JPH0329275B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method and apparatus for producing a fine-grained, high-concentration coal-water slurry that does not contain coarse particles. [Prior Art] By fluidizing coal, which is a solid fuel, a highly concentrated coal-water slurry can be used not only for transportation and storage but also for direct combustion. Furthermore, it is an effective fuel because it can reduce ash and sulfur content. Methods for producing high-concentration coal-water slurry include wet methods, dry methods, wet and dry combined methods, and wet methods include high-concentration adjustment methods, low-concentration pulverization and concentration methods, and the like. The wet high concentration adjustment method uses a ball mill etc.
Wet pulverization is performed by supplying pulverized coal, a dispersant consisting of water and a surfactant, and the coal concentration is approximately 60%.
Produce a highly concentrated coal-water slurry of more than % by weight.
At this time, a stabilizer is additionally added as required. When burning a highly concentrated coal-water slurry in a combustion device such as a boiler, the combustion time is affected by the coal fuel ratio, ash content, particle size, oxygen concentration, combustion temperature, etc. If the residence time is not sufficient for the combustion time, unburned carbon will remain in the combustion residue, including fly ash, which is discharged together with the combustion gas. This results in a final combustion loss. Furthermore, when reducing the air ratio and lowering the combustion temperature to a certain extent in order to suppress NO _x emissions in the combustion gas, the combustion time similarly increases. In particular, when burning a highly concentrated coal-water slurry containing coarse particles, an increase in the unburned carbon content in the combustion residue, including fly ash, and an increase in the air ratio lead to _NOx emissions in the combustion gas. Therefore, the challenge is to realize a method and apparatus for producing a highly concentrated coal-water slurry that is made of fine particles and does not contain coarse particles. In particular, it is also required that these be realized economically. FIG. 3 shows a conventional method for producing a fine-grained high-concentration coal-water slurry and the configuration of an apparatus. In Figure 3, 1 is pre-crushed coal, 2
is a metering machine for coal 1. 3 indicates a mill, and a ball mill or the like is used. 4 is water to the mill 3, and when the coal 1 is supplied to the mill 3 together with water and a dispersant 5, it is crushed in the mill 3, becomes a slurry, flows out, becomes a fine particle high concentration coal water slurry 7, and is sent to the pump 6. Transported by. mill 3
The body length is longer than the body diameter, and the body length to body diameter ratio is 4 to 8.
It is. Further, the length-to-body-diameter ratio of the mill used in the conventional method and apparatus for producing high-concentration coal-water slurry is 2 to 3. Increasing the length-to-body diameter ratio in this way increases the residence time of the coal-water mixture system moving within the mill and enhances the grinding action with the grinding media, resulting in a highly concentrated coal-water slurry consisting of fine particles. is manufactured. FIG. 4 shows another conventional method for producing a fine-grained high-concentration coal-water slurry and the configuration of an apparatus. In FIG. 4, 3a is a first mill, 3b is a second mill, and 9 is a classifier. 1, 2, 4, and 5 are the same as those shown in FIG. 3, so their explanation will be omitted. The slurry 8 from the first mill 3a is classified in a classifier 9, and most of it flows as an underflow 9a, and an overflow 9b is crushed in the second mill 3b to become a slurry 10, which is transferred to a coal cleaning device 11 as necessary. It is demineralized. 1
2 indicates tailings. At this time, the coal concentration of the slurries 9 and 10 entering the coal cleaning device 11 is a dilute slurry with a coal concentration of about 30% by weight or less. Water 15 is separated from the slurry 13 in a dewatering device 14 to make the slurry into a furnace slag with a coal concentration of 60% by weight or more, and the slurry is then made into a fluidized state in a regulating device 16 to produce a fine-grained high-concentration coal-water slurry 7.
It is transported by a pump 6. [Problems to be Solved by the Invention] However, in any of the above-mentioned conventional methods and apparatuses for producing fine-grained, high-concentration coal-water slurry, it is difficult to easily produce fine-grained, high-concentration coal-water slurry that does not contain coarse particles. There was a problem that it was difficult to manufacture using. That is, when a long mill with a length-to-body-diameter ratio of 4 to 8 is used, the crushing action is enhanced to produce a fine-grained, highly concentrated coal-water slurry, but some of the coal supplied in the mill and Part of the coal that has been pulverized collides with the pulverizing media and flows out of the mill without sufficient pulverizing action, resulting in a slurry containing coarse particles. In particular, in the process of manufacturing highly concentrated coal-water slurry with a coal concentration of approximately 60% by weight or more, the viscosity of the mixed system increases as the crushing action progresses, and under such conditions, the outflow of coarse particles is promoted. It had the disadvantage of being In addition, when two mills are used, most of the slurry from the first mill is sent to the next process, and only the remainder is sent to the second mill, but the grinding process is done in a dilute, low-concentration state. carried out and further dehydration equipment,
