JPH11347432A - Operation control method of roller mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely judge a mill operation state to prevent abnormal operation in an operation control method of a roller mill. SOLUTION: In this operation control method of a roller mill, raw coal 1 is fed onto a table 3 arranged in a mill casing 14 and is pulverized by a roll 4 to made it into pulverized coal, the pulverized coal is sent into a rotary classifier 12 in the upper part by an ascending current fed from the lower part of the table 3, also it is classified by the rotary classifier into fine pulverized coal and coarse pulverized coal, the fine pulverized coal 8 is discharged to the outside and also the coarse pulverized coal 7 is returned onto the table and pulverized again. At the time of operation, a differential pressure between the lower part and the upper part of the table is measured, also a differential pressure between the lower part of the table and an outlet part of the rotary classifier and based on the both differential pressures, a load put on the roller mill is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the operation of a roller mill which is used for pulverizing coal in a pulverized coal-fired boiler and incorporates a rotary classifier.

[0002]

2. Description of the Related Art As a rigid roller mill for pulverizing coal or the like, a roller mill having a rotary classifier built inside a cyclone-type fixed classifier, for example, a roller mill shown in FIG. 4 is known. . This roller mill was raised by a table 3 for receiving raw coal 1 falling from a coal feed pipe 2, a roller 4 for crushing the raw coal 1 on the table 3, and hot air 5 supplied from a gap between the mill casing 14 and the table 3. Classification auxiliary cone 10 for introducing pulverized coal 6 and rotary classifier 1 for classifying pulverized coal 8 classified by classification auxiliary cone 10
2 is provided.

[0003] Reference numeral 11 denotes a swirl vane, which classifies the pulverized coal 6 into coarse coal 7 and fine coal 8, drops only the coarse coal 7, drops it onto the table 3 and returns it to the return coal 9. . Reference numeral 13 denotes a mill outlet pipe for discharging the pulverized coal 8 to the outside.

Conventionally, the table differential pressure gauge 15, that is, the differential pressure between the lower part and the upper part of the table 3, is measured by the table differential pressure gauge 15 as the most important data of the judgment items of the mill operation state, as shown in FIG. as described above, when the mill load changes, the table differential pressure is, for example, 300~350mmH ₂ O
It was judged that the mill was at the limit of stable operation, and control was performed to reduce the load applied to the roll mill.

[0005]

However, the above-mentioned conventional roller mill operation control means has the following problems. In other words, when the mill operating pressure exceeds the stable operation limit, the table differential pressure is rather reduced, so that the determination of the mill operation state may be erroneous and the operation of the mill may be abnormal, leading to a stop of the mill operation. Therefore, it is dangerous to determine the mill operation state from the table differential pressure, and other monitoring items have been demanded.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a roller mill operation control method capable of accurately determining a mill operation state and preventing an abnormal operation or the like.

[0007]

The present invention has the following features to attain the object mentioned above. That is, in the roller mill operation control method according to the present invention, raw coal is supplied onto a table arranged in a mill casing, pulverized by a roll into pulverized coal, and the pulverized coal is supplied by an upward airflow supplied from a lower portion of the table. An operation control method of a roller mill that feeds into the upper rotary classifier, classifies into pulverized coal and coarse coal by the rotary classifier, discharges the fine coal to the outside, and returns the coarse coal to the table to grind again. During operation, the differential pressure between the lower part of the table and the upper part of the table is measured, and the differential pressure between the lower part of the table and the outlet of the rotary classifier is measured. A technique of controlling the load applied to the roller mill based on the value of the differential pressure is employed.

[0008] In this roller mill operation control method, during operation, the differential pressure between the lower part of the table and the upper part of the table (ie, the differential pressure of the table) is measured, and the lower part of the table and the outlet of the rotary classifier are measured. To measure the differential pressure between (i.e., the mill differential pressure) and control the load applied to the roller mill based on the values of these two differential pressures, for example,
Even if the table differential pressure shows a decreasing trend due to an increase in the load of the mill, when the simultaneously monitored mill differential pressure shows an increasing trend, it is determined that the mill operation is abnormal, and control to reduce the mill load is performed. . That is, it is possible to detect an operation abnormality that is difficult to determine by only one of the table differential pressure and the mill differential pressure alone by considering the fluctuations of both differential pressures in combination.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a roll mill operation control method according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the rigid roll mill according to the present embodiment is provided at the upper part of a mill casing 14 so as to penetrate and supply raw coal, and is attached to the upper part of the mill casing 14. Classifying auxiliary corn 10,
Rotary classifier 12 installed in the classifying cone 10
And a table 3 disposed immediately below the coal feed pipe 2, and a roll 4 disposed on the upper surface of the table 3 for crushing raw coal and the like.

The classifying auxiliary cone 10 has a cylindrical swirl vane 11 at an upper part and an inverted conical shape having a lower part opened at a lower part. The rotary classifier 12 is a rotary wing rotatably mounted on the coal feed pipe 2. A mill outlet pipe 13 serving as an outlet of the pulverized coal 8 is provided in an upper portion of the mill casing 14 so as to penetrate inside the rotary classifier 12. Also, the mill casing 14
A hot air inlet 14 a for supplying hot air (ascending airflow) 5 from below to above the table 3 is provided at a lower portion of the table 3.

