JPH068419B2 - Method for producing coal-water slurry - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a coal-water slurry, and particularly to a coal-water slurry having a high coal concentration and good fluidity with a small amount of a surfactant required. The present invention relates to a manufacturing method.

(Prior Art) In recent years, in order to improve the handling property of coal, which is a solid fuel, the technology of making a fluid fuel easy to handle by dispersing pulverized coal in water to form a slurry has been actively developed. ing. In order to produce a high-coal concentration and low-viscosity coal-water slurry that can be directly spray-burned as a boiler fuel, the coal packing density is adjusted by adjusting the coal particles forming the slurry to a wide particle size distribution. It is important to increase the concentration to increase the concentration and to reduce the viscosity by stably dispersing the coal particles in water by using an appropriate additive.

As a method for producing such a coal-water slurry, generally, a method of wet-milling coal using a continuous ball mill and adding a surfactant is generally used. However, when producing a coal-water slurry using a ball mill, in order to prepare a wide particle size distribution such that the packing density is high,
It is necessary to grind under conditions of high coal concentration (usually 60% by weight or more), but in such a state, there is a problem that the viscosity becomes high and the grinding does not proceed. For this reason, the viscosity at the time of pulverization is reduced by adding a surfactant, but since the coal particles are coarse at the initial stage of pulverization, unnecessary adsorption such as excess surfactant adsorbing in multiple layers occurs, and pulverization progresses. Will not be adsorbed on the new surface generated by. As a result, there is a problem that the required amount of the surfactant finally increases. Further, since the crushing is performed under the condition of high concentration and high viscosity, the movement of the balls in the mill is suppressed, and there is a problem that the crushing ability is lowered.

In order to solve these problems, a method in which a ball mill has multiple chambers to fill balls corresponding to the particle size of coal and a surfactant is added in multiple stages (Japanese Patent Application No. 57-191767) or a part of the pulverized product is used. Method of recirculating to the mill (Japanese Patent Application No. 58-3087)
No. 4) has been proposed, but a pulverization power unit for pulverizing coal with a hard glob pulverizability index (HGI, JIS-M8801) of about 50 at a coal concentration of about 70% and about 200% passing through 200 mesh. Is about 50 kwh / t, and the dose of the surfactant is about 0.5% with respect to coal. If the electricity unit price is 23 yen / kwh and the surfactant is 300 yen / kg, the power and the surfactant cost are 115 each.
It is 0 yen / t coal and 1500 yen / t coal. If the unit price of raw coal is 15,000 yen / t, this is 7.7% and 10% of the raw coal cost, which is an enormous value.

In order to solve such a problem, the inventors of the present invention have proposed a method for producing a high-concentration coal-water slurry using a wet ring roller mill at a low power cost (Japanese Patent Application No. 59-20376).
No. 1). Coal using this wet vertical ring roller mill
A system diagram of the water slurry manufacturing device is shown in FIG. In FIG. 6, the coal A in the bunker 1 passes through the feeder 2 and from the coal feed pipe 4 at the top of the wet type vertical ring roller mill 3 and the water B,
The surfactant liquid B and the pH adjusting liquid D are injected into the mill from the respective tanks 5, 6, and 7 by the respective pumps 8, 9 and 10 via the coal feeding pipe 4. The mixture of coal, water and additives crushed in the ring roller mill 3 is sent from a discharge port 11 at the bottom of the mill to a slurry distributor 13 by a slurry pump 12, part of which is fed from a coal feed pipe 4 of the mill into the mill. Circulated. The remaining slurry distributed by the distributor 13 is a coarse particle separator 14 installed above the mill.
The coarse particles sent to the mill and separated by gravity are fed into the coal feeding pipe 4 of the mill.
To be recirculated into the mill 3. The coal-water slurry that has passed through the coarse particle separator 14 is stored in the slurry tank 15 as a product.

