JPS5887195A - Method for deashing coal - Google Patents

Abstract

PURPOSE:To granulate fine coal powder in a good yield and to improve a deashing rate, by adding a binder to a slurry of fine coal powder in water, revolving a motor at a high speed to form granulated coal powder having a small diameter, and rotating the motor at a low speed to enlarge the particle size of the granulated coal powder. CONSTITUTION:A slurry 13 of fine coal powder in water and an emulsion type binder 11 contg. fuel oil are introduced into an agitating tank 1 equipped with agitating blades 5 and a plurality of fixed backles 3. A motor 9 is driven at a high speed. Stirring is conducted such that the agitating blades 5 are revolved at a peripheral speed of 12.5-30m/s. The binder 11 is well-dispersed in the slurry 13 to deposit the binder on the whole surface of fine coal powder. Ash deposited on fine coal powder is released, and the growth of granulated coal powder in size is inhibited to a particle size of 1.5mm. or below. Then the motor is revolved at a low speed such that the agitating blades are revolved at a peripheral speed of 2.5-10m/s to enlarge the particle size of the granulated coal powder to an average particle size of 2mm. or above.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and removing ash from coal, and particularly to a coal deashing process suitable for increasing the deashing rate and the recovery rate of coal.

In the conventional coal deashing process using the underwater granulation method, the ash was separated at the same time as pellet-shaped granules were obtained by stirring at a relatively low speed. Since the granules are granulated before the surface of the particles has been sufficiently covered, and the ash remains in the granules, the deashing rate cannot be sufficiently increased.

An object of the present invention is to provide a coal deashing process that improves the deashing rate and recovery rate.゛The main point of the present invention is to add a hydrophobic binder to pulverized coal and water pulp in an emulsion state, and to granulate it by stirring the powder.
The basic component is to provide a stirring effect by high-speed rotation, and then a stirring effect by low-speed rotation.The high-speed stirring sufficiently spreads the binder over the coal surface to liberate ash, and the primary low-speed stirring separates the coal particles. The purpose of this method is to obtain the effect of growing large-diameter granules into a shape that can improve the recovery rate of coal.

An embodiment of the present invention is shown below in Fig. 1, Fig. 2, Fig. 3, @
This will be explained based on FIG.

Granulation is carried out using a stirring device as shown in FIG. The stirring device is composed of a stirring tank 1, a stirring structure NILf'I stirring 1a2 which rotates a blade 2a, and a baffle 3 fixed in the tank 1. A binder 5 in the form of an emulsion consisting of pulverized coal (-200 meds - 80) with a concentration of 28 oz., a water bulb 4 and heavy oil (30% of coal) is placed in the sieve 1 and granulated with stirring. Note that the rotation speed of the stirrer 2 is variable.

The rotation speed variable means may be configured such that a motor is connected to the rotation shaft of the blade 2a via a transmission, and the rotation speed of the blade 2a is changed by switching the transmission, or a variable speed motor is connected to the rotation shaft of the blade 2a. The configuration may be such that the rotation speed is changed by connecting the motors and controlling the speed of the motor.

Figure 2 shows the relationship between the granulation time and the average particle diameter of the granulated product when granulating using this method.
When the rotation speed is constant at 00 rpm, curve 7 is the rotation speed of 180 Orpm.
In a constant case, curve 8 shows the case where granulation is performed at a rotation speed of 20 Orpm after 10-order stirring granulation at a rotation speed of 180 Orpm. Each granulation end point 9, 10 and 11 (both 45TI
The ash content in the granulated coal is based on the converted base (lA1
5 each (without the binder and water in A1)
．． 1%, 3°9 section and 39q6. The ash content of raw coal is 8 on a converted basis (without moisture in raw coal).
+10%, so the deashing rates are 394%, 54%, and 54%, respectively.

Figure 3 shows the relationship between the granulated coal particle size and the coal recovery rate, and the points corresponding to the granulation end points of 9.10 and 13 are 12.14 and 13, respectively, and the coal recovery rate is 10096. , 94 honors and 100 rank.

