CA2051326C - Device for automatic regulation of the process of separating froth concentrate from gangue in a floatation machine - Google Patents

Abstract

The automatic regulator device comprises a channel for measuring the level and density of pulp in the chamber of a floatation machine, in which two bubbling pipes are in communication with a differential pressure pickup connected to the input of a frother flow-rate regulating channel and to one input of a correction unit whose other input is connected to a pressure pickup communicating with one of the bubbling pipes.
The output of the correction unit is connected to the input of a circuit designed to regulate the rate of flow of water with frother in a pulp level stabilizing channel, the output of said circuit being connected to an actuator valve installed on a Pipeline feeding water with frother and furnishing a control signal with respect to a pulp level deviation from a preset value. A water-and-frother flow transducer is connected to the input of a circuit designed to regulate the gangue discharge rate in the pulp level stabilizing channel, the output of said circuit being connected to the drive of the actuator valve installed on a gangue discharge branch pipe, said output developing a control signal with respect to a deviation of the water-and-frother flow rate from a preset value.

Description

3 ~ ~

Field of the Invention The pre~ent invention relate~ to concentration of mineral raw materials by floatation of hard particles of a useful constituent thereof and, more particularly, to a device for automatic regulation of the process of separating froth concentrate from gangue in a floatat-ion machine.
The invention can find applications in ferrous and nonferrous metallurgy, coal and diamond indus-tries for floatation of mineral resources, in which a .
valuable cO~tituent represents fairly ~mall or largeinclusions possessing hydrophobic properties . Background Art In prior art floatation machine 9 the proce~s of separating froth concentrate from gangue involve~
either froth floatation at which the source feed is pulp containing small fractions of a material to be concentrated or a combination of froth floatation and froth separation at which the s~urce feed contains both small fracti~n~ of a material to be separated and a large fraction thereof supplied to the froth lay-er. The technique~ involving froth floatation and a combination of froth floatation and froth ~eparation are characterized by the need to maintain a predeter-mined pulp level in the chamber of a floatation ma-chine relative to its overflow threshold, thereby keep-in~ the froth layer thicknes~ and the pulp-froth inter-~ n ~ ~ 32 ~ ~

face within required limits; to ensure a predetermined ratio between liquid and gaseous ph~es in the pulp supplied to the chamber of a floatation machine, the density and level of the pulp in the chamber being pri-marily determined by said ratio; to maintain optimalconcentration in the aerated pulp of frother supplied both with circulating water and directly with the source feed, which determines the size, degree of dis-persion and the lifting speed of air bubbles and, con~
9equently, the density of the aerated pulp; to provide .
an optimal speed of supplying the source feed to the bulk of the aerated pulp in the chamber of a floatat-ion machine, variations of said speed adversely affect-.
ing flow hydrodynamics; to discharge gangue from the chamber with minimum losses of the pulp liquid phase;and to rapidly restore the pulp level and density in the chamber to preset values.
Variations of the pulp level and, consequently, of the froth layer and also of the ratio between the solid, liquid and gaseous phases of the pulp are attri-butable, firstly, to changes in the quantity of the source solid and water in the chamber of a floatation machine and, secnndly, to changes in liquid phase losses when gangue is discharged due to a var~ing amount of the solid and large and heavy fractions thereof. Variations of the pulp level in the chamber of a floatation machine are also attributable to 3 ~ ~

changes in the pulp density due to a varying concen-tration of frother in the pulp.
A change in the speed of 9upplying the pulp to the chamber of a floatation machine i9 caused by a va-riation of the solid - water ratio in the pulp. Thus, the disturbing factors affecting the process of froth floatatisn include changes in the quantity of the so-lid and liquid phases of the pulp fed to the chamber of a floatation machine, changes in the quantity of the liquid phase lost in discharging the gangue due to a varying content of large and heavy fractions therein, and changes in the concentration of frother in circu-lating water supplied to the chamber, which cause vari-ations of the liquid and ga~eous phases in the pulp and, consequently, of the pulp level and density in the chamber of a floatation machine.
From the aforesaid it follows that, at the pre-sent time, a vital problem in the art i3 quality regu-lation of the processes of froth floatation and froth separation combined with froth floatation, which involves related adjustment of several parameters.
This problem is particularly acute with large-capaci-ty floatation machines due to great sluggishness of a floatation installation comprising such machines and also due to the presence of powerful disturbing fact-ors which are widely different.
The above problem i9 partially solved in a known 3 ~ ~ A

-device for automatic regulation of the process of sepa-rating froth concentrate from gangue in a floatation machine (cf. G.M.Kovin et al. "Systemy avtomatichesko-go kontrolya i upravlenia tekhnologicheskimi protsessa-mi flotatsionnykh ustanovok". Moscow, "Nedra" Publish_ers, 1981, pp.69-73), comprising a pulp level measur-ing circuit wherein a bubbling pipe located in the chamber of the floatation machine communicates with a pressure pickup and with an air flow regulator. The output of the pressure pickup is ccnnected to a pulp level recorder and to the input of a circuit designed to regulate the rate of discharging gangue from the chamber of the floatation machine, the output of said circuit being connected to the drive of a contr~l valve inqtalled Dn ~ branch pipe used to discharge gangue from the chamber of the floatation machine. ~he foregoing device also includes a frother flow-rate re-gulating circuit wherein the rate of frother flow is regulated in proportion to the flow of gangue dis-charged from the chamber as pulp.
Such an automatic regulator device does not pro-vide for required regulation quality due to the fact that, during measurements of the pulp level in the chamber of the floatation machine, no account is taken of the error associated with pulp density variations.
If no pulp density monitoring means are provided, frother metering with respect to the flo~ rate of 3 ~

gangue discharged as pulp is very appro~imate and up-sets the proces~es of froth formation and hydrodynam-ics in the chamber due to considerable variation~ of the pulp density, which hinders the process of pulp level stabilization. Furthermore, the absence nf such a regulating factor as stabilization of the flow rate of water containing frother during floatation impairs the pulp density.
Thus, the foregoing automatic regulator device does not provide for required regulation quality, part-icularly with large-capacity floatation machine~ due to the influence of powerful disturbing factors and great sluggishness of floatation in~tallations utiliz-ing such machine 8, The above problem i9 partially solved in another known device for automatic regulation of the process of separating froth concen~rate from gangue in a float-ation machine (cf. GB, A, 2180779), comprising a chan-nel for measuring a pulp level and density in the cham-ber of the floatation machine, in which two bubbling pipes installed at different levels in the bulk of the pulp in the chamber of the floatation machine are in communication with air flow.regulators and a differen-tial pressure pickup connected to the input of a chan-nel. designed to regulate the flow rate of frothersupplied to the chamber of the floatation machine and to one data input of a pulp level correction un~t '.J
'_ }~

