Method for electrolytic production of bismuth from alloy containing lead, tin and bismuth, and electrolysis cell for realising said method

FIELD: chemistry.

SUBSTANCE: method involves anodic dissolution of tin and lead in a molten electrolyte of zinc, potassium and sodium chlorides, and depositing lead and tin on the wall of the cathode bath. The process is carried out while blowing the starting alloy with air and periodically adding ammonium chloride into the electrolyte by ejection feeding. The electrolysis cell has a lined heated cathode bath in which there is an anode cup with an insulated graphite current lead. The graphite current lead is hollow and has a nozzle with a channel for feeding air to the bottom of the anode cup. The graphite current lead has in its lower part a disc with air distribution channels.

EFFECT: reduced sludge formation, easier maintenance and high quality of the product.

3 cl, 1 dwg

 

The invention relates to the refining of heavy nonferrous metals by electrolytic method in the molten salt.

There is a method of electrolytic refining of low-melting metals in molten chlorides in the presence of ammonium chloride. However, it is used for refining of India [1].

Known and accepted as a prototype method of electrolysis, which consists in anodic dissolution electronegative tin and lead in the molten electrolyte and to separate them from bismuth from bismuthide lead by electrolysis of molten salts [2].

The method is carried out in a known electrolytic cell for refining bismuth containing a bath of the cathode metal, the anode capacity, graphite anode current lead with an insulator and a drain device [3].

The disadvantage of this cell is that of a conical screen makes cleaning sludge. Known electrolyzer adopted for the prototype [4], in which the anode Cup mounted on the stand tall, 0.8-1.2 height of the anode Cup and the cathode tub is equipped with a pocket with a bottom wall and a drain hole at a height of 0.6-1.0 height of the stand.

The disadvantage of this cell is that the surface of the anode alloy and the walls of the cathode of the bath covered with sludge. On the wall of the cathode of the bath is deposited lead and the electrolyte is depleted on lead and then begins to besiege the I zinc in the form of a sponge. Sponge floats covers the surface of the electrolyte. The sponge is deposited lead, particles (droplets) which are not dumped into drops due to the presence of zinc. Rich lead sponge is deposited on the surface of the molten anode alloy, hindering the diffusion of tin ions. Cathodic bath electrolytic cell requires monthly stripped from sludge, to mix, to store sludge for recycling and monthly to unload and load the anode Cup. Not timely stirring and scraping sludge leads to lower quality products. Recycling of marriage leads to lower productivity and efficiency of the process.

The disadvantages of this method are eliminated by the fact that the alloy containing lead, tin, bismuth purge air and periodically vmeshivat ammonium chloride ejection air purge.

The technical result of the invention is achieved by the fact that, as in the known method, tin and lead are dissolved from the alloy containing lead, tin, bismuth in molten electrolyte and deposited on the wall of the cathode, but additionally the melt of an alloy containing lead, tin, bismuth purge air and vmeshivat ammonium chloride.

The technical result is achieved by the fact that ammonium chloride chloridum zinc in the sponge, releasing lead to merge in drops. The air ejection captures chloride, shumilkin) and blows alloy, containing lead, tin, bismuth, accelerating dissolution. Creates an intensive mixing of the surface of the anode and the electrolyte, creating threads stirring of the electrolyte composition on the surface of the anode and cathode wall.

The essence of the proposed design is that the graphite current lead is made hollow and provided with a fitting to channel air flow to the bottom of the anode Cup and fitting electrical power supply is connected through the valve with a tank for ejection of the powder feeder of ammonium chloride in the melt. In addition, graphite feeding in the lower part of the disc is inserted with channels and holes for air distribution.

The design of the cell is illustrated in longitudinal section in the drawing.

Cathode tub 1, provided with a heater 2, is placed in the anode Cup 3, stand 4. In the anode Cup 3 submerged hollow graphite conductors 5, insulated quartz tube 6. Cathode tub 1 is equipped with a siphon pocket 7 with the bottom wall 8, a drain hole 9.

On top of the graphite current lead 5 to the thread and put the nozzle 10 connected to the duct through the ejector 11, over which is mounted a hopper 12 for ammonium chloride. The hopper is provided with a valve 13. In the lower part on the current lead 5 and the screw planted the heel 14 and the disk 15 with 16 channels of output air from the hollow of the busbar 5.

