JPH0323116B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly concentrated coal-water slurry, and particularly to a method for producing a stable slurry using a multi-stage liquid feeding method.

Recently, coal has been increasingly used in place of oil, mainly in thermal power plants. However, coal, which is a fixed fuel, is difficult to handle, and transportation costs have a large impact on coal prices. Therefore, efforts are being made to actively develop technologies to turn coal into a slurry so that it can be handled as a fluid.

One of them is a mixture of heavy oil and coal.
There is COM (Coal and Oil Mixture). but
In the case of COM, the weight ratio of heavy oil to coal is approximately 1:1, so it cannot be said to be a completely oil-free fuel, and there are few advantages in terms of price. Furthermore, methacol, which is a mixture of methanol and coal, is expensive and has not yet reached the practical stage.

In contrast, CWM, which is a mixture of coal and water,
(Coal and Water Mixture) is quite practical in terms of price and has been attracting attention recently. this
CWM is generally produced by adding water to coal and wet-pulverizing it. but,
If the water content in CWM is high, the thermal efficiency during combustion will be reduced, and if the water content is low, the viscosity of CWM will increase, resulting in a large pressure loss during transportation. Additionally, since CWM is composed of coal particles and water, there is a storage problem in that the coal particles settle and separate from the water over time. In order to eliminate these drawbacks, CWM with high coal concentration, low viscosity, and good stability can be produced by adjusting the particle size distribution of coal particles and adding additives. The disadvantage is that the amount of charcoal is large and the cost is high.

Conventionally, in order to produce a slurry with high coal concentration, low viscosity, and good stability, it has been necessary to add additives to the supplied coal and water and to grind the coal to a particle size that maximizes the coal filling rate. It is said to be desirable. As shown in Fig. 1, such a method involves simultaneously supplying coal and additive liquid to the wet tube mill 5 from the coal hopper 1 and the liquid supply tank 3 through the supply pipes 2 and 4 to achieve a high coal concentration. There is a method of pulverizing (generally 60 to 80%, based on weight, the same applies hereinafter) (high concentration wet pulverization method), but if additives are added all at once, excess additives will be adsorbed to the coal surface and the additives will be The disadvantage is that the amount of consumption is high and the additive is expensive, so adding a large amount will increase the cost of the product slurry. In addition, in the figure,
6 is a slurry discharge pipe, and 7 is a slurry adjustment tank. Therefore, it is a major challenge to supply as little amount of additive as possible and to produce a stable and highly concentrated slurry.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a method for producing an inexpensive coal-water slurry with high coal concentration, low viscosity, and a small amount of additives.

The present invention provides a method for producing a highly concentrated coal-water slurry in which coal and additives are supplied into a wet tube mill and wet-pulverized, in which the additives are supplied in multiple stages along the direction of pulverization of coal in the tube mill. Features.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 2 is a conceptual diagram of a coal-water slurry manufacturing apparatus showing an embodiment of the present invention. In the figure, the coal stored in the coal hopper 1 is transferred to the fixed quantity coal supply pipe 2.
At the same time, water and additives are supplied from the liquid supply tank 3 to the same wet tube mill 5 through the liquid supply pipe 4. The coal concentration at this time is 50-80% (preferably 60-70%)
The liquid containing additives is divided into three parts and supplied into the wet tube mill from three liquid supply nozzles 8 provided along the pulverizing direction (progressing direction) of coal in the tube mill. The coal-water slurry (CWM) produced in the wet tube mill is sent to a slurry adjustment tank 7 through a slurry discharge pipe 6, and from there is transported to a combustor or the like by a slurry pump or the like as required.

When coal is crushed in a wet tube mill,
The coal particle size near the inlet is large and the surface area of the coal is small, so the amount of additives attached to the surface is small, but the coal particle size near the mill outlet is very fine and the surface area is large, so the amount of additives attached to the surface is small. The amount of additives that adhere to the surface also increases. That is, the amount of additive can be significantly reduced by adjusting the amount of additive depending on the coal particle size, that is, by performing multistage liquid supply.