whose other data input is connected to a pressure pick-up communicating with one of the bubbling pipes, while the output of Yaid pulp level correction unit is con-nected to the input of a channel used for stabilizing the pulp level in the chamber of the floatation machine and incorporating a circuit designed to regulate the rate of discharging gangue from the chamber of the floatation machine and connected to a gangue-di~charge control valve installed on a branch pipe adapted to discharge gangue from the chamber of the floatation machine.
Similarly to the previously mentioned device, the lastdescribed automatic regulator device does not pro-vide for required regulation quality, a disadvantage associated with the fact that stabilization of the pulp level solely by changing the rate of gangue dis-charge from the chamber of a floatation machine iq ge-nerally ineffective, particularly with large-capacity floatation machines due to great sluggishness of a floatation installation comprising such a machine and also due to the presence of strong disturbing effects and an insufficient regulating action to rapidly re-store the pulp level to a preset value. A mere increase in the gain of the pulp level stabilizing channel at a high level of disturbances will result in system driving, overcontrol and an excessive regu-lation time whereby regulation quality will be appre-ciably impaired. The utilization of a more powerfulcontrol valve in discharging gangue from the chamber of a highly efficient floatation machine increases its own sluggishness and, as a re~ult, the sluggishness of the floatation installation comprising automatic means in addition to the floatation machine and impairs regulation quality.
In the disclosed automatic regulator device, the rate of gangue discharge from the chamber of the float-ation machine can be changed by the use of a controlvalve having a nonlinear flow characteristic, a feat-ure making it impossible to obtain required regulation quality. Such a control valve does not provide for the maximum free discharge of gangue from the chamber of .
the floatation machine with minimum losses of the pulp liquid phase, which gives rise to pulp level disturb-ances in the chamber of the floatation machine. A ver-tical position of the afore-mentioned contr~l valve (with the seat of a shut-~ff valve located horizontal-ly) may cause complete or partial pressing-in of the branch pipe used to discharge gangue from the chamber of the floatation machine in floatation of ore con-taining a great number of large and heavy ~ractions.
Consequently, the gangue discharge rate will change (decrease) and there will occur additional pulp level disturbances in the chamber of the floatation machine, a factor R~her decreasing regulation quality, r, In its operation, the floatation machine uses cir-culating water with a residual concentration of froth-er amounting to 70 - 80 % of it~ working concentration, The rate of water flow changes as the source feed is supplied to the chamber of the floatation machine and losses occur in discharging gangue from the chamber of the floatation machine. This causes changes in the pulp level and density and also in flow hydrodynamics in the chamber of the floatation machine. Hence, maintaining - 10 the working concentration of frother in the pulp in the chamber of the floatation machine solely by changing the additional supply of frot-her t~ the chamber of the floatation machine without stabilizing the flow rate of water containing frother will fail to provide, on .
the one hand, adequate stabilization of water-air ratios in the bulk of aerated pulp and, consequently, of the pulp level and density and, on the other hand, a stable speed of supplying the source feed to the .. . . .
chamber of the floatation machine and, in effect, stable pulp flow hydrodynamics in the chamber of the floatation machine.

Brief Description of the Invention The object of the invention is to create a device for automatic regulation of the process of separating froth concentrate from gangue in a floatation machine, which wo~ld ellharce regulation quality.

The foregoing object i9 attained by that in a de-vice for automatic regulation of the proceqs of separat-ing froth concentrate from gangue in a floatation mach-ine, comprising a channel for measuring the level and density of pulp in a chamber of a floatation machine, in which two bubbling pipe~ installed at different levels in the bulk of the pulp in the chamber of the floatation machine communicate with air flow regulators and with a differential pres~ure pickup connected to the input o~ a channel for controlling the flow rate of frother suppli-ed to the chamber of the floatation machine and to one data input of a pulp level correction unit whose other data input is connected to a pre~sure pickup comminicat-ing with one of the bubbling pipes, while its output i9 connected to the input of a channel for stabilizing the pulp level in the chamber of the floatation machine, wherein a circuit for regulating the rste of gangue dis-charge from the chamber of the floatation machine iq con-nected to a drive of a gangue-discharge control valve 20 installed on a branch pipe used to discharge gangue from the chamber of the floatation machine, in which, accord-ing to the invention, the channel for stabilizing the pulp level in the chamber of the floatation machine addi-tionally include~ a circuit for controlling the flow rate , 7 ~ ~ r of water and frother ~upplied to the chamber, its input receiving a signal corresponding to a corrected value of the pulp level in the chamber of the floatation machine, the pipeline for feeding water and frother to the chamber of the floatation machine mounting a control valve con-nected to the output of the circuit for controlling the flow rate of water containing frother and supplied to the chamber, and a water-and-frother flow tran~ducer whose output is connected to the input of the circuit for regu-lating the rate of gangue discharge from the chamber ofthe floatation machine, which produces at its output a control signal in response to a deviation of the flow rate of water and frother from a preset value.
It i~ of advantage that, in the automatic regulator device, according to the invention, the circuit for con-trolling the flow rate of water containing frother and supplied to the chamber should include a pulp level con-trol having its output connected to one input of a cir-cuit for comparing a corrected pulp level value with a preset value, and a water-and-frother flow ~egulator having its input connected to the output of the circuit for comparing a corrected pulp level value with a preset value.

It is also advantageou9 that, in the automatic regu-lator device, according to the invention, the g~ngue-dis-charge control valve comprisine a cylindrical case with an outlet, having on one of its end9 a flange for con-nection with the branch pipe used to discharge gangue P-from the chamber of the floatation machine and accommo-dating a seat and a shut-off valve provided with a rod for connection with the drive of the gangue-discharge -control valve should be designed so that its cylindrical .
case is placed in a substantially horizontal position and the outlet is found in its lower portion, whereas the shut-aff valve has a cylindrical section and another section representing a parabolic cone connected with said cylindrical section and facing said seat, its axis being displaced towards the upper portion of the cylin-drical case relative to the axis of the hole in said seat.
It is further advantageous that, in the automatic regulator device, according to the invention, the cross--sectional area of the cylindrical section of the shut--off valve should be determined as follows:
S - ~1 - k)- Sn , where S - cross-sectional area of cylindrical section;
Sn ~ area of hole in seat;
k - proportionality factor equalling minimum-to--mA~imum load ratio of floatation machine.

