JP3910515B2 - Centrifugal dryer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention is a wall surface having a heat transfer surface of the heat medium on the inside, and reduces the moisture content of the dried material consisting of water and solids such as solution, mud, paste, cream, lump, granule, powder, etc. Or it is related with the dryer to dry and its operating method .
[0002]
[Prior art]
In conventional dryers, a direct heating type in which hot air and a material to be dried are brought into contact with, and a heating medium is passed through a jacket, cylinder, thin tube, or dish, and heat is supplied from the wall surface to the material to be dried, or room temperature is dried. There are drying apparatuses such as indirect heating type that evaporates in vacuum, infrared drying, high frequency drying, ultrasonic drying and the like. These dryers are all from solution, mud, glue, mud to powder, granular, flakes, etc., as seen in the table on page 17 of “Drying Equipment” by Noboru Kubota (Energy Conservation Center). There is no drying device that can be applied to these conditions, and a dryer that matches the conditions is selected.
[0003]
Among them, the indirect heating type has a possibility that it can be used in a relatively wide range from a slurry shape to a granular shape, but it can be used only under special conditions for a solution state to a slurry shape. In the case of the vertical dryer in the indirect heating type, it becomes a batch type, but it can be fed regardless of the form of the dried material, whether it is liquid or cake, and charged There is a merit that you can drive flexibly according to the amount. For the indirect heating type, a device with a jacket that passes the heat medium around the inner tub, a device that puts the heat medium in a disk and places the material to be dried on it, or a device that evaporates moisture by vacuuming below room temperature, etc. There is.
[0004]
Furthermore, the material to be dried was subjected to centrifugal force by blades with different widths whose inner side surfaces were roughly aligned, held down on the inner surface of the tank, and water was evaporated by applying heat from the tank wall by heat exchange. . In this apparatus, the effect which gives centrifugal force to the to-be-dried object by a blade | wing, and the effect which crushes the lump which falls from upper part by the hit | damage of the edge | tip of the blade | wing arrange | positioned discontinuously were aimed. A tank having a wide upper portion and a narrow lower portion has a shape with a high escape effect with less obstacles when water vapor escapes as bubbles on the wall surface and when gas escapes from the surface of the object to be dried.
[0005]
In a conventional dryer, there is a method in which the contents placed on the blades are rubbed against the tank wall and exchanged with a high-temperature heat medium passed through the jacket. However, the material to be dried starts from sludge and is dried a little to form a paste or cream, further dried to form a cake or lump, and further dried to be granular. When considering a series of drying processes, it seems that it is often difficult to place an object to be dried on a blade itself.
[0006]
[Problems to be solved by the invention]
As an indirect heating method, there are many vertical tanks with the same diameter as the upper part, but the lower part has the same diameter as the upper part. It tries to dissipate to the top as a bubble. At that time, there is a problem that bubbles generated in the vertical upper part are obstructed and difficult to escape. In addition, when the dried product is pasted as paste, the water vapor generated on the tank wall tends to dissipate from the surface of the adhered layer, but it is also easily dissipated in the vertical direction. In vertical tanks where the water path is long and water vapor is difficult to escape, there is a problem that water vapor is slowly dissipated.
[0007]
Furthermore, in a liquid stirring apparatus, when the viscosity is low, the saddle type, propeller type, and turbine type plate blades arranged around the central axis are known to have low power consumption and high stirring efficiency. FIG. 5 is a cross-sectional view showing the conventional principle of the stirring device. A stirring shaft 12 is provided at the center of the tank 11, and a stirring blade 13 is directly attached to the stirring shaft 12. In this structure, the fluid is sucked into the blade along the stirring shaft 12 as shown at 14, discharged in the tangential direction of the rotation of the blade 13 as shown at 15, and collides with the tank wall. However, when the viscosity of the liquid increases, rotation is likely to occur only near the center in this blade structure, and the effect of stirring around the surroundings is small. When considered as a dryer, even if the content is initially low viscosity, it must have a blade structure that takes into account that the concentration increases with drying.
[0008]
In addition, if the drying progresses and becomes paste-like or cream-like and adheres to the wall surface, scraping is necessary. It is necessary to adhere. Near the center, the blade or arm attached to the blade, or the paste-like or cream-like dried material dropped on the bottom surface is hard to work with centrifugal force, so it is less likely to be blown to the wall surface, resulting in poor drying efficiency was there.
