JPS6211894B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a batch granulation method for powder, and is suitable for granulating powder such as iron oxide, which is produced as a by-product in, for example, a hydrochloric acid recovery device. It is related to. [Prior art and its problems] For example, as a hydrochloric acid recovery device from pickling waste liquid, etc.
Rusna type, Lurgi type, NKK type, Otsu type, and other types of equipment have been developed, but most of the equipment, except for the Rurgi type, use the spray roasting method. The problem with the spray roasting method is that iron oxide with a particle size of about 200 μm or less is produced as a by-product, and the iron oxide scatters during equipment operation or maintenance and inspection, making it difficult to handle. In addition, because it is difficult to handle, its commercial value is low as a raw material for paints such as ferrite and red iron, and a more effective use has been sought. One type of granulator for powder and granules is a pan-type granulator. This involves putting the ingredients on a rotating pan,
This is granulated by spraying water on it. The granulation mechanism in this process is thought to be as follows. In rolling granulation, when water is sprayed onto a dry raw material, areas with a high water content are generated locally, forming so-called cores. As the core rolls, dry powder or powder with low water content adheres to the periphery, and the water in the core leaches to the surface and further adheres powder to grow. Since the bonding force between powder particles is mainly due to the capillary suction force of water, grain growth stops when water no longer leaches to the surface. Therefore, there is an optimum value for the amount of water to be supplied to the raw material, and if the amount of water is small, the particle size will become smaller and at the same time, the amount of fine powder will increase. Conversely, if the amount of water is too large, large lumps tend to form. In addition, since it is closely related to the generation of nuclei, good results cannot be obtained unless the spray conditions are appropriate. As described above, in the conventional powder granulation method using a pan-type granulator, it is generally difficult to spray the optimal amount of water onto the powder, and as a result, the growth of the nuclei is insufficient. granulation yield is low,
There was a problem that granulation took a long time. The present invention was made in view of the problems of the prior art described above, and its purpose is to provide a batch-type granulation method for powder that shortens the granulation time and has a high granulation yield. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a batch-type granulation method for powder by charging raw material powder together with a binder into a pan of a pan-type granulator, and then In the batch-type powder granulation method in which the powder is granulated while rotating the pan and then the pan is stopped to take out the granulated material, after the raw material powder has formed a nucleus, only the raw material powder is further granulated. The powder is added continuously and is configured to promote the growth of the core of the powder. [Operation] In this configuration, the raw material powder and the binder are charged into the pan, and after the preparation is completed, only the raw material powder is continuously added at the stage where the core is formed while rotating the pan. Therefore, due to the binder having a binder distribution in the radial direction and leaching to the core surface, the raw material powder newly introduced into the pan adheres to the core surface, promoting the growth of the core. At the same time, the raw material powder is sequentially adhered to the surface of the core, and finally the core surface is in a dry state in which no binder leaches out, and granulation is completed. [Example] Fig. 1 shows a schematic configuration of a granulator used in the batch-type granulation method for powder according to the present invention, and shows a part of the granulator main body in cross section. The diagram is
2 is a diagram showing a procedure for granulating iron oxide powder by applying the method according to the present invention using the apparatus shown in FIG. 1. FIG. In FIG. 1, the granulator includes a granulator main body 1 supported at an angle with respect to a horizontal plane by a support 12 extending upward from a pedestal 10, and an iron oxide supply line 2 provided in the main body 1. It is comprised of a supply feeder 2A, a water supply line 3 and valve 3A as a granulation binder, and a pellet discharge line 4 and discharge valve 4A provided below the main body 1. The granulator main body 1 is arranged concentrically with a cylindrical pan cover 14 assembled to a column 12 via a disc-shaped support frame 6 and rotates around a central axis 16. Possible pan 18 with a cylindrical external appearance and axis 2 disposed within pan 18
The granulator body 1 is composed of a stirring plate 22 that can be rotated around 0, and drive motors 24 and 26 that are installed on the outer surface of the pan cover 14 and drive the pan 18 and the stirring plate 22. It is arranged to be inclined by α. The upper peripheral edge of the pan 18 is supported by a bearing (not shown) provided around the upper peripheral edge of the pan cover, and the bottom 18A of the pan is supported by a thrust bearing (not shown) provided on the support frame 6. (not shown). A V-belt 30 is wound around the outer peripheral surface of the pan 18 and a pulley 28 which is rotatably attached to a drive shaft 24A of a drive motor 24, and the pan 18 is moved around the axis 16 by the drive motor 24. The iron oxide powder supplied into the pan 18 is mixed with water and granulated by rotating slowly. Further, an opening is formed in the center of the bottom 18A of the pan 18, and a pellet discharge gate 31 supported by the support frame body 6 is arranged in this opening with a slight gap between the opening and the pellet discharge gate 31. The granulated pellets are discharged from the pellet discharge line 4 into a pellet hopper 8 provided on a pedestal 10 by operating a lever 7 for adjusting the pellet discharge amount. A support frame body 3 is provided on the outer surface of the pan cover 14.