This is a case where the stirring device 16 stirs at low speed.

In this case, the valve that has been subjected to high-speed stirring by the stirring device 15 is caused to flow into the stirring device 16 through the pipe 17, and low-speed stirring is performed. In this way, continuous processing is possible and efficient, and the motor for stirring the heat is connected to the stirring device 15.
The stirring device 16 needs to be rotated at a constant high speed, and the stirring device 16 needs to be rotated at a constant low speed, so there is an advantage that a means for varying the rotation speed is not required.

Similar results can be obtained with this method.

In such a case, in order to avoid a short path of the pulp, that is, a sudden flow of pulp that has not been sufficiently subjected to high-speed agitation treatment into the low-speed agitation treatment side, the high-speed and low-speed
It is better to connect 1000 stirring devices in series.

Whether using the stirring device shown in Figure 1 or using multiple stirring devices in series as shown in Figure 4, the valve is first stirred at high speed; In order to release as much ash as possible, we also use high-speed agitation power to increase the growth rate of coal particles due to the bonds between the coal particles. The coal particles are brought into contact with each other so that the ash can be released.Then, in the heat, the ash content is sufficiently released and becomes full!The sticky coal particles are stirred at low speed to bring each coal particle into contact and bind them together via a binder. At this time, since the stirring force is slow, the coal particles that are in contact with each other cannot separate, and the coal particles gradually become larger in diameter, until the coal is collected using a sieve. The collection rate will improve as the size becomes smaller so that it won't come out.

In each example, m-wells were stirred for a long time due to high-speed rotation. Carry out the rotation at a speed that allows the growth rate of the granules to grow to a larger diameter, and when the average particle size of the granules reaches about 1 m+u, move on to stirring at a low speed. Preferably, low speed rotation - heavy stirring 1! It is preferable to carry out troweling at a speed of 4 rotations until the granules grow rapidly, and collect the granules at four points where the average particle diameter of the granules becomes 3 holes or more.

However, the average particle diameter of the granules may be of any value depending on the size of the recovery sieve and the desired deashing rate. The high/low speed stirring rotational speed may also be different from this example depending on the granulation conditions, desired deashing rate, and recovery rate.

As described above, in the underwater granulation process of coal, the present invention first applies a stirring action to the liquid to be treated using high-speed rotation and heat to sufficiently spread the binder to the coal to improve the deashing rate, Next, a stirring action is applied by low-speed rotation to promote the granulation growth of the coal, and the diameter of the recovery chamber for the granulated coal can be increased, making it possible to recover granulated coal with a high ash rate. You can get the desired effect.

[Brief explanation of the drawing]