[0009]
Moreover, when drying of a to-be-dried material progresses and becomes cake shape, scraping of a wall surface or crushing of a cake is required. As a dewatering cake crusher, a vertical high-speed crusher with a stirring blade having a rod shape is known, but the rod-type stirring blade has a crushing effect, but has a problem that it cannot be used because it has a small stirring effect. .
[0010]
The present invention provides a drying apparatus having high drying efficiency, which is effective for drying a dried material consisting of solids and moisture such as sludge, mud, cake, lump, granule, and powder. Is.
[0011]
[Means for Solving the Problems]
In the present invention, four devices for performing evaporation, drying, scraping, crushing, and centrifugal force are performed for drying. First, the tank structure was inverted frustoconical, and jackets were placed on the outer periphery and bottom, and the second was the shape of the blade that was convenient for scraping, crushing, and centrifugal force. The third is to increase the rotation speed of the stirring blades, and the fourth is to scrape the position and number of the blades to improve the crushing effect.
[0012]
By adopting an inverted frustoconical shape, when the material to be dried is liquid, the liquid that has been discharged in the tangential direction of the blades and moved to the wall surface receives heat conduction from the wall surface and moves upward. Similarly, it can move with little overlap with the liquid that has undergone heat conduction. The liquid that has undergone heat conduction further moves downward near the central axis, undergoes heat conduction at the bottom surface, and again moves toward each blade.
Furthermore, when the temperature rises further on the wall surface and the bubbled vapor moves upward, the resistance decreases, and even when the material to be dried adheres to the wall surface in the form of paste or cream, the water vapor generated on the wall surface When the gas evaporates, the dissipation path is shortened, and the vapor rising speed is increased. Further, since the jacket also has an inverted frustoconical shape, the fluid layer boundary film coefficient is small when the heat flow of the jacket rises from below to above, and the heat transfer coefficient is larger than when it is vertical.
[0013]
The second is about the shape of the blades.
As for the shape of the stirring blade having a large stirring effect, the vertical, propeller, and turbine plate blades arranged near the shaft have low power consumption for low and medium viscosity, and large blades full of the tank are used for high viscosity. It is known to be effective.
Therefore, in the present invention, the high viscosity is regarded as important, and the blade is attached in the vicinity of the tank wall surface, and the stirring effect at the low viscosity is also borne by the arm provided with the blade. The shape of the blades was a saddle shape, which was slightly thicker at the front, rear, and middle of the rotation so that the thicker part was close to the wall surface.
Considering the case where the liquid has low viscosity, the blades are tilted and attached, and the liquid is moved upward by the blades by moving the blades upward by lowering the height at the front of the rotation and by raising the blades at the rear. It is possible to provide a downward movement effect in the vicinity of the rotation axis. The arm also exhibits an effect on the swirling of the liquid.
[0014]
Further, in consideration of the case where the material to be dried is further dried, the viscosity is increased, and the paste becomes a paste or cream and adheres to the wall surface, a part of the end of the blade is brought close to the wall surface. In this case, even if it is not scraped off at the front surface of the end portion of the blade, as a shape of the blade, a part of the blade is inflated so that the swelled portion comes close to the wall surface. At the stage where drying does not proceed, it is scraped off in the form of a paste, adheres to the blades, falls, and adheres to the bottom arm. Since the adhering substance has a high viscosity, it is necessary to increase the centrifugal force by increasing the rotational speed of the stirring blade in order to adhere to the wall surface again.
[0015]
Therefore, at the rotation speed which is the third device of the present invention, it can be rotated at a high speed such as a maximum of 800 rpm. As drying progresses, a part is scraped off as a lump and falls to the bottom.
In addition, the paste-like to-be-dried material which fell to the lower part was made to move to a wall surface by the blade | wing which scrapes off the lowermost lower surface. The lowermost blade has a structure in which a blade structure capable of covering from the wall surface to the vicinity of the rotation axis is attached to the arm on the lowermost surface.
When the drying further proceeds to form a cake or a lump, the arm of the stirring blade or the end of the rotating front surface of the blade has a crushing effect during the rotation.
[0016]
Further, when the drying progresses and becomes granular, powder may be formed. Therefore, it is necessary to reduce the rotation speed of the stirring blade so that dust does not flow out through the exhaust port. Therefore, the minimum rotation is 50 rpm. However, in order to discharge after drying, it is better that the rotation speed is slower.
[0017]
The fourth is about the position and number of blades.
