RU2819227C1 - Method for automatic control of loading of matte into mill - Google Patents

Abstract

FIELD: various technological processes; physics.

SUBSTANCE: invention relates to a method for controlling a mill load, which can be used in ore-dressing industry when grinding ores to prevent overloading of mills. In the method, overload is determined from change in trends of active power consumed by the mill and values of inverse vibration velocity of the mill, which are measured after a given time interval. Number of time intervals k is set, data stacks are formed containing measured values in amount k+1, after which increments of values of inverse vibration velocity and active power are determined in the i-th time interval inside the corresponding stack by mathematical expression ΔW _ji =W _j(i+1)  – W _j1 , where j=1 is the reciprocal of the vibration velocity; j=2 is active power; W _j1 is the first element of the corresponding stack; i=1, 2, …, k. Then estimates of trends are determined by mathematical expression

where α _jm – estimates of trends of values of inverse vibration velocity and active power; k _ji =1, 2, …, k; m=1, 2, … Mill overload is determined by satisfying the ratio α _1m >0 and α _2m <0. When overloading the mill, the loading of the crushed material is reduced step-by-step. After exiting the overload, the mill load is increased step-by-step until the initial flow rate of the ground material into the mill is restored.

EFFECT: method provides higher accuracy of determining mill overload, which enables to reduce the amount of second metals in copper and nickel concentrates.

1 cl, 4 dwg, 1 tbl, 1 ex

Description

The invention relates to the control of technological processes and can be used in the automated control of processing plants, in particular in the flotation separation of copper-nickel matte.

There is a known method for automatically controlling loading into a mill drum (patent No. 1577831, class B02C 25/00), in which the ore flow into the mill and its loading level are measured, the values of the measured values are statistically processed, the significance level of increments in loading and mill productivity is determined, the permissible loading speed and, depending on the sign of the increment, form a control action based on a stepwise change in the supply of the original ore. To develop control actions, the method involves statistical processing of initial signals (parameters) that determine the rate of change (increment) of constant coefficients that limit the level of influence, which, against the background of a high level of technological interference when developing a control action, does not provide the necessary quality of control.

There is a known method for controlling the grinding process in a drum mill (patent No. 206265 C1, class B02C 25/00), which provides for the correction of the task of the extreme controller Δϕ of the mill load depending on the difference between the current and the set value of the active power of the mill drive, and the set power value is determined by interval τ _i according to the signs of the presence of overload, taking into account the coefficient calculated statistically for each class of mill. This method has significant drawbacks that affect the reliability and accuracy of the calculation of both the base power and the correction value, since the calculation uses coefficients determined statistically with a small sample, and the base power is determined not by the forecast method, but by the fact of the number of overloads (n _j ), including possible emergency situations, that is, the depth of overload is not taken into account. Using drive power data to correct the setpoint (grinding mode) is a necessary but not sufficient condition; it is also necessary to take into account the dynamics of changes in the load itself on the mill.

There is a known method of automatic control (patent No. 2375116 C1, class B02C 25/00 dated December 10, 2009), adopted as a prototype. This method involves controlling the loading of the mill by stabilizing the stock of material when it deviates from a given value, correcting the mill's productivity for the finished product, determining the current values of the stock of material and pulp density, taking into account transient processes between the moments of determining increments and issuing control actions, measuring the current value of power, consumed by the mill to assess the moment of overload, highlighting high-frequency power fluctuations and correcting the task according to them in the mill productivity control loop.

The disadvantage of the prototype is the low accuracy of determining the moment of overload based on high-frequency power fluctuations, since the electrical characteristics of the mill drive, including harmonic power fluctuations, are affected by the nature of the network load: fluctuations in the network voltage and phase asymmetry of the power supply system of the mills, which leads to a decrease in reliability and the quality of control over the loading of crushed material into the mill.

The technical result of the invention is to increase the reliability and quality of control of loading matte into the mill, which is achieved by the fact that in the method of automatically controlling the loading of matte into the mill, including measurement and stabilization at given values of mill productivity, density of the finished product, measurement of power consumed by the mill, determination of the moment of approach overload of the mill and a sequential step-by-step change in the flow of matte into the mill in the direction of exiting the overload mode, additionally measure the vibration speed of the mill and calculate the inverse vibration speed. Then stacks of values of reverse vibration velocity and active power consumed by the mill are formed. To do this, set the time interval Δτ between adjacent measurements and the number of intervals k and form stacks for the values of reverse vibration velocity and active power of dimension k+1.

Then the increment values of the reverse vibration velocity and active power consumed by the mill are estimated using the equation:

where j=1 is the reciprocal of the vibration velocity;

j=2 - active power consumed by the mill.

ΔW _ji - increments of reverse vibration velocity and active power in the i-th time interval within the corresponding stack;

W _j1 - first element of stacks;

i=1, 2, …, k of the corresponding stack.

Then, after completing the set of stack elements, estimates of the trend values of the reverse vibration velocity and active power are determined using the mathematical expression:

where a _jm are estimates of the values of the reverse vibration velocity and active power trends;

k _ji - 1, 2, …, k;

m=1, 2, …

The approximation of mill overload is determined by the fulfillment of the relationship:

where a _1m is an estimate of the trend in the reverse vibration speed of the mill;

a _2m - assessment of the trend in the value of active power consumed by the mill.

In this case, the task for the flow of matte into the mill is reduced step by step according to the following equation:

until the fulfillment of relation (3) ceases.

After that, the task for the flow of matte into the mill is gradually increased to the initial value in effect at the time the mill overload began according to the equation:

Where - current task for matte consumption;

- previous task for matte consumption;

ΔQ is the step of changing the task for the consumption of matte.

Figure 1 shows a block diagram of the automatic control system (ACS) for loading matte into the mill. Figure 2 shows a block diagram of the control algorithm for loading matte into the mill. Figure 3 shows the static loading characteristics of the mill. Figure 4 shows graphs of the values of active power and reverse vibration velocity.

The proposed method is carried out as follows.

Figure 1 shows a block diagram of an automatic control system for loading into a mill. To measure active power (item 1), an E-848/13-M1 active power converter is used. To measure vibration velocity (item 2), the VK-310S sensor is used. To control the flow rate of the matte, a vibrating feeder (item 3) is used. The consumption of the matte is measured with a tape weight meter (item 4). The density of the classifier discharge is measured with a Berthold density meter (item 5). Water flow into the classifier is measured with a Krohne electromagnetic flow meter (item 6). To change the water flow into the classifier, use a control valve (item 7).

According to the block diagram of the algorithm for controlling the loading of matte into the mill (Fig. 2), the values of vibration speed and active power consumed by the mill are periodically measured. Then the reverse vibration velocity is calculated.

Figure 3 shows the static characteristics of the mill loading: the dependence of the reverse vibration velocity W ₁ =f(M) and the active power consumed by the mill W ₂ =f(M) on the filling of the mill with crushed material M.

M _n - nominal mill filling;

M _lane - “overload” of the mill;

ΔM _p - operating loading range.

From the static characteristics it is clear that the exit from the overload state is carried out by shifting the emergency point to the left relative to the value of M _per , by step-by-step reducing the task for loading into the mill. To achieve this goal, set the time interval Δτ between adjacent measurements of vibration velocity and active power and set the number of time intervals k. After this, the corresponding data stacks of dimension k+1 are filled with the values of the reverse vibration velocity and active power. Then the increments of the reverse vibration velocity and active power are determined according to the equation:

where j=1 is the reciprocal value of the vibration velocity;

j=2 - active power consumed by the mill;

ΔW _ji - increments of reverse vibration velocity and active power in the i-th time interval within the corresponding stack;

W _j1 - first element of stacks; i=1, 2, …, k of the corresponding stack.