In addition, in the conventional method shown in Fig. 1, since the additive is supplied in one stage, there is a large excess of additive near the mill entrance, and the excess additive is adsorbed on the coal surface in multiple layers. Because it gets into the pores of the coal, more additive than necessary is consumed. Figure 2 shows an example of liquid feeding in three parts, but if the liquid is fed in two parts or in multiple stages depending on the coal properties or the size of the mill, or if the liquid is supplied in multiple stages, the amount of additive can be adjusted by adjusting the particle surface area. It may be increased in stages according to the increase in the amount.

FIG. 3 shows a method of dispersing and supplying the additive liquid into the mill using one liquid supply nozzle 8' which can widely disperse the additive liquid. According to this method, the number of liquid supply nozzles can be reduced and the apparatus can be simplified.

Figure 4 shows a method of supplying additives in the form of powder.
0 into the mill 5 and sprayed from the additive nozzle 13. At this time, air from the air supply pipe 11 is used as the transport gas. Also, water is supplied into the mill from the water supply pipe 12. Since this method supplies additives and water separately, it is possible to maintain a constant moisture concentration within the mill.

FIG. 5 shows an example in which the present invention is applied to a multi-chamber mill; in this case, liquid supply nozzles 8 are installed at two locations, one on the inlet side and one on the outlet side of the mill.

FIG. 6 shows an example of application of the present invention to a multi-stage wet grinding process. Coal is supplied to the first stage mill 5, and additive liquid is supplied from the tank 3 accordingly. The slurry made here is sent to the secondary wet tube mill 14, and further to the secondary liquid supply tank 1.
From step 7, additives are added and crushed. The slurry produced here is further sent to the tertiary wet tube mill 15 from the secondary product slurry discharge pipe 19, and the tertiary liquid supply tank 1
Additives are supplied from 8 and the final product CWM is removed from the product slurry discharge pipe 16.

FIG. 7 shows an example of application to a process in which large particles are classified from a product slurry using a classifier 20 and then circulated through a recycling pipe 21 to the mill inlet. In this case, the final product is extracted from the system through the product slurry discharge pipe 22.

Figure 8 shows a wet tube mill with a diameter of 950 mm and a length of 1900 mm. Miike charcoal is used as the raw material coal, and the total amount of additives is kept constant and added in one stage (additives 0.4
%) and when the additive was added in three stages (the additive concentration in each stage from the mill inlet was 0.1%, 0.2%, and 0.1%). In the figure, 30 indicates one-stage addition, and 31 indicates three-stage addition. From this result, it is clear that when the slurry viscosity is the same, the coal concentration is higher when the slurry is added in three stages. In other words, when producing CWM with the same coal concentration and viscosity, it can be seen that adding additives in multiple stages requires a smaller amount of additives.