There was a problem in that the equipment and operation were complicated because a high concentration coal water slurry was produced using a regulating device and the like. The present invention solves these conventional problems, and can produce a highly concentrated coal-water slurry consisting of fine particles without coarse particles. An object of the present invention is to provide a method and apparatus for producing an excellent fine-grained, high-concentration coal-water slurry that has a low unburned carbon content and can suppress NO _x emission concentration. [Means for Solving the Problems] In order to achieve the above object, the present invention removes coarse particles in the slurry flowing out from the first mill, and then supplies the slurry to the second mill for pulverization. A first mill that supplies water and a dispersant for pulverization, a classifier that removes coarse particles from the slurry flowing out from the first mill, and a second mill that supplies and pulverizes the slurry from which coarse particles have been removed are connected in series. The first mill and the second mill are ball mills, each with a length-to-body diameter ratio of 2 to 4, and the classifiers include a vibrating sieve, a cylindrical classifier, a horizontal disc classifier, and a horizontal classifier. It uses one of the moving classifiers. [Function] The present invention has the following effects due to the above configuration. That is, in producing a fine-grained high-concentration coal-water slurry, coarse particles in the slurry flowing out from the first mill are removed by a classifier, and then the slurry is supplied to the second mill for pulverization. The grinding action is achieved under a sufficiently long residence time in a highly concentrated state up to the mill discharge end, and a highly concentrated coal-water slurry consisting of fine particles without coarse particles can be produced. When the fuel is supplied to a combustion device and burned, the amount of unburned carbon in the combustion residue is small, and the _NOx emission concentration can be suppressed. [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 1, 3a is a first mill, 3b is a second mill, and 9 is a classifier. Coal 1 is supplied to the first mill 3a together with water 4 and a dispersant 5 under the operation of a metering feeder 2 so as to obtain a slurry with a predetermined coal concentration, and is pulverized in the first mill 3a to form a slurry. It is leaked as 8. In the slurry 8, coarse particles 9b contained in the slurry 8 are separated and removed from the system in a classifier 9, and the underflow 9a is directly transferred to the second mill 3b.
and crushed in the second mill 3b,
Fine particle high concentration coal water slurry 7 that does not contain coarse particles
and is transported by the pump 6. In addition, the coarse particles 9b are returned to the first mill 3a via appropriate means, and coal 1, water 4, dispersant 5
It is also possible to be crushed together. The coal concentrations of the slurry 8, the underflow 9a, and the fine particle high concentration coal water slurry 7 are substantially the same and are about 60% by weight or more. In the first mill 3a, a part of the supplied coal 1 and a part of the coal that has been pulverized collide with the pulverizing media and flow out of the first mill 3a without the sufficient pulverizing action of the grinding. The slurry 8 containing coarse particles is obtained, but the underflow slurry 9a is supplied to the second mill 3b without containing coarse particles and is pulverized. Therefore, during pulverization, since the above-mentioned coarse particles are not present, the coal particles in the slurry collide with the pulverizing media, and the pulverization proceeds without any problems, promoting the pulverizing action, and the coal particles no longer contain coarse particles. A highly concentrated coal-water slurry 7 containing no fine particles is produced. The first mill 3a and the second mill 3b are ball mills, each having a length to diameter ratio of 2 to 4. Therefore, the crushing action progresses under a sufficiently long residence time in the state of highly concentrated coal-water slurry from the coal supply end of the first mill to the slurry discharge end of the second mill, and a predetermined result is obtained. A fine-grained, highly concentrated coal-water slurry having a particle size distribution can be produced. The above method achieves remarkable fineness in particle size distribution characteristics when compared with the particle size distribution of a highly concentrated coal-water slurry produced by a ball mill with a length-to-body-diameter ratio of approximately 3. In addition, by using many improved types and structures of the first mill 3a and the second mill 3b, a method for producing a fine-grained high-concentration coal-water slurry with excellent grinding efficiency (power consumption) and grinding characteristics is provided. and devices. The classifier 9 includes a vibrating sieve with a sieve surface, a structure using a cylindrical classifier with slits, a structure using a rotatable horizontal disc-shaped classifier with a sieve surface, and a structure with a continuous sieve surface. We are applying a structure that uses a horizontally moving classifier that moves by moving. Classification here means separating and removing particles that inhibit the process from the raw slurry that contains particles that inhibit the process.
In this example, coarse particles in the slurry from the first mill are removed for the grinding process by the second mill. For this reason, the opening size of each classification body of the classifier 9 can be made significantly larger than the average particle size of the fine-grained high-concentration coal-water slurry 7, and even though the slurry 8 exhibits high viscosity, Since it can easily pass through the classifier 9, the processing capacity of the classifier 9 can be increased, and even when producing a large volume of fine-grained, high-concentration coal-water slurry, it can be processed without using a classifier with excessive external dimensions. It is possible. Experimental examples based on the above embodiments will be shown below. The coal used to produce the fine-grained high-concentration coal-water slurry had the following properties.

