JPH0696123B2 - Roller mill continuous operation method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous operation method of a roller mill when pulverizing a pulverizing raw material such as limestone using a roller mill.

2. Description of the Related Art As a method for automatically operating a roller mill, there is known a method of detecting a pressure difference between an inlet side pressure and an exhaust side pressure of the roller mill and adjusting a raw material supply amount according to the detected pressure difference (Japanese Patent Laid-Open Publication No. Sho-06-09).
58-223450, Japanese Patent Publication No. 60-31544, etc.). In this method, when the differential pressure becomes larger than the set differential pressure, the speed of the pulverized raw material supply device is reduced to reduce the supply amount, and conversely, when the differential pressure becomes smaller than the set differential pressure, the pulverized raw material supply device is set. In order to increase the feed rate by increasing the speed, the roller mill is automatically operated under the condition of a constant differential pressure range.

Problems to be Solved by the Invention When a crushing raw material crushed by a roller mill (hereinafter simply referred to as a mill) is a natural mineral such as ore, it often contains a hard mineral as an impurity, for example, limestone. In the case of a mine, hard silicate minerals are present in the limestone deposit, and this is mixed during mining, so that hard impurities are contained in limestone as a crushing raw material.

If a pulverization raw material containing hard impurities (hereinafter simply referred to as impurities) is pulverized by a mill, the impurities are difficult to be pulverized, so that the impurities are not discharged from the mill and remain in the mill. The impurities accumulated in the mill interfere with the crushing action, and when the amount of impurities increases, the crushing may be impossible at last. And, forcibly crushing these impurities by taking time, etc., is not a good idea because it also deteriorates the quality of the crushed product (product).

When the raw material supply amount is adjusted by detecting the differential pressure of the mill in the actual crushing operation, if the impurities accumulate in the mill and impair the crushing ability, the differential pressure increases and the raw material supply amount decreases. Finally, the raw material supply is stopped. Running the mill as it is means that only the impurities are crushed over time without crushing the raw materials, and during that time the main part of the crushing mechanism of the mill is abraded and the mill is damaged. become.

Normally, before such a condition is reached, an operator detects the situation by sound or visual inspection, and shuts down the grinding plant including the mill. Then, the manhole of the mill is opened, and the impurities inside are manually removed, but if the worker does not notice this situation, the above trouble will continue.

Not only is it troublesome to remove impurities accompanied by idle rotation, but work inside and outside the mill, which is in a high temperature state due to heat generated by crushing, is dangerous, and loss due to idle rotation of the crushing plant is large.

The present invention solves the above-mentioned problems, and directly or indirectly grasps the residence state of impurities in the mill from the differential pressure between the pressure on the intake side and the pressure on the exhaust side of the mill to discharge the impurities. It is an object to determine the timing to be taken, to automatically discharge the impurities in the mill, and to restart the operation of the mill after discharging the impurities.

Operation FIG. 1 is a block diagram showing an embodiment of the present invention.

The pulverized raw material supplied from the raw material supply device 1 to the roller mill 3 is pulverized by the mill 3 and rises in the mill 3 along an ascending air stream, and is classified by the classifier 4 into coarse powder and fine powder. The classified coarse powder descends along the inner wall surface of the mill 3 and is ground again. The classified fine powder is discharged together with the airflow from the mill 3 and collected by the recovery device 5, and only the air is returned by the blower 6 from the duct below the mill 3 to form the ascending airflow. The differential pressure (P) between the intake side pressure and the exhaust side pressure of the mill 3 is detected by the differential pressure gauge 7, and a signal is transmitted to the supply amount controller 8. It is known that the magnitude of the differential pressure (P) corresponds to an increase / decrease of the pulverized raw material pulverized in the mill 3, and the raw material supply amount is controlled so that the differential pressure (P) is maintained within a certain range. The increase or decrease means that the raw material is supplied according to the crushing capacity. The supply amount controller 8 compares the set value preset according to the purpose of crushing with the differential pressure (P), and raises and lowers the rotation speed of the motor 2 of the raw material supply device 1 stepwise so as to correct the deviation. Increase or decrease the raw material supply. At this time, the number of stages in which the rotation of the motor 2 is changed can be selected according to preference, from ones close to continuous change to two stages of operation and stop.

In a normal case, the raw material supply amount is repeatedly increased and decreased, and the retention amount in the mill 3 is increased, and even if the supply is temporarily stopped, the crushing progresses to normal recovery immediately.

