JPH0347899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulverizer, and more particularly to a pulverizer configured to significantly reduce the amount of pulverized material falling to the bottom of the device.

Due to recent changes in the fuel situation, the number of large boilers for business use such as large boilers for thermal power plants that use coal as fuel is increasing.In this case, the coal is pulverized in a pulverizer that uses balls or rollers. Airflow is transported to the burner section. By pulverizing the coal in this way (for example, 70% or more of the amount that passes through 200 mesh), the surface area of the coal per unit amount increases, improving combustibility, and since it burns in a short time, controllability is also greatly improved. There is an advantage to doing so.

FIG. 1 shows, as an example, a pulverizer called a vertical ball mill among the coal pulverizers. Coal C to be pulverized falls through the coal feed pipe 8 of the pulverizer main body 1 and reaches the pulverizer. The crushing section includes an upper fixed wheel 6 to which a pressing force is applied by a pressurizing device 4, a lower roller 9 rotated by a drive device 41, and these upper fixed wheels 6.
and a plurality of crushing balls 7 which are disposed between the lower rollers 9 and are crushing bodies that roll with the rotation of the lower rollers 9.
It is formed from. The coal that has reached the crushing section is moved to the crushing ball arrangement section by the centrifugal force generated by the rotation of the lower roller 9 and is crushed. The pulverized coal is supplied from the air port 17 and is caused to rise inside the device by air (usually high-temperature air is used to dry the coal) ejected from the perforated plate 15. It falls into the crushing section and undergoes primary classification. Further, the airflow containing the remaining pulverized coal is given a swirling force by the guide vanes 12 of the classifier 11 and flows into the classifier 11. In the classifier 11, large-diameter particles descend through the classifier due to the swirl of this airflow, fall into the crushing section, and are re-pulverized.
On the other hand, the pulverized coal flows into the pulverized coal pipe 13 along with the airflow and is transported to the burner by the airflow.

2 and 3 relate to the structure of the perforated plate attached to the above apparatus. The perforated plate 15 is the lower roller 9
The perforated plate is formed and arranged in an annular shape so as to surround the outer periphery of the perforated plate, and an air injection port is formed in the perforated plate. This air injection port is formed as a slit as shown in Figure 3, and the air flows through this slit 1.
8, and ejects from the gap between the perforated plate 15 and the lower roller 9. The pulverized coal forms a layer on the perforated plate 15, and is blown upward by the air jetted from the perforated plate.A vortex of the jet gas is generated on the wall of the slit 18, and this vortex The pulverized coal is attracted to fall through this slit to the bottom of the device. Due to an increase in the volume of the lower air chamber due to an increase in the capacity of recent crushing devices, the uneven flow within the air chamber becomes larger, and the amount of pulverized coal that falls due to this uneven flow tends to increase. FIG. 4 specifically shows the falling state of coal. In the figure, gas flowing into the air injection port 18 from the lower part of the perforated plate 15 (usually the atmosphere, but a mixture of combustion gas, etc., or other gases may be used) A is injected from the air injection port 18 into the injected coal bed to scatter and raise the pulverized coal. In this case, the airflow is disturbed at the side edge 15a of the inlet portion of the air injection port 18, and a vortex area 20 is formed along the wall surface of the air injection port 18. In this vortex region 20, a flow is formed that flows backward toward the inlet side of the air injection port, so that a part of the pulverized coal is attracted and falls to the lower part of the perforated plate.

Fallen coal is heated by high-temperature gas, making it dangerous and easily ignited. Therefore, it is cooled down by water spraying, etc., but the removal of fallen coal relies on manual labor, so it contains moisture. Discharging coal will require a lot of effort.

In addition, one method to reduce the fall of pulverized coal is to reduce the width of the slit and increase the injection speed, but this increases the pressure loss in the perforated plate and significantly increases the power cost of the blower. There is a problem with doing so. Furthermore, when the diameter is reduced, once the pulverized coal becomes clogged, it is difficult for the pulverized coal to fall down, resulting in the injection port being blocked for a long time.

This invention has been constructed in view of the above-mentioned problems, and an object of the present invention is to provide a crushing device that can significantly reduce the falling amount of crushed materials such as crushed coal without increasing the pressure loss of the perforated plate. .

In short, this invention provides a lower roller that rotates in a horizontal plane below within the crusher main body, a crusher that crushes the material to be crushed between the lower roller, and a gap between the crusher main body casing and the lower roller. A pulverizer is provided with a perforated plate having a gas jet port, and is configured to classify the crushed material by supplying gas from below the perforated plate, the periphery of the inlet portion of the gas jet port formed in the perforated plate. This pulverizer is characterized in that it is configured with a curved surface so as to suppress the generation of a vortex of the injected gas on the wall surface of the gas injection port.

Examples of the present invention will be described below.

In FIG. 5, the inlet portion of the air injection port formed in the perforated plate 15, that is, the lower peripheral edge of the air injection port is rounded. (Hereinafter, this shaping section will be referred to as the "R section.") By forming this R section 21, the gas A smoothly flows into the air injection port, and no vortex is formed. For this reason, there is hardly any pulverized material being attracted, and the amount of falling pulverized material is significantly reduced.

FIG. 6 is a diagram showing the result of investigating the relationship between the radius of the R section and the amount of falling coal when the R section of the peripheral edge of the air injection port inlet is shaped to have a circumferential cross section. In the figure, "without R" means that the conventional R part is not formed.
"2R" has an R part with a radius of 2mm, "3R"
"5R" means that an R part with a radius of 3 mm is formed, and "5R" means that an R part with a radius of 5 mm is formed. As is clear from this diagram, when an R section is formed, the amount of coal falling decreases, and especially when it is formed at 5R, the amount of coal falling becomes a negligible amount. In addition, in practical use R
should be 1.5 mm or more.

In addition, smoothing the flow of gas by forming the R part in this way also reduces the pressure loss across the perforated plate, and for the same amount of gas injection, the power cost of the blower is lower than that of the conventional type. It was confirmed that this could be reduced by approximately 20%.

By carrying out this invention, the flow of gas passing through the air injection port becomes smooth, and there is almost no induced fall of the pulverized material due to the eddy current, and the amount of falling pulverized material as a whole of the apparatus can be significantly reduced.

Furthermore, this smooth flow of air can also reduce the pressure loss of the perforated plate and reduce the power cost of the blower.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the coal crushing device, Fig. 2 is a sectional view of the perforated plate, Fig. 3 is a view taken along line A-A in Fig. 2, Fig. 4 is a sectional view of the air injection port, and Fig. 5 is a sectional view of the coal crushing device. The figure is a sectional view of the air injection port according to the present invention, and FIG. 6 is a diagram showing the relationship between the air injection port inlet shape and the relative value of the amount of falling coal. 15... Perforated plate, 18... Air injection port, 21...
...R section.

Claims (1)

[Claims] 1. A lower roller that rotates in a horizontal plane below the crusher main body, a crusher that crushes the material to be crushed between the lower roller, and a gas jet installed between the crusher main body casing and the lower roller. A pulverizer is equipped with a perforated plate having an outlet, and the pulverized material is classified by supplying gas from below the perforated plate,
A pulverizer characterized in that the periphery of the inlet portion of the gas injection port formed in the perforated plate is configured with a curved surface so as to suppress the generation of a vortex of the injection gas on the wall surface of the gas injection port.