It is known that a single stage or a plurality of stages of blades are provided on a shaft in a saddle-type, propeller-type, or turbine-type plate blade disposed near the shaft used as a stirring blade having a large stirring effect. In the present invention, the blades are arranged in a spiral shape from the lower side to the upper side or from the upper side to the lower side, and the blades are arranged at the apexes of the triangle as viewed from above. As a result, the number of blades necessary for scraping off the material to be dried adhered to the wall surface can be arranged. Furthermore, it is effective to improve the crushing effect by the arms and blades of the object to be dried.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention will be described based on examples with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of the present invention. A jacket 2 for injecting a heat medium is provided around and at the bottom of an inverted frustoconical inner tank 1, and the jacket is provided with a heat medium inlet 22 and a drain outlet 23. Is provided. The inner tank is provided with a plurality of arms 4 on only one side in a direction perpendicular to the input port 20, the discharge port 21, the rotation shaft 3, and the rotation shaft 3. A stirring blade 5 is installed at the tip of the arm 4. The stirring blade 5 is provided with a low gradient at the front in the rotational direction and a high gradient at the rear. Moreover, the blade | wing 6 which scrapes off a bottom face is provided in the lowest stage. These blades are driven by a motor 7 via a rotating shaft 3. A bearing 8 for the rotating shaft 3 is provided at the bottom of the inner tank. In addition, a hole 9 for removing water vapor is provided, and a vacuum device is attached to enable vacuum.
[0019]
FIG. 2 is a cross-sectional view showing an embodiment of the present invention. A jacket 2 for injecting a heat medium around the bottom and the entire bottom of the inverted frustoconical inner tank 1 is provided. The jacket has a heat medium inlet 22 and a drain outlet. 23 is provided. The inner tank is provided with a plurality of arms 4 on only one side in a direction perpendicular to the input port 20, the discharge port 21, the rotation shaft 3, and the rotation shaft 3. A stirring blade 5 is installed at the tip of the arm 4. The stirring blade 5 is provided with a low gradient at the front in the rotational direction and a high gradient at the rear. Moreover, the blade | wing 6 which scrapes off a bottom face is provided in the lowest stage. These blades are driven by a motor 7 via a rotating shaft 3. In addition, a hole 9 for removing water vapor is provided, and a vacuum device is attached to enable vacuum.
[0020]
FIG. 3 is a plan view showing the shape of the blade, and shows the arm 4, the blade 5, and the blade 6, (a) is one in which one end of the blade 5 is widened, and (b) is the inside of the blade 5. (C) shows the blade | wing 6 provided in the lowest step.
In both (a) and (b), the wide part has a shape closer to the inner tank wall surface than the other part. Further, the front of the rotation may be a wider side or a narrower side. The effect is increased by arranging the blades of (a) or (b) to be slightly inclined from the horizontal and (c) provided at the lowermost stage to be slightly raised. In addition, the blades may have the same width, but in that case, by attaching them at an angle, the lower part comes close to the wall surface of the inverted frustoconical shape, so that a scraping effect by the blade ends can be obtained.
[0021]
FIG. 4 is a layout view of the blades as viewed from above. The arms were raised so that the blades had a triangular shape when viewed from above, and the blades were provided at the tips of the arms.
When a gas such as high-temperature steam of 100 ° C. or higher is introduced into the jacket 2 of this apparatus, a liquid material to be dried such as sludge is introduced into the inner tank 1, and the rotary shaft 3 is driven by the motor 7. It moves to the wall surface of the inner tank 1 by the discharge force in the tangential direction, receives heat conduction from the wall surface, the liquid moves upward while turning, moves downward near the rotation axis, receives heat conduction from the bottom surface, The lowermost blade 6 moves upward.
In the paste-like material to be dried, it is attached to the wall surface by the centrifugal force of the blade 5 and swung on the wall surface, scraped off at a portion near the wall surface of the blade 5 and dropped to the lower part, but the rotational speed is Since it is large, it is splashed again on the wall surface by centrifugal force, and drying proceeds on the wall surface. Some of the objects to be dried that have fallen on the bottom surface are dried on the bottom surface, scraped off at a portion near the bottom surface of the lowermost blade 6 and moved upward. As the drying further proceeds, the material to be dried attached to the wall surface becomes cake-like or lump-like, and when part of it is scraped off by the blade, it falls as a lump and is crushed by the end of the front side of the blade 5 on the rotating side. . The crushed lump is again blown to the wall surface by centrifugal force and further dried.
[0022]
Furthermore, in the present invention, the tank is sealed, and a hole 9 for extracting steam is provided in the upper lid, and a vacuum device is added to the hole so that heating and vacuum can be performed simultaneously, and the surface of the object to be dried The water evaporated from the water is removed to speed up drying.
