JPS6410038B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for deashing coal.

Ash attached to or contained in coal deteriorates combustion efficiency, causes pollution, and has an adverse effect on combustion equipment, so it is necessary to remove this ash.

The conventional method for deashing coal is to pulverize the coal so that it contains about 70 to 80% of coal particles of 200 mesh or less, to make it easier for the ash in the coal to come out, and then to process this pulverized coal into coal granulation. method is known. This coal granulation treatment is performed by adding water to pulverized coal to form a slurry, adding oil as a binder to this slurry, and stirring the slurry. In this way, the ash adhering to the pulverized coal is liberated into the water while being stirred, and oil, which has a much stronger affinity for coal than ash, adheres to the coal instead of the ash. This oil acts as a binder, causing the coal particles to coagulate and eventually become combined and granulated into large particles. The granules are collected and separated from the liquid portion of the slurry through a sieve, and the ash, which has a weak affinity for oil, is discharged through the sieve together with the liquid portion of the slurry without agglomerating.

The aggregation will be explained. As is well known, the granulation process can be broadly divided into agglomeration process, in which coal particles simply aggregate into small aggregates with weak bonding force, and growth process, in which surrounding coal particles are drawn in and grow to form aggregates with strong bonding force. During the process, the aggregate rotates and revolves in the agitated water stream, and further draws surrounding coal particles into a shape that has a smooth outer peripheral surface with good drainage and a small surface area for water to adhere to, i.e., a spherical or ellipsoidal shape. It sequentially undergoes a concentration process in which it becomes a dense aggregate with greater bonding strength. With this increase in density, water within the aggregate can be discharged to the outside. The aggregation refers to an aggregation process, and the agglomerate refers to granules obtained by the aggregation process.

According to this conventional method, coal particles are combined in water in which a large amount of free ash is suspended, so it is easy to incorporate floating ash during the combination, and a large amount of ash is contained in the granules. It will be included.
For this reason, there was a drawback that the deashing rate was poor.

An object of the present invention is to improve the deashing rate of coal.

The gist of the present invention is, as a basic component, in a method of granulating pulverized coal by adding oil to a slurry made by mixing pulverized coal and water and applying a stirring action, after the start of the stirring action, The coal deashing method is characterized in that clean water is added to the slurry before the stirring action ends, and the granulation process is carried out in an atmosphere with a low ash content.

While experimenting to confirm the relationship between the stirring time (same as the granulation time) in the granulation process, the particle size of the granules, and the residual ash content, the inventor discovered that If the stirring action in Zone A in the figure) is performed at high speed, the ash will be easily separated from the coal due to the large amount of energy, and the oil as a binder will be better distributed to the coal, resulting in the first
As shown in graph line 1 in the figure, the residual ash content changes from point a to point b.
At the same time, as shown in graph line 2, the granulated coal particle size increases from point f to point g, and aggregation progresses. Between points b and c, that is, between points g and h, the coal aggregates are alternately crushed and combined under the action of high-speed stirring, and the residual ash content and particle size remain constant. Become. If only the coal is collected through a sieve, coal aggregates with a high deashing rate can be recovered, but the particle size is still 0.5 mm or less, and a large amount of coal passes through the sieves, resulting in a low recovery rate. Therefore, in order to further increase the particle size, the inventors
A slow stirring action was applied in the B zone so that the coal aggregates were not crushed. As a result, the coal particles grew together and increased in particle size, as shown by graph line 2 in FIG. 1, and became large enough to be easily collected. However, in the process of bonding and growing to a large diameter, the ash released into the water is mixed into the granulated coal, resulting in a sharp increase in the residual ash content in zone B, as shown in graph line 1 in Figure 1. I learned something.

The present invention may provide an embodiment described below as an embodiment of the present invention in order to improve the recovery rate and the deashing rate.

That is, slurry, which is a mixture of finely pulverized coal and water, is introduced into the first high-speed stirring tank 4 from the transport pipe 3 shown in FIG. Put it in from Thereafter, the stirring blades 6 in the first high-speed stirring tank 4 are rotated at high speed to stir the slurry at high speed, and a part of the coal is agglomerated. The coal aggregates produced in the first high-speed stirring tank 4 are put into the second high-speed stirring tank 8 along with the slurry including unagglomerated coals through a transport pipe 7, where the stirring blades 9 in the second high-speed stirring tank 8 are inserted into the second high-speed stirring tank 8. The slurry is stirred at high speed by rotating at high speed, and the agglomeration of unagglomerated materials is promoted.
The high-speed stirring action in each of the first and second high-speed stirring tanks 4 and 8 is such that the power consumption for high-speed stirring is 30 KW/m ³ or more.

Approximately 10 minutes after the start of granulation, the slurry containing coal that has completely become aggregates in the second high-speed stirring tank 8 is introduced into the first low-speed stirring tank 11 through the transport pipe 10. Furthermore, clean water is supplied from the feed nozzle 12 to the first
It is added to the low speed stirring tank 11. Then, the stirring blades 13 in the first low-speed stirring tank 11 are rotated at low speed to apply a low-speed stirring action to the slurry. here,
By clean water is meant a liquid that contains no or negligible ash, which is the object of removal. Therefore, in order to increase the degree of binding and growth of coal aggregates, clean water may contain oil as a binder. Since the coal is stirred at a low speed in the first low-speed stirring tank 11, the coal aggregates grow to a large diameter and increase the degree of bonding without being pulverized by stirring. The slurry containing coal aggregates that have grown to a certain extent is transferred from the first low-speed stirring tank 11 into the second low-speed stirring tank 15 via the transport pipe 14, and the stirring blades 16 in the second low-speed stirring tank 15 are rotated at low speed. A slow stirring action is applied to the slurry to grow coal aggregates to a desired particle size. The low-speed stirring action in each tank 11 and 15 consumes power of 29KW/ ^m3.
The following shall be made. Once the coal aggregates have combined to a desired particle size, a slurry containing the coal aggregates as granulated coal is transported from the second low-speed stirring tank 15 to the sieve 18 through the discharge pipe 17, and is granulated onto the sieve 18. The granulated coal is collected and the slurry liquid component containing ash is removed under a sieve.