~ he length of the section repre9enting a parabolic cone is equal to the travel length of the drive of the gangue-di~charge control valve.
It is preferable that, in the automatic regulator .. .. . .. ..
device, according to the invention, the misalignment of the a~is of the ~hut-off valve relative to the a~is of the hole in the seat should be equal to the differ-ence between radii of the cylindrical section of the shut-off valve and of the hole in the seat.
, It is also preferable that, in the automatic regu-lator device, according to the invention, the shut --off valve comprised in the gangue-discharge control .
valve should be provided with a pulp reflector dispos-ed on the end face of its cylindrical section.
It is further preferable that, in the automatic regulator device, according to the invention, the pulp reflector should repre~ent a disk with a circular de-pres~ion on its lateral surface.
In the proposed device, in addition to the cir-cuit for regulating the rate of gangue discharge from the chamber of the floatation machine, the pulplevel stabi-lizing channel includes a circuit ~or controlling~the flow rate of water and frother supplied to the chamber, which provides an additi~nal control action comprising a change in the flow rate of water and frother and ~ub-~equent stabilization of said flow rate.
Such a change in the flow rate of water and froth-er fed to the chamber con titutes the second control action amplifying the regulating effect associated with a change in the rate of gangue discharge from the chamber of the floatation machine and aimed at attain-ing faster stabilization of the pulp level in the cham-ber. There occurs a decrease in maximum de~iation of the pulp level in the chamber of the floatation ma-chine from a preset value. Also decreased is the time required to adju~t the pulp level from the occurrence of a pulp level deviation tD the attainment of a pre-determined level.
- The stabilization of said flow rate ~f water and frother following a change in said flow rate of water àrd fr~ther fed to the chamber of the floatation ma-chine involves stabilization of the rate at which the source feed is supplied to the bulk of aerated pulp in the chamber of the floatation machine and, conse--quently, stabilization of pulp flow hydrodynamics in the chamber of the floatation machine, as well as sta-bilization of the water-and-air ratios and, in effect, of the pulp level and density in the chamber of the flsatation machine.

2 ~

The stabilization of the flow rate of water and frother in conjunction with the control action of the channel for controlling the rate of frother flow will substantially improve stabilization of the pulp densi-ty in the chamber of the floatation machine and, ineffect, the pulp level stabilization.
The control action ba~ed on changing the flow rate of water and frother is interrelated with the con-trol action involving a change in the rate of gangue di~charge from the chamber of the floatation machine and with a di~turbing factor attributable to a pulp level deviation from a preset value. A change in the pulp level has a disturbing influence ~n variation~ of the flow rate of water and frother, whereas said ~ari-ations of the flow rate of water and frother e~ert adisturbing effect on changes in the rate of gangue dis-charge from the chamber of the floatation machine.
Such characteristics as the pulp level, the flow rate of water and frother and the rate of gangue discharge from the chamber of the floatation machine are inter-related so that the control process ends after the pulp level in the chamber and the flow rate of water and frother reach predetermined values. Taking into account the fact that the pulp level control time is several times smaller than the pulp density control time in the chamber of the floatation machine there will not be any significant changes in the pulp densi-~ 15 ~

ty or undesirable variations of pulp flow hydrodynam-ic~ in the chamber of the floatation machine during pulp level stabilization while a change occurs in the .
flow rate of water and frother. Inasmuch, as the pulp level in the chamber of the floatation machine is a prime parameter, a change in the flow rate of water and frother and its subsequent stabilization will, as a whole, prove out and en~ure quality control of the floatation process, The regulation quality is also increased by including in the proposed device a control valve for changing the rate of gangue discharge from the chamber of the floatation machine whose flow characteristic is essentially linear. Thi~ flow characteristic is made linear due to the fact that the shut- off valve has a working section representing a parabolic cone. A hori-- zontal position of said control valve prevent~ the pressing of the branch pipe used to discharge gangue from the chamber of the floatation machine in caqe the gangue contains many large and heavy fractions and substantially decrease pulp level disturbances caused by a change in the rate of gangue discharge, a feature appreciably improving the control quality. A
vertical displacement of the shut-off valve comprised in the control valve relatiYe to the seat axis pro-vides for the maximum free discharge of gangue from the chamber of the floatation machine with mini~llm - 16 ~

~ ~ n ~ ~ 3 ~ ~

losses of the pulp liquid phase, which improves the pulp level stabilization.
Therefore, in accordance with the present invention, there is provided a flotation control apparatus comprising:
a flotation machine comprising a pulp filled chamber, said machine being provided with a gangue discharge branch pipe, a source feed pipe line, a frother meter means for feeding a frother and pipeline means for feeding water-and-frother;
said means for measuring the level and density of the pulp comprising first and second bubbling pipes installed at different levels in said chamber with respect to the level of the pulp i said means for measuring the level and density of the pulp further comprises first and second regulator means for regulating the air flow rate fed to the bubbling pipes, said first and second regulator means being connected to the first and second bubbling pipes respectively;
said means for measuring the level and density of the pulp further comprising a differential transducer means connected with the first and second bubbling pipes and having an output serving as the first output of said means for measuring the level and density of the pulp, and said first outlet develops a signal corresponding to the density of the pulp;
said means for measuring the level and density of the pulp further comprising a pressure detection means connected with the first bubbling pipe and having an output;
said means for measuring the level and density of the pulp further comprising correction means having first and second data inputs and an output, said correcting means is connected via said first and second data inputs to the output of said pressure detection means and said differential transducer means, respectively, said output of said correction means serving as the second output of said means for measuring the level and density of the pulp, said correction means develops an output signal which corresponds to the increase in the level of pulp corrected for density;

., ~ . ~ , 3 ~ ~ ~
control means for regulating the flow rate of frother fed to said chamber of the flotation machine, having an input and an output and connected via said input to the first output of said means for measuring the level and density of pulp and via said output to said frother meter means; stabilization means for stabilizing the level of pulp in the chamber of the flotation machine, having first and second input and first and second output; said stabilization means comprises a first circuit means for controlling the flow rate of the water-and-frother being supplied to the chamber, said first circuit means for controlling the flow rate of the water-and-frother having an input serving as the first input of said pulp level stabilization means, said stabilization means being connected via its first input to the second output of said means for measuring the level and density of the pulp, said first circuit means having a first output serving as the first output of the pulp level stabilization means; a second circuit means for regulating the rate of gangue discharged from the chamber of the flotation machine, having an input and an output serving, respectively, as the second input of said means for stabilizing the level of the pulp and the second output thereof;
a water-and-frother control valve means installed on said pipeline feeding water-and-frother to said chamber of the flotation machine and having an input connected to the first output of said pulp level stabilization means, which furnishes the first control signal in response to an increase in the pulp level deviation from a preset value;
a gangue-discharge control valve means installed on said branch pipe used for discharging gangue from said chamber of the flotation machine;
said gangue-discharge valve control means having drive means which has an input connected to the second output of the pulp level stabilization means;
a water-and-frother flow transducer means installed on said pipeline feeding water-and-frother, having an output connected to the second input of said pulp level stabilization - 17a -at means, which develops at the second output of the stabiliz ion means the second control signal fed to said drive means of the gangue-discharge control valve means in response to a deviation of the flow rate of water-and-frother from a preset value.