Next, FIG. 7 shows the structure of a typical wet ball race mill as a wet vertical ring roller mill, in which the crushing section has an upper fixed wheel to which a pressing force is applied by a crushing table 17 and a pressure device 18. (Upper ring) 19, a lower roller (lower ring) 21 installed at an end of the crushing table 17 rotated by the drive device 20, and a lower link 21 arranged between the upper ring 19 and the lower ring 21.
It is composed of a plurality of crushing balls 22 that roll with the rotation of the crushing machine, and a scraping bar 23 for cleaning the inside of the coal feeding pipe, which is installed so as to be installed from the center of the crushing table 17. Coal A that is wet-milled includes circulating slurry from a distributor 13 (FIG. 6), coarse slurry from a coarse particle separator 14 (FIG. 6), water,
Grinding machine main body 1 with surfactant liquid and pH adjusting liquid
6 is supplied to the coal feeding pipe 4. The mixture of coal, water and additives supplied to the coal feeding pipe 4 drops inside the coal feeding pipe 4, but the mixture adhering to the inner surface of the coal feeding pipe 4 is crushed by the crushing table 17
It is scraped off by a cleaning scraping bar 23 which rotates together with it, and is dispersed on the crushing table 17. The mixture of coal, water and additives dispersed on the grinding table 17
The particles are moved to the crushing ball arrangement portion by the centrifugal force generated by the rotation of and are compressed and ground between the balls and the lower ring. The crushed coal flows down from the space between the end of the lower ring 21 and the crusher body 16 into the slurry weir 24 under the crushing table 17, and is mixed by the mixing paddle 25 installed at the bottom of the rotating crushing table 17. It is discharged from the discharge port 11.

(Problems to be Solved by the Invention) When the coal of the hard glove grindability index of 50 is crushed to 70% through 200 mesh at a coal concentration of about 70% using this wet ball race mill, the power consumption unit is 30 kwh.
/ T, which was reduced to 2/3 that in the case of using a ball mill, but the required amount of surfactant was 0.5% with respect to coal, as in the case of using a ball mill. This accounts for about 10% of raw coal cost (1500 yen / t coal),
Coal-water slurry is a major obstacle to practical use as a boiler fuel.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to produce a coal-water slurry having a high coal concentration and a low viscosity, which is suitable as a fuel for a boiler, etc., with low power and a small amount of surfactant required, and a method for producing the same. To provide.

(Means for Solving the Problems) In short, the present invention is to perform wet pulverization of coal using a wet type vertical ring roller mill having a pulverization ring and a roller to form a coal-
In the method for producing a water slurry, a surfactant is added after pulverizing coal. It is preferable to add the surfactant after pulverizing the coal with a wet ring roller mill and further adjusting the viscosity distribution.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples. FIG. 1 shows an example of an apparatus suitable for carrying out the present invention. In FIG. 1, coal A in a bunker 1 passes through a feeder 2 from a coal feed pipe 4 at the top of a wet ring roller mill 3, and water B and a pH adjusting agent liquid D from tanks 5 and 7, respectively, pumps 8 and 10 respectively. Is injected into the mill 3 via the coal feeding pipe 4. FIG. 2 shows a structural example of a typical wet ball race mill as the wet vertical ring roller mill 3. The crushing unit is the crushing table 1
7. An upper fixed wheel (upper ring) 19 to which a pressing force is applied by a pressurizing device 18, a lower roller (lower ring) 21 installed at an end of the crushing table 17 rotated by a drive device 20, Upper ring 19 and lower ring 21
And a plurality of crushing balls 22 which are disposed between the crushing balls and roll with the rotation of the lower ring 21, and a scooping bar 23 for cleaning the inside of the coal feeding pipe which is installed in a centered manner from the center of the crushing table 17. . Although the coal, water and the pH adjusting agent liquid supplied to the coal feeding pipe 4 and the circulating slurry from the distributor 13 (Fig. 1) and the coarse particle separator 14 (Fig. 1) fall in the coal feeding pipe 4. The mixture adhering to the inner surface of the coal feeding pipe 4 is scraped off by the cleaning scraping bar 23 which rotates together with the crushing table 17, and is dispersed on the crushing table 17. The mixture of coal, water and additives dispersed on the crushing table 17 moves to the crushing ball arrangement portion by the centrifugal force generated by the rotation of the crushing table 17, and is compressed and ground between the balls and the lower ring. The crushed coal is fed from the space between the lower ring 21 end and the crusher body 16 to the slurry weir 24 under the crushing table 17.
Run down.

Here, the difference from the prior art shown in FIG. 6 is that the surfactant liquid C is supplied from the tank 6 (FIG. 1) to the inlet 26 by the pump 9 (FIG. 1) and added into the slurry weir 24. That's what I did. The coal slurry and the surfactant are discharged from the discharge port 11 while being mixed by the mixing paddle 25 installed at the bottom of the rotating crushing table 17. First
In the figure, the slurry discharged from the mill 3 is sent to a slurry distributor 13 by a slurry pump 12, and a part of the slurry is circulated from a coal feed pipe 4 of the mill into the mill. The remaining slurry distributed by the distributor 13 is sent to the coarse particle separator 14 installed above the mill, and the separated coarse particles are recirculated from the coal feeding pipe 4 of the mill into the mill 3 by gravity. . Coarse grain separator 14
Coal-water slurries that have passed through the market have a slurry rank of 1
Stored at 5.

In the ring roller mill according to the above-described embodiment of the present invention, the powder table 17 is used even under the condition of high coal concentration and high viscosity.
The coal is guided to the crushing section by the centrifugal force due to the rotation of the and is forcedly crushed. Further, since the crushing mechanism is compression and grinding, the particle size distribution generated is a wide particle size distribution suitable for increasing the concentration of the slurry. Further, since the surfactant is supplied to the mill inlet, that is, to the coal-water slurry after the crushing of the mixing paddle 25 without being supplied to the raw coal supplying section or the crushing section, the viscosity in the crushing section becomes higher. As a result, a wider particle size distribution is produced. A coal-water slurry containing a minimum of surfactant is also used in the distributor 13 and the coarse grain separator 1.
Since it is circulated in the mill through No. 4, it is possible to avoid the wasteful use of the surfactant due to multilayer adsorption or the like. Since the surfactant can be added in an amount corresponding to the particle size of the coal in the slurry weir 24 after the coal has passed through the crushing section, that is, the surface area of the produced particles, the required amount of the surfactant is a conventional wet ball mill or wet ring roller mill (special It can be greatly reduced as compared with the case of Japanese Patent Application No. 59-203761).

FIG. 3 shows another embodiment of the present invention. Unlike the method of adding a surfactant into the slurry weir 24 as shown in FIGS. 1 and 2, the line mixer is provided downstream of the slurry pump 12. 27 is provided and a surfactant is added to the inlet of the line mixer. Even in this way, the first
It is possible to achieve the same effect as the embodiment shown in FIGS. Also, without installing the line mixer 27,
A surfactant may be injected into the inlet of the sly pump 12. In this case, as the slurry pump 12, a single-screw screw type pump or a twin-screw screw type pump having an excellent mixing effect is effective. Although the pH adjusting agent liquid D is added from the coal feeding pipe 4 of the ring roller mill 3 in the examples of the present invention (FIGS. 1, 2 and 3), it is added from the same position as the surfactant liquid C. The method may be used.

FIG. 4 shows an example of the apparatus configuration of the third embodiment of the present invention. In the present embodiment, in addition to the addition of the surfactant C from the line 3A into the slurry weir 24 by the pump 9 as in the first embodiment (see FIGS. 1 and 2) of the present invention, branching is performed. Coarse-grain separator 14 via line 14A
It is characterized in that it was added to. Coarse grain separator 1
4 is a small amount of coarse particles mixed in the slurry (usually about 300μ
m-1000 μm or more) for preventing clogging of burner chips and the like. High-concentration coal-water slurry has a Newtonian fluid-like behavior in which the viscosity does not change depending on the flow state, like ordinary water, or has a large apparent viscosity in a low-speed flow state (that is, low shear rate) that is close to a stationary state. On the contrary, many of them behave like a pseudo-plastic fluid where the viscosity decreases at high shear rates. In the apparatus configuration as shown in FIG. 3, the shear rate in the pipe, the distributor 13, the coarse grain separator 14 represented by a strainer or a sieve bend, etc. is relatively low. Therefore, when handling a slurry that behaves like a pseudo-plastic fluid, the flow resistance in the coarse particle separator increases due to the high viscosity at low speeds, clogging of the screen occurs and pressure loss increases, resulting in pump power consumption. May increase and cause troubles such as clogging of the coarse particle separator. According to this embodiment, since the viscosity of the slurry is reduced by adding the surfactant to the coarse particle separator 14, the troubles described above can be prevented and the blunt can be operated safely and with low power. .

FIG. 5 shows a device configuration example of the fourth embodiment of the present invention. In this embodiment, a roll crusher 28 is installed in place of the coarse particle separator 14 in the third embodiment of the present invention (see FIG. 4), and the surfactant C is rolled by the pump 9 via the line 28A. It is characterized in that it is supplied to the crusher 28. That is, the present embodiment is characterized in that a product slurry is obtained by crushing with a roll crusher 28 instead of removing a small amount of coarse particles of about 300 to 1,000 μm or more. The roll crusher 28 in the present embodiment crushes coarse particles by sandwiching them between narrow rolls (drums) whose rotation speed and direction can be adjusted with each other. The maximum grain inside can be adjusted by the gap diameter. According to the present embodiment, when the slurry passes between the two rolls, a high shearing force acts and mixing with the surfactant is effectively promoted, so that the viscosity of the slurry can be further reduced. .

Example 1 Coal having a hard grindability index of 50, a case where a coal-water slurry was produced by a conventional wet ball mill method and a method using a wet ring roller mill shown in FIGS. 5 and 6, and FIGS. Table 1 shows the results of comparing the slurry properties, the pulverization power consumption and the required amount of the surfactant when the slurry was produced by the method of the present invention shown in FIG.

As is clear from this table, the required amount of the surfactant was reduced from 0.5% in the conventional method to 0.3%, and it was possible to achieve a reduction of about 40%. This is 600 per ton of coal
This is a yen savings of about 1.5 billion yen per year at a 1,000 MW class power plant that consumes about 300 t / h of coal.

(Effects of the Invention) According to the present invention, a high-concentration coal-water slurry suitable for direct spray combustion as a fuel for a boiler or the like can be produced at a low cost by significantly reducing the required amount of a surfactant. You can

[Brief description of drawings]

FIG. 1 is a system diagram of a coal-water slurry production apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a structure of a wet ball race mill suitable as the wet ring roller mill shown in FIG. FIG. 3, FIG. 4 and FIG. 5 are system diagrams of the coal-water slurry manufacturing apparatus according to the second, third and fourth embodiments of the present invention respectively, and FIG. 6 is a conventional wet ring roller mill. Diagram of the coal-water slurry production equipment using
FIG. 6 is an explanatory view showing the structure of a wet ball race mill used as the conventional wet ring roller mill shown in FIG. A ... Coal, B ... Water, C ... Surfactant liquid, D ... pH adjusting liquid, E ... Slurry, 1 ... Bunker, 2 ... Feeder, 3 ... Wet vertical link roller mill, 4 ... Coal feeding pipe, 13 ... Distributor, 1
4 ... Coarse grain separator, 15 ... Slurry tank, 16 ... Wet vertical ball race mill, 17 ... Grinding cable, 18 ... Pressurizing device, 19 ... Upper ring, 20 ... Drive device, 21 ... Lower ring, 22 ... Grinding Ball, 23 ... scraper, 24 ... weir,
25 ... Mixing paddle, 26 ... Surfactant liquid inlet.

Claims (6)

[Claims] 1. A method for producing coal-water slurry by wet-milling coal with a wet-ring roller mill having a milling ring and a roller, wherein a surfactant is added after the coal has been milled. Water slurry manufacturing method. 2. A method for producing a coal-water slurry according to claim 1, wherein a surfactant is added in the mixing weir after crushing coal in the mill. 3. A coal-water slurry according to claim 1, wherein the coal-water slurry is taken out of the mill and a surfactant is added in a line mixer provided outside the mill. Method. 4. A ring roller mill according to any one of claims 1 to 3, wherein a part of the coal ground in the ring roller mill is recycled to the mill through a distributor to remove coal, water and a surfactant. The weight of coal is 50 to 8 with respect to the total weight.
A method for producing a coal-water slurry, which comprises preparing 0% of a coal-water slurry. 5. The coal-water slurry taken out as a product through a distributor is introduced into a coarse particle separator according to claim 4, and a surfactant is added to the coarse particle separator to add coarse particles in the slurry. A method for producing a coal-water slurry, which comprises removing particles. 6. The method according to claim 4, wherein the coal-water slurry taken out as a product through a distributor is introduced into a roll crusher, and coarse particles in the slurry are crushed while a surfactant is added to the roll crusher. A method for producing a coal-water slurry, comprising: