JPS6147195B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a highly concentrated coal-water slurry in which coal is handled as a fluid fuel and can be directly fed into boilers and other furnaces for various purposes. Coal is a solid and is usually crushed into pieces of less than 2 inches and transported in bulk by railcars or other means.
However, during this transportation, loading and unloading operations before and after the transportation, fine coal powder (usually 0.5mm
) may be blown away by wind, etc., causing problems with dust generation. Furthermore, since coal originally exists below the earth's surface,
When coal is mined, it reacts with oxygen in the air, causing heat generation and even spontaneous combustion, which is often observed. This spontaneous ignition characteristic depends on the type of coal, but it is also related to the time it is left in the air, and may ignite during coal storage, transportation, or cargo handling. As mentioned above, bulk transportation of coal presents various handling problems, and various solutions are being researched. Among these, highly concentrated slurry, which handles coal in a fluid state, is attracting the most attention. This involves pulverizing coal into a fluid state using a small amount of water as a medium, and it can be handled in the same way as petroleum. In this case, the end use
For example, in the combustion process of thermal power plants, etc., it is desirable to increase the solid concentration of coal as much as possible so that it can be burned economically without going through a dehydration process. Coal contains more or less unburned matter (ash) that is widely distributed even in its fine details. Therefore, in the highly concentrated slurries mentioned above, reducing the ash content in the coal not only improves the economics of handling and transportation, but also reduces wear on the boiler walls in end uses such as combustion. , it also increases boiler efficiency. Also,
If it were possible to reduce the content of sulfur in coal in addition to ash, it would be extremely meaningful as it would reduce the concentration of _SOx in combustion exhaust gas. A flotation machine is usually used for coal deashing and desulfurization processes, but flotation requires a coal concentration of 10 to 25% in the slurry. Originally, deashing by flotation is based on a physical phenomenon, that is, the separation of coal and ash due to the difference in specific gravity, so it is desirable to reduce the frequency of collisions between coal and ash and allow free movement. , treated at low concentrations. Although the slurry obtained after deashing has a high solids concentration (15-30%), a dehydration step is required to obtain the desired high concentration slurry. Solids concentration of highly concentrated coal-water slurry is 60%
Since the above is preferable, a large amount of water will be discharged from the dehydration process. The present invention recirculates this large amount of discharged water and flotation machine tail (ash content is removed) treated water,
The purpose is to improve the economic efficiency of producing highly concentrated slurry. That is, the method for producing a highly concentrated coal-water slurry of the present invention introduces finely pulverized coal into a flotation machine to remove part of the ash contained in the coal, and then removes the partially deashed coal. In the method of producing a highly concentrated coal-water slurry by dehydrating a slurry containing the same, the water dehydrated in the dehydration treatment and/or the water from which ash has been removed from the flotation machine tail is circulated to the flotation machine. Features. Illustrated in FIG. 1 is one embodiment of the present invention. Coal slurry 5 containing a large amount of fine particles with a particle size of 200 mesh or less is fed into a flotation machine 1 at a solid concentration of 10 to 25%, where it is deashed and desulfurized. Slurry containing deashed coal, i.e. clean coal, has a solids concentration of 15 to 30
%, and is fed into the flotation floss thickener 2 via line 6. Here, the slurry is somewhat concentrated and led to a dehydrator 3 such as a filter via a line 7 to obtain a highly concentrated coal-water slurry 8 with a solids concentration of 60% or more. The water dewatered in the dewatering process, ie the floss thickener 2 and the dehydrator 3, is recycled to the flotation machine 1 via lines 9 and 10 to 14, respectively. Further, the flotation machine tail is supplied to the flotation machine tail and the thickener 4 via line 11, and the clarified liquid (water from which ash has been removed) is recirculated from the overflow weir via lines 12 and 14. The waste sludge 13 containing ash is supplied to a treatment process. The present invention may circulate the entire amount of water thus recovered from the dewatering process and the flotation machine tail, or may circulate a portion thereof. Of course, dehydration or removal of ash from the tail of the flotation machine is not limited to the means shown in Figure 1. If it is possible to increase the concentration from a low concentration to a high concentration all at once, the thickener 2 in FIG. 1 can be omitted and the flotation froth can be led directly to the dehydrator 3. Table 1 shows the characteristics of deashing by flotation, and it can be seen that when the slurry concentration is low, ash can be removed with a high coal recovery rate.

[Table] According to the present invention, when producing a highly concentrated coal-water slurry by partially removing the ash content, by collecting and circulating a large amount of water, it is possible to effectively utilize the water and the flotation reagent.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram for one embodiment of the present invention. 1...flotation machine, 2, 4...stickner, 3...
Dehydrator.

Claims (1)

[Claims] 1 Finely crushed coal is introduced into a flotation machine to remove part of the ash contained in the coal, and then the slurry containing the partially deashed coal is dehydrated to form a highly concentrated coal-water slurry. A method for producing a highly concentrated coal-water slurry, characterized in that water dehydrated in the dehydration treatment and/or water from which ash has been removed from the tail of the flotation machine is circulated to the flotation machine.