Fig. 1 is an autopsy cross-sectional view of the stirring device used in one embodiment of the present invention, Fig. 2 is a performance curve diagram showing the relationship between stirring time and particle size of granulated material at each stirring rotation speed, and Fig. 3 2 is a diagram showing the relationship between the recovery rates of coal treated with each performance curve in FIG. 2, and FIG. 4 is an autopsy cross-sectional view of a stirring equipment according to another embodiment of the present invention. 1... Stirring tank, 2... Stirrer, 3...
Baffle, 4...pulverized coal, water pulp, 5...
... Binder, 6 ... Particle size one-hour curve when rotating at low speed, 7 ... Calibration diameter one-hour curve when simultaneously stirring at high speed, 8
... Particle size one-hour curve during combined stirring rotation at high and low speeds, 9 ... Pelletization end point during low interstitial stirring rotation, 1
0...End point of granulation during high-speed stirring rotation, 11...
...Pelletization end point during high speed and low speed combined stirring rotation, 12
...... Granule recovery rate point during low oil stirring rotation, 13.
...Granulated material recovery rate point during combined mixing at high and low speeds,
14... Granule collection point during bird oil stirring rotation, 15,
16... Stirring device agent Patent attorney Susuki 1) Kochi Toshi 1 Figure 4 Continued from page 1 of Figure 4 Inventor Katsumi Muroi 502 Kandatecho, Tsuchiura City, Hitachi, Ltd. Mechanical Research Laboratory 0 Applicant: Hitachi, Ltd., No. 1, Marunouchi-5-chome, Chiyoda-ku, Tokyo Written amendment (from XA) Case description 1982 Patent Application No. 185345 Name of the bow invention Coal deashing method Name of the person making the amendment 1!1 (5101 Stock Co., Ltd. 11th
Representative name of Tachi Seisakusho 3 1) Masaru
Contents of the amendment by Shigeyo Osamu As shown in the appendix, the title of the invention in the amended specification is a method for granulating and deashing coal, which is below the scope of the claims, and the high-speed stirring action is based on the stirring ash method. DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for granulating and deashing coal. [Prior art] When burning a mixed fuel made by mixing heavy oil and coal in a boiler, in order to achieve a high combustion rate, it has traditionally been necessary to remove the ash and sulfur content from the coal before mixing the coal with the heavy oil. was considered. Conventionally, oil-in-water granulation is known as a method for removing ash from coal. The conventional oil-in-water granulation method is a method in which a mixed liquid prepared by adding a small amount of heavy oil to a slurry liquid of pulverized coal and water is stirred. According to this method, while the mixed liquid is being stirred, heavy oil that has good affinity for coal adheres to the pulverized coal, and the pulverized coals are combined with each other using the heavy oil as a binder to form granulated coal. In addition, ash, which has a weak affinity with heavy oil, floats in the mixed liquid in a state separated from the pulverized coal without being significantly bonded. Here, when the mixed liquid is passed through a sieve, the granulated coal having a large diameter remains on the sieve, and the mixed liquid and ash pass through the sieve and are discharged. Therefore, granulated coal with a low ash content is collected on the sieve. In such an oil-in-water granulation method, pulverized coal is made into large-diameter granulated coal that can be recovered at a high rate by sieving. However, in the conventional oil-in-water granulation method,
In order to improve the coal recovery rate, the mixed liquid was merely given a slow stirring action that tends to cause the diameter of the granulated coal to increase. For this reason, the pulverized coals bond together before the binder is sufficiently attached to the pulverized coals. Therefore, it is difficult to fill the bonding spaces between the pulverized coal with a binder and prevent water and ash from forming between the pulverized coals. Therefore, the granulated coal produced by the combination of pulverized coal contains a large amount of water and ash. [Object of the Invention] The object of the present invention is to recover the pulverized coal in the slurry liquid as granulated coal at a high rate, and at the same time to improve the deashing rate. [Summary of the Invention] The basic constituent elements of the present invention are a granulation method in which a mixed solution of a slurry of pulverized coal and water and a binder added is stirred;
A method of producing coal characterized by applying a high-speed stirring action to the mixed liquid to produce small-diameter granulated coal, and then applying a low-speed stirring action to the mixed liquid to enlarge the small-diameter granulated coal. This is a granulation deashing method, which prevents pulverized coal from becoming large-diameter granulated coal through high-speed stirring action, sufficiently attaches a binder to pulverized coal, and removes pulverized coal with a high ash content. away from the
Next, using a slow stirring action, the bonding state of the pulverized coal, which is filled with a binder to prevent moisture and ash from entering between the bonds, is rapidly promoted, and the particle size of the granulated coal is rapidly increased. As a result, large-diameter granulated coal that is easy to recover can be obtained with a high deashing rate. [Embodiment of the Invention] In FIG. 1, a plurality of baffles 3 are fixed to the inner surface of a stirring tank 1. A stirring blade 5 is placed in the stirring tank 1, and this blade 5 is fixed to a shaft 7. The shaft 7 extends upward and is connected to the rotating shaft of a variable speed electric motor 9. The motor 9 may be installed in the stirring tank l, or it may be installed in a separate part from the stirring tank l. A slurry liquid 13 with a concentration of 28% made by mixing pulverized coal (200 mesh powder - 80%) with water is placed in the stirring tank 1. Next, a binder 11 in the form of nibbles containing an amount of heavy oil with a coal-to-coal ratio of 30 inches is placed in the stirring tank 1. Next, the motor 9 is driven at a high rotation speed to rotate the blade 5 at a circumferential speed of 15 m/s. In this way, the mixed liquid of the binder 11 and the slurry liquid 13 is subjected to a high-speed stirring action by the blades 5, and further hits the baffle 3 to form a turbulent flow state and is well stirred. Due to the high-speed stirring action, the binder 11 is diffused throughout the slurry liquid and adheres well to the entire surface of the pulverized coal. The ash attached to the pulverized coal is separated from the pulverized coal by the high-speed stirring energy. This high speed stirring action continues for approximately 10 minutes. The song @15 shown in FIG. 2 shows the average particle size of the granulated coal obtained when a high-speed stirring action is continued to be applied to the mixed liquid in the stirring tank l for a long time. As is clear from this curve 15, under high-speed stirring action, the pulverized coal aggregates and the average particle size of the granulated coal increases to only about 13 mm (point 17). , the speed of increasing the diameter also becomes slower. In this state, even if you try to collect granulated coal with a sieve, a large amount of pulverized coal will pass through the sieve openings, and the recovery rate will drop to 95 inches (point 19 in Figure 3). It becomes uneconomical in terms of power. Therefore, the high-speed stirring action is limited to 10 minutes after the start of stirring. During this period of about 10 minutes, the pulverized coal is granulated to about 0.4 ml in diameter through a binder, thereby increasing its diameter. During this time, the mixed liquid in the stirring tank 1 is vigorously stirred by the high-speed stirring action, so that the binder 11 is sufficiently attached to the entire surface of each particle of pulverized coal within a short time. In this way, the entire surface is sufficiently coated with binder 11.
Ash that has low affinity with the binder 11 does not adhere to the pulverized coal coated with the pulverized coal, and only the pulverized coals bond with each other. After applying a high-speed stirring action to the mixed liquid for about 10 minutes, the rotational speed of the motor 9 is reduced to a low rotational speed, and the circumferential speed of the blade 5 is set to 9 m/s. In this way, the stirring tank l
A slow stirring action can be applied to the mixed liquid of the liquid 13 and the binder 11 inside. In this way, by reducing the stirring energy applied to the mixed liquid, the phenomena in which the bond of pulverized coal, that is, the granulated coal is destroyed or the promotion of the initial bonding state is disturbed due to large stirring energy, are reduced. Therefore, as shown in FIG. 2, the average particle size of the granulated coal gradually increases along the curve 15 for about 10 minutes, but after 10 minutes, the granulated coal increases as shown by the curve 21. The average particle size of the charcoal increases more rapidly than in the case of curve 15 (point)
At the same time as point 19 (45 minutes later), the temperature exceeds 311I as shown by point 23. When the average particle size of granulated coal reaches 311, the point shown in Figure 3)25
As shown, the coal recovery rate reaches nearly 100 cm, and the amount of pulverized coal passing through the sieve becomes almost zero. Moreover, in the early stage of stirring, the entire surface of the pulverized coal particles can be sufficiently coated with the binder 11 so that there is almost no uncoated part, so when the pulverized coal is combined, the bonding agent 11 The gap is now filled with the binder 11. For this reason, there is no room for moisture or ash to enter into the gaps between the bonds, and the ash content in the granulated coal is as low as 39% based on anhydrous coal. By the way, from the initial stage of stirring, slow stirring action is applied to slurry liquid 1.
