RU2720865C1 - Suspension control method in flotation machine - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to flotation process control and can be used to control suspension level in flotation machine chambers at dressing plants. Method of controlling the level of a suspension in a flotation machine using an electrically conductive probe involves periodic uniform movement of the probe along the arc with its immersion into a level-controlled suspension, and the value of the level is determined from the passage time of the probe through the suspension. Measurement starts immediately from the moment the probe touches the suspension. After passing from the suspension, the probe is subjected to cleaning of the suspended particles of the suspension.

EFFECT: high accuracy and reliability of measuring the level of suspension in a flotation machine.

1 cl, 1 dwg

Description

The invention relates to the field of process control of flotation and can be used to control the level of suspension in the chambers of flotation machines in processing plants.

Automatic control of the level of suspension in flotation machines is a measurement of the level of the suspension, which is located under a layer of foam relative to the upper edge of its discharge side. Level change occurs in a narrow range, as a rule, it is 25-30 mm. Deviation of the level beyond the lower limit of the range leads to the loss of a useful component (for example, potassium chloride) with flotation tails, since not all of the useful component manages to pass into the foam product. Deviation of the level beyond the upper boundary of the range leads to a decrease in the quality of the flotation concentrate, since the thickness of the merged foam layer increases, and with it the number of related components (for example, sodium chloride) increases. Therefore, for high-quality control of the flotation process, high measurement accuracy is required - no worse than ± (1-2) mm.

A known method of measuring the level of liquids in technological apparatuses using an electrically conductive probe by mechanical measurement of the length of the connecting cable from the start point of the probe to its contact with the controlled fluid (Golovkov B.Yu., Reibman L.A., Kolpikov G.G. Automation systems and means processing plants., M. "Nedra", 1990, S. 39. However, the mechanical method for measuring the length of the connecting cable is not accurate enough and is not used to control the level of suspension in the flotation machines.

A known method of measuring the level of the pulp using an electrically conductive probe, implemented in a device for automatically controlling the thickness of the foam layer and the level of the pulp in the chambers of flotation machines, in accordance with which the mechanical method of measuring the controlled portion of the cable length is replaced by an electropulse method of tracking the movement of the electric probe (a.s. SU 501769, B03D 1/02, 02/05/1976) - a prototype.

The measurement is as follows. The program unit periodically starts the reversible electric motor, while the conductive probe starts its movement in the vertical direction from the upper position determined by the limit switch to contact with the suspension. Simultaneously with the beginning of the probe movement, the program unit includes a time meter (timer). At the moment when the probe touches the surface of the suspension, an electrical circuit is closed, the program unit stops the time meter and converts the obtained time period into a signal proportional to the level of the suspension in the flotation machine.

This invention has the following disadvantages that reduce the accuracy and reliability of measurements.

The obtained (controlled) time interval consists of two segments: the 1st segment is the idle stroke of the probe from the beginning of the stroke to the upper limit of the measurement range, the 2nd segment is the working stroke of the probe proportional to the level of the suspension. The working time span is only part of the controlled time span. For example, the actual idle value is 10 cm, and the working stroke (level measurement range) is 2.5 cm, we get the proportion of the working stroke 2.5 / 12.5 = 0.2 or 20%, which reduces the sensitivity of the method and increases the error measurements. If the error of the total time interval, reduced to the length, is 0.5 mm, then the measurement error will be 0.5 / 0.2 = 2.5 mm or 10% of the measurement range.

As a result of the formation of foam on the surface of the suspension, the upper limit of the measurement range becomes blurred, there is an error in contacting the probe with the suspension, which is significant with respect to the narrow measurement range.

The method does not include the operation of cleaning the conductive probe, while the suspension in the flotation machine contains clay particles that contaminate the conductive probe and impair the contact of the probe with the suspension, which reduces the reliability of the measurement and may lead to measurement failure.

The technical result of the invention is to increase the accuracy and reliability of measuring the level of suspension in the flotation machine.

The technical result is achieved by the fact that the conductive probe is brought into uniform motion along the arc with its immersion in the suspension, and the value of the suspension level in the flotation machine is determined by the time the probe is immersed in the suspension, the probe, after exiting the suspension, is cleaned of adhering particles of the suspension.

In the proposed method, the measurement begins immediately from the moment the probe is in contact with the suspension. Measurement of idle time of the probe from the beginning of the stroke to contact with the suspension is not performed. The proportion of the stroke increases to 100%, while in the prototype it is 20%. This allows to reduce the measurement error.

The path (working stroke) of the probe increases, respectively, and the measurement time. For the prototype, it is equivalent to the measured level, and for the proposed method is equivalent to the probe mileage along the arc. As the contact time increases, the error from the fuzzy contact of the probe with the suspension is significantly reduced, thereby increasing the accuracy of the measurements.

The introduction of the operation of cleaning the electric probe from the sticking of foam particles allows to improve the contact of the probe with the suspension and to increase the reliability of measurements.

The essence of the invention is illustrated by the scheme (Fig. 1).

The method is as follows.

Using the control unit 1, the reversible engine 2 is periodically started to move, which, through the axis 3 and the rod 4, leads the conductive probe 5 to uniform movement along the arc 6 from point 7 to point 8 and vice versa. When moving along an arc, the probe passes through the foam 9 and is in contact with the electrically conductive suspension 10, plunging to a depth from the measured level 11 to the lower boundary 12 of the measuring range. The conductive probe 5 and the grounded plate 13 located in the suspension are connected to the transducer 14 and form an electric circuit. When the probe is in contact with the suspension, it closes through the suspension to an earthed plate 13, an impulse appears in the converter, which includes a timer (time meter) 15. When the probe exits the suspension, the circuit is interrupted in the converter, an impulse appears that turns off the timer. The timer records the time between pulses - t _and. , which depends on the time the probe is immersed in the suspension, respectively, on the measured level of the suspension in the flotation machine, and transfers it to the output transducer 16. The output transducer processes the timer signal (time - t _and ) in accordance with the formula:

H = R (1-cos (π⋅t _and / Т), where

N - controlled level of suspension in the flotation machine, mm;

R is the distance from the axis of rotation to the contact surface of the probe, mm;

t _and - contact time of the probe with the suspension (immersion in the suspension), s;

T is the time of the virtual revolution of the probe around the axis, sec.

The calculation result is converted into an output signal proportional to the level of suspension in the flotation machine.

To exclude the influence of the contamination factor of the probe by particles of the suspension on the reliability of contact between the probe and the suspension and the reliability of measurements, the probe is cleaned, for example, by passing it between two cleaning cheeks.

An example implementation of the method.

The calculation of the level of the suspension was carried out according to the source data: R = 500 mm; T = 60 s; measuring range D = 25 mm. The measured value of the pulse duration t _and = 3.0 s.

H = R (1-cos (π⋅t _and / Т) = 500 (1-cos (3.1415⋅3 / 60) = 6.16 mm.

The calculation of the arc length L was carried out according to the formula: L = 2π⋅R⋅t _and / T = 2π 500 3/60 = 157.2 mm

As the calculation shows, the length of the arc L is greater than the stroke length of the probe in the prototype (equivalent to the measured level H). Correspondingly increases the accuracy of measurements.

Claims (2)

1. A method of controlling the level of suspension in a flotation machine using an electrically conductive probe, characterized in that the probe is brought into periodic uniform movement along the arc with its immersion in a level-controlled suspension, and the level value is determined by the time the probe passes through the suspension. 2. The method according to p. 1, characterized in that the probe after leaving the suspension is subjected to cleaning from adhering particles of the suspension.

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