At this time, if hard impurities are present in the pulverized raw material as described above, they are hard to be pulverized and thus stay in the mill 3. Even if the differential pressure (P) rises and the raw material supply amount decreases, the impurities are not crushed easily, so the proportion of impurities in the accumulated material in the mill 3 gradually increases, and finally the raw material supply is completely stopped. In such a state, effective grinding is not performed, and the components of the mill 3 are unnecessarily worn. Further, the slightly crushed impurities and the worn parts of the components of the mill 3 are mixed in the fine powder product to deteriorate its quality.

The method of the present invention catches the occurrence of this trouble in advance and tries to deal with it, and compares the differential pressure (P) with a reference differential pressure (Ps) which is predetermined according to the purpose of crushing, by a comparison circuit 9. To do. The comparison circuit 9 gives an output to the integrating circuit 10 only during the time when the differential pressure (P) is smaller than the reference differential pressure (Ps). The integrating circuit 10 receives a command from the sampling timer 11 and compares the sampling circuit (T) with the comparison circuit 9 for each sampling time (T).
The outputs from are integrated and the integrated value (t ₁ ) is given to the comparison circuit 12. The comparator circuit 12 compares the integrated value (t ₁ ) with the reference time (ts) for each sampling time (T) according to a command from the sampling timer 11, and when the integrated value (t ₁ ) is smaller than the reference time (ts), It is judged that the impurities are discharged, and a signal is given to the control circuit 13.

Now, the output condition of the comparison circuit 9 is reversed and the differential pressure (P)
Is given to the integrating circuit (10) for a time longer than the reference differential pressure (Ps), and the integrated value of the integrating circuit 10 is t ₂ . Further, the conditions of the comparison circuit 12 are also reversed, and when the integrated value (t ₂ ) is larger than the reference time (ts'), the impurity discharge timing is set.

Here, the integrated value (t ₂ ) of the time when P> Ps is given by T−t ₁ , and if ts ′ is a value equal to T−ts, the time of giving t ₂ −ts ′ is t ₁ <ts. The effect is the same regardless of which is given.

Further, in order to obtain the integrated value (t ₁ or t ₂ ), the differential pressure (P) is directly compared with the reference differential pressure (Ps) as described above, and as shown in FIG. Accumulate the integrated value (t ₃ ) of the time when the rotation of the motor 2 is operated on the higher speed side than the predetermined reference value or the integrated value (t ₄ ) of the operation time on the lower speed side (including stop), and t ₃ for t ₁ or t ₄ for t ₂
The same effect can be obtained even if the above is changed. This is because the rotation speed of the motor 2 of the raw material supply device 1 is determined by comparing the differential pressure (P) with the set differential pressure as described above, so that the motor 2 is either higher or lower than the reference value. The fact that the mill is operating on the side indirectly indicates whether the mill differential pressure is smaller or larger than the set value.

This method of determining the discharge time of impurities by obtaining t ₃ or t _{4 based} on the operating state of the motor 2 of the raw material supply device 1 is particularly advantageous when the number of stages for changing the rotation of the motor 2 is small, for example, high speed, In the case of three stages of low speed and stop, the integrated value (t ₃ or t ₄ ) can be obtained simply by integrating the operating time of the relay for operating the motor 2 at high speed or low speed (including stop). The comparison circuit 9 can be omitted,
The present invention can be easily implemented by retrofitting an existing crushing plant.

The control circuit 13 has priority over the supply amount regulator 8 and the raw material supply device 1
The motor 2 and the blower 6 are stopped, the drive motor 15 of the mill 3 is rotated at a low speed, and the outlet 14 provided in the lower part of the crushing chamber of the mill 3 is opened to discharge impurities and the like. If necessary, operate auxiliary circuits such as displays.

When the discharge of impurities and the like is completed after a certain period of time (for example, 5 minutes), a signal is output from the control circuit 13 to close the outlet 14 and
The blower 6, the drive motor 15 of the mill 3, the motor 2 of the raw material supply device 1, and the like are restarted, and the entire crushing work is restored.

In addition, the drive motor 15 of the mill 3 is used to discharge impurities.
When rotating at a low speed, it is necessary to reduce the rotation to such an extent that the accumulated matter in the mill 3 is discharged from the outlet, and the rotation speed thereof may be set to about 1/3 of that during normal operation. For this purpose, it is preferable to use a variable speed motor, an inverter, or the like as the drive motor 15, but in order to easily implement it, the drive motor 15 is inchingly moved by using a timer or the like so as to equivalently rotate at a low speed. can do.

The elements of each circuit constituting the present invention described above are not limited to those obtained by combining a relay, a timer, etc., but a sequencer, a microcomputer, etc. can be applied.