If it continues to be added to the mixture of 3 and binder 11, the second
As shown in the curve n shown in the figure, after 45 minutes, the average particle diameter of the granulated coal becomes 3 mm larger at point) 29, so the coal recovery rate becomes as shown at point) 28 in Figure 3. It shows a value close to 100%. However, since the stirring action is slow, the binder 11 does not sufficiently adhere to the entire surface of the pulverized coal particles. Therefore, the bonding gaps between the pulverized coals are not filled with the binder 11, and moisture and ash tend to enter the bonding gaps. Therefore, the moisture and ash content in the granulated coal increases, and the ash growth rate shows a high value of 51% based on anhydrous coal. The pulverized coal (raw coal) used in this example has an ash content of 84% based on anhydrous coal, so it is initially added to a mixed solution of In one case where a high-speed stirring action is applied followed by a low-speed stirring action, the deashing rate is 54%. If the low-speed stirring action is continued from the beginning, the deashing rate will only reach 39 degrees, so the deashing rate is improved in this example. In this way, this embodiment has the advantage of being able to improve the coal recovery rate and the deashing rate at the same time. In this embodiment, the high-low speed stirring action is selected by switching the rotational speed of the variable speed motor 9, but the motor 9 is of a constant speed type, and the constant speed motor and shaft 6 are connected to each other. By connecting the two through a transmission and selecting the rotation speed of the wing bar 5 between high and low speeds by the transmission, it is possible to select a high or low speed stirring action. Another embodiment of the invention will be described below with reference to FIG. The stirring tank 31 is installed at a lower position than the stirring tank 31. A plurality of baffles are fixed inside each stirring tank 31, 33. A stirring blade 37 is arranged inside the stirring tank 31 . A shaft 39 is connected to the blade 37. A constant speed motor 4 is mounted on the shaft 39 to generate high speed rotation.
One rotating shaft is connected. The motor 41 is fixed to other members around the stirring tank 31. Similarly, a stirring blade 0 is arranged inside the stirring tank, and this blade 43 is connected to a motor 47 via a shaft 45. This motor 47 is a constant speed motor set to rotate at a low speed. The stirring tank 31 and the stirring tank 31 are connected to each other by a shaft 49. Further, the stirring tank and the sieve 51 are connected by a grate. The sieve 51 is attached to the tank 55. A drain pipe 57 is connected to the lower part of the tank 55. In such an embodiment, the same slurry liquid 1 as in the previous embodiment is used.
3 and the binder 11 are continuously injected into the stirring tank 31. The slurry liquid 13 and the binder 11 are subjected to a high-speed stirring action by blades that rotate at high speed by the rotational force of the motor 41. This ensures that the binder 1 is applied to the entire surface of the pulverized coal particles.
1 is attached. The pulverized coal to which the binder 11 has sufficiently adhered is
The mixed liquid of the slurry liquid and the binder 11 is introduced into the stirring tank 33 through the gutter 49. Inside this stirring tank,
The mixed liquid is subjected to a slow stirring action by the blade 431 rotated by the rotational force of the motor 47. Therefore, the average particle size of the granulated coal rapidly increases in the stirring tank. Moreover, since the pulverized coal has already been sufficiently coated with the binder 11 by the high-speed stirring action in the stirring tank 31, granulated coal is produced without moisture or ash entering into the bonding gaps of the pulverized coal. Therefore, granulated coal has a state in which the recovery rate is high due to the increase in diameter and a state in which the deashing rate is high. The granulated coal in the stirring tank is poured down onto the sieve 51 together with the mixed liquid. For this reason, the granulated coal accumulates on the sieve 51, and the ash-containing mixed liquid is poured into the tank 5. The mixed liquid containing ash is drained out of the tank 5 through a drain pipe 57. Therefore, granulated coal with a high deashing rate can be extracted with a high recovery rate. In this example, since the motors 41 and 47 are used for high-speed stirring and low-speed stirring, there is no need to worry about switching the motor rotation speed, and the motors 49 and 49 have both high-speed stirring action and low-speed stirring action. Separate stirring tanks 31, 3 connected
Since it is executed within 3 hours, it is possible to continuously create granulated coal.
