JPH0469199B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for deashing a highly concentrated coal water slurry. More specifically, the present invention relates to increasing the efficiency of the coal recovery rate in a deashing method for highly concentrated coal water slurry. Highly concentrated coal water slurry consists of 60-85% coal (weight%), surfactant 0.01-5.0% by weight (based on coal powder),
It is a slurry fuel with the remaining percentage being water.
Coal concentration and surfactant addition rate vary depending on the type of coal. Coal contains ash, and if ash is present when a high-concentration coal water slurry is burned in a boiler, the efficiency of the boiler will decrease, so it is preferable to remove as much ash as possible before combustion. Further, by making the residual ash content in coal the same for each type of coal, it is possible to minimize variations in calorific value and combustion efficiency depending on the type of coal. Based on this background, a coal high concentration water slurry manufacturing process incorporating a conventional deashing process will be explained along the flow sheet of FIG. Raw coal 30 is put into a raw coal receiving tank 31 and supplied to a coal crusher 33 by a feeder 32. Coal crusher 33
In this case, raw coal 30 of about 30 to 50 mm is mixed with fine coal 3 of about 3 mm or less.
Crush into 4 pieces. This fine coal 34 is
The coal is separated into coal 37 larger than 3 mm and coal 36 smaller than 3 mm. Coal 36 smaller than 3 mm is stored in a fine coal receiving tank 38. On the other hand, coal 37 of 3 mm or more is returned to the raw coal receiving tank 31 again. Coal 36 smaller than 3 mm stored in the fine coal receiving tank 36
is supplied to a pulverizer (usually a wet pulverizer) 40 at a constant rate by a quantitative feeder 39, and water 43
Particle size less than 200 mesh while being mixed with 70-95%
The coal is pulverized into pulverized coal 41 as shown in FIG. Pulverized coal 41
is in the form of water slurry (lime concentration approximately 45-55% by weight)
The pulverized coal is received in the pulverized coal storage tank 42. Then, the pulverized coal 10 is adjusted to a concentration of about 5 to 20% by weight by water 14 separated from the dehydrator 2 after the flotation machine 1, and the flotation machine 1 is fed with a foaming agent 24 and a collecting agent 25. Coal 11 with a low ash content (clean coal) and coal (tail) 12 with a high ash content are separated. Coal (tail) 12 with a high ash content is sent to a wastewater treatment facility and disposed of. Coal with low ash content (clean coal) 11
is dehydrated by a dehydrator 2 to a coal concentration of about 20% water by weight, and water 14 separated by the dehydrator 2 is reused to adjust the concentration of pulverized coal 10 to be supplied to the flotation machine 1. Clean coal 13, which is cake-like and has a moisture content of approximately 20%, is
In the slurry adjustment tank 3, the coal concentration is readjusted to the final coal concentration of the coal high concentration water slurry 15 using a surfactant aqueous solution 26. The above is a method for producing a highly concentrated coal water slurry incorporating a conventional deashing means. However, in the conventional method, clean coal 11 and tail 12 differ depending on the coal type.
The ratio of the divisions differs greatly. In other words, the relationship between the recovery rate of coal to clean coal 11 in coal and the deashing rate tends to be as shown in FIG. 4, but it can be seen that it varies considerably depending on the type of coal. When the deashing rate is held constant, the coal recovery rate differs depending on the type of coal.On the other hand, when the coal recovery rate is held constant, the deashing rate differs, and it is difficult to deash a highly concentrated coal water slurry with several types of coal. However, if you try to produce coal using a small range of coal types, you will have to limit the types of coal you use in certain facilities, which is a big problem in countries like Japan where a large proportion of imported coal is used. be. In addition, when trying to produce clean coal 11 with a high deashing rate by using a flotation machine with pulverized coal of 70 to 95% less than 200 mesh, the coal recovery rate decreases drastically, resulting in inefficient deashing. It is a means. The present invention eliminates the drawbacks of the conventional methods. When deashing a highly concentrated water slurry of coal, the present invention first deashes fine coal with a grain size of 70 to 95% below 200 mesh using a flotation machine, and the tail coal of the flotation machine is used to remove heavy oil, light oil, Mix a binder such as kerosene,
A highly concentrated coal water slurry characterized by flotating a slurry containing flocculated tail coal to recover the coal content, mixing it with coal with a low ash content flotated in a flotation machine, and then dewatering it. Concerning decalcification methods. FIG. 2 shows only the deashing means in the conventional method shown in FIG. 1, while FIG.
1 shows a demineralization means according to the present invention. In FIG. 3, the pulverized coal 10 is mixed with water 14 separated from the dehydrator 2 after the flotation machine 1 to produce about 5 to 20%
The concentration was adjusted to % by weight, and a foaming agent 24 was added to the flotation machine 1.
Coal with a low ash content (accuracy) 11 and coal with a high ash content (tail) 12 are supplied together with the collector 25.
It is divided into Coal with high ash content (tail) 12
is introduced into the tail coal recovery device 4. An example of the tail coal recovery device 4 used in the present invention is shown in the fifth example.
As shown in the figure. i.e. coal with high ash content (tail)
The concentration of 12 is adjusted to about 1 to 20% by weight using water 14 separated from the dehydrator 2 after the flotation machine 1, and a binder 27 such as heavy oil, light oil, kerosene, etc. is dispersed and mixed in the mixer 5. The charcoal in the coal (tail) 12 with a high ash content forms a floc with a binder 27 such as heavy oil, light oil, kerosene, etc. , the floc particle size is the optimum particle size for flotation separation.
200 meshes or more and 80 meshes or less). At this time, the ash content in the coal (tail) 12 with a high ash content is
It remains suspended in water. A foaming agent 24 such as aliphatic alcohol and a collecting agent 25 (a mixture of a foaming agent and a collecting agent is called a flotation agent) such as heavy oil, light oil, kerosene, etc. are added to the slurry 17 in such a state. Then, when it is passed through a flotation separator 7, coal (floe) containing a binder 27 such as heavy oil, light oil, kerosene, etc.
It is separated into ash 18 and ash 19, which is suspended in water as it is, and can be deashed. Table 1 shows an example of operational data for such a tail coal recovery device 4.

[Table] As can be seen from the operational data example in Table 1, by introducing the coal (tail) 12 with a high ash content from the flotation machine 1 into the tail coal recovery device, the coal (tail) 12 with a high ash content can be removed. The coal content can be recovered with high efficiency, and the deashing process as a whole has the feature that the coal content can be recovered with high efficiency and with little residual ash content. The deashing process according to the present invention can recover a wide range of coal types with high efficiency and low residual ash content compared to conventional deashing processes. or,
Compared to adopting an oil-added granulation device as the tail coal recovery device 4, in the present invention, the tail coal is collected in an agglomeration step, whereas in the oil-added granulation device, it is separated using a screen, etc. It is necessary to carry out granulation to the desired particle size (about several mm). Therefore, the method of the present invention has the following advantages compared to conventional demineralization processes. (1) The oil addition rate can be reduced. (2) The tail coal recovery processing time can be significantly shortened (the granulation time can be omitted by changing only the agglomeration time). (3) Energy saving (reduction of stirring power) can be achieved. (4) It is possible to improve the deashing rate (preventing ash inclusion during the granulation process). Coal (floe) 1 containing a binder 27 such as heavy oil, light oil, kerosene, etc. recovered in this way
Coal 8 is sent to a dehydrator 2 together with the coal (clean coal) 11 with less ash sent from the flotation machine 1 to reduce the moisture content.
It is dehydrated to 20%, stirred and adjusted together with an aqueous surfactant solution 26 in a slurry adjustment tank 3, and adjusted to a final coal concentration of a high coal concentration water slurry 15. Thus, the method of the present invention can be applied to a wide range of coal types with a high coal recovery rate in the deashing process of highly concentrated coal water slurry.

[Brief explanation of drawings]

Figure 1 shows a flow sheet of a coal-concentrated water slurry production process that incorporates a conventional deashing process, and Figure 2 shows only the conventional deashing process shown in Figure 1. . Figure 3 shows
This shows the demineralization process of the present invention, and the fourth
The figure shows the relationship between the recovery rate of coal to refined ash and the deashing rate. FIG. 5 shows an example of a tail coal recovery device used in the present invention.

Claims (1)

[Claims] 1. When deashing a highly concentrated coal water slurry, fine coal with a particle size of 70 to 95% below 200 mesh is first deashed in a flotation machine, and the tail coal of the flotation machine is mixed with heavy oil,
A slurry containing binders such as light oil and kerosene is mixed, and the slurry containing flocculated tail coal is flotated to recover the coal content. After mixing with low ash coal flotated in a flotation machine, it is dehydrated. Characterized by
Deashing method for highly concentrated coal water slurry.