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Electric furnace treatment of soot
When the processing of lead-containing raw materials, in addition to crude lead, blast furnace dust are also valuable semifinished product.
The soot is smelted by a three-phase three-electrode electric furnace. The graphite electrode has a diameter of 300 mm. The furnace has a power of 2300 kVA. The furnace is supplied by a transformer with a low voltage of 54 volts (min) and 103 volts (maximum) and up to 6000 volts. The floor bed area is 5 m 2 . The size of the melting space of the furnace is as follows: length 3.3 meters, width 1.5 meters, height 1.95 meters. Magnesium brick bottom is lined with concrete on the high temperature stability of the seat cushion; furnace wall lined with chrome-magnesite brick; arched top, lined with a chrome magnesite-chrome.
The components of the smelted soot are as follows: Pb 52 to 60%, Zn 11.7 to 18.7%, Cd 0.8 to 1.37%, S to 5 to 6.5%, Sb to 0.1 to 1.3%, and As 0.1 to 1.45%. Sodium sulfate (Na 2 SO 4 68.1%, Na 2 C 22.8%, Na 2 O 3.65%) was used as a vulcanizing agent according to the content of zinc , and soda ash Na 2 CO 3 93.5% and K 2 were used for slag formation. CO 3 3 to 5%.
When the zinc content in the soot is higher than 14%, the composition of the charge is (% by weight): lead soot 100, sodium sulfide 20-25, coke 12-15. When the zinc content in the soot is less than 14%, the composition of the charge is: if the dust is 100, the soda ash is 20-25, and the coke is 8-12. The coke was charged according to the molten pool cover layer of 50 to 100 mm.
The furnace charge is uniformly filled into the furnace within 50 to 100 minutes, and the furnace is not allowed at this time, and the unmelted furnace material slope is not allowed to be formed in the furnace. The charge is applied to the furnace at a depth of 1100 to 1200 mm, and a burning yellow flame appears on the surface of the furnace. This flame marks the depletion of the slag- copper melt of cadmium and lead. After the fire through (100 ~ 1200 ° C), the molten pool is precipitated for 10 to 15 minutes.
The characteristics of the electric furnace smelting products are listed in Table 1.
Table 1 Chemical composition of products of electric furnace smelting blast furnace soot (%)
Smelting product
Pb
Cu
Zn
Sb
As
S
Cd
Black lead
96.5~98.5
0.06~0.65
-
0.1 to 0.16
0.25~0.5
-
-
Bronze-slag melt
0.75~2.7
0.15～0.45
17.5~26.0
0.05~0.5
0.6～2.2
11.7~11.5
0.05~0.10
Cadmium sublimate
22.5 to 29.7
15.5~27.0
-
0.04~0.12
1.3 to 3.5
4.5 to 6.8
5.8~8.5
The temperature in the electric furnace exhaust gas is 800 to 1000 °C. The exhaust gas enters the interior of the brickwork with a water jacket and is cooled to 100-130 ° C and sent to the bag filter. Commercial cadmium sublimate with cadmium content above 5%. Exhaust gas with a soot content of not more than 0.02 g/ m3 is discharged into the flue.
Matte - slag melt (Pb <2.6%) in the ingot mold was cooled, crushed and stored, to facilitate further processing and recovery of non-ferrous metals.
Furnace dust of the process with sodium sulfate or soda ash (Na 2 CO 3), it is characterized by a considerable number of nodules and the accumulated high SiO 2 content in the furnace viscous material, zinc sulfide and oxide. At this time, the technical and economical decline of the process, lead and sulfides and oxides. At this time, the technical and economic indicators of the process drop sharply, and the loss of lead and cadmium increases with the slag-copper melt, the power consumption increases, and the production of the smelted product is complicated. In the prior practice, in order to remove nodules and thick materials, a method of smelting water slag (3 to 5 tons of slag in one furnace) is used for cleaning. This is smelted 2 to 3 times until the furnace is completely cleaned.
The soot treatment process (Fig. 1) that has been developed and promoted is an effective method for extracting lead and antimony into crude lead. The cadmium content of the lift produced by the electric furnace smelting dust is high and can be smoothly processed in the zinc plant to recover all valuable components. Electrothermal methods can be used to treat materials containing lead, zinc and cadmium, which are produced by various industrial sectors.
Fig.1 Flow chart of processing smelting soot in blast furnace containing lead-recycled raw materials