Here, the specifications of the slurry, stirring tank, etc. will be explained.

The slurry was made by mixing pulverized coal (200 mesh under 80%) with water, and the concentration was 28% (weight ratio). The temperature was room temperature.

The slurry supply rate is 2.7 tons/h.

The oil is Middle East C heavy oil, and is supplied in the form of an emulsion so that the ratio to coal is 30% (weight ratio).

Clean water is water, and its supply amount is 2.7m ³ /h.

The dimensions of the first high-speed stirring tank 4 and the second high-speed stirring tank 8 are as follows.

Inner diameter of tanks 4 and 8: 593.8mm Amount of slurry charged in each tank 4 and 8: Approx. 180 Shape of stirring blades 6 and 9: Disk with claws (2 stages) Diameter of stirring blades 6 and 9: 270mm Stirring blade Peripheral speed of 6 and 9: approximately 15 m/S The dimensions of the first low speed stirring tank 11 and the second low speed stirring tank 15 are as follows.

Inner diameter of tanks 11 and 15: 800mm Amount of slurry in each tank 11 and 15
: Approx. 400 Shape, etc. of stirring blades 13, 16 : Paddle (2 stages) Diameter of stirring blades 13, 16 : 640 mm Circumferential speed of stirring blades 13, 16 : Approx. 9 m/S 1st high speed stirring tank 4, 2nd high speed stirring The residence time of the slurry in each tank 8 is approximately 5 minutes.

The residence time of the slurry in the first low-speed stirring tank 11 and the second low-speed stirring tank 15 is about 20 minutes, respectively.

According to this embodiment, during the high-speed stirring process in the first and second high-speed stirring tanks 4 and 8 (zone A in FIG. 2), more than 8% of the pulverized coal remains in the pulverized coal. The ash content rapidly decreases from point a to point b shown in FIG. 2, and the granule diameter increases from point f to point g, reaching an equilibrium state and reaching points c and h. First low speed stirring tank 11
The low-speed stirring action starts from point c in Figure 2 for graph 1a showing the residual ash content, and from point h in Figure 2 for graph line 2a showing the particle size of granulated coal.
Zone B due to low-speed stirring starts from this point, but the ash density in the first low-speed stirring tank 11 is diluted by adding clean water from the feed nozzle 12 into the first low-speed stirring tank 11. Since the coal is agitated and granulation progresses in this state, the probability that ash will be mixed in and contained while the coal aggregates aggregate and grow to a large diameter decreases. Therefore, immediately after starting low-speed stirring, d shown in Figure 2.
Although the residual ash content increases to the point, the increase value can be kept low compared to the graph line 1 in zone B shown in FIG. 1 where no clean water was added.
In addition, the granulated coal particle size is determined by graph line 2a shown in FIG.
As the coal concentration in the slurry in the first low-speed stirring tank 11 becomes thinner with the addition of clean water, the particle size increase rate per unit time is slightly reduced, but the coal is discharged from the second low-speed stirring tank 15. In some cases, the particle size in the A zone has grown to a large particle size exceeding about 0.5 mm, so the amount of coal that passes through the sieve 18 is extremely small, and the coal recovered on the sieve 18 has a recovery rate of 99.5% or more. The recovery rate is greatly improved compared to the maximum of 80% when the granule diameter is approximately 0.5 mm. Moreover, according to the processing procedure shown in FIG. 3, the slurry can be sequentially fed to each tank and granulated coal can be continuously produced, which is efficient.

As described above, according to the present invention, since clean water is added to the slurry that has undergone the aggregation process to further advance the granulation process, the suspended ash content density in the stirred liquid can be reduced. Granulated coal with a high deashing rate can be obtained.
In addition, we have multiple high-speed stirring tanks and multiple low-speed stirring tanks, so the slurry that has passed between the stirring tanks (including the slurry that has not turned into the desired granules) can be stirred at a predetermined speed in the next tank. (desired granules can be obtained), and therefore slurry can be continuously supplied.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between granulation time, residual ash content, and granule diameter using a new coal granulation method developed by the inventor of the present invention, which has improved the conventional coal granulation method. FIG. 3 is a graph showing the relationship between granulation time, residual ash content, and granulation particle diameter based on a method according to an embodiment of the present invention, and FIG. 3 is a processing flowchart according to an embodiment of the present invention. 3, 7, 14...transport pipe, 4...first high-speed stirring tank,
5, 12...Feed nozzle, 6, 9, 13, 16
... Stirring blade, 8... Second high speed stirring tank, 11... First low speed stirring tank, 15... Second low speed stirring tank, 17... Discharge pipe,
18...Sieve.

Claims (1)

[Claims] 1 In an underwater granulation method in which pulverized coal is granulated by adding oil to a slurry made by mixing pulverized coal and water and applying a stirring action, pulverized coal is granulated while passing through multiple stirring tanks connected in series. Pulverized coal is granulated by applying high-speed stirring to the slurry and oil that are continuously supplied in each stirring tank so that the particle size of the granules is 0.5 mm or less. The particle size of the granulated material changes as it passes through the stirring tank sequentially.
A method for underwater granulation of coal, characterized by applying a slow stirring action to the slurry so that the slurry becomes 1.0 mm or more, and adding clean water to the first tank of a stirring tank to which this slow stirring action is applied.