Brief Decription of the Accompanying Drawings The invention will now be described further with reference to specific embodiments thereof, taken in conjunction with the accompanying drawings, wherein:
Fig. 1 is a general view of a floatation installation with a channel for measuring the level and density of pulp in the chamber of a floatation machine, a channel for controlling the flow rate of frother and a channel for stabilizing the pulp level in the chamber of a floatation machine, comprising a circuit for regulating the rate of gangue discharge and a circuit for controlling the flow rate of water and frother, according to the invention;
Fig. 2 is a functional diagram showing a pulp level correction unit, the frother flow control channel and the pulp level stabilizing channel according to the invention; and Fig. 3 is a general view of a gangue-discharge control valve (a longitudinal view of a case), according to the invention.

Detailed Description of the Invention The proposed device for automatic regulation of the process of separating froth concentrate from gangue in a floatation machine will be described by - 17b -~' ~ ..

J

way of example by reference to a floatation installat-ion comprising a ~ingle-chamber floatation machine with source feed supplied a~ small fraction~ of ore on the underside of a chamber 1 (Fig. 1) through a pipe-line 2~ The chamber 1 has a gangue-discharge branch pipe 3 in its lower portion and a chute 4 adapted to . . .
collect froth concentrate and disposed in the upper portion of the chamber. The device forming the ~ubject of the present inve~tion include~ a channel 5 for mea-suring the level and denqity of pulp in the cha~ber ofthe floatation machine, in whlch two bubbling pipes 6 and 7 installed at different levels Y and X in the pulp in the chamber 1 of the floatation machine are connected with air flow regulators 8 and 9, re~pective_ ly, and with a differential pressure pickup 10. The buobling pipe 6 i~ also in communication wit~ a pre~-ure pickup 11 who~e output i~ connected to a data input 12 of a pulp level correction unit 13 included in the pulp level and density measuring channel 5. A
data input 14 of the correction unit 13 is connected to the output of the differential pres~ure pickup 10, while its output is connected to the input of a pulp level recorder 15 and to an input 16 of a channel 17 for stabilizing the level of pulp in the chamber of the floatation machine.
The channel 17 for stabilizing the level of pulp in the chamber of the floatation machine incorporate~

3 ~!~ b ~

a circuit 18 for controlling the flow rate of water and frother ~upplied to the chamber, its input ~erving a~ the input 16 of the pulp level ~tabilizing channel 17, which receives a 9ignal corre~ponding to the pulp level in the chamber 1 after correction for den~ity.
The output of the circuit 18 for controlling the flow rate of water and frother serve~ as an output 19 of the pulp level stabilizing channel 17 and is connected with a control valve 20 in~talled on a pipeline 21 feeding water and frother to the chamber of the float-ation machine. The pipeline 21 al90 mounts a water-and_ -froth flow transducer 22 whose output is connected to the input of a circuit 23 for regulating the rate of gangue discharge from the chamber of the floatation machine, which ~erves as an in~ut 24 of the pulp level ~tabilizing channel 17.
The circuit 23 for regulating the rate of gangue discharge has its output acting as a second output 25 of the pulp level stabilizing channel 17 connected to a drive 26, say a pneumatic drive of a gangue-dis-charge valve 27 installed on the branch pipe 3 u~ed to discharge gangue from the chamber of the floatation machine. The circuit 23 develop~ at its output a con-trol signal in response to a devia,ion of the flow rate of water and frother from a preset value.
The device forming the subject of the present invention further compri~es a channel 28 for control-ling the flow rate of frother, which is connected vi~
its input to the output of the differential pressure pickup 10 and to the input of a pulp density recorder 29, while its output is connected to a frother meter 30 which is connected via a pipeline 31 to a-service .
tank 32 holding frother and to the pipeline 2 suppl.y-ing the source feed to the chamber of the floatation m~chine.
In the floatation installation of Fig. 1 frother, -~ulp and water are mixed up directly in the pipeline 2.
If in addition to frother the pulp~includes other floatation agents, the installation may comprise a mi~-.
ing tank wherein these float~tion agent8 are broughtin contact with the solid phase of the pulp.
The pulp level correction unit 13 comprise~ ana-log current-to-voltage converters 33 (~ig, 2 ?, 34, the input of the first conv~rter serving as the input 12, while the input of the second converter serves as the ~ input 14 of the pulp level correction unit 13. The out-put of the analog current-to-voltage converter 33 i8 connected to an input 35 of a unit 36 used to divide a pulp level signal by a pulp den~ity signal and having its input 37 connected to the output of the analog current-to-voltage converter 34. The output of the divider unit 36 is connected to the input of a multi-plier unit 38 whose OlltpUt is connected to the input of an analog voltage-to-current converter 39. ~he out-- put of the analog voltage-to-current converter 39 serves as the output of the pulp level correction unit 13 and is connected to the input of the pulp level re-corder t5 and to the input 16 of the pulp level ~tabi-lizing channel 17.
The channel 28 for controlling the flow rate of frother comprises a pulp density control 40 whose out-put is connected to one input 41 of a circuit 42 used to oompare a meaqured pulp density value with a preset value and having its other input 43 combined with the input of the channel 28 for controlling the flow rate of frother. The output of the comparison circuit 42 is connected to the input of an analog pulse-length regu-lator 44 whose output i~ connected to a pulse-~ength control input 45 of an automatic frother metering ~y8-tem 46 having its pulse-frequency control input 47 con-nected to the input 43 of the comparison circuit 42.
The automatic frother metering system 46 develops at its output current pulseq adjuqtable in frequency and length, said output ~erving as the output of the chan-nel 28 for controlling the flow rate of frother.
The circuit 18 for controlling the flow rate of water and frother supplied to the chamber, comprised in the channel 17 for stabilizing the level of pulp in the chamber of the floatation machine, is pro~ided with a pulp level control 48 having it~q output connect-ed to one input 49 of a aircuit used to compare a cor-rected pulp level value with a preset value, its other input 51 serving as the input 16 of the pulp level sta-, bilizing channel 17. Ihe output of the compariscn cir-.
cuit 50 is connected to the input of a means 52 for oontrolling the flow rate of water and frother, itq output being connected to the input of an electropneu-matic converter 53. ~he output of the electropneumatic con~erter 53 functions as the output of the circuit t8 for controlling the flow rate of water and frother supplied to the chamber and also as the output 19 of - the pulp level stabilizing channel 17 and is connected to the control ~alve 20 provided with a pneum~tic actuatorO
In the pulp level stahilizing channel 17, the cir-t5 cuit 23 for regulating the rate of gangue discharge from the chamber of the floatation machine comprises a means 54 for controlling the flow rate of water and . .
frother, ~aid means having its output connected to one input 55 of a circuit 56 used to compare a measured value of the ~ater flow rate with a preset value. It~
other input 57 serves as the inpv.t of the circuit 23 for regulating the rate of gangue discharge and also as the input 24 of the pulp level stabilizing channel 17 and is conn cted to the output of the water-and_ -frother flow transducer 22. ~he output of the compari-son circuit 56 i~ colmected to the input of a means 58 for regulating the rate of gangue di~charge from the - 22 ~

