SU654290A1 - Method of regulating the maximum throughput of ball mill - Google Patents

Description

one.

The invention relates to the field of grinding materials, in particular to the optimization of dust systems with ball drum-ventilated mills of thermal power plants.

There is a method of extremal regulation of the power supply of the mill, based on maintaining the specified transmission coefficient of the mill 1. However, this method does not provide the maximum productivity of the mill.

Closest to the invention is a method of controlling the maximum performance of a ball mill, including the inclusion of an extreme control system in operation and a step-by-step change in the performance of the feeder 2.

This method is based on different durations of the transition process after the trial step. If the capacity of the mill in terms of productivity for a given composition of the comminuted material is not yet exhausted, then when the power changes in one direction or another, the transient process ends in a certain time and the unit passes to the steady state

with a new value of 1i1rk l cnonioi ki.

If the mill has reached the maximum possible output, with increasing feed, the self-starting process of the damming of the mill and the circulating load all the time increase. The optimal point lies on the boundary of the lzukh regions — stable (the transition process has a definite time) and unstable (transition time) 01-process indefinitely). The control is conducted according to the rate of change of the circulating load or the noise level of the mill caused by the test step. Search steps, the magnitude of which is constant or proportional to the control action, are performed over a certain time interval.

The disadvantage of the constant-step control method is considerable fluctuations in searching for the optimum with capturing unstable states, since reversal with this control method can occur only on the falling parts of the characteristic.

The control method with proportional schag is devoid of this disadvantage. but

Static performance of the mill through the channel output - input performance is a straight line extending from the origin at a 45 ° angle for the critical mode, after which the static characteristic decreases. The absence of the decay of the steepness of the static characteristic as it moves toward the extremum does not allow one to apply the method of adjustment with proportional pitch.

The aim of the invention is to improve the quality of regulation.

This is achieved by the fact that in the method of controlling the maximum performance of a ball mill, including the inclusion of an extreme control system in operation and stepwise change in the performance of the feeder, the maximum performance interval between the maximum possible performance under the best conditions and the maximum possible performance under the worst conditions, turning on the system of extreme regulation to set the performance of the feeder, equal to the middle of the maximum throughput interval, and measuring the resistance of the mill to the flow of the transporting drying agent; in the process of step-by-step performance changes, the feeder, when the resistance of the mill reaches a critical value at which the mill goes into overload mode, reduces the feeder’s performance by one quarter of the maximum performance interval, and if there is no critical value signal, the feeder’s performance is increased by one quarter maximum performance interval, with a sequence of operations performed multiple times, each the change in the capacity of the feeder by an amount two times less than the previous value.

In the drawing, a block diagram of a device implementing this control method is presented.

The device contains a ball drum mill 1, a feeder 2 of the material being crushed, a feeder motor 3, a feeder regulator 4, a regulator motor 5, a separator 6, a cyclone 7, pulverized coal tank 8, a mill fan 9, a sensor 10 of the critical current of the mill fan, the time relay unit 11, the extreme adjustment unit 12, the setting unit 13, the regulator position sensor 14, the phase-sensitive amplifier 15, and the block 16 for eliminating the overload mode.

The maximum productivity of a mill is not constant and is determined by a number of factors - the size and moisture content of the material being grinded, its grindability coefficient, ball loading, the mill lining condition, etc. The maximum performance oscillation interval for this type of mill is determined experimentally when testing the mill in various modes of operation. Under the best working conditions of the mill - the minimum size and moisture content of the material being crushed, the maximum coefficient of grinding, optimum ball loading and the unworn lining of the mill - the maximum possible performance increases compared to the worst conditions, when the size and humidity of the material are maximum, its coefficient of grinding is minimal, ball loading is different from optimal and the mill lining is already worn out.

When the control system is turned on, the performance of the feeder is set to equal to the middle of the interval between the maximum capacity of the mill under the best conditions of operation and the maximum possible performance under the worst conditions, and., 5 measure the resistance of the mill to the flow of the transporting drying agent, which is judged measure, for example, the current of the mill fan.

When the mill is operated up to the overload mode, the level of the ball-fuel mass in the mill fluctuates slightly, therefore the resistance of the kettle to the flow of the drying agent remains almost unchanged and the current consumed by the mill fan also fluctuates slightly. Current fluctuations in the order of a few percent.

35 In this case, the sensor of the critical current signal does not issue. When the mill goes into overload mode, the level of the ball-fuel mass in the mill increases, the resistance of the mill increases and the current consumed by the mill fan begins to decrease. When reducing the current by 20-30%, the critical current sensor will work.

If, during the transient flow time in the mill, a critical current signal is received, the material feed to the mill is stopped for the time needed to eliminate the effects of overload, after which the feeder capacity is reduced by one quarter of the maximum capacity interval. If during the transient process in the mill the signal of the critical 10 current value does not arrive, the capacity of the feeder is increased by one quarter of the specified interval. The operation is performed repeatedly, depending on the specified degree of search accuracy, each time changing the performance of the feeder by an amount two times smaller than the previous one.

After reaching the maximum performance periodically produced

an increase in the performance of the feeder by the magnitude of the last step in the absence of a critical current signal or a decrease in the performance of the feeder by a specified amount of gfi reaching the signal of a critical value. The frequency of applying the verification signals is determined by obtaining the minimum total losses caused on the one hand by the inaccuracy of maintaining maximum performance, changes, under the influence of various vozmushayuschie factors, and on the other - the frequency of stay and the time of the mill in overload.

The control system shown in the drawing reflects a device that realizes the proposed method for controlling the maximum performance of a ball-type drum mill. The system works as follows.

The input of the phase-sensitive amplifier 15 receives signals from the setpoint 13 and the position sensor 14 is controlled by its feeder organ. Depending on these signals, the phase-sensitive amplifier 15 acts on the electric motor 5 regulating its organ, mixing it, and in such a position that the flow rate of the material entering the mill is equal to the specified one. The sensor 14 position of the regulator of the feeder at a constant rotational speed of the electric motor of the feeder characterizes the consumption of material entering the mill. When the system is put into operation, the task of supplying power, set by setter 13, corresponds to the middle of the interval of maximum productivity of a mill of this type. At the same time, when the system is turned on, the transient process time relay unit 11 is turned on, which pulses out after a period of time equal to the duration of the transient process in the mill. If during this time the critical current sensor 10 generates a signal, it enters the overload mode elimination unit 16, which stops the electric motor 3 of the feeder for the time required to eliminate the overload, issues a signal to the time relay unit 11, restoring it to its original state, at which a new countdown begins, and to extreme adjustment unit 12, which generates a signal to reduce the performance of the feeder by one quarter of the maximum performance interval of the mill. If during the transition process the signal from the sensor 10 does not receive the critical current of the mill fan, then the supply is periodically

a test pulse per extreme adjustment unit, which produces a signal to increase the capacity of the feeder by one quarter of the maximum performance interval, then by one eighth of the interval, and so on, until the mill reaches its maximum performance with a given degree of accuracy.

After the mill reaches its maximum performance, the time relay unit increases the period for applying the test signal.

Claims (2)

1. The copyright certificate number 521012, cl. B 02 C 25/00, 1975. 2. Aref'ev BA and others. The system of extreme control of grinding aggregates. Central Scientific Research Institute of Information and TEN nonferrous metallurgy, M., 1964. p. ten.