JPH0765060B2 - Method and apparatus for producing coal-water slurry - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a coal-water slurry and an apparatus therefor, and more particularly to a line for introducing a slurry supplied from a wet tube mill into a product tank via a strainer. The present invention relates to a coal-water slurry manufacturing method and apparatus suitable for stable operation of a strainer in a coal-water slurry manufacturing apparatus having the above and stabilizing slurry in a product tank.

[Conventional technology]

Fuels used in combustion devices such as boilers include fluid fuels such as heavy oil and LNG, and solid fuels such as coal. A coal-water slurry obtained by suspending coal with an additive such as a surfactant and water to form a slurry has attracted attention as a boiler fuel because it facilitates handling during transportation and storage.

The slurry is required to have a high concentration and a low viscosity in order to improve the handling property in transportation and storage and the combustibility in a combustion device such as a boiler. For this reason, the particle size distribution of coal particles in the slurry must be within a certain range.

Conventionally, in the production of coal-water slurry, raw coal and additives such as surfactants and water are supplied to a wet tube mill,
Collision of coal in the mill with balls contained in the mill results in a coal-water slurry. This slurry is once stored in a sump tank and then introduced into a strainer via a pump. In the strainer, coarse coal particles that have not been sufficiently crushed by the wet tube mill are cut, and the slurry with a predetermined particle size distribution is stored in the product tank, and the combustion device such as the boiler is converted to the combustion device according to the operation. be introduced.

[Problems to be solved by the invention]

In a wet tube mill, because coal is crushed by the collision of coal with balls, the slurry temperature in the mill rises,
It reaches almost 80 ℃. Such high temperature slurry is stored in the sump tank and then introduced into the strainer. Therefore, during the operation of the strainer, the water existing on the surface of the coal particles due to the surface tension is easily separated from the coal particles, and the water content mainly passes through the screen of the strainer to increase the amount of water in the product slurry. Not only is it impossible to obtain a predetermined high-concentration slurry, but also the coal particles in the vicinity of the screen surface increase and a viscous layer is formed, which makes continuous operation of the strainer difficult.

If the slurry taken out of the strainer is still hot, the water in the slurry stored in the product tank evaporates, this vapor condenses in the tank, and the condensed water is stored in the product tank. A water layer is formed on the surface of the slurry and the thickening phenomenon of the slurry occurs. Therefore, there is a problem in that the characteristics of the slurry that supplies the product slurry from the product tank to the combustion device such as a boiler fluctuates over time, making it difficult to transport the slurry by pipes.

Furthermore, if the temperature of the slurry is high between the wet tube mill and the product tank, the additive contained in the slurry deteriorates, which promotes alteration of the slurry and changes the slurry characteristics. is there.

The object of the present invention is to solve the above-mentioned problems of the prior art,
You can continuously stabilize the operation of the strainer,
Another object of the present invention is to provide a method for producing a coal-water slurry and an apparatus therefor capable of constantly stabilizing the characteristics of the product slurry.

[Means for solving problems]

The above-mentioned purpose is higher than normal temperature in a stage before introducing the hot coal-water slurry taken out from the mill into the strainer,
And a method of cooling so that the temperature is 50 ° C. or lower, preferably 40 to 50 ° C., and an apparatus for carrying out this method is coal from a mill to a strainer.
By providing a slurry cooler and a slurry temperature detector on the water slurry supply line, and providing means for controlling the amount of cooling water for the slurry cooler based on the deviation between the output value of the slurry temperature detector and the temperature set value. To be achieved.

[Action]

Since the temperature of the high-temperature coal-water slurry introduced into the strainer is cooled so that the temperature falls within a predetermined range, in the strainer, water existing due to surface tension on the surface of the coal particles becomes difficult to separate from the coal particles, and the strainer The coal particles and the water adhering to the surface of the coal particles efficiently pass through the screen. So the coal that passed through the screen
The concentration of the water slurry is adjusted within a predetermined range, and since the viscous layer of coal particles is not formed near the screen surface, the operation of the strainer is stabilized.

Since the evaporation of water in the slurry stored in the product tank is significantly reduced, a layer of condensed water is less likely to be formed on the surface layer of the slurry in the product tank, and the thickening phenomenon of the slurry can be suppressed. Further, the process of reaching the product tank and the coal-water slurry stored in the product tank are released from the high temperature state, so that deterioration of additives such as surfactants in the slurry due to high temperature can be avoided.