chamber of the floatation machine, said mean~ having its output connected to the input of an electropneu-matic converter 590 The output of ~aid ¢onverter serves a~ the output of the circuit 23 for regulating the rate of gangue discharge and also as the output 25 of the pulp level stabilizing channel 17 and is con-nected to the drive 26 of the valve 27 controlling the discharge of gangue from the chamber of the floatation machine.
The valve 27 controlling the discharge of gangue and placed on the branch pipe 3 (Fig. 1) used to dis-charge gangue from the chamber of the floatation mach-ine is provided ~ith a horizontally disposed cylindric-al case 60 (Fig. 3) with a lining 61, for e~ample, a rubber lining, ~aid case having in it~ lower portion a hole 62 adapted to discharge gangue, Fitted on one of the end~ of the case 60 is a flange 63 for connecti~n -with the discharge branch pipe 3 (Fig. 1). A seat 64 made of a suitable wear-resistan~ material, for example, rubber,-is installed in the case 60 (~ig, 3~, more par-ticularly, within the flange 63. The case 60 also con-tains a shut-off ~alve having a cylindrical section 65 and a section 66 representing a parab~lic cone connect-ed with said cylindrical ~ection and facing the seat 64, The cylin~rical section 65 is rigidly linked with a rod 67 and with a pulp reflector 68 made of a suit-, able wear-resistant material and disposed on the end face of the cylindrical section 65. ~he rod 67 i~
in~erted in a plain bearing 69 placed on a cover 70 of the caqe 60 with a lining 71, for example, a rubber lining and linked with the rod of the drive 26 (Fig. 1) of the control valve 27. ~he "0" axi~ (Fig. 3) of the shut-off valve aligned with the axis of the ca~e 60 i~
displaced upwards relative to the ~01~ axi~ of the hole in the seat 64, the eccentricity value being equal to the difference between the radiu~ R1 of the hole in the seat 64 and the radiu~ R2 of the cylindric-.. . . .
al section 65 of the shut-off valve. This provide~ for the maximum free discharge of gangue from the chamber 1 (Fig.~1) of -che ~loatation machine with min;ml~m losses of the liquid phase of the pulp (water mixed ~5 with frother) and prevents the clogging of the hole in the ~eat 64 (Fig. 3 ~ and the gangue-discharge branch pipe 3 (Fig. 1) with foreign object~ and al90 when the discharge gangue contain~ many large and heavy fract-ions.
~he cro~-sectional area S of the cylindrical section 65 (Figo 3 ) of th~ ~hut-off valve i~ determin-~ , _ ed from the following equation:
S = (1 - k)- S /t/
where Sn - area of hole in ~eat 64; and k - proportionality factor equalling min;ml~m--to-maximum load ratio of floatation machi-ne.
- ~4 -Such a relationship is chosen to ensure that the variation range of the flow section of the gangue-dis-charge branch pipe 3 (~'ig. 1) correqponds to the vari-ation range of the initial load acting on the float-ation machine.
The length of the section 66 (Fig.~3) of the ~hut--off valve representing a parabolic cone is equal to the m~ u~ travel length of ~he drive 26 (Fig. 1) of the gangue-discharge control va~ve 27. ~he generatri~
of the section 66 (Fig. 3) i8 determined from the fol-lowlng equation:
1.
i l /2/
where S1 ~ cross-sectional area of section 66 repre-senting parabolic cone at distance i from vertex;
S - cross-sectional area of cylindrical section 65 sf shut-off valve;
l - length of section 66 representing parabolic cone;
li - distance from verte~ of section 66 repre-senting parabolic cone to cross-section of section 66 at distance i from vertex.
Such a shape and length of the section 66 repre-senting a parabolic cone make essentially linear the flow characteristic of the gangue-discharge control valve 27 (Fig. 1) and ensure continuous variations of the rate of gangue discharge, a factor substantially improving quality of automatic pulp level control.
The pulp reflector 68 (Fig. 3) protects the rod 67 from we~r under the action of pulp, particularly abrasive pulp, thereby increasing operational reliabili-ty of the gangue-discharge control valve 27 tFig. 1).
The pulp reflector 68 (Fig. 3) is made QS a disk having on its lateral surface a circular depression 72 designed to remove the pulp ~ed through the gap bet-ween the pulp reflector 68 and the lining 61.
The afore-mentioned advantages of the gangue-dis-charge control valve 27 (Fig. 1) are particularly apparent when said valve is used for regulating the discharge rate ~f abrasive pulp and pulp containing a substantial percentage of large and heavy fractions.
The automatic frother ~etering system 46 (Fig. 2) described above uses circuitry widely known to those skilled in the art.
The proposed device for automatic regulati~n of the process of separating froth concentrate from gangue in a floatation machine operates as follows.
AQ froth concentrate is separated from gangue ln a fl~a~ation machine, continuouq mea~urements are made of the level and density of pulp in the chamber 1 2~ (Fig. 1) of the floatation machine.
It is known that variations of the pulp density in the chamber of the floatation machine result in a '1~11_ pressure change in the bubbling pipes. The pressure in each of the bubbling pipes i~ determined as p . p ~ h /3/

where P - pressu.re in each bubbling pipe;
~ - den~ity of pulp (or liquid) surrounding bubbling pipes;
h - depth of immersion of each bubbling pipe in pulp (or liquid).
In the proposed device, pres~ure P1 of the bubbl-ing pipe 6 i~ proportional both to pulp den~ity ~ and to depth Y of it~ immersion in the pulp, that is, Accordingly, pressure P2 in the bubbling pipe 7 will be determined as P2 ~ ~ ~ X /5/

where ~ is depth of immersion of the bubbling pipe 7 in the pulp.
Subtracting equation /4/ from equation /5/ we get ~P = P2 ~ P~ ~ ~ (X - Y) /6/

where ~P is a differential pressure in the bubbling pipes 6 and 7.
Since X - y s Z where Z is a height difference of the bubbling pipes 6 and 7, we shall have ~P ~ Z ~ p . /7/

