SU1526829A1 - Method of automatic control of consumption ratio of liquid and solid phases of flows when charging mills - Google Patents

Abstract

The invention relates to the automation of wet grinding processes in drum mills and can be used in the mining, construction and other industries. It improves control accuracy. To achieve this goal, the flow rates of the liquid and solid phases of the mill input streams are measured, their current ratio is determined, the pulp flow density at the mill discharge is measured, the correction task is calculated to control the ratio of the flow rates of the liquid and solid phases of the input streams pulp at the discharge of the mill and periodically change the flow of the additional water into the mill depending on the deviation of the current ratio of the flow rates of the liquid and solid phases of the input streams from its calculated the corrected task, taking into account the maximum time of the transition process measured in advance through the channel, the flow of additional water — the density of the pulp at the mill discharge. 1 il.

Description

The invention relates to the field of automating the process of wet grinding of materials in drum mills and can be used in the processing plants of ferrous and nonferrous metallurgy, the chemical industry, the building materials industry and other industries, where there are similar processes.

The purpose of the invention is to improve the accuracy of control.

The validity of the method is as follows.

The main task of maintaining a given ratio of the liquid and solid phases of the flows in the mill load is to ensure the specified density (solid content) in the drum of the mill. Due to the difficulty of measuring the actual density value in the drum, its closest estimate is the density of the output flow (discharge) of the mill.

The system of automatic control of the ratio of input flows in the mill load maintains the specified ratio, in conjunction with the indication

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with some flaws. This leads to fluctuations in the density of the pulp at the discharge of the mill and, accordingly, changes in the uniformity and grinding conditions in the drum. The measured values of the pulp density at the discharge are converted into values of the ratio of the liquid and solid phases in accordance with the expression

Me mt

Jjllprzm (.) f. (fn-f .-

Where

fft

FT

D - value of the ratio of the phase consumption by mass, relative units;

Mj is the mass flow rate of the liquid phase;

MT is the mass flow rate of the solid phase;

- water density, usually take Og 1.0

- density of the solid phase of the material being crushed,

cp „is the pulp flow density,

t / m

The obtained value of the phase ratio is real, which is provided in the load, and almost always differs from the specified ratio. Based on a comparison of the obtained current value of the ratio and the set value, a correction value is generated to correct the reference by the ratio of the phases in the mill load.

A drum mill is a facility with a significant transport delay in the control channel: the flow of water into the drum is the density of the pulp at the discharge of the mill, and long transients, which in aggregate can be for most large mills (2 ... 5) minutes. Therefore, in order to estimate the actual current phase ratio of the fluxes, the current density values are measured in the proposed method with a delay of an interval that ensures the complete completion of the transient process on the control channel.

In addition, the pulp density values under the influence of various technical and technological reasons fluctuate around a certain average value and, therefore, to increase the accuracy of estimating the density of the pulp on the drain, their values are determined at a certain time interval and averaged. Averaging Time Interval

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it is determined for practically every concrete mill in such a manner that this interval estimate is as little as possible different from the actual average value (mathematical expectation). Thus, for an MMC 70x23 mill under the conditions of one of the processing plants, the averaging interval is assumed to be 2 minutes.

Thus, the correction of the task by the ratio of Laz fluxes is introduced periodically, and the correction period is equal to the sum of the delay intervals of the removal of the early density and their averaging. In this case, the data acquisition delay interval is assumed to be equal to or greater than the maximum transient time over the control channel of the mill.

The drawing shows one of the variants of the block diagram of the control method implementation.

The scheme for implementing the method includes a drum 1 of the mill, a block 2 for determining the flow rate of the crushed material, a block 3 for determining the flow rate of the liquid phase, blocks A and 5 for determining the current ratio of the flow rates of the control output 4, an actuator 6 for controlling the flow of the additional water, a meter 7 pulp density in the flow at the mill discharge, block 8 for determining the values of the ratio Ж: Т from the density of the pulp flow, block 9 for determining the data collection delay intervals and averaging the current values for the ratio audio, determining unit 10 of the averaged value of the ratio W: T, determining unit 11 of the correction value for controlling the ratio of W: T phases at the mill inlet.

According to the proposed method, the control is carried out in the following manner.

Using blocks 2 and 3, the flow rates of the liquid and solid phases in the flows of water, ore, generalized sands, and other recirculating flows at the inlet of the mill are determined, respectively. These blocks include measures of mass flow rates, variable-ratio signal converters, and sum1 {matching elements.

Based on the obtained flow rates in block 4, the flow rates of the ratio of the flow rates G: T phases to

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the entrance of the mill. The obtained values of the ratio in block 5 are compared with the set value of the flow ratio and, if necessary, a corresponding control action is generated on the actuator 6. At the discharge of the mill, the current value of the flow density of the pulp is determined by means of the pulp density meter 7, which in block 8 D is converted to the current value of the ratio G: T phases in accordance with the expression (1).

In block 9, the necessary delay intervals for the removal of the ratio values are determined experimentally by the maximum transition time by the control channel; water flow rate - pulp flow density at the drain; the delay interval is chosen to be greater than or equal to this time, and the data acquisition interval and their averaging according to the degree of dynamism of the output pulp flow.

Next, in block 10, the average value of the ratio is determined at a given interval. In block 11, this value is compared with the set value of the ratio based on the requirements for providing the required grinding mode in the mill drum and, if necessary, correcting the set value of the ratio G: T phases in the mill drum input streams, which are fed to block 5.

As a result of the control of the proposed method, the specified ratio of the liquid and solid phases of the input streams is maintained with the required accuracy, under real conditions of instability of the measuring characteristics of flow rate sensors at the mill entrance and the dynamic parameters of the mill 1 changing through the control channel. This will allow to maintain the specified optimum grinding mode and pulp density in the drum and will ensure a reduction in the granular oscillation at the discharge of the mill, c.1.

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Testing the method under production conditions showed that the dispersion of pulp density at the discharge of melon decreased by 12%, and the dispersion of the finished grade (-0.074 mm) decreased by 8%.

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Claims (1)

Invention Formula 35 45 ten A method of automatically controlling the ratio of the flow rates of the liquid and solid phases of the flows in the mill load, including measuring the flow rates of the liquid , 5, and the solid phases of the input streams are small, setting their current ratio. Changing the flow rate of the added water and measuring the density of the pulp flow at the mill drain, is about 20 so that, in order to improve the control accuracy, the maximum time of the transition process is measured through the canal of the added water flow - the density of the pulp flow 25 at the mill discharge, set the required intervals of averaging and data delay, calculate the specified values of the ratio of the liquid and solid phases of the pulp flow density 30 at the end of a predetermined data delay interval, averaged over a predetermined averaging time interval, and a correction task is calculated to control the ratio of the flow rates of the liquid and solid phases of the input streams, and the change in the flow rate of the added water is performed periodically according to the deviation of the current cost ratio d0 liquid and the solid phases of the input streams mills from its calculated correction task, and the data delay time interval is greater than or equal to the maximum transition time th process of the flow channel of water added - flux density pulp mill and the drain period change makeup water flow is taken to be the sum of intervals and averaging the delay time. Phase flow fKtfd / mu Bottom hard qjOM In Aobovo nol Soda