Electrolysis works SL is blowing. In the anode Cup 3 is loaded alloy containing 3-10% bismuth, 3-6% tin, the rest lead. Cathode tub 1 is loaded electrolyte containing: 80-70% of zinc chloride, 15-8% potassium chloride, 15-10% sodium chloride, the rest of the chloride of lead. Using the heater 2, the electrolyte is melted and maintained at a temperature of 360-450°C. To electrical power supply 5 is supplied a constant current of 4-6, with a cathode current density of 0.2-0.8 a/cm2. Due to the passage of current cations of tin and lead alloy anode Cup 3 pass into the salt melt and run down the wall of the cathode 1 bath. The metal flows down the wall and collects at the bottom of the cathode 1 bath. The alloy containing lead, tin, bismuth in the anode Cup 3 and the electrolyte above him stirred the air flow through the ejector 11, the fitting 10, the hollow cathode 5 and the slit 16 between the fifth and the disk 15. Air flow is regulated by valve and is controlled by a rotameter. The electrolyte bubbles rises and moves to the periphery to the walls of the cathode 1 (arrow). Once the change in the hopper 12 is loaded ammonium chloride, opens the valve 13 to its suction ejector and flow through the anode Cup in the molten electrolyte. When such loading ammonium chloride absorbed by the electrolyte is more effective than when applying the top surface. At least reduce the amount of metal in the anode Cup 3 dogroses the original alloy, containing lead, tin, bismuth.

The load operation of an alloy containing lead, tin, bismuth in the anode Cup is repeated to obtain alloy containing 65-79% bismuth. The cathode is an alloy of lead with tin drained through the siphon pocket 7 (arrow) and through the drain hole 9 after the opening of the tube. The composition of the cathode metal: tin - 5,4%; lead - 94,5%; bismuth - 0,04%.. Upon receipt of the metal in the anode Cup containing more than 65% of bismuth, reload the original alloy containing lead, tin, bismuth stop and continue the electrolysis 5 o'clock Get anodic alloy containing 99% of bismuth, 0,12% tin, 0.15% of lead. The obtained cathode metal second stage leave as current as the cathode metal starts to bismuth content of 0.1-0.5%.

The technical result of the proposed method is that the blend of ammonium chloride in the electrolyte prevents the formation of sludge sponge zinc chloride and hydrolysis of zinc from oxidation from the surface.

The technical result of the proposed cell that mixing of the alloy containing lead, tin, bismuth updates the contact surfaces of the metal-electrolyte interface, ensures the homogeneity of the composition and thereby accelerates the process.

Execution graphite electrical power supply 5 is hollow and its supply fitting 10 with a channel feeds the air to the bottom of the anode Cup provides him with additional function - supplying air to the anode. When this air is heated and cooled current lead. The connecting fitting 10 of the electrical power supply 5 with the hopper 12 powder provides economical ejection flow of ammonium chloride in the molten anode metal. In the lower part of the hollow graphite current lead 5 is equipped with a disk 15 with 16 channels for air distribution. This ensures the dispersion of air around the perimeter of the electrical power supply in different directions. Thus, in the proposed cell known individual nodes combine to create additional properties and provide a significant reduction sliming (5-6 times), simplify maintenance and improve product quality.

Literature

1. Auth. St. USSR №531380 - Suturin S.N., Nikitina E, d'yakov, V.E. and other - Way electrolytic refining India, publ. BI 25-78-233.

2. Delimarsky J.K., Zarubitsky OG and other Nonferrous metallurgy. No. 15, 1974, p.23-25.

3. Pat. Of the Russian Federation No. 2114936 from 03.12.1996, IPC SS 7/00, - Dyakov V.E., Ruban A.A., Dugelny A.P. Electrolyzer for the separation of metals in molten salts, publ.: BI No. 19-98.

4. Pat. RF - no 2096532, SS 7/00 - Dyakov VE Electrolyzer separation of lead and bismuth.

1. The way the electrolytic production of bismuth alloy containing lead, tin and bismuth, including anodic dissolution of tin and lead in the melt of the electrolyte salts of chloride of zinc, potassium,sodium and deposition of lead and tin on the cathode wall of the bath, characterized in that the process is conducted with the blowing of the original alloy air and periodic blend of ammonium chloride in the electrolyte ejection flow.

2. The electrolyzer for receiving bismuth alloy containing lead, tin and bismuth, including lined heated cathode bath and placed in it the anode Cup with isolated graphite electrical power supply, characterized in that the graphite current lead is made hollow and provided with a fitting to channel air supply and ejection of the powder feeder of ammonium chloride in the melt at the bottom of the anode Cup.

3. The electrolyzer according to claim 2, characterized in that the hollow graphite feeding in the lower part have a disk with channels for air distribution.



 

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