JPS62158791A - Method and apparatus for production of coal-water slurry - Google Patents

Abstract

PURPOSE:To produce the titled slurry with the minimized power consumption for grinding and thus low cost, by charging a ball mill with coal, water and a dispersant at a specific range of a ratio of the volume of grinding balls in the mill to the volume of slurry and conducting grinding. CONSTITUTION:A process for preparing a coal-water slurry which comprises feeding coal, water and a dipsersant into a ball mill and rotating the mill, wherein the ratio (VB/VS) of the volume (VB) of grinding balls disposed in the mill to the volume (VS) of the slurry prepd. in the mill is set at 2-5. When VB/VS is in the range of 2-3, the power source unit is the smallest, which is by about 30% lower than that of the conventional mills exhibiting a VB/VS value of about 1.5. Application of this process to production of a highly concentrated slurry enables a slurry fuel to be manufactured in an economical manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for producing coal-water slurry using a ball mill.

BACKGROUND OF THE INVENTION Powder slurry transportation technology has been studied for a long time as a method for transporting solid powder in a fluid state that is easy to handle. In recent years, the above-mentioned slurry transportation technology has been applied to the transportation of coal.1 It is safe, without problems such as spontaneous combustion of coal or dust scattering, and can be transported through pipes, making it easy to handle and improving transportation efficiency. The development of manufacturing technology for coal-water slurry that can improve the performance of coal-water slurry is actively being carried out.

In the coal-water slurry, the coal transport efficiency can be improved by increasing the coal content as much as possible, and by reducing the water content, the coal-water slurry can be directly combusted without dehydration in the transport machine. Since it has become possible to do so, high concentration technology has been developed to increase the coal concentration in the coal water slurry. It is a well-known fact that increasing the solid temperature in a slurry increases its viscosity.1 In a coal-water slurry, the coal concentration is kept as high as possible while keeping the viscosity low enough to allow pipe transportation. Firstly, the particle size distribution of the coal particles in the coal-water slurry is adjusted to increase the concentration, and secondly, a dispersant is further added to increase the dispersibility of the coal particles. There is a known method of reducing the viscosity by using (Japanese Patent Publication No. 56-501568), and there are many methods of producing a highly concentrated and low viscosity coal water slurry in addition to the above-mentioned publicly known methods. It is based on the two basic principles mentioned above.

The method for producing coal water slurry according to these known examples is (1
) A method in which coal, water, and a dispersant are mixed in predetermined amounts and wet-pulverized using a tube mill to directly produce a highly concentrated coal-water slurry; (2) Coal is pulverized into several types of particles Q, and then these are (3) Wet method using a tube mill in the coexistence of water and dispersant at a low coal concentration. There are products manufactured by dehydrating and concentrating the resulting slurry after pulverization to increase the concentration. By any of these methods, the coal production degree is 70% by weight or more and the viscosity is about 1,500 cP.
A coal water slurry with high fluidity can be obtained as follows.

As described above, the technology for producing a highly concentrated and low viscosity coal-water slurry appears to have been established. However, the main purpose of using coal is to burn it and use it as a cheap fuel, and as mentioned above, it is made into a fluid to improve safety and operability in transporting and handling coal.

Furthermore, it is effective to improve the transport efficiency by making the slurry highly concentrated and low in viscosity, but the coal crushing power required to satisfy the above two basic principles for producing coal-water slurry is and the amount of dispersant is true and only in the prior art.

It cannot be said that coal-water slurry has necessarily been established as an economical form of coal utilization.Incidentally, the power cost for coal crushing required to satisfy the first basic principle varies somewhat depending on the type of coal, but at present That's about 0.2 yen/1,0OO
Kca Q, and the price of coal is currently about 2 yen/1000
Since it is Kcaa, the cost increases by about 10% just for the crushing power in producing one coal-water slurry. Like this 1
The reason why the crushing power is high in the production of coal-water slurry is because, as mentioned above, the coal is crushed into a wide particle size distribution necessary to achieve high concentration and low viscosity. ) needs to be increased. Generally, it is well known that the smaller the particle size of a solid, the greater the specific surface area and the greater the power required for pulverization. It is also well known that the smaller the particle size, the lower the efficiency of mechanical pulverization and the need for extra power, which dramatically increases the required power.

