JPH044493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for atomizing pulverized coal-water slurry,
In particular, the present invention relates to an atomization method suitable for preventing blockage of pulverized coal-water slurry passages.

In recent years, as energy sources have become more diversified, coal has been increasingly used as fuel for combustion devices such as commercial boilers.

Various coal combustion methods have been known for a long time, but
One of these is a combustion method that uses pulverized coal made into a slurry by adding water (hereinafter referred to as CWM) instead of liquid fuel such as heavy oil, which is attracting attention. According to this combustion method, conventional oil-fired combustion equipment equipped with a medium spray burner can be applied as is without any special equipment changes, and there are other advantages such as no need to use liquid fuel such as heavy oil. be.

However, conventional media atomization burners have a fuel passage and an atomized medium passage, and the space between them is simply a metal wall, so if this burner is used as is for CWM, It was found that various troubles such as those described below occur. One of them is due to heat transfer from the atomizing medium.
Moisture in the CWM evaporates from the passage walls, so
The coal content in the CWM gradually solidifies from the wall surface and eventually blocks the passage. Further, the nozzle tip is heated by flame radiation in the furnace, and in this case as well, there is a problem that the CWM nozzle or atomization chamber in the nozzle tip is clogged for the same reason as above. In order to solve the problem of continuous supply of CWM due to the above-mentioned blockage, it is possible to reduce the viscosity by lowering the concentration of pulverized coal in CWM, but in this case, the amount of heat released to the atmosphere due to exhaust gas increases, resulting in a disadvantage that the thermal efficiency of the entire plant decreases. Furthermore, if the viscosity of the CWM is lowered, the pulverized coal in the CWM will more easily settle, and may partially solidify and block the CWM passage. Furthermore, as mentioned above, on the high concentration side of pulverized coal, there is a limit due to solidification that progresses from the wall surface, and on the other hand, on the low viscosity side, there is a limit on solidification due to sedimentation of pulverized coal, so the pulverized coal concentration of practical CWM is There is a problem that the range is narrow and therefore concentration control becomes extremely difficult.

An object of the present invention is to provide a CWM atomization method that prevents clogging of CWM passages and the like during CWM atomization.

The inventors avoided blockage in the CWM passage by keeping the pressure of the CWM in the CWM passage higher than the saturation pressure of water corresponding to the temperature of the atomizing medium and preventing boiling of the water contained in the CWM. It has been found that in order to prevent boiling, the temperature of the CWM is kept low, thereby lowering the saturation pressure of water, and making the pressure of the CWM relatively higher than the saturation pressure of water.

The present invention provides a pulverized coal-water slurry atomization method in which a pulverized coal-water slurry and an atomization medium are collided and merged into an atomization chamber from separate passages to atomize the slurry. characterized in that the pressure of the slurry is maintained higher than the saturation pressure of the water, which corresponds to the temperature of the atomizing medium.

To keep the above CWM pressure high, CWM
It is possible to increase the CWM supply flow rate to compensate for the flow resistance of the nozzle, but the flow rate cannot be increased at low loads when the CWM flow rate decreases, so there is no option other than increasing the flow rate.
A means is required to maintain the CWM pressure high and prevent the water contained in the CWM from boiling.

In addition to increasing the flow rate mentioned above, as means to increase the relative pressure of the CWM, methods that can prevent the temperature rise of the CWM are widely applied. A thermal insulation structure provided, a combination thereof, etc. can be shown. The above-mentioned heat insulating structure may have independent or continuous hollow chambers in the metal base material of the relevant portion, or may be constructed of a non-metallic material with poor thermal conductivity.
In addition, when the above-mentioned communicating hollow chamber is provided, it is also possible to introduce a cooling medium into the chamber from the outside to perform forced cooling.

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

FIG. 1 is used in one embodiment of the present invention.
FIG. 3 is a cross-sectional view of a CWM atomizing burner. This burner device includes an inner cylinder 4 provided at the center forming a CWM passage 5, and an inner cylinder 4 provided outside the inner cylinder 4.
an outer cylinder 3 forming an annular passage 7 for atomizing medium (e.g. steam) between the outer periphery of the CWM passage 5, a CWM nozzle 8 provided at the furnace side tip of the CWM passage 5, and a furnace side of the atomizing medium passage 7. A generally plurality of atomizing medium nozzles 10 provided at the side tips, an atomizing chamber 9 communicating with the CWM nozzle 8 and the atomizing medium nozzle 10, and an atomizing chamber 9.
A nozzle tip 11 is fixed by a cap 12 at the tip end on the furnace side. Inside the inner cylinder 4, according to the present invention, a plurality of independent heat-insulating hollow chambers 6 are provided along the burner axis. They are arranged one after the other to form a heat insulating structure.