A horizontal arm 34 extends above the pan 18 from the upper end of the support frame body 32, and a rotating shaft 36 supported by the horizontal arm 34 and having an axis 20 parallel to the axis 16 rotates the pan 18. It protrudes into 18. A stirring plate 22 is fitted to the downwardly protruding end of the rotating shaft 36, and a protrusion 22A is provided on the surface of the stirring plate 22 facing the bottom surface of the pan 18.
is formed. A V-belt 42 is installed between a pulley 38 that is attached to the rotating shaft 36 and a pulley 40 that is attached to the drive shaft 26A of the drive motor 26.
The stirring plate 22 is rotated by the drive motor 26 to the rotating shaft 36.
The pan 18 rotates about the axis 20 in a direction opposite to the direction of rotation of the pan 18 at a high speed. The stirring plate 22 is driven to rotate while the pan 18 is rotating, and has the function of increasing the mixing efficiency of the iron oxide powder and water (uniform mixing in a short time), as well as destroying large nuclei. It is effective in making the pellet diameter uniform, and has the effect of particularly increasing granulation efficiency (creating pellets of uniform particle size in a short time) when the target pellet size is 10 mm or less. Note that the reference numeral 44 indicates the direction from the horizontal member 34 to the arm 45.
A scraper is provided at a position near the bottom of the pan 18 through which it does not interfere with the rotation of the stirring plate 22 to prevent powder from adhering to the bottom of the pan. Next, the procedure of the method according to the present invention will be explained using the apparatus shown in FIG. Iron oxide powder is fed by rotary feeder 2A from line 2, while water as a binder is fed from line 3.
A predetermined amount is charged into the pan 18 via the supply valve 3A, and after the charging is completed, the granulator starts a mixing operation by rotating the pan 18 and stirring plate 22. In the case of batch granulation, granulation can be divided into four stages: (a) mixing, (b) nucleation, (c) nucleus growth, and (d) finishing, as shown in Figure 2. can. The pellets that have reached the target size through the finishing step (d) are dropped into the pellet hopper 8 by opening the discharge valve 4A, and one batch is completed. In the above operation, as shown in FIG. 2, the iron oxide feeder 2A is opened during charging, closed during (a) mixing and (b) nucleation, and opened during subsequent stages. Further, the water supply valve 3A is opened at the time of preparation, but is closed after the start of mixing. The procedure of the granulation method shown in Figure 2 is the procedure when using an experimental machine.
Pelletization time may vary depending on the model and capacity. In this case, the optimal procedure can be determined by the following method. (1) Creation of nucleation characteristic curve We repeated granulation tests with various amounts of moisture on a fixed amount of powder, and observed the nucleation time and time to reach a sticky state, as shown in Figure 3. A nucleation characteristic curve is obtained. In the figure, A indicates a sticky region, B indicates a region suitable for nuclear growth, and C indicates a crumbly region. (2) Next, from an industrial perspective, calculate the amount of powder and moisture charged into the pan of the granulator based on the above graph, and also calculate the powder input speed during nucleus growth and the powder input speed during finishing. The granulation procedure is determined by this decision. In the present invention, the most important step in the granulation operation is the nucleus growth step (c), and it has been experimentally confirmed that the pellet size, strength, etc. are determined in this step. That is, the formed nucleus has a moisture distribution in the radial direction, and it is thought that the driving force for the growth of the nucleus is to apply rolling energy while keeping the surface moisture of the nucleus in an appropriate area. As a method for realizing this in a granulator, it has been confirmed that it is extremely effective to continuously introduce iron oxide powder into the pan of the granulator during the nucleus growth step. That is, by continuously adding this iron oxide powder, the time required for nucleus growth was reduced to two-thirds compared to the conventional iron oxide granulation method in which iron oxide powder was not added during nucleus growth. Moreover, the granulation yield was also improved by 8%. The appropriate value for the surface moisture of the core was 20 to 30% when a pan-type granulator with a stirring plate was used and the rotation speed of the stirring plate was 750 rpm and the rotation speed of the pan was 80 rpm. If the surface moisture of the pellets falls below a suitable value, the growth of the nuclei becomes difficult and the granulation operation proceeds directly to the finishing step. By adding more iron oxide powder,
Finally, the surface of the pellets is dried and granulation can be completed. Generally, it is effective to continuously introduce a smaller amount of iron oxide powder into the pan during the finishing step than during the nucleus growth step. In addition, if the charging speed at the time of iron oxide preparation is the same as the charging speed at the time of nucleus growth, the charging speed of the iron oxide powder can be changed over in two stages. Moreover, the reduction in granulation time can also be explained as follows. As shown in FIG. 3 Since the iron oxide powder is injected, the optimum moisture content state for nucleation is reached, for example, as shown in Fig. 3 Y, and in this state _, the nucleus grows. After going through steps and preparation steps, it reaches the target size. Now, in the optimum moisture value state for nucleation shown in Fig. 3 Y,
Let t ₂ be the time from the start of granulation to the formation of nuclei, and t ₃ be the time from the start of granulation to the end of the finishing step. _In the state indicated by For example, the process moves to point Q (the symbol Q indicates the starting point of nucleation in the optimal moisture value state) as shown in FIG. In this case, the time required from the start of granulation to the end of the finishing step is t ₁ + (t ₃ - t ₂ ), and compared to the granulation time t ₃ in the state indicated by Y, the granulation time is t ₂ - _{t 1} . Grain time becomes shorter. Examples of the characteristics of the iron oxide pellets produced as described above are shown in the table below. According to the above embodiment, by applying the powder batch granulation method according to the present invention when iron oxide by-produced in a hydrochloric acid recovery device is granulated, the hydrochloric acid recovery device can be granulated in a short time. The iron oxide powder produced as a by-product can be granulated. In addition, since the granulation time is shortened, environmental pollution caused by iron oxide can be solved, and the bulk specific gravity of pelletized iron oxide can be increased to more than three times that of powdered iron oxide, making it easier to handle. Furthermore, as shown in the table, the produced pellets have considerable strength, so they generally satisfy the requirements as a sintering raw material for blast furnaces, and the commercial value of iron oxide can be increased.

〔Effect of the invention〕

According to the present invention, raw material powder and a binder are placed in a pan, and when the bread is rotated and a nucleus is formed, only the raw material powder is continuously added. The growth of the core is promoted by the adhesion of the raw material powder introduced into the core surface, which reduces the granulation time of the powder and ultimately creates a dry state in which the binder does not leach onto the core surface. Since the cores grow sufficiently until they become granulated, it is possible to improve the yield of powder granulation.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of a granulation device to which the method according to the present invention is applied, FIG. 2 is a diagram showing the operating procedure of the device in FIG. 1, and FIG. 3 is an example of the method according to the present invention. It is a figure showing an example of a nucleation characteristic curve in. 1... Granulator, 2... Iron oxide supply line, 3...
...Water supply line, 4...Pellet discharge line, 1
0... Frame, 12... Support, 14... Pan cover, 18... Bread, 22... Stirring plate.

Claims (1)

[Claims] 1 Powder batch type in which raw powder is charged together with a binder into a pan of a pan-type granulator, and then the powder is granulated while rotating the pan, and then the pan is stopped and the granulated product is taken out. A batch-type granulation method for powder, characterized in that after the raw material powder forms a nucleus, only the raw material powder is continuously added to promote the growth of the core of the powder.