The values of the sampling time (T), the reference differential pressure (Ps) or (Ps ′) (or the rotation reference value of the motor 2 of the raw material supply device 1) and the reference time (Ts or Ts ′) are the values of the grinding plant. Optimum conditions are set according to the composition and ability, the purpose of crushing, the properties of the crushing raw material, etc., but these values can be determined by experience and test operation.

Example Using a crushing plant mainly composed of a roller mill having a nominal size of 50 inches, limestone was crushed as a raw material, and the crushing ability of the method according to the present invention and the conventional method were compared. At this time, the raw material supply amount was adjusted by setting the differential pressure to 160 mmAq and switching the speed of the motor of the raw material supply device to three stages of high speed, low speed and stop.

As an embodiment of the present invention, the control circuit shown in FIG. 2 is configured, and the reference time (ts) with respect to the integrated time (t ₃ ) during high-speed operation of the motor of the raw material supply device is 34 seconds, and the sampling time (T ) Was set for 300 seconds and the impurity discharge time was set for 5 minutes.

The crushing capacity when limestone is crushed for about 60 hours in total is 6.1 T / H
Met.

Similarly, when limestone was crushed for a total of about 60 hours by the conventional method of inputting the discharge work for determining the impurity discharge timing, the crushing capacity was 4.6 T / H.

The limestone used as a crushing raw material in this comparison was the same lot that had little fluctuation.

The reason why the crushing capacity of the method of the present invention is larger than that of the conventional method is that the idle loss at the time of discharging impurities is small, but in the conventional method, a large amount of impurities are accumulated in the mill. The impurity discharge timing is detected only when the crushing ability is significantly decreased, whereas in the method of the present invention, the impurities are discharged in a short time before the crushing ability is significantly decreased. Is crushed.

Further, since the impurities are not forcibly crushed, it is convenient because the deterioration of quality and the inclusion of coarse particles due to the inclusion of impurities in the crushed product are avoided.

EFFECTS OF THE INVENTION As described above, according to the method of the present invention, it is possible to increase the crushing capacity, to enable unmanned operation, to improve safety by eliminating dangerous work, and to improve quality by preventing foreign matter from being mixed into crushed products. There is great value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram showing another embodiment. In the figure, 1 ... Raw material supply device, 3 ... Roller mill, 6 ... Blower, 7 ... Differential pressure gauge, 8 ... Supply amount controller, 9 ... Comparison circuit, 10 ... Integration circuit, 11 ... Sampling Timer, 12 …… Comparison circuit, 13 …… Control circuit, 14 …… Exit port, 15 …… Drive motor

Claims (3)

[Claims] 1. A means for detecting the differential pressure between the inlet side pressure and the exhaust side pressure of a roller mill and adjusting the raw material supply amount by stepwise increasing or decreasing the speed of the raw material supply device according to the value of the differential pressure. In the automatic operation method of the roller mill including the above, the integrated value (t ₁ ) of the time when the differential pressure (P) takes a value smaller than the reference differential pressure (Ps) or the differential pressure ( P) is greater than the reference differential pressure (Ps), the integrated value (t ₂ ) of the time is integrated, and the integrated value (t ₁ or t ₂ ) is compared with the reference time (ts or ts'), t ₁ <ts or t ₂ > ts ′
When it became, the blower and the raw material supply device were stopped, the drive motor of the roller mill was rotated at a low speed, and the outlet provided at the bottom of the crushing chamber of the roller mill was opened to discharge impurities and the like accumulated inside. After that, the outlet is closed and the blower, the roller mill, and the raw material supply device are restarted, respectively, and a continuous operation method of the roller mill. 2. A means for detecting the differential pressure between the inlet side pressure and the exhaust side pressure of the roller mill, and adjusting the raw material supply amount by stepwise increasing or decreasing the speed of the raw material supply device according to the value of the differential pressure. In a method for automatically operating a roller mill equipped with, the integrated value (t ₃ ) of the time during which the raw material supply device is operating at a high speed equal to or higher than a reference value or the low speed equal to or less than the reference value is operated at each sampling time (T). The integrated value (t ₄ ) of the specified time is integrated, and the integrated value (t ₃ or t ₄ ) and the reference time (ts or t
s ′), and when t ₃ <ts or t ₄ > ts ′, the blower and the raw material supply device are stopped, the drive motor of the roller mill is rotated at a low speed, and the lower part of the grinding chamber of the roller mill A method for continuously operating a roller mill, characterized in that after the impurities and the like that have accumulated inside are discharged by opening the outlet provided in, the outlet is closed and the blower, the roller mill, and the raw material supply device are restarted. 3. The low speed rotation of the drive motor of the roller mill is
The continuous operation method of the roller mill according to claim 1 or 2, which is carried out by inching the drive motor.