Although much research has been conducted for a long time on the pulverization of various solids using various types of pulverizers, there are a large number of factors that affect the efficiency of pulverizers, and the structure and operating conditions of these pulverizers have not yet been finalized. It is difficult to say that this is the case, and it is generally accepted that the optimal grinding conditions vary depending on the properties of the fixed object to be ground. Incidentally, there has been no research on wet pulverization at relatively high concentrations, which is the object of the present invention, and the structure and operating conditions of the pulverizer are currently determined by trial and error. This is because in high-concentration wet pulverization, the slurry that is the material to be pulverized becomes a highly viscous fluid, and the operating mode of the pulverizing media (for example, balls, beads, hammers, etc.) in this is dry pulverization or low-concentration wet pulverization. This is because the viscosity changes significantly compared to that in a low-viscosity material such as . As described above, the technical issue of reducing the pulverization cost of coal-water slurry has not yet been resolved.

[Object of the Invention] The present invention was made in view of the above circumstances, and its purpose is to reduce the total crushing power required for producing one coal-water slurry.

[Summary of the invention]

That is, one of the features of the present invention is that in a coal-water slurry production method in which coal, water, and a dispersant are supplied into a ball mill and the ball mill is rotated to produce a coal-water slurry, the volume of the grinding balls in the mill is The present invention provides a method for producing a coal-water slurry in which the coal-water slurry is produced by setting g = 2 to 5.

5. Other features of the present invention include a mill body that is supported so as to be able to rotate once, a crushing ball charged into the mill body, and a coal supply port that supplies coarse powder coal provided at one end of the mill body. , a slurry outlet provided at the other end of the mill body;
In the coal-water slurry production apparatus having piping for supplying water and a dispersant into the mill main body, the coal-water slurry attached to the mouth of the slurry volume VB in the mill is compared to the volume VB of the grinding balls in the mill. Located in slurry manufacturing equipment.

[Embodiments of the invention]

Example 1 First, the effects of various factors on the coal pulverization speed under high concentration coal-water slurry production conditions were investigated.

The outline of the tube mill used is shown in FIG.
A port 2 is provided, into which the water-1 dispersant is fed, and an outlet 3 is provided on the other hand for taking out the coal slurry that has been pulverized in a ball and mixed with the water-1 dispersant. The other end of the mill body 1 where the outlet 3 is provided is formed into a tapered shape with a small diameter, and the outlet 3 is formed in this tapered portion by a plurality of long holes provided radially from the horizontal axis of the mill body 1. 6 also. Adjustment plates 4 of different widths can be attached to the tapered portion, and by changing the widths of the adjustment plates 4, the opening area of the outlet 3 and the downstream position in the height direction from which the coal slurry is taken out can be changed. The mill body 1 is supported at both ends by bearings 5, and a gear 6 provided on the outer periphery of the mill body 1 meshes with a gear 8 attached to the shaft of a motor 7.
By driving the motor 7, the mill body 1 is rotated using the bearing 5 as a fulcrum.

Using this tube mill, we investigated the effects of various crushing conditions on the coal crushing speed through batch operation. The examined crushing conditions are shown in the table below.

A steel ball with a specific gravity of about 8.0 was used as the grinding ball.

The particle size distribution index of balls indicates the slope of the logarithmic plot of the cumulative weight proportion of balls with a certain particle size or less and the particle size. It was varied between 35 and 7%. Further, the ratio VB/Vs of the volume VB of the ball to the volume VB of the slurry was varied between 0.3 and 2.5.

The experimental procedure is as follows. First, a predetermined amount of grinding balls having a predetermined particle size distribution are filled into a mill, and further a predetermined amount of lump coal (particle size 10-60), water, and a dispersant are added. The amount of water was adjusted so that the coal concentration of the slurry in the mill was approximately 63%. Further, an anionic dispersant was added at a ratio of 0.5% to the dry coal heavy electricity.

As a result, the results shown in FIG. 2 were obtained. Figure 2 shows the outer surface area of the pulverized coal obtained from the particle size distribution by sampling the pulverized coal at fixed time intervals under various conditions.
It is plotted against.

Here, S is the total surface area of the ball and Vs is the volume of the filled slurry. The outer surface area of pulverized coal is considered to be an indicator of the degree of pulverization, and this value increases as the pulverization progresses. The results shown in FIG. 2 show that the longer the pulverization time and the larger the surface area of the balls relative to the volume of the slurry, the larger the outer surface area of the pulverized coal becomes. That is, it shows that it is well pulverized.

It is natural that the grinding progresses as the grinding time becomes longer, but what should be noted here is the second point. If pulverization is performed for the same amount of time, the smaller the amount of slurry relative to the ball, the more the pulverization progresses, that is, the higher the pulverization speed.

