RU2189402C1 - Technology processing waste of hard alloys - Google Patents

Abstract

FIELD: hydraulic metallurgy of refractory metals, electrochemical processing of waste of hard alloys containing wolfram. SUBSTANCE: technology processing waste of hard alloys includes anode dissolution of waste in electrolyte based on hydrochloric or sulfuric acid. Anode dissolution is carried out under condition of asymmetric reversible current with exposure to forward electric current with periodic change-over of direction of current to backward direction. Process is conducted with concentration of hydrochloric or sulfuric acid equal to 30.0-150.0 g/l; duration of action of backward current τ_b=0.5-2.0 s; ratio of forward current to backward current τ_f/τ_b= 5.0-15.0; density of forward current j_f=1.0-5.0 kA/sq.m and ratio of backward current to forward current j_b/j_f=0.5-2.0, where τ_f is duration of action of forward current, s; τ_b is duration of action of backward current, s; j_f is density of forward current, kA/sq.m; j_b is density of backward current, kA/sq.m. EFFECT: enhanced productivity of process of electrolysis, increased current efficiency, diminished usage of reagents and improved sanitary and hygiene conditions of work. 2 tbl

Description

 The invention relates to hydrometallurgy of refractory metals and can be used in the electrochemical processing of waste tungsten-containing hard alloys.

A known method of refining alloys (RF patent 2044112, IPC ⁷ C 25 C 1/00, publ. 07/01/93), comprising carrying out electrolysis in an electrolyte solution by passing direct electric current with periodic switching direction to the opposite upon reaching a given potential difference, when this, the force of the reverse current is set 1.1 - 10 times greater than the current strength corresponding to the evolution of gas from a given electrolyte, and the process is conducted at this magnitude of the force of the reverse current to reduce the rate of change of the potential difference by 10 - 100 times, then reduce current strength to the value of the potential of dissolution of electronegative impurities and switch the direction of the current to the straight line when the thickness of the cathode layer reaches a value of (0.05-0.5) L, where L is the interelectrode distance.

 This method cannot be used for processing waste tungsten-containing alloys, because tungsten is not electrochemically separated from aqueous electrolytes, in addition, the method has a complex hardware design.

Closest to the claimed method is a method of anodic dissolution of waste carbide hard alloys of type VK and TTK in electrolytes containing HNO ₃ , H ₂ SO ₄ or Hcl using a constant, alternating sinusoidal or half-wave electric current (Palant A.A., Levin A. M., Bryukvin V.A. / Electrochemical processing of tungsten-containing carbide wastes of hard alloys. // Non-ferrous metals. 1999. 8. P. 42-45.)
The disadvantage of the prototype is the low current efficiency at anodic dissolution at constant current (49-67% based on WO ₃ , and at alternating sinusoidal current it is 20-25%, which is explained by the formation of oxide films that increase the capacity of the double electrode layer, and increase capacitive component of current.

With a half-wave electrolysis mode in electrolytes based on HNO ₃ , the current efficiency increases, however, the use of HNO ₃ requires special equipment and is associated with the release of harmful nitrous gases.

Another disadvantage of the prototype is the high consumption of acid (350-400 g / l in the initial solutions) and reagent for its neutralization (residual concentration of HNO ₃ in cobalt solutions 320-350 g / l).

 The objective of the proposed technical solution is to create a method for processing solid alloy waste with high productivity and low consumption of reagents, improving working conditions.

 The technical result consists in the intensification of the process by expanding the range of current densities and increasing current efficiency.

This technical result is achieved by the fact that in the known method of processing tungsten carbide-based carbide wastes comprising anodic dissolution in an electrolyte based on hydrochloric or sulfuric acid, according to the invention, the anodic dissolution is carried out in an asymmetric reversible current mode under the influence of direct electric current with periodic switching of direction reverse current, while the process is conducted at a concentration of hydrochloric or sulfuric acid of 30-150 g / l, the duration of the reverse current τ _arr = 0.5 - 2 s, the ratio of τ _ol / τ _arr = 5 - 15, the density of the forward current j _ol = 1.0 - 5.0 kA / m ² and the ratio of the reverse current to the forward j _arr / j _ol = 0.5 - 2.0,
where τ _CR - the time of the direct current, s,
τ _arr - the duration of the reverse current, s,
j _pp is the direct current density, kA / m ² ,
j _o6p is the reverse current density, kA / m ² .

 Optimal electrolysis conditions have been experimentally established, and at values higher or lower than the indicated concentrations, densities and duration of the forward and reverse current and their relations, the anode current output decreases.

 It was found that an increase in acid concentration leads to a decrease in current efficiency due to the appearance of a competing process of chlorine evolution on the anode.

 The essence of the method is illustrated by a specific example.

Example
The behavior of the VK-15 alloy having the following composition was investigated,%: WС 85; From 15.

As a source of reversible current, a device of the RIT series was used (manufactured according to A.S. USSR 1458956, MPK ⁷ N 02 M 9/06, published on 02.15.89), which allows adjusting both direct and reverse current in a wide range of variation.

Anodic dissolution was carried out under the action of a reversible asymmetric current in an aqueous solution of hydrochloric acid at a concentration of 50 g / l and an aqueous solution of sulfuric acid at a concentration of 50 g / l with a duration of the reverse current of τ _arr = 1 s, the ratio of τ _pr / τ _arr = 5, direct density current j _pr = 5.0 kA / m ² , the ratio of reverse current to forward _jspr / j _pr = 1.5 and room temperature.

 When dissolving, two electrodes of a soluble alloy are used. The discharge of cobalt ions on the electrodes during the cathode period does not occur, because the overvoltage of hydrogen evolution at the VC in acidic solutions is lower than the overvoltage of cobalt evolution, as a result of which only hydrogen was released at the cathode.

 When the current direction changes, the abundant evolution of hydrogen on the dissolving electrode causes peeling of the formed dense tungsten oxide film from its surface, which prevents electrolysis and reduces the current efficiency.

τ_обр и j_oбр/j_пр являются оптимальными).The output current in hydrochloric acid under the conditions indicated above was 99.28% (some other examples are given in Tables 1 and 2, the indicated values of С _HCl ,

and τ _{arr obr} j / j are optimum _etc.).

 Using the proposed method in comparison with the prototype will improve the performance of the anodic dissolution, increase the anode current efficiency, use cheaper and safer electrolytes and reduce the consumption of reagents.

Claims (1)

A method of processing waste alloys based on tungsten carbide by their anodic dissolution in an electrolyte based on hydrochloric or sulfuric acid, characterized in that the anodic dissolution is carried out in the mode of asymmetric reversible current under the action of direct electric current with periodic switching of the current direction to the opposite, while the concentration hydrochloric or sulfuric acid is equal to 30-150 g / l, the duration of the reverse current τ _arr = 0.5-2.0 s, the ratio of τ _pr / τ _arr = 5-15, the density of the direct current j _pr = 1.0-5 0 kA / m ^2, otno ix reverse current to direct _mod j / j _pr = 0.5 - 2.0, where τ _straight - forward current action time, s; τ _arr - time of the reverse current, s; j _CR - direct current density, kA / m ² ; j _arr is the density of the reverse current, kA / m ² .

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