JPS60187353A - Control of discharge amount of foreign matter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of foreign matter discharged in a coal pulverizer.

A ring roller that dries, crushes, and classifies the coal for the purpose of finely pulverizing the coal, and also automatically discharges foreign matter (other minerals with high specific gravity during backfilling, or rocks, iron pieces, etc. mixed into the coal). In a type crusher, foreign matter removal is critical.

Generally, backfilling contains 10 to 30% ash, and among them, Sin and free Si OL accelerate wear of the mill grinding part. Also, hard rocks, iron pieces, etc. mixed in the supplied coal have similar adverse effects. For this reason, it is necessary to prevent these foreign substances from accumulating in the grinding section of the mill as much as possible, and to discharge them to the outside of the mill as soon as possible (a small amount must always be discharged).

In the automatic discharge function of foreign matter, the open area of the hot gas blasting chamber is constant, so if the mill load (coal processing N) changes, a large amount of coal may be discharged together with foreign matter. This was not desirable in terms of resource conservation as it resulted in a lot of waste.

Here, to explain the general operation of fine pulverization of coal with reference to Figures 1 to 4, first, in the figure, 1 is a bowl, 2 is a reduction section, 3 is a coal feed pipe, 4 is a roll, and 5 is a hot gas entrance, 6
is a hot gas blow-off port, 7 is a turning vane, 8 is a deflection vane,
9 is a fine powder outlet, 10 is an internal conical tube, 11 is a mill lower part,
12 is a main shaft, and 13 is a scraper.

Now, the bowl 1 is rotated by a separately installed motor via a speed reducer 2 (normally 35RPM for large size to 90RPM for small size).
M). Coal (backfilling) is charged onto the bowl 1 from the coal feed pipe 3. The introduced coal is sent toward the outer periphery of the bowl by the centrifugal force caused by the rotation of the bowl 1, and is crushed between the bowls and the rolls 4.

At this time, the roll 4 is driven (rotated) by the rotational force of the bowl 1.

On the other hand, hot gas used for drying coal and classifying and transporting pulverized coal is sent from hot gas port 5 at the bottom of the mill. Hot gas is mainly supplied through hot gas blow-off ports 6 specially installed around the bowl.
The air is blown out from 2 to 4 places on the circumference of the bowl (some of it flows out from the gap around the bowl), and the deflection vane 7 causes the air to reach the bow 9.
The direction is changed to 0° (toward the center), and the fine powder (including some coarse powder) in the pulverized coal on the upper surface of the bowl is separated from the pulverized coal layer on the second bowl (-order classification) and transferred to the mill. send

The hot gas containing fine powder is further changed in direction by 90 degrees (horizontal direction) at the top of the mill, and the deflection vane 8 changes the flow into a horizontal swirling flow to apply centrifugal force to the pulverized coal particles, separating the fine powder and coarse particles. The powder is separated (secondary classification), and the fine powder is transported by hot gas from the central outlet 9 of the mill top to a boiler or pulverized coal storage facility. The coarse powder is collected onto a bowl by the internal conical tube 10 and ground again. Note that the deflection vane angle can usually be adjusted from outside the mill in order to adjust the fineness of the mill outlet.

Foreign matter in coal (things with a higher specific gravity than coal, coal is 0.
3 to 0, 4) are from the hot gas blow-off port 6 to the mill lower part 1.
1, and is automatically discharged to the outside of the mill from the lower opening of the mill by a scraper 13 attached to the main shaft 12. Note that the mill air volume needs to be changed appropriately depending on the load for coal crushing and mill body vibration. Therefore, the flow rate of hot gas blowing up changes depending on the load.

The object of the present invention is to appropriately discharge foreign matter in the entire load range of the mill, suppress coal discharge, reduce waste, and improve the economical efficiency of mill operation.

Conventionally, coal properties (crushability index, ash content %), grinding part wear degree, coal throughput, raw coal particle size, etc. have been considered empirically as factors related to the amount of foreign matter discharged.

This time, when I had the opportunity to collect data on the amount of foreign matter discharged, I happened to find that the amount of foreign matter discharged changes with changes in the amount of hot gas.
We were able to collect data as shown in Figure 7. As can be seen from Figure 7, the amount of foreign matter discharged (foreign matter discharge rate 0.02%
In the above, most of coal) is dominated by the hot gas blowing speed,
When the amount of hot gas is constant, the amount of foreign matter discharged can be reduced by reducing the hot gas blowing area.

Therefore, the present inventors have developed the present invention by focusing on the fact that when the mill load decreases and the air volume decreases, the blowing area can be reduced. That is, the present invention provides a method for adjusting the amount of foreign matter discharged, which makes it possible to adjust the blow-whisker area from the outside during mill operation, thereby making it possible to freely adjust the amount of foreign matter discharged so that the amount of foreign matter discharged is always appropriate. This is what we intend to provide.

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 5 and 6 show embodiments of the present invention, in which 14 is a damper blade, 15 is a damper shaft, 16 is a damper shaft boss, 17 is a lever, 18 is a lever fixing plate, and 19 is a fixing bolt.

In the embodiment shown in the drawings, a part of the hot gas blow-off port 6 has a damper (damper blades 14, damper shaft 15) that can be freely opened and closed by a lever 17 from outside the mill, and the lever I7 is operated according to the mill load. By changing the damper opening degree, the amount of foreign matter discharged can be maintained at an appropriate level at all times.

Now, when actually carrying out the implementation, it is necessary to make sure that there is no accumulation of coal and that no protrusions protrude beyond the height of the two sides of the outer periphery of the bowl (
It is necessary to take into consideration the following factors: (not withstand wear due to coal collisions), that movable parts do not stick due to pulverized coal, that operation is reliable, etc., but according to the present invention, each of the above items can be satisfied, and waste can be reduced. , the mill operating economy can be improved.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of a conventional coal crushing device, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 is a sectional view taken along line B-B in Fig. 1.
4 is a sectional view taken along the line C-C in FIG. 3, FIG.
The figure is a front view of a part of the lever outside the mill, and FIG. 7 is a diagram showing the relationship between the foreign matter discharge rate and the hot gas blowing speed. Description of the main parts of the diagram 6 - Hot gas blow-off port 14 - Damper blade 15 - Damper shaft 16 - Damper shaft boss 17 - Lever 18 - Lever fixing plate Patent applicant Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] A method for adjusting the amount of foreign matter discharged, characterized in that the hot gas blow-up opening area can be adjusted from outside the mill during operation of the mill, so that an appropriate amount of foreign matter can always be discharged.