[Table] Figure 2 shows the particle size of the fine-grained high-concentration coal-water slurry based on the above example, and the figure shows the particle size of the conventional technology for comparison. In FIG. 2, curve group a is based on the present invention, and curve group b is based on the conventional same length same diameter ratio 5.
curve group c also shows the curves produced by a mill having a conventional length-to-body diameter ratio of 3. The horizontal axis focuses on 74 μm or less, which is the target particle size suitable for combustion of fine-grained high-concentration coal-water slurry, and the vertical axis focuses on 150 μm or more, which similarly targets unsuitable particle size. The reason why all of them are shown as a group of curves is because a large number of experimental values were aggregated. As is clear from FIG. 2, according to the curve group a according to the present invention,
It is found that in the case of about 85% of 74 μm, particles of 150 μm or more are significantly reduced compared to curve groups b and c. Furthermore, the combustion characteristics of the fine-grained, highly concentrated coal-water slurry are as follows.The coal type was bituminous coal, and the combustion device output was equivalent to 600 MW of electrical output.

[Table] In this way, it is possible to produce a fine-grained, high-concentration coal-water slurry consisting of fine particles that do not contain coarse particles, and when it is supplied to a combustion equipment and burned, the unburned carbon content in the combustion residue is small _and NO It is found that the concentration is suppressed. It goes without saying that the aspects of the mill and classifier in the present invention are not limited to those of the above-mentioned embodiments. [Effects of the Invention] As is clear from the above embodiments, the present invention
Coarse particles in the slurry from the mill are removed by a classifier and fed to the second mill for pulverization.Since the pulverizing action is performed using a slurry with sufficient residence time, it is possible to create a fine, high-concentration coal water that does not contain coarse particles. Slurry can be manufactured using a simple manufacturing method and device without requiring complicated equipment or operation, and when fed to a combustion device and combusted, the unburned carbon content in the combustion residue is small and NO _x emission concentration is suppressed. can do. In addition, since the processing capacity of the classifier can be increased, it is not only possible to produce a large volume of fine-grained, highly concentrated coal-water slurry, but also by using a mill with improved type and structure. The effects are great, including the ability to provide a method and apparatus for producing a fine-grained, highly concentrated coal-water slurry with excellent pulverization efficiency (power consumption) and pulverization properties.

[Brief explanation of drawings]

FIG. 1 is a process diagram of a method for producing fine grained high-concentration coal-water slurry according to an embodiment of the present invention, FIG. 2 is an explanatory diagram comparing the particle size distribution of the same method with that of conventional technology, FIG. 4 is a process diagram of a conventional method for producing fine-grained, highly concentrated coal-water slurry. 1...Coal, 3a...First mill, 3b...Second mill,
4... Water, 5... Dispersant, 7... Fine particle high concentration coal water slurry, 8... Slurry, 9... Classifier, 9b... Coarse particles.

Claims (1)

[Claims] 1. A method for producing a fine-grained high-concentration coal-water slurry, which comprises removing coarse particles in the slurry flowing out from a first mill, and then supplying the slurry to a second mill for pulverization. 2. A first mill that supplies and pulverizes coal, water, and a dispersant, a classifier that removes coarse particles in the slurry flowing out from the first mill, and a second mill that supplies and pulverizes the slurry from which coarse particles have been removed. An apparatus for producing fine grained, highly concentrated coal-water slurry, characterized in that: and are arranged in series. 3. The apparatus for producing a fine-grained high-concentration coal-water slurry according to claim 2, wherein the first mill and the second mill are ball mills, and each has a length-to-body diameter ratio of 2 to 4. 4. The apparatus for producing fine-grained, high-concentration coal-water slurry according to claim 2, characterized in that a vibrating sieve is used as a classifier. 5. The apparatus for producing a fine-grained high-concentration coal-water slurry according to claim 2, characterized in that a cylindrical classifier is used as the classifier. 6. The method for producing a fine-grained high-concentration coal-water slurry according to claim 2, characterized in that a horizontal disc-shaped classifier is used as the classifier. 7. The apparatus for producing fine-grained high-concentration coal-water slurry according to claim 2, characterized in that a horizontally moving classifier is used as the classifier.