Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/06—Operating or servicing

Definitions

• the invention relates to a method for the electrolytic demetallization of a solution containing metal ions, in which an electrical direct current between an immersed in the solution anode and cathode is controlled by means of programmable control in such a way that the current intensity gradually increases to an approximately constant value at intervals which follow one another in time is lowered until the residual concentration of the metal ions falls below a predetermined value, and a device for current control of an electrolytic demetallization cell.
• Electrode loading is in chronological order Levels reduced; A ph-regulating redox system is added to the solution to be desilvered.
• a constant current is gradually lowered with the aid of a programmable controller at successive intervals until the residual concentration falls below a predetermined value.
• the electrode loading can be carried out by a pre-programmable, automatic control with the aid of a programmable controller, in which all or at least some of the variables to be controlled are automatically controlled according to a preselectable program.
• the object of the invention is to provide a method for automatic current control in metal depletion cells using the highest possible current density on the electrodes; furthermore, a device is to be created with an independent regulator which takes the course of the electrochemical process into account and which gradually reduces the cell current; In addition, the automatic current control is also to be used in cells with a large number of cathodes which face one or two anodes.
• the task is solved with regard to the procedural task by d characterizing features of claim 1.
• An advantageous embodiment of the method is specified in claim 2.
• the setpoint value of the current is preferably lowered by an amount in each case which is in the range from 1: 1.5 to 1: 7 in relation to the previous setpoint value.
• the solution is fed to the metal depletion cell in batches.
• the evaluation electronics have a monostable multivibrator for pulse generation; the input of the setpoint generator is provided with a pulse counter, the counter reading corresponding in each case to a predetermined setpoint value of the current.
• Figure 1 shows the relationship between the maximum possible current densities and the concentration of the solution in mg / 1 for copper deposition
• Figure 2 shows the course of action using a control loop
• FIG. 3 shows the schematic assignment of individual components of the device according to the invention.
• the function shown in FIG. 1 divides the diagram into an area I in which no gassing takes place and an area II in which the current density on the electrodes of the demetallization cell is so high in relation to the content of the solution that hydrogen evolution takes place .
• the electrode plate serving as cathode has an area of 480 x 690 mm and is made of expanded copper.
• depletion takes place in stage 1 with a current of 10 A per cathode.
• the functional relationship between a solution with a content of 280 mg / 1 is shown using position A in area I.
• the depletion takes place in stage 1 with a constant current of 10 A until point X. the characteristic curve of the gassing range II is reached and the evolution of hydrogen begins.
• a predetermined hydrogen content of 1% in point B is reached, the content has dropped to approximately 215 mg / l.
• the current per cathode is reduced to 9 A in stage 2, this switching point being designated C.
• the content of the solution is demetallized with the constant current until the hydrogen evolution starts again at the point and, after reaching the predetermined hydrogen content of 1% in point D, again a reduction to a current of 8 A in Switching point E occurs in stage 3.
• the solution is constantly de-metallized with a current of 8 A until the characteristic line is broken through at point X- and hydrogen evolution begins again.
• the predetermined hydrogen value of, for example, 1% in point F of the diagram the system switches to a lower level, which results in a cathode current of 7 A; this stage 4 begins at point G, again demetalizing until the characteristic curve is passed at point X.
• the cathode current is again reduced by one stage to 6 A per cathode at switching point I.
• This cycle repeats itself until the depletion in point K has a residual content of approx. 10 mg 1; after reaching point K, a signal is triggered and the solution is changed in batches.
• the setpoints of the currents of the individual stages are stored in the setpoint generator 1; from the output from the setpoint adjuster control variable W and the size of the cell current Ist ⁇ X and the difference is formed as Regelabwei ⁇ monitoring the controller 2 supplied.
• Controller 2 generates a manipulated variable Y, which is fed to the actuator 3 for controlling the current in the cell.
• the actuator 3 passes the control signal as a current or signal of the strength of the cell current to the cell 4, while at the same time the signal X is supplied as the actual variable to the differential input of the controller 2.
• the setpoint W. is specified as the command variable for the current strength in the cell, where, for example, due to a control deviation due to an actual variable X which is too small.
• the current intensity of the controller 2 outputs a manipulated variable Y until the actuator 3 generates an actual variable X that the command variable W_. corresponds and the control deviation thus becomes zero;
• the controlled current X .. is now supplied to the cell 4 until a pulse Z is emitted due to the hydrogen development in the cell, which switches the counter of the setpoint generator 1 from position 1 to position 2 and thus from setpoint W.
• FIG. 3 schematically shows the device according to the invention in a block diagram; the reference numbers of the cycle of effects used in FIG. 2 are adopted as far as possible.
• the cell shown up to now with reference number 4 is divided here into the actual electrolytic cell 5 and the measuring head acting as a hydrogen sensor 6, which is connected via an electrical line to the evaluation electronics 7, which in turn connects to the input of the setpoint generator 1 connected is.
• the setpoint generator 1 has a counter 8, which counts the pulses Z generated by the evaluation electronics 7 for each hydrogen gas evolution detected by the measuring head 6 and exceeding a predetermined threshold value, and a setpoint w for each of the counter readings Strength of cell current I generated; the target values correspond in number to the levels of the counter; for example, eight setpoints W for the current strengths, which are fed to the differential input 9 of the controller 2, are also stored at eight counting positions.
• the output of the controller 2 emits its control signal a from the input 10 of the actuator 3 serving for current control.
• the actuator 3 works as a voltage-controlled current source and uses the voltage transmitted as the control signal Y to generate an output current proportional to the voltage, which is supplied to the cell 5.
• the current I output via the terminals 11, 12 generates a voltage proportional to the current I at the shunt 13, which voltage is supplied to the differential input 9 of the controller 2 as the control variable X for the actual value of the current.
• the hydrogen sensor 6 sends an electrical signal to the evaluation electronics 7, which forms a pulse from the signal emitted by the measuring head and sends this to the input of the counter 8 of the setpoint generator 1 forwards.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)
• Electrolytic Production Of Metals (AREA)

Applications Claiming Priority (2)

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• 1990
  • 1990-03-03 DE DE4006751A patent/DE4006751A1/de active Granted
• 1991
  • 1991-01-12 CA CA002076759A patent/CA2076759A1/en not_active Abandoned
  • 1991-01-12 US US07/923,941 patent/US5362369A/en not_active Expired - Fee Related
  • 1991-01-12 JP JP91502435A patent/JPH05504791A/ja active Pending
  • 1991-01-12 EP EP91902217A patent/EP0518867A1/de not_active Withdrawn
  • 1991-01-12 WO PCT/EP1991/000044 patent/WO1991014023A2/de not_active Application Discontinuation

Non-Patent Citations (1)

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