Hence, a pressure difference in the bubbling pipes 6 and 7 will be propor'ional to the pulp densi~y in the chamber 1 of the floatation machine and-to a height difference of the bubbling pipe~ 6 and 7 immers-.
ed in the pulp and will not depend on pulp level vari-ationq in the chamber 1 of the floatation machine.
The signals conveying information on pressure in the bubbling pipes 6 and 7 are applied to the input of the differential pressure pickup 10, in which they are converted into a direct-current signal proportional to - the pulp density, which-i~ fed to the input of the pulp density recorder 29, to the input of the channel 28 for controlling the flow rate of frother and to the data input 14 of the pulp level correction unit 13.
The measurement of the pulp level in the chamber 1 of the floatation machine in~olves the measurement t5 of pressure in the bubbling pipe 6 by meanQ of the pressure pickup 11. I-nasmuch, as pressure Pt in the bubbling pipe 6 depends both on the pulp level in the chamber 1 of the float~tion machine determined by t~e depth Y of immersion o~ the bubbling pipe 6 in the pulp and on the pulp density according to equatiOn /4/, the direct-current signal at the output of the pre~-ure pickup 11 will be also dependent on the pulp level and density in the chamber 1 of the floatation machine.
To eliminate error~ in pulp level measurements due to variations of ~he pulp density in the chamber 1 of the floatation machine, the direct-current, signal derived from the output of the pressure pickup 11 i~ applied - 28 ~

-,~ s~ 3 ~

to the data input 12 of the pulp level correction unit 13, whence said ~ignal is fed to the input of the ana-log current-to-voltage converter 33 (Fig. 2) to be con-verted into a proportional d.c. voltage applied to the input 35 of the divider unit 36. ~he direct-current signal proportional to the pulp density is fed to the input of the analog current-to-voltage converter 34 ~ .
via the data input 14 of the pulp level correction unit 13, in which it i~ converted into a proportional d~co voltage applied thereafter to the input 37 of the divider unit 36. The d~c. voltage proportional to the .
ratio of the signal arriving at the input 35 to the ~ignal arriving at the input 37 of the divider u~it 36 .
is applied from the output of the divider unit 36 to the multiplier unit 38. The output voltage of the mul-tiplier unit 38 is ~ed to the input o~ the analog volt-age-to-current converter 39 wherein it i8 converted into direct current which is subsequently applied to the input of the pulp level recorder 15 and t~ the input 16 of the pulp level ~tabilizing channel 17.
When froth concentrate is separated from gangue in the floatation machine, related adjustments are made of such parameters as the pulp level and den~ity in the chamber 1 (Fig. 1) o~ the floatation machine and the flow rate of water and frother supplied to the chamber 1 of the floatation machine.
Related par~metric adju~t~ent~ involve, in this 'É ~

case, certain difficulties associated with the fact that, during separation of froth concentrate from gangue in the chamber 1 of the floatation machine, there occurs a change in residual concentration of frother in circulating water supplied to the chamber 1 of the floatation machine. This cau~es variations of the pulp density in the chamber 1 and necessitates con--trol of the flow rate of frother supplied to the cham-b~r 1 of the floatation machine with a view to restor-ing the pulp density and ensuring the separation of , froth concentrate from gangue in the chamber 1 of the .
floatation machine. The pulp density variations cause an additional change in the level of the pulp in the .
chamber 1 of the floatation machine. The pulp level in the chamber 1 is a prime parameter ginCQ its excessive increase causes the clogging ~f ~roth concentrate with gangue and impairs the extraction of a u~eful constitu-ent from the source feed supplied to the froth layer , due to the fact that the position of the froth layer ha~ changed. An excessive decrea~e in the pulp level re~ults in a lesser yield of froth concentrate and in losses of the useful constituent due to untimely dis-charge of froth concentrate into the frother collect-ion chute 4 ~vhereby the useful constituent will ~ettle on the bottom of the chamber 1 of the floatat-ion machine. With the ~bove factor taken i~tn account, the proposed device for regulating the separation ~ r~

.. ~ . ~

process i9 designed so that the pulp level is stab1liz-ed by controlling the rate of gangue discharge from the chamber 1 of the floatation machine and al30 the flow rate of water and frother supplied to the chamber 1 of the floatation machine with sub~equent stabilization of the flow rate of water and frother to provide for indirect ~tabilization of the pulp density in the cham-ber 1 of the floatation machine.
The rate of frother flow is controlled by means 1Q of the channel 28 for controlling the flow rate of frother, its input receiving a current ~ignal from the output of the differential pr~ssure pickup 10~ which is proportional to the pulp density in the chamber t of the floatation machine. The channel 28 for control-ling the flow rate of frother produces an output sign-al representing direct-current pulses varying in fre-quency and length and applied to the frother meter 30 which operates, thus feeding portions of frother to the chamber 1 of the floatation machine. In the chan-nel 28 for controlling the flow rate of frother, adirect-current signal proportional to the pulp density is fed to the input 47 (Fig~ 2) controlling the fre-quency of pul~es furnished by the automatic frother metering ~ystem 46 and also to the input 43 of the circuit 42 u~ed to compare a measured value of the pulp density with a preset value, the input 41 of said ~ircuit receivi~g a direct-current signal from the control 40 to obtain the desired density of the pulp . - -When the ~ignal~ indicative of the measured andpreset pulp densit~es are ,equal, the differential sign-al at the output of the compariso~ circuit 42 is zero.
The analog pul3e-length regulator 44 produces a direct--current signal which has a constant magnitude and is applied to the pulse-len~th control input 45 of the . .
automatic frother metering system 46. The output signal of this system represents square d,c. pulses, the fre-quency of which i~ proportional to the direct-current .
signal at the input 47 ~f the system 46, whereas their duration is proportional to the direct-current signal at its input 45. The square dcc. pulse~ derived from the automatic frother metering ~ystem 46 are applied to the input of the frother meter 30 which operates feeding portions of frother to the chamber 1 (Fig. 1) of the floatation machine.
.
When the signal proportional to the pulp density increases or decreases, the frequency of the output pulses-of the automatic frother metering ~ystem 46 (Figa 2) will increase or decrease accordingly. At the same time, the comparison circuit 42 will develop at its output a direct-current ~ignal corresponding to the difference between the signal proportional to the measured pulp density and the signal from the pulp density control 40. Theresfter, the differential signal ls fed to the input of the analog pulse-length regulator 44 whose output signal increases or decreases according to the proportional-plus-ir.tegral control law. Ne~t, the output 9ignal of the analog pulse-length regulator 44 is applied to the pul9e-length control input 45 of the automatic frother metering sy~tem 46 ,, , whereby the duration of lts output ~quare d.o. pulses will increase or decrea3e. Thus, the frequency and duration of the doc~ pulses at the output of the auto-matic frother metering system 46 increa~e or decrease,which causes a corresponding increase or decrease in the supply of frother to the chamber 1 (Fig. 1~ of the floatation machine. A change in the frother sup ly brings.about a variation of frother c~ncentration ~n the pulp fed through the pipeline 2 to the chamber 1 .
of the floatation machine and, consequently, a variat-ion of the pulp density in the chamber 1. The flow rate of frother changes until the pulp density equal~
a preset value.
Whe~ froth concentrate is separated from gangue, the pulp level in the chamber 1 of the floatation ma-chine will be stabilized by means of the pulp level stabilizing channel 17 whose input 16 receives a di-rect-current ~ignal proportional to a corrected value of the pulp level in the chamber 1 of the floatation machine, said direct-current ~ignal coming from the output of the pulp level correction unit 13. ~he input - 33 ~