Further, the roll mill according to the present embodiment includes a table differential pressure gauge 15 for measuring a table differential pressure which is a differential pressure between a lower portion of the table 3 and an upper portion of the table 3, a rotary classifier and a lower portion of the table 3 12 outlets (mill outlet tube 1
(Near 3) is provided with a mill differential pressure gauge 16 for measuring the differential pressure between the mills.

The process of pulverizing coal in this roller mill will be described. First, raw coal 1 is dropped from coal feed pipe 2 onto table 3, and pulverized coal 6 pulverized by rollers 4 is passed through mill casing 14 and table 3. Hot air supplied from 5
As a result, the space between the classifying auxiliary cone 10 and the mill casing 14 is raised and flows into the opening of the swirl vane 11 of the classifying auxiliary cone 10.

The pulverized coal 6 is classified into coarse coal 7 and fine coal 8 by the swirl vane 11, and the coarse coal 7 falls on the inner wall surface of the auxiliary classification cone 10, returns to the table 3 and falls as the coal 9. Re-crushed. The pulverized coal 8 is a rotary classifier 12
The pulverized coal 8a and the pulverized coal 8b in the pulverized coal are thereby classified, and the pulverized coal 8b falls on the table 3 as the return charcoal 9 on the inner wall surface of the classifying auxiliary cone 10 and is re-pulverized.
Is discharged from the mill outlet pipe 13 as a product. Further, during the operation state of the coal pulverization and classification process, the differential pressure state in the mill casing 14 is sequentially monitored by the table differential pressure gauge 15 and the mill differential pressure gauge 16.

The means for determining the operation state of the mill in this embodiment will be described below.

When the load on the mill is increased, for example, when the number of revolutions of the rotary classifier 12 is increased, the coarse coal 8b to be classified increases, and the return coal 9 on the table 3, that is, the circulating coal increases, and the mill coal increases. Since the powder concentration in the inside increases, the table differential pressure measured by the table differential pressure gauge 15 and the mill differential pressure gauge 16
The mill differential pressure measured at increases.

In the normal operation of the mill, as shown in FIG. 2, both the table differential pressure and the mill differential pressure stabilize for a certain period of time (for example, about 30 minutes). The powder concentration with the rotary classifier 12 increases, the classification efficiency decreases, and the return coal 9
, The table differential pressure tends to decrease.

On the other hand, the concentration between the auxiliary classifying cone 10 and the rotary classifier 12 increases, and the pressure difference during this period increases significantly. Therefore, as shown in FIG. (e.g., 30 minutes) even after more than on the increase, for example, been determined that the mill operation abnormality when it reaches the 600~650mmH ₂ O control to reduce the mill load (e.g., the rotational speed of the rotary classifier Reduction, reduction of coal supply, increase of roller load, etc.). Thereby, stabilization of the mill operation is achieved.

[0019]

According to the roll mill operation control method of the present invention, the following effects can be obtained. That is, during operation, the differential pressure between the lower part of the table and the upper part of the table is measured, and the differential pressure between the lower part of the table and the outlet of the rotary classifier is measured. Based on the control of the load applied to the roller mill, the operation abnormality that could not be determined only by the table differential pressure is monitored by the mill differential pressure, thereby accurately determining the mill operation state and preventing the mill operation abnormality. And stable operation of the power plant and the like can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a roll mill in an embodiment of a roll mill operation control method according to the present invention.

FIG. 2 is a graph showing a change in table differential pressure when a mill load is increased in an embodiment of the roll mill operation control method according to the present invention.

FIG. 3 is a graph showing a change in mill differential pressure when the mill load is increased in one embodiment of the roll mill operation control method according to the present invention.

FIG. 4 is a sectional view showing a roll mill in a conventional example of the roll mill operation control method according to the present invention.

FIG. 5 is a graph showing a change in table differential pressure when the load on the mill changes in a conventional example of the roll mill operation control method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 raw coal 3 table 4 roll 5 hot air (rising air) 7 coarse coal 8 pulverized coal 10 classification auxiliary cone 12 rotary classifier 14 mill casing 15 table differential pressure gauge 16 mill differential pressure gauge

Continuing from the front page (72) Inventor Shuichi Sakota 1-1, Akunouracho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard

Claims (1)

[Claims] 1. A raw coal is supplied to a table arranged in a mill casing and is pulverized by a roll into pulverized coal, and the pulverized coal is sent to an upper rotary classifier by an ascending air current supplied from a lower portion of the table. A method for controlling the operation of a roller mill for classifying pulverized coal and coarse coal by the rotary classifier, discharging the fine coal to the outside, returning the coarse coal to a table, and grinding again. Measure the differential pressure between the lower part of the table and the upper part of the table, measure the differential pressure between the lower part of the table and the outlet of the rotary classifier, and based on the values of these two differential pressures, An operation control method for a roller mill, comprising controlling a load applied to the roller mill.