intervals on the periphery. Reference numeral 2 denotes a group of blades for uniformly dispersing the material to be dried, which has a bolt-like shape as a whole, and has a screw groove 2a at its lower end for screwing into the screw hole 1e.
However, a bolt head 5 is also provided at the upper end. Reference numeral 3 designates a cylindrical blade cover made of a super hard material such as super hard steel or ceramic, which is removably fitted onto the blade 2 in order to increase the abrasion durability of the blade 2; A blade attachment member serving as an annular collar body having the role of supporting and fixing the top end of the second group,
A hole for inserting the blade 2 is provided at the peripheral edge. It is not necessary to give bolt shapes to all of the 2 groups of blades, and the blades 2 other than a few necessary for assembling the disk are simply rod-shaped bodies, and the upper and lower ends are connected to the disk body 1 and the blade attachment member. Alternatively, a screw hole 2b may be provided on the end surface of the blade 2, and the screw hole 2b may be provided on the end surface of the blade 2, and the screw hole 2b may be fitted into the fitting recess provided on each opposing surface of the peripheral edge of the blade 2. They may be fastened together using short bolts inserted through them. As the disk constituent material, a metal material with excellent corrosion resistance, wear resistance, and toughness, such as stainless steel, is used. FIG. 2 is a system diagram of a spray drying apparatus for ceramic material slurry incorporating the spray drying disk of the present invention, in which 10 is a drying chamber, and A is a spray dryer of the present invention attached to the center of the ceiling in the chamber 10. A drying disk, 11 a rotating shaft of the disk A, 12 a driving motor for the disk A, 13 a driving belt for the rotating shaft 11, 14 a discharge machine for supplying ceramic material slurry to the disk A, 15
is a descending tube of slurry. The slurry is passed through a de-iron machine 17 by a pump 16 to remove iron present in the material.
, and then pushed up to the top of the drying chamber 10 by the pump 18. Also 2
0 is a hot air generating furnace for generating hot air to be supplied into the drying chamber 10, 21 is a burner, 22 is a blower, 23 is a hot air pipe, and 24 is a drying chamber 1
The pressure chamber 25 provided at the top of the drying chamber 24 is a hot air discharge slit formed around the slurry flow lower cylinder 15 in order to discharge the hot air in the pressure chamber 24 into the drying chamber 10. 30 is a dry ceramic powder accumulation part formed at the bottom of the funnel-shaped drying chamber 10, 31 is a suction pipe for the deposited powder, 32 is a powder suction blower, 33 is a cyclone for powder collection, and 34 is a powder storage The tank, 35, is a powder outlet, and 36 is a pipe for hot exhaust from the cyclone 33 and for circulating the fine powder in the exhaust into the drying chamber 10. 40 is a dust removal cyclone for discharging the air in the drying chamber 10 into the atmosphere while separating and collecting fine powder floating in the air; 41 is an inlet port of the dust removal cyclone 40 that opens into the tank 34; 42 is an intake blower, 43 is a dust collector, and 44 is an exhaust pipe. Next, a description will be given of the operation of the above slurry drying apparatus incorporating the spray drying disk according to the present invention. Raw materials for molding ceramic products such as alumina and silica are pulverized through a coarse crusher and a pulverizing mill, mixed with water in the pulverizing mill or stirring tank to form a slurry, and then deironated by a pump 16. After being fed into the machine to remove iron that colors the product, the slurry flow lower cylinder 15 is pushed up to the top of the drying chamber 10 by the pump 18 and is placed so as to wrap around the rotating shaft 11 of the spraying disk A. is continuously fed to the upper end of the The slurry flowing out from the lower end of the lower slurry flow tube 15 spreads out in an annular shape near the top end of the disc body 1, which has an inverted funnel-like outer shape, and then flows down along the funnel-shaped slope. However, the disk A is rotated by the motor 12 on the rotating shaft 1.
Since it is rotated at high speed around 1, a strong centrifugal force is exerted on the slurry. Unlike the conventional spray drying disk, the funnel-shaped slope of the disk body 1 of the present invention is not a smooth curved surface as shown in FIG. When the slurry flows down the staircase surface, the adhesion force of the slurry to the surface of the disk body 1 becomes stronger than the centrifugal force exerted on the slurry on the vertical plane 1b, and the slurry is hardly scattered. . However, when it reaches the horizontal surface 1c, the flow velocity of the slurry decreases, so it is temporarily deposited on this horizontal surface and the thickness of the slurry layer increases, and the above-mentioned adhesion force is no longer applied to the top surface of the slurry, causing the centrifugal phenomenon that disk A exhibits. The acting force blows off the slurry on at least this top surface portion at high speed, and the slurry is evenly distributed in the circumferential direction of the disk due to the presence of the two groups of blades, and is then deposited into the upper space in the drying chamber. It is dispersed in the form of a spray. The slurry that has escaped scattering adheres to the second vertical surface 1b and flows down, and then reaches the second horizontal surface 1c, where a fraction of the total amount of the slurry is scattered. By repeating this phenomenon, the amount of slurry that reaches the bottom layer is reduced. Thus, the fact that the slurry is scattered in several stages in the height direction of the disk body 1 makes it possible to spread the spray of slurry into the drying chamber 10 at the top of the disk, unlike in the conventional case. This means that it is possible to obtain a much larger effect than when the particles are scattered only from the bottom surface. In this case, the number of steps, that is, the number of horizontal surfaces 1c, was eight. Horizontal surface 1c
Instead of making each stage uniformly horizontal, if you tilt the upper stage upward and the lower stage downward, the direction of the slurry scattering will be slightly vertical rather than horizontal. Since it is deflected, the spray diffusion area can be further expanded. In addition, inorganic powders with high specific gravity tend to separate and settle from the aqueous phase of the slurry, and powders with larger particle sizes tend to reach the lower steps. It makes perfect sense that centrifugal force would be exerted. Furthermore, exerting more than necessary centrifugal force on the slurry means that the slurry is in the drying chamber 1.
Since the particles reach the 0 wall and adhere as shown in b in the figure, reducing the drying yield, it is unlikely that scattering will start at the upper or middle steps of the stairs where a smaller centrifugal force is applied. It will be beneficial from this aspect as well. The annular groove 1d provided in the bottom flat surface of the disk body 1 functions as a slurry reservoir for adjusting the amount of slurry scattered on this flat surface, which is the main slurry scattering site. The slurry jet (solid line arrow in FIG. 2) continuously supplied in the form of a spray to the upper space in the drying chamber 10 as described above is passed through the hot air piping 23 from the hot air generating furnace 20 for heating inside the chamber 10. After being fed into the pressure chamber 24, the slurry encounters a hot air flow (indicated by a broken line arrow in FIG. 2) ejected from the hot air discharge slit 25 around the lower slurry flow tube 15, thereby exchanging heat and being rapidly dehydrated and dried. The dry powder falls to the accumulation part 30 at the lower end of the chamber and accumulates therein, and is sent into the cyclone 33 by the suction force of the powder suction blower 32 via the pipe 31 with a cyclone 33 interposed therebetween, where the dust-like fine powder is separated. Top reservoir tank 3 under
Fall within 4. On the other hand, the hot air containing dusty powder that has undergone heat exchange and is accumulated in the drying chamber 10 is sucked into the cyclone 40, removed from dust, and then released into the atmosphere. The spray drying disk of the present invention having the structure shown in FIG. 1 and the conventional spray drying disk illustrated in FIGS.
or 50, each for a period of one month using the actually operating equipment shown in Figure 2, under the conditions of keeping the same maximum outer diameter and the same operating conditions. The results of the performance comparison test are summarized in Table 1.