24 of the pulp level stabilizing channel 17 simultane_ ou~ly receives a direct-current signal from the output of the flow tran~ducer 22 for water and frother 9uppli-ed to the chamber 1 of the floatation machine via the pipeline 21. The pulp level stabilizing channel 17 ef-fect~ two control actions. The first control action is provided at the autput 19 of the pulp level ~tabil1z-ing chsnnel 17 by the circuit 18 for controlling the flow rate of water and frother ~upplied to the chamber.
The qecond control action i8 provided at the output 25 of the pulp level stabilizing channel 1? by the cir-cuit 23 for regulating the rate of gangue dischar~e.
The channel 17 for stabili~lng the pulp level in the chamber of the floatation machine is formed SQ that . .
the pr~ces~ control ends only after the pulp level in the chamber 1 of the floatation machine and the flow rate of water and frother supplied to the chamber 1 of the floatation machine reach preset values.
In the cha~nel 17 for stabilizing the pulp level in the chamber of the floatation machine, a direct--current si~nal proportional to a corrected value of the pulp level in the chamber 1 is fed to the input 51 (Fig. 2) of the circuit 50 for comparing a corrected value of the pulp level with a preset value, the input 49 of said circuit receiving a direct-current signal from the pulp level control 48. When the signal from the pulp level control 48 and the signal corre~pond-~ 34 ~

ing to a corrected value of the pulp level and fed tothe input 51 of the compari~on circuit 50 are equal, the output signal of said compari~on circuit is zero.
The output ~ignal of the compari~on circuit 50 i~
applied to the input of the means 52 for contr~lling the flow rate of water and frother, which produces a direct-current signal having a constant magnitude and fed to the input of the electropneumatic converter 53 wherein it is converted into a proportional pneumatic ~ . . .
signal. Thereafter, said signal is applied to the con-trol valve 20 having a pneumatic actuator and install-ed on the pipeline 21.-Water containing frother is .
supplied through the control valve 20 to the chamber 1 (Fig. 1) of the floatation machine. The pipeline 21 i8 provided with the water-and-frother flou transducer 22 whose output direct-current signal is proportional to the flow rate of water and frother supplied over the , pipeline 21 to the chamber 1 of the floatation machine.

The output signal of the water-and-frother flow trans-ducer 22 is applied to the input 57 (Fig. 2) of the . . .
circuit 56 for comparing the measured flow rate of -water and frother with a preset value, the second input 55 of said circuit receiving a direct-current signal from the water-and-frother flow control 54.
When the above signals are equal, the output signal of the compari~on circuit 56 is zero. The output si~nal .
of the comparison circuit 56 is fed to the input of ~ 35 the analog means 58 for regulating the rate of gangue .
discharge from the chamber of the floatation machine~
Said analog means furni9he9 a direct-current signal having a constant magnitude and fed to the input of the electropneumatic converter 59 wherein it is converted .
into a proportional pneumatic ~ignal. Ne~t, said signal i~ applied to the pneumatic drive 26 of the control valve 27 enabling the di~charge of gangue from the .. . . .
chamber of the floatation machine. The gangue i~ dis-charged from the chamber 1 (Fig. 1) of the floatation machine through the control valve 27.
As the pulp level in the chamber 1 of the float-ation m~chine lncrea~es or decrea~e~, there will occur a corresponding increa~e or decrease in the amplitude of the 9ignal at the input 51 (Fig. 2) of the circuit 50 for comparing a corrected value of the pulp level with a preset value. The compari~on cir-cuit 50 develops at its output a direct-current signal equal to the difference between the signal from the pulp level control 48 and the signal corresponding to .
a corrected value of the pulp level and fed to the input of the analog means 52 for controlling the flow rate of water containing frother. The direct-current signal at thè output of said analog means will increase or decrea~e according to the proportional--plus-integral control law and come to the input of the electropneumatic converter 53 wherein it i~ con-verted into a proportional pneumatic signal. Ne~t, said ~ignal comes to the control valve 20. Thus, there will occur a decrease or increase in the flow rate of water .
containing frother and supplied via the control valve 20 to the chamber 1 (Fig. 1) of the floatation machine, which partially compensates for an increase or decrease in the pulp level in the chamber 1 of the floatation machine.
As the flow rate of water containing frother de-creases or increases, there will occur a corresponding decrea~e or increase in the amplitude of the direct--current signal at the output of the water-and-frother flow transducer 22, ~aid signal being fed to the input 57 (Fig. 2) of the circuit 56 for comparing the measur-ed flow rate of water and frother with a preset value.The latter circuit develops at its output a.signal indicative of the difference between the signal frnm the means 54 for controlling the flow rate of water containing frother and the signal corresponding to the 20 measured flow rateof~ r and frother. Then the differ-ential signal is applied to the input of the analog means 58 for regulating the rate of gan~ue discharge from the chamber of the floatation machine, the output signal of said means decreasing or increasing accord-ing to the proportional-plus-integral control law.
Said output direct-current signal is fed to the input of the electropneumatic converter 59 wherein it is 37 ~