Good processing efficiency. Further, in the case of this embodiment, the mixed liquid is likely to be subjected to a low-speed stirring action without being sufficiently subjected to a high-speed stirring action. This state is generally referred to as a short path. If this short pass occurs, the pulverized coal will not be sufficiently coated with the binder 11, resulting in a slightly lower deashing rate. Therefore, it is necessary to prevent this short pass. If it is necessary to prevent this short path, between both stirring tanks 31 and 33,
, 33, and another stirring tank is placed at the middle height of the stirring tank 31.
and another stirring tank, and then connect this other stirring tank and the bottom of the stirring tank with a wire. Furthermore, a stirring blade rotated by a motor that rotates at high speed is placed in the above-mentioned another stirring tank. In this case, a high-speed stirring action is applied to the mixed liquid in the stirring tank 31, and then the stirring tank 3
The mixed liquid in 1 is put into a stirring tank placed between the two stirring cypresses 31 and 33 using a hoop, and a high-speed stirring action is applied to the mixed liquid here as well, and then the mixed liquid is poured from the stirring tank placed in the middle. The mixed solution is poured into a stirring tank using a sieve, where a slow stirring action is applied to the mixed solution. According to this method,
The probability that the mixed liquid flows into the stirring seed part without being subjected to a sufficient high-speed stirring action is reduced, the binder can be sufficiently attached to the pulverized coal, and the deashing rate can be improved. In addition, if granulated coal that is not sufficiently large in diameter tends to flow into the sieve 51, another stirring tank may be installed between the stirring seed part and the sieve 51 at a lower position than the stirring tank. The agitating tank and the agitating tank 51 are connected with a comb, this separate agitating tank and the sieve 51 are connected with a comb, and a stirring blade rotated by a motor that rotates at a low speed is placed in this separate agitating tank. In this case, the mixed liquid that has been subjected to a high-speed stirring action in the stirring tank 31 is then subjected to a slow stirring action in the stirring tank, and then is poured into another stirring tank. In this separate stirring tank, the mixed liquid is subjected to a slow stirring action. Thereafter, the mixed liquid is drained onto a sieve 51. According to such a method, the probability that the liquid mixture is poured onto the sieve without being subjected to sufficient low-speed stirring action is reduced, and the granulated coal becomes sufficiently large in diameter and can be taken out onto the sieve. Further, in order to reliably provide a sufficient high-speed stirring action and a sufficient low-speed stirring action to the mixed liquid, the following method can be adopted. That is, the four stirring tanks are connected in series, and the mixed liquid that has been stirred at high speed in the first stirring tank is again stirred at high speed in the second stirring tank. A mixed solution subjected to a high-speed stirring action in a stirring tank is given a slow stirring action in a third stirring tank, and then a slow stirring action is given again to the mixed solution in a fourth stirring tank, The mixture is then poured from the fourth stirring tank onto a sieve. The heat of this method simultaneously reduces the probability that the mixture will not be subjected to sufficient high-speed agitation and instead will be subjected to low-speed agitation, and the probability that the mixed liquid will not be subjected to sufficient low-speed agitation and be poured onto the sieve. As a result, granulated coal with a large diameter and high deashing rate can be obtained. In any of the examples, the rotational speed of the stirring blade, the time for applying high-speed stirring action to the mixed liquid, and the time for applying low-speed stirring action to the mixed liquid are appropriate depending on the desired deashing rate and granule size. This is determined by the following. The relationship between the circumferential speed of the stirring blade, the average particle diameter of the granulated coal, and the deashing rate obtained by the present inventors is shown in a graph as shown in FIG. 4. That is, the circumferential speed of the stirring blade is 2.5 m 7' s or more1
In the range below orn/S, the deashing rate (solid line curve shown in Figure 4) is 30 to 40%, and the average particle size of granulated coal (dotted line curve shown in Figure 4) is 2 or more. When granulated coal with an average particle size of 2 tom or more is collected using a sieve with a roughness of 0.5 U+, which is commonly used in practice due to classification efficiency, the recovery rate is 99 or more, which is extremely high. It shows a high recovery rate. If the circumferential speed of the stirring blade is less than 2.5 m/'s, granulated coal will not be produced, or even if it is produced, the granulated coal will not be produced. The average particle size is not large and furthermore, deashing does not proceed.In particular, in cases where granulated coal is produced continuously in preparation for multiple stirring tanks in series, the circumferential speed of the stirring blade is 2.゜5 m /