In the apparatus configured as described above, the CWM 1 passes through the CWM passage 5 and is then ejected from the CWM nozzle 8 into the atomization chamber 9. On the other hand, the steam 2, which is an example of an atomizing medium whose temperature is normally raised to about 200°C, passes through the atomizing medium passage 7 and is then jetted into the atomizing chamber 9 from the atomizing medium nozzle 10 in a swirling flow. Atomize the CWM. The atomized CWM is mixed with combustion air 13 flowing outside the outer cylinder 3 and then combusted. The combustion air 13 is generally preheated to 300 to 350°C in many cases to improve combustion.

The CWM 1 is in an environment where it is easily heated by the steam 2 flowing through the atomization medium passage 7 and the combustion air 13 flowing outside the outer cylinder 3 while passing through the CWM passage 5, but as described above, the inner cylinder 4 is constructed with an insulating structure. The heating is suppressed by making the CWM
The saturation pressure of the water inside can be made relatively lower than the CWM pressure, so even during low load operation
The water in the CWM will not boil, so the coal will not solidify and block the passageways.

Next, FIG. 2 shows another burner device used for carrying out the present invention, except that the outer cylinder 3A is also formed of a heat insulating structure having the same structure as the inner cylinder 4 of FIG. 1. It has a similar configuration. In this case, the passage within the inner cylinder 4 becomes the atomized medium passage 7, while the annular passage formed between the outer periphery of the inner cylinder 4 and the inner periphery of the outer cylinder 3A becomes the CWM passage 5.

In a device with such a configuration, heating of the CWM is suppressed as well as in the case of the device shown in Fig. 1, and
The effect of preventing blockage of the CWM passage can be obtained.

Furthermore, FIG. 3 shows the nozzle tip of another device used for carrying out the present invention. This device has an independent hollow chamber 61 perpendicular to the burner axis at the tip on the furnace side, and an outer periphery of the CWM nozzle 8. Independent hollow chamber 6
The nozzle tip 11 has the same structure as the nozzle chip 11 shown in FIG.

With this configuration, it is possible to suppress flame radiation of the furnace body and heating by the atomizing medium passing through the passage 7, so in addition to preventing clogging of the CWM passage,
It is also possible to prevent clogging of the CWM nozzle 8 and the atomization chamber 9.

In the above embodiment, for example, as shown in FIG.
By inserting a heat insulating material into the hollow chamber 6 of the CWM atomizing burner, the heat insulating effect can be further improved. Further, the hollow chamber may have a communicating structure, in which case a cooling medium can be forcibly injected from the outside to provide a cooling effect.

The communicating hollow chamber described above can also be communicated with the hollow chamber of the nozzle chip shown in Fig. 3, and a cooling medium can be forcibly injected from the outside into the entire communicating chamber thus obtained to further improve the cooling effect. You can also do it. Furthermore, the same effect can be obtained by using a nozzle chip made entirely of a non-metallic material with low thermal conductivity in place of the nozzle chip shown in FIG.
Furthermore, the present invention is not limited to the type of burner (two-fluid burner) shown in each embodiment, but is widely applicable to known medium spray type burners.

As described above, according to the present invention, by making the pressure of the CWM sent through the CWM passage higher than the saturation pressure of water at the temperature of the atomizing medium, the coal content in the CWM is gradually solidified from the wall surface in the CWM passage. This makes it possible to eliminate the disadvantage of clogging and clogging, and as a result, CWM combustion can be performed at a high rate without clogging, even during low-load operation where water boiling is likely to occur. .

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a CWM atomizing burner used in carrying out the present invention, FIG. The figure shows another CWM used to implement the invention.
FIG. 3 is a side sectional view showing a nozzle tip of the atomizing burner. 1...CWM, 2...Atomization medium, 3,3A...
Outer cylinder, 4... Inner cylinder, 5... CWM passage, 6, 6
1,62...Hollow chamber, 7...Atomization medium passage, 8...
... CWM nozzle, 9 ... atomization chamber, 10 ... atomization medium nozzle, 11 ... nozzle tip, 13 ... combustion air.

Claims (1)

[Claims] 1 In a pulverized coal-water slurry atomization method in which a pulverized coal-water slurry and an atomization medium are collided and merged into an atomization chamber from separate passages to atomize the slurry, the pulverized coal-water slurry is
A method for atomizing a pulverized coal-water slurry, characterized in that the pressure of the slurry in the water slurry passage is maintained higher than the saturation pressure of water corresponding to the temperature of the atomizing medium.