After this, using the least squares method, estimates of trends in the values of reverse vibration velocity and active power are calculated according to the equation:

where a _jm are estimates of the values of the reverse vibration velocity and active power trends; k _ji =1, 2, …, k;

m=1, 2, …

Then the signs of the estimates of trends in the values of reverse vibration velocity and active power are checked. If the relation is satisfied:

which means the moment the mill is overloaded, they begin to step by step reduce the task of loading the matte into the mill according to the equation:

until the relation stops fulfilling:

After that, the task for the flow of matte into the mill is gradually increased to the initial value in effect at the time the mill overload began according to the equation:

Example of concrete execution

The target for matte consumption was 24 t/h.

The trend of reverse vibration velocity and active power was assessed using the last five measurements. In this case, the number of time intervals between measurements is k=4. The time interval between adjacent measurements Δτ was taken equal to 1 minute.

Using equations 1 and 2, we determine the values of the estimates of the trends in the reverse vibration velocity a ₁₁ and active power a ₂₁ :

Subsequent values of a _1m and a _2m are calculated similarly. Table 1 shows the numerical values of the calculations.

As can be seen from Table 1, at the 101st minute the condition of mill overload (a _1m >0) and (a _2m <0) was formed. The target for matte consumption was reduced by 100 kg per minute. After 11 minutes, the reciprocal vibration speed of the mill began to decrease (a _1m <0) and from that moment they began to increase the matte consumption target every minute with the same step of 100 kg/min until the original matte consumption target was restored to 24 t/h.

The use of the proposed method for automatically controlling the loading of matte into the mill makes it possible to increase the accuracy of determining the moment the mill is overloaded with crushed material, promptly exit the mill overload mode with a subsequent shock-free return to the original task for the consumption of matte, which also increases the reliability of the system for automatically controlling the loading of matte into the mill and safety equipment operation.

At the same time, a decrease in the yield of the finished class -45 microns in the mill classifier discharge is prevented in the event of its “overload”, which allows, during flotation separation of the matte, to reduce the amount of second metals in copper and nickel concentrates by 0.04%.

Claims (23)

A method for automatically controlling the loading of matte into a mill, including measurement and stabilization at given values of mill productivity and density of the finished product, measurement of the power consumed by the mill, determination of the moment of approaching mill overload and a sequential step-by-step change in the flow of matte into the mill in the direction of exiting the overload mode, characterized in that , which additionally measures the vibration velocity of the mill and calculates the inverse value of the vibration velocity, sets the time interval Δ τ between adjacent measurements of the vibration velocity and active power, sets the number of time intervals k and generates data stacks for the inverse vibration velocity and active power values of dimension k +1, then evaluates the values increments of reverse vibration velocity and active power consumed by the mill according to the mathematical expression Δ W _ji =W _{j ( i +1)} - W _{j 1} , where j=1 is the reciprocal value of the vibration velocity; j=2 - active power consumed by the mill; Δ W _ji - increments of reverse vibration velocity and active power in the i -th time interval within the corresponding stack; W _{j 1} - the first element of the corresponding stack; i = 1, 2, …, k , then, after completing the set of stack elements, estimates of trends in the values of reverse vibration velocity and active power are determined periodically over a time interval Δ τ using the mathematical expression: where a _jm are estimates of trends in reverse vibration velocity and active power; k _ji =1, 2, …, k ; m =1, 2, …, then the moment of approaching mill overload is determined by fulfilling the relation ( a _{1 m} >0) and ( a _{2 m} <0), where a _{1 m} is an assessment of the trend in the reverse vibration speed of the mill; a _{2 m} - assessment of the trend in the amount of active power consumed by the mill, then, if the condition [( a _1m >0) and ( a _2m <0)] is met, the task for the flow of matte into the mill is step by step reduced according to the equation: until the end of the condition [( a _1m >0) and ( a _2m <0)], after which the task for the flow of matte into the mill is step by step increased to the initial value at the time of the start of the mill overload according to the equation: Where - current task for matte consumption; - previous task for matte consumption; ΔQ is the step of changing the task for the consumption of matte.

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