Although this example shows the results of a batch test, in an actual production plant, coal pulverization and slurry production are performed continuously. When coal slurry is continuously manufactured using a certain mill under conditions where the filling amount of the balls is constant, the results of this example show that reducing the amount of slurry held in the mill in some way increases the grinding speed. Ta. but,
The residence time of the slurry in the mill also decreases as the amount retained decreases. Therefore, if the effect of reducing the retention time is greater than the increase in the grinding speed by reducing the retained amount in continuous grinding, there is no effect of reducing the retained amount. However, as shown in Figure 2, For example, if the retention amount v8 is set to 172, the residence time will also be 1 in continuous pulverization.
/2, but the outer surface area of the pulverized coal is larger when the retained amount is reduced to 1/2. In other words, it was found that the pulverization of coal was more advanced. This result shows that when the same mill is used to continuously produce the same pulverized coal slurry, the throughput increases when the amount of slurry held in the mill is reduced. In other words, the crushing power (
This means that the power consumption (power consumption) can be reduced.

In order to confirm the results of this example, a continuous production test of coal slurry was conducted using the mill shown in FIG.

Example 2 The coal and dispersant used in the test were the same as in Example 1. The grinding ball is 35 with a particle size distribution index of 3.8.
% filling rate @ VB /
VB was changed by changing the size of the opening of the mill outlet opening using the adjustment plate 4 to adjust the amount of slurry in the mill.

The flow sheet of the apparatus is shown in FIG. 3. Coal in the hopper 9 was fed from the mill inlet at a constant speed by a screw feeder 10. In addition, the water 11 and the dispersant 12 are supplied by a quantitative feeder 13.14, so that the coal concentration of the slurry in the mill is 63.
The amount of the dispersant added in weight % was the same as in Example 1.

Figure 4 shows the relationship between the amount of coal particles passing through 200 meshes in the production slurry and VB/Vs when coal is supplied at a rate of 20 kg/h.When operating at the same coal processing speed, the amount of passing through 200 meshes It was found that VB/VB reached a maximum value between 2 and 3, and the grinding efficiency was highest. It can be seen that when VB /v8 becomes 2 or less, the operating conditions are inefficient for a pulverizer for high concentration coal slurry. These factors are considered to be related to the contact efficiency between the slurry and the ball at the time of ball-to-ball collision. If there is too much slurry relative to the balls, it is thought that when the balls collide with other balls during mill rotation, the speed of the balls will decrease due to the viscous resistance of the slurry, reducing the collision energy and reducing the grinding efficiency. .

On the other hand, if there is too little slurry relative to the balls, the drop in speed of the balls due to the viscous resistance of the slurry will be small and the collision energy will increase, but since the amount of slurry between the colliding balls is small, the crushing efficiency will still decrease and the VB When /Vs becomes 5 or more, it particularly decreases.

From the above considerations, it can be inferred that the grinding efficiency is greatly influenced by the ratio of the balls in the mill to the amount of slurry. Because it moves in a viscous fluid, the form of motion is thought to be different from that in dry grinding or low-concentration wet grinding in conventional mills.

Next, the amount of coal and water 9 dispersant supplied was adjusted so that the amount of coal particles passing through the 200 mesh in the slurry produced by changing the opening of the opening hole was 75%, and a slurry with the same properties was obtained. The amount of power required (power unit) was measured and compared. The results are shown in Fig. 5. As predicted from the previous results, the power source unit has a minimum VB/Vs of 2 to 3, and the conventional mill (Vo/Vs of about 1.5 ), and the effect of power reduction by applying the present invention to the production of high-concentration coal slurry is obvious.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the power required for pulverizing one piece of coal in the production of a high-concentration coal-water slurry, and it becomes possible to produce a more economical slurry fuel.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the crusher according to the present invention, Fig. 2 is a graph showing the results of Example 1, Fig. 3 is a flow sheet of the apparatus used in Example 2, and Figs. 4 and 5 are 3 is a graph showing the results of Example 2. 1... Mill body, 2... Inlet, 3... Outlet, 4...
...adjustment plate, 5...bearing, 6, 8...gear, 7...
·motor.

Claims (1)

[Claims] 1. In a coal-water slurry production method in which coal, water, and a dispersant are supplied into a ball mill and the ball mill is rotated to produce a coal-water slurry, the volume V of the grinding balls in the mill is
The ratio between _B and the volume of slurry in the mill V_S is expressed as (V_
B) A method for producing a coal-water slurry, characterized in that the coal-water slurry is produced by setting /(V_S)=2 to 5. 2. A rotatably supported mill body, pulverizing balls loaded into the mill body, a coal supply port provided at one end of the mill body for supplying coarse powder coal, and the other end of the mill body. In a coal-water slurry production apparatus having a slurry outlet provided in the mill body and piping for supplying water and a dispersant into the mill body, the volume of the slurry in the mill is The ratio of V_B (V_B)/(V
A coal-water slurry manufacturing apparatus, characterized in that an adjustment plate for adjusting _S) to 2 to 5 is attached to a slurry outlet.