Example of Invention

In the present invention, the high temperature coal-water slurry in the process from the mill to the screen is higher than normal temperature and is 50 ° C.
It is cooled so that

Figure 1 shows the relationship between the coal-water slurry (CWM) filtration time and the cumulative CWM passage rate in the strainer. Here, the cumulative passage rate (%) is defined as in (1) below.

As shown in FIG. 1, when the temperature of the CWM supplied to the strainer is 50 ° C., the cumulative passage rate is higher than that of the CWM of 80 ° C. for the same filtration time. In addition, the cumulative passage rate is smaller at the same filtration time than when the CWM temperature is 50 ° C at room temperature.

Figure 2 shows the relationship between CWM temperature and initial passage speed. Here, the initial passage speed is obtained from tan θ of the tangent to the curve obtained from the relationship between the filtration time and the CWM cumulative passage rate as shown in FIG.

As shown in Fig. 2, the initial passage speed of CWM in the strainer shows a substantially constant value below 50 ° C, and the initial passage speed gradually decreases above 50 ° C. Therefore the first
From Fig. 2 and Fig. 2, if the high temperature CWM taken out from the mill before it is supplied to the strainer is cooled to 50 ° C or less, the cumulative CWM passage rate and the initial passage speed can be maintained at a high level. I understand.

FIG. 4 shows the time-dependent changes in CWM storage temperature and CWM viscosity in the product tank. In Figure 4, A: degree of polymerization 30
Of CWM with the addition of anionic surfactant, B: CWM with the addition of anionic surfactant with a degree of polymerization of 30, and C: CWM with the addition of anionic surfactant of the degree of polymerization of 7.

As shown in FIG. 4, the CWMs of A and B are maintained at about 1500 cP after about 20 days elapsed at any storage temperature of 40 ° C., 50 ° C. and 60 ° C. On the other hand, the viscosity of CWM of C increases as the number of elapsed days increases, and the viscosity of CWM increases to nearly 2000 cP after about 20 days elapsed.

A suitable viscosity for CWM pipe transportation is usually 2000 cP or less, preferably 1500 cP. Therefore, each CWM of A, B, C
It is possible to use any of the anionic surfactants added to, but it has been shown that CWM added with an anionic surfactant having a degree of polymerization of 30 is particularly effective. From the viewpoint of suppressing the thickening phenomenon of CWM as much as possible, the anionic surfactant added to CWM preferably has a degree of polymerization of about 20 to 50. Furthermore, FIG. 4 shows that when the storage temperature of CWM in the product tank is 40 ° C., the thickening phenomenon of CWM is hardly observed.

As described above, from the results of FIGS. 1 to 4, when CWM before being supplied to the strainer is cooled to 50 ° C. or less, there is no hindrance to the operation of the strainer, and the thickening phenomenon in the product tank can be suppressed. Recognize. In order to more reliably suppress the thickening phenomenon of CWM in the product tank as well as the stable operation of the strainer, it is effective to cool the CWM to about 40 ° C before it is supplied to the strainer. Further, depending on the selection of the anionic surfactant, it is sufficient to cool the CWM so as to be in the range of 40 ° C to 50 ° C.

If the temperature for cooling the CWM is lower than the room temperature, the passing speed of the strainer of the CWM will decrease depending on the season, and the thickening phenomenon will occur in the product tank, which is also disadvantageous in terms of thermal energy. The cooling temperature of the CWM is at least higher than room temperature and may be 50 ° C. or lower.

FIG. 5 is a schematic configuration diagram showing an embodiment of a coal-water slurry producing apparatus according to the present invention. In FIG. 5, a water cooling jacket 2 is attached to the outer peripheral surface of the main body of the wet tube mill 1, and low temperature water is supplied to the water cooling jacket 2 from a water cooler 3. Water from the water tank 5 is supplied to the water cooler 3 via the pump 4. A sump tank 6 is installed on the slurry outlet side of the wet tube mill 1, and the slurry stored in the sump tank 6 is pumped by a pump 7
After being cooled by the slurry cooler 8 via the strainer 9
Has been introduced to. A slurry temperature detector 10 is installed in the middle of the slurry supply line from the slurry cooler 8 to the strainer 9, and based on the deviation between the output value of the slurry temperature detector 10 and the slurry temperature set value, the slurry cooler 8 A controller 12 that outputs an opening degree control signal to a control valve 11 that adjusts the amount of cooling water introduced therein is installed. 13 is a product tank.