If it is S, the stirring energy is weak, so the granulated coal will settle and will not flow out to the next cypress or onto the sieve, making it impossible to produce large-diameter granulated coal. Therefore, a slow stirring action for increasing the diameter of granulated coal that cannot be recovered means that the peripheral speed of the stirring blade is 2.5 m/s or more and 1
It is desirable that the speed is 0 m/s or less, and moreover, considering the safety factor, it should be 35 m/s or more and 9 m/s.
The following is preferable. Furthermore, as is clear from the graph in Figure 4, the deashing rate tends to increase as the peripheral speed of the stirring blade increases; when the peripheral speed is 12.57 n/s, the average particle size of the granulated coal is approximately 15
A noticeable bend can be seen at this point, and as the circumferential speed increases from this part, it becomes gentle and the circumferential speed reaches 2.5 m/s.
The demineralization rate reaches a maximum value of 60 cm between ~30 m/8 and does not reach a higher rate. 7. Therefore, it is desirable that the circumferential speed of the stirring blade during high-speed stirring is 12.5 m/s or more, which dramatically improves the deashing rate. In addition, the circumferential speed of the stirring blade is 12.5 m/
Since the deashing rate decreases rapidly below 12.5 m/s, the lower limit of the circumferential speed of the stirring blade during high-speed stirring action is 12.5 m/s.
It is economically preferable to set the upper limit to 30 m/8 in view of the large diameter limit of the granulated coal with respect to the consumption of stirring energy. In particular, when a high deashing rate is desired, the circumferential speed of the stirring blades should be set at a high speed of stirring (25 m/s ~
30 m/s), and within this circumferential speed range of 25 m/s to 30 m/g, the average particle size of the granulated coal does not exceed l111. Therefore, the mixed liquid is stirred at a speed that maintains the average particle size of the granulated coal not to exceed 1111 as a high-speed stirring action, and then a slow stirring action is applied to the mixed liquid. Very good results can be obtained in terms of improving the deashing rate and improving the recovery rate. In addition, by setting the slow stirring action so that the average particle size of the granulated coal is 3n or more, the recovery rate can be almost 100% when using a sieve with a roughness of 0.5 t*. reached, indicating an extremely high recovery rate. [Effects of the Invention] As described above, in the present invention, a high-speed stirring action is applied to a mixed liquid of a slurry of pulverized coal and water and a binder to sufficiently adhere the binder to the pulverized coal, and then a low-speed Since a stirring action is imparted to the mixed liquid to increase the diameter of the granulated coal and to reduce the ash content, it is possible to obtain the effect that granulated coal with a high deashing rate can be recovered at a high rate. 4. Brief Description of the Drawings FIG. 1 shows a first embodiment of the present invention, and is a sectional view of a coal granulating apparatus. Figure 2 is a graph explaining the present invention, in which stirring time (horizontal axis) and average particle diameter of granulated coal (vertical axis)
Indicates the relationship between FIG. 3 is a graph explaining the present invention, showing the relationship between the average particle diameter of granulated coal (horizontal axis) and coal recovery rate (vertical axis). Figure 4 is a graph explaining the present invention, showing the relationship between the peripheral speed of the stirring blade (horizontal axis), the deashing rate (left vertical axis), and the average particle diameter of granulated coal (right vertical axis). show. FIG. 5 is a sectional view of a coal granulator according to a second embodiment of the present invention. 1,,31.33... Stirring tank, 5,37.43
... Stirring blade, 9.41.47 ... Motor, 11 ... Binder, 13 ... Slurry liquid of water and pulverized coal, 49. 53...Sieve 0, 51...Sieve 0

Claims (1)

[Claims] 1. In a granulation method in which a hydrophobic binder is added to a valve between coal particles and water and a stirring action is applied, the stirring action is first applied by high-speed rotation, and then the stirring action is applied by low-speed rotation. A coal deashing method characterized by adding stirring action. 2. The coal deashing method according to claim 1, wherein the stirring action by high-speed rotation and the stirring action by low-speed rotation are performed in the same stirring treatment tank by changing the rotational speed of the stirrer. 3. The coal deashing method according to claim @1, characterized in that the stirring action by high-speed rotation and the stirring action by low-speed rotation are performed separately in each connected stirring treatment tank.