[Table] In the above embodiment, the unevenness provided on the upper surface of the disk body 1 has a step-like shape consisting of a series of right angles, but may have a shape similar to a step consisting of a continuous wave-like curved surface. In this case, each wave crest is
The slurry is scattered not in a single horizontal direction but in a vertically deflected state, and the slurry spray is dispersed over a wider area in the upper space within the drying chamber 10, thereby increasing the efficiency of heat exchange with hot air. The improvement effect is enhanced.

[Brief explanation of drawings]

Fig. 1 is a perspective view including a partially broken surface of a disk for spray drying of the present invention, Fig. 2 is a system diagram of a spray drying apparatus for ceramic material slurry incorporating the disk of the present invention, and Fig. 3 is a conventional FIG. 4 is a perspective view including a partially broken surface of a spray drying disk, and is an explanatory side cross-sectional view after a conventional disk has been used for a considerable period of time. In the figure 1... Disc body, 1a... Rotating shaft hole,
1b, 1c...Step-like unevenness, 2...Blade, 3
...Blade cover, 4...Blade mounting member.

Claims (1)

[Claims] 1. Supplying slurry to the upper surface of the rotated disk,
A spray drying disk for drying the slurry by applying a centrifugal force to the slurry to scatter it in an outer circumferential direction, characterized in that the top surface of the disk is provided with irregularities. 2. The unevenness is characterized by being formed by one or more steps formed by concentric cylindrical surfaces whose radius increases stepwise downward and which are concentric with the center of rotation. A spray drying disk according to claim 1. 3. The spray drying disk according to claim 1, wherein the unevenness is formed by a circular protrusion or groove concentric with the center of rotation.