converted into a proportional pneumatic signal. Next, ~aid signal i9 applied to the pneumatic drive 26 of the control valve 27 enabling the discharge of gangue from the chamber of the floatation machine. The drive 26 moves, in proportion to the pneumatic signal, its rod and, consequently, the rod 67 (Fig. 3) of the gangue-discharge control valve 27 whereby the ~hut-off valve comprised in the control valve 27 will move re-lative to the seat 64. There occur~ a linear increase (decrease) in the flow section of the hole in the seat 64 of the control valve 27 enabling the discharge of gangue from the chamber of the floatation machine, which causes a corresponding increase (decrease) in the rate of gangue discharge from the chamber 1 ~Fig.1) of the floatation machine and restoration of the - preset pulp level in the chamber 1 of the floatation machine.
At the moment the pulp level in the chamber 1 of the floatation machine reaches a preset value, the flow rate of ~ater containing frother and supplied to the chamber 1 may differ from the rating. An error signal from the output of the circuit 56 (~ig. 2) for comparing the measured flow rate of water and frother with a preset value is applied to the input of the analog means 58 for regulating the rate of gangue dis-charge from the chamber of the floatation machine, which continues to generate a control signal, a factor 3 ~ ~
causing a decrease (increase) in the rate of gangue discharge from the chamber 1 (Fig. 1) of the floatation machine. Consequently, there will occur a slight devi-ation of the pulp level in the chamber 1 of the float-ation machine, which results in a variation of theflow rate of water containing frother and ~upplied to the chamber 1 of the floatation machine.
Thus, the flow rate of water containing frother and supplied to the chamber 1 of the floatatlon machine and the rate of gangue discharge from the chamber 1 of the floatation machine will be controlled until the pulp level in the chamber 1 and the flow rate of water containing frother and supplied to the chamber 1 of the floatation machine reach preset values.
~o avoid system driving during the control action, the analog control means 52 (Fig. 2) and 58 are differ-ently adju~ted, more particularly, the analog means 58 is characterized by a smaller gain and a larger inte-gration period a~ compared with the analog means 52.
Such a structure of the proposed device for auto-matic regulation of the process of separating froth concentrate from gangue in the floatation machine and also the utilization of the discharge valve with a linear flow characteristic make it possible to decrease a maximum deviation of the pulp level and density from preset values during the csntrol action and to reduce fluctuations and the t-me ~,f controlling the pulp level and density in the chamber of the floatation machine.

39 ~

Claims (3)

1. A flotation control apparatus comprising:
a flotation machine comprising a pulp filled chamber, said machine being provided with a gangue discharge branch pipe, a source feed pipe line, a frother meter means for feeding a frother and pipeline means for feeding water-and-frother;
said means for measuring the level and density of the pulp comprising first and second bubbling pipes installed at different levels in said chamber with respect to the level of the pulp;
said means for measuring the level and density of the pulp further comprises first and second regulator means for regulating the air flow rate fed to the bubbling pipes, said first and second regulator means being connected to the first and second bubbling pipes respectively;
said means for measuring the level and density of the pulp further comprising a differential transducer means connected with the first and second bubbling pipes and having an output serving as the first output of said means for measuring the level and density of the pulp, and said first outlet develops a signal corresponding to the density of the pulp;
said means for measuring the level and density of the pulp further comprising a pressure detection means connected with the first bubbling pipe and having an output;
said means for measuring the level and density of the pulp further comprising correction means having first and second data inputs and an output, said correcting means is connected via said first and second data inputs to the output of said pressure detection means and said differential transducer means, respectively, said output of said correction means serving as the second output of said means for measuring the level and density of the pulp, said correction means develops an output signal which corresponds to the increase in the level of pulp corrected for density;

control means for regulating the flow rate of frother fed to said chamber of the flotation machine, having an input and an output and connected via said input to the first output of said means for measuring the level and density of pulp and via said output to said frother meter means; stabilization means for stabilizing the level of pulp in the chamber of the flotation machine, having first and second input and first and second output; said stabilization means comprises a first circuit means for controlling the flow rate of the water-and-frother being supplied to the chamber, said first circuit means for controlling the flow rate of the water-and-frother having an input serving as the first input of said pulp level stabilization means, said stabilization means being connected via its first input to the second output of said means for measuring the level and density of the pulp, said first circuit means having a first output serving as the first output of the pulp level stabilization means; a second circuit means for regulating the rate of gangue discharged from the chamber of the flotation machine, having an input and an output serving, respectively, as the second input of said means for stabilizing the level of the pulp and the second output thereof;
a water-and-frother control valve means installed on said pipeline feeding water-and-frother to said chamber of the flotation machine and having an input connected to the first output of said pulp level stabilization means, which furnishes the first control signal in response to an increase in the pulp level deviation from a preset value;
a gangue-discharge control valve means installed on said branch pipe used for discharging gangue from said chamber of the flotation machine;
said gangue-discharge valve control means having drive means which has an input connected to the second output of the pulp level stabilization means;
a water-and-frother flow transducer means installed on said pipeline feeding water-and-frother, having an output connected to the second input of said pulp level stabilization means, which develops at the second output of the stabilization means the second control signal fed to said drive means of the gangue-discharge control valve means in response to a deviation of the flow rate of water-and-frother from a preset value.

2. The flotation control apparatus as claimed in claim 1, wherein the pulp level correction means comprises:
a first current to voltage converter means having an input serving as the first data input of the correcting means which receives a signal from the pressure detection means, and said first converter means having an output;
a second current to voltage converter means having an input serving as the second data input of said correction means which receives a signal from the differential transducer means, said signal corresponding to the pulp density, and said second converter means having an output;
a first divider means having first and second input connected to the output of the first and second current to voltage converter means, respectively, and an output which is the ratio of the signals of the first input to the second input of the divider means;
a first multiplier means having an input connected to the output of the first divider means and the multiplier means having an output which is connected to the input of a voltage to current converter means which has an output which corresponds to the second output of the means for measuring the level and density of the pulp.

3. The flotation control apparatus as claimed in claim 1, wherein said first circuit means for controlling the flow rate of the water-and-frother being admitted to the chamber comprises:
a comparison circuit means for comparing an output signal of the pulp level correction means with a preset value, said comparison circuit means having a first input connected to the output of the pulp level correction means, a second input and an output;

means for setting the preset value having an output connected with the second input of the comparison circuit means, and;
means for regulating the flow rate of the water-and-frother having an input connected to the output of the comparison circuit means and said output of the regulating means serving as the first control signal of the pulp stabilizing means.