【The invention's effect】
[0023]
Since the present invention is configured as described above, the following effects can be obtained.
[0024]
When the object to be dried is a liquid, the entire liquid is swirled by the arms and blades, and the liquid whose heat has been exchanged on the wall surface and bottom surface rises upward and descends near the rotating shaft to be exchanged with the internal liquid. When the temperature of the entire liquid rises and the liquid temperature rises, the gas evaporates from the wall surface and the bottom surface.
[0025]
If the material to be dried is pasty or creamy, the material adhering to the wall has less moisture and has a higher solid content and can be dropped from the wall by the blade scraping effect. After the dried product falls, the dried product is blown again by the rotational force of the blades, adheres to the wall surface, and dries.
[0026]
In the case where the object to be dried is cake-like or lump-like, since the end of the tip of the blade has a crushing effect, even if it is cake-like or lump-like, it has an effect of drying with high efficiency.
[0027]
In the above description, the case where the liquid object to be dried becomes paste or cream as it is dried, further becomes cake or lump, and becomes further granular has been described. The present invention is suitable for the treatment of such an object to be dried.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a centrifugal dryer.
FIG. 2 is a cross-sectional view of a centrifugal dryer.
FIG. 3 is a plan view showing shapes of various blades of the centrifugal dryer.
FIG. 4 is a plan view of a centrifugal dryer.
FIG. 5 is a cross-sectional view of a conventional stirrer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inner tank 2 Jacket 3 Rotating shaft 4 Arm 5 Blade 6 Lowermost layer blade 7 Motor 8 Bearing 9 Steam vent 11 Tank 12 Rotating shaft 13 Stirring blade 14 Liquid flow toward the axial direction 15 Liquid flow toward the tangential direction Input port 21 Exhaust port 22 Heat medium inlet 23 Drain outlet

Claims (2)

The liquid to-be-dried product becomes paste-like or cream-like as it is dried, further becomes a lump, and further becomes granular, for drying in this order,
  An inverted frustoconical inner tub having an inlet and an outlet for dried objects;
  Equipped around the inner tank and the bottom, a jacket provided with an inlet and outlet for the heat medium,
  A rotating shaft that is rotationally driven by a motor and has a plurality of arms in a direction perpendicular to the shaft;
  A stirring blade disposed at the tip of the arm;
  A blade that scrapes off the bottom surface of the inner tank provided at the lowermost stage of the rotating shaft,
  The stirring blade is spirally arranged from the lower side to the upper side or from the upper side to the lower side of the rotating shaft, has a bowl shape, and has a low gradient at the front in the rotational direction and a high gradient at the rear. Make it a little thicker in the middle so that the thicker part is closer to the wall,
  When the material to be dried is cake-like or lump-shaped, the motor is driven at a higher rotational speed of the stirring blade than before, and when the material to be dried is granular, the rotational speed of the stirring blade is decreased more than before. It is driven like this, The centrifugal dryer characterized by the above-mentioned. An inverted frustoconical inner tub having an inlet and an outlet for dried objects;
  Equipped around the inner tank and the bottom, a jacket provided with an inlet and outlet for the heat medium,
  A rotating shaft that is rotationally driven by a motor and has a plurality of arms in a direction perpendicular to the shaft;
  A stirring blade disposed at the tip of the arm;
  A blade that scrapes off the bottom surface of the inner tank provided at the lowermost stage of the rotating shaft,
  The stirring blade is spirally arranged from the lower side of the rotating shaft to the upper side or from the upper side to the lower side, and the shape is bowl-shaped, using a low gradient in the front in the rotation direction and a high gradient in the rear,
  When the material to be dried has a low viscosity, the liquid is swirled by the blade and the arm, the temperature of the whole liquid is raised, the gas is evaporated from the wall surface and the bottom surface, and the paste or cream is formed.
  When the object to be dried is pasty or creamy, the material attached to the wall is dropped from the wall by the scraping effect of the blades, and the rotating force of the blades is again dropped after the material to be dried scraped off from the wall is dropped. The part to be dried that has been blown to the wall by the bottom surface is allowed to dry on the bottom surface, and is scraped and dried at the part near the bottom surface of the blades provided in the lowermost stage to form a cake or lump,
  If the material to be dried is cake-like or lump-like, the rotating speed of the stirring blade is increased more than before, and the crushed lump is again subjected to centrifugal force by the crushing effect of the stirring blade arm or blade tip. To dry and proceed to granulation,
  An operation method of a centrifugal dryer, wherein when the material to be dried is granular, the rotational speed of the stirring blade is reduced more than before.

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