Next, the operation of the coal-water slurry manufacturing apparatus configured as described above will be described.

Cooling water is supplied to the mill 1 from the water cooler 3 together with coal, and the coal is crushed in the mill and mixed with water.
In this process, cooling water is introduced into the mill 1 and the cooling water is introduced from the water cooler 3 into the water cooling jacket 2. Therefore, the excessive temperature rise of CWM and the evaporation of water in CWM caused by the pulverization of coal in the mill 1 are suppressed. However, the temperature of CWM taken out from the mill 1 is about 80 ° C., and this high temperature CWM is stored in the sump tank 6 and then introduced into the strainer 9 via the slurry cooler 8. At the inlet of the strainer 9, a slurry temperature detector 10 detects the temperature of the slurry. The output signal from the slurry temperature detector 10 is input to the controller 12.

Controller 12 should be above room temperature and below 50 ° C
The slurry temperature set value that is predetermined according to the type of anionic surfactant added to CWM and the concentration of CWM is input, and control is performed based on the deviation between the output value from the slurry temperature detector 10 and the set value. An opening control signal is output to the valve 11. Then, the opening of the control valve 11 is controlled to control the amount of cooling water introduced from the water cooler 3 into the slurry cooler 8, and CWM adjusted to a predetermined temperature is supplied to the strainer 9. Since the CWM from the strainer 9 is higher than room temperature and adjusted to 50 ° C. or lower, it is introduced and stored in the product tank 13 while being kept within the temperature range.

〔The invention's effect〕

According to the present invention as described below, since a viscous layer of coal particles is not formed in the vicinity of the screen surface in the strainer, CWM can be continuously and stably processed, and CWM passing through the screen of the strainer has a predetermined concentration. In addition, the viscosity of CWM in the product tank can be suppressed and the viscosity of CWM can be maintained at a level suitable for pipe transportation, and deterioration of the additive of CWM at high temperature can be prevented.

[Brief description of drawings]

Fig. 1 is a graph showing the relationship between the filtration time of CWM in the strainer and the cumulative passage rate of CWM, Fig. 2 is a graph showing the relationship between the CWM temperature in the strainer and the initial passage speed of CWM, and Fig. 3 is the graph of CWM. FIG. 4 is an explanatory view showing the definition of the initial passage speed, FIG. 4 is a graph showing changes with time of storage temperature of CWM and viscosity of CWM, and FIG. 5 is an embodiment of a coal-water slurry production apparatus according to the present invention. It is a schematic block diagram which shows. 1 ... Mill, 2 ... Water cooling jacket, 3 ... Water cooler, 5
…… Water tank, 6 …… Sump tank, 8 …… Slurry cooler, 9 …… Strainer, 10 …… Slurry temperature detector, 11…
… Control valve, 12… Controller, 13… Product tank.

Claims (5)

[Claims] Claim: What is claimed is: 1. Coal and water are mixed at a predetermined ratio in a mill, and the coal is crushed to produce a high-concentration coal-water slurry,
In the method for producing a coal-water slurry in which coarse particles in the coal-water slurry are removed by a strainer and the slurry from the strainer is stored in a product tank, the high temperature coal-water slurry taken out from the mill is aforesaid. A method for producing a coal-water slurry, which comprises cooling to a temperature higher than room temperature and 50 ° C. or lower before reaching a strainer. 2. The coal-water slurry taken out of the mill is cooled to a temperature range of 40 ° C. to 50 ° C. before reaching the strainer.
Item 6. A method for producing a coal-water slurry according to the item. 3. The coal-water slurry according to claim 1, wherein the coal-water slurry withdrawn from the mill is cooled to 40 ° C. before reaching the strainer. Production method. 4. The method for producing a coal-water slurry according to claim 1, wherein the coal-water slurry is added with an anionic surfactant having a degree of polymerization of 20 to 50. . 5. A mill for mixing coal and water in a predetermined ratio and pulverizing the coal to produce a high-concentration coal-water slurry, and removing coarse particles in the coal-water slurry from the mill. In a coal-water slurry manufacturing apparatus equipped with a strainer for and a product tank for storing coal-water slurry from the strainer, a slurry installed on a coal-water slurry supply line connecting the mill and the strainer. A cooler, a slurry temperature detector installed on the upstream side of the strainer, and means for controlling the amount of cooling water for the slurry cooler based on the deviation between the output value of the temperature detector and the temperature set value. An apparatus for producing coal-water slurry, which is characterized by being provided.