FIG. 9 is an explanatory diagram showing still another embodiment of the present invention using a multi-chamber mill. In the figure, coal A is supplied from a coal hopper 1 into a mill 5 via a coal feeder 52. Water B and additive liquid C are quantitatively supplied from the respective tanks 54 and 55 to the recovery tank 65 by the respective pumps 56 and 57, and are mixed with the coarse particles separated by the coarse particle separator 60 by the agitator 66. The slurry is then injected into the mill 5 from the recovery tank 65 via the coarse slurry recovery pipe 64.
The mill 5 is divided into two chambers by installing a partition plate 71 such as a screen, and each chamber is filled with balls of different diameters. That is, in this case, the first
The chamber is filled with large diameter balls of about 75 to 40 mm, and the second chamber is filled with small diameter balls of about 40 to 12 mm. The slurry that has passed through the partition plate 71 is efficiently crushed by small-diameter balls in the second chamber, and the particle surfaces are efficiently wetted by the additive newly added from the liquid supply pipe 70, thereby reducing the viscosity. The slurry discharged from the mill 5 is mixed in a tank 58 with separately supplied additives or additive particles by a stirrer to further reduce the viscosity. In this way, as the surface is generated by pulverizing the particles, additives or additive liquid are added in small amounts in multiple stages inside and outside the mill, and by effectively mixing them with the particles, There is no waste of the agent, and the amount used can be reduced. Next, the CWM produced in the mill 5 enters a slurry tank 58, where it is adjusted by adding additive liquid, water, etc. as necessary from supply pipes 80 and 81, and then roughened by a pump 59. Enter grain separator 60. The coarse particle separator 60 is provided with a vibration generator 72 that applies vibration or ultrasonic waves to the screen 61. The vibrations or ultrasonic waves from the vibration generator reduce the viscosity of the slurry present near the screen 61, making it easier for the slurry gas to pass through the screen 61.
Further, due to the vibration, coarse particles that do not pass through the screen 61 tend to overflow the screen 61. The vibration generator 22 may be provided independently, but it is also possible to utilize the vibration of the mill 5. The product passes through the screen 61 and is transported to the outside of the system through the discharge hole 62.
Coarse particles that do not pass through overflow on the screen 61, enter the recovery tank 65 through the discharge hole 63, are mixed with water B and additive liquid C as described above, and are injected into the mill 5 via the coarse particle slurry recovery pipe 64. be done.

According to the above embodiment, the water and additive liquid to the mill are first supplied to the recovery tank 65 and mixed with the coarse slurry, so that the solids concentration of the coarse slurry is approximately 35
% or less, resulting in a viscosity almost equal to that of water.Also, since the slurry is circulated through the recovery pipe 64 into the mill 5 by gravity flow, uniform quality can be achieved.
CWM can be manufactured continuously. In addition, as described above, the additives can be supplied and adjusted from inside the mill, that is, from the supply pipe 64 at the inlet, the supply pipe 70 at the outlet, and the supply pipe 80 of the slurry tank 58, so that the additives can be adjusted in a rational manner. Add,
The amount used can be reduced.

In the above embodiment, the coarse slurry from the recovery tank 65 is returned to the mill 5 by gravity, but a pump may be provided midway to supply the coarse slurry in a fixed amount. In this way, the circulating coarse slurry is quantitatively supplied to the mill by the pump in the same way as the additive liquid, so fluctuations in the milling system are reduced and more stable operation can be achieved.

As described above, according to the present invention, by feeding additives in multiple stages within a tube mill,
The amount of additives used can be reduced, making it possible to lower the cost of CWM.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the flow of a coal-water slurry manufacturing apparatus using a conventional wet mill, and FIGS. 2 to 7 and 9 are flowcharts of a similar apparatus for carrying out the present invention, respectively. The figure 8, which shows
FIG. 3 is a diagram showing experimental results (relationship between viscosity and coal concentration) in the case of single-stage addition and multi-stage addition using a small wet mill. 1...Coal hopper, 2...Coal supply pipe, 3...
...Liquid supply tank, 4...Liquid supply pipe, 5...Wet tube mill, 6...Slurry discharge pipe, 7...Slurry adjustment tank, 8...Liquid supply nozzle.

Claims (1)

[Claims] 1. A method for producing a highly concentrated coal-water slurry in which coal and additives are supplied into a wet tube mill and wet-pulverized, in which the additives are supplied in multiple stages along the direction of pulverization of coal in the tube mill. A method for producing a highly concentrated coal-water slurry. 2. A method for producing a highly concentrated coal-water slurry according to claim 1, characterized in that the slurry concentration is adjusted by supplying an additive in powder form. 3 In claim 1, there is a plurality of wet tube mills or a tube mill with multiple chambers, and each tube mill or each chamber supplies an amount of additive according to the surface area of the pulverized coal. A method for producing a highly concentrated coal-water slurry, characterized by: